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Sample records for functionally graded coatings

  1. Functionally graded mullite coatings for gas turbines

    NASA Astrophysics Data System (ADS)

    Kulkarni, Tushar

    The next generation of heat exchangers and gas turbines require high performance materials as they need to operate at higher temperatures for higher efficiency. SiC and Si3N4 are promising candidates as they have excellent high temperature properties. However, when used in complex combustion environments found in gas-turbine applications, these materials have two major concerns; namely hot-corrosion and recession. It is well established that environmental barrier coatings (EBC) can be utilized to overcome these limitations. Although chemical vapor deposited (CVD) mullite (3Al2O 3.2SiO2) coatings developed before this study have shown promise in protecting Si-based substrates, there is concern that the silica content within the mullite coating itself might be susceptible to hot-corrosion and recession during long term exposure to corrosive atmospheres containing Na/V salts and water vapor. There is thus strong motivation to substantially reduce or even virtually eliminate the silica component from the surfaces of mullite coatings that are in direct contact with atmospheres containing corrosive oxides and steam. In this study, CVD has been used to deposit mullite coatings with potential promise to protect Si-based ceramics for high temperature applications. The composition of these functionally graded mullite coatings was varied from silica-rich close to the coating/substrate (SiC) interface for coefficient of thermal expansion match to alumina-rich towards the outer surface of the coating. In the process, the highest alumina-rich mullite ever reported has been deposited. The phase transformation and hot-corrosion behavior of the coatings was also investigated in this work. The coatings show immense potential to protect Si-based ceramics. It is expected that these coatings will have very broad impact by enabling gas turbines to operate at higher temperatures leading to improved fuel efficiency and reduced emissions.

  2. Ni-based Metal Matrix Composite Functionally Graded Coatings

    NASA Astrophysics Data System (ADS)

    Amado, J. M.; Montero, J.; Tobar, M. J.; Yáñez, A.

    Functional graded materials (FGMs) are a class of composites that have a continuous variation of material properties. One of the aims of such variation is to relieve the stress concentrations that appear in laminated materials. Coating techniques using powder as filler material can be adapted for the manufacture of composition gradients by means of a mixing unit in a powder feed system which is the basis of the laser cladding technology. The aim of this paper is to get coats with layers of the highest possible ceramic concentration on a metal matrix composite (MMC) with the help of the FGM methodology.

  3. Novel Investigation on Nanostructured Multilayer and Functionally Graded Ni-P Electroless Coatings on Stainless Steel

    NASA Astrophysics Data System (ADS)

    Anvari, S. R.; Monirvaghefi, S. M.; Enayati, M. H.

    2015-06-01

    In this study, step-wise multilayer and functionally graded Ni-P coatings were deposited with electroless in which the content of phosphorus and nickel would be changed gradually and step-wise through the thickness of the coatings, respectively. To compare the properties of these coatings with Ni-P single-layer coatings, three types of coatings with different phosphorus contents were deposited. Heat treatment of coatings was performed at 400 °C for 1 h. The microstructure and phase transformation of coatings were characterized by SEM/EDS, TEM, and XRD. The mechanical properties of coatings were studied by nanoindentation test. According to the results of the single-layer coatings, low P coating had the maximum hardness and also the ratio of hardness ( H) to elasticity modulus ( E) for the mentioned coating was maximum. In addition, low and medium P coatings had crystalline and semi-crystalline structure, respectively. The mentioned coatings had <111> texture and after heat treatment their texture didn't change. While high P coating had amorphous structure, after heat treatment it changed to crystalline structure with <100> texture for nickel grains. Furthermore, the results showed that functionally graded and step-wise multilayer coatings were deposited successfully by using the same initial bath and changing the temperature and pH during deposition. Nanoindentation test results showed that the hardness of the mentioned coatings changed from 670 Hv near the substrate to 860 Hv near the top surface of coatings. For functionally graded coating the hardness profile had gradual changes, while step-wise multilayer coating had step-wise hardness profile. After heat treatment trend of hardness profiles was changed, so that near the substrate, hardness was measured 1400 Hv and changed to 1090 Hv at the top coat.

  4. Deposition and Characterization of HVOF Thermal Sprayed Functionally Graded Coatings Deposited onto a Lightweight Material

    NASA Astrophysics Data System (ADS)

    Hasan, M.; Stokes, J.; Looney, L.; Hashmi, M. S. J.

    2009-02-01

    There is a significant interest in lightweight materials (like aluminum, magnesium, titanium, and so on) containing a wear resistance coating, in such industries as the automotive industry, to replace heavy components with lighter parts in order to decrease vehicle weight and increase fuel efficiency. Functionally graded coatings, in which the composition, microstructure, and/or properties vary gradually from the bond coat to the top coat, may be applied to lightweight materials, not only to decrease weight, but also to enhance components mechanical properties by ensuring gradual microstructural (changes) together with lower residual stress. In the current work, aluminum/tool-steel functionally graded coatings were deposited onto lightweight aluminum substrates. The graded coatings were then characterized in terms of residual stress and hardness. Results show that residual stress increased with an increase in deposition thickness and a decrease in number of layers. However, the hardness also increased with an increase in deposition thickness and decrease in number of layers. Therefore, an engineer must compromise between the hardness and stress values while designing a functionally graded coating-substrate system.

  5. Concept of functionally graded materials for advanced thermal barrier coating applications

    SciTech Connect

    Lee, W.Y.; Stinton, D.P.; Berndt, C.C.; Erdogan, F.; Lee, Y.D.; Mutasim, Z.

    1996-12-01

    This article explores the concept of creating functionally graded metal-ceramic composite microstructures for thermal barrier coatings used in gas-turbine applications. From a thermomechanical perspective, this concept offers the possibility of significantly improving the life and reliability of thermal barrier coatings. However, prior research reveals that progress has been somewhat limited because of the oxidative instability exhibited by some metal-ceramic composite microstructures. The present study addresses some of the materials criteria and research issues associated with preparing chemically stable, yet mechanically durable, graded metal-ceramic microstructures for realistic application environments.

  6. Microstructure and Properties of Thermally Sprayed Functionally Graded Coatings for Polymeric Substrates

    NASA Technical Reports Server (NTRS)

    Ivosevic, M.; Knight, R.; Kalidindi, S. R.; Palmese, G. R.; Sutter, J. K.

    2003-01-01

    The use of polymer matrix composites (PMCs) in the gas flow path of advanced turbine engines offers significant benefits for aircraft engine performance but their useful lifetime is limited by their poor erosion resistance. High velocity oxy-fuel (HVOF) sprayed polymer/cermet functionally graded (FGM) coatings are being investigated as a method to address this technology gap by providing erosion and oxidation protection to polymer matrix composites. The FGM coating structures are based on a polyimide matrix filled with varying volume fractions of WC-Co. The graded coating architecture was produced using a combination of internal and external feedstock injection, via two computer-controlled powder feeders and controlled substrate preheating. Porosity, coating thickness and volume fraction of the WC-Co filler retained in the coatings were determined using standard metallographic techniques and computer image analysis. The pull-off strength (often referred to as the adhesive strength) of the coatings was evaluated according to the ASTM D 4541 standard test method, which measured the greatest normal tensile force that the coating could withstand. Adhesive/cohesive strengths were determined for three different types of coating structures and compared based on the maximum indicated load and the surface area loaded. The nature and locus of the fractures were characterized according to the percent of adhesive and/or cohesive failure, and the tested interfaces and layers involved were analyzed by Scanning Electron Microscopy.

