Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources.

PubMed

Rutherford, Michael E; Chapman, David J; White, Thomas G; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E

2016-05-01

The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits).

Evaluating scintillator performance in time-resolved hard X-ray studies at synchrotron light sources

PubMed Central

Rutherford, Michael E.; Chapman, David J.; White, Thomas G.; Drakopoulos, Michael; Rack, Alexander; Eakins, Daniel E.

2016-01-01

The short pulse duration, small effective source size and high flux of synchrotron radiation is ideally suited for probing a wide range of transient deformation processes in materials under extreme conditions. In this paper, the challenges of high-resolution time-resolved indirect X-ray detection are reviewed in the context of dynamic synchrotron experiments. In particular, the discussion is targeted at two-dimensional integrating detector methods, such as those focused on dynamic radiography and diffraction experiments. The response of a scintillator to periodic synchrotron X-ray excitation is modelled and validated against experimental data collected at the Diamond Light Source (DLS) and European Synchrotron Radiation Facility (ESRF). An upper bound on the dynamic range accessible in a time-resolved experiment for a given bunch separation is calculated for a range of scintillators. New bunch structures are suggested for DLS and ESRF using the highest-performing commercially available crystal LYSO:Ce, allowing time-resolved experiments with an interframe time of 189 ns and a maximum dynamic range of 98 (6.6 bits). PMID:27140147

Nanoscale magnetic imaging using picosecond thermal gradients

NASA Astrophysics Data System (ADS)

Fuchs, Gregory

Research and development in spintronics is challenged by the lack of table-top magnetic imaging technologies that posses the simultaneous temporal resolution and spatial resolution to characterize magnetization dynamics in emerging spintronic devices. In addition, many of the most exciting magnetic material systems for spintronics are difficult to image with any method. To address this challenge, we developed a spatiotemporal magnetic microscope based on picosecond heat pulses that stroboscopically transduces an in-plane magnetization into a voltage signal. When the magnetic device contains a magnetic metal like FeCoB or NiFe, we use the time-resolved anomalous Nernst effect. When it contains a magnetic insulator/normal metal bilayer like yttrium iron garnet/platinum, we use the combination of the time-resolved longitudinal spin Seebeck effect and the inverse spin Hall effect. We demonstrate that these imaging modalities have time resolutions in the range of 10-100 ps and sensitivities in the range of 0.1 - 0.3° /√{Hz} , which enables not only static magnetic imaging, but also phase-sensitive ferromagnetic resonance imaging. One application of this technology is for magnetic torque vector imaging, which we apply to a spin Hall device. We find an unexpected variation in the spin torque vector that suggests conventional, all-electrical FMR measurements of spin torque vectors can produce a systematic error as large as 30% when quantifying the spin Hall efficiency. Finally, I will describe how time-resolved magnetic imaging can greatly exceed the spatial resolution of optical diffraction. We demonstrate scanning a sharp gold tip to create near-field thermal transfer from a picosecond laser pulse to a magnetic sample as the basis of a nanoscale spatiotemporal microscope. We gratefully acknowledge support from the AFOSR (FA9550-14-1-0243) and the NSF through the Cornell Center for Materials Research (DMR-1120296).

Unmixing the Materials and Mechanics Contributions in Non-resolved Object Signatures

DTIC Science & Technology

2008-09-01

abundances from hyperspectral or multi-spectral time - resolved signatures. A Fourier analysis of temporal variation of material abundance provides...factorization technique to extract the temporal variation of material abundances from hyperspectral or multi-spectral time - resolved signatures. A Fourier...approximately one hundred wavelengths in the visible spectrum. The frame rate for the instrument was not large enough to collect time resolved data. However

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cheng, Shiwang; Xie, Shi-Jie; Carrillo, Jan-Michael Y.

Polymer nanocomposites (PNCs) are important materials that are widely used in many current technologies and potentially have broader applications in the future due to their excellent property of tunability, light weight and low cost. But, expanding the limits in property enhancement remains a fundamental scientific challenge. We demonstrate that well-dispersed, small (diameter ~1.8 nm) nanoparticles with attractive interactions lead to unexpectedly large and qualitatively new changes in PNC structural dynamics in comparison to conventional composites based on particles of diameter ~10-50 nm. At the same time, the zero-shear viscosity at high temperatures remains comparable to that of the neat polymer,more » thereby retaining good processibility and resolving a major challenge in PNC applications. These results suggest that the nanoparticle mobility and relatively short lifetimes of nanoparticlepolymer associations open qualitatively new horizons in tunability of macroscopic properties in nanocomposites with high potential for the development of new functional materials.« less

Synthesis, structure, and optoelectronic properties of II-IV-V 2 materials

DOE PAGES

Martinez, Aaron D.; Fioretti, Angela N.; Toberer, Eric S.; ...

2017-03-07

II-IV-V 2 materials offer the promise of enhanced functionality in optoelectronic devices due to their rich ternary chemistry. In this review, we consider the potential for new optoelectronic devices based on nitride, phosphide, and arsenide II-IV-V 2 materials. As ternary analogs to the III-V materials, these compounds share many of the attractive features that have made the III-Vs the basis of modern optoelectronic devices (e.g. high mobility, strong optical absorption). Control of cation order parameter in the II-IV-V 2 materials can produce significant changes in optoelectronic properties at fixed chemical composition, including decoupling band gap from lattice parameter. Recent progressmore » has begun to resolve outstanding questions concerning the structure, dopability, and optical properties of the II-IV-V 2 materials. Furthermore, remaining research challenges include growth optimization and integration into heterostructures and devices.« less

Biomimetic actuators using electroactive polymers (EAP) as artificial muscles

NASA Technical Reports Server (NTRS)

Bar-Cohen, Yoseph

2006-01-01

Evolution has resolved many of nature's challenges leading to lasting solutions with maximal performance and effective use of resources. Nature's inventions have always inspired human achievements leading to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems and many other benefits. The field of mimicking nature is known as Biomimetics and one of its topics includes electroactive polymers that gain the moniker artificial muscles. Integrating EAP with embedded sensors, self-repair and many other capabilities that are used in composite materials can add greatly to the capability of smart biomimetic systems. Such development would enable fascinating possibilities potentially turning science fiction ideas into engineering reality.

Time-resolved structural studies at synchrotrons and X-ray free electron lasers: opportunities and challenges

PubMed Central

Neutze, Richard; Moffat, Keith

2012-01-01

X-ray free electron lasers (XFELs) are potentially revolutionary X-ray sources because of their very short pulse duration, extreme peak brilliance and high spatial coherence, features that distinguish them from today’s synchrotron sources. We review recent time-resolved Laue diffraction and time-resolved wide angle X-ray scattering (WAXS) studies at synchrotron sources, and initial static studies at XFELs. XFELs have the potential to transform the field of time-resolved structural biology, yet many challenges arise in devising and adapting hardware, experimental design and data analysis strategies to exploit their unusual properties. Despite these challenges, we are confident that XFEL sources are poised to shed new light on ultrafast protein reaction dynamics. PMID:23021004

Rapid Development of Gossamer Propulsion for NASA Inner Solar System Science Missions

NASA Technical Reports Server (NTRS)

Young, Roy M.; Montgomery, Edward E.

2006-01-01

Over a two and one-half year period dating from 2003 through 2005, NASA s In-Space Propulsion Program matured solar sail technology from laboratory components to full systems, demonstrated in as relevant a space environment as could feasibly be simulated on the ground. This paper describes the challenges identified; as well as the approaches taken toward solving a broad set of issues spanning material science, manufacturing technology, and interplanetary trajectory optimization. Revolutionary advances in system structural predictive analysis and characterization testing occurred. Also addressed are the remaining technology challenges that might be resolved with further ground technology research, geared toward reducing technical risks associated with future space validation and science missions.

Dense Nonaqueous Phase Liquids at Former Manufactured Gas Plants: Challenges to Modeling and Remediation

PubMed Central

Birak, P.S.; Miller, C.T.

2008-01-01

The remediation of dense non-aqueous phase liquids (DNAPLs) in porous media continues to be one of the most challenging problems facing environmental scientists and engineers. Of all the environmentally relevant DNAPLs, tars in the subsurface at former manufactured gas plants (FMGP’s) pose one of the biggest challenges due to their complex chemical composition and tendency to alter wettability. To further our understanding of these complex materials, we consulted historic documentation to evaluate the impact of gas manufacturing on the composition and physicochemical nature of the resulting tars. In the recent literature, most work to date has been focused in a relatively narrow portion of the expected range of tar materials, which has yielded a bias toward samples of relatively low viscosity and density. In this work, we consider the dissolution and movement of tars in the subsurface, models used to predict these phenomena, and approaches used for remediation. We also explore the open issues and detail important gaps in our fundamental understanding of these extraordinarily complex systems that must be resolved to reach a mature level of understanding. PMID:19176266

The Challenge of Learning Physics Before Mathematics: A Case Study of Curriculum Change in Taiwan

NASA Astrophysics Data System (ADS)

Chiu, Mei-Shiu

2016-12-01

The aim of this study was to identify challenges in implementing a physics-before- 10 mathematics curriculum. Obviously, students need to learn necessary mathematics skills in order to develop advanced physics knowledge. In the 2010 high school curriculum in Taiwan, however, grade 11 science students study two-dimensional motion in physics without prior learning experiences of trigonometry in mathematics. The perspectives of three curriculum developers, 22 mathematics and physics teachers, two principals, and 45 science students were obtained by interview. The results of qualitative data analysis revealed six challenges and suggested likely solutions. The national level includes political and social challenges, resolved by respecting teachers as professionals; the teacher level includes knowledge and teaching challenges, resolved by increasing teacher trans-literal capacities; and the student level includes learning and justice challenges, resolved by focusing on students' diverse developments in cross-domain learning.

High-Density Stretchable Electrode Grids for Chronic Neural Recording

PubMed Central

Tybrandt, Klas; Khodagholy, Dion; Dielacher, Bernd; Stauffer, Flurin; Renz, Aline F.; Buzsáki, György; Vörös, János

2018-01-01

Electrical interfacing with neural tissue is key to advancing diagnosis and therapies for neurological disorders, as well as providing detailed information about neural signals. A challenge for creating long-term stable interfaces between electronics and neural tissue is the huge mechanical mismatch between the systems. So far, materials and fabrication processes have restricted the development of soft electrode grids able to combine high performance, long-term stability, and high electrode density, aspects all essential for neural interfacing. Here, this challenge is addressed by developing a soft, high-density, stretchable electrode grid based on an inert, high-performance composite material comprising gold-coated titanium dioxide nanowires embedded in a silicone matrix. The developed grid can resolve high spatiotemporal neural signals from the surface of the cortex in freely moving rats with stable neural recording quality and preserved electrode signal coherence during 3 months of implantation. Due to its flexible and stretchable nature, it is possible to minimize the size of the craniotomy required for placement, further reducing the level of invasiveness. The material and device technology presented herein have potential for a wide range of emerging biomedical applications. PMID:29488263

Time-resolved Small Angle X-ray Scattering During the Formation of Detonation Nano-Carbon Condensates

NASA Astrophysics Data System (ADS)

Bagge-Hansen, Michael; Hammons, Josh; Nielsen, Mike; Lauderbach, Lisa; Hodgin, Ralph; Bastea, Sorin; van Buuren, Tony; Pagoria, Phil; May, Chadd; Jensen, Brian; Gustavsen, Rick; Watkins, Erik; Firestone, Millie; Dattelbaum, Dana; Fried, Larry; Cowan, Matt; Willey, Trevor

2017-06-01

Carbon nanomaterials are spontaneously generated under high pressure and temperature conditions present during the detonation of many high explosive (HE) materials. Thermochemical modeling suggests that the phase, size, and morphology of carbon condensates are strongly dependent on the type of HE used and associated evolution of temperature and pressure during the very early stages of detonation. Experimental validation of carbon condensation under these extreme conditions has been technically challenging. Here, we present synchrotron-based, time-resolved small-angle x-ray scattering (TR-SAXS) measurements collected during HE detonations, acquired from discrete sub-100 ps x-ray pulses, every 153.4 ns. We select from various HE materials and geometries to explore a range of achievable pressures and temperatures that span detonation conditions and, correspondingly, generate an array of nano-carbon products, including nano-diamonds and nano-onions. The TR-SAXS patterns evolve rapidly over the first few hundred nanoseconds. Comparing the results with modeling offers significant progress towards a general carbon equation of state. Prepared by LLNL under Contract DE-AC52-07NA27344.

Spatially resolved multicomponent gels

NASA Astrophysics Data System (ADS)

Draper, Emily R.; Eden, Edward G. B.; McDonald, Tom O.; Adams, Dave J.

2015-10-01

Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this ‘self-sorted network’ is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Yue; Hrubiak, Rostislav; Rod, Eric

An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. Furthermore, the new capabilities have demonstrated clear benefits and provide new opportunities in researchmore » areas including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.« less

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team

DOE PAGES

Meng, Yue; Hrubiak, Rostislav; Rod, Eric; ...

2015-07-17

An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. Furthermore, the new capabilities have demonstrated clear benefits and provide new opportunities in researchmore » areas including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.« less

New developments in laser-heated diamond anvil cell with in situ synchrotron x-ray diffraction at High Pressure Collaborative Access Team

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, Yue; Hrubiak, Rostislav; Rod, Eric

An overview of the in situ laser heating system at the High Pressure Collaborative Access Team, with emphasis on newly developed capabilities, is presented. Since its establishment at the beamline 16-ID-B a decade ago, laser-heated diamond anvil cell coupled with in situ synchrotron x-ray diffraction has been widely used for studying the structural properties of materials under simultaneous high pressure and high temperature conditions. Recent developments in both continuous-wave and modulated heating techniques have been focusing on resolving technical issues of the most challenging research areas. The new capabilities have demonstrated clear benefits and provide new opportunities in research areasmore » including high-pressure melting, pressure-temperature-volume equations of state, chemical reaction, and time resolved studies.« less

Evolutions of Advanced Stamping CAE — Technology Adventures and Business Impact on Automotive Dies and Stamping

NASA Astrophysics Data System (ADS)

Wang, Chuantao (C. T.)

2005-08-01

In the past decade, sheet metal forming and die development has been transformed to a science-based and technology-driven engineering and manufacturing enterprise from a tryout-based craft. Stamping CAE, especially the sheet metal forming simulation, as one of the core components in digital die making and digital stamping, has played a key role in this historical transition. The stamping simulation technology and its industrial applications have greatly impacted automotive sheet metal product design, die developments, die construction and tryout, and production stamping. The stamping CAE community has successfully resolved the traditional formability problems such as splits and wrinkles. The evolution of the stamping CAE technology and business demands opens even greater opportunities and challenges to stamping CAE community in the areas of (1) continuously improving simulation accuracy, drastically reducing simulation time-in-system, and improving operationalability (friendliness), (2) resolving those historically difficult-to-resolve problems such as dimensional quality problems (springback and twist) and surface quality problems (distortion and skid/impact lines), (3) resolving total manufacturability problems in line die operations including blanking, draw/redraw, trim/piercing, and flanging, and (4) overcoming new problems in forming new sheet materials with new forming techniques. In this article, the author first provides an overview of the stamping CAE technology adventures and achievements, and industrial applications in the past decade. Then the author presents a summary of increasing manufacturability needs from the formability to total quality and total manufacturability of sheet metal stampings. Finally, the paper outlines the new needs and trends for continuous improvements and innovations to meet increasing challenges in line die formability and quality requirements in automotive stamping.

Understanding polymorphism in organic semiconductor thin films through nanoconfinement.

PubMed

Diao, Ying; Lenn, Kristina M; Lee, Wen-Ya; Blood-Forsythe, Martin A; Xu, Jie; Mao, Yisha; Kim, Yeongin; Reinspach, Julia A; Park, Steve; Aspuru-Guzik, Alán; Xue, Gi; Clancy, Paulette; Bao, Zhenan; Mannsfeld, Stefan C B

2014-12-10

Understanding crystal polymorphism is a long-standing challenge relevant to many fields, such as pharmaceuticals, organic semiconductors, pigments, food, and explosives. Controlling polymorphism of organic semiconductors (OSCs) in thin films is particularly important given that such films form the active layer in most organic electronics devices and that dramatic changes in the electronic properties can be induced even by small changes in the molecular packing. However, there are very few polymorphic OSCs for which the structure-property relationships have been elucidated so far. The major challenges lie in the transient nature of metastable forms and the preparation of phase-pure, highly crystalline thin films for resolving the crystal structures and evaluating the charge transport properties. Here we demonstrate that the nanoconfinement effect combined with the flow-enhanced crystal engineering technique is a powerful and likely material-agnostic method to identify existing polymorphs in OSC materials and to prepare the individual pure forms in thin films at ambient conditions. With this method we prepared high quality crystal polymorphs and resolved crystal structures of 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene), including a new polymorph discovered via in situ grazing incidence X-ray diffraction and confirmed by molecular mechanic simulations. We further correlated molecular packing with charge transport properties using quantum chemical calculations and charge carrier mobility measurements. In addition, we applied our methodology to a [1]benzothieno[3,2-b][1]1benzothiophene (BTBT) derivative and successfully stabilized its metastable form.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Chen, E-mail: chuang3@fsu.edu

A key element in the density functional embedding theory (DFET) is the embedding potential. We discuss two major issues related to the embedding potential: (1) its non-uniqueness and (2) the numerical difficulty for solving for it, especially for the spin-polarized systems. To resolve the first issue, we extend DFET to finite temperature: all quantities, such as the subsystem densities and the total system’s density, are calculated at a finite temperature. This is a physical extension since materials work at finite temperatures. We show that the embedding potential is strictly unique at T > 0. To resolve the second issue, wemore » introduce an efficient iterative embedding potential solver. We discuss how to relax the magnetic moments in subsystems and how to equilibrate the chemical potentials across subsystems. The solver is robust and efficient for several non-trivial examples, in all of which good quality spin-polarized embedding potentials were obtained. We also demonstrate the solver on an extended periodic system: iron body-centered cubic (110) surface, which is related to the modeling of the heterogeneous catalysis involving iron, such as the Fischer-Tropsch and the Haber processes. This work would make it efficient and accurate to perform embedding simulations of some challenging material problems, such as the heterogeneous catalysis and the defects of complicated spin configurations in electronic materials.« less

Radioisotope identification method for poorly resolved gamma-ray spectrum of nuclear security concern

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ninh, Giang Nguyen; Phongphaeth, Pengvanich, E-mail: phongphaeth.p@chula.ac.th; Nares, Chankow

Gamma-ray signal can be used as a fingerprint for radioisotope identification. In the context of radioactive and nuclear materials security at the border control point, the detection task can present a significant challenge due to various constraints such as the limited measurement time, the shielding conditions, and the noise interference. This study proposes a novel method to identify the signal of one or several radioisotopes from a poorly resolved gamma-ray spectrum. In this method, the noise component in the raw spectrum is reduced by the wavelet decomposition approach, and the removal of the continuum background is performed using the baselinemore » determination algorithm. Finally, the identification of radioisotope is completed using the matrix linear regression method. The proposed method has been verified by experiments using the poorly resolved gamma-ray signals from various scenarios including single source, mixing of natural uranium with five of the most common industrial radioactive sources (57Co, 60Co, 133Ba, 137Cs, and 241Am). The preliminary results show that the proposed algorithm is comparable with the commercial method.« less

Big Effect of Small Nanoparticles: A Shift in Paradigm for Polymer Nanocomposites

DOE PAGES

Cheng, Shiwang; Xie, Shi-Jie; Carrillo, Jan-Michael Y.; ...

2017-01-04

Polymer nanocomposites (PNCs) are important materials that are widely used in many current technologies and potentially have broader applications in the future due to their excellent property of tunability, light weight and low cost. But, expanding the limits in property enhancement remains a fundamental scientific challenge. We demonstrate that well-dispersed, small (diameter ~1.8 nm) nanoparticles with attractive interactions lead to unexpectedly large and qualitatively new changes in PNC structural dynamics in comparison to conventional composites based on particles of diameter ~10-50 nm. At the same time, the zero-shear viscosity at high temperatures remains comparable to that of the neat polymer,more » thereby retaining good processibility and resolving a major challenge in PNC applications. These results suggest that the nanoparticle mobility and relatively short lifetimes of nanoparticlepolymer associations open qualitatively new horizons in tunability of macroscopic properties in nanocomposites with high potential for the development of new functional materials.« less

Recent Advances in Flexible and Stretchable Bio-Electronic Devices Integrated with Nanomaterials.

PubMed

Choi, Suji; Lee, Hyunjae; Ghaffari, Roozbeh; Hyeon, Taeghwan; Kim, Dae-Hyeong

2016-06-01

Flexible and stretchable electronics and optoelectronics configured in soft, water resistant formats uniquely address seminal challenges in biomedicine. Over the past decade, there has been enormous progress in the materials, designs, and manufacturing processes for flexible/stretchable system subcomponents, including transistors, amplifiers, bio-sensors, actuators, light emitting diodes, photodetector arrays, photovoltaics, energy storage elements, and bare die integrated circuits. Nanomaterials prepared using top-down processing approaches and synthesis-based bottom-up methods have helped resolve the intrinsic mechanical mismatch between rigid/planar devices and soft/curvilinear biological structures, thereby enabling a broad range of non-invasive, minimally invasive, and implantable systems to address challenges in biomedicine. Integration of therapeutic functional nanomaterials with soft bioelectronics demonstrates therapeutics in combination with unconventional diagnostics capabilities. Recent advances in soft materials, devices, and integrated systems are reviewes, with representative examples that highlight the utility of soft bioelectronics for advanced medical diagnostics and therapies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Advances in Raman spectroscopy for In Situ Identification of Minerals and Organics on Diverse Planetary Surfaces: from Mars to Titan

NASA Astrophysics Data System (ADS)

Blacksberg, J.; Alerstam, E.; Maruyama, Y.; Cochrane, C.; Rossman, G. R.

2015-12-01

We present recent developments in time-resolved Raman spectroscopy for in situ planetary surface exploration, aimed at identification of both minerals and organics. Raman is a non-destructive surface technique that requires no sample preparation. Raman spectra are highly material specific and can be used for identification of a wide range of unknown samples. In combination with micro-scale imaging and point mapping, Raman spectroscopy can be used to directly interrogate rocks and regolith materials, while placing compositional analyses within a microtextural context, essential for understanding surface evolutionary pathways. Due to these unique capabilities, Raman spectroscopy is of great interest for the exploration of all rocky and icy bodies, for example Mars, Venus, the Moon, Mars' moons, asteroids, comets, Europa, and Titan. In this work, we focus on overcoming one of the most difficult challenges faced in Raman spectroscopy: interference from background fluorescence of the very minerals and organics that we wish to characterize. To tackle this problem we use time-resolved Raman spectroscopy, which separates the Raman from background processes in the time domain. This same technique also enables operation in daylight without the need for light shielding. Two key components are essential for the success of this technique: a fast solid-state detector and a short-pulse laser. Our detector is a custom developed Single Photon Avalanche Diode (SPAD) array, capable of sub-ns time-gating. Our pulsed lasers are solid-state miniature pulsed microchip lasers. We discuss optimization of laser and detector parameters for our application. We then present Raman spectra of particularly challenging planetary analog samples to demonstrate the unique capabilities of this time-resolved Raman instrument, for example, Mars-analog clays and Titan-analog organics. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA).

Strategies for the Challenges Facing Women in Higher Education Administration.

ERIC Educational Resources Information Center

Rehnke, Mary Ann

Women administrators in higher education must deal not only with the usual challenges facing administrators (decision-making, resolving conflict, and advancing professionally), but also with the effects of sex stereotyping. Women are not seen as decision-makers, nor as conflict-resolvers, and are often viewed as supporting personnel rather than…

Bragg coherent diffractive imaging of single-grain defect dynamics in polycrystalline films

NASA Astrophysics Data System (ADS)

Yau, Allison; Cha, Wonsuk; Kanan, Matthew W.; Stephenson, G. Brian; Ulvestad, Andrew

2017-05-01

Polycrystalline material properties depend on the distribution and interactions of their crystalline grains. In particular, grain boundaries and defects are crucial in determining their response to external stimuli. A long-standing challenge is thus to observe individual grains, defects, and strain dynamics inside functional materials. Here we report a technique capable of revealing grain heterogeneity, including strain fields and individual dislocations, that can be used under operando conditions in reactive environments: grain Bragg coherent diffractive imaging (gBCDI). Using a polycrystalline gold thin film subjected to heating, we show how gBCDI resolves grain boundary and dislocation dynamics in individual grains in three-dimensional detail with 10-nanometer spatial and subangstrom displacement field resolution. These results pave the way for understanding polycrystalline material response under external stimuli and, ideally, engineering particular functions.

Excited state and charge-carrier dynamics in perovskite solar cell materials

NASA Astrophysics Data System (ADS)

Ponseca, Carlito S., Jr.; Tian, Yuxi; Sundström, Villy; Scheblykin, Ivan G.

2016-02-01

Organo-metal halide perovskites (OMHPs) have attracted enormous interest in recent years as materials for application in optoelectronics and solar energy conversion. These hybrid semiconductors seem to have the potential to challenge traditional silicon technology. In this review we will give an account of the recent development in the understanding of the fundamental light-induced processes in OMHPs from charge-photo generation, migration of charge carries through the materials and finally their recombination. Our and other literature reports on time-resolved conductivity, transient absorption and photoluminescence properties are used to paint a picture of how we currently see the fundamental excited state and charge-carrier dynamics. We will also show that there is still no fully coherent picture of the processes in OMHPs and we will indicate the problems to be solved by future research.

Bragg coherent diffractive imaging of single-grain defect dynamics in polycrystalline films

DOE PAGES

Yau, Allison; Cha, Wonsuk; Kanan, Matthew W.; ...

2017-05-19

Polycrystalline material properties depend on the distribution and interactions of their crystalline grains. In particular, grain boundaries and defects are crucial in determining their response to external stimuli. A long-standing challenge is thus to observe individual grains, defects, and strain dynamics inside functional materials. Here we report a technique capable of revealing grain heterogeneity, including strain fields and individual dislocations, that can be used under operando conditions in reactive environments: grain Bragg coherent diffractive imaging (gBCDI). Using a polycrystalline gold thin film subjected to heating, we show how gBCDI resolves grain boundary and dislocation dynamics in individual grains in three-dimensionalmore » detail with 10-nanometer spatial and subangstrom displacement field resolution. Finally, these results pave the way for understanding polycrystalline material response under external stimuli and, ideally, engineering particular functions.« less

Resolving ultrafast exciton migration in organic solids at the nanoscale

NASA Astrophysics Data System (ADS)

Penwell, Samuel B.; Ginsberg, Lucas D. S.; Noriega, Rodrigo; Ginsberg, Naomi S.

2017-11-01

Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.

The valence-fluctuating ground state of plutonium

DOE PAGES

Janoschek, Marc; Das, Pinaki; Chakrabarti, Bismayan; ...

2015-07-10

A central issue in material science is to obtain understanding of the electronic correlations that control complex materials. Such electronic correlations frequently arise because of the competition of localized and itinerant electronic degrees of freedom. Although the respective limits of well-localized or entirely itinerant ground states are well understood, the intermediate regime that controls the functional properties of complex materials continues to challenge theoretical understanding. We have used neutron spectroscopy to investigate plutonium, which is a prototypical material at the brink between bonding and nonbonding configurations. In addition, our study reveals that the ground state of plutonium is governed bymore » valence fluctuations, that is, a quantum mechanical superposition of localized and itinerant electronic configurations as recently predicted by dynamical mean field theory. Our results not only resolve the long-standing controversy between experiment and theory on plutonium’s magnetism but also suggest an improved understanding of the effects of such electronic dichotomy in complex materials.« less

Nondestructive Evaluation of Advanced Materials with X-ray Phase Mapping

NASA Technical Reports Server (NTRS)

Hu, Zhengwei

2005-01-01

X-ray radiation has been widely used for imaging applications since Rontgen first discovered X-rays over a century ago. Its large penetration depth makes it ideal for the nondestructive visualization of the internal structure and/or defects of materials unobtainable otherwise. Currently used nondestructive evaluation (NDE) tools, X-ray radiography and tomography, are absorption-based, and work well in heavy-element materials where density or composition variations due to internal structure or defects are high enough to produce appreciable absorption contrast. However, in many cases where materials are light-weight and/or composites that have similar mass absorption coefficients, the conventional absorption-based X-ray methods for NDE become less useful. Indeed, the light-weight and ultra-high-strength requirements for the most advanced materials used or developed for current flight mission and future space exploration pose a great challenge to the standard NDE tools in that the absorption contrast arising from the internal structure of these materials is often too weak to be resolved. In this presentation, a solution to the problem, the use of phase information of X-rays for phase contrast X-ray imaging, will be discussed, along with a comparison between the absorption-based and phase-contrast imaging methods. Latest results on phase contrast X-ray imaging of lightweight Space Shuttle foam in 2D and 3D will be presented, demonstrating new opportunities to solve the challenging issues encountered in advanced materials development and processing.

Emergence of charge density waves and a pseudogap in single-layer TiTe2.

PubMed

Chen, P; Pai, Woei Wu; Chan, Y-H; Takayama, A; Xu, C-Z; Karn, A; Hasegawa, S; Chou, M Y; Mo, S-K; Fedorov, A-V; Chiang, T-C

2017-09-11

Two-dimensional materials constitute a promising platform for developing nanoscale devices and systems. Their physical properties can be very different from those of the corresponding three-dimensional materials because of extreme quantum confinement and dimensional reduction. Here we report a study of TiTe 2 from the single-layer to the bulk limit. Using angle-resolved photoemission spectroscopy and scanning tunneling microscopy and spectroscopy, we observed the emergence of a (2 × 2) charge density wave order in single-layer TiTe 2 with a transition temperature of 92 ± 3 K. Also observed was a pseudogap of about 28 meV at the Fermi level at 4.2 K. Surprisingly, no charge density wave transitions were observed in two-layer and multi-layer TiTe 2 , despite the quasi-two-dimensional nature of the material in the bulk. The unique charge density wave phenomenon in the single layer raises intriguing questions that challenge the prevailing thinking about the mechanisms of charge density wave formation.Due to reduced dimensionality, the properties of 2D materials are often different from their 3D counterparts. Here, the authors identify the emergence of a unique charge density wave (CDW) order in monolayer TiTe 2 that challenges the current understanding of CDW formation.

Survey of Dust Issues for Lunar Seals and the RESOLVE Project

NASA Technical Reports Server (NTRS)

Proctor, Margaret P.; Dempsey, Paula

2006-01-01

Lunar dust poses a technical challenge for sealing applications on the moon. A survey of seals used in Apollo lunar missions is presented as well as lunar soil characteristics and a description of the lunar environment. Seal requirements and technical challenges for the volatiles characterization oven and hydrogen reduction reaction chamber of the RESOLVE project are discussed. The purpose of the RESOLVE project is to find water or ice in lunar soil and demonstrate the ability to produce water, and hence oxygen and hydrogen, from lunar regolith for life support and propellants.

Material separation in x-ray CT with energy resolved photon-counting detectors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Xiaolan; Meier, Dirk; Taguchi, Katsuyuki

Purpose: The objective of the study was to demonstrate that, in x-ray computed tomography (CT), more than two types of materials can be effectively separated with the use of an energy resolved photon-counting detector and classification methodology. Specifically, this applies to the case when contrast agents that contain K-absorption edges in the energy range of interest are present in the object. This separation is enabled via the use of recently developed energy resolved photon-counting detectors with multiple thresholds, which allow simultaneous measurements of the x-ray attenuation at multiple energies. Methods: To demonstrate this capability, we performed simulations and physical experimentsmore » using a six-threshold energy resolved photon-counting detector. We imaged mouse-sized cylindrical phantoms filled with several soft-tissue-like and bone-like materials and with iodine-based and gadolinium-based contrast agents. The linear attenuation coefficients were reconstructed for each material in each energy window and were visualized as scatter plots between pairs of energy windows. For comparison, a dual-kVp CT was also simulated using the same phantom materials. In this case, the linear attenuation coefficients at the lower kVp were plotted against those at the higher kVp. Results: In both the simulations and the physical experiments, the contrast agents were easily separable from other soft-tissue-like and bone-like materials, thanks to the availability of the attenuation coefficient measurements at more than two energies provided by the energy resolved photon-counting detector. In the simulations, the amount of separation was observed to be proportional to the concentration of the contrast agents; however, this was not observed in the physical experiments due to limitations of the real detector system. We used the angle between pairs of attenuation coefficient vectors in either the 5-D space (for non-contrast-agent materials using energy resolved photon-counting acquisition) or a 2-D space (for contrast agents using energy resolved photon-counting acquisition and all materials using dual-kVp acquisition) as a measure of the degree of separation. Compared to dual-kVp techniques, an energy resolved detector provided a larger separation and the ability to separate different target materials using measurements acquired in different energy window pairs with a single x-ray exposure. Conclusions: We concluded that x-ray CT with an energy resolved photon-counting detector with more than two energy windows allows the separation of more than two types of materials, e.g., soft-tissue-like, bone-like, and one or more materials with K-edges in the energy range of interest. Separating material types using energy resolved photon-counting detectors has a number of advantages over dual-kVp CT in terms of the degree of separation and the number of materials that can be separated simultaneously.« less

High-Density Stretchable Electrode Grids for Chronic Neural Recording.

PubMed

Tybrandt, Klas; Khodagholy, Dion; Dielacher, Bernd; Stauffer, Flurin; Renz, Aline F; Buzsáki, György; Vörös, János

2018-04-01

Electrical interfacing with neural tissue is key to advancing diagnosis and therapies for neurological disorders, as well as providing detailed information about neural signals. A challenge for creating long-term stable interfaces between electronics and neural tissue is the huge mechanical mismatch between the systems. So far, materials and fabrication processes have restricted the development of soft electrode grids able to combine high performance, long-term stability, and high electrode density, aspects all essential for neural interfacing. Here, this challenge is addressed by developing a soft, high-density, stretchable electrode grid based on an inert, high-performance composite material comprising gold-coated titanium dioxide nanowires embedded in a silicone matrix. The developed grid can resolve high spatiotemporal neural signals from the surface of the cortex in freely moving rats with stable neural recording quality and preserved electrode signal coherence during 3 months of implantation. Due to its flexible and stretchable nature, it is possible to minimize the size of the craniotomy required for placement, further reducing the level of invasiveness. The material and device technology presented herein have potential for a wide range of emerging biomedical applications. © 2018 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lechman, Jeremy B.; Battaile, Corbett Chandler.; Bolintineanu, Dan

This report summarizes a project in which the authors sought to develop and deploy: (i) experimental techniques to elucidate the complex, multiscale nature of thermal transport in particle-based materials; and (ii) modeling approaches to address current challenges in predicting performance variability of materials (e.g., identifying and characterizing physical- chemical processes and their couplings across multiple length and time scales, modeling information transfer between scales, and statically and dynamically resolving material structure and its evolution during manufacturing and device performance). Experimentally, several capabilities were successfully advanced. As discussed in Chapter 2 a flash diffusivity capability for measuring homogeneous thermal conductivity ofmore » pyrotechnic powders (and beyond) was advanced; leading to enhanced characterization of pyrotechnic materials and properties impacting component development. Chapter 4 describes success for the first time, although preliminary, in resolving thermal fields at speeds and spatial scales relevant to energetic components. Chapter 7 summarizes the first ever (as far as the authors know) application of TDTR to actual pyrotechnic materials. This is the first attempt to actually characterize these materials at the interfacial scale. On the modeling side, new capabilities in image processing of experimental microstructures and direct numerical simulation on complicated structures were advanced (see Chapters 3 and 5). In addition, modeling work described in Chapter 8 led to improved prediction of interface thermal conductance from first principles calculations. Toward the second point, for a model system of packed particles, significant headway was made in implementing numerical algorithms and collecting data to justify the approach in terms of highlighting the phenomena at play and pointing the way forward in developing and informing the kind of modeling approach originally envisioned (see Chapter 6). In both cases much more remains to be accomplished.« less

Nanoscale Characterization of Carrier Dynamic and Surface Passivation in InGaN/GaN Multiple Quantum Wells on GaN Nanorods.

PubMed

Chen, Weijian; Wen, Xiaoming; Latzel, Michael; Heilmann, Martin; Yang, Jianfeng; Dai, Xi; Huang, Shujuan; Shrestha, Santosh; Patterson, Robert; Christiansen, Silke; Conibeer, Gavin

2016-11-23

Using advanced two-photon excitation confocal microscopy, associated with time-resolved spectroscopy, we characterize InGaN/GaN multiple quantum wells on nanorod heterostructures and demonstrate the passivation effect of a KOH treatment. High-quality InGaN/GaN nanorods were fabricated using nanosphere lithography as a candidate material for light-emitting diode devices. The depth- and time-resolved characterization at the nanoscale provides detailed carrier dynamic analysis helpful for understanding the optical properties. The nanoscale spatially resolved images of InGaN quantum well and defects were acquired simultaneously. We demonstrate that nanorod etching improves light extraction efficiency, and a proper KOH treatment has been found to reduce the surface defects efficiently and enhance the luminescence. The optical characterization techniques provide depth-resolved and time-resolved carrier dynamics with nanoscale spatially resolved mapping, which is crucial for a comprehensive and thorough understanding of nanostructured materials and provides novel insight into the improvement of materials fabrication and applications.

Toward picosecond time-resolved X-ray absorption studies of interfacial photochemistry

NASA Astrophysics Data System (ADS)

Gessner, Oliver; Mahl, Johannes; Neppl, Stefan

2016-05-01

We report on the progress toward developing a novel picosecond time-resolved transient X-ray absorption spectroscopy (TRXAS) capability for time-domain studies of interfacial photochemistry. The technique is based on the combination of a high repetition rate picosecond laser system with a time-resolved X-ray fluorescent yield setup that may be used for the study of radiation sensitive materials and X-ray spectroscopy compatible photoelectrochemical (PEC) cells. The mobile system is currently deployed at the Advanced Light Source (ALS) and may be used in all operating modes (two-bunch and multi-bunch) of the synchrotron. The use of a time-stamping technique enables the simultaneous recording of TRXAS spectra with delays between the exciting laser pulses and the probing X-ray pulses spanning picosecond to nanosecond temporal scales. First results are discussed that demonstrate the viability of the method to study photoinduced dynamics in transition metal-oxide semiconductor (SC) samples under high vacuum conditions and at SC-liquid electrolyte interfaces during photoelectrochemical water splitting. Opportunities and challenges are outlined to capture crucial short-lived intermediates of photochemical processes with the technique. This work was supported by the Department of Energy Office of Science Early Career Research Program.

Modeling defect cluster evolution in irradiated structural materials: Focus on comparing to high-resolution experimental characterization studies

DOE PAGES

Wirth, Brian D.; Hu, Xunxiang; Kohnert, Aaron; ...

2015-03-02

Exposure of metallic structural materials to irradiation environments results in significant microstructural evolution, property changes, and performance degradation, which limits the extended operation of current generation light water reactors and restricts the design of advanced fission and fusion reactors. Further, it is well recognized that these irradiation effects are a classic example of inherently multiscale phenomena and that the mix of radiation-induced features formed and the corresponding property degradation depend on a wide range of material and irradiation variables. This inherently multiscale evolution emphasizes the importance of closely integrating models with high-resolution experimental characterization of the evolving radiation-damaged microstructure. Lastly,more » this article provides a review of recent models of the defect microstructure evolution in irradiated body-centered cubic materials, which provide good agreement with experimental measurements, and presents some outstanding challenges, which will require coordinated high-resolution characterization and modeling to resolve.« less

Synthesis and characterization of a nanocrystalline diamond aerogel

PubMed Central

Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.; Laurence, Ted A.; Kilcoyne, A. L. David; Wang, Yinmin; Willey, Trevor M.; Visbeck, Kenneth S.; Fakra, Sirine C.; Evans, William J.; Zaug, Joseph M.; Satcher, Joe H.

2011-01-01

Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel’s void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material reveal the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel. PMID:21555550

Synthesis and characterization of a nanocrystalline diamond aerogel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pauzauskie, Peter J.; Crowhurst, Jonathan C.; Worsley, Marcus A.

2011-07-06

Aerogel materials have myriad scientific and technological applications due to their large intrinsic surface areas and ultralow densities. However, creating a nanodiamond aerogel matrix has remained an outstanding and intriguing challenge. Here we report the high-pressure, high-temperature synthesis of a diamond aerogel from an amorphous carbon aerogel precursor using a laser-heated diamond anvil cell. Neon is used as a chemically inert, near-hydrostatic pressure medium that prevents collapse of the aerogel under pressure by conformally filling the aerogel's void volume. Electron and X-ray spectromicroscopy confirm the aerogel morphology and composition of the nanodiamond matrix. Time-resolved photoluminescence measurements of recovered material revealmore » the formation of both nitrogen- and silicon- vacancy point-defects, suggesting a broad range of applications for this nanocrystalline diamond aerogel.« less

Understanding teacher responses to constructivist learning environments: Challenges and resolutions

NASA Astrophysics Data System (ADS)

Rosenfeld, Melodie; Rosenfeld, Sherman

2006-05-01

The research literature is just beginning to uncover factors involved in sustaining constructivist learning environments, such as Project-Based Learning (PBL). Our case study investigates teacher responses to the challenges of constructivist environments, since teachers can play strong roles in supporting or undermining even the best constructivist environments or materials. We were invited to work as mediators with a middle-school science staff that was experiencing conflicts regarding two learning environments, PBL (which was the school's politically correc learning environment) and traditional. With mediated group workshops, teachers were sensitized to their own and colleagues' individual learning differences (ILDs), as measured by two styles inventories (the LSI - Kolb, 1976; and the LCI - Johnston & Dainton, 1997). Using these inventories, a learning-environment questionnaire, field notes, and delayed interviews a year later, we found that there was a relationship between teachers' preferred styles, epistemological beliefs, and their preferred teaching environment. Moreover, when the participating teachers, including early-adopters and nonvolunteers to PBL, became more sensitive to their colleagues' preferences, many staff conflicts were resolved and some mismatched teachers expressed more openness to PBL. We argue that having teachers understand their own ILDs and related responses to constructivist learning environments can contribute to resolving staff conflicts and sustaining such environments. We present a cognitive model and a strategy which illustrate this argument.

Nano Traditional Chinese Medicine: Current Progresses and Future Challenges.

PubMed

Huang, Yi; Zhao, Yinglan; Liu, Fang; Liu, Songqing

2015-01-01

Nano traditional Chinese medicine (nano TCM) refers to bioactive ingredients, bioactive parts, medicinal materials or complex prescription, being approximately 100 nm in size, which are processed by nanotechnology. Nano TCM is a product of the TCM modernization, and is an application of nanotechnology in the field of TCM. This article reviews literatures on researches of nano TCM, which were published in the past 15 years. Different nanotechnologies have been used in preparation of Nano TCM in view of the varying aims of the study. The mechanical crushing technology is the main approach for nanolization of TCM material and complex prescription, and nanoparticulate drug delivery systems is the main approach for nanolization of bioactive ingredients or bioactive parts in TCM. Nano TCM has a number of advantages, for example, enhancing the bioavailability of TCM, reducing the adverse effects of TCM, achieving sustained release, attaining targeted delivery, enhancing pharmacological effects and improving the administration route of TCM. However, there are still many problems that must be resolved in nano TCM research. The main challenges to nano TCM include the theory system of TCM modernization, preparation technology, safety and stability, etc.

Dual- and Multi-Energy CT: Principles, Technical Approaches, and Clinical Applications

PubMed Central

Leng, Shuai; Yu, Lifeng; Fletcher, Joel G.

2015-01-01

In x-ray computed tomography (CT), materials having different elemental compositions can be represented by identical pixel values on a CT image (ie, CT numbers), depending on the mass density of the material. Thus, the differentiation and classification of different tissue types and contrast agents can be extremely challenging. In dual-energy CT, an additional attenuation measurement is obtained with a second x-ray spectrum (ie, a second “energy”), allowing the differentiation of multiple materials. Alternatively, this allows quantification of the mass density of two or three materials in a mixture with known elemental composition. Recent advances in the use of energy-resolving, photon-counting detectors for CT imaging suggest the ability to acquire data in multiple energy bins, which is expected to further improve the signal-to-noise ratio for material-specific imaging. In this review, the underlying motivation and physical principles of dual- or multi-energy CT are reviewed and each of the current technical approaches is described. In addition, current and evolving clinical applications are introduced. © RSNA, 2015 PMID:26302388

Imaging inert fluorinated gases in cracks: perhaps in David's ankles.

PubMed

Kuethe, Dean O; Scholz, Markus D; Fantazzini, Paola

2007-05-01

Inspired by the challenge of determining the nature of cracks on the ankles of Michelangelo's statue David, we discovered that one can image SF(6) gas in cracks in marble samples with alacrity. The imaging method produces images of gas with a signal-to-noise ratio (SNR) of 100-250, which is very high for magnetic resonance imaging (MRI) in general, let alone for an image of a gas at thermal equilibrium polarization. To put this unusual SNR in better perspective, we imaged SF(6) in a crack in a marble sample and imaged the lung tissue of a live rat (a more familiar variety of sample to many MRI scientists) using the same pulse sequence, the same size coils and the same MRI system. In both cases, we try to image subvoxel thin sheets of material that should appear bright against a darker background. By choosing imaging parameters appropriate for the different relaxation properties of SF(6) gas versus lung tissue and by choosing voxel sizes appropriate for the different goals of detecting subvoxel cracks on marble versus resolving subvoxel thin sheets of tissue, the SNR for voxels full of material was 220 and 14 for marble and lung, respectively. A major factor is that we chose large voxels to optimize SNR for detecting small cracks and we chose small voxels for resolving lung features at the expense of SNR. Imaging physics will cooperate to provide detection of small cracks on marble, but David's size poses a challenge for magnet designers. For the modest goal of imaging cracks in the left ankle, we desire a magnet with an approximately 32-cm gap and a flux density of approximately 0.36 T that weighs <500 kg.

Femtosecond electron imaging of defect-modulated phonon dynamics

PubMed Central

Cremons, Daniel R.; Plemmons, Dayne A.; Flannigan, David J.

2016-01-01

Precise manipulation and control of coherent lattice oscillations via nanostructuring and phonon-wave interference has the potential to significantly impact a broad array of technologies and research areas. Resolving the dynamics of individual phonons in defect-laden materials presents an enormous challenge, however, owing to the interdependent nanoscale and ultrafast spatiotemporal scales. Here we report direct, real-space imaging of the emergence and evolution of acoustic phonons at individual defects in crystalline WSe2 and Ge. Via bright-field imaging with an ultrafast electron microscope, we are able to image the sub-picosecond nucleation and the launch of wavefronts at step edges and resolve dispersion behaviours during propagation and scattering. We discover that the appearance of speed-of-sound (for example, 6 nm ps−1) wavefronts are influenced by spatially varying nanoscale strain fields, taking on the appearance of static bend contours during propagation. These observations provide unprecedented insight into the roles played by individual atomic and nanoscale features on acoustic-phonon dynamics. PMID:27079790

Resolving ultrafast exciton migration in organic solids at the nanoscale.

PubMed

Penwell, Samuel B; Ginsberg, Lucas D S; Noriega, Rodrigo; Ginsberg, Naomi S

2017-11-01

Effectiveness of molecular-based light harvesting relies on transport of excitons to charge-transfer sites. Measuring exciton migration, however, has been challenging because of the mismatch between nanoscale migration lengths and the diffraction limit. Instead of using bulk substrate quenching methods, here we define quenching boundaries all-optically with sub-diffraction resolution, thus characterizing spatiotemporal exciton migration on its native nanometre and picosecond scales. By transforming stimulated emission depletion microscopy into a time-resolved ultrafast approach, we measure a 16-nm migration length in poly(2,5-di(hexyloxy)cyanoterephthalylidene) conjugated polymer films. Combined with Monte Carlo exciton hopping simulations, we show that migration in these films is essentially diffusive because intrinsic chromophore energetic disorder is comparable to chromophore inhomogeneous broadening. Our approach will enable previously unattainable correlation of local material structure to exciton migration character, applicable not only to photovoltaic or display-destined organic semiconductors but also to explaining the quintessential exciton migration exhibited in photosynthesis.

Laser-induced phase separation of silicon carbide

PubMed Central

Choi, Insung; Jeong, Hu Young; Shin, Hyeyoung; Kang, Gyeongwon; Byun, Myunghwan; Kim, Hyungjun; Chitu, Adrian M.; Im, James S.; Ruoff, Rodney S.; Choi, Sung-Yool; Lee, Keon Jae

2016-01-01

Understanding the phase separation mechanism of solid-state binary compounds induced by laser–material interaction is a challenge because of the complexity of the compound materials and short processing times. Here we present xenon chloride excimer laser-induced melt-mediated phase separation and surface reconstruction of single-crystal silicon carbide and study this process by high-resolution transmission electron microscopy and a time-resolved reflectance method. A single-pulse laser irradiation triggers melting of the silicon carbide surface, resulting in a phase separation into a disordered carbon layer with partially graphitic domains (∼2.5 nm) and polycrystalline silicon (∼5 nm). Additional pulse irradiations cause sublimation of only the separated silicon element and subsequent transformation of the disordered carbon layer into multilayer graphene. The results demonstrate viability of synthesizing ultra-thin nanomaterials by the decomposition of a binary system. PMID:27901015

Direct Phase-resolved strain Measurements in Cementitious materials (Prop.2001-061)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Watkins, Thomas R; BIernacki, Joseph J.; Wang, R

J. J. Biernacki, S. E. Mikel, C. J. Parnham, R. Wang, J. Bai, T. R. Watkins, M. Lance and C. R. Hubbard, "Direct Phase-Resolved Strain Measurements in Cementitious Materials," pp. 57-72 in Transport Properties and Concrete Quality: Materials Science of Concrete, Special Volume. Edited by B. Mobasher and J. P Skalny, ACerS, Westerville, OH, 2007.

Educational Leadership: Key Challenges and Ethical Tensions

ERIC Educational Resources Information Center

Duignan, Patrick

2007-01-01

"Educational Leadership" is a major research book on contemporary leadership challenges for educational leaders. In this groundbreaking new work, educational leaders in schools, including teachers, are provided with ways of analysing and resolving common but complex leadership challenges. Ethical tensions inherent in these challenges are…

Nanomaterials and Water Purification: Opportunities and Challenges

NASA Astrophysics Data System (ADS)

Savage, Nora; Diallo, Mamadou S.

2005-10-01

Advances in nanoscale science and engineering suggest that many of the current problems involving water quality could be resolved or greatly ameliorated using nanosorbents, nanocatalysts, bioactive nanoparticles, nanostructured catalytic membranes and nanoparticle enhanced filtration among other products and processes resulting from the development of nanotechnology. Innovations in the development of novel technologies to desalinate water are among the most exciting and promising. Additionally, nanotechnology-derived products that reduce the concentrations of toxic compounds to sub-ppb levels can assist in the attainment of water quality standards and health advisories. This article gives an overview of the use of nanomaterials in water purification. We highlight recent advances on the development of novel nanoscale materials and processes for treatment of surface water, groundwater and industrial wastewater contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses. In addition, we discuss some challenges associated with the development of cost effective and environmentally acceptable functional nanomaterials for water purification.

Functional Stability of the Human Kappa Opioid Receptor Reconstituted in Nanodiscs Revealed by a Time-Resolved Scintillation Proximity Assay

PubMed Central

Hansen, Randi Westh; Wang, Xiaole; Golab, Agnieszka; Bornert, Olivier; Oswald, Christine; Wagner, Renaud; Martinez, Karen Laurence

2016-01-01

Long-term functional stability of isolated membrane proteins is crucial for many in vitro applications used to elucidate molecular mechanisms, and used for drug screening platforms in modern pharmaceutical industry. Compared to soluble proteins, the understanding at the molecular level of membrane proteins remains a challenge. This is partly due to the difficulty to isolate and simultaneously maintain their structural and functional stability, because of their hydrophobic nature. Here we show, how scintillation proximity assay can be used to analyze time-resolved high-affinity ligand binding to membrane proteins solubilized in various environments. The assay was used to establish conditions that preserved the biological function of isolated human kappa opioid receptor. In detergent solution the receptor lost high-affinity ligand binding to a radiolabelled ligand within minutes at room temperature. After reconstitution in Nanodiscs made of phospholipid bilayer the half-life of high-affinity ligand binding to the majority of receptors increased 70-fold compared to detergent solubilized receptors—a level of stability that is appropriate for further downstream applications. Time-resolved scintillation proximity assay has the potential to screen numerous conditions in parallel to obtain high levels of stable and active membrane proteins, which are intrinsically unstable in detergent solution, and with minimum material consumption. PMID:27035823

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, P.; Pai, Woei Wu; Chan, Y. -H.

Two-dimensional materials constitute a promising platform for developing nanoscale devices and systems. Their physical properties can be very different from those of the corresponding three-dimensional materials because of extreme quantum confinement and dimensional reduction. Here in this paper we report a study of TiTe 2 from the single-layer to the bulk limit. Using angle-resolved photoemission spectroscopy and scanning tunneling microscopy and spectroscopy, we observed the emergence of a (2 × 2) charge density wave order in single-layer TiTe 2 with a transition temperature of 92 ± 3 K. Also observed was a pseudogap of about 28 meV at the Fermimore » level at 4.2 K. Surprisingly, no charge density wave transitions were observed in two-layer and multi-layer TiTe 2 , despite the quasi-two-dimensional nature of the material in the bulk. The unique charge density wave phenomenon in the single layer raises intriguing questions that challenge the prevailing thinking about the mechanisms of charge density wave formation.« less

Challenges of the ward round teaching based on the experiences of medical clinical teachers

PubMed Central

Arabshahi, Kamran Soltani; Haghani, Fariba; Bigdeli, Shoaleh; Omid, Athar; Adibi, Peyman

2015-01-01

Background: Holding educational sessions in a clinical environment is a major concern for faculty members because of its special difficulties and restrictions. This study attempts to recognize the challenges of the ward round teaching through investigating the experiences of clinical teachers in 2011. Materials and Methods: This qualitative research is carried out through purposive sampling with maximum variation from among the clinical teachers of major departments in Isfahan University of Medical Sciences (9 persons). The sampling continued until data saturation. Data were collected through semi-structured interview and analyzed through Collaizzi method. Data reliability and validity was confirmed through the four aspects of Lincoln and Guba method (credibility, conformability, transferability, and dependability). Results: Three major themes and their related sub-themes (minor themes) were found out including the factors related to the triad of clinical teaching (patient, learner, and clinical teacher) (concern about patient's welfare, poor preparation, lack of motivation, ethical problems), factors related to the educational environment (stressful environment, humiliating environment and poor communication) and the factors related to the educational system of the clinical environment (poor organizing and arrangement of resources, poor system's monitoring, bad planning and inadequate resource). Conclusion: Ward round teaching has many concerns for teachers, and this should be recognized and resolved by authorities and teachers. If these problems are not resolved, it would affect the quality of clinical teaching. PMID:26109975

Superior pseudocapacitive behavior of confined lignin nanocrystals for renewable energy-storage materials.

PubMed

Kim, Sung-Kon; Kim, Yun Ki; Lee, Hyunjoo; Lee, Sang Bok; Park, Ho Seok

2014-04-01

Strong demand for high-performance energy-storage devices has currently motivated the development of emerging capacitive materials that can resolve their critical challenge (i.e., low energy density) and that are renewable and inexpensive energy-storage materials from both environmental and economic viewpoints. Herein, the pseudocapacitive behavior of lignin nanocrystals confined on reduced graphene oxides (RGOs) used for renewable energy-storage materials is demonstrated. The excellent capacitive characteristics of the renewable hybrid electrodes were achieved by synergizing the fast and reversible redox charge transfer of surface-confined quinone and the interplay with electron-conducting RGOs. Accordingly, pseudocapacitors with remarkable rate and cyclic performances (~96 % retention after 3000 cycles) showed a maximum capacitance of 432 F g(-1), which was close to the theoretical capacitance of 482 F g(-1) and sixfold higher than that of RGO (93 F g(-1)). The chemical strategy delineated herein paves the way to develop advanced renewable electrodes for energy-storage applications and understand the redox chemistry of electroactive biomaterials. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Improved algorithm for estimating optical properties of food and biological materials using spatially-resolved diffuse reflectance

USDA-ARS?s Scientific Manuscript database

In this research, the inverse algorithm for estimating optical properties of food and biological materials from spatially-resolved diffuse reflectance was optimized in terms of data smoothing, normalization and spatial region of reflectance profile for curve fitting. Monte Carlo simulation was used ...

Exploration Challenges: Transferring Ground Repair Techniques to Space Flight Application

NASA Technical Reports Server (NTRS)

McLemore, Carole A.; Kennedy, James P.; Rose, Frederick A.; Evans, Brian W.

2007-01-01

Fulfilling NASA's Vision for Space Exploration will demand an extended presence in space at distances from our home planet that exceed our current experience in space logistics and maintenance. The ability to perform repairs in lieu of the customary Orbital Replacement Unit (ORU) process where a faulty part is replaced will be elevated from contingency to routine to sustain operations. The use and cost effectiveness of field repairs for ground based operations in industry and the military have advanced with the development of technology in new materials, new repair techniques and new equipment. The unique environments, accessibility constraints and Extra Vehicular Activity (EVA) issues of space operations will require extensive assessment and evolution of these technologies to provide an equivalent and expected level of assurance to mission success. Challenges include the necessity of changes in design philosophy and policy, extremes in thermal cycling, disruptive forces (such as static charge and wind entrainment) on developed methods for control of materials, dramatically increased volatility of chemicals for cleaning and other compounds due to extremely low pressures, the limits imposed on dexterity and maneuverability by current EVA equipment and practices, and the necessity of unique verification methodology. This paper describes these challenges in and discusses the effects on the established ground techniques for repair. The paper also describes the leading repair methodology candidates and their beneficial attributes for resolving these issues with the evolution of technology.

Modeling Pair Distribution Functions of Rare-Earth Phosphate Glasses Using Principal Component Analysis.

PubMed

Cole, Jacqueline M; Cheng, Xie; Payne, Michael C

2016-11-07

The use of principal component analysis (PCA) to statistically infer features of local structure from experimental pair distribution function (PDF) data is assessed on a case study of rare-earth phosphate glasses (REPGs). Such glasses, codoped with two rare-earth ions (R and R') of different sizes and optical properties, are of interest to the laser industry. The determination of structure-property relationships in these materials is an important aspect of their technological development. Yet, realizing the local structure of codoped REPGs presents significant challenges relative to their singly doped counterparts; specifically, R and R' are difficult to distinguish in terms of establishing relative material compositions, identifying atomic pairwise correlation profiles in a PDF that are associated with each ion, and resolving peak overlap of such profiles in PDFs. This study demonstrates that PCA can be employed to help overcome these structural complications, by statistically inferring trends in PDFs that exist for a restricted set of experimental data on REPGs, and using these as training data to predict material compositions and PDF profiles in unknown codoped REPGs. The application of these PCA methods to resolve individual atomic pairwise correlations in t(r) signatures is also presented. The training methods developed for these structural predictions are prevalidated by testing their ability to reproduce known physical phenomena, such as the lanthanide contraction, on PDF signatures of the structurally simpler singly doped REPGs. The intrinsic limitations of applying PCA to analyze PDFs relative to the quality control of source data, data processing, and sample definition, are also considered. While this case study is limited to lanthanide-doped REPGs, this type of statistical inference may easily be extended to other inorganic solid-state materials and be exploited in large-scale data-mining efforts that probe many t(r) functions.

Improving acute patient flow and resolving emergency department overcrowding in New Zealand hospitals--the major challenges and the promising initiatives.

PubMed

Ardagh, Michael W; Tonkin, Gary; Possenniskie, Clare

2011-10-14

To determine the most common challenges to improving acute patient flow and resolving emergency department (ED) overcrowding in New Zealand hospitals, and to share some of the promising initiatives that have been implemented in response to them. To facilitate progress towards achievement of the Shorter Stays in Emergency Departments Health Target (the Target), the authors visited every District Health Board (DHB) in New Zealand. These visits followed a standardised visit format and subsequent to each visit a report was produced that noted the observed challenges, initiatives and successes in relation to the DHB's pursuit of the Target. Using these reports, the significant challenges and the promising initiatives across all of the DHBs were collated. Access to hospital beds, access to diagnostic tests and inpatient team delays were the most common challenges, followed by increased demand for ED services, ED facility deficiencies, ED staff deficiencies, delay to discharge of inpatients, difficulty engaging hospital clinical staff in changes, difficulty accessing aged care beds, and problems at nights and weekends. Promising initiatives were noted in relation to each of these. To improve acute care, resolve ED overcrowding and achieve the Target we need a comprehensive, whole of system approach and some significant changes to the way we use our physical and human resources. To address common challenges we need to share our experiences and expertise.

Mapping forces in a 3D elastic assembly of grains

NASA Astrophysics Data System (ADS)

Saadatfar, Mohammad; Sheppard, Adrian P.; Senden, Tim J.; Kabla, Alexandre J.

