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  • richardmitnick 12:51 pm on March 18, 2017 Permalink | Reply
    Tags: A Humanist Among the Scientists: A Conversation with Maura Dykstra, Caltech   

    From Caltech: “A Humanist Among the Scientists: A Conversation with Maura Dykstra” 

    Caltech Logo

    Caltech

    03/17/2017
    Lori Dajose
    (626) 395-1217
    ldajose@caltech.edu

    1
    Maura Dykstra. Credit: Caltech

    When you walk into Maura Dykstra’s new office at Caltech, one of the first things you notice is a table covered in scrolls, brushes, and calligraphic Chinese characters. For Dykstra, a new assistant professor of history, calligraphy is not just a hobby—it is practice to help her read and analyze historical documents. Dykstra is a historian studying the policies, government, and everyday life in China during the last dynasty—from the 17th to the early 20th century. We sat down with her to discuss Chinese history, calligraphy, her hobbies, and the importance of teaching history to science students.

    What is the focus of your research?

    I’m interested in how people are governed and how policy decisions—made in order to help society flourish and keep people from doing bad things—produce opportunities for cheating, produce opportunities for beauty, and produce unexpected consequences. I’m interested in how all of the institutions that we live with today are a combination of incredible human invention and sometimes strange circumstance.

    What led you to study history?

    I dropped out of high school when I was 15—partly because I hated history. I hated the expectation that I was supposed to listen to what teachers were saying and look for clues about how they understood reality in order to present those things back to them as answers about universal truths. I really didn’t like this vision of how knowledge worked. It involved generalizations about complicated historical truths and it demanded the student’s acquiescence to the instructor’s view of how the world worked. It didn’t encourage the student to wonder about the world of the past or the future.

    My mother’s condition for letting me drop out was that I continue my schooling, so I took some classes at City College of San Francisco. I dabbled in philosophy and film, only to drop out after three semesters to join an internet company back when that was the fashionable thing to do. I taught myself programming and HTML, and dreamed about the way that these new tools of communication and exchange would revolutionize the world by facilitating the transfer of information.

    After the September 11 terrorist attacks, that new world I had expected to emerge seemed far away. Foolish, even. I realized that I wasn’t interested in spending the rest of my life chasing around people’s HTML problems. I was actually interested in trying to do something that would make the world a more bearable place for myself and for the other people around me. Something that could bring people closer together and allow them to express their differences in productive ways as a more immediate goal for those of us who had been dreaming of a global information society but woke up in a divided world.

    I went back to school to take some history classes out of curiosity and, in the course of doing that, I developed the conviction that history can actually help us solve problems today. History gives us a perspective on the questions of the present day that requires us to expand our point of view beyond the most obvious parameters. A careful attention to how things came to be imbues us with an appreciation for the possibilities of what might have been and opens us up to questions that people caught up in the current moment might forget to ask. I believe that historical inquiry can offer insight not only into specific problems in the current day but also into the assumptions behind those problems and the world that exists beyond them. I decided to commit myself to the study of history when I realized how powerfully it can redefine the way that we ask questions about our lives today.

    What’s it like to be a historian at Caltech?

    In general, the link between humanities learning and practical problems in the current day is an extremely tenuous and sometimes problematic one. The lessons that we learn from humanities are often several steps removed from current problems. The important thing becomes attention to how those intermediate steps between research and theory and then application both within and beyond the humanities disciplines can be navigated. What is uniquely wonderful about working at Caltech is that I get to be in the same place as people who are working on the problems of today and in a community where a conversation across disciplines is encouraged.

    If I am puzzling out a problem about contracts and the game theory around contract enforcement, or if I’m interested in the political implications of a certain legal system, or if I’m curious about information policies and their influence on democratic institutions, I can actually go find someone here who studies that subject. More likely than not they will agree that conversations about shared subjects across disciplinary boundaries are opportunities for exploration. The collaborative, cross-disciplinary profile of Caltech’s faculty makes these conversations not only possible, but genuinely exciting.

    Why is history important for STEM students?

    I believe the best way to contribute to the knowledge of this generation, and to make the best possible future for the world, is to expand our imagination of what’s possible. One of the things you often find in history is that people make choices that turn out to be not very beneficial for them because at the time they were facing a problem, they couldn’t imagine anything other than a binary option, or they couldn’t draw on other traditions and ways they translate into their own problem.

    It’s important for people who will go on to become political leaders or intellectual figures or innovators to understand some of the complexity involved in operating across systems with very distinct historical characteristics. I think many people who get involved in the humanities in general and in history in particular do it because they want to find a better way to have a conversation about things that matter with people they don’t already agree with. When we simply discuss the things that are in front of us with our own perspective as the guiding compass, we miss a lot of opportunities for thinking outside of ourselves.

    What do you like to do in your free time?

    There are all sorts of things I do to make sure that I don’t just stay in my head. In addition to doing calligraphy, I am a potter, so sometimes I do ceramics. I enjoy cooking. I am a fencer and a martial artist. When I was doing postdoctoral research at Harvard, I worked at a press that used 19th-century technology to print things. I learned how to set type. I learned how to carve plates to make intaglio prints.

    Of course, I love to travel. That’s one of the best parts of the job. I get to go all over the place chasing down materials. I get to visit all sorts of beautiful, interesting places. When you’re a historian, your laboratory is the world—and the more you study it, the more interesting it becomes.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 10:14 am on March 16, 2017 Permalink | Reply
    Tags: , , Caltech, , Deep-sea corals, Desmophyllum dianthus, , Study: Cold Climates and Ocean Carbon Sequestration, Why the earth goes through periodic climate change   

    From Caltech: “Study: Cold Climates and Ocean Carbon Sequestration” 

    Caltech Logo

    Caltech

    03/14/2017

    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    Tony Wang (left) and Jess Adkins (right) with samples of Desmophyllum dianthus fossils.

    Deep-sea corals reveal why atmospheric carbon was reduced during colder time periods

    We know a lot about how carbon dioxide (CO2) levels can drive climate change, but how about the way that climate change can cause fluctuations in CO2 levels? New research from an international team of scientists reveals one of the mechanisms by which a colder climate was accompanied by depleted atmospheric CO2 during past ice ages.

    The overall goal of the work is to better understand how and why the earth goes through periodic climate change, which could shed light on how man-made factors could affect the global climate.

    Earth’s average temperature has naturally fluctuated by about 4 to 5 degrees Celsius over the course of the past million years as the planet has cycled in and out of glacial periods. During that time, the earth’s atmospheric CO2 levels have fluctuated between roughly 180 and 280 parts per million (ppm) every 100,000 years or so. (In recent years, man-made carbon emissions have boosted that concentration up to over 400 ppm.)

    About 10 years ago, researchers noticed a close correspondence between the fluctuations in CO2 levels and in temperature over the last million years. When the earth is at its coldest, the amount of CO2 in the atmosphere is also at its lowest. During the most recent ice age, which ended about 11,000 years ago, global temperatures were 5 degrees Celsius lower than they are today, and atmospheric CO2 concentrations were at 180 ppm.

    Using a library of more than 10,000 deep-sea corals collected by Caltech’s Jess Adkins, an international team of scientists has shown that periods of colder climates are associated with higher phytoplankton efficiency and a reduction in nutrients in the surface of the Southern Ocean (the ocean surrounding the Antarctic), which is related to an increase in carbon sequestration in the deep ocean. A paper about their research appears the week of March 13 in the online edition of the Proceedings of the National Academy of Sciences.

