News Article | February 23, 2017
The International Nurses Association is pleased to welcome Cynthia E. McDaniel, BSN, MSN, to their prestigious organization with her upcoming publication in the Worldwide Leaders in Healthcare. Cynthia E. McDaniel is a Registered Nurse with more than 34 years of experience in her field and an extensive expertise in all facets of nursing, especially home care. Cynthia is currently serving patients as Nurse Coordinator for Jewish Home Lifecare in New York City, New York. Cynthia attended Halifax Community College in Weldon, North Carolina, where she graduated with her Associate of Applied Science Degree in Nursing in 1982. An advocate for continuing education, she went on to gain her Bachelor of Science Degree in Nursing at North Carolina A&T State University in Greensboro, before obtaining her Master of Science Degree in Adult Nursing from Parsons School of Design – The New School. For her hard work and dedication, Cynthia was voted Healthcare Professional of the Year by the New York State United Teachers. Furthermore, Cynthia participates in several breast cancer walks, including the Avon Breast Cancer Walk. She attributes her success to her passion for nursing and caring for her patients. When she is not assisting patients, Cynthia enjoys shopping and spending quality time with her family. Learn more about Cynthia E. McDaniel here: http://inanurse.org/network/index.php?do=/4128294/info/ and be sure to read her upcoming publication in the Worldwide Leaders in Healthcare.
News Article | February 22, 2017
When John Crocker, a professor of chemical and biomolecular engineering in the University of Pennsylvania's School of Engineering and Applied Science was a graduate student, his advisor gathered together everyone in his lab to "throw down the gauntlet" on a new challenge in the field. Someone had predicted that if one could grow colloidal crystals that had the same structure as carbon atoms in a diamond structure, it would have special optical properties that could revolutionize photonics. In this material, called a photonic bandgap material, or PBM, light would act in a way mathematically analogous to how electrons move in a semi-conductor. "The technological implication is that such materials would allow for the construction of 'transistors' for light, the ability to trap light at specific locations and build microcircuits for light and more efficient LEDs and lasers," Crocker said. At the time, Crocker decided to pursue his own projects, leaving the pursuit of PBMs to others. Twenty years later, Crocker's own graduate student Yifan Wang produced this elusive diamond structure while working on a different problem, serendipitously. This put them on the path to achieving PBMs, the "holy grail of directed particle self-assembly," Crocker said. "It's a classic story of serendipity in scientific discovery. You can't anticipate these things. You just get lucky sometimes and something amazing comes out." The research was led by Crocker, Wang, professor Talid Sinno of SEAS and graduate student Ian Jenkins. The results have been published in Nature Communications. To be a PBM, a material needs to have a crystal-like structure not on the scale of atoms but on the lengthscale of the light wavelength. "In other words," Crocker said, "you need to sculpt or arrange some transparent material into an array of spheres with a particular symmetry, and the spheres or holes need to be hundreds of nanometers in size." Back in the 1990s, Crocker said, scientists believed there would be a lot of different possible ways to arrange the spheres and grow the needed structure using colloid crystals similar to how crystals of semi-conductors are grown: colloidal spheres spontaneously arranging themselves into different crystal lattices. Opals are a natural example of this. They are formed when silica in groundwater forms microscopic spheres, which crystallize underground and then become fossilized in solids. Although opals don't have the right symmetry to be PBMs, their iridescent appearance results from their periodic crystal structure being on scales comparable to the wavelength of light. To form a PBM, the major goal is to arrange transparent microscopic spheres into a 3-D pattern that mimics the atomic arrangement of carbon atoms in a diamond lattice. This structure, unlike other crystals, lacks certain symmetry directions of other crystals where light can behave normally, allowing the diamond structure to maintain the PBM effect. Scientists assumed they would be able to make synthetic opals with different structures using different materials to produce PBMs. But this proved more difficult than they had thought and, 20 years