Metastable Polymeric Nitrogen: The Ultimate Green High-Energy-Density Material

NASA Astrophysics Data System (ADS)

Ciezak, Jennifer

2007-06-01

High-energy-high-density materials offering increased stability, vulnerability, and environmental safety are being aggressively pursued to meet the requirements of the DoD Joint Visions and Future Force. Nearly two decades ago, it was proposed that polymeric nitrogen would exceed all of these requirements and possess nearly five times the energy of any conventional energetic material in use today. The present study details an investigation into nitrogen polymerization using a novel high-pressure approach utilizing sodium azide as the starting material. Due to the weaker bonding structure of the anionic azide chains in comparison to a N-N triple bond, one expects that the azide chains will create single-covalently bonded polymeric networks more easily than diatomic nitrogen. A polymeric form of sodium azide was synthesized at high pressures, but the material was not metastable at ambient conditions, which precluded performance testing. Quantum chemical calculations have indicated stabilization of the polymeric structure at ambient conditions may be possible with the addition of hydrogen. Vibrational spectroscopic characterization suggests that a meta-stable polymeric form of nitrogen has been synthesized under high-pressure using sodium azide/hydrogen as the starting materials. This material remains stable at ambient conditions upwards of two weeks depending on the storage conditions.

Selective Plasma Etching of Polymeric Substrates for Advanced Applications

PubMed Central

Puliyalil, Harinarayanan; Cvelbar, Uroš

2016-01-01

In today’s nanoworld, there is a strong need to manipulate and process materials on an atom-by-atom scale with new tools such as reactive plasma, which in some states enables high selectivity of interaction between plasma species and materials. These interactions first involve preferential interactions with precise bonds in materials and later cause etching. This typically occurs based on material stability, which leads to preferential etching of one material over other. This process is especially interesting for polymeric substrates with increasing complexity and a “zoo” of bonds, which are used in numerous applications. In this comprehensive summary, we encompass the complete selective etching of polymers and polymer matrix micro-/nanocomposites with plasma and unravel the mechanisms behind the scenes, which ultimately leads to the enhancement of surface properties and device performance. PMID:28335238

Dynamics of a New 5D Hyperchaotic System of Lorenz Type

NASA Astrophysics Data System (ADS)

Zhang, Fuchen; Chen, Rui; Wang, Xingyuan; Chen, Xiusu; Mu, Chunlai; Liao, Xiaofeng

Ultimate boundedness of chaotic dynamical systems is one of the fundamental concepts in dynamical systems, which plays an important role in investigating the stability of the equilibrium, estimating the Lyapunov dimension of attractors and the Hausdorff dimension of attractors, the existence of periodic solutions, chaos control, chaos synchronization. However, it is often difficult to obtain the bounds of the hyperchaotic systems due to the complex algebraic structure of the hyperchaotic systems. This paper has investigated the boundedness of solutions of a nonlinear hyperchaotic system. We have obtained the global exponential attractive set and the ultimate bound set for this system. To obtain the ellipsoidal ultimate bound, the ultimate bound of the proposed system is theoretically estimated using Lagrange multiplier method, Lyapunov stability theory and optimization theory. To show the ultimate bound region, numerical simulations are provided.

Tuning Amphiphilicity of Particles for Controllable Pickering Emulsion

PubMed Central

Wang, Zhen; Wang, Yapei

2016-01-01

Pickering emulsions with the use of particles as emulsifiers have been extensively used in scientific research and industrial production due to their edge in biocompatibility and stability compared with traditional emulsions. The control over Pickering emulsion stability and type plays a significant role in these applications. Among the present methods to build controllable Pickering emulsions, tuning the amphiphilicity of particles is comparatively effective and has attracted enormous attention. In this review, we highlight some recent advances in tuning the amphiphilicity of particles for controlling the stability and type of Pickering emulsions. The amphiphilicity of three types of particles including rigid particles, soft particles, and Janus particles are tailored by means of different mechanisms and discussed here in detail. The stabilization-destabilization interconversion and phase inversion of Pickering emulsions have been successfully achieved by changing the surface properties of these particles. This article provides a comprehensive review of controllable Pickering emulsions, which is expected to stimulate inspiration for designing and preparing novel Pickering emulsions, and ultimately directing the preparation of functional materials. PMID:28774029

Insight from first principles into the stability and magnetism of alkali-metal superoxide nanoclusters

NASA Astrophysics Data System (ADS)

Arcelus, Oier; Suaud, Nicolas; Katcho, Nebil A.; Carrasco, Javier

2017-05-01

Alkali-metal superoxides are gaining increasing interest as 2p magnetic materials for information and energy storage. Despite significant research efforts on bulk materials, gaps in our knowledge of the electronic and magnetic properties at the nanoscale still remain. Here, we focused on the role that structural details play in determining stability, electronic structure, and magnetic couplings of (MO2)n (M = Li, Na, and K, with n = 2-8) clusters. Using first-principles density functional theory based on the Perdew-Burke-Ernzerhof and Heyd-Scuseria-Ernzerhof functionals, we examined the effect of atomic structure on the relative stability of different polymorphs within each investigated cluster size. We found that small clusters prefer to form planar-ring structures, whereas non-planar geometries become more stable when increasing the cluster size. However, the crossover point depends on the nature of the alkali metal. Our analysis revealed that electrostatic interactions govern the highly ionic M-O2 bonding and ultimately control the relative stability between 2-D and 3-D geometries. In addition, we analyzed the weak magnetic couplings between superoxide molecules in (NaO2)4 clusters comparing model Hamiltonian methods based on Wannier function projections onto πg states with wave function-based multi-reference calculations.

Research on the Risk Early Warning Method of Material Supplier Performance in Power Industry

NASA Astrophysics Data System (ADS)

Chen, Peng; Zhang, Xi

2018-01-01

The early warning of supplier performance risk is still in the initial stage interiorly, and research on the early warning mechanism to identify, analyze and prevent the performance risk is few. In this paper, a new method aiming at marerial supplier performance risk in power industry is proposed, firstly, establishing a set of risk early warning indexes, Then use the ECM method to classify the indexes to form different risk grades. Then, improving Crock Ford risk quantization model by considering three indicators, including the stability of power system, economic losses and successful bid ratio to form the predictive risk grade, and ultimately using short board effect principle to form the ultimate risk grade to truly reflect the supplier performance risk. Finally, making empirical analysis on supplier performance and putting forward the counter measures and prevention strategies for different risks.

Graphene-Based Materials for Lithium-Ion Hybrid Supercapacitors.

PubMed

Ma, Yanfeng; Chang, Huicong; Zhang, Miao; Chen, Yongsheng

2015-09-23

Lithium-ion hybrid supercapacitors (LIHSs), also called Li-ion capacitors, have attracted much attention due to the combination of the rapid charge-discharge and long cycle life of supercapacitors and the high energy-storage capacity of lithium-ion batteries. Thus, LIHSs are expected to become the ultimate power source for hybrid and all-electric vehicles in the near future. As an electrode material, graphene has many advantages, including high surface area and porous structure, high electric conductivity, and high chemical and thermal stability, etc. Compared with other electrode materials, such as activated carbon, graphite, and metal oxides, graphene-based materials with 3D open frameworks show higher effective specific surface area, better control of channels, and higher conductivity, which make them better candidates for LIHS applications. Here, the latest advances in electrode materials for LIHSs are briefly summarized, with an emphasis on graphene-based electrode materials (including 3D graphene networks) for LIHS applications. An outlook is also presented to highlight some future directions. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

One-pot, exchange-free, room-temperature synthesis of sub-10 nm aqueous, noninteracting, and stable zwitterated iron oxide nanoparticles.

PubMed

Estephan, Zaki G; Hariri, Hanaa H; Schlenoff, Joseph B

2013-02-26

Stable aqueous dispersions of superparamagnetic iron oxide nanoparticles were synthesized in one step in the presence of a zwitterionic siloxane as the stabilizing/capping/solubilizing ligand. The hydrodynamic diameter of the particles was tuned by controlling the concentration of zwitterion siloxane, which ultimately yielded monodisperse nanoparticles small enough for renal filtration (<6 nm diameter). The zwitterated nanoparticles were readily dispersed and stable in aqueous media in the pH range 6-9 but exhibited lower magnetization values than nonzwitterated materials due to amorphous content and spin canting, typical for particles of such size. Turbidimetry and light scattering studies revealed no interaction between the particles and proteins, suggesting the materials will circulate well in vivo.

Analytical electron microscopy of biogenic and inorganic carbonates

NASA Technical Reports Server (NTRS)

Blake, David F.

1989-01-01

In the terrestrial sedimentary environment, the mineralogically predominant carbonates are calcite-type minerals (rhombohedral carbonates) and aragonite-type minerals (orthorhombic carbonates). Most common minerals precipitating either inorganically or biogenically are high magnesium calcite and aragonite. High magnesium calcite (with magnesium carbonate substituting for more than 7 mole percent of the calcium carbonate) is stable only at temperatures greater than 700 C or thereabouts, and aragonite is stable only at pressures exceeding several kilobars of confining pressure. Therefore, these carbonates are expected to undergo chemical stabilization in the diagenetic environment to ultimately form stable calcite and dolomite. Because of the strong organic control of carbonate deposition in organisms during biomineralization, the microchemistry and microstructure of invertebrate skeletal material is much different than that present in inorganic carbonate cements. The style of preservation of microstructural features in skeletal material is therefore often quite distinctive when compared to that of inorganic carbonate even though wholesale recrystallization of the sediment has taken place. Microstructural and microchemical comparisons are made between high magnesium calcite echinoderm skeletal material and modern inorganic high magnesium calcite inorganic cements, using analytical electron microscopy and related techniques. Similar comparisons are made between analogous materials which have undergone stabilization in the diagenetic environment. Similar analysis schemes may prove useful in distinguishing between biogenic and inorganic carbonates in returned Martian carbonate samples.

Semiautomated Sample Preparation for Protein Stability and Formulation Screening via Buffer Exchange.

PubMed

Ying, William; Levons, Jaquan K; Carney, Andrea; Gandhi, Rajesh; Vydra, Vicky; Rubin, A Erik

2016-06-01

A novel semiautomated buffer exchange process workflow was developed to enable efficient early protein formulation screening. An antibody fragment protein, BMSdab, was used to demonstrate the workflow. The process afforded 60% to 80% cycle time and scientist time savings and significant material efficiencies. These efficiencies ultimately facilitated execution of this stability work earlier in the drug development process, allowing this tool to inform the developability of potential candidates for development from a formulation perspective. To overcome the key technical challenges, the protein solution was buffer-exchanged by centrifuge filtration into formulations for stability screening in a 96-well plate with an ultrafiltration membrane, leveraging automated liquid handling and acoustic volume measurements to allow several cycles of exchanges. The formulations were transferred into a vacuum manifold and sterile filtered into a rack holding 96 glass vials. The vials were sealed with a capmat of individual caps and placed in stability stations. Stability of the samples prepared by this process and by the standard process was demonstrated to be comparable. This process enabled screening a number of formulations of a protein at an early pharmaceutical development stage with a short sample preparation time. © 2015 Society for Laboratory Automation and Screening.

Strong, ductile, and thermally stable Cu-based metal-intermetallic nanostructured composites.

PubMed

Dusoe, Keith J; Vijayan, Sriram; Bissell, Thomas R; Chen, Jie; Morley, Jack E; Valencia, Leopolodo; Dongare, Avinash M; Aindow, Mark; Lee, Seok-Woo

2017-01-09

Bulk metallic glasses (BMGs) and nanocrystalline metals (NMs) have been extensively investigated due to their superior strengths and elastic limits. Despite these excellent mechanical properties, low ductility at room temperature and poor microstructural stability at elevated temperatures often limit their practical applications. Thus, there is a need for a metallic material system that can overcome these performance limits of BMGs and NMs. Here, we present novel Cu-based metal-intermetallic nanostructured composites (MINCs), which exhibit high ultimate compressive strengths (over 2 GPa), high compressive failure strain (over 20%), and superior microstructural stability even at temperatures above the glass transition temperature of Cu-based BMGs. Rapid solidification produces a unique ultra-fine microstructure that contains a large volume fraction of Cu 5 Zr superlattice intermetallic compound; this contributes to the high strength and superior thermal stability. Mechanical and microstructural characterizations reveal that substantial accumulation of phase boundary sliding at metal/intermetallic interfaces accounts for the extensive ductility observed.

Hydrogen-oxygen proton-exchange membrane fuel cells and electrolyzers

NASA Technical Reports Server (NTRS)

Baldwin, R.; Pham, M.; Leonida, A.; Mcelroy, J.; Nalette, T.

1989-01-01

Hydrogen-oxygen solid polymer electrolyte (SPE) fuel cells and SPE electrolyzers (products of Hamilton Standard) both use a Proton-Exchange Membrane (PEM) as the sole electrolyte. These solid electrolyte devices have been under continuous development for over 30 years. This experience has resulted in a demonstrated ten-year SPE cell life capability under load conditions. Ultimate life of PEM fuel cells and electrolyzers is primarily related to the chemical stability of the membrane. For perfluorocarbon proton exchange membranes an accurate measure of the membrane stability is the fluoride loss rate. Millions of cell hours have contributed to establishing a relationship between fluoride loss rates and average expected ultimate cell life. This relationship is shown. Several features have been introduced into SPE fuel cells and SPE electrolyzers such that applications requiring greater than or equal to 100,000 hours of life can be considered. Equally important as the ultimate life is the voltage stability of hydrogen-oxygen fuel cells and electrolyzers. Here again the features of SPE fuel cells and SPE electrolyzers have shown a cell voltage stability in the order of 1 microvolt per hour. That level of stability has been demonstrated for tens of thousands of hours in SPE fuel cells at up to 500 amps per square foot (ASF) current density.

Swept-frequency feedback interferometry using terahertz frequency QCLs: a method for imaging and materials analysis.

PubMed

Rakić, Aleksandar D; Taimre, Thomas; Bertling, Karl; Lim, Yah Leng; Dean, Paul; Indjin, Dragan; Ikonić, Zoran; Harrison, Paul; Valavanis, Alexander; Khanna, Suraj P; Lachab, Mohammad; Wilson, Stephen J; Linfield, Edmund H; Davies, A Giles

2013-09-23

The terahertz (THz) frequency quantum cascade laser (QCL) is a compact source of high-power radiation with a narrow intrinsic linewidth. As such, THz QCLs are extremely promising sources for applications including high-resolution spectroscopy, heterodyne detection, and coherent imaging. We exploit the remarkable phase-stability of THz QCLs to create a coherent swept-frequency delayed self-homodyning method for both imaging and materials analysis, using laser feedback interferometry. Using our scheme we obtain amplitude-like and phase-like images with minimal signal processing. We determine the physical relationship between the operating parameters of the laser under feedback and the complex refractive index of the target and demonstrate that this coherent detection method enables extraction of complex refractive indices with high accuracy. This establishes an ultimately compact and easy-to-implement THz imaging and materials analysis system, in which the local oscillator, mixer, and detector are all combined into a single laser.

Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

DOE PAGES

Bufford, Daniel C.; Wang, Morris; Liu, Yue; ...

2016-04-01

The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, whilemore » engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.« less

Visible light active 2D C3N4-CdS hetero-junction photocatalyst for effective removal of azo dye by photodegradation

NASA Astrophysics Data System (ADS)

Ghosh Chaudhuri, Rajib; Chaturvedi, Ashwin; Iype, Eldhose

2018-03-01

A hetero-junction two dimensional photocatalyst that consists of organic semiconductor carbon nitride (C3N4) and inorganic semiconductor CdS, which acts as the light harvesting units and heterogeneous catalyst, was developed for the degradation of azo dye methyl orange (MO). Both materials are visible light active semiconductor. So the effective band gap of this heterojunction materials does not significantly change the visible light activity, but the injection of electrons from excited C3N4 to CdS increases the stability of hole-electron pair and that ultimately enhances the photocatalytic activity. This heterojunction catalyst finally can remove 97% of dyes and that is comparatively higher than individual pure materials. Finally, by using DFT analysis the band structure and the level diagrams of this photocatalyst are also analyzed.

Synthesis and microstructure of electrodeposited and sputtered nanotwinned face-centered-cubic metals

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

Bufford, Daniel C.; Wang, Morris; Liu, Yue

The remarkable properties of nanotwinned (NT) face-centered-cubic (fcc) metals arise directly from twin boundaries, the structures of which can be initially determined by growth twinning during the deposition process. When we understand the synthesis process and its relation to the resulting microstructure, and ultimately to material properties, we realize how key it is to understanding and utilizing these materials. Furthermore, our article presents recent studies on electrodeposition and sputtering methods that produce a high density of nanoscale growth twins in fcc metals. Nanoscale growth twins tend to form spontaneously in monolithic and alloyed fcc metals with lower stacking-fault energies, whilemore » engineered approaches are necessary for fcc metals with higher stacking-fault energies. Finally, growth defects and other microstructural features that influence nanotwin behavior and stability are introduced here, and future challenges in fabricating NT materials are highlighted.« less

Biodegradability of Plastics: Challenges and Misconceptions.

PubMed

Kubowicz, Stephan; Booth, Andy M

2017-11-07

Plastics are one of the most widely used materials and, in most cases, they are designed to have long life times. Thus, plastics contain a complex blend of stabilizers that prevent them from degrading too quickly. Unfortunately, many of the most advantageous properties of plastics such as their chemical, physical and biological inertness and durability present challenges when plastic is released into the environment. Common plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) are extremely persistent in the environment, where they undergo very slow fragmentation (projected to take centuries) into small particles through photo-, physical, and biological degradation processes 1 . The fragmentation of the material into increasingly smaller pieces is an unavoidable stage of the degradation process. Ultimately, plastic materials degrade to micron-sized particles (microplastics), which are persistent in the environment and present a potential source of harm for organisms.

Strand Plasticity Governs Fatigue in Colloidal Gels

NASA Astrophysics Data System (ADS)

van Doorn, Jan Maarten; Verweij, Joanne E.; Sprakel, Joris; van der Gucht, Jasper

2018-05-01

The repeated loading of a solid leads to microstructural damage that ultimately results in catastrophic material failure. While posing a major threat to the stability of virtually all materials, the microscopic origins of fatigue, especially for soft solids, remain elusive. Here we explore fatigue in colloidal gels as prototypical inhomogeneous soft solids by combining experiments and computer simulations. Our results reveal how mechanical loading leads to irreversible strand stretching, which builds slack into the network that softens the solid at small strains and causes strain hardening at larger deformations. We thus find that microscopic plasticity governs fatigue at much larger scales. This gives rise to a new picture of fatigue in soft thermal solids and calls for new theoretical descriptions of soft gel mechanics in which local plasticity is taken into account.

Materials and technologies for soft implantable neuroprostheses

NASA Astrophysics Data System (ADS)

Lacour, Stéphanie P.; Courtine, Grégoire; Guck, Jochen

2016-10-01

Implantable neuroprostheses are engineered systems designed to restore or substitute function for individuals with neurological deficits or disabilities. These systems involve at least one uni- or bidirectional interface between a living neural tissue and a synthetic structure, through which information in the form of electrons, ions or photons flows. Despite a few notable exceptions, the clinical dissemination of implantable neuroprostheses remains limited, because many implants display inconsistent long-term stability and performance, and are ultimately rejected by the body. Intensive research is currently being conducted to untangle the complex interplay of failure mechanisms. In this Review, we emphasize the importance of minimizing the physical and mechanical mismatch between neural tissues and implantable interfaces. We explore possible materials solutions to design and manufacture neurointegrated prostheses, and outline their immense therapeutic potential.

The effect of matrix microstructure on cyclic response and fatigue behavior of particle- reinforced 2219 aluminum: Part I. room temperature behavior

NASA Astrophysics Data System (ADS)

Vyletel, G. M.; Allison, J. E.; van Aken, D. C.

1995-12-01

The low-cycle and high-cycle fatigue behavior and cyclic response of naturally aged and overaged 2219/TiC/15p and unreinforced 2219 Al were investigated using plastic strain-controlled and stress-controlled testing. In addition, the influence of grain size on the particle-reinforced materials was examined. In both reinforced and unreinforced materials, the naturally aged conditions were cyclically unstable, exhibiting an initial hardening behavior followed by an extended region of cyclic stability and ultimately a softening region. The overaged reinforced material was cyclically stable for the plastic strains examined, while the overaged unreinforced material exhibited cyclic hardening at plastic strains greater than 2.5 × 10-4. Decreasing grain size of particle-reinforced materials modestly increased the cyclic flow stress of both naturally aged and overaged materials. Reinforced and unreinforced materials exhibited similar fatigue life behaviors; however, the reinforced and unreinforced naturally aged materials had superior fatigue lives in comparison to the overaged materials. Grain size had no effect on the fatigue life behavior of the particle-reinforced materials. The fatigue lives were strongly influenced by the presence of clusters of TiC particles and exogenous Al3Ti intermetallics.

High Energy Density Li-ion Cells for EV’s Based on Novel, High Voltage Cathode Material Systems

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

Kepler, Keith D.; Slater, Michael

This Li-ion cell technology development project had three objectives: to develop advanced electrode materials and cell components to enable stable high-voltage operation; to design and demonstrate a Li-ion cell using these materials that meets the PHEV40 performance targets; and to design and demonstrate a Li-ion cell using these materials that meets the EV performance targets. The major challenge to creating stable high energy cells with long cycle life is system integration. Although materials that can give high energy cells are known, stabilizing them towards long-term cycling in the presence of other novel cell components is a major challenge. The majormore » technical barriers addressed by this work include low cathode specific energy, poor electrolyte stability during high voltage operation, and insufficient capacity retention during deep discharge for Si-containing anodes. Through the course of this project, Farasis was able to improve capacity retention of NCM materials for 4.4+ V operation, through both surface treatment and bulk-doping approaches. Other material advances include increased rate capability and of HE-NCM materials through novel synthesis approach, doubling the relative capacity at 1C over materials synthesized using standard methods. Silicon active materials proved challenging throughout the project and ultimately were the limiting factor in the energy density vs. cycle life trade off. By avoiding silicon anodes for the lower energy PHEV design, we manufactured cells with intermediate energy density and long cycle life under high voltage operation for PHEV applications. Cells with high energy density for EV applications were manufactured targeting a 300 Wh/kg design and were able to achieve > 200 cycles.« less

Biomechanical behavior of bone scaffolds made of additive manufactured tricalciumphosphate and titanium alloy under different loading conditions.

PubMed

Wieding, Jan; Fritsche, Andreas; Heinl, Peter; Körner, Carolin; Cornelsen, Matthias; Seitz, Hermann; Mittelmeier, Wolfram; Bader, Rainer

2013-12-16

The repair of large segmental bone defects caused by fracture, tumor or infection remains challenging in orthopedic surgery. The capability of two different bone scaffold materials, sintered tricalciumphosphate and a titanium alloy (Ti6Al4V), were determined by mechanical and biomechanical testing. All scaffolds were fabricated by means of additive manufacturing techniques with identical design and controlled pore geometry. Small-sized sintered TCP scaffolds (10 mm diameter, 21 mm length) were fabricated as dense and open-porous samples and tested in an axial loading procedure. Material properties for titanium alloy were determined by using both tensile (dense) and compressive test samples (open-porous). Furthermore, large-sized open-porous TCP and titanium alloy scaffolds (30 mm in height and diameter, 700 µm pore size) were tested in a biomechanical setup simulating a large segmental bone defect using a composite femur stabilized with an osteosynthesis plate. Static physiologic loads (1.9 kN) were applied within these tests. Ultimate compressive strength of the TCP samples was 11.2 ± 0.7 MPa and 2.2 ± 0.3 MPa, respectively, for the dense and the open-porous samples. Tensile strength and ultimate compressive strength was 909.8 ± 4.9 MPa and 183.3 ± 3.7 MPa, respectively, for the dense and the open-porous titanium alloy samples. Furthermore, the biomechanical results showed good mechanical stability for the titanium alloy scaffolds. TCP scaffolds failed at 30% of the maximum load. Based on recent data, the 3D printed TCP scaffolds tested cannot currently be recommended for high load-bearing situations. Scaffolds made of titanium could be optimized by adapting the biomechanical requirements.

Genesis and growth of extracellular vesicle-derived microcalcification in atherosclerotic plaques

PubMed Central

Hutcheson, Joshua D.; Goettsch, Claudia; Bertazzo, Sergio; Maldonado, Natalia; Ruiz, Jessica L.; Goh, Wilson; Yabusaki, Katsumi; Faits, Tyler; Bouten, Carlijn; Franck, Gregory; Quillard, Thibaut; Libby, Peter; Aikawa, Masanori; Weinbaum, Sheldon; Aikawa, Elena

2015-01-01

Clinical evidence links arterial calcification and cardiovascular risk. Finite-element modelling of the stress distribution within atherosclerotic plaques has suggested that subcellular microcalcifications in the fibrous cap may promote material failure of the plaque, but that large calcifications can stabilize it. Yet the physicochemical mechanisms underlying such mineral formation and growth in atheromata remain unknown. Here, by using three-dimensional collagen hydrogels that mimic structural features of the atherosclerotic fibrous cap, and high-resolution microscopic and spectroscopic analyses of both the hydrogels and of calcified human plaques, we demonstrate that calcific mineral formation and maturation results from a series of events involving the aggregation of calcifying extracellular vesicles, and the formation of microcalcifications and ultimately large calcification zones. We also show that calcification morphology and the plaque’s collagen content – two determinants of atherosclerotic plaque stability - are interlinked. PMID:26752654

Design of Perovskite Oxides as Anion-Intercalation-Type Electrodes for Supercapacitors: Cation Leaching Effect.

PubMed

Liu, Yu; Dinh, Jim; Tade, Moses O; Shao, Zongping

2016-09-14

Oxygen ions can be exploited as a charge carrier to effectively realize a new type of anion-intercalation supercapacitor. In this study, to get some useful guidelines for future materials development, we comparatively studied SrCoO3-δ (SC), Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF), and Co3O4 as electrodes in supercapacitors with aqueous alkaline electrolyte. The effect of interaction between the electrode materials with the alkaline solution was focused on the structure and specific surface area of the electrode material, and ultimately the electrochemical performance was emphasized. Both BSCF and SC were found to experience cation leaching in alkaline solution, resulting in an increase in the specific surface area of the material, but overleaching caused the damage of perovskite structure of BSCF. Barium leaching was more serious than strontium, and the cation leaching was component dependent. Although high initial capacitance was achieved for BSCF, it was not a good candidate as intercalation-type electrode for supercapacitor because of poor cycling stability from serious Ba(2+) and Sr(2+) leaching. Instead, SC was a favorable electrode candidate for practical use in supercapacitors due to its high capacity and proper cation leaching capacity, which brought beneficial effect on cycling stability. It is suggested that cation leaching effect should be seriously considered in the development of new perovskite materials as electrodes for supercapacitors.

Effects of simulated clay gouges on the sliding behavior of Tennessee sandston

NASA Astrophysics Data System (ADS)

Shimamoto, Toshihiko; Logan, John M.

1981-06-01

The effects of simulated fault gouge on the sliding behavior of Tennessee sandstone are studied experimentally with special reference to the stabilizing effect of clay minerals mixed into the gouge. About 30 specimens with gouge composed of pure clays, of homogeneously mixed clay and anhydrite, or of layered clay and anhydrite, along a 35° precut are deformed dry in a triaxial apparatus at a confining pressure of 100 MPa, with a shortening rate of about 5 · 10 -4/sec, and at room temperature. Pure clay gouges exhibit only stable sliding, and the ultimate frictional strength is very low for bentonite (mont-morillonite), intermediate for chlorite and illite, and considerably higher for kaolinite. Anhydrite gouge shows violent stick-slip at 100 MPa confining pressure. When this mineral is mixed homogeneously with clays, the frictional coefficient of the mixed gouge, determined at its ultimate frictional strength, decreases monotonically with an increase in the clay content. The sliding mode changes from stick-slip to stable sliding when the frictional coefficient of the mixed clay-anhydrite gouge is lowered down below 90-95% of the coefficient of anhydrite gouge. The stabilizing effect of clay in mixed gouge is closely related to the ultimate frictional strength of pure clays; that is, the effect is conspicuous only for a mineral with low frictional strength. Only 15-20% of bentonite suppresses the violent stick-slip of anhydrite gouge. In contrast, violent stick-slip occurs even if the gouge contains as much as 75% of kaolinite. The behavior of illite and chlorite is intermediate between that of kaolinite and bentonite. Bentonite—anhydrite two-layer gouge exhibits stable sliding even when the bentonite content is only 5%. Thus, the presence of a thin, clay-rich layer in a fault zone stabilizes the behavior much more effectively than do the clay minerals mixed homogeneously with the gouge. This result brings out the mechanical significance of internal structures of a fault zone in understanding the effects of intrafault materials on the fault motion. Based on the present experimental results incorporated with some other experimental data, it is argued that although the stabilizing effect of montmorillonite and vermiculite is indeed remarkable at room temperature, the effect should be much less pronounced at elevated temperatures, due perhaps to the dewatering of the clays. In most geological environments where shallow earthquakes occur, the stabilizing effect of clays is probably not so conspicuous as to completely suppress the unstable motion of a fault.

Self-Stabilizing Measurement of Phase

NASA Astrophysics Data System (ADS)

Vinjanampathy, Sai

2014-05-01

Measuring phase accurately constitutes one of the most important task in precision measurement science. Such measurements can be deployed to measure everything from fundamental constants to measuring detuning and tunneling rates of atoms more precisely. Quantum mechanics enhances the ultimate bounds on the precision of such measurements possible, and exploit coherence and entanglement to reduce the phase uncertainty. In this work, we will describe a method to stabilize a decohering two-level atom and use the stabilizing measurements to learn the unknown phase acquired by the atom. Such measurements will employ a Bayesian learner to do active feedback control on the atom. We will discuss some ultimate bounds employed in precision metrology and an experimental proposal for the implementation of this scheme. Financial support from Ministry of Education, Singapore.

Revealing Anisotropic Spinel Formation on Pristine Li- and Mn-Rich Layered Oxide Surface and Its Impact on Cathode Performance

DOE PAGES

Kuppan, Saravanan; Shukla, Alpesh Khushalchand; Membreno, Daniel; ...

2017-01-06

Surface properties of cathode particles play important roles in the transport of ions and electrons and they may ultimately dominate cathode's performance and stability in lithium-ion batteries. Through the use of carefully prepared Li 1.2Ni 0.13Mn 0.54Co 0.13O 2 crystal samples with six distinct morphologies, surface transition-metal redox activities and crystal structural transformation are investigated as a function of surface area and surface crystalline orientation. Complementary depth-profiled core-level spectroscopy, namely, X-ray absorption spectroscopy, electron energy loss spectroscopy, and atomic-resolution scanning transmission electron microscopy, are applied in the study, presenting a fine example of combining advanced diagnostic techniques with a well-definedmore » model system of battery materials. Here, we report the following findings: (1) a thin layer of defective spinel with reduced transition metals, similar to what is reported on cycled conventional secondary particles in the literature, is found on pristine oxide surface even before cycling, and (2) surface crystal structure and chemical composition of both pristine and cycled particles are facet dependent. Oxide structural and cycling stabilities improve with maximum expression of surface facets stable against transition-metal reduction. Finally, the intricate relationships among morphology, surface reactivity and structural transformation, electrochemical performance, and stability of the cathode materials are revealed.« less

Novel Functionally Graded Thermal Barrier Coatings in Coal-Fired Power Plant Turbines

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

Zhang, Jing

This project presents a detailed investigation of a novel functionally graded coating material, pyrochlore oxide, for thermal barrier coating (TBC) in gas turbines used in coal-fired power plants. Thermal barrier coatings are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The ultimate goal of this research is to develop a manufacturing process to produce the novel low thermal conductivity and high thermal stability pyrochlore oxide based coatings with improved high-temperature durability. The current standard TBC, yttria stabilized zirconia (YSZ), has service temperatures limited to <1200°C, due to sintering and phase transitionmore » at higher temperatures. In contrast, pyrochlore oxide, e.g., lanthanum zirconate (La 2Zr 2O 7, LZ), has demonstrated lower thermal conductivity and better thermal stability, which are crucial to high temperature applications, such as gas turbines used in coal-fired power plants. Indiana University – Purdue University Indianapolis (IUPUI) has collaborated with Praxair Surface Technologies (PST), and Changwon National University in South Korea to perform the proposed research. The research findings are critical to the extension of current TBCs to a broader range of high-temperature materials and applications. Several tasks were originally proposed and accomplished, with additional new opportunities identified during the course of the project. In this report, a description of the project tasks, the main findings and conclusions are given. A list of publications and presentations resulted from this research is listed in the Appendix at the end of the report.« less

The role of fiber and matrix in crash energy absorption of composite materials

NASA Technical Reports Server (NTRS)

Farley, G. L.; Bird, R. K.; Modlin, J. T.

1986-01-01

Static crushing tests were conducted on tube specimens fabricated from graphite/epoxy, Kevlar/epoxy and hybrid combinations of graphite-Kevlar/epoxy to examine the influence the fiber and matrix constitutive properties and laminate architecture have on energy absorption. Fiber and matrix ultimate failure strain were determined to significantly effect energy absorption. The energy absorption capability of high ultimate failure strain materials (AS-6/F185 and AS-6/HST-7) was less than materials having lower ultimate failure strain. Lamina stacking sequence had up to a 300 percent change in energy absorption for the materials tested. Hybridizing with graphite and Kevlar reinforcements resulted in materials with high energy absorption capabilities that have postcrushing integrity.

FOREWORD: Focus on the Degradation and Stability of Polymers

NASA Astrophysics Data System (ADS)

Terano, Minoru

2008-06-01

Modern society is so reliant on polymers that products incorporating these macromolecules are almost 'invisible'. Polymers are indispensable materials used for manufacturing compact disks, clothes, lightweight airplanes, automobiles, footware and even the humble polystyrene boxes for packing our favorite hamburgers and fries. But, like many other materials, polymers degrade and become unstable, so a deeper understanding of the physical mechanisms responsible for degradation is necessary to address issues such as potential applications, recycling and the impact of polymer-products on the environment. In particular, polymers are highly vulnerable to oxidative degradation at elevated temperatures and in sunlight. Unfortunately, in spite of extensive research on polymer degradation, our knowledge is still incomplete. The analysis of polymer degradation and stability has recently become harder and more complicated because of the wider range of polymer applications, including blends and composites. Notably, composites with nanofillers are being studied for automotive, electrical and other industrial applications. With this background, the 1st International Symposium on Ultimate Stability of NanoStructured Polymers and Composites (NT2007) was held in October at the Japan Advanced Institute of Science and Technology in Ishikawa Prefecture. The meeting provided a forum to discuss advanced research achievements to resolve problems in this field of research. The papers selected for this focus issue describe recent discoveries on the stability, weatherability and flame retardancy of polymers, as well as providing an insight into degradation mechanisms of nanostructured polymers and composites. We hope that this focus issue will serve as a timely source of information about one of the most important topics in polymer science and related technologies.

Cryogenic Properties of Aluminum Beryllium and Beryllium Materials

NASA Technical Reports Server (NTRS)

Gamwell, Wayne R.; McGill, Preston B.

2003-01-01

Ultimate tensile strength, yield strength, and elongation were obtained for the aluminum-beryllium alloy, AlBeMetl62 (38%Al-62%Be), at cryogenic (-195.5 C (-320 F) and (-252.8 C) (-423 F)) temperatures, and for an optical grade beryllium, O-30H (99%Be), at -252.8 C. AlBeMetl62 material was purchased to the requirements of SAE-AMS7912, "Aluminum-Beryllium Alloy, Extrusions." O-30H material was purchased to the requirements of Brush Wellman Inc. specification O-30H Optical Grade Beryllium. The ultimate tensile and yield strengths for extruded AlBeMetl62 material increased with decreasing temperature, and the percent elongation decreased with decreasing temperature. Design properties for the ultimate tensile strength, yield strength, and percent elongation for extruded AlBeMetl62 were generated. It was not possible to distinguish a difference in the room and cryogenic ultimate strength for the hot isostatically pressed (HIP'ed) O-30H material. The O30H elongation decreased with decreasing temperature.

Barochemistry: Predictive Solid State Chemistry

NASA Astrophysics Data System (ADS)

Yoo, Choong-Shik

The application of compression energy comparable to that of chemical bonds, but substantially greater than those of defects and grain boundaries in solids allows us to pursue novel concepts of high-pressure chemistry (or barochemistry) in materials development by design. At such extreme pressures, simple molecular solids covert into densely packed extended network structures that can be predicted from first principles. In recent years, a significant number of new materials and novel extended structures have been designed and discovered in highly compressed states of the first- and second- row elemental solids, including Li, C, H2,N2, O2, CO, CO2, and H2O. These extended solids are extremely hard, have high energy density, and exhibit novel electronic and nonlinear optical properties that are superior to other known materials at ambient conditions. However, these materials are often formed at formidable pressures and are highly metastable at ambient conditions; only a few systems have been recovered, limiting the materials within a realm of fundamental scientific discoveries. Therefore, an exciting new research area has emerged on the barochemistry to understand and, ultimately, control the stability, bonding, structure, and properties of low Z extended solids. In this paper, we will present our recent research to develop hybrid low Z extended solids amenable to scale up synthesis and ambient stabilization, utilizing kinetically controlled processes in dense solid mixtures and discuss the governing fundamental principles of barochemistry. This work was performed in support of the NSF (DMR-1203834), DTRA (HDTRA1-12-01-0020), and DARPA (W31P4Q-12-1-0009).

Ab initio study of radiation effects on the Li4Ti5O12 electrode used in lithium-ion batteries

NASA Astrophysics Data System (ADS)

Samin, Adib; Kurth, Michael; Cao, Lei

2015-04-01

Lithium-ion batteries are currently in wide use owing to their high energy density and enhanced capabilities. Li4Ti5O12 is a promising anode material for lithium-ion batteries because of its advantageous properties. Lithium-ion batteries could be exposed to radiation occurring in various conditions such as during outer space exploration and nuclear accidents. In this study, we apply density functional theory to explore the effect of radiation damage on this electrode and, ultimately, on the performance of the battery. It was found that radiation could affect the structural stability of the material. Furthermore, the electrode was shown to undergo a transition from insulator to metal, following the defects due to radiation. In addition, the effect of radiation on the intercalation potential was found to be highly dependent on the nature of the defect induced.

[Monolithic column-gold composite substrate preparation and application to SERS detection of pigment].

PubMed

Xie, Yun-Fei; Li, Yan; Yu, Hui; Qian, He; Yao, Wei-Rong

2014-03-01

In the present study, we developed a novel SERS substrate with the porous monolith material combined with classic gold nanoparticles, and erythrosine as the research object, by adjusting the different experimental conditions for optimal SERS enhancements, including system pH and mixing time, and ultimately selected the optimum pH value 5.06 and mixing time 25 min. Compared with the traditional gold plastic substrate enhancement effect, the experimental conditions were applied to the monolith substrate SERS detection of dye erythrosine, different concentrations of samples were used for erythrosine SERS detection, and the detection limit reached 0.1 g x mL(-1). The method uses the payload of gold nanoparticles in mesoporous materials to effectively enhance the SERS signal. And this method has the advantages of simpleness and good stability, which provides a favorable theoretical basis for the rapid prohibited colorings screening.

Hydrogen-oxygen proton-exchange membrane fuel cells and electrolyzers

NASA Technical Reports Server (NTRS)

Baldwin, R.; Pham, M.; Leonida, A.; Mcelroy, J.; Nalette, T.

1989-01-01

Hydrogen-oxygen SPE fuel cells and SPE electrolyzers (products of Hamilton Standard) both use a Proton-Exchange Membrane (PEM) as the sole electrolyte. The SPE cells have demonstrated a ten year life capability under load conditions. Ultimate life of PEM fuel cells and electrolyzers is primarily related to the chemical stability of the membrane. For perfluorocarbon proton-exchange membranes an accurate measure of the membrane stability is the fluoride loss rate. Millions of cell hours have contributed to establishing a relationship between fluroride loss rates and average expected ultimate cell life. Several features were introduced into SPE fuel cells and SPE electrolyzers such that applications requiring greater than or equal to 100,000 hours of life can be considered. Equally important as the ultimate life is the voltage stability of hydrogen-oxygen fuel cells and electrolyzers. Here again the features of SPE fuel cells and SPE electrolyzers have shown a cell voltage stability in the order of 1 microvolt per hour. That level of stability were demonstrated for tens of thousands of hours in SPE fuel cells at up to 500 amps per square foot (ASF) current density. The SPE electrolyzers have demonstrated the same at 1000 ASF. Many future extraterrestrial applications for fuel cells require that they be self recharged. To translate the proven SPE cell life and stability into a highly reliable extraterrestrial electrical energy storage system, a simplification of supporting equipment is required. Static phase separation, static fluid transport and static thermal control will be most useful in producting required system reliability. Although some 200,000 SPE fuel cell hours were recorded in earth orbit with static fluid phase separation, no SPE electrolyzer has, as yet, operated in space.

Augmenting Photoinduced Charge Transport in a Single-Component Gel System: Controlled In Situ Gel-Crystal Transformation at Room Temperature.

PubMed

Satapathy, Sitakanta; Prabakaran, Palani; Prasad, Edamana

2018-04-20

Smart single-component materials with versatile functions require pre-programming of a higher order molecular assembly. An electroactive supergelator (c=0.07 wt %) triphenylamine core-appended poly(aryl ether) dendron (TPAPAE) is described, where substantial dendritic effects improve the order and crystallinity by switching the local minima from self-assembled molecular wires to thermodynamically favorable global minima of ordered crystals, ripened within the fibers. Controlled in situ phase change at room temperature ultimately stabilized the mixed valence states in the single-component supramolecular assembly with photoluminescence and photoinduced charge transport amplified by two orders of magnitude. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

The effect of small streamwise velocity distortion on the boundary layer flow over a thin flat plate with application to boundary layer stability theory

NASA Technical Reports Server (NTRS)

Goldstein, M. E.; Leib, S. J.; Cowley, S. J.

1990-01-01

Researchers show how an initially linear spanwise disturbance in the free stream velocity field is amplified by leading edge bluntness effects and ultimately leads to a small amplitude but linear spanwise motion far downstream from the edge. This spanwise motion is imposed on the boundary layer flow and ultimately causes an order-one change in its profile shape. The modified profiles are highly unstable and can support Tollmein-Schlichting wave growth well upstream of the theoretical lower branch of the neutral stability curve for a Blasius boundary layer.

Defects, Entropy, and the Stabilization of Alternative Phase Boundary Orientations in Battery Electrode Particles

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

Heo, Tae Wook; Tang, Ming; Chen, Long-Qing

Using a novel statistical approach that efficiently explores the space of possible defect configurations, our present study investigates the chemomechanical coupling between interfacial structural defects and phase boundary alignments within phase-separating electrode particles. Applied to the battery cathode material Li XFePO 4 as an example, the theoretical analysis reveals that small, defect-induced deviations from an ideal interface can lead to dramatic shifts in the orientations of phase boundaries between Li-rich and Li-lean phases, stabilizing otherwise unfavorable orientations. Significantly, this stabilization arises predominantly from configurational entropic factors associated with the presence of the interfacial defects rather than from absolute energetic considerations.more » The specific entropic factors pertain to the diversity of defect configurations and their contributions to rotational/orientational rigidity of phase boundaries. Comparison of the predictions with experimental observations indicates that the additional entropy contributions indeed play a dominant role under actual cycling conditions, leading to the conclusion that interfacial defects must be considered when analyzing the stability and evolution kinetics of the internal phase microstructure of strongly phase-separating systems. Possible implications for tuning the kinetics of (de)lithiation based on selective defect incorporation are discussed. Ultimately, this understanding can be generalized to the chemomechanics of other defective solid phase boundaries.« less

Defects, Entropy, and the Stabilization of Alternative Phase Boundary Orientations in Battery Electrode Particles

DOE PAGES

Heo, Tae Wook; Tang, Ming; Chen, Long-Qing; ...

2016-01-04

Using a novel statistical approach that efficiently explores the space of possible defect configurations, our present study investigates the chemomechanical coupling between interfacial structural defects and phase boundary alignments within phase-separating electrode particles. Applied to the battery cathode material Li XFePO 4 as an example, the theoretical analysis reveals that small, defect-induced deviations from an ideal interface can lead to dramatic shifts in the orientations of phase boundaries between Li-rich and Li-lean phases, stabilizing otherwise unfavorable orientations. Significantly, this stabilization arises predominantly from configurational entropic factors associated with the presence of the interfacial defects rather than from absolute energetic considerations.more » The specific entropic factors pertain to the diversity of defect configurations and their contributions to rotational/orientational rigidity of phase boundaries. Comparison of the predictions with experimental observations indicates that the additional entropy contributions indeed play a dominant role under actual cycling conditions, leading to the conclusion that interfacial defects must be considered when analyzing the stability and evolution kinetics of the internal phase microstructure of strongly phase-separating systems. Possible implications for tuning the kinetics of (de)lithiation based on selective defect incorporation are discussed. Ultimately, this understanding can be generalized to the chemomechanics of other defective solid phase boundaries.« less

What the ultimate polymeric electro-optic materials will be: guest-host, crosslinked, or side-chain?

NASA Astrophysics Data System (ADS)

Zhang, Cheng; Zhang, Hua; Oh, Min-Cheol; Dalton, Larry R.; Steier, William H.

2003-07-01

Material processing and device fabrication of many different electro-optic (EO) polymers developed at USC are reviewed. Detailed discussion is given to guest-host CLD/APCs, crosslinking perfluorocyclobutane (PFCB) polymer CX1, and thermally stable side-chain polymers CX2 and CX3. Excellent EO performance (1.4V at 1.31 μm, 2.1 V at 1.55 μm) was achieved in CLD/APC Mach-Zehnder modulators (2-cm, push-pull). CLD/APCs also possess low optical losses (1.2 dB/cm in slab waveguides and in thick core channel waveguides). However, the guest-host materials only have limited thermal stability (110-132 °C in short term, <60 °C in long term) and require special techniques in device fabrication. The crosslinking polymer CX1 was able to provide long-term stability at 85 oC when fully cured. It also has a low optical loss (comparable to CLD/APCs) before curing and decent EO coefficient when poled at 180 °C. However, after the films were poled at the crosslinking temperatures (200 °C or above), the transmissions of the waveguides and EO activity became very poor due to poling-induced chromophore degradation. By judicial molecular design of both chromophore and monomer structures to suppress thermal motion of polymer segments, we were able to realize the same or even better thermal stability in side-chain polymers CX2 and CX3. Since no curing is needed, devices can be poled at their optimal poling temperatures, and all good properties can be obtained simultaneously. Despite the excellent solubility in chlorinated solvents, these side-chain polymers are resistant to some other organic solvents or solutions such as acetone, photoresist and various UV-curable liquids.

Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection.

PubMed

Ding, Hong; Dwaraknath, Shyam S; Garten, Lauren; Ndione, Paul; Ginley, David; Persson, Kristin A

2016-05-25

With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO2 compounds which provides a rich chemical and structural polymorph space. We find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO2 substrates, where the VO2 brookite phase would be preferentially grown on the a-c TiO2 brookite plane while the columbite and anatase structures favor the a-b plane on the respective TiO2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. These criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.

Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection

DOE PAGES

Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren; ...

2016-05-04

With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO 2 compounds which provides a rich chemical and structural polymorph space. Here, we find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO 2 substrates, where the VO 2 brookite phase would be preferentially grown on the a-c TiO 2 brookite plane whilemore » the columbite and anatase structures favor the a-b plane on the respective TiO 2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO 2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. Our criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.« less

Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection

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

Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren

With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO2 compounds which provides a rich chemical and structural polymorph space. We find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO2 substrates, where the VO2 brookite phase would be preferentially grown on the a-c TiO2 brookite plane while the columbite and anatase structuresmore » favor the a-b plane on the respective TiO2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. These criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.« less

Computational Approach for Epitaxial Polymorph Stabilization through Substrate Selection

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

Ding, Hong; Dwaraknath, Shyam S.; Garten, Lauren

With the ultimate goal of finding new polymorphs through targeted synthesis conditions and techniques, we outline a computational framework to select optimal substrates for epitaxial growth using first principle calculations of formation energies, elastic strain energy, and topological information. To demonstrate the approach, we study the stabilization of metastable VO 2 compounds which provides a rich chemical and structural polymorph space. Here, we find that common polymorph statistics, lattice matching, and energy above hull considerations recommends homostructural growth on TiO 2 substrates, where the VO 2 brookite phase would be preferentially grown on the a-c TiO 2 brookite plane whilemore » the columbite and anatase structures favor the a-b plane on the respective TiO 2 phases. Overall, we find that a model which incorporates a geometric unit cell area matching between the substrate and the target film as well as the resulting strain energy density of the film provide qualitative agreement with experimental observations for the heterostructural growth of known VO 2 polymorphs: rutile, A and B phases. The minimal interfacial geometry matching and estimated strain energy criteria provide several suggestions for substrates and substrate-film orientations for the heterostructural growth of the hitherto hypothetical anatase, brookite, and columbite polymorphs. Our criteria serve as a preliminary guidance for the experimental efforts stabilizing new materials and/or polymorphs through epitaxy. The current screening algorithm is being integrated within the Materials Project online framework and data and hence publicly available.« less

Attrition and erosion: assessment and diagnosis.

PubMed

Meyers, Ian

2012-04-01

The management of patients with extensively worn and badly broken down dentitions presents a difficult challenge in dental practice and restorative treatments are often complex, time consuming and costly to implement, so careful case selection and treatment planning is essential. Ultimately the success of any restorative intervention is very dependent on the stability of the oral environment and the status of the remaining tooth structure. Prior to the commencement of any restorative treatment an understanding of the importance of the disease process, the risk factors in the mouth, and the intrinsic and extrinsic factors which affect the oral balance is critical. While there is a growing range of materials and techniques available for cost effective and conservative management of these cases, failure to take a systematic approach to assessment and stabilization may result in early restorative failure, rapid recurrence of the problems and a repeat restoration cycle. Therefore successful management of these patients must include an appropriate mix of preventive and restorative strategies.

Organic Optoelectronic Devices Employing Small Molecules

NASA Astrophysics Data System (ADS)

Fleetham, Tyler Blain

Organic optoelectronic devices have remained a research topic of great interest over the past two decades, particularly in the development of efficient organic photovoltaics (OPV) and organic light emitting diodes (OLED). In order to improve the efficiency, stability, and materials variety for organic optoelectronic devices a number of emitting materials, absorbing materials, and charge transport materials were developed and employed in a device setting. Optical, electrical, and photophysical studies of the organic materials and their corresponding devices were thoroughly carried out. Two major approaches were taken to enhance the efficiency of small molecule based OPVs: developing material with higher open circuit voltages or improved device structures which increased short circuit current. To explore the factors affecting the open circuit voltage (VOC) in OPVs, molecular structures were modified to bring VOC closer to the effective bandgap, DeltaE DA, which allowed the achievement of 1V VOC for a heterojunction of a select Ir complex with estimated exciton energy of only 1.55eV. Furthermore, the development of anode interfacial layer for exciton blocking and molecular templating provide a general approach for enhancing the short circuit current. Ultimately, a 5.8% PCE was achieved in a single heterojunction of C60 and a ZnPc material prepared in a simple, one step, solvent free, synthesis. OLEDs employing newly developed deep blue emitters based on cyclometalated complexes were demonstrated. Ultimately, a peak EQE of 24.8% and nearly perfect blue emission of (0.148,0.079) was achieved from PtON7dtb, which approaches the maximum attainable performance from a blue OLED. Furthermore, utilizing the excimer formation properties of square-planar Pt complexes, highly efficient and stable white devices employing a single emissive material were demonstrated. A peak EQE of over 20% for pure white color (0.33,0.33) and 80 CRI was achieved with the tridentate Pt complex, Pt-16. Furthermore, the development of a series of tetradentate Pt complexes yielded highly efficient and stable single doped white devices due to their halogen free tetradentate design. In addition to these benchmark achievements, the systematic molecular modification of both emissive and absorbing materials provides valuable structure-property relationship information that should help guide further developments in the field.

Distribution of chloride, pH, resistivity, and sulfate levels in backfill for mechanically-stabilized earth walls and implications for corrosion testing.

DOT National Transportation Integrated Search

2015-05-01

The ultimate goals of this research were to improve quality, speed completion, and reduce risk in mechanically-stabilized : earth (MSE) wall projects. Research objectives were to assure (1) that variability in the corrosion properties of soil (pH, : ...

Growth kinetics of physical vapor transport processes: Crystal growth of the optoelectronic material mercurous chloride

NASA Technical Reports Server (NTRS)

Singh, N. B.; Duval, W. M.

1991-01-01

Physical vapor transport processes were studied for the purpose of identifying the magnitude of convective effects on the crystal growth process. The effects of convection on crystal quality were were studied by varying the aspect ratio and those thermal conditions which ultimately affect thermal convection during physical vapor transport. An important outcome of the present study was the observation that the convection growth rate increased up to a certain value and then dropped to a constant value for high aspect ratios. This indicated that a very complex transport had occurred which could not be explained by linear stability theory. Better quality crystals grown at a low Rayleigh number confirmed that improved properties are possible in convectionless environments.

Sensitivity Analysis of Stability Problems of Steel Structures using Shell Finite Elements and Nonlinear Computation Methods

NASA Astrophysics Data System (ADS)

Kala, Zdeněk; Kala, Jiří

2011-09-01

The main focus of the paper is the analysis of the influence of residual stress on the ultimate limit state of a hot-rolled member in compression. The member was modelled using thin-walled elements of type SHELL 181 and meshed in the programme ANSYS. Geometrical and material non-linear analysis was used. The influence of residual stress was studied using variance-based sensitivity analysis. In order to obtain more general results, the non-dimensional slenderness was selected as a study parameter. Comparison of the influence of the residual stress with the influence of other dominant imperfections is illustrated in the conclusion of the paper. All input random variables were considered according to results of experimental research.

High efficiency and stable white OLED using a single emitter

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

Li, Jian

2016-01-18

The ultimate objective of this project was to demonstrate an efficient and stable white OLED using a single emitter on a planar glass substrate. The focus of the project is on the development of efficient and stable square planar phosphorescent emitters and evaluation of such class of materials in the device settings. Key challenges included improving the emission efficiency of molecular dopants and excimers, controlling emission color of emitters and their excimers, and improving optical and electrical stability of emissive dopants. At the end of this research program, the PI has made enough progress to demonstrate the potential of excimer-basedmore » white OLED as a cost-effective solution for WOLED panel in the solid state lighting applications.« less

Recent progress on thin-film encapsulation technologies for organic electronic devices

NASA Astrophysics Data System (ADS)

Yu, Duan; Yang, Yong-Qiang; Chen, Zheng; Tao, Ye; Liu, Yun-Fei

2016-03-01

Among the advanced electronic devices, flexible organic electronic devices with rapid development are the most promising technologies to customers and industries. Organic thin films accommodate low-cost fabrication and can exploit diverse molecules in inexpensive plastic light emitting diodes, plastic solar cells, and even plastic lasers. These properties may ultimately enable organic materials for practical applications in industry. However, the stability of organic electronic devices still remains a big challenge, because of the difficulty in fabricating commercial products with flexibility. These organic materials can be protected using substrates and barriers such as glass and metal; however, this results in a rigid device and does not satisfy the applications demanding flexible devices. Plastic substrates and transparent flexible encapsulation barriers are other possible alternatives; however, these offer little protection to oxygen and water, thus rapidly degrading the devices. Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation into the flexible devices. Because of these (and other) reasons, there has been an intense interest in developing transparent barrier materials with much lower permeabilities, and their market is expected to reach over 550 million by 2025. In this study, the degradation mechanism of organic electronic devices is reviewed. To increase the stability of devices in air, several TFE technologies were applied to provide efficient barrier performance. In this review, the degradation mechanism of organic electronic devices, permeation rate measurement, traditional encapsulation technologies, and TFE technologies are presented.

Dentin bond strength of two resin-ceramic computer-aided design/computer-aided manufacturing (CAD/CAM) materials and five cements after six months storage.

PubMed

Flury, Simon; Schmidt, Stefanie Zita; Peutzfeldt, Anne; Lussi, Adrian

2016-10-01

The aim was to investigate dentin bond strength of two resin-ceramic materials and five cements after 24 h and six months storage. Cylinders (n=15/group) of Lava Ultimate (3M ESPE) and VITA ENAMIC (VITA Zahnfabrik) were cemented to mid-coronal dentin of 300 extracted human molars with RelyX Ultimate (3M ESPE), PANAVIA F2.0 (Kuraray), Variolink II (Ivoclar Vivadent), els cem (Saremco Dental), or Ketac Cem Plus (3M ESPE). Shear bond strength (SBS) was measured after 24 h or six months storage (37°C, 100% humidity) and statistically analyzed (significance level: α=0.05). SBS varied markedly between Lava Ultimate and VITA ENAMIC, between the five cements, and between storage of either 24 h or six months. After six months, SBS was highest when Lava Ultimate was cemented with RelyX Ultimate and when VITA ENAMIC was cemented with RelyX Ultimate or with Variolink II. Lava Ultimate was somewhat more sensitive to storage than was VITA ENAMIC.

Persistent electrochemical performance in epitaxial VO 2(B)

DOE PAGES

Lee, Shinbuhm; Sun, Xiao -Guang; Lubimtsev, Andrew A.; ...

2017-03-07

Discovering high-performance energy storage materials is indispensable for renewable energy, electric vehicle performance, and mobile computing. Owing to the open atomic framework and good room temperature conductivity, bronze-phase vanadium dioxide [VO 2(B)] has been regarded as a highly promising electrode material for Li ion batteries. However, previous attempts were unsuccessful to show the desired cycling performance and capacity without chemical modification. Here, we show with epitaxial VO 2(B) films that one can accomplish the theoretical limit for capacity with persistent charging–discharging cyclability owing to the high structural stability and unique open pathways for Li ion conduction. Atomic-scale characterization by scanningmore » transmission electron microscopy and density functional theory calculations also reveal that the unique open pathways in VO 2(B) provide the most stable sites for Li adsorption and diffusion. Furthermore, this work ultimately demonstrates that VO 2(B) is a highly promising energy storage material and has no intrinsic hindrance in achieving superior cyclability with a very high power and capacity in a Li-ion conductor.« less

Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

DOE PAGES

Jiao, Z. B.; Luan, J. H.; Miller, M. K.; ...

2016-02-19

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

PubMed Central

Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

2016-01-01

The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

Evaluation of the Elastic Properties of Thirteen Silicone Interocclusal Recording Materials

PubMed Central

Zietek, Marek

2016-01-01

Background. Addition silicones are popular as dental impression materials and are used in bite registration procedures. Objective. This study aimed to compare the postsetting elasticities and other mechanical properties of thirteen addition silicone interocclusal recording materials. Materials and Methods. The following materials were investigated: Colorbite D, Futar D, Genie Bite, Jet Blue Bite fast, Memoreg 2, O-Bite, Occlufast Rock, Omni-Bite Plus, Regidur i, Registrado X-tra, Regofix transparent, StoneBite, and Variotime Bite. Thirty specimens of each material were tested. The elasticities and strengths of the materials were measured with a universal testing machine, and computer software was used to determine the E-moduli, ultimate tensile strengths, and ultimate elongations of the specimens. Results. The results were subjected to statistical analysis using the Kruskal-Wallis test (p ≤ 0.05). The statistics revealed that the mean E-modulus values varied significantly across the materials (p = 0.000) and were highest for the StoneBite and Registrado X-tra and lowest for the Regofix transparent. The ultimate tensile strengths were highest for the Regofix transparent and Registrado X-tra (p = 0.000) and lowest for the Jet Blue Bite fast and Memoreg 2 (p = 0.000). The elongation percentages at the point of breaking varied significantly across the materials (p = 0.000); the lowest value was observed for the StoneBite, whereas the Regofix transparent nearly doubled original length. Conclusions. The authors concluded that materials with the high E-moduli and great ultimate tensile strengths may be most useful clinically. Registrado X-tra and StoneBite best met these criteria. PMID:27747239

A Computational Investigation for Determining the Natural Frequencies and Damping Effects of Diaphragm-Implemented Spacecraft Propellant Tanks

NASA Technical Reports Server (NTRS)

Lenahen, Brian; Bernier, Adrien; Gangadharan, Sathya; Sudermann, James; Marsell, Brandon

2012-01-01

Spin-stabilization maneuvers are typically performed by spacecraft entering low-earth orbit to maintain attitude stability. These maneuvers induce periodic fluid movement inside the spacecraft's propellant tank known as fuel slosh, which is responsible for creating forces and moments on the sidewalls of the propellant tank. These forces and moments adversely affect spin-stabilization and risk jeopardizing the mission of the spacecraft. Therefore, propellant tanks are designed with propellant management devices (PMD's) such as barnes or diaphragms which work to counteract the forces and moments associated with fuel slosh. However, despite the presence of PMD's, the threat of spin-stabilization interference still exists should the propellant tank be excited at its natural frequency. When the fluid is excited at its natural frequency, the forces and moments acting on the propellant tank are amplified and may result in destabilizing the spacecraft. Thus, a computational analysis is conducted concerning diaphragm-implemented propellant tanks excited at their natural frequencies. Using multi-disciplinary computational fluid dynamics (CFD) software, computational models are developed to reflect potential scenarios that spacecraft propellant tanks could experience. By simulating the propellant tank under a wide array of parameters and variables including fill-level, gravity and diaphragm material and shape, a better understanding is gained as to how these parameters individually and collectively affect liquid propellant tanks and ultimately, spacecraft attitude dynamics.

The ultimate state of polymeric materials and laminated and fibrous composites under asymmetric high-cycle loading

NASA Astrophysics Data System (ADS)

Golub, V. P.; Pogrebniak, A. D.; Kochetkova, E. S.

2008-01-01

The prediction of the high-cycle fatigue strength of polymeric and composite materials in asymmetric loading is considered. The problem is solved on the basis of a nonlinear model of ultimate state allowing us to describe all typical forms of the diagrams of ultimate stresses. The material constants of the model are determined from the results of fatigue tests in symmetric reversed cycling, in a single fatigue test with the minimum stress equal to zero, and in a short-term strength test. The fatigue strength characteristics of some polymers, glass-fiber laminates, glass-fiber-reinforced plastics, organic-fiber-reinforced plastics, and wood laminates in asymmetric tension-compression, bending, and torsion have been calculated and approved experimentally.

Laser Speckle Strain Imaging reveals the origin of delayed fracture in a soft solid

PubMed Central

Dussi, Simone; Frijns, Raoul A. M.; van der Gucht, Jasper; Sprakel, Joris

2018-01-01

Stresses well below the critical fracture stress can lead to highly unpredictable delayed fracture after a long period of seemingly quiescent stability. Delayed fracture is a major threat to the lifetime of materials, and its unpredictability makes it difficult to prevent. This is exacerbated by the lack of consensus on the microscopic mechanisms at its origin because unambiguous experimental proof of these mechanisms remains absent. We present an experimental approach to measure, with high spatial and temporal resolution, the local deformations that precipitate crack nucleation. We apply this method to study delayed fracture in an elastomer and find that a delocalized zone of very small strains emerges as a consequence of strongly localized damage processes. This prefracture deformation zone grows exponentially in space and time, ultimately culminating in the nucleation of a crack and failure of the material as a whole. Our results paint a microscopic picture of the elusive origins of delayed fracture and open the way to detect damage well before it manifests macroscopically. PMID:29736415

Enhancing regenerative approaches with nanoparticles

PubMed Central

Habibovic, Pamela

2017-01-01

In this review, we discuss recent developments in the field of nanoparticles and their use in tissue regeneration approaches. Owing to their unique chemical properties and flexibility in design, nanoparticles can be used as drug delivery systems, to create novel features within materials or as bioimaging agents, or indeed these properties can be combined to create smart multifunctional structures. This review aims to provide an overview of this research field where the focus will be on nanoparticle-based strategies to stimulate bone regeneration; however, the same principles can be applied for other tissue and organ regeneration strategies. In the first section, nanoparticle-based methods for the delivery of drugs, growth factors and genetic material to promote tissue regeneration are discussed. The second section deals with the addition of nanoparticles to materials to create nanocomposites. Such materials can improve several material properties, including mechanical stability, biocompatibility and biological activity. The third section will deal with the emergence of a relatively new field of research using nanoparticles in advanced cell imaging and stem cell tracking approaches. As the development of nanoparticles continues, incorporation of this technology in the field of regenerative medicine will ultimately lead to new tools that can diagnose, track and stimulate the growth of new tissues and organs. PMID:28404870

Enhancing regenerative approaches with nanoparticles.