2012-01-01

Our understanding of the elasticity and rheology of disordered materials, such as granular piles, foams, emulsions or dense suspensions relies on improving experimental tools to characterise their behaviour at the particle scale. While 2D observations are now routinely carried out in laboratories, 3D measurements remain a challenge. In this paper, we use a simple model system, a packing of soft elastic spheres, to illustrate the capability of X-ray microtomography to characterise the internal structure and local behaviour of granular systems. Image analysis techniques can resolve grain positions, shapes and contact areas; this is used to investigate the material's microstructure and its evolution upon strain. In addition to morphological measurements, we develop a technique to quantify contact forces and estimate the internal stress tensor. As will be illustrated in this paper, this opens the door to a broad array of static and dynamical measurements in 3D disordered systems.

Hierarchical micro-architectures of electrodes for energy storage

NASA Astrophysics Data System (ADS)

Yue, Yuan; Liang, Hong

2015-06-01

The design of electrodes for the electrochemical energy storage devices, particularly Lithium ion batteries (LIBs) and Supercapacitors (SCs), has extraordinary importance in optimization of electrochemical performance. Regardless of the materials used, the architecture of electrodes is crucial for charge transport efficiency and electrochemical interactions. This report provides a critical review of the prototype architectural design and micro- and nano-material properties designated to electrodes of LIBs and SCs. An alternative classification criterion is proposed that divides reported hierarchical architectures into two categories: aligned and unaligned structures. The structures were evaluated and it was found that the aligned architectures are superior to the unaligned in the following characteristics: 1) highly-organized charger pathways, 2) tunable interspaces between architecture units, and 3) good electric-contacted current collectors prepared along with electrodes. Based on these findings, challenges and potential routes to resolve those are provided for future development.

X-ray Diffraction and Multi-Frame Phase Contrast Imaging Diagnostics for IMPULSE at the Advanced Photon Source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Iverson, Adam; Carlson, Carl; Young, Jason

2013-07-08

The diagnostic needs of any dynamic loading platform present unique technical challenges that must be addressed in order to accurately measure in situ material properties in an extreme environment. The IMPULSE platform (IMPact system for Ultrafast Synchrotron Experiments) at the Advanced Photon Source (APS) is no exception and, in fact, may be more challenging, as the imaging diagnostics must be synchronized to both the experiment and the 60 ps wide x-ray bunches produced at APS. The technical challenges of time-resolved x-ray diffraction imaging and high-resolution multi-frame phase contrast imaging (PCI) are described in this paper. Example data from recent IMPULSEmore » experiments are shown to illustrate the advances and evolution of these diagnostics with a focus on comparing the performance of two intensified CCD cameras and their suitability for multi-frame PCI. The continued development of these diagnostics is fundamentally important to IMPULSE and many other loading platforms and will benefit future facilities such as the Dynamic Compression Sector at APS and MaRIE at Los Alamos National Laboratory.« less

Silicon clathrates for lithium ion batteries: A perspective

NASA Astrophysics Data System (ADS)

Warrier, Pramod; Koh, Carolyn A.

2016-12-01

Development of novel energy storage techniques is essential for the development of sustainable energy resources. Li-ion batteries have the highest rated energy density among rechargeable batteries and have attracted a lot of attention for energy storage in the last 15-20 years. However, significant advancements are required in anode materials before Li-ion batteries become viable for a wide variety of applications, including in renewable energy storage, grid storage, and electric vehicles. While graphite is the current standard anode material in commercial Li-ion batteries, it is Si that exhibits the highest specific energy density among all materials considered for this purpose. Si, however, suffers from significant volume expansion/contraction and the formation of a thick solid-electrolyte interface layer. To resolve these issues, Si clathrates are being considered for anode materials. Clathrates are inclusion compounds and contain cages in which Li could be captured. While Si clathrates offer promising advantages due to their caged structure which enables negligible volume change upon Li insertion, there remains scientific challenges and knowledge gaps to be overcome before these materials can be utilized for Li-ion battery applications, i.e., understanding lithiation/de-lithiation mechanisms, optimizing guest concentrations, as well as safe and economic synthesis routes.

Amorphous MoS3 as the sulfur-equivalent cathode material for room-temperature Li-S and Na-S batteries.

PubMed

Ye, Hualin; Ma, Lu; Zhou, Yu; Wang, Lu; Han, Na; Zhao, Feipeng; Deng, Jun; Wu, Tianpin; Li, Yanguang; Lu, Jun

2017-12-12

Many problems associated with Li-S and Na-S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS 3 as such a material for room-temperature Li-S and Na-S batteries. In Li-S batteries, MoS 3 exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS 3 can also be used as the cathode material of even more challenging Na-S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS 3 It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates.

Amorphous MoS3 as the sulfur-equivalent cathode material for room-temperature Li–S and Na–S batteries

PubMed Central

Ye, Hualin; Ma, Lu; Zhou, Yu; Wang, Lu; Han, Na; Zhao, Feipeng; Deng, Jun; Wu, Tianpin; Li, Yanguang; Lu, Jun

2017-01-01

Many problems associated with Li–S and Na–S batteries essentially root in the generation of their soluble polysulfide intermediates. While conventional wisdom mainly focuses on trapping polysulfides at the cathode using various functional materials, few strategies are available at present to fully resolve or circumvent this long-standing issue. In this study, we propose the concept of sulfur-equivalent cathode materials, and demonstrate the great potential of amorphous MoS3 as such a material for room-temperature Li–S and Na–S batteries. In Li–S batteries, MoS3 exhibits sulfur-like behavior with large reversible specific capacity, excellent cycle life, and the possibility to achieve high areal capacity. Most remarkably, it is also fully cyclable in the carbonate electrolyte under a relatively high temperature of 55 °C. MoS3 can also be used as the cathode material of even more challenging Na–S batteries to enable decent capacity and good cycle life. Operando X-ray absorption spectroscopy (XAS) experiments are carried out to track the structural evolution of MoS3. It largely preserves its chain-like structure during repetitive battery cycling without generating any free polysulfide intermediates. PMID:29180431

Identifying the Atomic-Level Effects of Metal Composition on the Structure and Catalytic Activity of Peptide-Templated Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Merrill, Nicholas A.; McKee, Erik M.; Merino, Kyle C.

2015-10-12

Bioinspired approaches for the formation of metallic nanomaterials have been extensively employed for a diverse range of applications including diagnostics and catalysis. These materials can often be used under sustainable conditions; however, it is challenging to control the material size, morphology, and composition simultaneously. Here we have employed the R5 peptide, which forms a 3D scaffold to direct the size and linear shape of bimetallic PdAu nanomaterials for catalysis. The materials were prepared at varying Pd:Au ratios to probe optimal compositions to achieve maximal catalytic efficiency. These materials were extensively characterized at the atomic level using transmission electron microscopy, extendedmore » X-ray absorption fine structure spectroscopy, and atomic pair distribution function analysis derived from high-energy X-ray diffraction patterns to provide highly resolved structural information. The results confirmed PdAu alloy formation, but also demonstrated that significant surface structural disorder was present. The catalytic activity of the materials was studied for olefin hydrogenation, which demonstrated enhanced reactivity from the bimetallic structures.These results present a pathway to the bioinspired production of multimetallic materials with enhanced properties, which can be assessed via a suite of characterization methods to fully ascertain structure/function relationships.« less

Characterization and imaging of nanostructured materials using tabletop extreme ultraviolet light sources

NASA Astrophysics Data System (ADS)

Karl, Robert; Knobloch, Joshua; Frazer, Travis; Tanksalvala, Michael; Porter, Christina; Bevis, Charles; Chao, Weilun; Abad Mayor, Begoña.; Adams, Daniel; Mancini, Giulia F.; Hernandez-Charpak, Jorge N.; Kapteyn, Henry; Murnane, Margaret

2018-03-01

Using a tabletop coherent extreme ultraviolet source, we extend current nanoscale metrology capabilities with applications spanning from new models of nanoscale transport and materials, to nanoscale device fabrication. We measure the ultrafast dynamics of acoustic waves in materials; by analyzing the material's response, we can extract elastic properties of films as thin as 11nm. We extend this capability to a spatially resolved imaging modality by using coherent diffractive imaging to image the acoustic waves in nanostructures as they propagate. This will allow for spatially resolved characterization of the elastic properties of non-isotropic materials.

Overview of Megacity Air Pollutant Emissions and Impacts

NASA Astrophysics Data System (ADS)

Kolb, C. E.

2013-05-01

The urban metabolism that characterizes major cities consumes very large qualities of humanly produced and/or processed food, fuel, water, electricity, construction materials and manufactured goods, as well as, naturally provided sunlight, precipitation and atmospheric oxygen. The resulting urban respiration exhalations add large quantities of trace gas and particulate matter pollutants to urban atmospheres. Key classes of urban primary air pollutants and their sources will be reviewed and important secondary pollutants identified. The impacts of these pollutants on urban and downwind regional inhabitants, ecosystems, and climate will be discussed. Challenges in quantifying the temporally and spatially resolved urban air pollutant emissions and secondary pollutant production rates will be identified and possible measurement strategies evaluated.

Spectrally-resolved internal quantum efficiency and carrier dynamics of semipolar [Formula: see text] core-shell triangular nanostripe GaN/InGaN LEDs.

PubMed

Okur, Serdal; Rishinaramangalam, Ashwin K; Mishkat-Ul-Masabih, Saadat; Nami, Mohsen; Liu, Sheng; Brener, Igal; Brueck, Steven R J; Feezell, Daniel F

2018-06-08

We investigate the spectrally resolved internal quantum efficiency (IQE) and carrier dynamics in semipolar [Formula: see text] core-shell triangular nanostripe light-emitting diodes (TLEDs) using temperature-dependent photoluminescence (TDPL) and time-resolved photoluminescence (TRPL) at various excitation energy densities. Using electroluminescence, photoluminescence, and cathodoluminescence measurements, we verify the origins of the broad emission spectra from the nanostructures and confirm that localized regions of high-indium-content InGaN exist along the apex of the nanostructures. Spectrally resolved IQE measurements are then performed, with the spectra integrated from 400-450 nm and 450-500 nm to obtain the IQE of the QWs mainly near the sidewalls and apex of the TLEDs, respectively. TDPL and TRPL are used to decouple the radiative and non-radiative carrier lifetimes for different regions of the emission spectra. We observe that the IQE is higher for the spectral region between 450 nm and 500 nm compared to the IQE between 400 and 450 nm. This result is in contrast to the typical observation that the IQE of planar GaN-based LEDs is lower for longer wavelengths (i.e., higher indium contents). We also observe a longer non-radiative recombination lifetime for the longer wavelength portion of the spectrum. Several explanations are proposed for the improved IQE and longer non-radiative lifetime observed near the apex of the nanostructures. The results show that nanostructures may be leveraged to design more efficient green LEDs, potentially addressing a long-standing challenge in GaN-based materials.

Spectrally-resolved internal quantum efficiency and carrier dynamics of semipolar (10\\bar{1}1) core-shell triangular nanostripe GaN/InGaN LEDs

NASA Astrophysics Data System (ADS)

Okur, Serdal; Rishinaramangalam, Ashwin K.; Mishkat-Ul-Masabih, Saadat; Nami, Mohsen; Liu, Sheng; Brener, Igal; Brueck, Steven R. J.; Feezell, Daniel F.

2018-06-01

We investigate the spectrally resolved internal quantum efficiency (IQE) and carrier dynamics in semipolar (10\\bar{1}1) core–shell triangular nanostripe light-emitting diodes (TLEDs) using temperature-dependent photoluminescence (TDPL) and time-resolved photoluminescence (TRPL) at various excitation energy densities. Using electroluminescence, photoluminescence, and cathodoluminescence measurements, we verify the origins of the broad emission spectra from the nanostructures and confirm that localized regions of high-indium-content InGaN exist along the apex of the nanostructures. Spectrally resolved IQE measurements are then performed, with the spectra integrated from 400–450 nm and 450–500 nm to obtain the IQE of the QWs mainly near the sidewalls and apex of the TLEDs, respectively. TDPL and TRPL are used to decouple the radiative and non-radiative carrier lifetimes for different regions of the emission spectra. We observe that the IQE is higher for the spectral region between 450 nm and 500 nm compared to the IQE between 400 and 450 nm. This result is in contrast to the typical observation that the IQE of planar GaN-based LEDs is lower for longer wavelengths (i.e., higher indium contents). We also observe a longer non-radiative recombination lifetime for the longer wavelength portion of the spectrum. Several explanations are proposed for the improved IQE and longer non-radiative lifetime observed near the apex of the nanostructures. The results show that nanostructures may be leveraged to design more efficient green LEDs, potentially addressing a long-standing challenge in GaN-based materials.

Determination of the band parameters of bulk 2H-MX2 (M = Mo, W; X = S, Se) by angle-resolved photoemission spectroscopy

PubMed Central

Kim, Beom Seo; Rhim, Jun-Won; Kim, Beomyoung; Kim, Changyoung; Park, Seung Ryong

2016-01-01

Monolayer MX2 (M = Mo, W; X = S, Se) has recently been drawn much attention due to their application possibility as well as the novel valley physics. On the other hand, it is also important to understand the electronic structures of bulk MX2 for material applications since it is very challenging to grow large size uniform and sustainable monolayer MX2. We performed angle-resolved photoemission spectroscopy and tight binding calculations to investigate the electronic structures of bulk 2H-MX2. We could extract all the important electronic band parameters for bulk 2H-MX2, including the band gap, direct band gap size at K (-K) point and spin splitting size. Upon comparing the parameters for bulk 2H-MX2 (our work) with mono- and multi-layer MX2 (published), we found that stacked layers, substrates for thin films, and carrier concentration significantly affect the parameters, especially the band gap size. The origin of such effect is discussed in terms of the screening effect. PMID:27805019

Coupling Sodium Dodecyl Sulfate–Capillary Polyacrylamide Gel Electrophoresis with MALDI-TOF-MS via a PTFE Membrane

PubMed Central

Lu, Joann J.; Zhu, Zaifang; Wang, Wei; Liu, Shaorong

2011-01-01

Sodium dodecyl sulfate (SDS)–polyacrylamide gel electrophoresis (PAGE) is a fundamental analytical technique for proteomic research, and SDS–capillary gel electrophoresis (CGE) is its miniaturized version. Compared to conventional slab-gel electrophoresis, SDS-CGE has many advantages such as increased separation efficiency, reduced separation time and automated operation. SDS-CGE is not widely accepted in proteomic research primarily due to the difficulties in identifying the well-resolved proteins. MALDI–TOF–MS is an outstanding platform for protein identifications. Coupling the two would solve the problem but is extremely challenging because the MS detector has no access to the SDS-CGE resolved proteins and the SDS interferes with MS detection. In this work we introduce an approach to address these issues. We discover that poly(tetrafluoroethylene) (PTFE) membranes are excellent materials for collecting SDS-CGE separated proteins. We demonstrate that we can wash off the SDS bound to the collected proteins and identify these proteins on-membrane with MALDI-TOF-MS. We also show that we can immunoblot and Coomassie-stain the proteins collected on these membranes. PMID:21309548

In Situ X-Ray Studies of Crystallization Kinetics and Ordering in Functional Organic and Hybrid Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Bin; Keum, Jong K.; Geohegan, David B.

In-Situ and time-resolved X-ray scattering and diffraction is dedicated to yielding the change of structural information as the materials are processed or grown in a controlled environment. In this chapter, we introduce the use of in situ and time-resolved X-ray techniques to understand molecular packing, crystal orientation, and phase transformation during the synthesis and processing of functional organic semiconductors, organic nanowires, and hybrid perovskite materials.

Polychromatic microdiffraction characterization of defect gradients in severely deformed materials.

PubMed

Barabash, Rozaliya I; Ice, Gene E; Liu, Wenjun; Barabash, Oleg M

2009-01-01

This paper analyzes local lattice rotations introduced in severely deformed polycrystalline titanium by friction stir welding. Nondestructive three-dimensional (3D) spatially resolved polychromatic X-ray microdiffraction, is used to resolve the local crystal structure of the restructured surface from neighboring local structures in the sample material. The measurements reveal strong gradients of strain and geometrically necessary dislocations near the surface and illustrate the potential of polychromatic microdiffraction for the study of deformation in complex materials systems.

Increasing Immunization Compliance by Reducing Provisional Admittance

ERIC Educational Resources Information Center

Davis, Wendy S.; Varni, Susan E.; Barry, Sara E.; Frankowski, Barbara L.; Harder, Valerie S.

2016-01-01

Students in Vermont with incomplete or undocumented immunization status are provisionally admitted to schools and historically had a calendar year to resolve their immunization status. The process of resolving these students' immunization status was challenging for school nurses. We conducted a school-based quality improvement effort to increase…

Numerically modeling Brownian thermal noise in amorphous and crystalline thin coatings

NASA Astrophysics Data System (ADS)

Lovelace, Geoffrey; Demos, Nicholas; Khan, Haroon

2018-01-01

Thermal noise is expected to be one of the noise sources limiting the astrophysical reach of Advanced LIGO (once commissioning is complete) and third-generation detectors. Adopting crystalline materials for thin, reflecting mirror coatings, rather than the amorphous coatings used in current-generation detectors, could potentially reduce thermal noise. Understanding and reducing thermal noise requires accurate theoretical models, but modeling thermal noise analytically is especially challenging with crystalline materials. Thermal noise models typically rely on the fluctuation-dissipation theorem, which relates the power spectral density of the thermal noise to an auxiliary elastic problem. In this paper, we present results from a new, open-source tool that numerically solves the auxiliary elastic problem to compute the Brownian thermal noise for both amorphous and crystalline coatings. We employ the open-source deal.ii and PETSc frameworks to solve the auxiliary elastic problem using a finite-element method, adaptive mesh refinement, and parallel processing that enables us to use high resolutions capable of resolving the thin reflective coating. We verify numerical convergence, and by running on up to hundreds of compute cores, we resolve the coating elastic energy in the auxiliary problem to approximately 0.1%. We compare with approximate analytic solutions for amorphous materials, and we verify that our solutions scale as expected with changing beam size, mirror dimensions, and coating thickness. Finally, we model the crystalline coating thermal noise in an experiment reported by Cole et al (2013 Nat. Photon. 7 644–50), comparing our results to a simpler numerical calculation that treats the coating as an ‘effectively amorphous’ material. We find that treating the coating as a cubic crystal instead of as an effectively amorphous material increases the thermal noise by about 3%. Our results are a step toward better understanding and reducing thermal noise to increase the reach of future gravitational-wave detectors.

Large-eddy simulation of wind turbine wake interactions on locally refined Cartesian grids

NASA Astrophysics Data System (ADS)

Angelidis, Dionysios; Sotiropoulos, Fotis

2014-11-01

Performing high-fidelity numerical simulations of turbulent flow in wind farms remains a challenging issue mainly because of the large computational resources required to accurately simulate the turbine wakes and turbine/turbine interactions. The discretization of the governing equations on structured grids for mesoscale calculations may not be the most efficient approach for resolving the large disparity of spatial scales. A 3D Cartesian grid refinement method enabling the efficient coupling of the Actuator Line Model (ALM) with locally refined unstructured Cartesian grids adapted to accurately resolve tip vortices and multi-turbine interactions, is presented. Second order schemes are employed for the discretization of the incompressible Navier-Stokes equations in a hybrid staggered/non-staggered formulation coupled with a fractional step method that ensures the satisfaction of local mass conservation to machine zero. The current approach enables multi-resolution LES of turbulent flow in multi-turbine wind farms. The numerical simulations are in good agreement with experimental measurements and are able to resolve the rich dynamics of turbine wakes on grids containing only a small fraction of the grid nodes that would be required in simulations without local mesh refinement. This material is based upon work supported by the Department of Energy under Award Number DE-EE0005482 and the National Science Foundation under Award number NSF PFI:BIC 1318201.

In-pile Thermal Conductivity Characterization with Time Resolved Raman

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Xinwei; Hurley, David H.

The project is designed to achieve three objectives: (1) Develop a novel time resolved Raman technology for direct measurement of fuel and cladding thermal conductivity. (2) Validate and improve the technology development by measuring ceramic materials germane to the nuclear industry. (3) Conduct instrumentation development to integrate optical fiber into our sensing system for eventual in-pile measurement. We have developed three new techniques: time-domain differential Raman (TD-Raman), frequency-resolved Raman (FR-Raman), and energy transport state-resolved Raman (ET-Raman). The TD-Raman varies the laser heating time and does simultaneous Raman thermal probing, the FR-Raman probes the material’s thermal response under periodical laser heatingmore » of different frequencies, and the ET-Raman probes the thermal response under steady and pulsed laser heating. The measurement capacity of these techniques have been fully assessed and verified by measuring micro/nanoscale materials. All these techniques do not need the data of laser absorption and absolute material temperature rise, yet still be able to measure the thermal conductivity and thermal diffusivity with unprecedented accuracy. It is expected they will have broad applications for in-pile thermal characterization of nuclear materials based on pure optical heating and sensing.« less

Spectroscopic Diagnosis of Excited-State Aromaticity: Capturing Electronic Structures and Conformations upon Aromaticity Reversal.

PubMed

Oh, Juwon; Sung, Young Mo; Hong, Yongseok; Kim, Dongho

2018-03-06

Aromaticity, the special energetic stability derived from cyclic [4 n + 2]π-conjugated electronic structures, has been the topic of intense interest in chemistry because it plays a critical role in rationalizing molecular stability, reactivity, and physical/chemical properties. Recently, the pioneering work by Colin Baird on aromaticity reversal, postulating that aromatic (antiaromatic) character in the ground state reverses to antiaromatic (aromatic) character in the lowest excited triplet state, has attracted much scientific attention. The completely reversed aromaticity in the excited state provides direct insight into understanding the photophysical/chemical properties of photoactive materials. In turn, the application of aromatic molecules to photoactive materials has led to numerous studies revealing this aromaticity reversal. However, most studies of excited-state aromaticity have been based on the theoretical point of view. The experimental evaluation of aromaticity in the excited state is still challenging and strenuous because the assessment of (anti)aromaticity with conventional magnetic, energetic, and geometric indices is difficult in the excited state, which practically restricts the extension and application of the concept of excited-state aromaticity. Time-resolved optical spectroscopies can provide a new and alternative avenue to evaluate excited-state aromaticity experimentally while observing changes in the molecular features in the excited states. Time-resolved optical spectroscopies take advantage of ultrafast laser pulses to achieve high time resolution, making them suitable for monitoring ultrafast changes in the excited states of molecular systems. This can provide valuable information for understanding the aromaticity reversal. This Account presents recent breakthroughs in the experimental assessment of excited-state aromaticity and the verification of aromaticity reversal with time-resolved optical spectroscopic measurements. To scrutinize this intriguing and challenging scientific issue, expanded porphyrins have been utilized as the ideal testing platform for investigating aromaticity because they show distinct aromatic and antiaromatic characters with aromaticity-specific spectroscopic features. Expanded porphyrins exhibit perfect aromatic and antiaromatic congener pairs having the same molecular framework but different numbers of π electrons, which facilitates the study of the pure effect of aromaticity by comparative analyses. On the basis of the characteristics of expanded porphyrins, time-resolved electronic and vibrational absorption spectroscopies capture the changes in electronic structure and molecular conformations driven by the change in aromaticity and provide clear evidence for aromaticity reversal in the excited states. The approaches described in this Account pave the way for the development of new and alternative experimental indices for the evaluation of excited-state aromaticity, which will enable overarching and fundamental comprehension of the role of (anti)aromaticity in the stability, dynamics, and reactivity in the excited states with possible implications for practical applications.

Emergence of charge density waves and a pseudogap in single-layer TiTe 2

DOE PAGES

Chen, P.; Pai, Woei Wu; Chan, Y. -H.; ...

2017-09-11

Two-dimensional materials constitute a promising platform for developing nanoscale devices and systems. Their physical properties can be very different from those of the corresponding three-dimensional materials because of extreme quantum confinement and dimensional reduction. Here in this paper we report a study of TiTe 2 from the single-layer to the bulk limit. Using angle-resolved photoemission spectroscopy and scanning tunneling microscopy and spectroscopy, we observed the emergence of a (2 × 2) charge density wave order in single-layer TiTe 2 with a transition temperature of 92 ± 3 K. Also observed was a pseudogap of about 28 meV at the Fermimore » level at 4.2 K. Surprisingly, no charge density wave transitions were observed in two-layer and multi-layer TiTe 2 , despite the quasi-two-dimensional nature of the material in the bulk. The unique charge density wave phenomenon in the single layer raises intriguing questions that challenge the prevailing thinking about the mechanisms of charge density wave formation.« less

A hot tip: imaging phenomena using in situ multi-stimulus probes at high temperatures

NASA Astrophysics Data System (ADS)

Nonnenmann, Stephen S.

2016-02-01

Accurate high temperature characterization of materials remains a critical challenge to the continued advancement of various important energy, nuclear, electronic, and aerospace applications. Future experimental studies must assist these communities to progress past empiricism and derive deliberate, predictable designs of material classes functioning within active, extreme environments. Successful realization of systems ranging from fuel cells and batteries to electromechanical nanogenerators and turbines requires a dynamic understanding of the excitation, surface-mediated, and charge transfer phenomena which occur at heterophase interfaces (i.e. vapor-solid, liquid-solid, solid-solid) and impact overall performance. Advancing these frontiers therefore necessitates in situ (operando) characterization methods capable of resolving, both spatially and functionally, the coherence between these complex, collective excitations, and their respective response dynamics, through studies within the operating regime. This review highlights recent developments in scanning probe microscopy in performing in situ imaging at high elevated temperatures. The influence of and evolution from vacuum-based electron and tunneling microscopy are briefly summarized and discussed. The scope includes the use of high temperature imaging to directly observe critical phase transition, electronic, and electrochemical behavior under dynamic temperature settings, thus providing key physical parameters. Finally, both challenges and directions in combined instrumentation are proposed and discussed towards the end.

"Together, We Are Strong": A Qualitative Study of Happy, Enduring African American Marriages

ERIC Educational Resources Information Center

Marks, Loren D.; Hopkins, Katrina; Chaney, Cassandra; Monroe, Pamela A.; Nesteruk, Olena; Sasser, Diane D.

2008-01-01

Thirty African American married couples (N = 60 individuals) were interviewed regarding the challenges and benefits of their happy, enduring marriages. Qualitative coding and analysis revealed 4 key themes: (1) Challenges in African American Marriages, (2) Overcoming External Challenges to Marriage, (3) Resolving Intramarital Conflict, and (4)…

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope.

PubMed

Hieckmann, Ellen; Nacke, Markus; Allardt, Matthias; Bodrov, Yury; Chekhonin, Paul; Skrotzki, Werner; Weber, Jörg

2016-05-28

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared.

Comprehensive Characterization of Extended Defects in Semiconductor Materials by a Scanning Electron Microscope

PubMed Central

Hieckmann, Ellen; Nacke, Markus; Allardt, Matthias; Bodrov, Yury; Chekhonin, Paul; Skrotzki, Werner; Weber, Jörg

2016-01-01

Extended defects such as dislocations and grain boundaries have a strong influence on the performance of microelectronic devices and on other applications of semiconductor materials. However, it is still under debate how the defect structure determines the band structure, and therefore, the recombination behavior of electron-hole pairs responsible for the optical and electrical properties of the extended defects. The present paper is a survey of procedures for the spatially resolved investigation of structural and of physical properties of extended defects in semiconductor materials with a scanning electron microscope (SEM). Representative examples are given for crystalline silicon. The luminescence behavior of extended defects can be investigated by cathodoluminescence (CL) measurements. They are particularly valuable because spectrally and spatially resolved information can be obtained simultaneously. For silicon, with an indirect electronic band structure, CL measurements should be carried out at low temperatures down to 5 K due to the low fraction of radiative recombination processes in comparison to non-radiative transitions at room temperature. For the study of the electrical properties of extended defects, the electron beam induced current (EBIC) technique can be applied. The EBIC image reflects the local distribution of defects due to the increased charge-carrier recombination in their vicinity. The procedure for EBIC investigations is described for measurements at room temperature and at low temperatures. Internal strain fields arising from extended defects can be determined quantitatively by cross-correlation electron backscatter diffraction (ccEBSD). This method is challenging because of the necessary preparation of the sample surface and because of the quality of the diffraction patterns which are recorded during the mapping of the sample. The spatial resolution of the three experimental techniques is compared. PMID:27285177

Silicon clathrates for lithium ion batteries: A perspective

DOE Office of Scientific and Technical Information (OSTI.GOV)

Warrier, Pramod, E-mail: pramod.warrier@gmail.com; Koh, Carolyn A.

2016-12-15

Development of novel energy storage techniques is essential for the development of sustainable energy resources. Li-ion batteries have the highest rated energy density among rechargeable batteries and have attracted a lot of attention for energy storage in the last 15–20 years. However, significant advancements are required in anode materials before Li-ion batteries become viable for a wide variety of applications, including in renewable energy storage, grid storage, and electric vehicles. While graphite is the current standard anode material in commercial Li-ion batteries, it is Si that exhibits the highest specific energy density among all materials considered for this purpose. Si,more » however, suffers from significant volume expansion/contraction and the formation of a thick solid-electrolyte interface layer. To resolve these issues, Si clathrates are being considered for anode materials. Clathrates are inclusion compounds and contain cages in which Li could be captured. While Si clathrates offer promising advantages due to their caged structure which enables negligible volume change upon Li insertion, there remains scientific challenges and knowledge gaps to be overcome before these materials can be utilized for Li-ion battery applications, i.e., understanding lithiation/de-lithiation mechanisms, optimizing guest concentrations, as well as safe and economic synthesis routes.« less

Granular rheology: measuring boundary forces with laser-cut leaf springs

NASA Astrophysics Data System (ADS)

Tang, Zhu; Brzinski, Theodore A.; Daniels, Karen E.

2017-06-01

In granular physics experiments, it is a persistent challenge to obtain the boundary stress measurements necessary to provide full a rheological characterization of the dynamics. Here, we describe a new technique by which the outer boundary of a 2D Couette cell both confines the granular material and provides spatially- and temporally- resolved stress measurements. This key advance is enabled by desktop laser-cutting technology, which allows us to design and cut linearly-deformable walls with a specified spring constant. By tracking the position of each segment of the wall, we measure both the normal and tangential stress throughout the experiment. This permits us to calculate the amount of shear stress provided by basal friction, and thereby determine accurate values of μ(I).

Depth- and momentum- resolved electronic structure at buried oxide interfaces from standing-wave angle-resolved photoemission

NASA Astrophysics Data System (ADS)

Fadley, Charles

2015-03-01

It is clear that interfaces in complex oxide heterostructures often represent emergent materials that possess surprising properties not associated with the parent oxides, such as two-dimensional electron gases (2DEGs), superconductivity, and magnetism. A detailed knowledge of the composition, atomic structure, and electronic structure through such interfaces is thus critical. Photomission (PES) and angle-resolved photoemission (ARPES) represent techniques of choice for such studies, but have certain limitations in being too surface sensitive and in not being able to focus specifically on buried interfaces or heterostructure layers. In this talk, I will discuss combining two newer elements of PES/ARPES to deal with this challenge: - the use of soft x-rays in the ca. few hundred-to-2000 eV regime, or even into the true hard x-ray regime, to probe more deeply into the structure, and - tailoring of the x-ray intensity profile into a strong standing wave (SW) through reflection from a multilayer heterostructure to provide much enhanced depth resolution. The relative advantages of soft/hard x-ray PES and ARPES and their complementarity to conventional VUV ARPES in the ca. 5-150 eV regime will be considered. As illustrative examples, by combining SW-PES and SW-ARPES, it has been possible to measure for the first time the detailed concentration profiles and momentum-resolved electronic structure at the SrTiO3/La0.67Sr0.33MnO3 interface and to directly measure the depth profile of the 2DEG at SrTiO3/GdTiO3 interfaces. Future directions for such measurements will also be discussed. Supported by US DOE Contract No. DE-AC02-05CH11231, ARO-MURI Grant W911-NF-09-1-0398, and the PALM-APTCOM Project (France).

Based on time and spatial-resolved SERS mapping strategies for detection of pesticides.

PubMed

Ma, Bingbing; Li, Pan; Yang, Liangbao; Liu, Jinhuai

2015-08-15

For the sensitive and convenient detection of pesticides, several sensing methods and materials have been widely explored. However, it is still a challenge to obtain sensitive, simple detection techniques for pesticides. Here, the simple and sensitive Time-resolved SERS mapping (T-SERS) and Spatial-resolved SERS mapping (S-SERS) are presented for detection of pesticides by using Au@Ag NPs as SERS substrate. The Time-resolved SERS mapping (T-SERS) is based on state translation nanoparticles from the wet state to the dry state to realize SERS measurements. During the SERS measurement, adhesive force drives the particles closer together and then average interparticle gap becomes smaller. Following, air then begins to intersperse into the liquid network and the particles are held together by adhesive forces at the solid-liquid-air interface. In the late stage of water evaporation, all particles are uniformly distributed. Thus, so called hotspots matrix that can hold hotspots between every two adjacent particles in efficient space with minimal polydispersity of particle size are achieved, accompanying the red-shift of surface plasmon peak and appearance of an optimal SPR resonated sharply with excitation wavelength. Here, we found that the T-SERS method exhibits the detection limits of 1-2 orders of magnitude higher than that of S-SERS. On the other hand, the T-SERS is very simple method with high detection sensitivity, better reproducibility (RSD=10.8%) and is beneficial to construction of a calibration curve in comparison with that of Spatial-resolved SERS mapping (S-SERS). Most importantly, as a result of its remarkable sensitivity, T-SERS mapping strategies have been applied to detection of several pesticides and the detect limit can down to 1nM for paraoxon, 0.5nM for sumithion. In short, T-SERS mapping measurement promises to open a market for SERS practical detection with prominent advantages. Copyright © 2015. Published by Elsevier B.V.

Spatially Resolving Ocean Color and Sediment Dispersion in River Plumes, Coastal Systems, and Continental Shelf Waters

NASA Technical Reports Server (NTRS)

Aurin, Dirk Alexander; Mannino, Antonio; Franz, Bryan

2013-01-01

Satellite remote sensing of ocean color in dynamic coastal, inland, and nearshorewaters is impeded by high variability in optical constituents, demands specialized atmospheric correction, and is limited by instrument sensitivity. To accurately detect dispersion of bio-optical properties, remote sensors require ample signal-to-noise ratio (SNR) to sense small variations in ocean color without saturating over bright pixels, an atmospheric correction that can accommodate significantwater-leaving radiance in the near infrared (NIR), and spatial and temporal resolution that coincides with the scales of variability in the environment. Several current and historic space-borne sensors have met these requirements with success in the open ocean, but are not optimized for highly red-reflective and heterogeneous waters such as those found near river outflows or in the presence of sediment resuspension. Here we apply analytical approaches for determining optimal spatial resolution, dominant spatial scales of variability ("patches"), and proportions of patch variability that can be resolved from four river plumes around the world between 2008 and 2011. An offshore region in the Sargasso Sea is analyzed for comparison. A method is presented for processing Moderate Resolution Imaging Spectroradiometer (MODIS) Aqua and Terra imagery including cloud detection, stray lightmasking, faulty detector avoidance, and dynamic aerosol correction using short-wave- and near-infrared wavebands in extremely turbid regions which pose distinct optical and technical challenges. Results showthat a pixel size of approx. 520 mor smaller is generally required to resolve spatial heterogeneity in ocean color and total suspended materials in river plumes. Optimal pixel size increases with distance from shore to approx. 630 m in nearshore regions, approx 750 m on the continental shelf, and approx. 1350 m in the open ocean. Greater than 90% of the optical variability within plume regions is resolvable with 500 m resolution, and small, but significant, differences were found between peak and nadir river flow periods in terms of optimal resolution and resolvable proportion of variability.

Localized states in advanced dielectrics from the vantage of spin- and symmetry-polarized tunnelling across MgO.

PubMed

Schleicher, F; Halisdemir, U; Lacour, D; Gallart, M; Boukari, S; Schmerber, G; Davesne, V; Panissod, P; Halley, D; Majjad, H; Henry, Y; Leconte, B; Boulard, A; Spor, D; Beyer, N; Kieber, C; Sternitzky, E; Cregut, O; Ziegler, M; Montaigne, F; Beaurepaire, E; Gilliot, P; Hehn, M; Bowen, M

2014-08-04

Research on advanced materials such as multiferroic perovskites underscores promising applications, yet studies on these materials rarely address the impact of defects on the nominally expected materials property. Here, we revisit the comparatively simple oxide MgO as the model material system for spin-polarized solid-state tunnelling studies. We present a defect-mediated tunnelling potential landscape of localized states owing to explicitly identified defect species, against which we examine the bias and temperature dependence of magnetotransport. By mixing symmetry-resolved transport channels, a localized state may alter the effective barrier height for symmetry-resolved charge carriers, such that tunnelling magnetoresistance decreases most with increasing temperature when that state is addressed electrically. Thermal excitation promotes an occupancy switchover from the ground to the excited state of a defect, which impacts these magnetotransport characteristics. We thus resolve contradictions between experiment and theory in this otherwise canonical spintronics system, and propose a new perspective on defects in dielectrics.

Depth-Resolved Multispectral Sub-Surface Imaging Using Multifunctional Upconversion Phosphors with Paramagnetic Properties

PubMed Central

Ovanesyan, Zaven; Mimun, L. Christopher; Kumar, Gangadharan Ajith; Yust, Brian G.; Dannangoda, Chamath; Martirosyan, Karen S.; Sardar, Dhiraj K.

2015-01-01

Molecular imaging is very promising technique used for surgical guidance, which requires advancements related to properties of imaging agents and subsequent data retrieval methods from measured multispectral images. In this article, an upconversion material is introduced for subsurface near-infrared imaging and for the depth recovery of the material embedded below the biological tissue. The results confirm significant correlation between the analytical depth estimate of the material under the tissue and the measured ratio of emitted light from the material at two different wavelengths. Experiments with biological tissue samples demonstrate depth resolved imaging using the rare earth doped multifunctional phosphors. In vitro tests reveal no significant toxicity, whereas the magnetic measurements of the phosphors show that the particles are suitable as magnetic resonance imaging agents. The confocal imaging of fibroblast cells with these phosphors reveals their potential for in vivo imaging. The depth-resolved imaging technique with such phosphors has broad implications for real-time intraoperative surgical guidance. PMID:26322519

Environmental decision support systems (EDSS) development - Challenges and best practices

Treesearch

B. S. McIntosh; J. C. Ascough II; S. Chen; J. Chew; S. Cuddy; A. Elmahdi; D. Haase; J. Harou; D. Hepting; A. J. Jakeman; A. Kassahun; S. Lautenbach; K. Matthews; W. Merritt; N. W. T. Quinn; I. Rodriguez-Roda; S. Sieber; M. Stavenga; A. Sulis; J. Ticehurst; M. J. Twery; M. Volk; M. Wrobel; H. van Delden; S. El-Sawah; A. Rizzoli; A. Voinov

2011-01-01

Despite the perceived value of DSS in informing environmental and natural resource management, DSS tools often fail to be adopted by intended end users. By drawing together the experience of a global group of EDSS developers, we have identified and assessed key challenges in EDSS development and offer recommendations to resolve them. Challenges related to engaging end...

Measurement and evaluation of the radiative properties of a thin solid fuel

NASA Technical Reports Server (NTRS)

Pettegrew, Richard; Street, Kenneth; Pitch, Nancy; Tien, James; Morrison, Phillip

2003-01-01

Accurate modeling of combustion systems requires knowledge of the radiative properties of the system. Gas phase properties are well known, but detailed knowledge of surface properties is limited. Recent work has provided spectrally resolved data for some solid fuels, but only for the unburned material at room temperature, and for limited sets of previously burned and quenched samples. Due to lack of knowledge of the spectrally resolved properties at elevated temperatures, as well as processing limitations in the modeling effort, graybody values are typically used for the fuels surface radiative properties. However, the spectrally resolved properties for the fuels at room temperature can be used to give a first-order correction for temperature effects on the graybody values. Figure 1 shows a sample of the spectrally resolved emittance/absorptance for a thin solid fuel of the type commonly used in combustion studies, from approximately 2 to 20 microns. This plot clearly shows a strong spectral dependence across the entire range. By definition, the emittance is the ratio of the emitted energy to that of a blackbody at the same temperature. Therefore, to determine a graybody emittance for this material, the spectrally resolved data must be applied to a blackbody curve. The total area under the resulting curve is ratioed to the total area under the blackbody curve to yield the answer. Due to the asymmetry of the spectrally resolved emittance and the changing shape of the blackbody curve as the temperature increases, the relative importance of the emittance value at any given wavelength will change as a function of temperature. Therefore, the graybody emittance value for a given material will change as a function of temperature even if the spectral dependence of the radiative properties remains unchanged. This is demonstrated in Figures 2 and 3, which are plots of the spectrally resolved emittance for KimWipes (shown in Figure 1) multiplied by the blackbody curves for 300 K (Figure 2) and 800 K (Figure 3). Each figure also shows the blackbody curve for that temperature. Ratioing the areas under the curve for each of these figures give a graybody emittance of 0.64 at 300 K, and 0.46 at 800 K. It is recognized that materials undergoing pyrolysis will change in composition as they heat up, and that the radiative properties of the materials may have inherent temperature dependence. Both of these effects will contribute to changes in the radiative characteristics of a given material, and are not accounted for here. However, this paper demonstrates the temperature dependence of graybody radiative properties, and provides a method for a first-order correction (for temperature) to the graybody values if the spectrally resolved properties are known.

Spatially confined low-power optically pumped ultrafast synchrotron x-ray nanodiffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Joonkyu; Zhang, Qingteng; Chen, Pice

2015-08-27

The combination of ultrafast optical excitation and time-resolved synchrotron x-ray nanodiffraction provides unique insight into the photoinduced dynamics of materials, with the spatial resolution required to probe individual nanostructures or small volumes within heterogeneous materials. Optically excited x-ray nanobeam experiments are challenging because the high total optical power required for experimentally relevant optical fluences leads to mechanical instability due to heating. For a given fluence, tightly focusing the optical excitation reduces the average optical power by more than three orders of magnitude and thus ensures sufficient thermal stability for x-ray nanobeam studies. Delivering optical pulses via a scannable fiber-coupled opticalmore » objective provides a well-defined excitation geometry during rotation and translation of the sample and allows the selective excitation of isolated areas within the sample. Finally, experimental studies of the photoinduced lattice dynamics of a 35 nm BiFeO 3 thin film on a SrTiO 3 substrate demonstrate the potential to excite and probe nanoscale volumes.« less

DE-FOA-EE0005502 Advanced Percussive Drilling Technology for Geothermal Exploration and Development Phase II Report.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Jiann-Cherng; Raymond, David W.; Prasad, Somuri V.

Percussive hammers are a promising advance in drilling technology for geothermal since they rely upon rock reduction mechanisms that are well-suited for use in the hard, brittle rock characteristic of geothermal formations. The project research approach and work plan includes a critical path to development of a high-temperature (HT) percussive hammer using a two- phase approach. The work completed in Phase I of the project demonstrated the viability of percussive hammers and that solutions to technical challenges in design, material technology, and performance are likely to be resolved. Work completed in Phase II focused on testing the findings from Phasemore » I and evaluating performance of the materials and designs at high- operating temperatures. A high-operating temperature (HOT) drilling facility was designed, built, and used to test the performance of the DTH under extreme conditions. Results from the testing indicate that a high-temperature capable hammer can be developed and is a viable alternative for user in the driller's toolbox.« less

Advanced Percussive Drilling Technology for Geothermal Exploration and Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Su, Jiann; Raymond, David; Prasad, Somuri

Percussive hammers are a promising advance in drilling technology for geothermal since they rely upon rock reduction mechanisms that are well-suited for use in the hard, brittle rock characteristic of geothermal formations. The project research approach and work plan includes a critical path to development of a high-temperature (HT) percussive hammer using a two phase approach. The work completed in Phase I of the project demonstrated the viability of percussive hammers and that solutions to technical challenges in design, material technology, and performance are likely to be resolved. Work completed in Phase II focused on testing the findings from Phasemore » I and evaluating performance of the materials and designs at high operating temperatures. A high-operating temperature (HOT) drilling facility was designed, built, and used to test the performance of the DTH under extreme conditions. Results from the testing indicate that a high-temperature capable hammer can be developed and is a viable alternative for use in the driller’s toolbox.« less

X-ray fluorescence at nanoscale resolution for multicomponent layered structures: A solar cell case study

DOE Office of Scientific and Technical Information (OSTI.GOV)

West, Bradley M.; Stuckelberger, Michael; Jeffries, April

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral formmore » and numerically applicable framework. Here, the procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se 2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.« less

X-ray fluorescence at nanoscale resolution for multicomponent layered structures: A solar cell case study

DOE PAGES

West, Bradley M.; Stuckelberger, Michael; Jeffries, April; ...

2017-01-01

The study of a multilayered and multicomponent system by spatially resolved X-ray fluorescence microscopy poses unique challenges in achieving accurate quantification of elemental distributions. This is particularly true for the quantification of materials with high X-ray attenuation coefficients, depth-dependent composition variations and thickness variations. A widely applicable procedure for use after spectrum fitting and quantification is described. This procedure corrects the elemental distribution from the measured fluorescence signal, taking into account attenuation of the incident beam and generated fluorescence from multiple layers, and accounts for sample thickness variations. Deriving from Beer–Lambert's law, formulae are presented in a general integral formmore » and numerically applicable framework. Here, the procedure is applied using experimental data from a solar cell with a Cu(In,Ga)Se 2 absorber layer, measured at two separate synchrotron beamlines with varied measurement geometries. This example shows the importance of these corrections in real material systems, which can change the interpretation of the measured distributions dramatically.« less

Modeling pair distribution functions of rare-earth phosphate glasses using principal component analysis

DOE PAGES

Cole, Jacqueline M.; Cheng, Xie; Payne, Michael C.

2016-10-18

The use of principal component analysis (PCA) to statistically infer features of local structure from experimental pair distribution function (PDF) data is assessed on a case study of rare-earth phosphate glasses (REPGs). Such glasses, co-doped with two rare-earth ions (R and R’) of different sizes and optical properties, are of interest to the laser industry. The determination of structure-property relationships in these materials is an important aspect of their technological development. Yet, realizing the local structure of co-doped REPGs presents significant challenges relative to their singly-doped counterparts; specifically, R and R’ are difficult to distinguish in terms of establishing relativemore » material compositions, identifying atomic pairwise correlation profiles in a PDF that are associated with each ion, and resolving peak overlap of such profiles in PDFs. This study demonstrates that PCA can be employed to help overcome these structural complications, by statistically inferring trends in PDFs that exist for a restricted set of experimental data on REPGs, and using these as training data to predict material compositions and PDF profiles in unknown co-doped REPGs. The application of these PCA methods to resolve individual atomic pairwise correlations in t(r) signatures is also presented. The training methods developed for these structural predictions are pre-validated by testing their ability to reproduce known physical phenomena, such as the lanthanide contraction, on PDF signatures of the structurally simpler singly-doped REPGs. The intrinsic limitations of applying PCA to analyze PDFs relative to the quality control of source data, data processing, and sample definition, are also considered. Furthermore, while this case study is limited to lanthanide-doped REPGs, this type of statistical inference may easily be extended to other inorganic solid-state materials, and be exploited in large-scale data-mining efforts that probe many t(r) functions.« less

Surface Treated Natural Fibres as Filler in Biocomposites

NASA Astrophysics Data System (ADS)

Schwarzova, I.; Stevulova, N.; Singovszka, E.; Terpakova, E.

2015-11-01

Biocomposites based on natural fibres as organic filler have been studied for several years because traditional building materials such as concrete are increasingly being replaced by advanced composite materials. Natural fibres are a potential replacement of glass fibres in composite materials. Inherent advantages such as low density, biodegradability and comparable specific mechanical properties make natural fibres an attractive option. However, limitations such as poor thermal stability, moisture absorption and poor compatibility with matrix are challenges that need to be resolved. The primary objective of this research was to study the effect of surface treatment on properties of hemp hurds like a natural lignocellulosic material and composites made thereof. Industrial hemp fibre is the one of the most suitable fibres for use in composite materials because of its good specific properties, as well as it being biologically degradable and CO2 neutral. Improving interfacial bonding between fibres and matrix is an important factor in using hemp fibres as reinforcement in composites. In order to improve interfacial bonding, modifications can be made to the hemp fibres to remove non- cellulosic compounds, separate hemp fibres from their bundles, and modify the fibre surface. This paper contains the comparison of FTIR spectra caused by combination of physical and chemical treatment of hemp material with unmodified sample. Modification of hemp hurds was carried out by NaOH solution and by ultrasonic treatment (deionized water and NaOH solution were used as the cleaning mediums).

Chemical and Structural Stability of Lithium-Ion Battery Electrode Materials under Electron Beam

DOE PAGES

Lin, Feng; Markus, Isaac M.; Doeff, Marca M.; ...

2014-07-16

Our investigation of chemical and structural dynamics in battery materials is essential to elucidation of structure-property relationships for rational design of advanced battery materials. Spatially resolved techniques, such as scanning/transmission electron microscopy (S/TEM), are widely applied to address this challenge. But, battery materials are susceptible to electron beam damage, complicating the data interpretation. In this study, we demonstrate that, under electron beam irradiation, the surface and bulk of battery materials undergo chemical and structural evolution equivalent to that observed during charge-discharge cycling. In a lithiated NiO nanosheet, a Li2CO3-containing surface reaction layer (SRL) was gradually decomposed during electron energy loss spectroscopy (EELS) acquisition. For cycled LiNi 0.4Mn 0.4Co 0.18Ti 0.02O 2 particles, repeated electron beam irradiation induced a phase transition from an Rmore » $$\\bar{3}$$m layered structure to an rock-salt structure, which is attributed to the stoichiometric lithium and oxygen removal from R$$\\bar{3}$$m 3a and 6c sites, respectively. Nevertheless, it is still feasible to preserve pristine chemical environments by minimizing electron beam damage, for example, in using fast electron imaging and spectroscopy. Finally, the present study provides examples of electron beam damage on lithium-ion battery materials and suggests that special attention is necessary to prevent misinterpretation of experimental results.« less

Simulating faults and plate boundaries with a transversely isotropic plasticity model

NASA Astrophysics Data System (ADS)

Sharples, W.; Moresi, L. N.; Velic, M.; Jadamec, M. A.; May, D. A.

2016-03-01

In mantle convection simulations, dynamically evolving plate boundaries have, for the most part, been represented using an visco-plastic flow law. These systems develop fine-scale, localized, weak shear band structures which are reminiscent of faults but it is a significant challenge to resolve the large- and the emergent, small-scale-behavior. We address this issue of resolution by taking into account the observation that a rock element with embedded, planar, failure surfaces responds as a non-linear, transversely isotropic material with a weak orientation defined by the plane of the failure surface. This approach partly accounts for the large-scale behavior of fine-scale systems of shear bands which we are not in a position to resolve explicitly. We evaluate the capacity of this continuum approach to model plate boundaries, specifically in the context of subduction models where the plate boundary interface has often been represented as a planar discontinuity. We show that the inclusion of the transversely isotropic plasticity model for the plate boundary promotes asymmetric subduction from initiation. A realistic evolution of the plate boundary interface and associated stresses is crucial to understanding inter-plate coupling, convergent margin driven topography, and earthquakes.

IRMPD Spectroscopy Sheds New (Infrared) Light on the Sulfate Pattern of Carbohydrates.

PubMed

Schindler, B; Barnes, L; Gray, C J; Chambert, S; Flitsch, S L; Oomens, J; Daniel, R; Allouche, A R; Compagnon, I

2017-03-16

IR spectroscopy of gas-phase ions is proposed to resolve positional isomers of sulfated carbohydrates. Mass spectrometric fingerprints and gas-phase vibrational spectra in the near and mid-IR regions were obtained for sulfated monosaccharides, yielding unambiguous signatures of sulfated isomers. We report the first systematic exploration of the biologically relevant but notoriously challenging deprotonated state in the near IR region. Remarkably, anions displayed very atypical vibrational profiles, which challenge the well-established DFT (Density Functionnal Theory) modeling. The proposed approach was used to elucidate the sulfate patterns in glycosaminoglycans, a ubiquitous class of mammalian carbohydrates, which is regarded as a major challenge in carbohydrate structural analysis. Isomeric glycosaminoglycan disaccharides from heparin and chondroitin sources were resolved, highlighting the potential of infrared multiple photon dissociation spectroscopy as a novel structural tool for carbohydrates.

Rethinking Difficulties of Teaching Inquiry-Based Practical Work: Stories from elementary pre-service teachers

NASA Astrophysics Data System (ADS)

Kim, Mijung; Tan, Aik-Ling

2011-03-01

To alleviate teachers' reluctance toward practical work, there has been much discussion on teachers' pedagogical content knowledge, teaching materials, and failsafe strategies for practical work. Despite these efforts, practical work is still regarded as a challenging task for many elementary science teachers. To understand the complexity of teachers' conflicts in practical work, this study examines teachers' ideas about teaching and learning that influence teachers' decision-making and action on teaching practical work. More important than knowing technical-rational aspects of practical work is to understand the internal contradictions that teachers have to resolve within themselves regarding their capabilities and beliefs about science teaching and practical work. Using stories and experiences of 38 third-year university students in a science method course in Korea, we seek to understand the conflicts and negotiations that they experience as they make decisions regarding practical work throughout their course. Reflective writings and group discussions on their lived experiences and concerns were used to probe participants' ideas on teaching using practical work. From written and verbal data, themes were saturated in terms of the aspects which could (dis)encourage their practice. Results suggest that there are multifactorial challenges in pre-service teachers' understandings and concerns in practical work. Besides time, materials, and curriculum, pedagogical assumptions and values also compositely challenge the minds of teachers. As the pre-service elementary teachers negotiated within themselves the importance of science in classroom and social levels, the question is raised about their identities as pre-service elementary teachers to appreciate the balance between science teaching and practical work.

The Co-Teaching Journey: A Systematic Grounded Theory Study Investigating How Secondary School Teachers Resolve Challenges in Co-Teaching

ERIC Educational Resources Information Center

Gerst, Sharon

2012-01-01

The purpose of this systematic grounded theory study was to explain how problems inherent in co-teaching relationships are resolved by secondary school special education and general education teachers at an urban school district in Eastern Iowa. The participants were general and special education secondary school teachers involved in effective…

Development of a New Time-Resolved Laser-Induced Fluorescence Technique

NASA Astrophysics Data System (ADS)

Durot, Christopher; Gallimore, Alec

2012-10-01

We are developing a time-resolved laser-induced fluorescence (LIF) technique to interrogate the ion velocity distribution function (VDF) of EP thruster plumes down to the microsecond time scale. Better measurements of dynamic plasma processes will lead to improvements in simulation and prediction of thruster operation and erosion. We present the development of the new technique and results of initial tests. Signal-to-noise ratio (SNR) is often a challenge for LIF studies, and it is only more challenging for time-resolved measurements since a lock-in amplifier cannot be used with a long time constant. The new system uses laser modulation on the order of MHz, which enables the use of electronic filtering and phase-sensitive detection to improve SNR while preserving time-resolved information. Statistical averaging over many cycles to further improve SNR is done in the frequency domain. This technique can have significant advantages, including (1) larger spatial maps enabled by shorter data acquisition time and (2) the ability to average data without creating a phase reference by modifying the thruster operating condition with a periodic cutoff in discharge current, which can modify the ion velocity distribution.

Identifying Fossil Biosignatures and Minerals in Mars Analog Materials Using Time-Resolved Raman Spectroscopy

NASA Astrophysics Data System (ADS)

Shkolyar, S.; Farmer, J.; Alerstam, E.; Maruyama, Y.; Blacksberg, J.

2013-12-01

Mars sample return has been identified as a top priority in the planetary science decadal survey. A Mars sample selection and caching mission would be the likely first step in this endeavor. Such a mission would aim to select and prioritize for return to Earth aqueously formed geological samples present at a selected site on Mars, based upon their potential for biosignature capture and preservation. If evidence of past life exists and is found, it is likely to come via the identification of fossilized carbonaceous matter of biological origin (kerogen) found in the selected samples analyzed in laboratories after return to Earth. Raman spectroscopy is considered one of the primary techniques for analyzing materials in situ and selecting the most promising samples for Earth return. We have previously performed a pilot study to better understand the complexities of identifying kerogen using Raman spectroscopy. For the study, we examined a variety of Mars analog materials representing a broad range of mineral compositions and kerogen maturities. The study revealed that kerogen identification in many of the most promising lithologies is often impeded by background fluorescence that originates from long (>10 ns to ms) and short (<1 ns) lifetime fluorophores in both the mineral matrixes and preserved organic matter in the samples. This work explores the potential for time-gated Raman spectroscopy to enable clear kerogen and mineral identifications in such samples. The JPL time-resolved Raman system uses time gating to reduce background fluorescence. It uses a custom-built SPAD (single photon avalanche diode) detector, featuring a 1-ns time-gate, and electronically variable gate delay. Results for a range of fluorescent samples show that the JPL system reduces fluorescence, allowing the identification of both kerogen and mineral components more successfully than with conventional Raman systems. In some of the most challenging samples, the detection of organic matter is hindered by a combination of short lifetime fluorescence and weak Raman scattering coming from preserved kerogen grains. Fluorescence Lifetime Imaging Microscopy (FLIM) measurements were also performed to characterize the lifetimes of both components in the samples and to inform future system improvements such as shorter time gating. Here, we will discuss the results, along with identified challenges to the consistent and reliable in situ identification of kerogen in samples on Mars.

Spectral data of specular reflectance, narrow-angle transmittance and angle-resolved surface scattering of materials for solar concentrators.

PubMed

Good, Philipp; Cooper, Thomas; Querci, Marco; Wiik, Nicolay; Ambrosetti, Gianluca; Steinfeld, Aldo

2016-03-01

The spectral specular reflectance of conventional and novel reflective materials for solar concentrators is measured with an acceptance angle of 17.5 mrad over the wavelength range 300-2500 nm at incidence angles 15-60° using a spectroscopic goniometry system. The same experimental setup is used to determine the spectral narrow-angle transmittance of semi-transparent materials for solar collector covers at incidence angles 0-60°. In addition, the angle-resolved surface scattering of reflective materials is recorded by an area-scan CCD detector over the spectral range 350-1050 nm. A comprehensive summary, discussion, and interpretation of the results are included in the associated research article "Spectral reflectance, transmittance, and angular scattering of materials for solar concentrators" in Solar Energy Materials and Solar Cells.

Femtosecond-resolved ablation dynamics of Si in the near field of a small dielectric particle

PubMed Central

Kühler, Paul; Puerto, Daniel; Mosbacher, Mario; Leiderer, Paul; Garcia de Abajo, Francisco Javier

2013-01-01

Summary In this work we analyze the ablation dynamics of crystalline Si in the intense near field generated by a small dielectric particle located at the material surface when being irradiated with an infrared femtosecond laser pulse (800 nm, 120 fs). The presence of the particle (7.9 μm diameter) leads to a strong local enhancement (ca. 40 times) of the incoming intensity of the pulse. The transient optical response of the material has been analyzed by means of fs-resolved optical microscopy in reflection configuration over a time span from 0.1 ps to about 1 ns. Characteristic phenomena like electron plasma formation, ultrafast melting and ablation, along with their characteristic time scales are observed in the region surrounding the particle. The use of a time resolved imaging technique allows us recording simultaneously the material response at ordinary and large peak power densities enabling a direct comparison between both scenarios. The time resolved images of near field exposed regions are consistent with a remarkable temporal shift of the ablation onset which occurs in the sub-picosend regime, from about 500 to 800 fs after excitation. PMID:24062976

Use of a size-resolved 1-D resuspension scheme to evaluate resuspended radioactive material associated with mineral dust particles from the ground surface.

PubMed

Ishizuka, Masahide; Mikami, Masao; Tanaka, Taichu Y; Igarashi, Yasuhito; Kita, Kazuyuki; Yamada, Yutaka; Yoshida, Naohiro; Toyoda, Sakae; Satou, Yukihiko; Kinase, Takeshi; Ninomiya, Kazuhiko; Shinohara, Atsushi

2017-01-01

A size-resolved, one-dimensional resuspension scheme for soil particles from the ground surface is proposed to evaluate the concentration of radioactivity in the atmosphere due to the secondary emission of radioactive material. The particle size distributions of radioactive particles at a sampling point were measured and compared with the results evaluated by the scheme using four different soil textures: sand, loamy sand, sandy loam, and silty loam. For sandy loam and silty loam, the results were in good agreement with the size-resolved atmospheric radioactivity concentrations observed at a school ground in Tsushima District, Namie Town, Fukushima, which was heavily contaminated after the Fukushima Dai-ichi Nuclear Power Plant accident in March 2011. Though various assumptions were incorporated into both the scheme and evaluation conditions, this study shows that the proposed scheme can be applied to evaluate secondary emissions caused by aeolian resuspension of radioactive materials associated with mineral dust particles from the ground surface. The results underscore the importance of taking soil texture into account when evaluating the concentrations of resuspended, size-resolved atmospheric radioactivity. Copyright © 2016 Elsevier Ltd. All rights reserved.