later, it still hasn't been accomplished. To finally create these diamond lattices, the Penn researchers used DNA-covered microspheres in two slightly different sizes. "These spontaneously form colloidal crystals when incubated at the correct temperature, due to the DNA forming bridges between the particles," Crocker said. "Under certain conditions, the crystals have a double diamond structure, two interpenetrating diamond lattices, each made up by one size or 'flavor' of particle." They then crosslinked these crystals together into a solid. Crocker describes the achievement as good luck. The researchers hadn't set out to create this diamond structure. They had been doing a "mix and pray" experiment: Wang was adjusting five material variables to explore the parameter space. To date, this has produced 11 different crystals, one of which was the surprising double diamond structure. "Often times when something unexpected happens, it opens up a door to a new technological approach," Sinno said. "There could be new physics as opposed to dusty old textbook physics." Now that they've cleared a significant hurdle on the path to creating PBMs, the researchers need to figure out how to switch out the materials for high index particles and selectively dissolve one species to leave them with one self-assembled diamond lattice of colloidal microspheres. If able to successfully produce a PBM, the material would be like a "semi-conductor for light," having unusual optical properties that don't exist in any natural materials. Normal transparent materials have an index of refraction between 1.3 and 2.5. These PBMs could have a very high index of refraction, or even a negative index of refraction that refracts light backwards. Such materials could be used to make lenses, cameras and microscopes with better performance, or possibly even "invisibility cloaks," solid objects that would redirect all light rays around a central compartment, rendering objects there invisible. Although the researchers have been able to reproduce this experimentally more than a dozen times, Sinno and Jenkins have been unable to reproduce the findings in simulation. It's the only structure of the 11 crystals that Wang produced that they haven't been able to replicate in simulation. "This is the one structure we've found so far that we can't explain which is probably not unrelated to the fact that nobody predicted that you could form it with this system," Sinno said. "There are several other papers we've had in the past that really show how powerful our approaches are in explaining everything. In a way, the fact that none of this worked adds evidence that something fundamentally different is taking place here." The researchers currently think that a different, unknown crystal grows and then transforms into the double diamond crystals, but this idea has proven difficult to confirm. "You're used to writing papers when you understand something," Crocker said. "So we had a dilemma. Normally when we find something we chew on it for a while, we do simulations and then when it all makes sense we write it up. In this case, we had to triple-check everything and then make a judgment call to say that this is an exciting discovery and other people beyond us can also work on this and think about and help us try to solve this mystery."
News Article | February 15, 2017
The International Nurses Association is pleased to welcome Carla Peterson, RN, to their prestigious organization with her upcoming publication in the Worldwide Leaders in Healthcare. Carla Peterson is a Registered Nurse with 21 years of experience in her field and an extensive expertise in all facets of nursing. Carla is currently serving patients as a RN Abstractor within West Virginia Medical Institute and Quality Insights in Rapid City, South Dakota. Carla Peterson attended Miles Community College in Miles City, Montana, graduating with her Associate of Applied Science Degree in Medical Administration in 1990. An advocate for continuing education, Carla received her Associate of Applied Science Degree in Nursing in 1995 within the same educational venue. Carla has a wealth of experience in many areas of nursing, and is now renowned for her excellence in coding and auditing, emergency room nursing, and for her expertise in clinical documentation improvement. She attributes her success to hard work, and when she is not assisting patients, Carla enjoys visiting her parents’ ranch in Montana, and undertaking community service involving children and horses. Learn more about Carla Peterson here: http://inanurse.org/network/index.php?do=/4135522/info/ and be sure to read her upcoming publication in the Worldwide Leaders in Healthcare.