  7. Processing and Characterization of Functionally Graded Hydroxyapatite Coatings for Biomedical Implants

    NASA Astrophysics Data System (ADS)

    Bai, Xiao

    Hydroxyapatite [Ca10(PO4)6(OH) 2, HA] has been widely applied as a coating on various biomedical bone/dental implants to improve biocompatibility and bioactivity. It has been observed that primary reasons leading to implantation failure of commercial HA coated implants processed by plasma spraying are the poor mechanical properties of coatings and infections accompanied by implantation. It has been also reported an ideal coating should be able to stimulate new bone growth at the initial stage of implantation and stay stable both mechanically and chemically thereafter. This research has investigated a functionally graded hydroxyapatite (FGHA) coating that is capable of improving the stability of implants, facilitating recovery, and preventing infections after implantation. A series of FGHA coatings with incorporated Ag 0 ˜ 13.53 wt. % has been deposited onto Ti substrate using ion beam assisted deposition (IBAD) with in-situ heat treatment. The compositional, microstructural, mechanical, and biological properties of coatings have been analyzed via various tests. The relationship among processing parameters, coating properties and biological behaviors has been established and the processing parameters for processing FGHA coatings with/without incorporated Ag have been optimized. Microstructure observations of coating cross section via transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) for set temperature coatings deposited at 450°C ˜ 750°C reveals that in-situ substrate temperature is the primary factor controlling the crystallinity of the coatings. The microstructure observation of cross section via TEM/STEM for both FGHA coatings with/without incorporated Ag has shown that coatings are dense and have a gradually decreased crystallinity from substrate/coating interface to top surface. In particular, the interface has an atomically intermixed structure; the region near the interface has a columnar grain structure whereas

  8. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect

    Prof. Stratis V. Sotirchos

    2001-02-01

    The main objective of this research project was the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Since alumina has excellent resistance to corrosion but coefficient than silicon carbide, the key idea of this project has been to develop graded coatings with composition varying smoothly along their thickness between an inner (base) layer of mullite in contact with the silicon carbide component and an outer layer of pure alumina, which would function as the actual protective coating of the component. (Mullite presents very good adhesion towards silicon carbide and has thermal expansion coefficient very close to that of the latter.)

  9. Thermal spraying of functionally graded calcium phosphate coatings for biomedical implants

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Khor, K. A.; Cheang, P.

    1998-03-01

    Biomedical requirements in a prosthesis are often complex and diverse in nature. Biomaterials for implants have to display a wide range of adaptability to suit the various stages of the bio-integration process of any foreign material into the human body. Often, a combination of materials is needed. The preparation of a functionally graded bioceramic coating composed of essentially calcium phosphate compounds is explored. The coating is graded in accordance to adhesive strength, bioactivity, and bioresorbability. The bond coat on the Ti-6Al-4V stub is deposited with a particle range of the hydroxyapatite (HA) that will provide a high adhesive strength and bioactivity but have poor bioresorption properties. The top coat, however, is composed of predominantly α-tricalcium phosphate (α-TCP) that is highly bioresorbable. This arrangement has the propensity of allowing accelerated bio-integration of the coating by the body tissues as the top layer is rapidly resorbed, leaving the more bioactive intermediate layer to facilitate the much needed bioactive properties for proper osteoconduction. The processing steps and problems are highlighted, as well as the results of post-spray heat treatment.

  10. Functionally Graded Alumina/Mullite Coatings for Protection of Silicon Carbide Ceramic Components from Corrosion

    SciTech Connect

    Sotirchos, S.V.

    1997-04-01

    During the six months of this reporting period, we accomplished the following: Preparatory work was done on the development of the feed supply system (for mixtures of AlCl{sub 3}, SiCl{sub 4}, H{sub 2} and CO{sub 2}) and effluent treatment section for the CVD system we plan to employ for coating preparation. A comprehensive literature survey of past work done on the chemical vapor deposition of silica, alumina and aluminosilicates (mullite) was carried out, and work was initiated on the study of thermochemical equilibrium in the Al/Si/Cl/C/O/H system so as to identify the boundaries of the region of the space of operating parameters and conditions where preparation of functionally graded mullite/ alumina coatings through CVD from metal chloride, CO{sub 2}, and H{sub 2} is feasible. Since the alumina/mullite films that are proposed to be developed can also be applied to carbon matrix composites provided that a layer that bridges the gap that exists between the thermal expansion coefficient of carbon and that of mullite is employed, experiments were conducted on the preparation of compositionally graded carbon/silicon carbide coatings. Deposition from mixtures of ethylene and methyltrichlorosilane or tetrachlorosilane (silicon tetrachloride) in hydrogen was used for the preparation of SiC/C coatings, and our experiments focused on the study of the occurrence of multiple steady states in the deposition process and the effects of the type of chlorosilane on the deposition rate and the deposit composition and their variation along the length of the reactor. The results showed that when operation is carried out outside the multiplicity region, codeposition of SiC and C from ethylene and chlorosilanes is a feasible route for preparation of SiC/C graded coatings.

  11. Deposition and characterization of plasma sprayed Ni-5A1/ magnesia stabilized zirconia based functionally graded thermal barrier coating

    NASA Astrophysics Data System (ADS)

    Baig, M. N.; Khalid, F. A.

    2014-06-01

    Thermal barrier coatings (TBCs) are employed to protect hot section components in industrial and aerospace gas turbine engines. Conventional TBCs frequently fail due to high residual stresses and difference between coefficient of thermal expansion (CTE) of the substrate & coatings. Functionally graded thermal barrier coatings (FG-TBCs) with gradual variation in composition have been proposed to minimize the problem. In this work, a five layered functionally graded thermal barrier coating system was deposited by atmospheric plasma spray (APS) technique on Nimonic 90 substrates using Ni-5Al as bond coat (BC) and magnesia stabilized zirconia as top coat (TC). The coatings were characterized by SEM, EDS, XRD & optical profilometer. Microhardness and coefficient of thermal expansion of the five layers deposited as individual coatings were also measured. The deposited coating system was oxidized at 800°C. SEM analysis showed that five layers were successfully deposited by APS to produce a FG-TBC. The results also showed that roughness (Ra) of the individual layers decreased with an increase in TC content in the coatings. It was found that microhardness and CTE values gradually changed from bond coat to cermet layers to top coat. The oxidized coated sample revealed parabolic behavior and changes in the surface morphology and composition of coating.

  12. Preparation of a Functionally Graded Fluoropolymer Thin Film and Its Application to Antireflective Coating

    NASA Astrophysics Data System (ADS)

    Senda, Kazuo; Matsuda, Tsuyoshi; Kawanishi, Takumi; Tanaka, Kuniaki; Usui, Hiroaki

    2013-05-01

    Fluoropolymer thin films were prepared by the ion-assisted vapor deposition polymerization (IAD) of 2-(perfluorohexyl) ethylacrylate (Rf-6) under Ar ion irradiation. The ion acceleration voltage Va largely affected the film characteristics. With increasing Va, the adhesion strength between the film and the substrate improved, while the surface energy and the refractive index increased. To attain a high adhesion strength, a low surface energy, and a low optical reflectivity simultaneously, a functionally graded film was prepared by varying Va from 300 to 0 V continually in the course of film growth. As a consequence, an antireflective coating with good adhesion and low surface energy was obtained. The optical reflectivity of a glass substrate was reduced from 4.9 to 0.55% at a wavelength of 400 nm by depositing a 100-nm-thick single-layer functionally graded fluoropolymer film. The surface energy of this film was 8.5 mJ/m2.

  13. The surface crack problem for a functionally graded coating bonded to a homogeneous layer

    NASA Astrophysics Data System (ADS)

    Kasmalkar, Maheendra B.