    “It is critical to understand why atmospheric CO2 concentration was lower during the ice ages. This will help us understand how the ocean will respond to ongoing anthropogenic CO2 emissions,” says Xingchen (Tony) Wang, lead author of the study. Wang was a graduate student at Princeton while conducting the research in the lab of Daniel Sigman, Dusenbury Professor of Geological and Geophysical Sciences. He is now a Simons Foundation Postdoctoral Fellow on the Origins of Life at Caltech.

    There is 60 times more carbon in the ocean than in the atmosphere—partly because the ocean is so big. The mass of the world’s oceans is roughly 270 times greater than that of the atmosphere. As such, the ocean is the greatest regulator of carbon in the atmosphere, acting as both a sink and a source for atmospheric CO2.

    Biological processes are the main driver of CO2 absorption from the atmosphere to the ocean. Just like photosynthesizing trees and plants on land, plankton at the surface of the sea turn CO2 into sugars that are eventually consumed by other creatures. As the sea creatures who consume those sugars—and the carbon they contain—die, they sink to the deep ocean, where the carbon is locked away from the atmosphere for a long time. This process is called the “biological pump.”

    A healthy population of phytoplankton helps lock away carbon from the atmosphere. In order to thrive, phytoplankton need nutrients—notably, nitrogen, phosphorus, and iron. In most parts of the modern ocean, phytoplankton deplete all of the available nutrients in the surface ocean, and the biological pump operates at maximum efficiency.

    However, in the modern Southern Ocean, there is a limited amount of iron—which means that there are not enough phytoplankton to fully consume the nitrogen and phosphorus in the surface waters. When there is less living biomass, there is also less that can die and sink to the bottom—which results in a decrease in carbon sequestration. The biological pump is not currently operating as efficiently as it theoretically could.

    To track the efficiency of the biological pump over the span of the past 40,000 years, Adkins and his colleagues collected more than 10,000 fossils of the coral Desmophyllum dianthus.

    Why coral? Two reasons: first, as it grows, coral accretes a skeleton around itself, precipitating calcium carbonate (CaCO3) and other trace elements (including nitrogen) out of the water around it. That process creates a rocky record of the chemistry of the ocean. Second, coral can be precisely dated using a combination of radiocarbon and uranium dating.

    “Finding a few centimeter-tall fossil corals 2,000 meters deep in the ocean is no trivial task,” says Adkins, Smits Family Professor of Geochemistry and Global Environmental Science at Caltech.

    Adkins and his colleagues collected coral from the relatively narrow (500-mile) gap known as the Drake Passage between South America and Antarctica (among other places). Because the Southern Ocean flows around Antarctica, all of its waters funnel through that gap—making the samples Adkins collected a robust record of the water throughout the Southern Ocean.

    Wang analyzed the ratios of two isotopes of nitrogen atoms in these corals – nitrogen-14 (14N, the most common variety of the atom, with seven protons and seven neutrons in its nucleus) and nitrogen-15 (15N, which has an extra neutron). When phytoplankton consume nitrogen, they prefer 14N to 15N. As a result, there is a correlation between the ratio of nitrogen isotopes in sinking organic matter (which the corals then eat as it falls to the seafloor) and how much nitrogen is being consumed in the surface ocean—and, by extension, the efficiency of the biological pump.

    A higher amount of 15N in the fossils indicates that the biological pump was operating more efficiently at that time. An analogy would be monitoring what a person eats in their home. If they are eating more of their less-liked foods, then one could assume that the amount of food in their pantry is running low.

    Indeed, Wang found that higher amounts of 15N were present in fossils corresponding to the last ice age, indicating that the biological pump was operating more efficiently during that time. As such, the evidence suggests that colder climates allow more biomass to grow in the surface Southern Ocean—likely because colder climates experience stronger winds, which can blow more iron into the Southern Ocean from the continents. That biomass consumes carbon, then dies and sinks, locking it away from the atmosphere.

    Adkins and his colleagues plan to continue probing the coral library for further details about the cycles of ocean chemistry changes over the past several hundred thousand years.

    The study is titled “Deep-sea coral evidence for lower Southern Ocean surface nitrate concentrations during the last ice age.” Coauthors include scientists from Caltech, Princeton University, Pomona College, the Max Planck Institute for Chemistry in Germany, University of Bristol, and ETH Zurich in Switzerland. This research was funded by the National Science Foundation, Princeton University, the European Research Council, and the Natural Environment Research Council.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 9:06 am on March 8, 2017 Permalink | Reply
    Tags: , , , Caltech, Cosmic Environments and Their Influence in Star Formation, ,   

    From UC Riverside: “Cosmic Environments and Their Influence in Star Formation” 

    UC Riverside bloc

    UC Riverside

    March 6, 2017
    Sean Nealon

    1
    Simulations of the cosmic web. The filaments connecting structures are shown. Such structures are predicted by numerical simulations of matter distribution in the universe at different times through the age of the universe. Credit: Illustris Simulation

    Researchers at UC Riverside and Caltech team up on Astrophysical Journal paper

    The scaffolding that holds the large-scale structure of the universe constitutes galaxies, dark matter and gas (from which stars are forming), organized in complex networks known as the cosmic web. This network comprises dense regions known as galaxy clusters and groups that are woven together through thread-like structures known as filaments. These filaments form the backbone of the cosmic web and host a large fraction of the mass in the universe, as well as sites of star formation activity.

    While there is ample evidence that environments shape and direct the evolution of galaxies, it is not clear how galaxies behave in the larger, global cosmic web and in particular in the more extended environment of filaments.

    In a joint collaboration between the California Institute of Technology and the University of California, Riverside, astronomers have performed an extensive study of the properties of galaxies within filaments formed at different times during the age of the universe.

    In a just-published paper, astronomers used a sample of 40,000 galaxies in the COSMOS field, a large and contiguous patch of sky with deep enough data to look at galaxies very far away, and with accurate distance measurements to individual galaxies. The large area covered by COSMOS allowed sampling volumes of different densities within the cosmic web.

    Using techniques developed to identify the large-scale structures, they cataloged the cosmic web to its components: clusters, filaments, and sparse regions devoid of any object, extending into the universe as it was 8 billion years ago. The galaxies were then divided into those that are central to their local environment (the center of gravity) and those that roam around in their host environments (satellites).

    “What makes this study unique is the observation of thousands of galaxies in different filaments spanning a significant fraction of the age of the Universe” said Behnam Darvish a postdoctoral scholar at Caltech who is the lead author on the paper. “When we consider the distant universe, we look back in time to when the cosmic web and filaments were younger and had not yet fully evolved and therefore, could study the joint evolution of the large scale structures and galaxies associated with them.”

    2
    Observational data in the COSMOS survey show filamentary structures at different redshifts (look-back times). At higher redshifts, galaxies become younger and one could look at the newly formed structures. No image credit.

    The researchers measured the star formation activity in galaxies located in different environments.

    “It was reassuring when we found that the average star-formation activity declined from the sparsely populated regions of the cosmic web to mildly populated filaments and dense clusters,” said Bahram Mobasher, a professor of physics and astronomy at the University of California, Riverside. “However, the surprising finding was that the decline was especially steep for satellite galaxies.”

    He emphasized: “The inevitable conclusion from this was that the majority of satellite galaxies stop forming stars relatively fast during the last 5 billion years as they fall to dense environments of clusters by way of the filaments, while this process is much slower for central galaxies.”

    The fast cessation of star formation experienced by satellite galaxies can be explained by “ram-pressure stripping,” which is loss of star-forming gas within a galaxy as it moves within a denser environment, such as a cluster.

    “Compared to the central galaxies, it is the smaller gravitational pull of the satellite galaxies produced by their smaller mass, that results in a more efficient loss of gas and hence, a slow-down in star formation activity with respect to the more massive central galaxies” said Chris Martin, a professor of astronomy at Caltech.