News Article | February 17, 2017
The Hong Kong Polytechnic University (PolyU) is celebrating its 80th Anniversary this year with a Global Leader Lecture Series in which influential leaders in different professions around the globe will be invited to PolyU to deliver lectures on a wide range of topics covering healthcare, business, innovation and entrepreneurship, art and culture, sports and sustainable urban development. The series will provide the university community with a unique opportunity to learn from the stimulating insights and fresh perspectives of the speakers, and help inspire students to dream big and to bring positive changes to the world. Kicking off the series, the Faculties of Applied Science and Textiles (FAST) and Health and Social Sciences (FHSS) of PolyU had the honour of having Dr Marie-Paule Kieny, Assistant Director-General, Health Systems and Innovation, of the World Health Organization (WHO) to present a lecture entitled “Vaccine Development during the Ebola Public Health Emergency: Lessons Learnt and Perspectives for Enhanced Preparedness” which took place on 15th February. Ebola hemorrhagic fever was first described in 1976. The most widespread Ebola outbreak on record began in Guinea in December 2013, infecting more than 28,000 and killing over 11,300 people in many countries including Guinea, Liberia and Sierra Leone by 2016. In the absence of vaccines, and with insufficient diagnostics and medical teams, WHO led the development of an effective vaccine, demonstrating the possibility of compressing the research and development (R&D) time needed from a decade or longer to less than one year. During 2015-2016, Dr Kieny played a leading role in WHO's Ebola research activities by developing and evaluating innovative antiviral drugs and vaccines. She is currently in charge of Zika Virus R&D in WHO as well as the preparation of a WHO R&D Blueprint to accelerate global research preparedness for future outbreaks. The challenges and obstacles that global public health agencies face when devising a rapid response to control emerging infectious diseases was the highlight of Dr Kieny’s lecture. Professor Timothy W. Tong, President of PolyU, said, “At PolyU, our scholars and scientists have been focusing on research that can improve public health. We have active research programmes in drug development, vaccine studies, infection control and food safety……We have also been collaborating with the World Health Organization to exchange views and expertise on various health issues.” Through the PolyU 80th Anniversary Global Leader Lecture Series, PolyU promotes knowledge sharing by bringing global leaders to inspire us, and in this lecture, by sharing innovative R&D processes needed to control public health emergencies like the Ebola outbreak. For further information, please visit http://www.polyu.edu.hk/fast/80anniversary/who/.
News Article | February 23, 2017
Researchers from the UCLA Henry Samueli School of Engineering and Applied Science have developed a new antenna array that greatly expands the operation bandwidth and level of sensitivity for imaging and sensing systems that use terahertz frequencies. Terahertz frequencies are an underused part of the electromagnetic spectrum that lies between the infrared and microwave bands. The unique features of this part of the spectrum could be useful for biological sensing and medical imaging, chemical identification and material characterization. “For example, a terahertz-based imaging system could allow doctors to see how wounds are healing underneath bandages,” says Mona Jarrahi, associate professor of electrical engineering in the UCLA Henry Samueli School of Engineering and Applied Science and the principal investigator of the research. The study was published in Scientific Reports, an open-access journal from Nature. However terahertz technology is not yet mature. One component researchers are aiming to make more efficient is a terahertz detector, which receives the terahertz signals, much like photodetectors in a camera that sense light to produce an image. By operating across a broader bandwidth, the new nanoscale antenna array developed by Jarrahi and Nezih Tolga Yardimci, a UCLA graduate student in electrical engineering, can extract more information about material characteristics. The device’s higher signal-to-noise ratios mean it can find faint target signals. For example, the new terahertz detector can be tuned to detect certain chemicals even when target molecules are present in miniscule amounts. It can also be used to image both the surface of the skin, and deeper tissue layers. The unique nanoscale geometry of the antenna array addresses the bandwidth and sensitivity problems of previously used terahertz detectors, the researchers say. “Up close, it looks like a row of small grates,” Yardimci says. “We specifically designed the dimensions of the nanoantenna elements and their spacing such that an incoming terahertz beam is focused into nanoscale dimensions, where it efficiently interacts with a stream of optical pump photons to produce an electrical signal proportional to the terahertz beam intensity.” Jarrahi says, “The broad operation bandwidth and high sensitivity of this new type of terahertz detector extends the scope and potential uses of terahertz waves for many imaging and sensing applications.” The research was supported by financial support from Moore Inventor Fellowship and the Presidential Early Career Award for Scientists and Engineers.