PubMed

van Rijt, Sabine; Habibovic, Pamela

2017-04-01

In this review, we discuss recent developments in the field of nanoparticles and their use in tissue regeneration approaches. Owing to their unique chemical properties and flexibility in design, nanoparticles can be used as drug delivery systems, to create novel features within materials or as bioimaging agents, or indeed these properties can be combined to create smart multifunctional structures. This review aims to provide an overview of this research field where the focus will be on nanoparticle-based strategies to stimulate bone regeneration; however, the same principles can be applied for other tissue and organ regeneration strategies. In the first section, nanoparticle-based methods for the delivery of drugs, growth factors and genetic material to promote tissue regeneration are discussed. The second section deals with the addition of nanoparticles to materials to create nanocomposites. Such materials can improve several material properties, including mechanical stability, biocompatibility and biological activity. The third section will deal with the emergence of a relatively new field of research using nanoparticles in advanced cell imaging and stem cell tracking approaches. As the development of nanoparticles continues, incorporation of this technology in the field of regenerative medicine will ultimately lead to new tools that can diagnose, track and stimulate the growth of new tissues and organs. © 2017 The Author(s).

Corrosion Testing of Zirconia, Beryllia and Magnesia Ceramics in Molten Alkali Metal Carbonates at 900°C

NASA Astrophysics Data System (ADS)

Kaplan, Valery; Lubomirsky, Igor

An electrochemical cell containing molten Li2CO3-Li2O has been proposed for the conversion of the greenhouse gas CO2 to CO, which can then either be used to power gas turbines or converted to methanol. Since efficient electrolysis takes place at 900°C, the materials which can be used in such a cell must satisfy stringent requirements. In the current work, we have examined the static corrosion resistance of zirconia, beryllia and magnesia ceramics at 900°C in the Li2CO3-Li2O mixture and in a Li-Na-K carbonate eutectic mixture with the ultimate objective of identifying suitable electrically insulating materials. Conclusions regarding material stability were based on elemental analysis of the melt, primarily via X-ray photoelectron spectroscopy, a particularly sensitive technique. It was found that magnesia is completely stable for at least 33 hrs in a Li2CO3-Li2O melt, while a combined lithium titanate/lithium zirconate layer forms on the zirconia ceramic as detected by XRD. Under the same melt conditions, beryllia shows considerable leaching into solution. In a Li-Na-K carbonate eutectic mixture containing 10.2 mol% oxide at 900°C under standard atmospheric conditions, magnesia showed no signs of degradation. Stabilization of the zirconia content of the eutectic mixture at 0.01-0.02 at% after 2 hrs is again explained by the formation of a lithium titanate/ lithium zirconate coating. On the basis of these results, we conclude that only magnesia can be satisfactorily used as an insulating material in electrolysis cells containing Li2CO3-Li2O melts.

As you reap, so shall you sow: coupling of harvesting and inoculating stabilizes the mutualism between termites and fungi

PubMed Central

Aanen, Duur K

2006-01-01

At present there is no consensus theory explaining the evolutionary stability of mutualistic interactions. However, the question is whether there are general ‘rules’, or whether each particular mutualism needs a unique explanation. Here, I address the ultimate evolutionary stability of the ‘agricultural’ mutualism between fungus-growing termites and Termitomyces fungi, and provide a proximate mechanism for how stability is achieved. The key to the proposed mechanism is the within-nest propagation mode of fungal symbionts by termites. The termites suppress horizontal fungal transmission by consuming modified unripe mushrooms (nodules) for food. However, these nodules provide asexual gut-resistant spores that form the inoculum of new substrate. This within-nest propagation has two important consequences: (i) the mutualistic fungi undergo severe, recurrent bottlenecks, so that the fungus is likely to be in monoculture and (ii) the termites ‘artificially’ select for high nodule production, because their fungal food source also provides the inoculum for the next harvest. I also provide a brief comparison of the termite–fungus mutualism with the analogous agricultural mutualism between attine ants and fungi. This comparison shows that—although common factors for the ultimate evolutionary stability of mutualisms can be identified—the proximate mechanisms can be fundamentally different between different mutualisms. PMID:17148364

Testing atomic mass models with radioactive beams

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

Haustein, P.E.

1989-01-01

Significantly increased yields of new or poorly characterized exotic isotopes that lie far from beta-decay stability can be expected when radioactive beams are used to produce these nuclides. Measurements of the masses of these new species are very important. Such measurements are motivated by the general tendency of mass models to diverge from one another upon excursions from the line of beta-stability. Therefore in these regions (where atomic mass data are presently nonexistent or sparse) the models can be tested rigorously to highlight the features that affect the quality of their short-range and long-range extrapolation properties. Selection of systems tomore » study can be guided, in part, by a desire to probe those mass regions where distinctions among mass models are most apparent and where yields of exotic isotopes, produced via radioactive beams, can be optimized. Identification of models in such regions that have good predictive properties will aid materially in guiding the selection of additional experiments which ultimately will provide expansion of the atomic mass database for further refinement of the mass models. 6 refs., 5 figs.« less

Powering up the future: radical polymers for battery applications.

PubMed

Janoschka, Tobias; Hager, Martin D; Schubert, Ulrich S

2012-12-18

Our society's dependency on portable electric energy, i.e., rechargeable batteries, which permit power consumption at any place and in any time, will eventually culminate in resource wars on limited commodities like lithium, cobalt, and rare earth metals. The substitution of conventional metals as means of electric charge storage by organic and polymeric materials, which may ultimately be derived from renewable resources, appears to be the only feasible way out. In this context, the novel class of organic radical batteries (ORBs) excelling in rate capability (i.e., charging speed) and cycling stability (>1000 cycles) sets new standards in battery research. This review examines stable nitroxide radical bearing polymers, their processing to battery systems, and their promising performance. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Facile and Green Production of Impurity-Free Aqueous Solutions of WS2 Nanosheets by Direct Exfoliation in Water.

PubMed

Pan, Long; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying

2016-12-01

To obtain 2D materials with large quantity, low cost, and little pollution, liquid-phase exfoliation of their bulk form in water is a particularly fascinating concept. However, the current strategies for water-borne exfoliation exclusively employ stabilizers, such as surfactants, polymers, or inorganic salts, to minimize the extremely high surface energy of these nanosheets and stabilize them by steric repulsion. It is worth noting, however, that the remaining impurities inevitably bring about adverse effects to the ultimate performances of 2D materials. Here, a facile and green route to large-scale production of impurity-free aqueous solutions of WS 2 nanosheets is reported by direct exfoliation in water. Crucial parameters such as initial concentration, sonication time, centrifugation speed, and centrifugation time are systematically evaluated to screen out an optimized condition for scaling up. Statistics based on morphological characterization prove that substantial fraction (66%) of the obtained WS 2 nanosheets are one to five layers. X-ray diffraction and Raman characterizations reveal a high quality with few, if any, structural distortions. The water-borne exfoliation route opens up new opportunities for easy, clean processing of WS 2 -based film devices that may shine in the fields of, e.g., energy storage and functional nanocomposites owing to their excellent electrochemical, mechanical, and thermal properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Variation of mechanical properties and oxidation with radiation dose and source in highly crosslinked remelted UHMWPE.

PubMed

Fung, Mitchell; Bowsher, John G; Van Citters, Douglas W

2018-06-01

Ultra-high molecular weight polyethylene (UHMWPE) is the current gold standard for bearing materials used in total joint arthroplasty. High-dose radiation is commonly used to crosslink UHMWPE, thereby improving its wear resistance. A subsequent remelting step eliminates trapped residual free radicals to promote oxidative stability on the shelf, and to prevent material degradation over the long term. Assessment of clinically retrieved, highly crosslinked UHMWPE devices shows signs of unanticipated oxidation occurring in vivo, despite the absence of free radicals prior to implantation. These findings warrant further investigation into possible factors impacting this phenomenon along with its clinical implications. The overall objective of this work is to quantify the influence of irradiation dose and source on UHMWPE's oxidative stability, along with the effects of oxidation on the ultimate mechanical properties, including strength, ductility, and toughness. The results showed a strong positive correlation between maximum oxidation and initial transvinylene content. Critical oxidation levels in the context of mechanical property loss were determined for e-beam and gamma treatments at various radiation doses. Further, it was shown that critical oxidation was more dependent on radiation dose and less dependent on source. If in vivo oxidation persists in these devices, this can potentially lead to mechanical failure (e.g. fatigue damage) as observed in terminally gamma-sterilized devices. Copyright © 2018 Elsevier Ltd. All rights reserved.

Stability of multiloop LQ regulators with nonlinearities. I - Regions of attraction. II - Regions of ultimate boundedness

NASA Technical Reports Server (NTRS)

Joshi, S. M.

1986-01-01

An investigation is conducted for the closed loop stability of linear time-invariant systems controlled by linear quadratic (LQ) regulators, in cases where nonlinearities exist in the control channels lying outside the stability sector in regions away from the origin. The estimate of the region of attraction thus obtained furnishes methods for the selection of performance function weights for more robust LQ designs. Attention is then given to the closed loop stability of linear time-invariant systems controlled by the LQ regulators when the nonlinearities in the loops escape the stability sector in a bounded region containing the origin.

Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials

DOE PAGES

Mu, Linqin; Lin, Ruoqian; Xu, Rong; ...

2018-04-18

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. Here, we observe that the mechanical breakdown of charged Li 1-xNi 0.4Mn 0.4Co 0.2O 2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformationsmore » from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles; i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.« less

Oxygen Release Induced Chemomechanical Breakdown of Layered Cathode Materials

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

Mu, Linqin; Lin, Ruoqian; Xu, Rong

Chemical and mechanical properties interplay on the nanometric scale and collectively govern the functionalities of battery materials. Understanding the relationship between the two can inform the design of battery materials with optimal chemomechanical properties for long-life lithium batteries. Herein, we report a mechanism of nanoscale mechanical breakdown in layered oxide cathode materials, originating from oxygen release at high states of charge under thermal abuse conditions. Here, we observe that the mechanical breakdown of charged Li 1-xNi 0.4Mn 0.4Co 0.2O 2 materials proceeds via a two-step pathway involving intergranular and intragranular crack formation. Owing to the oxygen release, sporadic phase transformationsmore » from the layered structure to the spinel and/or rocksalt structures introduce local stress, which initiates microcracks along grain boundaries and ultimately leads to the detachment of primary particles; i.e., intergranular crack formation. Furthermore, intragranular cracks (pores and exfoliations) form, likely due to the accumulation of oxygen vacancies and continuous phase transformations at the surfaces of primary particles. Finally, finite element modeling confirms our experimental observation that the crack formation is attributable to formation of oxygen vacancies, oxygen release, and phase transformations. This study is designed to directly observe the chemomechanical behavior of layered oxide cathode materials and provides a chemical basis for strengthening primary and secondary particles by stabilizing the oxygen anions in the lattice.« less

Characterization of polymeric nanoparticles for intravenous delivery: Focus on stability.

PubMed

Oliveira, Claudia L; Veiga, Francisco; Varela, Carla; Roleira, Fernanda; Tavares, Elisiário; Silveira, Isabel; Ribeiro, Antonio J

2017-02-01

The nano-bio interaction has been of increased focus in the past years but very limited results have been obtained for polymeric nanoparticles (NP). Not only is needed to broaden the results obtained with model NP towards other nano-materials used for clinical application but the colloidal stability of NP as a variable consequence of the formation of the protein corona has been significantly understated. The lack and heterogeneity of assays to study NP stability and represent the biological environment call for the standardization of assays to improve the representativeness and comparability of results. In this paper, uncoated and PAH-coated PLGA NP have been prepared and characterized in regard to their potential for intravenous administration. The comparative study of the stability of NP in three media used to represent the biological environment-bovine serum albumin (BSA) solution, mouse and human plasma - revealed that both formulations were unstable in human plasma as opposed to the results obtained for other media. This unexpected behavior in plasmas of different origins could be correlated with a significant variation of the amount of proteins adsorbed to NP and, ultimately, with an approximately 6-fold difference in total protein concentration between the plasma samples. These results suggest that inter-species variation could impact on the colloidal stability of NP and enhance the need to understand the correlation between biological media and identify protocol-related interferences which, altogether, may evidence a relevant factor compromising in vitro- in vivo correlation and the translation of delivery systems aimed at intravenous administration. Copyright © 2016 Elsevier B.V. All rights reserved.

Two-stage system based on a software-defined radio for stabilizing of optical frequency combs in long-term experiments.

PubMed

Cížek, Martin; Hucl, Václav; Hrabina, Jan; Smíd, Radek; Mikel, Břetislav; Lazar, Josef; Cíp, Ondřej

2014-01-20

A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. A stabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10(-11).

A comparative study to check fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate resin reinforced with different materials: An in vitro study.

PubMed

Gupt, Parikshit; Nagpal, Archana; Samra, Rupandeep Kaur; Verma, Ramit; Kaur, Jasjeet; Abrol, Surbhi

2017-01-01

The purpose of the study was to evaluate the fracture strength of provisional fixed partial dentures made of autopolymerizing polymethylmethacrylate (PMMA) resin using different types of reinforcement materials to determine the best among them. Fifty samples were made (10 samples for each group) with autopolymerizing PMMA resin using reinforcement materials (stainless steel wire: looped and unlooped and glass fiber: loose and unidirectional) as 3-unit posterior bridge. The test specimens were divided into five groups depending on the reinforcing material as Group I, II, III, IV, and V; Group I: PMMA unreinforced (control group), Group II: PMMA reinforced with stainless steel wire (straight ends), Group III: PMMA reinforced with stainless steel wire (looped ends), Group IV: PMMA reinforced with unidirectional glass fibers, and Group V: PMMA reinforced with randomly distributed glass fibers. Universal testing machine was used to evaluate and compare the fracture strength of samples. Comparison of mean ultimate force and ultimate stress was done employing one-way analysis of variance and Tukey's post hoc tests. The highest and lowest mean ultimate force and mean ultimate stress were of Group IV and I, respectively. Tukey's post hoc honestly significant difference multiple comparison for mean ultimate force and stress shows the increase in strength to be statistically significant ( P < 0.05) except for the samples reinforced with randomly distributed glass fibers ( P > 0.05). Unidirectional glass fibers showed the maximum strength, which was comparable to mean values of both stainless steel wire groups. Low cost and easy technique of using stainless steel wire make it the material of choice over the unidirectional glass fiber for reinforcement in nonesthetic areas where high strength is required.

Evaluation of the interfacial bond properties between carbon phenolic and glass phenolic composites

NASA Technical Reports Server (NTRS)

Jordan, K.; Clinton, R.; Jeelani, S.

1991-01-01

The effects of moisture and surface finish on the mechanical and physical properties of the interfacial bond between carbon/phenolic (C/P) and glass/phenolic (G/P) composite materials have been studied. Test results indicate that moisture substantially degrades the integrity of the interfacial bond between C/P and G/P materials. The apparent effect of the autoclave curing of the C/P material reduces the ultimate interlaminar shear length of the C/P material by 20 percent compared to the hydroclave curing of the C/P material. The variation in applied surface finishes is found to have no appreciable effect on the ultimate interlaminar shear strength of the interface in the wet laminate.

Consecutive anaerobic-aerobic treatment of the organic fraction of municipal solid waste and lignocellulosic materials in laboratory-scale landfill-bioreactors.

PubMed

Pellera, Frantseska-Maria; Pasparakis, Emmanouil; Gidarakos, Evangelos

2016-10-01

The scope of this study is to evaluate the use of laboratory-scale landfill-bioreactors, operated consecutively under anaerobic and aerobic conditions, for the combined treatment of the organic fraction of municipal solid waste (OFMSW) with two different co-substrates of lignocellulosic nature, namely green waste (GW) and dried olive pomace (DOP). According to the results such a system would represent a promising option for eventual larger scale applications. Similar variation patterns among bioreactors indicate a relatively defined sequence of processes. Initially operating the systems under anaerobic conditions would allow energetic exploitation of the substrates, while the implementation of a leachate treatment system ultimately aiming at nutrient recovery, especially during the anaerobic phase, could be a profitable option for the whole system, due to the high organic load that characterizes this effluent. In order to improve the overall effectiveness of such a system, measures towards enhancing methane contents of produced biogas, such as substrate pretreatment, should be investigated. Moreover, the subsequent aerobic phase should have the goal of stabilizing the residual materials and finally obtain an end material eventually suitable for other purposes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Defining a Materials Database for the Design of Copper Binary Alloy Catalysts for Electrochemical CO2 Conversion.

PubMed

Lee, Chan Woo; Yang, Ki Dong; Nam, Dae-Hyun; Jang, Jun Ho; Cho, Nam Heon; Im, Sang Won; Nam, Ki Tae

2018-01-24

While Cu electrodes are a versatile material in the electrochemical production of desired hydrocarbon fuels, Cu binary alloy electrodes are recently proposed to further tune reaction directionality and, more importantly, overcome the intrinsic limitation of scaling relations. Despite encouraging empirical demonstrations of various Cu-based metal alloy systems, the underlying principles of their outstanding performance are not fully addressed. In particular, possible phase segregation with concurrent composition changes, which is widely observed in the field of metallurgy, is not at all considered. Moreover, surface-exposed metals can easily form oxide species, which is another pivotal factor that determines overall catalytic properties. Here, the understanding of Cu binary alloy catalysts for CO 2 reduction and recent progress in this field are discussed. From the viewpoint of the thermodynamic stability of the alloy system and elemental mixing, possible microstructures and naturally generated surface oxide species are proposed. These basic principles of material science can help to predict and understand metal alloy structure and, moreover, act as an inspiration for the development of new binary alloy catalysts to further improve CO 2 conversion and, ultimately, achieve a carbon-neutral cycle. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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

Shrestha, Triratna; Alsagabi, Sultan; Charit, Indrajit

The modified 9Cr-1Mo steel (Grade 91) is a material of choice in fossil-fuel-fired power plants with increased efficiency, service life, and reduction in emission of greenhouse gases. It is also considered a prospective material for the Next Generation Nuclear Power Plant for application in reactor pressure vessels at temperatures up to 650°C. In this paper, heat treatment of the modified 9Cr-1Mo steel was studied by normalizing and tempering the steel at various temperatures and times, with the ultimate goal of improving its creep resistance and optimizing material hardness. The microstructural evolution of the heat treated steels was correlated with themore » differential scanning calorimetric results. Optical microscopy, scanning and transmission electron microscopy in conjunction with microhardness profiles and calorimetric plots were used to understand the evolution of microstructure including precipitate structures in modified 9Cr-1Mo steel and relate it to the mechanical behavior of the steel. Thermo-CalcTM calculations were used to support experimental work and provide guidance in terms of the precipitate stability and microstructural evolution. Furthermore, the carbon isopleth and temperature dependencies of the volume fraction of different precipitates were constructed. The predicted and experimentally observed results were found to be in good agreement.« less

Ultrastrong Polyoxyzole Nanofiber Membranes for Dendrite-Proof and Heat-Resistant Battery Separators.

PubMed

Hao, Xiaoming; Zhu, Jian; Jiang, Xiong; Wu, Haitao; Qiao, Jinshuo; Sun, Wang; Wang, Zhenhua; Sun, Kening

2016-05-11

Polymeric nanomaterials emerge as key building blocks for engineering materials in a variety of applications. In particular, the high modulus polymeric nanofibers are suitable to prepare flexible yet strong membrane separators to prevent the growth and penetration of lithium dendrites for safe and reliable high energy lithium metal-based batteries. High ionic conductance, scalability, and low cost are other required attributes of the separator important for practical implementations. Available materials so far are difficult to comply with such stringent criteria. Here, we demonstrate a high-yield exfoliation of ultrastrong poly(p-phenylene benzobisoxazole) nanofibers from the Zylon microfibers. A highly scalable blade casting process is used to assemble these nanofibers into nanoporous membranes. These membranes possess ultimate strengths of 525 MPa, Young's moduli of 20 GPa, thermal stability up to 600 °C, and impressively low ionic resistance, enabling their use as dendrite-suppressing membrane separators in electrochemical cells. With such high-performance separators, reliable lithium-metal based batteries operated at 150 °C are also demonstrated. Those polyoxyzole nanofibers would enrich the existing library of strong nanomaterials and serve as a promising material for large-scale and cost-effective safe energy storage.

Implant Surface Design Regulates Mesenchymal Stem Cell Differentiation and Maturation

PubMed Central

Boyan, B.D.; Cheng, A.; Olivares-Navarrete, R.; Schwartz, Z.

2016-01-01

Changes in dental implant materials, structural design, and surface properties can all affect biological response. While bulk properties are important for mechanical stability of the implant, surface design ultimately contributes to osseointegration. This article reviews the surface parameters of dental implant materials that contribute to improved cell response and osseointegration. In particular, we focus on how surface design affects mesenchymal cell response and differentiation into the osteoblast lineage. Surface roughness has been largely studied at the microscale, but recent studies have highlighted the importance of hierarchical micron/submicron/nanosurface roughness, as well as surface roughness in combination with surface wettability. Integrins are transmembrane receptors that recognize changes in the surface and mediate downstream signaling pathways. Specifically, the noncanonical Wnt5a pathway has been implicated in osteoblastic differentiation of cells on titanium implant surfaces. However, much remains to be elucidated. Only recently have studies been conducted on the differences in biological response to implants based on sex, age, and clinical factors; these all point toward differences that advocate for patient-specific implant design. Finally, challenges in implant surface characterization must be addressed to optimize and compare data across studies. An understanding of both the science and the biology of the materials is crucial for developing novel dental implant materials and surface modifications for improved osseointegration. PMID:26927483

Disinfection and Stabilization Processes

EPA Science Inventory

Municipal wastewater sludges are composed of organic and inorganic contaminants from domestic, commercial and industrial wastewaters entering collection systems. Many options are available for ultimate disposal of residual solids, however few of these options provide for benefic...

Telomeres and replicative senescence: Is it only length that counts?

PubMed

von Zglinicki, T

2001-07-26

Telomeres are well established as a major 'replicometer', counting the population doublings in primary human cell cultures and ultimately triggering replicative senescence. However, neither is the pace of this biological clock inert, nor is there a fixed threshold telomere length acting as the universal trigger of replicative senescence. The available data suggest that opening of the telomeric loop and unscheduled exposure of the single-stranded G-rich telomeric overhang might act like a semaphore to signal senescent cell cycle arrest. Short telomere length, telomeric single-strand breaks, low levels of loop-stabilizing proteins, or other factors may trigger this opening of the loop. Thus, both telomere shortening and the ultimate signalling into senescence are able to integrate different environmental and genetic factors, especially oxidative stress-mediated damage, which might otherwise become a thread to genomic stability.

Ultimate boundedness stability and controllability of hereditary systems

NASA Technical Reports Server (NTRS)

Chukwu, E. N.

1979-01-01

By generalizing the Liapunov-Yoshizawa techniques, necessary and sufficient conditions are given for uniform boundedness and uniform ultimate boundedness of a rather general class of nonlinear differential equations of neutral type. Among the applications treated by the methods are the Lienard equation of neutral type and hereditary systems of Lurie type. The absolute stability of this later equation is also investigated. A certain existence result of a solution of a neutral functional differential inclusion with two point boundary values is applied to study the exact function space controllability of a nonlinear neutral functional differential control system. A geometric growth condition is used to characterize both the function space and Euclidean controllability of another nonlinear delay system which has a compact and convex control set. This yields conditions under which perturbed nonlinear delay controllable systems are controllable.

Long-Term Stable Adhesion for Conducting Polymers in Biomedical Applications: IrOx and Nanostructured Platinum Solve the Chronic Challenge.

PubMed

Boehler, Christian; Oberueber, Felix; Schlabach, Sabine; Stieglitz, Thomas; Asplund, Maria

2017-01-11

Conducting polymers (CPs) have frequently been described as outstanding coating materials for neural microelectrodes, providing significantly reduced impedance or higher charge injection compared to pure metals. Usability has until now, however, been limited by poor adhesion of polymers like poly(3,4-ethylenedioxythiophene) (PEDOT) to metallic substrates, ultimately precluding long-term applications. The aim of this study was to overcome this weakness of CPs by introducing two novel adhesion improvement strategies that can easily be integrated with standard microelectrode fabrication processes. Iridium Oxide (IrOx) demonstrated exceptional stability for PEDOT coatings, resulting in polymer survival over 10 000 redox cycles and 110 days under accelerated aging conditions at 60 °C. Nanostructured Pt was furthermore introduced as a purely mechanical adhesion promoter providing 10-fold adhesion improvement compared to smooth Pt substrates by simply altering the morphology of Pt. This layer can be realized in a very simple process that is compatible with any electrode design, turning nanostructured Pt into a universal adhesion layer for CP coatings. By the introduction of these adhesion-promoting strategies, the weakness of CP-based neural probes can ultimately be eliminated and true long-term stable use of PEDOT on neural probes will be possible in future electrode generations.

Hollow spheres of iron carbide nanoparticles encased in graphitic layers as oxygen reduction catalysts.

PubMed

Hu, Yang; Jensen, Jens Oluf; Zhang, Wei; Cleemann, Lars N; Xing, Wei; Bjerrum, Niels J; Li, Qingfeng

2014-04-01

Nonprecious metal catalysts for the oxygen reduction reaction are the ultimate materials and the foremost subject for low-temperature fuel cells. A novel type of catalysts prepared by high-pressure pyrolysis is reported. The catalyst is featured by hollow spherical morphologies consisting of uniform iron carbide (Fe3 C) nanoparticles encased by graphitic layers, with little surface nitrogen or metallic functionalities. In acidic media the outer graphitic layers stabilize the carbide nanoparticles without depriving them of their catalytic activity towards the oxygen reduction reaction (ORR). As a result the catalyst is highly active and stable in both acid and alkaline electrolytes. The synthetic approach, the carbide-based catalyst, the structure of the catalysts, and the proposed mechanism open new avenues for the development of ORR catalysts. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polypyrrole/carbon nanotube supercapacitors: Technological advances and challenges

NASA Astrophysics Data System (ADS)

Afzal, Adeel; Abuilaiwi, Faraj A.; Habib, Amir; Awais, Muhammad; Waje, Samaila B.; Atieh, Muataz A.

2017-06-01

The supercapacitors are advanced electrochemical energy storage devices having characteristics such as high storage capacity, rapid delivery of charge, and long cycle life. Polypyrrole (PPy) - an electronically conducting polymer, and carbon nanotubes (CNT) with high surface area and exceptional electrical and mechanical properties are among the most frequently studied advanced electrode materials for supercapacitors. The asymmetric supercapacitors composed of PPy/CNT composite electrodes offer complementary benefits to improve the specific capacitance, energy density, and stability. This article presents an overview of the recent technological advances in PPy/CNT composite supercapacitors and their limitations. Various strategies for synthesis and fabrication of PPy/CNT composites are discussed along with the factors that influence their ultimate electrochemical performance. The drawbacks and challenges of modern PPy/CNT composite supercapacitors are also reviewed, and potential areas of concern are identified for future research and development.

Infrared Active Sm1-xndxnio3 Based Nano-Switchings For High Powers Laser Sources

NASA Astrophysics Data System (ADS)

Ngom, B. D.; Kana, J. B. Kana; Nemraoui, O.; Manyala, N.; Maaza, M.; Mdjoe, R.; Beye, A. C.

2008-09-01

This contribution was targeted to engineer novel thermochromic infrared nano-structured photonics. These smart optically tuneable materials are based on rare earth nickelates in the form of ReNiO3 where Re is bi-solution of rare earth metals of Samarium "Sm" and Neodynium "Nd." In addition to their Metal-Insulator tuneable transition temperature (MIT), these MIT oxide family exhibit a specific thermal stability and thus could be ideal to an ultimate optical limiting and other Non-Linear Optical properties for high power laser sources. This MIT thermochomic ReNiO3 system is novel in its nano-structured form and has not been investigated from nonlinear optical viewpoint. This contribution reports on the optimization of the synthesis of Sm1-xNdxNiO3 Nano-structures and investigation of their corresponding MIT electron dynamics.

Highly Loaded Composite Strut Test Results

NASA Technical Reports Server (NTRS)

Wu, K. C.; Jegley, Dawn C.; Barnard, Ansley; Phelps, James E.; McKeney, Martin J.

2011-01-01

Highly loaded composite struts from a proposed truss-based Altair lunar lander descent stage concept were selected for development under NASA's Advanced Composites Technology program. Predicted compressive member forces during launch and ascent of over -100,000 lbs were much greater than the tensile loads. Therefore, compressive failure modes, including structural stability, were primary design considerations. NASA's industry partner designed and built highly loaded struts that were delivered to NASA for testing. Their design, fabricated on a washout mandrel, had a uniform-diameter composite tube with composite tapered ends. Each tapered end contained a titanium end fitting with facing conical ramps that are overlaid and overwrapped with composite materials. The highly loaded struts were loaded in both tension and compression, with ultimate failure produced in compression. Results for the two struts tested are presented and discussed, along with measured deflections, strains and observed failure mechanisms.

Ultimate Longitudinal Strength of Composite Ship Hulls

NASA Astrophysics Data System (ADS)

Zhang, Xiangming; Huang, Lingkai; Zhu, Libao; Tang, Yuhang; Wang, Anwen

2017-01-01

A simple analytical model to estimate the longitudinal strength of ship hulls in composite materials under buckling, material failure and ultimate collapse is presented in this paper. Ship hulls are regarded as assemblies of stiffened panels which idealized as group of plate-stiffener combinations. Ultimate strain of the plate-stiffener combination is predicted under buckling or material failure with composite beam-column theory. The effects of initial imperfection of ship hull and eccentricity of load are included. Corresponding longitudinal strengths of ship hull are derived in a straightforward method. A longitudinally framed ship hull made of symmetrically stacked unidirectional plies under sagging is analyzed. The results indicate that present analytical results have a good agreement with FEM method. The initial deflection of ship hull and eccentricity of load can dramatically reduce the bending capacity of ship hull. The proposed formulations provide a simple but useful tool for the longitudinal strength estimation in practical design.

Development of optical fiber frequency and time distribution systems

NASA Technical Reports Server (NTRS)

Lutes, G.

1982-01-01

The development of ultra stable optical fiber distribution systems for the dissemination of frequency and timing references is reported. The ultimate design goals for these systems are a frequency stability of 10 to the -17 power for tau or = 100 sec and time stability of + or - 0.1 ns for 1 year and operation over distances or = 30 km. A prototype system is reviewed and progress is discussed.

Nanocomposite scaffold with enhanced stability by hydrogen bonds between collagen, polyvinyl pyrrolidone and titanium dioxide.

PubMed

Li, Na; Fan, Xialian; Tang, Keyong; Zheng, Xuejing; Liu, Jie; Wang, Baoshi

2016-04-01

In this study, three-dimensional (3D) nanocomposite scaffolds, as potential substrates for skin tissue engineering, were fabricated by freeze drying the mixture of type I collagen extracted from porcine skin and polyvinyl pyrrolidone (PVP)-coated titanium dioxide (TiO2) nanoparticles. This procedure was performed without any cross-linker or toxic reagents to generate porosity in the scaffold. Both morphology and thermal stability of the nanocomposite scaffold were examined. The swelling behavior, mechanical properties and hydrolytic degradation of the composite scaffolds were carefully investigated. Our results revealed that collagen, PVP and TiO2 are bonded together by four main hydrogen bonds, which is an essential action for the formation of nanocomposite scaffold. Using Coasts-Redfern model, we were able to calculate the thermal degradation apparent activation energy and demonstrated that the thermal stability of nanocomposites is dependent on amount of PVP incorporated. Furthermore, SEM images showed that the collagen fibers are wrapped and stabilized on scaffolds by PVP molecules, which improve the ultimate tensile strength (UTS). The UTS of PVP-contained scaffold is four times higher than that of scaffold without PVP, whereas ultimate percentage of elongation (UPE) is decreased, and PVP can enhance the degradation resistance. Copyright © 2015 Elsevier B.V. All rights reserved.

Bonding Effectiveness of Luting Composites to Different CAD/CAM Materials.

PubMed

Peumans, Marleen; Valjakova, Emilija Bajraktarova; De Munck, Jan; Mishevska, Cece Bajraktarova; Van Meerbeek, Bart

To evaluate the influence of different surface treatments of six novel CAD/CAM materials on the bonding effectiveness of two luting composites. Six different CAD/CAM materials were tested: four ceramics - Vita Mark II; IPS Empress CAD and IPS e.max CAD; Celtra Duo - one hybrid ceramic, Vita Enamic, and one composite CAD/CAM block, Lava Ultimate. A total of 60 blocks (10 per material) received various mechanical surface treatments: 1. 600-grit SiC paper; 2. sandblasting with 30-μm Al2O3; 3. tribochemical silica coating (CoJet). Subsequent chemical surface treatments involved either no further treatment (control), HF acid etching (HF), silanization (S, or HF acid etching followed by silanization (HF+S). Two specimens with the same surface treatment were bonded together using two dual-curing luting composites: Clearfil Esthetic Cement (self-etching) or Panavia SA Cement (self-adhesive). After 1 week of water storage, the microtensile bond strength of the sectioned microspecimens was measured and the failure mode was evaluated. The bonding performance of the six CAD/CAM materials was significantly influenced by surface treatment (linear mixed models, p < 0.05). The luting cement had a significant influence on bond strength for Celtra Duo and Lava Ultimate (linear mixed models, p < 0.05). Mechanical surface treatment significantly influenced the bond strength for Celtra Duo (p = 0.0117), IPS e.max CAD (p = 0.0115), and Lava Ultimate (p < 0.0001). Different chemical surface treatments resulted in the highest bond strengths for the six CAD/CAM materials: Vita Mark II and IPS Empress CAD: S, HF+S; Celtra Duo: HF, HF+S; IPS e.max CAD: HF+S; Vita Enamic: HF+S, S. For Lava Ultimate, the highest bond strengths were obtained with HF, S, HF+S. Failure analysis showed a relation between bond strength and failure type: more mixed failures were observed with higher bond strengths. Mainly adhesive failures were noticed if no further surface treatment was done. The percentage of adhesive failures was higher for CAD/CAM materials with higher flexural strength (Celtra Duo, IPS e.max CAD, and Lava Ultimate). The bond strength of luting composites to novel CAD/CAM materials is influenced by surface treatment. For each luting composite, an adhesive cementation protocol can be specified in order to obtain the highest bond to the individual CAD/CAM materials.

Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

NASA Astrophysics Data System (ADS)

Marvel, Christopher Jonathan

The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice diffusivity calculations conceptually suggested that increasing W alloying concentrations can decrease the grain growth rate. The strongest evidence of grain growth stagnation was via nanoscale oxide particle drag in highly contaminated electrodeposited alloys. Interestingly, W-segregation was also detected to the oxide phase boundaries and revealed a potential indirect mechanism of thermal stability. The phase stability of pure and contaminated Ni-W alloys was investigated with density functional theory. Primarily, the calculations suggested that the intermetallic phases NiW and NiW2 are thermodynamically unstable, meaning the binary phase diagram is incorrect, but the ternary carbides Ni 6W6C and Ni2W4C are stable. Several Ni-W binary and Ni-W-C ternary phase diagrams were constructed using a simplified CALPHAD approach to improve the understanding of Ni-W phase stability. Lastly, it was determined that the fabrication process greatly influences the impurity types and concentrations of the alloys, and therefore greatly dictate which thermal stability mechanisms are active. Mechanically alloyed samples were found to be the most resistant to grain growth. The findings of this research will hopefully guide future efforts to design more thermally stable nanocrystalline alloys. The link between phase stability and grain growth behavior of Ni-W was thoroughly discussed, as well as the dependence of bulk fabrication processing on the contamination found in the alloys. Ultimately, this research has greatly expanded the general understanding of nanocrystalline Ni-W microstructures, and it is likely that similar phenomena occur in other nanocrystalline systems.

Development of Low Cost Soil Stabilization Using Recycled Material

NASA Astrophysics Data System (ADS)

Ahmad, F.; Yahaya, A. S.; Safari, A.

2016-07-01

Recycled tyres have been used in many geotechnical engineering projects such as soil improvement, soil erosion and slope stability. Recycled tyres mainly in chip and shredded form are highly compressible under low and normal pressures. This characteristic would cause challenging problems in some applications of soil stabilization such as retaining wall and river bank projects. For high tensile stress and low tensile strain the use of fiberglass would be a good alternative for recycled tyre in some cases. To evaluate fiberglass as an alternative for recycled tyre, this paper focused on tests of tensile tests which have been carried out between fiberglass and recycled tyre strips. Fibreglass samples were produced from chopped strand fibre mat, a very low-cost type of fibreglass, which is cured by resin and hardener. Fibreglass samples in the thickness of 1 mm, 2 mm, 3 mm and 4 mm were developed 100 mm x 300 mm pieces. It was found that 3 mm fibreglass exhibited the maximum tensile load (MTL) and maximum tensile stress (MTS) greater than other samples. Statistical analysis on 3 mm fibreglass indicated that in the approximately equal MTL fibreglass samples experienced 2% while tyre samples experienced 33.9% ultimate tensile strain (UTST) respectively. The results also showed an approximately linear relationship between stress and strain for fibreglass samples and Young's modulus (E), ranging from 3581 MPa to 4728 MPa.

Functionalized graphene sheets for polymer nanocomposites.

PubMed

Ramanathan, T; Abdala, A A; Stankovich, S; Dikin, D A; Herrera-Alonso, M; Piner, R D; Adamson, D H; Schniepp, H C; Chen, X; Ruoff, R S; Nguyen, S T; Aksay, I A; Prud'Homme, R K; Brinson, L C

2008-06-01

Polymer-based composites were heralded in the 1960s as a new paradigm for materials. By dispersing strong, highly stiff fibres in a polymer matrix, high-performance lightweight composites could be developed and tailored to individual applications. Today we stand at a similar threshold in the realm of polymer nanocomposites with the promise of strong, durable, multifunctional materials with low nanofiller content. However, the cost of nanoparticles, their availability and the challenges that remain to achieve good dispersion pose significant obstacles to these goals. Here, we report the creation of polymer nanocomposites with functionalized graphene sheets, which overcome these obstacles and provide superb polymer-particle interactions. An unprecedented shift in glass transition temperature of over 40 degrees C is obtained for poly(acrylonitrile) at 1 wt% functionalized graphene sheet, and with only 0.05 wt% functionalized graphene sheet in poly(methyl methacrylate) there is an improvement of nearly 30 degrees C. Modulus, ultimate strength and thermal stability follow a similar trend, with values for functionalized graphene sheet- poly(methyl methacrylate) rivaling those for single-walled carbon nanotube-poly(methyl methacrylate) composites.

Removing Beam Current Artifacts in Helium Ion Microscopy: A Comparison of Image Processing Techniques.

PubMed

Barlow, Anders J; Portoles, Jose F; Sano, Naoko; Cumpson, Peter J

2016-10-01

The development of the helium ion microscope (HIM) enables the imaging of both hard, inorganic materials and soft, organic or biological materials. Advantages include outstanding topographical contrast, superior resolution down to <0.5 nm at high magnification, high depth of field, and no need for conductive coatings. The instrument relies on helium atom adsorption and ionization at a cryogenically cooled tip that is atomically sharp. Under ideal conditions this arrangement provides a beam of ions that is stable for days to weeks, with beam currents in the order of picoamperes. Over time, however, this stability is lost as gaseous contamination builds up in the source region, leading to adsorbed atoms of species other than helium, which ultimately results in beam current fluctuations. This manifests itself as horizontal stripe artifacts in HIM images. We investigate post-processing methods to remove these artifacts from HIM images, such as median filtering, Gaussian blurring, fast Fourier transforms, and principal component analysis. We arrive at a simple method for completely removing beam current fluctuation effects from HIM images while maintaining the full integrity of the information within the image.

Physico-mechanical and thermal characteristics of commercially available and newly developed dental flowable composites

NASA Astrophysics Data System (ADS)

Kamalak, Hakan; Canbay, C. Aksu; Yiğit, Oktay; Altin, Serdar

2018-03-01

In this study, we investigated the structural stability, thermal conductivity, thermal analysis, materials' homogeneity of newly developed flowable composites. 6 different dental flowable composite resins; Grandio Flow (GF), Charisma Flow (CF), Tetric N Flow (TNF), Clearfil Majesty Flow (CMF),3M Filtek Ultimate Flow (3MFU), Voco Amaris Flow (VFA) were used. Restorations were made in standard teflon molds and the materials were light-cured for 20s in a 6 mm × 2 mm teflon mould. After polymerization, samples were kept in distilled water at 37 °C/24 h .It was found that the composites have multiphase component such as metallic dopant and organic binder. The XRD investigation showed that there was a broad halo in the pattern which indicates the organic section in the composites. The FTIR results indicate the bond structure of the composites. The temperature dependence of the thermal conductivity of the composites were found below to 5 mW/K value depending on the type of the composites, which are low enough for dental application. The micro-hardness of the samples was analyzed and the result was compared.

Hendra virus fusion protein transmembrane domain contributes to pre-fusion protein stability

PubMed Central

Webb, Stacy; Nagy, Tamas; Moseley, Hunter; Fried, Michael; Dutch, Rebecca

2017-01-01

Enveloped viruses utilize fusion (F) proteins studding the surface of the virus to facilitate membrane fusion with a target cell membrane. Fusion of the viral envelope with a cellular membrane is required for release of viral genomic material, so the virus can ultimately reproduce and spread. To drive fusion, the F protein undergoes an irreversible conformational change, transitioning from a metastable pre-fusion conformation to a more thermodynamically stable post-fusion structure. Understanding the elements that control stability of the pre-fusion state and triggering to the post-fusion conformation is important for understanding F protein function. Mutations in F protein transmembrane (TM) domains implicated the TM domain in the fusion process, but the structural and molecular details in fusion remain unclear. Previously, analytical ultracentrifugation was utilized to demonstrate that isolated TM domains of Hendra virus F protein associate in a monomer-trimer equilibrium (Smith, E. C., Smith, S. E., Carter, J. R., Webb, S. R., Gibson, K. M., Hellman, L. M., Fried, M. G., and Dutch, R. E. (2013) J. Biol. Chem. 288, 35726–35735). To determine factors driving this association, 140 paramyxovirus F protein TM domain sequences were analyzed. A heptad repeat of β-branched residues was found, and analysis of the Hendra virus F TM domain revealed a heptad repeat leucine-isoleucine zipper motif (LIZ). Replacement of the LIZ with alanine resulted in dramatically reduced TM-TM association. Mutation of the LIZ in the whole protein resulted in decreased protein stability, including pre-fusion conformation stability. Together, our data suggest that the heptad repeat LIZ contributed to TM-TM association and is important for F protein function and pre-fusion stability. PMID:28213515

Hendra virus fusion protein transmembrane domain contributes to pre-fusion protein stability.

PubMed

Webb, Stacy; Nagy, Tamas; Moseley, Hunter; Fried, Michael; Dutch, Rebecca

2017-04-07

Enveloped viruses utilize fusion (F) proteins studding the surface of the virus to facilitate membrane fusion with a target cell membrane. Fusion of the viral envelope with a cellular membrane is required for release of viral genomic material, so the virus can ultimately reproduce and spread. To drive fusion, the F protein undergoes an irreversible conformational change, transitioning from a metastable pre-fusion conformation to a more thermodynamically stable post-fusion structure. Understanding the elements that control stability of the pre-fusion state and triggering to the post-fusion conformation is important for understanding F protein function. Mutations in F protein transmembrane (TM) domains implicated the TM domain in the fusion process, but the structural and molecular details in fusion remain unclear. Previously, analytical ultracentrifugation was utilized to demonstrate that isolated TM domains of Hendra virus F protein associate in a monomer-trimer equilibrium (Smith, E. C., Smith, S. E., Carter, J. R., Webb, S. R., Gibson, K. M., Hellman, L. M., Fried, M. G., and Dutch, R. E. (2013) J. Biol. Chem. 288, 35726-35735). To determine factors driving this association, 140 paramyxovirus F protein TM domain sequences were analyzed. A heptad repeat of β-branched residues was found, and analysis of the Hendra virus F TM domain revealed a heptad repeat leucine-isoleucine zipper motif (LIZ). Replacement of the LIZ with alanine resulted in dramatically reduced TM-TM association. Mutation of the LIZ in the whole protein resulted in decreased protein stability, including pre-fusion conformation stability. Together, our data suggest that the heptad repeat LIZ contributed to TM-TM association and is important for F protein function and pre-fusion stability. © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

BIOINDICATORS OF SUSTAINABLE DEVELOPMENT STRATEGIES IN SUBTROPICAL CLIMATES

EPA Science Inventory

Anthropogenic sediment and nutrients inputs to aquatic systems associated with urbanization are commonly cited as threatening water quality and ultimately overall ecosystem stability and productivity. Although anthropogenic nutrient sources are rarely detected as elevated diss...

Regions of attraction and ultimate boundedness for linear quadratic regulators with nonlinearities

NASA Technical Reports Server (NTRS)

Joshi, S. M.

1984-01-01

The closed-loop stability of multivariable linear time-invariant systems controlled by optimal linear quadratic (LQ) regulators is investigated for the case when the feedback loops have nonlinearities N(sigma) that violate the standard stability condition, sigma N(sigma) or = 0.5 sigma(2). The violations of the condition are assumed to occur either (1) for values of sigma away from the origin (sigma = 0) or (2) for values of sigma in a neighborhood of the origin. It is proved that there exists a region of attraction for case (1) and a region of ultimate boundedness for case (2), and estimates are obtained for these regions. The results provide methods for selecting the performance function parameters to design LQ regulators with better tolerance to nonlinearities. The results are demonstrated by application to the problem of attitude and vibration control of a large, flexible space antenna in the presence of actuator nonlinearities.

Temperature effects on the mechanical properties of annealed and HERF 304L stainless steel.

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

Antoun, Bonnie R.

2004-11-01

The effect of temperature on the tensile properties of annealed 304L stainless steel and HERF 304L stainless steel forgings was determined by completing experiments over the moderate range of -40 F to 160 F. Temperature effects were more significant in the annealed material than the HERF material. The tensile yield strength of the annealed material at -40 F averaged twenty two percent above the room temperature value and at 160 F averaged thirteen percent below. The tensile yield strength for the three different geometry HERF forgings at -40 F and 160 F changed less than ten percent from room temperature.more » The ultimate tensile strength was more temperature dependent than the yield strength. The annealed material averaged thirty six percent above and fourteen percent below the room temperature ultimate strength at -40 F and 160 F, respectively. The HERF forgings exhibited similar, slightly lower changes in ultimate strength with temperature. For completeness and illustrative purposes, the stress-strain curves are included for each of the tensile experiments conducted. The results of this study prompted a continuation study to determine tensile property changes of welded 304L stainless steel material with temperature, documented separately.« less

Ultrathin dendrimer-graphene oxide composite film for stable cycling lithium-sulfur batteries.

PubMed

Liu, Wen; Jiang, Jianbing; Yang, Ke R; Mi, Yingying; Kumaravadivel, Piranavan; Zhong, Yiren; Fan, Qi; Weng, Zhe; Wu, Zishan; Cha, Judy J; Zhou, Henghui; Batista, Victor S; Brudvig, Gary W; Wang, Hailiang

2017-04-04

Lithium-sulfur batteries (Li-S batteries) have attracted intense interest because of their high specific capacity and low cost, although they are still hindered by severe capacity loss upon cycling caused by the soluble lithium polysulfide intermediates. Although many structure innovations at the material and device levels have been explored for the ultimate goal of realizing long cycle life of Li-S batteries, it remains a major challenge to achieve stable cycling while avoiding energy and power density compromises caused by the introduction of significant dead weight/volume and increased electrochemical resistance. Here we introduce an ultrathin composite film consisting of naphthalimide-functionalized poly(amidoamine) dendrimers and graphene oxide nanosheets as a cycling stabilizer. Combining the dendrimer structure that can confine polysulfide intermediates chemically and physically together with the graphene oxide that renders the film robust and thin (<1% of the thickness of the active sulfur layer), the composite film is designed to enable stable cycling of sulfur cathodes without compromising the energy and power densities. Our sulfur electrodes coated with the composite film exhibit very good cycling stability, together with high sulfur content, large areal capacity, and improved power rate.

Increasing the Thermal Stability of Aluminum Titanate for Solid Oxide Fuel Cell Anodes

NASA Technical Reports Server (NTRS)

Bender, Jeffrey B.

2004-01-01

Solid-oxide fuel cells (SOFCs) show great potential as a power source for future space exploration missions. Because SOFCs operate at temperatures significantly higher than other types of fuel cells, they can reach overall efficiencies of up to 60% and are able to utilize fossil fuels. The SOFC team at GRC is leading NASA's effort to develop a solid oxide fuel cell with a power density high enough to be used for aeronautics and space applications, which is approximately ten times higher than ground transport targets. layers must be able to operate as a single unit at temperatures upwards of 900'C for at least 40,000 hours with less than ten percent degradation. One key challenge to meeting this goal arises from the thermal expansion mismatch between different layers. The amount a material expands upon heating is expressed by its coefficient of thermal expansion (CTE). If the CTEs of adjacent layers are substantially different, thermal stresses will arise during the cell's fabrication and operation. These stresses, accompanied by thermal cycling, can fracture and destroy the cell. While this is not an issue at the electrolyte-cathode interface, it is a major concern at the electrolyte-anode interface, especially in high power anode-supported systems. electrolyte are nearly identical. Conventionally, this has been accomplished by varying the composition of the anode to match the CTE of the yittria-stabilized zirconia (YSZ) electrolyte (approx.10.8x10(exp -6/degC). A Ni/YSZ composite is typically used as a base material for the anode due to its excellent electrochemical properties, but its CTE is about 13.4x10(exp -6/degC). One potential way to lower the CTE of this anode is to add a small percentage of polycrystalline Al2TiO5, with a CTE of 0.68x10(exp -6/degC, to the Ni/YSZ base. However, Al2TiO5 is thermally unstable and loses its effectiveness as it decomposes to Al2O3 and TiO2 between 750 C and 1280 C. be used as additives to increase the thermal stability of Al2TiO5 in SOFC operating conditions without adversely affecting the electrochemical properties of the SOFC anode. Three candidate materials were chosen through an extensive literature review: MgO, Fe2O3, and ZrTiO4. Although all three have been shown to prevent Al2TiO5 decomposition under various conditions, their effectiveness in the temperature range and atmosphere of the SOFC has not yet been evaluated. Several batches of Al2TiO5 with varying amounts of additives were prepared, exposed to reducing and oxidizing atmospheres at elevated temperatures, and the resulting decomposition of Al2TiO5 was measured. The most promising additives were further evaluated with the goal of ultimately preparing low CTE anodes that are chemically compatible to current systems. Adding minor constituents to stabilize Al2TiO5 could ultimately preserve its low CTE for the life of the fuel cell and improve the cell's long-term performance without a drop in anode conductivity. Further, these low CTE filler additions could allow the use of new sulfur tolerant anode materials, improving the viability of SOFCs for future aeronautics and space applications. Every SOFC consists of a cathode and an anode separated by an electrolyte, These three One way to avoid this problem is to design the cell such that the CTEs of the anode and The objective of this summer research project was to evaluate several materials that could

Nanoparticle "Theranostic" Platforms for Applications in Cancer

NASA Astrophysics Data System (ADS)

Steiner, Jason Michael

The study and implementation of nanotechnology as applied to biology is making substantial progress toward the expansion of the dialogue between synthetic and biological systems. This dialogue leads to a deeper understanding of the origins, manifestations, and characteristics of biological phenomenon that ultimately will lead to improved methods of diagnosing and treating a variety of pathologies. Perhaps the most prevalent application of this new technology is in the field of cancer research, encompassing an array of diagnostic and therapeutic approaches for in vivo utilization. These approaches include novel ways of enhancing tumor imaging for earlier detection or delivering toxic therapeutics directly to the site of action, sparing the systemic damage that so often accompanies cancer treatment. However, it is the combination of these essential and orthogonal functionalities that is the hallmark of the promise of nanotechnology. Such materials, coined as "theranostics" for their therapeutic and diagnostic capabilities, allow for a new depth of understanding of the behavior of nanoparticles in vivo, and in particular their efficacy as therapeutic treatments. This dissertation discusses the development of platforms and materials that may be employed as theranostic cancer agents from two distinct philosophical approaches---what may be called "traditional" and "non-traditional" nanotechnology. The "non-traditional" approach details the development of a novel DNA nanoparticle platform created through an exponential enrichment process for selected cell targeting. The products compose a novel class of nanoparticles that possess all of the naturally advantageous properties of DNA. The remainder of the dissertation presents a more "traditional" approach to hierarchical nanoparticle construction, discussing synthesis, stabilization and functionalization of theranostic materials of iron oxide and gold and their combination into novel nanostructures for more efficacious in vivo imaging agents. Ultimately, the preferred path between traditional non-traditional methods rests on whether biological selection is more powerful for functionality than rational design, or whether the most efficacious route is a combination thereof.

Two-Stage System Based on a Software-Defined Radio for Stabilizing of Optical Frequency Combs in Long-Term Experiments

PubMed Central

Čížek, Martin; Hucl, Václav; Hrabina, Jan; Šmíd, Radek; Mikel, Břetislav; Lazar, Josef; Číp, Ondřej

2014-01-01

A passive optical resonator is a special sensor used for measurement of lengths on the nanometer and sub-nanometer scale. Astabilized optical frequency comb can provide an ultimate reference for measuring the wavelength of a tunable laser locked to the optical resonator. If we lock the repetition and offset frequencies of the comb to a high-grade radiofrequency (RF) oscillator its relative frequency stability is transferred from the RF to the optical frequency domain. Experiments in the field of precise length metrology of low-expansion materials are usually of long-term nature so it is required that the optical frequency comb stay in operation for an extended period of time. The optoelectronic closed-loop systems used for stabilization of combs are usually based on traditional analog electronic circuits processing signals from photodetectors. From an experimental point of view, these setups are very complicated and sensitive to ambient conditions, especially in the optical part, therefore maintaining long-time operation is not easy. The research presented in this paper deals with a novel approach based on digital signal processing and a software-defined radio. We describe digital signal processing algorithms intended for keeping the femtosecond optical comb in a long-time stable operation. This need arose during specialized experiments involving measurements of optical frequencies of tunable continuous-wave lasers. The resulting system is capable of keeping the comb in lock for an extensive period of time (8 days or more) with the relative stability better than 1.6 × 10−11. PMID:24448169

Mexico: The Ultimate Domino?

DTIC Science & Technology

1988-05-01

five key issues confronting the two countries: foreign debt, trade, migration, illegal drugs, and foreign policy. The outlook for Mexican political ... stability is evaluated. The author concludes that Mexico’s financial condition presents near-term challenges, but its progress toward recovery, economic

Guidelines for Computing Longitudinal Dynamic Stability Characteristics of a Subsonic Transport

NASA Technical Reports Server (NTRS)

Thompson, Joseph R.; Frank, Neal T.; Murphy, Patrick C.

2010-01-01

A systematic study is presented to guide the selection of a numerical solution strategy for URANS computation of a subsonic transport configuration undergoing simulated forced oscillation about its pitch axis. Forced oscillation is central to the prevalent wind tunnel methodology for quantifying aircraft dynamic stability derivatives from force and moment coefficients, which is the ultimate goal for the computational simulations. Extensive computations are performed that lead in key insights of the critical numerical parameters affecting solution convergence. A preliminary linear harmonic analysis is included to demonstrate the potential of extracting dynamic stability derivatives from computational solutions.

Effect of antibodies on pathogen dynamics with delays and two routes of infection

NASA Astrophysics Data System (ADS)

Elaiw, A. M.; Almatrafi, A. A.; Hobiny, A. D.

2018-06-01

We study the global stability of pathogen dynamics models with saturated pathogen-susceptible and infected-susceptible incidence. The models incorporate antibody immune response and three types of discrete or distributed time delays. We first show that the solutions of the model are nonnegative and ultimately bounded. We determine two threshold parameters, the basic reproduction number and antibody response activation number. We establish the existence and stability of the steady states. We study the global stability analysis of models using Lyapunov method. The numerical simulations have shown that antibodies can reduce the pathogen progression.

Chairside CAD/CAM materials. Part 1: Measurement of elastic constants and microstructural characterization.

PubMed

Belli, Renan; Wendler, Michael; de Ligny, Dominique; Cicconi, Maria Rita; Petschelt, Anselm; Peterlik, Herwig; Lohbauer, Ulrich

2017-01-01

A deeper understanding of the mechanical behavior of dental restorative materials requires an insight into the materials elastic constants and microstructure. Here we aim to use complementary methodologies to thoroughly characterize chairside CAD/CAM materials and discuss the benefits and limitations of different analytical strategies. Eight commercial CAM/CAM materials, ranging from polycrystalline zirconia (e.max ZirCAD, Ivoclar-Vivadent), reinforced glasses (Vitablocs Mark II, VITA; Empress CAD, Ivoclar-Vivadent) and glass-ceramics (e.max CAD, Ivoclar-Vivadent; Suprinity, VITA; Celtra Duo, Dentsply) to hybrid materials (Enamic, VITA; Lava Ultimate, 3M ESPE) have been selected. Elastic constants were evaluated using three methods: Resonant Ultrasound Spectroscopy (RUS), Resonant Beam Technique (RBT) and Ultrasonic Pulse-Echo (PE). The microstructures were characterized using Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDX), Raman Spectroscopy and X-ray Diffraction (XRD). Young's modulus (E), Shear modulus (G), Bulk modulus (B) and Poisson's ratio (ν) were obtained for each material. E and ν reached values ranging from 10.9 (Lava Ultimate) to 201.4 (e.max ZirCAD) and 0.173 (Empress CAD) to 0.47 (Lava Ultimate), respectively. RUS showed to be the most complex and reliable method, while the PE method the easiest to perform but most unreliable. All dynamic methods have shown limitations in measuring the elastic constants of materials showing high damping behavior (hybrid materials). SEM images, Raman spectra and XRD patterns were made available for each material, showing to be complementary tools in the characterization of their crystal phases. Here different methodologies are compared for the measurement of elastic constants and microstructural characterization of CAD/CAM restorative materials. The elastic properties and crystal phases of eight materials are herein fully characterized. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Structure-Composition-Property Relationships in Polymeric Amorphous Calcium Phosphate-Based Dental Composites †

PubMed Central

O’Donnell, Justin N.R.; Schumacher, Gary E.; Antonucci, Joseph M.; Skrtic, Drago

2009-01-01

Our studies of amorphous calcium phosphate (ACP)-based materials over the last decade have yielded bioactive polymeric composites capable of protecting teeth from demineralization or even regenerating lost tooth mineral. The anti-cariogenic/re-mineralizing potential of these ACP composites originates from their propensity, when exposed to the oral environment, to release in a sustained manner sufficient levels of mineral-forming calcium and phosphate ions to promote formation of stable apatitic tooth mineral. However, the less than optimal ACP filler/resin matrix cohesion, excessive polymerization shrinkage and water sorption of these experimental materials can adversely affect their physicochemical and mechanical properties, and, ultimately, limit their lifespan. This study demonstrates the effects of chemical structure and composition of the methacrylate monomers used to form the matrix phase of composites on degree of vinyl conversion (DVC) and water sorption of both copolymers and composites and the release of mineral ions from the composites. Modification of ACP surface via introducing cations and/or polymers ab initio during filler synthesis failed to yield mechanically improved composites. However, moderate improvement in composite’s mechanical stability without compromising its remineralization potential was achieved by silanization and/or milling of ACP filler. Using ethoxylated bisphenol A dimethacrylate or urethane dimethacrylate as base monomers and adding moderate amounts of hydrophilic 2-hydroxyethyl methacrylate or its isomer ethyl-α-hydroxymethacrylate appears to be a promising route to maximize the remineralizing ability of the filler while maintaining high DVC. Exploration of the structure/composition/property relationships of ACP fillers and polymer matrices is complex but essential for achieving a better understanding of the fundamental mechanisms that govern dissolution/re-precipitation of bioactive ACP fillers, and, ultimately, the suitability of the composites for clinical evaluation. PMID:21966588

Effects of electron irradiation on LDPE/MWCNT composites

NASA Astrophysics Data System (ADS)

Yang, Jianqun; Li, Xingji; Liu, Chaoming; Rui, Erming; Wang, Liqin

2015-12-01

In this study, mutiwalled carbon nanotubes (MWCNTs) were incorporated into low density polyethylene (LDPE) in different concentrations (2%, 4% and 8%) using a melt blending process. Structural, thermal stability and tensile property of the unirradiated/irradiated LDPE/MWCNT composites by 110 keV electrons were investigated by means of scanning electron microscopy (SEM), small angle X-ray scattering (SAXS), Raman spectroscopy, electron paramagnetic resonance (EPR) spectroscopy, thermogravimetric analysis (TGA) and uniaxial tensile techniques. Experimental results show that the addition of MWCNTs obviously increases the ultimate tensile strength of LDPE and decreases the elongation at break, which is attributed to the homogeneous distribution of the MWCNTs in LDPE and intense interaction between MWCNTs and LDPE matrix. Also, the electron irradiation further increases the ultimate tensile strength of LDPE/MWCNT composites, which can be ascribed to the more intense interaction between MWCNTs and LDPE matrix, and the formation of crosslinking sites in LDPE matrix induced by the electron irradiation. The addition of MWCNTs significantly enhances thermal stability of the LDPE due to the hindering effect and the scavenging free radicals, while the electron irradiation decreases thermal stability of the LDPE/MWCNT composites since the structure of the MWCNTs and LDPE matrix damages.

Ultimate linewidth reduction of a semiconductor laser frequency-stabilized to a Fabry-Pérot interferometer.

PubMed

Bahoura, Messaoud; Clairon, André

2003-11-01

We report a theoretical dynamical analysis on effect of semiconductor laser phase noise on the achievable linewidth when locked to a Fabry-Pérot cavity fringe using a modulation-demodulation frequency stabilization technique such as the commonly used Pound-Drever-Hall frequency locking scheme. We show that, in the optical domain, the modulation-demodulation operation produces, in the presence of semiconductor laser phase noise, two kinds of excess noise, which could be much above the shot noise limit, namely, conversion noise (PM-to-AM) and intermodulation noise. We show that, in typical stabilization conditions, the ultimate semiconductor laser linewidth reduction can be severely limited by the intermodulation excess noise. The modulation-demodulation operation produces the undesirable nonlinear intermodulation effect through which the phase noise spectral components of the semiconductor laser, in the vicinity of even multiples of the modulation frequency, are downconverted into the bandpass of the frequency control loop. This adds a spurious signal, at the modulation frequency, to the error signal and limits the performance of the locked semiconductor laser. This effect, reported initially in the microwave domain using the quasistatic approximation, can be considerably reduced by a convenient choice of the modulation frequency.

Reinforcement-Learning-Based Robust Controller Design for Continuous-Time Uncertain Nonlinear Systems Subject to Input Constraints.

PubMed

Liu, Derong; Yang, Xiong; Wang, Ding; Wei, Qinglai

2015-07-01

The design of stabilizing controller for uncertain nonlinear systems with control constraints is a challenging problem. The constrained-input coupled with the inability to identify accurately the uncertainties motivates the design of stabilizing controller based on reinforcement-learning (RL) methods. In this paper, a novel RL-based robust adaptive control algorithm is developed for a class of continuous-time uncertain nonlinear systems subject to input constraints. The robust control problem is converted to the constrained optimal control problem with appropriately selecting value functions for the nominal system. Distinct from typical action-critic dual networks employed in RL, only one critic neural network (NN) is constructed to derive the approximate optimal control. Meanwhile, unlike initial stabilizing control often indispensable in RL, there is no special requirement imposed on the initial control. By utilizing Lyapunov's direct method, the closed-loop optimal control system and the estimated weights of the critic NN are proved to be uniformly ultimately bounded. In addition, the derived approximate optimal control is verified to guarantee the uncertain nonlinear system to be stable in the sense of uniform ultimate boundedness. Two simulation examples are provided to illustrate the effectiveness and applicability of the present approach.

Cellulose nanofibers/reduced graphene oxide flexible transparent conductive paper.

