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  • richardmitnick 3:34 pm on December 10, 2018 Permalink | Reply
    Tags: GUSTO-Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory, , , Organic chemistry, , Selected by NASA, Terahertz laser for sensing and imaging outperforms its predecessors   

    From MIT News: “Terahertz laser for sensing and imaging outperforms its predecessors” 

    MIT News
    MIT Widget

    From MIT News

    December 10, 2018
    Rob Matheson

    1
    A tiny terahertz laser designed by MIT researchers is the first to reach three key performance goals at once: high power, tight beam, and broad frequency tuning.
    Courtesy of the researchers

    High-power, tunable design could be used for chemical detection in outer space, medical imaging, more.

    A terahertz laser designed by MIT researchers is the first to reach three key performance goals at once — high constant power, tight beam pattern, and broad electric frequency tuning — and could thus be valuable for a wide range of applications in chemical sensing and imaging.

    The optimized laser can be used to detect interstellar elements in an upcoming NASA mission that aims to learn more about our galaxy’s origins. Here on Earth, the high-power photonic wire laser could also be used for improved skin and breast cancer imaging, detecting drugs and explosives, and much more.

    The laser’s novel design pairs multiple semiconductor-based, efficient wire lasers and forces them to “phase lock,” or sync oscillations. Combining the output of the pairs along the array produces a single, high-power beam with minimal beam divergence. Adjustments to the individual coupled lasers allow for broad frequency tuning to improve resolution and fidelity in the measurements. Achieving all three performance metrics means less noise and higher resolution, for more reliable and cost-effective chemical detection and medical imaging, the researchers say.

    “People have done frequency tuning in lasers, or made a laser with high beam quality, or with high continuous wave power. But each design lacks in the other two factors,” says Ali Khalatpour, a graduate student in electrical engineering and computer science and first author on a paper describing the laser, published today in Nature Photonics. “This is the first time we’ve achieved all three metrics at the same time in chip-based terahertz lasers.”

    “It’s like ‘one ring to rule them all,’” Khalatpour adds, referring to the popular phrase from “The Lord of the Rings.”

    Joining Khalatpour on the paper are: Qing Hu, a distinguished professor of electrical engineering and computer science at MIT who has done pioneering work on terahertz quantum cascade lasers; and John L. Reno of the Sandia National Laboratories.

    Selected by NASA

    Last year, NASA announced the Galactic/Extragalactic ULDB Spectroscopic Terahertz Observatory (GUSTO), a 2021 mission to send a high-altitude balloon-based telescope carrying photonic wire lasers for detecting oxygen, carbon, and nitrogen emissions from the “interstellar medium,” the cosmic material between stars. Extensive data gathered over a few months will provide insight into star birth and evolution, and help map more of the Milky Way and nearby Large Magellanic Cloud galaxies.

    For a component of the GUSTO chemical detector, NASA selected a novel semiconductor-based terahertz laser previously designed by the MIT researchers. It is currently the best-performing terahertz laser. Such lasers are uniquely suited for spectroscopic measurement of oxygen concentrations in terahertz radiation, the band of the electromagnetic spectrum between microwaves and visible light.

    Terahertz lasers can send coherent radiation into a material to extract the material’s spectral “fingerprint.” Different materials absorb terahertz radiation to different degrees, meaning each has a unique fingerprint that appears as a spectral line. This is especially valuable in the 1-5 terahertz range: For contraband detection, for example, heroin’s signature is seen around 1.42 and 3.94 terahertz, and cocaine’s at around 1.54 terahertz.

    For years, Hu’s lab has been developing novel types of quantum cascade lasers, called “photonic wire lasers.” Like many lasers, these are bidirectional, meaning they emit light in opposite directions, which makes them less powerful. In traditional lasers, that issue is easily remedied with carefully positioned mirrors inside the laser’s body. But it’s very difficult to fix in terahertz lasers, because terahertz radiation is so long, and the laser so small, that most of the light travels outside the laser’s body.