News Article | February 27, 2017
Most strategies to combat climate change concentrate on reducing greenhouse gas emissions by substituting non-carbon energy sources for fossil fuels, but a task force commissioned in June 2016 by former U.S. Secretary of Energy Ernest Moniz proposed a framework in December 2016 for evaluating research and development on two additional strategies: recycling carbon dioxide and removing large amounts of carbon dioxide from the atmosphere. These strategies were developed under a single framework with the goal to produce an overall emissions reduction for the Earth of at least one billion tons of carbon dioxide per year. Task force members said that these approaches would complement carbon-free approaches based on electrification, including wind and solar energy, by fostering low-carbon strategies that retain liquid and gaseous fuels for distributive uses of energy in transport, buildings, and industry. These strategies could also enable overall net carbon removal from the atmosphere, if at some future time the world desires to reduce the global concentration of carbon dioxide. The task force considered only technologies that have the potential to achieve reductions on the scale of one billion metric tons of CO2 per year, which represents about 2.5 percent of annual global emissions (about 40 billion metric tons today). Arun Majumdar, a Stanford University professor who chaired the Task Force of the Secretary of Energy Advisory Board, said that research avenues at such a large scale could potentially include utilizing agricultural crops to store more carbon in the soil, re-using carbon dioxide to form plastics and fuels, and storing carbon dioxide in massive underground reservoirs while producing some fuels. "We are excited to have been able to provide the first steps toward a coherent strategy of research opportunities," Majumdar said. "The range of options that are ripe for research is truly impressive." The task force, made up of participants from eight universities, focused on entire systems. In one example, plants are modified to increase their efficiency in capturing carbon dioxide from the atmosphere during photosynthesis and to develop deeper roots to store the carbon in the soil. By the end of the process, the atmosphere has been scrubbed of the carbon dioxide, and carbon has been transferred from the atmosphere to the soil. Sally Benson, a Stanford professor and a task force member, said a great deal of research is still needed on this process and others included in the report. "Each of the strategies we reviewed has its own research frontier," she said. Because these strategies rely on industry-level solutions such as removing carbon dioxide at the smokestack or changing farming methods to retain carbon in the soil, they require development of new technology and new industrial processes. "The need is urgent, and we must develop and use multiple strategies to combat climate change," said task force member Emily A. Carter, dean of the School of Engineering and Applied Science and founding director of the Andlinger Center for Energy and the Environment at Princeton University. "But pursuing these research avenues will benefit not just climate change. As we have seen for more than a century, investment in science and engineering research pays off in new technologies, new industries, jobs, and societal benefits far beyond the initial expense and in ways we cannot predict." The task force recommendations were delivered in a report to Energy Secretary Ernest J. Moniz on Dec. 13, 2016. John Deutch, an emeritus professor and former provost at the Massachusetts Institute of Technology and the chair of the Secretary of Energy Advisory Board, said in a letter to Moniz that the report "has painted a scientifically interesting agenda for decarbonization that should be of interest to the scientific community writ large." The task force - made up of experts from Duke, Harvard, Georgia Tech, MIT, Princeton, Stanford, University of Illinois and Washington University, as well as a former official from ExxonMobil - cautioned that the development of systems to reduce CO2 emissions at such a scale would be difficult and complex. The members also said some of the techniques could have unexpected outcomes and urged the government to invest in research to evaluate the impacts of the technologies, both intended and unintended, beyond their ability to reduce atmospheric CO2. Taking steps to reduce atmospheric CO2 would require broad cooperation between academic researchers, government and policy leaders, and industry, the report concluded. An appendix to the report analyzes the flow of technology from labs to society and found all of these groups play a critical role in the development of new technology. The task force made five recommendations about research and development: - Improve and expand systems modeling. Members found that because of the complexity of large-scale CO2 reduction, improved models based on a systems approach are needed to evaluate impacts on the atmosphere, ecological systems, and the economy. - Harness the natural biological cycle in which plants absorb and store atmospheric CO2. There is a need to evaluate how to optimize crops to absorb greater amounts of carbon dioxide and store more carbon in the soil for long periods of time, without a major increase in needed resources such as water and fertilizer; how to promote agricultural techniques that extend the time that carbon remains in the soil; and how to use various biological resources, such as giant kelp, as a stock for biofuels. - Explore synthetic transformation of CO2 into useful fuels and products. Carbon dioxide can be converted to valuable chemicals and fuels but it requires energy to do so. A critical part of this system would be inexpensive carbon-free energy to drive this conversion. The task force recommended that the scientific community pursue research to explore better materials and systems that allow for reactions that would make CO2 conversion cheaper and more efficient. - Evaluate the storage of CO2 in geologic formations. Past work on enhanced oil recovery (EOR) focused on minimizing the storage of CO2 to extract hydrocarbons. The task force recommended developing advanced EOR where one would co-optimize CO2 storage and hydrocarbon extraction in such a way that substantially more carbon would be stored than is extracted in fossil fuels. - Study improved methods to separate and capture carbon dioxide from a mixture of gases, a process that is currently too expensive and energy intensive. Both discovery of improved substances to absorb carbon dioxide and development of processes able to separate and store carbon dioxide on a large scale are needed. Improved sorbents would reduce the cost of "direct air capture," which involves absorbing carbon dioxide directly from the air and concentrating it for use or storage. "Our report should help people appreciate the immense effort that will be required to reconfigure our energy system to make it sustainable in the face of climate change, geopolitical stability, and responsible use of land," said Robert Socolow, a professor emeritus of mechanical and aerospace engineering and co-director of the Carbon Mitigation Initiative at the Princeton Environmental Institute. "Our report provides a useful structure for addressing the pluses and minuses of several less familiar approaches."