PubMed

Gao, Kezheng; Shao, Ziqiang; Wu, Xue; Wang, Xi; Li, Jia; Zhang, Yunhua; Wang, Wenjun; Wang, Feijun

2013-08-14

The cellulose nanofibers (CNFs) paper exhibit high visible light transmittance, high mechanical strength, and excellent flexibility. Therefore, CNFs paper may be an excellent substrate material for flexible transparent electronic devices. In this paper, we endeavor to prepare CNFs-based flexible transparent conductive paper by layer-by-layer (LbL) assembly using divalent copper ions (Cu(2+)) as the crosslinking agent. The thickness of the reduced graphene oxide (RGO) active layer in the CNFs paper can be controlled by the cycle times of the LbL assembly. CNFs/[RGO]20 paper has the sheet resistances of ∼2.5 kΩ/□, and the transmittance of about 76% at a wavelength of 550 nm. Furthermore, CNFs/[RGO]20 paper inherits the excellent mechanical properties of CNFs paper, and the ultimate strength is about 136 MPa. CNFs-based flexible transparent conductive paper also exhibits excellent electrical stability and flexibility. Copyright © 2013. Published by Elsevier Ltd.

Origin and elimination of photocurrent hysteresis by fullerene passivation in CH 3NH 3PbI 3 planar heterojunction solar cells

DOE PAGES

Shao, Yuchuan; Xiao, Zhengguo; Bi, Cheng; ...

2014-12-15

The large photocurrent hysteresis observed in many organometal trihalide perovskite solar cells has become a major hindrance impairing the ultimate performance and stability of these devices, while its origin was unknown. Here we demonstrate the trap states on the surface and grain boundaries of the perovskite materials to be the origin of photocurrent hysteresis and that the fullerene layers deposited on perovskites can effectively passivate these charge trap states and eliminate the notorious photocurrent hysteresis. Fullerenes deposited on the top of the perovskites reduce the trap density by two orders of magnitude and double the power conversion efficiency of CHmore » 3NH 3PbI 3 solar cells. As a result, the elucidation of the origin of photocurrent hysteresis and its elimination by trap passivation in perovskite solar cells provides important directions for future enhancements to device efficiency.« less

Research on the Problem of High-Precision Deployment for Large-Aperture Space-Based Science Instruments

NASA Technical Reports Server (NTRS)

Lake, Mark S.; Peterson, Lee D.; Hachkowski, M. Roman; Hinkle, Jason D.; Hardaway, Lisa R.

1998-01-01

The present paper summarizes results from an ongoing research program conducted jointly by the University of Colorado and NASA Langley Research Center since 1994. This program has resulted in general guidelines for the design of high-precision deployment mechanisms, and tests of prototype deployable structures incorporating these mechanisms have shown microdynamically stable behavior (i.e., dimensional stability to parts per million). These advancements have resulted from the identification of numerous heretofore unknown microdynamic and micromechanical response phenomena, and the development of new test techniques and instrumentation systems to interrogate these phenomena. In addition, recent tests have begun to interrogate nanomechanical response of materials and joints and have been used to develop an understanding of nonlinear nanodynamic behavior in microdynamically stable structures. The ultimate goal of these efforts is to enable nano-precision active control of micro-precision deployable structures (i.e., active control to a resolution of parts per billion).

CuInP₂S₆ Room Temperature Layered Ferroelectric.

PubMed

Belianinov, A; He, Q; Dziaugys, A; Maksymovych, P; Eliseev, E; Borisevich, A; Morozovska, A; Banys, J; Vysochanskii, Y; Kalinin, S V

2015-06-10

We explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP2S6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleaved bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V-likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. The existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing "graphene family".

Effect of heat treatment on microstructure and hardness of Grade 91 steel

DOE PAGES

Shrestha, Triratna; Alsagabi, Sultan; Charit, Indrajit; ...

2015-01-21

The modified 9Cr-1Mo steel (Grade 91) is a material of choice in fossil-fuel-fired power plants with increased efficiency, service life, and reduction in emission of greenhouse gases. It is also considered a prospective material for the Next Generation Nuclear Power Plant for application in reactor pressure vessels at temperatures up to 650°C. In this paper, heat treatment of the modified 9Cr-1Mo steel was studied by normalizing and tempering the steel at various temperatures and times, with the ultimate goal of improving its creep resistance and optimizing material hardness. The microstructural evolution of the heat treated steels was correlated with themore » differential scanning calorimetric results. Optical microscopy, scanning and transmission electron microscopy in conjunction with microhardness profiles and calorimetric plots were used to understand the evolution of microstructure including precipitate structures in modified 9Cr-1Mo steel and relate it to the mechanical behavior of the steel. Thermo-CalcTM calculations were used to support experimental work and provide guidance in terms of the precipitate stability and microstructural evolution. Furthermore, the carbon isopleth and temperature dependencies of the volume fraction of different precipitates were constructed. The predicted and experimentally observed results were found to be in good agreement.« less

Microgravity

NASA Image and Video Library

1997-11-01

The goal of the ELF investigation is to improve our fundamental understanding of the effects of the flow environment on flame stability. The flame's stability refers to the position of its base and ultimately its continued existence. Combustion research focuses on understanding the important hidden processes of ignitions, flame spreading, and flame extinction. Understanding these processes will directly affect the efficiency of combustion operations in converting chemical energy to heat and will create a more balanced ecology and healthy environment by reducing pollutants emitted during combustion.

Effect of artificial toothbrushing and water storage on the surface roughness and micromechanical properties of tooth-colored CAD-CAM materials.

PubMed

Flury, Simon; Diebold, Elisabeth; Peutzfeldt, Anne; Lussi, Adrian

2017-06-01

Because of the different composition of resin-ceramic computer-aided design and computer-aided manufacturing (CAD-CAM) materials, their polishability and their micromechanical properties vary. Moreover, depending on the composition of the materials, their surface roughness and micromechanical properties are likely to change with time. The purpose of this in vitro study was to investigate the effect of artificial toothbrushing and water storage on the surface roughness (Ra and Rz) and the micromechanical properties, surface hardness (Vickers [VHN]) and indentation modulus (E IT ), of 5 different tooth-colored CAD-CAM materials when polished with 2 different polishing systems. Specimens (n=40 per material) were cut from a composite resin (Paradigm MZ100; 3M ESPE), a feldspathic ceramic (Vitablocs Mark II; Vita Zahnfabrik), a resin nanoceramic (Lava Ultimate; 3M ESPE), a hybrid dental ceramic (Vita Enamic; Vita Zahnfabrik), and a nanocomposite resin (Ambarino High-Class; Creamed). All specimens were roughened in a standardized manner and polished either with Sof-Lex XT discs or the Vita Polishing Set Clinical. Surface roughness, VHN, and E IT were measured after polishing and after storage for 6 months (tap water, 37°C) with periodic, artificial toothbrushing. The surface roughness, VHN, and E IT results were analyzed with a nonparametric ANOVA followed by Kruskal-Wallis and exact Wilcoxon rank sum tests (α=.05). Irrespective of polishing system and of artificial toothbrushing and storage, Lava Ultimate generally showed the lowest surface roughness and Vitablocs Mark II the highest. As regards micromechanical properties, the following ranking of the CAD-CAM materials was found (from highest VHN/E IT to lowest VHN/E IT ): Vitablocs Mark II > Vita Enamic > Paradigm MZ100 > Lava Ultimate > Ambarino High-Class. Irrespective of material and of artificial toothbrushing and storage, polishing with Sof-Lex XT discs resulted in lower surface roughness than the Vita Polishing Set Clinical (P≤.016). However, the polishing system generally had no influence on the micromechanical properties (P>.05). The effect of artificial toothbrushing and storage on surface roughness depended on the material and the polishing system: Ambarino High-Class was most sensitive to storage, Lava Ultimate and Vita Enamic were least sensitive. Artificial toothbrushing and storage generally resulted in a decrease in VHN and E IT for Paradigm MZ100, Lava Ultimate, and Ambarino High-Class but not for Vita Enamic and Vitablocs Mark II. Tooth-colored CAD-CAM materials with lower VHN and E IT generally showed better polishability. However, these materials were more prone to degradation by artificial toothbrushing and water storage than materials with higher VHN and E IT . Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

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

Anikovsky, V.V.; Karzov, G.P.; Timofeev, B.T.

The paper demonstrates an insufficiency of some requirements native Norms (when comparing them with the foreign requirements for the consideration of calculating situations): (1) leak before break (LBB); (2) short cracks; (3) preliminary loading (warm prestressing). In particular, the paper presents (1) Comparison of native and foreign normative requirements (PNAE G-7-002-86, Code ASME, BS 1515, KTA) on permissible stress levels and specifically on the estimation of crack initiation and propagation; (2) comparison of RF and USA Norms of pressure vessel material acceptance and also data of pressure vessel hydrotests; (3) comparison of Norms on the presence of defects (RF andmore » USA) in NPP vessels, developments of defect schematization rules; foundation of a calculated defect (semi-axis correlation a/b) for pressure vessel and piping components: (4) sequence of defect estimation (growth of initial defects and critical crack sizes) proceeding from the concept LBB; (5) analysis of crack initiation and propagation conditions according to the acting Norms (including crack jumps); (6) necessity to correct estimation methods of ultimate states of brittle an ductile fracture and elastic-plastic region as applied to calculating situation: (a) LBB and (b) short cracks; (7) necessity to correct estimation methods of ultimate states with the consideration of static and cyclic loading (warm prestressing effect) of pressure vessel; estimation of the effect stability; (8) proposals on PNAE G-7-002-86 Norm corrections.« less

Effect of Compression on the Molecular Arrangement of Itraconazole-Soluplus Solid Dispersions: Induction of Liquid Crystals or Exacerbation of Phase Separation?

PubMed

Singh, Abhishek; Bharati, Avanish; Frederiks, Pauline; Verkinderen, Olivier; Goderis, Bart; Cardinaels, Ruth; Moldenaers, Paula; Van Humbeeck, Jan; Van den Mooter, Guy

2016-06-06

Predensification and compression are unit operations imperative to the manufacture of tablets and capsules. Such stress-inducing steps can cause destabilization of solid dispersions which can alter their molecular arrangement and ultimately affect dissolution rate and bioavailability. In this study, itraconazole-Soluplus solid dispersions with 50% (w/w) drug loading prepared by hot-melt extrusion (HME) were investigated. Compression was performed at both pharmaceutically relevant and extreme compression pressures and dwell times. The starting materials, powder, and compressed solid dispersions were analyzed using modulated differential scanning calorimetry (MDSC), X-ray diffraction (XRD), small- and wide-angle X-ray scattering (SWAXS), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and broadband dielectric spectroscopy (BDS). MDSC analysis revealed that compression promotes phase separation of solid dispersions as indicated by an increase in glass transition width, occurrence of a peak in the nonreversing heat flow signal, and an increase in the net heat of fusion indicating crystallinity in the systems. SWAXS analysis ruled out the presence of mesophases. BDS measurements elucidated an increase in the Soluplus-rich regions of the solid dispersion upon compression. FTIR indicated changes in the spatiotemporal architecture of the solid dispersions mediated via disruption in hydrogen bonding and ultimately altered dynamics. These changes can have significant consequences on the final stability and performance of the solid dispersions.

Grout Isolation and Stabilization of Structures and Materials within Nuclear Facilities at the U.S. Department of Energy, Hanford Site, Summary - 12309

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

Phillips, S.J.; Phillips, M.; Etheridge, D.

2012-07-01

Per regulatory agreement and facility closure design, U.S. Department of Energy Hanford Site nuclear fuel cycle structures and materials require in situ isolation in perpetuity and/or interim physicochemical stabilization as a part of final disposal or interim waste removal, respectively. To this end, grout materials are being used to encase facilities structures or are being incorporated within structures containing hazardous and radioactive contaminants. Facilities where grout materials have been recently used for isolation and stabilization include: (1) spent fuel separations, (2) uranium trioxide calcining, (3) reactor fuel storage basin, (4) reactor fuel cooling basin transport rail tanker cars and casks,more » (5) cold vacuum drying and reactor fuel load-out, and (6) plutonium fuel metal finishing. Grout components primarily include: (1) portland cement, (2) fly ash, (3) aggregate, and (4) chemical admixtures. Mix designs for these typically include aggregate and non aggregate slurries and bulk powders. Placement equipment includes: (1) concrete piston line pump or boom pump truck for grout slurry, (2) progressive cavity and shearing vortex pump systems, and (3) extendable boom fork lift for bulk powder dry grout mix. Grout slurries placed within the interior of facilities were typically conveyed utilizing large diameter slick line and the equivalent diameter flexible high pressure concrete conveyance hose. Other facilities requirements dictated use of much smaller diameter flexible grout conveyance hose. Placement required direct operator location within facilities structures in most cases, whereas due to radiological dose concerns, placement has also been completed remotely with significant standoff distances. Grout performance during placement and subsequent to placement often required unique design. For example, grout placed in fuel basin structures to serve as interim stabilization materials required sufficient bearing i.e., unconfined compressive strength, to sustain heavy equipment yet, low breakout force to permit efficient removal by track hoe bucket or equivalent construction equipment. Further, flow of slurries through small orifice geometries of moderate head pressures was another typical design requirement. Phase separation of less than 1 percent was a typical design requirement for slurries. On the order of 30,000 cubic meters of cementitious grout have recently been placed in the above noted U.S. Department of Energy Hanford Site facilities or structures. Each has presented a unique challenge in mix design, equipment, grout injection or placement, and ultimate facility or structure performance. Unconfined compressive and shear strength, flow, density, mass attenuation coefficient, phase separation, air content, wash-out, parameters and others, unique to each facility or structure, dictate the grout mix design for each. Each mix design was tested under laboratory and scaled field conditions as a precursor to field deployment. Further, after injection or placement of each grout formulation, the material was field inspected either by standard laboratory testing protocols, direct physical evaluation, or both. (authors)« less

Ultimate strength capacity of a square hollow section filled with fibrous foamed concrete

NASA Astrophysics Data System (ADS)

Amirah Azra Khairuddin, Siti; Rahman, Norashidah Abd; Jamaluddin, Norwati; Jaini, Zainorizuan Mohd; Ali, Noorwirdawati

2017-11-01

Concrete-filled sections used as building columns have become popular due to their architectural and structural elements. In recent years, there has been a renewed call for the improvement of materials used as concrete to fill the composite columns. Among these materials, foamed concrete has received great attention due to its structural characteristics and its potential as a construction material used in hollow sections. However, its behaviors as infill material in a hollow section, such as its strength and failure mode, should be investigated. In this study, experimental research was conducted to compare the experimental and theoretical values of its ultimate strength capacity. Eight specimens of hollow steel sections with two different thicknesses were filled with fibrous foamed concrete and then subjected to compression load. The obtained results were compared with those obtained from a hollow section with the same thicknesses, but were filled with normal foamed concrete. Results show that the ultimate strength capacity of the experimental value is the same as that of the theoretical value based on Eurocode 4. The largest percentage values between theoretical and experimental results for thicknesses of 2 and 4 mm are 58% and 55%, respectively.

Development of rate expressions for the thermal decomposition of RDX

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

Erickson, K.L.; Behrens, R. Jr.; Bulusu, S.

Decomposition and combustion of energetic materials involve processes in both condensed and gas phases. Development of reliable models for design, performance, stability, and hazard analyses requires detailed understanding of the mechanisms for both the initial condensed phase decomposition of the energetic material and the subsequent reaction of the decomposition species to form the ultimate reaction products. Those mechanisms must be described in terms of constitutive rate expressions that can be incorporated into mathematical models. The thermal decomposition of RDX has been studied by Behrens and Bulusu using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS). Their work provides a basis formore » developing some of the constitutive rate expressions that are needed in models for design, performance, stability and hazard analyses involving RDX. Behrens and Bulusu have identified four primary reaction pathways that control the liquid-phase decomposition of RDX at temperatures between 200 and 215{degrees}C, and one that controls solid-phase decomposition at temperatures below 200{degrees}C. Two of the liquid-phase pathways appear to be first order in RDX. Arrhenius parameters for the first-order rate constants were evaluated from data reported by Behrens and Bulusu. Reaction rates extrapolated to temperatures between 370 and 450{degrees}C are in good agreement with global reaction rates observed by Trott et al. using high-speed photography and laser-heated thin-film samples. Furthermore, the STMBMS results of Behrens and Bulusu appear to be consistent with condensed-phase infrared results reported by Trott et al. and Erickson et al.« less

Development of rate expressions for the thermal decomposition of RDX

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

Erickson, K.L.; Behrens, R. Jr.; Bulusu, S.

Decomposition and combustion of energetic materials involve processes in both condensed and gas phases. Development of reliable models for design, performance, stability, and hazard analyses requires detailed understanding of the mechanisms for both the initial condensed phase decomposition of the energetic material and the subsequent reaction of the decomposition species to form the ultimate reaction products. Those mechanisms must be described in terms of constitutive rate expressions that can be incorporated into mathematical models. The thermal decomposition of RDX has been studied by Behrens and Bulusu using Simultaneous Thermogravimetric Modulated Beam Mass Spectrometry (STMBMS). Their work provides a basis formore » developing some of the constitutive rate expressions that are needed in models for design, performance, stability and hazard analyses involving RDX. Behrens and Bulusu have identified four primary reaction pathways that control the liquid-phase decomposition of RDX at temperatures between 200 and 215[degrees]C, and one that controls solid-phase decomposition at temperatures below 200[degrees]C. Two of the liquid-phase pathways appear to be first order in RDX. Arrhenius parameters for the first-order rate constants were evaluated from data reported by Behrens and Bulusu. Reaction rates extrapolated to temperatures between 370 and 450[degrees]C are in good agreement with global reaction rates observed by Trott et al. using high-speed photography and laser-heated thin-film samples. Furthermore, the STMBMS results of Behrens and Bulusu appear to be consistent with condensed-phase infrared results reported by Trott et al. and Erickson et al.« less

Materials Flow and Sustainability

USGS Publications Warehouse

Sznopek, John L.; Brown, William M.

1998-01-01

Materials extracted from the Earth are necessary to produce our most fundamental needs – food, clothing, and shelter. Materials are needed to maintain and improve our standard of living. Understanding the whole system of materials flow, from source to ultimate disposition, can help us better manage the use of natural resources and protect the environment.

Human iPSC-Derived Endothelial Cell Sprouting Assay in Synthetic Hydrogel Arrays

EPA Science Inventory

Activation of vascular endothelial cells (ECs) by growth factors initiates a cascade of events in vivo consisting of EC tip cell selection, sprout formation, EC stalk cell proliferation, and ultimately vascular stabilization by support cells. Although EC functional assays can rec...

Test method for mechanical properties of implantable catheters according to DIN 10555-3.

PubMed

Busch, J D; Schröder, H; Sellenschloh, K; Adam, G; Ittrich, H; Huber, G

2018-06-01

To enable causal analysis of port catheter failure, this study aimed to develop an experimental setup for uniaxial tensile tests that addresses the specific requirements of highly elastic medical catheters; and to quantify parameters of the catheters' mechanical competence with respect to effects of artificial aging. Segments of 6F-polyurethane catheters were tested in their native status, after chemical and after mechanical aging. Tension experiments were performed with a rate of 220 mm/min until catheter failure. Material behavior was analyzed based on load cell measurements of the universal test system and an additional optical distance registration. The Young's modulus, the ultimate stress and the ultimate strain were determined. Chemical aging significantly decreased Young's modulus (84%; p = 0.001) and ultimate stress (83%; p < 0.001), whereas mechanical aged samples demonstrated similar results for the Young's modulus (p = 0.772) and a non-significant rise of ultimate stress (13%; p = 0.128). Ultimate strain did not differ significantly regardless of the pretreatment. The results proof reliability, reproducibility and sensitivity to quantify artificial aging induced variations and also promise to detect deviations in material features caused by long-term clinical usage of catheters. Copyright © 2018 Elsevier Ltd. All rights reserved.

Recent progress in stabilizing hybrid perovskites for solar cell applications

NASA Astrophysics Data System (ADS)

Chen, Jianqing; Cai, Xin; Yang, Donghui; Song, Dan; Wang, Jiajia; Jiang, Jinghua; Ma, Aibin; Lv, Shiquan; Hu, Michael Z.; Ni, Chaoying

2017-07-01

Hybrid inorganic-organic perovskites have quickly evolved as a promising group of materials for solar cells and optoelectronic applications mainly owing to the inexpensive materials, relatively simple and versatile fabrication and high power conversion efficiency (PCE). The certified energy conversion efficiency for perovskite solar cell (PSC) has reached above 20%, which is compatible to the current best for commercial applications. However, long-term stabilities of the materials and devices remain to be the biggest challenging issue for realistic implementation of the PSCs. This article discusses the key issues related to the stability of perovskite absorbing layer including crystal structural stability, chemical stability under moisture, oxygen, illumination and interface reaction, effects of electron-transporting materials (ETM), hole-transporting materials (HTM), contact electrodes, ion migration and preparation conditions. Towards the end, prospective strategies for improving the stability of PSCs are also briefly discussed and summarized. We focus on recent understanding of the stability of materials and devices and our perspectives about the strategies for the stability improvement.

The nuclear arsenals and nuclear disarmament.

PubMed

Barnaby, F

1998-01-01

Current world stockpiles of nuclear weapons and the status of treaties for nuclear disarmament and the ultimate elimination of nuclear weapons are summarised. The need for including stockpiles of civil plutonium in a programme for ending production and disposing of fissile materials is emphasized, and the ultimate difficulty of disposing of the last few nuclear weapons discussed.

The emergence of DNA in the RNA world: an in silico simulation study of genetic takeover.

PubMed

Ma, Wentao; Yu, Chunwu; Zhang, Wentao; Wu, Sanmao; Feng, Yu

2015-12-07

It is now popularly accepted that there was an "RNA world" in early evolution of life. This idea has a direct consequence that later on there should have been a takeover of genetic material - RNA by DNA. However, since genetic material carries genetic information, the "source code" of all living activities, it is actually reasonable to question the plausibility of such a "revolutionary" transition. Due to our inability to model relevant "primitive living systems" in reality, it is as yet impossible to explore the plausibility and mechanisms of the "genetic takeover" by experiments. Here we investigated this issue by computer simulation using a Monte-Carlo method. It shows that an RNA-by-DNA genetic takeover may be triggered by the emergence of a nucleotide reductase ribozyme with a moderate activity in a pure RNA system. The transition is unstable and limited in scale (i.e., cannot spread in the population), but can get strengthened and globalized if certain parameters are changed against RNA (i.e., in favor of DNA). In relation to the subsequent evolution, an advanced system with a larger genome, which uses DNA as genetic material and RNA as functional material, is modeled - the system cannot sustain if the nucleotide reductase ribozyme is "turned off" (thus, DNA cannot be synthesized). Moreover, the advanced system cannot sustain if only DNA's stability, template suitability or replication fidelity (any of the three) is turned down to the level of RNA's. Genetic takeover should be plausible. In the RNA world, such a takeover may have been triggered by the emergence of some ribozyme favoring the formation of deoxynucleotides. The transition may initially have been "weak", but could have been reinforced by environmental changes unfavorable to RNA (such as temperature or pH rise), and would have ultimately become irreversible accompanying the genome's enlargement. Several virtues of DNA (versus RNA) - higher stability against hydrolysis, greater suitability as template and higher fidelity in replication, should have, each in its own way, all been significant for the genetic takeover in evolution. This study enhances our understandings of the relationship between information and material in the living world.

Aqueous Electrochemical Mechanisms in Actinide Residue Processing

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

Morris, David E.; Burns, Carol J.; Smith, Wayne H.

2000-12-31

Plutonium and uranium residues (e.g., incinerator ash, combustibles, and sand/slag/crucibles) resulting from the purification and processing of nuclear materials constitute an enormous volume of ''lean'' processing waste and represent a significant fraction of the U. S. Department of Energy's (DOE) legacy waste from fifty years of nuclear weapons production activities. Much of this material is presently in storage at sites throughout the DOE weapons production complex (most notably Rocky Flats, Savannah River and Hanford) awaiting further processing and/or final disposition. The chemical and physical stability of much of this material has been called into question recently by the Defense Nuclearmore » Facility Safety Board (DNFSB) and resulted in the issuance of a mandate by the DNFSB to undertake a program to stabilize these materials [1]. The ultimate disposition for much of these materials is anticipated to be geologic repositories such as the proposed Waste Isolation Pilot Plant in New Mexico. However, in light of the mandate to stabilize existing residues and the probable concomitant increase in the volume of material to be disposed as a result of stabilization (e.g., from repackaging at lower residue densities), the projected storage volume for these wastes within anticipated geologic repositories will likely be exceeded simply to handle existing wastes. Additional processing of some of these residue waste streams to reduce radionuclide activity levels, matrix volume, or both is a potentially important strategy to achieve both stabilization and volume reduction so that the anticipated geologic repositories will provide adequate storage volume. In general, the plutonium and uranium that remains in solid residue materials exists in a very stable chemical form (e.g., as binary oxides), and the options available to remove the actinides are limited. However, there have been some demonstrated successes in this vain using aqueous phase electrochemical methods such as the Catalyzed Electrochemical Plutonium Oxide Dissolution (CEPOD) process pioneered by workers at Pacific Northwest National Laboratory in the mid-1970s [2]. The basis for most of these mediated electrochemical oxidation/reduction (MEO/R) processes is the generation of a dissolved electrochemical catalyst, such as Ag2+, which is capable of oxidizing or reducing solid-phase actinide species or actinide sorbates via 7 heterogeneous electron transfer to oxidation states that have significantly greater solubilities (e.g., PuO2(s) to PuO2 2+ (dissolved)). The solubilized actinide can then be recovered by ion exchange or other mechanisms. These aqueous electrochemical methods for residue treatment have been considered in many of the ''trade studies'' to evaluate options for stabilization of the various categories of residue materials. While some concerns generally arise (e.g., large secondary waste volumes could results since the process stream normally goes th rough anion exchange or precipitation steps to remove the actinide), the real utility and versatility of these methods should not be overlooked. They are low temperature, ambient pressure processes that operate in a non-corrosive environment. In principle, they can be designed to be highly selective for the actinides (i.e., no substrate degradation occurs), they can be utilized for many categories of residue materials with little or no modification in hardware or operating conditions, and they can conceivably be engineered to minimize secondary waste stream volume. However, some fundamental questions remain concerning the mechanisms through which these processes act, and how the processes might be optimized to maximize efficiency while minimizing secondary waste. In addition, given the success achieved to date on the limited set of residues, further research is merited to extend the range of applicability of these electrochemical methods to other residue and waste streams. The principal goal of the work described here is to develop a fundamental understanding of the heterogeneous electron transfer thermodynamics and kinetics that lie at the heart of the MEO/R processes for actinide solids and actinide species entrained in or surface-bound to residue substrates. This has been accomplished as described in detail below through spectroscopic characterization of actinide-bearing substrates and electrochemical investigations of electron transfer reactions between uranium- and plutonium- (or surrogates) bearing solids (dispersed actinide solid phases and actinides sorbed to inorganic and organic colloids) and polarizable electrode materials. In general, the actinide solids or substrate-supported species were chosen to represent relevant residue materials (e.g., incinerator ash, sand/slag/crucible, and combustibles).« less

Tendon material properties vary and are interdependent among turkey hindlimb muscles

PubMed Central

Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P.; Roberts, Thomas J.

2012-01-01

SUMMARY The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress–strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r2=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity. PMID:22771746

Tendon material properties vary and are interdependent among turkey hindlimb muscles.

PubMed

Matson, Andrew; Konow, Nicolai; Miller, Samuel; Konow, Pernille P; Roberts, Thomas J

2012-10-15

The material properties of a tendon affect its ability to store and return elastic energy, resist damage, provide mechanical feedback and amplify or attenuate muscle power. While the structural properties of a tendon are known to respond to a variety of stimuli, the extent to which material properties vary among individual muscles remains unclear. We studied the tendons of six different muscles in the hindlimb of Eastern wild turkeys to determine whether there was variation in elastic modulus, ultimate tensile strength and resilience. A hydraulic testing machine was used to measure tendon force during quasi-static lengthening, and a stress-strain curve was constructed. There was substantial variation in tendon material properties among different muscles. Average elastic modulus differed significantly between some tendons, and values for the six different tendons varied nearly twofold, from 829±140 to 1479±106 MPa. Tendons were stretched to failure, and the stress at failure, or ultimate tensile stress, was taken as a lower-limit estimate of tendon strength. Breaking tests for four of the tendons revealed significant variation in ultimate tensile stress, ranging from 66.83±14.34 to 112.37±9.39 MPa. Resilience, or the fraction of energy returned in cyclic length changes was generally high, and one of the four tendons tested was significantly different in resilience from the other tendons (range: 90.65±0.83 to 94.02±0.71%). An analysis of correlation between material properties revealed a positive relationship between ultimate tensile strength and elastic modulus (r(2)=0.79). Specifically, stiffer tendons were stronger, and we suggest that this correlation results from a constrained value of breaking strain, which did not vary significantly among tendons. This finding suggests an interdependence of material properties that may have a structural basis and may explain some adaptive responses observed in studies of tendon plasticity.

Effects of Welding Parameters on Mechanical Properties in Electron Beam Welded CuCrZr Alloy Plates

NASA Astrophysics Data System (ADS)

Jaypuria, Sanjib; Doshi, Nirav; Pratihar, Dilip Kumar

2018-03-01

CuCrZr alloys are attractive structural materials for plasma-facing components (PFC) and heat sink element in the International Thermonuclear Experimental Reactor (ITER) fusion reactors. This material has gained so much attention because of its high thermal conductivity and fracture toughness, high resistance to radiation damage and stability at elevated temperatures. The objective of this work is to study the effects of electron beam welding parameters on the mechanical strength of the butt welded CuCrZr joint. Taguchi method is used as the design of experiments to optimize the input parameters, such as accelerating voltage, beam current, welding speed, oscillation amplitude and frequency. The joint strength and ductility are the desired responses, which are measured through ultimate tensile strength and percent elongation, respectively. Accelerating voltage and welding speed are found to have significant influence on the strength. A combination of low amplitude and high-frequency oscillation is suggested for the higher joint strength and ductility. There is a close agreement between Taguchi predicted results and experimental ones. Fractographic analysis of joint and weld zone analysis are carried out to study the failure behaviour and microstructural variation in the weld zone, respectively.

Effects of thermal cycling on graphie-fiber-reinforced 6061 aluminum

NASA Technical Reports Server (NTRS)

Dries, G. A.; Tompkins, S. S.

1986-01-01

Graphite-reinforced aluminum alloy metal-matrix composites are among materials being considered for structural components in dimensionally stable space structures. This application requires materials with low values of thermal expansions and high specific stiffnesses. They must remain stable during exposures to the space environment for periods extending to 20 years. The effects of thermal cycling on the thermal expansion behavior and mechanical properties of Thornel P100 graphite 6061 aluminum composites, as fabricated and after thermal processing to eliminate thermal strain hysteresis, have been investigated. Two groups of composites were studied: one was fabricated by hot roll bonding and the other by diffusion bonding. Processing significantly reduced strain hysteresis during thermal cycling in both groups and improved the ultimate tensile strength and modulus in the diffusion-bonded composites. Thermal cycling stabilized the as-fabricated composites by reducing the residual fabrication stress and increased the matrix strength by metallurgical aging. Thermal expansion behavior of both groups after processing was insensitive to thermal cycling. Data scatter was too large to determine effects of thermal cycling on the mechanical properties. The primary effects of processing and thermal cycling can be attributed to changes in the metallurgical condition and stress state of the matrix.

The evolution of hillslope strength following large earthquakes

NASA Astrophysics Data System (ADS)

Brain, Matthew; Rosser, Nick; Tunstall, Neil

2017-04-01

Earthquake-induced landslides play an important role in the evolution of mountain landscapes. Earthquake ground shaking triggers near-instantaneous landsliding, but has also been shown to weaken hillslopes, preconditioning them for failure during subsequent seismicity and/or precipitation events. The temporal evolution of hillslope strength during and following primary seismicity, and if and how this ultimately results in failure, is poorly constrained due to the rarity of high-magnitude earthquakes and limited availability of suitable field datasets. We present results obtained from novel geotechnical laboratory tests to better constrain the mechanisms that control strength evolution in Earth materials of differing rheology. We consider how the strength of hillslope materials responds to ground-shaking events of different magnitude and if and how this persists to influence landslide activity during interseismic periods. We demonstrate the role of stress path and stress history, strain rate and foreshock and aftershock sequences in controlling the evolution of hillslope strength and stability. Critically, we show how hillslopes can be strengthened rather than weakened in some settings, challenging conventional assumptions. On the basis of our laboratory data, we consider the implications for earthquake-induced geomorphic perturbations in mountain landscapes over multiple timescales and in different seismogenic settings.

Large-scale high-throughput computer-aided discovery of advanced materials using cloud computing

NASA Astrophysics Data System (ADS)

Bazhirov, Timur; Mohammadi, Mohammad; Ding, Kevin; Barabash, Sergey

Recent advances in cloud computing made it possible to access large-scale computational resources completely on-demand in a rapid and efficient manner. When combined with high fidelity simulations, they serve as an alternative pathway to enable computational discovery and design of new materials through large-scale high-throughput screening. Here, we present a case study for a cloud platform implemented at Exabyte Inc. We perform calculations to screen lightweight ternary alloys for thermodynamic stability. Due to the lack of experimental data for most such systems, we rely on theoretical approaches based on first-principle pseudopotential density functional theory. We calculate the formation energies for a set of ternary compounds approximated by special quasirandom structures. During an example run we were able to scale to 10,656 CPUs within 7 minutes from the start, and obtain results for 296 compounds within 38 hours. The results indicate that the ultimate formation enthalpy of ternary systems can be negative for some of lightweight alloys, including Li and Mg compounds. We conclude that compared to traditional capital-intensive approach that requires in on-premises hardware resources, cloud computing is agile and cost-effective, yet scalable and delivers similar performance.

Advanced Technology Composite Fuselage-Structural Performance

NASA Technical Reports Server (NTRS)

Walker, T. H.; Minguet, P. J.; Flynn, B. W.; Carbery, D. J.; Swanson, G. D.; Ilcewicz, L. B.

1997-01-01

Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC). This report addresses the program activities related to structural performance of the selected concepts, including both the design development and subsequent detailed evaluation. Design criteria were developed to ensure compliance with regulatory requirements and typical company objectives. Accurate analysis methods were selected and/or developed where practical, and conservative approaches were used where significant approximations were necessary. Design sizing activities supported subsequent development by providing representative design configurations for structural evaluation and by identifying the critical performance issues. Significant program efforts were directed towards assessing structural performance predictive capability. The structural database collected to perform this assessment was intimately linked to the manufacturing scale-up activities to ensure inclusion of manufacturing-induced performance traits. Mechanical tests were conducted to support the development and critical evaluation of analysis methods addressing internal loads, stability, ultimate strength, attachment and splice strength, and damage tolerance. Unresolved aspects of these performance issues were identified as part of the assessments, providing direction for future development.

A ZnO nanowire bio-hybrid solar cell

NASA Astrophysics Data System (ADS)

Yaghoubi, Houman; Schaefer, Michael; Yaghoubi, Shayan; Jun, Daniel; Schlaf, Rudy; Beatty, J. Thomas; Takshi, Arash

2017-02-01

Harvesting solar energy as a carbon free source can be a promising solution to the energy crisis and environmental pollution. Biophotovoltaics seek to mimic photosynthesis to harvest solar energy and to take advantage of the low material costs, negative carbon footprint, and material abundance. In the current study, we report on a combination of zinc oxide (ZnO) nanowires with monolayers of photosynthetic reaction centers which are self-assembled, via a cytochrome c linker, as photoactive electrode. In a three-probe biophotovoltaics cell, a photocurrent density of 5.5 μA cm-2 and photovoltage of 36 mV was achieved, using methyl viologen as a redox mediator in the electrolyte. Using ferrocene as a redox mediator a transient photocurrent density of 8.0 μA cm-2 was obtained, which stabilized at 6.4 μA cm-2 after 20 s. In-depth electronic structure characterization using photoemission spectroscopy in conjunction with electrochemical analysis suggests that the fabricated photoactive electrode can provide a proper electronic path for electron transport all the way from the conduction band of the ZnO nanowires, through the protein linker to the RC, and ultimately via redox mediator to the counter electrode.

Universal avalanche statistics and triggering close to failure in a mean-field model of rheological fracture

NASA Astrophysics Data System (ADS)

Baró, Jordi; Davidsen, Jörn

2018-03-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible for deformation. Avalanche models involving critical failure have determined common universality classes for stick-slip processes and fracture. However, not all empirical failure processes exhibit the trademarks of criticality. The rheological properties of materials introduce dissipation, usually reproduced in conceptual models as a hardening of the coarse grained elements of the system. Here, we investigate the effects of transient hardening on (i) the activity rate and (ii) the statistical properties of avalanches. We find the explicit representation of transient hardening in the presence of generalized viscoelasticity and solve the corresponding mean-field model of fracture. In the quasistatic limit, the accelerated energy release is invariant with respect to rheology and the avalanche propagation can be reinterpreted in terms of a stochastic counting process. A single universality class can be defined from such analogy, and all statistical properties depend only on the distance to criticality. We also prove that interevent correlations emerge due to the hardening—even in the quasistatic limit—that can be interpreted as "aftershocks" and "foreshocks."

Photoelectrochemical Stability and Alteration Products of n-Type Single-Crystal ZnO Photoanodes

DOE PAGES

Paulauskas, I. E.; Jellison, G. E.; Boatner, L. A.; ...

2011-01-01

The photoelectrochemical stability and surface-alteration characteristics of doped and undoped n-type ZnO single-crystal photoanode electrodes were investigated. The single-crystal ZnO photoanode properties were analyzed using current-voltage measurements plus spectral and time-dependent quantum-yield methods. These measurements revealed a distinct anodic peak and an accompanying cathodic surface degradation process at negative potentials. The features of this peak depended on time and the NaOH concentration in the electrolyte, but were independent of the presence of electrode illumination. Current measurements performed at the peak indicate that charging and discharging effects are apparently taking place at the semiconductor/electrolyte interface. This result is consistent with themore » significant reactive degradation that takes place on the ZnO single crystal photoanode surface and that ultimately leads to the reduction of the ZnO surface to Zn metal. The resulting Zn-metal reaction products create unusual, dendrite-like, surface alteration structural features that were analyzed using x-ray diffraction, energy-dispersive analysis, and scanning electron microscopy. ZnO doping methods were found to be effective in increasing the n-type character of the crystals. Higher doping levels result in smaller depletion widths and lower quantum yields, since the minority carrier diffusion lengths are very short in these materials.« less

A theory for the evolution of other-regard integrating proximate and ultimate perspectives.

PubMed

Akçay, Erol; Van Cleve, Jeremy; Feldman, Marcus W; Roughgarden, Joan

2009-11-10

Although much previous work describes evolutionary mechanisms that promote or stabilize different social behaviors, we still have little understanding of the factors that drive animal behavior proximately. Here we present a modeling approach to answer this question. Our model rests on motivations to achieve objectives as the proximate determinants of behavior. We develop a two-tiered framework by first modeling the dynamics of a social interaction at the behavioral time scale and then find the evolutionarily stable objectives that result from the outcomes these dynamics produce. We use this framework to ask whether "other-regarding" motivations, which result from a kind of nonselfish objective, can evolve when individuals are engaged in a social interaction that entails a conflict between their material payoffs. We find that, at the evolutionarily stable state, individuals can be other-regarding in that they are motivated to increase their partners' payoff as well as their own. In contrast to previous theories, we find that such motivations can evolve because of their direct effect on fitness and do not require kin selection or a special group structure. We also derive general conditions for the evolutionary stability of other-regarding motivations. Our conditions indicate that other-regarding motivations are more likely to evolve when social interactions and behavioral objectives are both synergistic.

Recrystallization behavior and thermal shock resistance of the W-1.0 wt% TaC alloy

NASA Astrophysics Data System (ADS)

Xie, Z. M.; Miao, S.; Zhang, T.; Liu, R.; Wang, X. P.; Fang, Q. F.; Hao, T.; Zhuang, Z.; Liu, C. S.; Lian, Y. Y.; Liu, X.; Cai, L. H.

2018-04-01

The high-temperature stability and good mechanical strength of tungsten (W) alloys are highly desirable for a wide range of fusion applications, which can be achieved by dispersion strengthening. In this paper, TaC dispersion effects on the thermal stabilities, tensile properties and thermal shock resistances have been investigated. A hot-rolled W-1.0 wt% TaC plate has been fabricated which contains the high tensile strength and elongation. Nanosized particles in the W matrix improve the recrystallization temperature to about 1400 °C and the ultimate tensile strength to 571 MPa at 500 °C through hindering grain boundary migration, pinning dislocations and refining grains. The effects of edge-localized mode like transient heat events on the rolled and recrystallized W-1.0 wt% TaC alloys were investigated systematically. The cracking threshold (100 shots) at room temperature is in the range of 0.33-0.44 GW/m2 for the rolled W-1.0 wt% TaC. Recrystallization degrades mechanical strength and makes the material more prone to thermal shock damages. Coarse Ta2O5 and Ta-Cx-Oy particles are easy to fracture and introduce a preferential crack initiation in W matrix during cyclic heat loads.

COMPARISON OF MICROBIAL POPULATIONS IN A CONVENTIONAL AND BIOREACTING MUNICIPAL SOLID WASTE LANDFILLS

EPA Science Inventory

Landfills are the ultimate reactors for biodegradation as they contain nutrients, bacteria, and various redox conditions which, then, change over time. Enhancement of the landill environment to optimize the rates of biodegradation and to ensure more rapid stabilization of the was...

Machinability of CAD-CAM materials.

PubMed

Chavali, Ramakiran; Nejat, Amir H; Lawson, Nathaniel C

2017-08-01

Although new materials are available for computer-aided design and computer-aided manufacturing (CAD-CAM) fabrication, limited information is available regarding their machinability. The depth of penetration of a milling tool into a material during a timed milling cycle may indicate its machinability. The purpose of this in vitro study was to compare the tool penetration rate for 2 polymer-containing CAD-CAM materials (Lava Ultimate and Enamic) and 2 ceramic-based CAD-CAM materials (e.max CAD and Celtra Duo). The materials were sectioned into 4-mm-thick specimens (n=5/material) and polished with 320-grit SiC paper. Each specimen was loaded into a custom milling apparatus. The apparatus pushed the specimens against a milling tool (E4D Tapered 2016000) rotating at 40 000 RPM with a constant force of 0.98 N. After a 6-minute timed milling cycle, the length of each milling cut was measured with image analysis software under a digital light microscope. Representative specimens and milling tools were examined with scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy. The penetration rate of Lava Ultimate (3.21 ±0.46 mm/min) and Enamic (2.53 ±0.57 mm/min) was significantly greater than that of e.max CAD (1.12 ±0.32 mm/min) or Celtra Duo (0.80 ±0.21 mm/min) materials. SEM observations showed little tool damage, regardless of material type. Residual material was found on the tools used with polymer-containing materials, and wear of the embedding medium was seen on the tools used with the ceramic-based materials. Edge chipping was noted on cuts made in the ceramic-based materials. Lava Ultimate and Enamic have greater machinability and less edge chipping than e.max CAD and Celtra Duo. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Biogas and methane yield in response to co- and separate digestion of biomass wastes.

PubMed

Adelard, Laetitia; Poulsen, Tjalfe G; Rakotoniaina, Volana

2015-01-01

The impact of co-digestion as opposed to separate digestion, on biogas and methane yield (apparent synergetic effects) was investigated for three biomass materials (pig manure, cow manure and food waste) under mesophilic conditions over a 36 day period. In addition to the three biomass materials (digested separately), 13 biomass mixtures (co-digested) were used. Two approaches for modelling biogas and methane yield during co-digestion, based on volatile solids concentration and ultimate gas and methane potentials, were evaluated. The dependency of apparent synergetic effects on digestion time and biomass mixture composition was further assessed using measured cumulative biogas and methane yields and specific biogas and methane generation rates. Results indicated that it is possible, based on known volatile solids concentration and ultimate biogas or methane yields for a set of biomass materials digested separately, to accurately estimate gas yields for biomass mixtures made from these materials using calibrated models. For the biomass materials considered here, modelling indicated that the addition of pig manure is the main cause of synergetic effects. Co-digestion generally resulted in improved ultimate biogas and methane yields compared to separate digestion. Biogas and methane production was furthermore significantly higher early (0-7 days) and to some degree also late (above 20 days) in the digestion process during co-digestion. © The Author(s) 2014.

Preliminary study of the biomechanical behavior and physical characteristics of tantalum (Ta)-coated prostheses.

PubMed

Duan, Yonghong; Liu, Lie; Wang, Ling; Guo, Fei; Li, Haoping; Shi, Lei; Li, Mao; Yin, Dayu; Jiang, Chi; Zhu, Qingsheng

2012-03-01

Use of Ta biomaterials in medicine started in the middle of the last century. The good biocompatibility and chemical stability, and the unique physical characteristics of Ta metal have resulted in many possible developments of Ta biomaterials. In this study, histopathological observation, histomorphometric analysis, scanning electron microscope (SEM) observation, energy-dispersive X-ray spectroscopy (EDX) analysis, biomechanical testing, and examination of the coating's mechanical strength have been used to evaluate the value of clinical application of Ta-coated prostheses prepared by a plasma-spraying process. Histopathological observation has demonstrated that the periprosthetic new bone tissues tightly and stably adhere to the Ta coating after the implantation, with no signs of loosening. Early after implantation, there is no significant difference in periprosthetic bone volume and ultimate shear strength between Ta-coated and Ti-coated prostheses (P > 0.05). EDX analysis suggests that the ultimate shear stress does not damage Ta coating. Mechanical strength testing shows that the adhesive strength and Vicker's surface hardness (HV) of the Ta coating are significantly higher than those of the Ti coating (P < 0.01). Ta coating has good stability and bone biocompatibility; the extraordinary physical characteristics of Ta coating have great significance in maintaining prosthetic stability and surface porosity after implantation.

Process for stabilizing the viscosity characteristics of coal derived materials and the stabilized materials obtained thereby

DOEpatents

Bronfenbrenner, James C.; Foster, Edward P.; Tewari, Krishna

1985-01-01

A process is disclosed for stabilizing the viscosity of coal derived materials such as an SRC product by adding up to 5.0% by weight of a light volatile phenolic viscosity repressor. The viscosity will remain stabilized for a period of time of up to 4 months.

Electro-Optically Active Monomers: Synthesis and Characterization of Thin Films of Liquid Crystalline Substituted Polyacetylenes

NASA Technical Reports Server (NTRS)

Duran, R. S.

1995-01-01

The overall objective of this study was the description of the behavior of mesogen substituted acetylene monomers and polymers in monolayer films at the air/water interface and as multilayer films including the formation of such films. Fundamental knowledge to be gained would include the effect of balancing hydrophilic and hydrophobic tendencies in a molecule more complex than the classical fatty acids or lipids. The effect of molecular shape on the packing and thus the ultimate stability of monolayers formed from these new molecules was explored. The work takes on the challenge of preorienting monomers in well-ordered arrays prior to attempting polymerization with the hope that order would be preserved in any resulting polymer. New knowledge gained with regard to the acetylenic monomers includes processing of the acetylene monomer into multi-layer films, followed by the design and synthesis of a second generation of improved monomer structure for superior LBK film transfer properties. A third generation of acetylenic monomer was synthesized which approaches more closely the goal of solid state polymerization of these materials. A parallel study took a different approach. The materials are pre-formed poly(phenylene-acetylene) polymers so questions about reactivity are mute. The materials are a variation on the well-known hairy-rod polymers with regard to their Langmuir film-forming properties. Overall, the goal was to demonstrate that these polymers could be processed into NLO materials with novel polar order.

Aging and neurodegeneration: Importance of quantifying thermoregulatory stability in a rodent model of aging

EPA Science Inventory

Over our lives, we are exposed to a multitude of insults including heat and cold stress, toxicants, radiation, drugs, oxidative stress, and many others. The cumulative impact of these insults may ultimately be responsible for the etiology of many diseases. Since all life processe...

The Stability of Orbital Configurations and the Ultimate Configurations of Planetary and Satellite Systems

NASA Technical Reports Server (NTRS)

Lissauer, Jack J.; Duncan, Martin J.

2004-01-01

The contents include the following: 1) Dynamical Evolution of the Earth-Moon Progenitors. 2) Dynamical Connections between Giant and Terrestrial Planets. 3) Dynamics of the Upsilon Andromedae Planetary System. 4) Dynamics of the Planets Orbiting GJ 876. and 5) Integrators for Planetary Accretion in Binaries.

A robust nonlinear stabilizer as a controller for improving transient stability in micro-grids.

PubMed

Azimi, Seyed Mohammad; Afsharnia, Saeed

2017-01-01

This paper proposes a parametric-Lyapunov approach to the design of a stabilizer aimed at improving the transient stability of micro-grids (MGs). This strategy is applied to electronically-interfaced distributed resources (EI-DRs) operating with a unified control configuration applicable to all operational modes (i.e. grid-connected mode, islanded mode, and mode transitions). The proposed approach employs a simple structure compared with other nonlinear controllers, allowing ready implementation of the stabilizer. A new parametric-Lyapunov function is proposed rendering the proposed stabilizer more effective in damping system transition transients. The robustness of the proposed stabilizer is also verified based on both time-domain simulations and mathematical proofs, and an ultimate bound has been derived for the frequency transition transients. The proposed stabilizer operates by deploying solely local information and there are no needs for communication links. The deteriorating effects of the primary resource delays on the transient stability are also treated analytically. Finally, the effectiveness of the proposed stabilizer is evaluated through time-domain simulations and compared with the recently-developed stabilizers performed on a multi-resource MG. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Experimental Study of Axially Tension Cold Formed Steel Channel Members

NASA Astrophysics Data System (ADS)

Apriani, Widya; Lubis, Fadrizal; Angraini, Muthia

2017-12-01

Experimental testing is commonly used as one of the steps to determine the cause of the collapse of a building structure. The collapse of structures can be due to low quality materials. Although material samples have passed laboratory tests and the existing technical specifications have been met but there may be undetected defects and known material after failure. In this paper will be presented Experimental Testing of Axially Tension Cold Formed Steel Channel Members to determine the cause of the collapse of a building roof truss x in Pekanbaru. Test of tensile strength material cold formed channel sections was performed to obtain the main characteristics of Cold Formed steel material, namely ultimate tensile strength loads that can be held by members and the yield stress possessed by channel sections used in construction. Analysis of axially tension cold formed steel channel section presents in this paper was conducted through experimental study based on specificationsAnnualBook of ASTM Standards: Metal Test methods and Analitical Procedures, Section 3 (1991). The result of capacity loads experimental test was compared with design based on SNI 03-7971-2013standard of Indonesia for the design of cold formed steel structural members. The results of the yield stress of the material will be seen against the minimum allowable allowable stress range. After the test, the percentace of ultimate axial tension capacity theory has a result that is 16.46% larger than the ultimate axial tension capacity experimental. When compared with the load that must be borne 5.673 kN/m it can be concluded that 2 specimens do not meet. Yield stress of member has fulfilled requirement that wass bigger than 550 MPa. Based on the curve obtained ultimate axial tension capacity theory, results greater than experimental. The greatest voltage value (fu) is achieved under the same conditions as its yield stress. For this specimen with a melting voltage value fy = 571.5068 MPa has fulfilled the minimum melting point value of 550 MPa required for standard mild steel materials in accordance with the code SNI 03-7971-2013 about Cold formed steel.

Experimental Study of Axially Tension Cold Formed Steel Channel Members

NASA Astrophysics Data System (ADS)

Apriani, Widya; Lubis, Fadrizal; Angraini, Muthia

2017-12-01

Experimental testing is commonly used as one of the steps to determine the cause of the collapse of a building structure. The collapse of structures can be due to low quality materials. Although material samples have passed laboratory tests and the existing technical specifications have been met but there may be undetected defects and known material after failure. In this paper will be presented Experimental Testing of Axially Tension Cold Formed Steel Channel Members to determine the cause of the collapse of a building roof truss x in Pekanbaru. Test of tensile strength material cold formed channel sections was performed to obtain the main characteristics of Cold Formed steel material, namely ultimate tensile strength loads that can be held by members and the yield stress possessed by channel sections used in construction. Analysis of axially tension cold formed steel channel section presents in this paper was conducted through experimental study based on specificationsAnnualBook of ASTM Standards: Metal Test methods and Analitical Procedures, Section 3 (1991). The result of capacity loads experimental test was compared with design based on SNI 03-7971- 2013standard of Indonesia for the design of cold formed steel structural members. The results of the yield stress of the material will be seen against the minimum allowable allowable stress range. After the test, the percentace of ultimate axial tension capacity theory has a result that is 16.46% larger than the ultimate axial tension capacity experimental. When compared with the load that must be borne 5.673 kN/m it can be concluded that 2 specimens do not meet. Yield stress of member has fulfilled requirement that wass bigger than 550 MPa. Based on the curve obtained ultimate axial tension capacity theory, results greater than experimental. The greatest voltage value (fu) is achieved under the same conditions as its yield stress. For this specimen with a melting voltage value fy = 571.5068 MPa has fulfilled the minimum melting point value of 550 MPa required for standard mild steel materials in accordance with the code SNI 03- 7971-2013 about Cold formed steel.

Attitude stability of spinning flexible spacecraft

NASA Technical Reports Server (NTRS)

Likins, P. W.; Barbera, F. J.

1971-01-01

The stability of spinning flexible satellites in a force-free environment was analyzed. The satellite was modeled as a rigid core having attached to it a flexible appendage idealized as a collection of particles (point masses) interconnected by springs. Both Liapunov and Routh-Hurwitz stability procedures are used. In the former, the Hamiltonian of the system, constrained through the angular momentum integral so as to admit complete damping, is used as a testing function. Equations of motion are written using the hybrid coordinate formulation, which readily accepts a modal coordinate transformation ultimately allowing truncation to a level amenable to literal stability analysis. Closed form stability criteria are generated for the first mode of a restricted appendage model lying in a plane containing the system center of mass and orthogonal to the spin axis. The effects of spin on flexible bodies are discussed by considering a very elementary particle model. Control of passively unstable spacecraft is briefly considered.

Quadrupole mass filter: design and performance for operation in stability zone 3.

PubMed

Syed, Sarfaraz U A H; Hogan, Thomas J; Antony Joseph, Mariya J; Maher, Simon; Taylor, Stephen

2013-10-01

The predicted performance of a quadrupole mass filter (QMF) operating in Mathieu stability zone 3 is described in detail using computer simulations. The investigation considers the factors that limit the ultimate maximum resolution (Rmax) and percentage transmission (%Tx), which can be obtained for a given QMF for a particular scan line of operation. The performance curve (i.e., the resolution (R) versus number (N) of radio frequency (rf) cycles experienced by the ions in the mass filter) has been modeled for the upper and lower tip of stability zone 3. The saturation behavior of the performance curve observed in practice for zone 3 is explained. Furthermore, new design equations are presented by examining the intersection of the scan line with stability zone 3. Resolution versus transmission characteristics of stability zones 1 and 3 are compared and the dependence of performance for zones 1 and 3 is related to particular instrument operating parameters.

Rapid Recovery of Clofazimine-Loaded Nanoparticles with Long-Term Storage Stability as Anti-Cryptosporidium Therapy.

PubMed

Feng, Jie; Zhang, Yingyue; McManus, Simon A; Ristroph, Kurt D; Lu, Hoang D; Gong, Kai; White, Claire E; Prud'homme, Robert K

2018-05-25

While the formulation of nanoparticle (NP) suspensions has been widely applied in materials and life science, the recovery of NPs from such a suspension into a solid state is practically important to confer long-term storage stability. However, solidification, while preserving the original nanoscale properties, remains a formidable challenge in the pharmaceutical and biomedical applications of NPs. Herein we combined flash nanoprecipitation (FNP) and spray-drying as a nanofabrication platform for NP formulation and recovery without compromising the dissolution kinetics of the active ingredient. Clofazimine was chosen to be the representative drug, which has been recently repurposed as a potential treatment for cryptosporidiosis. Clofazimine was encapsulated in NPs with low-cost surface coatings, hypromellose acetate succinate (HPMCAS) and lecithin, which were required by the ultimate application to global health. Spray-drying and lyophilization were utilized to produce dried powders with good long-term storage stability for application in hot and humid climatic zones. The particle morphology, yield efficiency, drug loading, and clofazimine crystallinity in the spray-dried powders were characterized. The in vitro release kinetics of spray-dried NP powders were compared to analogous dissolution profiles from standard lyophilized NP samples, crystalline clofazimine powder, and the commercially available formulation Lamprene. The spray-dried powders showed a supersaturation level of up to 60 times the equilibrium solubility and remarkably improved dissolution rates. In addition, the spray-dried powders with both surface coatings showed excellent stability during aging studies with elevated temperature and humidity, in view of the dissolution and release in vitro. Considering oral delivery for pediatric administration, the spray-dried powders show less staining effects with simulated skin than crystalline clofazimine and may be made into minitablets without additional excipients. These results highlight the potential of combining FNP and spray-drying as a feasible and versatile platform to design and rapidly recover amorphous NPs in a solid dosage form, with the advantages of satisfactory long-term storage stability, low cost, and easy scalability.

Plutonium inventories for stabilization and stabilized materials

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

Williams, A.K.

1996-05-01

The objective of the breakout session was to identify characteristics of materials containing plutonium, the need to stabilize these materials for storage, and plans to accomplish the stabilization activities. All current stabilization activities are driven by the Defense Nuclear Facilities Safety Board Recommendation 94-1 (May 26, 1994) and by the recently completed Plutonium ES&H Vulnerability Assessment (DOE-EH-0415). The Implementation Plan for accomplishing stabilization of plutonium-bearing residues in response to the Recommendation and the Assessment was published by DOE on February 28, 1995. This Implementation Plan (IP) commits to stabilizing problem materials within 3 years, and stabilizing all other materials withinmore » 8 years. The IP identifies approximately 20 metric tons of plutonium requiring stabilization and/or repackaging. A further breakdown shows this material to consist of 8.5 metric tons of plutonium metal and alloys, 5.5 metric tons of plutonium as oxide, and 6 metric tons of plutonium as residues. Stabilization of the metal and oxide categories containing greater than 50 weight percent plutonium is covered by DOE Standard {open_quotes}Criteria for Safe Storage of Plutonium Metals and Oxides{close_quotes} December, 1994 (DOE-STD-3013-94). This standard establishes criteria for safe storage of stabilized plutonium metals and oxides for up to 50 years. Each of the DOE sites and contractors with large plutonium inventories has either started or is preparing to start stabilization activities to meet these criteria.« less

Effect of 2 Bleaching Agents with a Content of High Concentrated Hydrogen Peroxide on Stained 2 CAD/CAM Blocks and a Nanohybrid Composite Resin: An AFM Evaluation

PubMed Central

Cengiz, Esra

2017-01-01

The aim of this study was to evaluate color stability of 3 restorative materials, discoloration ability of different solutions, efficacy of 2 office bleaching agents, and surface roughness and topography. Sixty specimens for Clearfil Majesty Esthetic (CME), Lava Ultimate (LU), and Vita Enamic (VE) were prepared. They were immersed into 3 staining solutions for 2 weeks and then they were bleached. According to the measured L⁎, a⁎, and b⁎ parameters described by CIELAB system, color changes (ΔE00), translucency parameters (TP), whiteness index values (W⁎), and changes in closeness to pure white (ΔW⁎) were calculated. Then 3 specimens from each group were scanned with an atomic force microscope for surface analysis. After staining, CME groups and control groups of LU and VE showed clinically acceptable color changes (ΔE00 < 1,8). After bleaching, while a reverse effect on color was observed, VE showed the furthest color values to pure white. There was no statistically significant difference between whiteness index values of LU and CME. LU was the most translucent material during the study and TP values of materials showed minimal differences. Most of the VE groups and a control group of LU showed surface roughness (Ra) values higher than critical value for biofilm accumulation (0,2 μm). PMID:28804719

CuInP 2S 6 Room Temperature Layered Ferroelectric

DOE PAGES

Belianinov, Alex; He, Qian; Dziaugys, Andrius; ...

2015-05-01

In this paper, we explore ferroelectric properties of cleaved 2-D flakes of copper indium thiophosphate, CuInP 2S 6 (CITP), and probe size effects along with limits of ferroelectric phase stability, by ambient and ultra high vacuum scanning probe microscopy. CITP belongs to the only material family known to display ferroelectric polarization in a van der Waals, layered crystal at room temperature and above. Our measurements directly reveal stable, ferroelectric polarization as evidenced by domain structures, switchable polarization, and hysteresis loops. We found that at room temperature the domain structure of flakes thicker than 100 nm is similar to the cleavedmore » bulk surfaces, whereas below 50 nm polarization disappears. We ascribe this behavior to a well-known instability of polarization due to depolarization field. Furthermore, polarization switching at high bias is also associated with ionic mobility, as evidenced both by macroscopic measurements and by formation of surface damage under the tip at a bias of 4 V—likely due to copper reduction. Mobile Cu ions may therefore also contribute to internal screening mechanisms. Finally, the existence of stable polarization in a van-der-Waals crystal naturally points toward new strategies for ultimate scaling of polar materials, quasi-2D, and single-layer materials with advanced and nonlinear dielectric properties that are presently not found in any members of the growing “graphene family”.« less

Silicon carbide as a basis for spaceflight optical systems

NASA Astrophysics Data System (ADS)

Curcio, Michael E.

1994-09-01

New advances in the areas of microelectronics and micro-mechanical devices have created a momentum in the development of lightweight, miniaturized, electro-optical space subsystems. The performance improvements achieved and new observational techniques developed as a result, have provided a basis for a new range of Small Explorer, Discovery-class and other low-cost mission concepts for space exploration. However, the ultimate objective of low-mass, inexpensive space science missions will only be achieved with a companion development in the areas of flight optical systems and sensor instrument benches. Silicon carbide (SiC) is currently emerging as an attractive technology to fill this need. As a material basis for reflective, flight telescopes and optical benches, SiC offers: the lightweight and stiffness characteristics of beryllium; glass-like inherent stability consistent with performance to levels of diffraction-limited visible resolution; superior thermal properties down to cryogenic temperatures; and an existing, commercially-based material and processing infrastructure like aluminum. This paper will describe the current status and results of on-going technology developments to utilize these material properties in the creation of lightweight, high- performing, thermally robust, flight optical assemblies. System concepts to be discussed range from an 18 cm aperture, 4-mirror, off-axis system weighing less than 2 kg to a 0.5 m, 15 kg reimager. In addition, results in the development of a thermally-stable, `GOES-like' scan mirror will be presented.

Atomic-scale understanding of non-stoichiometry effects on the electrochemical performance of Ni-rich cathode materials

NASA Astrophysics Data System (ADS)

Kong, Fantai; Liang, Chaoping; Longo, Roberto C.; Zheng, Yongping; Cho, Kyeongjae

2018-02-01

As the next-generation high energy capacity cathode materials for Li-ion batteries, Ni-rich oxides face the problem of obtaining near-stoichiometric phases due to excessive Ni occupying Li sites. These extra-Ni-defects drastically affect the electrochemical performance. Despite of its importance, the fundamental correlation between such defects and the key electrochemical properties is still poorly understood. In this work, using density-functional-theory, we report a comprehensive study on the effects of non-stoichiometric phases on properties of Ni-rich layered oxides. For instance, extra-Ni-defects trigger charge disproportionation reaction within the system, alleviating the Jahn-Teller distortion of Ni3+ ions, which constitutes an important reason for their low formation energies. Kinetic studies of these defects reveal their immobile nature, creating a "pillar effect" that increases the structural stability. Ab initio molecular dynamics revealed Li depletion regions surrounding extra-Ni-defects, which are ultimate responsible for the arduous Li diffusion and re-intercalation, resulting in poor rate performance and initial capacity loss. Finally, the method with combination of high valence cation doping and ion-exchange synthesis is regarded as the most promising way to obtain stoichiometric oxides. Overall, this work not only deepens our understanding of non-stoichiometric Ni-rich layered oxides, but also enables further optimizations of high energy density cathode materials.