    In the continuing search for materials which can withstand the grueling requirements of modern day applications, Functionally Graded Materials (FGMs) seem to be a promising alternative to conventional materials. These nonhomogeneous materials offer better interfacial properties by improving bond strength and reducing thermal mismatch. Before putting these materials into application, an important step in the design of FGMs is the stress analysis and fracture characterization. The fracture performance of FGM coatings on homogeneous substrates is the focus of this study. In this study, various internal and surface crack configurations in the coating and the substrate are subjected to mechanical and thermal loads. The analysis is linear elastic. The thermo-mechanical properties of the FGM coating are assumed to vary exponentially with the spatial coordinate. The equilibrium equations are solved using integral transforms. The resulting singular integral equations are solved using numerical integration. The results of interest for this mode I formulation are the stress intensity factors and the crack opening displacements. The effects of the nonhomogeneity parameter and various dimensionless length parameters are studied. One of the most important outcomes of this study is the theoretical proof that "kink" in material property at the interface does not introduce any singularity. In the numerical results it is observed that generally the stress intensity factors tend to increase with material nonhomogeneity. Also, it is observed that the substrate thickness tends to suppress cracking in the coating. In pure thermal loading, the surface cracks may either be arrested or there might be crack closure. The stress intensity factors from different loadings can be added up to obtain the resultant stress intensity factor for multiple loading. Results in this study have wide-ranging applications. They can be applied to thermal barrier coatings on turbine components, combustion

  14. Sliding Wear and Fretting Wear of DLC-Based, Functionally Graded Nanocomposite Coatings

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Pohlchuck, B.; Street, Kenneth W.; Zabinski, J. S.; Sanders, J. H.; Voevodin, A. a.; Wu, R. L. C.

    1999-01-01

    Improving the tribological functionality of diamondlike carbon (DLC) films--developing, good wear resistance, low friction, and high load-carrying capacity-was the aim of this investigation. Nanocomposite coatings consisting of an amorphous DLC (a-DLC) top layer and a functionally graded titanium-titanium carbon-diamondlike carbon (Ti-Ti(sub x) C(sub y)-DLC) underlayer were produced on AISI 440C stainless steel substrates by the hybrid technique of magnetron sputtering and pulsed-laser deposition. The resultant DLC films were characterized by Raman spectroscopy, scanning electron microscopy, and surface profilometry. Two types of wear experiment were conducted in this investioation: sliding friction experiments and fretting wear experiments. Unidirectional ball-on-disk sliding friction experiments were conducted to examine the wear behavior of an a-DLC/Ti-Ti(sub x) C(sub y)-DLC-coated AISI 440C stainless steel disk in sliding contact with a 6-mm-diameter AISI 440C stainless steel ball in ultrahigh vacuum, dry nitrogen, and humid air. Although the wear rates for both the coating and ball were low in all three environments, the humid air and dry nitrogen caused mild wear with burnishing, in the a-DLC top layer, and the ultrahigh vacuum caused relatively severe wear with brittle fracture in both the a-DLC top layer and the Ti-Ti(sub x) C(sub y)-DLC underlayer. For reference, amorphous hydrogenated carbon (H-DLC) films produced on a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coatings by using an ion beam were also examined in the same manner. The H-DLC films markedly reduced friction even in ultrahigh vacuum without sacrificing wear resistance. The H-DLC films behaved much like the a-DLC/Ti-Ti(sub x) C(sub y)-DLC nanocomposite coating in dry nitrogen and humid air, presenting low friction and low wear. Fretting wear experiments were conducted in humid air (approximately 50% relative humidity) at a frequency of 80 Hz and an amplitude of 75 micron on an a

  15. Micro-scratch and corrosion behavior of functionally graded HA-TiO2 nanostructured composite coatings fabricated by electrophoretic deposition.

    PubMed

    Farnoush, Hamidreza; Aghazadeh Mohandesi, Jamshid; Çimenoğlu, Hüseyin

    2015-06-01

    In the present study, functionally graded coatings of HA/TiO2 nanoparticles and HA-TiO2 nanocomposite coatings with 0, 10 and 20 wt% of TiO2 were fabricated by electrophoretic deposition on Ti-6Al-4V substrate. The functionally graded structure of HA/TiO2 coatings was formed by gradual addition of HA suspension into the deposition cell containing TiO2 nanoparticles. Micro-scratch test results showed the highest critical distances of crack initiation and delamination, normal load before failure and critical contact pressures for functionally graded coating. It was observed that the improvement of adhesion strength and fracture toughness of functionally graded coatings would be due to the reduction of thermal expansion coefficient mismatch between Ti-6Al-4V substrate and HA. The results of potentiodynamic polarization measurements showed that the graded structure of the coating could efficiently increase the corrosion resistance of substrate. PMID:25771254

  16. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect

    1997-10-01

    The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO{sub 2} and H{sub 2} will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this six-month reporting period, we continued the work on the development and construction of the thermogravimetric chemical vapor deposition system that we intend to employ for studying the deposition of alumina, silica, and aluminosilicates (such as mullite) from mixtures of metal chlorides in H{sub 2} and CO{sub 2}. Specifically, we worked on the development of the tubular flow reactor that will be used for producing aluminum chloride for delivery to the chemical vapor deposition system and of the vapor and gas supply system. Various problems arising from condensation of aluminum chlorides in some sections of the supply line were resolved, and we expect to perform experiments using mixtures containing AlCl{sub 3} in the next reporting period. Preliminary experiments on the

  17. FUNCTIONALLY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect

    1998-03-01

    The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO{sub 2} and H{sub 2} will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this reporting period, the construction and development of the chemical vapor deposition system was completed, and experiments were conducted on the deposition of alumina, silica, and aluminosilicates (such as mullite) from mixtures of AlCl{sub 3} and CH{sub 3}SiCl{sub 3} in CO{sub 2} and H{sub 2}. Work was mainly done on the investigation of the effects of the reaction temperature on the deposition kinetics. It was found that the temperature had a positive effect on the single oxides deposition rates and the codeposition rate. The apparent activation energy values extracted from the deposition rate vs. temperature curves in the high temperature region were similar for the three deposition processes, having a value around 20 kcal/mol. The codeposition rates were higher, by a

  18. Mechanical characterization of hybrid and functionally-graded aluminum open-cell foams with nanocrystalline-copper coatings

    NASA Astrophysics Data System (ADS)

    Sun, Yi

    Cellular/foam materials found in nature such as bone, wood, and bamboo are usually functionally graded by having a non-uniform density distribution and inhomogenous composition that optimizes their global mechanical performance. Inspired by such naturally engineered products, the current study was conducted towards the development of functionally graded hybrid metal foams (FGHMF) with electrodeposited (ED) nanocrystalline coatings. First, the deformation and failure mechanisms of aluminum/copper (Al/Cu) hybrid foams were investigated using finite element analyses at different scales. The micro-scale behavior was studied based on single ligament models discretized using continuum elements and the macro-scale behavior was investigated using beam-element based finite element models of representative unit volumes consisting of multiple foam cells. With a detailed constitutive material behavior and material failure considered for both the aluminum ligament and the nano-copper coating, the numerical models were able to capture the unique behavior of Al/Cu hybrid foams, such as the typically observed sudden load drop after yielding. The numerical models indicate that such load drop is caused by the fracture of foam ligaments initiated from the rupture of the ED nano-copper coating due to its low ductility. This failure mode jeopardizes the global energy absorption capacity of hybrid foams, especially when a thick coating is applied. With the purpose of enhancing the performance of Al/Cu hybrid foams, an annealing process, which increased the ductility of the nanocrystalline copper coating by causing recovery, recrystallination and grain growth, was introduced in the manufacturing of Al/Cu hybrid foams. Quasi-static experimental results indicate that when a proper amount of annealing is applied, the ductility of the ED copper can be effectively improved and the compressive and tensile behavior of Al/Cu hybrid foams can be significantly enhanced, including better energy

  19. Potential of direct metal deposition technology for manufacturing thick functionally graded coatings and parts for reactors components

    NASA Astrophysics Data System (ADS)

    Thivillon, L.; Bertrand, Ph.; Laget, B.; Smurov, I.

