Reppert P.M.,Defense Threat Reduction Agency
Journal of Environmental and Engineering Geophysics | Year: 2013
Seismic while drilling (SWD) with a rotary percussive drill used as the seismic source is presented. In addition to saving time by collecting seismic data while drilling, SWD also has the advantage of collecting a high data density with no additional effort and has a signal with a broad frequency spectrum. The only disadvantage is its signal-to-noise ratio is lower than many other seismic sources, although the signal-to-noise ratio is quite sufficient. The discussed methodology includes the triggering system and the stacking approach used to improve the signal-to-noise ratio. An example of SWD data is presented and compared to traditional down-hole (check-shot) data. Other examples of SWD are presented to demonstrate some of the data acquisition possibilities. © 2013 Copyright: © 2013 This is an Open Access article: verbatim copying and redistribution of this article are permitted in all media for any purpose, provided this notice is preserved along with the article's original URL. Source
Dr. Paul E. Sheehan, a research chemist in the Surface Chemistry Branch of the Chemistry Division at the U.S. Naval Research Laboratory (NRL), was inducted as a Fellow of the American Vacuum Society (AVS) by Dr. Steven George, 2014 AVS President, and Dr. Ellen Fisher, 2014 AVS Awards Committee Chair, at the awards ceremony during the 61st Annual AVS International Symposium and Exhibition. Sheehan was named an AVS Fellow in recognition of his exceptional contributions to the detailed understanding of sp2 carbon nanostructure properties, methods for nanoscale patterning of materials, and the basis of biological and chemical sensor performance. Sheehan has studied nanoscale phenomena and surface reactions for over two decades. He was a University Fellow at the University of North Carolina where he received a bachelor's degree in Chemistry-based Materials Science in 1993 while doing undergraduate research in the group of Prof. Royce Murray. He then studied nanomechanics at Harvard University where he received his master's degree (1995) and his doctorate (1998) in Chemical Physics under the direction of Prof. Charles Lieber. He then received a National Research Council Fellowship to pursue biosensing using magnetoelectronics at NRL under the direction of Dr. Richard Colton. In 2001, NRL hired Sheehan to pursue research focused on the use of scanning probe microscopy for the fabrication and characterization of nanostructures. In 2008, Sheehan became Head of the NRL Surface Nanoscience and Sensor Technology Section. The Section is a highly interdisciplinary team comprising about fourteen biochemists, chemists, engineers, and physicists who study nanometer scale phenomena at surfaces as well as bioelectronics for sensing and biotic/abiotic interfaces. Sheehan's current research focuses on the chemical functionalization of graphene to enhance its performance in biosensing and electronics as well as the generation of nanostructures for interfacing with biology. His research has been funded by the Navy, Air Force Office of Scientific Research, Defense Advanced Research Projects Agency, and Defense Threat Reduction Agency. The detailed exploration of the structures formed from sp2 carbon—fullerenes, carbon nanotubes, and graphene—has been a major focus of the physical sciences over the past three decades. The generation of these structures, the testing of their theoretically predicted properties, and their application have all met with substantial success. Some of Sheehan's earliest work explored the mechanical properties of carbon nanotubes and SiC nanorods, showing that the elastic modulus of the nanotubes matched the predicted (and superlative) value of ~1 TPa. This was achieved by using a scanning probe to push on nanotubes whose ends were pinned. ISI named the publication one of the top 10 papers in materials science for that decade. With the advent of graphene research, Sheehan explored the chemistry and functionalization of this fascinating material, helping to understand how new chemistries such as fluorination impacted its electronic, mechanical, and magnetic properties. Graphene's properties are quite subtle. Sheehan and co-workers recently showed that, unlike bulk graphite fluoride, fluorination of graphene was metastable and depends highly on the underlying substrate. He had previously explored this theme of graphene's interaction with its substrate in showing that electronic conduction in graphene on SiC is in fact anisotropic due to charge scattering by the underlying step edges. They subsequently published a series of papers exploring the changes