    In the laser selected for GUSTO, the researchers had developed a novel design for the wire lasers’ waveguides — which control how the electromagnetic wave travels along the laser — to emit unidirectionally. This achieved high efficiency and beam quality, but it didn’t allow frequency tuning, which NASA required.

    Taking a page from chemistry

    Building on their previous design, Khalatpour took inspiration from an unlikely source: organic chemistry. While taking an undergraduate class at MIT, Khalatpour took note of a long polymer chain with atoms lined along two sides. They were “pi-bonded,” meaning their molecular orbitals overlapped to make the bond more stable. The researchers applied the concept of pi-bonding to their lasers, where they created close connections between otherwise-independent wire lasers along an array. This novel coupling scheme allows phase-locking of two or multiple wire lasers.

    To achieve frequency tuning, the researchers use tiny “knobs” to change the current of each wire laser, which slightly changes how light travels through the laser — called the refractive index. That refractive index change, when applied to coupled lasers, creates a continuous frequency shift to the pair’s center frequency.

    For experiments, the researchers fabricated an array of 10 pi-coupled wire lasers. The laser operated with continuous frequency tuning in a span of about 10 gigahertz, and a power output of roughly 50 to 90 milliwatts, depending on how many pi-coupled laser pairs are on the array. The beam has a low beam divergence of 10 degrees, which is a measure of how much the beam strays from its focus over distances.

    The researchers are also currently building a system for imaging with high dynamic range — greater than 110 decibels — which can be used in many applications such as skin cancer imaging. Skin cancer cells absorb terahertz waves more strongly than healthy cells, so terahertz lasers could potentially detect them. The lasers previously used for the task, however, are massive and inefficient, and not frequency-tunable. The researchers’ chip-sized device matches or outstrips those lasers in output power, and offers tuning capabilities.

    “Having a platform with all those performance metrics together … could significantly improve imaging capabilities and extend its applications,” Khalatpour says.

    “This is very nice work — in the THz [range] it has been very difficult to obtain high power levels from lasers simultaneous with good beam patterns,” says Benjamin Williams, associate professor of physical and wave electronics at the University of California at Los Angeles. “The innovation is the novel way they have used to couple the multiple wire lasers together. This is tricky, since if all of the lasers in the array don’t radiate in phase, then the beam pattern will be ruined. They have shown that by properly spacing adjacent wire lasers, they can be coaxed into ‘wanting’ to operate in a coherent symmetric supermode — all collectively radiating together in lockstep. As a bonus, the laser frequency can be tuned … to the desired wavelength — an important feature for spectroscopy and … for astrophysics.”

    See the full article here .


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  • richardmitnick 5:53 pm on November 12, 2018 Permalink | Reply
    Tags: , , , MicroED-micro-electron diffraction, , NMR-nuclear magnetic resonance, Organic chemistry, , ,   

    From Caltech: “From Beaker to Solved 3-D Structure in Minutes” 

    Caltech Logo

    From Caltech

    11/12/2018

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

    1
    Graduate student Tyler Fulton prepares samples of small molecules in a lab at Caltech. Credit: Caltech

    2
    Close-up of a powder containing small molecules like those that gave rise to 3-D structures in the new study. (The copper piece is a sample holder used with microscopes.) Credit: Caltech/Stoltz Lab

    3
    Brian Stoltz and Tyler Fulton. Credit: Caltech

    UCLA/Caltech team uncovers a new and simple way to learn the structures of small molecules.

    In a new study that one scientist called jaw-dropping, a joint UCLA/Caltech team has shown that it is possible to obtain the structures of small molecules, such as certain hormones and medications, in as little as 30 minutes. That’s hours and even days less than was possible before.

    The team used a technique called micro-electron diffraction (MicroED), which had been used in the past to learn the 3-D structures of larger molecules, specifically proteins. In this new study, the researchers show that the technique can be applied to small molecules, and that the process requires much less preparation time than expected. Unlike related techniques—some of which involve growing crystals the size of salt grains—this method, as the new study demonstrates, can work with run-of-the-mill starting samples, sometimes even powders scraped from the side of a beaker.