High-Field Asymmetric-Waveform Ion Mobility Spectrometry and Electron Detachment Dissociation of Isobaric Mixtures of Glycosaminoglycans

NASA Astrophysics Data System (ADS)

Kailemia, Muchena J.; Park, Melvin; Kaplan, Desmond A.; Venot, Andre; Boons, Geert-Jan; Li, Lingyun; Linhardt, Robert J.; Amster, I. Jonathan

2014-02-01

High-field asymmetric waveform ion mobility spectrometry (FAIMS) is shown to be capable of resolving isomeric and isobaric glycosaminoglycan negative ions and to have great utility for the analysis of this class of molecules when combined with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) and tandem mass spectrometry. Electron detachment dissociation (EDD) and other ion activation methods for tandem mass spectrometry can be used to determine the sites of labile sulfate modifications and for assigning the stereochemistry of hexuronic acid residues of glycosaminoglycans (GAGs). However, mixtures with overlapping mass-to-charge values present a challenge, as their precursor species cannot be resolved by a mass analyzer prior to ion activation. FAIMS is shown to resolve two types of mass-to-charge overlaps. A mixture of chondroitin sulfate A (CSA) oligomers with 4-10 saccharides units produces ions of a single mass-to-charge by electrospray ionization, as the charge state increases in direct proportion to the degree of polymerization for these sulfated carbohydrates. FAIMS is shown to resolve the overlapping charge. A more challenging type of mass-to-charge overlap occurs for mixtures of diastereomers. FAIMS is shown to separate two sets of epimeric GAG tetramers. For the epimer pairs, the complexity of the separation is reduced when the reducing end is alkylated, suggesting that anomers are also resolved by FAIMS. The resolved components were activated by EDD and the fragment ions were analyzed by FTICR-MS. The resulting tandem mass spectra were able to distinguish the two epimers from each other.

Issues surrounding the health economic evaluation of genomic technologies

PubMed Central

Buchanan, James; Wordsworth, Sarah; Schuh, Anna

2014-01-01

Aim Genomic interventions could enable improved disease stratification and individually tailored therapies. However, they have had a limited impact on clinical practice to date due to a lack of evidence, particularly economic evidence. This is partly because health economists are yet to reach consensus on whether existing methods are sufficient to evaluate genomic technologies. As different approaches may produce conflicting adoption decisions, clarification is urgently required. This article summarizes the methodological issues associated with conducting economic evaluations of genomic interventions. Materials & methods A structured literature review was conducted to identify references that considered the methodological challenges faced when conducting economic evaluations of genomic interventions. Results Methodological challenges related to the analytical approach included the choice of comparator, perspective and timeframe. Challenges in costing centered around the need to collect a broad range of costs, frequently, in a data-limited environment. Measuring outcomes is problematic as standard measures have limited applicability, however, alternative metrics (e.g., personal utility) are underdeveloped and alternative approaches (e.g., cost–benefit analysis) underused. Effectiveness data quality is weak and challenging to incorporate into standard economic analyses, while little is known about patient and clinician behavior in this context. Comprehensive value of information analyses are likely to be helpful. Conclusion Economic evaluations of genomic technologies present a particular challenge for health economists. New methods may be required to resolve these issues, but the evidence to justify alternative approaches is yet to be produced. This should be the focus of future work in this field. PMID:24236483

Development of a novel high-entropy alloy with eminent efficiency of degrading azo dye solutions

PubMed Central

Lv, Z. Y.; Liu, X. J.; Jia, B.; Wang, H.; Wu, Y.; Lu, Z. P.

2016-01-01

In addition to its scientific importance, the degradation of azo dyes is of practical significance from the perspective of environmental protection. Although encouraging progress has been made on developing degradation approaches and materials, it is still challenging to fully resolve this long-standing problem. Herein, we report that high entropy alloys, which have been emerging as a new class of metallic materials in the last decade, have excellent performance in degradation of azo dyes. In particular, the newly developed AlCoCrTiZn high-entropy alloy synthesized by mechanical alloying exhibits a prominent efficiency in degradation of the azo dye (Direct Blue 6: DB6), as high as that of the best metallic glass reported so far. The newly developed AlCoCrTiZn HEA powder has low activation energy barrier, i.e., 30 kJ/mol, for the degrading reaction and thus make the occurrence of reaction easier as compared with other materials such as the glassy Fe-based powders. The excellent capability of our high-entropy alloys in degrading azo dye is attributed to their unique atomic structure with severe lattice distortion, chemical composition effect, residual stress and high specific surface area. Our findings have important implications in developing novel high-entropy alloys for functional applications as catalyst materials. PMID:27677462

Data-Driven Learning of Total and Local Energies in Elemental Boron

NASA Astrophysics Data System (ADS)

Deringer, Volker L.; Pickard, Chris J.; Csányi, Gábor

2018-04-01

The allotropes of boron continue to challenge structural elucidation and solid-state theory. Here we use machine learning combined with random structure searching (RSS) algorithms to systematically construct an interatomic potential for boron. Starting from ensembles of randomized atomic configurations, we use alternating single-point quantum-mechanical energy and force computations, Gaussian approximation potential (GAP) fitting, and GAP-driven RSS to iteratively generate a representation of the element's potential-energy surface. Beyond the total energies of the very different boron allotropes, our model readily provides atom-resolved, local energies and thus deepened insight into the frustrated β -rhombohedral boron structure. Our results open the door for the efficient and automated generation of GAPs, and other machine-learning-based interatomic potentials, and suggest their usefulness as a tool for materials discovery.

Data-Driven Learning of Total and Local Energies in Elemental Boron.

PubMed

Deringer, Volker L; Pickard, Chris J; Csányi, Gábor

2018-04-13

The allotropes of boron continue to challenge structural elucidation and solid-state theory. Here we use machine learning combined with random structure searching (RSS) algorithms to systematically construct an interatomic potential for boron. Starting from ensembles of randomized atomic configurations, we use alternating single-point quantum-mechanical energy and force computations, Gaussian approximation potential (GAP) fitting, and GAP-driven RSS to iteratively generate a representation of the element's potential-energy surface. Beyond the total energies of the very different boron allotropes, our model readily provides atom-resolved, local energies and thus deepened insight into the frustrated β-rhombohedral boron structure. Our results open the door for the efficient and automated generation of GAPs, and other machine-learning-based interatomic potentials, and suggest their usefulness as a tool for materials discovery.

Optical phenomena and antifrosting property on biomimetics slippery fluid-infused antireflective films via layer-by-layer comparison with superhydrophobic and antireflective films.

PubMed

Manabe, Kengo; Nishizawa, Shingo; Kyung, Kyu-Hong; Shiratori, Seimei

2014-08-27

Sophisticated material interfaces generated by natural life forms such as lotus leaves and Nepenthes pitcher plants have exceptional abilities to resolve challenges in wide areas of industry and medicine. The nano- and microstructures inspired by these natural materials can repel various liquids and form self-cleaning coatings. In particular, slippery liquid-infused surfaces are receiving remarkable interest as transparent, nonfouling, and antifrosting synthetic surfaces for solar cells and optical devices. Here we focus on the transparency of lubricant-infused texture on antireflective films fabricated by layer-by-layer self-assembly that decrease light scattering, which is important to maintain device properties. A slippery fluid-infused antireflective film composed of chitin nanofibers less than 50 nm in diameter prevented light scattering at the long-wavelength side by Rayleigh scattering to achieve 97.2% transmittance. Moreover, films composed of the same materials demonstrated three different morphologies: superhydrophilicity with antireflection, superhydrophobicity, and omniphobicity, mimicking the biological structures of moth eyes, lotus leaves, and pitcher plants, respectively. The effect of thermal changes on the ability of each film to prevent frost formation was investigated. The slippery fluid-infused antireflective film showed effective antifrosting behavior.

Cellulose nanomaterials as green nanoreinforcements for polymer nanocomposites

NASA Astrophysics Data System (ADS)

Dufresne, Alain

2017-12-01

Unexpected and attractive properties can be observed when decreasing the size of a material down to the nanoscale. Cellulose is no exception to the rule. In addition, the highly reactive surface of cellulose resulting from the high density of hydroxyl groups is exacerbated at this scale. Different forms of cellulose nanomaterials, resulting from a top-down deconstruction strategy (cellulose nanocrystals, cellulose nanofibrils) or bottom-up strategy (bacterial cellulose), are potentially useful for a large number of industrial applications. These include the paper and cardboard industry, use as reinforcing filler in polymer nanocomposites, the basis for low-density foams, additives in adhesives and paints, as well as a wide variety of filtration, electronic, food, hygiene, cosmetic and medical products. This paper focuses on the use of cellulose nanomaterials as a filler for the preparation of polymer nanocomposites. Impressive mechanical properties can be obtained for these materials. They obviously depend on the type of nanomaterial used, but the crucial point is the processing technique. The emphasis is on the melt processing of such nanocomposite materials, which has not yet been properly resolved and remains a challenge. This article is part of a discussion meeting issue `New horizons for cellulose nanotechnology'.

Rapid response sensor for analyzing Special Nuclear Material

DOE PAGES

Mitra, S. S.; Doron, O.; Chen, A. X.; ...

2015-06-18

Rapid in-situ analytical techniques are attractive for characterizing Special Nuclear Material (SNM). Present techniques are time consuming, and require sample dissolution. Proof-of-principal studies are performed to demonstrate the utility of employing low energy neutrons from a portable pulsed neutron generator for non-destructive isotopic analysis of nuclear material. In particular, time-sequenced data acquisition, operating synchronously with the pulsing of a neutron generator, partitions the characteristic elemental prompt gamma-rays according to the type of the reaction; inelastic neutron scattering reactions during the ON state and thermal neutron capture reactions during the OFF state of the generator. Thus, the key challenge is isolatingmore » these signature gamma- rays from the prompt fission and β-delayed gamma-rays that are also produced during the neutron interrogation. A commercial digital multi-channel analyzer has been specially customized to enable time-resolved gamma-ray spectral data to be acquired in multiple user-defined time bins within each of the ON/OFF gate periods of the neutron generator. Preliminary results on new signatures from depleted uranium as well as modeling and benchmarking of the concept are presented, however this approach should should be applicable for virtually all forms of SNM.« less

Challenge: The Arts as Collaborative Inquiry

ERIC Educational Resources Information Center

Hallmark, Elizabeth F.

2012-01-01

An immediate critical task of the arts education field is to resolve the polarities of low-quality integrative and overly marginalized discipline-specific approaches to teaching in schools. In pursuing this challenge, the author defines three teaching approaches--arts as craftsmanship, arts as play, and arts as inquiry--and calls for re-weighted…

Neonatal lipopolysaccharide challenge does not diminish the innate immune response to a subsequent lipopolysaccharide challenge in holstein bull calves

USDA-ARS?s Scientific Manuscript database

The innate immune response following experimental mastitis is quite variable between individual dairy cattle. An inflammatory response that minimizes collateral damage to the mammary gland while still effectively resolving the infection following pathogen exposure is beneficial to dairy producers. ...

Ecology and management of pinyon-juniper ecosystems in the Bureau of Indian Affairs Southwestern Region

Treesearch

John Waconda

2008-01-01

The large acreages of the woodland forest cover type on tribal lands continues to post challenges to this agency's overall management strategies. The development of management plans, evaluation of growth study plots, and anticipated biomass utilization can help resolve some of the challenges.

Challenges of Conducting Systematic Research in Australia's Northern Territory

ERIC Educational Resources Information Center

Helmer, Janet; Harper, Helen; Lea, Tess; Wolgemuth, Jennifer R.; Chalkiti, Kalotina

2014-01-01

This paper explores the challenges of conducting systematic research, using our experiences of conducting a study to evaluate the effectiveness of ABRACADABRA, an online tool for early childhood literacy instruction as the contextual framework. By discussing how the research team resolved such perennial issues as high teacher turnover, low or…

Relational Challenges and Recovery Processes in Male Survivors of Childhood Sexual Abuse

ERIC Educational Resources Information Center

Kia-Keating, Maryam; Sorsoli, Lynn; Grossman, Frances K.

2010-01-01

Male survivors of childhood sexual abuse face challenges resolving sexual victimization experiences with the ideals of masculinity, often experiencing intimacy problems, emotional discomfort, alienation, and anger. Little attention has been paid to how male survivors learn to develop long-term connections, disclose emotions in relationship…

Applying Scientific Principles to Resolve Student Misconceptions

ERIC Educational Resources Information Center

Yin, Yue

2012-01-01

Misconceptions about sinking and floating phenomena are some of the most challenging to overcome (Yin 2005), possibly because explaining sinking and floating requires students to understand challenging topics such as density, force, and motion. Two scientific principles are typically used in U.S. science curricula to explain sinking and floating:…

Organic/hybrid thin films deposited by matrix-assisted pulsed laser evaporation (MAPLE)

NASA Astrophysics Data System (ADS)

Stiff-Roberts, Adrienne D.; Ge, Wangyao

2017-12-01

Some of the most exciting materials research in the 21st century attempts to resolve the challenge of simulating, synthesizing, and characterizing new materials with unique properties designed from first principles. Achievements in such development for organic and organic-inorganic hybrid materials make them important options for electronic and/or photonic devices because they can impart multi-functionality, flexibility, transparency, and sustainability to emerging systems, such as wearable electronics. Functional organic materials include small molecules, oligomers, and polymers, while hybrid materials include inorganic nanomaterials (such as zero-dimensional quantum dots, one-dimensional carbon nanotubes, or two-dimensional nanosheets) combined with organic matrices. A critically important step to implementing new electronic and photonic devices using such materials is the processing of thin films. While solution-based processing is the most common laboratory technique for organic and hybrid materials, vacuum-based deposition has been critical to the commercialization of organic light emitting diodes based on small molecules, for example. Therefore, it is desirable to explore vacuum-based deposition of organic and hybrid materials that include larger macromolecules, such as polymers. This review article motivates the need for physical vapor deposition of polymeric and hybrid thin films using matrix-assisted pulsed laser evaporation (MAPLE), which is a type of pulsed laser deposition. This review describes the development of variations in the MAPLE technique, discusses the current understanding of laser-target interactions and growth mechanisms for different MAPLE variations, surveys demonstrations of MAPLE-deposited organic and hybrid materials for electronic and photonic devices, and provides a future outlook for the technique.

Spatially-resolved studies on the role of defects and boundaries in electronic behavior of 2D materials

NASA Astrophysics Data System (ADS)

Hus, Saban M.; Li, An-Ping

2017-08-01

Two-dimensional (2D) materials are intrinsically heterogeneous. Both localized defects, such as vacancies and dopants, and mesoscopic boundaries, such as surfaces and interfaces, give rise to compositional or structural heterogeneities. The presence of defects and boundaries can break lattice symmetry, modify the energy landscape, and create quantum confinement, leading to fascinating electronic properties different from the ;ideal; 2D sheets. This review summarizes recent progress in understanding the roles of defects and boundaries in electronic, magnetic, thermoelectric, and transport properties of 2D layered materials. The focus is on the understanding of correlation of atomic-scale structural information with electronic functions by interrogating heterogeneities individually. The materials concerned are graphene, transition metal dichalcogenides (TMDs), hexagonal boron nitride (hBN), and topological insulators (TIs). The experimental investigations benefit from new methodologies and techniques in scanning tunneling microscopy (STM), including spin-polarized STM, scanning tunneling potentiometry (STP), scanning tunneling thermopower microscopy, and multi-probe STM. The experimental effort is complemented by the computational and theoretical approaches, capable of discriminating between closely competing states and achieving the length scales necessary to bridge across features such as local defects and complex heterostructures. The goal is to provide a general view of current understanding and challenges in studying the heterogeneities in 2D materials and to evaluate the potential of controlling and exploiting these heterogeneities for novel functionalities and electron devices.

Ultrathin 2D Photocatalysts: Electronic-Structure Tailoring, Hybridization, and Applications.

PubMed

Di, Jun; Xiong, Jun; Li, Huaming; Liu, Zheng

2018-01-01

As a sustainable technology, semiconductor photocatalysis has attracted considerable interest in the past several decades owing to the potential to relieve or resolve energy and environmental-pollution issues. By virtue of their unique structural and electronic properties, emerging ultrathin 2D materials with appropriate band structure show enormous potential to achieve efficient photocatalytic performance. Here, the state-of-the-art progress on ultrathin 2D photocatalysts is reviewed and a critical appraisal of the classification, controllable synthesis, and formation mechanism of ultrathin 2D photocatalysts is presented. Then, different strategies to tailor the electronic structure of ultrathin 2D photocatalysts are summarized, including component tuning, thickness tuning, doping, and defect engineering. Hybridization with the introduction of a foreign component and maintaining the ultrathin 2D structure is presented to further boost the photocatalytic performance, such as quantum dots/2D materials, single atoms/2D materials, molecular/2D materials, and 2D-2D stacking materials. More importantly, the advancement of versatile photocatalytic applications of ultrathin 2D photocatalysts in the fields of water oxidation, hydrogen evolution, CO 2 reduction, nitrogen fixation, organic syntheses, and removal pollutants is discussed. Finally, the future opportunities and challenges regarding ultrathin 2D photocatalysts to bring about new opportunities for future research in the field of photocatalysis are also presented. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toward an efficient inverse characterization of the viscoelastic properties of anisotropic media based on the ultrasonic polar scan

NASA Astrophysics Data System (ADS)

Martens, A.; Kersemans, M.; Daemen, J.; Verboven, E.; Van Paepegem, W.; Degrieck, J.; Delrue, S.; Van Den Abeele, K.

2018-04-01

Composite materials (e.g., carbon fiber reinforced plastics (CFRP)) are increasingly used for critical components in several industrial sectors (e.g. aerospace, automotive). Their anisotropic nature makes it difficult to accurately determine material properties or to assess internal damages. To resolve these challenges, the Ultrasonic Polar Scan (UPS) technique has been introduced. In a UPS experiment, a fixed material spot is insonified at a multitude of incidence angles Ψ(θ,φ) for which the transmission amplitude as well as the associated arrival time (time-of-flight) are measured. Mapping these quantities on a polar diagram represents a fingerprint of the local viscoelasticity of the investigated material. In the present study, we propose a novel two-stage inversion scheme that is able to infer both the elastic and the viscous properties. In the first step, we solve the inverse problem of determining the elastic constants from time-of-flight UPS recordings. The second stage handles a similar inverse problem, but now operates on the amplitude landscape of a UPS experiment for determining the viscous part of the viscoelastic tensor. This two-stage procedure thus yields the viscoelastic tensor of the insonified material spot. The developed characterization scheme has been employed on both virtual (numerical) UPS recordings, to test the effectiveness of the method, and experimental UPS recordings of unidirectional C/E plates.

Time-resolved quantitative-phase microscopy of laser-material interactions using a wavefront sensor.

PubMed

Gallais, Laurent; Monneret, Serge

2016-07-15

We report on a simple and efficient technique based on a wavefront sensor to obtain time-resolved amplitude and phase images of laser-material interactions. The main interest of the technique is to obtain quantitative self-calibrated phase measurements in one shot at the femtosecond time-scale, with high spatial resolution. The technique is used for direct observation and quantitative measurement of the Kerr effect in a fused silica substrate and free electron generation by photo-ionization processes in an optical coating.

Detection of delamination defects in CFRP materials using ultrasonic signal processing.

PubMed

Benammar, Abdessalem; Drai, Redouane; Guessoum, Abderrezak

2008-12-01

In this paper, signal processing techniques are tested for their ability to resolve echoes associated with delaminations in carbon fiber-reinforced polymer multi-layered composite materials (CFRP) detected by ultrasonic methods. These methods include split spectrum processing (SSP) and the expectation-maximization (EM) algorithm. A simulation study on defect detection was performed, and results were validated experimentally on CFRP with and without delamination defects taken from aircraft. Comparison of the methods for their ability to resolve echoes are made.

Bioinspired Tuning of Hydrogel Permeability-Rigidity Dependency for 3D Cell Culture

NASA Astrophysics Data System (ADS)

Lee, Min Kyung; Rich, Max H.; Baek, Kwanghyun; Lee, Jonghwi; Kong, Hyunjoon

2015-03-01

Hydrogels are being extensively used for three-dimensional immobilization and culture of cells in fundamental biological studies, biochemical processes, and clinical treatments. However, it is still a challenge to support viability and regulate phenotypic activities of cells in a structurally stable gel, because the gel becomes less permeable with increasing rigidity. To resolve this challenge, this study demonstrates a unique method to enhance the permeability of a cell-laden hydrogel while avoiding a significant change in rigidity of the gel. Inspired by the grooved skin textures of marine organisms, a hydrogel is assembled to present computationally optimized micro-sized grooves on the surface. Separately, a gel is engineered to preset aligned microchannels similar to a plant's vascular bundles through a uniaxial freeze-drying process. The resulting gel displays significantly increased water diffusivity with reduced changes of gel stiffness, exclusively when the microgrooves and microchannels are aligned together. No significant enhancement of rehydration is achieved when the microgrooves and microchannels are not aligned. Such material design greatly enhances viability and neural differentiation of stem cells and 3D neural network formation within the gel.

Future Challenges in Heterogeneous Catalysis: Understanding Catalysts under Dynamic Reaction Conditions

PubMed Central

Kalz, Kai F.; Kraehnert, Ralph; Dvoyashkin, Muslim; Dittmeyer, Roland; Gläser, Roger; Krewer, Ulrike; Reuter, Karsten

2016-01-01

Abstract In the future, (electro‐)chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable energies. For example, power‐to‐chemical processes require a shift from steady‐state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both catalysts and reactors, because it is well‐known that the structure of catalysts is very dynamic. However, in‐depth studies of catalysts and catalytic reactors under such transient conditions have only started recently. This requires studies and advances in the fields of 1) operando spectroscopy including time‐resolved methods, 2) theory with predictive quality, 3) kinetic modelling, 4) design of catalysts by appropriate preparation concepts, and 5) novel/modular reactor designs. An intensive exchange between these scientific disciplines will enable a substantial gain of fundamental knowledge which is urgently required. This concept article highlights recent developments, challenges, and future directions for understanding catalysts under dynamic reaction conditions. PMID:28239429

Fast laboratory-based micro-computed tomography for pore-scale research: Illustrative experiments and perspectives on the future

NASA Astrophysics Data System (ADS)

Bultreys, Tom; Boone, Marijn A.; Boone, Matthieu N.; De Schryver, Thomas; Masschaele, Bert; Van Hoorebeke, Luc; Cnudde, Veerle

2016-09-01

Over the past decade, the wide-spread implementation of laboratory-based X-ray micro-computed tomography (micro-CT) scanners has revolutionized both the experimental and numerical research on pore-scale transport in geological materials. The availability of these scanners has opened up the possibility to image a rock's pore space in 3D almost routinely to many researchers. While challenges do persist in this field, we treat the next frontier in laboratory-based micro-CT scanning: in-situ, time-resolved imaging of dynamic processes. Extremely fast (even sub-second) micro-CT imaging has become possible at synchrotron facilities over the last few years, however, the restricted accessibility of synchrotrons limits the amount of experiments which can be performed. The much smaller X-ray flux in laboratory-based systems bounds the time resolution which can be attained at these facilities. Nevertheless, progress is being made to improve the quality of measurements performed on the sub-minute time scale. We illustrate this by presenting cutting-edge pore scale experiments visualizing two-phase flow and solute transport in real-time with a lab-based environmental micro-CT set-up. To outline the current state of this young field and its relevance to pore-scale transport research, we critically examine its current bottlenecks and their possible solutions, both on the hardware and the software level. Further developments in laboratory-based, time-resolved imaging could prove greatly beneficial to our understanding of transport behavior in geological materials and to the improvement of pore-scale modeling by providing valuable validation.

Spatial and spectral resolution of carbonaceous material from hematite (α-Fe2O3) using multivariate curve resolution-alternating least squares (MCR-ALS) with Raman microspectroscopic mapping: implications for the search for life on Mars.

PubMed

Smith, Joseph P; Smith, Frank C; Booksh, Karl S

2017-08-21

The search for evidence of extant or past life on Mars is a primary objective of both the upcoming Mars 2020 rover (NASA) and ExoMars 2020 rover (ESA/Roscosmos) missions. This search will involve the detection and identification of organic molecules and/or carbonaceous material within the Martian surface environment. For the first time on a mission to Mars, the scientific payload for each rover will include a Raman spectrometer, an instrument well-suited for this search. Hematite (α-Fe 2 O 3 ) is a widespread mineral on the Martian surface. The 2LO Raman band of hematite and the Raman D-band of carbonaceous material show spectral overlap, leading to the potential misidentification of hematite as carbonaceous material. Here we report the ability to spatially and spectrally differentiate carbonaceous material from hematite using multivariate curve resolution-alternating least squares (MCR-ALS) applied to Raman microspectroscopic mapping under both 532 nm and 785 nm excitation. For this study, a sample comprised of hematite, carbonaceous material, and substrate-adhesive epoxy in spatially distinct domains was constructed. Principal component analysis (PCA) reveals that both 532 nm and 785 nm excitation produce representative three-phase systems of hematite, carbonaceous material, and substrate-adhesive epoxy in the analyzed sample. MCR-ALS with Raman microspectroscopic mapping using both 532 nm and 785 nm excitation was able to resolve hematite, carbonaceous material, and substrate-adhesive epoxy by generating spatially-resolved chemical maps and corresponding Raman spectra of these spatially distinct chemical species. Moreover, MCR-ALS applied to the combinatorial data sets of 532 nm and 785 nm excitation, which contain hematite and carbonaceous material within the same locations, was able to resolve hematite, carbonaceous material, and substrate-adhesive epoxy. Using multivariate analysis with Raman microspectroscopic mapping, 785 nm excitation more effectively resolved hematite, carbonaceous material, and substrate-adhesive epoxy as compared to 532 nm excitation. To our knowledge, this is the first report of multivariate analysis methods, namely MCR-ALS, with Raman microspectroscopic mapping being employed to differentiate carbonaceous material from hematite. We have therefore provided an analytical methodology useful for the search for extant or past life on the surface of Mars.

Resolving the optical anisotropy of low-symmetry 2D materials.

PubMed

Shen, Wanfu; Hu, Chunguang; Tao, Jin; Liu, Jun; Fan, Shuangqing; Wei, Yaxu; An, Chunhua; Chen, Jiancui; Wu, Sen; Li, Yanning; Liu, Jing; Zhang, Daihua; Sun, Lidong; Hu, Xiaotang

2018-05-03

Optical anisotropy is one of the most fundamental physical characteristics of emerging low-symmetry two-dimensional (2D) materials. It provides abundant structural information and is crucial for creating diverse nanoscale devices. Here, we have proposed an azimuth-resolved microscopic approach to directly resolve the normalized optical difference along two orthogonal directions at normal incidence. The differential principle ensures that the approach is only sensitive to anisotropic samples and immune to isotropic materials. We studied the optical anisotropy of bare and encapsulated black phosphorus (BP) and unveiled the interference effect on optical anisotropy, which is critical for practical applications in optical and optoelectronic devices. A multi-phase model based on the scattering matrix method was developed to account for the interference effect and then the crystallographic directions were unambiguously determined. Our result also suggests that the optical anisotropy is a probe to measure the thickness with monolayer resolution. Furthermore, the optical anisotropy of rhenium disulfide (ReS2), another class of anisotropic 2D materials, with a 1T distorted crystal structure, was investigated, which demonstrates that our approach is suitable for other anisotropic 2D materials. This technique is ideal for optical anisotropy characterization and will inspire future efforts in BP and related anisotropic 2D nanomaterials for engineering new conceptual nanodevices.

Central serous chorioretinopathy treatment with spironolactone: a challenge-rechallenge case.

PubMed

Ryan, Edwin H; Pulido, Christine M

2015-01-01

To present a case of central serous chorioretinopathy (CSC) treatment with spironolactone in a challenge-rechallenge pattern. At presentation, fundus photography, fluorescein angiography, spectral domain optical coherence tomography, and enhanced depth imaging ocular coherence tomography were performed in both eyes. The patient was prescribed 25 mg spironolactone daily along with serum potassium monitoring. At follow-ups, spectral domain optical coherence tomography and enhanced depth imaging ocular coherence tomography were performed. A 37-year-old white male accountant presenting with CSC. Spironolactone treatment resolved the CSC. After the patient discontinued treatment, it returned. After returning to daily treatment, the CSC again resolved. Spironolactone was an effective treatment of CSC in this case. Other groups have reported similar findings with eplerenone, a similar drug.

A fully resolved consensus between fully resolved phylogenetic trees.

PubMed

Quitzau, José Augusto Amgarten; Meidanis, João

2006-03-31

Nowadays, there are many phylogeny reconstruction methods, each with advantages and disadvantages. We explored the advantages of each method, putting together the common parts of trees constructed by several methods, by means of a consensus computation. A number of phylogenetic consensus methods are already known. Unfortunately, there is also a taboo concerning consensus methods, because most biologists see them mainly as comparators and not as phylogenetic tree constructors. We challenged this taboo by defining a consensus method that builds a fully resolved phylogenetic tree based on the most common parts of fully resolved trees in a given collection. We also generated results showing that this consensus is in a way a kind of "median" of the input trees; as such it can be closer to the correct tree in many situations.

Integrated experimental setup for angle resolved photoemission spectroscopy of transuranic materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Graham, Kevin S.; Joyce, John J.; Durakiewicz, Tomasz

2013-09-15

We have developed the Angle Resolved Photoemission Spectroscopy (ARPES) system for transuranic materials. The ARPES transuranic system is an endstation upgrade to the Laser Plasma Light Source (LPLS) at Los Alamos National Laboratory. The LPLS is a tunable light source for photoemission with a photon energy range covering the vacuum ultraviolet (VUV) and soft x-ray regions (27–140 eV). The LPLS was designed and developed for transuranic materials. Transuranic photoemission is currently not permitted at the public synchrotrons worldwide in the VUV energy range due to sample encapsulation requirements. With the addition of the ARPES capability to the LPLS system theremore » is an excellent opportunity to explore new details centered on the electronic structure of actinide and transuranic materials.« less

Imaging powders with the atomic force microscope: from biominerals to commercial materials.

PubMed

Friedbacher, G; Hansma, P K; Ramli, E; Stucky, G D

1991-09-13

Atomically resolved images of pressed powder samples have been obtained with the atomic force microscope (AFM). The technique was successful in resolving the particle, domain, and atomic structure of pismo clam (Tivela stultorum) and sea urchin (Strongylocentrotus purpuratus) shells and of commercially available calcium carbonate (CaCO(3)) and strontium carbonate (SrCO(3)) powders. Grinding and subsequent pressing of the shells did not destroy the microstructure of these materials. The atomic-resolution imaging capabilities of AFM can be applied to polycrystalline samples by means of pressing powders with a grain size as small as 50 micrometers. These results illustrate that the AFM is a promising tool for material science and the study of biomineralization.

Lattice-Boltzmann Modeling of Community Challenge MicrofluidicExperiments to Evaluate the Effects of Wettability on Two-Fluid Flowin Porous Media

NASA Astrophysics Data System (ADS)

Miller, C. T.; McClure, J. E.; Bruning, K.

2017-12-01

Variations in the wettability of a solid material are well known to affect the flow of two fluids in a porous media. However, thesemechanisms have not been modeled with high fidelity at the microscale and such mechanisms are typically not included in macroscalemodels. Recent experimental work by Zhao, MacMinn, and Juanes published in the Proceedings of the National Academy of Sciences(2016) has investigated two-fluid displacement in microfluidic cells. Displacement patterns were investigated as a function of thecontact angle and the capillary number for both drainage and imbibition. These results yielded new mechanistic understanding ofprocesses such as pore filling and post bridging, which were imaged at high resolution. In a challenge to the pore-scale modeling community,the authors of this work released their experimental data and encouraged an international set of modeling research groups tosimulate the conditions that were experimentally observed. The intent is to compare the results that materialize to shed new light on thestate-of-science in pore-scale simulation of these challenging and interesting flow systems. In this work, we summarize the experimentalfindings and report on initial efforts to simulate these community challenge experiments using a high-resolution lattice-Boltzmann method(LBM). A three-dimensional, multiple-relaxation-time color model based on a 19-site lattice is advanced in this work to matchexperimental conditions in a novel manner. A computational approach is implemented for the LBM method on hybrid CPU-GPU nodes and shown toscale near optimally. A new algorithm is described to match experimental boundary conditions. A grid-resolution study is performedto determine the resolution needed to determine grid-independent numerical approximations. Finally, the LBM simulation results arecompared to the highly resolved microfluidic experiments, displacement mechanisms are investigated, and observations and analysis of thetopological state evolution of the system are reported.

Karhunen-Loève treatment to remove noise and facilitate data analysis in sensing, spectroscopy and other applications.

PubMed

Zaharov, V V; Farahi, R H; Snyder, P J; Davison, B H; Passian, A

2014-11-21

Resolving weak spectral variations in the dynamic response of materials that are either dominated or excited by stochastic processes remains a challenge. Responses that are thermal in origin are particularly relevant examples due to the delocalized nature of heat. Despite its inherent properties in dealing with stochastic processes, the Karhunen-Loève expansion has not been fully exploited in measurement of systems that are driven solely by random forces or can exhibit large thermally driven random fluctuations. Here, we present experimental results and analysis of the archetypes (a) the resonant excitation and transient response of an atomic force microscope probe by the ambient random fluctuations and nanoscale photothermal sample response, and (b) the photothermally scattered photons in pump-probe spectroscopy. In each case, the dynamic process is represented as an infinite series with random coefficients to obtain pertinent frequency shifts and spectral peaks and demonstrate spectral enhancement for a set of compounds including the spectrally complex biomass. The considered cases find important applications in nanoscale material characterization, biosensing, and spectral identification of biological and chemical agents.

Many-body interferometry of magnetic polaron dynamics

NASA Astrophysics Data System (ADS)

Ashida, Yuto; Schmidt, Richard; Tarruell, Leticia; Demler, Eugene

2018-02-01

The physics of quantum impurities coupled to a many-body environment is among the most important paradigms of condensed-matter physics. In particular, the formation of polarons, quasiparticles dressed by the polarization cloud, is key to the understanding of transport, optical response, and induced interactions in a variety of materials. Despite recent remarkable developments in ultracold atoms and solid-state materials, the direct measurement of their ultimate building block, the polaron cloud, has remained a fundamental challenge. We propose and analyze a platform to probe time-resolved dynamics of polaron-cloud formation with an interferometric protocol. We consider an impurity atom immersed in a two-component Bose-Einstein condensate where the impurity generates spin-wave excitations that can be directly measured by the Ramsey interference of surrounding atoms. The dressing by spin waves leads to the formation of magnetic polarons and reveals a unique interplay between few- and many-body physics that is signified by single- and multi-frequency oscillatory dynamics corresponding to the formation of many-body bound states. Finally, we discuss concrete experimental implementations in ultracold atoms.

Controlling Thermal Expansion: A Metal–Organic Frameworks Route

PubMed Central

2016-01-01

Controlling thermal expansion is an important, not yet resolved, and challenging problem in materials research. A conceptual design is introduced here, for the first time, for the use of metal–organic frameworks (MOFs) as platforms for controlling thermal expansion devices that can operate in the negative, zero, and positive expansion regimes. A detailed computer simulation study, based on molecular dynamics, is presented to support the targeted application. MOF-5 has been selected as model material, along with three molecules of similar size and known differences in terms of the nature of host–guest interactions. It has been shown that adsorbate molecules can control, in a colligative way, the thermal expansion of the solid, so that changing the adsorbate molecules induces the solid to display positive, zero, or negative thermal expansion. We analyze in depth the distortion mechanisms, beyond the ligand metal junction, to cover the ligand distortions, and the energetic and entropic effect on the thermo-structural behavior. We provide an unprecedented atomistic insight on the effect of adsorbates on the thermal expansion of MOFs as a basic tool toward controlling the thermal expansion. PMID:28190918

The Influence of Geometrical Structure of AlInGaN Double Quantum Well (DQWs) UV Diode Laser on Its Performance and Operating Parameters

NASA Astrophysics Data System (ADS)

Ghazai, A. J.; Thahab, S. M.; Hassan, H. Abu; Hassan, Z.

2010-07-01

The development of efficient MQWs active regions of quaternary InAlGaN in the ultraviolet (UV) region is an engaging challenge by itself. Demonstrating lasers at such low wavelength will require resolving a number of materials, growth and device design issues. However, the quaternary AlInGaN represents a more versatile material since the bandgap and lattice constant can be independently varied. We report a quaternary AlInGaN double-quantum wells (DQWs) UV laser diode (LDs) study by using the simulation program of Integrated System Engineering-Technical Computer Aided Design (ISE TCAD). Advanced physical models of semiconductor properties were used. In this paper, the enhancement in the performance of AlInGaN laser diode can be achieved by optimizing the laser structure geometry design. The AlInGaN laser diodes operating parameters such as internal quantum efficiency ηi, internal loss αi and transparency threshold current density show effective improvements that contribute to a better performance.

A multiphysics microstructure-resolved model for silicon anode lithium-ion batteries

NASA Astrophysics Data System (ADS)

Wang, Miao; Xiao, Xinran; Huang, Xiaosong

2017-04-01

Silicon (Si) is one of the most promising next generation anode materials for lithium-ion batteries (LIBs), but the use of Si in LIBs has been rather limited. The main challenge is its large volume change (up to 300%) during battery cycling. This can lead to the fracture of Si, failure at the interfaces between electrode components, and large dimensional change on the cell level. To optimize the Si electrode/battery design, a model that considers the interactions of different cell components is needed. This paper presents the development of a multiphysics microstructure-resolved model (MRM) for LIB cells with a-Si anode. The model considered the electrochemical reactions, Li transports in electrolyte and electrodes, dimensional changes and stresses, property evolution with the structure, and the coupling relationships. Important model parameters, such as the diffusivity, reaction rate constant, and apparent transfer coefficient, were determined by correlating the simulation results to experiments. The model was validated with experimental results in the literature. The use of this model was demonstrated in a parameter study of Si nanowall|Li cells. The specific and volumetric capacities of the cell as a function of the size, length/size ratio, spacing of the nanostructure, and Li+ concentration in electrolyte were investigated.

On-line IR analyzer system to monitor cephamycin C loading on ion-exchange resin

NASA Astrophysics Data System (ADS)

Shank, Sheldon; Russ, Warren; Gravatt, Douglas; Lee, Wesley; Donahue, Steven M.

1992-08-01

An on-line infrared analyzer is being developed for monitoring cephamycin C loading on ion exchange resin. Accurate measurement of product loading offers productivity improvements with direct savings from product loss avoidance, minimized raw material cost, and reduced off-line laboratory testing. Ultrafiltered fermentation broth is fed onto ion exchange columns under conditions which adsorb the product, cephamycin C, to the resin while allowing impurities to pass unretained. Product loading is stopped when the on-line analyzer determines that resin capacity for adsorbing product is nearly exhausted. Infrared spectroscopy has been shown capable of quantifying cephamycin C in the process matrix at concentrations that support process control decisions. Process-to-analyzer interface challenges have been resolved, including sample conditioning requirements. Analyzer requirements have been defined. The sample conditioning station is under design.

Observational Evidence of Magnetic Waves in the Solar Atmosphere

NASA Astrophysics Data System (ADS)

McIntosh, Scott W.

2012-03-01

The observational evidence in supporting the presence of magnetic waves in the outer solar atmosphere is growing rapidly - we will discuss recent observations and place them in context with salient observations made in the past. While the clear delineation of these magnetic wave "modes" is unclear, much can be learned about the environment in which they originated and possibly how they are removed from the system from the observations. Their diagnostic power is, as yet, untapped and their energy content (both as a mechanical source for the heating of coronal material and acceleration of the solar wind) remains in question, but can be probed observationally - raising challenges for modeling efforts. We look forward to the IRIS mission by proposing some sample observing sequences to help resolve some of the zoological issues present in the literature.

Elasticity and Anelasticity of Materials from Time-Resolved X-ray Diffraction

NASA Astrophysics Data System (ADS)

Sinogeikin, S. V.; Smith, J.; Lin, C.; Bai, L.; Rod, E.; Shen, G.

2014-12-01

Recent advances in synchrotron sources, x-ray optics, area detectors, and sample environment control have enabled many time-resolved experimental techniques for studying materials at extreme pressure and temperature conditions. The High Pressure Collaborative Access Team (HPCAT) at the Advanced Photon Source has made a sustained effort to develop and assemble a powerful collection of high-pressure apparatus for time-resolved research, and considerable time has been invested in developing techniques for collecting high-quality time-resolved x-ray scattering data. In this talk we will outline recently developed capabilities at HPCAT for studying elasticity and anelasticity of minerals using fast compression and cyclic compression-decompression. A few recent studies will be highlighted. For example, with fast x-ray area detectors having millisecond time resolution, accurate thermal equations of state of materials at temperatures up to 1000K and megabar pressures can be collected in a matter of seconds using membrane-driven diamond anvil cells (DAC), yielding unprecedented time and pressure resolution of true isotherms. Short duration of the experiments eliminates temperature variation during the experiments and in general allows volume measurements at higher pressures and temperatures. Alternatively, high-frequency (kilohertz range) radial diffraction measurements in a panoramic DAC combined with fast, precise cyclic loading/unloading by piezo drive could provide the short time scale necessary for studying rheology of minerals from the elastic response and lattice relaxation as a function of pressure, temperature and strain rate. Finally, we consider some possible future applications for time-resolved high-pressure, high-temperature research of mantle minerals.

Automatic generation of user material subroutines for biomechanical growth analysis.

PubMed

Young, Jonathan M; Yao, Jiang; Ramasubramanian, Ashok; Taber, Larry A; Perucchio, Renato

2010-10-01

The analysis of the biomechanics of growth and remodeling in soft tissues requires the formulation of specialized pseudoelastic constitutive relations. The nonlinear finite element analysis package ABAQUS allows the user to implement such specialized material responses through the coding of a user material subroutine called UMAT. However, hand coding UMAT subroutines is a challenge even for simple pseudoelastic materials and requires substantial time to debug and test the code. To resolve this issue, we develop an automatic UMAT code generation procedure for pseudoelastic materials using the symbolic mathematics package MATHEMATICA and extend the UMAT generator to include continuum growth. The performance of the automatically coded UMAT is tested by simulating the stress-stretch response of a material defined by a Fung-orthotropic strain energy function, subject to uniaxial stretching, equibiaxial stretching, and simple shear in ABAQUS. The MATHEMATICA UMAT generator is then extended to include continuum growth by adding a growth subroutine to the automatically generated UMAT. The MATHEMATICA UMAT generator correctly derives the variables required in the UMAT code, quickly providing a ready-to-use UMAT. In turn, the UMAT accurately simulates the pseudoelastic response. In order to test the growth UMAT, we simulate the growth-based bending of a bilayered bar with differing fiber directions in a nongrowing passive layer. The anisotropic passive layer, being topologically tied to the growing isotropic layer, causes the bending bar to twist laterally. The results of simulations demonstrate the validity of the automatically coded UMAT, used in both standardized tests of hyperelastic materials and for a biomechanical growth analysis.

Human-Nature Relationships in School Science: A Critical Discourse Analysis of a Middle-Grade Science Textbook

ERIC Educational Resources Information Center

Sharma, Ajay; Buxton, Cory A.

2015-01-01

Science education has a central role to play in preparing a scientifically literate citizenry that is capable of understanding complex environmental challenges facing human societies and making well-informed and evidence-based decisions that help resolve these challenges. However, evidence suggests that most Americans are poorly equipped with the…

Recent trends in spin-resolved photoelectron spectroscopy

NASA Astrophysics Data System (ADS)

Okuda, Taichi

2017-12-01

Since the discovery of the Rashba effect on crystal surfaces and also the discovery of topological insulators, spin- and angle-resolved photoelectron spectroscopy (SARPES) has become more and more important, as the technique can measure directly the electronic band structure of materials with spin resolution. In the same way that the discovery of high-Tc superconductors promoted the development of high-resolution angle-resolved photoelectron spectroscopy, the discovery of this new class of materials has stimulated the development of new SARPES apparatus with new functions and higher resolution, such as spin vector analysis, ten times higher energy and angular resolution than conventional SARPES, multichannel spin detection, and so on. In addition, the utilization of vacuum ultra violet lasers also opens a pathway to the realization of novel SARPES measurements. In this review, such recent trends in SARPES techniques and measurements will be overviewed.

Resolving the Framework Position of Organic Structure-Directing Agents in Hierarchical Zeolites via Polarized Stimulated Raman Scattering.

PubMed

Fleury, Guillaume; Steele, Julian A; Gerber, Iann C; Jolibois, F; Puech, P; Muraoka, Koki; Keoh, Sye Hoe; Chaikittisilp, Watcharop; Okubo, Tatsuya; Roeffaers, Maarten B J

2018-04-05

The direct synthesis of hierarchically intergrown silicalite-1 can be achieved using a specific diquaternary ammonium agent. However, the location of these molecules in the zeolite framework, which is critical to understand the formation of the material, remains unclear. Where traditional characterization tools have previously failed, herein we use polarized stimulated Raman scattering (SRS) microscopy to resolve molecular organization inside few-micron-sized crystals. Through a combination of experiment and first-principles calculations, our investigation reveals the preferential location of the templating agent inside the linear pores of the MFI framework. Besides illustrating the attractiveness of SRS microscopy in the field of material science to study and spatially resolve local molecular distribution as well as orientation, these results can be exploited in the design of new templating agents for the preparation of hierarchical zeolites.

Time-resolved X-ray excited optical luminescence using an optical streak camera

NASA Astrophysics Data System (ADS)

Ward, M. J.; Regier, T. Z.; Vogt, J. M.; Gordon, R. A.; Han, W.-Q.; Sham, T. K.

2013-03-01

We report the development of a time-resolved XEOL (TR-XEOL) system that employs an optical streak camera. We have conducted TR-XEOL experiments at the Canadian Light Source (CLS) operating in single bunch mode with a 570 ns dark gap and 35 ps electron bunch pulse, and at the Advanced Photon Source (APS) operating in top-up mode with a 153 ns dark gap and 33.5 ps electron bunch pulse. To illustrate the power of this technique we measured the TR-XEOL of solid-solution nanopowders of gallium nitride - zinc oxide, and for the first time have been able to resolve near-band-gap (NBG) optical luminescence emission from these materials. Herein we will discuss the development of the streak camera TR-XEOL technique and its application to the study of these novel materials.

X-ray Absorption Spectroscopy Characterization of Electrochemical Processes in Renewable Energy Storage and Conversion Devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farmand, Maryam

2013-05-19

The development of better energy conversion and storage devices, such as fuel cells and batteries, is crucial for reduction of our global carbon footprint and improving the quality of the air we breathe. However, both of these technologies face important challenges. The development of lower cost and better electrode materials, which are more durable and allow more control over the electrochemical reactions occurring at the electrode/electrolyte interface, is perhaps most important for meeting these challenges. Hence, full characterization of the electrochemical processes that occur at the electrodes is vital for intelligent design of more energy efficient electrodes. X-ray absorption spectroscopymore » (XAS) is a short-range order, element specific technique that can be utilized to probe the processes occurring at operating electrode surfaces, as well for studying the amorphous materials and nano-particles making up the electrodes. It has been increasingly used in recent years to study fuel cell catalysts through application of the and #916; and mgr; XANES technique, in combination with the more traditional X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS) techniques. The and #916; and mgr; XANES data analysis technique, previously developed and applied to heterogeneous catalysts and fuel cell electrocatalysts by the GWU group, was extended in this work to provide for the first time space resolved adsorbate coverages on both electrodes of a direct methanol fuel cell. Even more importantly, the and #916; and mgr; technique was applied for the first time to battery relevant materials, where bulk properties such as the oxidation state and local geometry of a cathode are followed.« less

Inverse Algorithm Optimization for Determining Optical Properties of Biological Materials from Spatially-Resolved Diffuse Reflectance

USDA-ARS?s Scientific Manuscript database

Optical characterization of biological materials is useful in many scientific and industrial applications like biomedical diagnosis and nondestructive quality evaluation of food and agricultural products. However, accurate determination of the optical properties from intact biological materials base...

DNA barcode based wildlife forensics for resolving the origin of claw samples using a novel primer cocktail.

PubMed

Khedkar, Gulab D; Abhayankar, Shil Bapurao; Nalage, Dinesh; Ahmed, Shaikh Nadeem; Khedkar, Chandraprakash D

2016-11-01

Excessive wildlife hunting for commercial purposes can have negative impacts on biodiversity and may result in species extinction. To ensure compliance with legal statutes, forensic identification approaches relying on molecular markers may be used to identify the species of origin of animal material from hairs, claw, blood, bone, or meat. Using this approach, DNA sequences from the COI "barcoding" gene have been used to identify material from a number of domesticated animal species. However, many wild species of carnivores still present great challenges in generating COI barcodes using standard "universal" primer pairs. In the work presented here, the mitochondrial COI gene was successfully amplified using a novel primer cocktail, and the products were sequenced to determine the species of twenty one unknown samples of claw material collected as part of forensic wildlife case investigations. Sixteen of the unknown samples were recognized to have originated from either Panthera leo or P. pardus individuals. The remaining five samples could be identified only to the family level due to the absence of reference animal sequences. This is the first report on the use of COI sequences for the identification of P. pardus and P. leo from claw samples as part of forensic investigations in India. The study also highlights the need for adequate reference material to aid in the resolution of suspected cases of illegal wildlife harvesting.

Development of Dielectric Elastomer Nanocomposites as Stretchable and Flexible Actuating Materials

NASA Astrophysics Data System (ADS)

Wang, Yu

Dielectric elastomers (DEs) are a new type of smart materials showing promising functionalities as energy harvesting materials as well as actuating materials for potential applications such as artificial muscles, implanted medical devices, robotics, loud speakers, micro-electro-mechanical systems (MEMS), tunable optics, transducers, sensors, and even generators due to their high electromechanical efficiency, stability, lightweight, low cost, and easy processing. Despite the advantages of DEs, technical challenges must be resolved for wider applications. A high electric field of at least 10-30 V/um is required for the actuation of DEs, which limits the practical applications especially in biomedical fields. We tackle this problem by introducing the multiwalled carbon nanotubes (MWNTs) in DEs to enhance their relative permittivity and to generate their high electromechanical responses with lower applied field level. This work presents the dielectric, mechanical and electromechanical properties of DEs filled with MWNTs. The micromechanics-based finite element models are employed to describe the dielectric, and mechanical behavior of the MWNT-filled DE nanocomposites. A sufficient number of models are computed to reach the acceptable prediction of the dielectric and mechanical responses. In addition, experimental results are analyzed along with simulation results. Finally, laser Doppler vibrometer is utilized to directly detect the enhancement of the actuation strains of DE nanocomposites filled with MWNTs. All the results demonstrate the effective improvement in the electromechanical properties of DE nanocomposites filled with MWNTs under the applied electric fields.

157-nm photomask handling and infrastructure: requirements and feasibility

NASA Astrophysics Data System (ADS)

Cullins, Jerry; Muzio, Edward G.

2001-09-01

Photomask handling is significantly more challenging for 157nm lithography than for any previous generation of optical lithography. First, pellicle materials are not currently available which meet all the requirements for 157nm lithography. Polymeric materials used at 193nm higher wavelengths are not transmissive at 157nm, while modified fused silica materials have adequate transmission and durability but have mechanical issues that need to be resolved. Second, the problem of molecular level contamination on the reticle must be solved. This contamination is due to the presence of oxygen, carbon dioxide, water, and other attenuators of 157nm radiation on the mask surface. It must be removed using something other than the lithography laser due to throughput and cost of ownership considerations. Third, there is the issue of removing attenuators from under the pellicle after a material becomes available. Both the ambient atmosphere and other introduced contaminants must be removed from the space between the reticle and pellicle after cleaning but before exposure. Forth are the potential issues for storage of reticles both during transportation from the mask shop and after it is in the wafer fab. Finally, the problems associated with operating in an optically inert dry environment must be addressed. The lack of moisture in the environment removes one of the key electrical discharge paths off of the reticle, which greatly increases the risk of electro-static damage to the pattern (ESD).

Temporal-resolved characterization of laser-induced plasma for spectrochemical analysis of gas shales

NASA Astrophysics Data System (ADS)

Xu, Tao; Zhang, Yong; Zhang, Ming; He, Yi; Yu, Qiaoling; Duan, Yixiang

2016-07-01

Optical emission of laser ablation plasma on a shale target surface provides sensitive laser-induced breakdown spectrometry (LIBS) detection of major, minor or trace elements. An exploratory study for the characterization of the plasma induced on shale materials was carried out with the aim to trigger a crucial step towards the quantitative LIBS measurement. In this work, the experimental strategies that optimize the plasma generation on a pressed shale pellet surface are presented. The temporal evolution properties of the plasma induced by ns Nd:YAG laser pulse at the fundamental wavelength in air were investigated using time-resolved space-integrated optical emission spectroscopy. The electron density as well as the temperatures of the plasma were diagnosed as functions of the decay time for the bulk plasma analysis. In particular, the values of time-resolved atomic and ionic temperatures of shale elements, such as Fe, Mg, Ca, and Ti, were extracted from the well-known Boltzmann or Saha-Boltzmann plot method. Further comparison of these temperatures validated the local thermodynamic equilibrium (LTE) within specific interval of the delay time. In addition, the temporal behaviors of the signal-to-noise ratio of shale elements, including Si, Al, Fe, Ca, Mg, Ba, Li, Ti, K, Na, Sr, V, Cr, and Ni, revealed the coincidence of their maximum values with LIBS LTE condition in the time frame, providing practical implications for an optimized LIBS detection of shale elements. Analytical performance of LIBS was further evaluated with the linear calibration procedure for the most concerned trace elements of Sr, V, Cr, and Ni present in different shales. Their limits of detection obtained are elementally dependent and can be lower than tens of parts per million with the present LIBS experimental configurations. However, the occurrence of saturation effect for the calibration curve is still observable with the increasing trace element content, indicating that, due to the complex composition of shale materials, the omnipresent "matrix effect" is still a great challenging for the performance of quantitative LIBS measurement even in the framework of the LTE approach.

Materials identification using a small-scale pixellated x-ray diffraction system

NASA Astrophysics Data System (ADS)

O'Flynn, D.; Crews, C.; Drakos, I.; Christodoulou, C.; Wilson, M. D.; Veale, M. C.; Seller, P.; Speller, R. D.

2016-05-01

A transmission x-ray diffraction system has been developed using a pixellated, energy-resolving detector (HEXITEC) and a small-scale, mains operated x-ray source (Amptek Mini-X). HEXITEC enables diffraction to be measured without the requirement of incident spectrum filtration, or collimation of the scatter from the sample, preserving a large proportion of the useful signal compared with other diffraction techniques. Due to this efficiency, sufficient molecular information for material identification can be obtained within 5 s despite the relatively low x-ray source power. Diffraction data are presented from caffeine, hexamine, paracetamol, plastic explosives and narcotics. The capability to determine molecular information from aspirin tablets inside their packaging is demonstrated. Material selectivity and the potential for a sample classification model is shown with principal component analysis, through which each different material can be clearly resolved.

A scalable multi-photon coincidence detector based on superconducting nanowires.

PubMed

Zhu, Di; Zhao, Qing-Yuan; Choi, Hyeongrak; Lu, Tsung-Ju; Dane, Andrew E; Englund, Dirk; Berggren, Karl K

2018-06-04

Coincidence detection of single photons is crucial in numerous quantum technologies and usually requires multiple time-resolved single-photon detectors. However, the electronic readout becomes a major challenge when the measurement basis scales to large numbers of spatial modes. Here, we address this problem by introducing a two-terminal coincidence detector that enables scalable readout of an array of detector segments based on superconducting nanowire microstrip transmission line. Exploiting timing logic, we demonstrate a sixteen-element detector that resolves all 136 possible single-photon and two-photon coincidence events. We further explore the pulse shapes of the detector output and resolve up to four-photon events in a four-element device, giving the detector photon-number-resolving capability. This new detector architecture and operating scheme will be particularly useful for multi-photon coincidence detection in large-scale photonic integrated circuits.

Particle Beam Radiography

NASA Astrophysics Data System (ADS)

Peach, Ken; Ekdahl, Carl

2014-02-01

Particle beam radiography, which uses a variety of particle probes (neutrons, protons, electrons, gammas and potentially other particles) to study the structure of materials and objects noninvasively, is reviewed, largely from an accelerator perspective, although the use of cosmic rays (mainly muons but potentially also high-energy neutrinos) is briefly reviewed. Tomography is a form of radiography which uses multiple views to reconstruct a three-dimensional density map of an object. There is a very wide range of applications of radiography and tomography, from medicine to engineering and security, and advances in instrumentation, specifically the development of electronic detectors, allow rapid analysis of the resultant radiographs. Flash radiography is a diagnostic technique for large high-explosive-driven hydrodynamic experiments that is used at many laboratories. The bremsstrahlung radiation pulse from an intense relativistic electron beam incident onto a high-Z target is the source of these radiographs. The challenge is to provide radiation sources intense enough to penetrate hundreds of g/cm2 of material, in pulses short enough to stop the motion of high-speed hydrodynamic shocks, and with source spots small enough to resolve fine details. The challenge has been met with a wide variety of accelerator technologies, including pulsed-power-driven diodes, air-core pulsed betatrons and high-current linear induction accelerators. Accelerator technology has also evolved to accommodate the experimenters' continuing quest for multiple images in time and space. Linear induction accelerators have had a major role in these advances, especially in providing multiple-time radiographs of the largest hydrodynamic experiments.

Application of spectroscopy and super-resolution microscopy: Excited state

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bhattacharjee, Ujjal

Photophysics of inorganic materials and organic molecules in complex systems have been extensively studied with absorption and emission spectroscopy.1-4 Steady-state and time-resolved fluorescence studies are commonly carried out to characterize excited-state properties of fluorophores. Although steady-state fluorescence measurements are widely used for analytical applications, time-resolved fluorescence measurements provide more detailed information about excited-state properties and the environment in the vicinity of the fluorophore. Many photophysical processes, such as photoinduced electron transfer (PET), rotational reorientation, solvent relaxation, and energy transfer, occur on a nanosecond (10 -9 s) timescale, thus affecting the lifetime of the fluorophores. Moreover, time-resolved microscopy methods, such asmore » lifetimeimaging, combine the benefits of the microscopic measurement and information-rich, timeresolved data. Thus, time-resolved fluorescence spectroscopy combined with microscopy can be used to quantify these processes and to obtain a deeper understanding of the chemical surroundings of the fluorophore in a small area under investigation. This thesis discusses various photophysical and super-resolution microscopic studies of organic and inorganic materials, which have been outlined below.« less

Opportunities and challenges for time-resolved studies of protein structural dynamics at X-ray free-electron lasers.

PubMed

Neutze, Richard

2014-07-17

X-ray free-electron lasers (XFELs) are revolutionary X-ray sources. Their time structure, providing X-ray pulses of a few tens of femtoseconds in duration; and their extreme peak brilliance, delivering approximately 10(12) X-ray photons per pulse and facilitating sub-micrometre focusing, distinguish XFEL sources from synchrotron radiation. In this opinion piece, I argue that these properties of XFEL radiation will facilitate new discoveries in life science. I reason that time-resolved serial femtosecond crystallography and time-resolved wide angle X-ray scattering are promising areas of scientific investigation that will be advanced by XFEL capabilities, allowing new scientific questions to be addressed that are not accessible using established methods at storage ring facilities. These questions include visualizing ultrafast protein structural dynamics on the femtosecond to picosecond time-scale, as well as time-resolved diffraction studies of non-cyclic reactions. I argue that these emerging opportunities will stimulate a renaissance of interest in time-resolved structural biochemistry.

Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

NASA Astrophysics Data System (ADS)

Kang, Zhitao; Banishev, Alexandr A.; Lee, Gyuhyon; Scripka, David A.; Breidenich, Jennifer; Xiao, Pan; Christensen, James; Zhou, Min; Summers, Christopher J.; Dlott, Dana D.; Thadhani, Naresh N.

2016-07-01

The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersed in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.

Exploration of CdTe quantum dots as mesoscale pressure sensors via time-resolved shock-compression photoluminescent emission spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kang, Zhitao; School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0245; Banishev, Alexandr A.

The nanometer size of CdTe quantum dots (QDs) and their unique optical properties, including size-tunable narrow photoluminescent emission, broad absorption, fast photoluminescence decay, and negligible light scattering, are ideal features for spectrally tagging the shock response of localized regions in highly heterogeneous materials such as particulate media. In this work, the time-resolved laser-excited photoluminescence response of QDs to shock-compression was investigated to explore their utilization as mesoscale sensors for pressure measurements and in situ diagnostics during shock loading experiments. Laser-driven shock-compression experiments with steady-state shock pressures ranging from 2.0 to 13 GPa were performed on nanocomposite films of CdTe QDs dispersedmore » in a soft polyvinyl alcohol polymer matrix and in a hard inorganic sodium silicate glass matrix. Time-resolved photoluminescent emission spectroscopy was used to correlate photoluminescence changes with the history of shock pressure and the dynamics of the matrix material surrounding the QDs. The results revealed pressure-induced blueshifts in emitted wavelength, decreases in photoluminescent emission intensity, reductions in peak width, and matrix-dependent response times. Data obtained for these QD response characteristics serve as indicators for their use as possible time-resolved diagnostics of the dynamic shock-compression response of matrix materials in which such QDs are embedded as in situ sensors.« less

Material quality frontiers of MOVPE grown AlGaAs for minority carrier devices

NASA Astrophysics Data System (ADS)

Heckelmann, S.; Lackner, D.; Dimroth, F.; Bett, A. W.