Caracterisation de nanofilms polymeriques deposes par plasma froid : Stabilite et proprietes mecaniques

NASA Astrophysics Data System (ADS)

Barrette, Jeremie

The current project is inscribed in the research axis on bioactive coatings of Dr. Sophie Lerouge's Laboratoire de Biomatériaux endovasculaires (LBeV). The aim of our work was to extract mechanical properties of a new plasma polymer called L-PPE :N (developed to enhance healing around stent-graft) and determine the effect of various experimental parameters on the stability behavior of our thin films (hundred nanometer thick coatings). Subsidiary to these goals, we also had in mind to test whether usual methods for characterizing polymers and films were applicable on our cold-plasma deposited material. Properties concerned by our endeavor included Young's modulus, hardness, storage and loss modulus, resistance to tearing, ultimate strain and aqueous stability under different temperature and pH for films of varying ratio of gases and thicknesses. Apparatus and work hypothesis used to succeed in our characterization work included, but was not limited to: a quartz crystal dissipative microbalance (QCM-D), a nanoindenter, an ellipsometer, and a tensile testing bench specifically designed for microscopic observation. Hypothesis attached to these methods are that each of these will work as intended for the characterization of our material. Furthermore, we also need to consider the properties of our film as constant throughout its volume (surface-wise for QCM-D analysis and thickness-wise for nanoindentation). QCM-D results allowed us to determine the best compromise of deposition gas ratio R=NH3/C2H4 of L-PPE:N for our biomedical application to be 0.75, from a stability and bioactivity point of view. Starting from that information, we submitted ratio 0.75 films to temperature, thickness and pH essays to make sure they could handle every situation we could need to put them through. Nanoindentation essays have helped us finding reduced modulus and hardness of 8.0 and 0.4 GPa for the 2 µm coating and 10.4 and 0.5 GPa for the 200 nm film, respectively. These values are greater than other biomaterials currently in use, and similar to other cold plasma materials. Further improvements to this work include, at this point of the L-PPE:N development, to start studying the impact of conventional sterilization methods on the stability, mechanical and biological properties of our film, and to submit our coating to a testing bench designed specifically to mimic the insertion and deployment of a stent-graft, in order to verify the structural integrity of the film afterwards.

Design Principles Guide Educators in Choosing and Using Curriculum Materials. Research Review

ERIC Educational Resources Information Center

Foster, Elizabeth

2018-01-01

Engaging with materials can shape the teaching experience, teachers' practices and mindsets, and, ultimately, students' learning experiences. This issue of "Learning Professional" looks at an area of emerging interest: curriculum materials and the role they play in the daily work of educators and leaders. Educators, researchers, and…

Research on medium and high temperature solar heat storage materials

NASA Technical Reports Server (NTRS)

Heine, D.; Jucker, J.; Koch, D.; Krahling, H.; Supper, W.

1979-01-01

Characteristics of solar heat storage materials, preliminary tests in which melting and solidification characteristics are tested, and service life and cycling tests are reported. Various aspects of corrosion are discussed as well as decision about ultimate selection of materials. A program for storage and evaluation of data is included.

Efficiency and threshold pump intensity of CW solar-pumped solid-state lasers

NASA Technical Reports Server (NTRS)

Hwang, In H.; Lee, Ja H.

1991-01-01

The authors consider the relation between the threshold pumping intensity, the material properties, the resonator parameters, and the ultimate slope efficiencies of various solid-state laser materials for solar pumping. They clarify the relation between the threshold pump intensity and the material parameters and the relation between the ultimate slope efficiency and the laser resonator parameters such that a design criterion for the solar-pumped solid-state laser can be established. Among the laser materials evaluated, alexandrite has the highest slope efficiency of about 12.6 percent; however, it does not seem to be practical for a solar-pumped laser application because of its high threshold pump intensity. Cr:Nd:GSGG is the most promising for solar-pumped lasing. Its threshold pump intensity is about 100 air-mass-zero (AM0) solar constants and its slope efficiency is about 12 percent when thermal deformation is completely prevented.

Development of Sorbents for Extraction and Stabilization of Nucleic Acids

DTIC Science & Technology

2016-09-13

traditional stabilization compounds. The materials were further shown to provide capture and subsequent stabilization of targets from a complex ...22 CAPTURE FROM COMPLEX SOLUTIONS...stabilization compounds (sugars and BSA). The materials were further shown to provide capture and subsequent stabilization of targets from a complex

Marginal and internal fit of CAD-CAM-fabricated composite resin and ceramic crowns scanned by 2 intraoral cameras.

PubMed

de Paula Silveira, Alessandra C; Chaves, Sacha B; Hilgert, Leandro A; Ribeiro, Ana Paula D

2017-03-01

The precision of fit of chairside computer-aided design and computer-aided manufacturing (CAD-CAM) complete crowns is affected by digital impression and restorative material. The purpose of this in vitro study was to evaluate by microcomputed tomography (μCT) the marginal and internal adaptation of composite resin and ceramic complete crowns fabricated with 2 different intraoral cameras and 2 restorative materials. Ten extracted human third molars received crown preparations. For each prepared molar, 2 digital impressions were made with different intraoral cameras of the CEREC system, Bluecam and Omnicam. Four groups were formed: LB (Lava Ultimate+Bluecam), EB (Emax+Bluecam), LO (Lava Ultimate+Omnicam), and EO (Emax+Omnicam). Before measuring the precision of fit, all crowns were stabilized with a silicone material. Each unit (crown + prepared tooth) was imaged with μCT, and marginal and internal discrepancies were analyzed. For the 2D analysis, 120 measurements were made of each crown for marginal adaptation, 20 for marginal discrepancy (MD), and 20 for absolute marginal discrepancy (AMD); and for internal adaptation, 40 for axial space (AS) and 40 for occlusal space (OS). After reconstructing the 3D images, the average internal space (AIS) was calculated by dividing the total volume of the internal space by the contact surface. Data were analyzed with 2-way ANOVA and quantile regression. Regarding marginal adaptation, no significant differences were observed among groups. For internal adaptation measured in the 2D evaluation, a significant difference was observed between LO and EO for the AS variable (Mann-Whitney test; P<.008). In assessment of AIS by the 3D reconstruction, LB presented significantly lower values than the other groups (Tukey post hoc test; P<.05). Bluecam presented lower values of AIS than Omnicam, and composite resin crowns showed less discrepancy than did ceramic crowns. The marginal adaptations assessed in all groups showed values within the clinically accepted range. Moreover, the composite resin blocks associated with the Bluecam intraoral camera demonstrated the best results for AIS compared with those of the other groups. Copyright © 2016 Editorial Council for the Journal of Prosthetic Dentistry. Published by Elsevier Inc. All rights reserved.

Solid impingement erosion mechanisms and characterization of erosion resistance of ductile metals

NASA Technical Reports Server (NTRS)

Rao, V. P.; Buckley, D. H.

1982-01-01

Experimental results pertaining to spherical glass bead and angular crushed glass particle impingement are presented. A concept of energy adsorption to explain the failure of material is proposed. The erosion characteristics of several pure metals were correlated with the proposed energy parameters and with other properties. Correlations of erosion and material properties were also carried out with these materials to study the effect of the angle of impingement. Analyses of extensive erosion data indicate that surface energy, strain energy, melting point, bulk modulus, hardness, ultimate resilience, atomic volume and product of linear coefficient of thermal expansion, bulk modulus, and temperature rise required for melting, and ultimate resilience, and hardness exhibit the best correlations. It appears that both energy and thermal properties contribute to the total erosion.

Multiple Small Diameter Drillings Increase Femoral Neck Stability Compared with Single Large Diameter Femoral Head Core Decompression Technique for Avascular Necrosis of the Femoral Head.

PubMed

Brown, Philip J; Mannava, Sandeep; Seyler, Thorsten M; Plate, Johannes F; Van Sikes, Charles; Stitzel, Joel D; Lang, Jason E

2016-10-26

Femoral head core decompression is an efficacious joint-preserving procedure for treatment of early stage avascular necrosis. However, postoperative fractures have been described which may be related to the decompression technique used. Femoral head decompressions were performed on 12 matched human cadaveric femora comparing large 8mm single bore versus multiple 3mm small drilling techniques. Ultimate failure strength of the femora was tested using a servo-hydraulic material testing system. Ultimate load to failure was compared between the different decompression techniques using two paired ANCOVA linear regression models. Prior to biomechanical testing and after the intervention, volumetric bone mineral density was determined using quantitative computed tomography to account for variation between cadaveric samples and to assess the amount of bone disruption by the core decompression. Core decompression, using the small diameter bore and multiple drilling technique, withstood significantly greater load prior to failure compared with the single large bore technique after adjustment for bone mineral density (p< 0.05). The 8mm single bore technique removed a significantly larger volume of bone compared to the 3mm multiple drilling technique (p< 0.001). However, total fracture energy was similar between the two core decompression techniques. When considering core decompression for the treatment of early stage avascular necrosis, the multiple small bore technique removed less bone volume, thereby potentially leading to higher load to failure.

Messianic Pedagogy

ERIC Educational Resources Information Center

Lewis, Tyson

2010-01-01

Famously, Walter Benjamin once wrote that behind historical materialism lies a disavowed theological "hunchback." More importantly, it is only through a rejuvenated relation with this theological hunchback that historical materialism can ultimately realize its own revolutionary possibilities. While the theological dimension of critical theory has…

Colour stainability of indirect CAD-CAM processed composites vs. conventionally laboratory processed composites after immersion in staining solutions.

PubMed

Arocha, Mariana A; Basilio, Juan; Llopis, Jaume; Di Bella, Enrico; Roig, Miguel; Ardu, Stefano; Mayoral, Juan R

2014-07-01

The aim of this study was to determine, by using a spectrophotometer device, the colour stainability of two indirect CAD/CAM processed composites in comparison with two conventionally laboratory-processed composites after being immersed 4 weeks in staining solutions such as coffee, black tea and red wine, using distilled water as control group. Two indirect CAD/CAM composites (Lava Ultimate and Paradigm MZ100) and two conventionally laboratory-processed composites (SR Adoro and Premise Indirect) of shade A2 were selected (160 disc samples). Colour stainability was measured after 4 weeks of immersion in three staining solutions (black tea, coffee, red wine) and distilled water. Specimen's colour was measured each week by means of a spectrophotometer (CIE L*a*b* system). Statistical analysis was carried out performing repeated ANOVA measurements and Tukey's HSD test to evaluate differences in ΔE00 measurements between groups; the interactions among composites, staining solutions and time duration were also evaluated. All materials showed significant discoloration (p<0.01) when compared to control group. The highest ΔE00 observed was with red wine, whereas black tea showed the lowest one. Indirect laboratory-processed resin composites showed the highest colour stability compared with CAD/CAM resin blocks. CAD/CAM processed composites immersed in staining solutions showed lower colour stability when compared to conventionally laboratory-processed resin composites. The demand for CAD/CAM restorations has been increasing; however, colour stainability for such material has been insufficiently studied. Moreover, this has not been performed comparing CAD/CAM processed composites versus laboratory-processed indirect composites by immersing in staining solutions for long immersion periods. Copyright © 2014 Elsevier Ltd. All rights reserved.

Long-term stability and properties of zirconia ceramics for heavy duty diesel engine components

NASA Technical Reports Server (NTRS)

Larsen, D. C.; Adams, J. W.

1985-01-01

Physical, mechanical, and thermal properties of commercially available transformation-toughened zirconia are measured. Behavior is related to the material microstructure and phase assemblage. The stability of the materials is assessed after long-term exposure appropriate for diesel engine application. Properties measured included flexure strength, elastic modulus, fracture toughness, creep, thermal shock, thermal expansion, internal friction, and thermal diffusivity. Stability is assessed by measuring the residual property after 1000 hr/1000C static exposure. Additionally static fatigue and thermal fatigue testing is performed. Both yttria-stabilized and magnesia-stabilized materials are compared and contrasted. The major limitations of these materials are short term loss of properties with increasing temperature as the metastable tetragonal phase becomes more stable. Fine grain yttria-stabilized material (TZP) is higher strength and has a more stable microstructure with respect to overaging phenomena. The long-term limitation of Y-TZP is excessive creep deformation. Magnesia-stabilized PSZ has relatively poor stability at elevated temperature. Overaging, decomposition, and/or destabilization effects are observed. The major limitation of Mg-PSZ is controlling unwanted phase changes at elevated temperature.

Lava ultimate resin nano ceramic for CAD/ CAM: customization case study.

PubMed

Koller, M; Arnetzl, G V; Holly, L; Arnetzl, G

2012-01-01

Lava Ultimate Resin Nano Ceramic (RNC) blocks are innovative new CAD/CAM materials that make it possible to achieve superior esthetic results in easy steps. The blocks are made of nano ceramic particles embedded in a highly cured resin matrix. Therefore, composite materials can be used to characterize and adjust resin nano ceramic restorations after milling. The milled RNC restorations can be individualized intra-orally or extra-orally, either before or after insertion. Unlike conventional ceramic restorations, customization and glaze firing is neither necessary nor possible with RNC restorations. This opens up the opportunity for intraoral individualization and adaptation of the restorations.

Polymerizable ultraviolet stabilizers for outdoor use

NASA Technical Reports Server (NTRS)

Vogl, O.

1982-01-01

Polymeric materials that are stable enough to use outdoors without changes in excess of 20 years are investigated. Ultraviolet stabilizers or plastic materials were synthesized, polymerizable ultraviolet stabilizers, particularly of the 2(2-hydroxyphenyl)2H-benzotriazole family were prepared their polymerization, copolymerization and grafting onto other polymers were demonstrated, and ultraviolet stabilizing systems were devised. These materials were evaluated from the photophysical point of view.

Synthetic fossilization of soft biological tissues and their shape-preserving transformation into silica or electron-conductive replicas

DOE PAGES

Townson, Jason L.; Lin, Yu-Shen; Chou, Stanley S.; ...

2014-12-08

Structural preservation of complex biological systems from the subcellular to whole organism level in robust forms, enabling dissection and imaging while preserving 3D context, represents an enduring grand challenge in biology. Here we report a simple immersion method for structurally preserving intact organisms via conformal stabilization within silica. This self-limiting process, which we refer to as silica bioreplication, occurs by condensation of water-soluble silicic acid proximally to biomolecular interfaces throughout the organism. Conformal nanoscopic silicification of all biomolecular features imparts structural rigidity enabling the preservation of shape and nano-to-macroscale dimensional features upon drying to form a biocomposite and further highmore » temperature oxidative calcination to form silica replicas or reductive pyrolysis to form electrically conductive carbon replicas of complete organisms. Ultimately, the simplicity and generalizability of this approach should facilitate efforts in biological preservation and analysis and could enable the development of new classes of biomimetic composite materials.« less

The catalyst layer and its dimensionality - A look into its ingredients and how to characterize their effects

NASA Astrophysics Data System (ADS)

Zamel, Nada

2016-03-01

Development of polymer electrolyte membrane (PEM) fuel cells throughout the years is established through its component optimization. This is especially true of its catalyst layer, where structuring of the layer has led to many breakthroughs. The catalyst layer acts as the heart of the cell, where it controls the half-cell reactions and their products. The complex nature of various transport phenomena simultaneously taking place in the layer requires the layer to be heterogeneous in structure. Hence, a delicate balance of the layer's ingredients, coupled with the understanding of the ingredients' interaction, is required. State-of-the-art catalyst layers are composed of a catalyst, its support, a solvent and a binder. Changes in the morphology, structure or material of any of these components ultimately affects the layer's activity and durability. In this review paper, we provide an overview of the various works tailored to understand how each component in the catalyst's ink affects the stability and life-time of the layer.

Giant Stark effect in double-stranded porphyrin ladder polymers

NASA Astrophysics Data System (ADS)

Pramanik, Anup; Kang, Hong Seok

2011-03-01

Using the first-principles calculations, we have investigated the stability and the electronic structure of two types of recently synthesized one-dimensional nanoribbons, i.e., double-stranded zinc(II) porphyrin ladder polymer (LADDER) arrays. First, electronic structure calculations were used to show that the LADDER is a semiconductor. Most importantly, the application of a transverse electric field significantly reduces the band gap of the LADDER, ultimately converting the LADDER to a metal at a field strength of 0.1 V/Å. The giant Stark effect in this case is almost as strong as that in boron nitride nanotubes and nanoribbons. In the presence of an electric field, hole conduction and electronic conduction will occur entirely through spatially separated strands, rendering these materials useful for nanoelectronic devices. Second, the substitution of hydrogen atoms in the porphyrin units or that of zinc ions with other kinds of chemical species is found to increase the binding strength of the LADDER and reduce the band gap.

Modelling toolkit for simulation of maglev devices

NASA Astrophysics Data System (ADS)

Peña-Roche, J.; Badía-Majós, A.

2017-01-01

A stand-alone App1 has been developed, focused on obtaining information about relevant engineering properties of magnetic levitation systems. Our modelling toolkit provides real time simulations of 2D magneto-mechanical quantities for superconductor (SC)/permanent magnet structures. The source code is open and may be customised for a variety of configurations. Ultimately, it relies on the variational statement of the critical state model for the superconducting component and has been verified against experimental data for YBaCuO/NdFeB assemblies. On a quantitative basis, the values of the arising forces, induced superconducting currents, as well as a plot of the magnetic field lines are displayed upon selection of an arbitrary trajectory of the magnet in the vicinity of the SC. The stability issues related to the cooling process, as well as the maximum attainable forces for a given material and geometry are immediately observed. Due to the complexity of the problem, a strategy based on cluster computing, database compression, and real-time post-processing on the device has been implemented.

Observation of optomechanical buckling transitions

PubMed Central

Xu, H.; Kemiktarak, U.; Fan, J.; Ragole, S.; Lawall, J.; Taylor, J. M.

2017-01-01

Correlated phases of matter provide long-term stability for systems as diverse as solids, magnets and potential exotic quantum materials. Mechanical systems, such as buckling transition spring switches, can have engineered, stable configurations whose dependence on a control variable is reminiscent of non-equilibrium phase transitions. In hybrid optomechanical systems, light and matter are strongly coupled, allowing engineering of rapid changes in the force landscape, storing and processing information, and ultimately probing and controlling behaviour at the quantum level. Here we report the observation of first- and second-order buckling transitions between stable mechanical states in an optomechanical system, in which full control of the nature of the transition is obtained by means of the laser power and detuning. The underlying multiwell confining potential we create is highly tunable, with a sub-nanometre distance between potential wells. Our results enable new applications in photonics and information technology, and may enable explorations of quantum phase transitions and macroscopic quantum tunnelling in mechanical systems. PMID:28248293

Method of Construction for Geopolymer Soil Stabilized Platforms

DTIC Science & Technology

2017-12-20

of the geopolymer core compressive strength tests. The degree of seepage varied from pavement to pavement due to mix design and additives, ultimately...Department of the Army position unless so designated by other authorized documents. DESTROY THIS REPORT WHEN NO LONGER NEEDED. DO NOT RETURN IT TO THE...20 3.5 Test pavement ................................................................................................ 23

Promise or Peril: The Strategic Defense Initiative.

ERIC Educational Resources Information Center

Brzezinski, Zbigniew, Ed.; And Others

The major policy debate touched off by President Reagan's March 1983 speech announcing the Strategic Defense Initiative (SDI) was the reopening of one that had begun 35 years before. Then and now the ultimate question is what kind of strategic posture is most likely to contribute to mutual strategic stability? The answer is central to national…

Non-iterative Voltage Stability

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

Makarov, Yuri V.; Vyakaranam, Bharat; Hou, Zhangshuan

2014-09-30

This report demonstrates promising capabilities and performance characteristics of the proposed method using several power systems models. The new method will help to develop a new generation of highly efficient tools suitable for real-time parallel implementation. The ultimate benefit obtained will be early detection of system instability and prevention of system blackouts in real time.

Developing an On-Line Interactive Health Psychology Module

ERIC Educational Resources Information Center

Upton, Dominic; Cooper, Carol

2006-01-01

On-line teaching material in health psychology was developed which ensured a range of students could access appropriate material for their course and level of study. This material has been developed around the concept of smaller "content chunks" which can be combined into whole units of learning (topics), and ultimately, a module. On the…

Polyimide/carbon Nanocomposites

NASA Technical Reports Server (NTRS)

Harris, Frank W.

2003-01-01

The goal of this product is to design and characterize well-defined conductive nanocomposite materials. The materials will be composed of a polymer matrix composed of rigid-backbone polyimides, and will be filled with modified or unmodified multi-walled carbon nanotubes (MWNTs). The ultimate design of this project is to create composite materials with optical clarity and a high conductivity.

Microbial carbon pump and its significance for carbon sequestration in soils

NASA Astrophysics Data System (ADS)

Liang, Chao

2017-04-01

Studies of the decomposition, transformation and stabilization of soil organic carbon have dramatically increased in recent years due to growing interest in studying the global carbon cycle as it pertains to climate change. While it is readily accepted that the magnitude of the organic carbon reservoir in soils depends upon microbial involvement because soil carbon dynamics are ultimately the consequence of microbial growth and activity, it remains largely unknown how these microbe-mediated processes lead to soil carbon stabilization. Here, two pathways, ex vivo modification and in vivo turnover, were defined to jointly explain soil carbon dynamics driven by microbial catabolism and/or anabolism. Accordingly, a conceptual framework consisting of the raised concept of the soil "microbial carbon pump" (MCP) was demonstrated to describe how microbes act as an active player in soil carbon storage. The hypothesis is that the long-term microbial assimilation process may facilitate the formation of a set of organic compounds that are stabilized (whether via protection by physical interactions or a reduction in activation energy due to chemical composition), ultimately leading to the sequestration of microbial-derived carbon in soils. The need for increased efforts was proposed to seek to inspire new studies that utilize the soil MCP as a conceptual guideline for improving mechanistic understandings of the contributions of soil carbon dynamics to the responses of the terrestrial carbon cycle under global change.

Optimization of protein buffer cocktails using Thermofluor.

PubMed

Reinhard, Linda; Mayerhofer, Hubert; Geerlof, Arie; Mueller-Dieckmann, Jochen; Weiss, Manfred S

2013-02-01

The stability and homogeneity of a protein sample is strongly influenced by the composition of the buffer that the protein is in. A quick and easy approach to identify a buffer composition which increases the stability and possibly the conformational homogeneity of a protein sample is the fluorescence-based thermal-shift assay (Thermofluor). Here, a novel 96-condition screen for Thermofluor experiments is presented which consists of buffer and additive parts. The buffer screen comprises 23 different buffers and the additive screen includes small-molecule additives such as salts and nucleotide analogues. The utilization of small-molecule components which increase the thermal stability of a protein sample frequently results in a protein preparation of higher quality and quantity and ultimately also increases the chances of the protein crystallizing.

Stabilizing Waste Materials for Landfills

ERIC Educational Resources Information Center

Environmental Science and Technology, 1977

1977-01-01

The test procedures used to evaluate the suitability of landfilled materials of varying stability and to determine the leachate from such materials are reviewed. A process for stabilizing a mixture of sulfur dioxide sludge, fly ash, and bottom ash with lime and other additives for deposition in landfills is detailed. (BT)

Challenges for Synchrotron X-Ray Optics

NASA Astrophysics Data System (ADS)

Freund, Andreas K.

2002-12-01

It is the task of x-ray optics to adapt the raw beam generated by modern sources such as synchrotron storage rings to a great variety of experimental requirements in terms of intensity, spot size, polarization and other parameters. The very high quality of synchrotron radiation (source size of a few microns and beam divergence of a few micro-radians) and the extreme x-ray flux (power of several hundred Watts in a few square mm) make this task quite difficult. In particular the heat load aspect is very important in the conditioning process of the brute x-ray power to make it suitable for being used on the experimental stations. Cryogenically cooled silicon crystals and water-cooled diamond crystals can presently fulfill this task, but limits will soon be reached and new schemes and materials must be envisioned. A major tendency of instrument improvement has always been to concentrate more photons into a smaller spot utilizing a whole variety of focusing devices such as Fresnel zone plates, refractive lenses and systems based on bent surfaces, for example, Kirkpatrick-Baez systems. Apart from the resistance of the sample, the ultimate limits are determined by the source size and strength on one side, by materials properties, cooling, mounting and bending schemes on the other side, and fundamentally by the diffraction process. There is also the important aspect of coherence that can be both a nuisance and a blessing for the experiments, in particular for imaging techniques. Its conservation puts additional constraints on the quality of the optical elements. The overview of the present challenges includes the properties of present and also mentions aspects of future x-ray sources such as the "ultimate" storage ring and free electron lasers. These challenges range from the thermal performances of monochromators to the surface quality of mirrors, from coherence preservation of modern multilayers to short pulse preservation by crystals, and from micro- and nano-focusing techniques to the accuracy and stability of mechanical supports.

Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 Steel

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

Brown, Neil R.; Serrano De Caro, Magdalena; Rodriguez, Edward A.

2012-08-28

The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in elevated temperature design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module. LANL staff immediately proposed HT-9 for the reactor vessel and components, as well as fuel clad and ducting, due to itsmore » superior thermal qualities. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, there are several key deliverables that must first be successfully accomplished. The most important key deliverable is the research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which becomes the basis for an ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Although this report provides a cursory review of the available data, a much more comprehensive study of open-source data would be necessary. This report serves three purposes: (a) provides a list of already existing material data information that could ultimately be made available to the ASME Code, (b) determines the HT-9 material properties data missing from available sources that would be required and (c) estimates the necessary material testing required to close the gap. Ultimately, the gap analysis demonstrates that certain material properties testing will be required to fulfill the necessary information package for an ASME Code Case.« less

Integrating the stabilization of nuclear materials

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

Dalton, H.F.

1996-05-01

In response to Recommendation 94-1 of the Defense Nuclear Facilities Safety Board, the Department of Energy committed to stabilizing specific nuclear materials within 3 and 8 years. These efforts are underway. The Department has already repackaged the plutonium at Rocky Flats and metal turnings at Savannah River that had been in contact with plastic. As this effort proceeds, we begin to look at activities beyond stabilization and prepare for the final disposition of these materials. To describe the plutonium materials being stabilize, Figure 1 illustrates the quantities of plutonium in various forms that will be stabilized. Plutonium as metal comprisesmore » 8.5 metric tons. Plutonium oxide contains 5.5 metric tons of plutonium. Plutonium residues and solutions, together, contain 7 metric tons of plutonium. Figure 2 shows the quantity of plutonium-bearing material in these four categories. In this depiction, 200 metric tons of plutonium residues and 400 metric tons of solutions containing plutonium constitute most of the material in the stabilization program. So, it is not surprising that much of the work in stabilization is directed toward the residues and solutions, even though they contain less of the plutonium.« less

Improved ceramic heat exchange material

NASA Technical Reports Server (NTRS)

Mccollister, H. L.

1977-01-01

Improved corrosion resistant ceramic materials that are suitable for use as regenerative heat exchangers for vehicular gas turbines is reported. Two glass-ceramic materials, C-144 and C-145, have superior durability towards sulfuric acid and sodium sulfate compared to lithium aluminosilicate (LAS) Corning heat exchange material 9455. Material C-144 is a leached LAS material whose major crystalline phase is silica keatite plus mullite, and C-145 is a LAS keatite solid solution (S.S.) material. In comparison to material 9455, material C-144 is two orders of magnitude better in dimensional stability to sulfuric acid at 300 C, and one order of magnitude better in stability to sodium sulfate at 1000 C. Material C-145 is initially two times better in stability to sulfuric acid, and about one order of magnitude better in stability to sodium sulfate. Both C-144 and C-145 have less than 300 ppm delta L/L thermal expansion from ambient to 1000 C, and good dimensional stability of less than approximately 100 ppm delta L/L after exposure to 1000 C for 100 hours. The glass-ceramic fabrication process produced a hexagonal honeycomb matrix having an 85% open frontal area, 50 micrometer wall thickness, and less than 5% porosity.

Effect of laser frequency noise on fiber-optic frequency reference distribution

NASA Technical Reports Server (NTRS)

Logan, R. T., Jr.; Lutes, G. F.; Maleki, L.

1989-01-01

The effect of the linewidth of a single longitude-mode laser on the frequency stability of a frequency reference transmitted over a single-mode optical fiber is analyzed. The interaction of the random laser frequency deviations with the dispersion of the optical fiber is considered to determine theoretically the effect on the Allan deviation (square root of the Allan variance) of the transmitted frequency reference. It is shown that the magnitude of this effect may determine the limit of the ultimate stability possible for frequency reference transmission on optical fiber, but is not a serious limitation to present system performance.

Dynamic Stability Instrumentation System (DSIS). Volume 3; User Manual

NASA Technical Reports Server (NTRS)

Daniels, Taumi S.; Boyden, Richmond P.; Dress, David A.; Jordan, Thomas L.

1996-01-01

The paper is an operating manual for the Dynamic Stability Instrumentation System in specific NASA Langley wind tunnels. The instrumentation system performs either a synchronous demodulation or a Fast Fourier Transform on dynamic balance strain gage signals, and ultimately computes aerodynamic coefficients. The dynamic balance converts sting motor rotation into pitch or yaw plane or roll axis oscillation, with timing information provided by a shaft encoder. Additional instruments control model attitude and balance temperature and monitor sting vibrations. Other instruments perform self-calibration and diagnostics. Procedures for conducting calibrations and wind-off and wind-on tests are listed.

7 CFR 58.933 - Stabilizers.

Code of Federal Regulations, 2011 CFR

2011-01-01

... Materials § 58.933 Stabilizers. Shall be those permitted by the Food and Drug Administration's “Standards of Identity” as optional ingredients for specific products. Stabilizers shall be free from extraneous material... 7 Agriculture 3 2011-01-01 2011-01-01 false Stabilizers. 58.933 Section 58.933 Agriculture...

7 CFR 58.933 - Stabilizers.

Code of Federal Regulations, 2010 CFR

2010-01-01

... Materials § 58.933 Stabilizers. Shall be those permitted by the Food and Drug Administration's “Standards of Identity” as optional ingredients for specific products. Stabilizers shall be free from extraneous material... 7 Agriculture 3 2010-01-01 2010-01-01 false Stabilizers. 58.933 Section 58.933 Agriculture...

Distinct Litter Stabilization Dynamics Pathways for Decomposition of Pine Needle and Fine Root Within Soil

NASA Astrophysics Data System (ADS)

Mambelli, S.; Filley, T. R.; Bird, J.; Dawson, T.; Torn, M. S.

2008-12-01

The chemical composition of litter imparts a strong control on the initial rates of microbial decay but it is unclear how plant chemistry influences the ultimate stabilization of soil organic matter (SOM) and the nature of the products stabilized. We determined the concentration and 13C enrichment of lignin phenols and substituted fatty acids (SFA) in SOM fractions from an experiment in which 13C- and 15N-labeled needles or fine roots were added to the mineral soil in a Ponderosa pine (Pinus ponderosa) forest in the Sierra Nevada, CA, USA. 1.5 y after litter addition, we analyzed bulk soil (< 2 mm), free light fraction (LF, mean residence time (MRT) ~5 y) and alkali/acid insoluble humin (MRT ~270 y) fractions. Needles contained nearly 2 and 3x the lignin and SFA content per organic carbon unit as did roots. Lignin and SFA decreased from the free LF to the bulk soil to the humin fraction; and molecular properties were more similar within a SOM fraction regardless of the litter source. However, LF and humin from the root addition contained more lignin than from the needle addition. Based upon the relative movement of litter-derived 13C and 15N into SOM fractions during 1.5 y, it was proposed that the 13C accumulation in the humin fraction for needles was derived from high C/N, needle-derived biopolymer molecular fragments that are surficially associated with particles. In contrast, the root-derived material entering SOM fractions was much lower in C/N and was likely from microbial by-products. Consistent with this hypothesis, both lignin and SFA in the LF and humin fractions amended with enriched needles were highly enriched (+ 30-60 permil) with respect to the SOM fractions from soils amended with roots. These differences were large even considering the lower concentration of SFA and lignin in root material. Although the chemistry and MRT of LF and humin were dramatically different, the extent of 13C-enrichment among lignin and SFA were comparable for the needle experiment while most lignin phenols for the humin from the root addition had greater 13C content than SFA. This indicates that molecular fragments of plant biopolymers can readily associate with both labile and stabilized SOM fractions. At the same time, these results suggest that distinct decomposition and stabilization pathways exist for litters, such as needles vs. roots, of different chemical quality.

Origin of Long-Term Storage Stability and Nitric Oxide Release Behavior of CarboSil Polymer Doped with S-Nitroso-N-acetyl-D-penicillamine.

PubMed

Wo, Yaqi; Li, Zi; Brisbois, Elizabeth J; Colletta, Alessandro; Wu, Jianfeng; Major, Terry C; Xi, Chuanwu; Bartlett, Robert H; Matzger, Adam J; Meyerhoff, Mark E

2015-10-14

The prolonged and localized delivery of nitric oxide (NO), a potent antithrombotic and antimicrobial agent, has many potential biomedical applications. In this work, the origin of the long-term storage stability and sustained NO release mechanism of S-nitroso-N-acetyl-D-penicillamine (SNAP)-doped CarboSil 20 80A polymer, a biomedical thermoplastic silicone-polycarbonate-urethane, is explored. Long-term (22 days) localized NO release is achieved by utilizing a cross-linked silicone rubber as topcoats, which can greatly reduce the amount of SNAP, NAP, and NAP disulfide leaching from the SNAP-doped CarboSil films, as measured by LC-MS. Raman spectroscopy and powder X-ray diffraction characterization of SNAP-doped CarboSil films demonstrate that a polymer-crystal composite is formed during the solvent evaporation process when SNAP exceeds its solubility in CarboSil (ca. 3.4-4.0 wt %). Further, when exceeding this solubility threshold, SNAP exists in an orthorhombic crystal form within the bulk of the polymer. The proposed mechanism of sustained NO release in SNAP-doped CarboSil is that the solubilized SNAP in the polymer matrix decomposes and releases NO, primarily in the water-rich regions near the polymer/solution interface, and the dissolved SNAP in the bulk polymeric phase becomes unsaturated, resulting in the dissolution of crystalline SNAP within the bulk of the polymer. This is a very slow process that ultimately leads to NO release at the physiological flux levels for >3 weeks. The increased stability of SNAP within CarboSil is attributed to the intermolecular hydrogen bonds between the SNAP molecules that crystallize. This crystallization also plays a key role in maintaining RSNO stability within the CarboSil polymer for >8 months at 37 °C (88.5% remains). Further, intravascular catheters fabricated with this new material are demonstrated to significantly decrease the formation of Staphylococcus aureus biofilm (a leading cause of nosocomial bloodstream infections) (in vitro) over a 7 day period, with 5 log units reduction of viable cell count on catheter surfaces. It is also shown that the NO release catheters can greatly reduce thrombus formation on the catheter surfaces during 7 h implantation in rabbit veins, when compared to the control catheters fabricated without SNAP. These results suggest that the SNAP-doped CarboSil system is a very attractive new composite material for creating long-term NO release medical devices with increased stability and biocompatibility.

Study on structure, mechanical property and cell cytocompatibility of electrospun collagen nanofibers crosslinked by common agents.

PubMed

Luo, Xueshi; Guo, Zhenzhao; He, Ping; Chen, Tian; Li, Lihua; Ding, Shan; Li, Hong

2018-07-01

Collagen electrospun scaffolds properly reproduce the framework of the extracellular matrix (ECM) of tissues that are natural with the fibrous morphology of the protein by coupling large biomimetism of the biological material. However, traditional solvents employed for collagen electrospinning lead to poor mechanical attributes and bad hydro-stability. In this work, by N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride with N-hydroxysulfosuccinimide (EDC-NHS), glutaraldehyde (GTA) and genipin (GP) respectively, electrospun collagen fibers cross-linked, effectively stabilized the fiber morphology over 2months and improved the mechanical properties in both dry and wet state, especially EDC-NHS with large ultimate tensile stress and ε b . The secondary structure of collagen structure still remained and had no obvious difference among various crosslinked samples according to FTIR. On the cell assessment, electrospun collagen fibers crosslinked by EDC-NHS, GTA and GP, were found to support cell adhesion, spreading and proliferation of MC3T3-E1. By contrast, GTA was more effective in preserving explicit fibrous morphology with a relatively lower cell viability both in FBS and BSA soaked mats. Interestingly, GP also had the similar cytocompatibility of MC3T3-E1 as EDC-NHS did. The study proved the feasibility of chemical crosslinker to electrospun collagen for biomedical application. Copyright © 2018. Published by Elsevier B.V.

10 CFR 110.32 - Information required in an application for a specific license/NRC Form 7.

Code of Federal Regulations, 2010 CFR

2010-01-01

... equipment or material. (c) Country of origin of equipment or material, and any other countries that have... characteristics, route of transit of shipment, and ultimate disposition (including forms of management) of the...-level waste compact or State to accept the material for management purposes or disposal. (7) Description...

Performance evaluation of subgrade stabilization with recycled materials.

DOT National Transportation Integrated Search

2016-02-29

Due to rising costs of good quality acceptable materials for remove/replace options and traditional : subgrade stabilization materials, MDOT is in need to identify potential recycled materials to treat : unacceptable subgrade soils. Use of recycled m...

Stability limits and transformation pathways of α-quartz under high pressure

NASA Astrophysics Data System (ADS)

Hu, Q. Y.; Shu, J.-F.; Yang, W. G.; Park, C.; Chen, M. W.; Fujita, T.; Mao, H.-K.; Sheng, H. W.

2017-03-01

Ubiquitous on Earth, α-quartz plays an important role in modern science and technology. However, despite extensive research in the past, the mechanism of the polymorphic transitions of α-quartz at high pressures remains poorly understood. Here, combining in situ single-crystal x-ray diffraction experiment and advanced ab initio modeling, we report two stability limits and competing transition pathways of α-quartz under high pressure. Under near-equilibrium compression conditions at room temperature, α-quartz transits to a new P 2 /c silica phase via a structural intermediate. If the thermally activated transition is kinetically suppressed, the ultimate stability of α-quartz is controlled by its phonon instability and α-quartz collapses into a different crystalline phase. Our studies reveal that pressure-induced solid-state transformation of α-quartz undergoes a succession of structural stability limits, due to thermodynamic and mechanical catastrophes, and exhibits a hierarchy of transition pathways contingent upon kinetic conditions.

Introducing correlations into carrier transport simulations of disordered materials through seeded nucleation: impact on density of states, carrier mobility, and carrier statistics

NASA Astrophysics Data System (ADS)

Brown, J. S.; Shaheen, S. E.

2018-04-01

Disorder in organic semiconductors has made it challenging to achieve performance gains; this is a result of the many competing and often nuanced mechanisms effecting charge transport. In this article, we attempt to illuminate one of these mechanisms in the hopes of aiding experimentalists in exceeding current performance thresholds. Using a heuristic exponential function, energetic correlation has been added to the Gaussian disorder model (GDM). The new model is grounded in the concept that energetic correlations can arise in materials without strong dipoles or dopants, but may be a result of an incomplete crystal formation process. The proposed correlation has been used to explain the exponential tail states often observed in these materials; it is also better able to capture the carrier mobility field dependence, commonly known as the Poole-Frenkel dependence, when compared to the GDM. Investigation of simulated current transients shows that the exponential tail states do not necessitate Montroll and Scher fits. Montroll and Scher fits occur in the form of two distinct power law curves that share a common constant in their exponent; they are clearly observed as linear lines when the current transient is plotted using a log-log scale. Typically, these fits have been found appropriate for describing amorphous silicon and other disordered materials which display exponential tail states. Furthermore, we observe the proposed correlation function leads to domains of energetically similar sites separated by boundaries where the site energies exhibit stochastic deviation. These boundary sites are found to be the source of the extended exponential tail states, and are responsible for high charge visitation frequency, which may be associated with the molecular turnover number and ultimately the material stability.

Discovery-Synthesis, Design, and Prediction of Chalcogenide Phases

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

Kanatzidis, Mercouri G.

The discovery of new materials and their efficient syntheses is a fundamental goal of chemistry. A related objective is to identify foundational and rational approaches to enhance the art of synthesis by combining the exquisite predictability of organic synthesis with the high yields of solid-state chemistry. In contrast to so-called solid-state methods, inorganic syntheses in liquid fluxes permit bond formation, framework assembly, and crystallization at lower temperatures because of facile diffusion and chemical reactions with and within the flux itself. The fluxes are bona fide solvents similar to conventional organic or aqueous solvents. Such reactions can produce a wide rangemore » of materials, often metastable, from oxides to intermetallics, but typically the formation mechanisms are poorly understood. This article discusses how one can design, perform, observe, understand, and engineer the formation of compounds from inorganic melts. The focus is also design concepts such as "dimensional reduction", "phase homologies", and "panoramic synthesis", and their broad applicability. When well-defined building blocks are present and stable in the reaction, prospects for increased structural diversity and product control increase substantially. Common structural motifs within these materials systems may be related to structural precursors in the melt that may be controlled by tuning reaction conditions and composition. Stabilization of a particular building block is often accomplished with tuning of the flux composition, which controls the Lewis basicity and redox potential. In such tunable and dynamic fluxes, the synthesis can be directed toward new materials. Using complementary techniques of in situ X-ray diffraction, we can create time-dependent maps of reaction space and probe the mobile species present in melts. Lastly, certain thoughts toward the ultimate goal of targeted materials synthesis by controlling inorganic melt chemistry are discussed.« less

Introducing correlations into carrier transport simulations of disordered materials through seeded nucleation: impact on density of states, carrier mobility, and carrier statistics.

PubMed

Brown, J S; Shaheen, S E

2018-04-04

Disorder in organic semiconductors has made it challenging to achieve performance gains; this is a result of the many competing and often nuanced mechanisms effecting charge transport. In this article, we attempt to illuminate one of these mechanisms in the hopes of aiding experimentalists in exceeding current performance thresholds. Using a heuristic exponential function, energetic correlation has been added to the Gaussian disorder model (GDM). The new model is grounded in the concept that energetic correlations can arise in materials without strong dipoles or dopants, but may be a result of an incomplete crystal formation process. The proposed correlation has been used to explain the exponential tail states often observed in these materials; it is also better able to capture the carrier mobility field dependence, commonly known as the Poole-Frenkel dependence, when compared to the GDM. Investigation of simulated current transients shows that the exponential tail states do not necessitate Montroll and Scher fits. Montroll and Scher fits occur in the form of two distinct power law curves that share a common constant in their exponent; they are clearly observed as linear lines when the current transient is plotted using a log-log scale. Typically, these fits have been found appropriate for describing amorphous silicon and other disordered materials which display exponential tail states. Furthermore, we observe the proposed correlation function leads to domains of energetically similar sites separated by boundaries where the site energies exhibit stochastic deviation. These boundary sites are found to be the source of the extended exponential tail states, and are responsible for high charge visitation frequency, which may be associated with the molecular turnover number and ultimately the material stability.

Using X-ray Microscopy To Understand How Nanoporous Materials Can Be Used To Reduce the Large Volume Change in Alloy Anodes

DOE PAGES

Cook, John B.; Lin, Terri C.; Detsi, Eric; ...

2017-01-05

Tin metal is an attractive negative electrode material to replace graphite in Li-ion batteries due to its high energy density. However, tin undergoes a large volume change upon alloying with Li, which pulverizes the particles, and ultimately leads to short cycling lifetimes. Nevertheless, nanoporous materials have been shown to extend battery life well past what is observed in nonporous material. Despite the exciting potential of porous alloying anodes to significantly increase the energy density in Li-ion batteries, the fundamental physics of how nanoscale architectures accommodate the electrochemically induced volume changes are poorly understood. Here, operando transmission X-ray microscopy has beenmore » used to develop an understanding of the mechanisms that govern the enhanced cycling stability in nanoporous tin. We found that in comparison to dense tin, nanoporous tin undergoes a 6-fold smaller areal expansion after lithiation, as a result of the internal porosity and unique nanoscale architecture. The expansion is also more gradual in nanoporous tin compared to the dense material. The nanoscale resolution of the microscope used in this study is ~30 nm, which allowed us to directly observe the pore structure during lithiation and delithiation. We found that nanoporous tin remains porous during the first insertion and desinsertion cycle. This observation is key, as fully closed pores could lead to mechanical instability, electrolyte inaccessibility, and short lifetimes. Here, while tin was chosen for this study because of its high X-ray contrast, the results of this work should be general to other alloy-type systems, such as Si, that also suffer from volume change based cycling degradation.« less

Using X-ray Microscopy To Understand How Nanoporous Materials Can Be Used To Reduce the Large Volume Change in Alloy Anodes

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

Cook, John B.; Lin, Terri C.; Detsi, Eric

Tin metal is an attractive negative electrode material to replace graphite in Li-ion batteries due to its high energy density. However, tin undergoes a large volume change upon alloying with Li, which pulverizes the particles, and ultimately leads to short cycling lifetimes. Nevertheless, nanoporous materials have been shown to extend battery life well past what is observed in nonporous material. Despite the exciting potential of porous alloying anodes to significantly increase the energy density in Li-ion batteries, the fundamental physics of how nanoscale architectures accommodate the electrochemically induced volume changes are poorly understood. Here, operando transmission X-ray microscopy has beenmore » used to develop an understanding of the mechanisms that govern the enhanced cycling stability in nanoporous tin. We found that in comparison to dense tin, nanoporous tin undergoes a 6-fold smaller areal expansion after lithiation, as a result of the internal porosity and unique nanoscale architecture. The expansion is also more gradual in nanoporous tin compared to the dense material. The nanoscale resolution of the microscope used in this study is ~30 nm, which allowed us to directly observe the pore structure during lithiation and delithiation. We found that nanoporous tin remains porous during the first insertion and desinsertion cycle. This observation is key, as fully closed pores could lead to mechanical instability, electrolyte inaccessibility, and short lifetimes. Here, while tin was chosen for this study because of its high X-ray contrast, the results of this work should be general to other alloy-type systems, such as Si, that also suffer from volume change based cycling degradation.« less

Discovery-Synthesis, Design, and Prediction of Chalcogenide Phases

DOE PAGES

Kanatzidis, Mercouri G.

2017-03-09

The discovery of new materials and their efficient syntheses is a fundamental goal of chemistry. A related objective is to identify foundational and rational approaches to enhance the art of synthesis by combining the exquisite predictability of organic synthesis with the high yields of solid-state chemistry. In contrast to so-called solid-state methods, inorganic syntheses in liquid fluxes permit bond formation, framework assembly, and crystallization at lower temperatures because of facile diffusion and chemical reactions with and within the flux itself. The fluxes are bona fide solvents similar to conventional organic or aqueous solvents. Such reactions can produce a wide rangemore » of materials, often metastable, from oxides to intermetallics, but typically the formation mechanisms are poorly understood. This article discusses how one can design, perform, observe, understand, and engineer the formation of compounds from inorganic melts. The focus is also design concepts such as "dimensional reduction", "phase homologies", and "panoramic synthesis", and their broad applicability. When well-defined building blocks are present and stable in the reaction, prospects for increased structural diversity and product control increase substantially. Common structural motifs within these materials systems may be related to structural precursors in the melt that may be controlled by tuning reaction conditions and composition. Stabilization of a particular building block is often accomplished with tuning of the flux composition, which controls the Lewis basicity and redox potential. In such tunable and dynamic fluxes, the synthesis can be directed toward new materials. Using complementary techniques of in situ X-ray diffraction, we can create time-dependent maps of reaction space and probe the mobile species present in melts. Lastly, certain thoughts toward the ultimate goal of targeted materials synthesis by controlling inorganic melt chemistry are discussed.« less

Application of advanced techniques for the assessment of bio-stability of biowaste-derived residues: A minireview.

PubMed

Lü, Fan; Shao, Li-Ming; Zhang, Hua; Fu, Wen-Ding; Feng, Shi-Jin; Zhan, Liang-Tong; Chen, Yun-Min; He, Pin-Jing

2018-01-01

Bio-stability is a key feature for the utilization and final disposal of biowaste-derived residues, such as aerobic compost or vermicompost of food waste, bio-dried waste, anaerobic digestate or landfilled waste. The present paper reviews conventional methods and advanced techniques used for the assessment of bio-stability. The conventional methods are reclassified into two categories. Advanced techniques, including spectroscopic (fluorescent, ultraviolet-visible, infrared, Raman, nuclear magnetic resonance), thermogravimetric and thermochemolysis analysis, are emphasized for their application in bio-stability assessment in recent years. Their principles, pros and cons are critically discussed. These advanced techniques are found to be convenient in sample preparation and to supply diversified information. However, the viability of these techniques as potential indicators for bio-stability assessment ultimately lies in the establishment of the relationship of advanced ones with the conventional methods, especially with the methods based on biotic response. Furthermore, some misuses in data explanation should be noted. Copyright © 2017 Elsevier Ltd. All rights reserved.

Investigating the Effectiveness of the Incredible Years Basic Parenting Programme for Foster Carers in Northern Ireland

ERIC Educational Resources Information Center

McDaniel, Benny; Braiden, Hannah Jane; Onyekwelu, June; Murphy, Mary; Regan, Hassan

2011-01-01

Children who are looked after experience significantly higher levels of social, emotional and behavioural difficulties than children who live with their family of origin. Such difficulties tend to be pervasive and can have detrimental consequences for placement stability, and ultimately for the child's ability to reach their potential. Government…

Tensile strengths of polyamide based 3D printed polymers in liquid nitrogen

NASA Astrophysics Data System (ADS)

Cruz, P.; Shoemake, E. D.; Adam, P.; Leachman, J.

2015-12-01

Advances in additive manufacturing technology have made 3D printing a viable solution for many industries, allowing for the manufacture of designs that could not be made through traditional subtractive methods. Applicability of additive manufacturing in cryogenic applications is hindered, however, by a lack of accurate material properties information. Nylon is available for printing using fused deposition modeling (FDM) and selective laser sintering (SLS). We selected 5 SLS (DuraForm® EX, DuraForm® HST, DuraForm® PA, PA 640-GSL, and PA 840-GSL) and 2 FDM (Nylon 12, ULTEM) nylon variants based on the bulk material properties and printed properties at room temperature. Tensile tests were performed on five samples of each material while immersed in liquid nitrogen at approximately 77 Kelvin. Samples were tested in XY and, where available, Z printing directions to determine influence on material properties. Results show typical SLS and FDM nylon ultimate strength retention at 77 K, when compared to (extruded or molded) nylon ultimate strength.

Space Shuttle Main Engine structural analysis and data reduction/evaluation. Volume 1: Aft Skirt analysis

NASA Technical Reports Server (NTRS)

Berry, David M.; Stansberry, Mark

1989-01-01

Using the ANSYS finite element program, a global model of the aft skirt and a detailed nonlinear model of the failure region was made. The analysis confirmed the area of failure in both STA-2B and STA-3 tests as the forging heat affected zone (HAZ) at the aft ring centerline. The highest hoop strain in the HAZ occurs in this area. However, the analysis does not predict failure as defined by ultimate elongation of the material equal to 3.5 percent total strain. The analysis correlates well with the strain gage data from both the Wyle influence test of the original design aft sjirt and the STA-3 test of the redesigned aft skirt. it is suggested that the sensitivity of the failure area material strength and stress/strain state to material properties and therefore to small manufacturing or processing variables is the most likely cause of failure below the expected material ultimate properties.

Dynamic Stability of Maglev Systems,

DTIC Science & Technology

1992-04-01

AD-A259 178 ANL-92/21 Materials and Components Dynamic Stability of Technology Division Materials and Components Maglev Systems Technology Division...of Maglev Systems Y. Cai, S. S. Chen, and T. M. Mulcahy Materials and Components Technology Division D. M. Rote Center for Transportation Research...of Maglev System with L-Shaped Guideway ......................................... 6 3 Stability of M aglev System s

Production, microstructure and mechanical properties of two different austenitic ODS steels

NASA Astrophysics Data System (ADS)

Gräning, T.; Rieth, M.; Hoffmann, J.; Möslang, A.

2017-04-01

This article is to summarize and examine processing parameters of novel developed austenitic oxide dispersed strengthened (ODS) steels. Comparing hot-rolled and extruded conditions after the same degree of deformation after and before annealing, are just some examples to give insights into the complex processing of austenitic ODS steels. One of the major drawbacks of the material is the more sophisticated production process. Due to a ductile matrix material with an increased stickiness during milling, a two-step milling procedure with the use of ZrO2 milling balls was applied to raise the production yield and to use the abrasion of the ZrO2 as an additional element to facilitate the formation of nano-sized precipitates. To get a better understanding how the different powder particle sizes after milling affect final properties, sieving was applied and revealed a serious effect in terms of precipitate size, distribution and mechanical properties. Grain sizes in relation to the precipitate size, annealing time and processing parameters were determined and compared to the mechanical properties. Hardness and tensile test have pointed out, that the precipitate size and number are more important in respect to the ultimate tensile strength than the grain size and that in this study hot-rolled material exhibited the better properties. The investigation of the microstructure illustrated the stability of precipitates during annealing at 1100 °C for 40 h. These heat treatments also led to a consistent grain size, due to the pinning effect of the grain boundaries, caused by precipitates.

Design and validation of inert homemade explosive simulants for X-ray-based inspection systems

NASA Astrophysics Data System (ADS)

Faust, Anthony A.; Nacson, Sabatino; Koffler, Bruce; Bourbeau, Éric; Gagne, Louis; Laing, Robin; Anderson, C. J.

2014-05-01

Transport Canada (TC), the Canadian Armed Forces, and other public security agencies have an interest in the assessment of the potential utility of advanced explosives detection technologies to aid in the detection and interdiction of commercial grade, military grade, and homemade or improvised explosives (HME or IE). The availability of suitable, non-hazardous, non-toxic, explosive simulants is of concern when assessing the potential utility of such detection systems. Lack of simulants limits the training opportunities, and ultimately the detection probability, of security personnel using these systems. While simulants for commercial and military grade explosives are available for a wide variety of detection technologies, the design and production of materials to simulate improvised explosives has not kept pace with this emerging threat. Funded by TC and the Canadian Safety and Security Program, Defence Research and Development Canada (DRDC), Visiontec Systems, and Optosecurity engaged in an effort to develop inert, non-toxic Xray interrogation simulants for IE materials such as ammonium nitrate, potassium chlorate, and triacetone triperoxide. These simulants were designed to mimic key X-ray interrogation-relevant material properties of real improvised explosives, principally their bulk density and effective atomic number. Different forms of the simulants were produced and tested, simulating the different explosive threat formulations that could be encountered by front line security workers. These simulants comply with safety and stability requirements, and as best as possible match form and homogeneity. This paper outlines the research program, simulant design, and validation.

Relaxation pathways of photoexcited iodide-methanol clusters: a computational investigation.

PubMed

Mak, Chun C; Peslherbe, Gilles H

2014-06-26

Upon photoexcitation of iodide-methanol clusters, I(-)(CH3OH)n, to a charge-transfer-to-solvent (CTTS) excited state, extensive relaxation was found to occur, accompanied by a convoluted modulation of the stability of the excited electron, which ultimately decreases substantially. In order to develop a molecular-level understanding of the relaxation processes of CTTS excited I(-)(CH3OH)n, high-level quantum chemical calculations are first used to investigate the ground, excited, and ionized states of I(-)(CH3OH)n (n = 2). Because of the relatively small size of I(-)(CH3OH)2, it was possible to characterize the contributions of solvent-solvent interactions to the stability of the CTTS excited cluster relative to dissociation into methanol, iodine, and a free electron, which exhibits a substantial dependence on the cluster geometric configuration. Ab initio molecular dynamics simulations of CTTS excited I(-)(CH3OH)3 are then performed to shed some light onto the nature of the relaxation pathways involved in the modulation of the stability of the excited electron in larger clusters. Simulation results suggest that separation of I and (CH3OH)3(-) accompanied by solvent reorganization in the latter can initially stabilize the excited electron, while gradual cluster fragmentation to I, (CH3OH)2(-), and CH3OH ultimately destabilizes it. This work shows, for the first time, that the inability of small CTTS excited I(-)(CH3OH)n to retain a solvated electron may be attributed to the limited hydrogen-bonding capacity of CH3OH, which increases the propensity for fragmentation to smaller clusters with lower excess-electron binding energies, and highlights the critical role of intricate molecular interactions in the electron solvation process.

Sex-Linked Behavior: Evolution, Stability, and Variability.

PubMed

Fine, Cordelia; Dupré, John; Joel, Daphna

2017-07-29

Common understanding of human sex-linked behaviors is that proximal mechanisms of genetic and hormonal sex, ultimately shaped by the differential reproductive challenges of ancestral males and females, act on the brain to transfer sex-linked predispositions across generations. Here, we extend the debate on the role of nature and nurture in the development of traits in the lifetime of an individual, to their role in the cross-generation transfer of traits. Advances in evolutionary theory that posit the environment as a source of trans-generational stability, and new understanding of sex effects on the brain, suggest that the cross-generation stability of sex-linked patterns of behavior are sometimes better explained in terms of inherited socioenvironmental conditions, with biological sex fostering intrageneration variability. Copyright © 2017 Elsevier Ltd. All rights reserved.

Sex-Linked Behavior: Evolution, Stability, and Variability.

PubMed

Fine, Cordelia; Dupré, John; Joel, Daphna

2017-09-01

Common understanding of human sex-linked behaviors is that proximal mechanisms of genetic and hormonal sex, ultimately shaped by the differential reproductive challenges of ancestral males and females, act on the brain to transfer sex-linked predispositions across generations. Here, we extend the debate on the role of nature and nurture in the development of traits in the lifetime of an individual, to their role in the cross-generation transfer of traits. Advances in evolutionary theory that posit the environment as a source of trans-generational stability, and new understanding of sex effects on the brain, suggest that the cross-generation stability of sex-linked patterns of behavior are sometimes better explained in terms of inherited socioenvironmental conditions, with biological sex fostering intrageneration variability. Copyright © 2017 Elsevier Ltd. All rights reserved.

Biomechanical characteristics of single-row repair in comparison to double-row repair with consideration of the suture configuration and suture material.

PubMed

Baums, M H; Buchhorn, G H; Spahn, G; Poppendieck, B; Schultz, W; Klinger, H-M

2008-11-01

The aim of the study was to evaluate the time zero mechanical properties of single- versus double-row configuration for rotator cuff repair in an animal model with consideration of the stitch technique and suture material. Thirty-two fresh-frozen sheep shoulders were randomly assigned to four repair groups: suture anchor single-row repair coupled with (1) braided, nonabsorbable polyester suture sized USP No. 2 (SRAE) or (2) braided polyblend polyethylene suture sized No. 2 (SRAH). The double-row repair was coupled with (3) USP No. 2 (DRAE) or (4) braided polyblend polyethylene suture No. 2 (DRAH). Arthroscopic Mason-Allen stitches were used (single-row) and combined with medial horizontal mattress stitches (double-row). Shoulders were cyclically loaded from 10 to 180 N. Displacement to gap formation of 5- and 10-mm at the repair site, cycles to failure, and the mode of failure were determined. The ultimate tensile strength was verified in specimens that resisted to 3,000 cycles. DRAE and DRAH had a lower frequency of 5- (P = 0.135) and 10-mm gap formation (P = 0.135). All DRAE and DRAH resisted 3,000 cycles while only three SRAE and one SRAH resisted 3,000 cycles (P < 0.001). The ultimate tensile strength in double-row specimens was significantly higher than in others (P < 0.001). There was no significant variation in using different suture material (P > 0.05). Double-row suture anchor repair with arthroscopic Mason-Allen/medial mattress stitches provides initial strength superior to single-row repair with arthroscopic Mason-Allen stitches under isometric cyclic loading as well as under ultimate loading conditions. Our results support the concept of double-row fixation with arthroscopic Mason-Allen/medial mattress stitches in rotator cuff tears with improvement of initial fixation strength and ultimate tensile load. Use of new polyblend polyethylene suture material seems not to increase the initial biomechanical aspects of the repair construct.

A uni-extension study on the ultimate material strength and extreme extensibility of atherosclerotic tissue in human carotid plaques.

PubMed

Teng, Zhongzhao; Feng, Jiaxuan; Zhang, Yongxue; Sutcliffe, Michael P F; Huang, Yuan; Brown, Adam J; Jing, Zaiping; Lu, Qingsheng; Gillard, Jonathan H

2015-11-05

Atherosclerotic plaque rupture occurs when mechanical loading exceeds its material strength. Mechanical analysis has been shown to be complementary to the morphology and composition for assessing vulnerability. However, strength and stretch thresholds for mechanics-based assessment are currently lacking. This study aims to quantify the ultimate material strength and extreme extensibility of atherosclerotic components from human carotid plaques. Tissue strips of fibrous cap, media, lipid core and intraplaque hemorrhage/thrombus were obtained from 21 carotid endarterectomy samples of symptomatic patients. Uni-extension test with tissue strips was performed until they broke or slid. The Cauchy stress and stretch ratio at the peak loading of strips broken about 2mm away from the clamp were used to characterize their ultimate strength and extensibility. Results obtained indicated that ultimate strength of fibrous cap and media were 158.3 [72.1, 259.3] kPa (Median [Inter quartile range]) and 247.6 [169.0, 419.9] kPa, respectively; those of lipid and intraplaque hemorrhage/thrombus were 68.8 [48.5, 86.6] kPa and 83.0 [52.1, 124.9] kPa, respectively. The extensibility of each tissue type were: fibrous cap - 1.18 [1.10, 1.27]; media - 1.21 [1.17, 1.32]; lipid - 1.25 [1.11, 1.30] and intraplaque hemorrhage/thrombus - 1.20 [1.17, 1.44]. Overall, the strength of fibrous cap and media were comparable and so were lipid and intraplaque hemorrhage/thrombus. Both fibrous cap and media were significantly stronger than either lipid or intraplaque hemorrhage/thrombus. All atherosclerotic components had similar extensibility. Moreover, fibrous cap strength in the proximal region (closer to the heart) was lower than that of the distal. These results are helpful in understanding the material behavior of atherosclerotic plaques. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

Code of Federal Regulations, 2012 CFR

2012-10-01

... of 4.25 shall not exceed the minimum ultimate strength of the material. They shall be so designed as... the initial surveys, and may be required at periodical surveys and at annual surveys or at more...

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

Code of Federal Regulations, 2014 CFR

2014-10-01

... of 4.25 shall not exceed the minimum ultimate strength of the material. They shall be so designed as... the initial surveys, and may be required at periodical surveys and at annual surveys or at more...

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

Code of Federal Regulations, 2011 CFR

2011-10-01

... of 4.25 shall not exceed the minimum ultimate strength of the material. They shall be so designed as... the initial surveys, and may be required at periodical surveys and at annual surveys or at more...

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

Code of Federal Regulations, 2010 CFR

2010-10-01

... of 4.25 shall not exceed the minimum ultimate strength of the material. They shall be so designed as... the initial surveys, and may be required at periodical surveys and at annual surveys or at more...

46 CFR 42.15-30 - Hatchways closed by weathertight covers of steel or other equivalent material fitted with gaskets...

Code of Federal Regulations, 2013 CFR

2013-10-01

... of 4.25 shall not exceed the minimum ultimate strength of the material. They shall be so designed as... the initial surveys, and may be required at periodical surveys and at annual surveys or at more...

Research notes : naturally occurring hazardous materials, natural doesn't always equal healthy.

DOT National Transportation Integrated Search

2009-05-01

The ultimate objective of this work is to assure that ODOT maintenance and construction activities take the presence of these hazardous materials into account. In this way, ODOT can protect the health of those who work on ODOT projects and the genera...

Nickel-titanium wire as a flexor tendon suture material: an ex vivo study.

PubMed

Karjalainen, T; Göransson, H; Viinikainen, A; Jämsä, T; Ryhänen, J

2010-07-01

Nickel-titanium shape memory alloy (NiTi) is a new suture material that is easy to handle, is strong, and biocompatible. The purpose of this study was to evaluate the material properties and biomechanical behaviour of 150 microm and 200 microm NiTi wires in flexor tendon repair. Braided polyester (4-0 Ethibond) was used as control. Fifty fresh-frozen porcine flexor tendons were repaired using the Pennington modification of the Kessler repair or a double Kessler technique. NiTi wires were stiffer and reached higher tensile strength compared to braided polyester suture. Repairs with 200 microm NiTi wire had a higher yield force, ultimate force and better resistance to gapping than 4-0 braided polyester repairs. Repairs made with 200 microm NiTi wire achieved higher stiffness and ultimate force than repairs made with 150 microm NiTi wire.

On thermal stress failure of the SNAP-19A RTG heat shield

NASA Technical Reports Server (NTRS)

Pitts, W. C.; Anderson, L. A.

1974-01-01

Results of a study on thermal stress problems in an amorphous graphite heat shield that is part of the launch-abort protect system for the SNAP-19A radio-isotope thermoelectric generators (RTG) that will be used on the Viking Mars Lander are presended. The first result is from a thermal stress analysis of a full-scale RTG heat source that failed to survive a suborbital entry flight test, possibly due to thermal stress failure. It was calculated that the maximum stress in the heat shield was only 50 percent of the ultimate strength of the material. To provide information on the stress failure criterion used for this calculation, some heat shield specimens were fractured under abort entry conditions in a plasma arc facility. It was found that in regions free of stress concentrations the POCO graphite heat shield material did fracture when the local stress reached the ultimate uniaxial stress of the material.