    “We took the lowest-brow samples you can get and obtained the highest-quality structures in barely any time,” says Caltech professor of chemistry Brian Stoltz, who is a co-author on the new study, published in the journal ACS Central Science. “When I first saw the results, my jaw hit the floor.” Initially released on the pre-print server Chemrxiv in mid-October, the article has been viewed more than 35,000 times.

    The reason the method works so well on small-molecule samples is that while the samples may appear to be simple powders, they actually contain tiny crystals, each roughly a billion times smaller than a speck of dust. Researchers knew about these hidden microcrystals before, but did not realize they could readily reveal the crystals’ molecular structures using MicroED. “I don’t think people realized how common these microcrystals are in the powdery samples,” says Stoltz. “This is like science fiction. I didn’t think this would happen in my lifetime—that you could see structures from powders.”

    4
    This movie [animated in the full article] is an example of electron diffraction (MicroED) data collection, in which electrons are fired at a nanocrystal while being continuously rotated. Data from the movie are ultimately converted to a 3-D chemical structure. Credit: UCLA/Caltech

    The results have implications for chemists wishing to determine the structures of small molecules, which are defined as those weighing less than about 900 daltons. (A dalton is about the weight of a hydrogen atom.) These tiny compounds include certain chemicals found in nature, some biological substances like hormones, and a number of therapeutic drugs. Possible applications of the MicroED structure-finding methodology include drug discovery, crime lab analysis, medical testing, and more. For instance, Stoltz says, the method might be of use in testing for the latest performance-enhancing drugs in athletes, where only trace amounts of a chemical may be present.

    “The slowest step in making new molecules is determining the structure of the product. That may no longer be the case, as this technique promises to revolutionize organic chemistry,” says Robert Grubbs, Caltech’s Victor and Elizabeth Atkins Professor of Chemistry and a winner of the 2005 Nobel Prize in Chemistry, who was not involved in the research. “The last big break in structure determination before this was nuclear magnetic resonance spectroscopy, which was introduced by Jack Roberts at Caltech in the late ’60s.”

    Like other synthetic chemists, Stoltz and his team spend their time trying to figure out how to assemble chemicals in the lab from basic starting materials. Their lab focuses on such natural small molecules as the fungus-derived beta-lactam family of compounds, which are related to penicillins. To build these chemicals, they need to determine the structures of the molecules in their reactions—both the intermediate molecules and the final products—to see if they are on the right track.

    One technique for doing so is X-ray crystallography, in which a chemical sample is hit with X-rays that diffract off its atoms; the pattern of those diffracting X-rays reveals the 3-D structure of the targeted chemical. Often, this method is used to solve the structures of really big molecules, such as complex membrane proteins, but it can also be applied to small molecules. The challenge is that to perform this method a chemist must create good-sized chunks of crystal from a sample, which isn’t always easy. “I spent months once trying to get the right crystals for one of my samples,” says Stoltz.

    Another reliable method is NMR (nuclear magnetic resonance), which doesn’t require crystals but does require a relatively large amount of a sample, which can be hard to amass. Also, NMR provides only indirect structural information.

    Before now, MicroED—which is similar to X-ray crystallography but uses electrons instead of X-rays—was mainly used on crystallized proteins and not on small molecules. Co-author Tamir Gonen, an electron crystallography expert at UCLA who began developing the MicroED technique for proteins while at the Howard Hughes Medical Institute in Virginia, said that he only started thinking about using the method on small molecules after moving to UCLA and teaming up with Caltech.

    “Tamir had been using this technique on proteins, and just happened to mention that they can sometimes get it to work using only powdery samples of proteins,” says Hosea Nelson (PhD ’13), an assistant professor of chemistry and biochemistry at UCLA. “My mind was blown by this, that you didn’t have to grow crystals, and that’s around the time that the team started to realize that we could apply this method to a whole new class of molecules with wide-reaching implications for all types of chemistry.”