2017-04-01

In this study, secondary ion mass spectroscopy of oxygen, deep level transient spectroscopy and power dependent relative photoluminescence are compared regarding their ability to resolve differences in AlxGa1-xAs material quality. AlxGa1-xAs samples grown with two different trimethylaluminum sources showing low and high levels of oxygen contamination are compared. As tested in the growth of minority carrier devices, i.e. AlxGa1-xAs solar cells, the two precursors clearly lead to different device characteristics. It is shown that secondary ion mass spectroscopy could not resolve the difference in oxygen concentration, whereas deep level transient spectroscopy and photoluminescence based measurements indicate the influence of the precursor oxygen level on the material quality.

Unsupervised data mining in nanoscale x-ray spectro-microscopic study of NdFeB magnet

DOE Office of Scientific and Technical Information (OSTI.GOV)

Duan, Xiaoyue; Yang, Feifei; Antono, Erin

Novel developments in X-ray based spectro-microscopic characterization techniques have increased the rate of acquisition of spatially resolved spectroscopic data by several orders of magnitude over what was possible a few years ago. This accelerated data acquisition, with high spatial resolution at nanoscale and sensitivity to subtle differences in chemistry and atomic structure, provides a unique opportunity to investigate hierarchically complex and structurally heterogeneous systems found in functional devices and materials systems. However, handling and analyzing the large volume data generated poses significant challenges. Here we apply an unsupervised data-mining algorithm known as DBSCAN to study a rare-earth element based permanentmore » magnet material, Nd 2Fe 14B. We are able to reduce a large spectro-microscopic dataset of over 300,000 spectra to 3, preserving much of the underlying information. Scientists can easily and quickly analyze in detail three characteristic spectra. Our approach can rapidly provide a concise representation of a large and complex dataset to materials scientists and chemists. For instance, it shows that the surface of common Nd 2Fe 14B magnet is chemically and structurally very different from the bulk, suggesting a possible surface alteration effect possibly due to the corrosion, which could affect the material’s overall properties.« less

Avoiding bias effects in NMR experiments for heteronuclear dipole-dipole coupling determinations: principles and application to organic semiconductor materials.

PubMed

Kurz, Ricardo; Cobo, Marcio Fernando; de Azevedo, Eduardo Ribeiro; Sommer, Michael; Wicklein, André; Thelakkat, Mukundan; Hempel, Günter; Saalwächter, Kay

2013-09-16

Carbon-proton dipole-dipole couplings between bonded atoms represent a popular probe of molecular dynamics in soft materials or biomolecules. Their site-resolved determination, for example, by using the popular DIPSHIFT experiment, can be challenged by spectral overlap with nonbonded carbon atoms. The problem can be solved by using very short cross-polarization (CP) contact times, however, the measured modulation curves then deviate strongly from the theoretically predicted shape, which is caused by the dependence of the CP efficiency on the orientation of the CH vector, leading to an anisotropic magnetization distribution even for isotropic samples. Herein, we present a detailed demonstration and explanation of this problem, as well as providing a solution. We combine DIPSHIFT experiments with the rotor-directed exchange of orientations (RODEO) method, and modifications of it, to redistribute the magnetization and obtain undistorted modulation curves. Our strategy is general in that it can also be applied to other types of experiments for heteronuclear dipole-dipole coupling determinations that rely on dipolar polarization transfer. It is demonstrated with perylene-bisimide-based organic semiconductor materials, as an example, in which measurements of dynamic order parameters reveal correlations of the molecular dynamics with the phase structure and functional properties. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Unsupervised data mining in nanoscale x-ray spectro-microscopic study of NdFeB magnet

DOE PAGES

Duan, Xiaoyue; Yang, Feifei; Antono, Erin; ...

2016-09-29

Novel developments in X-ray based spectro-microscopic characterization techniques have increased the rate of acquisition of spatially resolved spectroscopic data by several orders of magnitude over what was possible a few years ago. This accelerated data acquisition, with high spatial resolution at nanoscale and sensitivity to subtle differences in chemistry and atomic structure, provides a unique opportunity to investigate hierarchically complex and structurally heterogeneous systems found in functional devices and materials systems. However, handling and analyzing the large volume data generated poses significant challenges. Here we apply an unsupervised data-mining algorithm known as DBSCAN to study a rare-earth element based permanentmore » magnet material, Nd 2Fe 14B. We are able to reduce a large spectro-microscopic dataset of over 300,000 spectra to 3, preserving much of the underlying information. Scientists can easily and quickly analyze in detail three characteristic spectra. Our approach can rapidly provide a concise representation of a large and complex dataset to materials scientists and chemists. For instance, it shows that the surface of common Nd 2Fe 14B magnet is chemically and structurally very different from the bulk, suggesting a possible surface alteration effect possibly due to the corrosion, which could affect the material’s overall properties.« less

Communication—indentation of Li-ion pouch cell: Effect of material homogenization on prediction of internal short circuit

DOE PAGES

Kumar, A.; Kalnaus, Sergiy; Simunovic, Srdjan; ...

2016-09-12

We performed finite element simulations of spherical indentation of Li-ion pouch cells. Our model fully resolves different layers in the cell. The results of the layer resolved models were compared to the models available in the literature that treat the cell as an equivalent homogenized continuum material. Simulations were carried out for different sizes of the spherical indenter. Here, we show that calibration of a failure criterion for the cell in the homogenized model depends on the indenter size, whereas in the layer-resoled model, such dependency is greatly diminished.

Enforcement actions: Significant actions resolved, material licensees. Semiannual progress report, July--December 1995: Volume 14, Numbers 3 and 4, Part 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-02-01

This compilation summarizes significant enforcement actions that have been resolved during the period (July--December 1995) and includes copies of letters, Notices, and Orders sent by the Nuclear Regulatory Commission to material licensees with respect to these enforcement actions. It is anticipated that the information in this publication will be widely disseminated to managers and employees engaged in activities licensed by the NRC, so that actions can be taken to improve safety by avoiding future violations similar to those described in this publication.

Direct observation of back energy transfer in blue phosphorescent materials for organic light emitting diodes by time-resolved optical waveguide spectroscopy.

PubMed

Hirayama, H; Sugawara, Y; Miyashita, Y; Mitsuishi, M; Miyashita, T

2013-02-25

We demonstrate a high-sensitive transient absorption technique for detection of excited states in an organic thin film by time-resolved optical waveguide spectroscopy. By using a laser beam as a probe light, we detect small change in the transient absorbance which is equivalent to 10 -7 absorbance unit in a conventional method. This technique was applied to organic thin films of blue phosphorescent materials for organic light emitting diodes. We directly observed the back energy transfer from emitting guest molecules to conductive host molecules.

Diplomatic Solutions to Additive Challenges

DTIC Science & Technology

Additive manufacturing (AM) technology, colloquially known as 3D printing , will bring significant benefits to society, but also poses great risks...regimes, are not sufficient to address the challenges presented by 3D printing technology. The DOS should evaluate and promote unconventional strategies...from printed weapons proliferation. Working with other nations to resolve the appropriate balance between development and security, and to promote norms

Ethical Issues in Public Health Practice in Michigan

PubMed Central

Gollust, Sarah E.; Goold, Susan D.; Jacobson, Peter D.

2009-01-01

Objectives. We sought to ascertain the types of ethical challenges public health practitioners face in practice and to identify approaches used to resolve such challenges. Methods. We conducted 45 semistructured interviews with public health practitioners across a range of occupations (e.g., health officers, medical directors, sanitarians, nurses) at 13 health departments in Michigan. Results. Through qualitative analysis, we identified 5 broad categories of ethical issues common across occupations and locations: (1) determining appropriate use of public health authority, (2) making decisions related to resource allocation, (3) negotiating political interference in public health practice, (4) ensuring standards of quality of care, and (5) questioning the role or scope of public health. Participants cited a variety of values guiding their decision-making that did not coalesce around core values often associated with public health, such as social justice or utilitarianism. Public health practitioners relied on consultations with colleagues to resolve challenges, infrequently using frameworks for decision-making. Conclusions. Public health practitioners showed a nuanced understanding of ethical issues and navigated ethical challenges with minimal formal assistance. Decision-making guides that are empirically informed and tailored for practitioners might have some value. PMID:19059850

Bionanocomposites materials for food packaging applications: Concepts and future outlook.

PubMed

Youssef, Ahmed M; El-Sayed, Samah M

2018-08-01

Bionanocomposites materials open a chance for the usage of novel, high performance, lightweight, and ecofriendly composite materials making them take place the traditional non-biodegradable plastic packaging materials. Biopolymers like polysaccharides such as chitosan (CS), carboxymethyl cellulose (CMC), starch and cellophane could be used to resolve environmental hazards owing to their biodegradability and non-toxicity. In addition these advantages, polysaccharides have some disadvantages for example poor mechanical properties and low resistance to water. Therefore, nanomaterials are used to improve the thermal, mechanical and gas barrier properties without hindering their biodegradable and non-toxic characters. Furthermore, the most favorable nanomaterials are layered silicate nanoclays for example montmorillonite (MMT) and kaolinite, zinc oxide (ZnO-NPs), titanium dioxide (TiO 2 -NPs), and silver nanoparticles (Ag-NPs). In packaging application, the improvement of barrier properties of prepared films against oxygen, carbon dioxide, flavor compounds diffusion through the packaging films. Wide varieties of nanomaterials are suitable to offer smart and/or intelligent properties for food packaging materials, as demonstrated by oxygen scavenging capability, antimicrobial activity, and sign of the level of exposure to various harmful features for instance oxygen levels or insufficient temperatures. The compatibility between nanomaterials and polymers matrix consider the most challenge for the preparation of bionanocomposites as well as getting whole distribution of nanoparticles into the polymer matrix. We keen in this review the development of packaging materials performance and their mechanical, degradability and thermal stability as well as antibacterial activity for utilization of bionanocomposites in different packaging application is considered. Copyright © 2018 Elsevier Ltd. All rights reserved.

A direct vulnerable atherosclerotic plaque elasticity reconstruction method based on an original material-finite element formulation: theoretical framework

PubMed Central

Bouvier, Adeline; Deleaval, Flavien; Doyley, Marvin M; Yazdani, Saami K; Finet, Gérard; Le Floc'h, Simon; Cloutier, Guy; Pettigrew, Roderic I; Ohayon, Jacques

2016-01-01

The peak cap stress (PCS) amplitude is recognized as a biomechanical predictor of vulnerable plaque (VP) rupture. However, quantifying PCS in vivo remains a challenge since the stress depends on the plaque mechanical properties. In response, an iterative material finite element (FE) elasticity reconstruction method using strain measurements has been implemented for the solution of these inverse problems. Although this approach could resolve the mechanical characterization of VPs, it suffers from major limitations since (i) it is not adapted to characterize VPs exhibiting high material discontinuities between inclusions, and (ii) does not permit real time elasticity reconstruction for clinical use. The present theoretical study was therefore designed to develop a direct material-FE algorithm for elasticity reconstruction problems which accounts for material heterogeneities. We originally modified and adapted the extended FE method (Xfem), used mainly in crack analysis, to model material heterogeneities. This new algorithm was successfully applied to six coronary lesions of patients imaged in vivo with intravascular ultrasound. The results demonstrated that the mean relative absolute errors of the reconstructed Young's moduli obtained for the arterial wall, fibrosis, necrotic core, and calcified regions of the VPs decreased from 95.3±15.56%, 98.85±72.42%, 103.29±111.86% and 95.3±10.49%, respectively, to values smaller than 2.6 × 10−8±5.7 × 10−8% (i.e. close to the exact solutions) when including modified-Xfem method into our direct elasticity reconstruction method. PMID:24240392

Resolving Rapid Variation in Energy for Particle Transport

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haut, Terry Scot; Ahrens, Cory Douglas; Jonko, Alexandra

2016-08-23

Resolving the rapid variation in energy in neutron and thermal radiation transport is needed for the predictive simulation capability in high-energy density physics applications. Energy variation is difficult to resolve due to rapid variations in cross sections and opacities caused by quantized energy levels in the nuclei and electron clouds. In recent work, we have developed a new technique to simultaneously capture slow and rapid variations in the opacities and the solution using homogenization theory, which is similar to multiband (MB) and to the finite-element with discontiguous support (FEDS) method, but does not require closure information. We demonstrated the accuracymore » and efficiency of the method for a variety of problems. We are researching how to extend the method to problems with multiple materials and the same material but with different temperatures and densities. In this highlight, we briefly describe homogenization theory and some results.« less

[Merging different biobanks under one roof : Benefits and constraints on the way to a centralized biobank using the example of the BMBH].

PubMed

Schmitt, S; Döllinger, C; Maier, A; Herpel, E; Schirmacher, P; Kirsten, R

2018-05-23

Founded in 1386, Heidelberg University is Germany's oldest and one of Europe's most reputable universities. As a scientific hub in Germany, Heidelberg is home to several internationally renowned medical research facilities that have an enormous demand for biomaterial samples and data-especially in the field of translational and cancer research.The main objective of the BMBF-funded project "BioMaterialBank Heidelberg" (BMBH) was the harmonization of local biobanking under the same administrative roof through the implementation of common and standardized project, data, and quality management procedures.In the very beginning, existing structures and processes of the participating biobanks in Heidelberg were identified and a common administrative structure with central representatives for IT and quality management (QM) was established to coordinate all BMBH activities.Over time, implementation of consented structures and processes took place, also revealing organizational challenges that had to be solved concerning, for example, differences in sample handling and the definition of consistent access regulations.We will discuss below these challenges as well as the opportunities of building a centralized biobank and show how issues can be resolved using the example of the BMBH.

Calculating the pre-consumer waste footprint: A screening study of 10 selected products.

PubMed

Laurenti, Rafael; Moberg, Åsa; Stenmarck, Åsa

2017-01-01

Knowledge about the total waste generated by the production of consumer goods can help raise awareness among policy-makers, producers and consumers of the benefits of closing loops in a future circular economy, avoiding unnecessary production and production steps and associated generation of large amounts of waste. In strict life cycle assessment practice, information on waste outputs from intermediate industrial processes of material and energy transformation is translated into and declared as potential environmental impacts, which are often not reported in the final results. In this study, a procedure to extract available intermediate data and perform a systematic pre-consumer waste footprint analysis was developed. The pre-consumer waste footprint concept was tested to analyse 10 generic products, which provided some novel and interesting results for the different product categories and identified a number of challenges that need to be resolved in development of the waste footprint concept. These challenges include standardised data declaration on waste in life cycle assessment, with a separation into waste categories illustrating the implicit environmental and scale of significance of waste types and quantities (e.g. hazardous waste, inert waste, waste for recycling/incineration) and establishment of a common definition of waste throughout sectors and nations.

Spatiotemporally Resolved Acoustics in a Photoelastic Granular Material

NASA Astrophysics Data System (ADS)

Owens, Eli; Daniels, Karen

2010-03-01

In granular materials, stress transmission is manifested as force chains that propagate through the material in a branching structure. We send acoustic pulses into a two dimensional photoelastic granular material in which force chains are visible and investigate how the force chains influence the amplitude, speed, and dispersion of the sound waves. We observe particle scale dynamics using two methods, movies which provide spatiotemporally resolved measurements and accelerometers within individual grains. The movies allow us to visualize the sound's path through the material, revealing that the sound travels primarily along the force chains. Using the brightness of the photoelastic particles as a measure of the force chain strength, we observe that the sound travels both faster and at higher amplitude along the strong force chains. An exception to this trend is seen in transient force chains that only exist while the sound is closing particle contacts. We also measure the frequency dependence of the amplitude, speed, and dispersion of the sound wave.

Observation of nanoscale magnetic fields using twisted electron beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Grillo, Vincenzo; Harvey, Tyler R.; Venturi, Federico

Electron waves give an unprecedented enhancement to the field of microscopy by providing higher resolving power compared to their optical counterpart. Further information about a specimen, such as electric and magnetic features, can be revealed in electron microscopy because electrons possess both a magnetic moment and charge. In-plane magnetic structures in materials can be studied experimentally using the effect of the Lorentz force. On the other hand, full mapping of the magnetic field has hitherto remained challenging. Here we measure a nanoscale out-of-plane magnetic field by interfering a highly twisted electron vortex beam with a reference wave. We implement amore » recently developed holographic technique to manipulate the electron wavefunction, which gives free electrons an additional unbounded quantized magnetic moment along their propagation direction. Our finding demonstrates that full reconstruction of all three components of nanoscale magnetic fields is possible without tilting the specimen.« less

Nonlinear two-dimensional terahertz photon echo and rotational spectroscopy in the gas phase.

PubMed

Lu, Jian; Zhang, Yaqing; Hwang, Harold Y; Ofori-Okai, Benjamin K; Fleischer, Sharly; Nelson, Keith A

2016-10-18

Ultrafast 2D spectroscopy uses correlated multiple light-matter interactions for retrieving dynamic features that may otherwise be hidden under the linear spectrum; its extension to the terahertz regime of the electromagnetic spectrum, where a rich variety of material degrees of freedom reside, remains an experimental challenge. We report a demonstration of ultrafast 2D terahertz spectroscopy of gas-phase molecular rotors at room temperature. Using time-delayed terahertz pulse pairs, we observe photon echoes and other nonlinear signals resulting from molecular dipole orientation induced by multiple terahertz field-dipole interactions. The nonlinear time domain orientation signals are mapped into the frequency domain in 2D rotational spectra that reveal J-state-resolved nonlinear rotational dynamics. The approach enables direct observation of correlated rotational transitions and may reveal rotational coupling and relaxation pathways in the ground electronic and vibrational state.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brahlek, Matthew; Koirala, Nikesh; Salehi, Maryam

Topological insulators (TI) are a phase of matter that host unusual metallic states on their surfaces. Unlike the states that exist on the surface of conventional materials, these so-called topological surfaces states (TSS) are protected against disorder-related localization effects by time reversal symmetry through strong spin-orbit coupling. By combining transport measurements, angle-resolved photo-emission spectroscopy and scanning tunneling microscopy, we show that there exists a critical level of disorder beyond which the TI Bi 2Se 3 loses its ability to protect the metallic TSS and transitions to a fully insulating state. The absence of the metallic surface channels dictates that theremore » is a change in material’s topological character, implying that disorder can lead to a topological phase transition even without breaking the time reversal symmetry. This observation challenges the conventional notion of topologically-protected surface states, and will provoke new studies as to the fundamental nature of topological phase of matter in the presence of disorder.« less

Structures technology for a new generation of rotorcraft

NASA Technical Reports Server (NTRS)

Bartlett, Felton D., Jr.

1989-01-01

This paper presents an overview of structures research at the U. S. Army Aerostructures Directorate. The objectives of this research are to investigate, explore, and demonstrate emerging technologies that will provide lighter, safer, more survivable, and more cost-effective structures for rotorcraft in the 1990s and beyond. The emphasis of today's R&D is to contribute proven structures technology to the U. S. rotorcraft industry and Army aviation that directly impacts tomorrow's fleet readiness and mission capabilities. The primary contributor toward meeting these challenges is the development of high-strength and durable composites to minimize structural weight while maximizing cost effectiveness. Special aviation issues such as delamination of dynamic components, impact damage to thin skins, crashworthiness, and affordable manufacturing need to be resolved before the full potential of composites technology can be realized. To that end, this paper highlights research into composites structural integrity, crashworthiness, and materials applications which addresses these issues.

Observation of nanoscale magnetic fields using twisted electron beams

DOE PAGES

Grillo, Vincenzo; Harvey, Tyler R.; Venturi, Federico; ...

2017-09-25

Electron waves give an unprecedented enhancement to the field of microscopy by providing higher resolving power compared to their optical counterpart. Further information about a specimen, such as electric and magnetic features, can be revealed in electron microscopy because electrons possess both a magnetic moment and charge. In-plane magnetic structures in materials can be studied experimentally using the effect of the Lorentz force. On the other hand, full mapping of the magnetic field has hitherto remained challenging. Here we measure a nanoscale out-of-plane magnetic field by interfering a highly twisted electron vortex beam with a reference wave. We implement amore » recently developed holographic technique to manipulate the electron wavefunction, which gives free electrons an additional unbounded quantized magnetic moment along their propagation direction. Our finding demonstrates that full reconstruction of all three components of nanoscale magnetic fields is possible without tilting the specimen.« less

Friction force microscopy: a simple technique for identifying graphene on rough substrates and mapping the orientation of graphene grains on copper

NASA Astrophysics Data System (ADS)

Marsden, A. J.; Phillips, M.; Wilson, N. R.

2013-06-01

At a single atom thick, it is challenging to distinguish graphene from its substrate using conventional techniques. In this paper we show that friction force microscopy (FFM) is a simple and quick technique for identifying graphene on a range of samples, from growth substrates to rough insulators. We show that FFM is particularly effective for characterizing graphene grown on copper where it can correlate the graphene growth to the three-dimensional surface topography. Atomic lattice stick-slip friction is readily resolved and enables the crystallographic orientation of the graphene to be mapped nondestructively, reproducibly and at high resolution. We expect FFM to be similarly effective for studying graphene growth on other metal/locally crystalline substrates, including SiC, and for studying growth of other two-dimensional materials such as molybdenum disulfide and hexagonal boron nitride.

Challenges in disposing of anthrax waste.

PubMed

Lesperance, Ann M; Stein, Steve; Upton, Jaki F; Toomey, Chris

2011-09-01

Disasters often create large amounts of waste that must be managed as part of both immediate response and long-term recovery. While many federal, state, and local agencies have debris management plans, these plans often do not address chemical, biological, and radiological contamination. The Interagency Biological Restoration Demonstration's (IBRD) purpose was to holistically assess all aspects of an anthrax incident and assist in the development of a plan for long-term recovery. In the case of wide-area anthrax contamination and the follow-on response and recovery activities, a significant amount of material would require decontamination and disposal. Accordingly, IBRD facilitated the development of debris management plans to address contaminated waste through a series of interviews and workshops with local, state, and federal representatives. The outcome of these discussions was the identification of 3 primary topical areas that must be addressed: planning, unresolved research questions, and resolving regulatory issues.

Challenges in Disposing of Anthrax Waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lesperance, Ann M.; Stein, Steven L.; Upton, Jaki F.

2011-09-01

Disasters often create large amounts of waste that must be managed as part of both immediate response and long-term recovery. While many federal, state, and local agencies have debris management plans, these plans often do not address chemical, biological, and radiological contamination. The Interagency Biological Restoration Demonstration’s (IBRD) purpose was to holistically assess all aspects of an anthrax incident and assist the development of a plan for long-term recovery. In the case of wide-area anthrax contamination and the follow-on response and recovery activities, a significant amount of material will require decontamination and disposal. Accordingly, IBRD facilitated the development of debrismore » management plans to address contaminated waste through a series of interviews and workshops with local, state, and federal representatives. The outcome of these discussion was the identification of three primary topical areas that must be addressed: 1) Planning; 2) Unresolved research questions, and resolving regulatory issues.« less

Understanding healthcare professionals' self-efficacy to resolve interprofessional conflict.

PubMed

Sexton, Martha; Orchard, Carole

2016-05-01

Conflict within interprofessional healthcare teams, when not effectively resolved, has been linked to detrimental consequences; however, effective conflict resolution has been shown to enhance team performance, increase patient safety, and improve patient outcomes. Alarmingly, knowledge of healthcare professionals' ability to resolve conflict has been limited, largely due to the challenges that arise when researchers attempt to observe a conflict occurring in real time. Research literature has identified three central components that seem to influence healthcare professional's perceived ability to resolve conflict: communication competence, problem-solving ability, and conflict resolution education and training. The purpose of this study was to investigate the impact of communication competence, problem-solving ability, and conflict resolution education and training on healthcare professionals' perceived ability to resolve conflicts. This study employed a cross-sectional survey design. Multiple regression analyses demonstrated that two of the three central components-conflict resolution education and training and communication competence-were found to be statistically significant predictors of healthcare professionals' perceived ability to resolve conflict. Implications include a call to action for clinicians and academicians to recognize the importance of communication competence and conflict resolution education and training as a vital area in interprofessional pre- and post-licensure education and collaborative practice.

Which Came First, the Yardang or the Platy Flow?

NASA Image and Video Library

2014-02-13

One of the great strengths of the HiRISE camera onboard NASA Mars Reconnaissance Orbiter is that its high resolution can help resolve interesting questions. Here, is the platy flow material younger than the yardang-forming material?

Developing radiation tolerant polymer nanocomposites using C 60 as an additive

DOE PAGES

Christian, Jonathan H.; Wilson, Jason; Nicholson, James C.; ...

2016-04-13

In nuclear facilities utilizing plutonium, polymeric materials are subjected to long-term, close-contact, and continuous α radiation exposure, which can lead to compounding material degradation and eventual failure. Herein we model the attenuation of α particles by linear-low-density polyethylene (LLDPE), polyvinyl alcohol (PVA) thin films, and C 60 using Monte Carlo N-Particle Extended (MCNPX) software. The degradation of these materials was investigated experimentally by irradiating them with a beam of α particles of 5.8 MeV energy at a tandem Van de Graaff accelerator delivering a dose rate of 2.95 × 10 6 rad s –1 over a 7.1 mm 2 samplemore » area. Our development of a method to test α particle-induced material degradation using a tandem accelerator is significant as degradation from naturally occurring α sources (i.e. Pu, Am) occurs too slowly for these sources to be used in practical experiments. Our results show that PVA nanocomposites containing 5 wt% C 60 were found to withstand about 7 times the α dose of undoped PVA films before a puncture in the film was detected. When these films were adhered to a LLDPE sheet the dual layer polymer was capable of withstanding about 13 times the dose of LLDPE and nearly twice the dose of the doped PVA thin film alone. Doping polymers with C 60 is an attractive way to generate more durable, radiation tolerant materials without increasing the thickness of the material which would lead to greater waste for disposal. Furthermore, the results herein help to resolve a prevalent technical challenge faced in nuclear facilities that utilize polymeric materials for nuclear processing and disposal.« less

A Primer for Analyzing Nested Data: Multilevel Modeling in SPSS Using an Example from a REL Study. REL 2015-046

ERIC Educational Resources Information Center

O'Dwyer, Laura M.; Parker, Caroline E.

2014-01-01

Analyzing data that possess some form of nesting is often challenging for applied researchers or district staff who are involved in or in charge of conducting data analyses. This report provides a description of the challenges for analyzing nested data and provides a primer of how multilevel regression modeling may be used to resolve these…

Time-resolved Sensing of Meso-scale Shock Compression with Multilayer Photonic Crystal Structures

NASA Astrophysics Data System (ADS)

Scripka, David; Lee, Gyuhyon; Summers, Christopher J.; Thadhani, Naresh

2017-06-01

Multilayer Photonic Crystal structures can provide spatially and temporally resolved data needed to validate theoretical and computational models relevant for understanding shock compression in heterogeneous materials. Two classes of 1-D photonic crystal multilayer structures were studied: optical microcavities (OMC) and distributed Bragg reflectors (DBR). These 0.5 to 5 micron thick structures were composed of SiO2, Al2O3, Ag, and PMMA layers fabricated primarily via e-beam evaporation. The multilayers have unique spectral signatures inherently linked to their time-resolved physical states. By observing shock-induced changes in these signatures, an optically-based pressure sensor was developed. Results to date indicate that both OMCs and DBRs exhibit nanosecond-resolved spectral shifts of several to 10s of nanometers under laser-driven shock compression loads of 0-10 GPa, with the magnitude of the shift strongly correlating to the shock load magnitude. Additionally, spatially and temporally resolved spectral shifts under heterogeneous laser-driven shock compression created by partial beam blocking have been successfully demonstrated. These results illustrate the potential for multilayer structures to serve as meso-scale sensors, capturing temporal and spatial pressure profile evolutions in shock-compressed heterogeneous materials, and revealing meso-scale pressure distributions across a shocked surface. Supported by DTRA Grant HDTRA1-12-1-005 and DoD, AFOSR, National Defense Science and Eng. Graduate Fellowship, 32 CFR 168a.

Seventh international conference on time-resolved vibrational spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dyer, R.B.; Martinez, M.A.D.; Shreve, A.

1997-04-01

The International Conference on Time-Resolved Vibrational Spectroscopy (TRVS) is widely recognized as the major international forum for the discussion of advances in this rapidly growing field. The 1995 conference was the seventh in a series that began at Lake Placid, New York, 1982. Santa Fe, New Mexico, was the site of the Seventh International Conference on Time-Resolved Vibrational Spectroscopy, held from June 11 to 16, 1995. TRVS-7 was attended by 157 participants from 16 countries and 85 institutions, and research ranging across the full breadth of the field of time-resolved vibrational spectroscopy was presented. Advances in both experimental capabilities formore » time-resolved vibrational measurements and in theoretical descriptions of time-resolved vibrational methods continue to occur, and several sessions of the conference were devoted to discussion of these advances and the associated new directions in TRVS. Continuing the interdisciplinary tradition of the TRVS meetings, applications of time-resolved vibrational methods to problems in physics, biology, materials science, and chemistry comprised a large portion of the papers presented at the conference.« less

Analysis of Biaxial Stress Fields in Plates Cracking at Elevated Temperatures

DTIC Science & Technology

1989-10-19

used . Based on the enhanced theory, it is predicted that the minimum resolvable stress amplitude using thermographic stress analysis will be...because of limitations in the commercial thermographic equipment used . Based on the enhanced theory, it is predicted that the minimum resolvable stress...amplitude using thermographic stress analysis will be approximately independent of temperature, provided relevant thermal and mechanical material

Short-period cyclic loading system for in situ X-ray observation of anelastic properties at high pressure.

PubMed

Yoshino, Takashi; Yamazaki, Daisuke; Tange, Yoshinori; Higo, Yuji

2016-10-01

To determine the anelastic properties of materials of the Earth's interior, a short-period cyclic loading system was installed for in situ X-ray radiographic observation under high pressure to the multi-anvil deformation DIA press at the bending magnet beam line BL04B1 at SPring-8. The hydraulic system equipped with a piston controlled by a solenoid was designed so as to enable producing smooth sinusoidal stress in a wide range of oscillation period from 0.2 to 100 s and generating variable amplitudes. Time resolved X-ray radiography imaging of the sample and reference material provides their strain as a function of time during cyclic loading. A synchrotron X-ray radiation source allows us to resolve their strain variation with time even at the short period (<1 s). The minimum resolved strain is as small as 10 -4 , and the shortest oscillation period to detect small strain is 0.5 s. Preliminary experimental results exhibited that the new system can resolve attenuation factor Q -1 at upper mantle conditions. These results are in quantitative agreement with previously reported data obtained at lower pressures.

Mesoscopic structural phase progression in photo-excited VO 2 revealed by time-resolved x-ray diffraction microscopy

DOE PAGES

Zhu, Yi; Cai, Zhonghou; Chen, Pice; ...

2016-02-26

Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase seperated regions. The ability to simultanousely track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of- the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO 2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation ismore » initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO 2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, which is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO 2. Lastly, the direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.« less

Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy

NASA Astrophysics Data System (ADS)

Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J.; Jung, Il Woong; Walko, Donald A.; Dufresne, Eric M.; Jeong, Jaewoo; Samant, Mahesh G.; Parkin, Stuart S. P.; Freeland, John W.; Evans, Paul G.; Wen, Haidan

2016-02-01

Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

Mesoscopic structural phase progression in photo-excited VO2 revealed by time-resolved x-ray diffraction microscopy.

PubMed

Zhu, Yi; Cai, Zhonghou; Chen, Pice; Zhang, Qingteng; Highland, Matthew J; Jung, Il Woong; Walko, Donald A; Dufresne, Eric M; Jeong, Jaewoo; Samant, Mahesh G; Parkin, Stuart S P; Freeland, John W; Evans, Paul G; Wen, Haidan

2016-02-26

Dynamical phase separation during a solid-solid phase transition poses a challenge for understanding the fundamental processes in correlated materials. Critical information underlying a phase transition, such as localized phase competition, is difficult to reveal by measurements that are spatially averaged over many phase separated regions. The ability to simultaneously track the spatial and temporal evolution of such systems is essential to understanding mesoscopic processes during a phase transition. Using state-of-the-art time-resolved hard x-ray diffraction microscopy, we directly visualize the structural phase progression in a VO2 film upon photoexcitation. Following a homogenous in-plane optical excitation, the phase transformation is initiated at discrete sites and completed by the growth of one lattice structure into the other, instead of a simultaneous isotropic lattice symmetry change. The time-dependent x-ray diffraction spatial maps show that the in-plane phase progression in laser-superheated VO2 is via a displacive lattice transformation as a result of relaxation from an excited monoclinic phase into a rutile phase. The speed of the phase front progression is quantitatively measured, and is faster than the process driven by in-plane thermal diffusion but slower than the sound speed in VO2. The direct visualization of localized structural changes in the time domain opens a new avenue to study mesoscopic processes in driven systems.

Medicine, madness and murderers: the context of English forensic psychiatric hospitals.

PubMed

McDonald, Ruth; Furtado, Vivek; Völlm, Birgit

2017-08-21

Purpose The purpose of this paper is to add to the understanding of context by shedding light on the relationship between context and organisational actors' abilities to resolve ongoing challenges. Design/methodology/approach The authors used qualitative data collection (interviews and focus groups with staff and site visits to English forensic psychiatry hospitals) and the analysis was informed by Lefebvre's writings on space. Findings Responses to ongoing challenges were both constrained and facilitated by the context, which was negotiated and co-produced by the actors involved. Various (i.e. societal and professional) dimensions of context interacted to create tensions, which resulted in changes in service configuration. These changes were reconciled, to some extent, via discourse. Despite some resolution, the co-production of context preserved contradictions which mean that ongoing challenges were modified, but not resolved entirely. Originality/value The paper highlights the importance of viewing context as co-produced in a continuous manner. This helps us to delineate and understand its dynamic nature and its relationship with the everyday actions and beliefs of the organisational actors concerned.

Moral experience and ethical challenges in an emergency department in Pakistan: emergency physicians' perspectives.

PubMed

Zafar, Waleed

2015-04-01

Emergency departments (ED) are often stressful environments posing unique ethical challenges-issues that primarily raise moral rather than clinical concerns-in patient care. Despite this, there are very few reports of what emergency physicians find ethically challenging in their everyday work. Emergency medicine (EM) is a relatively young but rapidly growing specialty that is gaining acceptance worldwide. The aim of this study was to explore the perspectives of EM residents and physicians regarding the common ethical challenges they face during patient care in one of only two academic EM departments in Pakistan. These challenges could then be addressed in residents' training and departmental practice guidelines. A qualitative research design was employed and in-depth interviews were conducted with ED physicians. Participants were encouraged to think of specific examples from their work, to highlight the particular ethical concerns raised and to describe in detail the process by which those concerns were addressed or left unresolved. Transcripts were analysed using grounded theory methods. Thirteen participants were interviewed and they described four key challenges: how to provide highest quality care with limited resources; how to be truthful to patients; what to do when it is not possible to provide or continue treatment to patients; and when (and when not) to offer life-sustaining treatments. Participants' accounts provided important insights into how physicians tried to resolve these challenges in the 'local moral world' of an ED in Pakistan. The study highlights the need for developing systematic and contextually appropriate mechanisms for resolving common ethical challenges in the EDs and for training residents in moral problem solving. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Developing Marine Science Instructional Materials Using Integrated Scientist-Educator Collaborative Design Teams: A Discussion of Challenges and Success Developing Real Time Data Projects for the COOL Classroom

NASA Astrophysics Data System (ADS)

McDonnell, J.; Duncan, R. G.; Glenn, S.

2007-12-01

Current reforms in science education place increasing demands on teachers and students to engage not only with scientific content but also to develop an understanding of the nature of scientific inquiry (AAAS, 1993; NRC, 1996). Teachers are expected to engage students with authentic scientific practices including posing questions, conducting observations, analyzing data, developing explanations and arguing about them using evidence. This charge is challenging for many reasons most notably the difficulty in obtaining meaningful data about complex scientific phenomena that can be used to address relevant scientific questions that are interesting and understandable to K-12 students. We believe that ocean sciences provide an excellent context for fostering scientific inquiry in the classroom. Of particular interest are the technological and scientific advances of Ocean Observing Systems, which allow scientists to continuously interact with instruments, facilities, and other scientists to explore the earth-ocean- atmosphere system remotely. Oceanographers are making long-term measurements that can also resolve episodic oceanic processes on a wide range of spatial and temporal scales crucial to resolving scientific questions related to Earth's climate, geodynamics, and marine ecosystems. The availability of a diverse array of large data sets that are easily accessible provides a unique opportunity to develop inquiry-based learning environments in which students can explore many important questions that reflect current research trends in ocean sciences. In addition, due to the interdisciplinary nature of the ocean sciences these data sets can be used to examine ocean phenomena from a chemical, physical, or biological perspective; making them particularly useful for science teaching across the disciplines. In this session we will describe some of the efforts of the Centers for Ocean Sciences Education Excellence- Mid Atlantic (COSEE MA) to develop instructional materials, in which students use real-time-data (RTD) to generate explanations about important ocean phenomena. We will discuss our use of an Instructional Design Model (Gauge 1987) to: 1) assess our audience need, 2) develop an effective collaborative design team, 3) develop and evaluate the instructional product, and 4) implement professional development designed to familiarize teachers with oceans sciences as a context for scientific inquiry.

In vitro antigen-specific induction of IL-22 in human subjects that resolved HCV infection

PubMed Central

Cusick, Matthew F; Libbey, Jane E; Fujinami, Robert S; Eckels, David D

2012-01-01

Aims To determine if in vitro production of IL-22 and IL-17 correlated with resolution of HCV infection. Materials & methods Human peripheral blood cells isolated from a well-defined cohort of resolved and chronic HCV-infected subjects were used to measure HCV-, influenza- and mitogen-activated T-cell proliferation. In addition, IL-22 and IL-17 production was measured via ELISAs and flow cytometry. Results Resolved HCV subjects had a significantly higher T-cell proliferative response to recombinant NS3 protein compared with chronic HCV subjects. Resolved subjects had a dose-dependent IL-22 response to recombinant NS3 compared with chronic HCV subjects. Conclusion IL-22 production is associated with antigen-specific induction of CD4 + T cells in individuals that resolved HCV infection, suggesting a potential role for IL-22 in HCV clearance. PMID:23185211

Silicon carbide composite for light water reactor fuel assembly applications

NASA Astrophysics Data System (ADS)

Yueh, Ken; Terrani, Kurt A.

2014-05-01

The feasibility of using SiCf-SiCm composites in light water reactor (LWR) fuel designs was evaluated. The evaluation was motivated by the desire to improve fuel performance under normal and accident conditions. The Fukushima accident once again highlighted the need for improved fuel materials that can maintain fuel integrity to higher temperatures for longer periods of time. The review identified many benefits as well as issues in using the material. Issues perceived as presenting the biggest challenges to the concept were identified to be flux gradient induced differential volumetric swelling, fragmentation and thermal shock resistance. The oxidation of silicon and its release into the coolant as silica has been identified as an issue because existing plant systems have limited ability for its removal. Detailed evaluation using available literature data and testing as part of this evaluation effort have eliminated most of the major concerns. The evaluation identified Boiling Water Reactor (BWR) channel, BWR fuel water tube, and Pressurized Water Reactor (PWR) guide tube as feasible applications for SiC composite. A program has been initiated to resolve some of the remaining issues and to generate physical property data to support the design of commercial fuel components.

Sun, Ocean, Nuclear Bombs, and Fossil Fuels: Radiocarbon Variations and Implications for High-Resolution Dating

NASA Astrophysics Data System (ADS)

Dutta, Koushik

2016-06-01

Radiocarbon, or 14C, is a radiometric dating method ideally suited for providing a chronological framework in archaeology and geosciences for timescales spanning the last 50,000 years. 14C is easily detectable in most common natural organic materials and has a half-life (5,730±40 years) relevant to these timescales. 14C produced from large-scale detonations of nuclear bombs between the 1950s and the early 1960s can be used for dating modern organic materials formed after the 1950s. Often these studies demand high-resolution chronology to resolve ages within a few decades to less than a few years. Despite developments in modern, high-precision 14C analytical methods, the applicability of 14C in high-resolution chronology is limited by short-term variations in atmospheric 14C in the past. This article reviews the roles of the principal natural drivers (e.g., solar magnetic activity and ocean circulation) and the anthropogenic perturbations (e.g., fossil fuel CO2 and 14C from nuclear and thermonuclear bombs) that are responsible for short-term 14C variations in the environment. Methods and challenges of high-resolution 14C dating are discussed.

Probing and Manipulating the Interfacial Defects of InGaAs Dual-Layer Metal Oxides at the Atomic Scale.

PubMed

Wu, Xing; Luo, Chen; Hao, Peng; Sun, Tao; Wang, Runsheng; Wang, Chaolun; Hu, Zhigao; Li, Yawei; Zhang, Jian; Bersuker, Gennadi; Sun, Litao; Pey, Kinleong

2018-01-01

The interface between III-V and metal-oxide-semiconductor materials plays a central role in the operation of high-speed electronic devices, such as transistors and light-emitting diodes. The high-speed property gives the light-emitting diodes a high response speed and low dark current, and they are widely used in communications, infrared remote sensing, optical detection, and other fields. The rational design of high-performance devices requires a detailed understanding of the electronic structure at this interface; however, this understanding remains a challenge, given the complex nature of surface interactions and the dynamic relationship between the morphology evolution and electronic structures. Herein, in situ transmission electron microscopy is used to probe and manipulate the structural and electrical properties of ZrO 2 films on Al 2 O 3 and InGaAs substrate at the atomic scale. Interfacial defects resulting from the spillover of the oxygen-atom conduction-band wavefunctions are resolved. This study unearths the fundamental defect-driven interfacial electric structure of III-V semiconductor materials and paves the way to future high-speed and high-reliability devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Time-resolved fluorescence and ultrafast energy transfer in a zinc (hydr)oxide-graphite oxide mesoporous composite

NASA Astrophysics Data System (ADS)

Secor, Jeff; Narinesingh, Veeshan; Seredych, Mykola; Giannakoudakis, Dimitrios A.; Bandosz, Teresa; Alfano, Robert R.

2015-01-01

Ultrafast energy decay kinetics of a zinc (hydr)oxide-graphite oxide (GO) composite is studied via time-resolved fluorescence spectroscopy. The time-resolved emission is spectrally decomposed into emission regions originating from the zinc (hydr)oxide optical gap, surface, and defect states of the composite material. The radiative lifetime of deep red emission becomes an order of magnitude longer than that of GO alone while the radiative lifetime of the zinc optical gap is shortened in the composite. An energy transfer scheme from the zinc (hydr)oxide to GO is considered.

Linking the Grain Scale to Experimental Measurements and Other Scales

NASA Astrophysics Data System (ADS)

Vogler, Tracy

2017-06-01

A number of physical processes occur at the scale of grains that can have a profound influence on the behavior of materials under shock loading. Examples include inelastic deformation, pore collapse, fracture, friction, and internal wave reflections. In some cases such as the initiation of energetics and brittle fracture, these processes can have first order effects on the behavior of materials: the emergent behavior from the grain scale is the dominant one. In other cases, many aspects of the bulk behavior can be described by a continuum description, but some details of the behavior are missed by continuum descriptions. The multi-scale model paradigm envisions flow of information from smaller scales (atomic, dislocation, etc.) to the grain or mesoscale and the up to the continuum scale. A significant challenge in this approach is the need to validate each step. For the grain scale, diagnosing behavior is challenging because of the small spatial and temporal scales involved. Spatially resolved diagnostics have begun to shed light on these processes, and, more recently, advanced light sources have started to be used to probe behavior at the grain scale. In this talk, I will discuss some interesting phenomena that occur at the grain scale in shock loading, experimental approaches to probe the grain scale, and efforts to link the grain scale to smaller and larger scales. Sandia National Laboratories is a multi-mission laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE.

Next Step Toward Widespread Residential Deep Energy Retrofits

DOE Office of Scientific and Technical Information (OSTI.GOV)

McIlvaine, J.; Saunders, S.; Bordelon, E.

The complexity of deep energy retrofits warrants additional training to successfully manage multiple improvements that will change whole house air, heat, and moisture flow dynamics. The home performance contracting industry has responded to these challenges by aggregating skilled labor for assessment of and implementation under one umbrella. Two emerging business models are profiled that seek to resolve many of the challenges, weaknesses, opportunities, and threats described for the conventional business models.

Time- and Space-Resolved Spectroscopic Investigation on Pi-Conjugated Nanostructures - 2

DTIC Science & Technology

2016-01-12

15. SUBJECT TERMS Materials Characterization, Materials Chemistry, Nonlinear Optical Materials, Spectroscopy 16. SECURITY CLASSIFICATION...nanostructures will translate into new ground-breaking developments that not only allow the structure-property relationships to be probed in greater detail... spectroscopy . I. Experimental method 1. Steady-state Spectroscopy - UV-Vis-NIR Absorption & Emission Steady-state Spectroscopy - NIR

Revealing the ultrafast charge carrier dynamics in organo metal halide perovskite solar cell materials using time resolved THz spectroscopy

NASA Astrophysics Data System (ADS)

Ponseca, C. S., Jr.; Sundström, V.

2016-03-01

Ultrafast charge carrier dynamics in organo metal halide perovskite has been probed using time resolved terahertz (THz) spectroscopy (TRTS). Current literature on its early time characteristics is unanimous: sub-ps charge carrier generation, highly mobile charges and very slow recombination rationalizing the exceptionally high power conversion efficiency for a solution processed solar cell material. Electron injection from MAPbI3 to nanoparticles (NP) of TiO2 is found to be sub-ps while Al2O3 NPs do not alter charge dynamics. Charge transfer to organic electrodes, Spiro-OMeTAD and PCBM, is sub-ps and few hundreds of ps respectively, which is influenced by the alignment of energy bands. It is surmised that minimizing defects/trap states is key in optimizing charge carrier extraction from these materials.

Sensitivity Analysis and Requirements for Temporally and Spatially Resolved Thermometry Using Neutron Resonance Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, Juan Carlos; Barnes, Cris William; Mocko, Michael Jeffrey

This report is intended to examine the use of neutron resonance spectroscopy (NRS) to make time- dependent and spatially-resolved temperature measurements of materials in extreme conditions. Specifically, the sensitivities of the temperature estimate on neutron-beam and diagnostic parameters is examined. Based on that examination, requirements are set on a pulsed neutron-source and diagnostics to make a meaningful measurement.

A Development Strategy for Creating a Suite of Reference Materials for the in-situ Microanalysis of Non-conventional Raw Materials

NASA Astrophysics Data System (ADS)

Renno, A. D.; Merchel, S.; Michalak, P. P.; Munnik, F.; Wiedenbeck, M.

2010-12-01

Recent economic trends regarding the supply of rare metals readily justify scientific research into non-conventional raw materials, where a particular need is a better understanding of the relationship between mineralogy, microstructure and the distribution of key metals within ore deposits (geometallurgy). Achieving these goals will require an extensive usage of in-situ microanalytical techniques capable of spatially resolving material heterogeneities which can be key for understanding better resource utilization. The availability of certified reference materials (CRMs) is an essential prerequisite for (1) validating new analytical methods, (2) demonstrating data quality to the contracting authorities, (3) supporting method development and instrument calibration, and (4) establishing traceability between new analytical approaches and existing data sets. This need has led to the granting of funding by the European Union and the German Free State of Saxony for a program to develop such reference materials . This effort will apply the following strategies during the selection of the phases: (1) will use exclusively synthetic minerals, thereby providing large volumes of homogeneous starting material. (2) will focus on matrices which are capable of incorporating many ‘important’ elements while avoid exotic compositions which would not be optimal matrix matches. (3) will emphasise those phases which remain stable during the various microanalytical procedure. This initiative will assess the homogeneity of the reference materials at sampling sizes ranging between 50 and 1 µm; it is also intended to document crystal structural homogeneity too, as this too may potentially impact specific analytical methods. As far as possible both definitive methods as well as methods involving matrix corrections will be used for determining the compositions of the of the individual materials. A critical challenge will be the validation of the determination of analytes concentrations as sub-µg sampling masses. It is planned to cooperate with those who are interested in the development of such reference materials and we invite them to take part in round-robin exercises.

Toward a standard lexicon for ecosystem services

EPA Science Inventory

The complex, widely dispersed, and cumulative environmental challenges currently facing society require holistic, transdisciplinary approaches to resolve. The concept of ecosystem services (ES) has become more widely accepted both as a framework that cuts across the dimensions of...

Perspectives in Super-resolved Fluorescence Microscopy: What comes next?

NASA Astrophysics Data System (ADS)

Cremer, Christoph; Birk, Udo

2016-04-01

The Nobel Prize in Chemistry 2014 has been awarded to three scientists involved in the development of STED and PALM super-resolution fluorescence microscopy (SRM) methods. They have proven that it is possible to overcome the hundred year old theoretical limit for the resolution potential of light microscopy (of about 200 nm for visible light), which for decades has precluded a direct glimpse of the molecular machinery of life. None of the present-day super-resolution techniques have invalidated the Abbe limit for light optical detection; however, they have found clever ways around it. In this report, we discuss some of the challenges still to be resolved before arising SRM approaches will be fit to bring about the revolution in Biology and Medicine envisaged. Some of the challenges discussed are the applicability to image live and/or large samples, the further enhancement of resolution, future developments of labels, and multi-spectral approaches.

Pediatric pleural empyema: one of the management challenges in children of Democratic Republic of Congo.

PubMed

Simbi, Kibwe Alphonse; Kazadi, Valentin; Aissi, Louis-Marie; Katsuva, François Mbahewaka; Luboya, Numbi Oscar; Tshilolo, Léon; Zanardo, Vincenzo

2017-06-23

Empyema is a serious complication characterized by purulent exudate and bacteria in the pleural space, which may progress to necrosis, cavitations or fistulas in the thoracic cavity. It remains a major challenge throughout low-income countries. Objectives were to emphasize the role of basic medical and radiologic approach and to resolve a severe lung complication when facilities are inadequate. A five-year-old female was referred with distress respiratory to the Emergency Unit of Monkole, a large public-private missionary hospital in Kinshasa, Congo. Chest X-ray showed a massive empyema that was resolved by immediate drainage and antibiotiocs. Results were rapid improvement and discharge after 3 weeks. A classic medical and imaging approach is a winning return in low-income countries. According to the British Thoracic Society guidelines, pleural effusion with compromising respiratory function can be managed by drainage and antibiotics.

Let's talk conflict: using mediation in healthcare security disputes.

PubMed

Armstrong, Brad

2013-01-01

Healthcare security administrators face weekly, if not daily challenges and conflict. This article considers that security leaders must anticipate disputes in highly complex healthcare systems. When disputes cannot be resolved by organizational efforts, security administrators may be in a position to recommend or participate in mediation. Here the concept of mediation is introduced to healthcare security leaders as a viable means to resolve disputes with patients, visitors, and the community. This includes a description of the facilitative versus evaluative mediation processes, as well as pragmatic guidance when preparing for mediation.

Femtosecond to picosecond transient effects in WSe 2 observed by pump-probe angle-resolved photoemission spectroscopy.

PubMed

Liu, Ro-Ya; Ogawa, Yu; Chen, Peng; Ozawa, Kenichi; Suzuki, Takeshi; Okada, Masaru; Someya, Takashi; Ishida, Yukiaki; Okazaki, Kozo; Shin, Shik; Chiang, Tai-Chang; Matsuda, Iwao

2017-11-22

Time-dependent responses of materials to an ultrashort optical pulse carry valuable information about the electronic and lattice dynamics; this research area has been widely studied on novel two-dimensional materials such as graphene, transition metal dichalcogenides (TMDs) and topological insulators (TIs). We report herein a time-resolved and angle-resolved photoemission spectroscopy (TRARPES) study of WSe 2 , a layered semiconductor of interest for valley electronics. The results for below-gap optical pumping reveal energy-gain and -loss Floquet replica valence bands that appear instantaneously in concert with the pump pulse. Energy shift, broadening, and complex intensity variation and oscillation at twice the phonon frequency for the valence bands are observed at time scales ranging from the femtosecond to the picosecond and beyond. The underlying physics is rich, including ponderomotive interaction, dressing of the electronic states, creation of coherent phonon pairs, and diffusion of charge carriers - effects operating at vastly different time domains.

Controllable embedding of sulfur in high surface area nitrogen doped three dimensional reduced graphene oxide by solution drop impregnation method for high performance lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Zegeye, Tilahun Awoke; Tsai, Meng-Che; Cheng, Ju-Hsiang; Lin, Ming-Hsien; Chen, Hung-Ming; Rick, John; Su, Wei-Nien; Kuo, Chung-Feng Jeffrey; Hwang, Bing-Joe

2017-06-01

High capacity lithium-sulfur batteries with stable cycle performance and sulfur loadings greater than 70 wt% are regarded as promising candidates for energy storage devices. However, it has been challenged to achieving practical application of sulfur cathode because of low loading of active sulfur and poor cycle performance. Herein, we design novel nanocomposite cathode materials consist of sulfur (80 wt%) embedded within nitrogen doped three-dimensional reduced graphene oxide (N-3D-rGO) by controllable sulfur-impregnation method. Nitrogen doping helps increase the surface area by ten times from pristine graphene, and pore volume by seven times. These structural features allow the cathode to hold more sulfur. It also adsorbs polysulfides and prevents their detachment from the host materials; thereby achieving stable cycle performance. The solution drop sulfur-impregnation method provides uniform distribution of nano-sulfur in controlled manner. The material delivers a high initial discharge capacity of 1042 mAhg-1 and 916 mAhg-1 with excellent capacity retention of 94.8% and 81.9% at 0.2 C and 0.5 C respectively after 100 cycles. Thus, the combination of solution drop and nitrogen doping opens a new chapter for resolving capacity fading as well as long cycling problems and creates a new strategy to increase sulfur loading in controlled mechanism.

Role of phase instabilities in the early response of bulk fused silica during laser-induced breakdown

NASA Astrophysics Data System (ADS)

Demange, P.; Negres, R. A.; Raman, R. N.; Colvin, J. D.; Demos, S. G.

2011-08-01

We report on the experimental and hydrocode modeling investigation of the early material response to localized energy deposition via nanosecond laser pulses in bulk fused silica. A time-resolved microscope system was used to acquire transient images with adequate spatial and temporal resolution to resolve the material behavior from the onset of the process. These images revealed a high-pressure shock front propagating at twice the speed of sound at ambient conditions and bounding a region of modified material at delays up to one nanosecond. Hydrocode simulations matching the experimental conditions were also performed and indicated initial pressures of ˜40 GPa and temperatures of ˜1 eV at the absorption region. Both the simulations and the image data show a clear boundary between distinct material phases, a hot plasma and solid silica, with a suggestion that growth of perturbations at the Rayleigh-Taylor unstable interface between the two phases is the seed mechanism for the growth of cracks into the stressed solid.

Time-resolved transillumination and optical tomography

NASA Astrophysics Data System (ADS)

de Haller, Emmanuel B.

1996-01-01

In response to an invitation by the editor-in-chief, I would like to present the current status of time-domain imaging. With exciting new photon diffusion techniques being developed in the frequency domain and promising optical coherence tomography, time-resolved transillumination is in constant evolution and the subject of passionate discussions during the numerous conferences dedicated to this subject. The purpose of time-resolved optical tomography is to provide noninvasive, high-resolution imaging of the interior of living bodies by the use of nonionizing radiation. Moreover, the use of visible to near-infrared wavelength yields metabolic information. Breast cancer screening is the primary potential application for time-resolved imaging. Neurology and tissue characterization are also possible fields of applications. Time- resolved transillumination and optical tomography should not only improve diagnoses, but the welfare of the patient. As no overview of this technique has yet been presented to my knowledge, this paper briefly describes the various methods enabling time-resolved transillumination and optical tomography. The advantages and disadvantages of these methods, as well as the clinical challenges they face are discussed. Although an analytic and computable model of light transport through tissues is essential for a meaningful interpretation of the transillumination process, this paper will not dwell on the mathematics of photon propagation.

Forming a Turbomachinery Seals Working Group: An Overview and Discussion

NASA Technical Reports Server (NTRS)

Proctor, Margaret P.

2007-01-01

Purose: Identify technical challenges to improving turbomachinery seal leakage and wear performance, reliability and cost effectiveness. Develop a coordinated effort to resolve foundational issues for turbomachinery seal technologies. Identify and foster opportunities for collaboration. Advocate for funding.

3 CFR 8479 - Proclamation 8479 of March 1, 2010. Irish-American Heritage Month, 2010

Code of Federal Regulations, 2011 CFR

2011-01-01

... challenges with resolve and determination. In the face of violence perpetuated by some—testing a hard-earned... communities, Irish Americans are a people whose hard work and resilience have brought them great opportunity...

Recycling production designs: the value of coordination and flexibility in aluminum recycling operations

NASA Astrophysics Data System (ADS)

Brommer, Tracey H.

The growing motivation for aluminum recycling has prompted interest in recycling alternative and more challenging secondary materials. The nature of these alternative secondary materials necessitates the development of an intermediate recycling facility that can reprocess the secondary materials into a liquid product Two downstream aluminum remelters will incorporate the liquid products into their aluminum alloy production schedules. Energy and environmental benefits result from delivering the products as liquid but coordination challenges persist because of the energy cost to maintain the liquid. Further coordination challenges result from the necessity to establish a long term recycling production plan in the presence of long term downstream aluminum remelter production uncertainty and inherent variation in the daily order schedule of the downstream aluminum remelters. In this context a fundamental question arises, considering the metallurgical complexities of dross reprocessing, what is the value of operating a coordinated set of by-product reprocessing plants and remelting cast houses? A methodology is presented to calculate the optimal recycling center production parameters including 1) the number of recycled products, 2) the volume of recycled products, 3) allocation of recycled materials across recycled products, 4) allocation of recycled products across finished alloys, 4) the level of flexibility for the recycling center to operate. The methods implemented include, 1) an optimization model to describe the long term operations of the recycling center, 2) an uncertainty simulation tool, 3) a simulation optimization method, 4) a dynamic simulation tool with four embedded daily production optimization models of varying degrees of flexibility. This methodology is used to quantify the performance of several recycling center production designs of varying levels of coordination and flexibility. This analysis allowed the identification of the optimal recycling center production design based on maximizing liquid recycled product incorporation and minimizing cast sows. The long term production optimization model was used to evaluate the theoretical viability of the proposed two stage scrap and aluminum dross reprocessing operation including the impact of reducing coordination on model performance. Reducing the coordination between the recycling center and downstream remelters by reducing the number of recycled products from ten to five resulted in only 1.3% less secondary materials incorporated into downstream production. The dynamic simulation tool was used to evaluate the performance of the calculated recycling center production plan when resolved on a daily timeframe for varying levels of operational flexibility. The dynamic simulation revealed the optimal performance corresponded to the fixed recipe with flexible production daily optimization model formulation. Calculating recycled product characteristics using the proposed simulation optimization method increased profitability in cases of uncertain downstream remelter production and expensive aluminum dross and post-consumed secondary materials. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs@mit.edu)

The Next Step Toward Widespread Residential Deep Energy Retrofits

DOE Office of Scientific and Technical Information (OSTI.GOV)

McIlvaine, J.; Martin, E.; Saunders, S.

The complexity of deep energy retrofits warrants additional training to successfully manage multiple improvements that will change whole house air, heat, and moisture flow dynamics. The home performance contracting industry has responded to these challenges by aggregating skilled labor for assessment of and implementation under one umbrella. Two emerging business models are profiled that seek to resolve many of the challenges, weaknesses, opportunities, and threats described for the conventional business models.

Element-resolved Kikuchi pattern measurements of non-centrosymmetric materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vos, Maarten, E-mail: maarten.vos@anu.edu.au

2017-01-15

Angle-resolved electron Rutherford backscattering (ERBS) measurements using an electrostatic electron energy analyser can provide unique access to element-resolved crystallographic information. We present Kikuchi pattern measurements of the non-centrosymmetric crystal GaP, separately resolving the contributions of electrons backscattered from Ga and P. In comparison to element-integrated measurements like in the method of electron backscatter diffraction (EBSD), the effect of the absence of a proper 4-fold rotation axis in the point group of GaP can be sensed with a much higher visibility via the element-resolved Ga to P intensity ratio. These element-resolved measurements make it possible to experimentally attribute the previously observedmore » point-group dependent effect in element-integrated EBSD measurements to the larger contribution of electrons scattered from Ga compared to P. - Highlights: •Element specific Kikuchi patterns are presented for GaP. •Absence of a proper four-fold rotation axis is demonstrated. •Ga and P intensity variations after 90 degree rotation have opposite phase. •The asymmetry in the total intensity distribution resembles that of Ga.« less

41 CFR 51-8.3 - Definitions.

Code of Federal Regulations, 2014 CFR

2014-07-01

... request. Such copies can take the form of paper copy, audio-visual materials, or machine readable materials (e.g., magnetic tape or disk), among others. (g) The term search includes all time spent looking... time spent resolving general legal or policy issues regarding the application of exemptions. [54 FR...