The Audit Opinion of the DISA FY 2011 Working Capital Fund Financial Statements Was Not Adequately Supported

DTIC Science & Technology

2013-04-26

President’s Council on Integrity and Efficiency MD&A Management Discussion and Analysis MFR Memorandum for Record NoF Notification of...memorandums for record ( MFRs ) would have a material impact on the financial statements and ultimately Acuity’s opinion, • perform adequate completeness...the deficiencies identified by DISA in its FBWT MFRs would impact the reliability of the financial statements and ultimately Acuity’s opinion

Complex dynamics of a new 3D Lorenz-type autonomous chaotic system

NASA Astrophysics Data System (ADS)

Zhang, Fuchen; Liao, Xiaofeng; Zhang, Guangyun; Mu, Chunlai

2017-12-01

This paper investigates a new three-dimensional continuous quadratic autonomous chaotic system which is not topologically equivalent to the Lorenz system. The dynamical behaviours of this system are further investigated in detail, including the ultimate boundedness, the invariant sets and the global attraction domain according to Lyapunov stability theory of dynamical systems. The innovation of the paper lies in the fact that this paper not only proves this chaotic system is globally bounded for the parameters of this system but also gives a family of mathematical expressions of global exponential attractive sets with respect to the parameters of this system. To validate the ultimate bound estimation, numerical simulations are also investigated. Numerical simulations verify the effectiveness and feasibility of the theoretical scheme.

Estimation of regions of attraction and ultimate boundedness for multiloop LQ regulators. [Linear Quadratic

NASA Technical Reports Server (NTRS)

Joshi, S. M.

1984-01-01

Closed-loop stability is investigated for multivariable linear time-invariant systems controlled by optimal full state feedback linear quadratic (LQ) regulators, with nonlinear gains present in the feedback channels. Estimates are obtained for the region of attraction when the nonlinearities escape the (0.5, infinity) sector in regions away from the origin and for the region of ultimate boundedness when the nonlinearities escape the sector near the origin. The expressions for these regions also provide methods for selecting the performance function parameters in order to obtain LQ designs with better tolerance for nonlinearities. The analytical results are illustrated by applying them to the problem of controlling the rigid-body pitch angle and elastic motion of a large, flexible space antenna.

Method of preparation of carbon materials for use as electrodes in rechargeable batteries

DOEpatents

Doddapaneni, Narayan; Wang, James C. F.; Crocker, Robert W.; Ingersoll, David; Firsich, David W.

1999-01-01

A method of producing carbon materials for use as electrodes in rechargeable batteries. Electrodes prepared from these carbon materials exhibit intercalation efficiencies of .apprxeq.80% for lithium, low irreversible loss of lithium, long cycle life, are capable of sustaining a high rates of discharge and are cheap and easy to manufacture. The method comprises a novel two-step stabilization process in which polymeric precursor materials are stabilized by first heating in an inert atmosphere and subsequently heating in air. During the stabilization process, the polymeric precursor material can be agitated to reduce particle fusion and promote mass transfer of oxygen and water vapor. The stabilized, polymeric precursor materials can then be converted to a synthetic carbon, suitable for fabricating electrodes for use in rechargeable batteries, by heating to a high temperature in a flowing inert atmosphere.

Evaluating the cement stabilization of arsenic-bearing iron wastes from drinking water treatment.

PubMed

Clancy, Tara M; Snyder, Kathryn V; Reddy, Raghav; Lanzirotti, Antonio; Amrose, Susan E; Raskin, Lutgarde; Hayes, Kim F

2015-12-30

Cement stabilization of arsenic-bearing wastes is recommended to limit arsenic release from wastes following disposal. Such stabilization has been demonstrated to reduce the arsenic concentration in the Toxicity Characteristic Leaching Procedure (TCLP), which regulates landfill disposal of arsenic waste. However, few studies have evaluated leaching from actual wastes under conditions similar to ultimate disposal environments. In this study, land disposal in areas where flooding is likely was simulated to test arsenic release from cement stabilized arsenic-bearing iron oxide wastes. After 406 days submersed in chemically simulated rainwater, <0.4% of total arsenic was leached, which was comparable to the amount leached during the TCLP (<0.3%). Short-term (18 h) modified TCLP tests (pH 3-12) found that cement stabilization lowered arsenic leaching at high pH, but increased leaching at pH<4.2 compared to non-stabilized wastes. Presenting the first characterization of cement stabilized waste using μXRF, these results revealed the majority of arsenic in cement stabilized waste remained associated with iron. This distribution of arsenic differed from previous observations of calcium-arsenic solid phases when arsenic salts were stabilized with cement, illustrating that the initial waste form influences the stabilized form. Overall, cement stabilization is effective for arsenic-bearing wastes when acidic conditions can be avoided. Copyright © 2015 Elsevier B.V. All rights reserved.

Adaptive polymeric nanomaterials utilizing reversible covalent and hydrogen bonding

NASA Astrophysics Data System (ADS)

Neikirk, Colin

Adaptive materials based on stimuli responsive and reversible bonding moieties are a rapidly developing area of materials research. Advances in supramolecular chemistry are now being adapted to novel molecular architectures including supramolecular polymers to allow small, reversible changes in molecular and nanoscale structure to affect large changes in macroscale properties. Meanwhile, dynamic covalent chemistry provides a complementary approach that will also play a role in the development of smart adaptive materials. In this thesis, we present several advances to the field of adaptive materials and also provide relevant insight to the areas of polymer nanocomposites and polymer nanoparticles. First, we have utilized the innate molecular recognition and binding capabilities of the quadruple hydrogen bonding group ureidopyrimidinone (UPy) to prepare supramolecular polymer nanocomposites based on supramolecular poly(caprolactone) which show improved mechanical properties, but also an increase in particle aggregation with nanoparticle UPy functionalization. We also present further insight into the relative effects of filler-filler, filler-matrix, and matrix-matrix interactions using a UPy side-chain functional poly(butyl acrylate). These nanocomposites have markedly different behavior depending on the amount of UPy sidechain functionality. Meanwhile, our investigations of reversible photo-response showed that coumarin functionality in polymer nanoparticles not only facilitates light mediated aggregation/dissociation behavior, but also provides a substantial overall reduction in particle size and improvement in nanoparticle stability for particles prepared by Flash NanoPrecipitation. Finally, we have combined these stimuli responsive motifs as a starting point for the development of multiresponsive adaptive materials. The synthesis of a library of multifunctional materials has provided a strong base for future research in this area, although our initial investigations were ultimately unsuccessful due to photodegradation of the UPy moiety in chloroform solution. This thesis has provided the Priestley lab with a solid base for the further investigation of the diverse applications and unsolved science of stimuli responsive adaptive materials.

The importance of anabolism in microbial control over soil carbon storage

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

Liang, Chao; Schimel, Joshua P.; Jastrow, Julie D.

Studies of the decomposition, transformation and stabilization of soil organic matter (SOM) have dramatically increased in recent years owing to growing interest in studying the global carbon (C) cycle as it pertains to climate change. While it is readily accepted that the magnitude of the organic C reservoir in soils depends upon microbial involvement, as soil C dynamics are ultimately the consequence of microbial growth and activity, it remains largely unknown how these microorganism-mediated processes lead to soil C stabilization. Here, we define two pathways—ex vivo modification and in vivo turnover—which jointly explain soil C dynamics driven by microbial catabolismmore » and/or anabolism. Accordingly, we use the conceptual framework of the soil ‘microbial carbon pump’ (MCP) to demonstrate how microorganisms are an active player in soil C storage. The MCP couples microbial production of a set of organic compounds to their further stabilization, which we define as the entombing effect. This integration captures the cumulative long-term legacy of microbial assimilation on SOM formation, with mechanisms (whether via physical protection or a lack of activation energy due to chemical composition) that ultimately enable the entombment of microbial-derived C in soils. We propose a need for increased efforts and seek to inspire new studies that utilize the soil MCP as a conceptual guideline for improving mechanistic understandings of the contributions of soil C dynamics to the responses of the terrestrial C cycle under global change.« less

Rapidly progressive Scheuermann's disease in an adolescent after pectus bar placement treated with posterior vertebral-column resection: case report and review of the literature.

PubMed

Sugrue, Patrick A; OʼShaughnessy, Brian A; Blanke, Kathy M; Lenke, Lawrence G

2013-02-15

Case report and review of the literature. This case illustrates the importance of the costosternal complex in maintaining the stability and alignment of the thoracic spine. The patient was iatrogenically destabilized by placement of a pectus bar leading to rapid symptomatic progression of his Scheuermann's kyphosis, ultimately requiring surgical correction. Scheuermann's kyphosis is a disease process defined by strict radiographical and clinical criteria. Surgical treatment is generally recommended for curves greater than 75°. This case demonstrates the critical role of the costosternal complex in maintaining the stability of the thoracic spine. The patient described in this report underwent placement of a pectus bar for correction of symptomatic pectus excavatum. He subsequently developed a progressive symptomatic Scheuermann's kyphosis as a result of the destabilization of his costosternal complex. This patient ultimately required removal of the pectus bar and posterior instrumented kyphosis correction. Progressive symptomatic Scheuermann's kyphosis (105°) corrected by removal of the pectus bar, T11 posterior vertebral-column resection and T4-L3 instrumented posterior spinal fusion. The patient had an uneventful immediate postoperative course. He was discharged neurologically intact with dramatic kyphosis correction and significant symptomatic improvement. Radiographs obtained 3 years postoperatively reveal stable thoracolumbar correction. The costosternal complex plays a critically important role in the intrinsic stability of the thoracic spine. Iatrogenic disruption of the costosternal complex can result in rapid progression of thoracic/thoracolumbar kyphosis in the setting of Scheuermann's disease.

The Nature of Scientific Revolutions from the Vantage Point of Chaos Theory: Toward a Formal Model of Scientific Change

ERIC Educational Resources Information Center

Perla, Rocco J.; Carifio, James

2005-01-01

In sharp contrast to the early positivist view of the nature of science and scientific knowledge, Kuhn argues that the scientific enterprise involves states of continuous, gradual development punctuated by comparatively rare instances of turmoil and change, which ultimately brings about a new stability and a qualitatively changed knowledge base.…

LiT"gloss"

ERIC Educational Resources Information Center

LeLoup, Jean; Ponterio, Robert

2007-01-01

Reading in a second language (L2) is important for a variety of reasons. Reading authentic materials, in particular, allows L2 learners to engage with native speaker content, and ultimately the target culture. One body of authentic materials is that of literary texts, including those of more traditional prose fiction, poetry, and drama, but also…

Tunable infrared reflectance by phonon modulation

DOEpatents

Ihlefeld, Jon F.; Sinclair, Michael B.; Beechem, III, Thomas E.

2018-03-06

The present invention pertains to the use of mobile coherent interfaces in a ferroelectric material to interact with optical phonons and, ultimately, to affect the material's optical properties. In altering the optical phonon properties, the optical properties of the ferroelectric material in the spectral range near-to the phonon mode frequency can dramatically change. This can result in a facile means to change to the optical response of the ferroelectric material in the infrared.

Towards the Ultimate Membranes: Two-dimensional Nanoporous Materials and Films.

PubMed

Agrawal, Kumar Varoon

2018-05-30

The energy-efficient separation of molecules has been a popular topic in chemistry and chemical engineering as a consequence of the large energy-footprint of separation processes in the chemical industry. The Laboratory of Advanced Separations (LAS) at EPFL, led by Prof. Kumar Varoon Agrawal, is focused to develop next-generation, high-performance membranes that can improve the energy efficiency of hydrogen purification, carbon capture, hydrocarbon and water purification. For this, LAS is seeking to develop the ultimate nanoporous membranes, those with a thickness of 1 nm and possessing an array of size-selective nanopores. In this article, the research activities at LAS, especially in the bottom-up and top-down synthesis of chemically and thermally stable, nanoporous two-dimensional materials and membranes are discussed.

Digital exchange of graphic arts material: the ultimate challenge

NASA Astrophysics Data System (ADS)

McDowell, David Q.

1996-02-01

The digital exchange of graphic arts material - particularly advertising material for publications- in an open standardized environment represents the ultimate challenge for electronic data exchange. To meet the needs of publication advertising, the graphic arts industry must be able to transmit advertisements in an open environment where there are many senders and many receivers of the material. The material being transmitted consists of combinations of pictorial material, text, and line art with these elements superimposed on top of each other and/or interrelated in complex ways. The business relationships established by the traditional workflow environment, the combination of aesthetic and technical requirements, and the large base of existing hardware and software play a major role in limiting the options available. Existing first- and second-generation standards are focused on the CEPS environment, which operates on and stores data as raster files. The revolution in personal computer hardware and software, and the acceptance of these tools by the graphic arts community, dictates that standards must also be created and implemented for this world of vector/raster-based systems. The requirements for digital distribution of advertising material for publications, the existing graphic arts standards base, and the anticipation of future standards developments in response to these needs are explored.

Digital exchange of graphic arts material: the ultimate challenge

NASA Astrophysics Data System (ADS)

McDowell, David Q.

1996-01-01

The digital exchange of graphic arts material -- particularly advertising material for publications -- in an open standardized environment represents the ultimate challenge for electronic data exchange. To meet the needs of publication advertising, the graphic arts industry must be able to transmit advertisements in an open environment where there are many senders and many receivers of the material. The material being transmitted consists of combinations of pictorial material, text, and line art with these elements superimposed on top of each other and/or interrelated in complex ways. The business relationships established by the traditional workflow environment, the combination of aesthetic and technical requirements, and the large base of existing hardware and software play a major role in limiting the options available. Existing first- and second-generation standards are focused on the CEPS environment, which operates on and stores data as raster files. The revolution in personal computer hardware and software, and the acceptance of these tools by the graphic arts community, dictates that standards must also be created and implemented for this world of vector/raster-based systems. The requirements for digital distribution of advertising material for publications, the existing graphic arts standards base, and the anticipation of future standards developments in response to these needs are explored.

Formulation/cure technology for ultrahigh molecular weight silphenylene-siloxane polymers

NASA Technical Reports Server (NTRS)

Hundley, N. H.; Patterson, W. J.

1985-01-01

Molecular weights above one million were achieved for methylvinylsilphenylene-siloxane terpolymers using a two-stage polymerization technique which was successfully scaled up to 200 grams. The resulting polymer was vulcanized by two different formulations and compared to an identically formulated commercial methylvinyl silicone on the basis of ultimate strength, Young's modulus, percent elongation at failure, and tear strength. Relative thermal/oxidative stabilities of the elastomers were assessed by gradient and isothermal thermogravimetric analyses performed in both air and nitrogen. The experimental elastomer exhibited enhanced thermal/oxidative stability and possed equivalent or superior mechanical properties. The effect of variations in prepolymer molecular weight on mechanical properties was also investigated.

Improved multistage wide band laser frequency stabilization

NASA Astrophysics Data System (ADS)

Kawamura, Seiji; Abramovici, Alex; Zucker, Michael E.

1997-01-01

Suppression of laser frequency fluctuations is an essential technology for planned interferometric detectors for astrophysical gravitational waves. Because of the low degree of residual frequency noise which is ultimately required, control topologies comprising two or more cascaded loops are favored. One such topology, used in the Laser Interferometer Gravitational-Wave Observatory 40 m interferometer, relied on electro-optic Pockels cell phase correction as a fast actuator for the final stage. This actuation method proved susceptible to spurious amplitude modulation effects, which provided an unintended parasitic feedback path. An alternate arrangement, which achieves comparably effective frequency stabilization without using a phase correcting Pockels cell, was introduced and successfully tested.

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

Ronold, K.O.; Nielsen, N.J.R.; Tura, F.

This paper demonstrates how a structural reliability method can be applied as a rational means to analyze free spans of submarine pipelines with respect to failure in ultimate loading, and to establish partial safety factors for design of such free spans against this failure mode. It is important to note that the described procedure shall be considered as an illustration of a structural reliability methodology, and that the results do not represent a set of final design recommendations. A scope of design cases, consisting of a number of available site-specific pipeline spans, is established and is assumed representative for themore » future occurrence of submarine pipeline spans. Probabilistic models for the wave and current loading and its transfer to stresses in the pipe wall of a pipeline span is established together with a stochastic representation of the material resistance. The event of failure in ultimate loading is considered as based on a limit state which is reached when the maximum stress over the design life of the pipeline exceeds the yield strength of the pipe material. The yielding limit state is considered an ultimate limit state (ULS).« less

Validation of Different Combination of Three Reversing Half-Hitches Alternating Posts (RHAPs) Effects on Arthroscopic Knot Integrity.

PubMed

Chong, Alexander Cm; Prohaska, Daniel J; Bye, Brian P

2017-05-01

With arthroscopic techniques being used, the importance of knot tying has been examined. Previous literature has examined the use of reversing half-hitches on alternating posts (RHAPs) on knot security. Separately, there has been research regarding different suture materials commonly used in the operating room. The specific aim of this study was to validate the effect of different stacked half-hitch configuration and different braided suture materials on arthroscopic knot integrity. Three different suture materials tied with five different RHAPs in arthroscopic knots were compared. A single load-to-failure test was performed and the mean ultimate clinical failure load was obtained. Significant knot holding strength improvement was found when one half-hitch was reversed as compared to baseline knot. When two of the half-hitches were reversed, there was a greater improvement with all knots having a mean ultimate clinical failure load greater than 150 newtons (N). Comparison of the suture materials demonstrated a higher mean ultimate clinical failure load when Force Fiber ® was used and at least one half-hitch was reversed. Knots tied with either Force Fiber ® or Orthocord ® showed 0% chance of knot slippage while knots tied with FiberWire ® or braided fishing line had about 10 and 30% knot slippage chances, respectively. A significant effect was observed in regards to both stacked half-hitch configuration and suture materials used on knot loop and knot security. Caution should be used with tying three RHAPs in arthroscopic surgery, particularly with a standard knot pusher and arthroscopic cannulas. The findings of this study indicated the importance of three RHAPs in performing arthroscopic knot tying and provided evidence regarding discrepancies of maximum clinical failure loads observed between orthopaedic surgeons, thereby leading to better surgical outcomes in the future.

Reconstruction of railroads and highways with in-situ reclamation materials.

DOT National Transportation Integrated Search

2011-03-01

The resilient modulus and plastic deformation of recycled roadway materials with and without fly ash stabilization were characterized using a large-scale model experiment (LSME). Stabilization of recycled pavement materials (RPM) and road surface gra...

Method of preparation of carbon materials for use as electrodes in rechargeable batteries

DOEpatents

Doddapaneni, N.; Wang, J.C.F.; Crocker, R.W.; Ingersoll, D.; Firsich, D.W.

1999-03-16

A method is described for producing carbon materials for use as electrodes in rechargeable batteries. Electrodes prepared from these carbon materials exhibit intercalation efficiencies of {approx_equal} 80% for lithium, low irreversible loss of lithium, long cycle life, are capable of sustaining a high rates of discharge and are cheap and easy to manufacture. The method comprises a novel two-step stabilization process in which polymeric precursor materials are stabilized by first heating in an inert atmosphere and subsequently heating in air. During the stabilization process, the polymeric precursor material can be agitated to reduce particle fusion and promote mass transfer of oxygen and water vapor. The stabilized, polymeric precursor materials can then be converted to a synthetic carbon, suitable for fabricating electrodes for use in rechargeable batteries, by heating to a high temperature in a flowing inert atmosphere. 4 figs.

Examination of lignocellulosic fibers for chemical, thermal, and separations properties: Addressing thermo-chemical stability issues

NASA Astrophysics Data System (ADS)

Johnson, Carter David

Natural fiber-plastic composites incorporate thermoplastic resins with fibrous plant-based materials, sometimes referred to as biomass. Pine wood mill waste has been the traditional source of natural fibrous feedstock. In anticipation of a waste wood shortage other fibrous biomass materials are being investigated as potential supplements or replacements. Perennial grasses, agricultural wastes, and woody biomass are among the potential source materials. As these feedstocks share the basic chemical building blocks; cellulose, hemicellulose, and lignin, they are collectively called lignocellulosics. Initial investigation of a number of lignocellulosic materials, applied to fiber-plastic composite processing and material testing, resulted in varied results, particularly response to processing conditions. Less thermally stable lignocellulosic filler materials were physically changed in observable ways: darkened color and odor. The effect of biomass materials' chemical composition on thermal stability was investigated an experiment involving determination of the chemical composition of seven lignocellulosics: corn hull, corn stover, fescue, pine, soy hull, soy stover, and switchgrass. These materials were also evaluated for thermal stability by thermogravimetric analysis. The results of these determinations indicated that both chemical composition and pretreatment of lignocellulosic materials can have an effect on their thermal stability. A second study was performed to investigate what effect different pretreatment systems have on hybrid poplar, pine, and switchgrass. These materials were treated with hot water, ethanol, and a 2:1 benzene/ethanol mixture for extraction times of: 1, 3, 6, 12, and 24 hours. This factorial experiment demonstrated that both extraction time and medium have an effect on the weight percent of extractives removed from all three material types. The extracted materials generated in the above study were then subjected to an evaluation of thermal stability by thermogravimetric analysis in a subsequent experiment. Overlay plots, combining individual weight loss curves, demonstrate that the experimental factors, solvent system and extraction time, produce effects on the thermal stability of the treated biomass samples. These data also indicated that the individual lignocellulosic materials had unique responses to the type of solvent used for pretreatment. Increasing extraction time had either no correlation with or a positive effect on thermal stability of the biomass samples.

Certification Issues Relating to ABDR

DTIC Science & Technology

2010-05-01

design techniques, among them increased utilization of advanced fibre reinforced materials or advanced metal alloys with higher material allowables for...most cases as a combination of a high strength/modulus carbon fibre and a hot curing thermoset resin. A high percentage of modern fighter aircraft’s...34Limited Fibre Strain Approach" at ultimate design loadcases, where the reduced material allowables account for a low energy impact damage level

Thermal Microstructural Stability of AZ31 Magnesium after Severe Plastic Deformation

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

Young, John P.; Askari, Hesam A.; Hovanski, Yuri

2015-03-01

Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energymore » for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon-Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys’s model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.« less

One-Dimensional Hetero-Nanostructures for Rechargeable Batteries.

PubMed

Mai, Liqiang; Sheng, Jinzhi; Xu, Lin; Tan, Shuangshuang; Meng, Jiashen

2018-04-17

Rechargeable batteries are regarded as one of the most practical electrochemical energy storage devices that are able to convert and store the electrical energy generated from renewable resources, and they function as the key power sources for electric vehicles and portable electronics. The ultimate goals for electrochemical energy storage devices are high power and energy density, long lifetime, and high safety. To achieve the above goals, researchers have tried to apply various morphologies of nanomaterials as the electrodes to enhance the electrochemical performance. Among them, one-dimensional (1D) materials show unique superiorities, such as cross-linked structures for external stress buffering and large draw ratios for internal stress dispersion. However, a homogeneous single-component electrode material can hardly have the characteristics of high electronic/ionic conductivity and high stability in the electrochemical environment simultaneously. Therefore, designing well-defined functional 1D hetero-nanostructures that combine the advantages and overcome the limitations of different electrochemically active materials is of great significance. This Account summarizes fabrication strategies for 1D hetero-nanostructures, including nucleation and growth, deposition, and melt-casting and electrospinning. Besides, the chemical principles for each strategy are discussed. The nucleation and growth strategy is suitable for growing and constructing 1D hetero-nanostructures of partial transition metal compounds, and the experimental conditions for this strategy are relatively accessible. Deposition is a reliable strategy to synthesize 1D hetero-nanostructures by decorating functional layers on 1D substrate materials, on the condition that the preobtained substrate materials must be stable in the following deposition process. The melt-casting strategy, in which 1D hetero-nanostructures are synthesizes via a melting and molding process, is also widely used. Additionally, the main functions of 1D hetero-nanostructures are summarized into four aspects and reviewed in detail. Appropriate surface modification can effectively restrain the structure deterioration and the regeneration of the solid-electrolyte interphase layer caused by the volume change. A porous or semihollow external conducting material coating provides advanced electron/ion bicontinuous transmission. Suitable atomic heterogeneity in the crystal structure is beneficial to the expansion and stabilization of the ion diffusion channels. Multiphase-assisted structural design is also an accessible way for the sulfur electrode material restriction. Moreover, some outlooks about the further industrial production, more effective and cheaper fabrication strategies, and new heterostructures with smaller-scale composition are given in the last part. By providing an overview of fabrication methods and performance-enhancing mechanisms of 1D hetero-nanostructured electrode materials, we hope to pave a new way to facile and efficient construction of 1D hetero-nanostructures with practical utility.

Thermally Stabilized Transmit/Receive Modules

NASA Technical Reports Server (NTRS)

Hoffman, James; DelCastillo, Linda; Miller, Jennifer; Birur, Gaj

2011-01-01

RF-hybrid technologies enable smaller packaging and mass reduction in radar instruments, especially for subsystems with dense electronics, such as electronically steered arrays. We are designing thermally stabilized RF-hybrid T/R modules using new materials for improved thermal performance of electronics. We are combining advanced substrate and housing materials with a thermal reservoir material, and develop new packaging techniques to significantly improve thermal-cycling reliability and performance stability over temperature.

What LDEF means for development and testing of materials

NASA Technical Reports Server (NTRS)

Whitaker, Ann F.; Stuckey, Wayne K.; Stein, Bland A.

1993-01-01

The Long Duration Exposure Facility (LDEF) served as the ultimate laboratory to provide combined space environmental effects on materials. The LDEF structure and its 57 experiments contained an estimated 12,000 to 14,000 specimens of materials and materials processes. It not only provided information about the resistance of these materials to the space environment but gives us direction into future needs for spacecraft materials development and testing. This paper provides an overview of the materials effects observed on the satellite and suggests recommendations for the future work in space-qualified materials development and space environmental simulation.

JackIn Head: Immersive Visual Telepresence System with Omnidirectional Wearable Camera.

PubMed

Kasahara, Shunichi; Nagai, Shohei; Rekimoto, Jun

2017-03-01

Sharing one's own immersive experience over the Internet is one of the ultimate goals of telepresence technology. In this paper, we present JackIn Head, a visual telepresence system featuring an omnidirectional wearable camera with image motion stabilization. Spherical omnidirectional video footage taken around the head of a local user is stabilized and then broadcast to others, allowing remote users to explore the immersive visual environment independently of the local user's head direction. We describe the system design of JackIn Head and report the evaluation results of real-time image stabilization and alleviation of cybersickness. Then, through an exploratory observation study, we investigate how individuals can remotely interact, communicate with, and assist each other with our system. We report our observation and analysis of inter-personal communication, demonstrating the effectiveness of our system in augmenting remote collaboration.

Fundamental limits on beam stability at the Advanced Photon Source.

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

Decker, G. A.

1998-06-18

Orbit correction is now routinely performed at the few-micron level in the Advanced Photon Source (APS) storage ring. Three diagnostics are presently in use to measure and control both AC and DC orbit motions: broad-band turn-by-turn rf beam position monitors (BPMs), narrow-band switched heterodyne receivers, and photoemission-style x-ray beam position monitors. Each type of diagnostic has its own set of systematic error effects that place limits on the ultimate pointing stability of x-ray beams supplied to users at the APS. Limiting sources of beam motion at present are magnet power supply noise, girder vibration, and thermal timescale vacuum chamber andmore » girder motion. This paper will investigate the present limitations on orbit correction, and will delve into the upgrades necessary to achieve true sub-micron beam stability.« less

Rotorcraft Weight Trends in Light of Structural Material Characteristics

DTIC Science & Technology

1987-04-26

torsion W weight for tota We weight empty v tail rotor 0 mass ratio got ultimate to specific weight I wVater S specific gravity * twist, torsion...imagined meters. An alternate way of expressing the weight effectiveness of materials may be based on the specific gravity of the material. In this...specific weight of distilled water at 40C, and 6. is the specific gravity of the considered structural material. Since, obviously, 7,, - const, it may

Materials Examination of the Vertical Stabilizer from American Airlines Flight 587

NASA Technical Reports Server (NTRS)

Fox, Matthew R.; Schultheisz, Carl R.; Reeder, James R.; Jensen, Brian J.

2005-01-01

The first in-flight failure of a primary structural component made from composite material on a commercial airplane led to the crash of American Airlines Flight 587. As part of the National Transportation Safety Board investigation of the accident, the composite materials of the vertical stabilizer were tested, microstructure was analyzed, and fractured composite lugs that attached the vertical stabilizer to the aircraft tail were examined. In this paper the materials testing and analysis is presented, composite fractures are described, and the resulting clues to the failure events are discussed.

Teeth and bones: applications of surface science to dental materials and related biomaterials

NASA Astrophysics Data System (ADS)

Jones, F. H.

2001-05-01

Recent years have seen a considerable upsurge in publications concerning the surface structure and chemistry of materials with biological or biomedical applications. Within the body, gas-solid interactions become relatively less significant and solid-liquid or solid-solid interfaces dominate, providing new challenges for the surface scientist. The current paper aims to provide a timely review of the use of surface analysis and modification techniques within the biomaterials field. A broad overview of applications in a number of related areas is given with particular attention focusing on those materials commonly encountered in dentistry and oral or maxillofacial implantology. Several specific issues of current interest are discussed. The interaction between synthetic and natural solids, both in the oral environment and elsewhere in the body is important in terms of adhesion, related stresses and strains and ultimately the longevity of a dental restoration, biomedical implant, or indeed the surrounding tissue. Exposure to body fluids, of course, can also affect stability, leading to the degradation or corrosion of materials within the body. Whilst this could potentially be harmful, e.g., if cytotoxic elements are released, it may alternatively provide a route to the preferential release of beneficial substances. Furthermore, in some cases, the controlled disintegration of a biomaterial is desirable, allowing the removal of an implant, e.g., without the need for further surgery. The presence of cells in the immediate bioenvironment additionally complicates the situation. A considerable amount of current research activity is targeted at the development of coatings or surface treatments to encourage tissue growth. If this is to be achieved by stimulating enhanced cell productivity, determination of the relationship between cell function and surface composition is essential.

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

Tan, Lizhen; Yang, Ying; Tyburska-Puschel, Beata

The mission of the Nuclear Energy Enabling Technologies (NEET) program is to develop crosscutting technologies for nuclear energy applications. Advanced structural materials with superior performance at elevated temperatures are always desired for nuclear reactors, which can improve reactor economics, safety margins, and design flexibility. They benefit not only new reactors, including advanced light water reactors (LWRs) and fast reactors such as sodium-cooled fast reactor (SFR) that is primarily designed for management of high-level wastes, but also life extension of the existing fleet when component exchange is needed. Developing and utilizing the modern materials science tools (experimental, theoretical, and computational tools)more » is an important path to more efficient alloy development and process optimization. Ferritic-martensitic (FM) steels are important structural materials for nuclear reactors due to their advantages over other applicable materials like austenitic stainless steels, notably their resistance to void swelling, low thermal expansion coefficients, and higher thermal conductivity. However, traditional FM steels exhibit a noticeable yield strength reduction at elevated temperatures above ~500°C, which limits their applications in advanced nuclear reactors which target operating temperatures at 650°C or higher. Although oxide-dispersion-strengthened (ODS) ferritic steels have shown excellent high-temperature performance, their extremely high cost, limited size and fabricability of products, as well as the great difficulty with welding and joining, have limited or precluded their commercial applications. Zirconium has shown many benefits to Fe-base alloys such as grain refinement, improved phase stability, and reduced radiation-induced segregation. The ultimate goal of this project is, with the aid of computational modeling tools, to accelerate the development of a new generation of Zr-bearing ferritic alloys to be fabricated using conventional steelmaking practices, which have excellent radiation resistance and enhanced high-temperature creep performance greater than Grade 91.« less

Representing Clarity: Using Universal Design Principles to Create Effective Hybrid Course Learning Materials

ERIC Educational Resources Information Center

Spiegel, Cheri Lemieux

2012-01-01

This article describes how the author applied principles of universal design to hybrid course materials to increase student understanding and, ultimately, success. Pulling the three principles of universal design--consistency, color, and icon representation--into the author's Blackboard course allowed her to change the types of reading skills…

Laser Crystal

NASA Technical Reports Server (NTRS)

1998-01-01

Lightning Optical Corporation, under an SBIR (Small Business Innovative Research) agreement with Langley Research Center, manufactures oxide and fluoride laser gain crystals, as well as various nonlinear materials. The ultimate result of this research program is the commercial availability in the marketplace of a reliable source of high-quality, damage resistant laser material, primarily for diode-pumping applications.

An Integrated Modeling Platform for Human and Ecological Exposure and Risk in Multimedia Environmental Systems (HE2RMES)

EPA Science Inventory

When considering potentially hazardous materials in the context of initial use, reuse, recycling, or ultimate disposal in the landscape, a crux of most decision will be understanding the cumulative contaminant exposure and risk of a given material to human health and well-being. ...

A Primer on Wound Healing in Colorectal Surgery in the Age of Bioprosthetic Materials

PubMed Central

Lundy, Jonathan B.

2014-01-01

Wound healing is a complex, dynamic process that is vital for closure of cutaneous injuries, restoration of abdominal wall integrity after laparotomy closure, and to prevent anastomotic dehiscence after bowel surgery. Derangements in healing have been described in multiple processes including diabetes mellitus, corticosteroid use, irradiation for malignancy, and inflammatory bowel disease. A thorough understanding of the process of healing is necessary for clinical decision making and knowledge of the current state of the science may lead future researchers in developing methods to enable our ability to modulate healing, ultimately improving outcomes. An exciting example of this ability is the use of bioprosthetic materials used for abdominal wall surgery (hernia repair/reconstruction). These bioprosthetic meshes are able to regenerate and remodel from an allograft or xenograft collagen matrix into site-specific tissue; ultimately being degraded and minimizing the risk of long-term complications seen with synthetic materials. The purpose of this article is to review healing as it relates to cutaneous and intestinal trauma and surgery, factors that impact wound healing, and wound healing as it pertains to bioprosthetic materials. PMID:25435821

Biocatalytic material comprising multilayer enzyme coated fiber

DOEpatents

Kim, Jungbae [Richland, WA; Kwak, Ja Hun [Richland, WA; Grate, Jay W [West Richland, WA

2009-11-03

The present invention relates generally to high stability, high activity biocatalytic materials and processes for using the same. The materials comprise enzyme aggregate coatings having high biocatalytic activity and stability useful in heterogeneous environment. These new materials provide a new biocatalytic immobilized enzyme system with applications in bioconversion, bioremediation, biosensors, and biofuel cells.

The effect of different beverages on the color and translucency of flowable composites.

PubMed

Karadas, Muhammet

2016-11-01

This study examined the changes in color and translucency of flowable composites after immersion in different beverages. Thirty composite samples were prepared from four flowable composites (G-aenial Universal Flo, Filtek Ultimate, Esthelite Flow Quick, and Clearfil Majesty ES Flow) and a microhybrid composite (Filtek Z-250) and stored in distilled water at 37°C for 24 h. The samples were randomly divided into seven groups and then immersed in different beverages (Red Bull, coffee, black tea, Pepsi Cola, orange juice, and distilled water) for 7 days. The CIE L*a*b* values of each sample were measured against white and black backgrounds using a spectrophotometer before and after immersion. Data were analyzed using two-way analysis of variance and Tukey's post-hoc test (p < 0.05). The color changes were significantly different among the composite materials after immersion in beverages (p < 0.05). Filtek Ultimate and Esthelite Flow Quick exhibited less discoloration than did G-aenial Universal Flo and Clearfil Majesty ES Flow. No significant difference was found between Filtek Z-250 and either Filtek Ultimate or Esthelite Flow Quick (p > 0.05). Among the beverages, black tea and coffee caused the highest discoloration of all the materials. Immersion in coffee and black tea resulted in the highest negative changes in the translucency of the materials. The degree of discoloration for the composite resins depended on the material used and drinking beverage. SCANNING 38:701-709, 2016. © 2016 Wiley Periodicals, Inc. © Wiley Periodicals, Inc.

Joint Task Force Headquarters Master Training Guide

DTIC Science & Technology

2003-09-01

roles, and relationships that differ from those of Service organizations. (6) Understand the rotation policy for individual augmentees assigned to the...JTF. Although the Combatant Commander ultimately establishes individual and unit rotation policies, they will not necessarily be uniform. One...Service might have a 90-day rotation policy while the other Services have 120-day or 179-day rotation policies. To stabilize key billets, consider

Topical Meeting of Broadband Analog and Digital Optoelectronics

DTIC Science & Technology

1992-01-01

effects [2]. Laser nonlinearitics can be minimised by careful design of the device to maximise the relaxation oscillation resonance frequency [2...feedback loop ultimately limits the stability of the circuit and determines the maximum frequency of operation. With hybrid circuit constructioi. this...range and number of accessible frequency channels), the tuning lever, and the filter selectivity (which determines the side-mode suppression ratio (SMSR

Nanotechnology in bone tissue engineering.

PubMed

Walmsley, Graham G; McArdle, Adrian; Tevlin, Ruth; Momeni, Arash; Atashroo, David; Hu, Michael S; Feroze, Abdullah H; Wong, Victor W; Lorenz, Peter H; Longaker, Michael T; Wan, Derrick C

2015-07-01

Nanotechnology represents a major frontier with potential to significantly advance the field of bone tissue engineering. Current limitations in regenerative strategies include impaired cellular proliferation and differentiation, insufficient mechanical strength of scaffolds, and inadequate production of extrinsic factors necessary for efficient osteogenesis. Here we review several major areas of research in nanotechnology with potential implications in bone regeneration: 1) nanoparticle-based methods for delivery of bioactive molecules, growth factors, and genetic material, 2) nanoparticle-mediated cell labeling and targeting, and 3) nano-based scaffold construction and modification to enhance physicochemical interactions, biocompatibility, mechanical stability, and cellular attachment/survival. As these technologies continue to evolve, ultimate translation to the clinical environment may allow for improved therapeutic outcomes in patients with large bone deficits and osteodegenerative diseases. Traditionally, the reconstruction of bony defects has relied on the use of bone grafts. With advances in nanotechnology, there has been significant development of synthetic biomaterials. In this article, the authors provided a comprehensive review on current research in nanoparticle-based therapies for bone tissue engineering, which should be useful reading for clinicians as well as researchers in this field. Copyright © 2015 Elsevier Inc. All rights reserved.

Testing low-mode symmetry control with low-adiabat, extended pulse-lengths in BigFoot implosions on the National Ignition Facility

NASA Astrophysics Data System (ADS)

Hohenberger, Matthias; Casey, D. T.; Thomas, C. A.; Baker, K. L.; Spears, B. K.; Khan, S. F.; Hurricane, O. A.; Callahan, D.

2017-10-01

The Bigfoot approach to indirect-drive inertial confinement fusion (ICF) has been developed as a compromise trading high-convergence and areal densities for high implosion velocities, large adiabats and hydrodynamic stability. Shape control and predictability are maintained by using relatively short laser pulses and merging the shocks within the DT-ice layer. These design choices ultimately limit the theoretically achievable performance, and one strategy to increase the 1-D performance is to reduce the shell adiabat by extending the pulse shape. However, this can result in loss of low-mode symmetry control, as the hohlraum ``bubble,'' the high-Z material launched by the outer-cone beams during the early part of the laser pulse, has more time to expand and will eventually intercept inner-cone beams preventing them from reaching the hohlraum waist, thus losing equatorial capsule drive. We report on experimental results exploring shape control and predictability with extended pulse shapes in BigFoot implosions. Prepared by LLNL under Contract DE-AC52-07NA27344.

Taming Self-Organization Dynamics to Dramatically Control Porous Architectures.

PubMed

Daly, Ronan; Sader, John E; Boland, John J

2016-03-22

We demonstrate templating of functional materials with unexpected and intricate micro- and nanostructures by controlling the condensation, packing, and evaporation of water droplets on a polymer solution. Spontaneous evaporation of a polymer solution induces cooling of the liquid surface and water microdroplet condensation from the ambient vapor. These droplets pack together and act as a template to imprint an entangled polymer film. This breath figure (BF) phenomenon is an example of self-organization that involves the long-range ordering of droplets. Equilibrium-based analysis provides many insights into contact angles and drop stability of individual drops, but the BF phenomenon remains poorly understood thus far, preventing translation to real applications. Here we investigate the dynamics of this phenomenon to separate out the competing influences and then introduce a modulation scheme to ultimately manipulate the water vapor-liquid equilibrium independently from the solvent evaporation. This approach to BF control provides insights into the mechanism, a rationale for microstructure design, and evidence for the benefits of dynamical control of self-organization systems. We finally present dramatically different porous architectures from this approach reminiscent of microscale Petri dishes, conical flasks, and test tubes.

Mechanical degradation of fuel cell membranes under fatigue fracture tests

NASA Astrophysics Data System (ADS)

Khorasany, Ramin M. H.; Sadeghi Alavijeh, Alireza; Kjeang, Erik; Wang, G. G.; Rajapakse, R. K. N. D.

2015-01-01

The effects of cyclic stresses on the fatigue and mechanical stability of perfluorosulfonic acid (PFSA) membranes are experimentally investigated under standard fuel cell conditions. The experiments are conducted ex-situ by subjecting membrane specimens to cyclic uniaxial tension at controlled temperature and relative humidity. The fatigue lifetime is measured in terms of the number of cycles until ultimate fracture. The results indicate that the membrane fatigue lifetime is a strong function of the applied stress, temperature, and relative humidity. The fatigue life increases exponentially with reduced stresses in all cases. The effect of temperature is found to be more significant than that of humidity, with reduced fatigue life at high temperatures. The maximum membrane strain at fracture is determined to decrease exponentially with increasing membrane lifetime. At a given fatigue life, a membrane exposed to fuel cell conditions is shown to accommodate more plastic strain before fracture than one exposed to room conditions. Overall, the proposed ex-situ membrane fatigue experiment can be utilized to benchmark the fatigue lifetime of new materials in a fraction of the time and cost associated with conventional in-situ accelerated stress testing methods.

Carbon Nanotubes as an Ultrafast Emitter with a Narrow Energy Spread at Optical Frequency.

PubMed

Li, Chi; Zhou, Xu; Zhai, Feng; Li, Zhenjun; Yao, Fengrui; Qiao, Ruixi; Chen, Ke; Cole, Matthew Thomas; Yu, Dapeng; Sun, Zhipei; Liu, Kaihui; Dai, Qing

2017-08-01

Ultrafast electron pulses, combined with laser-pump and electron-probe technologies, allow ultrafast dynamics to be characterized in materials. However, the pursuit of simultaneous ultimate spatial and temporal resolution of microscopy and spectroscopy is largely subdued by the low monochromaticity of the electron pulses and their poor phase synchronization to the optical excitation pulses. Field-driven photoemission from metal tips provides high light-phase synchronization, but suffers large electron energy spreads (3-100 eV) as driven by a long wavelength laser (>800 nm). Here, ultrafast electron emission from carbon nanotubes (≈1 nm radius) excited by a 410 nm femtosecond laser is realized in the field-driven regime. In addition, the emitted electrons have great monochromaticity with energy spread as low as 0.25 eV. This great performance benefits from the extraordinarily high field enhancement and great stability of carbon nanotubes, superior to metal tips. The new nanotube-based ultrafast electron source opens exciting prospects for extending current characterization to sub-femtosecond temporal resolution as well as sub-nanometer spatial resolution. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Assessment of Embedded Conjugated Polymer Sensor Arrays for Potential Load Transmission Measurement in Orthopaedic Implants

PubMed Central

Micolini, Carolina; Holness, Frederick Benjamin; Johnson, James A.

2017-01-01

Load transfer through orthopaedic joint implants is poorly understood. The longer-term outcomes of these implants are just starting to be studied, making it imperative to monitor contact loads across the entire joint implant interface to elucidate the force transmission and distribution mechanisms exhibited by these implants in service. This study proposes and demonstrates the design, implementation, and characterization of a 3D-printed smart polymer sensor array using conductive polyaniline (PANI) structures embedded within a polymeric parent phase. The piezoresistive characteristics of PANI were investigated to characterize the sensing behaviour inherent to these embedded pressure sensor arrays, including the experimental determination of the stable response of PANI to continuous loading, stability throughout the course of loading and unloading cycles, and finally sensor repeatability and linearity in response to incremental loading cycles. This specially developed multi-material additive manufacturing process for PANI is shown be an attractive approach for the fabrication of implant components having embedded smart-polymer sensors, which could ultimately be employed for the measurement and analysis of joint loads in orthopaedic implants for in vitro testing. PMID:29186079

Fabrication of nanocapsule carriers from multilayer-coated vaterite calcium carbonate nanoparticles.

PubMed

Biswas, Aniket; Nagaraja, Ashvin T; McShane, Michael J

2014-12-10

Nanosized luminescent sensors were prepared as reagents for optical sensing and imaging of oxygen using ratiometric emission properties of a two-dye system. Polymeric capsules were fabricated utilizing poly(vinylsulfonic acid) (PVSA)-stabilized vaterite CaCO3 nanoparticles (CCNPs) as sacrificial templates. The buffer and polymeric surfactant requirements of the layer-by-layer (LbL) process were evaluated toward deposition of multilayer coatings and, ultimately, formation of hollow capsules using these interesting materials. CCNPs were found to be more stable in alkaline NaHCO3 buffer after repeated cycles of washing under sonication and resuspension. An intermediate PVSA concentration was required to maximize the loading of oxygen-sensitive porphyrin and oxygen-insensitive fluorescent nanoparticles in the CCNPs while maintaining minimal nanoparticle size. The CCNPs were then coated with polyelectrolyte multilayers and subsequent removal of the CaCO3 core yielded nanocapsules containing dye and fluorescent nanoparticles. The resulting nanocapsules with encapsulated luminophores functioned effectively as oxygen sensors with a quenching response of 89.28 ± 2.59%, and O2 (S = 1/2) = 20.91 μM of dissolved oxygen.

Robust adaptive relative position and attitude control for spacecraft autonomous proximity.

PubMed

Sun, Liang; Huo, Wei; Jiao, Zongxia

2016-07-01

This paper provides new results of the dynamical modeling and controller designing for autonomous close proximity phase during rendezvous and docking in the presence of kinematic couplings and model uncertainties. A globally defined relative motion mechanical model for close proximity operations is introduced firstly. Then, in spite of the kinematic couplings and thrust misalignment between relative rotation and relative translation, robust adaptive relative position and relative attitude controllers are designed successively. Finally, stability of the overall system is proved that the relative position and relative attitude are uniformly ultimately bounded, and the size of the ultimate bound can be regulated small enough by control system parameters. Performance of the controlled overall system is demonstrated via a representative numerical example. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Stability of Materials in High Temperature Water Vapor: SOFC Applications

NASA Technical Reports Server (NTRS)

Opila, E. J.; Jacobson, N. S.

2010-01-01

Solid oxide fuel cell material systems require long term stability in environments containing high-temperature water vapor. Many materials in fuel cell systems react with high-temperature water vapor to form volatile hydroxides which can degrade cell performance. In this paper, experimental methods to characterize these volatility reactions including the transpiration technique, thermogravimetric analysis, and high pressure mass spectrometry are reviewed. Experimentally determined data for chromia, silica, and alumina volatility are presented. In addition, data from the literature for the stability of other materials important in fuel cell systems are reviewed. Finally, methods for predicting material recession due to volatilization reactions are described.

In-office bleaching efficacy on stain removal from CAD/CAM and direct resin composite materials.

PubMed

Alharbi, Amal; Ardu, Stefano; Bortolotto, Tissiana; Krejci, Ivo

2018-01-01

To evaluate the efficacy of in-office bleaching on stain removal from stained resin composite and ceramic computer-assisted design/computer-assisted manufacturing (CAD/CAM) blocks and direct resin composites. Forty disk-shaped samples were fabricated from each of nine materials: six CAD/CAM (VITABLOCS Mark II, Paradigm MZ100, Exp Vita Hybrid Ceramic, VITA ENAMIC, Exp Kerr, and LAVA Ultimate) and three direct resin composites (Filtek Supreme, Venus Diamond, and Filtek Silorane). Samples were randomly divided into five groups (n = 8), each stained with a particular staining solution. Using a calibrated spectrophotometer and a black background, L*a*b* values were assessed before and after 120 days of staining. Samples were subjected to in-office bleaching using 40% hydrogen peroxide gel for one hour. At subsequent assessment, color change (ΔE) was calculated as the difference between L*a*b* values. Both ANOVA and the Duncan test were used to identify differences between groups (α = 0.05). Bleaching resulted in significant differences in ΔE values for all materials (P < .001). Bleaching efficacy was highly influenced by material composition and staining solution. Residual color values after bleaching for ceramic and hybrid ceramics ranged from -0.49 to 2.35, within the clinically acceptable maximum of 3.3. Values after bleaching for resin-based CAD/CAM ranged from -0.7 to 7.08 while direct resin composites values ranged from -1.47 to 25.13. Coffee left the greatest residual color on all materials. Based on material nature, 40% hydrogen peroxide bleaching can remove staining. The new resin-based CAD/CAM blocks showed promising results in terms of color stability. Bleaching using 40% hydrogen peroxide can be an effective method to remove stains from dental restorations. In this way, restoration replacement as a result of discoloration may no longer be necessary. © 2017 Wiley Periodicals, Inc.

Engineering 3D bicontinuous hierarchically macro-mesoporous LiFePO4/C nanocomposite for lithium storage with high rate capability and long cycle stability

PubMed Central

Zhang, Qian; Huang, Shao-Zhuan; Jin, Jun; Liu, Jing; Li, Yu; Wang, Hong-En; Chen, Li-Hua; Wang, Bin-Jie; Su, Bao-Lian

2016-01-01

A highly crystalline three dimensional (3D) bicontinuous hierarchically macro-mesoporous LiFePO4/C nanocomposite constructed by nanoparticles in the range of 50~100 nm via a rapid microwave assisted solvothermal process followed by carbon coating have been synthesized as cathode material for high performance lithium-ion batteries. The abundant 3D macropores allow better penetration of electrolyte to promote Li+ diffusion, the mesopores provide more electrochemical reaction sites and the carbon layers outside LiFePO4 nanoparticles increase the electrical conductivity, thus ultimately facilitating reverse reaction of Fe3+ to Fe2+ and alleviating electrode polarization. In addition, the particle size in nanoscale can provide short diffusion lengths for the Li+ intercalation-deintercalation. As a result, the 3D macro-mesoporous nanosized LiFePO4/C electrode exhibits excellent rate capability (129.1 mA h/g at 2 C; 110.9 mA h/g at 10 C) and cycling stability (87.2% capacity retention at 2 C after 1000 cycles, 76.3% at 5 C after 500 cycles and 87.8% at 10 C after 500 cycles, respectively), which are much better than many reported LiFePO4/C structures. Our demonstration here offers the opportunity to develop nanoscaled hierarchically porous LiFePO4/C structures for high performance lithium-ion batteries through microwave assisted solvothermal method. PMID:27181195

Engineering 3D bicontinuous hierarchically macro-mesoporous LiFePO4/C nanocomposite for lithium storage with high rate capability and long cycle stability.

PubMed

Zhang, Qian; Huang, Shao-Zhuan; Jin, Jun; Liu, Jing; Li, Yu; Wang, Hong-En; Chen, Li-Hua; Wang, Bin-Jie; Su, Bao-Lian

2016-05-16

A highly crystalline three dimensional (3D) bicontinuous hierarchically macro-mesoporous LiFePO4/C nanocomposite constructed by nanoparticles in the range of 50~100 nm via a rapid microwave assisted solvothermal process followed by carbon coating have been synthesized as cathode material for high performance lithium-ion batteries. The abundant 3D macropores allow better penetration of electrolyte to promote Li(+) diffusion, the mesopores provide more electrochemical reaction sites and the carbon layers outside LiFePO4 nanoparticles increase the electrical conductivity, thus ultimately facilitating reverse reaction of Fe(3+) to Fe(2+) and alleviating electrode polarization. In addition, the particle size in nanoscale can provide short diffusion lengths for the Li(+) intercalation-deintercalation. As a result, the 3D macro-mesoporous nanosized LiFePO4/C electrode exhibits excellent rate capability (129.1 mA h/g at 2 C; 110.9 mA h/g at 10 C) and cycling stability (87.2% capacity retention at 2 C after 1000 cycles, 76.3% at 5 C after 500 cycles and 87.8% at 10 C after 500 cycles, respectively), which are much better than many reported LiFePO4/C structures. Our demonstration here offers the opportunity to develop nanoscaled hierarchically porous LiFePO4/C structures for high performance lithium-ion batteries through microwave assisted solvothermal method.

Minimum intervention dentistry and the management of tooth wear in general practice.

PubMed

Meyers, I A

2013-06-01

The incidence of tooth wear, or non-carious tooth surface loss (NCTSL), is increasing and oral rehabilitation of patients with non-carious tooth loss requires strategies that address all the factors relevant to the aetiology and pathogenesis of the condition. The multifactorial nature of tooth wear and the variability in its clinical presentation provides treatment challenges for the clinician and successful management must be more than just restoration. Management must include an appropriate mix of preventive and restorative strategies and an understanding that long-term restorative success is affected by the patient's oral environment, and how diet, lifestyle and medical status can modify this environment. Ultimately, the success of any restorative intervention is very dependent on the stability of the oral environment and the condition of the remaining tooth structure. Minimum intervention dentistry (MID) philosophies are ideally suited to tooth wear cases and an overall MID strategy involving diagnosis, recognition and control of predisposing factors, stabilization of the oral environment, remineralization and restoration of the tooth structure, and ongoing maintenance can be implemented. When restorative treatment is required, contemporary materials and techniques are available that can provide cost-effective and conservative restorative alternatives for patients unable to undergo the complex indirect restorative techniques that are both costly and time consuming to implement. These minimally invasive approaches are not only an economically viable solution, but can provide aesthetic and functional rehabilitation and maintain tooth structure as a precursor to more complex restorative options when required. © 2013 Australian Dental Association.

Study on VCSEL laser heating chip in nuclear magnetic resonance gyroscope

NASA Astrophysics Data System (ADS)

Liang, Xiaoyang; Zhou, Binquan; Wu, Wenfeng; Jia, Yuchen; Wang, Jing

2017-10-01

In recent years, atomic gyroscope has become an important direction of inertial navigation. Nuclear magnetic resonance gyroscope has a stronger advantage in the miniaturization of the size. In atomic gyroscope, the lasers are indispensable devices which has an important effect on the improvement of the gyroscope performance. The frequency stability of the VCSEL lasers requires high precision control of temperature. However, the heating current of the laser will definitely bring in the magnetic field, and the sensitive device, alkali vapor cell, is very sensitive to the magnetic field, so that the metal pattern of the heating chip should be designed ingeniously to eliminate the magnetic field introduced by the heating current. In this paper, a heating chip was fabricated by MEMS process, i.e. depositing platinum on semiconductor substrates. Platinum has long been considered as a good resistance material used for measuring temperature The VCSEL laser chip is fixed in the center of the heating chip. The thermometer resistor measures the temperature of the heating chip, which can be considered as the same temperature of the VCSEL laser chip, by turning the temperature signal into voltage signal. The FPGA chip is used as a micro controller, and combined with PID control algorithm constitute a closed loop control circuit. The voltage applied to the heating resistor wire is modified to achieve the temperature control of the VCSEL laser. In this way, the laser frequency can be controlled stably and easily. Ultimately, the temperature stability can be achieved better than 100mK.

Bulk-Heterojunction Organic Solar Cells: Five Core Technologies for Their Commercialization.

PubMed

Kang, Hongkyu; Kim, Geunjin; Kim, Junghwan; Kwon, Sooncheol; Kim, Heejoo; Lee, Kwanghee

2016-09-01

The past two decades of vigorous interdisciplinary approaches has seen tremendous breakthroughs in both scientific and technological developments of bulk-heterojunction organic solar cells (OSCs) based on nanocomposites of π-conjugated organic semiconductors. Because of their unique functionalities, the OSC field is expected to enable innovative photovoltaic applications that can be difficult to achieve using traditional inorganic solar cells: OSCs are printable, portable, wearable, disposable, biocompatible, and attachable to curved surfaces. The ultimate objective of this field is to develop cost-effective, stable, and high-performance photovoltaic modules fabricated on large-area flexible plastic substrates via high-volume/throughput roll-to-roll printing processing and thus achieve the practical implementation of OSCs. Recently, intensive research efforts into the development of organic materials, processing techniques, interface engineering, and device architectures have led to a remarkable improvement in power conversion efficiencies, exceeding 11%, which has finally brought OSCs close to commercialization. Current research interests are expanding from academic to industrial viewpoints to improve device stability and compatibility with large-scale printing processes, which must be addressed to realize viable applications. Here, both academic and industrial issues are reviewed by highlighting historically monumental research results and recent state-of-the-art progress in OSCs. Moreover, perspectives on five core technologies that affect the realization of the practical use of OSCs are presented, including device efficiency, device stability, flexible and transparent electrodes, module designs, and printing techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Black Phosphorus Flexible Thin Film Transistors at Gighertz Frequencies.

PubMed

Zhu, Weinan; Park, Saungeun; Yogeesh, Maruthi N; McNicholas, Kyle M; Bank, Seth R; Akinwande, Deji

2016-04-13

Black phosphorus (BP) has attracted rapidly growing attention for high speed and low power nanoelectronics owing to its compelling combination of tunable bandgap (0.3 to 2 eV) and high carrier mobility (up to ∼1000 cm(2)/V·s) at room temperature. In this work, we report the first radio frequency (RF) flexible top-gated (TG) BP thin-film transistors on highly bendable polyimide substrate for GHz nanoelectronic applications. Enhanced p-type charge transport with low-field mobility ∼233 cm(2)/V·s and current density of ∼100 μA/μm at VDS = -2 V were obtained from flexible BP transistor at a channel length L = 0.5 μm. Importantly, with optimized dielectric coating for air-stability during microfabrication, flexible BP RF transistors afforded intrinsic maximum oscillation frequency fMAX ∼ 14.5 GHz and unity current gain cutoff frequency fT ∼ 17.5 GHz at a channel length of 0.5 μm. Notably, the experimental fT achieved here is at least 45% higher than prior results on rigid substrate, which is attributed to the improved air-stability of fabricated BP devices. In addition, the high-frequency performance was investigated through mechanical bending test up to ∼1.5% tensile strain, which is ultimately limited by the inorganic dielectric film rather than the 2D material. Comparison of BP RF devices to other 2D semiconductors clearly indicates that BP offers the highest saturation velocity, an important metric for high-speed and RF flexible nanosystems.

Atomic Force Microscopy of virus capsids uncover the interplay between mechanics, structure and function

NASA Astrophysics Data System (ADS)

de Pablo, Pedro J.

The basic architecture of a virus consists of the capsid, a shell made up of repeating protein subunits, which packs, shuttles and delivers their genome at the right place and moment. Viral particles are endorsed with specific physicochemical properties which confer to their structures certain meta-stability whose modulation permits fulfilling each task of the viral cycle. These natural designed capabilities have impelled using viral capsids as protein containers of artificial cargoes (drugs, polymers, enzymes, minerals) with applications in biomedical and materials sciences. Both natural and artificial protein cages have to protect their cargo against a variety of physicochemical aggressive environments, including molecular impacts of highly crowded media, thermal and chemical stresses, and osmotic shocks. Viral cages stability under these ambiences depend not only on the ultimate structure of the external capsid, which rely on the interactions between protein subunits, but also on the nature of the cargo. During the last decade our lab has focused on the study of protein cages with Atomic Force Microscopy (AFM) (figure 1). We are interested in stablishing links of their mechanical properties with their structure and function. In particular, mechanics provide information about the cargo storage strategies of both natural and virus-derived protein cages. Mechanical fatigue has revealed as a nanosurgery tool to unveil the strength of the capisd subunit bonds. We also interrogated the electrostatics of individual protein shells. Our AFM-fluorescence combination provided information about DNA diffusing out cracked-open protein cages in real time.

Highly defective oxides as sinter resistant thermal barrier coating

DOEpatents

Subramanian, Ramesh

2005-08-16

A thermal barrier coating material formed of a highly defective cubic matrix structure having a concentration of a stabilizer sufficiently high that the oxygen vacancies created by the stabilizer interact within the matrix to form multi-vacancies, thereby improving the sintering resistance of the material. The concentration of stabilizer within the cubic matrix structure is greater than that concentration of stabilizer necessary to give the matrix a peak ionic conductivity value. The concentration of stabilizer may be at least 30 wt. %. Embodiments include a cubic matrix of zirconia stabilized by at least 30-50 wt. % yttria, and a cubic matrix of hafnia stabilized by at least 30-50 wt. % gadolinia.

Biomaterials for drug delivery systems.

PubMed

Buckles, R G

1983-01-01

Drug delivery systems have unusual materials requirements which derive mainly from their therapeutic role: to administer drugs over prolonged periods of time at rates that are independent of patient-to-patient variables. The chemical nature of the surfaces of such devices may stimulate biorejection processes which can be enhanced or suppressed by the simultaneous presence of the drug that is being administered. Selection of materials for such systems is further complicated by the need for compatibility with the drug contained within the system. A review of selected drug delivery systems is presented. This leads to a definition of the technologies required to develop successfully such systems as well as to categorize the classes of drug delivery systems available to the therapist. A summary of the applications of drug delivery systems will also be presented. There are five major challenges to the biomaterials scientist: (1) how to minimize the influence on delivery rate of the transient biological response that accompanies implantation of any object; (2) how to select a composition, size, shape, and flexibility that optimizes biocompatibility; (3) how to make an intravascular delivery system that will retain long-term functionality; (4) how to make a percutaneous lead for those delivery systems that cannot be implanted but which must retain functionality for extended periods; and (5) how to make biosensors of adequate compatibility and stability to use with the ultimate drug delivery system-a system that operates with feedback control.

Technetium incorporation into goethite (α-FeOOH): An atomic-scale investigation

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

Smith, Frances N.; Taylor, Christopher D.; Um, Wooyong

2015-11-17

During the processing of low-activity radioactive waste to generate solid waste forms (e.g., glass), technetium-99 (Tc) is of concern because of its volatility. A variety of materials are under consideration to capture Tc from waste streams, including the iron oxyhydroxide, goethite (α-FeOOH), which was experimentally shown to sequester Tc(IV). This material could ultimately be incorporated into glass or other low-temperature waste form matrices. However, questions remain regarding the incorporation mechanism for Tc(IV) in goethite, which has implications for predicting the long-term stability of Tc in waste forms under changing conditions. Here, quantum-mechanical calculations were used to evaluate the energy ofmore » five different charge-compensated Tc(IV) incorporation scenarios in goethite. The two most stable incorporation mechanisms involve direct substitution of Tc(IV) onto Fe(III) lattice sites and charge balancing either by removing one nearby H+ (i.e., within 5 Å), or by creating an Fe(III) vacancy when substituting 3 Tc(IV) for 4 Fe(III), with the former being preferred over the latter relative to gas-phase ions. When corrections for hydrated references phases are applied, the Fe(III)-vacancy mechanism becomes more energetically competitive. Calculated incorporation energies and optimized bond-lengths are presented. Proton movement is observed to satisfy under-coordinated bonds surrounding vacancies in the goethite structure.« less

The Lyapunov-Krasovskii theorem and a sufficient criterion for local stability of isochronal synchronization in networks of delay-coupled oscillators

NASA Astrophysics Data System (ADS)

Grzybowski, J. M. V.; Macau, E. E. N.; Yoneyama, T.

2017-05-01

This paper presents a self-contained framework for the stability assessment of isochronal synchronization in networks of chaotic and limit-cycle oscillators. The results were based on the Lyapunov-Krasovskii theorem and they establish a sufficient condition for local synchronization stability of as a function of the system and network parameters. With this in mind, a network of mutually delay-coupled oscillators subject to direct self-coupling is considered and then the resulting error equations are block-diagonalized for the purpose of studying their stability. These error equations are evaluated by means of analytical stability results derived from the Lyapunov-Krasovskii theorem. The proposed approach is shown to be a feasible option for the investigation of local stability of isochronal synchronization for a variety of oscillators coupled through linear functions of the state variables under a given undirected graph structure. This ultimately permits the systematic identification of stability regions within the high-dimensionality of the network parameter space. Examples of applications of the results to a number of networks of delay-coupled chaotic and limit-cycle oscillators are provided, such as Lorenz, Rössler, Cubic Chua's circuit, Van der Pol oscillator and the Hindmarsh-Rose neuron.