    This investigation served as a pilot study for future large-volume and relatively deep surveys, which will peer into dimmer and younger galaxies in the Universe, such as LSST, Euclid, and WFIRST.

    In addition to Darvish, Mobasher and Martin, the authors are: Nick Scoville and Shoubaneh Hemmati of Caltech, David Sobral of Lancaster University in the United Kingdom, Andra Stroe of the European Southern Observatory, and Jeyhan Kartaltepe of the Rochester Institute of Technology.

    The research was funded by NASA.

    Mario De Leo Winkler, a postdoctoral researcher in the UCR Department of Physics and Astronomy, made significant contributions to this article.

    See the full article here .

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    UC Riverside Campus

    The University of California, Riverside is one of 10 universities within the prestigious University of California system, and the only UC located in Inland Southern California.

    Widely recognized as one of the most ethnically diverse research universities in the nation, UCR’s current enrollment is more than 21,000 students, with a goal of 25,000 students by 2020. The campus is in the midst of a tremendous growth spurt with new and remodeled facilities coming on-line on a regular basis.

    We are located approximately 50 miles east of downtown Los Angeles. UCR is also within easy driving distance of dozens of major cultural and recreational sites, as well as desert, mountain and coastal destinations.

     
  • richardmitnick 6:47 pm on March 6, 2017 Permalink | Reply
    Tags: , Caltech, , , New Materials Could Turn Water into the Fuel of the Future, photoanodes,   

    From Caltech: “New Materials Could Turn Water into the Fuel of the Future” 

    Caltech Logo

    Caltech

    03/06/2017

    Robert Perkins
    (626) 395-1862
    rperkins@caltech.edu

    1
    Scientists at JCAP create new materials by spraying combinations of elements onto thin plates. Credit: Caltech

    2
    John Gregoire tests the properties of newly created materials. Credit: Caltech

    Researchers at Caltech and Lawrence Berkeley National Laboratory (Berkeley Lab) have—in just two years—nearly doubled the number of materials known to have potential for use in solar fuels.

    They did so by developing a process that promises to speed the discovery of commercially viable solar fuels that could replace coal, oil, and other fossil fuels.

    Solar fuels, a dream of clean-energy research, are created using only sunlight, water, and carbon dioxide (CO2). Researchers are exploring a range of target fuels, from hydrogen gas to liquid hydrocarbons, and producing any of these fuels involves splitting water.

    Each water molecule is comprised of an oxygen atom and two hydrogen atoms. The hydrogen atoms are extracted, and then can be reunited to create highly flammable hydrogen gas or combined with CO2 to create hydrocarbon fuels, creating a plentiful and renewable energy source. The problem, however, is that water molecules do not simply break down when sunlight shines on them—if they did, the oceans would not cover most of the planet. They need a little help from a solar-powered catalyst.

    To create practical solar fuels, scientists have been trying to develop low-cost and efficient materials, known as photoanodes, that are capable of splitting water using visible light as an energy source. Over the past four decades, researchers identified only 16 of these photoanode materials. Now, using a new high-throughput method of identifying new materials, a team of researchers led by Caltech’s John Gregoire and Berkeley Lab’s Jeffrey Neaton and Qimin Yan have found 12 promising new photoanodes.

    A paper about the method and the new photoanodes appears the week of March 6 in the online edition of the Proceedings of the National Academy of Sciences. The new method was developed through a partnership between the Joint Center for Artificial Photosynthesis (JCAP) at Caltech, and Berkeley Lab’s Materials Project, using resources at the Molecular Foundry and the National Energy Research Scientific Computing Center (NERSC).



    LBL NERSC Cray XC30 Edison supercomputer

    NERSC CRAY Cori supercomputer

    “This integration of theory and experiment is a blueprint for conducting research in an increasingly interdisciplinary world,” says Gregoire, JCAP thrust coordinator for Photoelectrocatalysis and leader of the High Throughput Experimentation group. “It’s exciting to find 12 new potential photoanodes for making solar fuels, but even more so to have a new materials discovery pipeline going forward.”

    “What is particularly significant about this study, which combines experiment and theory, is that in addition to identifying several new compounds for solar fuel applications, we were also able to learn something new about the underlying electronic structure of the materials themselves,” says Neaton, the director of the Molecular Foundry.

    Previous materials discovery processes relied on cumbersome testing of individual compounds to assess their potential for use in specific applications. In the new process, Gregoire and his colleagues combined computational and experimental approaches by first mining a materials database for potentially useful compounds, screening it based on the properties of the materials, and then rapidly testing the most promising candidates using high-throughput experimentation.

    In the work described in the PNAS paper, they explored 174 metal vanadates—compounds containing the elements vanadium and oxygen along with one other element from the periodic table.

    The research, Gregoire says, reveals how different choices for this third element can produce materials with different properties, and reveals how to “tune” those properties to make a better photoanode.

    “The key advance made by the team was to combine the best capabilities enabled by theory and supercomputers with novel high throughput experiments to generate scientific knowledge at an unprecedented rate,” Gregoire says.

    The study is titled Solar fuels photoanode materials discovery by integrating high-throughput theory and experiment. Other authors from Caltech include JCAP research engineers Santosh Suram, Lan Zhou, Aniketa Shinde, and Paul Newhouse. This research was funded by the DOE. JCAP is a DOE Energy Innovation Hub focused on developing a cost-effective method of turning sunlight, water, and CO2 into fuel. It is led by Caltech with Berkeley Lab as a major partner. The Materials Project is a DOE program based at Berkeley Lab that aims to remove the guesswork from materials design in a variety of applications. The Molecular Foundry and NERSC are both DOE Office of Science User Facilities located at Berkeley Lab.

    See the full article here .

    Please help promote STEM in your local schools.

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    Stem Education Coalition

    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 2:45 pm on February 24, 2017 Permalink | Reply
    Tags: , Caltech, , Nucleotides, Seesaw Compiler   

    From Caltech: “Computing with Biochemical Circuits Made Easy” 

    Caltech Logo
    Caltech

    1
    Detail from painting “What Dreams Are Made Of.” Credit: Ann Erpino

    Electronic circuits are found in almost everything from smartphones to spacecraft and are useful in a variety of computational problems from simple addition to determining the trajectories of interplanetary satellites. At Caltech, a group of researchers led by Assistant Professor of Bioengineering Lulu Qian is working to create circuits using not the usual silicon transistors but strands of DNA.

    The Qian group has made the technology of DNA circuits accessible to even novice researchers—including undergraduate students—using a software tool they developed called the Seesaw Compiler. Now, they have experimentally demonstrated that the tool can be used to quickly design DNA circuits that can then be built out of cheap “unpurified” DNA strands, following a systematic wet-lab procedure devised by Qian and colleagues.

    A paper describing the work appears in the February 23 issue of Nature Communications.

    Although DNA is best known as the molecule that encodes the genetic information of living things, they are also useful chemical building blocks. This is because the smaller molecules that make up a strand of DNA, called nucleotides, bind together only with very specific rules—an A nucleotide binds to a T, and a C nucleotide binds to a G. A strand of DNA is a sequence of nucleotides and can become a double strand if it binds with a sequence of complementary nucleotides.

    DNA circuits are good at collecting information within a biochemical environment, processing the information locally and controlling the behavior of individual molecules. Circuits built out of DNA strands instead of silicon transistors can be used in completely different ways than electronic circuits. “A DNA circuit could add ‘smarts’ to chemicals, medicines, or materials by making their functions responsive to the changes in their environments,” Qian says. “Importantly, these adaptive functions can be programmed by humans.”