    The team tested several samples of varying qualities, without ever attempting to crystallize them, and were able to determine their structures thanks to the samples’ ample microcrystals. They succeeded in getting structures for ground-up samples of the brand-name drugs Tylenol and Advil, and they were able to identify distinct structures from a powdered mixture of four chemicals.

    The UCLA/Caltech team says it hopes this method will become routine in chemistry labs in the future.

    “In our labs, we have students and postdocs making totally new and unique molecular entities every day,” says Stoltz. “Now we have the power to rapidly figure out what they are. This is going to change synthetic chemistry.”

    The study was funded by the National Science Foundation, the National Institutes of Health, the Department of Energy, a Beckman Young Investigators award, a Searle Scholars award, a Pew Scholars award, the Packard Foundation, the Sloan Foundation, the Pew Charitable Trusts, and the Howard Hughes Medical Institute. Other co-authors include Christopher Jones,Michael Martynowycz, Johan Hattne, and Jose Rodriguez of UCLA; and Tyler Fulton of Caltech.

    See the full article here .


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  • richardmitnick 5:36 pm on January 10, 2018 Permalink | Reply
    Tags: , , , , , , , , , Organic chemistry, STXM-scanning transmission X-ray microscope, We’re looking at the organic ingredients that can lead to the origin of life” including the amino acids needed to form proteins,   

    From LBNL: “Ingredients for Life Revealed in Meteorites That Fell to Earth” 

    Berkeley Logo

    Berkeley Lab

    January 10, 2018
    Glenn Roberts Jr.
    geroberts@lbl.gov
    (510) 486-5582

    1
    A blue crystal recovered from a meteorite that fell near Morocco in 1998. The scale bar represents 200 microns (millionths of a meter). (Credit: Queenie Chan/The Open University, U.K.)

    Two wayward space rocks, which separately crashed to Earth in 1998 after circulating in our solar system’s asteroid belt for billions of years, share something else in common: the ingredients for life. They are the first meteorites found to contain both liquid water and a mix of complex organic compounds such as hydrocarbons and amino acids.

    A detailed study of the chemical makeup within tiny blue and purple salt crystals sampled from these meteorites, which included results from X-ray experiments at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), also found evidence for the pair’s past intermingling and likely parents. These include Ceres, a brown dwarf planet that is the largest object in the asteroid belt, and the asteroid Hebe, a major source of meteorites that fall on Earth.

    The study, published Jan. 10 in the journal Science Advances, provides the first comprehensive chemical exploration of organic matter and liquid water in salt crystals found in Earth-impacting meteorites. The study treads new ground in the narrative of our solar system’s early history and asteroid geology while surfacing exciting possibilities for the existence of life elsewhere in Earth’s neighborhood.

    “It’s like a fly in amber,” said David Kilcoyne, a scientist at Berkeley Lab’s Advanced Light Source (ALS), which provided X-rays that were used to scan the samples’ organic chemical components, including carbon, oxygen, and nitrogen.

    LBNL/ALS

    Kilcoyne was part of the international research team that prepared the study.

    While the rich deposits of organic remnants recovered from the meteorites don’t provide any proof of life outside of Earth, Kilcoyne said the meteorites’ encapsulation of rich chemistry is analogous to the preservation of prehistoric insects in solidified sap droplets.

    Queenie Chan, a planetary scientist and postdoctoral research associate at The Open University in the U.K. who was the study’s lead author, said, “This is really the first time we have found abundant organic matter also associated with liquid water that is really crucial to the origin of life and the origin of complex organic compounds in space.”

    She added, “We’re looking at the organic ingredients that can lead to the origin of life,” including the amino acids needed to form proteins.

    If life did exist in some form in the early solar system, the study notes that these salt crystal-containing meteorites raise the “possibility of trapping life and/or biomolecules” within their salt crystals. The crystals carried microscopic traces of water that is believed to date back to the infancy of our solar system – about 4.5 billion years ago.