in conduction in graphene due to functionalization, most recently showing that electronic conductivity in graphene can be completely eliminated by hydrogenation and then completely restored to its pristine state by simple heating. The manipulation of matter at the nanoscale has been a dominant theme in Sheehan's career. He has written several reviews on nanolithography as well as developed several advances in scanning probe techniques to modify locally both soft and hard materials. He made significant contributions to the understanding of the mode of patterning of Dip Pen Nanolithography (DPN), where material deposits from an AFM tip onto a substrate. He showed that a water meniscus was not needed to transfer molecules from the tip to the surface as previously thought, and offered a detailed model of the mass transfer processes occurring in the system. Based on the insights gained from that effort, he went on to develop a variant of DPN called thermal DPN where a heated scanning probe controlled the flow of a molecule by varying its viscosity. More recently, he has focused on using the heat scanning probes to pattern graphene into functional devices. This could mean either using thermal DPN to write thin polymer masks for subsequent processing or by creating molecular templates. A more fundamental insight was that the heatable scanning probes could control local temperature with nanometer resolution and so induce reactions at that length scale. This led to the highly local removal of oxygen from graphene oxide to form thin nanoribbons of conducting graphene. Beyond the manipulation of matter at the nanoscale, Sheehan has had an ongoing interest in the physical phenomena undergirding sensor performance. Upon arriving at NRL, he pursued a novel approach to biodetection where a magnetic bead would be bound to a giant magnetoresistive (GMR) sensor if a target biomolecule such as DNA was present. The benefit of this approach is that magnetic interference is relatively rare in biological systems and the giant response by the GMR sensor to the presence of the magnetic bead makes this a highly sensitive and selective approach. Indeed, it remains one of the most effective means of directly detecting low concentrations of biomolecules. Work on the microfabricated sensors stimulated his interest in the effect of scaling sensor size. In 2005, he published a simple paper on the scaling of biosensors to the nanoscale, a popular undertaking at the time. The upshot was that, for many applications, mass transport made this an unwise choice. Others used the results to point out that many reported results were in fact impossible. His interest in sensing extended to biological approaches to sensing where he modeled how magnetotactic bacteria know how to swim north. With his developing interest in graphene nanostructures, he set out to understand how to use this new material to build inexpensive yet sensitive detectors for both chemical and biological agents. The fundamental insight was that graphene oxide, a very inexpensive derivative of graphene, could be readily and cheaply formed into sensors that had lower electronic noise and greater amenability to chemical functionalization than the carbon nanotube networks used to date. Efforts to fully utilize and understand these new materials continue to this day. His research has garnered other recognition and accolades too. His nanofabrication work has been widely reported in the general science and popular press, including in the New York Times, CBS's SmartPlanet, C&EN, and TV Globo Brazil. His nanofabrication work was selected as a Department of Defense R&D accomplishment in Defense Nanotechnology Research and Development Programs. One of his biosensor papers was cited as the Most Outstanding Contribution out of >1000 submissions to the Biosensors 2008 conference, the leading conference in the biosensors community. It too was highlighted in the popular press in the Economist and on National Public Radio (NPR). In 2009, Sheehan and his co-inventors received the NRL Edison Patent award for their patent on Thermal Dip Pen Nanolithography. Sheehan also has received three Alan Berman Research Publication Awards in his 13 years as a federal employee. About the U.S. Naval Research Laboratory The U.S. Naval Research Laboratory provides the advanced scientific capabilities required to bolster our country's position of global naval leadership. The Laboratory, with a total complement of approximately 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 90 years and continues to advance research further than you can imagine. For more information, visit the NRL website or join the conversation on Twitter, Facebook, and YouTube.