41 CFR 51-8.3 - Definitions.

Code of Federal Regulations, 2012 CFR

2012-07-01

... request. Such copies can take the form of paper copy, audio-visual materials, or machine readable materials (e.g., magnetic tape or disk), among others. (g) The term search includes all time spent looking... time spent resolving general legal or policy issues regarding the application of exemptions. [54 FR...

Computational time-resolved and resonant x-ray scattering of strongly correlated materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bansil, Arun

Basic-Energy Sciences of the Department of Energy (BES/DOE) has made large investments in x-ray sources in the U.S. (NSLS-II, LCLS, NGLS, ALS, APS) as powerful enabling tools for opening up unprecedented new opportunities for exploring properties of matter at various length and time scales. The coming online of the pulsed photon source, literally allows us to see and follow the dynamics of processes in materials at their natural timescales. There is an urgent need therefore to develop theoretical methodologies and computational models for understanding how x-rays interact with matter and the related spectroscopies of materials. The present project addressed aspectsmore » of this grand challenge of x-ray science. In particular, our Collaborative Research Team (CRT) focused on developing viable computational schemes for modeling x-ray scattering and photoemission spectra of strongly correlated materials in the time-domain. The vast arsenal of formal/numerical techniques and approaches encompassed by the members of our CRT were brought to bear through appropriate generalizations and extensions to model the pumped state and the dynamics of this non-equilibrium state, and how it can be probed via x-ray absorption (XAS), emission (XES), resonant and non-resonant x-ray scattering, and photoemission processes. We explored the conceptual connections between the time-domain problems and other second-order spectroscopies, such as resonant inelastic x-ray scattering (RIXS) because RIXS may be effectively thought of as a pump-probe experiment in which the incoming photon acts as the pump, and the fluorescent decay is the probe. Alternatively, when the core-valence interactions are strong, one can view K-edge RIXS for example, as the dynamic response of the material to the transient presence of a strong core-hole potential. Unlike an actual pump-probe experiment, here there is no mechanism for adjusting the time-delay between the pump and the probe. However, the core hole predominantly decays via Auger processes, thereby providing an internal time-scale, which limits intermediate-state processes to timescales of a few femtoseconds. Accordingly, a number of activities directed at modeling K-, L- and M-edge RIXS in correlated materials were also pursused by our CRT. Our research effort supported by this CMCSN grant substantially advanced the understanding of x-ray scattering processes in the time-domain as well as in the more conventional scattering channels, including time-resolved photoemission, and how such processes can be modeled realistically in complex correlated materials more generally. The modeling of relaxation processes involved in time-domain spectroscopies is important also for understanding photoinduced effects such as energy conversion in photosynthesis and solar cell applications, and thus impacts the basic science for energy needs.« less

Compact high-resolution spectrographs for large and extremely large telescopes: using the diffraction limit

NASA Astrophysics Data System (ADS)

Robertson, J. Gordon; Bland-Hawthorn, Joss

2012-09-01

As telescopes get larger, the size of a seeing-limited spectrograph for a given resolving power becomes larger also, and for ELTs the size will be so great that high resolution instruments of simple design will be infeasible. Solutions include adaptive optics (but not providing full correction for short wavelengths) or image slicers (which give feasible but still large instruments). Here we develop the solution proposed by Bland-Hawthorn and Horton: the use of diffraction-limited spectrographs which are compact even for high resolving power. Their use is made possible by the photonic lantern, which splits a multi-mode optical fiber into a number of single-mode fibers. We describe preliminary designs for such spectrographs, at a resolving power of R ~ 50,000. While they are small and use relatively simple optics, the challenges are to accommodate the longest possible fiber slit (hence maximum number of single-mode fibers in one spectrograph) and to accept the beam from each fiber at a focal ratio considerably faster than for most spectrograph collimators, while maintaining diffraction-limited imaging quality. It is possible to obtain excellent performance despite these challenges. We also briefly consider the number of such spectrographs required, which can be reduced by full or partial adaptive optics correction, and/or moving towards longer wavelengths.

Pressure-induced kinetics of the α to ω transition in zirconium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jacobsen, M. K.; Velisavljevic, N., E-mail: nenad@lanl.gov; Sinogeikin, S. V.

Diamond anvil cells (DAC) coupled with x-ray diffraction (XRD) measurements are one of the primary techniques for investigating structural stability of materials at high pressure-temperature (P-T) conditions. DAC-XRD has been predominantly used to resolve structural information at set P-T conditions and, consequently, provides P-T phase diagram information on a broad range of materials. With advances in large scale synchrotron x-ray facilities and corresponding x-ray diagnostic capabilities, it is now becoming possible to perform sub-second time resolved measurements on micron sized DAC samples. As a result, there is an opportunity to gain valuable information about the kinetics of structural phase transformationsmore » and extend our understanding of material behavior at high P-T conditions. Using DAC-XRD time resolved measurements, we have investigated the kinetics of the α to ω transformation in zirconium. We observe a clear time and pressure dependence in the martensitic α-ω transition as a function of pressure-jump, i.e., drive pressure. The resulting data are fit using available kinetics models, which can provide further insight into transformation mechanism that influence transformation kinetics. Our results help shed light on the discrepancies observed in previous measurements of the α-ω transition pressure in zirconium.« less

Pressure-induced kinetics of the α to ω transition in zirconium

DOE PAGES

Jacobsen, M. K.; Velisavljevic, N.; Sinogeikin, S. V.

2015-07-13

Diamond anvil cells (DAC) coupled with x-ray diffraction (XRD) measurements are one of the primary techniques for investigating structural stability of materials at high pressure-temperature (P-T) conditions. DAC-XRD has been predominantly used to resolve structural information at set P-T conditions and, consequently, provides P-T phase diagram information on a broad range of materials. With advances in large scale synchrotron x-ray facilities and corresponding x-ray diagnostic capabilities, it is now becoming possible to perform sub-second time resolved measurements on micron sized DAC samples. As a result, there is an opportunity to gain valuable information about the kinetics of structural phase transformationsmore » and extend our understanding of material behavior at high P-T conditions. Using DAC-XRD time resolved measurements, we have investigated the kinetics of the α to ω transformation in zirconium. We observe a clear time and pressure dependence in the martensitic α-ω transition as a function of pressure-jump, i.e., drive pressure. The resulting data are fit using available kinetics models, which can provide further insight into transformation mechanism that influence transformation kinetics. Our results help shed light on the discrepancies observed in previous measurements of the α-ω transition pressure in zirconium.« less

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy.

PubMed

Jobst, Johannes; van der Torren, Alexander J H; Krasovskii, Eugene E; Balgley, Jesse; Dean, Cory R; Tromp, Rudolf M; van der Molen, Sense Jan

2016-11-29

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the 'chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of.

Spatially resolved positron annihilation spectroscopy on friction stir weld induced defects.

PubMed

Hain, Karin; Hugenschmidt, Christoph; Pikart, Philip; Böni, Peter

2010-04-01

A friction stir welded (FSW) Al alloy sample was investigated by Doppler broadening spectroscopy (DBS) of the positron annihilation line. The spatially resolved defect distribution showed that the material in the joint zone becomes completely annealed during the welding process at the shoulder of the FSW tool, whereas at the tip, annealing is prevailed by the deterioration of the material due to the tool movement. This might be responsible for the increased probability of cracking in the heat affected zone of friction stir welds. Examination of a material pairing of steel S235 and the Al alloy Silafont36 by coincident Doppler broadening spectroscopy (CDBS) indicates the formation of annealed steel clusters in the Al alloy component of the sample. The clear visibility of Fe in the CDB spectra is explained by the very efficient trapping at the interface between steel cluster and bulk.

General theoretical description of angle-resolved photoemission spectroscopy of van der Waals structures

NASA Astrophysics Data System (ADS)

Amorim, B.

2018-04-01

We develop a general theory to model the angle-resolved photoemission spectroscopy (ARPES) of commensurate and incommensurate van der Waals (vdW) structures, formed by lattice mismatched and/or misaligned stacked layers of two-dimensional materials. The present theory is based on a tight-binding description of the structure and the concept of generalized umklapp processes, going beyond previous descriptions of ARPES in incommensurate vdW structures, which are based on continuous, low-energy models, being limited to structures with small lattice mismatch/misalignment. As applications of the general formalism, we study the ARPES bands and constant energy maps for two structures: twisted bilayer graphene and twisted bilayer MoS2. The present theory should be useful in correctly interpreting experimental results of ARPES of vdW structures and other systems displaying competition between different periodicities, such as two-dimensional materials weakly coupled to a substrate and materials with density wave phases.

Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strong, Kevin; Buchheit, Thomas E.; Diebold, Thomas Wayne

Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has beenmore » designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.« less

Stress Mapping in Glass-to-Metal Seals using Indentation Crack Lengths

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buchheit, Thomas E.; Strong, Kevin; Newton, Clay S.

Predicting the residual stress which develops during fabrication of a glass-to-metal compression seal requires material models that can accurately predict the effects of processing on the sealing glass. Validation of the predictions requires measurements on representative test geometries to accurately capture the interaction between the seal materials during a processing cycle required to form the seal, which consists of a temperature excursion through the glass transition temperature of the sealing glass. To this end, a concentric seal test geometry, referred to as a short cylinder seal, consisting of a stainless steel shell enveloping a commercial sealing glass disk has beenmore » designed, fabricated, and characterized as a model validation test geometry. To obtain data to test/validate finite element (FE) stress model predictions of this geometry, spatially-resolved residual stress was calculated from the measured lengths of the cracks emanating from radially positioned Vickers indents in the glass disk portion of the seal. The indentation crack length method is described, and the spatially-resolved residual stress determined experimentally are compared to FE stress predictions made using a nonlinear viscoelastic material model adapted to inorganic sealing glasses and an updated rate dependent material model for 304L stainless steel. The measurement method is a first to achieve a degree of success for measuring spatially resolved residual stress in a glass-bearing geometry and a favorable comparison between measurements and simulation was observed.« less

Challenges of microtome‐based serial block‐face scanning electron microscopy in neuroscience

PubMed Central

WANNER, A. A.; KIRSCHMANN, M. A.

2015-01-01

Summary Serial block‐face scanning electron microscopy (SBEM) is becoming increasingly popular for a wide range of applications in many disciplines from biology to material sciences. This review focuses on applications for circuit reconstruction in neuroscience, which is one of the major driving forces advancing SBEM. Neuronal circuit reconstruction poses exceptional challenges to volume EM in terms of resolution, field of view, acquisition time and sample preparation. Mapping the connections between neurons in the brain is crucial for understanding information flow and information processing in the brain. However, information on the connectivity between hundreds or even thousands of neurons densely packed in neuronal microcircuits is still largely missing. Volume EM techniques such as serial section TEM, automated tape‐collecting ultramicrotome, focused ion‐beam scanning electron microscopy and SBEM (microtome serial block‐face scanning electron microscopy) are the techniques that provide sufficient resolution to resolve ultrastructural details such as synapses and provides sufficient field of view for dense reconstruction of neuronal circuits. While volume EM techniques are advancing, they are generating large data sets on the terabyte scale that require new image processing workflows and analysis tools. In this review, we present the recent advances in SBEM for circuit reconstruction in neuroscience and an overview of existing image processing and analysis pipelines. PMID:25907464

Recent Advances in Fluorescence Lifetime Analytical Microsystems: Contact Optics and CMOS Time-Resolved Electronics.

PubMed

Wei, Liping; Yan, Wenrong; Ho, Derek

2017-12-04

Fluorescence spectroscopy has become a prominent research tool with wide applications in medical diagnostics and bio-imaging. However, the realization of combined high-performance, portable, and low-cost spectroscopic sensors still remains a challenge, which has limited the technique to the laboratories. A fluorescence lifetime measurement seeks to obtain the characteristic lifetime from the fluorescence decay profile. Time-correlated single photon counting (TCSPC) and time-gated techniques are two key variations of time-resolved measurements. However, commercial time-resolved analysis systems typically contain complex optics and discrete electronic components, which lead to bulkiness and a high cost. These two limitations can be significantly mitigated using contact sensing and complementary metal-oxide-semiconductor (CMOS) implementation. Contact sensing simplifies the optics, whereas CMOS technology enables on-chip, arrayed detection and signal processing, significantly reducing size and power consumption. This paper examines recent advances in contact sensing and CMOS time-resolved circuits for the realization of fully integrated fluorescence lifetime measurement microsystems. The high level of performance from recently reported prototypes suggests that the CMOS-based contact sensing microsystems are emerging as sound technologies for application-specific, low-cost, and portable time-resolved diagnostic devices.

Recent Advances in Fluorescence Lifetime Analytical Microsystems: Contact Optics and CMOS Time-Resolved Electronics

PubMed Central

Yan, Wenrong; Ho, Derek

2017-01-01

Fluorescence spectroscopy has become a prominent research tool with wide applications in medical diagnostics and bio-imaging. However, the realization of combined high-performance, portable, and low-cost spectroscopic sensors still remains a challenge, which has limited the technique to the laboratories. A fluorescence lifetime measurement seeks to obtain the characteristic lifetime from the fluorescence decay profile. Time-correlated single photon counting (TCSPC) and time-gated techniques are two key variations of time-resolved measurements. However, commercial time-resolved analysis systems typically contain complex optics and discrete electronic components, which lead to bulkiness and a high cost. These two limitations can be significantly mitigated using contact sensing and complementary metal-oxide-semiconductor (CMOS) implementation. Contact sensing simplifies the optics, whereas CMOS technology enables on-chip, arrayed detection and signal processing, significantly reducing size and power consumption. This paper examines recent advances in contact sensing and CMOS time-resolved circuits for the realization of fully integrated fluorescence lifetime measurement microsystems. The high level of performance from recently reported prototypes suggests that the CMOS-based contact sensing microsystems are emerging as sound technologies for application-specific, low-cost, and portable time-resolved diagnostic devices. PMID:29207568

A Perspective on the Application of Spatially Resolved ARPES for 2D Materials

PubMed Central

Cattelan, Mattia

2018-01-01

In this paper, a perspective on the application of Spatially- and Angle-Resolved PhotoEmission Spectroscopy (ARPES) for the study of two-dimensional (2D) materials is presented. ARPES allows the direct measurement of the electronic band structure of materials generating extremely useful insights into their electronic properties. The possibility to apply this technique to 2D materials is of paramount importance because these ultrathin layers are considered fundamental for future electronic, photonic and spintronic devices. In this review an overview of the technical aspects of spatially localized ARPES is given along with a description of the most advanced setups for laboratory and synchrotron-based equipment. This technique is sensitive to the lateral dimensions of the sample. Therefore, a discussion on the preparation methods of 2D material is presented. Some of the most interesting results obtained by ARPES are reported in three sections including: graphene, transition metal dichalcogenides (TMDCs) and 2D heterostructures. Graphene has played a key role in ARPES studies because it inspired the use of this technique with other 2D materials. TMDCs are presented for their peculiar transport, optical and spin properties. Finally, the section featuring heterostructures highlights a future direction for research into 2D material structures. PMID:29702567

A Perspective on the Application of Spatially Resolved ARPES for 2D Materials.

PubMed

Cattelan, Mattia; Fox, Neil A

2018-04-27

In this paper, a perspective on the application of Spatially- and Angle-Resolved PhotoEmission Spectroscopy (ARPES) for the study of two-dimensional (2D) materials is presented. ARPES allows the direct measurement of the electronic band structure of materials generating extremely useful insights into their electronic properties. The possibility to apply this technique to 2D materials is of paramount importance because these ultrathin layers are considered fundamental for future electronic, photonic and spintronic devices. In this review an overview of the technical aspects of spatially localized ARPES is given along with a description of the most advanced setups for laboratory and synchrotron-based equipment. This technique is sensitive to the lateral dimensions of the sample. Therefore, a discussion on the preparation methods of 2D material is presented. Some of the most interesting results obtained by ARPES are reported in three sections including: graphene, transition metal dichalcogenides (TMDCs) and 2D heterostructures. Graphene has played a key role in ARPES studies because it inspired the use of this technique with other 2D materials. TMDCs are presented for their peculiar transport, optical and spin properties. Finally, the section featuring heterostructures highlights a future direction for research into 2D material structures.

Challenges and opportunities of open data in ecology.

PubMed

Reichman, O J; Jones, Matthew B; Schildhauer, Mark P

2011-02-11

Ecology is a synthetic discipline benefiting from open access to data from the earth, life, and social sciences. Technological challenges exist, however, due to the dispersed and heterogeneous nature of these data. Standardization of methods and development of robust metadata can increase data access but are not sufficient. Reproducibility of analyses is also important, and executable workflows are addressing this issue by capturing data provenance. Sociological challenges, including inadequate rewards for sharing data, must also be resolved. The establishment of well-curated, federated data repositories will provide a means to preserve data while promoting attribution and acknowledgement of its use.

Optimization of the Inverse Algorithm for Estimating the Optical Properties of Biological Materials Using Spatially-resolved Diffuse Reflectance Technique

USDA-ARS?s Scientific Manuscript database

Determination of the optical properties from intact biological materials based on diffusion approximation theory is a complicated inverse problem, and it requires proper implementation of inverse algorithm, instrumentation, and experiment. This work was aimed at optimizing the procedure of estimatin...

Options for Replacing and Reformatting Deteriorated Materials.

ERIC Educational Resources Information Center

Banks, Jennifer

This resource guide focuses on handling library materials that are too deteriorated to benefit from other preservation treatments. Hopeless case items, that would require an unreasonable amount of conservation work to fix, can be resolved through a process of reselecting items by replacing them or reformatting them. The reselection integrates…

Insensitivity of Astrocytes to Interleukin-10 Signaling following Peripheral Immune Challenge Results in Prolonged Microglial Activation in the Aged Brain

PubMed Central

Norden, Diana M.; Trojanowski, Paige J.; Walker, Frederick R.; Godbout, Jonathan P.

2017-01-01

Immune-activated microglia from aged mice produce exaggerated levels of cytokines. Despite high levels of microglial IL-10 in the aged brain, neuroinflammation was prolonged and associated with depressive-like deficits. Because astrocytes respond to IL-10 and, in turn, attenuate microglial activation, we investigated if astrocyte-mediated resolution of microglial activation was impaired with age. Here, aged astrocytes had a dysfunctional profile with higher GFAP, lower glutamate transporter expression, and significant cytoskeletal re-arrangement. Moreover, aged astrocytes had reduced expression of growth factors and IL-10 Receptor-1 (IL-10R1). Following in vivo LPS immune challenge, aged astrocytes had a molecular signature associated with reduced responsiveness to IL-10. This IL-10 insensitivity of aged astrocytes resulted in a failure to induce IL-10R1 and TGFβ and resolve microglial activation. Additionally, adult astrocytes reduced microglial activation when co-cultured ex vivo, while aged astrocytes did not. Consistent with the aging studies, IL-10RKO astrocytes did not augment TGFβ after immune challenge and failed to resolve microglial activation. Collectively, a major cytokine-regulatory loop between activated microglia and astrocytes is impaired in the aged brain. PMID:27318131

Standardized patient walkthroughs in the National Drug Abuse Treatment Clinical Trials Network: common challenges to protocol implementation.

PubMed

Fussell, Holly E; Kunkel, Lynn E; McCarty, Dennis; Lewy, Colleen S

2011-09-01

Training research staff to implement clinical trials occurring in community-based addiction treatment programs presents unique challenges. Standardized patient walkthroughs of study procedures may enhance training and protocol implementation. Examine and discuss cross-site and cross-study challenges of participant screening and data collection procedures identified during standardized patient walkthroughs of multi-site clinical trials. Actors portrayed clients and "walked through" study procedures with protocol research staff. The study completed 57 walkthroughs during implementation of 4 clinical trials. Observers and walkthrough participants identified three areas of concern (consent procedures, screening and assessment processes, and protocol implementation) and made suggestions for resolving the concerns. Standardized patient walkthroughs capture issues with study procedures previously unidentified with didactic training or unscripted rehearsals. Clinical trials within the National Drug Abuse Treatment Clinical Trials Network are conducted in addiction treatment centers that vary on multiple dimensions. Based on walkthrough observations, the national protocol team and local site leadership modify standardized operating procedures and resolve cross-site problems prior to recruiting study participants. The standardized patient walkthrough improves consistency across study sites and reduces potential site variation in study outcomes.

Challenges of Implementing a Communication-and-Resolution Program Where Multiple Organizations Must Cooperate.

PubMed

Mello, Michelle M; Armstrong, Sarah J; Greenberg, Yelena; McCotter, Patricia I; Gallagher, Thomas H

2016-12-01

To implement a communication-and-resolution program (CRP) in a setting in which liability insurers and health care facilities must collaborate to resolve incidents involving a facility and separately insured clinicians. Six hospitals and clinics and a liability insurer in Washington State. Sites designed and implemented CRPs and contributed information about cases and operational challenges over 20 months. Data were qualitatively analyzed. Data from interviews with personnel responsible for CRP implementation were triangulated with data on program cases collected by sites and notes recorded during meetings with sites and among project team members. Sites experienced small victories in resolving particular cases and streamlining some working relationships, but they were unable to successfully implement a collaborative CRP. Barriers included the insurer's distance from the point of care, passive rather than active support from top leaders, coordinating across departments and organizations, workload, nonparticipation by some physicians, and overcoming distrust. Operating CRPs where multiple organizations must collaborate can be highly challenging. Success likely requires several preconditions, including preexisting trust among organizations, active leadership engagement, physicians' commitment to participate, mechanisms for quickly transmitting information to insurers, tolerance for missteps, and clear protocols for joint investigations and resolutions. © Health Research and Educational Trust.

The diagnostic value of component-resolved diagnostics in peanut allergy in children attending a Regional Paediatric Allergology Clinic.

PubMed

van Veen, Leonieke N; Heron, Michiel; Batstra, Manou; van Haard, Paul M M; de Groot, Hans

2016-06-02

To date, diagnosing food allergies in children still presents a diagnostic dilemma, leading to uncertainty concerning the definite diagnosis of peanut allergy, as well as to the need for strict diets and the potential need for adrenalin auto-injectors. This uncertainty in particular is thought to contribute to a lower quality of life. In the diagnostic process double-blind food challenges are considered the gold standard, but they are time-consuming as well as potentially hazardous. Other diagnostic tests have been extensively studied and among these component-resolved diagnostics appeared to present a promising alternative: Ara h2, a peanut storage protein in previous studies showed to have a significant predictive value. Sixty-two out of 72 children, with suspected peanut allergy were analyzed using serum specific IgE and/or skin prick tests and specific IgE to several components of peanut (Ara h 1, 2, 3, 6, 8, 9). Subsequently, double-blind food challenges were performed. The correlation between the various diagnostic tests and the overall outcome of the double-blind food challenges were studied, in particular the severity of the reaction and the eliciting dose. The double-blind provocation with peanut was positive in 33 children (53 %). There was no relationship between the eliciting dose and the severity of the reaction. A statistically significant relationship was found between the skin prick test, specific IgE directed to peanut, Ara h 1, Ara h 2 or Ara h 6, and the outcome of the food challenge test, in terms of positive or negative (P < .001). However, we did not find any relationship between sensitisation to peanut extract or the different allergen components and the severity of the reaction or the eliciting dose. There was no correlation between IgE directed to Ara h 3, Ara h 8, Ara h 9 and the clinical outcome of the food challenge. This study shows that component-resolved diagnostics is not superior to specific IgE to peanut extract or to skin prick testing. At present, it cannot replace double-blind placebo-controlled food challenges for determination of the eliciting dose or the severity of the peanut allergy in our patient group.

Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics.

PubMed

Davis, Caitlin M; Reddish, Michael J; Dyer, R Brian

2017-05-05

Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of <0.2mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50ns to 0.5ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics. Copyright © 2017 Elsevier B.V. All rights reserved.

Dual time-resolved temperature-jump fluorescence and infrared spectroscopy for the study of fast protein dynamics

NASA Astrophysics Data System (ADS)

Davis, Caitlin M.; Reddish, Michael J.; Dyer, R. Brian

2017-05-01

Time-resolved temperature-jump (T-jump) coupled with fluorescence and infrared (IR) spectroscopy is a powerful technique for monitoring protein dynamics. Although IR spectroscopy of the polypeptide amide I mode is more technically challenging, it offers complementary information because it directly probes changes in the protein backbone, whereas, fluorescence spectroscopy is sensitive to the environment of specific side chains. With the advent of widely tunable quantum cascade lasers (QCL) it is possible to efficiently probe multiple IR frequencies with high sensitivity and reproducibility. Here we describe a dual time-resolved T-jump fluorescence and IR spectrometer and its application to study protein folding dynamics. A Q-switched Ho:YAG laser provides the T-jump source for both time-resolved IR and fluorescence spectroscopy, which are probed by a QCL and Ti:Sapphire laser, respectively. The Ho:YAG laser simultaneously pumps the time-resolved IR and fluorescence spectrometers. The instrument has high sensitivity, with an IR absorbance detection limit of < 0.2 mOD and a fluorescence sensitivity of 2% of the overall fluorescence intensity. Using a computer controlled QCL to rapidly tune the IR frequency it is possible to create a T-jump induced difference spectrum from 50 ns to 0.5 ms. This study demonstrates the power of the dual time-resolved T-jump fluorescence and IR spectroscopy to resolve complex folding mechanisms by complementary IR absorbance and fluorescence measurements of protein dynamics.

The future of community pharmacy practice in South Africa in the light of the proposed new qualification for pharmacists: implications and challenges.

PubMed

Malangu, Ntambwe

2014-08-15

Community or retail pharmacies are regarded as one of the most common sources of health services throughout the world. In South Africa, community pharmacies have been providing some primary health care services to clients who could afford to pay. These services included screening, family planning, and emergency care for minor ailments. With the introduction of the new qualification, community pharmacies are poised to become providers of expanded services.  This paper describes the contents, the implications and challenges of the new qualification in light with future directions for community pharmacy practice in South Africa. Its purpose is to inform relevant stakeholders in South Africa and those outside South Africa that may pursue similar offerings. Published papers were identified through searches in MEDLINE and Google Scholar using a combination of search terms, namely: 'community, retail pharmacy, pharmacist/non-medical prescribing, South Africa'. Only articles published in English were considered. In addition, documents from the Ministry of Health of South Africa, the South African Pharmacy Council and curricula materials from schools of pharmacy were also reviewed. Laureates of the new qualification will essentially have the right to examine, diagnose, prescribe and monitor the treatment of their clients or patients. In doing so, this expanded function of prescribing for primary healthcare will imply several practice and infrastructural adjustments; and with many challenges laying ahead in need to be addressed. In conclusion, the authorized pharmacist prescriber qualification augurs a new era for community pharmacy practice in South Africa. This has many implications and some challenges that need to be managed. The pharmacy profession, academia, legislators and political decision-makers need to work together to resolve outstanding issues in a constructive manner.

Electronic Structure at Oxide Interfaces

DTIC Science & Technology

2014-06-01

of materials with desired correlated electron properties such as ferromagnetism with a high Curie temperature, high transition temperature...approximation and therefore the canonical Mott picture is unable to account for the insulating behavior of these materials . We resolve this apparent...the two materials . LaTiO3 shows insulating behavior with a small excitation gap set by Ti d-d transitions and a wide energy separation between Ti d

Global trade and assisted reproductive technologies: regulatory challenges in international surrogacy.

PubMed

Nelson, Erin

2013-01-01

International surrogacy is an increasingly common phenomenon and an important global health challenge. Legal rules are a key consideration for the participants in international surrogacy arrangements. In some cases the law can help to resolve the complex issues that arise in this context, but it is important to consider the role played by law in contributing to the complex conflicts that such arrangements can generate. © 2013 American Society of Law, Medicine & Ethics, Inc.

MILITARY PAY: Processes for Retaining Injured Army National Guard and Reserve Soldiers on Active Duty Have Been Improved, but Some Challenges Remain

DTIC Science & Technology

2007-05-01

Active Duty Have Been Improved, but Some Challenges Remain The Army’s MRP program has largely resolved the widespread delays in order processing that...interviewed confirmed that they did not experience gaps in pay and associated benefits because of order processing delays. However, some of the...and injured reserve component soldiers we interviewed, these improvements have virtually eliminated the widespread delays in order processing that

General practice on-the-job training in Chinese urban community: a qualitative study on needs and challenges.

PubMed

Zhao, Yali; Chen, Rui; Wang, Bo; Wu, Tao; Huang, Yafang; Guo, Aimin

2014-01-01

On-the-job training is an important strategy for general practitioners to deliver appropriately community health services in China. The development of basic professional competence for general practitioners is the main goal of on-the-job training program. The aim of this study was to explore the needs of and the challenges to on-the-job training for general practitioners, and to provide advices for policy-makers to carry out this program more effectively. We conducted 3 nominal group techniques, 17 in-depth interviews and 3 focus groups to identify the status of, needs of and challenges to on-the-job training for general practitioners in Liaoning, Ningxia, and Fujian provinces from September 2011 until December 2011. Audiotapes and transcripts were analyzed to identify major themes. Content analysis of the data was completed from January 2012 to March 2012. Basic theoretical knowledge and clinical skills were the main needs for general practitioners during on-the-job training. The challenges during training included the time contradiction between work and training, deficiencies of qualified preceptors, and lack of training funds. Participants gave recommendations how to resolve the above problems. In order to improve the outcomes of general practice on-the-job training, it is necessary for government officials to resolve the contradiction between work and training, train preceptors continuously, and increase financial support in the training program.

Time for a change: addressing R&D and commercialization challenges for antibacterials

PubMed Central

Payne, David J.; Miller, Linda Federici; Findlay, David; Anderson, James; Marks, Lynn

2015-01-01

The antibacterial therapeutic area has been described as the perfect storm. Resistance is increasing to the point that our hospitals encounter patients infected with untreatable pathogens, the overall industry pipeline is described as dry and most multinational pharmaceutical companies have withdrawn from the area. Major contributing factors to the declining antibacterial industry pipeline include scientific challenges, clinical/regulatory hurdles and low return on investment. This paper examines these challenges and proposes approaches to address them. There is a need for a broader scientific agenda to explore new approaches to discover and develop antibacterial agents. Additionally, ideas of how industry and academia could be better integrated will be presented. While promising progress in the regulatory environment has been made, more streamlined regulatory paths are still required and the solutions will lie in global harmonization and clearly defined guidance. Creating the right incentives for antibacterial research and development is critical and a new commercial model for antibacterial agents will be proposed. One key solution to help resolve both the problem of antimicrobial resistance (AMR) and lack of new drug development are rapid, cost-effective, accurate point of care diagnostics that will transform antibacterial prescribing and enable more cost-effective and efficient antibacterial clinical trials. The challenges of AMR are too great for any one group to resolve and success will require leadership and partnerships among academia, industry and governments globally. PMID:25918443

A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt)

DOE PAGES

Hilsabeck, T. J.; Frenje, J. A.; Hares, J. D.; ...

2016-08-02

Here we present a time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording.more » Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.« less

A stretch/compress scheme for a high temporal resolution detector for the magnetic recoil spectrometer time (MRSt)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hilsabeck, T. J.; Frenje, J. A.; Hares, J. D.

Here we present a time-resolved detector concept for the magnetic recoil spectrometer for time-resolved measurements of the NIF neutron spectrum. The measurement is challenging due to the time spreading of the recoil protons (or deuterons) as they transit an energy dispersing magnet system. Ions arrive at the focal plane of the magnetic spectrometer over an interval of tens of nanoseconds. We seek to measure the time-resolved neutron spectrum with 20 ps precision by manipulating an electron signal derived from the ions. A stretch-compress scheme is employed to remove transit time skewing while simultaneously reducing the bandwidth requirements for signal recording.more » Simulation results are presented along with design concepts for structures capable of establishing the required electromagnetic fields.« less

Becoming homeless, being homeless, and resolving homelessness among women.

PubMed

Finfgeld-Connett, Deborah

2010-07-01

The purpose of this investigation was to more comprehensively articulate the experiences of homeless women and make evidence-based inferences regarding optimal social services. This study was conducted using qualitative meta-synthesis methods. As youth, homeless women experience challenging circumstances that leave them ill-prepared to prevent and resolve homelessness in adulthood. Resolution of homelessness occurs in iterative stages: crisis, assessment, and sustained action. To enhance forward progression through these stages, nurses are encouraged to promote empowerment in concordance with the Transtheoretical and Harm Reduction Models. Services that are highly valued include physical and mental health care and child care assistance.

Focused Research Group in Correlated Electron and Complex Materials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Ziqiang

While the remarkable physical properties of correlated and complex electronic materials hold great promise for technological applications, one of the key values of the research in this field is its profound impact on fundamental physics. The transition metal oxides, pnictides, and chalcogenides play a key role and occupy an especially important place in this field. The basic reason is that the outer shell of transition metals contains the atomic d-orbitals that have small spatial extent, but not too small to behave as localized orbtials. These d-electrons therefore have a small wave function overlap in a solid, e.g. in an octahedralmore » environment, and form energy bands that are relatively narrow and on the scale of the short-range intra-atomic Coulomb repulsion (Hubbard U). In this intermediate correlation regime lies the challenge of the many-body physics responsible for new and unconventional physical properties. The study of correlated electron and complex materials represents both the challenge and the vitality of condensed matter and materials physics and often demands close collaborations among theoretical and experimental groups with complementary techniques. Our team has a track record and a long-term research goal of studying the unusual complexities and emergent behaviors in the charge, spin, and orbital sectors of the transition metal compounds in order to gain basic knowledge of the quantum electronic states of matter. During the funding period of this grant, the team continued their close collaborations between theory, angle-resolved photoemission spectroscopy, and scanning tunneling microscopy and made significant progress and contributions to the field of iron-based superconductors, copper-oxide high-temperature superconductors, triangular lattice transition metal oxide cobaltates, strontium ruthenates, spin orbital coupled iridates, as well as topological insulators and other topological quantum states of matter. These results include both new discoveries and the resolution to outstanding and unresolved issues. It should be emphasized that the DOE funding provided the crucial support for the close and meaningful collaborations of the focused research group that go far beyond simply putting the research papers from each group together. Indeed, the majority of the publications involved multiple PIs and collaborations between theory and experiments.« less

FREUD, JUNG AND BOAS: THE PSYCHOANALYTIC ENGAGEMENT WITH ANTHROPOLOGY REVISITED.

PubMed

Kenny, Robert

2015-06-20

Sigmund Freud's and C. G. Jung's turn to evolutionist anthropological material after 1909 is usually seen as a logical progression of their long-term interest in such material. It is also seen that they used this material ignorant of the significant challenges to the evolutionist paradigm underpinning such material, in particular the challenges led by Franz Boas. This paper argues otherwise: that both psychologists' turnings to such material was a new development, that neither had shown great interest in such material before 1909, and that their turnings to such material, far from being taken in ignorance of the challenges to evolutionist anthropology, were engagements with those challenges, because the evolutionist paradigm lay at the base of psychoanalysis. It argues that it is no coincidence that this engagement occurred after their return from America in 1909, where they had come into first-hand contact with the challenges of Franz Boas.

Freud, Jung and Boas: the psychoanalytic engagement with anthropology revisited

PubMed Central

Kenny, Robert

2015-01-01

Sigmund Freud's and C. G. Jung's turn to evolutionist anthropological material after 1909 is usually seen as a logical progression of their long-term interest in such material. It is also seen that they used this material ignorant of the significant challenges to the evolutionist paradigm underpinning such material, in particular the challenges led by Franz Boas. This paper argues otherwise: that both psychologists' turnings to such material was a new development, that neither had shown great interest in such material before 1909, and that their turnings to such material, far from being taken in ignorance of the challenges to evolutionist anthropology, were engagements with those challenges, because the evolutionist paradigm lay at the base of psychoanalysis. It argues that it is no coincidence that this engagement occurred after their return from America in 1909, where they had come into first-hand contact with the challenges of Franz Boas. PMID:26665301

THE IMPACT OF SOCIAL CAPITAL ON ENVIRONMENTAL RISK REDUCTION IN MONCURE

EPA Science Inventory

Despite rigorous efforts to understand and resolve environmental justice (EJ) issues, the complexity of the issues associated with many of these EJ communities continues to bring challenges to community residents and environmental researchers. Moncure, NC, located in northern Cha...

3 CFR 8928 - Proclamation 8928 of January 21, 2013. National Day of Hope and Resolve, 2013

Code of Federal Regulations, 2014 CFR

2014-01-01

... opportunity. Millions of men, women, and children have made service their mission, reaffirming that America's... challenges of our age together. And when our grandchildren reflect on the history we leave, let them say we...

The African Peace and Security Architecture: Myth or Reality

DTIC Science & Technology

2013-03-01

resolving the conflicts. Efforts by African leaders to create continental peace and security mechanisms failed miserably . Consequently, Africans depended...Framework Document, October 2001), 14. 6 Andre Le Sage, “Africa’s Irregular Security Threats: Challenges for U.S. Engagement,” (Strategic Forum

Spatially resolved D-T(2) correlation NMR of porous media.

PubMed

Zhang, Yan; Blümich, Bernhard

2014-05-01

Within the past decade, 2D Laplace nuclear magnetic resonance (NMR) has been developed to analyze pore geometry and diffusion of fluids in porous media on the micrometer scale. Many objects like rocks and concrete are heterogeneous on the macroscopic scale, and an integral analysis of microscopic properties provides volume-averaged information. Magnetic resonance imaging (MRI) resolves this spatial average on the contrast scale set by the particular MRI technique. Desirable contrast parameters for studies of fluid transport in porous media derive from the pore-size distribution and the pore connectivity. These microscopic parameters are accessed by 1D and 2D Laplace NMR techniques. It is therefore desirable to combine MRI and 2D Laplace NMR to image functional information on fluid transport in porous media. Because 2D Laplace resolved MRI demands excessive measuring time, this study investigates the possibility to restrict the 2D Laplace analysis to the sum signals from low-resolution pixels, which correspond to pixels of similar amplitude in high-resolution images. In this exploratory study spatially resolved D-T2 correlation maps from glass beads and mortar are analyzed. Regions of similar contrast are first identified in high-resolution images to locate corresponding pixels in low-resolution images generated with D-T2 resolved MRI for subsequent pixel summation to improve the signal-to-noise ratio of contrast-specific D-T2 maps. This method is expected to contribute valuable information on correlated sample heterogeneity from the macroscopic and the microscopic scales in various types of porous materials including building materials and rock. Copyright © 2014 Elsevier Inc. All rights reserved.

Sequential Release of Proteins from Structured Multishell Microcapsules.

PubMed

Shimanovich, Ulyana; Michaels, Thomas C T; De Genst, Erwin; Matak-Vinkovic, Dijana; Dobson, Christopher M; Knowles, Tuomas P J

2017-10-09

In nature, a wide range of functional materials is based on proteins. Increasing attention is also turning to the use of proteins as artificial biomaterials in the form of films, gels, particles, and fibrils that offer great potential for applications in areas ranging from molecular medicine to materials science. To date, however, most such applications have been limited to single component materials despite the fact that their natural analogues are composed of multiple types of proteins with a variety of functionalities that are coassembled in a highly organized manner on the micrometer scale, a process that is currently challenging to achieve in the laboratory. Here, we demonstrate the fabrication of multicomponent protein microcapsules where the different components are positioned in a controlled manner. We use molecular self-assembly to generate multicomponent structures on the nanometer scale and droplet microfluidics to bring together the different components on the micrometer scale. Using this approach, we synthesize a wide range of multiprotein microcapsules containing three well-characterized proteins: glucagon, insulin, and lysozyme. The localization of each protein component in multishell microcapsules has been detected by labeling protein molecules with different fluorophores, and the final three-dimensional microcapsule structure has been resolved by using confocal microscopy together with image analysis techniques. In addition, we show that these structures can be used to tailor the release of such functional proteins in a sequential manner. Moreover, our observations demonstrate that the protein release mechanism from multishell capsules is driven by the kinetic control of mass transport of the cargo and by the dissolution of the shells. The ability to generate artificial materials that incorporate a variety of different proteins with distinct functionalities increases the breadth of the potential applications of artificial protein-based materials and provides opportunities to design more refined functional protein delivery systems.

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

NASA Technical Reports Server (NTRS)

Su, Ching-Hua; Brebrick, Robert F.; Burger, Arnold; Dudley, Michael; Matyi, Richard J.; Ramachandran, Narayanan; Sha, Yi-Gao; Volz, Martin; Shih, Hung-Dah

2000-01-01

Interest in optical devices which can operate in the visible spectrum has motivated research interest in the II-VI wide band gap semiconductor materials. The recent challenge for semiconductor opto-electronics is the development of a laser which can operate at short visible wavelengths. In the past several years, major advances in thin film technology such as molecular beam epitaxy and metal organic chemical vapor deposition have demonstrated the applicability of II-VI materials to important devices such as light-emitting diodes, lasers, and ultraviolet detectors. With an energy gap of 2.7 eV at room temperature, and an efficient band- to-band transition, ZnSe has been studied extensively as the primary candidate for a blue light emitting diode for optical displays, high density recording, and military communications. By employing a ternary or quaternary system, the energy band gap of II-VI materials can be tuned to a specific range. While issues related to the compositional inhomogeneity and defect incorporation are still to be fully resolved, ZnSe bulk crystals and ZnSe-based heterostructures such as ZnSe/ZnSeS, ZnSe/ZnCdSe and ZnCdSe/ZnSeS have showed photopumped lasing capability in the blue-green region at a low threshold power and high temperatures. The demonstration of its optical bistable properties in bulk and thin film forms also make ZnSe a possible candidate material for the building blocks of a digital optical computer. Despite this, developments in the crystal growth of bulk H-VI semiconductor materials has not advanced far enough to provide the low price, high quality substrates needed for the thin film growth technology.

Focused-electron-beam-induced processing (FEBIP) for emerging applications in carbon nanoelectronics

NASA Astrophysics Data System (ADS)

Fedorov, Andrei G.; Kim, Songkil; Henry, Mathias; Kulkarni, Dhaval; Tsukruk, Vladimir V.

2014-12-01

Focused-electron-beam-induced processing (FEBIP), a resist-free additive nanomanufacturing technique, is an actively researched method for "direct-write" processing of a wide range of structural and functional nanomaterials, with high degree of spatial and time-domain control. This article attempts to critically assess the FEBIP capabilities and unique value proposition in the context of processing of electronics materials, with a particular emphasis on emerging carbon (i.e., based on graphene and carbon nanotubes) devices and interconnect structures. One of the major hurdles in advancing the carbon-based electronic materials and device fabrication is a disjoint nature of various processing steps involved in making a functional device from the precursor graphene/CNT materials. Not only this multi-step sequence severely limits the throughput and increases the cost, but also dramatically reduces the processing reproducibility and negatively impacts the quality because of possible between-the-step contamination, especially for impurity-susceptible materials such as graphene. The FEBIP provides a unique opportunity to address many challenges of carbon nanoelectronics, especially when it is employed as part of an integrated processing environment based on multiple "beams" of energetic particles, including electrons, photons, and molecules. This avenue is promising from the applications' prospective, as such a multi-functional (electron/photon/molecule beam) enables one to define shapes (patterning), form structures (deposition/etching), and modify (cleaning/doping/annealing) properties with locally resolved control on nanoscale using the same tool without ever changing the processing environment. It thus will have a direct positive impact on enhancing functionality, improving quality and reducing fabrication costs for electronic devices, based on both conventional CMOS and emerging carbon (CNT/graphene) materials.

On beyond the standard model for high explosives: challenges & obstacles to surmount

DOE Office of Scientific and Technical Information (OSTI.GOV)

Menikoff, Ralph Ds

2009-01-01

Plastic-bonded explosives (PBX) are heterogeneous materials. Nevertheless, current explosive models treat them as homogeneous materials. To compensate, an empirically determined effective burn rate is used in place of a chemical reaction rate. A significant limitation of these models is that different burn parameters are needed for applications in different regimes; for example, shock initiation of a PBX at different initial temperatures or different initial densities. This is due to temperature fluctuations generated when a heterogeneous material is shock compressed. Localized regions of high temperatures are called hot spots. They dominate the reaction for shock initiation. The understanding of hot spotmore » generation and their subsequent evolution has been limited by the inability to measure transients on small spatial ({approx} 1 {micro}m) and small temporal ({approx} 1 ns) scales in the harsh environment of a detonation. With the advances in computing power, it is natural to try and gain an understanding of hot-spot initiation with numerical experiments based on meso-scale simulations that resolve material heterogeneities and utilize realistic chemical reaction rates. However, to capture the underlying physics correctly, such high resolution simulations will require more than fast computers with a large amount of memory. Here we discuss some of the issues that need to be addressed. These include dissipative mechanisms that generate hot spots, accurate thermal propceties for the equations of state of the reactants and products, and controlling numerical entropy error from shock impedance mismatches at material interfaces. The later can generate artificial hot spots and lead to premature reaction. Eliminating numerical hot spots is critical for shock initiation simulations due to the positive feedback between the energy release from reaction and the hydrodynamic flow.« less

MicroCT with energy-resolved photon-counting detectors

PubMed Central

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, BMW; Patt, B E; Frey, E C

2011-01-01

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with Kabsorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences. PMID:21464527

MicroCT with energy-resolved photon-counting detectors.

PubMed

Wang, X; Meier, D; Mikkelsen, S; Maehlum, G E; Wagenaar, D J; Tsui, B M W; Patt, B E; Frey, E C

2011-05-07

The goal of this paper was to investigate the benefits that could be realistically achieved on a microCT imaging system with an energy-resolved photon-counting x-ray detector. To this end, we built and evaluated a prototype microCT system based on such a detector. The detector is based on cadmium telluride (CdTe) radiation sensors and application-specific integrated circuit (ASIC) readouts. Each detector pixel can simultaneously count x-ray photons above six energy thresholds, providing the capability for energy-selective x-ray imaging. We tested the spectroscopic performance of the system using polychromatic x-ray radiation and various filtering materials with K-absorption edges. Tomographic images were then acquired of a cylindrical PMMA phantom containing holes filled with various materials. Results were also compared with those acquired using an intensity-integrating x-ray detector and single-energy (i.e. non-energy-selective) CT. This paper describes the functionality and performance of the system, and presents preliminary spectroscopic and tomographic results. The spectroscopic experiments showed that the energy-resolved photon-counting detector was capable of measuring energy spectra from polychromatic sources like a standard x-ray tube, and resolving absorption edges present in the energy range used for imaging. However, the spectral quality was degraded by spectral distortions resulting from degrading factors, including finite energy resolution and charge sharing. We developed a simple charge-sharing model to reproduce these distortions. The tomographic experiments showed that the availability of multiple energy thresholds in the photon-counting detector allowed us to simultaneously measure target-to-background contrasts in different energy ranges. Compared with single-energy CT with an integrating detector, this feature was especially useful to improve differentiation of materials with different attenuation coefficient energy dependences.

Overcoming challenges integrating patient-generated data into the clinical EHR: lessons from the CONtrolling Disease Using Inexpensive IT--Hypertension in Diabetes (CONDUIT-HID) Project.

PubMed

Marquard, Jenna L; Garber, Lawrence; Saver, Barry; Amster, Brian; Kelleher, Michael; Preusse, Peggy

2013-10-01

The CONDUIT-HID intervention integrates patients' electronic blood pressure measurements directly into the clinical EHR using Microsoft HealthVault as an intermediary data store. The goal of this paper is to describe generalizable categories of patient and technical challenges encountered in the development and implementation of this inexpensive, commercial off-the-shelf consumer health informatics intervention, examples of challenges within each category, and how the example challenges were resolved prior to conducting an RCT of the intervention. The research team logged all challenges and mediation strategies during the technical development of the intervention, conducted home visits to observe patients using the intervention, and conducted telephone calls with patients to understand challenges they encountered. We then used these data to iteratively refine the intervention. The research team identified a variety of generalizable categories of challenges associated with patients uploading data from their homes, patients uploading data from clinics because they did not have or were not comfortable using home computers, and patients establishing the connection between HealthVault and the clinical EHR. Specific challenges within these categories arose because: (1) the research team had little control over the device and application design, (2) multiple vendors needed to coordinate their actions and design changes, (3) the intervention use cases were not anticipated by the device and application designers, (4) PHI accessed on clinic computers needed to be kept secure, (5) the research team wanted the data in the clinical EHR to be valid and reliable, (6) patients needed the ability to share only the data they wanted, and (7) the development of some EHR functionalities were new to the organization. While these challenges were varied and complex, the research team was able to successfully resolve each one prior to the start of the RCT. By identifying these generalizable categories of challenges, we aim to help others proactively search for and remedy potential challenges associated with their interventions, rather than reactively responding to problems as they arise. We posit that this approach will significantly increase the likelihood that these types of interventions will be successful. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

Resolved motion rate and resolved acceleration servo-control of wheeled mobile robots

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muir, P.F.; Neuman, C.P.; Carnegie-Mellon Univ., Pittsburgh, PA

1989-01-01

Accurate motion control of wheeled mobile robots (WMRs) is required for their application to autonomous, semi-autonomous and teleoperated tasks. The similarities between WMRs and stationary manipulators suggest that current, successful, model-based manipulator control algorithms may be applied to WMRs. Special characteristics of WMRs including higher-pairs, closed-chains, friction and unactuated and unsensed joints require innovative modeling methodologies. The WMR modeling challenge has been recently overcome, thus enabling the application of manipulator control algorithms to WMRs. This realization lays the foundation for significant technology transfer from manipulator control to WMR control. We apply two Cartesian-space manipulator control algorithms: resolved motion rate (kinematics-based)more » and resolved acceleration (dynamics-based) control to WMR servo-control. We evaluate simulation studies of two exemplary WMRs: Uranus (a three degree-of-freedom WMR constructed at Carnegie Mellon University), and Bicsun-Bicas (a two degree-of-freedom WMR being constructed at Sandia National Laboratories) under the control of these algorithms. Although resolved motion rate servo-control is adequate for the control of Uranus, resolved acceleration servo-control is required for the control of the mechanically simpler Bicsun-Bicas because it exhibits more dynamic coupling and nonlinearities. Successful accurate motion control of these WMRs in simulation is driving current experimental research studies. 18 refs., 7 figs., 5 tabs.« less

International challenge to model the long-range transport of radioxenon released from medical isotope production to six Comprehensive Nuclear-Test-Ban Treaty monitoring stations

DOE PAGES

Maurer, Christian; Baré, Jonathan; Kusmierczyk-Michulec, Jolanta; ...

2018-03-08

After performing a first multi-model exercise in 2015 a comprehensive and technically more demanding atmospheric transport modelling challenge was organized in 2016. Release data were provided by the Australian Nuclear Science and Technology Organization radiopharmaceutical facility in Sydney (Australia) for a one month period. Measured samples for the same time frame were gathered from six International Monitoring System stations in the Southern Hemisphere with distances to the source ranging between 680 (Melbourne) and about 17,000 km (Tristan da Cunha). Participants were prompted to work with unit emissions in pre-defined emission intervals (daily, half-daily, 3-hourly and hourly emission segment lengths) andmore » in order to perform a blind test actual emission values were not provided to them. Despite the quite different settings of the two atmospheric transport modelling challenges there is common evidence that for long-range atmospheric transport using temporally highly resolved emissions and highly space-resolved meteorological input fields has no significant advantage compared to using lower resolved ones. As well an uncertainty of up to 20% in the daily stack emission data turns out to be acceptable for the purpose of a study like this. Model performance at individual stations is quite diverse depending largely on successfully capturing boundary layer processes. No single model-meteorology combination performs best for all stations. Moreover, the stations statistics do not depend on the distance between the source and the individual stations. Finally, it became more evident how future exercises need to be designed. Set-up parameters like the meteorological driver or the output grid resolution should be pre-scribed in order to enhance diversity as well as comparability among model runs.« less

Discovery and resolve: the Human Genetics Society of Australasia Oration 2011.

PubMed

Pearn, John

2011-10-01

Human genetics spans every facet of biology from molecular science, through laboratory and clinical practice, to psychology and anthropology. In each of these areas, the history of human genetics has been punctuated by paradigm shifts in knowledge. Each such new concept has been received with skepticism, often with perplexity, and sometimes with frank incredulity. Such comprise the datum milestones along the path leading to our present corpus of genetic knowledge. In parallel to the personal threats to Copernicus and Galileo in the field of astronomy in the 17th century, almost all genetic discoveries of the 19th and 20th centuries were seen as challenges to the received wisdom, and sometimes the social order, of their time and place. Researchers, scientists and clinicians encountering such new and often-heretical paradigm shifts have required considerable resolve to promote and publish their work. Just as in the field of astronomy, new directions in genetics have threatened not only the reputations and sometimes the careers of scientists, but also have been challenges to fundamental religious and sociological beliefs in society more broadly. Examples followed the discovery of biological sexual dimorphism (in plants as well as animals) by Nehemiah Grew (1641-1712). Darwinian evolution, Mendel's First and Second Laws, the existence of mitochondrial genes, apoptosis and its genetic basis, and uniparental disomy are more recent examples. Many of these new revelations, which today have led to the current understanding of fundamental biology, were discovered by individuals working in relative isolation. To promote and publish findings that fundamentally challenge received wisdom continues to require considerable resolve, if not courage. Herein lies a message for all clinicians and researchers.

International challenge to model the long-range transport of radioxenon released from medical isotope production to six Comprehensive Nuclear-Test-Ban Treaty monitoring stations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maurer, Christian; Baré, Jonathan; Kusmierczyk-Michulec, Jolanta

After performing a first multi-model exercise in 2015 a comprehensive and technically more demanding atmospheric transport modelling challenge was organized in 2016. Release data were provided by the Australian Nuclear Science and Technology Organization radiopharmaceutical facility in Sydney (Australia) for a one month period. Measured samples for the same time frame were gathered from six International Monitoring System stations in the Southern Hemisphere with distances to the source ranging between 680 (Melbourne) and about 17,000 km (Tristan da Cunha). Participants were prompted to work with unit emissions in pre-defined emission intervals (daily, half-daily, 3-hourly and hourly emission segment lengths) andmore » in order to perform a blind test actual emission values were not provided to them. Despite the quite different settings of the two atmospheric transport modelling challenges there is common evidence that for long-range atmospheric transport using temporally highly resolved emissions and highly space-resolved meteorological input fields has no significant advantage compared to using lower resolved ones. As well an uncertainty of up to 20% in the daily stack emission data turns out to be acceptable for the purpose of a study like this. Model performance at individual stations is quite diverse depending largely on successfully capturing boundary layer processes. No single model-meteorology combination performs best for all stations. Moreover, the stations statistics do not depend on the distance between the source and the individual stations. Finally, it became more evident how future exercises need to be designed. Set-up parameters like the meteorological driver or the output grid resolution should be pre-scribed in order to enhance diversity as well as comparability among model runs.« less

Cow's milk allergic children-Can component-resolved diagnostics predict duration and severity?

PubMed

Petersen, Thomas Houmann; Mortz, Charlotte Gotthard; Bindslev-Jensen, Carsten; Eller, Esben

2018-03-01

Cow's milk allergy (CMA) affects 2% of all children. This study investigatescomponent-resolved diagnostics(CRD) to cow's milk proteins in children suspected of CMA, by correlating the level of CRD with outcome of the oral challenge. Furthermore, we evaluate the ability of serial CRD measurements to distinguish children with persistent CMA from children developing tolerance. We included data from 78 children referred to the Allergy Centre during a 13-year period. Results from oral food challenges including threshold, severity, and sensitization data (IgE antibodies to whole milk protein, IgE components toward milk and skin prick test (SPT)) were collected. The milk allergic children were re-evaluated with sensitization data and rechallenges regularly. Thirty-nine children had negative first challenges, and 39 had positive first challenges. The positive group was rechallenged and separated into 3 groups depending on time to remission. At inclusion, children with persistent CMA had significantly larger size of SPT and higher levels of s-IgE to milk and CRD compared to the other groups. SPT wheal size was significantly larger in children with persistent CMA compared to children outgrowing CMA. Furthermore, a correlation between s-IgE level to cow's milk and casein and the severity of the allergic reaction elicited by food challenges was found. Oral food challenge cannot be replaced by s-IgE to whole milk protein or milk components nor SPT in the diagnosis of CMA; however, high levels of milk components and s-IgE to milk increase the risk of a long-lasting or persisting CMA. © 2018 EAACI and John Wiley and Sons A/S. Published by John Wiley and Sons Ltd.

An angle-resolved, wavelength-dispersive x-ray fluorescence spectrometer for depth profile analysis of ion-implanted semiconductors using synchrotron radiation

NASA Astrophysics Data System (ADS)

Schmitt, W.; Hormes, J.; Kuetgens, U.; Gries, W. H.

1992-01-01

An apparatus for angle-resolved, wavelength-dispersive x-ray fluorescence spectroscopy with synchrotron radiation has been built and tested at the beam line BN2 of the Bonn electron stretcher and accelerator (ELSA). The apparatus is to be used for nondestructive depth profile analysis of ion-implanted semiconductors as part of the multinational Versailles Project of Advanced Materials and Standards (VAMAS) project on ion-implanted reference materials. In particular, the centroid depths of depth profiles of various implants is to be determined by use of the angle-resolved signal ratio technique. First results of measurements on implants of phosphorus (100 keV, 1016 cm-2) and sulfur (200 keV, 1014 cm-2) in silicon wafers using ``white'' synchrotron radiation are presented and suggest that it should be generally possible to measure the centroid depth of an implant at dose densities as low as 1014 cm-2. Some of the apparative and technical requirements are discussed which are peculiar to the use of synchrotron radiation in general and to the use of nonmonochromatized radiation in particular.

Spectrally resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography

PubMed Central

Cong, Wenxiang; Shen, Haiou; Wang, Ge

2011-01-01

The nanophosphors, or other similar materials, emit near-infrared (NIR) light upon x-ray excitation. They were designed as optical probes for in vivo visualization and analysis of molecular and cellular targets, pathways, and responses. Based on the previous work on x-ray fluorescence computed tomography (XFCT) and x-ray luminescence computed tomography (XLCT), here we propose a spectrally-resolving and scattering-compensated x-ray luminescence/fluorescence computed tomography (SXLCT or SXFCT) approach to quantify a spatial distribution of nanophosphors (other similar materials or chemical elements) within a biological object. In this paper, the x-ray scattering is taken into account in the reconstruction algorithm. The NIR scattering is described in the diffusion approximation model. Then, x-ray excitations are applied with different spectra, and NIR signals are measured in a spectrally resolving fashion. Finally, a linear relationship is established between the nanophosphor distribution and measured NIR data using the finite element method and inverted using the compressive sensing technique. The numerical simulation results demonstrate the feasibility and merits of the proposed approach. PMID:21721815

Time-resolved visible/near-infrared spectrometric observations of the Galaxy 11 geostationary satellite

NASA Astrophysics Data System (ADS)

Bédard, Donald; Wade, Gregg A.

2017-01-01

Time-resolved spectrometric measurements of the Galaxy 11 geostationary satellite were collected on three consecutive nights in July 2014 with the 1.6-m telescope at the Observatoire du Mont-Mégantic in Québec, Canada. Approximately 300 low-resolution spectra (R ≈ 700 , where R = λ / Δλ) of the satellite were collected each night, covering a spectral range between 425 and 850 nm. The two objectives of the experiment were to conduct material-type identification from the spectra and to study how the spectral energy distribution inferred from these measurements varied as the illumination and observation geometry changed on nightly timescales. We present results that indicate the presence of a highly reflective aluminized surface corresponding to the solar concentrator arrays of the Galaxy 11 spacecraft. Although other material types could not be identified using the spectra, the results showed that the spectral energy distribution of the reflected sunlight from the Galaxy 11 spacecraft varied significantly, in a systematic manner, over each night of observation. The variations were quantified using colour indices calculated from the time-resolved spectrometric measurements.

In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Yining; Yarbrough, John M.; Mittal, Ashutosh

Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials. Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have provenmore » to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall. We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. As a result, we believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.« less

In situ label-free imaging of hemicellulose in plant cell walls using stimulated Raman scattering microscopy

DOE PAGES

Zeng, Yining; Yarbrough, John M.; Mittal, Ashutosh; ...