    To build a DNA circuit that can, for example, compute the square root of a number between 0 and 16, researchers first have to carefully design a mixture of single and partially double-stranded DNA that can chemically recognize a set of DNA strands whose concentrations represent the value of the original number. Mixing these together triggers a cascade of zipping and unzipping reactions, each reaction releasing a specific DNA strand upon binding. Once the reactions are complete, the identities of the resulting DNA strands reveal the answer to the problem.

    With the Seesaw Compiler, a researcher could tell a computer the desired function to be calculated and the computer would design the DNA sequences and mixtures needed. However, it was not clear how well these automatically designed DNA sequences and mixtures would work for building DNA circuits with new functions; for example, computing the rules that govern how a cell evolves by sensing neighboring cells, defined in a classic computational model called “cellular automata.”

    “Constructing a circuit made of DNA has thus far been difficult for those who are not in this research area, because every circuit with a new function requires DNA strands with new sequences and there are no off-the-shelf DNA circuit components that can be purchased,” says Chris Thachuk, senior postdoctoral scholar in computing and mathematical sciences and second author on the paper. “Our circuit-design software is a step toward enabling researchers to just type in what they want to do or compute and having the software figure out all the DNA strands needed to perform the computation, together with simulations to predict the DNA circuit’s behavior in a test tube. Even though these DNA strands are still not off-the-shelf products, we have now shown that they do work well for new circuits with user-designed functions.”

    “In the 1950s, only a few research labs that understood the physics of transistors could build early versions of electronic circuits and control their functions,” says Qian. “But today many software tools are available that use simple and human-friendly languages to design complex electronic circuits embedded in smart machines. Our software is kind of like that: it translates simple and human-friendly descriptions of computation to the design of complex DNA circuits.”

    The Seesaw Compiler was put to the test in 2015 in a unique course at Caltech, taught by Qian and called “Design and Construction of Programmable Molecular Systems” (BE/CS 196 ab). “How do you evaluate the accessibility of a new technology? You give the technology to someone who is intellectually capable but has minimal prior background,” Qian says.

    “The students in this class were undergrads and first-year graduate students majoring in computer science and bioengineering,” says Anupama Thubagere, a graduate student in biology and bioengineering and first author on the paper. “I started working with them as a head teaching assistant and together we soon discovered that using the Seesaw Compiler to design a DNA circuit was easy for everyone.”

    However, building the designed circuit in the wet lab was not so simple. Thus, with continued efforts after the class, the group set out to develop a systematic wet-lab procedure that could guide researchers—even novices like undergraduate students—through the process of building DNA circuits. “Fortunately, we found a general solution to every challenge that we encountered, now making it easy for everyone to build their own DNA circuits,” Thubagere says.

    The group showed that it was possible to use cheap, “unpurified” DNA strands in these circuits using the new process. This was only possible because steps in the systematic wet-lab procedure were designed to compensate for the lower synthesis quality of the DNA strands.

    “We hope that this work will convince more computer scientists and researchers from other fields to join our community in developing increasingly powerful molecular machines and to explore a much wider range of applications that will eventually lead to the transformation of technology that has been promised by the invention of molecular computers,” Qian says.

    The paper is titled, Compiler-aided systematic construction of large-scale DNA strand displacement circuits using unpurified components. Other Caltech co-authors include graduate students Robert Johnson and Kevin Cherry, alumnus Joseph Berleant (BS ’16), and undergraduate Diana Ardelean. The work was funded by the National Science Foundation, the Banting Postdoctoral Fellowships program, the Burroughs Wellcome Fund, and Innovation in Education funds from Caltech.

    See the full article here .

    Please help promote STEM in your local schools.

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    Caltech campus
    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 2:26 pm on February 2, 2017 Permalink | Reply
    Tags: , , Caltech, ,   

    From Caltech: “Protein Chaperone Takes Its Job Seriously” 

    Caltech Logo

    Caltech

    02/02/2017

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    Structural rendering of a ribosomal protein (yellow and red) bound to its chaperone (blue). By capturing an atomic-resolution snapshot of the pair of proteins interacting with each other, Ferdinand Huber, a graduate student in the lab of André Hoelz revealed that chaperones can protect their ribosomal proteins by tightly packaging them up. The red region illustrates where the dramatic shape alterations occur when the ribosomal protein is released from the chaperone during ribosome assembly. Credit: Huber and Hoelz/Caltech

    2
    A diagram of the cell showing the process by which chaperone proteins (red) transport ribosomal proteins (beige) to the nucleus. The chaperones bind to the ribosomal proteins and usher them into the nucleus, while also protecting the proteins from liquidation machinery. Once a ribosomal protein reaches a growing ribosome (green and purple), the chaperone releases it. The nearly complete ribosome units exit the nucleus where they undergo final assembly. Credit: Huber and Hoelz/Caltech

    For proteins, this would be the equivalent of the red-carpet treatment: each protein belonging to the complex machinery of ribosomes—components of the cell that produce proteins—has its own chaperone to guide it to the right place at the right time and protect it from harm.

    In a new Caltech study, researchers are learning more about how ribosome chaperones work, showing that one particular chaperone binds to its protein client in a very specific, tight manner, almost like a glove fitting a hand. The researchers used X-ray crystallography to solve the atomic structure of the ribosomal protein bound to its chaperone.

    “Making ribosomes is a bit like baking a cake. The individual ingredients come in protective packaging that specifically fits their size and shape until they are unwrapped and blended into a batter,” says André Hoelz, professor of chemistry at Caltech, a Heritage Medical Research Institute (HMRI) Investigator, and Howard Hughes Medical Institute (HHMI) Faculty Scholar.” What we have done is figure out how the protective packaging fits one ribosomal protein, and how it comes unwrapped.” Hoelz is the principal investigator behind the study published February 2, 2017, in the journal Nature Communications. The finding has potential applications in the development of new cancer drugs designed specifically to disable ribosome assembly.

    In all cells, genetic information is stored as DNA and transcribed into mRNAs that code for proteins. Ribosomes translate the mRNAs into amino acids, linking them together into polypeptide chains that fold into proteins. More than a million ribosomes are produced per day in an animal cell.

    Building ribosomes is a formidable undertaking for the cell, involving about 80 proteins that make up the ribosome itself, strings of ribosomal RNA, and more than 200 additional proteins that guide and regulate the process. “Ribosome assembly is a dynamic process, where everything happens in a certain order. We are only now beginning to elucidate the many steps involved,” says Hoelz.

    To make matters more complex, the proteins making up a ribosome are first synthesized outside the nucleus of a cell, in the cytoplasm, before being transported into the nucleus where the initial stages of ribosome assembly take place.

    Chaperone proteins help transport ribosomal proteins to the nucleus while also protecting them from being chopped up by a cell’s protein shredding machinery. The components that specifically aim this machinery at unprotected ribosomal proteins, recently identified by Raymond Deshaies, professor of biology at Caltech and an HHMI Investigator, ensures that equal numbers of the various ribosomal proteins are available for building the massive structure of a ribosome.

    3
    Structural rendering of a chaperone called Acl4 bound to ribosomal protein L4

    Previously, Hoelz and his team, in collaboration with the laboratory of Ed Hurt at the University of Heidelberg, discovered that a ribosomal protein called L4 is bound by a chaperone called “Assembly chaperone of RpL4,” or Acl4. The chaperone ushers L4 through the nucleus, protecting it from harm, and delivers it to a developing ribosome at a precise time and location. In the new study, the team used X-ray crystallography, a process that involves exposing protein crystals to high-energy X-rays, to solve the structure of the bound pair. The technique was performed at Caltech’s Molecular Observatory beamline at the Stanford Synchrotron Radiation Lightsource.