News Article | February 27, 2017
VANCOUVER, BC / ACCESSWIRE / February 27, 2017 / CopperBank Resources Corp. ("CopperBank" or the "Company") (CSE: CBK) (OTC PINK: CPPKF) announces that it has appointed Brigitte Dejou as an independent director and Colin Burge has joined the company's technical advisory team. Mr. Kovacevic comments, "I have known Brigitte and Colin for many years and have direct experience with both of them. CopperBank's technical team now comprises of ten shareholder aligned members who have a combined two hundred and fifty years of industry experience. Colin was a vital element to the team at Cobre Panama, who delineated a tremendous amount of additional pounds of copper from the time I was an investor in the early development of that project. Brigitte has a deep knowledge base that rounds out our technical team, especially due to her direct experience in Alaska, where she participated with the geological interpretation that added many years of mine life to TECK's Red Dog mine district. Both Brigitte and Colin will be great assets to CopperBank's stakeholders as we continue our thorough data analysis and plan the important next steps for the Pyramid Copper porphyry deposit, The San Diego Bay prospect and our Contact Copper Oxide Project." Ms. Dejou holds both a Bachelor of Engineering degree and a Masters of Applied Science degree from Ecole Polytechnique de Montréal and is a member of the Ordre des Ingénieurs du Québec. Ms. Dejou has 25 years of experience in mineral exploration, including 18 years within Teck Cominco (now TECK) managing various exploration programs and two years with Osisko Mining Corporation working on the evaluation of new projects and QA/QC of existing drilling programs (Canadian Malartic, Duparquet, Hammond Reef). Ms. Dejou brings a wealth of experience in running a variety of exploration projects from grass-roots to pre-feasibility stage across North America (including Red Dog, El Limon-Morelos, Polaris, and Mesaba). She was also instrumental in the discovery of the Aktigiruk deposit. She has explored for a variety of commodities both for base metals (sedex and MVT Zn-Pb, porphyry Cu, magmatic Cu-Ni, VMS) and precious metals (Au, Ag, PGE). Since 2012, Ms. Dejou is Vice President Exploration for LaSalle Exploration. Mr. Burge is a discovery oriented exploration geologist with 30 years' experience in project development with First Quantum Minerals and predecessor companies. Mr. Burge was part of a corporate development team at Inmet Mining Corp. that discovered and delineated more than 30 billion pounds of copper at the Cobre Panama Project, leading to First Quantum Minerals $5 billion dollar acquisition of the company. He gained valuable experience working with First Quantum for 3 years as the project transitions to a mining operation and has excellent technical skills in exploration data management and the application of exploration tools, as well as a strong ability to think creatively. Mr. Burge graduated from the University of Waterloo with a Bachelor of Earth Science in 1981 and is a licensed professional geologist in British Columbia. Shareholders are encouraged to visit the Company's website for further details and biographies of each individual of CopperBank's technical team: www.copperbankcorp.com The Company also announces that Robert McLeod will be stepping down from the Board of Directors and will remain as an important member of CopperBank's technical team. Mr. McLeod will remain as a Qualified Person for the company. Certain information in this release may constitute "forward-looking information" under applicable securities laws and necessarily involve risks and uncertainties. Forward-looking information included herein is made as of the date of this news release and CopperBank does not intend, and does not assume any obligation, to update forward-looking information unless required by applicable securities laws. Forward-looking information relates to future events or future performance and reflects management of CopperBank's expectations or beliefs regarding future events. In certain cases, forward-looking information can be identified by the use of words such as "plans," or "believes," or variations of such words and phrases or statements that certain actions, events or results "may," "could," "would," "might," or "will be taken," "occur," or "be achieved," or the negative of these terms or comparable terminology. Examples of forward-looking information in this news release include, but are not limited to, statements with respect to the Company's ongoing review of its existing portfolio, the involvement of CopperBank in any potential divestiture, spin-out, partnership, or other transactions involving the Company's portfolio assets, and the ability of the Company to complete any such transactions, the ability of CopperBank to enter into transactions that will ultimately enhance shareholder value, and the anticipated issuance of one million shares in connection with the satisfaction of certain loans between CopperBank and management. This forward-looking information is based, in part, on assumptions and factors that may change or prove to be incorrect, thus causing actual results, performance, or achievements to be materially different from those expressed or implied by forward-looking information. Such factors and assumptions include, but are not limited to the Company's ability to identify and complete