    2009-03-01

    Direct metal deposition (DMD) is an automated 3D deposition process arising from laser cladding technology with co-axial powder injection to refine or refurbish parts. Recently DMD has been extended to manufacture large-size near-net-shape components. When applied for manufacturing new parts (or their refinement), DMD can provide tailored thermal properties, high corrosion resistance, tailored tribology, multifunctional performance and cost savings due to smart material combinations. In repair (refurbishment) operations, DMD can be applied for parts with a wide variety of geometries and sizes. In contrast to the current tool repair techniques such as tungsten inert gas (TIG), metal inert gas (MIG) and plasma welding, laser cladding technology by DMD offers a well-controlled heat-treated zone due to the high energy density of the laser beam. In addition, this technology may be used for preventative maintenance and design changes/up-grading. One of the advantages of DMD is the possibility to build functionally graded coatings (from 1 mm thickness and higher) and 3D multi-material objects (for example, 100 mm-sized monolithic rectangular) in a single-step manufacturing cycle by using up to 4-channel powder feeder. Approved materials are: Fe (including stainless steel), Ni and Co alloys, (Cu,Ni 10%), WC compounds, TiC compounds. The developed coatings/parts are characterized by low porosity (<1%), fine microstructure, and their microhardness is close to the benchmark value of wrought alloys after thermal treatment (Co-based alloy Stellite, Inox 316L, stainless steel 17-4PH). The intended applications concern cooling elements with complex geometry, friction joints under high temperature and load, light-weight mechanical support structures, hermetic joints, tubes with complex geometry, and tailored inside and outside surface properties, etc.

  20. Buckling of graded coatings: A continuum model

    NASA Astrophysics Data System (ADS)

    Chiu, Tz-Cheng

    2000-12-01

    Requirements for the protection of hot section components in many high temperature applications such as earth-to-orbit winged planes and advanced turbine systems have led to the application of thermal barrier coatings (TBCs) that utilize ceramic coatings on metal substrates. An alternative concept to homogeneous ceramic coatings is the functionally graded materials (FGM) in which the composition of the coating is intentionally graded to improve the bonding strength and to reduce the magnitude of the residual and thermal stresses. A widely observed failure mode in such layered systems is known to be interface cracking that leads to spallation fracture. In most cases, the final stage of the failure process for a thin coating appears to be due to buckling instability under thermally or mechanically induced compressive stress. The objective of this study is to develop a solution to the buckling instability problem by using continuum elasticity rather than a structural mechanics approach. The emphasis in the solution will be on the investigation of the effect of material inhomogeneity in graded coatings on the instability load, the postbuckling behavior, and fracture mechanics parameters such as the stress intensity factors and strain energy release rate. In this analysis, a nonlinear continuum theory is employed to examine the interface crack problem. The analytical solution of the instability problem permits the study of the effect of material inhomogeneity upon the inception of buckling and establishes benchmark results for the numerical solutions of related problems. To study the postbuckling behavior and to calculate the stress intensity factors and strain energy release rate a geometrically nonlinear finite element procedure with enriched crack-tip element is developed. Both plane strain and axisymmetric interface crack problems in TBCs with either homogeneous or graded coating are then considered by using the finite element procedure. It is assumed that the

  1. Functionally graded materials for thermal barrier coatings in advanced gas turbine systems research. Semi-annual report, May 1--December 31, 1996

    SciTech Connect

    1997-08-01

    A combination of two new production methods, reaction-bonded metal oxide (RBMO) and electrochemical processing, have been utilized to create a functionally graded thermal barrier coating. Electrochemical processing, which includes both electrodeposition (EDEP) and electrophoretic deposition (EPD), has been used to deposit both the metallic and ceramic layers of the coating. EPD has been used to deposit the RBMO precursor powders, which exhibit the dual properties of both a metal and ceramic due to its composite nature. A summary of the FGM production methods and resulting characterization of the produced coatings for the eleventh and twelfth quarters (5/96--12/96), as well as a project summary, are outlined in this final report.

  2. Functionally graded boron carbide

    SciTech Connect

    Petrovic, J.J.; McClellan, K.J.; Kise, C.D.; Hoover, R.C.; Scarborough, W.K.

    1998-12-31

    Lightweight body armor is important for the protection of US soldiers in the field. Here, fabrication techniques were developed for producing graded porosity B{sub 4}C, and for producing aluminum-B{sub 4}C and epoxy-B{sub 4}C functionally graded materials. The key fabrication aspect was obtaining the graded porosity B{sub 4}C. The feasibility of producing graded porosity B{sub 4}C using a grading of carbon densification aid produced from a gradient of furfuryl alcohol carbon precursor was demonstrated. This approach is quite promising, but it was not optimized in the present investigation. Graded porosity B{sub 4}C materials were produced by a layering approach using different size distributions of B{sub 4}C powders in the green state, and then densifying the layered assembly by hot pressing at 1,900 C. The hardness of uninfiltrated graded B{sub 4}C, aluminum infiltrated B{sub 4}C, and epoxy infiltrated B{sub 4}C was observed to be similar.

  3. Graded coatings for metallic implant alloys

    SciTech Connect

    Saiz, Eduardo; Tomsia, Antoni P.; Fujino, Shigeru; Gomez-Vega, Jose M.

    2002-08-01

    Graded glass and glass-hydroxyapatite coatings on Ti-based and Co-Cr alloys have been prepared using a simple enameling technique. The composition of the glasses has been tailored to match the thermal expansion of the alloys. By controlling the firing time, and temperature, it has been possible to control the reactivity between the glass and the alloy and to fabricate coatings (25 to 150 mu m thick) with excellent adhesion to the substrate, resistant to corrosion and able to precipitate hydroxyapatite during in vitro tests in simulated body fluid.

  4. Fatigue Characterization of Functionally Graded Metallic Alloys

    NASA Astrophysics Data System (ADS)

    Silva, F. S.

    2008-02-01

    Functionally graded components exhibit spatial variations of mechanical properties in contrast with, and as an alternative to, purely homogeneous components. A large class of graded materials, however, are in fact mostly homogeneous materials with property variations (chemical or mechanical) restricted to a specific area or layer produced by applying for example a coating or by introducing sub-surface residual stresses. However, it is also possible to obtain graded materials with a smooth transition of mechanical properties along the entire component, for example in a 40 mm component. This is possible, for example, by using centrifugal casting technique or incremental melting and solidification technique. In this paper we will study fully metallic functionally graded components with a smooth gradient, focusing on fatigue crack propagation. Fatigue propagation will be assessed in the direction parallel to the gradation (in different homogeneous layers of the functionally graded component) to assess what would be fatigue crack propagation on the direction perpendicular to the gradation. Fatigue crack growth rate (standard mode I fatigue crack growth) will be correlated to the mode I stress intensity factor range. Other mechanical properties of different layers of the component (Young's modulus) will also be considered in this analysis. The effect of residual stresses along the component gradation on crack propagation will also be taken into account. A qualitative analysis of the effects of some important features, present in functionally graded materials, will be made based on the obtained results.

  5. Single-step laser deposition of functionally graded coating by dual ‘wire powder’ or ‘powder powder’ feeding—A comparative study

    NASA Astrophysics Data System (ADS)

    Syed, Waheed Ul Haq; Pinkerton, Andrew J.; Liu, Zhu; Li, Lin

    2007-07-01

    The creation of iron-copper (Fe-Cu) alloys has practical application in improving the surface heat conduction and corrosion resistance of, for example, conformal cooling channels in steel moulds, but is difficult to achieve because the elements have got low inter-solubility and are prone to solidification cracking. Previous work by these authors has reported a method to produce a graded iron-nickel-copper coating in a single-step by direct diode laser deposition (DLD) of nickel wire and copper powder as a combined feedstock. This work investigates whether dual powder feeds can be used in that process to afford greater geometric flexibility and compares attributes of the 'nickel wire and copper powder' and 'nickel powder and copper powder' processes for deposition on a H13 tool steel substrate. In wire-powder deposition, a higher temperature developed in the melt pool causing a clad with a smooth gradient structure. The nickel powder in powder-powder deposition did not impart much heat into the melt pool so the melt pool solidified with sharp composition boundaries due to single metal melting in some parts. In wire-powder experiments, a graded structure was obtained by varying the flow rates of wire and powder. However, a graded structure was not realised in powder-powder experiments by varying either the feed or the directions. Reasons for the differences and flow patterns in the melt pools and their effect on final part properties of parts produced are discussed.