    “This was not an easy structure to solve,” says Ferdinand Huber, a graduate student at Caltech in the Hoelz lab and first author of the new study. “Solving the structure was incredibly exciting because you could see with your eyes, for the very first time, how the chaperone embraces the ribosomal protein to protect it.”

    Hoelz says that the structure was a surprise because it was not known previously that chaperones hold on to their ribosomal proteins so tightly. He says they want to study other chaperones in the future to see if they function in a similar fashion to tightly guard ribosomal proteins. The results may lead to the development of new drugs for cancer therapy by preventing cancer cells from supplying the large numbers of ribosomes required for tumor growth.

    The study, called “Molecular Basis for Protection of Ribosomal Protein L4 from Cellular Degradation,” was funded by a PhD fellowship of the Boehringer Ingelheim Fonds, a Faculty Scholar Award of the Howard Hughes Medical Research Institute, a Heritage Medical Research Institute Principal Investigatorship, a Kimmel Scholar Award of the Sidney Kimmel Foundation for Cancer Research, a Teacher-Scholar Award of the Camille & Henry Dreyfus Foundation, and Caltech startup funds.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”
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  • richardmitnick 1:43 pm on January 31, 2017 Permalink | Reply
    Tags: , , , Caltech, , , vortex coronagraph   

    From Caltech: “Keck Observatory’s New Planet Imager Delivers First Science” 

    Caltech Logo
    Caltech
    01/30/2017

    Whitney Clavin
    (626) 395-1856
    wclavin@caltech.edu

    1
    An image of the brown dwarf HIP 79124 B, which is separated from its host star by 23 astronomical units (an astronomical unit is the distance between our sun and Earth). The vortex coronagraph was used to suppress the much brighter host star, allowing its dim companion to be imaged for the first time. Credit: NASA/JPL-Caltech

    2
    An image of the dusty disk of planetary material surrounding the star called HD 141569, located 380 light-years away. It was taken using the vortex coronagraph on the W.M. Keck Observatory. The vortex suppressed the star in the center, revealing light from the innermost ring of planetary material around the star (blue). The disk is made of olivine particles and extends from 23 to 70 astronomical units from the star—around where the outer planets lie in our solar system. Credit: NASA/JPL-Caltech

    3
    A picture of a vortex mask (left), which is made out of synthetic diamond. The mask is 1 centimeter in diameter and 0.3 millimeters thick. The vortex’s engraved pattern of grooves is very similar to a compact disk, making it look like a miniature version of a CD. The image at right zooms into the mask’s center with a scanning electron microscope. This view reveals the microstructure of the mask, highlighting its concentric grooves, which have a thickness of about 1/100th that of a human hair. No image credit.

    A new instrument on the W. M. Keck Observatory in Hawaii has delivered its first images, showing a ring of planet-forming dust around a star and, separately, a cool star-like body, called a brown dwarf, lying near to its companion star.

    The device, called the vortex coronagraph, was recently installed inside the Near Infrared Camera 2 (NIRC2), the workhorse infrared imaging camera at Keck. The vortex coronagraph has the potential to image planetary systems and brown dwarfs closer to their host stars than was possible previously. It was invented in 2005 by Dimitri Mawet while he was at the University of Liège in Belgium. Mawet is currently associate professor of astronomy at Caltech and a senior research scientist at NASA’s Jet Propulsion Laboratory (JPL). The Keck vortex coronagraph was built by the University of Liège, Uppsala University in Sweden, JPL, and Caltech.

    “The vortex coronagraph allows us to peer into the regions around stars where giant planets like Jupiter and Saturn supposedly form,” says Mawet. “Before now, we were only able to image gas giants that are born much farther out. With the vortex, we will be able to see planets orbiting as close to their stars as Jupiter is to our sun, or about two to three times closer than what was possible before.”

    The new vortex results are presented in two papers, both published in the January 2017 issue of The Astronomical Journal. One study, led by Gene Serabyn of JPL, the overall lead of the Keck vortex project, presents the first direct image of the brown dwarf called HIP 79124 B. This brown dwarf is located 23 astronomical units from a star in a nearby star-forming region called Scorpius-Centaurus (an astronomical unit is the distance between our sun and Earth).

    “The ability to see very close to stars also allows us to search for planets around more distant stars, where the planets and stars would appear closer together. Having the ability to survey distant stars for planets is important for catching planets still forming,” says Serabyn, who also led team that tested a predecessor of the vortex device at the Hale Telescope at Caltech’s Palomar Observatory near San Diego.

    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA
    Caltech Palomar 200 inch Hale Telescope interior
    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA

    In 2010, the team took images of three planets orbiting in the distant reaches of the star system called HR 8799.

    The second vortex study, led by Mawet, presents an image of the innermost of three rings of dusty planet-forming material around the young star called HD 141569 A. The results, when combined with infrared data from NASA’s Spitzer and WISE missions, and the European Space Agency’s Herschel mission, reveal that the star’s planet-forming material is made up of pebble-size grains of olivine, one of the most abundant silicates in Earth’s mantle. In addition, the data show that the temperature of the innermost ring imaged by the vortex is around 100 Kelvin (or minus 173 Celsius degrees), a bit warmer than our asteroid belt.

    NASA/Spitzer Telescope
    NASA/Spitzer Telescope

    NASA/WISE Telescope
    NASA/WISE Telescope

    ESA/Herschel spacecraft
    “ESA/Herschel spacecraft

    “The three rings around this young star are nested like Russian dolls and undergoing dramatic changes reminiscent of planetary formation,” says Mawet. “We have shown that silicate grains have agglomerated into pebbles, which are the building blocks of planet embryos.”

    How the vortex sees planets

    The first science images and results from the vortex instrument demonstrate its ability to image planet-forming regions hidden under the glare of stars. Stars outshine planets by a factor of a few thousands to a few billions, making the dim light of planets very difficult to see. The closer a planet is to its star, the more difficult it is to image. To deal with this challenge, researchers have invented Instruments called coronagraphs, which typically use tiny masks to block the starlight, much like blocking the bright sun with your hand or a car visor to see better.

    What makes the vortex coronagraph unique is that it does not block the starlight with a mask, but instead redirects the light away from the detectors using a technique in which light waves are combined and canceled out. Because the vortex doesn’t require a mask, it has the advantage of taking images of regions closer to stars than other coronagraphs. Mawet likens the process to the eye of a storm.

    “The instrument is called a vortex coronagraph because the starlight is centered on an optical singularity, which creates a dark hole at the location of the image of the star,” says Mawet. “Hurricanes have a singularity at their centers where the wind speeds drop to zero—the eye of the storm. Our vortex coronagraph is basically the eye of an optical storm where we send the starlight.”

    A team at the University of Liège, led by Olivier Absil, designed a portion of the Keck vortex coronagraph called the phase mask, which consists of concentric microstructures that force the starlight waves to swirl about the mask’s center, creating the vortex singularity. This mask was forged at Uppsala University by Mikael Karlsson and his team, who etched the concentric microstructures into synthetic diamond. The etching is done in a plasma chamber where the diamond is bombarded by argon and oxygen ions, ripping the carbon atoms out of the diamond crystal.

    The vortex was installed at Keck in the spring of 2015 by Keith Matthews, chief instrument scientist at Caltech, who has worked on dozens of astronomical instruments in his more than 50-year career at the Institute. The coronagraph was optimized and is operated with the help of the Keck Observatory staff. “Once the device is in there, users can operate it remotely from the base of the mountain or even from their home universities,” says Matthews.