2016-11-22

Plant hemicellulose (largely xylan) is an excellent feedstock for renewable energy production and second only to cellulose in abundance. Beyond a source of fermentable sugars, xylan constitutes a critical polymer in the plant cell wall, where its precise role in wall assembly, maturation, and deconstruction remains primarily hypothetical. Effective detection of xylan, particularly by in situ imaging of xylan in the presence of other biopolymers, would provide critical information for tackling the challenges of understanding the assembly and enhancing the liberation of xylan from plant materials. Raman-based imaging techniques, especially the highly sensitive stimulated Raman scattering (SRS) microscopy, have provenmore » to be valuable tools for label-free imaging. However, due to the complex nature of plant materials, especially those same chemical groups shared between xylan and cellulose, the utility of specific Raman vibrational modes that are unique to xylan have been debated. Here, we report a novel approach based on combining spectroscopic analysis and chemical/enzymatic xylan removal from corn stover cell walls, to make progress in meeting this analytical challenge. We have identified several Raman peaks associated with xylan content in cell walls for label-free in situ imaging xylan in plant cell wall. We demonstrated that xylan can be resolved from cellulose and lignin in situ using enzymatic digestion and label-free SRS microscopy in both 2D and 3D. As a result, we believe that this novel approach can be used to map xylan in plant cell walls and that this ability will enhance our understanding of the role played by xylan in cell wall biosynthesis and deconstruction.« less

Progress and Prospects in Stretchable Electroluminescent Devices

NASA Astrophysics Data System (ADS)

Wang, Jiangxin; Lee, Pooi See

2017-03-01

Stretchable electroluminescent (EL) devices are a new form of mechanically deformable electronics that are gaining increasing interests and believed to be one of the essential technologies for next generation lighting and display applications. Apart from the simple bending capability in flexible EL devices, the stretchable EL devices are required to withstand larger mechanical deformations and accommodate stretching strain beyond 10%. The excellent mechanical conformability in these devices enables their applications in rigorous mechanical conditions such as flexing, twisting, stretching, and folding.The stretchable EL devices can be conformably wrapped onto arbitrary curvilinear surface and respond seamlessly to the external or internal forces, leading to unprecedented applications that cannot be addressed with conventional technologies. For example, they are in demand for wide applications in biomedical-related devices or sensors and soft interactive display systems, including activating devices for photosensitive drug, imaging apparatus for internal tissues, electronic skins, interactive input and output devices, robotics, and volumetric displays. With increasingly stringent demand on the mechanical requirements, the fabrication of stretchable EL device is encountering many challenges that are difficult to resolve. In this review, recent progresses in the stretchable EL devices are covered with a focus on the approaches that are adopted to tackle materials and process challenges in stretchable EL devices and delineate the strategies in stretchable electronics. We first introduce the emission mechanisms that have been successfully demonstrated on stretchable EL devices. Limitations and advantages of the different mechanisms for stretchable EL devices are also discussed. Representative reports are reviewed based on different structural and material strategies. Unprecedented applications that have been enabled by the stretchable EL devices are reviewed. Finally, we summarize with our perspectives on the approaches for the stretchable EL devices and our proposals on the future development in these devices.

Computational catalyst screening: Scaling, bond-order and catalysis

DOE PAGES

Abild-Pedersen, Frank

2015-10-01

Here, the design of new and better heterogeneous catalysts needed to accommodate the growing demand for energy from renewable sources is an important challenge for coming generations. Most surface catalyzed processes involve a large number of complex reaction networks and the energetics ultimately defines the turn-over-frequency and the selectivity of the process. In order not to get lost in the large quantities of data, simplification schemes that still contain the key elements of the reaction are required. Adsorption and transition state scaling relations constitutes such a scheme that not only maps the reaction relevant information in terms of few parametersmore » but also provides an efficient way of screening for new materials in a continuous multi-dimensional energy space. As with all relations they impose certain restrictions on what can be achieved and in this paper, I show why these limitations exist and how we can change the behavior through an energy-resolved approach that still maintains the screening capabilities needed in computational catalysis.« less

Lithium-Sulfur Capacitors.

PubMed

Kim, Mok-Hwa; Kim, Hyun-Kyung; Xi, Kai; Kumar, R Vasant; Jung, Dae Soo; Kim, Kwang-Bum; Roh, Kwang Chul

2018-02-21

Although many existing hybrid energy storage systems demonstrate promising electrochemical performances, imbalances between the energies and kinetics of the two electrodes must be resolved to allow their widespread commercialization. As such, the development of a new class of energy storage systems is a particular challenge, since future systems will require a single device to provide both a high gravimetric energy and a high power density. In this context, we herein report the design of novel lithium-sulfur capacitors. The resulting asymmetric systems exhibited energy densities of 23.9-236.4 Wh kg -1 and power densities of 72.2-4097.3 W kg -1 , which are the highest reported values for an asymmetric system to date. This approach involved the use of a prelithiated anode and a hybrid cathode material exhibiting anion adsorption-desorption in addition to the electrochemical reduction and oxidation of sulfur at almost identical rates. This novel strategy yielded both high energy and power densities, and therefore establishes a new benchmark for hybrid systems.

Ab initio calculations of the concentration dependent band gap reduction in dilute nitrides

NASA Astrophysics Data System (ADS)

Rosenow, Phil; Bannow, Lars C.; Fischer, Eric W.; Stolz, Wolfgang; Volz, Kerstin; Koch, Stephan W.; Tonner, Ralf

2018-02-01

While being of persistent interest for the integration of lattice-matched laser devices with silicon circuits, the electronic structure of dilute nitride III/V-semiconductors has presented a challenge to ab initio computational approaches. The origin of the computational problems is the strong distortion exerted by the N atoms on most host materials. Here, these issues are resolved by combining density functional theory calculations based on the meta-GGA functional presented by Tran and Blaha (TB09) with a supercell approach for the dilute nitride Ga(NAs). Exploring the requirements posed to supercells, it is shown that the distortion field of a single N atom must be allowed to decrease so far that it does not overlap with its periodic images. This also prevents spurious electronic interactions between translational symmetric atoms, allowing us to compute band gaps in very good agreement with experimentally derived reference values. In addition to existing approaches, these results offer a promising ab initio avenue to the electronic structure of dilute nitride semiconductor compounds.

A feasibility work on the applications of MRE to automotive components

NASA Astrophysics Data System (ADS)

Kim, S. H.; Park, Y. J.; Cha, A. R.; Kim, G. W.; Bang, J. H.; Lim, C. S.; Choi, S. B.

2018-03-01

A feasibility work on the application of magneto-rheological elastomers (MREs) to automotive components, such as engine mounts is presented. While vehicle components require the high resonance frequency in terms of ride quality and handling, it is required to have the low resonance frequency to isolate the incoming vibration. With the conventional automotive technologies, it is challenging to combine these two conflicting performance trade-offs, ride quality including handling, and NVH (noise, vibration and harshness). Over the last decades, MREs, one of the new emerging smart materials, have been widely used to resolve this technical limitation. For example, an advanced engine mount was developed by using MRE to isolate the vibration transmitting from engines. In this paper, we will focus on rear cross member bushes, which is a key component for isolating the vibration from the road, and demonstrate their improved performance by utilizing MRE. The resonance frequency shift induced by the stiffness change of MRE will be presented through the frequency response functions estimated by simulation result.

Lead Telluride Quantum Dot Solar Cells Displaying External Quantum Efficiencies Exceeding 120%

PubMed Central

2015-01-01

Multiple exciton generation (MEG) in semiconducting quantum dots is a process that produces multiple charge-carrier pairs from a single excitation. MEG is a possible route to bypass the Shockley-Queisser limit in single-junction solar cells but it remains challenging to harvest charge-carrier pairs generated by MEG in working photovoltaic devices. Initial yields of additional carrier pairs may be reduced due to ultrafast intraband relaxation processes that compete with MEG at early times. Quantum dots of materials that display reduced carrier cooling rates (e.g., PbTe) are therefore promising candidates to increase the impact of MEG in photovoltaic devices. Here we demonstrate PbTe quantum dot-based solar cells, which produce extractable charge carrier pairs with an external quantum efficiency above 120%, and we estimate an internal quantum efficiency exceeding 150%. Resolving the charge carrier kinetics on the ultrafast time scale with pump–probe transient absorption and pump–push–photocurrent measurements, we identify a delayed cooling effect above the threshold energy for MEG. PMID:26488847

Disorder-driven topological phase transition in B i 2 S e 3 films

DOE PAGES

Brahlek, Matthew; Koirala, Nikesh; Salehi, Maryam; ...

2016-10-03

Topological insulators (TI) are a phase of matter that host unusual metallic states on their surfaces. Unlike the states that exist on the surface of conventional materials, these so-called topological surfaces states (TSS) are protected against disorder-related localization effects by time reversal symmetry through strong spin-orbit coupling. By combining transport measurements, angle-resolved photo-emission spectroscopy and scanning tunneling microscopy, we show that there exists a critical level of disorder beyond which the TI Bi 2Se 3 loses its ability to protect the metallic TSS and transitions to a fully insulating state. The absence of the metallic surface channels dictates that theremore » is a change in material’s topological character, implying that disorder can lead to a topological phase transition even without breaking the time reversal symmetry. This observation challenges the conventional notion of topologically-protected surface states, and will provoke new studies as to the fundamental nature of topological phase of matter in the presence of disorder.« less

28 CFR 16.24 - Procedure in the event of a demand where disclosure is not otherwise authorized.

Code of Federal Regulations, 2010 CFR

2010-07-01

... the appearance and testimony of a present or former Department employee, or the production of material... present or former employee of the Department or the production of material from Department files without... resolve a disagreement concerning disclosure, the Assistant Attorneys General in charge of the two...

76 FR 9052 - Notice of Lodging of Consent Decree Under the Clean Air Act

Federal Register 2010, 2011, 2012, 2013, 2014

2011-02-16

.... CEMEX, Inc. and CEMEX Construction Materials Atlantic, LLC, Civil Action No. 3:11-cv-00037, was lodged... located in Greene County, Ohio. The proposed Decree resolves the United States' claims against CEMEX, Inc. and CEMEX Construction Materials Atlantic, LLC (``Defendants'') by requiring Defendants to install and...

7 CFR 1717.854 - Advance approval-100 percent private financing of distribution, subtransmission and headquarters...

Code of Federal Regulations, 2010 CFR

2010-01-01

... material findings and recommendations made in the most recent Loan Fund and Accounting Review; (iv... compliance, and management letter; (v) Resolved all outstanding material accounting issues with RUS; and (vi... restructuring agreement, or any other agreement with RUS. (d) Right of normal review reserved. RUS reserves the...

Surface-geophysical techniques used to detect existing and infilled scour holes near bridge piers

USGS Publications Warehouse

Placzek, Gary; Haeni, F.P.

1995-01-01

Surface-geophysical techniques were used with a position-recording system to study riverbed scour near bridge piers. From May 1989 to May 1993. Fathometers, fixed- and swept-frequency con- tinuous seismic-reflection profiling (CSP) systems, and a ground-penetrating radar (GPR) system were used with a laser-positioning system to measure the depth and extent of existing and infilled scour holes near bridge piers. Equipment was purchased commercially and modified when necessary to interface the components and (or) to improve their performance. Three 200-kHz black-and-white chart- recording Fathometers produced profiles of the riverbed that included existing scour holes and exposed pier footings. The Fathometers were used in conjunction with other geophysical techniques to help interpret the geophysical data. A 20-kHz color Fathometer delineated scour-hole geometry and, in some cases, the thickness of fill material in the hole. The signal provided subbottom information as deep as 10 ft in fine-grained materials and resolved layers of fill material as thin as 1 foot thick. Fixed-frequency and swept-frequency CSP systems were evaluated. The fixed-frequency system used a 3.5-, 7.0-, or 14-kHz signal. The 3.5-kHz signal pene- trated up to 50 ft of fine-grained material and resolved layers as thin as 2.5-ft thick. The 14-kHz signal penetrated up to 20 ft of fine-grained material and resolved layers as thin as 1-ft thick. The swept-frequency systems used a signal that swept from 2- to 16-kHz. With this system, up to 50 ft of penetration was achieved, and fill material as thin as 1 ft was resolved. Scour-hole geometry, exposed pier footings, and fill thickness in scour holes were detected with both CSP systems. The GPR system used an 80-, 100-, or 300-megahertz signal. The technique produced records in water up to 15 ft deep that had a specific conductance less than 200x11ms/cm. The 100-MHz signal penetrated up to 40 ft of resistive granular material and resolved layers as thin as 2-ft thick. Scour-hole geometry, the thickness of fill material in scour holes, and riverbed deposition were detected using this technique. Processing techniques were applied after data collection to assist with the interpretation of the data. Data were transferred from the color Fathometer, CSP, and GPR systems to a personal computer, and a commercially available software package designed to process GPR data was used to process the GPR and CSP data. Digital filtering, predictive-deconvolution, and migration algorithms were applied to some of the data. The processed data were displayed and printed as color amplitude or wiggle-trace plots. These processing methods eased and improved the interpretation of some of the data, but some interference from side echoes from bridge piers and multiple reflections remained in the data. The surface-geophysical techniques were applied at six bridge sites in Connecticut. Each site had different water depths, specific conductance, and riverbed materials. Existing and infilled scour holes, exposed pier footings, and riverbed deposition were detected by the surveys. The interpretations of the geophysical data were confirmed by comparing the data with lithologic and (or) probing data.

Decision for the Draft.

ERIC Educational Resources Information Center

Chambers, John Whiteclay, II

2002-01-01

Discusses why U.S. President Woodrow Wilson decided to institute the military draft. Provides background information on when Wilson changed from insisting on using volunteers in the military to his resolve for instituting the draft, due to a challenge of power by former U.S. President Theodore Roosevelt. (CMK)

FIELD APPLICATIONS OF ROBOTIC SYSTEMS IN HAZARDOUS WASTE SITE OPERATIONS

EPA Science Inventory

The cleanup of hazardous waste sites is a challenging and complex field that offers numerous opportunities for the application of robotic technology. he contamination problem, long in the making, will take decades to resolve. ur ingenuity in developing robotic tools to assist in ...

Media Violence: The Search for Solutions.

ERIC Educational Resources Information Center

Thoman, Elizabeth

1995-01-01

Discusses the influence of mass media depictions of violence on children and provides suggestions for media literacy education. Calls for reducing children's exposure to media violence; changing the impact of violent images; stressing alternatives to violence for resolving conflicts; challenging the social supports for media violence; and…

78 FR 54743 - National Preparedness Month, 2013

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-06

... again, America faces crises that test our readiness and challenge our resolve--from natural disasters like hurricanes, tornadoes, and floods to shootings, cyber incidents, and even acts of terrorism. While... our efforts on readying ourselves, our families, our neighborhoods, and our Nation for any crisis we...

Working Memory Compensates for Hearing Related Phonological Processing Deficit

ERIC Educational Resources Information Center

Classon, Elisabet; Rudner, Mary; Ronnberg, Jerker

2013-01-01

Acquired hearing impairment is associated with gradually declining phonological representations. According to the Ease of Language Understanding (ELU) model, poorly defined representations lead to mismatch in phonologically challenging tasks. To resolve the mismatch, reliance on working memory capacity (WMC) increases. This study investigated…

Challenges for developing biopesticides against Varroa destructor (Mesostigamata: Varroidae)

USDA-ARS?s Scientific Manuscript database

Control of the major pest of apiculture, the ectoparasitic mite Varroa destructor, using biopesticides would resolve many of the problems experienced with other forms of control, such as chemical control, hive manipulation or selection of resistant strains. Several research groups have developed and...

Gender classification from video under challenging operating conditions

NASA Astrophysics Data System (ADS)

Mendoza-Schrock, Olga; Dong, Guozhu

2014-06-01

The literature is abundant with papers on gender classification research. However the majority of such research is based on the assumption that there is enough resolution so that the subject's face can be resolved. Hence the majority of the research is actually in the face recognition and facial feature area. A gap exists for gender classification under challenging operating conditions—different seasonal conditions, different clothing, etc.—and when the subject's face cannot be resolved due to lack of resolution. The Seasonal Weather and Gender (SWAG) Database is a novel database that contains subjects walking through a scene under operating conditions that span a calendar year. This paper exploits a subset of that database—the SWAG One dataset—using data mining techniques, traditional classifiers (ex. Naïve Bayes, Support Vector Machine, etc.) and traditional (canny edge detection, etc.) and non-traditional (height/width ratios, etc.) feature extractors to achieve high correct gender classification rates (greater than 85%). Another novelty includes exploiting frame differentials.

A Discrete Constraint for Entropy Conservation and Sound Waves in Cloud-Resolving Modeling

NASA Technical Reports Server (NTRS)

Zeng, Xi-Ping; Tao, Wei-Kuo; Simpson, Joanne

2003-01-01

Ideal cloud-resolving models contain little-accumulative errors. When their domain is so large that synoptic large-scale circulations are accommodated, they can be used for the simulation of the interaction between convective clouds and the large-scale circulations. This paper sets up a framework for the models, using moist entropy as a prognostic variable and employing conservative numerical schemes. The models possess no accumulative errors of thermodynamic variables when they comply with a discrete constraint on entropy conservation and sound waves. Alternatively speaking, the discrete constraint is related to the correct representation of the large-scale convergence and advection of moist entropy. Since air density is involved in entropy conservation and sound waves, the challenge is how to compute sound waves efficiently under the constraint. To address the challenge, a compensation method is introduced on the basis of a reference isothermal atmosphere whose governing equations are solved analytically. Stability analysis and numerical experiments show that the method allows the models to integrate efficiently with a large time step.

Between worst and best: developing criteria to identify promising practices in health promotion and disease prevention for the Canadian Best Practices Portal.

PubMed

Fazal, Nadia; Jackson, Suzanne F; Wong, Katy; Yessis, Jennifer; Jetha, Nina

2017-11-01

In health promotion and chronic disease prevention, both best and promising practices can provide critical insights into what works for enhancing the healthrelated outcomes of individuals and communities, and how/why these practices work in different situations and contexts. The promising practices criteria were developed using the Public Health Agency of Canada's (PHAC's) existing best practices criteria as the foundation. They were modified and pilot tested (three rounds) using published interventions. Theoretical and methodological issues and challenges were resolved via consultation and in-depth discussions with a working group. The team established a set of promising practices criteria, which differentiated from the best practices criteria via six specific measures. While a number of complex challenges emerged in the development of these criteria, they were thoroughly discussed, debated and resolved. The Canadian Best Practices Portal's screening criteria allow one to screen for both best and promising practices in the fields of public health, health promotion, chronic disease prevention, and potentially beyond.

Surface Material Characterization from Non-resolved Multi-band Optical Observations

DTIC Science & Technology

2012-09-01

functions ( BRDFs ) — then a forward model of the spectral signature of the entire body could be constructed by summing contributions from all reflecting...buffering). 3.3.2 Material Bi-directional Reflectance Distribution Functions ( BRDFs ) Notably, the satellite wire-frame and attitude models together...environments and/or created numerical BRDF models . For instance, BRDFs for several spacecraft materials — such as solar array panels, milled aluminum

Correlation, temperature and disorder: Recent developments in the one-step description of angle-resolved photoemission

NASA Astrophysics Data System (ADS)

Braun, Jürgen; Minár, Ján; Ebert, Hubert

2018-04-01

Various apparative developments extended the potential of angle-resolved photoemission spectroscopy tremendously during the last two decades. Modern experimental arrangements consisting of new photon sources, analyzers and detectors supply not only extremely high angle and energy resolution but also spin resolution. This provides an adequate platform to study in detail new materials like low-dimensional magnetic structures, Rashba systems, topological insulator materials or high TC superconductors. The interest in such systems has grown enormously not only because of their technological relevance but even more because of exciting new physics. Furthermore, the use of photon energies from few eV up to several keV makes this experimental technique a rather unique tool to investigate the electronic properties of solids and surfaces. The following article reviews the corresponding recent theoretical developments in the field of angle-resolved photoemission with a special emphasis on correlation effects, temperature and relativistic aspects. The most successful theoretical approach to deal with angle-resolved photoemission is the so-called spectral function or one-step formulation of the photoemission process. Nowadays, the one-step model allows for photocurrent calculations for photon energies ranging from a few eV to more than 10 keV, to deal with arbitrarily ordered and disordered systems, to account for finite temperatures, and considering in addition strong correlation effects within the dynamical mean-field theory or similar advanced approaches.

Challenges in Scale-Resolving Simulations of turbulent wake flows with coherent structures

NASA Astrophysics Data System (ADS)

Pereira, Filipe S.; Eça, Luís; Vaz, Guilherme; Girimaji, Sharath S.

2018-06-01

The objective of this work is to investigate the challenges encountered in Scale-Resolving Simulations (SRS) of turbulent wake flows driven by spatially-developing coherent structures. SRS of practical interest are expressly intended for efficiently computing such flows by resolving only the most important features of the coherent structures and modelling the remainder as stochastic field. The success of SRS methods depends upon three important factors: i) ability to identify key flow mechanisms responsible for the generation of coherent structures; ii) determine the optimum range of resolution required to adequately capture key elements of coherent structures; and iii) ensure that the modelled part is comprised nearly exclusively of fully-developed stochastic turbulence. This study considers the canonical case of the flow around a circular cylinder to address the aforementioned three key issues. It is first demonstrated using experimental evidence that the vortex-shedding instability and flow-structure development involves four important stages. A series of SRS computations of progressively increasing resolution (decreasing cut-off length) are performed. An a priori basis for locating the origin of the coherent structures development is proposed and examined. The criterion is based on the fact that the coherent structures are generated by the Kelvin-Helmholtz (KH) instability. The most important finding is that the key aspects of coherent structures can be resolved only if the effective computational Reynolds number (based on total viscosity) exceeds the critical value of the KH instability in laminar flows. Finally, a quantitative criterion assessing the nature of the unresolved field based on the strain-rate ratio of mean and unresolved fields is examined. The two proposed conditions and rationale offer a quantitative basis for developing "good practice" guidelines for SRS of complex turbulent wake flows with coherent structures.

An online, energy-resolving beam profile detector for laser-driven proton beams

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metzkes, J.; Rehwald, M.; Obst, L.

In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ∼4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energymore » can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source.« less

An online, energy-resolving beam profile detector for laser-driven proton beams.

PubMed

Metzkes, J; Zeil, K; Kraft, S D; Karsch, L; Sobiella, M; Rehwald, M; Obst, L; Schlenvoigt, H-P; Schramm, U

2016-08-01

In this paper, a scintillator-based online beam profile detector for the characterization of laser-driven proton beams is presented. Using a pixelated matrix with varying absorber thicknesses, the proton beam is spatially resolved in two dimensions and simultaneously energy-resolved. A thin plastic scintillator placed behind the absorber and read out by a CCD camera is used as the active detector material. The spatial detector resolution reaches down to ∼4 mm and the detector can resolve proton beam profiles for up to 9 proton threshold energies. With these detector design parameters, the spatial characteristics of the proton distribution and its cut-off energy can be analyzed online and on-shot under vacuum conditions. The paper discusses the detector design, its characterization and calibration at a conventional proton source, as well as the first detector application at a laser-driven proton source.

Progress in efficient doping of high aluminum-containing group III-nitrides

NASA Astrophysics Data System (ADS)

Liang, Y.-H.; Towe, E.

2018-03-01

The group III-nitride (InN, GaN, and AlN) class of semiconductors has become one of two that are critical to a number of technologies in modern life—the other being silicon. Light-emitting diodes made from (In,Ga)N, for example, dominate recent innovations in general illumination and signaling. Even though the (In,Ga)N materials system is fairly well established and widely used in advanced devices, challenges continue to impede development of devices that include aluminum-containing nitride films such as (Al,Ga)N. The main difficulty is efficient doping of films with aluminum-rich compositions; the problem is particularly severe for p-type doping, which is essential for Ohmic contacts to bipolar device structures. This review briefly summarizes the fundamental issues related to p-type doping, and then discusses a number of approaches that are being pursued to resolve the doping problem or for circumventing the need for p-type doping. Finally, we discuss an approach to doping under liquid-metal-enabled growth by molecular beam epitaxy. Recent results from a number of groups appear to indicate that p-type doping of nitride films under liquid-metal-enabled growth conditions might offer a solution to the doping problem—at least for materials grown by molecular beam epitaxy.

Intermediate Band Gap Solar Cells: The Effect of Resonant Tunneling on Delocalization

NASA Astrophysics Data System (ADS)

William, Reid; Mathew, Doty; Sanwli, Shilpa; Gammon, Dan; Bracker, Allan

2011-03-01

Quantum dots (QD's) have many unique properties, including tunable discrete energy levels, that make them suitable for a variety of next generation photovoltaic applications. One application is an intermediate band solar cell (IBSC); in which QD's are incorporated into the bulk material. The QD's are tuned to absorb low energy photons that would otherwise be wasted because their energy is less than the solar cell's bulk band gap. Current theory concludes that identical QD's should be arranged in a superlattice to form a completely delocalized intermediate band maximizing absorption of low energy photons while minimizing the decrease in the efficiency of the bulk material. We use a T-matrix model to assess the feasibility of forming a delocalized band given that real QD ensembles have an inhomogeneous distribution of energy levels. Our results suggest that formation of a band delocalized through a large QD superlattice is challenging; suggesting that the assumptions underlying present IBSC theory require reexamination. We use time-resolved photoluminescence of coupled QD's to probe the effect of delocalized states on the dynamics of absorption, energy transport, and nonradiative relaxation. These results will allow us to reexamine the theoretical assumptions and determine the degree of delocalization necessary to create an efficient quantum dot-based IBSC.

Orion EFT-1 Catalytic Tile Experiment Overview and Flight Measurements

NASA Technical Reports Server (NTRS)

Salazar, Giovanni; Amar, Adam; Hyatt, Andrew; Rezin, Marc D.

2016-01-01

This paper describes the design and results of a surface catalysis flight experiment flown on the Orion Multipurpose Crew Vehicle during Exploration Flight Test 1 (EFT1). Similar to previous Space Shuttle catalytic tile experiments, the present test consisted of a highly catalytic coating applied to an instrumented TPS tile. However, the present catalytic tile experiment contained significantly more instrumentation in order to better resolve the heating overshoot caused by the change in surface catalytic efficiency at the interface between two distinct materials. In addition to collecting data with unprecedented spatial resolution of the "overshoot" phenomenon, the experiment was also designed to prove if such a catalytic overshoot would be seen in turbulent flow in high enthalpy regimes. A detailed discussion of the results obtained during EFT1 is presented, as well as the challenges associated with data interpretation of this experiment. Results of material testing carried out in support of this flight experiment are also shown. Finally, an inverse heat conduction technique is employed to reconstruct the flight environments at locations upstream and along the catalytic coating. The data and analysis presented in this work will greatly contribute to our understanding of the catalytic "overshoot" phenomenon, and have a significant impact on the design of future spacecraft.

Imaging of conformational changes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michl, Josef

2016-03-13

Control of intramolecular conformational change in a small number of molecules or even a single one by an application of an outside electric field defined by potentials on nearby metal or dielectric surfaces has potential applications in both 3-D and 2-D nanotechnology. Specifically, the synthesis, characterization, and understanding of designed solids with controlled built-in internal rotational motion of a dipole promises a new class of materials with intrinsic dielectric, ferroelectric, optical and optoelectronic properties not found in nature. Controlled rotational motion is of great interest due to its expected utility in phenomena as diverse as transport, current flow in molecularmore » junctions, diffusion in microfluidic channels, and rotary motion in molecular machines. A direct time-resolved observation of the dynamics of motion on ps or ns time scale in a single molecule would be highly interesting but is also very difficult and has yet to be accomplished. Much can be learned from an easier but still challenging comparison of directly observed initial and final orientational states of a single molecule, which is the basis of this project. The project also impacts the understanding of surface-enhanced Raman spectroscopy (SERS) and single-molecule spectroscopic detection, as well as the synthesis of solid-state materials with tailored properties from designed precursors.« less

Science with Synthetic Stellar Surveys

NASA Astrophysics Data System (ADS)

Sanderson, Robyn Ellyn

2018-04-01

A new generation of observational projects is poised to revolutionize our understanding of the resolved stellar populations of Milky-Way-like galaxies at an unprecedented level of detail, ushering in an era of precision studies of galaxy formation. In the Milky Way itself, astrometric, spectroscopic and photometric surveys will measure three-dimensional positions and velocities and numerous chemical abundances for stars from the disk to the halo, as well as for many satellite dwarf galaxies. In the Local Group and beyond, HST, JWST and eventually WFIRST will deliver pristine views of resolved stars. The groundbreaking scale and dimensionality of this new view of resolved stellar populations in galaxies challenge us to develop new theoretical tools to robustly compare these surveys to simulated galaxies, in order to take full advantage of our new ability to make detailed predictions for stellar populations within a cosmological context. I will describe a framework for generating realistic synthetic star catalogs and mock surveys from state-of-the-art cosmological-hydrodynamical simulations, and present several early scientific results from, and predictions for, resolved stellar surveys of our Galaxy and its neighbors.

Probing microscopic material properties inside simulated membranes through spatially resolved three-dimensional local pressure fields and surface tensions

PubMed Central

Kasson, Peter M.; Hess, Berk; Lindahl, Erik

2013-01-01

Cellular lipid membranes are spatially inhomogeneous soft materials. Materials properties such as pressure and surface tension thus show important microscopic-scale variation that is critical to many biological functions. We present a means to calculate pressure and surface tension in a 3D-resolved manner within molecular-dynamics simulations and show how such measurements can yield important insight. We also present the first corrections to local virial and pressure fields to account for the constraints typically used in lipid simulations that otherwise cause problems in highly oriented systems such as bilayers. Based on simulations of an asymmetric bacterial ion channel in a POPC bilayer, we demonstrate how 3D-resolved pressure can probe for both short-range and long-range effects from the protein on the membrane environment. We also show how surface tension is a sensitive metric for inter-leaflet equilibrium and can be used to detect even subtle imbalances between bilayer leaflets in a membrane-protein simulation. Since surface tension is known to modulate the function of many proteins, this effect is an important consideration for predictions of ion channel function. We outline a strategy by which our local pressure measurements, which we make available within a version of the GROMACS simulation package, may be used to design optimally equilibrated membrane-protein simulations. PMID:23318532

When worlds collide: challenges and opportunities for conservation of biodiversity in the Hawaiian Islands

USGS Publications Warehouse

Atkinson, Carter T.; Pratt, Thane K.; Banko, Paul C.; Jacobi, James D.; Woodworth, Bethany L.

2013-01-01

This chapter identifies four key challenges and opportunities for long-term conservation of biodiversity in the Hawaii's Islands. Following are the challenges that need to be resolved for remaining species of native forest birds to survive into the next century: invasive species, landscape processes, social factors, and climate change. These challenges are also relevant to other threatened terrestrial taxonomic groups (i.e., plants and invertebrates) in the Hawaiian Islands. Such threats are familiar to conservation biologists the world over, but rarely do they act as synergistically as they do in the Hawaiian Islands. The chapter reviews conservation successes and failures in Hawaii, and provides an example of the possible future course of conservation in other island communities.

Squeezing water from a stone: high-throughput sequencing from a 145-year old holotype resolves (barely) a cryptic species problem in flying lizards.

PubMed

McGuire, Jimmy A; Cotoras, Darko D; O'Connell, Brendan; Lawalata, Shobi Z S; Wang-Claypool, Cynthia Y; Stubbs, Alexander; Huang, Xiaoting; Wogan, Guinevere O U; Hykin, Sarah M; Reilly, Sean B; Bi, Ke; Riyanto, Awal; Arida, Evy; Smith, Lydia L; Milne, Heather; Streicher, Jeffrey W; Iskandar, Djoko T

2018-01-01

We used Massively Parallel High-Throughput Sequencing to obtain genetic data from a 145-year old holotype specimen of the flying lizard, Draco cristatellus . Obtaining genetic data from this holotype was necessary to resolve an otherwise intractable taxonomic problem involving the status of this species relative to closely related sympatric Draco species that cannot otherwise be distinguished from one another on the basis of museum specimens. Initial analyses suggested that the DNA present in the holotype sample was so degraded as to be unusable for sequencing. However, we used a specialized extraction procedure developed for highly degraded ancient DNA samples and MiSeq shotgun sequencing to obtain just enough low-coverage mitochondrial DNA (721 base pairs) to conclusively resolve the species status of the holotype as well as a second known specimen of this species. The holotype was prepared before the advent of formalin-fixation and therefore was most likely originally fixed with ethanol and never exposed to formalin. Whereas conventional wisdom suggests that formalin-fixed samples should be the most challenging for DNA sequencing, we propose that evaporation during long-term alcohol storage and consequent water-exposure may subject older ethanol-fixed museum specimens to hydrolytic damage. If so, this may pose an even greater challenge for sequencing efforts involving historical samples.

Human ribonuclease H1 resolves R-loops and thereby enables progression of the DNA replication fork.

PubMed

Parajuli, Shankar; Teasley, Daniel C; Murali, Bhavna; Jackson, Jessica; Vindigni, Alessandro; Stewart, Sheila A

2017-09-15

Faithful DNA replication is essential for genome stability. To ensure accurate replication, numerous complex and redundant replication and repair mechanisms function in tandem with the core replication proteins to ensure DNA replication continues even when replication challenges are present that could impede progression of the replication fork. A unique topological challenge to the replication machinery is posed by RNA-DNA hybrids, commonly referred to as R-loops. Although R-loops play important roles in gene expression and recombination at immunoglobulin sites, their persistence is thought to interfere with DNA replication by slowing or impeding replication fork progression. Therefore, it is of interest to identify DNA-associated enzymes that help resolve replication-impeding R-loops. Here, using DNA fiber analysis, we demonstrate that human ribonuclease H1 (RNH1) plays an important role in replication fork movement in the mammalian nucleus by resolving R-loops. We found that RNH1 depletion results in accumulation of RNA-DNA hybrids, slowing of replication forks, and increased DNA damage. Our data uncovered a role for RNH1 in global DNA replication in the mammalian nucleus. Because accumulation of RNA-DNA hybrids is linked to various human cancers and neurodegenerative disorders, our study raises the possibility that replication fork progression might be impeded, adding to increased genomic instability and contributing to disease. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Advanced wide-field surface plasmon microscopy of single adsorbing nanoparticles

NASA Astrophysics Data System (ADS)

Nizamov, Shavkat; Scherbahn, Vitali; Mirsky, Vladimir M.

2017-05-01

In-situ detection and characterization of nanoparticles in biological media as well as in food or other complex samples is still a big challenge for existing analytical methods. Here we describe a label-free and cost-effective analytical method for detection of nanoparticles in the concentration range 106 -1010 NPs/ml. The proposed method is based on the surface plasmon resonance microscopy (SPRM) with a large field of view ( 1.3mm2 ). It is able to detect and count adsorbing nanoparticles individually, totally up to the hundreds of thousands of NPs on the sensor surface. At constant diffusion conditions the detection rate is proportional to the number concentration of NPs, this provides an approach to determine the NPs concentration. The adsorption of nanoparticle can be manipulated by the surface functionalization, pH and electrolyte concentration of suspensions. Images of detected nanoparticles can be quantified in order to characterize them individually. The image intensity grows quasi-linearly with nanoparticle size for the given material. However, the size and material of nanoparticle cannot be resolved directly from the image. For determination of chemical composition, SPRM can be assisted by electrochemical analysis. In this case, the gold sensor surface is used both as a resonant media for plasmon microscopy and as a working electrode. Under potential sweep, the adsorbed NPs can be subjected to electrochemical dissolution, which is detected optically. The potential of this conversion characterizes the material of NPs.

Ultrafast Microscopy of Energy and Charge Transport

NASA Astrophysics Data System (ADS)

Huang, Libai

The frontier in solar energy research now lies in learning how to integrate functional entities across multiple length scales to create optimal devices. Advancing the field requires transformative experimental tools that probe energy transfer processes from the nano to the meso lengthscales. To address this challenge, we aim to understand multi-scale energy transport across both multiple length and time scales, coupling simultaneous high spatial, structural, and temporal resolution. In my talk, I will focus on our recent progress on visualization of exciton and charge transport in solar energy harvesting materials from the nano to mesoscale employing ultrafast optical nanoscopy. With approaches that combine spatial and temporal resolutions, we have recently revealed a new singlet-mediated triplet transport mechanism in certain singlet fission materials. This work demonstrates a new triplet exciton transport mechanism leading to favorable long-range triplet exciton diffusion on the picosecond and nanosecond timescales for solar cell applications. We have also performed a direct measurement of carrier transport in space and in time by mapping carrier density with simultaneous ultrafast time resolution and 50 nm spatial precision in perovskite thin films using transient absorption microscopy. These results directly visualize long-range carrier transport of 220nm in 2 ns for solution-processed polycrystalline CH3NH3PbI3 thin films. The spatially and temporally resolved measurements reported here underscore the importance of the local morphology and establish an important first step towards discerning the underlying transport properties of perovskite materials.

A direct electron detector for time-resolved MeV electron microscopy

DOE PAGES

Vecchione, T.; Denes, P.; Jobe, R. K.; ...

2017-03-15

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here in this paper, we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μm spatial resolution and less than 20 analogue-to-digital converter count RMS pixelmore » noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

A direct electron detector for time-resolved MeV electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vecchione, T.; Denes, P.; Jobe, R. K.

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μmμm spatial resolution and less than 20 analogue-to-digital converter count RMS pixel noise. The uniquemore » capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

A direct electron detector for time-resolved MeV electron microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vecchione, T.; Denes, P.; Jobe, R. K.

The introduction of direct electron detectors enabled the structural biology revolution of cryogenic electron microscopy. Direct electron detectors are now expected to have a similarly dramatic impact on time-resolved MeV electron microscopy, particularly by enabling both spatial and temporal jitter correction. Here in this paper, we report on the commissioning of a direct electron detector for time-resolved MeV electron microscopy. The direct electron detector demonstrated MeV single electron sensitivity and is capable of recording megapixel images at 180 Hz. The detector has a 15-bit dynamic range, better than 30-μm spatial resolution and less than 20 analogue-to-digital converter count RMS pixelmore » noise. The unique capabilities of the direct electron detector and the data analysis required to take advantage of these capabilities are presented. The technical challenges associated with generating and processing large amounts of data are also discussed.« less

TRADITIONAL METALLURGY, NANOTECHNOLOGIES AND STRUCTURAL MATERIALS: A SORBY AWARD LECTURE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Louthan, M

2007-07-17

Traditional metallurgical processes are among the many ''old fashion'' practices that use nanoparticles to control the behavior of materials. Many of these practices were developed long before microscopy could resolve nanoscale features, yet the practitioners learned to manipulate and control microstructural elements that they could neither see nor identify. Furthermore, these early practitioners used that control to modify microstructures and develop desired material properties. Centuries old colored glass, ancient high strength steels and medieval organ pipes derived many of their desirable features through control of nanoparticles in their microstructures. Henry Sorby was among the first to recognize that the propertiesmore » of rocks, minerals, metals and organic materials were controlled by microstructure. However, Mr. Sorby was accused of the folly of trying to study mountains with a microscope. Although he could not resolve nanoscale microstructural features, Mr. Sorby's observations revolutionized the study of materials. The importance of nanoscale microstructural elements should be emphasized, however, because the present foundation for structural materials was built by manipulating those features. That foundation currently supports several multibillion dollar industries but is not generally considered when the nanomaterials revolution is discussed. This lecture demonstrates that using nanotechnologies to control the behavior of metallic materials is almost as old as the practice of metallurgy and that many of the emergent nanomaterials technologists are walking along pathways previously paved by traditional metallurgists.« less

New validated recipes for double-blind placebo-controlled low-dose food challenges.

PubMed

Winberg, Anna; Nordström, Lisbeth; Strinnholm, Åsa; Nylander, Annica; Jonsäll, Anette; Rönmark, Eva; West, Christina E

2013-05-01

Double-blind placebo-controlled food challenges are considered the most reliable method to diagnose or rule out food allergy. Despite this, there are few validated challenge recipes available. The present study aimed to validate new recipes for low-dose double-blind placebo-controlled food challenges in school children, by investigating whether there were any sensory differences between the active materials containing cow's milk, hen's egg, soy, wheat or cod, and the placebo materials. The challenge materials contained the same hypoallergenic amino acid-based product, with or without added food allergens. The test panels consisted of 275 school children, aged 8-10 and 14-15 yr, respectively, from five Swedish schools. Each participant tested at least one recipe. Standardized blinded triangle tests were performed to investigate whether any sensory differences could be detected between the active and placebo materials. In our final recipes, no significant differences could be detected between the active and placebo materials for any challenge food (p > 0.05). These results remained after stratification for age and gender. The taste of challenge materials was acceptable, and no unfavourable side effects related to test materials were observed. In summary, these new validated recipes for low-dose double-blinded food challenges contain common allergenic foods in childhood; cow's milk, hen's egg, soy, wheat and cod. All test materials contain the same liquid vehicle, which facilitates preparation and dosing. Our validated recipes increase the range of available recipes, and as they are easily prepared and dosed, they may facilitate the use of double-blind placebo-controlled food challenges in daily clinical practice. © 2013 John Wiley & Sons A/S. Published by Blackwell Publishing Ltd.

Making Peace in Violent Times: A Constructivist Approach to Conflict Resolution.

ERIC Educational Resources Information Center

Carlsson-Paige, Nancy; Levin, Diane E.

1992-01-01

Suggests actions that teachers can take to challenge the use of violence by children. Actions include providing early intervention and teaching specific skills to help children resolve conflicts. Discusses adaptation to children's developmental levels and creation of classroom contexts supportive of nonviolence. (LB)

Strategies for Resolving the Cyber Attribution Challenge

DTIC Science & Technology

2013-05-01

grant- ing the United States extraterritoriality in the prosecution of US citizens engaged in child sex tourism .10 Furthermore, section 40 7202 of the...the Internet Gover - nance Forum. The United States has been active in venues such as the Organization for Economic Cooperation and Devel- opment in

Islamist Movement Challenges Universities

ERIC Educational Resources Information Center

Lindsey, Ursula

2013-01-01

In Tunisian and Egyptian universities, scholars face a growing Islamist resolve to remake their countries on the basis of religious principles. Both Tunisia and Egypt face questions that could affect higher education across the Middle East and North Africa: Can their new Islamist governments spread conservative religious values and also create…

Is Something Wrong with my Baby?

ERIC Educational Resources Information Center

Wieder, Serena

2011-01-01

Parents are often the first to recognize early signs of developmental challenges, launching the family into an unanticipated journey that sometimes resolves quickly but sometimes not. Development depends on nurturing relationships that provide the necessary experiences to allow the child to develop. Equally important are the relationships that…

Teachers and Human Rights Education

ERIC Educational Resources Information Center

Osler, Audrey; Starkey, Hugh

2010-01-01

Why do teachers need to be familiar with human rights? In multicultural societies, whose values take precedence? How do schools resolve tensions between children's rights and teachers' rights? Campaigners, politicians and the media cite human rights to justify or challenge anything from peaceful protest to military action. The phrase "human…

Material Challenges and Opportunities for Commercial Electric Aircraft

NASA Technical Reports Server (NTRS)

Misra, Ajay

2014-01-01

Significant reduction in carbon dioxide emission for future air transportation system will require adoption of electric propulsion system and more electric architectures. Various options for aircraft electric propulsion include hybrid electric, turboelectric, and full electric system. Realization of electric propulsion system for commercial aircraft applications will require significant increases in power density of electric motors and energy density of energy storage system, such as the batteries and fuel cells. In addition, transmission of MW of power in the aircraft will require high voltage power transmission system to reduce the weight of the power transmission system. Finally, there will be significant thermal management challenges. Significant advances in material technologies will be required to meet these challenges. Technologies of interest include materials with higher electrical conductivity than Cu, high thermal conductivity materials, and lightweight electrically insulating materials with high breakdown voltage, high temperature magnets, advanced battery and fuel cell materials, and multifunctional materials. The presentation will include various challenges for commercial electric aircraft and provide an overview of material improvements that will be required to meet these challenges.

Quantifying electronic band interactions in van der Waals materials using angle-resolved reflected-electron spectroscopy

PubMed Central

Jobst, Johannes; van der Torren, Alexander J. H.; Krasovskii, Eugene E.; Balgley, Jesse; Dean, Cory R.; Tromp, Rudolf M.; van der Molen, Sense Jan

2016-01-01

High electron mobility is one of graphene's key properties, exploited for applications and fundamental research alike. Highest mobility values are found in heterostructures of graphene and hexagonal boron nitride, which consequently are widely used. However, surprisingly little is known about the interaction between the electronic states of these layered systems. Rather pragmatically, it is assumed that these do not couple significantly. Here we study the unoccupied band structure of graphite, boron nitride and their heterostructures using angle-resolved reflected-electron spectroscopy. We demonstrate that graphene and boron nitride bands do not interact over a wide energy range, despite their very similar dispersions. The method we use can be generally applied to study interactions in van der Waals systems, that is, artificial stacks of layered materials. With this we can quantitatively understand the ‘chemistry of layers' by which novel materials are created via electronic coupling between the layers they are composed of. PMID:27897180

Time-resolved Fast Neutron Radiography of Air-water Two-phase Flows

NASA Astrophysics Data System (ADS)

Zboray, Robert; Dangendorf, Volker; Mor, Ilan; Tittelmeier, Kai; Bromberger, Benjamin; Prasser, Horst-Michael

Neutron imaging, in general, is a useful technique for visualizing low-Z materials (such as water or plastics) obscured by high-Z materials. However, when significant amounts of both materials are present and full-bodied samples have to be examined, cold and thermal neutrons rapidly reach their applicability limit as the samples become opaque. In such cases one can benefit from the high penetrating power of fast neutrons. In this work we demonstrate the feasibility of time-resolved, fast neutron radiography of generic air-water two-phase flows in a 1.5 cm thick flow channel with Aluminum walls and rectangular cross section. The experiments have been carried out at the high-intensity, white-beam facility of the Physikalisch-Technische Bundesanstalt, Germany. Exposure times down to 3.33 ms have been achieved at reasonable image quality and acceptable motion artifacts. Different two-phase flow regimes such as bubbly slug and churn flows have been examined. Two-phase flow parameters like the volumetric gas fraction, bubble size and bubble velocities have been measured.

Measurements of spatially resolved velocity variations in shock compressed heterogeneous materials using a line-imaging velocity interferometer

NASA Astrophysics Data System (ADS)

Trott, Wayne M.; Knudson, Marcus D.; Chhabildas, Lalit C.; Asay, James R.

2000-04-01

Relatively straightforward changes in the design of a conventional optically recording velocity interferometer system (ORVIS) can be used to produce a line-imaging instrument that allows adjustment of spatial resolution over a wide range. As a result, line-imaging ORVIS can be tailored to various specific applications involving dynamic deformation of heterogeneous materials as required by their characteristic length scales (ranging from a few μm for ferroelectric ceramics to a few mm for concrete). A line-imaging system has been successfully interfaced to a compressed gas gun driver and fielded on numerous tests in combination with simultaneous dual delay-leg, "push-pull" VISAR measurements. These tests include shock loading of glass-reinforced polyester composites, foam reverberation experiments (measurements at the free surface of a thin aluminum plate impacted by foam), and measurements of dispersive velocity in a shock-loaded explosive simulant (sugar). Results are presented that illustrate the capability for recording detailed spatially resolved material response.

Anisotropic Electron-Photon and Electron-Phonon Interactions in Black Phosphorus

DOE PAGES

Ling, Xi; Huang, Shengxi; Hasdeo, Eddwi; ...

2016-03-10

Orthorhombic black phosphorus (BP) and other layered materials, such as gallium telluride (GaTe) and tin selenide (SnSe), stand out among two-dimensional (2D) materials owing to their anisotropic in-plane structure. This anisotropy adds a new dimension to the properties of 2D materials and stimulates the development of angle-resolved photonics and electronics. However, understanding the effect of anisotropy has remained unsatisfactory to-date, as shown by a number of inconsistencies in the recent literatures. We use angle-resolved absorption and Raman spectroscopies to investigate the role of anisotropy on the electron-photon and electron-phonon interactions in BP. We highlight a non-trivial dependence between anisotropies andmore » flake thickness, photon and phonon energies. We show that once understood, the anisotropic optical absorption appears to be a reliable and simple way to identify the crystalline orientation of BP, which cannot be determined from Raman spectroscopy without the explicit consideration of excitation wavelength and flake thickness, as commonly used previously.« less

Inner Structure in the TW Hya Circumstellar Disk

NASA Astrophysics Data System (ADS)

Akeson, Rachel L.; Millan-Gabet, R.; Ciardi, D.; Boden, A.; Sargent, A.; Monnier, J.; McAlister, H.; ten Brummelaar, T.; Sturmann, J.; Sturmann, L.; Turner, N.

2011-05-01

TW Hya is a nearby (50 pc) young stellar object with an estimated age of 10 Myr and signs of active accretion. Previous modeling of the circumstellar disk has shown that the inner disk contains optically thin material, placing this object in the class of "transition disks". We present new near-infrared interferometric observations of the disk material and use these data, as well as previously published, spatially resolved data at 10 microns and 7 mm, to constrain disk models based on a standard flared disk structure. Our model demonstrates that the constraints imposed by the spatially resolved data can be met with a physically plausible disk but this requires a disk containing not only an inner gap in the optically thick disk as previously suggested, but also some optically thick material within this gap. Our model is consistent with the suggestion by previous authors of a planet with an orbital radius of a few AU. This work was conducted at the NASA Exoplanet Science Institute, California Institute of Technology.

The effect of plastic strain on the evolution of crystallographic texture in Zircaloy-2

NASA Astrophysics Data System (ADS)

Ballinger, R. G.; Lucas, G. E.; Pelloux, R. M.

1984-09-01

The evolution of crystallographic texture during plastic deformation was investigated in Zircaloy-2 using X-ray and metallographic techniques. Inverse pole figures, the resolved fraction of basal poles, and the volume fraction of twinned material, were determined as a function of plastic strain for several strain paths and initial textures at 298 K and 623 K. Incremental transverse platic strain ratios ( R) were mesured as a function of plastic strain. Texture rotation occurs early in the deformation process, after as little as 1.5% plastic strain. For compressive plastic strains, the resolved fraction of basal poles increases in the direction parallel to the strain axis. For tensile plastic strains, the resolved fraction of basal poles decreases in the direction parallel to the strain axis. The rate of change of the resolved fraction of basal poles with plastic strain is a function of the initial resolved fraction of basal poles. The texture rotation can be explained by considering the operation of the principal tensile twinning systems, {101¯2}<1¯011>.

DOE Office of Scientific and Technical Information (OSTI.GOV)

David, M.-L.; Pailloux, F.; Mauchamp, V.

The understanding of the mechanisms of helium bubble formation and evolution in materials requires the quantitative determination of several key quantities such as the helium density in the bubbles. Helium nanobubbles of about 16 nm in diameter were created in silicon by helium implantation at high fluence and subsequent annealing. Individual nanobubbles were analyzed by spatially resolved Electron Energy-loss Spectroscopy (EELS). We report on the in situ probing of helium desorption from the nanobubbles under electron irradiation. This opens new perspectives for a more accurate determination of the helium density through spatially resolved EELS.

Elaboration and Characterization of Nano-Sized AlxMoyOz/Al Thermites

DTIC Science & Technology

2006-07-01

corresponding micrographs are not the experiments of time resolved shown here). In the Th. 1 material, the cinematography . micron-sized MoO 3...necessary to know cinelnalogra/)hy andspec’troscot)y- the effective power (P) delivered by the laser The time resolved cinematography (TRC) is source as...necessary to initiate the film paper ((D P 1.4 amm). The combustion rate 8 PU 614/2006 (Vr) is measured by ultra fast cinematography the lower are the

Spectrally resolved white light interferometry to measure material dispersion over a wide spectral band in a single acquisition.

PubMed

Arosa, Yago; Lago, Elena López; Varela, Luis Miguel; de la Fuente, Raúl

2016-07-25

In this paper we apply spectrally resolved white light interferometry to measure refractive and group index over a wide spectral band from 400 to 1000 nm. The output of a Michelson interferometer is spectrally decomposed by a homemade prism spectrometer with a high resolution camera. The group index is determined directly from the phase extracted from the spectral interferogram while the refractive index is estimated once its value at a given wavelength is known.

Time Resolved Phonon Spectroscopy, Version 1.0

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goett, Johnny; Zhu, Brian

TRPS code was developed for the project "Time Resolved Phonon Spectroscopy". Routines contained in this piece of software were specially created to model phonon generation and tracking within materials that interact with ionizing radiation, particularly applicable to the modeling of cryogenic radiation detectors for dark matter and neutrino research. These routines were created to link seamlessly with the open source Geant4 framework for the modeling of radiation transport in matter, with the explicit intent of open sourcing them for eventual integration into that code base.

The main challenges that remain in applying high-throughput sequencing to clinical diagnostics.

PubMed

Loeffelholz, Michael; Fofanov, Yuriy

2015-01-01

Over the last 10 years, the quality, price and availability of high-throughput sequencing instruments have improved to the point that this technology may be close to becoming a routine tool in the diagnostic microbiology laboratory. Two groups of challenges, however, have to be resolved in order to move this powerful research technology into routine use in the clinical microbiology laboratory. The computational/bioinformatics challenges include data storage cost and privacy concerns, requiring analysis to be performed without access to cloud storage or expensive computational infrastructure. The logistical challenges include interpretation of complex results and acceptance and understanding of the advantages and limitations of this technology by the medical community. This article focuses on the approaches to address these challenges, such as file formats, algorithms, data collection, reporting and good laboratory practices.

Materials for optical memory: Resolved hyperfine structure in KY3F10:Ho3+

NASA Astrophysics Data System (ADS)

Popova, M. N.

2013-08-01

Basic principles of creating a quantum optical memory (QOM) and requirements for relevant materials, in particular, for crystals doped with rare-earth ions, are briefly reviewed. A combined approach to studying the hyperfine structure, which is essential for QOM applications, is presented on the example of KY3F10:Ho3+.

48 CFR 311.7001 - Section 508 accessibility standards for HHS Web site content and communications materials.

Code of Federal Regulations, 2011 CFR

2011-10-01

... standards, and resolve any related issues. (c) Based on those discussions, the Project Officer shall provide... communication must meet the accessibility standards in 36 CFR 1194.22, “Web-based intranet and Internet... standards for HHS Web site content and communications materials. 311.7001 Section 311.7001 Federal...

48 CFR 311.7001 - Section 508 accessibility standards for HHS Web site content and communications materials.

Code of Federal Regulations, 2013 CFR

2013-10-01

... standards, and resolve any related issues. (c) Based on those discussions, the Project Officer shall provide... communication must meet the accessibility standards in 36 CFR 1194.22, “Web-based intranet and Internet... standards for HHS Web site content and communications materials. 311.7001 Section 311.7001 Federal...

48 CFR 311.7001 - Section 508 accessibility standards for HHS Web site content and communications materials.

Code of Federal Regulations, 2012 CFR

2012-10-01

... standards, and resolve any related issues. (c) Based on those discussions, the Project Officer shall provide... communication must meet the accessibility standards in 36 CFR 1194.22, “Web-based intranet and Internet... standards for HHS Web site content and communications materials. 311.7001 Section 311.7001 Federal...

48 CFR 311.7001 - Section 508 accessibility standards for HHS Web site content and communications materials.

Code of Federal Regulations, 2014 CFR

2014-10-01

... standards, and resolve any related issues. (c) Based on those discussions, the Project Officer shall provide... communication must meet the accessibility standards in 36 CFR 1194.22, “Web-based intranet and Internet... standards for HHS Web site content and communications materials. 311.7001 Section 311.7001 Federal...

General Practice On-the-Job Training in Chinese Urban Community: A Qualitative Study on Needs and Challenges

PubMed Central

Wang, Bo; Wu, Tao; Huang, Yafang; Guo, Aimin

2014-01-01

Background On-the-job training is an important strategy for general practitioners to deliver appropriately community health services in China. The development of basic professional competence for general practitioners is the main goal of on-the-job training program. The aim of this study was to explore the needs of and the challenges to on-the-job training for general practitioners, and to provide advices for policy-makers to carry out this program more effectively. Methods We conducted 3 nominal group techniques, 17 in-depth interviews and 3 focus groups to identify the status of, needs of and challenges to on-the-job training for general practitioners in Liaoning, Ningxia, and Fujian provinces from September 2011 until December 2011. Audiotapes and transcripts were analyzed to identify major themes. Content analysis of the data was completed from January 2012 to March 2012. Results Basic theoretical knowledge and clinical skills were the main needs for general practitioners during on-the-job training. The challenges during training included the time contradiction between work and training, deficiencies of qualified preceptors, and lack of training funds. Participants gave recommendations how to resolve the above problems. Conclusions In order to improve the outcomes of general practice on-the-job training, it is necessary for government officials to resolve the contradiction between work and training, train preceptors continuously, and increase financial support in the training program. PMID:24728399

Time for a change: addressing R&D and commercialization challenges for antibacterials.

PubMed

Payne, David J; Miller, Linda Federici; Findlay, David; Anderson, James; Marks, Lynn

2015-06-05

The antibacterial therapeutic area has been described as the perfect storm. Resistance is increasing to the point that our hospitals encounter patients infected with untreatable pathogens, the overall industry pipeline is described as dry and most multinational pharmaceutical companies have withdrawn from the area. Major contributing factors to the declining antibacterial industry pipeline include scientific challenges, clinical/regulatory hurdles and low return on investment. This paper examines these challenges and proposes approaches to address them. There is a need for a broader scientific agenda to explore new approaches to discover and develop antibacterial agents. Additionally, ideas of how industry and academia could be better integrated will be presented. While promising progress in the regulatory environment has been made, more streamlined regulatory paths are still required and the solutions will lie in global harmonization and clearly defined guidance. Creating the right incentives for antibacterial research and development is critical and a new commercial model for antibacterial agents will be proposed. One key solution to help resolve both the problem of antimicrobial resistance (AMR) and lack of new drug development are rapid, cost-effective, accurate point of care diagnostics that will transform antibacterial prescribing and enable more cost-effective and efficient antibacterial clinical trials. The challenges of AMR are too great for any one group to resolve and success will require leadership and partnerships among academia, industry and governments globally. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

An electron energy loss spectrometer based streak camera for time resolved TEM measurements.

PubMed

Ali, Hasan; Eriksson, Johan; Li, Hu; Jafri, S Hassan M; Kumar, M S Sharath; Ögren, Jim; Ziemann, Volker; Leifer, Klaus

2017-05-01

We propose an experimental setup based on a streak camera approach inside an energy filter to measure time resolved properties of materials in the transmission electron microscope (TEM). In order to put in place the streak camera, a beam sweeper was built inside an energy filter. After exciting the TEM sample, the beam is swept across the CCD camera of the filter. We describe different parts of the setup at the example of a magnetic measurement. This setup is capable to acquire time resolved diffraction patterns, electron energy loss spectra (EELS) and images with total streaking times in the range between 100ns and 10μs. Copyright © 2016 Elsevier B.V. All rights reserved.

Challenges and strategies for improving pediatric immunizations in New Jersey.

PubMed

Morgan, Robert; Paul, Sindy M; Palley, Robert

2004-01-01

Only through committed, comprehensive, and enthusiastic participation can this public health concern be resolved. The collaboration initiated through the CARE program and the Child Health Statewide Leadership Council is only the first step. Solving the problem will require the efforts of the entire New Jersey community.

Resolving International Teaching Assistant Language Inadequacy through Dialogue: Challenges and Opportunities for Clarity and Credibility

ERIC Educational Resources Information Center

Li, Li; Mazer, Joseph P.; Ju, Ran

2011-01-01

Guided by Giddens' structuration theory, this study highlights structures that both enable and constrain nonnative English-speaking teachers and students in American college classrooms. Before international teaching assistants (ITAs) step into their American classrooms, several semishaped class structures are already in place: students (mostly…

Internationalisation of Higher Education and Nation Building: Resolving Language Policy Dilemmas in Lithuania

ERIC Educational Resources Information Center

Bulajeva, Tatjana; Hogan-Brun, Gabrielle

2014-01-01

Our paper discusses trends and challenges faced by Lithuanian Higher Education (HE) internationalisation policy processes in the context of European and global internationalisation tendencies. Using 2001-2011 EU mobility statistics and data from recent HE Lithuanian strategic programmes aimed at promoting the internationalisation of university…

Assessment Intelligence in Small Group Learning

ERIC Educational Resources Information Center

Xing, Wanli; Wu, Yonghe

2014-01-01

Assessment of groups in CSCL context is a challenging task fraught with many confounding factors collected and measured. Previous documented studies are by and large summative in nature and some process-oriented methods require time-intensive coding of qualitative data. This study attempts to resolve these problems for teachers to assess groups…

Positive Strategies for Students with Behavior Problems

ERIC Educational Resources Information Center

Crimmins, Daniel; Farrell, Anne F.; Smith, Philip W.; Bailey, Alison

2007-01-01

When a student's challenging behavior can not be resolved through either traditional disciplinary approaches or schoolwide positive behavior support (PBS), what can a teacher do next? This manual has effective solutions for educators from grades K-12. Developed specifically for use with children with persistent or severe behavior problems, this…

Tilling the Soil of the European Higher Education Area

ERIC Educational Resources Information Center

Burnett, John

2007-01-01

The Bologna Process presents both opportunities and challenges for teachers in the European area. As tensions surface between different forms of national legislation, accreditation and quality assurance, projects need to be developed that model ways of resolving problems within a European context. Utilising their links and network of contacts…

Adolescent Pregnancy and Parenthood. Highlights: An ERIC/CAPS Digest.