  6. Functionally graded alumina-based thin film systems

    DOEpatents

    Moore, John J.; Zhong, Dalong

    2006-08-29

    The present invention provides coating systems that minimize thermal and residual stresses to create a fatigue- and soldering-resistant coating for aluminum die casting dies. The coating systems include at least three layers. The outer layer is an alumina- or boro-carbide-based outer layer that has superior non-wettability characteristics with molten aluminum coupled with oxidation and wear resistance. A functionally-graded intermediate layer or "interlayer" enhances the erosive wear, toughness, and corrosion resistance of the die. A thin adhesion layer of reactive metal is used between the die substrate and the interlayer to increase adhesion of the coating system to the die surface.

  7. Antireflective graded index silica coating, method for making

    DOEpatents

    Yoldas, Bulent E.; Partlow, Deborah P.

    1985-01-01

    Antireflective silica coating for vitreous material is substantially non-reflecting over a wide band of radiations. This is achieved by providing the coating with a graded degree of porosity which grades the index of refraction between that of air and the vitreous material of the substrate. To prepare the coating, there is first prepared a silicon-alkoxide-based coating solution of particular polymer structure produced by a controlled proportion of water to alkoxide and a controlled concentration of alkoxide to solution, along with a small amount of catalyst. The primary solvent is alcohol and the solution is polymerized and hydrolized under controlled conditions prior to use. The prepared solution is applied as a film to the vitreous substrate and rapidly dried. It is thereafter heated under controlled conditions to volatilize the hydroxyl radicals and organics therefrom and then to produce a suitable pore morphology in the residual porous silica layer. The silica layer is then etched in order to enlarge the pores in a graded fashion, with the largest of the pores remaining being sufficiently small that radiations to be passed through the substrate are not significantly scattered. For use with quartz substrates, extremely durable coatings which display only 0.1% reflectivity have been prepared.

  8. Creation of a functional graded nanobiomembrane using a new electrospinning system for drug release control and an in vitro validation of drug release behavior of the coating membrane.

    PubMed

    Park, Chan-Hee; Chung, Min-Young; Unnithan, Afeesh Rajan; Kim, Cheol Sang

    2015-05-01

    Functional graded nanobiomembranes (FGMs) with multiple layers were created by a single process using a novel electrospinning system equipped with a generator and a PCI type motion board as a controller in order to control the drug release rate. By varying physical apparatus-related parameters such as nozzle-to-collector distance via a robot and the collector moving velocity the FGMs were formed. For the membrane base layer, poly-(ε-caprolactone) (PCL) with paclitaxel (PTX) was dissolved in a solvent (dichloromethane, N,N-dimethylformamide) and electrospun. For the top layers, the PCL solution was electrospun according to the distance and FGM system parameters, which can move the collector location at a constant ratio. It was observed that pore size, porosity, and permeability were higher when the membrane was spun at the far distance. The top surface of FGM is more porous, rougher, more permeable, and more hydrophilic so as to be active to the surrounding tissue cells. Meanwhile, the porous inside membrane was as low as the membrane spun at a close distance. Thus it induced a slow drug release due to the internal structure of FGM, which is considered to be very effective for slow drug release as well as bioactivity and bioconductivity. PMID:25746254

  9. Fracture behaviour of functionally graded materials

    NASA Astrophysics Data System (ADS)

    Marur, Prabhakar R.

    Functionally graded materials (FGMs) are special composites consisting of two constituent phases whose composition change continuously along one direction. The gradual transition in material properties alleviates thermal mismatch problems experienced by cladded and coated components. The microstructure of FGM is usually heterogenous and the dominant failure mode of FGM is the crack initiation and propagation from the inclusions. Hence, the knowledge of crack growth and propagation is important in designing components involving FGM. The interface crack problem is studied by examining the asymptotic behavior of stress and displacement fields around the crack in FGM, and by comparing the results with known solutions for bimaterial systems. The, focus is on characterizing the influence of material nonhomogeneity on the fracture parameters, and determining the fracture strength of FGM under quasi-static and dynamic loading. The numerical and experimental techniques developed in this study are unified for both bimaterial and FGM, permitting direct comparison of fracture parameters and test results obtained for different material types. A crack opening displacement (COD) extrapolation technique is developed for the numerical computation of the fracture parameters from finite element analysis, and a new strain gage technique is devised for complex SIF measurement in both bimaterial and FGM. A simple and highly repeatable FGM manufacturing process has been established, and the continuous variation of material properties is evaluated using a novel technique involving ultrasonic wave velocity and local contact stiffness measurements. The nature of singular field around the crack in FGM is studied by varying material gradient, the position of the crack in the graded region and the crack length. The various fracture parameters are compared with that computed for homogenous and bimaterial counterparts. The numerical results show that the crack in FGM, regardless of the position

  10. Interfaces in graded coatings on titanium-based implants

    PubMed Central

    Lopez-Esteban, S.; Gutierrez-Gonzalez, C. F.; Gremillard, L.; Saiz, E.; Tomsia, A. P.

    2013-01-01

    Graded bilayered glass-ceramic composite coatings on Ti6Al4V substrates were fabricated using an enameling technique. The layers consisted of a mixture of glasses in the CaO-MgO-Na2O-K2O-P2O5 system with different amounts of calcium phosphates (CPs). Optimum firing conditions have been determined for the fabrication of coatings having good adhesion to the metal, while avoiding deleterious reactions between the glass and the ceramic particles. The final coatings do not crack or delaminate. The use of high-silica layers (>60 wt % SiO2) in contact with the alloy promotes long-term stability of the coating; glass-metal adhesion is achieved through the formation of a nanostructured Ti5Si3 layer. A surface layer containing a mixture of a low-silica glass (~53 wt % SiO2) and synthetic hydroxyapatite particles promotes the precipitation of new apatite during tests in vitro. The in vitro behavior of the coatings in simulated body fluid depends both on the composition of the glass matrix and the CP particles, and is strongly affected by the coating design and the firing conditions. PMID:18384170

  11. Functionally Graded Adhesives for Composite Joints

    NASA Technical Reports Server (NTRS)

    Stapleton, Scott E.; Waas, Anthony M.; Arnold, Steven M.

    2012-01-01

    Adhesives with functionally graded material properties are being considered for use in adhesively bonded joints to reduce the peel stress concentrations located near adherend discontinuities. Several practical concerns impede the actual use of such adhesives. These include increased manufacturing complications, alterations to the grading due to adhesive flow during manufacturing, and whether changing the loading conditions significantly impact the effectiveness of the grading. An analytical study is conducted to address these three concerns. An enhanced joint finite element, which uses an analytical formulation to obtain exact shape functions, is used to model the joint. Furthermore, proof of concept testing is conducted to show the potential advantages of functionally graded adhesives. In this study, grading is achieved by strategically placing glass beads within the adhesive layer at different densities along the joint.

  12. Graded index antireflective coatings for glass. Second annual report

    SciTech Connect

    Haggerty, J.S.

    1980-05-01

    M.I.T. is conducting research which will lead to a process for forming broad band antireflective (AR) coatings on glass. Use of these coatings increases the extractable heat from flat-plate solar collectors by 30 to 50% compared with their performance under equivalent solar flux, surface temperature and ambient conditions without broad band AR coatings. Graded index surface films can virtually eliminate reflection losses if controlled properly. Graded index films on a borosilicate glass (Corning Glass Works No. 7740, Pyrex) has been demonstrated. While glass treated this way exhibited adequate optical properties, the glass itself, cannot be fabricated by the float glass process because of excessive working temperatures, and consequently is too expensive for solar applications. The objective of this work is to define glass compositions and processing steps which will result in graded index surface films (which exhibit broad band AR characteristics) on glasses which can be fabricated by the float glass process. The mechanism by which these graded index surface films are produced on glass surfaces consists of preferentially etching one phase from a phase separated glass. The film which remains consists of a porous structure in which the fraction of solid phase increases continuously from the free surface toward the bulk glass. Scattering effects are eliminated by limiting the size of the pore structure to dimensions which are substantially less than the wavelength of light. With this structure, the local index of refraction is proportional to the fraction of solid phase which is present. Characterizations are intended to define the microstructural and chemical nature of the surface film throughout its thickness. Progress is reported. (WHK)