    What’s next for the vortex

    In the future, the vortex will look at many more young planetary systems, in particular planets near the “ice lines,” which are the region around a star where temperatures have become cold enough for volatile molecules, such as water, methane, and carbon dioxide, to condense into solid icy grains. Ice lines are thought to delineate the transition between rocky planets and gas giants.

    Surveys of the ice-line region by the vortex coronagraph will help answer ongoing puzzles about a class of hot, giant planets found extremely close to their stars—the “hot Jupiters” and “hot Neptunes.” Did these planets first form close to the ice lines and migrate in, or did they form in situ, right next to their star? “With a bit of luck, we might catch planets in the process of migrating through the planet-forming disk, by looking at these very young objects,” says Mawet.

    This month, a privately funded project called Breakthrough Initiatives announced that it is partnering with the European Southern Observatory to use similar vortex technology to find and image a putative Earth-like planet in the nearby Alpha Centauri star system. What’s more, results from Keck’s vortex coronagraph will help with a planet imager planned for the future Thirty Meter Telescope and with proposed NASA space missions, such as the Habitable Exoplanet Imaging Mission (HabEx) and the Large UV/Optical/IR Surveyor (LUVOIR), which would use next-generation vortex coronagraphs currently being designed in Mawet’s group at Caltech.

    The challenge of these facilities is to image planets even closer to their stars than those at the ice line, which includes Earth-like rocky planets. When combined with data from spectrograph instruments, which can identify molecules in planets’ atmospheres, the images could help astronomers identify possible signs of life.

    “The power of the vortex lies in its ability to image planets very close to their star, something that we can’t do for Earth-like planets yet,” says Serabyn. “The vortex coronagraph may be key to taking the first images of a pale blue dot like our own.”

    The Keck Observatory is managed by Caltech and the University of California. In 1996, the NASA joined as a one-sixth partner in the Keck Observatory. JPL is managed by Caltech for NASA.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 3:07 pm on January 14, 2017 Permalink | Reply
    Tags: , , , Caltech, , , Keck Cosmic Web Imager   

    From Caltech via EurekaAlert: “New Caltech instrument poised to image the cosmic web” 

    Caltech Logo
    Caltech

    1

    EurekaAlert

    12-Jan-2017
    Whitney Clavin
    wclavin@caltech.edu
    626-395-1856

    Keck Cosmic Web Imager ships from Caltech to Keck Observatory

    2
    Hector Rodriguez, senior mechanical technician, works on the Keck Cosmic Web Imager in a clean room at Caltech. Caltech

    An instrument designed to image the vast web of gas that connects galaxies in the universe has been shipped from Los Angeles to Hawaii, where it will be integrated into the W. M. Keck Observatory.

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory, Mauna Kea, Hawaii, USA

    The instrument, called the Keck Cosmic Web Imager, or KCWI, was designed and built by a team at Caltech led by Professor of Physics Christopher Martin. It will be one of the best instruments in the world for taking spectral images of cosmic objects–detailed images where each pixel can be viewed in all wavelengths of visible light. Such high-resolution spectral information will enable astronomers to study the compositions, velocities, and masses of many objects, such as stars and galaxies, in ways that were not possible before.

    One of KCWI’s main goals, and a passion of Martin’s for the past 30 years, is to answer the question: What is the gas around galaxies doing?

    “For decades, astronomers have demonstrated that galaxies evolve. Now we’re trying to figure out how and why,” says Martin. “We know the gas around galaxies is ultimately fueling them, but it is so faint–we still haven’t been able to get a close look at it and understand how this process works.”

    Martin and his team study what is called the cosmic web–a vast network of streams of gas between galaxies. Recently, the scientists have found evidence supporting what is called the cold flow model, in which this gas funnels into the cores of galaxies, where it condenses and forms new stars.

    3
    The forming galaxy with binary quasars as it fits into the timeline of the Universe. We’re seeing it 10 billion years ago, during the epoch of galaxy formation. Credit: Caltech Academic Media Technologies

    Researchers had predicted that the gas filaments would first flow into a large ring-like structure around the galaxy before spiraling into it–exactly what Martin and his team found using the Palomar Cosmic Web Imager, a precursor to KCWI, at Caltech’s Palomar Observatory near San Diego.

    Caltech Palomar Cosmic Web Imager
    Caltech Palomar Cosmic Web Imager

    “We measured the kinematics, or motion, of the gas around a galaxy and found a very large rotating disk connected to a gas filament,” says Martin. “It was the smoking gun for the cold flow model.”

    With KCWI, the researchers will get a closer look at the gas filaments and ring-like structures around galaxies that range from 10 to 12 billion light-years away, an era when our universe was roughly 2 to 4 billion years old. Not only can KCWI take more detailed pictures than the Palomar Cosmic Web Imager, it has other advances such as better mirror coatings. The combination of these improvements with the fact that KCWI is being installed at one of the twin 10-meter Keck telescopes–the world’s largest observatory with some of the darkest known skies on Earth–means that KCWI will have an improved performance by more than an order of magnitude over the Palomar Cosmic Web Imager.

    KCWI will map the gas flowing from the intergalactic medium–the space between galaxies–into many young galaxies, revealing, for the first time, the dominant mode of galaxy formation in the early universe. The instrument will also search for supergalactic winds from galaxies that drive gas back into the intergalactic medium. How gas flows into and out of forming galaxies is the central open question in the formation of cosmic structures.

    “We designed KCWI to study very dim and diffuse objects, our main emphasis being on the wispy cosmic web and the interactions of galaxies with their surroundings,” says Mateusz (Matt) Matuszewski, the instrument scientist for the project.

    KCWI is also designed to be more a general-purpose instrument than the Palomar’s Cosmic Web Imager, which is mainly for studies of the cosmic web. It will study everything from gas jets around young stars to the winds of dead stars and supermassive black holes and more. “The instrument is really versatile,” says Matuszewski. “Observers can configure the optics to adjust the spatial and spectral scales and resolutions to suit their interests.”

    The nuts and bolts of KCWI

    Scientists and engineers have been busy assembling the highly complex elements of the KCWI instrument at Caltech since 2012. The instrument is about the size of an ice cream truck and weighs over 4,000 kilograms. The core feature of KCWI is its ability to capture spectral information about objects, such as galaxies, across a wide image. Typically, astronomers capture spectra using instruments called spectrographs, which have narrow slit-shaped windows. The spectrograph breaks apart light from the slit into each of the colors making up the target object, just like a prism that spreads light into a rainbow. But traditional spectrographs cannot be used to capture spectral information across an entire image.

    “Traditional spectrographs use multiple small slits to capture many stars or the cores of many galaxies,” says Martin. “Now, we want to look at features that are extended across the sky, such as stellar jets and galaxies, which have complex structures, velocities, and gas flows. If you can only look through a slit, you can only see a small part of what is going on. But we want to see the whole picture. That’s why we need an imaging spectrograph, a device that gives you an image for every single wavelength across a wide view.”

    To create a spectrograph that can image more extended objects like galaxies, KCWI uses what is called an integral field design, which basically divides an image up into 24 slits, and gathers all the spectral information at once.

    “If you’re looking at something big in the sky, it’s inefficient to just have one slit and step your way across that object, so an integral field spectrograph combines a number of slit-shaped mirrors together across a continuous field of view,” says Patrick Morrissey, the project scientist for KCWI who now works at JPL. “Imagine looking into a broken mirror–the reflected image is shifted around depending on the angles of the pieces. This is how the integral field spectrograph works. A series of mirrors works together to make a square-shaped stack of slits across an image appear as a single traditional vertical slit.”

    KCWI has the highest spectral resolution of any integral field spectrograph, which means it can better break apart the rainbow of light to see more colors, or wavelengths. The first phase of the instrument, now on its way to Keck, covers the blue side of the visible spectrum, spanning wavelength ranges from 3500 to 5600 Angstroms. A second phase, extending coverage to the red side of the spectrum, out to 10400 Angstroms, will be built next.