Comparative characterization of a novel cad-cam polymer-infiltrated-ceramic-network

PubMed Central

Pascual, Agustín; Camps, Isabel; Grau-Benitez, María

2015-01-01

Background The field of dental ceramics for CAD-CAM is enriched with a new innovative material composition having a porous three-dimensional structure of feldspathic ceramic infiltrated with acrylic resins.The aim of this study is to determine the mechanical properties of Polymer-Infiltrated-Ceramic-Network (PICN) and compare its performance with other ceramics and a nano-ceramic resin available for CAD-CAM systems. Material and Methods In this study a total of five different materials for CAD-CAM were investigated. A polymer-infiltrated ceramic (Vita Enamic), a nano-ceramic resin (Lava Ultimate), a feldspathic ceramic (Mark II), a lithium disilicate ceramic (IPS-e max CAD) and finally a Leucite based ceramic (Empress - CAD). From CAD-CAM blocks, 120 bars (30 for each material cited above) were cut to measure the flexural strength with a three-point-bending test. Strain at failure, fracture stress and Weibull modulus was calculated. Vickers hardness of each material was also measured. Results IPS-EMAX presents mechanical properties significantly better from the other materials studied. Its strain at failure, flexural strength and hardness exhibited significantly higher values in comparison with the others. VITA ENAMIC and LAVA ULTIMATE stand out as the next most resistant materials. Conclusions The flexural strength, elastic modulus similar to a tooth as well as having less hardness than ceramics make PICN materials an option to consider as a restorative material. Key words:Ceramic infiltrated with resin, CAD-CAM, Weibull modulus, flexural strength, micro hardness. PMID:26535096

High-volume manufacturing compatible dry development rinse process (DDRP): patterning and defectivity performance for EUVL

NASA Astrophysics Data System (ADS)

Sayan, Safak; Vanelderen, Pieter; Hetel, Iulian; Chan, BT; Raghavan, Praveen; Blanco, Victor; Foubert, Philippe; D'urzo, Lucia; De Simone, Danilo; Vandenberghe, Geert

2017-04-01

There are many knobs available that change the chemical and physical properties of the photoresists to "break" the RLS (Resolution, Sensitivity, Line edge/width roughness) trade-off, however those are not enough today to realize a material to satisfy all requirements at once for 7nm technology and beyond. DDRP improves the ultimate achievable resolution via pattern collapse mitigation, hence the priority of requirements for the EUV photoresist development may be changed with more focus on Sensitivity and LWR. This may potentially provide a new conceptual approach towards EUV PR development for DDRP applications. We have previously demonstrated pattern collapse (PC) mitigation via DDRP on different EUVL photoresists (including different resist platforms), achieving ultimate resolution and exposure latitude improvements [1,2]. In this contribution, we report patterning and material defect performance of HVM compatible (all aqueous) dry development rinse material. We will also report on process window improvement on 2-dimensional metal structures towards standard cell size reduction with elimination of mask layer(s) using single EUV exposure.

Structural design/margin assessment

NASA Technical Reports Server (NTRS)

Ryan, R. S.

1993-01-01

Determining structural design inputs and the structural margins following design completion is one of the major activities in space exploration. The end result is a statement of these margins as stability, safety factors on ultimate and yield stresses, fracture limits (fracture control), fatigue lifetime, reuse criteria, operational criteria and procedures, stability factors, deflections, clearance, handling criteria, etc. The process is normally called a load cycle and is time consuming, very complex, and involves much more than structures. The key to successful structural design is the proper implementation of the process. It depends on many factors: leadership and management of the process, adequate analysis and testing tools, data basing, communications, people skills, and training. This process and the various factors involved are discussed.

Urey prize lecture: On the diversity of plausible planetary systems

NASA Technical Reports Server (NTRS)

Lissauer, J. J.

1995-01-01

Models of planet formation and of the orbital stability of planetary systems are used to predict the variety of planetary and satellite systems that may be present within our galaxy. A new approximate global criterion for orbital stability of planetary systems based on an extension of the local resonance overlap criterion is proposed. This criterion implies that at least some of Uranus' small inner moons are significantly less massive than predicted by estimates based on Voyager volumes and densities assumed to equal that of Miranda. Simple calculations (neglecting planetary gravity) suggest that giant planets which acrete substantial amounts of gas while their envelopes are extremely distended ultimately rotate rapidly in the prgrade direction.

Prediction of packaging seal life using thermoanalytical techniques

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

Nigrey, P.J.

1997-11-01

In this study, Thermogravimetric Analysis (TGA) has been used to study silicone, Viton and Ethylene Propylene (EPDM) rubber. The studies have shown that TGA accurately predicts the relative order of thermo-oxidative stability of these three materials from the calculated activation energies. As expected, the greatest thermal stability was found in silicone rubber followed by Viton and EPDM rubber. The calculated lifetimes for these materials were in relatively close agreement with published values. The preliminary results also accurately reflect decreased thermal stability and lifetime for EPDM rubber exposed to radiation and chemicals. These results suggest TGA provides a rapid method tomore » evaluate material stability.« less

Effects of climate change and UV-B on materials.

PubMed

Andrady, Anthony L; Hamid, Halim S; Torikai, Ayako

2003-01-01

The outdoor service life of common plastic materials is limited by their susceptibility to solar ultraviolet radiation. Of the solar wavelengths the UV-B component is particularly efficient in bringing about photodamage in synthetic and naturally occurring materials. This is particularly true of plastics, rubber and wood used in the building and agricultural industries. Any depletion in the stratospheric ozone layer and resulting increase in the UV-B component of terrestrial sunlight will therefore tend to decrease the service life of these materials. The extent to which the service life is reduced is, however, difficult to estimate as it depends on several factors. These include the chemical nature of the material, the additives it contains, the type and the amount of light-stabilizers (or protective coatings) used, and the amount of solar exposure it receives. Concomitant climate change is likely to increase the ambient temperature and humidity in some of the same regions likely to receive increased UV-B radiation. These factors, particularly higher temperatures, are also well known to accelerate the rate of photodegradation of materials, and may therefore further limit the service life of materials in these regions. To reliably assess the damage to materials as a consequence of ozone layer depletion, the wavelength sensitivity of the degradation process, dose-response relationships for the material and the effectiveness of available stabilizers need to be quantified. The data needed for the purpose are not readily available at this time for most of the commonly used plastics or wood materials. Wavelength sensitivity of a number of common plastic materials and natural biopolymers are available and generally show the damage (per photon) to decrease exponentially with the wavelength. Despite the relatively higher fraction of UV-A in sunlight, the UV-B content is responsible for a significant part of light-induced damage of materials. The primary approach to mitigation relies on the effectiveness of the existing light stabilizers (such as hindered amine light stabilizers, HALS) used in plastics exposed to harsh solar UV conditions coupled with climate change factors. In developing advanced light-stabilizer technologies, more light-resistant grades of common plastics, or surface protection technologies for wood, the harsh weathering environment created by the simultaneous action of increased UV-B levels due to ozone depletion as well as the relevant climate change factors need to be taken into consideration. Recent literature includes several studies on synergism of HALS-based stabilizers, stabilizer effectiveness in the new m-polyolefins and elucidation of the mechanism of stabilization afforded by titania pigment in vinyl plastics.

Ethanol production with dilute acid hydrolysis using partially dried lignocellulosics

DOEpatents

Nguyen, Quang A.; Keller, Fred A.; Tucker, Melvin P.

2003-12-09

A process of converting lignocellulosic biomass to ethanol, comprising hydrolyzing lignocellulosic materials by subjecting dried lignocellulosic material in a reactor to a catalyst comprised of a dilute solution of a strong acid and a metal salt to lower the activation energy (i.e., the temperature) of cellulose hydrolysis and ultimately obtain higher sugar yields.

40 CFR 266.22 - Standards applicable to storers of materials that are to be used in a manner that constitutes...

Code of Federal Regulations, 2010 CFR

2010-07-01

... materials that are to be used in a manner that constitutes disposal who are not the ultimate users. 266.22 Section 266.22 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES (CONTINUED) STANDARDS FOR THE MANAGEMENT OF SPECIFIC HAZARDOUS WASTES AND SPECIFIC TYPES OF HAZARDOUS WASTE...

The production of homozygous tree material

Treesearch

Reinhard F. Stettler; George E. Howe

1966-01-01

Homozygous trees will never be the desired ultimate step in a forest tree improvement program. However, they will serve many purposes in forest genetics research: (1) in the detection of genetic markers; (2) in the isolation of traits under simple genetic control for the study of growth and differentiation phenomena; (3) as a tool as well as reference material in the...

Optical properties and light irradiance of monolithic zirconia at variable thicknesses.

PubMed

Sulaiman, Taiseer A; Abdulmajeed, Aous A; Donovan, Terrence E; Ritter, André V; Vallittu, Pekka K; Närhi, Timo O; Lassila, Lippo V

2015-10-01

The aims of this study were to: (1) estimate the effect of polishing on the surface gloss of monolithic zirconia, (2) measure and compare the translucency of monolithic zirconia at variable thicknesses, and (3) determine the effect of zirconia thickness on irradiance and total irradiant energy. Four monolithic partially stabilized zirconia (PSZ) brands; Prettau® (PRT, Zirkonzahn), Bruxzir® (BRX, Glidewell), Zenostar® (ZEN, Wieland), Katana® (KAT, Noritake), and one fully stabilized zirconia (FSZ); Prettau Anterior® (PRTA, Zirkonzahn) were used to fabricate specimens (n=5/subgroup) with different thicknesses (0.5, 0.7, 1.0, 1.2, 1.5, and 2.0mm). Zirconia core material ICE® Zircon (ICE, Zirkonzahn) was used as a control. Surface gloss and translucency were evaluated using a reflection spectrophotometer. Irradiance and total irradiant energy transmitted through each specimen was quantified using MARC® Resin Calibrator. All specimens were then subjected to a standardized polishing method and the surface gloss, translucency, irradiance, and total irradiant energy measurements were repeated. Statistical analysis was performed using two-way ANOVA and post-hoc Tukey's tests (p<0.05). Surface gloss was significantly affected by polishing (p<0.05), regardless of brand and thickness. Translucency values ranged from 5.65 to 20.40 before polishing and 5.10 to 19.95 after polishing. The ranking from least to highest translucent (after polish) was: BRX=ICE=PRT

Material and Device Stability in Perovskite Solar Cells.

PubMed

Kim, Hui-Seon; Seo, Ja-Young; Park, Nam-Gyu

2016-09-22

Organic-inorganic halide perovskite solar cells have attracted great attention because of their superb efficiency reaching 22 % and low-cost, facile fabrication processing. Nevertheless, stability issues in perovskite solar cells seem to block further advancements toward commercialization. Thus, device stability is one of the important topics in perovskite solar cell research. In the beginning, the poor moisture resistivity of the perovskite layer was considered as a main problem that hindered further development of perovskite solar cells, which encouraged engineering of the perovskite or protection of the perovskite by a buffer layer. Soon after, other parameters affecting long-term stability were sequentially found and various attempts have been made to enhance intrinsic and extrinsic stability. Here we review the recent progresses addressing stability issues in perovskite solar cells. In this report, we investigated factors affecting stability from material and device points of view. To gain a better understanding of the stability of the bulk perovskite material, decomposition mechanisms were investigated in relation to moisture, photons, and heat. Stability of full device should also be carefully examined because its stability is dependent not only on bulk perovskite but also on the interfaces and selective contacts. In addition, ion migration and current-voltage hysteresis were found to be closely related to stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ultimate Tensile Strength as a Function of Test Rate for Various Ceramic Matrix Composites at Elevated Temperatures

NASA Technical Reports Server (NTRS)

Choi, Sung R.; Bansal, Narottam P.; Gyekenyesi, John P.

2002-01-01

Ultimate tensile strength of five different continuous fiber-reinforced ceramic composites, including SiC/BSAS (2D 2 types), SiC/MAS-5 (2D), SiC/SiC (2D enhanced), and C/SiC(2D) was determined as a function of test rate at I 100 to 1200 'C in air. All five composite materials exhibited a significant dependency of ultimate strength on test rate such that the ultimate strength decreased with decreasing test rate, similar to the behavior observed in many advanced monolithic ceramics at elevated temperatures. The application of the preloading technique as well as the prediction of life from one loading configuration (constant stress rate) to another (constant stress loading) for SiC/BSAS suggested that the overall macroscopic failure mechanism of the composites would be the one governed by a power-law type of damage evolution/accumulation, analogous to slow crack growth commonly observed in advanced monolithic ceramics.

Role of anisotropy in determining stability of electrodeposition at solid-solid interfaces

NASA Astrophysics Data System (ADS)

Ahmad, Zeeshan; Viswanathan, Venkatasubramanian

2017-10-01

We investigate the stability of electrodeposition at solid-solid interfaces for materials exhibiting an anisotropic mechanical response. The stability of electrodeposition or resistance to the formation of dendrites is studied within a linear stability analysis. The deformation and stress equations are solved using the Stroh formalism and faithfully recover the boundary conditions at the interface. The stability parameter is used to quantify the stability of different solid-solid interfaces incorporating the full anisotropy of the elastic tensor of the two materials. Results show a high degree of variability in the stability parameter depending on the crystallographic orientation of the solids in contact, and point to opportunities for exploiting this effect in developing Li metal anodes.

Optical studies of dynamical processes in disordered materials

NASA Astrophysics Data System (ADS)

Yen, William M.

1990-12-01

The research continues to focus on the study of the structure and the dynamic behavior of insulating solids which can be activated optically. The physical processes which produce relaxation and energy transfer in the optical excited states were of particular interest. The studies were based principally on optical laser spectroscopic techniques which reveal a more detailed view of the materials of interest and which will ultimately lead to the development of more efficient optoelectronic materials.

Application of Toxicity Identification and Evaluation Procedures for Dredged Material Management

DTIC Science & Technology

2017-02-01

that may pose a risk to human health and the environment. The potential for risk ultimately depends on the final disposition of the dredged material... human health and ecological receptors. This information is also useful when evaluating dredged material for open water disposal since it could eliminate...and potential for exposure to humans or ecological receptors. The Inland Testing and Ocean Disposal Manuals establish a multi-step testing protocol

Laccase-based biocathodes: Comparison of chitosan and Nafion.

PubMed

El Ichi-Ribault, S; Zebda, A; Laaroussi, A; Reverdy-Bruas, N; Chaussy, D; Belgacem, M N; Suherman, A L; Cinquin, P; Martin, D K

2016-09-21

Chitosan and Nafion(®) are both reported as interesting polymers to be integrated into the structure of 3D electrodes for biofuel cells. Their advantage is mainly related to their chemical properties, which have a positive impact on the stability of electrodes such as the laccase-based biocathode. For optimal function in implantable applications the biocathode requires coating with a biocompatible semi-permeable membrane that is designed to prevent the loss of enzyme activity and to protect the structure of the biocathode. Since such membranes are integrated into the electrodes ultimately implanted, they must be fully characterized to demonstrate that there is no interference with the performance of the electrode. In the present study, we demonstrate that chitosan provides superior stability compared with Nafion(®) and should be considered as an optimum solution to enhance the biocompatibility and the stability of 3D bioelectrodes. Copyright © 2016 Elsevier B.V. All rights reserved.

Identification of the molecular genetic basis of the low palmitic acid seed oil trait in soybean mutant line RG3 and association analysis of molecular markers with elevated seed stearic acid and reduced seed palmitic acid

USDA-ARS?s Scientific Manuscript database

The fatty acid composition of vegetable oil is becoming increasingly critical for the ultimate functionality and utilization in foods and industrial products. Partial chemical hydrogenation of soybean oil increases oxidative stability and shelf life but also results in the introduction of trans fats...

JPRS Report, Latin America.

DTIC Science & Technology

1987-07-10

of Industry Discusses Divestment, Government Stability (Franklin McKnight; THE DAILY GLEANER, 26 May 87) 77 NAR Leaders Air Wide-Ranging Views...situation on the Persian Gulf. Now that the main industrialized countries are meeting in Venice to discuss, among other issues, the possibility of...rules of origin and 1 the regime of fiscal incentives , to industry ," he said. ] He said his own personal 4 i image of the ultimate shape I : of the

Fatty Acid Synthase Activity as a Target for c-Met Driven Prostate Cancer

DTIC Science & Technology

2013-07-01

to aid future studies. Identification is a highly significant finding with regard to the potential for future therapeutic development targeted at...Met trafficking, stability, and ultimately oncogenic potential . Palmitoylation defective mutants will be used in animal models of c-Met driven tumor...growth (Aim 2). In addition, future work toward identifying the enzyme responsible for palmitoylation of c- Met will provide a new specific target

High Power Electric Double-Layer Capacitors based on Room-Temperature Ionic Liquids and Nanostructured Carbons

NASA Astrophysics Data System (ADS)

Perez, Carlos R.

The efficient storage of electrical energy constitutes both a fundamental challenge for 21st century science and an urgent requirement for the sustainability of our technological civilization. The push for cleaner renewable forms of energy production, such as solar and wind power, strongly depends on a concomitant development of suitable storage methods to pair with these intermittent sources, as well as for mobile applications, such as vehicles and personal electronics. In this regard, Electrochemical Double-Layer Capacitors (supercapacitors) represent a vibrant area of research due to their environmental friendliness, long lifetimes, high power capability, and relative underdevelopment when compared to electrochemical batteries. Currently supercapacitors have gravimetric energies one order of magnitude lower than similarly advanced batteries, while conversly enjoying a similar advantage over them in terms of power. The challenge is to increase the gravimentric energies and conserve the high power. On the material side, research focuses on highly porous supports and electrolytes, the critical components of supercapacitors. Through the use of electrolyte systems with a wider electrochemical stability window, as well as properly tailored carbon nanomaterials as electrodes, significant improvements in performance are possible. Room Temperature Ionic Liquids and Carbide-Derived Carbons are promising electrolytes and electrodes, respectively. RTILs have been shown to be stable at up to twice the voltage of organic solvent-salt systems currently employed in supercapacitors, and CDCs are tunable in pore structure, show good electrical conductivity, and superior demonstrated capability as electrode material. This work aims to better understand the interplay of electrode and electrolyte parameters, such as pore structure and ion size, in the ultimate performance of RTIL-based supercapacitors in terms of power, energy, and temperature of operation. For this purpose, carbon nanomaterials such as nanoporous CDC nanopowders, vertically aligned carbon nanotube arrays, and single wall carbon nanotube aerogels, were synthesized and used as electrodes, alongside RTIL electrolytes with systematically varying ion sizes and compositions. While electrode/electrolyte development can take place along parallel lines, both must be properly matched to the device's ultimate operating conditions and specific application. The resulting devices exhibit good performance characteristics, and the best temperature range of any electrochemical storage device to date.

Highly sensitive detection of nanoparticles with a self-referenced and self-heterodyned whispering-gallery Raman microlaser.

PubMed

Özdemir, Şahin Kaya; Zhu, Jiangang; Yang, Xu; Peng, Bo; Yilmaz, Huzeyfe; He, Lina; Monifi, Faraz; Huang, Steven He; Long, Gui Lu; Yang, Lan

2014-09-16

Optical whispering-gallery-mode resonators (WGMRs) have emerged as promising platforms for label-free detection of nano-objects. The ultimate sensitivity of WGMRs is determined by the strength of the light-matter interaction quantified by quality factor/mode volume, Q/V, and the resolution is determined by Q. To date, to improve sensitivity and precision of detection either WGMRs have been doped with rare-earth ions to compensate losses and increase Q or plasmonic resonances have been exploited for their superior field confinement and lower V. Here, we demonstrate, for the first time to our knowledge, enhanced detection of single-nanoparticle-induced mode splitting in a silica WGMR via Raman gain-assisted loss compensation and WGM Raman microlaser. In particular, the use of the Raman microlaser provides a dopant-free, self-referenced, and self-heterodyned scheme with a detection limit ultimately determined by the thermorefractive noise. Notably, we detected and counted individual nanoparticles with polarizabilities down to 3.82 × 10(-6) μm(3) by monitoring a heterodyne beatnote signal. This level of sensitivity is achieved without exploiting plasmonic effects, external references, or active stabilization and frequency locking. Single nanoparticles are detected one at a time; however, their characterization by size or polarizability requires ensemble measurements and statistical averaging. This dopant-free scheme retains the inherited biocompatibility of silica and could find widespread use for sensing in biological media. The Raman laser and operation band of the sensor can be tailored for the specific sensing environment and the properties of the targeted materials by changing the pump laser wavelength. This scheme also opens the possibility of using intrinsic Raman or parametric gain for loss compensation in other systems where dissipation hinders progress and limits applications.

Estimation of Ultimate Tensile Strength of dentin Using Finite Element Analysis from Endodontically Treated Tooth

NASA Astrophysics Data System (ADS)

Sinthaworn, S.; Puengpaiboon, U.; Warasetrattana, N.; Wanapaisarn, S.

2018-01-01

Endodontically treated teeth were simulated by finite element analysis in order to estimate ultimate tensile strength of dentin. Structures of the endodontically treated tooth cases are flared root canal, restored with different number of fiber posts {i.e. resin composite core without fiber post (group 1), fiber post No.3 with resin composite core (group 2) and fiber post No.3 accessory 2 fiber posts No.0 with resin composite core (group 3)}. Elastic modulus and Poisson’s ratio of materials were selected from literatures. The models were loaded by the average fracture resistances load of each groups (group 1: 361.80 N, group 2: 559.46 N, group 3: 468.48 N) at 135 degree angulation in respect to the longitudinal axis of the teeth. The stress analysis and experimental confirm that fracture zone is at dentin area. To estimate ultimate tensile strength of dentin, trial and error of ultimate tensile strength were tested to obtain factor of safety (FOS) equal to 1.00. The result reveals that ultimate tensile strength of dentin of group 1, 2, 3 are 38.89, 30.96, 37.19 MPa, respectively.

Electronically conducting hybrid material as high performance catalyst support for electrocatalytic application

NASA Astrophysics Data System (ADS)

Rajesh, B.; Ravindranathan Thampi, K.; Bonard, J.-M.; Mathieu, H. J.; Xanthopoulos, N.; Viswanathan, B.

The electronically conducting hybrid material based on transition metal oxide and conducting polymer has been used as the catalyst support for Pt nanoparticles. The Pt nanoparticles loaded hybrid organic (polyaniline)-inorganic (vanadium pentoxide) composite has been used as the electrode material for methanol oxidation, a reaction of importance for the development of direct methanol fuel cells (DMFC). The hybrid material exhibited excellent electrochemical and thermal stability in comparison to the physical mixture of conducting polymer and transition metal oxide. The Pt nanoparticles loaded hybrid material exhibited high electrocatalytic activity and stability for methanol oxidation in comparison to the Pt supported on the Vulcan XC 72R carbon support. The higher activity and stability is attributed to the better CO tolerance of the composite material.

SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

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

Wang, Yingyong; Jin, Guoqiang; Tong, Xili

2011-11-15

Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: {yields} SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. {yields} The dopped MCM-41 materials show a wormhole-like mesoporous structure. {yields} The thermal stability of the dopped materials have an increment of almost 100 {sup o}C compared with the pure MCM-41. {yields} The hydrothermal stability of the dopped materials is also bettermore » than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N{sub 2} physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 {sup o}C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.« less

Amine–Oxide Hybrid Materials for CO 2 Capture from Ambient Air

DOE PAGES

Didas, Stephanie A.; Choi, Sunho; Chaikittisilp, Watcharop; ...

2015-09-10

Oxide supports functionalized with amine moieties have been used for decades as catalysts and chromatographic media. Owing to the recognized impact of atmospheric CO 2 on global climate change, the study of the use of amine-oxide hybrid materials as CO 2 sorbents has exploded in the past decade. While the majority of the work has concerned separation of CO 2 from dilute mixtures such as flue gas from coal-fired power plants, it has been recognized by us and others that such supported amine materials are also perhaps uniquely suited to extract CO 2 from ultradilute gas mixtures, such as ambientmore » air. As unique, low temperature chemisorbents, they can operate under ambient conditions, spontaneously extracting CO 2 from ambient air, while being regenerated under mild conditions using heat or the combination of heat and vacuum. This Account describes the evolution of our activities on the design of amine-functionalized silica materials for catalysis to the design, characterization, and utilization of these materials in CO 2 separations. New materials developed in our laboratory, such as hyperbranched aminosilica materials, and previously known amine-oxide hybrid compositions, have been extensively studied for CO 2 extraction from simulated ambient air (400 ppm of CO 2). The role of amine type and structure (molecular, polymeric), support type and structure, the stability of the various compositions under simulated operating conditions, and the nature of the adsorbed CO 2 have been investigated in detail. The requirements for an effective, practical air capture process have been outlined and the ability of amine-oxide hybrid materials to meet these needs has been discussed. Ultimately, the practicality of such a “direct air capture” process is predicated not only on the physicochemical properties of the sorbent, but also how the sorbent operates in a practical process that offers a scalable gas-solid contacting strategy. In conclusion, the utility of low pressure drop monolith contactors is suggested to offer a practical mode of amine sorbent/air contacting for direct air capture.« less

Amine–Oxide Hybrid Materials for CO 2 Capture from Ambient Air

DOE PAGES

Didas, Stephanie A.; Choi, Sunho; Chaikittisilp, Watcharop; ...

2015-09-10

CONSPECTUS: Oxide supports functionalized with amine moieties have been used for decades as catalysts and chromatographic media. Owing to the recognized impact of atmospheric CO2 on global climate change, the study of the use of amine-oxide hybrid materials as CO2 sorbents has exploded in the past decade. While the majority of the work has concerned separation of CO2 from dilute mixtures such as flue gas from coal-fired power plants, it has been recognized by us and others that such supported amine materials are also perhaps uniquely suited to extract CO2 from ultradilute gas mixtures, such as ambient air. As unique,more » low temperature chemisorbents, they can operate under ambient conditions, spontaneously extracting CO2 from ambient air, while being regenerated under mild conditions using heat or the combination of heat and vacuum. This Account describes the evolution of our activities on the design of amine-functionalized silica materials for catalysis to the design, characterization, and utilization of these materials in CO2 separations. New materials developed in our laboratory, such as hyperbranched aminosilica materials, and previously known amine-oxide hybrid compositions, have been extensively studied for CO2 extraction from simulated ambient air (400 ppm of CO2). The role of amine type and structure (molecular, polymeric), support type and structure, the stability of the various compositions under simulated operating conditions, and the nature of the adsorbed CO2 have been investigated in detail. The requirements for an effective, practical air capture process have been outlined and the ability of amine−oxide hybrid materials to meet these needs has been discussed. Ultimately, the practicality of such a “direct air capture” process is predicated not only on the physicochemical properties of the sorbent, but also how the sorbent operates in a practical process that offers a scalable gas−solid contacting strategy. In this regard, the utility of low pressure drop monolith contactors is suggested to offer a practical mode of amine sorbent/air contacting for direct air capture.« less

Investigation of the Thermal Stability of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) Materials Proposed for Inert Matrix Fuel Applications.

PubMed

Hayes, John R; Grosvenor, Andrew P; Saoudi, Mouna

2016-02-01

Inert matrix fuels (IMF) consist of transuranic elements (i.e., Pu, Am, Np, Cm) embedded in a neutron transparent (inert) matrix and can be used to "burn up" (transmute) these elements in current or Generation IV nuclear reactors. Yttria-stabilized zirconia has been extensively studied for IMF applications, but the low thermal conductivity of this material limits its usefulness. Other elements can be used to stabilize the cubic zirconia structure, and the thermal conductivity of the fuel can be increased through the use of a lighter stabilizing element. To this end, a series of Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials has been synthesized via a co-precipitation reaction and characterized by multiple techniques (Nd was used as a surrogate for Am). The long-range and local structures of these materials were studied using powder X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy. Additionally, the stability of these materials over a range of temperatures has been studied by annealing the materials at 1100 and 1400 °C. It was shown that the Nd(x)Sc(y)Zr(1-x-y)O(2-δ) materials maintained a single cubic phase upon annealing at high temperatures only when both Nd and Sc were present with y ≥ 0.10 and x + y > 0.15.

Does artificial aging affect mechanical properties of CAD/CAM composite materials.

PubMed

Egilmez, Ferhan; Ergun, Gulfem; Cekic-Nagas, Isil; Vallittu, Pekka K; Lassila, Lippo V J

2018-01-01

The purpose of this study was to determine the flexural strength and Weibull characteristics of different CAD/CAM materials after different in vitro aging conditions. The specimens were randomly assigned to one of the six in vitro aging conditions: (1) water storage (37°C, 3 weeks), (2) boiling water (24h), (3) hydrochloric acid exposure (pH: 1.2, 24h), (4) autoclave treatment (134°C, 200kPa, 12h), (5) thermal cycling (5000 times, 5-55°C), (6) cyclic loading (100N, 50,000 cycles). No treatment was applied to the specimens in control group. Three-point bending test was used for the calculation of flexural strength. The reliability of the strength was assessed by Weibull distribution. Surface roughness and topography was examined by coherence scanning interferometry. Evaluated parameters were compared using the Kruskall-Wallis or Mann-Whitney U test. Water storage, autoclave treatment and thermal cycling significantly decreased the flexural strength of all materials (p<0.05), whereas HCl exposure or cyclic loading did not affect the properties (p>0.05). Weibull moduli of Cerasmart™ and Lava™ Ultimate were similar with control. Vita Enamic ® exhibited similar Weibull moduli in all aging groups except the HCl treated group (p>0.05). R a values of Cerasmart™ and Lava™ Ultimate were in the range of 0.053-0.088μm in the aged groups. However R a results of Vita Enamic ® were larger than 0.2μm. Flexural strength of newly developed restorative CAD/CAM materials was significantly decreased by artificial aging. Cyclic loading or HCl exposure does not affect to the flexural strength and structural reliability of Cerasmart™ and Lava™ Ultimate. Copyright © 2017 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.

Mechanical design of mussel byssus: material yield enhances attachment strength

PubMed

Bell; Gosline

1996-01-01

The competitive dominance of mussels in the wave-swept rocky intertidal zone is in part due to their ability to maintain a secure attachment. Mussels are tethered to the substratum by a byssus composed of numerous extracellular, collagenous threads secreted by the foot. Each byssal thread has three serially arranged parts: a corrugated proximal region, a smooth distal region and an adhesive plaque. This study examines the material and structural properties of the byssal threads of three mussel species: Mytilus californianus, M. trossulus, and M. galloprovincialis. Tensile tests in general reveal similar material properties among species: the proximal region has a lower initial modulus, a lower ultimate stress and a higher ultimate strain than the distal region. The distal region also yields at a stress well below its ultimate value. In whole thread tests, the proximal region and adhesive plaque are common sites of structural failure and are closely matched in strength, while the distal region appears to be excessively strong. We propose that the high strength of the distal region is the byproduct of a material designed to yield and extend before structural failure occurs. Experimental and theoretical evidence is presented suggesting that thread yield and extensibility provide two important mechanisms for increasing the overall attachment strength of the mussel: (1) the reorientation of threads towards the direction of applied load, and (2) the 'recruitment' of more threads into tension and the consequent distribution of applied load over a larger cross-sectional area, thereby reducing the stress on each thread. This distal region yield behavior is most striking for M. californianus and may be a key to its success in extreme wave-swept environments.

Stain susceptibility of composite and ceramic CAD/CAM blocks versus direct resin composites with different resinous matrices.

PubMed

Alharbi, Amal; Ardu, Stefano; Bortolotto, Tissiana; Krejci, Ivo

2017-04-01

To evaluate the stain susceptibility of CAD/CAM blocks and direct composite after long term exposure to various staining agents. 40 disk-shaped samples were fabricated from each of nine materials; six CAD/CAM (Vitablocs Mark II, Paradigm MZ100, Experimental Vita Hybrid Ceramic, Vita Enamic, Experimental Kerr and Lava Ultimate) and three direct composites (Filtek Supreme, Venus Diamond and Filtek Silorane). Samples were randomly divided into five groups (n = 8) according to different staining solutions (distilled water, tea, red wine, coffee and artificial saliva). Initial L*a*b* values were assessed using a calibrated digital spectrophotometer. Specimens were immersed in staining solutions and stored in an incubator at 37 °C for 120 days. L*a*b* values were assessed again and color change (∆E) was calculated as difference between recorded L*a*b* values. ANOVA, and Duncan test were used to identify differences between groups (α = 0.05). Significant differences in ∆E values were detected between materials (p = 0.000). Among all staining solutions, the highest ∆E value was observed with red wine. The new CAD/CAM blocks (Vita Enamic, Vita Hybrid Ceramic and Lava Ultimate) showed the highest resistance to staining compared to the MZ100 composite resin blocks. Filtek Silorane, a direct composite, showed high stain resistance values compared to CAD/CAM materials and other direct composites. Ceramic and composite CAD/CAM blocks had lower staining susceptibility than methacrylate based direct composite. Staining susceptibility of the new resin based CAD/CAM materials Vita Enamic and Lava Ultimate was comparable to feldspathic ceramic blocks (Vitablocs Mark II). Filtek Silorane showed promising results that were comparable to some CAD/CAM blocks.

Influence of Water Content on Pullout Behaviour of Geogrid

NASA Astrophysics Data System (ADS)

Chen, Rong; Song, Yang-yang; Hao, Dong-xue; Gao, Yu-cong

2017-06-01

The interaction between geogrid and soil is fundamental and crucial factor on safety and stability of geogrid-reinforced earth structure. Therefore, the interface index between geogrid and soil is of vital importance in the design of reinforced earth structures. The pullout behaviour of geogrid in soil is studied, an experimental investigation is conducted using geogrid in four groups of soil with 20%, 24%, 28%, 32% water contents, which correspond to normal stresses of 50, 100, 200 and 300 kPa respectively. The results indicate that the geogrid embedded in soil mainly represents pullout failure, and the ultimate pullout force is sensitive to water content. It decreases with the increase of the water content firstly. Besides, the water content influences the process of the pullout behaviour. The increase of water content leads to the ultimate pullout force soon.

40 CFR 86.412-78 - Maintenance instructions, submission to Administrator.

Code of Federal Regulations, 2010 CFR

2010-07-01

... systems. (2) Any revision to the maintenance instructions which will affect emissions shall be supplied to..., distributors, dealers, repair facilities, and ultimate purchasers. Any material not translated into the English...

Neural network modeling of conditions of destruction of wood plank based on measurements

NASA Astrophysics Data System (ADS)

Filkin, V.; Kaverzneva, T.; Lazovskaya, T.; Lukinskiy, E.; Petrov, A.; Stolyarov, O.; Tarkhov, D.

2016-11-01

The paper deals with the possibility of predicting the ultimate load breaking timber sample based on the loading force dependence on the deflection before destruction. Prediction of mechanical properties of wood is handicapped by complex anisotropic structures. The anisotropic nature of the material and, in a great measure, the random nature of wood grain local features defining moment of destruction lead to a significant dependence of the required load on the individual characteristics of a particular bar. The ultimate load is sought as a function of the coefficients of the neural network approximation of the loading force dependence on the deflection. For this purpose, a number of experiments on timber sample loading until the destruction is conducted. Modeling of the conditions of material destruction may provide the required safety control in building industry.

[Effect of moisture content on anaerobic methanization of municipal solid waste].

PubMed

Qu, Xian; He, Pin-Jing; Shao, Li-Ming; Bouchez, Théodore

2009-03-15

Biogas production, gas and liquid characteristics were investigated for comparing the effect of moisture content on methanization process of MSW with different compositions of food waste and cellulosic waste. Batch reactors were used to study the anaerobic methanization of typical Chinese and French municipal solid waste (MSW) and cellulosic waste with different moisture content, as 35%, field capacity (65%-70%), 80%, and saturated state (> 95%). The results showed that for the typical Chinese and French waste, which contained putrescible waste, the intermediate product, VFA, was diluted by high content of water, which helped to release the VFA inhibition on hydrolysis and methanization. Mass amount of methane was produced only when the moisture content of typical French waste was higher than 80%, while higher content of moisture was needed when the content of putrescible waste was higher in MSW, as > 95% for typical Chinese waste. Meanwhile the methane production rate and the ultimate cumulated methane production were increased when moisture content was leveled up. The ultimate cumulated methane production of the typical French waste with saturated state was 0.6 times higher than that of the waste with moisture content of 80%. For cellulosic waste, high moisture content of cellulosic materials contributed to increase the attachment area of microbes and enzyme on the surface of the materials, which enhance the waste hydrolysis and methanization. When the moisture content of the cellulosic materials increased from field capacity (65%) to saturated state (> 95%), the ultimate cumulated methane production increased for 3.8 times.

Mechanical and thermal stability of graphene and graphene-based materials

NASA Astrophysics Data System (ADS)

Galashev, A. E.; Rakhmanova, O. R.

2014-10-01

Graphene has rapidly become one of the most popular materials for technological applications and a test material for new condensed matter ideas. This paper reviews the mechanical properties of graphene and effects related to them that have recently been discovered experimentally or predicted theoretically or by simulation. The topics discussed are of key importance for graphene's use in integrated electronics, thermal materials, and electromechanical devices and include the following: graphene transformation into other sp^2 hybridization forms; stability to stretching and compression; ion-beam-induced structural modifications; how defects and graphene edges affect the electronic properties and thermal stability of graphene and related composites.

Investigation on mechanical properties of basalt composite fabrics (experiment study)

NASA Astrophysics Data System (ADS)

Talebi Mazraehshahi, H.; Zamani, H.

2010-06-01

To fully appreciate the role and application of composite materials to structures, correct understanding of mechanical behaviors required for selection of optimum material. Fabric reinforced composites are composed of a matrix that is reinforced with pliable fabric, glass fabric is most popular reinforcement for different application specially in aircraft structure, although other fabric material are also used. At this study new fabric material called basalt with epoxy resin introduced and mechanical behaviors of this material investigated from view point of testing. For this study two type of fabric with different thickness used. Comparison between this composite reinforcement with popular reinforcement as carbon, glass, kevlar performed. To determine mechanical properties of epoxy based basalt fabric following test procedure performed : 1). Tensile testing according to ASTM D3039 in 0° and 90° direction to find ultimate strength in tension and shear, modulus of elasticity, elangation and ultimate strain. 2). Compression testing according to EN 2850 ultimate compression strength and maximum deformation under compression loading. 3). Shear testing according to ASTM D3518-94 to find in plane shear response of polymer matrix composites materials. 4). Predict flexural properties of sandwich construction which manufactured from basalt facing with PVC foam core according to ASTM C393-94. Material strength properties must be based on enough tests of material to meet the test procedure specifications [1]. For this reason six specimens were manufactured for testing and the tests were performed on them using an INSTRON machine model 5582. In the study, the effect of percent of resin in basalt reinforced composite was investigated. Also the weights of the ballast based composites with different percent of resin were measured with conventional composites. As the weight is an important parameter in aerospace industry when the designer wants to replace one material with another, the effect of weight must be considered. Weight measurement showed that the replacement of glass fabric reinforcement with basalt fabric has little effect on weight. Investigation also shows that mechanical behavior of basalt fabric is higher than glass fabric. This is due to the excellent mechanical properties of the ballast fabric such as Young modulus and strength in compare with the glass fabric. Figure1 shows the samples which used for tensile testing in warp direction.

Understanding Environmental Stability of Two-Dimensional Materials and Extending Their Shelf Life by Surface Functionalization

NASA Astrophysics Data System (ADS)

Yang, Sijie

Since the discovery of graphene, two dimensional materials (2D materials) have become a focus of interest for material research due to their many unique physical properties embedded in their 2D structure. While they host many exciting potential applications, some of these 2D materials are subject to environmental instability issues induced by interaction between material and gas molecules in air, which poses a barrier to further application and manufacture. To overcome this, it is necessary to understand the origin of material instability and interaction with molecules commonly found in air, as well as developing a reproducible and manufacturing compatible method to post-process these materials to extend their lifetime. In this work, the very first investigation on environmental stability on Te containing anisotropic 2D materials such as GaTe and ZrTe 3 is reported. Experimental results have demonstrated that freshly exfoliated GaTe quickly deteriorate in air, during which the Raman spectrum, surface morphology, and surface chemistry undergo drastic changes. Environmental Raman spectroscopy and XPS measurements demonstrate that H2O molecules in air interact strongly on the surface while O2, N 2, and inert gases don't show any detrimental effects on GaTe surface. Moreover, the anisotropic properties of GaTe slowly disappear during the aging process. To prevent this gas/material interaction based surface transformation, diazonium based surface functionalization is adopted on these Te based 2D materials. Environmental Raman spectroscopy results demonstrate that the stability of functionalized Te based 2D materials exhibit much higher stability both in ambient and extreme conditions. Meanwhile, PL spectroscopy, angle resolved Raman spectroscopy, atomic force microscopy measurements confirm that many attractive physical properties of the material are not affected by surface functionalization. Overall, these findings unveil the degradation mechanism of Te based 2D materials as well as provide a way to significantly enhance their environmental stability through an inexpensive and reproducible surface chemical functionalization route.

Large-deflection-theory Analysis of the Effect of Web Initial Curvature on the Ultimate Strength of Steel Plate Girder

NASA Astrophysics Data System (ADS)

Kala, Jiří; Kala, Zdeněk

2011-09-01

The objective of the paper is to analyze the influence of initial imperfections on the behaviour of thin-walled girders welded of slender plate elements. In parallel with experiments, one of the ultimate load tests was computer modelled. In so doing, the girder was modelled, using the geometrically and materially non-linear variant of the shell finite element method, by the ANSYS program. The shape changing during loading process is often accompanying with sudden "snap-through" i. e. rapid curvature change.

Deformable Mirror Materials Issue Assessment

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

Rudd, R E

2008-05-27

It was a pleasure to speak with you and Dr. Olivier Guyon about your project to develop a coronagraph and in particular about materials science considerations in the development of the deformable mirror (DM) for the coronagraph. The coronagraph application will demand more of a DM than previous applications with regard to precision, and since the characterization and modeling tools are currently under development, you asked me to comment on materials issues that might impact the DM design and testing. I have not conducted research on this question, and my own research on modeling MEMS has not included DM systems.more » I am only in a position to discuss some general considerations that may help in developing a research plan for the DM system. As I understand it, the relevant points about the DM system are as follows. The DM surface needs to be positioned to less than 1 {angstrom} RMS of the desired shape, and be stable to 0.3 {angstrom} RMS for an hour. In the ultimate application in space the stability requirements may be greater. For example, the DM shape can be set using a bright star and then allow the coronagraph to be turned to a dim star to collect data for several hours, counting on the mirror shape to be stable. The DM is made of a polysilicon membrane coated with one or more metal layers for the reflective surface and actuated by 32x32 or 64x64 electrostatic actuators on the back side. The uncertainty in the position of any one actuator should be at the few-picometer level or less averaged over the 300-{micro}m region of the actuator. Currently, experiments are conducted that can characterize the surface shape to the 1 nm level, and it is anticipated that the experiments will be able to characterize the shape at the sub-Angstrom level but not in the immediate future. Regarding stability, under relatively large deformations (10's of nm), the DM mirror surface shows no hysteresis at the measurable nm level. Let me begin by saying that I am not aware of any article in the literature that directly assesses surface position stability at the sub-Angstrom level across 100's of microns of surface. Interferometry is typically used for precise metrology over areas this large, but not typically at the sub-Angstrom level. For the purpose of these comments, I assume that it will be possible to measure the precision of the mirror shape and stability at the requisite sub-Angstrom level at some point during the coronagraph development using interferometers or some other high-precision metrology technique. The hope is that the comments at this point may identify some potential issues that can be resolved early in the development to avoid costly surprises in the later stages.« less

Several vapor phase chemical treatments for dimensional stabilization of wood

Treesearch

H.M. Barnes; E.T. Choong; R.C. Mcllhenny

1969-01-01

A bench-scale system for the impregnation of wood with volatile compounds was constructed for the purpose of testing the system concept and evaluating various polymeric bulking materials as dimensional stabilizing agents. Provisions were incorporated for recycling the treating material, introduction of two separate materials alternately or simultaneously, timed-cycle...

LABORATORY STUDIES ON THE STABILITY AND TRANSPORT OF INORGANIC COLLOIDS THROUGH NATURAL AQUIFER MATERIAL

EPA Science Inventory

The stability and transport of radio-labeled Fe2O3 particles were studied using laboratory batch and column techniques. Core material collected from shallow sand and gravel aquifer was used as the immobile column matrix material. Variables in the study included flow rate, pH, i...

Role of anisotropy in determining stability of electrodeposition at solid-solid interfaces

DOE PAGES

Ahmad, Zeeshan; Viswanathan, Venkatasubramanian

2017-10-24

Here, we investigate the stability of electrodeposition at solid-solid interfaces for materials exhibiting an anisotropic mechanical response. The stability of electrodeposition or resistance to the formation of dendrites is studied within a linear stability analysis. The deformation and stress equations are solved using the Stroh formalism and faithfully recover the boundary conditions at the interface. The stability parameter is used to quantify the stability of different solid-solid interfaces incorporating the full anisotropy of the elastic tensor of the two materials. Our results show a high degree of variability in the stability parameter depending on the crystallographic orientation of the solidsmore » in contact, and point to opportunities for exploiting this effect in developing Li metal anodes.« less

Design of advanced beams considering elasto-plastic behaviour of material

NASA Astrophysics Data System (ADS)

Tolun, S.

1992-10-01

The paper proposes a computational procedure for precise calculation of limit and ultimate or design loads, which must be carried by an advanced aviation beam, without permanent distortion and without rupture. Among several stress-strain curve representations, one that is suitable for a particular material is chosen for applied loads, yield, and failure load calculations, and then nonlinear analysis is performed.

Site Directed Nucleation and Growth of Ceramic Films on Metallic Surfaces

DTIC Science & Technology

2009-04-30

ceramics and other nanoscale composite materials research with the ultimate goal being the cell-free, nanocrystalline assembly of adaptive bioceramic...for high temperature or high wear environments. Other applications/technology developments for this research include adaptive materials, wear...bound vesicles that form the surface membrane of gastropod nacre. 19 Folia formation was observed by recovering titanium and aluminum disc implants

Lodgepole pine bole wood density 1 and 11 years after felling in central Montana

Treesearch

Duncan C. Lutes; Colin C. Hardy

2013-01-01

Estimates of large dead and down woody material biomass are used for evaluating ecological processes and making ecological assessments, such as for nutrient cycling, wildlife habitat, fire effects, and climate change science. Many methods are used to assess the abundance (volume) of woody material, which ultimately require an estimate of wood density to convert volume...

Towards the Ultimate Multi-Junction Solar Cell using Transfer Printing

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

Lumb, Matthew P.; Meitl, Matt; Schmieder, Kenneth J.

2016-11-21

Transfer printing is a uniquely enabling technology for the heterogeneous integration of III-V materials grown on dissimilar substrates. In this paper, we present experimental results for a mechanically stacked tandem cell using GaAs and GaSb-based materials capable of harvesting the entire solar spectrum with 44.5% efficiency. We also present the latest results toward developing an ultra-high performance heterogeneous cell, integrating materials grown on GaAs, InP and GaSb platforms.

Tuning critical failure with viscoelasticity: How aftershocks inhibit criticality in an analytical mean field model of fracture.

NASA Astrophysics Data System (ADS)

Baro Urbea, J.; Davidsen, J.

2017-12-01

The hypothesis of critical failure relates the presence of an ultimate stability point in the structural constitutive equation of materials to a divergence of characteristic scales in the microscopic dynamics responsible of deformation. Avalanche models involving critical failure have determined universality classes in different systems: from slip events in crystalline and amorphous materials to the jamming of granular media or the fracture of brittle materials. However, not all empirical failure processes exhibit the trademarks of critical failure. As an example, the statistical properties of ultrasonic acoustic events recorded during the failure of porous brittle materials are stationary, except for variations in the activity rate that can be interpreted in terms of aftershock and foreshock activity (J. Baró et al., PRL 2013).The rheological properties of materials introduce dissipation, usually reproduced in atomistic models as a hardening of the coarse-grained elements of the system. If the hardening is associated to a relaxation process the same mechanism is able to generate temporal correlations. We report the analytic solution of a mean field fracture model exemplifying how criticality and temporal correlations are tuned by transient hardening. We provide a physical meaning to the conceptual model by deriving the constitutive equation from the explicit representation of the transient hardening in terms of a generalized viscoelasticity model. The rate of 'aftershocks' is controlled by the temporal evolution of the viscoelastic creep. At the quasistatic limit, the moment release is invariant to rheology. Therefore, the lack of criticality is explained by the increase of the activity rate close to failure, i.e. 'foreshocks'. Finally, the avalanche propagation can be reinterpreted as a pure mathematical problem in terms of a stochastic counting process. The statistical properties depend only on the distance to a critical point, which is universal for any parametrization of the transient hardening and a whole category of fracture models.

Shape memory polyurethanes with oxidation-induced degradation: In vivo and in vitro correlations for endovascular material applications.

PubMed

Weems, Andrew C; Wacker, Kevin T; Carrow, James K; Boyle, Anthony J; Maitland, Duncan J

2017-09-01

The synthesis of thermoset shape memory polymer (SMP) polyurethanes from symmetric, aliphatic alcohols and diisocyanates has previously demonstrated excellent biocompatibility in short term in vitro and in vivo studies, although long term stability has not been investigated. Here we demonstrate that while rapid oxidation occurs in these thermoset SMPs, facilitated by the incorporation of multi-functional, branching amino groups, byproduct analysis does not indicate toxicological concern for these materials. Through complex multi-step chemical reactions, chain scission begins from the amines in the monomeric repeat units, and results, ultimately, in the formation of carboxylic acids, secondary and primary amines; the degradation rate and product concentrations were confirmed using liquid chromatography mass spectrometry, in model compound studies, yielding a previously unexamined degradation mechanism for these biomaterials. The rate of degradation is dependent on the hydrogen peroxide concentration, and comparison of explanted samples reveals a much slower rate in vivo compared to the widely accepted literature in vitro real-time equivalent of 3% H 2 O 2 . Cytotoxicity studies of the material surface, and examination of the degradation product accumulations, indicate that degradation has negligible impact on cytotoxicity of these materials. This paper presents an in-depth analysis on the degradation of porous, shape memory polyurethanes (SMPs), including traditional surface characterization as well as model degradation compounds with absolute quantification. This combination of techniques allows for determination of rates of degradation as well as accumulation of individual degradation products. These behaviors are used for in vivo-in vitro comparisons for determination of real time degradation rates. Previous studies have primarily been limited to surface characterization without examination of degradation products and accumulation rates. To our knowledge, our work presents a unique example where a range of material scales (atomistic-scale model compounds along with macroscopic porous SMPs) are used in conjunction with ex planted samples for calculation of degradation rates and toxicological risk. Copyright © 2017 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Evaluation of five CAD/CAM materials by microstructural characterization and mechanical tests: a comparative in vitro study.

PubMed

Sonmez, Nesrin; Gultekin, Pinar; Turp, Volkan; Akgungor, Gokhan; Sen, Deniz; Mijiritsky, Eitan

2018-01-08

Polymer infiltrated ceramics and nano-ceramic resins are the new restorative materials which have been developed in order to enhance the adverse properties of glass-matrix ceramics and resin composites. The aim of the present in vitro study was to evaluate the characteristics of various CAD/CAM materials through mechanical, microstructural, and SEM analysis. Five test groups (n = 22) were formed by using the indicated CAD/CAM blocks: VITA Enamic (VITA Zahnfabrik), Lava Ultimate (3 M ESPE), IPS e.max CAD (Ivoclar Vivadent), IPS Empress CAD (Ivoclar Vivadent), and VITA Mark II (VITA Zahnfabrik). Two specimens from each test group were used for XRD and EDS analysis. Remaining samples were divided into two subgroups (n = 10). One subgroup specimens were thermocycled (5 °C to 55 °C, 30s, 10,000 cycles) whereas the other were not. All of the specimens were evaluated in terms of flexural strength, Vickers hardness, and fracture toughness. Results were statistically analyzed using two-way ANOVA, one-way ANOVA, Tukey's HSD, and Student's t tests (α = .05). Fractured specimens were evaluated using SEM. The highest Vickers microhardness value was found for VITA Mark II (p < .001), however flexural strength and fracture toughness results were lowest conversely (p < .05). IPS e.max CAD was found to have the highest flexural strength (p < .001). Fracture toughness of IPS e.max CAD was also higher than other tested block materials (p < .001). Lava Ultimate and VITA Enamic's mechanical properties were affected negatively from thermocycling (p < .05). Microhardness, flexural strength, and fracture toughness values of Lava Ultimate and VITA Enamic were found to be similar to VITA Mark II and IPS Empress CAD groups. It should be realised that simulated aging process seem to affect ceramic-polymer composite materials more significantly than glass ceramics.

Crohn's Disease Variants of Nod2 Are Stabilized by the Critical Contact Region of Hsp70.

PubMed

Schaefer, Amy K; Wastyk, Hannah C; Mohanan, Vishnu; Hou, Ching-Wen; Lauro, Mackenzie L; Melnyk, James E; Burch, Jason M; Grimes, Catherine L

2017-08-29

Nod2 is a cytosolic, innate immune receptor responsible for binding to bacterial cell wall fragments such as muramyl dipeptide (MDP). Upon binding, subsequent downstream activation of the NF-κB pathway leads to an immune response. Nod2 mutations are correlated with an increased susceptibility to Crohn's disease (CD) and ultimately result in a misregulated immune response. Previous work had demonstrated that Nod2 interacts with and is stabilized by the molecular chaperone Hsp70. In this work, it is shown using purified protein and in vitro biochemical assays that the critical Nod2 CD mutations (G908R, R702W, and 1007fs) preserve the ability to bind bacterial ligands. A limited proteolysis assay and luciferase reporter assay reveal regions of Hsp70 that are capable of stabilizing Nod2 and rescuing CD mutant activity. A minimal 71-amino acid subset of Hsp70 that stabilizes the CD-associated variants of Nod2 and restores a proper immune response upon activation with MDP was identified. This work suggests that CD-associated Nod2 variants could be stabilized in vivo with a molecular chaperone.

Phenomenally High Transduction Air/gas Transducers for Practical Non-Contact Ultrasonic Applications

NASA Astrophysics Data System (ADS)

Bhardwaj, Mahesh C.

2009-03-01

Based on novel acoustic impedance matching layers and high coupling piezoelectric materials this paper describes exceptionally high air/gas transduction ultrasonic transducers. By providing applications oriented performance of these transducers we also usher in the era of much desired Non-Contact Ultrasound (NCU) testing and analysis of a wide range of materials including early stage formation of materials such as uncured composite prepregs, green ceramics and powder metals, plastics, elastomers, porous, hygroscopic, chemically bonded and other materials. Besides quality control, ultimately NCU offers timely opportunities for cost-effective materials production, energy savings, and environment protection.

The biomechanical strength of a hardware-free femoral press-fit method for ACL bone-tendon-bone graft fixation.

PubMed

Arnold, M P; Burger, L D; Wirz, D; Goepfert, B; Hirschmann, M T

2017-04-01

The purpose was to investigate graft slippage and ultimate load to failure of a femoral press-fit fixation technique for anterior cruciate ligament (ACL) reconstruction. Nine fresh-frozen knees were used. Standardized harvesting of the B-PT-B graft was performed. The femora were cemented into steel rods, and a tunnel was drilled outside-in into the native ACL footprint and expanded using a manual mill bit. The femoral bone block was fixed press-fit. To pull the free end of the graft, it was fixed to a mechanical testing machine using a deep-freezing technique. A motion capture system was used to assess three-dimensional micro-motion. After preconditioning of the graft, 1000 cycles of tensile loading were applied. Finally, an ultimate load to failure test was performed. Graft slippage in mm ultimate load to failure as well as type of failure was noted. In six of the nine measured specimens, a typical pattern of graft slippage was observed during cyclic loading. For technical reasons, the results of three knees had to be discarded. 78.6 % of total graft slippage occurred in the first 100 cycles. Once the block had settled, graft slippage converged to zero, highlighting the importance of initial preconditioning of the graft in the clinical setting. Graft slippage after 1000 cycles varied around 3.4 ± 3.2 mm (R = 1.3-9.8 mm) between the specimens. Ultimate loading (n = 9) revealed two characteristic patterns of failure. In four knees, the tendon ruptured, while in five knees the bone block was pulled out of the femoral tunnel. The median ultimate load to failure was 852 N (R = 448-1349 N). The implant-free femoral press-fit fixation provided adequate primary stability with ultimate load to failure pull forces at least equal to published results for interference screws; hence, its clinical application is shown to be safe.

Designer biomaterials for mechanobiology

NASA Astrophysics Data System (ADS)

Li, Linqing; Eyckmans, Jeroen; Chen, Christopher S.

2017-12-01

Biomaterials engineered with specific bioactive ligands, tunable mechanical properties and complex architecture have emerged as powerful tools to probe cell sensing and response to physical properties of their material surroundings, and ultimately provide designer approaches to control cell function.

40 CFR 63.1252 - Standards: General.

Code of Federal Regulations, 2011 CFR

2011-07-01

... that does not ultimately allow for recycling of material back to the PMPU. (D) Any control device for... have no effect on the production-indexed consumption factor for the PMPU. (4) The owner or operator may...

40 CFR 63.1252 - Standards: General.

Code of Federal Regulations, 2012 CFR

2012-07-01

... that does not ultimately allow for recycling of material back to the PMPU. (D) Any control device for... have no effect on the production-indexed consumption factor for the PMPU. (4) The owner or operator may...

40 CFR 63.1252 - Standards: General.

Code of Federal Regulations, 2014 CFR

2014-07-01

... that does not ultimately allow for recycling of material back to the PMPU. (D) Any control device for... have no effect on the production-indexed consumption factor for the PMPU. (4) The owner or operator may...

40 CFR 63.1252 - Standards: General.

Code of Federal Regulations, 2010 CFR

2010-07-01

... that does not ultimately allow for recycling of material back to the PMPU. (D) Any control device for... have no effect on the production-indexed consumption factor for the PMPU. (4) The owner or operator may...

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

Ahmad, Zeeshan; Viswanathan, Venkatasubramanian

Here, we investigate the stability of electrodeposition at solid-solid interfaces for materials exhibiting an anisotropic mechanical response. The stability of electrodeposition or resistance to the formation of dendrites is studied within a linear stability analysis. The deformation and stress equations are solved using the Stroh formalism and faithfully recover the boundary conditions at the interface. The stability parameter is used to quantify the stability of different solid-solid interfaces incorporating the full anisotropy of the elastic tensor of the two materials. Our results show a high degree of variability in the stability parameter depending on the crystallographic orientation of the solidsmore » in contact, and point to opportunities for exploiting this effect in developing Li metal anodes.« less

Design and evaluation of foamed asphalt base materials.

DOT National Transportation Integrated Search

2013-05-01

Foamed asphalt stabilized base (FASB) combines reclaimed asphalt pavement (RAP), recycled : concrete (RC), and/or graded aggregate base (GAB) with a foamed asphalt binder to produce a : partially stabilized base material. The objectives of this study...

Design and evaluation of foamed asphalt base materials : [research summary].

DOT National Transportation Integrated Search

2013-05-01

Foamed asphalt stabilized base (FASB) combines reclaimed asphalt pavement (RAP), : recycled concrete (RC), and/or graded aggregate base (GAB) with a foamed asphalt : binder to produce a partially stabilized base material. Although widely used, most :...

DEMONSTRATION BULLETIN - SOLIDIFICATION/ STABILIZATION PROCESS, SOLIDTECH, INC.

EPA Science Inventory

The Soliditech solidification/stabilization technology mixes hazardous waste materials in soils or sludges with pozzolanic material (cement, fly ash, or kiln dust), a proprietary additive called Urrichem, other proprietary additives, and water. The process is designed to aid ...

Efficient first-principles prediction of solid stability: Towards chemical accuracy

NASA Astrophysics Data System (ADS)

Zhang, Yubo; Kitchaev, Daniil A.; Yang, Julia; Chen, Tina; Dacek, Stephen T.; Sarmiento-Pérez, Rafael A.; Marques, Maguel A. L.; Peng, Haowei; Ceder, Gerbrand; Perdew, John P.; Sun, Jianwei

2018-03-01

The question of material stability is of fundamental importance to any analysis of system properties in condensed matter physics and materials science. The ability to evaluate chemical stability, i.e., whether a stoichiometry will persist in some chemical environment, and structure selection, i.e. what crystal structure a stoichiometry will adopt, is critical to the prediction of materials synthesis, reactivity and properties. Here, we demonstrate that density functional theory, with the recently developed strongly constrained and appropriately normed (SCAN) functional, has advanced to a point where both facets of the stability problem can be reliably and efficiently predicted for main group compounds, while transition metal compounds are improved but remain a challenge. SCAN therefore offers a robust model for a significant portion of the periodic table, presenting an opportunity for the development of novel materials and the study of fine phase transformations even in largely unexplored systems with little to no experimental data.

High-Thermal- and Air-Stability Cathode Material with Concentration-Gradient Buffer for Li-Ion Batteries.

PubMed

Shi, Ji-Lei; Qi, Ran; Zhang, Xu-Dong; Wang, Peng-Fei; Fu, Wei-Gui; Yin, Ya-Xia; Xu, Jian; Wan, Li-Jun; Guo, Yu-Guo

2017-12-13

Delivery of high capacity with high thermal and air stability is a great challenge in the development of Ni-rich layered cathodes for commercialized Li-ion batteries (LIBs). Herein we present a surface concentration-gradient spherical particle with varying elemental composition from the outer end LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM) to the inner end LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA). This cathode material with the merit of NCM concentration-gradient protective buffer and the inner NCA core shows high capacity retention of 99.8% after 200 cycles at 0.5 C. Furthermore, this cathode material exhibits much improved thermal and air stability compared with bare NCA. These results provide new insights into the structural design of high-performance cathodes with high energy density, long life span, and storage stability materials for LIBs in the future.

Recycling of spent adsorbents for oxyanions and heavy metal ions in the production of ceramics.

PubMed

Verbinnen, Bram; Block, Chantal; Van Caneghem, Jo; Vandecasteele, Carlo

2015-11-01

Spent adsorbents for oxyanion forming elements and heavy metals are classified as hazardous materials and they are typically treated by stabilization/solidification before landfilling. The use of lime or cement for stabilization/solidification entails a high environmental impact and landfilling costs are high. This paper shows that mixing spent adsorbents in the raw material for the production of ceramic materials is a valuable alternative to stabilize oxyanion forming elements and heavy metals. The produced ceramics can be used as construction material, avoiding the high economic and environmental impact of stabilization/solidification followed by landfilling. To study the stabilization of oxyanion forming elements and heavy metals during the production process, two series of experiments were performed. In the first series of experiments, the main pollutant, Mo was adsorbed onto iron-based adsorbents, which were then mixed with industrial sludge (3 w/w%) and heated at 1100°C for 30 min. Mo was chosen, as this element is easily adsorbed onto iron-based adsorbents and it is the element that is the most difficult to stabilize (i.e. the highest temperatures need to be reached before the concentrations in the leachate are reduced). Leaching concentration from the 97/3 sludge/adsorbent mixture before heating ranged between 85 and 154 mg/kg; after the heating process they were reduced to 0.42-1.48 mg/kg. Mo was actually stabilized, as the total Mo concentration after addition was not affected by the heat treatment. In the second series of experiments, the sludge was spiked with other heavy metals and oxyanion forming elements (Cr, Ni, Cu, Zn, As, Cd and Pb) in concentrations 5 times higher than the initial concentrations; after heat treatment the leachate concentrations were below the regulatory limit values. The incorporation of spent adsorbents in ceramic materials is a valuable and sustainable alternative to the existing treatment methods, saving raw materials in the ceramics production process and avoiding the use of stabilizing agents. Besides, spent adsorbents added to the raw material for ceramic products, may improve their aesthetic and structural properties. Copyright © 2015 Elsevier Ltd. All rights reserved.

2004 research briefs :Materials and Process Sciences Center.

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

Cieslak, Michael J.