  13. A functionally graded titanium/hydroxyapatite film obtained by sputtering.

    PubMed

    Ozeki, Kazuhide; Yuhta, Toshio; Fukui, Yasuhiro; Aoki, Hideki; Nishimura, Ikuya

    2002-03-01

    A functionally graded film of titanium/hydroxyapatite (HA) was prepared on a titanium substrate using a radio frequency magnetron sputtering. The ratio of titanium to HA was controlled by moving the target shutter. The film was composed of five layers, with overall film thickness of 1 microm. The HA was concentrated close to the surface, while the titanium concentration increased with proximity to the substrate. The bonding strength between the film and the substrate was 15.2 MPa in a pull-out test and the critical load from a scratch test was 58.85 mN. The corresponding values of a pure HA sputtered film were 8.0 MPa and 38.47 mN, respectively. The bonding strength of a pure HA plasma spray coating was 10.4 MPa in the pull-out test. The graded film and the pure HA film were sputter-coated to a thickness of 1 microm on titanium columns (10 mm in length and 4 mm in diameter). These columns were implanted in diaphyses of the femora of six adult dogs and a push-out test was carried out after 2, 4, and 12 weeks. After 12 weeks, the push-out strengths of the graded film, the pure HA film and the non-coated columns were 3.7, 3.5, and 1.0 MPa. PMID:15348621

  14. Direct Laser Synthesis of Functional Coatings

    SciTech Connect

    P. Schaaf; Michelle D. Shinn; E. Carpene; J. Kaspar

    2005-06-01

    The direct laser synthesis of functional coatings employs the irradiation of materials with short intensive laser pulses in a reactive atmosphere. The material is heated and plasma is ignited in the reactive atmosphere. This leads to an intensive interaction of the material with the reactive species and a coating is directly formed on the materials surface. By that functional coatings can be easily produced a fast way on steel, aluminium, and silicon by irradiation in nitrogen, methane, or even hydrogen. The influence of the processing parameters to the properties of the functional coatings will be presented for titanium nitride coating produced on titanium with the free electron laser.

  15. Fracture Toughness of Functionally Graded Steels

    NASA Astrophysics Data System (ADS)

    Nazari, Ali; Mohandesi, Jamshid Aghazadeh; Riahi, Shadi

    2012-04-01

    In this study, fracture toughness of functionally graded steels in both crack divider and crack arrester configurations has been studied. Spot-welded plain carbon steel and austenitic stainless steel with different thicknesses and arrangements were used as electrodes of electroslag remelting to produce functionally graded steels. Fracture toughness of the specimens in crack divider configuration was found to depend on the arrangements of the primary electrodes' pieces together with the type of the containing phases. In crack arrester configuration, the fracture toughness was found to depend on the crack tip position and the distance of the crack tip with respect to the bainitic or martensitic intermediate layers.

  16. Nanoindentation of functionally graded hybrid polymer/metal thin films

    NASA Astrophysics Data System (ADS)

    Nunes, J.; Piedade, A. P.

    2013-11-01

    Hybrid functionally graded coatings (2D-FGC) were deposited by magnetron co-sputtering from poly(tetrafluoroethylene) (PTFE) and AISI 316L stainless steel (316L) targets. The carbon and fluorine content varied from 7.3 to 23.7 at.% and from 0 to 57 at.%, respectively. The surface modification was developed to change the surface of 316L vascular stents in order to improve the biocompatibility of the outmost layer of the metallic biomaterial. In-depth XPS analysis revealed the presence of a graded chemical composition accompanied by the variation of the film structure. These results were complemented by those of transmission electron microscopy (TEM) analysis that highlighted the nanocomposite nature of the coatings. The nanomechanical characterization of 2D-FGC was performed by nanoindentation at several loads on the thin films deposited onto two different steel substrates: 316L and AISI M2. The study allowed establishing 0.7 mN as the load that characterized the coatings without substrate influence. Both hardness and Young modulus decrease with the increase of fluorine content due to the evolution in chemical composition, chemical bonds and structure.

  17. Anti-friction Coating for Drilling of Green Austempered Ductile Iron (ADI) grade

    NASA Astrophysics Data System (ADS)

    Meena, A.; El Mansori, M.; Ghidossi, P.; Mkaddem, A.

    2011-05-01

    In this paper the anti-friction performance of two types of coating, post-coated coating and PVD-TiAlN coating were investigated when drilling green austempered ductile iron (ADI) grade. The green ADI grade is produced by a new processing technology known as continuous casting-heat treatment process. The effect of coatings on tool wear and surface finish of the holes when drilling using coolant were reported. Results showed that the tool with post-coated coating has higher anti-friction properties as compared to PVD-TiAlN coating in terms of tool wear and surface roughness. Results also showed that there is a formation of preventive aluminum oxide layer during machining for both types of coating.

  18. Effect of Layer-Graded Bond Coats on Edge Stress Concentration and Oxidation Behavior of Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Ghosn, Louis J.; Miller, Robert A.

    1998-01-01

    Thermal barrier coating (TBC) durability is closely related to design, processing and microstructure of the coating Z, tn systems. Two important issues that must be considered during the design of a thermal barrier coating are thermal expansion and modulus mismatch between the substrate and the ceramic layer, and substrate oxidation. In many cases, both of these issues may be best addressed through the selection of an appropriate bond coat system. In this study, a low thermal expansion and layer-graded bond coat system, that consists of plasma-sprayed FeCoNiCrAl and FeCrAlY coatings, and a high velocity oxyfuel (HVOF) sprayed FeCrAlY coating, is developed to minimize the thermal stresses and provide oxidation resistance. The thermal expansion and oxidation behavior of the coating system are also characterized, and the strain isolation effect of the bond coat system is analyzed using the finite element method (FEM). Experiments and finite element results show that the layer-graded bond coat system possesses lower interfacial stresses. better strain isolation and excellent oxidation resistance. thus significantly improving the coating performance and durability.

  19. Impact of Functionally Graded Cylinders: Theory

    NASA Technical Reports Server (NTRS)

    Aboudi, Jacob; Pindera, Marek-Jerzy; Arnold, S. M. (Technical Monitor)

    2001-01-01

    This final report summarizes the work funded under the Grant NAG3-2411 during the 04/05/2000-04/04/2001 period. The objective of this one-year project was to generalize the theoretical framework of the two-dimensional higher-order theory for the analysis of cylindrical functionally graded materials/structural components employed in advanced aircraft engines developed under past NASA Glenn funding. The completed generalization significantly broadens the theory's range of applicability through the incorporation of dynamic impact loading capability into its framework. Thus, it makes possible the assessment of the effect of damage due to fuel impurities, or the presence of submicron-level debris, on the life of functionally graded structural components. Applications involving advanced turbine blades and structural components for the reusable-launch vehicle (RLV) currently under development will benefit from the completed work. The theory's predictive capability is demonstrated through a numerical simulation of a one-dimensional wave propagation set up by an impulse load in a layered half-plane. Full benefit of the completed generalization of the higher-order theory described in this report will be realized upon the development of a related computer code.