    Chan said the similarity of the crystals found in the meteorites – one of which smashed into the ground near a children’s basketball game in Texas in March 1998 and the other which hit near Morocco in August 1998 – suggest that their asteroid hosts may have crossed paths and mixed materials.

    There are also structural clues of an impact – perhaps by a small asteroid fragment impacting a larger asteroid, Chan said.

    This opens up many possibilities for how organic matter may be passed from one host to another in space, and scientists may need to rethink the processes that led to the complex suite of organic compounds on these meteorites.

    “Things are not as simple as we thought they were,” Chan said.

    There are also clues, based on the organic chemistry and space observations, that the crystals may have originally been seeded by ice- or water-spewing volcanic activity on Ceres, she said.

    “Everything leads to the conclusion that the origin of life is really possible elsewhere,” Chan said. “There is a great range of organic compounds within these meteorites, including a very primitive type of organics that likely represent the early solar system’s organic composition.”

    Chan said the two meteorites that yielded the 2-millimeter-sized salt crystals were carefully preserved at NASA’s Johnson Space Center in Texas, and the tiny crystals containing organic solids and water traces measure just a fraction of the width of a human hair. Chan meticulously collected these crystals in a dust-controlled room, splitting off tiny sample fragments with metal instruments resembling dental picks.

    2
    These ALS X-ray images show organic matter (magenta, bottom) sampled from a meteorite, and carbon (top). (Credit: Berkeley Lab)

    “What makes our analysis so special is that we combined a lot of different state-of-the-art techniques to comprehensively study the organic components of these tiny salt crystals,” Chan said.

    Yoko Kebukawa, an associate professor of engineering at Yokohama National University in Japan, carried out experiments for the study at Berkeley Lab’s ALS in May 2016 with Aiko Nakato, a postdoctoral researcher at Kyoto University in Japan. Kilcoyne helped to train the researchers to use the ALS X-ray beamline and microscope.

    The beamline equipped with this X-ray microscope (a scanning transmission X-ray microscope, or STXM) is used in combination with a technique known as XANES (X-ray absorption near edge structure spectroscopy) to measure the presence of specific elements with a precision of tens of nanometers (tens of billionths of a meter).

    “We revealed that the organic matter was somewhat similar to that found in primitive meteorites, but contained more oxygen-bearing chemistry,” Kebukawa said. “Combined with other evidence, the results support the idea that the organic matter originated from a water-rich, or previously water-rich parent body – an ocean world in the early solar system, possibly Ceres.”

    Kebukawa also used the same STXM technique to study samples at the Photon Factory, a research site in Japan. And the research team enlisted a variety of other chemical experimental techniques to explore the samples’ makeup in different ways and at different scales.

    Chan noted that there are some other well-preserved crystals from the meteorites that haven’t yet been studied, and there are plans for follow-up studies to identify if any of those crystals may also contain water and complex organic molecules.

    3
    Ceres, a dwarf planet in the asteroid belt pictured here in this false-color image, may be the source of organic matter found in two meteorites that crashed to Earth in 1998. (Credit: NASA)

    Kebukawa said she looks forward to continuing studies of these samples at the ALS and other sites: “We may find more variations in organic chemistry.”

    The Advanced Light Source is a DOE Office of Science User Facility.

    Scientists at NASA Johnson Space Center, Kochi Institute for Core Sample Research in Japan, Carnegie Institution of Washington, Hiroshima University, The University of Tokyo, the High-Energy Accelerator Research Organization (KEK) in Japan, and The Graduate University for Advanced Studies (SOKENDAI) in Japan also participated in the study. The work was supported by the U.S. DOE Office of Science, the Universities Space Research Association, NASA, the National Institutes of Natural Sciences in Japan, Japan Society for the Promotion of Science, and The Mitsubishi Foundation.

    See the full article here .

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