ERIC Educational Resources Information Center

Danziger, Sandra; Farber, Naomi

This digest reviews trends in adolescent sexual activity and discusses conceptual and programmatic approaches to pregnancy prevention. It discusses a pregnant adolescent's choices for resolving an unplanned pregnancy (i.e. abortion, adoption, keeping the baby, and marriage), and the challenges faced by teenage parents. The final section touches on…

Antecedent Assessment and Intervention: Supporting Children and Adults with Developmental Disabilities in Community Settings

ERIC Educational Resources Information Center

Luiselli, James K., Ed.

2006-01-01

Challenging behavior is a significant barrier to communication, education, and positive social relationships. This practical book helps psychologists, educators, rehabilitation specialists, and other professionals recognize and address the causes of these problems in individuals with developmental disabilities--and resolve even the most difficult…

Fostering Collaboration through IT Tools: An Experimental Study of Public Deliberation on Water Sustainability

ERIC Educational Resources Information Center

Hu, Qian

2011-01-01

Most of challenges facing today's government cannot be resolved without collaborative efforts from multiple non-state stakeholders, organizations, and active participation from citizens. Collaborative governance has become an important form of management practice. Yet the success of this inclusive management approach depends on whether government…

CASMI: Virtual Learning Collaborative Environment for Mathematical Enrichment

ERIC Educational Resources Information Center

Freiman, Viktor; Manuel, Dominic; Lirette-Pitre, Nicole

2007-01-01

Challenging problems can make mathematics more attractive to all learners, including the gifted. Application problems that one still finds in regular textbooks often can be resolved by applying a single mathematical concept, operation, or formula. These problems do not require a higher order of thinking. They are, therefore, less cognitively and…

Facebook: The New Classroom Commons?

ERIC Educational Resources Information Center

Schwartz, Harriet L.

2010-01-01

There has been much discussion about the issue of boundaries on Facebook. Some suggest faculty members can resolve potential dilemmas in relation to students by making sensible decisions about what to post and by fine-tuning privacy settings. But the challenges and opportunities run deeper. For those who want to be appropriately accessible to…

The Secondary School Principalship and the Challenge of Change.

ERIC Educational Resources Information Center

Tompkins, Ellsworth; Trump, J. Lloyd

In his role as the manager of educational change, the secondary school principal is responsible for determining programs and procedures, enlisting teacher aid in those determinations, resolving staff resistance to change, identifying staff members as effective change agents, and working with them to implement change. To produce significant gains…

The Efficacy of Multidimensional Constraint Keys in Database Query Performance

ERIC Educational Resources Information Center

Cardwell, Leslie K.

2012-01-01

This work is intended to introduce a database design method to resolve the two-dimensional complexities inherent in the relational data model and its resulting performance challenges through abstract multidimensional constructs. A multidimensional constraint is derived and utilized to implement an indexed Multidimensional Key (MK) to abstract a…

Universal penetration test apparatus with fluid penetration sensor

DOEpatents

Johnson, Phillip W.; Stampfer, Joseph F.; Bradley, Orvil D.

1999-01-01

A universal penetration test apparatus for measuring resistance of a material to a challenge fluid. The apparatus includes a pad saturated with the challenge fluid. The apparatus includes a compression assembly for compressing the material between the pad and a compression member. The apparatus also includes a sensor mechanism for automatically detecting when the challenge fluid penetrates the material.

Challenging Cognitive Control by Mirrored Stimuli in Working Memory Matching

PubMed Central

Wirth, Maria; Gaschler, Robert

2017-01-01

Cognitive conflict has often been investigated by placing automatic processing originating from learned associations in competition with instructed task demands. Here we explore whether mirror generalization as a congenital mechanism can be employed to create cognitive conflict. Past research suggests that the visual system automatically generates an invariant representation of visual objects and their mirrored counterparts (i.e., mirror generalization), and especially so for lateral reversals (e.g., a cup seen from the left side vs. right side). Prior work suggests that mirror generalization can be reduced or even overcome by learning (i.e., for those visual objects for which it is not appropriate, such as letters d and b). We, therefore, minimized prior practice on resolving conflicts involving mirror generalization by using kanji stimuli as non-verbal and unfamiliar material. In a 1-back task, participants had to check a stream of kanji stimuli for identical repetitions and avoid miss-categorizing mirror reversed stimuli as exact repetitions. Consistent with previous work, lateral reversals led to profound slowing of reaction times and lower accuracy in Experiment 1. Yet, different from previous reports suggesting that lateral reversals lead to stronger conflict, similar slowing for vertical and horizontal mirror transformations was observed in Experiment 2. Taken together, the results suggest that transformations of visual stimuli can be employed to challenge cognitive control in the 1-back task. PMID:28503160

Frequency-resolved Raman for transient thermal probing and thermal diffusivity measurement

DOE PAGES

Wang, Tianyu; Xu, Shen; Hurley, David H.; ...

2015-12-18

Steady state Raman has been widely used for temperature probing and thermal conductivity/conductance measurement in combination with temperature coefficient calibration. In this work, a new transient Raman thermal probing technique: frequency-resolved Raman (FR-Raman) is developed for probing the transient thermal response of materials and measuring their thermal diffusivity. The FR-Raman uses an amplitude modulated square-wave laser for simultaneous material heating and Raman excitation. The evolution profile of Raman properties: intensity, Raman wavenumber, and emission, against frequency are measured experimentally and reconstructed theoretically. They are used for fitting to determine the thermal diffusivity of the material under test. A Si cantilevermore » is used to investigate the capacity of this new technique. The cantilever’s thermal diffusivity is determined as 9.57 × 10 -5 m 2/s, 11.00 × 10 -5 m 2/s and 9.02 × 10 -5 m 2/s by fitting the Raman intensity, wavenumber and emission. The deviation from the reference value is largely attributed to thermal stress-induced material deflection and Raman drift, which could be significantly suppressed by using a higher sensitivity Raman spectrometer with lower laser energy. As a result, the FR-Raman provides a novel way for transient thermal characterization of materials with a ?m spatial resolution.« less

Exploring time-resolved photoluminescence for nanowires using a three-dimensional computational transient model.

PubMed

Ren, Dingkun; Scofield, Adam C; Farrell, Alan C; Rong, Zixuan; Haddad, Michael A; Laghumavarapu, Ramesh B; Liang, Baolai; Huffaker, Diana L

2018-04-26

Time-resolved photoluminescence (TRPL) has been implemented experimentally to measure the carrier lifetime of semiconductors for decades. For the characterization of nanowires, the rich information embedded in TRPL curves has not been fully interpreted and meaningfully mapped to the respective material properties. This is because their three-dimensional (3-D) geometries result in more complicated mechanisms of carrier recombination than those in thin films and analytical solutions cannot be found for those nanostructures. In this work, we extend the intrinsic power of TRPL by developing a full 3-D transient model, which accounts for different material properties and drift-diffusion, to simulate TRPL curves for nanowires. To show the capability of the model, we perform TRPL measurements on a set of GaAs nanowire arrays grown on silicon substrates and then fit the measured data by tuning various material properties, including carrier mobility, Shockley-Read-Hall recombination lifetime, and surface recombination velocity at the GaAs-Si heterointerface. From the resultant TRPL simulations, we numerically identify the lifetime characteristics of those material properties. In addition, we computationally map the spatial and temporal electron distributions in nanowire segments and reveal the underlying carrier dynamics. We believe this study provides a theoretical foundation for interpretation of TRPL measurements to unveil the complex carrier recombination mechanisms in 3-D nanostructured materials.

Femtosecond mega-electron-volt electron microdiffraction

DOE PAGES

Shen, X.; Li, R. K.; Lundstrom, U.; ...

2017-09-01

To understand and control the basic functions of physical, chemical and biological processes from micron to nano-meter scale, an instrument capable of visualizing transient structural changes of inhomogeneous materials with atomic spatial and temporal resolutions, is required. One such technique is femtosecond electron microdiffraction, in which a short electron pulse with femtosecond-scale duration is focused into a micron-scale spot and used to obtain diffraction images to resolve ultrafast structural dynamics over a localized crystalline domain. In this letter, we report the experimental demonstration of time-resolved mega-electron-volt electron microdiffraction which achieves a 5 μm root-mean-square (rms) beam size on the samplemore » and a 110 fs rms temporal resolution. Using pulses of 10k electrons at 4.2 MeV energy with a normalized emittance 3 nm-rad, we obtained high quality diffraction from a single 10 μm paraffin ( C 44 H 90) crystal. The phonon softening mode in optical-pumped polycrystalline Bi was also time-resolved, demonstrating the temporal resolution limits of the instrument. In conclusion, this new characterization capability will open many research opportunities in material and biological sciences.« less

Simulations of the impact of localized defects on ICF implosions

NASA Astrophysics Data System (ADS)

Milovich, Jose; Robey, Harry; Weber, Christopher; Sepke, Scott; Clark, Daniel; Koning, Joe; Smalyuk, Vladimir; Martinez, David

2016-10-01

Recent experiments have identified the tent membranes that support the capsule as a source of a large azimuthal perturbation at the point of departure from the surface. Highly-resolved 2D simulations have shown that vorticity generated by the interaction of the ablated capsule material and the tent allows for the penetration of cold ablator material into the burning hot-spot likely cooling the central burning plasma. These observations have motivated the search for alternative supporting methods. One of the techniques being considered uses the existing fill-tube (needed to deliver the cryogenic fuel) supported against gravity by a thin rod (cantilever) spanning the hohlraum diameter. Recent experiments have assessed the perturbation induced on the target as the rod is positioned along the fill-tube at different distances from the capsule surface and found optical-depth modulations oriented along the cantilever direction, possibly caused by laser spot shadowing or hydro-coupling. To fully understand the data we have undertaken an extensive study of highly-resolved 2D integrated simulations abled to resolve the 12 um diameter cantilever. Results of our computations and comparison with the experiments will be presented. Prepared by LLNL under Contract DE-AC52-07NA27344.

Femtosecond mega-electron-volt electron microdiffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, X.; Li, R. K.; Lundstrom, U.

To understand and control the basic functions of physical, chemical and biological processes from micron to nano-meter scale, an instrument capable of visualizing transient structural changes of inhomogeneous materials with atomic spatial and temporal resolutions, is required. One such technique is femtosecond electron microdiffraction, in which a short electron pulse with femtosecond-scale duration is focused into a micron-scale spot and used to obtain diffraction images to resolve ultrafast structural dynamics over a localized crystalline domain. In this letter, we report the experimental demonstration of time-resolved mega-electron-volt electron microdiffraction which achieves a 5 μm root-mean-square (rms) beam size on the samplemore » and a 110 fs rms temporal resolution. Using pulses of 10k electrons at 4.2 MeV energy with a normalized emittance 3 nm-rad, we obtained high quality diffraction from a single 10 μm paraffin ( C 44 H 90) crystal. The phonon softening mode in optical-pumped polycrystalline Bi was also time-resolved, demonstrating the temporal resolution limits of the instrument. In conclusion, this new characterization capability will open many research opportunities in material and biological sciences.« less

Numerical investigation of porous materials composites reinforced with natural fibers

NASA Astrophysics Data System (ADS)

Chikhi, M.; Metidji, N.; Mokhtari, F.; Merzouk, N. k.

2018-05-01

The present article tends to predict the effective thermal properties of porous biocomposites materials. The composites matrix consists on porous materials namely gypsum and the reinforcement is a natural fiber as date palm fibers. The numerical study is done using Comsol software resolving the heat transfer equation. The results are fitted with theoretical model and experimental results. The results of this study indicate that the porosity has an effect on the Effective thermal conductivity biocompoites.

Impact of time-resolved MRA on diagnostic accuracy in patients with symptomatic peripheral artery disease of the calf station.

PubMed

Hansmann, Jan; Michaely, Henrik J; Morelli, John N; Diehl, Steffen J; Meyer, Mathias; Schoenberg, Stefan O; Attenberger, Ulrike I

2013-12-01

The purpose of this article is to evaluate the added diagnostic accuracy of time-resolved MR angiography (MRA) of the calves compared with continuous-table-movement MRA in patients with symptomatic lower extremity peripheral artery disease (PAD) using digital subtraction angiography (DSA) correlation. Eighty-four consecutive patients with symptomatic PAD underwent a low-dose 3-T MRA protocol, consisting of continuous-table-movement MRA, acquired from the diaphragm to the calves, and an additional time-resolved MRA of the calves; 0.1 mmol/kg body weight (bw) of contrast material was used (0.07 mmol/kg bw for continuous-table-movement MRA and 0.03 mmol/kg bw for time-resolved MRA). Two radiologists rated image quality on a 4-point scale and stenosis degree on a 3-point scale. An additional assessment determined the degree of venous contamination and whether time-resolved MRA improved diagnostic confidence. The accuracy of stenosis gradation with continuous-table-movement and time-resolved MRA was compared with that of DSA as a correlation. Overall diagnostic accuracy was calculated for continuous-table-movement and time-resolved MRA. Median image quality was rated as good for 578 vessel segments with continuous-table-movement MRA and as excellent for 565 vessel segments with time-resolved MRA. Interreader agreement was excellent (κ = 0.80-0.84). Venous contamination interfered with diagnosis in more than 60% of continuous-table-movement MRA examinations. The degree of stenosis was assessed for 340 vessel segments. The diagnostic accuracies (continuous-table-movement MRA/time-resolved MRA) combined for the readers were obtained for the tibioperoneal trunk (84%/93%), anterior tibial (69%/87%), posterior tibial (85%/91%), and peroneal (67%/81%) arteries. The addition of time-resolved MRA improved diagnostic confidence in 69% of examinations. The addition of time-resolved MRA at the calf station improves diagnostic accuracy over continuous-table-movement MRA alone in symptomatic patients with PAD.

Structured literature review of responses of cattle to viral and bacterial pathogens causing bovine respiratory disease complex.

PubMed

Grissett, G P; White, B J; Larson, R L

2015-01-01

Bovine respiratory disease (BRD) is an economically important disease of cattle and continues to be an intensely studied topic. However, literature summarizing the time between pathogen exposure and clinical signs, shedding, and seroconversion is minimal. A structured literature review of the published literature was performed to determine cattle responses (time from pathogen exposure to clinical signs, shedding, and seroconversion) in challenge models using common BRD viral and bacterial pathogens. After review a descriptive analysis of published studies using common BRD pathogen challenge studies was performed. Inclusion criteria were single pathogen challenge studies with no treatment or vaccination evaluating outcomes of interest: clinical signs, shedding, and seroconversion. Pathogens of interest included: bovine viral diarrhea virus (BVDV), bovine herpesvirus type 1 (BHV-1), parainfluenza-3 virus, bovine respiratory syncytial virus, Mannheimia haemolytica, Mycoplasma bovis, Pastuerella multocida, and Histophilus somni. Thirty-five studies and 64 trials were included for analysis. The median days to the resolution of clinical signs after BVDV challenge was 15 and shedding was not detected on day 12 postchallenge. Resolution of BHV-1 shedding resolved on day 12 and clinical signs on day 12 postchallenge. Bovine respiratory syncytial virus ceased shedding on day 9 and median time to resolution of clinical signs was on day 12 postchallenge. M. haemolytica resolved clinical signs 8 days postchallenge. This literature review and descriptive analysis can serve as a resource to assist in designing challenge model studies and potentially aid in estimation of duration of clinical disease and shedding after natural pathogen exposure. Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

Source of Volatiles in Earth's Deep Mantle from Neon Isotope Systematics in the South Atlantic

NASA Astrophysics Data System (ADS)

Williams, C. D.; Mukhopadhyay, S.

2016-12-01

The noble gases play an important role in understanding Earth's accretion and subsequent evolution. Neon isotopes in particular have the potential to distinguish between distinct sources of Earth's volatiles e.g., acquisition of nebular gas, solar wind implanted materials or chondritic meteorites and their components. The neon isotopic composition of the deep mantle remains subject to debate with the majority of mantle-derived basalts displaying maximum 20Ne/22Ne ratios less than 12.5, similar to values determined for the convective mantle (20Ne/22Ne = 12.49 +/- 0.04; [1]). These values are also much lower than those of solar wind (20Ne/22Ne = 13.8; [2,3]) and estimates of the nebular gas (20Ne/22Ne = 13.4; [4]) but comparable to solar wind implanted meteoritic materials (20Ne/22Ne = 12.5-12.7; [5]). Here we determine the neon isotopic composition of mantle-derived materials from the south Atlantic. These samples display strong linear correlations in 20Ne/22Ne-21Ne/22Ne space with maximum 20Ne/22Ne ratios that are resolvable from and higher than materials derived from the convecting mantle as well as models of solar wind implantation. These results supplement a growing database of mantle materials characterized by 20Ne/22Ne ratios greater than 12.5, challenging the notion that the entire mantle acquired volatiles from solar wind implanted meteoritic materials. In this presentation we will explore alternative origins for these volatiles and provide testable predictions for each scenario. [1] G. Holland, C.J. Ballentine.. Nature 441 (2006), 186-191. [2] A. Gimberg et al. GCA 72 (2008), 626-645. [3] V.S. Heber et al. GCA 73 (2009), 7414-7432. [4] V. S. Heber et al. ApJ 759 (2012), 121. [5] R. Wieler in: D. Porcelli, C.J. Ballentine, R. Wieler (Eds.), Reviews in Mineralogy and Geochemistry 47 (2002), 21-70.

Maximal Rashba-like spin splitting via kinetic-energy-coupled inversion-symmetry breaking.

PubMed

Sunko, Veronika; Rosner, H; Kushwaha, P; Khim, S; Mazzola, F; Bawden, L; Clark, O J; Riley, J M; Kasinathan, D; Haverkort, M W; Kim, T K; Hoesch, M; Fujii, J; Vobornik, I; Mackenzie, A P; King, P D C

2017-09-27

Engineering and enhancing the breaking of inversion symmetry in solids-that is, allowing electrons to differentiate between 'up' and 'down'-is a key goal in condensed-matter physics and materials science because it can be used to stabilize states that are of fundamental interest and also have potential practical applications. Examples include improved ferroelectrics for memory devices and materials that host Majorana zero modes for quantum computing. Although inversion symmetry is naturally broken in several crystalline environments, such as at surfaces and interfaces, maximizing the influence of this effect on the electronic states of interest remains a challenge. Here we present a mechanism for realizing a much larger coupling of inversion-symmetry breaking to itinerant surface electrons than is typically achieved. The key element is a pronounced asymmetry of surface hopping energies-that is, a kinetic-energy-coupled inversion-symmetry breaking, the energy scale of which is a substantial fraction of the bandwidth. Using spin- and angle-resolved photoemission spectroscopy, we demonstrate that such a strong inversion-symmetry breaking, when combined with spin-orbit interactions, can mediate Rashba-like spin splittings that are much larger than would typically be expected. The energy scale of the inversion-symmetry breaking that we achieve is so large that the spin splitting in the CoO 2 - and RhO 2 -derived surface states of delafossite oxides becomes controlled by the full atomic spin-orbit coupling of the 3d and 4d transition metals, resulting in some of the largest known Rashba-like spin splittings. The core structural building blocks that facilitate the bandwidth-scaled inversion-symmetry breaking are common to numerous materials. Our findings therefore provide opportunities for creating spin-textured states and suggest routes to interfacial control of inversion-symmetry breaking in designer heterostructures of oxides and other material classes.

2D evaluation of spectral LIBS data derived from heterogeneous materials using cluster algorithm

NASA Astrophysics Data System (ADS)

Gottlieb, C.; Millar, S.; Grothe, S.; Wilsch, G.

2017-08-01

Laser-induced Breakdown Spectroscopy (LIBS) is capable of providing spatially resolved element maps in regard to the chemical composition of the sample. The evaluation of heterogeneous materials is often a challenging task, especially in the case of phase boundaries. In order to determine information about a certain phase of a material, the need for a method that offers an objective evaluation is necessary. This paper will introduce a cluster algorithm in the case of heterogeneous building materials (concrete) to separate the spectral information of non-relevant aggregates and cement matrix. In civil engineering, the information about the quantitative ingress of harmful species like Cl-, Na+ and SO42- is of great interest in the evaluation of the remaining lifetime of structures (Millar et al., 2015; Wilsch et al., 2005). These species trigger different damage processes such as the alkali-silica reaction (ASR) or the chloride-induced corrosion of the reinforcement. Therefore, a discrimination between the different phases, mainly cement matrix and aggregates, is highly important (Weritz et al., 2006). For the 2D evaluation, the expectation-maximization-algorithm (EM algorithm; Ester and Sander, 2000) has been tested for the application presented in this work. The method has been introduced and different figures of merit have been presented according to recommendations given in Haddad et al. (2014). Advantages of this method will be highlighted. After phase separation, non-relevant information can be excluded and only the wanted phase displayed. Using a set of samples with known and unknown composition, the EM-clustering method has been validated regarding to Gustavo González and Ángeles Herrador (2007).

Analyzing genetic diversity in conifers...isozyme resolution by starch gel electrophoresis

Treesearch

M. Thompson Conkle

1972-01-01

Enzymes in forest tree materials can be resolved by starch gel electrophoresis. A gel slab is prepared in a mold assembled from glass and plastic. Wicks containing an aqueous extract of macerated plant material are inserted in the gel and processed. The gel is sliced, stained, examined, and photographed. Isozyme bands produced by differential migration of enzymes...

Adaptive Design of Confirmatory Trials: Advances and Challenges

PubMed Central

Lai, Tze Leung; Lavori, Philip W.; Tsang, Ka Wai

2015-01-01

The past decade witnessed major developments in innovative designs of confirmatory clinical trials, and adaptive designs represent the most active area of these developments. We give an overview of the developments and associated statistical methods in several classes of adaptive designs of confirmatory trials. We also discuss their statistical difficulties and implementation challenges, and show how these problems are connected to other branches of mainstream Statistics, which we then apply to resolve the difficulties and bypass the bottlenecks in the development of adaptive designs for the next decade. PMID:26079372

Investigation of energy transfer mechanisms between Bi(2+) and Tm(3+) by time-resolved spectrum.

PubMed

Li, Yang; Sharafudeen, Kaniyarakkal; Dong, Guoping; Ma, Zhijun; Qiu, Jianrong

2013-11-01

Here, we report for the first time the optical properties of Bi(2+) and Tm(3+) co-doped germanate glasses and elucidate the potential of this material as substrates to improve the performance of CdTe solar cell. A strong emission peak at 800nm is observed under the excitation of 450-700nm in this material. The energy transfer processes from the transitions of Bi(2+) [(2)P3/2(1)→(2)P1/2]: Tm(3+) [(3)H6→(3)H4] are investigated by time-resolved luminescence spectroscopy. A cover glass exhibiting an ultra-broadband response spectrum covering the entire solar visible wavelength region is suggested to enhance the conversion efficiency of CdTe solar cells significantly. Copyright © 2013 Elsevier B.V. All rights reserved.

Universal penetration test apparatus with fluid penetration sensor

DOEpatents

Johnson, P.W.; Stampfer, J.F.; Bradley, O.D.

1999-02-02

A universal penetration test apparatus is described for measuring resistance of a material to a challenge fluid. The apparatus includes a pad saturated with the challenge fluid. The apparatus includes a compression assembly for compressing the material between the pad and a compression member. The apparatus also includes a sensor mechanism for automatically detecting when the challenge fluid penetrates the material. 23 figs.

Proceedings of "Optical Probes of Dynamics in Complex Environments"

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sension, R; Tokmakoff, A

2008-04-01

This document contains the proceedings from the symposium on Optical Probes of Dynamics in Complex Environments, which organized as part of the 235th National Meeting of the American Chemical Society in New Orleans, LA from April 6 to 10, 2008. The study of molecular dynamics in chemical reaction and biological processes using time ƒresolved spectroscopy plays an important role in our understanding of energy conversion, storage, and utilization problems. Fundamental studies of chemical reactivity, molecular rearrangements, and charge transport are broadly supported by the DOE Office of Science because of their role in the development of alternative energy sources, themore » understanding of biological energy conversion processes, the efficient utilization of existing energy resources, and the mitigation of reactive intermediates in radiation chemistry. In addition, time resolved spectroscopy is central to all of DOEs grand challenges for fundamental energy science. This symposium brought together leaders in the field of ultrafast spectroscopy, including experimentalists, theoretical chemists, and simulators, to discuss the most recent scientific and technological advances. DOE support for this conference was used to help young US and international scientists travel to the meeting. The latest technology in ultrafast infrared, optical, and xray spectroscopy and the scientific advances that these methods enable were covered. Particular emphasis was placed on new experimental methods used to probe molecular dynamics in liquids, solids, interfaces, nanostructured materials, and biomolecules.« less

Resolving Electrode Morphology’s Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Komini Babu, Siddharth; Chung, Hoon T.; Zelenay, Piotr

This paper reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nano-scale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and are subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacymore » of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion® loading. The associated transport properties were evaluated from pore/particlescale simulations within the nano-CT imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion® ionomer loading. We show that this is primarily a result of distinct changes in ionomer’s spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.« less

Resolving Electrode Morphology’s Impact on Platinum Group Metal-Free Cathode Performance Using Nano-CT of 3D Hierarchical Pore and Ionomer Distribution

DOE PAGES

Komini Babu, Siddharth; Chung, Hoon T.; Zelenay, Piotr; ...

2016-11-02

This paper reports on the characterization of polymer electrolyte fuel cell (PEFC) cathodes featuring a platinum group metal-free (PGM-free) catalyst using nano-scale resolution X-ray computed tomography (nano-CT) and morphological analysis. PGM-free PEFC cathodes have gained significant interest in the past decade since they have the potential to dramatically reduce PEFC costs by eliminating the large platinum (Pt) raw material cost. However, several challenges remain before they are commercially viable. Since these catalysts have lower volumetric activity, the PGM-free cathodes are thicker and are subject to increased gas and proton transport resistances that reduce the performance. To better understand the efficacymore » of the catalyst and improve electrode performance, a detailed understanding the correlation between electrode fabrication, morphology, and performance is crucial. In this work, the pore/solid structure and the ionomer distribution was resolved in three dimensions (3D) using nano-CT for three PGM-free electrodes of varying Nafion® loading. The associated transport properties were evaluated from pore/particlescale simulations within the nano-CT imaged structure. These characterizations are then used to elucidate the microstructural origins of the dramatic changes in fuel cell performance with varying Nafion® ionomer loading. We show that this is primarily a result of distinct changes in ionomer’s spatial distribution. The significant impact of electrode morphology on performance highlights the importance of PGM-free electrode development in concert with efforts to improve catalyst activity and durability.« less

Using smart materials to solve new challenges in the automotive industry

NASA Astrophysics Data System (ADS)

Gath, Kerrie K.; Maranville, Clay; Tardiff, Janice

2018-03-01

Ford has an extensive history of developing and utilizing smart and innovative materials in its vehicles. In this paper, we present new challenges the automotive industry is facing and explore how intelligent uses of smart materials can help provide solutions. We explore which vehicle attributes may provide most advantageous for the use smart materials, and discuss how smart material have had technical challenges that limit their use. We also look at how smart materials such as gecko inspired adhesion is providing opportunities during the vehicle assembly process by improving manufacturing quality, environmental sustainability, and worker safety. An emerging area for deployment of smart materials may involve autonomous vehicles and mobility solutions, where customer expectations are migrating toward a seamless and adaptive experience leading to new expectations for an enhanced journey. Another area where smart materials are influencing change is interior and exterior design including smart textiles, photochromatic dyes, and thermochromatic materials. The key to advancing smart materials in automotive industry is to capitalize on the smaller niche applications where there will be an advantage over traditional methods. Ford has an extensive history of developing and utilizing smart and innovative materials. Magnetorheological fluids, thermoelectric materials, piezoelectric actuators, and shape memory alloys are all in production. In this paper we present new challenges the automotive industry is facing and explore how intelligent uses of smart materials can help provide solutions. We explore which vehicle attributes may provide most advantageous for the use smart materials, and discuss how smart materials have had technical challenges that limit their use. An emerging area for deployment of smart materials may involve autonomous vehicles and mobility solutions, where customer expectations may require a seamless and adaptive experience for users having various expectations.

Space and time-resolved probing of heterogeneous catalysis reactions using lab-on-a-chip

NASA Astrophysics Data System (ADS)

Navin, Chelliah V.; Krishna, Katla Sai; Theegala, Chandra S.; Kumar, Challa S. S. R.

2016-03-01

Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors.Probing catalytic reactions on a catalyst surface in real time is a major challenge. Herein, we demonstrate the utility of a continuous flow millifluidic chip reactor coated with a nanostructured gold catalyst as an effective platform for in situ investigation of the kinetics of catalytic reactions by taking 5-(hydroxymethyl)furfural (HMF) to 2,5-furandicarboxylic acid (FDCA) conversion as a model reaction. The idea conceptualized in this paper can not only dramatically change the ability to probe the time-resolved kinetics of heterogeneous catalysis reactions but also used for investigating other chemical and biological catalytic processes, thereby making this a broad platform for probing reactions as they occur within continuous flow reactors. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06752a

Sustainable Materials Management Challenge Data

EPA Pesticide Factsheets

Sustainable Materials Management (SMM) is a systemic approach to using and reusing materials more productively over their entire lifecycles. It represents a change in how our society thinks about the use of natural resources and environmental protection. By looking at a product's entire lifecycle we can find new opportunities to reduce environmental impacts, conserve resources, and reduce costs. There are multiple challenge programs available as part of the SMM program, including the Food Recovery Challenge, the Electronics Challenge, the Federal Green Challenge, and the WasteWise program. As part of EPA's Food Recovery Challenge, organizations pledge to improve their sustainable food management practices and report their results. The SMM Electronics Challenge encourages electronics manufacturers, brand owners and retailers to strive to send 100 percent of the used electronics they collect from the public, businesses and within their own organizations to third-party certified electronics refurbishers and recyclers. The Federal Green Challenge, a national effort under the EPA??s Sustainable Materials Management Program, challenges EPA and other federal agencies throughout the country to lead by example in reducing the federal government's environmental impact. EPA??s WasteWise encourages organizations and businesses to achieve sustainability in their practices and reduce select industrial wastes. WasteWise is part of EPA??s sustaina

Student Grading Policies: Legal Issues and Administrative Review

ERIC Educational Resources Information Center

Gregory, Richard A.

2005-01-01

This case study focuses on the legal aspects of school district grading policies. Given parental and student challenges to assigned grades, a school district and its employees must be prepared to respond appropriately to substantive and procedural claims. Moreover, when these claims cannot be resolved at the building level, administrative reviews,…

Decisions You Can Live with

ERIC Educational Resources Information Center

Glanz, Jeffrey

2009-01-01

Resolving ethical dilemmas is no easy task, and there are no ready-made recipes or guidelines to follow. A principal, as a critically thinking individual with a well-thought-out belief system, will be challenged to think on his or her feet when confronting situations that require ethical decision making. This article presents three ethical…

DoD Yellow Ribbon Program For Reintegration

Science.gov Websites

their families get the support and care they need. VIDEO Video Link Yellow Ribbon Program Eases Post Reintegration Program will help them resolve Velazquez' No. 1 post-deployment challenge: finding a civilian job reintegration event regarding post-traumatic stress: "I need your help." Story Program Fills Gap for

An Interdisciplinary Design Project in Second Life: Creating a Virtual Marine Science Learning Environment

ERIC Educational Resources Information Center

Triggs, Riley; Jarmon, Leslie; Villareal, Tracy A.

2010-01-01

Virtual environments can resolve many practical and pedagogical challenges within higher education. Economic considerations, accessibility issues, and safety concerns can all be somewhat alleviated by creating learning activities in a virtual space. Because of the removal of real-world physical limitations like gravity, durability and scope,…

Oh Canada! Too Many Children in Poverty for Too Long

ERIC Educational Resources Information Center

Rothman, Laurel

2007-01-01

Canada faces steep, yet surmountable challenges in its efforts to significantly reduce child and family poverty. Most recent data indicate that more than one million Canadian children and their families live in low-income households. Although the House of Commons unanimously resolved to "seek to achieve the goal of eliminating poverty among…

Social Acceptance of Wind: A Brief Overview (Presentation)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lantz, E.

This presentation discusses concepts and trends in social acceptance of wind energy, profiles recent research findings, and discussions mitigation strategies intended to resolve wind power social acceptance challenges as informed by published research and the experiences of individuals participating in the International Energy Agencies Working Group on Social Acceptance of Wind Energy

Learning: Meeting the Challenges of Older Adulthood.

ERIC Educational Resources Information Center

Wolf, Mary Alice

Erik Erikson's model (1963, 1982) is most useful to an understanding of development and aging. He describes lifelong growth as related to tasks that must be performed. At each stage of life, times of stability are followed by developmental crises. Upon resolving the crisis, the individual can enjoy the particular beauty and security of that…

Access to Health Care Among Latinos of Mexican Descent in "Colonias" in Two Texas Counties

ERIC Educational Resources Information Center

Ortiz, Larry; Arizmendi, Lydia; Cornelius, Llewellyn J.

2004-01-01

Critical to resolving the problem of health disparities among Latinos is examining the needs within ethnic subpopulations. This paper focused on the unique challenges encountered by one ethnic subpopulation -- Latinos of Mexican descent living in colonias. Findings reaffirm the importance of looking within ethnic subpopulations to understand the…

Exploiting Redundancy for Flexible Behavior: Unsupervised Learning in a Modular Sensorimotor Control Architecture

ERIC Educational Resources Information Center

Butz, Martin V.; Herbort, Oliver; Hoffmann, Joachim

2007-01-01

Autonomously developing organisms face several challenges when learning reaching movements. First, motor control is learned unsupervised or self-supervised. Second, knowledge of sensorimotor contingencies is acquired in contexts in which action consequences unfold in time. Third, motor redundancies must be resolved. To solve all 3 of these…

Examining Doctoral Students' Perceptions of Diversity in a Diversity Studies Specialization

ERIC Educational Resources Information Center

de Souza Correa, Daniel

2017-01-01

A recent challenge for contemporary education has been to efficiently educate the increasingly diverse American population (Holley, 2013). Seeking to resolve the problems related to the education of a diverse student population, colleges and universities across the United States have begun to require students to enroll in diversity courses…

Education, Democratization, and Globalization: A Challenge for Comparative Education. Guest Editorial Essay and Presidential Address.

ERIC Educational Resources Information Center

McGinn, Noel F.

1996-01-01

Comparative education can contribute to democratization by addressing four issues: declining democratic practice and civic participation in the industrialized world, reasons why education does not resolve this problem, impact of economic globalization on education and on democratization, and the urgency for comparative research on cultural…

Comprehensive Genome-wide Screen for Genes with Cis-acting Regulatory Elements That Respond to Marek's Disease Virus Infection

USDA-ARS?s Scientific Manuscript database

The comprehensive identification of genes underlying phenotypic variation of complex traits such as disease resistance remains one of the greatest challenges in biology despite having genome sequences and more powerful tools. Most genome-wide screens lack sufficient resolving power as they typically...

Explicating the Place of Play: Resolving Dilemmas of Research-to-Practice

ERIC Educational Resources Information Center

Ranz-Smith, Deborah J.

2012-01-01

Synthesizing research with practice in a meaningful manner continues to be a challenge, particularly in relation to securing the place of play in the school setting. The struggle for early childhood teacher educators in dealing with the realities of this research-to-practice dilemma requires constructive action. A theoretical framework that is…

AI challenges for spacecraft control programs

NASA Technical Reports Server (NTRS)

Lightfoot, Patricia

1986-01-01

The application of AI technology to the spacecraft and experiment command and control systems environment is proposed. The disadvantages of the present methods for analyzing and resolving spacecraft experiment command and control problems are discussed. The potential capabilities and advantages of using AI for the spacecraft and experiment command and control systems are described.

Literacy Teaching Method and Peace Building in Multi-Ethnic Communities of Nigeria

ERIC Educational Resources Information Center

Adelore, Omobola; Majaro-Majesty, Henry

2008-01-01

The challenge of peace building in Nigeria is increasing as communities continue to show adversary tendencies. This is happening even after many third party conflict transformation efforts have been expended to resolve and set a conducive climate for stakeholders to sustain peace. Some peace building assessment projects have indicated that the…

Towards an Integrated Approach to the Recognition of Professional Competence and Academic Learning

ERIC Educational Resources Information Center

Bravenboer, Darryll; Lester, Stan

2016-01-01

Purpose: The purpose of this paper is to discuss the benefits of reclaiming the idea of professional competence and challenges fragmented approaches to academic qualification and professional recognition. It is argued that academic programmes that are integrated with the requirements for professional recognition can resolve the potentially…

Time-Resolved Diffuse Optical Spectroscopy and Imaging Using Solid-State Detectors: Characteristics, Present Status, and Research Challenges.

PubMed

Alayed, Mrwan; Deen, M Jamal

2017-09-14

Diffuse optical spectroscopy (DOS) and diffuse optical imaging (DOI) are emerging non-invasive imaging modalities that have wide spread potential applications in many fields, particularly for structural and functional imaging in medicine. In this article, we review time-resolved diffuse optical imaging (TR-DOI) systems using solid-state detectors with a special focus on Single-Photon Avalanche Diodes (SPADs) and Silicon Photomultipliers (SiPMs). These TR-DOI systems can be categorized into two types based on the operation mode of the detector (free-running or time-gated). For the TR-DOI prototypes, the physical concepts, main components, figures-of-merit of detectors, and evaluation parameters are described. The performance of TR-DOI prototypes is evaluated according to the parameters used in common protocols to test DOI systems particularly basic instrumental performance (BIP). In addition, the potential features of SPADs and SiPMs to improve TR-DOI systems and expand their applications in the foreseeable future are discussed. Lastly, research challenges and future developments for TR-DOI are discussed for each component in the prototype separately and also for the entire system.

Microscopic time-resolved imaging of singlet oxygen by delayed fluorescence in living cells.

PubMed

Scholz, Marek; Dědic, Roman; Hála, Jan

2017-11-08

Singlet oxygen is a highly reactive species which is involved in a number of processes, including photodynamic therapy of cancer. Its very weak near-infrared emission makes imaging of singlet oxygen in biological systems a long-term challenge. We address this challenge by introducing Singlet Oxygen Feedback Delayed Fluorescence (SOFDF) as a novel modality for semi-direct microscopic time-resolved wide-field imaging of singlet oxygen in biological systems. SOFDF has been investigated in individual fibroblast cells incubated with a well-known photosensitizer aluminium phthalocyanine tetrasulfonate. The SOFDF emission from the cells is several orders of magnitude stronger and much more readily detectable than the very weak near-infrared phosphorescence of singlet oxygen. Moreover, the analysis of SOFDF kinetics enables us to estimate the lifetimes of the involved excited states. Real-time SOFDF images with micrometer spatial resolution and submicrosecond temporal-resolution have been recorded. Interestingly, a steep decrease in the SOFDF intensity after the photodynamically induced release of a photosensitizer from lysosomes has been demonstrated. This effect could be potentially employed as a valuable diagnostic tool for monitoring and dosimetry in photodynamic therapy.

State of Jet Noise Prediction-NASA Perspective

NASA Technical Reports Server (NTRS)

Bridges, James E.

2008-01-01

This presentation covers work primarily done under the Airport Noise Technical Challenge portion of the Supersonics Project in the Fundamental Aeronautics Program. To provide motivation and context, the presentation starts with a brief overview of the Airport Noise Technical Challenge. It then covers the state of NASA s jet noise prediction tools in empirical, RANS-based, and time-resolved categories. The empirical tools, requires seconds to provide a prediction of noise spectral directivity with an accuracy of a few dB, but only for axisymmetric configurations. The RANS-based tools are able to discern the impact of three-dimensional features, but are currently deficient in predicting noise from heated jets and jets with high speed and require hours to produce their prediction. The time-resolved codes are capable of predicting resonances and other time-dependent phenomena, but are very immature, requiring months to deliver predictions without unknown accuracies and dependabilities. In toto, however, when one considers the progress being made it appears that aeroacoustic prediction tools are soon to approach the level of sophistication and accuracy of aerodynamic engineering tools.

Challenges at the Frontiers of Matter and Energy: Transformative Opportunities for Discovery Science

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hemminger, John C.; Sarrao, John; Crabtree, George

FIVE TRANSFORMATIVE OPPORTUNITIES FOR DISCOVERY SCIENCE As a result of this effort, it has become clear that the progress made to date on the five Grand Challenges has created a springboard for seizing five new Transformative Opportunities that have the potential to further transform key technologies involving matter and energy. These five new Transformative Opportunities and the evidence supporting them are discussed in this new report, “Challenges at the Frontiers of Matter and Energy: Transformative Opportunities for Discovery Science.” Mastering Hierarchical Architectures and Beyond-Equilibrium Matter Complex materials and chemical processes transmute matter and energy, for example from CO2 and watermore » to chemical fuel in photosynthesis, from visible light to electricity in solar cells and from electricity to light in light emitting diodes (LEDs) Such functionality requires complex assemblies of heterogeneous materials in hierarchical architectures that display time-dependent away-from-equilibrium behaviors. Much of the foundation of our understanding of such transformations however, is based on monolithic single- phase materials operating at or near thermodynamic equilibrium. The emergent functionalities enabling next-generation disruptive energy technologies require mastering the design, synthesis, and control of complex hierarchical materials employing dynamic far-from-equilibrium behavior. A key guide in this pursuit is nature, for biological systems prove the power of hierarchical assembly and far- from-equilibrium behavior. The challenges here are many: a description of the functionality of hierarchical assemblies in terms of their constituent parts, a blueprint of atomic and molecular positions for each constituent part, and a synthesis strategy for (a) placing the atoms and molecules in the proper positions for the component parts and (b) arranging the component parts into the required hierarchical structure. Targeted functionality will open the door to significant advances in the harvesting, transforming (e.g., reducing CO2, splitting water, and fixing nitrogen), storing, and use of energy to create new materials, manufacturing processes, and technologies—the lifeblood of human societies and economic growth. Beyond Ideal Materials and Systems: Understanding the Critical Roles of Heterogeneity, Interfaces, and Disorder Real materials, both natural ones and those we engineer, are usually a complex mixture of compositional and structural heterogeneities, interfaces, and disorder across all spatial and temporal scales. It is the fluctuations and disorderly states of these heterogeneities and interfaces that often determine the system’s properties and functionality. Much of our fundamental scientific knowledge is based on “ideal” systems, meaning materials that are observed in “frozen” states or represented by spatially or temporally averaged states. Too often, this approach has yielded overly simplistic models that hide important nuances and do not capture the complex behaviors of materials under realistic conditions. These behaviors drive vital chemical transformations such as catalysis, which initiates most industrial manufacturing processes, and friction and corrosion, the parasitic effects of which cost the U.S. economy billions of dollars annually. Expanding our scientific knowledge from the relative simplicity of ideal, perfectly ordered, or structurally averaged materials to the true complexity of real-world heterogeneities, interfaces, and disorder should enable us to realize enormous benefits in the materials and chemical sciences, which translates to the energy sciences, including solar and nuclear power, hydraulic fracturing, power conversion, airframes, and batteries. Harnessing Coherence in Light and Matter Quantum coherence in light and matter is a measure of the extent to which a wave field vibrates in unison with itself at neighboring points in space and time. Although this phenomenon is expressed at the atomic and electronic scales, it can dominate the macroscopic properties of materials and chemical reactions such as superconductivity and efficient photosynthesis. In recent years, enormous progress has been made in recognizing, manipulating, and exploiting quantum coherence. This progress has already elucidated the role that symmetry plays in protecting coherence in key materials, taught us how to use light to manipulate atoms and molecules, and provided us with increasingly sophisticated techniques for controlling and probing the charges and spins of quantum coherent systems. With the arrival of new sources of coherent light and electron beams, thanks in large part to investments by the U.S. Department of Energy’s Office of Basic Energy Sciences (BES), there is now an opportunity to engineer coherence in heterostructures that incorporate multiple types of materials and to control complex, multistep chemical transformations. This approach will pave the way for quantum information processing and next-generation photovoltaic cells and sensors. Revolutionary Advances in Models, Mathematics, Algorithms, Data, and Computing Science today is benefiting from a convergence of theoretical, mathematical, computational, and experimental capabilities that put us on the brink of greatly accelerating our ability to predict, synthesize, and control new materials and chemical processes, and to understand the complexities of matter across a range of scales. Imagine being able to chart a path through a vast sea of possible new materials to find a select few with desired properties. Instead of the time-honored forward approach, in which materials with desired properties are found through either trial-and-error experiments or lucky accidents, we have the opportunity to inversely design and create new materials that possess the properties we desire. The traditional approach has allowed us to make only a tiny fraction of all the materials that are theoretically possible. The inverse design approach, through the harmonious convergence of theoretical, mathematical, computational, and experimental capabilities, could usher in a virtual cornucopia of new materials with functionalities far beyond what nature can provide. Similarly, enhanced mathematical and computational capabilities significantly enhance our ability to extract physical and chemical insights from vastly larger data streams gathered during multimodal and multidimensional experiments using advanced characterization facilities. Exploiting Transformative Advances in Imaging Capabilities across Multiple Scales Historically, improvements in imaging capabilities have always resulted in improved understanding of scientific phenomena. A prime challenge today is finding ways to reconstruct raw data, obtained by probing and mapping matter across multiple scales, into analyzable images. BES investments in new and improved imaging facilities, most notably synchrotron x-ray sources, free-electron lasers, electron microscopes, and neutron sources, have greatly advanced our powers of observation, as have substantial improvements in laboratory- scale technologies. Furthermore, BES is now planning or actively discussing exciting new capabilities. Taken together, these advances in imaging capabilities provide an opportunity to expand our ability to observe and study matter from the 3D spatial perspectives of today to true “4D” spatially and temporally resolved maps of dynamics that allow quantitative predictions of time-dependent material properties and chemical processes. The knowledge gained will impact data storage, catalyst design, drug delivery, structural materials, and medical implants, to name just a few key technologies. ENABLING SUCCESS Seizing each of these five Transformative Opportunities, as well as accelerating further progress on Grand Challenge research, will require specific, targeted investments from BES in the areas of synthesis, meaning the ability to make the materials and architectures that are envisioned; instrumentation and tools, a category that includes theory and computation; and human capital, the most important asset for advancing the Grand Challenges and Transformative Opportunities. While “Challenges at the Frontiers of Matter and Energy: Transformative Opportunities for Discovery Science” could be viewed as a sequel to the original Grand Challenges report, it breaks much new ground in its assessment of the scientific landscape today versus the scientific landscape just a few years ago. In the original Grand Challenges report, it was noted that if the five Grand Challenges were met, our ability to direct matter and energy would be measured only by the limits of human imagination. This new report shows that, prodded by those challenges, the scientific community is positioned today to seize new opportunities whose impacts promise to be transformative for science and society, as well as dramatically accelerate progress in the pursuit of the original Grand Challenges.« less

When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical.

PubMed

Voufack, Ariste Bolivard; Claiser, Nicolas; Lecomte, Claude; Pillet, Sébastien; Pontillon, Yves; Gillon, Béatrice; Yan, Zeyin; Gillet, Jean Michel; Marazzi, Marco; Genoni, Alessandro; Souhassou, Mohamed

2017-08-01

Joint refinement of X-ray and polarized neutron diffraction data has been carried out in order to determine charge and spin density distributions simultaneously in the nitronyl nitroxide (NN) free radical Nit(SMe)Ph. For comparison purposes, density functional theory (DFT) and complete active-space self-consistent field (CASSCF) theoretical calculations were also performed. Experimentally derived charge and spin densities show significant differences between the two NO groups of the NN function that are not observed from DFT theoretical calculations. On the contrary, CASSCF calculations exhibit the same fine details as observed in spin-resolved joint refinement and a clear asymmetry between the two NO groups.

A Private [School] Matter: The State of Materials Challenges in Private College Preparatory School Libraries in the Southeast United States

ERIC Educational Resources Information Center

Franklin, Renee E.

2008-01-01

Materials challenges and censorship occur often in public and private educational settings. Private schools and their library media centers are not subject to the First Amendment but research reported in this article examines the state of challenges to materials held in private schools media centers in the southeast United States as a way to gauge…

Novel system for picosecond photoemission spectroscopy

NASA Astrophysics Data System (ADS)

Haight, R.; Silberman, J. A.; Lilie, M. I.

1988-09-01

This article describes a laser-based source and detection scheme for performing time-resolved photoemission studies of materials. The pulsed laser source produces intense picosecond pulses of coherent radiation that are nearly continuously tunable from the near infrared to photon energies up to 13 eV. To achieve high sensitivity, a novel multianode time-of-flight spectrometer has been built that generates an angularly resolved intensity versus kinetic energy spectrum with better than 100-meV resolution. The source and detector provide an opportunity to study the electronic dynamics of excited systems on a picosecond time scale.

Direct mapping of ion diffusion times on LiCoO2 surfaces with nanometer resolution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Guo, Senli; Jesse, Stephen; Kalnaus, Sergiy

2011-01-01

The strong coupling between the molar volume and mobile ion concentration in ionically-conductive solids is used for spatially-resolved studies of ionic transport on the polycrystalline LiCoO2 surface by time-resolved spectroscopy. Strong variability between ionic transport at the grain boundaries and within the grains is observed, and the relationship between relaxation and hysteresis loop formation is established. The use of the strain measurements allows ionic transport be probed on the nanoscale, and suggests enormous potential for probing ionic materials and devices.

Resolved discrepancies between visible spontaneous Raman cross-section and direct near-infrared Raman gain measurements in TeO2-based glasses.

PubMed

Rivero, Clara; Stegeman, Robert; Couzi, Michel; Talaga, David; Cardinal, Thierry; Richardson, Kathleen; Stegeman, George

2005-06-13

Disagreements on the Raman gain response of different tellurite-based glasses, measured at different wavelengths, have been recently reported in the literature. In order to resolve this controversy, a multi-wavelength Raman cross-section experiment was conducted on two different TeO2-based glass samples. The estimated Raman gain response of the material shows good agreement with the directly-measured Raman gain data at 1064 nm, after correction for the dispersion and wavelength-dependence of the Raman gain process.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mankey, G J; Morton, S A; Tobin, J G

A spin- and angle-resolved x-ray photoelectron spectrometer for the study of magnetic materials will be discussed. It consists of a turntable with electron lenses connected to a large hemispherical analyzer. A mini-Mott spin detector is fitted to the output of the hemispherical analyzer. This system, when coupled to a synchrotron radiation source will allow determination of a complete set of quantum numbers of a photoelectron. This instrument will be used to study ferromagnetic, antiferromagnetic and nonmagnetic materials. Some prototypical materials systems to be studied with this instrument system will be proposed.

Material and Doping Dependence of the Nodal and Antinodal Dispersion Renormalizations in Single- and Multilayer Cuprates

DOE PAGES

Johnston, S.; Lee, W. S.; Chen, Y.; ...

2010-01-01

We presenmore » t a review of bosonic renormalization effects on electronic carriers observed from angle-resolved photoemission spectra in the cuprates. Specifically, we discuss the viewpoint that these renormalizations represent coupling of the electrons to the lattice and review how materials dependence, such as the number of Cu O 2 layers, and doping dependence can be understood straightforwardly in terms of several aspects of electron-phonon coupling in layered correlated materials.« less

Computational electrodynamics in material media with constraint-preservation, multidimensional Riemann solvers and sub-cell resolution - Part II, higher order FVTD schemes

NASA Astrophysics Data System (ADS)

Balsara, Dinshaw S.; Garain, Sudip; Taflove, Allen; Montecinos, Gino

2018-02-01

The Finite Difference Time Domain (FDTD) scheme has served the computational electrodynamics community very well and part of its success stems from its ability to satisfy the constraints in Maxwell's equations. Even so, in the previous paper of this series we were able to present a second order accurate Godunov scheme for computational electrodynamics (CED) which satisfied all the same constraints and simultaneously retained all the traditional advantages of Godunov schemes. In this paper we extend the Finite Volume Time Domain (FVTD) schemes for CED in material media to better than second order of accuracy. From the FDTD method, we retain a somewhat modified staggering strategy of primal variables which enables a very beneficial constraint-preservation for the electric displacement and magnetic induction vector fields. This is accomplished with constraint-preserving reconstruction methods which are extended in this paper to third and fourth orders of accuracy. The idea of one-dimensional upwinding from Godunov schemes has to be significantly modified to use the multidimensionally upwinded Riemann solvers developed by the first author. In this paper, we show how they can be used within the context of a higher order scheme for CED. We also report on advances in timestepping. We show how Runge-Kutta IMEX schemes can be adapted to CED even in the presence of stiff source terms brought on by large conductivities as well as strong spatial variations in permittivity and permeability. We also formulate very efficient ADER timestepping strategies to endow our method with sub-cell resolving capabilities. As a result, our method can be stiffly-stable and resolve significant sub-cell variation in the material properties within a zone. Moreover, we present ADER schemes that are applicable to all hyperbolic PDEs with stiff source terms and at all orders of accuracy. Our new ADER formulation offers a treatment of stiff source terms that is much more efficient than previous ADER schemes. The computer algebra system scripts for generating ADER time update schemes for any general PDE with stiff source terms are also given in the electronic supplements to this paper. Second, third and fourth order accurate schemes for numerically solving Maxwell's equations in material media are presented in this paper. Several stringent tests are also presented to show that the method works and meets its design goals even when material permittivity and permeability vary by an order of magnitude over just a few zones. Furthermore, since the method is unconditionally stable and sub-cell-resolving in the presence of stiff source terms (i.e. for problems involving giant variations in conductivity over just a few zones), it can accurately handle such problems without any reduction in timestep. We also show that increasing the order of accuracy offers distinct advantages for resolving sub-cell variations in material properties. Most importantly, we show that when the accuracy requirements are stringent the higher order schemes offer the shortest time to solution. This makes a compelling case for the use of higher order, sub-cell resolving schemes in CED.

Ara h 2 and Ara 6 are the best predictors of severe peanut allergy: a double-blind placebo-controlled study.

PubMed

Kukkonen, A K; Pelkonen, A S; Mäkinen-Kiljunen, S; Voutilainen, H; Mäkelä, M J

2015-10-01

Component-resolved diagnostics offers a modern tool in peanut allergy, but studies applying consistently double-blind placebo-controlled challenges are lacking. We aimed to optimize diagnostics for moderate-to-severe peanut allergy in a birch-endemic region and to create an oral-peanut challenge with its allergen activity characterized. We performed double-blind placebo-controlled peanut challenges for a referred sample of 6- to 18-year-olds with peanut sensitization or a high suspicion of peanut allergy, including anaphylaxis. We measured specific IgE (sIgE) to Ara h 1, 2, 3, 6, 8, and 9. Testing of allergen activity of the challenge products was by IgE microarray inhibition. Of the 102 patients, 69 were challenge positive: 25 (36%) had severe, 36 (52%) moderate, and 8 (12%) mild symptoms; 38 (37%) received adrenalin. SIgE to Ara h 6 AUC 0.98 (95%CI, 0.96-1.00) was the best marker of moderate-to-severe allergy. When sIgE to Ara h 2 and Ara h 6 was measured together, all (100%) severe reactions at low doses were successfully diagnosable. SIgE to Ara h 8 had no diagnostic value, AUC 0.42 (95%CI, 0.30-0.52). Both nonroasted and roasted peanut inhibited 100% of IgE binding to Ara h 1, 2, 3, and 6. Nonroasted peanut inhibited 87% of IgE binding to Ara h 8, roasted inhibited 30%. The products lacked Ara h 9 activity. Co-sensitization to Ara h 2 and Ara h 6 was associated with severe reactions distinguishing severe allergy from mild symptoms. SIgE to Ara h 8 added no diagnostic value. Component-resolved diagnostics reduce the need for oral challenges in peanut allergy. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

WE-FG-207B-04: Noise Suppression for Energy-Resolved CT Via Variance Weighted Non-Local Filtration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harms, J; Zhu, L

Purpose: The photon starvation problem is exacerbated in energy-resolved CT, since the detected photons are shared by multiple energy channels. Using pixel similarity-based non-local filtration, we aim to produce accurate and high-resolution energy-resolved CT images with significantly reduced noise. Methods: Averaging CT images reconstructed from different energy channels reduces noise at the price of losing spectral information, while conventional denoising techniques inevitably degrade image resolution. Inspired by the fact that CT images of the same object at different energies share the same structures, we aim to reduce noise of energy-resolved CT by averaging only pixels of similar materials - amore » non-local filtration technique. For each CT image, an empirical exponential model is used to calculate the material similarity between two pixels based on their CT values and the similarity values are organized in a matrix form. A final similarity matrix is generated by averaging these similarity matrices, with weights inversely proportional to the estimated total noise variance in the sinogram of different energy channels. Noise suppression is achieved for each energy channel via multiplying the image vector by the similarity matrix. Results: Multiple scans on a tabletop CT system are used to simulate 6-channel energy-resolved CT, with energies ranging from 75 to 125 kVp. On a low-dose acquisition at 15 mA of the Catphan©600 phantom, our method achieves the same image spatial resolution as a high-dose scan at 80 mA with a noise standard deviation (STD) lower by a factor of >2. Compared with another non-local noise suppression algorithm (ndiNLM), the proposed algorithms obtains images with substantially improved resolution at the same level of noise reduction. Conclusion: We propose a noise-suppression method for energy-resolved CT. Our method takes full advantage of the additional structural information provided by energy-resolved CT and preserves image values at each energy level. Research reported in this publication was supported by the National Institute Of Biomedical Imaging And Bioengineering of the National Institutes of Health under Award Number R21EB019597. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.« less

An Experimental Copyright Moratorium: Study of a Proposed Solution to the Copyright Photocopying Problem. Final Report to the American Society for Testing and Materials (ASTM).

ERIC Educational Resources Information Center

Heilprin, Laurence B.

The Committee to Investigate Copyright Problems (CICP), a non-profit organization dedicated to resolving the conflict known as the "copyright photocopying problem" was joined by the American Society for Testing and Materials (ASTM), a large national publisher of technical and scientific standards, in a plan to simulate a long-proposed…

Vibrational Energy in Molecules and Nanoparticles: Applications to Energetic Materials

DTIC Science & Technology

2009-01-30

of vibrational energy in a polyatomic molecule, nitromethane . Work on water and amino acids partially supported by AFOSR are developmental in nature...have characterized the surface vibrations of HMX explosive and their interaction with polymer binders. We have introduced a major improvement in SFG...Vibrational energy in nitromethane and benzene E. Time resolved spectroscopy of chemistry in flash-heated nanoenergetic materials F. Complete

Time-Resolved In Situ Measurements During Rapid Alloy Solidification: Experimental Insight for Additive Manufacturing

NASA Astrophysics Data System (ADS)

McKeown, Joseph T.; Zweiacker, Kai; Liu, Can; Coughlin, Daniel R.; Clarke, Amy J.; Baldwin, J. Kevin; Gibbs, John W.; Roehling, John D.; Imhoff, Seth D.; Gibbs, Paul J.; Tourret, Damien; Wiezorek, Jörg M. K.; Campbell, Geoffrey H.

2016-03-01

Additive manufacturing (AM) of metals and alloys is becoming a pervasive technology in both research and industrial environments, though significant challenges remain before widespread implementation of AM can be realized. In situ investigations of rapid alloy solidification with high spatial and temporal resolutions can provide unique experimental insight into microstructure evolution and kinetics that are relevant for AM processing. Hypoeutectic thin-film Al-Cu and Al-Si alloys were investigated using dynamic transmission electron microscopy to monitor pulsed-laser-induced rapid solidification across microsecond timescales. Solid-liquid interface velocities measured from time-resolved images revealed accelerating solidification fronts in both alloys. The observed microstructure evolution, solidification product, and presence of a morphological instability at the solid-liquid interface in the Al-4 at.%Cu alloy are related to the measured interface velocities and small differences in composition that affect the thermophysical properties of the alloys. These time-resolved in situ measurements can inform and validate predictive modeling efforts for AM.

Big Data in Reciprocal Space: Sliding Fast Fourier Transforms for Determining Periodicity

DOE PAGES

Vasudevan, Rama K.; Belianinov, Alex; Gianfrancesco, Anthony G.; ...

2015-03-03

Significant advances in atomically resolved imaging of crystals and surfaces have occurred in the last decade allowing unprecedented insight into local crystal structures and periodicity. Yet, the analysis of the long-range periodicity from the local imaging data, critical to correlation of functional properties and chemistry to the local crystallography, remains a challenge. Here, we introduce a Sliding Fast Fourier Transform (FFT) filter to analyze atomically resolved images of in-situ grown La5/8Ca3/8MnO3 films. We demonstrate the ability of sliding FFT algorithm to differentiate two sub-lattices, resulting from a mixed-terminated surface. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) of themore » Sliding FFT dataset reveal the distinct changes in crystallography, step edges and boundaries between the multiple sub-lattices. The method is universal for images with any periodicity, and is especially amenable to atomically resolved probe and electron-microscopy data for rapid identification of the sub-lattices present.« less

Big Data in Reciprocal Space: Sliding Fast Fourier Transforms for Determining Periodicity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasudevan, Rama K.; Belianinov, Alex; Gianfrancesco, Anthony G.