  20. Electrodeposited silk coatings for functionalized implant applications

    NASA Astrophysics Data System (ADS)

    Elia, Roberto

    The mechanical and morphological properties of titanium as well as its biocompatibility and osteoinductive characteristics have made it the material of choice for dental implant systems. Although the success rate of titanium implants exceeds 90% in healthy individuals, a large subset of the population has one or more risk factors that inhibit implant integration. Treatments and coatings have been developed to improve clinical outcomes via introduction of appropriate surface topography, texture and roughness or incorporation of bioactive molecules. It is essential that the coatings and associated deposition techniques are controllable and reproducible. Currently, methods of depositing functional coatings are dictated by numerous parameters (temperature, particle size distribution, pH and voltage), which result in variable coating thickness, strength, porosity and weight, and hinder or preclude biomolecule incorporation. Silk is a highly versatile protein with a unique combination of mechanical and physical properties, including tunable degradation, biocompatibility, drug stabilizing capabilities and mechanical properties. Most recently an electrogelation technique was developed which allows for the deposition of gels which dry seamlessly over the contoured topography of the conductive substrate. In this work we examine the potential use of silk electrogels as mechanically robust implant coatings capable of sequestering and releasing therapeutic agents. Electrodeposition of silk electrogels formed in uniform electric fields was characterized with respect to field intensity and deposition time. Gel formation kinetics were used to derive functions which allowed for the prediction of coating deposition over a range of process and solution parameters. Silk electrogel growth orientation was shown to be influenced by the applied electric field. Coatings were reproducible and tunable via intrinsic silk solution properties and extrinsic process parameters. Adhesion was

  1. Modeling Bamboo as a Functionally Graded Material

    SciTech Connect

    Silva, Emilio Carlos Nelli; Walters, Matthew C.; Paulino, Glaucio H.

    2008-02-15

    Natural fibers are promising for engineering applications due to their low cost. They are abundantly available in tropical and subtropical regions of the world, and they can be employed as construction materials. Among natural fibers, bamboo has been widely used for housing construction around the world. Bamboo is an optimized composite material which exploits the concept of Functionally Graded Material (FGM). Biological structures, such as bamboo, are composite materials that have complicated shapes and material distribution inside their domain, and thus the use of numerical methods such as the finite element method and multiscale methods such as homogenization, can help to further understanding of the mechanical behavior of these materials. The objective of this work is to explore techniques such as the finite element method and homogenization to investigate the structural behavior of bamboo. The finite element formulation uses graded finite elements to capture the varying material distribution through the bamboo wall. To observe bamboo behavior under applied loads, simulations are conducted considering a spatially-varying Young's modulus, an averaged Young's modulus, and orthotropic constitutive properties obtained from homogenization theory. The homogenization procedure uses effective, axisymmetric properties estimated from the spatially-varying bamboo composite. Three-dimensional models of bamboo cells were built and simulated under tension, torsion, and bending load cases.

  2. Functionally Graded Nickel Matrix Alumina Reinforced Nanocomposites

    NASA Astrophysics Data System (ADS)

    Young, Austin; Farias, Stephen; Cammarata, Robert

    2013-03-01

    Hierarchical structured nanocomposites are of great interest particularly in the fields of defense, aeronautics, and metamaterials. Previous work has demonstrated the ability to create uniform nickel matrices embedded with aluminum oxide nanoparticles via electrodeposition using a rotating disk electrode (RDE). This process allows for controlled enhancement of yield strength without negatively affecting other properties. The speed of the RDE controls the rate of particle incorporation, and therefore, particle volume fraction. Hierarchical structures can be formed by simply changing the rotation rate during electrodeposition. This allows for controlled variations of composite structure throughout the material. Simply layered and functionally graded hierarchical materials have been produced using this method with structural resolution of the order of single microns. These layered structures produced unique mechanical properties, even exceeding those of uniformly dispersed composites.

  3. Enhanced light extraction of Bi3Ge4O12 scintillator by graded-refractive-index antireflection coatings

    NASA Astrophysics Data System (ADS)

    Tong, Fei; Liu, Bo; Chen, Hong; Zhu, Zhichao; Gu, Mu

    2013-08-01

    A three-layer graded-refractive-index antireflection coating is designed and prepared on the one surface of the Bi3Ge4O12 scintillator by sol-gel technology. The emission intensity of the Bi3Ge4O12 with a graded-refractive-index antireflection coating exhibits a broadband and omnidirectional enhancement of 15.9% compared with the reference sample without coating. This significant enhancement is attributed to the decrease of Fresnel reflection, which is consistent with the measurement of transmission spectra. Additionally, it is evident that the graded-refractive-index coating is superior to the conventional quarter-wave coating due to the omnidirectionality advantage.

  4. Functionally Graded Nanophase Beryllium/Carbon Composites

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2003-01-01

    Beryllium, beryllium alloys, beryllium carbide, and carbon are the ingredients of a class of nanophase Be/Be2C/C composite materials that can be formulated and functionally graded to suit a variety of applications. In a typical case, such a composite consists of a first layer of either pure beryllium or a beryllium alloy, a second layer of B2C, and a third layer of nanophase sintered carbon derived from fullerenes and nanotubes. The three layers are interconnected through interpenetrating spongelike structures. These Be/Be2C/C composite materials are similar to Co/WC/diamond functionally graded composite materials, except that (1) W and Co are replaced by Be and alloys thereof and (2) diamond is replaced by sintered carbon derived from fullerenes and nanotubes. (Optionally, one could form a Be/Be2C/diamond composite.) Because Be is lighter than W and Co, the present Be/Be2C/C composites weigh less than do the corresponding Co/WC/diamond composites. The nanophase carbon is almost as hard as diamond. WC/Co is the toughest material. It is widely used for drilling, digging, and machining. However, the fact that W is a heavy element (that is, has high atomic mass and mass density) makes W unattractive for applications in which weight is a severe disadvantage. Be is the lightest tough element, but its toughness is less than that of WC/Co alloy. Be strengthened by nanophase carbon is much tougher than pure or alloy Be. The nanophase carbon has an unsurpassed strength-to-weight ratio. The Be/Be2C/C composite materials are especially attractive for terrestrial and aerospace applications in which there are requirements for light weight along with the high strength and toughness of the denser Co/WC/diamond materials. These materials could be incorporated into diverse components, including cutting tools, bearings, rocket nozzles, and shields. Moreover, because Be and C are effective as neutron moderators, Be/Be2C/C composites could be attractive for some nuclear applications.

  5. Creep behavior of pack cementation aluminide coatings on Grade 91 ferritic martensitic alloy

    SciTech Connect

    Bates, Brian; Zhang, Ying; Dryepondt, Sebastien N; Pint, Bruce A

    2014-01-01

    The creep behavior of various pack cementation aluminide coatings on Grade 91 ferritic-martensitic steel was investigated at 650 C in laboratory air. The coatings were fabricated in two temperature regimes, i.e., 650 or 700 C (low temperature) and 1050 C(high temperature), and consisted of a range of Al levels and thicknesses. For comparison, uncoated specimens heat-treated at 1050 C to simulate the high temperature coating cycle also were included in the creep test. All coated specimens showed a reduction in creep resistance, with 16 51% decrease in rupture life compared to the as-received bare substrate alloy. However, the specimens heat-treated at 1050 C exhibited the lowest creep resistance among all tested samples, with a surprisingly short rupture time of < 25 h, much shorter than the specimen coated at 1050 C. Factors responsible for the reduction in creep resistance of both coated and heat-treated specimens were discussed.

  6. Fatigue Crack Growth Analysis Models for Functionally Graded Materials

    SciTech Connect

    Dag, Serkan; Yildirim, Bora; Sabuncuoglu, Baris

    2008-02-15

    The objective of this study is to develop crack growth analysis methods for functionally graded materials (FGMs) subjected to mode I cyclic loading. The study presents finite elements based computational procedures for both two and three dimensional problems to examine fatigue crack growth in functionally graded materials. Developed methods allow the computation of crack length and generation of crack front profile for a graded medium subjected to fluctuating stresses. The results presented for an elliptical crack embedded in a functionally graded medium, illustrate the competing effects of ellipse aspect ratio and material property gradation on the fatigue crack growth behavior.

  7. The influence of target erosion grade in the optoelectronic properties of AZO coatings growth by magnetron sputtering

    NASA Astrophysics Data System (ADS)

    Zubizarreta, C.; G-Berasategui, E.; Ciarsolo, I.; Barriga, J.; Gaspar, D.; Martins, R.; Fortunato, E.