    KCWI to Climb Mauna Kea

    After KCWI arrives in Hawaii on January 18, engineers will guide it up to the top of Mauna Kea, where Keck is perched. A series of checkout and alignment tests is planned, and will be followed in a few months by the first observations through the Keck telescope.

    “There are train tracks around the telescope where the instruments are installed,” says Morrissey. “It’s like one of those old railroad roundhouses where the train would come in and they would spin it to an available space for storage. The telescope turns around, points to the instrument that the astronomer wants to use, and then they roll that instrument on. Soon KCWI will becomes part of the telescope.”

    KCWI is funded by the National Science Foundation, through the Association of Universities for Research in Astronomy (AURA) program, and by the Heising-Simons Foundation, the W.M. Keck Foundation, the Caltech Division of Physics, Mathematics and Astronomy, and the Caltech Optical Observatories.

    See the full article here .

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    The California Institute of Technology (commonly referred to as Caltech) is a private research university located in Pasadena, California, United States. Caltech has six academic divisions with strong emphases on science and engineering. Its 124-acre (50 ha) primary campus is located approximately 11 mi (18 km) northeast of downtown Los Angeles. “The mission of the California Institute of Technology is to expand human knowledge and benefit society through research integrated with education. We investigate the most challenging, fundamental problems in science and technology in a singularly collegial, interdisciplinary atmosphere, while educating outstanding students to become creative members of society.”

     
  • richardmitnick 12:56 pm on January 12, 2017 Permalink | Reply
    Tags: , Caltech, IC 3639, Monster black holes, , , NGC 1448, , , Type II supernova   

    From Space Science Laboratory at UC Berkeley: “NuSTAR – Black Holes Hide in our Cosmic Backyard” 

    UC Berkeley

    UC Berkeley

    SSL UC Berkeley

    Space Science Laboratory

    1
    No image caption. No image credit.

    NASA/NuSTAR

    NuSTAR

    January 12, 2017
    Christopher Scholz

    Monster black holes sometimes lurk behind gas and dust, hiding from the gaze of most telescopes. But they give themselves away when material they feed on emits high-energy X-rays that NASA’s NuSTAR (Nuclear Spectroscopic Telescope Array) mission can detect. That’s how NuSTAR recently identified two gas-enshrouded supermassive black holes, located at the centers of nearby galaxies.

    “These black holes are relatively close to the Milky Way, but they have remained hidden from us until now,” said Ady Annuar, a graduate student at Durham University in the United Kingdom, who presented the results at the American Astronomical Society meeting in Grapevine, Texas. “They’re like monsters hiding under your bed.”

    Both of these black holes are the central engines of what astronomers call “active galactic nuclei,” a class of extremely bright objects that includes quasars and blazars. Depending on how these galactic nuclei are oriented and what sort of material surrounds them, they appear very different when examined with telescopes.

    Active galactic nuclei are so bright because particles in the regions around the black hole get very hot and emit radiation across the full electromagnetic spectrum — from low-energy radio waves to high-energy X-rays. However, most active nuclei are believed to be surrounded by a doughnut-shaped region of thick gas and dust that obscures the central regions from certain lines of sight. Both of the active galactic nuclei that NuSTAR recently studied appear to be oriented such that astronomers view them edge-on. That means that instead of seeing the bright central regions, our telescopes primarily see the reflected X-rays from the doughnut-shaped obscuring material.

    “Just as we can’t see the sun on a cloudy day, we can’t directly see how bright these active galactic nuclei really are because of all of the gas and dust surrounding the central engine,” said Peter Boorman, a graduate student at the University of Southampton in the United Kingdom.

    Boorman led the study of an active galaxy called IC 3639, which is 170 million light years away.

    2
    IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory.

    This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japanese-led Suzaku satellite.

    NASA/Chandra Telescope
    NASA/Chandra Telescope

    JAXA/Suzaku satellite
    JAXA/Suzaku satellite

    The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed.

    Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA’s Chandra X-Ray Observatory and the Japan-led Suzaku satellite. NuSTAR also provided the first precise measurement of how much material is obscuring the central engine of IC 3639, allowing researchers to determine how luminous this hidden monster really is.

    More surprising is the spiral galaxy that Annuar focused on: NGC 1448.

    6
    NGC 1448 (also designated NGC 1457 and ESO 249-16) is a spiral galaxy located about 60 million light-years away in the constellation Horologium. It has a prominent disk of young and very bright stars surrounding its small, shining core. The galaxy is receding from us with 1168 kilometers per second.

    NGC 1448 has recently been a prolific factory of supernovae, the dramatic explosions that mark the death of stars: after a first one observed in this galaxy in 1983 (SN 1983S), two more have been discovered during the past decade.

    Visible as a red dot inside the disc, in the upper right part of the image, is the supernova observed in 2003 (Type II supernova SN 2003hn), whereas another one, detected in 2001 (Type Ia supernova SN 2001el), can be noticed as a tiny blue dot in the central part of the image, just below the galaxy’s core. If captured at the peak of the explosion, a supernova might be as bright as the whole galaxy that hosts it.

    A Type Ia supernova is a result from the violent explosion of a white dwarf star. This category of supernovae produces consistent peak luminosity. The stability of this luminosity allows these supernovae to be used as standard candles to measure the distance to their host galaxies because the visual magnitude of the supernovae depends primarily on the distance.

    A Type II supernova results from the rapid collapse and violent explosion of a massive star. A star must have at least 8 times, and no more than 40–50 times the mass of the Sun for this type of explosion. It is distinguished from other types of supernova by the presence of hydrogen in its spectrum. Type II supernovae are mainly observed in the spiral arms of galaxies and in H II regions, but not in elliptical galaxies.

    This image was obtained using the 8.2-metre telescopes of ESO’s Very Large Telescope. It combines exposures taken between July 2002 and the end of November 2003.

    ESO/VLT at Cerro Paranal, Chile, ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level
    ESO/VLT at Cerro Paranal, Chile, ESO/VLT at Cerro Paranal, with an elevation of 2,635 metres (8,645 ft) above sea level

    Credit: ESO

    The black hole in its center was only discovered in 2009, even though it is at the center of one of the nearest large galaxies to our Milky Way. By “near,” astronomers mean NGC 1448 is only 38 million light years away (one light year is about 6 trillion miles).

    Annuar’s study discovered that this galaxy also has a thick column of gas hiding the central black hole, which could be part of a doughnut-shaped region. X-ray emission from NGC 1448, as seen by NuSTAR and Chandra, suggests for the first time that, as with IC 3639, there must be a thick layer of gas and dust hiding the active black hole in this galaxy from our line of sight.

    Researchers also found that NGC 1448 has a large population of young (just 5 million year old) stars, suggesting that the galaxy produces new stars at the same time that its black hole feeds on gas and dust. Researchers used the European Southern Observatory New Technology Telescope to image NGC 1448 at optical wavelengths, and identified where exactly in the galaxy the black hole should be. A black hole’s location can be hard to pinpoint because the centers of galaxies are crowded with stars. Large optical and radio telescopes can help detect light from around black holes so that astronomers can find their location and piece together the story of their growth.

    “It is exciting to use the power of NuSTAR to get important, unique information on these beasts, even in our cosmic backyard where they can be studied in detail,” said Daniel Stern, NuSTAR project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California.