2004-01-01

This report is the latest in a continuing series that highlights the recent technical accomplishments associated with the work being performed within the Materials and Process Sciences Center. Our research and development activities primarily address the materials-engineering needs of Sandia's Nuclear-Weapons (NW) program. In addition, we have significant efforts that support programs managed by the other laboratory business units. Our wide range of activities occurs within six thematic areas: Materials Aging and Reliability, Scientifically Engineered Materials, Materials Processing, Materials Characterization, Materials for Microsystems, and Materials Modeling and Simulation. We believe these highlights collectively demonstrate the importance that a strong materials-sciencemore » base has on the ultimate success of the NW program and the overall DOE technology portfolio.« less

Dynamic Analysis of the Melanoma Model: From Cancer Persistence to Its Eradication

NASA Astrophysics Data System (ADS)

Starkov, Konstantin E.; Jimenez Beristain, Laura

In this paper, we study the global dynamics of the five-dimensional melanoma model developed by Kronik et al. This model describes interactions of tumor cells with cytotoxic T cells and respective cytokines under cellular immunotherapy. We get the ultimate upper and lower bounds for variables of this model, provide formulas for equilibrium points and present local asymptotic stability/hyperbolic instability conditions. Next, we prove the existence of the attracting set. Based on these results we come to global asymptotic melanoma eradication conditions via global stability analysis. Finally, we provide bounds for a locus of the melanoma persistence equilibrium point, study the case of melanoma persistence and describe conditions under which we observe global attractivity to the unique melanoma persistence equilibrium point.

Development of ultrastable filters and lasers for solar seismology

NASA Technical Reports Server (NTRS)

Rust, D. M.; Kunski, R.; Cohn, R. F.

1986-01-01

The Stable Solar Analyzer is a recently developed instrument for the measurement of solar magnetic fields and surface velocities that is being employed at the U.S. National Solar Observatory to study the subsurface convection cells of the sun and the structure of surface and subsurface magnetic fields. The Analyzer is expected to ultimately be flown aboard such spacecraft as the ESA/NASA Solar and Heliospheric Observatory. This instrument is based on a crystalline lithium niobate Fabry-Perot filter that is used in conjunction with a stabilized laser that furnishes an absolute wavelength reference; this laser Fabry-Perot combination has achieved wavelength stabilities of the order of 2 parts in 10 to the 10th, over a six-hour interval.

NETL- Severe Environment Corrosion Erosion Facility

ScienceCinema

None

2018-01-16

NETL's Severe Environment Corrosion Erosion Facility in Albany studies how new and old materials will stand up to new operating conditions. Work done in the lab supports NETL's oxy-fuel combustion oxidation work, refractory materials stability work, and the fuels program, in particular the hydrogen membrane materials stability work, to determine how best to upgrade existing power plants.

Current Methods for Modeling and Simulating Icing Effects on Aircraft Performance, Stability and Control

NASA Technical Reports Server (NTRS)

Ralvasky, Thomas P.; Barnhart, Billy P.; Lee, Sam

2008-01-01

Icing alters the shape and surface characteristics of aircraft components, which results in altered aerodynamic forces and moments caused by air flow over those iced components. The typical effects of icing are increased drag, reduced stall angle of attack, and reduced maximum lift. In addition to the performance changes, icing can also affect control surface effectiveness, hinge moments, and damping. These effects result in altered aircraft stability and control and flying qualities. Over the past 80 years, methods have been developed to understand how icing affects performance, stability and control. Emphasis has been on wind tunnel testing of two-dimensional subscale airfoils with various ice shapes to understand their effect on the flow field and ultimately the aerodynamics. This research has led to wind tunnel testing of subscale complete aircraft models to identify the integrated effects of icing on the aircraft system in terms of performance, stability, and control. Data sets of this nature enable pilot in the loop simulations to be performed for pilot training, or engineering evaluation of system failure impacts or control system design.

Selective simplification and reinforcement of microbial community in autothermal thermophilic aerobic digestion to enhancing stabilization process of sewage sludge by conditioning with ferric nitrate.

PubMed

Jin, Ningben; Shou, Zongqi; Yuan, Haiping; Lou, Ziyang; Zhu, Nanwen

2016-03-01

The effect of ferric nitrate on microbial community and enhancement of stabilization process for sewage sludge was investigated in autothermal thermophilic aerobic digestion. The disinhibition of volatile fatty acids (VFA) was obtained with alteration of individual VFA concentration order. Bacterial taxonomic identification by 454 high-throughput pyrosequencing found the dominant phylum Proteobacteria in non-dosing group was converted to phylum Firmicutes in dosing group after ferric nitrate added and simplification of bacteria phylotypes was achieved. The preponderant Tepidiphilus sp. vanished, and Symbiobacterium sp. and Tepidimicrobium sp. were the most advantageous phylotypes with conditioning of ferric nitrate. Consequently, biodegradable substances in dissolved organic matters increased, which contributed to the favorable environment for microbial metabolism and resulted in acceleration of sludge stabilization. Ultimately, higher stabilization level was achieved as ratio of soluble chemical oxygen demand to total chemical oxygen demand (TCOD) decreased while TCOD reduced as well in dosing group comparing to non-dosing group. Copyright © 2016 Elsevier Ltd. All rights reserved.

Current Methods Modeling and Simulating Icing Effects on Aircraft Performance, Stability, Control

NASA Technical Reports Server (NTRS)

Ratvasky, Thomas P.; Barnhart, Billy P.; Lee, Sam

2010-01-01

Icing alters the shape and surface characteristics of aircraft components, which results in altered aerodynamic forces and moments caused by air flow over those iced components. The typical effects of icing are increased drag, reduced stall angle of attack, and reduced maximum lift. In addition to the performance changes, icing can also affect control surface effectiveness, hinge moments, and damping. These effects result in altered aircraft stability and control and flying qualities. Over the past 80 years, methods have been developed to understand how icing affects performance, stability, and control. Emphasis has been on wind-tunnel testing of two-dimensional subscale airfoils with various ice shapes to understand their effect on the flowfield and ultimately the aerodynamics. This research has led to wind-tunnel testing of subscale complete aircraft models to identify the integrated effects of icing on the aircraft system in terms of performance, stability, and control. Data sets of this nature enable pilot-in-the-loop simulations to be performed for pilot training or engineering evaluation of system failure impacts or control system design.

Dynamical Stability and Evolution of Kepler’s compact inner multi-planet systems

NASA Astrophysics Data System (ADS)

Pu, Bonan

2017-06-01

NASA’s Kepler mission has revealed a population of highly compact inner multi-planet systems. These systems, typically consisting of 4-6 super-Earths, feature tight orbital spacing between planets as well as low orbital inclinations (~2 deg. ) and eccentricities (~2%). This stands in contrast to Kepler’s singles population, which appears to feature higher orbital obliquities and eccentricities, as well as a lower transit timing variation fraction indicative of lower true planet multiplicities.In this talk, I will present some previous and ongoing research aimed at understanding the dynamical evolution of these Kepler systems. First, I will present numerical N-body investigations on the long-term stability of multi-planet systems, the results of which suggest that Kepler’s systems are near the edge of stability. Next, I will discuss some current research on the dynamics of planetary close encounters and collisions, and their implications for the ultimate fate of dynamically unstable multi-planet systems. Finally, I will highlight some recent results on the dynamical stability and evolution of inner multi-planet systems when they are accompanied by external giant planet and/or stellar companions.

The ultimate disposition of depleted uranium

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

Not Available

1990-12-01

Significant amounts of the depleted uranium (DU) created by past uranium enrichment activities have been sold, disposed of commercially, or utilized by defense programs. In recent years, however, the demand for DU has become quite small compared to quantities available, and within the US Department of Energy (DOE) there is concern for any risks and/or cost liabilities that might be associated with the ever-growing inventory of this material. As a result, Martin Marietta Energy Systems, Inc. (Energy Systems), was asked to review options and to develop a comprehensive plan for inventory management and the ultimate disposition of DU accumulated atmore » the gaseous diffusion plants (GDPs). An Energy Systems task team, under the chairmanship of T. R. Lemons, was formed in late 1989 to provide advice and guidance for this task. This report reviews options and recommends actions and objectives in the management of working inventories of partially depleted feed (PDF) materials and for the ultimate disposition of fully depleted uranium (FDU). Actions that should be considered are as follows. (1) Inspect UF{sub 6} cylinders on a semiannual basis. (2) Upgrade cylinder maintenance and storage yards. (3) Convert FDU to U{sub 3}O{sub 8} for long-term storage or disposal. This will include provisions for partial recovery of costs to offset those associated with DU inventory management and the ultimate disposal of FDU. Another recommendation is to drop the term tails'' in favor of depleted uranium'' or DU'' because the tails'' label implies that it is waste.'' 13 refs.« less

Method for determining asphaltene stability of a hydrocarbon-containing material

DOEpatents

Schabron, John F; Rovani, Jr., Joseph F

2013-02-05

A method for determining asphaltene stability in a hydrocarbon-containing material having solvated asphaltenes therein is disclosed. In at least one embodiment, it involves the steps of: (a) precipitating an amount of the asphaltenes from a liquid sample of the hydrocarbon-containing material with an alkane mobile phase solvent in a column; (b) dissolving a first amount and a second amount of the precipitated asphaltenes by changing the alkane mobile phase solvent to a final mobile phase solvent having a solubility parameter that is higher than the alkane mobile phase solvent; (c) monitoring the concentration of eluted fractions from the column; (d) creating a solubility profile of the dissolved asphaltenes in the hydrocarbon-containing material; and (e) determining one or more asphaltene stability parameters of the hydrocarbon-containing material.

Mechanical performance and parameter sensitivity analysis of 3D braided composites joints.

PubMed

Wu, Yue; Nan, Bo; Chen, Liang

2014-01-01

3D braided composite joints are the important components in CFRP truss, which have significant influence on the reliability and lightweight of structures. To investigate the mechanical performance of 3D braided composite joints, a numerical method based on the microscopic mechanics is put forward, the modeling technologies, including the material constants selection, element type, grid size, and the boundary conditions, are discussed in detail. Secondly, a method for determination of ultimate bearing capacity is established, which can consider the strength failure. Finally, the effect of load parameters, geometric parameters, and process parameters on the ultimate bearing capacity of joints is analyzed by the global sensitivity analysis method. The results show that the main pipe diameter thickness ratio γ, the main pipe diameter D, and the braided angle α are sensitive to the ultimate bearing capacity N.

Disentangling controls on mineral-stabilized soil organic matter using a slurry incubation

NASA Astrophysics Data System (ADS)

Lavallee, J. M.; Cotrufo, M. F.; Paul, E. A.; Conant, R. T.

2014-12-01

Mineral-stabilized organic matter (OM) is the largest and oldest pool of soil carbon and nitrogen. Mineral stabilization limits OM availability to soil microbes, preventing its decomposition and prolonging its turnover. Thus, understanding controls on the decomposition of mineral-stabilized OM is key to understanding soil carbon and nitrogen dynamics. The very slow turnover of mineral-stabilized OM makes it challenging to study in a typical incubation, and as a result, many potential controls (temperature, OM chemistry, and mineralogy) on its turnover remain unclear. We aimed to better understand controls on decomposition of mineral-stabilized OM by employing a slurry incubation technique, which speeds up microbial processing of OM by maximizing OM accessibility to microbes. In a slurry incubation, we expect that any OM that is not stabilized on mineral surfaces will be available for decomposition and will be converted to CO2. Using this technique, we studied the interactive effects of incubation temperature, plant material type (aboveground vs. belowground), and soil fraction (silt vs. clay) on CO2 efflux and OM stabilization. We separated silt-sized and clay-sized fractions from an agricultural soil, added aboveground or belowground plant material to each, and incubated them at 15°C, 25°C and 35°C. The added plant material was isotopically labeled (13C and 15N), which allowed us to trace it through the system and distinguish between the responses of the new (derived from the plant material) and old (derived from what was already present in the silt and clay) OM to warming. We measured CO2 efflux and 13CO2 efflux throughout the incubation. We performed one short-term harvest at day 6 and one final harvest at day 60. Initial results show higher cumulative CO2 efflux at warmer temperatures regardless of plant material type or soil fraction. A larger fraction of that CO2 came from OM that was initially present in the silt and clay, rather than from the plant material that we added, which suggests faster turnover of that "old" OM at warmer temperatures. We will present CO2 efflux data in addition to total [C] and [N] and the isotopic ratios of 13C and 15N in the silt and clay at each harvest to explain how the interactions between warming, plant material type and soil fraction affect turnover of mineral stabilized OM.

Finite Element Analysis and Biomechanical Comparison of Short Posterior Spinal Instrumentation with Divergent Bridge Construct versus Parallel Tension Band Construct for Thoracolumbar Spine Fractures

PubMed Central

Ouellet, Jean A.; Richards, Corey; Sardar, Zeeshan M.; Giannitsios, Demetri; Noiseux, Nicholas; Strydom, Willem S.; Reindl, Rudy; Jarzem, Peter; Arlet, Vincent; Steffen, Thomas

2013-01-01

The ideal treatment for unstable thoracolumbar fractures remains controversial with posterior reduction and stabilization, anterior reduction and stabilization, combined posterior and anterior reduction and stabilization, and even nonoperative management advocated. Short segment posterior osteosynthesis of these fractures has less comorbidities compared with the other operative approaches but settles into kyphosis over time. Biomechanical comparison of the divergent bridge construct versus the parallel tension band construct was performed for anteriorly destabilized T11–L1 spine segments using three different models: (1) finite element analysis (FEA), (2) a synthetic model, and (3) a human cadaveric model. Outcomes measured were construct stiffness and ultimate failure load. Our objective was to determine if the divergent pedicle screw bridge construct would provide more resistance to kyphotic deforming forces. All three modalities showed greater stiffness with the divergent bridge construct. The FEA calculated a stiffness of 21.6 N/m for the tension band construct versus 34.1 N/m for the divergent bridge construct. The synthetic model resulted in a mean stiffness of 17.3 N/m for parallel tension band versus 20.6 N/m for the divergent bridge (p = 0.03), whereas the cadaveric model had an average stiffness of 15.2 N/m in the parallel tension band compared with 18.4 N/m for the divergent bridge (p = 0.02). Ultimate failure load with the cadaveric model was found to be 622 N for the divergent bridge construct versus 419 N (p = 0.15) for the parallel tension band construct. This study confirms our clinical experience that the short posterior divergent bridge construct provides greater stiffness for the management of unstable thoracolumbar fractures. PMID:24436856

Dimensional Stability of Grout-Type Materials Used as Connections for Prefabricated Bridge Elements

DOT National Transportation Integrated Search

2016-05-01

The research presented in this report focuses on addressing performance concerns related to dimensional stability (primarily early age shrinkage) of 11 commercially available grout-type materials. Some of these grouts, especially those classified as ...

Structural evaluation of asphalt pavements with full-depth reclaimed base.

DOT National Transportation Integrated Search

2012-12-01

Currently, MnDOT pavement design recommends granular equivalency, GE = 1.0 for non-stabilized full-depth : reclamation (FDR) material, which is equivalent to class 5 material. For stabilized full-depth reclamation (SFDR), : there was no guideline for...

Synthetic Covalent and Non-Covalent 2D Materials.

PubMed

Boott, Charlotte E; Nazemi, Ali; Manners, Ian

2015-11-16

The creation of synthetic 2D materials represents an attractive challenge that is ultimately driven by their prospective uses in, for example, electronics, biomedicine, catalysis, sensing, and as membranes for separation and filtration. This Review illustrates some recent advances in this diverse field with a focus on covalent and non-covalent 2D polymers and frameworks, and self-assembled 2D materials derived from nanoparticles, homopolymers, and block copolymers. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Environmental effects on composite airframes: A study conducted for the ARM UAV Program (Atmospheric Radiation Measurement Unmanned Aerospace Vehicle)

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

Noguchi, R.A.

1994-06-01

Composite materials are affected by environments differently than conventional airframe structural materials are. This study identifies the environmental conditions which the composite-airframe ARM UAV may encounter, and discusses the potential degradation processes composite materials may undergo when subjected to those environments. This information is intended to be useful in a follow-on program to develop equipment and procedures to prevent, detect, or otherwise mitigate significant degradation with the ultimate goal of preventing catastrophic aircraft failure.

ASTM METHODS

EPA Science Inventory

ASTM is a not-for-profit organization that provides a forum for producers, users, ultimate consumers, and those having a general interest (representatives of government and academia) to meet on common ground and write standards for materials, products, systems, and services. From...

77 FR 65220 - Certain Licensees Requesting Unescorted Access to Radioactive Material; Order Imposing...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-25

... of Section A of this attachment, in making a determination whether to approve and certify the... will ultimately be the decision of the licensee's Reviewing Official to determine whether an individual...

Light Transmission of Novel CAD/CAM Materials and Their Influence on the Degree of Conversion of a Dual-curing Resin Cement.

PubMed

Egilmez, Ferhan; Ergun, Gulfem; Cekic-Nagas, Isil; Vallittu, Pekka K; Lassila, Lippo V J

To evaluate the light transmission characteristics of different types, shades, and thicknesses of novel CAD/CAM materials and their effect on the degree of conversion (DC) of a dual-curing resin cement. Square specimens (12 × 12 mm2) of three CAD/CAM materials - GC Cerasmart, Lava Ultimate, Vita Enamic - of different thicknesses (1.00, 1.50, and 2.00 mm, n = 5 per thickness) were irradiated with an LED unit. The amount of transmitted light was quantified. Thereafter, the DC% of the dual-curing resin cement (RelyX Ultimate) was recorded after 15 min using Fourier transform infrared spectroscopy. Statistical analysis was performed using two-way ANOVA followed by the Tukey's HSD post-hoc test at a significance level of p < 0.05. Regression analysis was performed to investigate the correlation between the DC and radiant energy, and the DC and thickness. Although the type and shade of CAD/CAM material significantly affect transmitted light irradiation (p < 0.0001), degrees of conversion are similar when the CAD/CAM material or material shade were taken into consideration (p > 0.05). Conversely, material thickness significantly affected light transmission (p < 0.0001) and DC (p < 0.0001). Multiple effects of material, shade, and thickness did not significantly affect the evaluated parameters (p = 0.638 for light irradiation; p = 0.637 for DC). Linear regression analysis showed a correlation between delivered energy and DC% results of the Vita Enamic (R² = 0.4169, p < 0.0001). Reduced light transmission in 2-mm-thick specimens of all CAD/CAM materials indicates that proper curing of the cement beneath CAD/CAM materials should be ensured.

Method for removing hydrocarbon contaminants from solid materials

DOEpatents

Bala, Gregory A.; Thomas, Charles P.

1995-01-01

A system for removing hydrocarbons from solid materials. Contaminated solids are combined with a solvent (preferably terpene based) to produce a mixture. The mixture is washed with water to generate a purified solid product (which is removed from the system) and a drainage product. The drainage product is separated into a first fraction (consisting mostly of contaminated solvent) and a second fraction (containing solids and water). The first fraction is separated into a third fraction (consisting mostly of contaminated solvent) and a fourth fraction (containing residual solids and water). The fourth fraction is combined with the second fraction to produce a sludge which is separated into a fifth fraction (containing water which is ultimately reused) and a sixth fraction (containing solids). The third fraction is then separated into a seventh fraction (consisting of recovered solvent which is ultimately reused) and an eighth fraction (containing hydrocarbon waste).

Method for removing hydrocarbon contaminants from solid materials

DOEpatents

Bala, G.A.; Thomas, C.P.

1995-10-03

A system is described for removing hydrocarbons from solid materials. Contaminated solids are combined with a solvent (preferably terpene based) to produce a mixture. The mixture is washed with water to generate a purified solid product (which is removed from the system) and a drainage product. The drainage product is separated into a first fraction (consisting mostly of contaminated solvent) and a second fraction (containing solids and water). The first fraction is separated into a third fraction (consisting mostly of contaminated solvent) and a fourth fraction (containing residual solids and water). The fourth fraction is combined with the second fraction to produce a sludge which is separated into a fifth fraction (containing water which is ultimately reused) and a sixth fraction (containing solids). The third fraction is then separated into a seventh fraction (consisting of recovered solvent which is ultimately reused) and an eighth fraction (containing hydrocarbon waste). 4 figs.

Lunar Resource Assessment: Strategies for Surface Exploration

NASA Technical Reports Server (NTRS)

Spudis, Paul D.

1992-01-01

Use of the indigenous resources of space to support long-term human presence is an essential element of the settlement of other planetary bodies. We are in a very early stage of understanding exactly how and under what circumstances space resources will become important. The materials and processes to recover them that we now think are critical may not ultimately be the raison d'etre for a resource utilization program. However, the need for strategic thinking proceeds in parallel with efforts to implement such plans and it is not too soon to begin thinking how we could and should use the abundant resources of materials and energy available from the Moon. The following commodities from the Moon are discussed: (1) bulk regolith, for shielding and construction on the lunar surface (ultimately for export to human-tended stations in Earth-Moon space), and (2) oxygen and hydrogen, for propellant and life support.

Apparatus for removing hydrocarbon contaminants from solid materials

DOEpatents

Bala, G.A.; Thomas, C.P.

1996-02-13

A system is described for removing hydrocarbons from solid materials. Contaminated solids are combined with a solvent (preferably terpene based) to produce a mixture. The mixture is washed with water to generate a purified solid product (which is removed from the system) and a drainage product. The drainage product is separated into a first fraction (consisting mostly of contaminated solvent) and a second fraction (containing solids and water). The first fraction is separated into a third fraction (consisting mostly of contaminated solvent) and a fourth fraction (containing residual solids and water). The fourth fraction is combined with the second fraction to produce a sludge which is separated into a fifth fraction (containing water which is ultimately reused) and a sixth fraction (containing solids). The third fraction is then separated into a seventh fraction (consisting of recovered solvent which is ultimately reused) and an eighth fraction (containing hydrocarbon waste). 4 figs.

Apparatus for removing hydrocarbon contaminants from solid materials

DOEpatents

Bala, Gregory A.; Thomas, Charles P.

1996-01-01

A system for removing hydrocarbons from solid materials. Contaminated solids are combined with a solvent (preferably terpene based) to produce a mixture. The mixture is washed with water to generate a purified solid product (which is removed from the system) and a drainage product. The drainage product is separated into a first fraction (consisting mostly of contaminated solvent) and a second fraction (containing solids and water). The first fraction is separated into a third fraction (consisting mostly of contaminated solvent) and a fourth fraction (containing residual solids and water). The fourth fraction is combined with the second fraction to produce a sludge which is separated into a fifth fraction (containing water which is ultimately reused) and a sixth fraction (containing solids). The third fraction is then separated into a seventh fraction (consisting of recovered solvent which is ultimately reused) and an eighth fraction (containing hydrocarbon waste).

Case study comparison of functional vs. organic stability approaches for assessing threat potential at closed landfills in the USA.

PubMed

O'Donnell, Sean T; Caldwell, Michael D; Barlaz, Morton A; Morris, Jeremy W F

2018-05-01

Municipal solid waste (MSW) landfills in the USA are regulated under Subtitle D of the Resource Conservation and Recovery Act (RCRA), which includes the requirement to protect human health and the environment (HHE) during the post-closure care (PCC) period. Several approaches have been published for assessment of potential threats to HHE. These approaches can be broadly divided into organic stabilization, which establishes an inert waste mass as the ultimate objective, and functional stability, which considers long-term emissions in the context of minimizing threats to HHE in the absence of active controls. The objective of this research was to conduct a case study evaluation of a closed MSW landfill using long-term data on landfill gas (LFG) production, leachate quality, site geology, and solids decomposition. Evaluations based on both functional and organic stability criteria were compared. The results showed that longer periods of LFG and leachate management would be required using organic stability criteria relative to an approach based on functional stability. These findings highlight the somewhat arbitrary and overly stringent nature of assigning universal stability criteria without due consideration of the landfill's hydrogeologic setting and potential environmental receptors. This supports previous studies that advocated for transition to a passive or inactive control stage based on a performance-based functional stability framework as a defensible mechanism for optimizing and ending regulatory PCC. Copyright © 2018 Elsevier Ltd. All rights reserved.

Opportunities for Nondestructive Evaluation: Quantitative Characterization (Postprint)

DTIC Science & Technology

2017-07-01

between the design and the as- manufactured and, ultimately, the as-maintained state. As this occurs with the article of interest being placed in...TESTING (STINFO COPY) AIR FORCE RESEARCH LABORATORY MATERIALS AND MANUFACTURING DIRECTORATE WRIGHT-PATTERSON AIR FORCE BASE, OH 45433-7750 AIR FORCE...MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY ACRONYM(S) Air Force Research Laboratory Materials and Manufacturing

Army Research Laboratory S&T Campaign Plans 2015-2035

DTIC Science & Technology

2014-09-01

addressing propagation effects, impact of wind noise on detection range and angular accuracy. Use of vector sensors is one approach for potential advances...for the future warfighter, such as new protective and responsive materials, sensors , and munitions. Polymer Chemistry explores the molecular-level...ultimately enable the design and development of novel materials, molecular sensors , and nanoscale machines that exploit the exceptional capabilities of

Site Directed Nucleation and Growth of Ceramic Films on Metallic Surfaces

DTIC Science & Technology

2009-04-30

the ultimate goal being the cell-free, nanocrystalline assembly of adaptive bioceramic material systems. The ability to control or determine the...applications/technology developments for this research include adaptive materials, wear-resistant coatings, and optical coatings and gratings, and many...by Checa et al., which identified lipid bound vesicles that form the surface membrane of gastropod nacre.19 Folia formation was observed by

Cellular Therapy to Obtain Rapid Endochondral Bone Formation

DTIC Science & Technology

2012-03-01

biological information and involves the development of a novel biomaterial that can safely house the cells expressing the bone inductive factor to... produce the new bone at which time the material is then selectively eliminated. Ultimately this system has significant applicability. Often bone graft must...hypothesis will provide a safe and efficacious material for the production of bone leading to reliable fracture healing, circumventing the need for

Development of zwitterionic sulfobetaine block copolymer conjugation strategies for reduced platelet deposition in respiratory assist devices.

PubMed

Malkin, Alexander D; Ye, Sang-Ho; Lee, Evan J; Yang, Xiguang; Zhu, Yang; Gamble, Lara J; Federspiel, William J; Wagner, William R

2018-02-09

Respiratory assist devices, that utilize ∼2 m 2 of hollow fiber membranes (HFMs) to achieve desired gas transfer rates, have been limited in their adoption due to such blood biocompatibility limitations. This study reports two techniques for the functionalization and subsequent conjugation of zwitterionic sulfobetaine (SB) block copolymers to polymethylpentene (PMP) HFM surfaces with the intention of reducing thrombus formation in respiratory assist devices. Amine or hydroxyl functionalization of PMP HFMs (PMP-A or PMP-H) was accomplished using plasma-enhanced chemical vapor deposition. The generated functional groups were conjugated to low molecular weight SB block copolymers with N-hydroxysuccinimide ester or siloxane groups (SBNHS or SBNHSi) that were synthesized using reversible addition fragmentation chain transfer polymerization. The modified HFMs (PMP-A-SBNHS or PMP-H-SBNHSi) showed 80-95% reduction in platelet deposition from whole ovine blood, stability under the fluid shear of anticipated operating conditions, and uninhibited gas exchange performance relative to non-modified HFMs (PMP-C). Additionally, the functionalization and SBNHSi conjugation technique was shown to reduce platelet deposition on polycarbonate and poly(vinyl chloride), two other materials commonly found in extracorporeal circuits. The observed thromboresistance and stability of the SB modified surfaces, without degradation of HFM gas transfer performance, indicate that this approach is promising for longer term pre-clinical testing in respiratory assist devices and may ultimately allow for the reduction of anticoagulation levels in patients being supported for extended periods. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2018. © 2018 Wiley Periodicals, Inc.

The Role of Minimally Invasive Plate Osteosynthesis in Rib Fixation: A Review

PubMed Central

Bemelman, Michael; van Baal, Mark; Yuan, Jian Zhang; Leenen, Luke

2016-01-01

More than a century ago, the first scientific report was published about fracture fixation with plates. During the 1950’s, open reduction and plate fixation for fractures were standardized by the founders of Arbeitsgemeinschaft für osteosynthesefragen/Association for the Study of Internal Fixation. Since the introduction of plate fixation for fractures, several plates and screws have been developed, all with their own characteristics. To accomplice more fracture stability, it was thought the bigger the plate, the better. The counter side was a compromised blood supply of the bone, often resulting in bone necrosis and ultimately delayed or non-union. With the search and development of new materials and techniques for fracture fixation, less invasive procedures have become increasingly popular. This resulted in the minimally invasive plate osteosynthesis (MIPO) technique for fracture fixation. With the MIPO technique, procedures could be performed with smaller incisions and thus with less soft tissue damage and a better preserved blood supply. The last 5 years rib fixation has become increasingly popular, rising evidence has become available suggesting that surgical rib fixation improves outcome of patients with a flail chest or isolated rib fractures. Many surgical approaches for rib fixation have been described in the old literature, however, most of these techniques are obscure nowadays. Currently mostly large incisions with considerable surgical insult are used to stabilize rib fractures. We think that MIPO deserves a place in the surgical treatment of rib fractures. We present the aspects of diagnosis, preoperative planning and operative techniques in regard to MIPO rib fixation. PMID:26889439

Mechanical characterization and structural analysis of recycled fiber-reinforced-polymer resin-transfer-molded beams

NASA Astrophysics Data System (ADS)

Tan, Eugene Wie Loon

1999-09-01

The present investigation was focussed on the mechanical characterization and structural analysis of resin-transfer-molded beams containing recycled fiber-reinforced polymers. The beams were structurally reinforced with continuous unidirectional glass fibers. The reinforcing filler materials consisted entirely of recycled fiber-reinforced polymer wastes (trim and overspray). The principal resin was a 100-percent dicyclo-pentadiene unsaturated polyester specially formulated with very low viscosity for resin transfer molding. Variations of the resin transfer molding technique were employed to produce specimens for material characterization. The basic materials that constituted the structural beams, continuous-glass-fiber-reinforced, recycled-trim-filled and recycled-overspray-filled unsaturated polyesters, were fully characterized in axial and transverse compression and tension, and inplane and interlaminar shear, to ascertain their strengths, ultimate strains, elastic moduli and Poisson's ratios. Experimentally determined mechanical properties of the recycled-trim-filled and recycled-overspray-filled materials from the present investigation were superior to those of unsaturated polyester polymer concretes and Portland cement concretes. Mechanical testing and finite element analyses of flexure (1 x 1 x 20 in) and beam (2 x 4 x 40 in) specimens were conducted. These structurally-reinforced specimens were tested and analyzed in four-point, third-point flexure to determine their ultimate loads, maximum fiber stresses and mid-span deflections. The experimentally determined load capacities of these specimens were compared to those of equivalent steel-reinforced Portland cement concrete beams computed using reinforced concrete theory. Mechanics of materials beam theory was utilized to predict the ultimate loads and mid-span deflections of the flexure and beam specimens. However, these predictions proved to be severely inadequate. Finite element (fracture propagation) analyses of the flexure and beam specimens were also performed. These progressive failure analyses more closely approximated flexural behavior under actual testing conditions by reducing the elastic moduli of elements that were considered to have partially or totally failed. Individual element failures were predicted using the maximum stress, Tsai-Hill and Tsai-Wu failure criteria. Excellent predictions of flexural behavior were attributed to the progressive failure analyses combined with an appropriate failure criterion, and the reliable input material properties that were generated.

Strain Rate and Anisotropic Microstructure Dependent Mechanical Behaviors of Silkworm Cocoon Shells

PubMed Central

Xu, Jun; Zhang, Wen; Gao, Xiang; Meng, Wanlin; Guan, Juan

2016-01-01

Silkworm cocoons are multi-layered composite structures comprised of high strength silk fiber and sericin, and their mechanical properties have been naturally selected to protect pupas during metamorphosis from various types of external attacks. The present study attempts to gain a comprehensive understanding of the mechanical properties of cocoon shell materials from wild silkworm species Antheraea pernyi under dynamic loading rates. Five dynamic strain rates from 0.00625 s-1 to 12.5 s-1 are tested to show the strain rate sensitivity of the cocoon shell material. In the meantime, the anisotropy of the cocoon shell is considered and the cocoon shell specimens are cut along 0°, 45° and 90° orientation to the short axis of cocoons. Typical mechanical properties including Young’s modulus, yield strength, ultimate strength and ultimate strain are extracted and analyzed from the stress-strain curves. Furthermore, the fracture morphologies of the cocoon shell specimens are observed under scanning electron microscopy to help understand the relationship between the mechanical properties and the microstructures of the cocoon material. A discussion on the dynamic strain rate effect on the mechanical properties of cocoon shell material is followed by fitting our experimental results to two previous models, and the effect could be well explained. We also compare natural and dried cocoon materials for the dynamic strain rate effect and interestingly the dried cocoon shells show better overall mechanical properties. This study provides a different perspective on the mechanical properties of cocoon material as a composite material, and provides some insight for bio-inspired engineering materials. PMID:26939063

Global neural dynamic surface tracking control of strict-feedback systems with application to hypersonic flight vehicle.

PubMed

Xu, Bin; Yang, Chenguang; Pan, Yongping

2015-10-01

This paper studies both indirect and direct global neural control of strict-feedback systems in the presence of unknown dynamics, using the dynamic surface control (DSC) technique in a novel manner. A new switching mechanism is designed to combine an adaptive neural controller in the neural approximation domain, together with the robust controller that pulls the transient states back into the neural approximation domain from the outside. In comparison with the conventional control techniques, which could only achieve semiglobally uniformly ultimately bounded stability, the proposed control scheme guarantees all the signals in the closed-loop system are globally uniformly ultimately bounded, such that the conventional constraints on initial conditions of the neural control system can be relaxed. The simulation studies of hypersonic flight vehicle (HFV) are performed to demonstrate the effectiveness of the proposed global neural DSC design.

APPLICATIONS ANALYSIS REPORT: SITE PROGRAM DEMONSTRATION TEST SOLIDITECH, INC. SOLIDIFICATION/ STABILIZATION PROCESS

EPA Science Inventory

This Applications Analysis Report evaluates the Soliditech, Inc., solidification/ stabilization process for the on-site treatment of waste materials. The Soliditech process mixes and chemically treats waste material with Urrichem (a proprietary reagent), additives, pozzolanic mat...

Linear Dimensional Stability of Irreversible Hydrocolloid Materials Over Time.

PubMed

Garrofé, Analía B; Ferrari, Beatriz A; Picca, Mariana; Kaplan, Andrea E

2015-12-01

The aim of this study was to evaluate the linear dimensional stability of different irreversible hydrocolloid materials over time. A metal mold was designed with custom trays made of thermoplastic sheets (Sabilex, sheets 0.125 mm thick). Perforations were made in order to improve retention of the material. Five impressions were taken with each of the following: Kromopan 100 (LASCOD) [AlKr], which has dimensional stability of 100 hours, and Phase Plus (ZHERMACK) [AlPh], which has dimensional stability of 48 hours. Standardized digital photographs were taken at different time intervals (0, 15, 30, 45, 60, 120 minutes; 12, 24 and 96 hours), using an "ad-hoc" device. The images were analyzed with software (UTHSCSA Image Tool) by measuring the distance between intersection of the lines previously made at the top of the mold. The results were analyzed by ANOVA for repeated measures. Initial and final values were (mean and standard deviation): AlKr: 16.44 (0.22) and 16.34 (0.11), AlPh: 16.40 (0.06) and 16.18 (0.06). Statistical evaluation showed significant effect of material and time factors. Under the conditions in this study, time significantly affects the linear dimensional stability of irreversible hydrocolloid materials. Sociedad Argentina de Investigación Odontológica.

Structural stability and energetics of grain boundary triple junctions in face centered cubic materials

NASA Astrophysics Data System (ADS)

Adlakha, I.; Solanki, K. N.

2015-03-01

We present a systematic study to elucidate the role of triple junctions (TJs) and their constituent grain boundaries on the structural stability of nanocrystalline materials. Using atomistic simulations along with the nudge elastic band calculations, we explored the atomic structural and thermodynamic properties of TJs in three different fcc materials. We found that the magnitude of excess energy at a TJ was directly related to the atomic density of the metal. Further, the vacancy binding and migration energetics in the vicinity of the TJ were examined as they play a crucial role in the structural stability of NC materials. The resolved line tension which takes into account the stress buildup at the TJ was found to be a good measure in predicting the vacancy binding tendency near the TJ. The activation energy for vacancy migration along the TJ was directly correlated with the measured excess energy. Finally, we show that the resistance for vacancy diffusion increased for TJs with larger excess stored energy and the defect mobility at some TJs is slower than their constituent GBs. Hence, our results have general implications on the diffusional process in NC materials and provide new insight into stabilizing NC materials with tailored TJs.

[Simultaneous determination of ten benzotriazole ultraviolet stabilizers in food contact plastic materials by solid phase extraction and ultra performance liquid chromatography with tandem mass spectrometry].

PubMed

Gou, Xinlei; Zhao, Xinying; Chi, Haitao; Gao, Xia; Zhou, Mingqiang; Liu, Weili

2015-06-01

A sensitive method was developed for the simultaneous determination of ten benzotriazole ultraviolet stabilizers in food contact plastic materials by ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The sample was extracted by methanol-dichloromethane, and purified by a C18 solid-phase extraction (SPE) column. The separation was performed by using water containing 0. 1% (v/v) formic acid and methanol as the mobile phases with gradient elution at a flow rate of 0. 3 mL/min. The electrospray ionization (ESI) source in positive ion mode was used for the analysis of the ten benzotriazole ultraviolet stabilizers in multiple reaction monitoring (MRM) mode. The results showed that the standard curves were obtained with good correlation coefficients (r2 > 0.996) in their linear concentration ranges. The limits of detection (LODs, S/N = 3) for the ten benzotriazole ultraviolet stabilizers were in the range of 0.6-1.6 µg/kg. The mean recoveries for the ten benzotriazole ultraviolet stabilizers at three spiked levels (low, medium and high) were 75.2%-85.3% with relative standard deviations of 1.0%-5.7%. Ten kinds of food contact plastic materials were tested, and 2,2'-methylenebis (6-(benzotriazol-2-yl)-4-tert-octylphenol) (UV-360) was found in a sample of polyethylene (PE) material. The method is accurate, simple, rapid and feasible for the simultaneous determination of benzotriazole ultraviolet stabilizers in food plastic materials.

Fiber-optic sensor applications in civil and geotechnical engineering

NASA Astrophysics Data System (ADS)

Habel, Wolfgang R.; Krebber, Katerina

2011-09-01

Different types of fiber-optic sensors based on glass or polymeric fibers are used to evaluate material behavior or to monitor the integrity and long-term stability of load-bearing structure components. Fiber-optic sensors have been established as a new and innovative measurement technology in very different fields, such as material science, civil engineering, light-weight structures, geotechnical areas as well as chemical and high-voltage substations. Very often, mechanical quantities such as deformation, strain or vibration are requested. However, measurement of chemical quantities in materials and structure components, such as pH value in steel reinforced concrete members also provides information about the integrity of concrete structures. A special fiber-optic chemical sensor for monitoring the alkaline state (pH value) of the cementitious matrix in steel-reinforced concrete structures with the purpose of early detection of corrosion-initiating factors is described. The paper presents the use of several fiber-optic sensor technologies in engineering. One example concerns the use of highly resolving concrete-embeddable fiber Fabry-Perot acoustic emission (AE) sensors for the assessment of the bearing behaviour of large concrete piles in existing foundations or during and after its installation. Another example concerns fiber Bragg grating (FBG) sensors attached to anchor steels (micro piles) to measure the strain distribution in loaded soil anchors. Polymer optical fibers (POF) can be — because of their high elasticity and high ultimate strain — well integrated into textiles to monitor their deformation behaviour. Such "intelligent" textiles are capable of monitoring displacement of soil or slopes, critical mechanical deformation in geotechnical structures (dikes, dams, and embankments) as well as in masonry structures during and after earthquakes.

Mesostructured nanomagnetic polyhedral oligomeric silsesquioxanes (POSS) incorporated with dithiol organic anchors for multiple pollutants capturing in wastewater.

PubMed

He, Hai-Bo; Li, Bin; Dong, Jun-Ping; Lei, Yun-Yi; Wang, Tian-Lin; Yu, Qiong-Wei; Feng, Yu-Qi; Sun, You-Bao

2013-08-28

A functionalizable organosiliceous hybrid magnetic material was facilely constructed by surface polymerization of octavinyl polyhedral oligomeric silsesquioxane (POSS) on the Fe3O4 nanoparticles. The resultant Fe3O4@POSS was identified as a mesoporous architecture with an average particle diameter of 20 nm and high specific surface area up to 653.59 m(2) g(-1). After it was tethered with an organic chain containing dithiol via thiol-ene addition reaction, the ultimate material (Fe3O4@POSS-SH) still have moderate specific area (224.20 m(2) g(-1)) with almost identical porous morphology. It turns out to be a convenient, efficient single adsorbent for simultaneous elimination of inorganic heavy metal ions and organic dyes in simulate multicomponent wastewater at ambient temperature. The Fe3O4@POSS-SH nanoparticles can be readily withdrawn from aqueous solutions within a few seconds under moderate magnetic field and exhibit good stability in strong acid and alkaline aqueous matrices. Contaminants-loaded Fe3O4@POSS-SH can be easily regenerated with either methanol-acetic acid (for organic dyes) or hydrochloric acid (for heavy metal ions) under ultrasonication. The renewed one keeps appreciable adsorption capability toward both heavy metal ions and organic dyes, the removal rate for any of the pollutants exceeds 92% to simulate wastewater with multiple pollutants after repeated use for 5 cycles. Beyond the environmental remediation function, thanks to the pendant vinyl groups, the Fe3O4@POSS derived materials rationally integrating distinct or versatile functions could be envisaged and consequently a wide variety of applications may emerge.

Do biodegradable magnesium alloy intramedullary interlocking nails prematurely lose fixation stability in the treatment of tibial fracture? A numerical simulation.

PubMed

Wang, Haosen; Hao, Zhixiu; Wen, Shizhu

2017-01-01

Intramedullary interlocking nailing is an effective technique used to treat long bone fractures. Recently, biodegradable metals have drawn increased attention as an intramedullary interlocking nailing material. In this study, numerical simulations were implemented to determine whether the degradation rate of magnesium alloy makes it a suitable material for manufacturing biodegradable intramedullary interlocking nails. Mechano-regulatory and bone-remodeling models were used to simulate the fracture healing process, and a surface corrosion model was used to simulate intramedullary rod degradation. The results showed that magnesium alloy intramedullary rods exhibited a satisfactory degradation rate; the fracture healed and callus enhancement was observed before complete dissolution of the intramedullary rod. Delayed magnesium degradation (using surface coating techniques) did not confer a significant advantage over the non-delayed degradation process; immediate degradation also achieved satisfactory healing outcomes. However, delayed degradation had no negative effect on callus enhancement, as it did not cause signs of stress shielding. To avoid risks of individual differences such as delayed union, delayed degradation is recommended. Although the magnesium intramedullary rod did not demonstrate rapid degradation, its ability to provide high fixation stiffness to achieve earlier load bearing was inferior to that of the conventional titanium alloy and stainless steel rods. Therefore, light physiological loads should be ensured during the early stages of healing to achieve bony healing; otherwise, with increased loading and degraded intramedullary rods, the fracture may ultimately fail to heal. Copyright © 2016 Elsevier Ltd. All rights reserved.

Propulsion Research at the Propulsion Research Center of the NASA Marshall Space Flight Center

NASA Technical Reports Server (NTRS)

Blevins, John; Rodgers, Stephen

2003-01-01

The Propulsion Research Center of the NASA Marshall Space Flight Center is engaged in research activities aimed at providing the bases for fundamental advancement of a range of space propulsion technologies. There are four broad research themes. Advanced chemical propulsion studies focus on the detailed chemistry and transport processes for high-pressure combustion, and on the understanding and control of combustion stability. New high-energy propellant research ranges from theoretical prediction of new propellant properties through experimental characterization propellant performance, material interactions, aging properties, and ignition behavior. Another research area involves advanced nuclear electric propulsion with new robust and lightweight materials and with designs for advanced fuels. Nuclear electric propulsion systems are characterized using simulated nuclear systems, where the non-nuclear power source has the form and power input of a nuclear reactor. This permits detailed testing of nuclear propulsion systems in a non-nuclear environment. In-space propulsion research is focused primarily on high power plasma thruster work. New methods for achieving higher thrust in these devices are being studied theoretically and experimentally. Solar thermal propulsion research is also underway for in-space applications. The fourth of these research areas is advanced energetics. Specific research here includes the containment of ion clouds for extended periods. This is aimed at proving the concept of antimatter trapping and storage for use ultimately in propulsion applications. Another activity in this involves research into lightweight magnetic technology for space propulsion applications.

In situ x-ray diffraction studies of a new LiMg{sub 0.125}Ni{sub 0.75}O{sub 2} cathode material

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

Yang, X.Q.; Sun, X.; McBreen, J.

A Synchrotron x-ray source was used for In Situ x-ray diffraction studies during charge on a new LiMg{sub 0.125}Ti{sub 0.125}Ni{sub 0.75} cathode material synthesized by FMC Corp. It had been demonstrated by Gao that this new material has superior thermal stability than LiNiO{sub 2} and LiCo{sub 0.2}Ni{sub 0.8}O{sub 2} at over-charged state. In this current paper, studies on the relationship between the structural changes and thermal stability at over-charged state for these materials are presented. For the first time, the thermal stability of these materials are related to their structural changes during charge, especially to the formation and lattice constantmore » change of a hexagonal phase (H3). The spectral evidence support the hypothesis that the improvement of thermal stability is obtained by suppressing the formation of H3 phase and reducing the shrinkage of its lattice constant c when charged above 4.3 V.« less

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

Wang, Hsiu-Wen; Daemen, Luke L.; Cheshire, Michael C.

It is generally believed that H 2O and OH - are the key species stabilizing and controlling amorphous calcium carbonate “polyamorph” forms, and may in turn control the ultimate crystallization products during synthesis and in natural systems. Yet, the locations and hydrogen-bonding network of these species in ACC have never been measured directly using neutron diffraction. We report a synthesis route that overcomes the existing challenges with respect to yield quantities and deuteration, both of which are critically necessary for high quality neutron studies.

Soil stabilization with recycled materials improves subgrade performance : research spotlight.

DOT National Transportation Integrated Search

2016-02-29

The use of recycled materials for subgrade stabilization can provide the support needed for construction vehicle loading and more typical long-term traffic loading. This is a particular need in Michigan due to the prevalence of weak subgrade soils. U...

Kohn Anomaly and Phase Stability in Group VB Transition Metals

DOE PAGES

Landa, Alexander; Soderlind, Per; Naumov, Ivan; ...

2018-03-26

In the periodic table, only a few pure metals exhibit lattice or magnetic instabilities associated with Fermi surface nesting, the classical examples being α-U and Cr. Whereas α-U displays a strong Kohn anomaly in the phonon spectrum that ultimately leads to the formation of charge density waves (CDWs), Cr is known for its nesting-induced spin density waves (SDWs). Recently, it has become clear that a pronounced Kohn anomaly and the corresponding softening in the elastic constants is also the key factor that controls structural transformations and mechanical properties in compressed group VB metals—materials with relatively high superconducting critical temperatures. Thismore » article reviews the current understanding of the structural and mechanical behavior of these metals under pressure with an introduction to the concept of the Kohn anomaly and how it is related to the important concept of Peierls instability. We review both experimental and theoretical results showing different manifestations of the Kohn anomaly in the transverse acoustic phonon mode TA (ξ00) in V, Nb, and Ta. Specifically, in V the anomaly triggers a structural transition to a rhombohedral phase, whereas in Nb and Ta it leads to an anomalous reduction in yield strength.« less

Kohn Anomaly and Phase Stability in Group VB Transition Metals

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

Landa, Alexander; Soderlind, Per; Naumov, Ivan

In the periodic table, only a few pure metals exhibit lattice or magnetic instabilities associated with Fermi surface nesting, the classical examples being α-U and Cr. Whereas α-U displays a strong Kohn anomaly in the phonon spectrum that ultimately leads to the formation of charge density waves (CDWs), Cr is known for its nesting-induced spin density waves (SDWs). Recently, it has become clear that a pronounced Kohn anomaly and the corresponding softening in the elastic constants is also the key factor that controls structural transformations and mechanical properties in compressed group VB metals—materials with relatively high superconducting critical temperatures. Thismore » article reviews the current understanding of the structural and mechanical behavior of these metals under pressure with an introduction to the concept of the Kohn anomaly and how it is related to the important concept of Peierls instability. We review both experimental and theoretical results showing different manifestations of the Kohn anomaly in the transverse acoustic phonon mode TA (ξ00) in V, Nb, and Ta. Specifically, in V the anomaly triggers a structural transition to a rhombohedral phase, whereas in Nb and Ta it leads to an anomalous reduction in yield strength.« less

Nanoscale Chemical Imaging of Zeolites Using Atom Probe Tomography.

PubMed

Weckhuysen, Bert Marc; Schmidt, Joel; Peng, Linqing; Poplawsky, Jonathan

2018-05-02

Understanding structure-composition-property relationships in zeolite-based materials is critical to engineering improved solid catalysts. However, this can be difficult to realize as even single zeolite crystals can exhibit heterogeneities spanning several orders of magnitude, with consequences for e.g. reactivity, diffusion as well as stability. Great progress has been made in characterizing these porous solids using tomographic techniques, though each method has an ultimate spatial resolution limitation. Atom Probe Tomography (APT) is the only technique so far capable of producing 3-D compositional reconstructions with sub-nm-scale resolution, and has only recently been applied to zeolite-based catalysts. Herein, we discuss the use of APT to study zeolites, including the critical aspects of sample preparation, data collection, assignment of mass spectral peaks including the predominant CO peak, the limitations of spatial resolution for the recovery of crystallographic information, and proper data analysis. All sections are illustrated with examples from recent literature, as well as previously unpublished data and analyses to demonstrate practical strategies to overcome potential pitfalls in applying APT to zeolites, thereby highlighting new insights gained from the APT method. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanophotonic enhanced quantum emitters

NASA Astrophysics Data System (ADS)

Li, Xin; Zhou, Zhang-Kai; Yu, Ying; Gather, Malte; Di Falco, Andrea

2017-08-01

Quantum dots are excellent solid-state quantum sources, because of their stability, their narrow spectral linewidth, and radiative lifetime in the range of 1ns. Most importantly, they can be integrated into more complex nanophononics devices, to realize high quality quantum emitters of single photons or entangled photon sources. Recent progress in nanotechnology materials and devices has opened a number of opportunities to increase, optimize and ultimately control the emission property of single quantum dot. In this work, we present an approach that combines the properties of quantum dots with the flexibility of light control offered by nanoplasmonics and metamaterials structuring. Specifically, we show the nanophotonic enhancement of two types of quantum dots devices. The quantum dots are inserted into optical-positioned micropillar cavities, or decorated on the facets of core-shell GaAs/AlGaAs nanowires, fabricated with a bottom-up approach. In both cases, the metallic nanofeatures, which are designed to control the emission and the polarization state of the emitted light, are realized via direct electron-beam-induced deposition. This approach permits to create three-dimensional features with nanometric resolution and positional accuracy, and does not require wet lithographic steps and previous knowledge of the exact spatial arrangement of the quantum devices.

Anti-biofouling 3D porous systems: the blend effect of oxazoline-based oligomers on chitosan scaffolds.

PubMed

Correia, Vanessa G; Coelho, Margarida; Barroso, Telma; Raje, Vivek P; Bonifácio, Vasco D B; Casimiro, Teresa; Pinho, Mariana G; Aguiar-Ricardo, Ana

2013-01-01

The production, characterization and anti-biofouling activity of 3D porous scaffolds combining different blends of chitosan and oxazoline-based antimicrobial oligomers is reported. The incorporation of ammonium quaternized oligo(2-oxazoline)s into the composition of the scaffold enhances the stability of the chitosan scaffold under physiological conditions as well as its ability to repel protein adsorption. The blended scaffolds showed mean pore sizes in the range of 18-32 μm, a good pore interconnectivity and high porosity, as well as a large surface area, ultimate key features for anti-biofouling applications. Bovine serum albumin (BSA) adhesion profiles showed that the composition of the scaffolds plays a critical role in the chitosan-oligooxazoline system. Oligobisoxazoline-enriched scaffolds (20% w/w, CB8020) decreased protein adsorption (BSA) by up to 70%. Moreover, 1 mg of CB8020 was able to kill 99.9% of Escherichia coli cells upon contact, demonstrating its potential as promising material for production of tailored non-fouling 3D structures to be used in the construction of novel devices with applications in the biomedical field and water treatment processes.

Structural phase transitions in monolayer molybdenum dichalcogenides

NASA Astrophysics Data System (ADS)

Choe, Duk-Hyun; Sung, Ha June; Chang, Kee Joo

2015-03-01

The recent discovery of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs) has provided opportunities to develop ultimate thin channel devices. In contrast to graphene, the existence of moderate band gap and strong spin-orbit coupling gives rise to exotic electronic properties which vary with layer thickness, lattice structure, and symmetry. TMDs commonly appear in two structures with distinct symmetries, trigonal prismatic 2H and octahedral 1T phases which are semiconducting and metallic, respectively. In this work, we investigate the structural and electronic properties of monolayer molybdenum dichalcogenides (MoX2, where X = S, Se, Te) through first-principles density functional calculations. We find a tendency that the semiconducting 2H phase is more stable than the metallic 1T phase. We show that a spontaneous symmetry breaking of 1T phase leads to various distorted octahedral (1T') phases, thus inducing a metal-to-semiconductor transition. We discuss the effects of carrier doping on the structural stability and the modification of the electronic structure. This work was supported by the National Research Foundation of Korea (NRF) under Grant No. NRF-2005-0093845 and Samsung Science and Technology Foundation under Grant No. SSTFBA1401-08.

Reactive composite compositions and mat barriers

DOEpatents

Langton, Christine A.; Narasimhan, Rajendran; Karraker, David G.

2001-01-01

A hazardous material storage area has a reactive multi-layer composite mat which lines an opening into which a reactive backfill and hazardous material are placed. A water-inhibiting cap may cover the hazardous material storage area. The reactive multi-layer composite mat has a backing onto which is placed an active layer which will neutralize or stabilize hazardous waste and a fronting layer so that the active layer is between the fronting and backing layers. The reactive backfill has a reactive agent which can stabilize or neutralize hazardous material and inhibit the movement of the hazardous material through the hazardous material storage area.

Structural stability of rubble-pile asteroids

NASA Astrophysics Data System (ADS)

Sharma, Ishan

2013-03-01

Granular aggregates, like fluids, do not admit all manners of shapes and rotation rates. It is hoped that an analysis of a suspected granular asteroid’s equilibrium shape and its structural stability will help confirm its rubble-pile nature, and, perhaps, even constrain the asteroid’s material parameters. Equilibrium shapes have been analyzed in the past by several investigators (Holsapple, K.A. [2001]. Icarus 154, 432-448; Harris, A.W., Fahnestock, E.G., Pravec, P. [2009]. Icarus 199, 310-318; Sharma, I., Jenkins, J.T., Burns, J.A. [2009]. Icarus 200, 304-322). Here, we extend the classical Lagrange-Dirichlet stability theorem to the case of self-gravitating granular aggregates. This stability test is then applied to probe the stability of several near-Earth asteroids, and explore the influence of material parameters such as internal friction angle and plastic bulk modulus. Finally, we consider their structural stability to close planetary encounters. We find that it is possible for asteroids to be stable to small perturbations, but unstable to strong and/or extended perturbations as experienced during close flybys. Conversely, assuming stability in certain situations, it is possible to estimate material properties of some asteroids like, for example, 1943 Anteros.

Effect of modifications in mineralized collagen fibril and extra-fibrillar matrix material properties on submicroscale mechanical behavior of cortical bone.

PubMed

Wang, Yaohui; Ural, Ani

2018-06-01

A key length scale of interest in assessing the fracture resistance of bone is the submicroscale which is composed of mineralized collagen fibrils (MCF) and extra-fibrillar matrix (EFM). Although the processes through which the submicroscale constituents of bone contribute to the fracture resistance in bone have been identified, the extent of the modifications in submicroscale mechanical response due to the changes in individual properties of MCFs and EFM has not been determined. As a result, this study aims to quantify the influence of individual MCF and EFM material property modifications on the mechanical behavior (elastic modulus, ultimate strength, and resistance to failure) of bone at the submicroscale using a novel finite element modeling approach that incorporate 3D networks of MCFs with three different orientations as well as explicit representation of EFM. The models were evaluated under tensile loading in transverse (representing MCF separation) and longitudinal (representing MCF rupture) directions. The results showed that the apparent elastic modulus at the submicroscale under both loading directions for all orientations was only affected by the change in the elastic modulus of MCFs. MCF separation and rupture strengths were mainly dependent on the ultimate strength of EFM and MCFs, respectively, with minimal influence of other material properties. The extent of damage during MCF separation increased with increasing ultimate strength of EFM and decreased with increasing fracture energy of EFM with minimal contribution from elastic modulus of MCFs. For MCF rupture, there was an almost one-to-one linear relationship between the percent change in fracture energy of MCFs and the percent change in the apparent submicroscale fracture energy. The ultimate strength and elastic modulus of MCFs had moderate to limited influence on the MCF rupture fracture energy. The results of this study quantified the extent of changes that may be seen in the energy dissipation processes during MCF rupture and separation relative to the changes in the individual constituents of the tissue. This new knowledge significantly contributes to improving the understanding of how the material property alterations at the submicroscale that can occur due to diseases, age-related changes, and treatments affect the fracture processes at larger length scales. Copyright © 2018 Elsevier Ltd. All rights reserved.

Color stability of esthetic restorative materials: a spectrophotometric analysis.

PubMed

Poggio, Claudio; Ceci, Matteo; Beltrami, Riccardo; Mirando, Maria; Wassim, Jaffal; Colombo, Marco

2016-12-01

Objective: The aim of this in vitro study was to evaluate the color stability of different restorative materials (one microfilled composite, one nanofilled composite, one nanohybrid composite and one Ormocer-based composite) after exposure to different staining solutions (coffee, coca-cola and red wine). Material and methods: All materials were polymerized into silicon rings (2 mm ×6 mm ×8 mm) to obtain specimens identical in size. Thirty cylindrical specimens of each material were prepared. They were immersed in staining solutions over a 28-day test period. A colorimetric evaluation according to the CIE L*a*b* system was performed by a blind trained operator at 7, 14, 21, 28 days of the staining process. The Shapiro-Wilk test and Kruskal-Wallis ANOVA were applied to assess significant differences among restorative materials. The paired t -test was applied to test which CIE L*a*b* parameters significantly changed after immersion in staining solutions. Results: All restorative materials showed clinically perceptible color differences after immersion in coffee. L* and b* values showed the highest variability. Coca cola and red wine did not influence the color stability for all restorative materials except for Filtek Supreme XTE. Conclusions: Coffee caused a significant color change in all types of tested composite resins. Filtek Supreme XTE demonstrated alone a staining susceptibility to red wine; no other significant differences among the materials were demonstrated. Long-term exposure to some food dyes (coffee in particular) can significantly affect the color stability of modern esthetic restorative materials regardless of materials' different composition.

Tuning of Thermal Stability in Layered Li(NixMnyCoz)O2.

PubMed

Zheng, Jiaxin; Liu, Tongchao; Hu, Zongxiang; Wei, Yi; Song, Xiaohe; Ren, Yang; Wang, Weidong; Rao, Mumin; Lin, Yuan; Chen, Zonghai; Lu, Jun; Wang, Chongmin; Amine, Khalil; Pan, Feng

2016-10-12

Understanding and further designing new layered Li(Ni x Mn y Co z )O 2 (NMC) (x + y + z = 1) materials with optimized thermal stability is important to rechargeable Li batteries (LIBs) for electrical vehicles (EV). Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co) 3 -O-Li 3-x' ): each O atom bonds with three transition metals (TM) from the TM-layer and three to zero Li from fully discharged to charged states from the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. The synergistic effect between Li vacancies and raised valence state of Ni during delithiation process can aggravate instability of oxygen, and oxygen coordinated with more nickel (especially with high valence state) in LSCU becomes more unstable at a fixed delithiation state. The Ni/Li mixing would decrease the thermal stability of the "Ni═Mn" group NMC materials but benefit the thermal stability of "Ni-rich" group, because the Ni in the Li layer would form 180° Ni-O-Ni super exchange chains in "Ni-rich" NMC materials. Mn and Co doping can tune the initial valence state of Ni, local coordination environment of oxygen, and the Ni/Li disorder, thus to tune the thermal stability directly.

Tuning of Thermal Stability in Layered Li(Ni x Mn y Co z )O 2

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

Zheng, Jiaxin; Liu, Tongchao; Hu, Zongxiang

2016-09-19

Understanding and further designing new layered Li(Ni xMn yCo z)O 2 (NMC) (x + y + z = 1) materials with optimized thermal stability is important to rechargeable Li batteries (LIBs) for electrical vehicles (EV). Using ab initio calculations combined with experiments, we clarified how the thermal stability of NMC materials can be tuned by the most unstable oxygen, which is determined by the local coordination structure unit (LCSU) of oxygen (TM(Ni, Mn, Co) 3-O-Li 3-x'): each O atom bonds with three transition metals (TM) from the TM-layer and three to zero Li from fully discharged to charged states frommore » the Li-layer. Under this model, how the lithium content, valence states of Ni, contents of Ni, Mn, and Co, and Ni/Li disorder to tune the thermal stability of NMC materials by affecting the sites, content, and the release temperature of the most unstable oxygen is proposed. The synergistic effect between Li vacancies and raised valence state of Ni during delithiation process can aggravate instability of oxygen, and oxygen coordinated with more nickel (especially with high valence state) in LSCU becomes more unstable at a fixed delithiation state. The Ni/Li mixing would decrease the thermal stability of the “NiMn” group NMC materials but benefit the thermal stability of “Ni-rich” group, because the Ni in the Li layer would form 180° Ni-O-Ni super exchange chains in “Ni-rich” NMC materials. Mn and Co doping can tune the initial valence state of Ni, local coordination environment of oxygen, and the Ni/Li disorder, thus to tune the thermal stability directly.« less

NOx Sensor Development

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

Woo, L Y; Glass, R S

NO{sub x} compounds, specifically NO and NO{sub 2}, are pollutants and potent greenhouse gases. Compact and inexpensive NO{sub x} sensors are necessary in the next generation of diesel (CIDI) automobiles to meet government emission requirements and enable the more rapid introduction of more efficient, higher fuel economy CIDI vehicles. Because the need for a NO{sub x} sensor is recent and the performance requirements are extremely challenging, most are still in the development phase. Currently, there is only one type of NO{sub x} sensor that is sold commercially, and it seems unlikely to meet more stringent future emission requirements. Automotive exhaustmore » sensor development has focused on solid-state electrochemical technology, which has proven to be robust for in-situ operation in harsh, high-temperature environments (e.g., the oxygen stoichiometric sensor). Solid-state sensors typically rely on yttria-stabilized zirconia (YSZ) as the oxygen-ion conducting electrolyte and then target different types of metal or metal-oxide electrodes to optimize the response. Electrochemical sensors can be operated in different modes, including amperometric (a current is measured) and potentiometric (a voltage is measured), both of which employ direct current (dc) measurements. Amperometric operation is costly due to the electronics necessary to measure the small sensor signal (nanoampere current at ppm NO{sub x} levels), and cannot be easily improved to meet the future technical performance requirements. Potentiometric operation has not demonstrated enough promise in meeting long-term stability requirements, where the voltage signal drift is thought to be due to aging effects associated with electrically driven changes, both morphological and compositional, in the sensor. Our approach involves impedancemetric operation, which uses alternating current (ac) measurements at a specified frequency. The approach is described in detail in previous reports and several publications. Briefly, impedancemetric operation has shown the potential to overcome the drawbacks of other approaches, including higher sensitivity towards NO{sub x}, better long-term stability, potential for subtracting out background interferences, total NO{sub x} measurement, and lower cost materials and operation. Past LLNL research and development efforts have focused on characterizing different sensor materials and understanding complex sensing mechanisms. Continued effort has led to improved prototypes with better performance, including increased sensitivity (to less than 5 ppm) and long-term stability, with more appropriate designs for mass fabrication, including incorporation of an alumina substrate with an imbedded heater. Efforts in the last year to further improve sensor robustness have led to successful engine dynamometer testing with prototypes mounted directly in the engine manifold. Previous attempts had required exhaust gases to be routed into a separate furnace for testing due to mechanical failure of the sensor from engine vibrations. A more extensive cross-sensitivity study was also undertaken this last year to examine major noise factors including fluctuations in water, oxygen, and temperature. The quantitative data were then used to develop a strategy using numerical algorithms to improve sensor accuracy. The ultimate goal is the transfer of this technology to a supplier for commercialization. Due to the recent economic downturn, suppliers are demanding more comprehensive data and increased performance analysis before committing their resources to take the technology to market. Therefore, our NO{sub x} sensor work requires a level of technology development more thorough and extensive than ever before. The objectives are: (1) Develop an inexpensive, rapid-response, high-sensitivity and selective electrochemical sensor for oxides of nitrogen (NO{sub x}) for compression-ignition, direct-injection (CIDI) exhaust gas monitoring; (2) Explore and characterize novel, effective sensing methodologies based on impedance measurements and designs and manufacturing methods that could be compatible with mass fabrication; and (3) Collaborate with industry in order to (ultimately) transfer the technology to a supplier for commercialization.« less

Select geotechnical properties of a lime stabilized expansive soil amended with bagasse ash and coconut shell powder

NASA Astrophysics Data System (ADS)

James, Jijo; Pandian, P. Kasinatha

2018-03-01

Lime stabilization has been and still is one of the most preferred methods for stabilization of expansive soils. However, in the recent times, utilization of solid waste materials in soil stabilization has gained prominence as an effective means to manage wastes generated from various sources. In this work, an attempt has been made to utilize waste materials from two sources as auxiliary additives to lime in the stabilization of an expansive soil. Bagasse ash (BA), a waste by-product from the sugar industry and Coconut shell powder (CSP), a processed waste obtained from left over coconut shells of oil extraction industry were used as auxiliary additives. An expansive soil obtained from a local field was subjected to chemical, mineral, microstructural and geotechnical characterization in the laboratory and stabilized using 3% lime. The waste materials were subjected to chemical, mineral and microstructural characterization. The stabilization process was amended with four different contents viz. 0.25%, 0.5%, 1% and 2% of BA and CSP separately and the effect of the amendment was studied on the unconfined compressive strength (UCS), plasticity, swell-shrink and microstructural characteristics of the expansive soil. The results of the study indicated that BA amendment of lime stabilization performed better than CSP in improving the UCS, plasticity, swell-shrink and microstructure of the lime stabilized expansive soil.