Significant advances in atomically resolved imaging of crystals and surfaces have occurred in the last decade allowing unprecedented insight into local crystal structures and periodicity. Yet, the analysis of the long-range periodicity from the local imaging data, critical to correlation of functional properties and chemistry to the local crystallography, remains a challenge. Here, we introduce a Sliding Fast Fourier Transform (FFT) filter to analyze atomically resolved images of in-situ grown La5/8Ca3/8MnO3 films. We demonstrate the ability of sliding FFT algorithm to differentiate two sub-lattices, resulting from a mixed-terminated surface. Principal Component Analysis (PCA) and Independent Component Analysis (ICA) of themore » Sliding FFT dataset reveal the distinct changes in crystallography, step edges and boundaries between the multiple sub-lattices. The method is universal for images with any periodicity, and is especially amenable to atomically resolved probe and electron-microscopy data for rapid identification of the sub-lattices present.« less

Time-Resolved In Situ Measurements During Rapid Alloy Solidification: Experimental Insight for Additive Manufacturing

DOE PAGES

McKeown, Joseph T.; Zweiacker, Kai; Liu, Can; ...

2016-01-27

In research and industrial environments, additive manufacturing (AM) of metals and alloys is becoming a pervasive technology, though significant challenges remain before widespread implementation of AM can be realized. In situ investigations of rapid alloy solidification with high spatial and temporal resolutions can provide unique experimental insight into microstructure evolution and kinetics that are relevant for AM processing. Hypoeutectic thin-film Al–Cu and Al–Si alloys were investigated using dynamic transmission electron microscopy to monitor pulsed-laser-induced rapid solidification across microsecond timescales. Solid–liquid interface velocities measured from time-resolved images revealed accelerating solidification fronts in both alloys. We observed microstructure evolution, solidification product, andmore » presence of a morphological instability at the solid–liquid interface in the Al–4 at.%Cu alloy are related to the measured interface velocities and small differences in composition that affect the thermophysical properties of the alloys. These time-resolved in situ measurements can inform and validate predictive modeling efforts for AM.« less

Stimulated emission depletion microscopy resolves individual nitrogen vacancy centers in diamond nanocrystals.

PubMed

Arroyo-Camejo, Silvia; Adam, Marie-Pierre; Besbes, Mondher; Hugonin, Jean-Paul; Jacques, Vincent; Greffet, Jean-Jacques; Roch, Jean-François; Hell, Stefan W; Treussart, François

2013-12-23

Nitrogen-vacancy (NV) color centers in nanodiamonds are highly promising for bioimaging and sensing. However, resolving individual NV centers within nanodiamond particles and the controlled addressing and readout of their spin state has remained a major challenge. Spatially stochastic super-resolution techniques cannot provide this capability in principle, whereas coordinate-controlled super-resolution imaging methods, like stimulated emission depletion (STED) microscopy, have been predicted to fail in nanodiamonds. Here we show that, contrary to these predictions, STED can resolve single NV centers in 40-250 nm sized nanodiamonds with a resolution of ≈10 nm. Even multiple adjacent NVs located in single nanodiamonds can be imaged individually down to relative distances of ≈15 nm. Far-field optical super-resolution of NVs inside nanodiamonds is highly relevant for bioimaging applications of these fluorescent nanolabels. The targeted addressing and readout of individual NV(-) spins inside nanodiamonds by STED should also be of high significance for quantum sensing and information applications.

Whole-genome analyses resolve early branches in the tree of life of modern birds

PubMed Central

Jarvis, Erich D.; Mirarab, Siavash; Aberer, Andre J.; Li, Bo; Houde, Peter; Li, Cai; Ho, Simon Y. W.; Faircloth, Brant C.; Nabholz, Benoit; Howard, Jason T.; Suh, Alexander; Weber, Claudia C.; da Fonseca, Rute R.; Li, Jianwen; Zhang, Fang; Li, Hui; Zhou, Long; Narula, Nitish; Liu, Liang; Ganapathy, Ganesh; Boussau, Bastien; Bayzid, Md. Shamsuzzoha; Zavidovych, Volodymyr; Subramanian, Sankar; Gabaldón, Toni; Capella-Gutiérrez, Salvador; Huerta-Cepas, Jaime; Rekepalli, Bhanu; Munch, Kasper; Schierup, Mikkel; Lindow, Bent; Warren, Wesley C.; Ray, David; Green, Richard E.; Bruford, Michael W.; Zhan, Xiangjiang; Dixon, Andrew; Li, Shengbin; Li, Ning; Huang, Yinhua; Derryberry, Elizabeth P.; Bertelsen, Mads Frost; Sheldon, Frederick H.; Brumfield, Robb T.; Mello, Claudio V.; Lovell, Peter V.; Wirthlin, Morgan; Schneider, Maria Paula Cruz; Prosdocimi, Francisco; Samaniego, José Alfredo; Velazquez, Amhed Missael Vargas; Alfaro-Núñez, Alonzo; Campos, Paula F.; Petersen, Bent; Sicheritz-Ponten, Thomas; Pas, An; Bailey, Tom; Scofield, Paul; Bunce, Michael; Lambert, David M.; Zhou, Qi; Perelman, Polina; Driskell, Amy C.; Shapiro, Beth; Xiong, Zijun; Zeng, Yongli; Liu, Shiping; Li, Zhenyu; Liu, Binghang; Wu, Kui; Xiao, Jin; Yinqi, Xiong; Zheng, Qiuemei; Zhang, Yong; Yang, Huanming; Wang, Jian; Smeds, Linnea; Rheindt, Frank E.; Braun, Michael; Fjeldsa, Jon; Orlando, Ludovic; Barker, F. Keith; Jønsson, Knud Andreas; Johnson, Warren; Koepfli, Klaus-Peter; O’Brien, Stephen; Haussler, David; Ryder, Oliver A.; Rahbek, Carsten; Willerslev, Eske; Graves, Gary R.; Glenn, Travis C.; McCormack, John; Burt, Dave; Ellegren, Hans; Alström, Per; Edwards, Scott V.; Stamatakis, Alexandros; Mindell, David P.; Cracraft, Joel; Braun, Edward L.; Warnow, Tandy; Jun, Wang; Gilbert, M. Thomas P.; Zhang, Guojie

2015-01-01

To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data. We recovered a highly resolved tree that confirms previously controversial sister or close relationships. We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago. PMID:25504713

Whole-genome analyses resolve early branches in the tree of life of modern birds.

PubMed

Jarvis, Erich D; Mirarab, Siavash; Aberer, Andre J; Li, Bo; Houde, Peter; Li, Cai; Ho, Simon Y W; Faircloth, Brant C; Nabholz, Benoit; Howard, Jason T; Suh, Alexander; Weber, Claudia C; da Fonseca, Rute R; Li, Jianwen; Zhang, Fang; Li, Hui; Zhou, Long; Narula, Nitish; Liu, Liang; Ganapathy, Ganesh; Boussau, Bastien; Bayzid, Md Shamsuzzoha; Zavidovych, Volodymyr; Subramanian, Sankar; Gabaldón, Toni; Capella-Gutiérrez, Salvador; Huerta-Cepas, Jaime; Rekepalli, Bhanu; Munch, Kasper; Schierup, Mikkel; Lindow, Bent; Warren, Wesley C; Ray, David; Green, Richard E; Bruford, Michael W; Zhan, Xiangjiang; Dixon, Andrew; Li, Shengbin; Li, Ning; Huang, Yinhua; Derryberry, Elizabeth P; Bertelsen, Mads Frost; Sheldon, Frederick H; Brumfield, Robb T; Mello, Claudio V; Lovell, Peter V; Wirthlin, Morgan; Schneider, Maria Paula Cruz; Prosdocimi, Francisco; Samaniego, José Alfredo; Vargas Velazquez, Amhed Missael; Alfaro-Núñez, Alonzo; Campos, Paula F; Petersen, Bent; Sicheritz-Ponten, Thomas; Pas, An; Bailey, Tom; Scofield, Paul; Bunce, Michael; Lambert, David M; Zhou, Qi; Perelman, Polina; Driskell, Amy C; Shapiro, Beth; Xiong, Zijun; Zeng, Yongli; Liu, Shiping; Li, Zhenyu; Liu, Binghang; Wu, Kui; Xiao, Jin; Yinqi, Xiong; Zheng, Qiuemei; Zhang, Yong; Yang, Huanming; Wang, Jian; Smeds, Linnea; Rheindt, Frank E; Braun, Michael; Fjeldsa, Jon; Orlando, Ludovic; Barker, F Keith; Jønsson, Knud Andreas; Johnson, Warren; Koepfli, Klaus-Peter; O'Brien, Stephen; Haussler, David; Ryder, Oliver A; Rahbek, Carsten; Willerslev, Eske; Graves, Gary R; Glenn, Travis C; McCormack, John; Burt, Dave; Ellegren, Hans; Alström, Per; Edwards, Scott V; Stamatakis, Alexandros; Mindell, David P; Cracraft, Joel; Braun, Edward L; Warnow, Tandy; Jun, Wang; Gilbert, M Thomas P; Zhang, Guojie

2014-12-12

To better determine the history of modern birds, we performed a genome-scale phylogenetic analysis of 48 species representing all orders of Neoaves using phylogenomic methods created to handle genome-scale data. We recovered a highly resolved tree that confirms previously controversial sister or close relationships. We identified the first divergence in Neoaves, two groups we named Passerea and Columbea, representing independent lineages of diverse and convergently evolved land and water bird species. Among Passerea, we infer the common ancestor of core landbirds to have been an apex predator and confirm independent gains of vocal learning. Among Columbea, we identify pigeons and flamingoes as belonging to sister clades. Even with whole genomes, some of the earliest branches in Neoaves proved challenging to resolve, which was best explained by massive protein-coding sequence convergence and high levels of incomplete lineage sorting that occurred during a rapid radiation after the Cretaceous-Paleogene mass extinction event about 66 million years ago. Copyright © 2014, American Association for the Advancement of Science.

Near specular scatter analysis method with a new goniophotometer

NASA Astrophysics Data System (ADS)

Meyen, Stephanie; Sutter, Florian; Heller, Peter

2014-09-01

The challenge of improving component quality and reducing cost has focused the attention of the solar thermal power industry on reliable component characterization methods. Since the reflector plays a key role in the energy conversion chain, the analysis of its reflectance properties has become a lively discussed issue in recent years. State of the art measurement instruments for specular reflectance do not give satisfying results, because they do not resolve sufficiently the near specular scatter of possible low cost mirror material candidates. The measurement of the BRDF offers a better solution than the traditional approach of placing a detector in the specular reflected beam path. However, due to the requirement of high angular resolution in the range of 1 mrad (0.057°) or better and the challenge of measuring high dynamic differences between the specular peak and the scatter signal, typical commercial scanning goniophotometers capable of this are rare. These instruments also face the disadvantages of impractically long acquisition times and, to reach the high angular resolution, occupy a large space (several meters side length). We have taken on the appealing idea of a parallel imaging goniophotometer and designed a prototype based on this principle. A mirrored ellipsoid is used to redirect the reflected light coming from a sample towards a camera with a fisheye lens. This way the complete light distribution is captured simultaneously. A key feature allows the distinction of the high intensity specular peak and the low intensity scatter. In this article we explain the prototype design and demonstrate its functionality based on comparison measurements done with a commercial scanning goniophotometer. We identify limitations related in part to the concept and in part to the specific prototype and suggest improvements. Finally we conclude that the concept is well suitable for the analysis of near specular scatter of mirror materials, although less adequate for the analysis of rough surfaces that require a full 180° view angle. Results obtained with this instrument are useful to evaluate the performance of a reflector material for a specific concentrating solar collector design and also serve in other applications that require near specular scatter analysis like degradation and soiling research.

Lateral Temperature-Gradient Method for High-Throughput Characterization of Material Processing by Millisecond Laser Annealing.

PubMed

Bell, Robert T; Jacobs, Alan G; Sorg, Victoria C; Jung, Byungki; Hill, Megan O; Treml, Benjamin E; Thompson, Michael O

2016-09-12

A high-throughput method for characterizing the temperature dependence of material properties following microsecond to millisecond thermal annealing, exploiting the temperature gradients created by a lateral gradient laser spike anneal (lgLSA), is presented. Laser scans generate spatial thermal gradients of up to 5 °C/μm with peak temperatures ranging from ambient to in excess of 1400 °C, limited only by laser power and materials thermal limits. Discrete spatial property measurements across the temperature gradient are then equivalent to independent measurements after varying temperature anneals. Accurate temperature calibrations, essential to quantitative analysis, are critical and methods for both peak temperature and spatial/temporal temperature profile characterization are presented. These include absolute temperature calibrations based on melting and thermal decomposition, and time-resolved profiles measured using platinum thermistors. A variety of spatially resolved measurement probes, ranging from point-like continuous profiling to large area sampling, are discussed. Examples from annealing of III-V semiconductors, CdSe quantum dots, low-κ dielectrics, and block copolymers are included to demonstrate the flexibility, high throughput, and precision of this technique.

Topological Insulators: A New Platform for Fundamental Science and Applications

NASA Astrophysics Data System (ADS)

Bansil, Arun

2013-03-01

Topological insulators constitute a new phase of quantum matter whose recent discovery has focused world-wide attention on wide-ranging phenomena in materials driven by spin-orbit coupling effects well beyond their traditional role in determining magnetic properties. I will discuss how by exploiting electronic structure techniques we have been able to predict and understand the characteristics of many new classes of binary, ternary and quaternary topologically interesting systems. The flexibility of chemical, structural and magnetic parameters so obtained is the key ingredient for exploring fundamental science questions, including novel spin-textures and exotic superconducting states, as well as for the realization of multi-functional topological devices for thermoelectric, spintronics, information processing and other applications. I will also highlight new insights that have been enabled through our material-specific modeling of angle-resolved photoemission (ARPES) and scanning tunneling (STS) spectroscopies of topological surface states, including effects of the photoemission and tunneling matrix element, which is well-known to be important for a robust interpretation of various highly resolved spectroscopies. Work supported by the Materials Science & Engineering Division, Basic Energy Sciences, U. S. D. O. E.

Functional imaging of photovoltaic materials

NASA Astrophysics Data System (ADS)

Leite, Marina

For the past two decades, extensive efforts have been made to increase the short-circuit current (Jsc) of non-epitaxial solar cells to achieve higher efficiency devices. Yet, improvements in the overall device performance are still limited by the open-circuit voltage (Voc). We address this critical limiting factor of all promising materials for photovoltaics by realizing a novel nanoscale imaging platform with unprecedented spatial resolution (<100 nm), based on a variant of Kelvin-probe force microscopy. We mapped the local Voc of a variety of inorganic materials, and measured local changes >150 mV in CIGS, not resolved by conventional electrical measurements. To identify the origin of the instability frequently observed in perovskite solar cells, we leveraged our recently developed method to scan one frame in 16 seconds to spatially and temporally resolve their photo-voltage. Surprisingly, we observed local and reversible changes in the Voc of the devices upon post-illumination treatments. Our innovative functional imaging is non destructive and can be applied to other optoelectronic devices, such as LEDs and photodetectors. The author acknowledge APS and NSF (Award # 16-10833) for funding.

Measurement of Thicknesses of High-κ Gate-Dielectric Films on Silicon by Angle-Resolved XPS

NASA Astrophysics Data System (ADS)

Powell, Cedric; Smekal, Werner; Werner, Wolfgang

2006-03-01

We report on the use of a new NIST database for the Simulation of Electron Spectra for Surface Analysis (SESSA) in measuring thicknesses of candidate high-κ gate-dielectric materials (HfO2, HfSiO4, ZrO2, and ZrSiO4) on silicon by angle-resolved XPS. For conventional measurements of film thicknesses, effective attenuation lengths (EALs) have been computed for these materials from SESSA as a function of film thickness and photoelectron emission angle (i.e., to simulate the effects of tilting the sample). These EALs are believed to be more accurate than similar EALs obtained from the transport approximation because realistic cross sections are used for both elastic and inelastic scattering in the film and substrate materials. We also present ``calibration curves'' showing calculated ratios of selected photoelectron intensities from thin films of HfO2 on Si with an intermediate SiO2 layer. These ratios provide a simple and convenient means of determining the thicknesses of SiO2 and HfO2 films for particular measurement conditions.

Self-Assembly Driven Aggregation-Induced Emission of Copper Nanoclusters: A Novel Technology for Lighting.

PubMed

Liu, Yi; Yao, Dong; Zhang, Hao

2018-04-18

Because of the specific properties including HOMO-LUMO electronic transition, size-dependent fluorescent emission, and intense light absorption, metal nanoclusters (NCs) have been considered to be one of the most competitive color conversion materials in light-emitting diodes (LEDs). However, the monotonous emission color and the low emission stability and intensity of individual metal NCs strongly limit their universal application. Inspired by the concept of "aggregation-induced emission" (AIE), the utilization of highly ordered metal NC assemblies opens a door to resolve these problems. After self-assembly, the emission stability and intensity of metal NC assemblies are enhanced. At the same time, the emission color of metal NC assemblies become tunable. We termed this process as self-assembly driven AIE of metal NCs. In this review, we use Cu NCs as the example to convey the concept that the compact and ordered arrangement can efficiently improve the metal NCs' emission stability, tunability, and intensity. We first introduce the synthesis of 2D Cu NC self-assemblies and their emissions. We further summarize some of the factors that can affect the emissions of 2D Cu NC self-assemblies. We then discuss the utilization of 2D Cu NC self-assemblies as color conversion materials for LEDs. At last, we outline current challenges and our perspectives on the development of this area.

Radar interferometry offers new insights into threats to the Angkor site.

PubMed

Chen, Fulong; Guo, Huadong; Ma, Peifeng; Lin, Hui; Wang, Cheng; Ishwaran, Natarajan; Hang, Peou

2017-03-01

The conservation of World Heritage is critical to the cultural and social sustainability of regions and nations. Risk monitoring and preventive diagnosis of threats to heritage sites in any given ecosystem are a complex and challenging task. Taking advantage of the performance of Earth Observation technologies, we measured the impacts of hitherto imperceptible and poorly understood factors of groundwater and temperature variations on the monuments in the Angkor World Heritage site (400 km 2 ). We developed a two-scale synthetic aperture radar interferometry (InSAR) approach. We describe spatial-temporal displacements (at millimeter-level accuracy), as measured by high-resolution TerraSAR/TanDEM-X satellite images, to provide a new solution to resolve the current controversy surrounding the potential structural collapse of monuments in Angkor. Multidisciplinary analysis in conjunction with a deterioration kinetics model offers new insights into the causes that trigger the potential decline of Angkor monuments. Our results show that pumping groundwater for residential and touristic establishments did not threaten the sustainability of monuments during 2011 to 2013; however, seasonal variations of the groundwater table and the thermodynamics of stone materials are factors that could trigger and/or aggravate the deterioration of monuments. These factors amplify known impacts of chemical weathering and biological alteration of temple materials. The InSAR solution reported in this study could have implications for monitoring and sustainable conservation of monuments in World Heritage sites elsewhere.

Radar interferometry offers new insights into threats to the Angkor site

PubMed Central

Chen, Fulong; Guo, Huadong; Ma, Peifeng; Lin, Hui; Wang, Cheng; Ishwaran, Natarajan; Hang, Peou

2017-01-01

The conservation of World Heritage is critical to the cultural and social sustainability of regions and nations. Risk monitoring and preventive diagnosis of threats to heritage sites in any given ecosystem are a complex and challenging task. Taking advantage of the performance of Earth Observation technologies, we measured the impacts of hitherto imperceptible and poorly understood factors of groundwater and temperature variations on the monuments in the Angkor World Heritage site (400 km2). We developed a two-scale synthetic aperture radar interferometry (InSAR) approach. We describe spatial-temporal displacements (at millimeter-level accuracy), as measured by high-resolution TerraSAR/TanDEM-X satellite images, to provide a new solution to resolve the current controversy surrounding the potential structural collapse of monuments in Angkor. Multidisciplinary analysis in conjunction with a deterioration kinetics model offers new insights into the causes that trigger the potential decline of Angkor monuments. Our results show that pumping groundwater for residential and touristic establishments did not threaten the sustainability of monuments during 2011 to 2013; however, seasonal variations of the groundwater table and the thermodynamics of stone materials are factors that could trigger and/or aggravate the deterioration of monuments. These factors amplify known impacts of chemical weathering and biological alteration of temple materials. The InSAR solution reported in this study could have implications for monitoring and sustainable conservation of monuments in World Heritage sites elsewhere. PMID:28275729

Challenges in the repair of large abdominal wall hernias in Nigeria: review of available options in resource limited environments.

PubMed

Ezeome, E R; Nwajiobi, C E

2010-06-01

To evaluate the challenges and outcome of management of large abdominal wall hernias in a resource limited environment and highlight the options available to surgeons in similar conditions. A review of prospectively collected data on large abdominal wall hernias managed between 2003 and 2009. University of Nigeria Teaching Hospital, Enugu, Nigeria and surrounding hospitals. Patients with hernias more than 4 cm in their largest diameter, patients with closely sited multiple hernias or failed previous repairs and in whom the surgeon considers direct repair inappropriate. Demographics of patients with large hernias, methods of hernia repair, recurrences, early and late complications following the repair. There were 41 patients, comprising 28 females and 13 males with ages 14 - 73 years. Most (53.7%) were incisional hernias. Gynecological surgeries (66.7%) were the most common initiating surgeries. Fifteen of the patients (36.6%) have had failed previous repairs, 41.5% were obese, five patients presented with intestinal obstruction. Thirty nine of the hernias were repaired with prolene mesh, one with composite mesh and one by danning technique. Most of the patients had extra peritoneal mesh placement. Three patients needed ventilator support. After a mean follow up of 18.6 months, there was a single failed repair. Two post op deaths were related to respiratory distress. There were 12 wound infection and 8 superficial wound dehiscence, all of which except one resolved with dressing. One reoperation was done following mesh infection and extrusion. Large abdominal wall hernia repair in resource limited environments present several challenges with wound infection and respiratory distress being the most notable. Surgeons who embark on it in these environments must be prepared t o secure the proper tissue replacement materials and have adequate ventilation support.

Factor analysis of submicron particle size distributions near a major United States-Canada trade bridge.

PubMed

Ogulei, David; Hopke, Philip K; Ferro, Andrea R; Jaques, Peter A

2007-02-01

A factor analytic model has been applied to resolve and apportion particles based on submicron particle size distributions downwind of a United States-Canada bridge in Buffalo, NY. The sites chosen for this study were located at gradually increasing distances downwind of the bridge complex. Seven independent factors were resolved, including four factors that were common to all of the five sites considered. The common factors were generally characterized by the existence of two or more number and surface area modes. The seven factors resolved were identified as follows: fresh tail-pipe diesel exhaust, local/street diesel traffic, aged/evolved diesel particles, spark-ignition gasoline emissions, background urban emissions, heavy-duty diesel agglomerates, and secondary/transported material. Submicron (<0.5 microm) and ultrafine (<0.1 microm) particle emissions downwind of the bridge were dominated by commercial diesel truck emissions. Thus, this study obtained size distinction between fresh versus aged vehicle exhaust and spark-ignition versus diesel emissions based on the measured high time-resolution particle number concentrations. Because this study mainly used particles <300 nm in diameter, some sources that would usually exhibit number modes >100 nm were not resolved. Also, the resolved profiles suggested that the major number mode for fresh tailpipe diesel exhaust might exist below the detection limit of the spectrometer used. The average particle number contributions from the resolved factors were highest closest to the bridge.

Filament capturing with the multimaterial moment-of-fluid method*

DOE PAGES

Jemison, Matthew; Sussman, Mark; Shashkov, Mikhail

2015-01-15

A novel method for capturing two-dimensional, thin, under-resolved material configurations, known as “filaments,” is presented in the context of interface reconstruction. This technique uses a partitioning procedure to detect disconnected regions of material in the advective preimage of a cell (indicative of a filament) and makes use of the existing functionality of the Multimaterial Moment-of-Fluid interface reconstruction method to accurately capture the under-resolved feature, while exactly conserving volume. An algorithm for Adaptive Mesh Refinement in the presence of filaments is developed so that refinement is introduced only near the tips of filaments and where the Moment-of-Fluid reconstruction error is stillmore » large. Comparison to the standard Moment-of-Fluid method is made. As a result, it is demonstrated that using filament capturing at a given resolution yields gains in accuracy comparable to introducing an additional level of mesh refinement at significantly lower cost.« less

Resolving the percentage of component terrains within single resolution elements

NASA Technical Reports Server (NTRS)

Marsh, S. E.; Switzer, P.; Kowalik, W. S.; Lyon, R. J. P.

1980-01-01

An approximate maximum likelihood technique employing a widely available discriminant analysis program is discussed that has been developed for resolving the percentage of component terrains within single resolution elements. The method uses all four channels of Landsat data simultaneously and does not require prior knowledge of the percentage of components in mixed pixels. It was tested in five cases that were chosen to represent mixtures of outcrop, soil and vegetation which would typically be encountered in geologic studies with Landsat data. For all five cases, the method proved to be superior to single band weighted average and linear regression techniques and permitted an estimate of the total area occupied by component terrains to within plus or minus 6% of the true area covered. Its major drawback is a consistent overestimation of the pixel component percent of the darker materials (vegetation) and an underestimation of the pixel component percent of the brighter materials (sand).

Reduced photoconductivity observed by time-resolved terahertz spectroscopy in metal nanofilms with and without adhesion layers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alberding, Brian G.; Heilweil, Edwin J., E-mail: edwin.heilweil@nist.gov; Kushto, Gary P.

2016-05-30

Non-contact, optical time-resolved terahertz spectroscopy has been used to study the transient photoconductivity of nanometer-scale metallic films deposited on the fused quartz substrates. Samples of 8 nm thick gold or titanium show an instrument-limited (ca. 0.5 ps) decrease in conductivity following photoexcitation due to electron-phonon coupling and subsequent increased lattice temperatures which increases charge carrier scattering. In contrast, for samples of 8 nm gold with a 4 nm adhesion layer of titanium or chromium, a ca. 70 ps rise time for the lattice temperature increase is observed. These results establish the increased transient terahertz transmission sign change of metallic compared to semiconductor materials.more » The results also suggest nanoscale gold films that utilize an adhesion material do not consist of distinct layers.« less

An Improved Neutron Transport Algorithm for HZETRN

NASA Technical Reports Server (NTRS)

Slaba, Tony C.; Blattnig, Steve R.; Clowdsley, Martha S.; Walker, Steven A.; Badavi, Francis F.

2010-01-01

Long term human presence in space requires the inclusion of radiation constraints in mission planning and the design of shielding materials, structures, and vehicles. In this paper, the numerical error associated with energy discretization in HZETRN is addressed. An inadequate numerical integration scheme in the transport algorithm is shown to produce large errors in the low energy portion of the neutron and light ion fluence spectra. It is further shown that the errors result from the narrow energy domain of the neutron elastic cross section spectral distributions, and that an extremely fine energy grid is required to resolve the problem under the current formulation. Two numerical methods are developed to provide adequate resolution in the energy domain and more accurately resolve the neutron elastic interactions. Convergence testing is completed by running the code for various environments and shielding materials with various energy grids to ensure stability of the newly implemented method.

Challenges of the NGSS for Future Geoscience Education

NASA Astrophysics Data System (ADS)

Wysession, M. E.; Colson, M.; Duschl, R. A.; Lopez, R. E.; Messina, P.; Speranza, P.

2013-12-01

The new Next Generation Science Standards (NGSS), which spell out a set of K-12 performance expectations for life science, physical science, and Earth and space science (ESS), pose a variety of opportunities and challenges for geoscience education. Among the changes recommended by the NGSS include establishing ESS on an equal footing with both life science and physical sciences, at the full K-12 level. This represents a departure from the traditional high school curriculum in most states. In addition, ESS is presented as a complex, integrated, interdisciplinary, quantitative Earth Systems-oriented set of sciences that includes complex and politically controversial topics such as climate change and human impacts. The geoscience communities will need to mobilize in order to assist and aid in the full implementation of ESS aspects of the NGSS in as many states as possible. In this context, the NGSS highlight Earth and space science to an unprecedented degree. If the NGSS are implemented in an optimal manner, a year of ESS will be taught in both middle and high school. In addition, because of the complexity and interconnectedness of the ESS content (with material such as climate change and human sustainability), it is recommended (Appendix K of the NGSS release) that much of it be taught following physics, chemistry, and biology. However, there are considerable challenges to a full adoption of the NGSS. A sufficient work force of high school geoscientists qualified in modern Earth Systems Science does not exist and will need to be trained. Many colleges do not credit high school geoscience as a lab science with respect to college admission. The NGSS demand curricular practices that include analyzing and interpreting real geoscience data, and these curricular modules do not yet exist. However, a concerted effort on the part of geoscience research and education organizations can help resolve these challenges.

Detection and use of HT and DT gamma rays to diagnose mix in ICF capsules

NASA Astrophysics Data System (ADS)

Schmitt, M. J.; Kim, Y. H.; Herrmann, H. W.; McEvoy, A. M.; Zylstra, A.; Leatherland, A.; Gales, S.

2015-11-01

Recent results from Omega capsule implosion experiments containing HT-rich gas mixtures indicate that the 19.8 MeV gamma ray from aneutronic HT fusion can be measured using existing time-resolved gas Cherenkov detectors (GCDs). Additional dedicated experiments to characterize HT- γ emission in ICF experiments already have been planned. The concurrent temporally-resolved measurement of both HT- γs and DT- γs opens the door for in-depth exploration of interface mix in gas-filled ICF capsules. We propose a method to temporally resolve and observe the evolution of shell material into the capsule core as a function of fuel/shell interface temperature (which can be varied by varying the capsule shell thickness). Our proposed method uses a CD-lined plastic capsule filled with 50/50 HT gas and diagnosed using GCDs to temporally resolve both the HT ``clean'' and DT ``mix'' gamma ray burn histories. It will be shown that these burn history profiles are sensitive to the depth to which shell material mixes into the gas region. An experiment to observe these differences as a function of capsule shell thickness is proposed to determine if interface mixing is consistent with thermal diffusion (λion ~Tion2 /Zion2 ρ) at the gas/shell interface. Since hydrodynamic mixing from shell perturbations, such as the mounting stalk and glue, could complicate these types of capsule-averaged temporal measurements, simulations including their effects also will be shown. This research supported by the US DOE/NNSA, performed in part at LANL, operated by LANS LLC under contract DE-AC52-06NA25396.

Mesoporous g-C₃N₄ Nanosheets: Synthesis, Superior Adsorption Capacity and Photocatalytic Activity.

PubMed

Li, Dong-Feng; Huang, Wei-Qing; Zou, Lan-Rong; Pan, Anlian; Huang, Gui-Fang

2018-08-01

Elimination of pollutants from water is one of the greatest challenges in resolving global environmental issues. Herein, we report a high-surface-area mesoporous g-C3N4 nanosheet with remarkable high adsorption capacity and photocatalytic performance, which is prepared through directly polycondensation of urea followed by a consecutive one-step thermal exfoliation strategy. This one-pot method to prepare mesoporous g-C3N4 nanosheet is facile and rapid in comparison with others. The superior adsorption capacity of the fabricated mesoporous g-C3N4 nanostructures is demonstrated by a model organic pollutant-methylene blue (MB), which is up to 72.2 mg/g, about 6 times as that of the largest value of various g-C3N4 adsorbents reported so far. Moreover, this kind of porous g-C3N4 nanosheet exhibits high photocatalytic activity to MB and phenol degradation. Particularly, the regenerated samples show excellent performance of pollutant removal after consecutive adsorption/degradation cycles. Therefore, this mesoporous g-C3N4 nanosheet may be an attractive robust metal-free material with great promise for organic pollutant elimination.

Micro-porous layer stochastic reconstruction and transport parameter determination

NASA Astrophysics Data System (ADS)

El Hannach, Mohamed; Singh, Randhir; Djilali, Ned; Kjeang, Erik

2015-05-01

The Micro-Porous Layer (MPL) is a porous, thin layer commonly used in fuel cells at the interfaces between the catalyst layers and gas diffusion media. It is generally made from spherical carbon nanoparticles and PTFE acting as hydrophobic agent. The scale and brittle nature of the MPL structure makes it challenging to study experimentally. In the present work, a 3D stochastic model is developed to virtually reconstruct the MPL structure. The carbon nanoparticle and PTFE phases are fully distinguished by the algorithm. The model is shown to capture the actual structural morphology of the MPL and is validated by comparing the results to available experimental data. The model shows a good capability in generating a realistic MPL successfully using a set of parameters introduced to capture specific morphological features of the MPL. A numerical model that resolves diffusive transport at the pore scale is used to compute the effective transport properties of the reconstructed MPLs. A parametric study is conducted to illustrate the capability of the model as an MPL design tool that can be used to guide and optimize the functionality of the material.

Characterization of perovskite solar cells: Towards a reliable measurement protocol

NASA Astrophysics Data System (ADS)

Zimmermann, Eugen; Wong, Ka Kan; Müller, Michael; Hu, Hao; Ehrenreich, Philipp; Kohlstädt, Markus; Würfel, Uli; Mastroianni, Simone; Mathiazhagan, Gayathri; Hinsch, Andreas; Gujar, Tanaji P.; Thelakkat, Mukundan; Pfadler, Thomas; Schmidt-Mende, Lukas

2016-09-01

Lead halide perovskite solar cells have shown a tremendous rise in power conversion efficiency with reported record efficiencies of over 20% making this material very promising as a low cost alternative to conventional inorganic solar cells. However, due to a differently severe "hysteretic" behaviour during current density-voltage measurements, which strongly depends on scan rate, device and measurement history, preparation method, device architecture, etc., commonly used solar cell measurements do not give reliable or even reproducible results. For the aspect of commercialization and the possibility to compare results of different devices among different laboratories, it is necessary to establish a measurement protocol which gives reproducible results. Therefore, we compare device characteristics derived from standard current density-voltage measurements with stabilized values obtained from an adaptive tracking of the maximum power point and the open circuit voltage as well as characteristics extracted from time resolved current density-voltage measurements. Our results provide insight into the challenges of a correct determination of device performance and propose a measurement protocol for a reliable characterisation which is easy to implement and has been tested on varying perovskite solar cells fabricated in different laboratories.

Reaction Analysis of Shocked Nitromethane using Extended Lagrangian Born-Oppenheimer Molecular Dynamics

NASA Astrophysics Data System (ADS)

Perriot, Romain; Kober, Ed; Mniszewski, Sue; Martinez, Enrique; Niklasson, Anders; Yang, Ping; McGrane, Shawn; Cawkwell, Marc

2017-06-01

Characterizing the complex, rapid reactions of energetic materials under conditions of high temperatures and pressures presents strong experimental and computational challenges. The recently developed extended Lagrangian Born-Oppenheimer molecular dynamics formalism enables the long-term conservation of the total energy in microcanonical trajectories, and using a density functional tight binding formulation provides good chemical accuracy. We use this combined approach to study the evolution of temperature, pressure, and chemical species in shock-compressed liquid nitromethane over hundreds of picoseconds. The chemical species seen in nitromethane under shock compression are compared with those seen under static high temperature conditions. A reduced-order representation of the complex sequence of chemical reactions that characterize this system has been developed from the molecular dynamics simulations by focusing on classes of chemical reactions rather than specific molecular species. Time-resolved infra-red vibrational spectra were also computed from the molecular trajectories and compared to the chemical analysis. These spectra provide a time history of the species present in the system that can be compared directly with recent experiments at LANL.

Spike processing with a graphene excitable laser

PubMed Central

Shastri, Bhavin J.; Nahmias, Mitchell A.; Tait, Alexander N.; Rodriguez, Alejandro W.; Wu, Ben; Prucnal, Paul R.

2016-01-01

Novel materials and devices in photonics have the potential to revolutionize optical information processing, beyond conventional binary-logic approaches. Laser systems offer a rich repertoire of useful dynamical behaviors, including the excitable dynamics also found in the time-resolved “spiking” of neurons. Spiking reconciles the expressiveness and efficiency of analog processing with the robustness and scalability of digital processing. We demonstrate a unified platform for spike processing with a graphene-coupled laser system. We show that this platform can simultaneously exhibit logic-level restoration, cascadability and input-output isolation—fundamental challenges in optical information processing. We also implement low-level spike-processing tasks that are critical for higher level processing: temporal pattern detection and stable recurrent memory. We study these properties in the context of a fiber laser system and also propose and simulate an analogous integrated device. The addition of graphene leads to a number of advantages which stem from its unique properties, including high absorption and fast carrier relaxation. These could lead to significant speed and efficiency improvements in unconventional laser processing devices, and ongoing research on graphene microfabrication promises compatibility with integrated laser platforms. PMID:26753897

The Priority and Challenge of High-Power Performance of Low-Platinum Proton-Exchange Membrane Fuel Cells.

PubMed

Kongkanand, Anusorn; Mathias, Mark F

2016-04-07

Substantial progress has been made in reducing proton-exchange membrane fuel cell (PEMFC) cathode platinum loadings from 0.4-0.8 mgPt/cm(2) to about 0.1 mgPt/cm(2). However, at this level of cathode Pt loading, large performance loss is observed at high-current density (>1 A/cm(2)), preventing a reduction in the overall stack cost. This next developmental step is being limited by the presence of a resistance term exhibited at these lower Pt loadings and apparently due to a phenomenon at or near the catalyst surface. This issue can be addressed through the design of catalysts with high and stable Pt dispersion as well as through development and implementation of ionomers designed to interact with Pt in a way that does not constrain oxygen reduction reaction rates. Extrapolating from progress made in past decades, we are optimistic that the concerted efforts of materials and electrode designers can resolve this issue, thus enabling a large step toward fuel cell vehicles that are affordable for the mass market.

A novel integrated assessment methodology of urban water reuse.

PubMed

Listowski, A; Ngo, H H; Guo, W S; Vigneswaran, S

2011-01-01

Wastewater is no longer considered a waste product and water reuse needs to play a stronger part in securing urban water supply. Although treatment technologies for water reclamation have significantly improved the question that deserves further analysis is, how selection of a particular wastewater treatment technology relates to performance and sustainability? The proposed assessment model integrates; (i) technology, characterised by selected quantity and quality performance parameters; (ii) productivity, efficiency and reliability criteria; (iii) quantitative performance indicators; (iv) development of evaluation model. The challenges related to hierarchy and selections of performance indicators have been resolved through the case study analysis. The goal of this study is to validate a new assessment methodology in relation to performance of the microfiltration (MF) technology, a key element of the treatment process. Specific performance data and measurements were obtained at specific Control and Data Acquisition Points (CP) to satisfy the input-output inventory in relation to water resources, products, material flows, energy requirements, chemicals use, etc. Performance assessment process contains analysis and necessary linking across important parametric functions leading to reliable outcomes and results.

The evolution of porcine embryo in vitro production.

PubMed

Grupen, Christopher G

2014-01-01

The in vitro production of porcine embryos has presented numerous challenges to researchers over the past four decades. Some of the problems encountered were specific to porcine gametes and embryos and needed the concerted efforts of many to overcome. Gradually, porcine embryo in vitro production systems became more reliable and acceptable rates of blastocyst formation were achieved. Despite the significant improvements, the problem of polyspermic fertilization has still not been adequately resolved and the embryo in vitro culture conditions are still considered to be suboptimal. Whereas early studies focused on increasing our understanding of the reproductive processes involved, the technology evolved to the point where in vitro-matured oocytes and in vitro-produced embryos could be used as research material for developing associated reproductive technologies, such as SCNT and embryo cryopreservation. Today, the in vitro procedures used to mature oocytes and culture embryos are integral to the production of transgenic pigs by SCNT. This review discusses the major achievements, advances, and knowledge gained from porcine embryo in vitro production studies and highlights the future research perspectives of this important technology. Copyright © 2014 Elsevier Inc. All rights reserved.

Quantitative and Isolated Measurement of Far-Field Light Scattering by a Single Nanostructure

NASA Astrophysics Data System (ADS)

Kim, Donghyeong; Jeong, Kwang-Yong; Kim, Jinhyung; Ee, Ho-Seok; Kang, Ju-Hyung; Park, Hong-Gyu; Seo, Min-Kyo

2017-11-01

Light scattering by nanostructures has facilitated research on various optical phenomena and applications by interfacing the near fields and free-propagating radiation. However, direct quantitative measurement of far-field scattering by a single nanostructure on the wavelength scale or less is highly challenging. Conventional back-focal-plane imaging covers only a limited solid angle determined by the numerical aperture of the objectives and suffers from optical aberration and distortion. Here, we present a quantitative measurement of the differential far-field scattering cross section of a single nanostructure over the full hemisphere. In goniometer-based far-field scanning with a high signal-to-noise ratio of approximately 27.4 dB, weak scattering signals are efficiently isolated and detected under total-internal-reflection illumination. Systematic measurements reveal that the total and differential scattering cross sections of a Au nanorod are determined by the plasmonic Fabry-Perot resonances and the phase-matching conditions to the free-propagating radiation, respectively. We believe that our angle-resolved far-field measurement scheme provides a way to investigate and evaluate the physical properties and performance of nano-optical materials and phenomena.

Biomimetics--using nature to inspire human innovation.

PubMed

Bar-Cohen, Yoseph

2006-03-01

Evolution has resolved many of nature's challenges leading to lasting solutions. Nature has always inspired human achievements and has led to effective materials, structures, tools, mechanisms, processes, algorithms, methods, systems, and many other benefits (Bar-Cohen Y (ed) 2005 Biomimetics-Biologically Inspired Technologies (Boca Raton, FL: CRC Press) pp 1-552). This field, which is known as biomimetics, offers enormous potential for inspiring new capabilities for exciting future technologies. There are numerous examples of biomimetic successes that involve making simple copies, such as the use of fins for swimming. Others examples involved greater mimicking complexity including the mastery of flying that became possible only after the principles of aerodynamics were better understood. Some commercial implementations of biomimetics, including robotic toys and movie subjects, are increasingly appearing and behaving like living creatures. More substantial benefits of biomimetics include the development of prosthetics that closely mimic real limbs and sensory-enhancing microchips that are interfaced with the brain to assist in hearing, seeing and controlling instruments. A review is given of selected areas that were inspired by nature, and an outlook for potential development in biomimetics is presented.

Gas gun shock experiments with single-pulse x-ray phase contrast imaging and diffraction at the Advanced Photon Source

NASA Astrophysics Data System (ADS)

Luo, S. N.; Jensen, B. J.; Hooks, D. E.; Fezzaa, K.; Ramos, K. J.; Yeager, J. D.; Kwiatkowski, K.; Shimada, T.

2012-07-01

The highly transient nature of shock loading and pronounced microstructure effects on dynamic materials response call for in situ, temporally and spatially resolved, x-ray-based diagnostics. Third-generation synchrotron x-ray sources are advantageous for x-ray phase contrast imaging (PCI) and diffraction under dynamic loading, due to their high photon fluxes, high coherency, and high pulse repetition rates. The feasibility of bulk-scale gas gun shock experiments with dynamic x-ray PCI and diffraction measurements was investigated at the beamline 32ID-B of the Advanced Photon Source. The x-ray beam characteristics, experimental setup, x-ray diagnostics, and static and dynamic test results are described. We demonstrate ultrafast, multiframe, single-pulse PCI measurements with unprecedented temporal (<100 ps) and spatial (˜2 μm) resolutions for bulk-scale shock experiments, as well as single-pulse dynamic Laue diffraction. The results not only substantiate the potential of synchrotron-based experiments for addressing a variety of shock physics problems, but also allow us to identify the technical challenges related to image detection, x-ray source, and dynamic loading.

Achieving Transformational Materials Performance in a New Era of Science

ScienceCinema

Sarrao, John

2017-12-22

The inability of current materials to meet performance requirements is a key stumbling block for addressing grand challenges in energy and national security. Fortunately, materials research is on the brink of a new era - a transition from observation and validation of materials properties to prediction and control of materials performance. In this talk, I describe the nature of the current challenge, the prospects for success, and a specific facility concept, MaRIE, that will provide the needed capabilities to meet these challenges, especially for materials in extreme environments. MaRIE, for Matter-Radiation Interactions in Extremes, is Los Alamos' concept to realize this vision of 21st century materials research. This vision will be realized through enhancements to the current LANSCE accelerator, development of a fourth-generation x-ray light source co-located with the proton accelerator, and a comprehensive synthesis and characterization facility focused on controlling complex materials and the defect/structure link to materials performance.

Water-induced morphology changes in BaO/γ-Al2O3 NOx storage materials: an FTIR, TPD, and time-resolved synchrotron XRD study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Szanyi, Janos; Kwak, Ja Hun; Kim, Do Heui

2007-03-29

The effect of water on the morphology of BaO/Al2O3-based NOx storage materials was investigated using Fourier transform infrared spectroscopy, temperature programmed desorption, and time-resolved synchrotron X-ray diffraction techniques. The results of this multi-spectroscopy study reveal that, in the presence of water, surface Ba-nitrates convert to bulk nitrates, and water facilitates the formation of large Ba(NO3)2 particles. This process is completely reversible, i.e. after the removal of water from the storage material a significant fraction of the bulk nitrates re-convert to surface nitrates. NO2 exposure of a H2O-containing (wet) BaO/Al2O3 sample results in the formation of nitrites and bulk nitrates exclusively,more » i.e. no surface nitrates form. After further exposure to NO2, the nitrites completely convert to bulk nitrates. The amount of NOx taken up by the storage material is, however, essentially unaffected by the presence of water, regardless of whether the water was dosed prior to or after NO2 exposure. Based on the results of this study we are now able to explain most of the observations reported in the literature on the effect of water on NOx uptake on similar storage materials.« less

Materials Development in the Colombian Context: Some Considerations about Its Benefits and Challenges

ERIC Educational Resources Information Center

Ramos Holguín, Bertha; Aguirre Morales, Jahir

2014-01-01

Materials development is a field of study which has recently acquired significant importance in the Colombian context due to the fact that teachers, as materials developers, consider materials development as an area of knowledge that helps them to improve their teaching practices. However, the rationale, the gains as well as the challenges that…

Forest landscape restoration: increasing the positive impacts of forest restoration or simply the area under tree cover?

Treesearch

Stephanie Mansourian; John A. Stanturf; Mercy Afua Adutwumwaa Derkyi; Vera Lex Engel

2017-01-01

Restoring forest landscapes is critical in the face of continued global forest loss and degradation. In this article, weexplore some challenges underlying the delivery of global commitments to restore forest landscapes. We propose that threefundamental questions need to be resolved upfront for the effective implementation of Forest Landscape...

News

Science.gov Websites

attendees read about one of the four mission area working group chairmen who led a team to think combat rescue support for Inherent Resolve, and was one of the seven Airmen killed in an HH-60G Pave Hawk innovatively in tackling one of the Air Force's toughest agile combat support challenges during the San Antonio

Ganas of Showing the Way: A Grounded Theory Study of Hispanic Presidents in Higher Education

ERIC Educational Resources Information Center

Barrios Gutierrez, Eugenio

2010-01-01

In this dissertation, based on classical grounded theory (Glaser & Strauss, 1967, 1971; Glaser, 1978, 1992, 1993, 1994a, 1994b, 1996, 1998, 2001, 2003, 2004), second generation Hispanic presidents and chancellors in higher education were studied to discover how they continually try to resolve second culture-coping challenges, the…

Top-Down Influence in Young Children's Linguistic Ambiguity Resolution

ERIC Educational Resources Information Center

Rabagliati, Hugh; Pylkkanen, Liina; Marcus, Gary F.

2013-01-01

Language is rife with ambiguity. Do children and adults meet this challenge in similar ways? Recent work suggests that while adults resolve syntactic ambiguities by integrating a variety of cues, children are less sensitive to top-down evidence. We test whether this top-down insensitivity is specific to syntax or a general feature of children's…

Displaced Workers: A Challenge for Voc Ed. Information Series No. 255.

ERIC Educational Resources Information Center

Clark, Donald M.

Worker displacement is a priority human resource issue that must be resolved to improve economic productivity, to further revitalize the American economy, and to cope with growing international competition. The work force and work place of the 1980s are undergoing changes that could result in ever larger scale joblessness. These changes include…

Challenges, Not Barriers: The Work and Family Issues of Women Superintendents

ERIC Educational Resources Information Center

Reecks-Rodgers, Debra Ann

2013-01-01

Prior studies have indicated that qualified female administrators have not applied for superintendency positions because of possible work/family conflicts, but little research has been done on the work/family issues encountered by women in the superintendency or on the strategies they use to resolve these issues. In response, this study is an…

47 CFR 1.1911 - Demand for payment.

Code of Federal Regulations, 2010 CFR

2010-10-01

... additional period within to challenge the existence of, or amount of the non-tax debt if such time period has... cooperate to resolve the debt. The specific content, timing, and number of demand letters depend upon the type and amount of the debt, including, e.g., any notes and the terms of agreements of the parties, and...

Shaping the Future of Foreign Language Education: FLES, Articulation, and Proficiency. Report of Central States Conference on the Teaching of Foreign Languages.

ERIC Educational Resources Information Center

Lalande, John F. II, Ed.

Selected papers from the 1988 conference on foreign language issues for the future include: "Articulation for Elementary School Foreign Language Programs: Challenges and Opportunities" (Carol Ann Pesola); "Articulation: A Resolvable Problem?" (Dale L. Lange); "Profiles of Frustration: Second Language Learners with Specific Learning Disabilities"…

Design Thinking: A Process for Developing and Implementing Lasting District Reform. Knowledge Brief

ERIC Educational Resources Information Center

Rice, Erik

2011-01-01

Traditionally, challenges such as how to sustain district reform, how to build a leadership pipeline, how to create an integrated project, or how to best intervene with struggling students would be resolved with a team of "experts" developing a solution in isolation of the stakeholders involved. By contrast, design thinking centers on the…

Identifying Specific Genes Controlling Complex Traits Through A Genome-Wide Screen For cis-Acting Regulatory Elements - An Example Using Marek's Disease

USDA-ARS?s Scientific Manuscript database

The identification of specific genes underlying phenotypic variation of complex traits remains one of the greatest challenges in biology despite having genome sequences and more powerful tools. Most genome-wide screens lack sufficient resolving power as they typically depend on linkage. One altern...

Comprehensive Identification Of Specific Genes Controlling Complex Traits Through A Genome-Wide Screen for Cis-Acting Regulatory Elements - An Example Using Marek's Disease

USDA-ARS?s Scientific Manuscript database

The comprehensive identification of genes underlying phenotypic variation of complex traits remains a major challenge. Most genome-wide screens lack sufficient resolving power as they typically depend on linkage. An alternate method is to screen for allele-specific expression (ASE), a simple yet pow...

Clinical and Pastoral Issues and Challenges in Working with the Dying and Their Families

ERIC Educational Resources Information Center

Rayburn, Carole A.

2008-01-01

How might counseling professionals interact with clients facing their own or a loved one's serious illness or death and help prepare them for this severe stress and loss? Counseling professionals are encouraged to do no harm, be sensitive to beliefs and traditions, use life stories, and help resolve unfinished business.

Enactment of Teacher Identity in Resolving Student Disagreements in Small Group Peer Interactions

ERIC Educational Resources Information Center

Sharma, Bal Krishna

2013-01-01

This study presents a sequential analysis of the enactment of teacher identity in closing disagreements among students in small group peer interactions in an advanced academic writing class. In doing so, it discusses: (a) the micro-details of how oppositional stances and opinions are constructed, challenged and/or defended; (b) the sequential…

Critical Challenges in California Community Colleges: An Interview with Carl Ehmann

ERIC Educational Resources Information Center

Frost, Robert A.

2009-01-01

This interview took place in several meetings over a period of two weeks in late spring, 2008. Carl Ehmann had spent the past five months working with multiple California community college districts to resolve numerous, and multilevel, shortages in senior leadership positions. Robert A. Frost and Ehmann had come into contact through Frost's…

Cofermentation of Glucose, Xylose, and Cellobiose by the Beetle-Associated Yeast Spathaspora passalidarum

Treesearch

Tanya M. Long; Yi-Kai Su; Jennifer Headman; Alan Higbee; Laura B. Willis; Thomas W. Jeffries

2012-01-01

Fermentation of cellulosic and hemicellulosic sugars from biomass could resolve food-versus-fuel conflicts inherent in the bioconversion of grains. However, the inability to coferment glucose and xylose is a major challenge to the economical use of lignocellulose as a feedstock. Simultaneous cofermentation of glucose, xylose, and cellobiose is problematic for most...

Understanding the wicked nature of "unmanaged recreation" in Colorado's Front Range

Treesearch

Jeffrey J. Brooks; Patricia A. Champ

2006-01-01

Unmanaged recreation presents a challenge to both researchers and managers of outdoor recreation in the United States because it is shrouded in uncertainty resulting from disagreement over the definition of the problem, the strategies for resolving the problem, and the outcomes of management. Incomplete knowledge about recreation visitors’ values and relationships with...

The Failure of Legalization in Education: Alternative Dispute Resolution and the Education for All Handicapped Children Act of 1975.

ERIC Educational Resources Information Center

Goldberg, Steven S.

1989-01-01

A federal statute provided that parents may use the judicial process to challenge educators' decisions. Describes the intent of legalization; how reaction to an adversarial system led to the use of mediation in most states; and why this alternative model is not appropriate for resolving education questions. (MLF)

Case Studies in 21st Century School Administration: Addressing Challenges for Educational Leadership

ERIC Educational Resources Information Center

Gray, David L.; Smith, Agnes

2007-01-01

Authors David L. Gray and Agnes E. Smith have written a book of cases to give prospective school leaders opportunities to resolve complex issues in K-12 school settings through reflective questions, activities, and authentic assessment tools for skill development. "Case Studies in 21st Century School Administration" presents thought-provoking case…

Angle-resolved photoemission spectroscopy with 9-eV photon-energy pulses generated in a gas-filled hollow-core photonic crystal fiber

NASA Astrophysics Data System (ADS)

Bromberger, H.; Ermolov, A.; Belli, F.; Liu, H.; Calegari, F.; Chávez-Cervantes, M.; Li, M. T.; Lin, C. T.; Abdolvand, A.; Russell, P. St. J.; Cavalleri, A.; Travers, J. C.; Gierz, I.

2015-08-01

A recently developed source of ultraviolet radiation, based on optical soliton propagation in a gas-filled hollow-core photonic crystal fiber, is applied here to angle-resolved photoemission spectroscopy (ARPES). Near-infrared femtosecond pulses of only few μJ energy generate vacuum ultraviolet radiation between 5.5 and 9 eV inside the gas-filled fiber. These pulses are used to measure the band structure of the topological insulator Bi2Se3 with a signal to noise ratio comparable to that obtained with high order harmonics from a gas jet. The two-order-of-magnitude gain in efficiency promises time-resolved ARPES measurements at repetition rates of hundreds of kHz or even MHz, with photon energies that cover the first Brillouin zone of most materials.

Velocity measurement using frequency domain interferometer and chirped pulse laser

NASA Astrophysics Data System (ADS)

Ishii, K.; Nishimura, Y.; Mori, Y.; Hanayama, R.; Kitagawa, Y.; Sekine, T.; Sato, N.; Kurita, T.; Kawashima, T.; Sunahara, A.; Sentoku, Y.; Miura, E.; Iwamoto, A.; Sakagami, H.

2017-02-01

An ultra-intense short pulse laser induces a shock wave in material. The pressure of shock compression is stronger than a few tens GPa. To characterize shock waves, time-resolved velocity measurement in nano- or pico-second time scale is needed. Frequency domain interferometer and chirped pulse laser provide single-shot time-resolved measurement. We have developed a laser-driven shock compression system and frequency domain interferometer with CPA laser. In this paper, we show the principle of velocity measurement using a frequency domain interferometer and a chirped pulse laser. Next, we numerically calculated spectral interferograms and show the time-resolved velocity measurement can be done from the phase analysis of spectral interferograms. Moreover we conduct the laser driven shock generation and shock velocity measurement. From the spectral fringes, we analyze the velocities of the sample and shockwaves.

Reprint Of: Enhanced spatially-resolved trace analysis using combined SIMS-single-stage AMS

NASA Astrophysics Data System (ADS)

Grabowski, K. S.; Groopman, E. E.; Fahey, A. J.

2018-01-01

Secondary ion mass spectrometry (SIMS) provides spatially resolved trace analysis of solid materials, but can be complicated by unresolved abundant molecular isobars. By adding a 300-kV single-stage accelerator mass spectrometer (SSAMS) as a detector for a Cameca ims 4f SIMS, one can measure more abundant positive ions from the SIMS while removing molecular isobars, thus improving very low abundance trace element and isotope analysis. This paper describes important features and capabilities of such an integrated system at the Naval Research Laboratory using charge state +1 ions. Transmission loss is compared to molecule destruction as gas flow to the molecule-destruction cell increases. As most measurements tolerate more modest abundance sensitivities than for 14C analysis, a lower gas flow is acceptable, so good transmission of 20-50% for ions of interest can be maintained for a broad range of ion masses. This new instrument has measured isotope ratios for uranium, lead, rare earths, and other elements from particulates and localized regions, with molecule destruction enabling the measurement at low SIMS mass resolving power and thus high transmission, as examples will show. This new and world-unique instrument provides improved capabilities for applications in nuclear and other forensics, geochemistry, cosmochemistry, and the development of optical, electronic, multifunctional, and structural materials.

Enhanced spatially-resolved trace analysis using combined SIMS-single-stage AMS

NASA Astrophysics Data System (ADS)

Grabowski, K. S.; Groopman, E. E.; Fahey, A. J.

2017-11-01

Secondary ion mass spectrometry (SIMS) provides spatially resolved trace analysis of solid materials, but can be complicated by unresolved abundant molecular isobars. By adding a 300-kV single-stage accelerator mass spectrometer (SSAMS) as a detector for a Cameca ims 4f SIMS, one can measure more abundant positive ions from the SIMS while removing molecular isobars, thus improving very low abundance trace element and isotope analysis. This paper describes important features and capabilities of such an integrated system at the Naval Research Laboratory using charge state +1 ions. Transmission loss is compared to molecule destruction as gas flow to the molecule-destruction cell increases. As most measurements tolerate more modest abundance sensitivities than for 14C analysis, a lower gas flow is acceptable, so good transmission of 20-50% for ions of interest can be maintained for a broad range of ion masses. This new instrument has measured isotope ratios for uranium, lead, rare earths, and other elements from particulates and localized regions, with molecule destruction enabling the measurement at low SIMS mass resolving power and thus high transmission, as examples will show. This new and world-unique instrument provides improved capabilities for applications in nuclear and other forensics, geochemistry, cosmochemistry, and the development of optical, electronic, multifunctional, and structural materials.

Optimization and comprehensive characterization of metal hydride based hydrogen storage systems using in-situ Neutron Radiography

NASA Astrophysics Data System (ADS)

Börries, S.; Metz, O.; Pranzas, P. K.; Bellosta von Colbe, J. M.; Bücherl, T.; Dornheim, M.; Klassen, T.; Schreyer, A.

2016-10-01

For the storage of hydrogen, complex metal hydrides are considered as highly promising with respect to capacity, reversibility and safety. The optimization of corresponding storage tanks demands a precise and time-resolved investigation of the hydrogen distribution in scaled-up metal hydride beds. In this study it is shown that in situ fission Neutron Radiography provides unique insights into the spatial distribution of hydrogen even for scaled-up compacts and therewith enables a direct study of hydrogen storage tanks. A technique is introduced for the precise quantification of both time-resolved data and a priori material distribution, allowing inter alia for an optimization of compacts manufacturing process. For the first time, several macroscopic fields are combined which elucidates the great potential of Neutron Imaging for investigations of metal hydrides by going further than solely 'imaging' the system: A combination of in-situ Neutron Radiography, IR-Thermography and thermodynamic quantities can reveal the interdependency of different driving forces for a scaled-up sodium alanate pellet by means of a multi-correlation analysis. A decisive and time-resolved, complex influence of material packing density is derived. The results of this study enable a variety of new investigation possibilities that provide essential information on the optimization of future hydrogen storage tanks.

Disks and cones: resolving the dusty torus with mid-infrared interferometry.

NASA Astrophysics Data System (ADS)

Tristram, K.

2015-09-01

The thermal emission of dust is one of the main possibilities to study the (dusty) material of the so-called "torus" in AGN. Observations using interferometry in the mid-infrared have, in the last ten years, resolved and characterised this emission beyond simple fits of spectral energy distributions, leading to a great leap forward in our view of the dusty material surrounding AGN. I will present the most recent results of such observations, obtained with the instrument MIDI. More than 25 active nuclei could be observed with MIDI, showing that the dust distributions are parsec sized. The sizes roughly scale with the square root of the luminosity, albeit with a much large scatter than in the near-infrared. Detailed studies of a few well resolved sources, among them the illustrious nuclei of NGC1068 and the Circinus galaxy, show a two component structure: an inner disk-like emission region which is surrounded by a polar elongated emitter. The latter shows differential absorption in line with the one-sided ionisation cones observed in the optical. These results are in qualitative agreement with recent hydrodynamic simulations of AGN tori. In general, they confirm the concept of a dusty obscurer providing viewing-angle dependent obscuration of the central engine.