one or more transactions involving the Company's portfolio assets that enhance shareholder value as part of management's ongoing review of strategic alternatives in the current market conditions. By its very nature, forward-looking information involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by forward-looking information. Such factors include, but are not limited to, the risk that the Company will not be able to identify and complete one or more transactions involving the Company's portfolio assets that enhance shareholder value as part of management's ongoing review of strategic alternatives in the current market conditions. Although CopperBank has attempted to identify important factors that could cause actual actions, events, or results to differ materially from forward-looking information, there may be other factors that cause actions, events, or results not to be as anticipated, estimated, or intended. There can be no assurance that forward-looking information will prove to be accurate, as actual results and future events could differ materially from those anticipated by such forward-looking information. Accordingly, readers should not place undue reliance on forward-looking information. For more information on CopperBank and the risks and challenges of its businesses, investors should review the continuous disclosure filings that are available under CopperBank's profile at www.sedar.com.
News Article | February 15, 2017
One of the most feared and venomous arachnids in the world, the American brown recluse spider has long been known for its signature necro-toxic venom, as well as its unusual silk. Now, new research offers an explanation for how the spider is able to make its silk uncommonly strong. Researchers suggest that if applied to synthetic materials, the technique could inspire scientific developments and improve impact absorbing structures used in space travel. The study, published today in the journal Material Horizons, was produced by scientists from Oxford University's Department of Zoology, together with a team from the Applied Science Department at Virginia's College of William & Mary. Their surveillance of the brown recluse spider's spinning behaviour shows how, and to what extent, the spider manages to strengthen the silk it makes. From observing the arachnid, the team discovered that unlike other spiders, who produce round ribbons of thread, recluse silk is thin and flat. This structural difference is key to the thread's strength, providing the flexibility needed to prevent premature breakage and withstand the knots created during spinning which give each strand additional strength. Professor Hannes Schniepp from William & Mary explains: "The theory of knots adding strength is well proven. But adding loops to synthetic filaments always seems to lead to premature fibre failure. Observation of the recluse spider provided the breakthrough solution; unlike all spiders its silk is not round, but a thin, nano-scale flat ribbon. The ribbon shape adds the flexibility needed to prevent premature failure, so that all the microloops can provide additional strength to the strand." By using computer simulations to apply this technique to synthetic fibres, the team were able to test and prove that adding even a single loop significantly enhances the strength of the material. William & Mary PhD student Sean Koebley adds: "We were able to prove that adding even a single loop significantly enhances the toughness of a simple synthetic sticky tape. Our observations open the door to new fibre technology inspired by the brown recluse." Speaking on how the recluse's technique could be applied more broadly in the future, Professor Fritz Vollrath, of the Department of Zoology at Oxford University, expands: "Computer simulations demonstrate that fibres with many loops would be much, much tougher than those without loops. This right away suggests possible applications. For example carbon filaments could be looped to make them less brittle, and thus allow their use in novel impact absorbing structures. One example would be spider-like webs of carbon-filaments floating in outer space, to capture the drifting space debris that endangers astronaut lives' and satellite integrity." More information: S. R. Koebley et al. Toughness-enhancing metastructure in the recluse spider's looped ribbon silk, Mater. Horiz. (2017). DOI: 10.1039/C6MH00473C
News Article | February 15, 2017
Unlike other two-dimensional materials, scientists believe tungsten ditelluride has what are called topological electronic states. This means that it can have many different properties not just one. When one thinks about two-dimensional materials, graphene is probably the first that comes to mind. The tightly packed, atomically thin sheet of carbon first produced in 2004 has inspired countless avenues in research that could revolutionize everything from technology to drinking water. One of the most important properties of graphene is that it's what's called a zero bandgap semiconductor in that it can behave as both a metal and a semiconductor. But there are tons of other properties that 2-D materials can have. Some can insulate, others can emit light and still others can be spintronic, meaning they have magnetic properties. "Graphene is just graphene," said A.T. Charlie Johnson, a physics professor in Penn's School of Arts & Sciences. "It just does what graphene does. If you want to have