Solidification/Stabilization Resource Guide

EPA Pesticide Factsheets

This Solidification/Stabilization Resource Guide is intended to inform site cleanup managers of recently-published materials such as field reports and guidance documents that address issues relevant to solidification/stabilization technologies.

Material Processing Facility - Skylab Experiment M512

NASA Technical Reports Server (NTRS)

1972-01-01

This chart details Skylab's Materials Processing Facility experiment (M512). This facility, located in the Multiple Docking Adapter, was developed for Skylab and accommodated 14 different experiments that were carried out during the three marned missions. The abilities to melt and mix without the contaminating effects of containers, to suppress thermal convection and buoyancy in fluids, and to take advantage of electrostatic and magnetic forces and otherwise masked by gravitation opened the way to new knowledge of material properties and processes. This beginning would ultimately lead to the production of valuable new materials for use on Earth.

Uv-Light Stabilization Additive Package For Solar Cell Module And Laminated Glass Applications

DOEpatents

Hanoka, Jack I.; Klemchuk, Peter P.

2002-03-05

An ultraviolet light stabilization additive package is used in an encapsulant material that may be used in solar cell modules, laminated glass and a variety of other applications. The ultraviolet light stabilization additive package comprises a first hindered amine light stabilizer and a second hindered amine light stabilizer. The first hindered amine light stabilizer provides thermal oxidative stabilization, and the second hindered amine light stabilizer providing photo-oxidative stabilization.

Experimental Design for Evaluation of Co-extruded Refractory Metal/Nickel Base Superalloy Joints

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

ME Petrichek

2005-12-16

Prior to the restructuring of the Prometheus Program, the NRPCT was tasked with delivering a nuclear space reactor. Potential NRPCT nuclear space reactor designs for the Prometheus Project required dissimilar materials to be in contact with each other while operating at extreme temperatures under irradiation. As a result of the high reactor core temperatures, refractory metals were the primary candidates for many of the reactor structural and cladding components. They included the tantalum-base alloys ASTAR-811C and Ta-10W, the niobium-base alloy FS-85, and the molybdenum base alloys Moly 41-47.5 Rhenium. The refractory metals were to be joined to candidate nickel basemore » alloys such as Haynes 230, Alloy 617, or Nimonic PE 16 either within the core if the nickel-base alloys were ultimately selected to form the outer core barrel, or at a location exterior to the core if the nickel-base alloys were limited to components exterior to the core. To support the need for dissimilar metal joints in the Prometheus Project, a co-extrusion experiment was proposed. There are several potential methods for the formation of dissimilar metal joints, including explosive bonding, friction stir welding, plasma spray, inertia welding, HIP, and co-extrusion. Most of these joining methods are not viable options because they result in the immediate formation of brittle intermetallics. Upon cooling, intermetallics form in the weld fusion zone between the joined metals. Because brittle intermetallics do not form during the initial bonding process associated with HIP, co-extrusion, and explosive bonding, these three joining procedures are preferred for forming dissimilar metal joints. In reference to a Westinghouse Astronuclear Laboratory report done under a NASA sponsored program, joints that were fabricated between similar materials via explosive bonding had strengths that were directly affected by the width of the diffusion barrier. It was determined that the diffusion zone should not exceed a critical thickness (0.0005 in.). A diffusion barrier that exceeded this thickness would likely fail. The joint fabrication method must therefore mechanically bond the two materials causing little or no interdiffusion upon formation. Co-extrusion fits this description since it forms a mechanical joint between two materials by using heat and pressure. The two materials to be extruded are first assembled and sealed within a co-extrusion billet which is subsequently heated and then extruded through a die. For a production application, once the joint is formed, it is dejacketed to remove the outer canister. The remaining piece consists of two materials bonded together with a thin diffusion barrier. Therefore, the long-term stability of the joint is determined primarily by the kinetics of interdiffusion reaction between the two materials. An experimental design for co-extrusion of refractory metals and nickel-based superalloys was developed to evaluate this joining process and determine the long-term stability of the joints.« less

Double polymer sheathed carbon nanotube supercapacitors show enhanced cycling stability

NASA Astrophysics Data System (ADS)

Zhao, Wenqi; Wang, Shanshan; Wang, Chunhui; Wu, Shiting; Xu, Wenjing; Zou, Mingchu; Ouyang, An; Cao, Anyuan; Li, Yibin

2015-12-01

Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices.Pseudo-materials are effective in boosting the specific capacitance of supercapacitors, but during service their degradation may also be very strong, causing reduced cycling stability. Here, we show that a carbon nanotube sponge grafted by two conventional pseudo-polymer layers in sequence can serve as a porous supercapacitor electrode with significantly enhanced cycling stability compared with single polymer grafting. Creating conformal polymer coatings on the nanotube surface and the resulting double-sheath configuration are important structural factors leading to the enhanced performance. Combining different polymers as double sheaths as reported here might be a potential route to circumvent the dilemma of pseudo-materials, and to simultaneously improve the capacitance and stability for various energy storage devices. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr05978j

AN EVALUATION OF FACTORS AFFECTING THE SOLIDIFICATION/STABILIZATION OF HEAVY METAL SLUDGE

EPA Science Inventory

Solidification/stabilization (SIS) of hazardous waste involves mixing the waste with a binder material to enhance the physical properties of the waste and to immobilize contaminants that may be detrimental to the environment. Many hazardous wastes contain materials that are know...

Efficient first-principles prediction of solid stability: Towards chemical accuracy

DOE PAGES

Zhang, Yubo; Kitchaev, Daniil A.; Yang, Julia; ...

2018-03-09

The question of material stability is of fundamental importance to any analysis of system properties in condensed matter physics and materials science. The ability to evaluate chemical stability, i.e., whether a stoichiometry will persist in some chemical environment, and structure selection, i.e. what crystal structure a stoichiometry will adopt, is critical to the prediction of materials synthesis, reactivity and properties. In this paper, we demonstrate that density functional theory, with the recently developed strongly constrained and appropriately normed (SCAN) functional, has advanced to a point where both facets of the stability problem can be reliably and efficiently predicted for mainmore » group compounds, while transition metal compounds are improved but remain a challenge. SCAN therefore offers a robust model for a significant portion of the periodic table, presenting an opportunity for the development of novel materials and the study of fine phase transformations even in largely unexplored systems with little to no experimental data.« less

Efficient first-principles prediction of solid stability: Towards chemical accuracy

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

Zhang, Yubo; Kitchaev, Daniil A.; Yang, Julia

The question of material stability is of fundamental importance to any analysis of system properties in condensed matter physics and materials science. The ability to evaluate chemical stability, i.e., whether a stoichiometry will persist in some chemical environment, and structure selection, i.e. what crystal structure a stoichiometry will adopt, is critical to the prediction of materials synthesis, reactivity and properties. In this paper, we demonstrate that density functional theory, with the recently developed strongly constrained and appropriately normed (SCAN) functional, has advanced to a point where both facets of the stability problem can be reliably and efficiently predicted for mainmore » group compounds, while transition metal compounds are improved but remain a challenge. SCAN therefore offers a robust model for a significant portion of the periodic table, presenting an opportunity for the development of novel materials and the study of fine phase transformations even in largely unexplored systems with little to no experimental data.« less

An existence criterion for low-dimensional materials

NASA Astrophysics Data System (ADS)

Chen, Jiapeng; Wang, Biao; Hu, Yangfan

2017-10-01

The discovery of graphene and other two-dimensional (2-D) materials has stimulated a general interest in low-dimensional (low-D) materials. Whereas long time ago, Peierls (1935) and Landau's (1937) theoretical work demonstrated that any one- and two-dimensional materials could not exist in any finite temperature environment. Then, two basic issues became a central concern for many researchers: How can stable low-D materials exist? What kind of low-D materials are stable? Here, we establish an energy stability criterion for low-D materials, which seeks to provide a clear answer to these questions. For a certain kind of element, the stability of its specific low-D structure is determined by several derivatives of its interatomic potential. This atomistic-based approach is then applied to study any straight/planar, low-D, equal-bond-length elemental materials. We found that 1-D monatomic chains, 2-D honeycomb lattices, square lattices, and triangular lattices are the only four permissible structures, and the stability of these structures can only be understood by assuming multi-body interatomic potentials. Using this approach, the stable existence of graphene, silicene and germanene can be explained.

Assimilable organic carbon (AOC) variation in reclaimed water: Insight on biological stability evaluation and control for sustainable water reuse.

PubMed

Chen, Zhuo; Yu, Tong; Ngo, Huu Hao; Lu, Yun; Li, Guoqiang; Wu, Qianyuan; Li, Kuixiao; Bai, Yu; Liu, Shuming; Hu, Hong-Ying

2018-04-01

This review highlights the importance of conducting biological stability evaluation due to water reuse progression. Specifically, assimilable organic carbon (AOC) has been identified as a practical indicator for microbial occurrence and regrowth which ultimately influence biological stability. Newly modified AOC bioassays aimed for reclaimed water are introduced. Since elevated AOC levels are often detected after tertiary treatment, the review emphasizes that actions can be taken to either limit AOC levels prior to disinfection or conduct post-treatment (e.g. biological filtration) as a supplement to chemical oxidation based approaches (e.g. ozonation and chlorine disinfection). During subsequent distribution and storage, microbial community and possible microbial regrowth caused by complex interactions are discussed. It is suggested that microbial surveillance, AOC threshold values, real-time field applications and surrogate parameters could provide additional information. This review can be used to formulate regulatory plans and strategies, and to aid in deriving relevant control, management and operational guidance. Copyright © 2018 Elsevier Ltd. All rights reserved.

Marine ice regulates the future stability of a large Antarctic ice shelf

PubMed Central

Kulessa, Bernd; Jansen, Daniela; Luckman, Adrian J.; King, Edward C.; Sammonds, Peter R.

2014-01-01

The collapses of the Larsen A and B ice shelves on the Antarctic Peninsula in 1995 and 2002 confirm the impact of southward-propagating climate warming in this region. Recent mass and dynamic changes of Larsen B’s southern neighbour Larsen C, the fourth largest ice shelf in Antarctica, may herald a similar instability. Here, using a validated ice-shelf model run in diagnostic mode, constrained by satellite and in situ geophysical data, we identify the nature of this potential instability. We demonstrate that the present-day spatial distribution and orientation of the principal stresses within Larsen C ice shelf are akin to those within pre-collapse Larsen B. When Larsen B’s stabilizing frontal portion was lost in 1995, the unstable remaining shelf accelerated, crumbled and ultimately collapsed. We hypothesize that Larsen C ice shelf may suffer a similar fate if it were not stabilized by warm and mechanically soft marine ice, entrained within narrow suture zones. PMID:24751641

Carbonate stability in the reduced lower mantle

NASA Astrophysics Data System (ADS)

Dorfman, Susannah M.; Badro, James; Nabiei, Farhang; Prakapenka, Vitali B.; Cantoni, Marco; Gillet, Philippe

2018-05-01

Carbonate minerals are important hosts of carbon in the crust and mantle with a key role in the transport and storage of carbon in Earth's deep interior over the history of the planet. Whether subducted carbonates efficiently melt and break down due to interactions with reduced phases or are preserved to great depths and ultimately reach the core-mantle boundary remains controversial. In this study, experiments in the laser-heated diamond anvil cell (LHDAC) on layered samples of dolomite (Mg, Ca)CO3 and iron at pressure and temperature conditions reaching those of the deep lower mantle show that carbon-iron redox interactions destabilize the MgCO3 component, producing a mixture of diamond, Fe7C3, and (Mg, Fe)O. However, CaCO3 is preserved, supporting its relative stability in carbonate-rich lithologies under reducing lower mantle conditions. These results constrain the thermodynamic stability of redox-driven breakdown of carbonates and demonstrate progress towards multiphase mantle petrology in the LHDAC at conditions of the lowermost mantle.

Carbonate stability in the reduced lower mantle

DOE PAGES

Dorfman, Susannah M.; Badro, James; Nabiei, Farhang; ...

2018-05-01

Carbonate minerals are important hosts of carbon in the crust and mantle with a key role in the transport and storage of carbon in Earth’s deep interior over the history of the planet. Whether subducted carbonates efficiently melt and break down due to interactions with reduced phases or are preserved to great depths and ultimately reach the core-mantle boundary remains controversial. In this study, experiments in the laser-heated diamond anvil cell (LHDAC) on layered samples of dolomite (Mg,Ca)CO3 and iron at pressure and temperature conditions reaching those of the deep lower mantle show that carbon-iron redox interactions destabilize the MgCO3more » component, producing a mixture of diamond, Fe7C3, and (Mg,Fe)O. However, CaCO3 is preserved, supporting its relative stability in carbonate-rich lithologies under reducing lower mantle conditions. These results constrain the thermodynamic stability of redox-driven breakdown of carbonates and demonstrate progress towards multiphase mantle petrology in the LHDAC at conditions of the lowermost mantle.« less

Effects of elasticity and geometry on the locomotion of a model bacterium

NASA Astrophysics Data System (ADS)

Nguyen, Frank; Graham, Michael

2017-11-01

The locomotion of flagellated bacteria in viscous fluid provides the blueprint for a number of micro-scale engineering applications. The elasticities of both the hook protein (connecting cell body and flagellum) and the flagella themselves play a key role in determining the stability of locomotion. We use a coarse-grained discretization of elastic flagella connected to a rigid cell body to examine trajectories and flow fields for free swimmers. We indeed find that hook and/or flagellar buckling occurs above a critical flexibility relative to the swimmer's torque input. This renders straight swimming ineffective, though not necessarily undesirable in practice. Simulations with multiple flagella show bundling may partially stabilize the buckling effect. For a single flagellum or single bundle, we define a parameter space of characteristic angles tracking the overall time-averaged shape of the swimmer while also delineating stability boundaries between different modes of buckling. Ultimately our results may provide insight on how swimmers move through complex environments and how to design microrobotic swimmers for specific applications. NHS, GERS.

Instability of a cantilevered flexible plate in viscous channel flow

NASA Astrophysics Data System (ADS)

Balint, T. S.; Lucey, A. D.

2005-10-01

The stability of a flexible cantilevered plate in viscous channel flow is studied as a representation of the dynamics of the human upper airway. The focus is on instability mechanisms of the soft palate (flexible plate) that cause airway blockage during sleep. We solve the Navier Stokes equations for flow with Reynolds numbers up to 1500 fully coupled with the dynamics of the plate motion solved using finite-differences. The study is 2-D and based upon linearized plate mechanics. When both upper and lower airways are open, the plate is found to lose its stability through a flutter mechanism and a critical Reynolds number exists. When one airway is closed, the plate principally loses its stability through a divergence mechanism and a critical flow speed exists. However, below the divergence-onset flow speed, flutter can exist for low levels of structural damping in the flexible plate. Our results serve to extend understanding of flow-induced instability of cantilevered flexible plates and will ultimately improve the diagnosis and treatment of upper-airway disorders.

Quantum Dots Based Rad-Hard Computing and Sensors

NASA Technical Reports Server (NTRS)

Fijany, A.; Klimeck, G.; Leon, R.; Qiu, Y.; Toomarian, N.

2001-01-01

Quantum Dots (QDs) are solid-state structures made of semiconductors or metals that confine a small number of electrons into a small space. The confinement of electrons is achieved by the placement of some insulating material(s) around a central, well-conducting region. Thus, they can be viewed as artificial atoms. They therefore represent the ultimate limit of the semiconductor device scaling. Additional information is contained in the original extended abstract.

Thermal-stability studies of electrode materials for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Jiang, Junwei

2005-07-01

The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0.4 ≤ x ≤ 0.7) samples have excellent electrochemical properties and thermal stability and are being commercialized by industry. Li[(Ni0.5Mn0.5)xCo y(Li1/3Mn2/3)z]O2 (1/12 ≤ y ≤ 1/4, 1/6 ≤ z ≤ 1/3) samples have high specific capacity (200 mA h g-1), excellent cycling performance, and are safer than LiCoO2. The materials are suggested for energy cells used in cell phones, laptops, and so on.

Torsional strength of computer-aided design/computer-aided manufacturing-fabricated esthetic orthodontic brackets.

PubMed

Alrejaye, Najla; Pober, Richard; Giordano Ii, Russell

2017-01-01

To fabricate orthodontic brackets from esthetic materials and determine their fracture resistance during archwire torsion. Computer-aided design/computer-aided manufacturing technology (Cerec inLab, Sirona) was used to mill brackets with a 0.018 × 0.025-inch slot. Materials used were Paradigm MZ100 and Lava Ultimate resin composite (3M ESPE), Mark II feldspathic porcelain (Vita Zahnfabrik), and In-Ceram YZ zirconia (Vita Zahnfabrik). Ten brackets of each material were subjected to torque by a 0.018 × 0.025-inch stainless steel archwire (G&H) using a specially designed apparatus. The average moments and degrees of torsion necessary to fracture the brackets were determined and compared with those of commercially available alumina brackets, Mystique MB (Dentsply GAC). The YZ brackets were statistically significantly stronger than any other tested material in their resistance to torsion (P < .05). The mean torques at failure ranged from 3467 g.mm for Mark II to 11,902 g.mm for YZ. The mean torsion angles at failure ranged from 15.3° to 40.9°. Zirconia had the highest torsional strength among the tested esthetic brackets. Resistance of MZ100 and Lava Ultimate composite resin brackets to archwire torsion was comparable to commercially available alumina ceramic brackets.

Harvesting bioenergy with rationally designed complex functional materials

NASA Astrophysics Data System (ADS)

Kuang, Liangju

A key challenge in renewable energy is to capture, convert and store solar power with earth-abundant materials and environmentally benign technologies. The goal of this thesis is to develop rationally designed complex functional materials for bio-renewable energy applications. On one hand, photoconversion membrane proteins (MPs) are nature's nanoengineering feats for renewable energy management. Harnessing their functions in synthetic systems could help understand, predict, and ultimately control matter and energy at the nanoscale. This is particularly enticing in the post-genome era as recombinant or cell-free expression of many MPs with high yields becomes possible. However, the labile nature of lipid bilayers renders them unsuitable for use in a broad range of engineered systems. A knowledge gap exists about how to design robust synthetic nanomembranes as lipid-bilayer-mimics to support MP functions and how to direct hierarchical MP reconstitution into those membranes to form 2-D or 3-D ordered proteomembrane arrays. Our studies on proteorhodopsin (PR) and bacterial reaction center (BRC), the two light-harvesting MPs, reveal that a charge-interaction-directed reconstitution (CIDR) mechanism induces spontaneous reconstitution of detergent-solubilized MPs into various amphiphilic block copolymer membranes, many of which have far superior stability than lipid bilayers. Our preliminary data also suggest MPs are not enslaved by the biological membranes they derive from; rather, the chemically nonspecific material properties of MP-supporting membranes may act as allosteric regulators. Versatile chemical designs are possible to modulate the conformational energetics of MPs, hence their transport performance in synthetic systems. On the other hand, microalgae are widely regarded as a sustainable feedstock for biofuel production. Microalgae-derived biofuels have not been commercialized yet because current technologies for microalgae dewatering add a huge cost to the final product, and present a major bottleneck. We propose to solve the microalgae dewatering problem in the context of controlling colloidal stability, where inter-algal potential is tuned via surface engineering of novel coagulation agents. We report here a nanoparticle-pinched polymer brush design that combines two known colloidal destabilization agents (e.g., nanoparticle and polymer) into one system, and allows the use of an external field (e.g., magnetic force) to not only modulate inter-algae pair potentials, but also facilitate retrieval of the coagulation agents to be reused after algal oil extraction. We will discuss our extensive data on the preparation of well-defined nanoparticle-pinched polymer brushes, their structure-dependent coagulation performance on both fresh water and marine microalgae species, and their re-suability for continuous cycles of microalgae farming and harvesting.

[Simultaneous determination of 9 ultraviolet stabilizers in food plastic packaging materials by solid phase extraction-high performance liquid chromatography].

PubMed

Zhang, Juzhou; Li, Jing; Shao, Dongliang; Yao, Bangben; Jiang, Junshu

2012-02-01

An effective high performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of 9 ultraviolet stabilizers in food plastic packaging materials. The food packaging samples were firstly extracted by methanol-ethyl acetate, and then purified by a C18 solid-phase extraction (SPE) column. The target compounds were separated on a ZORBAX SB-C18 column (250 mm x 4.6 mm, 5 microm) in gradient elution mode using methanol and water as mobile phases. The detection wavelength was at 310 nm. The linear plots of the nine ultraviolet stabilizers were obtained between 0.2 and 10 mg/L, with the correlation coefficients of above 0. 999 for the nine ultraviolet stabilizers. The limits of detection for this method were in the range from 0.05 to 0.1 mg/L. The recoveries spiked in commercial food plastic packaging materials were in the range of 70.2% - 89.0% with the relative standard deviations of 0.4% - 4.5%. The results indicated that the method is simple, accurate, and suitable for the simultaneous determination of the nine ultraviolet stabilizers in food plastic packaging materials.

Origin of Outstanding Stability in the Lithium Solid Electrolyte Materials: Insights from Thermodynamic Analyses Based on First-Principles Calculations

DOE PAGES

Zhu, Yizhou; He, Xingfeng; Mo, Yifei

2015-10-06

First-principles calculations were performed to investigate the electrochemical stability of lithium solid electrolyte materials in all-solid-state Li-ion batteries. The common solid electrolytes were found to have a limited electrochemical window. Our results suggest that the outstanding stability of the solid electrolyte materials is not thermodynamically intrinsic but is originated from kinetic stabilizations. The sluggish kinetics of the decomposition reactions cause a high overpotential leading to a nominally wide electrochemical window observed in many experiments. The decomposition products, similar to the solid-electrolyte-interphases, mitigate the extreme chemical potential from the electrodes and protect the solid electrolyte from further decompositions. With the aidmore » of the first-principles calculations, we revealed the passivation mechanism of these decomposition interphases and quantified the extensions of the electrochemical window from the interphases. We also found that the artificial coating layers applied at the solid electrolyte and electrode interfaces have a similar effect of passivating the solid electrolyte. Our newly gained understanding provided general principles for developing solid electrolyte materials with enhanced stability and for engineering interfaces in all-solid-state Li-ion batteries.« less

Combined effect of oblateness, radiation and a circular cluster of material points on the stability of triangular liberation points in the R3BP

NASA Astrophysics Data System (ADS)

Singh, Jagadish; Taura, Joel John

2014-06-01

This paper studies the motion of an infinitesimal mass in the framework of the restricted three-body problem (R3BP) under the assumption that the primaries of the system are radiating-oblate spheroids, enclosed by a circular cluster of material points. It examines the effects of radiation and oblateness up to J 4 of the primaries and the potential created by the circular cluster, on the linear stability of the liberation locations of the infinitesimal mass. The liberation points are found to be stable for 0< μ< μ c and unstable for , where μ c is the critical mass value depending on terms which involve parameters that characterize the oblateness, radiation forces and the circular cluster of material points. The oblateness up to J 4 of the primaries and the gravitational potential from the circular cluster of material points have stabilizing propensities, while the radiation of the primaries and the oblateness up to J 2 of the primaries have destabilizing tendencies. The combined effect of these perturbations on the stability of the triangular liberation points is that, it has stabilizing propensity.

Evaluation of thermal stability in spectrally selective few-layer metallo-dielectric structures for solar thermophotovoltaics

NASA Astrophysics Data System (ADS)

Shimizu, Makoto; Kohiyama, Asaka; Yugami, Hiroo

2018-06-01

The thermal stability of spectrally selective few-layer metallo-dielectric structures is evaluated to analyze their potential as absorber and emitter materials in solar thermophotovoltaic (STPV) systems. High-efficiency (e.g., STPV) systems require materials with spectrally selective properties, especially at high temperatures (>1273 K). Aiming to develop such materials for high-temperature applications, we propose a few-layer structure composed of a refractory metal (i.e., Mo) nanometric film sandwiched between the layers of a dielectric material (i.e., hafnium oxide, HfO2) deposited on a Mo bulk substrate. In vacuum conditions (<5 × 10-2 Pa), the few-layer structure shows thermal stability at 1423 K for at least 1 h. At 1473 K, the spectral selectivity was degraded. This could have been caused by the oxidation of the Mo thin film by the residual oxygen through the grain boundaries of the upper HfO2 layer. This experiment showed the potential stability of few-layer structures for applications working at temperatures greater than 1273 K as well as the degradation mechanism of the few-layer structure. This characteristic is expected to help improve the thermal stability in few-layer structures further.

Encapsulation materials research

NASA Technical Reports Server (NTRS)

Willis, P. B.

1984-01-01

Encapsulation materials for solar cells were investigated. The different phases consisted of: (1) identification and development of low cost module encapsulation materials; (2) materials reliability examination; and (3) process sensitivity and process development. It is found that outdoor photothermal aging devices (OPT) are the best accelerated aging methods, simulate worst case field conditions, evaluate formulation and module performance and have a possibility for life assessment. Outdoor metallic copper exposure should be avoided, self priming formulations have good storage stability, stabilizers enhance performance, and soil resistance treatment is still effective.

Stability and Process of Destruction of Compressed Plate of Layered Composite Materials With Defects

NASA Astrophysics Data System (ADS)

Bokhoeva, L. A.; Rogov, V. E.; Chermoshentseva, A. S.; Lobanov, D. V.

2016-08-01

Interlayer defects in composite materials are a pressing problem, which affecting their performance characteristics. In this research, we considered the problem of the stability and of the fracture process of the compressed thin plate made of laminated composite materials with the interlayer defects. In this research we had got a critical equation for a plate with interlayer defect. The experiment showed the effect and the quantity of nano-dispersed additives on the mechanical properties of composite materials with interlayer defects.

Coating processes for increasing the moisture resistance of polyurethane baffle material

NASA Technical Reports Server (NTRS)

Bilow, N.; Sawko, P.

1974-01-01

An investigation was conducted with the objective to improve the hydrolytic stability of reticulated polyurethane baffle material. This material is used in fuel tanks of aircraft and ground vehicles. The most commonly used foam of this type is hydrolytically unstable. Potential moisture barrier coatings which were evaluated include Parylene, epoxy-polysulfide, polyether based polyurethanes, polysulfides, polyolefin rubbers, and several other materials. Parylene coatings of at least 0.2 mil were found to provide the greatest improvement in hydrolytic stability.

Color stability and marginal integrity of interim crowns: An in vitro study

PubMed Central

Elagra, Marwa I.; Rayyan, Mohammad R.; Alhomaidhi, Maisam M.; Alanaziy, Areej A.; Alnefaie, Mona O.

2017-01-01

Objective: Many commercial dental materials are used to fabricate interim restorations. This study aimed to compare the color stability and the marginal integrity of four different interim crown materials. Materials and Methods: An ivorine right maxillary central incisor was prepared for a full coverage all-ceramic restoration. A total of 36 specimens in the form of crowns were fabricated on the master die using four different materials (n = 9); Polymethyl methacrylate (PMMA) resin (TrimPLUS), PMMA computer-aided design, and computer-aided manufacturing (CAD-CAM) blocks (Ceramill TEMP), cold cure bis-acryl resin (Success CD), and bis-acryl resin dual-cure composite (TempSpan). Color change ΔE for each sample was calculated by measuring its color as Commission Internationale de l’Eclairage L* a* b* with a spectrophotometer before and after immersing in a concentrated tea solution for 7 days. Marginal gap was measured at four reference points using stereomicroscope at ×40. One-way ANOVA and the Tukey multiple comparisons test were used to determine any statistically significant difference between the four groups, (α = 0.05). Results: Success CD showed significantly the greatest color change (7.7) among all the tested materials, while no significant difference was found between the other three materials. TempSpan showed significantly the highest marginal gap formation (430.15 μm), while no significant difference was found between the three other materials. Conclusions: Bis-acryl resin composite materials demonstrated clinically noticeable change in color while PMMA materials demonstrated superior color stability. Dual cure interim materials exhibited significantly higher marginal discrepancy in comparison to PMMA and cold cure bis-acrylic resin materials. CAD-CAM PMMA material exhibited the best color stability and marginal integrity. PMID:28932142

Highly Efficient Oxygen-Storage Material with Intrinsic Coke Resistance for Chemical Looping Combustion-Based CO2 Capture.

PubMed

Imtiaz, Qasim; Kurlov, Alexey; Rupp, Jennifer Lilia Marguerite; Müller, Christoph Rüdiger

2015-06-22

Chemical looping combustion (CLC) and chemical looping with oxygen uncoupling (CLOU) are emerging thermochemical CO2 capture cycles that allow the capture of CO2 with a small energy penalty. Here, the development of suitable oxygen carrier materials is a key aspect to transfer these promising concepts to practical installations. CuO is an attractive material for CLC and CLOU because of its high oxygen-storage capacity (20 wt %), fast reaction kinetics, and high equilibrium partial pressure of oxygen at typical operating temperatures (850-1000 °C). However, despite its promising characteristics, its low Tammann temperature requires the development of new strategies to phase-stabilize CuO-based oxygen carriers. In this work, we report a strategy based on stabilization by co-precipitated ceria (CeO2-x ), which allowed us to increase the oxygen capacity, coke resistance, and redox stability of CuO-based oxygen carriers substantially. The performance of the new oxygen carriers was evaluated in detail and compared to the current state-of-the-art materials, that is, Al2 O3 -stabilized CuO with similar CuO loadings. We also demonstrate that the higher intrinsic oxygen uptake, release, and mobility in CeO2-x -stabilized CuO leads to a three times higher carbon deposition resistance compared to that of Al2 O3 -stabilized CuO. Moreover, we report a high cyclic stability without phase intermixing for CeO2-x -supported CuO. This was accompanied by a lower reduction temperature compared to state-of-the-art Al2 O3 -supported CuO. As a result of its high resistance towards carbon deposition and fast oxygen uncoupling kinetics, CeO2-x -stabilized CuO is identified as a very promising material for CLC- and CLOU-based CO2 capture architectures. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled formation of emulsion gels stabilized by salted myofibrillar protein under malondialdehyde (MDA)-induced oxidative stress.

PubMed

Zhou, Feibai; Sun, Weizheng; Zhao, Mouming

2015-04-15

This study presented the cold-set gelation of emulsions stabilized by salted myofibrillar protein (MP) under oxidative stress originated from malondialdehyde (MDA). Gel properties were compared over a range of MDA/NaCl concentrations including gel viscoelastic properties, strength, water-holding capacity (WHC), amount of protein entrapped, and microstructure. The oxidative stability of emulsion gels as indicated by lipid hydroperoxide was further determined and compared. Results indicated that emulsion stabilized by MP at swollen state under certain ionic strengths (0.2-0.6 M) was the premise of gel formation under MDA. In the presence of intermediate MDA concentrations (2.5-10 mM), the emulsion gels showed an improved elasticity, strength, WHC, and oxidative stability. This improvement should be mainly attributed to the enhanced protein-protein cross-linkings via MDA, which were homogeneously formed among absorbed and/or unabsorbed proteins, entrapping a greater amount and fractions of protein within network. Therefore, the oil droplets were better adherent to the gel matrix. Nevertheless, addition of high MDA concentrations (25-50 mM) led to the formation of excessive covalent bonds, which might break protein-protein bonds and trigger the desorption of protein from the interface. This ultimately caused "oil leak" phenomena as well as the collapse of gel structure and, thus, overall decreased gel properties and oxidative stability.

Process for preparing multilayer enzyme coating on a fiber

DOEpatents

Kim, Jungbae [Richland, WA; Kwak, Ja Hun [Richland, WA; Grate, Jay W [West Richland, WA

2009-11-03

A process for preparing high stability, high activity biocatalytic materials is disclosed and processes for using the same. The process involves coating of a material or fiber with enzymes and enzyme aggregate providing a material or fiber with high biocatalytic activity and stability useful in heterogeneous environments. In one illustrative approach, enzyme "seeds" are covalently attached to polymer nanofibers followed by treatment with a reagent that crosslinks additional enzyme molecules to the seed enzymes forming enzyme aggregates thereby improving biocatalytic activity due to increased enzyme loading and enzyme stability. This approach creates a useful new biocatalytic immobilized enzyme system with potential applications in bioconversion, bioremediation, biosensors, and biofuel cells.

Protopine, a novel microtubule-stabilizing agent, causes mitotic arrest and apoptotic cell death in human hormone-refractory prostate cancer cell lines.

PubMed

Chen, Chun-Han; Liao, Cho-Hwa; Chang, Ya-Ling; Guh, Jih-Hwa; Pan, Shiow-Lin; Teng, Che-Ming

2012-02-01

In this study, we investigated the anticancer effect of protopine on human hormone-refractory prostate cancer (HRPC) cells. Protopine exhibited an anti-proliferative effect by induction of tubulin polymerization and mitotic arrest, which ultimately led to apoptotic cell death. The data suggest that protopine increased the activity of cyclin-dependent kinase 1 (Cdk1)/cyclin B1 complex and that contributed to cell apoptosis by modulating mitochondria-mediated signaling pathways, such as Bcl-2 phosphorylation and Mcl-1 down-regulation. In conclusion, the data suggest that protopine is a novel microtubule stabilizer with anticancer activity in HRPC cells through apoptotic pathway by modulating Cdk1 activity and Bcl-2 family of proteins. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Density functional theory study of phase stability and defect thermodynamics in iron-oxyhydroxide mineral materials

NASA Astrophysics Data System (ADS)

Pinney, Nathan Douglas

Due to their high surface area and reactivity toward a variety of heavy metal and oxyanion species of environmental concern, Fe-(oxyhydr)oxide materials play an important role in the geochemical fate of natural and anthropogenic contaminants in soils, aquifers and surface water environments worldwide. In this research, ab initio simulations describe the bulk structure, magnetic properties, and relative phase stability of major Fe-(oxyhydr)oxide materials, including hematite, goethite, lepidocrocite, and ferrihydrite.These bulk models are employed in further studies of point defect and alloy/dopant thermodynamics in these materials, allowing construction of a phase stability model that better replicates the structure and composition of real materials. Li + adsorption at the predominant goethite (101) surface is simulated using ab initio methods, offering energetic and structural insight into the binding mechanisms of metal cations over a range of surface protonation conditions.

An alternative soil nailing system for slope stabilization: Akarpiles

NASA Astrophysics Data System (ADS)

Lim, Chun-Lan; Chan, Chee-Ming

2017-11-01

This research proposes an innovative solution for slope stabilization with less environmental footprint: AKARPILES. In Malaysia, landslide has become common civil and environmental problems that cause impacts to the economy, safety and environment. Therefore, effective slope stabilization method helps to improve the safety of public and protect the environment. This study focused on stabilizing surfacial slope failure. The idea of AKARPILES was generated from the tree roots system in slope stabilization. After the piles are installed in the slope and intercepting the slip plane, grout was pumped in and discharged through holes on the piles. The grout then filled the pores in the soil with random flow within the slip zone. SKW mixture was used to simulate the soil slope. There were two designs being proposed in this study and the prototypes were produced by a 3D printer. Trial mix of the grout was carried out to obtain the optimum mixing ratio of bentonite: cement: water. A series of tests were conducted on the single-pile-reinforced slope under vertical slope crest loading condition considering different slope gradients and nail designs. Parameters such as ultimate load, failure time and failure strain were recorded and compared. As comparison with the unreinforced slope, both designs of AKARPILES showed better but different performances in the model tests.

Stabilization of enzymes in ionic liquids via modification of enzyme charge.

PubMed

Nordwald, Erik M; Kaar, Joel L

2013-09-01

Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments. Copyright © 2013 Wiley Periodicals, Inc.

The performance of thermal control coatings on LDEF and implications to future spacecraft

NASA Technical Reports Server (NTRS)

Wilkes, Donald R.; Miller, Edgar R.; Mell, Richard J.; Lemaster, Paul S.; Zwiener, James M.

1993-01-01

The stability of thermal control coatings over the lifetime of a satellite or space platform is crucial to the success of the mission. With the increasing size, complexity, and duration of future missions, the stability of these materials becomes even more important. The Long Duration Exposure Facility (LDEF) offered an excellent testbed to study the stability and interaction of thermal control coatings in the low-Earth orbit (LEO) space environment. Several experiments on LDEF exposed thermal control coatings to the space environment. This paper provides an overview of the different materials flown and their stability during the extended LDEF mission. The exposure conditions, exposure environment, and measurements of materials properties (both in-space and postflight) are described. The relevance of the results and the implications to the design and operation of future space vehicles are also discussed.

Facile preparation of super durable superhydrophobic materials.

PubMed

Wu, Lei; Zhang, Junping; Li, Bucheng; Fan, Ling; Li, Lingxiao; Wang, Aiqin

2014-10-15

The low stability, complicated and expensive fabrication procedures seriously hinder practical applications of superhydrophobic materials. Here we report an extremely simple method for preparing super durable superhydrophobic materials, e.g., textiles and sponges, by dip coating in fluoropolymers (FPs). The morphology, surface chemical composition, mechanical, chemical and environmental stabilities of the superhydrophobic textiles were investigated. The results show how simple the preparation of super durable superhydrophobic textiles can be! The superhydrophobic textiles outperform their natural counterparts and most of the state-of-the-art synthetic superhydrophobic materials in stability. The intensive mechanical abrasion, long time immersion in various liquids and repeated washing have no obvious influence on the superhydrophobicity. Water drops are spherical in shape on the samples and could easily roll off after these harsh stability tests. In addition, this simple dip coating approach is applicable to various synthetic and natural textiles and can be easily scaled up. Furthermore, the results prove that a two-tier roughness is helpful but not essential with regard to the creation of super durable superhydrophobic textiles. The combination of microscale roughness of textiles and materials with very low surface tension is enough to form super durable superhydrophobic textiles. According to the same procedure, superhydrophobic polyurethane sponges can be prepared, which show high oil absorbency, oil/water separation efficiency and stability. Copyright © 2014 Elsevier Inc. All rights reserved.

Improving Stability of Zeolites in Aqueous Phase via Selective Removal of Structural Defects

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

Prodinger, Sebastian; Derewinski, Miroslaw A.; Vjunov, Aleksei

2016-03-13

This work reports significant improvement in the hydrothermal stability of a well-characterized BEA zeolite via the selective removal of structural defects. Recent work suggests that the presence of silanol defects destabilizes the framework integrity of most zeolites and makes them susceptible to hydrolysis of the siloxy bonds by hot liquid water. The described approach allows for a key removal of silanols as shown with 29Si-MAS-NMR. Subsequently, the material stability in hot liquid water, measured by retention of its crystallinity with X-ray diffraction (XRD), is found to be superior to defective zeolites. In addition, N2-sorption measurements (BET) and transmission electron microscopymore » (TEM) show the formation of different types of mesoporosity for water-treated stabilized and unmodified materials. While the sorption capacity for untreated materials drops, related to re-precipitation of dissolved silica and pore blocking, the stabilized material retains its microporosity and improves its overall sorption capacity. The authors would like to thank B. W. Arey (PNNL) for HIM measurements and I. Arslan for TEM imaging. This work was supported by the U. S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. SP and MD acknowledge support by the Materials Synthesis and Simulation Across Scales (MS3 Initiative) conducted under Laboratory Directed Research & Development Program at PNNL.« less

High calcium fly ash geopolymer stabilized lateritic soil and granulated blast furnace slag blends as a pavement base material.

PubMed

Phummiphan, Itthikorn; Horpibulsuk, Suksun; Rachan, Runglawan; Arulrajah, Arul; Shen, Shui-Long; Chindaprasirt, Prinya

2018-01-05

Granulated Blast Furnace Slag (GBFS) was used as a replacement material in marginal lateritic soil (LS) while class C Fly Ash (FA) was used as a precursor for the geopolymerization process to develop a low-carbon pavement base material at ambient temperature. Unconfined Compression Strength (UCS) tests were performed to investigate the strength development of geopolymer stabilized LS/GBFS blends. Scanning Electron Microscopy and X-ray Diffraction analysis were undertaken to examine the role of the various influencing factors on UCS development. The influencing factors studied included GBFS content, Na 2 SiO 3 :NaOH ratio (NS:NH) and curing time. The 7-day soaked UCS of FA geopolymer stabilized LS/GBFS blends at various NS:NH ratios tested was found to satisfy the specifications of the Thailand national road authorities. The GBFS replacement was found to be insignificant for the improvement of the UCS of FA geopolymer stabilized LS/GBFS blends at low NS:NH ratio of 50:50. Microstructural analysis indicated the coexistence of Calcium Silicate Hydrate (CSH) and Sodium Alumino Silicate Hydrate products in FA geopolymer stabilized LS/GBFS blends. This research enables GBFS, which is traditionally considered as a waste material, to be used as a replacement and partially reactive material in FA geopolymer pavement applications. Copyright © 2017 Elsevier B.V. All rights reserved.

Strategies to curb structural changes of lithium/transition metal oxide cathode materials & the changes' effects on thermal & cycling stability

DOE PAGES

Yu, Xiqian; Hu, Enyuan; Bak, Seongmin; ...

2015-12-07

Structural transformation behaviors of several typical oxide cathode materials during a heating process are reviewed in detail to provide in-depth understanding of the key factors governing the thermal stability of these materials. Furthermore, we also discuss applying the information about heat induced structural evolution in the study of electrochemically induced structural changes. All these discussions are expected to provide valuable insights for designing oxide cathode materials with significantly improved structural stability for safe, long-life lithium ion batteries, as the safety of lithium-ion batteries is a critical issue. As a result, it is widely accepted that the thermal instability of themore » cathodes is one of the most critical factors in thermal runaway and related safety problems.« less

Rapid oxidation/stabilization technique for carbon foams, carbon fibers and C/C composites

DOEpatents

Tan, Seng; Tan, Cher-Dip

2004-05-11

An enhanced method for the post processing, i.e. oxidation or stabilization, of carbon materials including, but not limited to, carbon foams, carbon fibers, dense carbon-carbon composites, carbon/ceramic and carbon/metal composites, which method requires relatively very short and more effective such processing steps. The introduction of an "oxygen spill over catalyst" into the carbon precursor by blending with the carbon starting material or exposure of the carbon precursor to such a material supplies required oxygen at the atomic level and permits oxidation/stabilization of carbon materials in a fraction of the time and with a fraction of the energy normally required to accomplish such carbon processing steps. Carbon based foams, solids, composites and fiber products made utilizing this method are also described.

Recent progress in degradation and stabilization of organic solar cells

NASA Astrophysics Data System (ADS)

Cao, Huanqi; He, Weidong; Mao, Yiwu; Lin, Xiao; Ishikawa, Ken; Dickerson, James H.; Hess, Wayne P.

2014-10-01

Stability is of paramount importance in organic semiconductor devices, especially in organic solar cells (OSCs). Serious degradation in air limits wide applications of these flexible, light-weight and low-cost power-generation devices. Studying the stability of organic solar cells will help us understand degradation mechanisms and further improve the stability of these devices. There are many investigations into the efficiency and stability of OSCs. The efficiency and stability of devices even of the same photoactive materials are scattered in different papers. In particular, the extrinsic degradation that mainly occurs near the interface between the organic layer and the cathode is a major stability concern. In the past few years, researchers have developed many new cathodes and cathode buffer layers, some of which have astonishingly improved the stability of OSCs. In this review article, we discuss the recent developments of these materials and summarize recent progresses in the study of the degradation/stability of OSCs, with emphasis on the extrinsic degradation/stability that is related to the intrusion of oxygen and water. The review provides detailed insight into the current status of research on the stability of OSCs and seeks to facilitate the development of highly-efficient OSCs with enhanced stability.

Ceramicrete stabilization of U-and Pu-bearing materials

DOEpatents

Wagh, Arun S.; Maloney, M. David; Thompson, Gary H.

2007-11-13

A method of stabilizing nuclear material is disclosed. Oxides or halides of actinides and/or transuranics (TRUs) and/or hydrocarbons and/or acids contaminated with actinides and/or TRUs are treated by adjusting the pH of the nuclear material to not less than about 5 and adding sufficient MgO to convert fluorides present to MgF.sub.2; alumina is added in an amount sufficient to absorb substantially all hydrocarbon liquid present, after which a binder including MgO and KH.sub.2PO.sub.4 is added to the treated nuclear material to form a slurry. Additional MgO may be added. A crystalline radioactive material is also disclosed having a binder of the reaction product of calcined MgO and KH.sub.2PO.sub.4 and a radioactive material of the oxides and/or halides of actinides and/or transuranics (TRUs). Acids contaminated with actinides and/or TRUs, and/or actinides and/or TRUs with or without oils and/or greases may be encapsulated and stabilized by the binder.

Meniscal material properties are minimally affected by matrix stabilization using glutaraldehyde and glycation with ribose.

PubMed

Hunter, Shawn A; Noyes, Frank R; Haridas, Balakrishna; Levy, Martin S; Butler, David L

2005-05-01

Knee meniscus replacement holds promise, but current allografts are susceptible to biodegradation. Matrix stabilization with glutaraldehyde, a crosslinking agent used clinically to fabricate cardiovascular bioprostheses, or with glycation, a process of crosslinking collagen with sugars such as ribose, is a potential means of rendering tissue resistant to such degradation. However, stabilization should not significantly alter meniscal material properties, which could disturb normal function in the knee. Our objective was to evaluate the effects of glutaraldehyde- and glycation-induced matrix stabilization on the material properties of porcine meniscus. Normal untreated meniscus specimens were tested in confined compression at one of three applied stresses (0.069, 0.208, 0.347 MPa), subjected to either a glutaraldehyde or glycation stabilization treatment, and then re-tested to measure changes in tissue aggregate modulus, permeability, and compressive strain at equilibrium. Changes in these properties significantly increased with glutaraldehyde concentration and exposure time to ribose. One glutaraldehyde and three glycation treatments did not alter aggregate modulus or compressive strain at equilibrium compared to controls (p > 0.10). However, all treatments increased permeability by at least 108% compared to controls (p < 0.001). This study reveals a dose-dependent relationship between meniscal material properties and certain stabilization conditions and identifies treatments that minimally affect these properties. Further research is necessary to determine whether these treatments prevent enzymatic degradation before and after surgical implantation in the knee.

Stability Improvements of DNA Photonic Devices

DTIC Science & Technology

2008-12-20

possible in such areas as photonics, separation process or biomedical materials . Recent research results on DNA-lipid complexes have shown various...onto Teflon- coated glass plate to obtain films by irradiating UV light to cause crosslinking reactions of the Adeka sol-gel materials Clear and...into sol-gel materials or synthetic polymers so that water permeation is prevented by glass or synthetic polymers to stabilize and to keep the optical

Catalyst Stability Benchmarking for the Oxygen Evolution Reaction: The Importance of Backing Electrode Material and Dissolution in Accelerated Aging Studies.

PubMed

Geiger, Simon; Kasian, Olga; Mingers, Andrea M; Nicley, Shannon S; Haenen, Ken; Mayrhofer, Karl J J; Cherevko, Serhiy

2017-09-18

In searching for alternative oxygen evolution reaction (OER) catalysts for acidic water splitting, fast screening of the material intrinsic activity and stability in half-cell tests is of vital importance. The screening process significantly accelerates the discovery of new promising materials without the need of time-consuming real-cell analysis. In commonly employed tests, a conclusion on the catalyst stability is drawn solely on the basis of electrochemical data, for example, by evaluating potential-versus-time profiles. Herein important limitations of such approaches, which are related to the degradation of the backing electrode material, are demonstrated. State-of-the-art Ir-black powder is investigated for OER activity and for dissolution as a function of the backing electrode material. Even at very short time intervals materials like glassy carbon passivate, increasing the contact resistance and concealing the degradation phenomena of the electrocatalyst itself. Alternative backing electrodes like gold and boron-doped diamond show better stability and are thus recommended for short accelerated aging investigations. Moreover, parallel quantification of dissolution products in the electrolyte is shown to be of great importance for comparing OER catalyst feasibility. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Intercritical heat treatments in ductile iron and steel

NASA Astrophysics Data System (ADS)

Aristizabal, Ricardo E.

Materials such as dual phase (DP) steels, transformation induced plasticity (TRIP) steels and dual phase ductile irons are produced by intercritical heat treatments. These materials can provide significant weight savings in the automotive industry. The goal of this dissertation is to study intercritical heat treatments in ductile iron and steel to optimize the production parameters. Three different aspects were addressed. First, common steels were intercritically austenitized and austempered (intercritically austempered) under a variety conditions. The results showed that common grade steels that were intercritically austempered exhibited tensile properties in the same range as DP and TRIP steels. The second study consisted of determining the effect of heat treatment conditions on the tensile properties of intercritically austenitized, quenched and tempered ductile iron (IAQ&TDI). The results showed that (1) ultimate tensile strength (UTS) and yield strength (YS) were determined by the volume fraction of martensite, (2) tempering improved the elongation 1.7-2.5 times with only a slight decrease in strength, (3) the carbon in austenite formed during the intercritical heat treatment of ductile iron with a ferritic-pearlitic matrix came from the carbon available in the matrix and that carbon diffusion from the graphite nodules was restricted, and (4) limited segregation of substitutional elements occurred during intercritical austenitizing. Finally, intercritically austempered ductile iron (IADI) alloyed with different amounts of manganese and nickel was produced. Tensile properties and microstructure were determined. Also, the stability of the austenite during deformation and the lattice strains of the ferrite and the austenite phases were determined using x-ray diffraction (XRD) and neutron diffraction. The results indicated that: 1) high manganese concentrations produced materials with large blocky, low carbon austenite particles at the intercellular boundaries which decreased the elongation of the materials and transformed to martensite during deformation at low strains. 2) Nickel and nickel-manganese alloys formed a combination of blocky and plate-like austenite particles, which were more stable during deformation and either transformed to martensite after yielding or did not transform at all.

Wear, strength, modulus and hardness of CAD/CAM restorative materials.

PubMed

Lawson, Nathaniel C; Bansal, Ritika; Burgess, John O

2016-11-01

To measure the mechanical properties of several CAD/CAM materials, including lithium disilicate (e.max CAD), lithium silicate/zirconia (Celtra Duo), 3 resin composites (Cerasmart, Lava Ultimate, Paradigm MZ100), and a polymer infiltrated ceramic (Enamic). CAD/CAM blocks were sectioned into 2.5mm×2.5mm×16mm bars for flexural strength and elastic modulus testing and 4mm thick blocks for hardness and wear testing. E.max CAD and half the Celtra Duo specimens were treated in a furnace. Flexural strength specimens (n=10) were tested in a three-point bending fixture. Vickers microhardness (n=2, 5 readings per specimen) was measured with a 1kg load and 15s dwell time. The CAD/CAM materials as well as labial surfaces of human incisors were mounted in the UAB wear device. Cusps of human premolars were mounted as antagonists. Specimens were tested for 400,000 cycles at 20N force, 2mm sliding distance, 1Hz frequency, 24°C, and 33% glycerin lubrication. Volumetric wear and opposing enamel wear were measured with non-contact profilometry. Data were analyzed with 1-way ANOVA and Tukey post-hoc analysis (alpha=0.05). Specimens were observed with SEM. Properties were different for each material (p<0.01). E.max CAD and Celtra Duo were generally stronger, stiffer, and harder than the other materials. E.max CAD, Celtra Duo, Enamic, and enamel demonstrated signs of abrasive wear, whereas Cerasmart, Lava Ultimate, Paradigm MZ100 demonstrated signs of fatigue. Resin composite and resin infiltrated ceramic materials have demonstrated adequate wear resistance for load bearing restorations, however, they will require at least similar material thickness as lithium disilicate restorations due to their strength. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Development of improved pyroelectric detectors. Measurements of pyroelectric material characteristics and FET characteristics

NASA Technical Reports Server (NTRS)

Weiner, S.; Beerman, H. P.; Schwarz, F. C.

1990-01-01

Research was undertaken to improve the detectivity of the pyroelectric detector with the ultimate goal of operation at or near the temperature-noise limit. Two general areas of investigation were undertaken: (1) to improve responsivity through the use of new materials; and (2) to reduce noise through improved field effect transistor characteristics, and improved electroding of the pyroelectric material. FET's are being obtained from various manufacturers, evaulated, and selected units tested for evaluation of characteristics critical to their use as preamplifiers with pyroelectric detectors.

Preparation of actinide boride materials via solid-state metathesis reactions and actinide dicarbollide precursors

NASA Astrophysics Data System (ADS)

Lupinetti, Anthony J.; Fife, Julie; Garcia, Eduardo; Abney, Kent D.

2000-07-01

Information gaps exist in the knowledge base needed for choosing among the alternate processes to be used in the safe conversion of fissile materials to optimal forms for safe interim storage, long-term storage, and ultimate disposition. The current baseline storage technology for various wastes uses borosilicate glasses.1 The focus of this paper is the synthesis of actinide-containing ceramic materials at low and moderate temperatures (200 °C-1000 °C) using molecular and polymeric actinide borane and carborane complexes.

Skylab

NASA Image and Video Library

1972-01-01

This chart details Skylab's Materials Processing Facility experiment (M512). This facility, located in the Multiple Docking Adapter, was developed for Skylab and accommodated 14 different experiments that were carried out during the three marned missions. The abilities to melt and mix without the contaminating effects of containers, to suppress thermal convection and buoyancy in fluids, and to take advantage of electrostatic and magnetic forces and otherwise masked by gravitation opened the way to new knowledge of material properties and processes. This beginning would ultimately lead to the production of valuable new materials for use on Earth.

Performances achieved to the Grid by a Full Power Converter Used in a Variable Speed Pumped Storage Plant

NASA Astrophysics Data System (ADS)

Claude, Jean-Michel

2017-04-01

The growth of renewable energies likes wind and solar requires pumped-storage plants to increase their performances to stabilize grid frequency and voltage. The introduction of a full-power converter constitutes the ultimate step forward to meet the requirement in a safe, reliable and sustainable manner. This article quickly introduces the converter topology and technology before describing the performances it aims to deliver to the grid. Finally, converter bypass is discussed.

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

Wang, Hsiu-Wen; Daemen, Luke L.; Cheshire, Michael C.

It is generally believed that H 2O and OH - are the key species stabilizing and controlling amorphous calcium carbonate “polyamorph” forms, and may in turn control the ultimate crystallization products during synthesis and in natural systems. Yet, the locations and hydrogen-bonding network of these species in ACC have never been measured directly using neutron diffraction. In this paper, we report a synthesis route that overcomes the existing challenges with respect to yield quantities and deuteration, both of which are critically necessary for high quality neutron studies.

Benefits of Intercritical Annealing in Quenching and Partitioning Steel

NASA Astrophysics Data System (ADS)

Wang, X.; Liu, L.; Liu, R. D.; Huang, M. X.

2018-03-01

Compared to the quenching and partitioning (Q&P) steel produced by full austenization annealing, the Q&P steel produced by the intercritical annealing shows a similar ultimate tensile stress but a larger tensile ductility. This property is attributable to the higher volume fraction and the better mechanical stability of the retained austenite after the intercritical annealing. Moreover, intercritical annealing produces more ferrite and fewer martensite phases in the microstructure, making an additional contribution to a higher work hardening rate and therefore a better tensile ductility.

Modeling, Analysis, and Control of Swarming Agents in a Probabilistic Framework

DTIC Science & Technology

2012-11-01

configurations, which can ultimately lead the swarm towards configurations close to the global minimum of the total potential of interactions. The drawback ...165–171, 1992. [6] H. Ye, H. Wang, and H. Wang, “Stabilization of a PVTOL aircraft and an inertia wheel pendulum using saturation technique,” IEEE...estimate its parameters. The drawback of this approach is that the assumed form of the field can be unrealistic. In the approach that we are presenting here

Metrological features of the rubidium two-photon standards of the BNM-LPTF and Kastler Brossel Laboratories

NASA Astrophysics Data System (ADS)

Hilico, L.; Felder, R.; Touahri, D.; Acef, O.; Clairon, A.; Biraben, F.

1998-11-01

We have built three optical frequency standards based on the two-photon transition of rubidium at 778nm, and analysed their performance over a period of more than three years. We discuss some systematic effects that could lead to the reproducibility we observe, and point out the possible improvements of the devices. We also examine the short and long term stabilities of the systems, and show that we have reached their ultimate performances.

Quadruplex digital flight control system assessment

NASA Technical Reports Server (NTRS)

Mulcare, D. B.; Downing, L. E.; Smith, M. K.

1988-01-01

Described are the development and validation of a double fail-operational digital flight control system architecture for critical pitch axis functions. Architectural tradeoffs are assessed, system simulator modifications are described, and demonstration testing results are critiqued. Assessment tools and their application are also illustrated. Ultimately, the vital role of system simulation, tailored to digital mechanization attributes, is shown to be essential to validating the airworthiness of full-time critical functions such as augmented fly-by-wire systems for relaxed static stability airplanes.

Targeting Alpha5 Beta1 Integrin to Prevent Metastatic Breast Cancer Cell Invasion: PhScN Target Site Definition and Plasma Stability

DTIC Science & Technology

2015-11-01

increased PhScN potency as a result of preventing endoproteolytic degradation. Finally, the in vivo lung extravasation and colonization data, as well as...successful colonization are late stages in breast cancer progression that are ultimately fatal. Hence, prevention of extravasation which leads to colony...Award Number: TITLE: “Targeting Alpha5 Beta1 Integrin to Prevent Metastatic Breast Cancer Cell Invasion: PhScN Target Site Definition and Plasma

The uncertainty principle and quantum chaos

NASA Technical Reports Server (NTRS)

Chirikov, Boris V.

1993-01-01

The conception of quantum chaos is described in some detail. The most striking feature of this novel phenomenon is that all the properties of classical dynamical chaos persist here but, typically, on the finite and different time scales only. The ultimate origin of such a universal quantum stability is in the fundamental uncertainty principle which makes discrete the phase space and, hence, the spectrum of bounded quantum motion. Reformulation of the ergodic theory, as a part of the general theory of dynamical systems, is briefly discussed.

A new photostabilizer: Hydrogenated benzoin derivatives

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

Yamaguchi, K.; Ohkatsu, Y.

1993-12-31

It is found that synergistic effects based on combined use of HALS (hindered Amine Light Stabilizers) with phenolic antioxidants consist of the action of HALS as hydrogen donor to quinones, derived from the phenol in autoxidation, excited by uv light. The finding has been realized as a new photostabilizer of hydrogenated benzoin derivatives. They are generally characterized by multifunctions. The o,o`-dihydroxyl-substituted derivatives inter alia extend the life of a phenolic antioxidant co-used, as hydrogen donor, as well as ultimately act as uv absorber.

Initial Diagnosis and Management of Coma.

PubMed

Traub, Stephen J; Wijdicks, Eelco F

2016-11-01

Coma represents a true medical emergency. Drug intoxications are a leading cause of coma; however, other metabolic disturbances and traumatic brain injury are also common causes. The general emergency department approach begins with stabilization of airway, breathing, and circulation, followed by a thorough physical examination to generate a limited differential diagnosis that is then refined by focused testing. Definitive treatment is ultimately disease-specific. This article presents an overview of the pathophysiology, causes, examination, and treatment of coma. Copyright © 2016 Elsevier Inc. All rights reserved.

Autonomous Control Modes and Optimized Path Guidance for Shipboard Landing in High Sea States

DTIC Science & Technology

2017-04-15

50 0 50 Singular Values Frequency (rad/s) S in g u la r V a lu e s ( d B ) controller . The non -output variables can be estimated by reliable linear...Contract # N00014-14-C-0004 Autonomous Control Modes and Optimized Path Guidance for Shipboard Landing in High Sea States Progress Report...recovery of a VTOL UAV. There is a clear need for additional levels of stability and control augmentation and, ultimately, fully autonomous landing

Interface reactions between silicon carbide and interlayers in silicon carbide copper metal matrix composites

NASA Astrophysics Data System (ADS)

Köck, T.; Brendel, A.; Bolt, H.

2007-05-01

Novel copper matrix composites reinforced with silicon carbide fibres are considered as a new generation of heat sink materials for the divertor of future fusion reactors. The divertor is exposed to intense particle bombardment and heat loads of up to 15 MW m-2. This component consists of the plasma-facing material which is bonded to the actively cooled heat sink. Due to its high thermal conductivity of about 400 W m-1 K-1 copper is a promising material for the heat sink. To increase the mechanical properties of copper at working temperature (823 K), silicon carbide fibres with a diameter of 140 μm are used to reinforce the interface area between the plasma-facing material and the heat sink. Push-out tests show that the adhesion between SiC fibre and Cu matrix without any interlayer is very low. To increase the fibre-matrix bonding the fibres are coated with Cr and W with a thickness of 300-400 nm before Cu deposition by magnetron sputtering. Push-out tests on these modified fibres show a significant increase in adhesion compared to the fibres without interlayer. XRD investigations after a heat treatment at 923 K show a chromium carbide (Cr23C6, Cr3C2) formation and the absence of chromium silicides. In the case of a W interlayer a W2C formation is detected and also no tungsten silicides. Single-fibre tensile tests were performed to investigate the influence of the reaction zone on the ultimate tensile strength of the fibres. The ultimate tensile strength for fibres without interlayer remains constant at about 2200 MPa after annealing at 923 K. The fibres with chromium and tungsten interlayers, respectively, show a decrease of about 30% of the ultimate tensile strength after the heat treatment at 923 K.

Transport and retention of surfactant- and polymer-stabilized engineered silver nanoparticles in silicate-dominated aquifer material

USDA-ARS?s Scientific Manuscript database

Packed column experiments were conducted to investigate the transport and blocking behavior of surfactant- and polymer-stabilized engineered silver nanoparticles (Ag-ENPs) in saturated natural aquifer material with varying silt and clay content, background solution chemistry, and flow velocity. Brea...

STABILIZATION OF MERCURY IN WASTE MATERIAL FROM THE SULFUR BANK MERCURY MINE, INNOVATIVE TECHNOLOGY EVALUATION REPORT

EPA Science Inventory

Three innovative technologies for stabilization of mercury were demonstrated in a treatability study performed on two waste rock materials from the Sulfur Bank Mercury Mine, a Superfund site in northern California. The treatability study was jointly sponsored by two EPA programs:...

Thermophysical properties of plasma sprayed coatings

NASA Technical Reports Server (NTRS)

Wilkes, K. E.; Lagedrost, J. F.

1973-01-01

Thermophysical properties of plasma sprayed materials were determined for the following plasma sprayed materials: CaO - stabilized ZrO2, Y2O3 - stabilized ZerO2, Al2O3, HfO2 Mo, nichrome, NiAl, Mo-ZrO2, and MoAl2O3 mixtures. In all cases the thermal conductivity of the as-sprayed materials was found to be considerably lower than that of the bulk material. The flash-laser thermal diffusivity technique was used both for diffusivity determination of single-layer materials and to determine the thermal contact resistance at the interface of two-layer specimens.