    NuSTAR is a Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. NuSTAR was developed in partnership with the Danish Technical University and the Italian Space Agency (ASI). The spacecraft was built by Orbital Sciences Corp., Dulles, Virginia. NuSTAR’s mission operations center is at UC Berkeley, and the official data archive is at NASA’s High Energy Astrophysics Science Archive Research Center. ASI provides the mission’s ground station and a mirror archive. JPL is managed by Caltech for NASA.

    See the full article here .

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  • richardmitnick 9:50 am on January 12, 2017 Permalink | Reply
    Tags: , Auroral Displays at Brown Dwarfs, , , Caltech   

    From astrobites: “Auroral Displays at Brown Dwarfs” 

    Astrobites bloc

    Astrobites

    Title: Magnetospherically driven optical and radio aurorae at the end of the stellar main sequence
    Authors: G.Hallinan, S. P. Littlefair, G. Cotter, et al.
    First Author’s Institution: California Institute of Technology
    Caltech Logo
    Status: Published in Nature (2015), open access

    Auroras are the spectacular light shows visible in the polar regions at Earth and other planets. In 2015 they were detected for the first time outside of the solar system. Brown dwarfs are objects often described as “failed stars”, meaning they are insufficiently massive to ignite hydrogen fusion in their cores. Today’s paper reports on the remarkable discovery that a particular brown dwarf plays host to auroral displays far more powerful than those found anywhere in the solar system.

    Brown dwarfs

    Artist's concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech
    Artist’s concept of a Brown dwarf [not quite a] star. NASA/JPL-Caltech

    Brown dwarfs occupy the region between giant planets and the lowest mass stars. It is generally accepted that they form in a manner similar to stars, i.e. the gravitational collapse of interstellar gas, but never reaching a mass sufficient to sustain hydrogen fusion in the core. As such, brown dwarfs are extremely cool, faint objects, making their detection much more difficult than ordinary stars. However, they provide an excellent opportunity to for us to better understand the physics that differentiates the stellar and planetary domains. Since their discovery many surveys have been performed which have revealed, amongst other things, the existence of complex weather systems and strong global magnetic fields.

    Auroras

    Understanding the interaction of the magnetic field at a brown dwarf with its nearby space environment is a key scientific goal. At Earth, space scientists observe the aurora as a means of revealing the structure and dynamics of the magnetic field, and the plasma which interacts with it. Before turning to auroras at brown dwarfs we shall briefly review at what we know about auroras from our studies at Earth and other solar system planets.

    The vibrant displays that we see are a result of charged particles (i.e. electrons and ions) from the plasma population around the Earth raining down along magnetic field lines, and colliding with molecules in the atmosphere. These collisions excite the atmospheric constituents to a higher energy state, causing the emission of a photon as they return to their original state.

    Auroral emissions aren’t just confined to Earth; they are found at other magnetised planets in the solar system, with Jupiter being a particularly spectacular example.

    3
    JUNE 30, 2016: Astronomers are using NASA’s Hubble Space Telescope to study auroras — stunning light shows in a planet’s atmosphere — on the poles of the largest planet in the solar system, Jupiter. The auroras were photographed during a series of Hubble Space Telescope Imaging Spectrograph far-ultraviolet-light observations taking place as NASA’s Juno spacecraft approaches and enters into orbit around Jupiter. The aim of the program is to determine how Jupiter’s auroras respond to changing conditions in the solar wind, a stream of charged particles emitted from the sun. Auroras are formed when charged particles in the space surrounding the planet are accelerated to high energies along the planet’s magnetic field. When the particles hit the atmosphere near the magnetic poles, they cause it to glow like gases in a fluorescent light fixture. Jupiter’s magnetosphere is 20,000 times stronger than Earth’s. These observations will reveal how the solar system’s largest and most powerful magnetosphere behaves. The full-color disk of Jupiter in this image was separately photographed at a different time by Hubble’s Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble project that annually captures global maps of the outer planets.
    Date 30 June 2016
    Source http://hubblesite.org/newscenter/archive/releases/2016/24
    Author NASA, ESA, and J. Nichols (University of Leicester)

    Neither are they confined only to the visible part of the spectrum; auroral emissions occur from radio frequencies through to UV and X-ray.

    Now we return to brown dwarfs. Since 2006 it has been known that a handful of brown dwarfs emit very regular and persistent radio bursts. These burst are pulsed at the rotation period of the dwarf, leading some researchers to suggest that they may be caused by auroras that are generated in a similar manner to Jupiter’s main auroral oval. The pulsing in this case may be due to the magnetic axis being tilted from the spin axis, so that as the dwarf rotates the auroral emission cones into our line of sight. This motivated the authors of today’s paper to target a particular brown dwarf, LSR J1835 + 3259, with simultaneous radio and optical observation, pursuing a possible relation between the two.

    4
    LSR J1835 + 3259. Image: http://images.zeit.de/ http://www.theweeklyobserver.com/ailed-star-shows-dazzling-display-of-northern-lights/5575/

    Radio observations were made using the Very Large Array (VLA) radio telescope, while simultaneously, optical measurements were made with the 5.1 m Hale telescope at the Palomar Observatory with follow-up observations from the 10 m Keck telescope.

    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA
    NRAO/VLA, on the Plains of San Agustin fifty miles west of Socorro, NM, USA

    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA
    Caltech Hale Telescope at Palomar interior
    Caltech Palomar 200 inch Hale Telescope, at Mt Wilson, CA, USA

    Keck Observatory, Mauna Kea, Hawaii, USA
    Keck Observatory Interior
    Keck Observatory, Mauna Kea, Hawaii, USA

    The results of the observations are shown in Figure 1, where the light curve from the optical measurements (Fig 1a) shows a clear periodicity of 2.84 h. Observations of the radio emission (Fig 1b) show the same periodicity, with a slight offset in phase causing it to lag slightly behind the optical emission. The authors attribute their findings to auroras which are driven by strong electric currents flowing in the magnetosphere of the dwarf.

    2
    Figure 1: (a) Optical measurements of Balmer line emission of LSR J1835 made using the Hale telescope. (b) Corresponding radio observations of the same object made using the VLA radio telescope. [Figure 1 from Hallinan et al. 2015]

    With this discovery many open questions are presented. What is the mechanism driving the auroras? It may be interaction with the interstellar medium, analogous to the process of the Earth’s magnetosphere interacting with the solar wind. Or it could be due to a continuously replenishing source of plasma mass outflow from within a closed magnetosphere, analogous to the mechanism producing Jupiter’s main auroral oval. Additionally, the source of the required plasma population is unknown, with the cool temperatures (∼2000 K) of brown dwarfs being unable to support significant ionisation of their atmospheres, and the lack of nearby stars restricting the possibility ionisation by stellar irradiation.

    Ultimately it is an exciting prospect that this discovery, along with the arrival of even more sensitive radio telescopes (e.g. the Square Kilometre Array), may pave the way towards detecting auroras at exoplanets.

    SKA Square Kilometer Array

    This which would add a novel technique to the exoplanet-detectors toolkit, and enable us to learn about the magnetic fields and plasma populations around those objects.

    See the full article here .

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    What do we do?

    Astrobites is a daily astrophysical literature journal written by graduate students in astronomy. Our goal is to present one interesting paper per day in a brief format that is accessible to undergraduate students in the physical sciences who are interested in active research.
    Why read Astrobites?

    Reading a technical paper from an unfamiliar subfield is intimidating. It may not be obvious how the techniques used by the researchers really work or what role the new research plays in answering the bigger questions motivating that field, not to mention the obscure jargon! For most people, it takes years for scientific papers to become meaningful.
    Our goal is to solve this problem, one paper at a time. In 5 minutes a day reading Astrobites, you should not only learn about one interesting piece of current work, but also get a peek at the broader picture of research in a new area of astronomy.

     
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