functioning systems that are based on 2-D materials, then you want 2-D materials that have all of the different physical properties that we know about." The ability of 2-D materials to have topological electronic states is a phenomenon that was pioneered by Charles Kane, the Christopher H. Browne Distinguished Professor of Physics at Penn. In this new research, Johnson, physics professor James Kikkawa and graduate students Carl Naylor and William Parkin were able to produce and measure the properties of a single layer of tungsten ditelluride. "Because tungsten ditelluride is three atoms thick, the atoms can be arranged in different ways," Johnson said. "These three atoms can take on slightly different configurations with respect to each other. One configuration is predicted to give these topological properties." Marija Drndi?, the Fay R. and Eugene L. Langberg Professor of Physics; Andrew Rappe, the Blanchard Professor of Chemistry and a professor of materials science and engineering in the School of Engineering and Applied Science, and Robert Carpick, the John Henry Towne Professor and chair of the Department of Mechanical Engineering and Applied Mechanics, also contributed to the research. "It's very much a Penn product," Johnson said. "We're collaborating with multiple other faculty members who investigate the material in their own ways, and we brought it all together to put a paper out there. Everybody comes along for the ride." The researchers were able to grow this material using a process called chemical vapor deposition. Using a hot-tube furnace, they heated a chip containing tungsten to the right temperature and then introduced a vapor containing tellurium. "Through good fortune and finding exactly the right conditions, these elements will chemically react and combine to form a monolayer, or three-atom-thick regions of this material," Johnson said. Although this material degrades extremely rapidly in air, Naylor, the paper's first author, figured out ways to protect the material so that it could be studied before it was destroyed. One thing the researchers found is that the material grows in little rectangular crystallites, rather than the triangles that other materials grow in. "This reflects the rectangular symmetry in the material," Johnson said. "They have a different structure so they tend to grow in different shapes." Although the research is still in its beginning stages and the researchers haven't yet been able to produce a continuous film, they hope to conduct experiments to show that it has the topological electronic properties that are predicted. One property of these topological systems is that any current traveling through the material would only be carried on the edges, and no current would travel through the center of the material. If researchers were able to produce single-layer-thick materials with this property, they may be able to route an electrical signal to go off into different locations. The ability of this material to have multiple properties could also have implications in quantum computing, which taps into the power of atoms and subatomic phenomena to perform calculations significantly faster than current computers. These 2-D materials might allow for an intrinsically error-tolerant form of quantum computing called topologically protected quantum computing, which requires both semiconducting and superconducting materials. "With these 2-D materials, you want to realize as many physical properties as possible," Johnson said. "Topological electronic states are interesting and they're new and so a lot of people have been trying to realize them in a 2-D material. We created the material where these are predicted to occur, so in that sense we've moved towards this very big goal in the field." Explore further: How light pulses can create channels that conduct electricity with no resistance in atomically thin semiconductors
News Article | February 22, 2017
Scientists have gotten better at predicting where earthquakes will occur, but they're still in the dark about when they will strike and how devastating they will be. In the search for clues that will help them better understand earthquakes, scientists at the University of Pennsylvania are studying a phenomenon called ageing. In ageing, the longer that materials are in contact with each other, the more force is required to move them. This resistance is called static friction. The longer something, such as a fault, is sitting still, the more static friction builds up and the stronger the fault gets. Even when the fault remains still, tectonic motion is still occurring; stress builds up in the fault as the plates shift until finally they shift so much that they exceed the static friction force and begin to slide. Because the fault grew stronger with time, the stress can build up to large levels, and a huge amount of energy is then released in the form of a powerful quake. "This ageing mechanism is critical in underlying the unstable behavior of faults that lead to earthquakes," said Robert Carpick, the John Henry Towne Professor and chair of the Department of Mechanical Engineering and Applied Mechanics in Penn's School of Engineering and Applied Science. "If you didn't have ageing, then the fault would move very easily and so you'd get much smaller earthquakes happening more frequently, or maybe even just smooth motion. Ageing leads to the occurrence of infrequent, large earthquakes