News Article | April 6, 2016
A team of engineers has developed and tested a type of steel with a record-breaking ability to withstand an impact without deforming permanently. The new steel alloy could be used in a wide range of applications, from drill bits, to body armor for soldiers, to meteor-resistant casings for satellites. The material is an amorphous steel alloy, a promising subclass of steel alloys made of arrangements of atoms that deviate from steel’s classical crystal-like structure, where iron atoms occupy specific locations. Researchers are increasingly looking to amorphous steel as a source of new materials that are affordable to manufacture, incredibly hard, but at the same time, not brittle. The researchers believe their work on the steel alloy, named SAM2X5-630, is the first to investigate how amorphous steels respond to shock. SAM2X5-630 has the highest recorded elastic limit for any steel alloy, according to the researchers — essentially the highest threshold at which the material can withstand an impact without deforming permanently. The alloy can withstand pressure and stress of up to 12.5 giga-Pascals or about 125,000 atmospheres without undergoing permanent deformations. The researchers, from the University of California, San Diego, the University of Southern California, and the California Institute of Technology, describe the material’s fabrication and testing in a recent issue of Nature Scientific Reports. “Because these materials are designed to withstand extreme conditions, you can process them under extreme conditions successfully,” says Olivia Graeve, a professor of mechanical engineering at the Jacobs School of Engineering at UC San Diego, who led the design and fabrication effort. Veronica Eliasson, an assistant professor at USC, led the testing efforts. To make the solid materials that comprise the alloy, Graeve and her team mixed metal powders in a graphite mold. The powders were then pressurized at 100 mega-Pascals, or 1000 atmospheres, and exposed to a powerful current of 10,000 Ampers at 1165 F (630 C) during a process called spark plasma sintering. The spark plasma sintering technique allows for enormous time and energy savings, Graeve says. “You can produce materials that normally take hours in an industrial setting in just a few minutes,” she says. The process created small crystalline regions that are only a few nanometers in size, with hints of structure, which researchers believe are key to the material’s ability to withstand stress. This finding is promising because it shows that the properties of these types of metallic glasses can be fine-tuned to overcome shortcomings such as brittleness, which have prevented them from becoming commercially applicable on a large scale, Eliasson says. Researchers at USC tested how the alloy responds to shock without undergoing permanent deformations by hitting samples of the material with copper plates fired from a gas gun at 500 to 1300 meters per second. The material did deform on impact, but not permanently. The Hugoniot Elastic Limit (the maximum shock a material can take without irreversibly deforming) of a 1.5-1.8 mm-thick piece of SAM2X5-630 was measured at 11.76 ± 1.26 giga-Pascals. By comparison, stainless steel has an elastic limit of 0.2 giga-Pascals, while that of tungsten carbide (a high-strength ceramic used in military armor) is 4.5 giga-Pascals. This isn’t to say that SAM2X5-630 has the highest elastic limit of any material known; diamonds top out at a whopping 60 giga-Pascals — they’re just not practical for many real-world applications. “The fact that the new materials performed so well under shock loading was very encouraging and should lead to plenty of future research opportunities,” says Eliasson. The primary focus of future research efforts on these alloys is increasing the weight of the materials to make them more resistant to impacts. In addition to Graeve and Eliasson, co-authors include: Gauri R. Khanolkar and Andrea M. Hodge at USC, Michael B. Rauls at Caltech and James Kelly from the Department of Mechanical and Aerospace Engineering at UC San Diego. This research was supported by the Defense Threat Reduction Agency, grant HDTRA1-11-1-0067.
A new paper-based test developed at MIT and other institutions can diagnose Zika virus infection within a few hours. The test, which distinguishes Zika from the very similar dengue virus, can be stored at room temperature and read with a simple electronic reader, making it potentially practical for widespread use. “We have a system that could be widely distributed and used in the field with low cost and very few resources,” says James Collins, the Termeer Professor of Medical Engineering and Science in MIT’s Department of Biological Engineering and Institute for Medical Engineering and Science (IMES) and the leader of the research team. An outbreak of the Zika virus that began in Brazil in April 2015 has been linked to a birth defect known as microcephaly. Many infected people experience no symptoms, and when symptoms do appear they are very similar to those of related viruses such as dengue and chikungunya. Currently, patients are diagnosed by testing whether they have antibodies against Zika in their bloodstream, or by looking for pieces of the viral genome in a patient’s blood sample, using a test known as polymerase chain reaction (PCR). However, these tests can take days or weeks to yield results, and the antibody test cannot discriminate accurately between Zika and dengue. “One of the key problems in the field is being able to distinguish what these patients have in areas where these viruses are co-circulating,” says Lee Gehrke, the Hermann L.F. von Helmholtz Professor in IMES and an author of the paper. Collins, Gehrke, and colleagues from Harvard University’s Wyss Institute for Biologically Inspired Engineering and other institutions described the new device in the May 6 online edition of Cell. The paper’s lead authors are Melissa Takahashi, an IMES postdoc; Dana Braff, an MIT graduate student; Keith Pardee, an assistant professor at the University of Toronto and former Wyss Institute research scientist; Alexander Green, an