that can be devastating." Scientists have been studying the movement of faults and ageing in geological materials at the macroscale for decades, producing phenomenological theories and models to describe their experimental results. But there's a problem when it comes to these models. "The models are not fundamental, not physically based, which means we cannot derive those models from basic physics," said Kaiwen Tian, a graduate student in Penn's School of Arts & Sciences. But a Penn-based project seeks to understand the friction of rocks from a more physical point of view at the nanoscale. In their most recent paper, published in Physical Review Letters, the researchers verified the first fundamental theory to describe ageing and explain what happens when load increases. The research was led by Tian and Carpick. David Goldsby, an associate professor in the Department of Earth and Environmental Science at Penn; Izabela Szlufarska, a professor of materials science and engineering at the University of Wisconsin-Madison; UW alumnus Yun Liu; and Nitya Gosvami, now an assistant professor in the Department of Applied Mechanics at IIT Delhi, also contributed to the study. Previous work from the group found that static friction is logarithmic with time. That means that if materials are in contact for 10 times longer, then the friction force required to move them doubles. While scientists had seen this behavior of rocks and geological materials at the macroscopic scale, these researchers observed it at the nanoscale. In this new study, the researchers varied the amount of normal force on the materials to find out how load affects the ageing behavior. "That's a very important question because load may have two effects," Tian said. "If you increase load, you will increase contact area. It may also affect the local pressure." To study this, the researchers used an atomic force microscope to investigate bonding strength where two surfaces meet. They used silicon oxide because it is a primary component of many rock materials. Using the small nanoscale tip of the AFM ensures that the interface is composed of a single contact point, making it easier to estimate the stresses and contact area. They brought a nanoscale tip made from silicon oxide into contact with a silicon oxide sample and held it there. After enough time passed, they slid the tip and measured the force required to initiate sliding. Carpick said this is analogous to putting a block on the floor, letting it sit for a while, and then pushing it and measuring how much force it takes for the block to start moving. They observed what happened when they pushed harder in the normal direction, increasing the load. They found that they doubled the normal force, and then the friction force required also doubled. Explaining it required looking very carefully the mechanism leading to this increase in friction force. "The key," Carpick said, "is we showed in our results how the dependence of the friction force on the holding time and the dependence of the friction force on the load combine. This was consistent with a model that assumes that the friction force is going up because we're getting chemical bonds forming at the interface, so the number of those bonds increase with time. And, when we push harder, what we're doing is increasing the area of contact between the tip and the sample, causing friction to go up with normal force." Prior to this research, it had been suggested that pushing harder might also cause those bonds to form more easily. The researchers found that this wasn't the case: to a good approximation, increasing the normal force simply increases the amount of contact and the number of sites where atoms can react. Currently, the group is looking at what happens when the tip sits on the sample for very short amounts of time. Previously they had been looking at hold times from one-tenth of a second to as much as 100 seconds. But now they're looking at timescales even shorter than one-tenth of a second. By looking at very short timescales, they can gain insights into the details of the energetics of the chemical bonds to see if some bonds can form easily and if others take longer to form. Studying bonds that form easily is important because those are the first bonds to form and might provide insight into what happens at the very beginning of the contact. In addition to providing a better understanding of earthquakes, this work could lead to more efficient nano-devices. Because many micro- and nano-devices are made from silicon, understanding friction is key to getting those devices to function more smoothly. But, most important, the researchers hope that somewhere down the line, a better understanding of ageing will enable them to predict when earthquakes will occur. "Earthquake locations can be predicted fairly well," Carpick said, "but when an earthquake is going to happen is very difficult to predict, and this is largely because there's a lack of physical understanding of the frictional mechanisms behind the earthquakes. We have long way to go to connect this work to earthquakes. However, this work gives us more fundamental insights into the mechanism behind this ageing and, in the long term, we think these kinds of insights could help us predict earthquakes and other frictional phenomena better." This research was supported by a grant from the Earth Sciences Division of the National Science Foundation.