assistant professor at Arizona State University and former Wyss Institute postdoc; and Guillaume Lambert, a visiting scholar at the Wyss Institute. The new device is based on technology that Collins and colleagues previously developed to detect the Ebola virus. In October 2014, the researchers demonstrated that they could create synthetic gene networks and embed them on small discs of paper. These gene networks can be programmed to detect a particular genetic sequence, which causes the paper to change color. Upon learning about the Zika outbreak, the researchers decided to try adapting their device to diagnose Zika, which has spread to other parts of South and North America since the outbreak began in Brazil. “In a small number of weeks, we developed and validated a relatively rapid, inexpensive Zika diagnostic platform,” says Collins, who is also a member of the Wyss Institute. Collins and his colleagues developed sensors, embedded in the paper discs, that can detect 24 different RNA sequences found in the Zika viral genome, which, like that of many viruses, is composed of RNA instead of DNA. When the target RNA sequence is present, it initiates a series of interactions that turns the paper from yellow to purple. This color change can be seen with the naked eye, but the researchers also developed an electronic reader that makes it easier to quantify the change, especially in cases where the sensor is detecting more than one RNA sequence. All of the cellular components necessary for this process — including proteins, nucleic acids, and ribosomes — can be extracted from living cells and freeze-dried onto paper. These paper discs can be stored at room temperature, making it easy to ship them to any location. Once rehydrated, all of the components function just as they would inside a living cell. The researchers also incorporated a step that boosts the amount of viral RNA in the blood sample before exposing it to the sensor, using a system called NASBA (nucleic acid sequence based amplification). This amplification step, which takes one to two hours, increases the test’s sensitivity 1 million-fold. Julius Lucks, an assistant professor of chemical and biomolecular engineering at Cornell University, says that this demonstration of rapidly customizable molecular sensors represents a huge leap for the field of synthetic biology. “What’s really exciting here is you can leverage all this expertise that synthetic biologists are gaining in constructing genetic networks and use it in a real-world application that is important and can potentially transform how we do diagnostics,” says Lucks, who was not involved in the research. The team tested the new device using synthesized RNA sequences corresponding to the Zika genome, which were were then added to human blood serum. The researchers showed that the device could detect very low viral RNA concentrations in those samples and could also distinguish Zika from dengue. The researchers then tested the device with samples taken from monkeys infected with the Zika virus. (Samples from human patients affected by the current Zika outbreak are very difficult to obtain.) They found that in these samples, the device could detect viral RNA concentrations as low as 2 or 3 parts per quadrillion. The researchers envision that this approach could also be adapted to other viruses that may emerge in the future. Collins now hopes to team up with other scientists to further develop the technology for diagnosing Zika. “Here we’ve done a nice proof-of-principle demonstration, but more work and additional testing would be needed to ensure safety and efficacy before actual deployment,” he says. “We’re not far off.” The research was funded by the Wyss Institute for Biologically Inspired Engineering, MIT’s Center for Microbiome Informatics and Therapeutics, the Defense Threat Reduction Agency, and the National Institutes of Health.
The University of California San Diego announces that a team of engineers has developed and tested SAM2X5-630, a type of amorphous steel with a record-breaking ability to withstand impact without deforming permanently. To make the solid materials that comprise the alloy, Prof. Olivia Graeve and her team first mixed iron and other powders in a graphite mold. The powders were then pressurized at 100 MPa or 1000 atmospheres, and exposed to a powerful current of 10,000 amperes at 1165°F during a process called spark plasma sintering. The process creates an amorphous structure that contains small crystalline regions that are only a few nanometers in size. Researchers believe that these small regions are key to the material's ability to withstand stress. This finding is promising because it shows that the properties of metallic glasses can be fine-tuned to overcome shortcomings such as brittleness, which have prevented them from becoming commercially applicable on a large scale. Researchers at the University of Southern California, led by Prof. Veronica Eliasson, tested how the alloy responds to shock without undergoing permanent deformation by hitting samples of the material with copper plates fired from a gas gun at 500 to 1300 meters per second. The material did deform on impact, but not permanently. The Hugoniot Elastic Limit is defined as the maximum shock a material can take without irreversibly deforming. The limit of a 1.5-1.8 mm-thick piece of SAM2X5-630 was measured at 11.76 GPa. By comparison, stainless steel has an elastic limit of 0.2 GPa, while that of tungsten carbide is 4.5 GPa. The primary focus of future research efforts on these alloys is increasing the weight of the materials to make them more resistant to impacts. In addition to Prof. Graeve and Prof. Eliasson, co-authors include Prof. Gauri R. Khanolkar and Prof. Andrea M. Hodge at USC, Prof.Michael B. Rauls at Caltech, and Prof. James Kelly from the Department of Mechanical and Aerospace Engineering at UC San Diego. This research was supported by the Defense Threat Reduction Agency, grant HDTRA1-11-1-0067. The full study "Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites," published on March 2, can be found online at http://www.nature.com/articles/srep22568