    2016-09-01

    Aluminum-doped zinc oxide (AZO) transparent conductor coating has emerged as promising substitute to tin-doped indium oxide (ITO) as electrode in optoelectronic applications such as photovoltaics or light emitting diodes (LEDs). Besides its high transmission in the visible spectral region and low resistivity, AZO presents a main advantage over other candidates such as graphene, carbon nanotubes or silver nanowires; it can be deposited using the technology industrially implemented to manufacture ITO layers, the magnetron sputtering (MS). This is a productive, reliable and green manufacturing technique. But to guarantee the robustness, reproducibility and reliability of the process there are still some issues to be addressed, such as the effect and control of the target state. In this paper a thorough study of the influence of the target erosion grade in developed coatings has been performed. AZO films have been deposited from a ceramic target by RF MS. Structure, optical transmittance and electrical properties of the produced coatings have been analyzed as function of the target erosion grade. No noticeable differences have been found neither in optoelectronic properties nor in the structure of the coatings, indicating that the RF MS is a stable and consistent process through the whole life of the target.

  8. Aeroelastic Tailoring of a Plate Wing with Functionally Graded Materials

    NASA Technical Reports Server (NTRS)

    Dunning, Peter D.; Stanford, Bret K.; Kim, H. Alicia; Jutte, Christine V.

    2014-01-01

    This work explores the use of functionally graded materials for the aeroelastic tailoring of a metallic cantilevered plate-like wing. Pareto trade-off curves between dynamic stability (flutter) and static aeroelastic stresses are obtained for a variety of grading strategies. A key comparison is between the effectiveness of material grading, geometric grading (i.e., plate thickness variations), and using both simultaneously. The introduction of material grading does, in some cases, improve the aeroelastic performance. This improvement, and the physical mechanism upon which it is based, depends on numerous factors: the two sets of metallic material parameters used for grading, the sweep of the plate, the aspect ratio of the plate, and whether the material is graded continuously or discretely.

  9. Monolithic graded-refractive-index glass-based antireflective coatings. Broadband/omnidirectional light harvesting and self-cleaning characteristics

    SciTech Connect

    Aytug, Tolga; Lupini, Andrew R.; Jellison, Gerald E.; Joshi, Pooran C.; Ivanov, Ilia H.; Liu, Tao; Wang, Peng; Menon, Rajesh; Trejo, Rosa M.; Lara-Curzio, Edgar; Hunter, Scott R.; Simpson, John T.; Paranthaman, M. Parans; Christen, David K.

    2015-04-23

    The design of multifunctional coatings impact impact the performance of many optical systems and components. Such coatings should be mechanically robust, and combine user-defined optical and wetting functions with scalable fabrication formulations. By taking cues from the properties of some natural biological structures, we report here the formation of low-refractive index antireflective glass films that embody omni-directional optical properties over a wide range of wavelengths, while also possessing specific wetting capabilities. The coatings comprise an interconnected network of nanoscale pores surrounded by a nanostructured silica framework. These structures result from a novel fabrication method that utilizes metastable spinodal phase separation in glass-based materials. The approach not only enables design of surface microstructures with graded-index antireflection characteristics, where the surface reflection is suppressed through optical impedance matching between interfaces, but also facilitates self-cleaning ability through modification of the surface chemistry. Based on near complete elimination of Fresnel reflections (yielding >95% transmission through a single-side coated glass) and corresponding increase in broadband transmission, the fabricated nanostructured surfaces are found to promote a general and an invaluable ~3–7% relative increase in current output of multiple direct/indirect bandgap photovoltaic cells. Moreover, these antireflective surfaces also demonstrate superior resistance against mechanical wear and abrasion. Unlike conventional counterparts, the present antireflective coatings are essentially monolithic, enabling simultaneous realization of graded index anti-reflectivity, self-cleaning capability, and mechanical stability within the same surface. Moreover, the concept represents a fundamental basis for development of advanced coated optical quality products, especially where environmental exposure is required.

  10. Monolithic graded-refractive-index glass-based antireflective coatings. Broadband/omnidirectional light harvesting and self-cleaning characteristics

    DOE PAGESBeta

    Aytug, Tolga; Lupini, Andrew R.; Jellison, Gerald E.; Joshi, Pooran C.; Ivanov, Ilia H.; Liu, Tao; Wang, Peng; Menon, Rajesh; Trejo, Rosa M.; Lara-Curzio, Edgar; et al

    2015-04-23

    The design of multifunctional coatings impact impact the performance of many optical systems and components. Such coatings should be mechanically robust, and combine user-defined optical and wetting functions with scalable fabrication formulations. By taking cues from the properties of some natural biological structures, we report here the formation of low-refractive index antireflective glass films that embody omni-directional optical properties over a wide range of wavelengths, while also possessing specific wetting capabilities. The coatings comprise an interconnected network of nanoscale pores surrounded by a nanostructured silica framework. These structures result from a novel fabrication method that utilizes metastable spinodal phase separationmore » in glass-based materials. The approach not only enables design of surface microstructures with graded-index antireflection characteristics, where the surface reflection is suppressed through optical impedance matching between interfaces, but also facilitates self-cleaning ability through modification of the surface chemistry. Based on near complete elimination of Fresnel reflections (yielding >95% transmission through a single-side coated glass) and corresponding increase in broadband transmission, the fabricated nanostructured surfaces are found to promote a general and an invaluable ~3–7% relative increase in current output of multiple direct/indirect bandgap photovoltaic cells. Moreover, these antireflective surfaces also demonstrate superior resistance against mechanical wear and abrasion. Unlike conventional counterparts, the present antireflective coatings are essentially monolithic, enabling simultaneous realization of graded index anti-reflectivity, self-cleaning capability, and mechanical stability within the same surface. Moreover, the concept represents a fundamental basis for development of advanced coated optical quality products, especially where environmental exposure is required.« less

  11. A functionally graded multilayer approach to the synthesis of boron containing ceramic thin films

    NASA Astrophysics Data System (ADS)

    Tavsanoglu, T.; Jeandin, M.; Addemir, O.; Yucel, O.

    2012-11-01

    Despite their excellent properties, adhesion problems are common for B4C and BCN thin films on different substrates when the film thickness exceeds about 500 nm. Three functionally graded multilayer designs; surface boronizing of the steel substrate before deposition (Boride underlayer/B4C), Ti/TiC/B4C and Ti/TiN/BCN structures were discussed in this study, to alleviate the adhesion problems. Cross-sectional FE-SEM examinations and elemental depth profiling by SIMS revealed the graded structure of the films. The elemental film composition measured by EPMA and the mechanical properties determined by nanoindentation demonstrated the graded chemical composition and the transition of the hardness and Young's modulus values between different layers respectively. The results demonstrated the possibility of growing well adherent boron containing ceramic coatings with thicknesses in the μm range by means of different graded underlayer designs.

  12. Graded composite diamond coatings with top-layer nanocrystallinity and interfacial integrity: Cross-sectional Raman mapping

    NASA Astrophysics Data System (ADS)

    Dumpala, Ravikumar; Ramamoorthy, B.; Rao, M. S. Ramachandra

    2014-01-01

    Cross-sectional structural characteristics of the CVD diamond coatings deposited on the tungsten carbide (WC-Co) substrates were analysed using Raman imaging technique. The grain size of the nanocrystalline diamond (NCD) coatings was observed to deviate from the nanocrystallinity with increasing thickness and exhibited the surface characteristics of microcrystalline diamond (MCD). However, thick diamond coatings with surface nanocrystallinity is the key requirement for load-bearing tribological applications. Tribological tests have clearly indicated the significance and need for the top-layer nanocrystallinity. Graded composite diamond coatings with an architecture of NCD/transition-layer/MCD/WC-Co are potentail candiadates to realize thick diamond coatings with top-layer nanocrystallinity. Residual stresses along the cross-section of the graded composite diamond coatings were analysed using Raman imaging technique, which confirmed the improved interfacial integrity of the graded composite diamond coatings

  13. An Anti-CD34 Antibody-Functionalized Clinical-Grade POSS-PCU Nanocomposite Polymer for Cardiovascular Stent Coating Applications: A Preliminary Assessment of Endothelial Progenitor Cell Capture and Hemocompatibility

    PubMed Central

    Farhatnia, Yasmin; G, Natasha; Lim, Jing; Teoh, Swee-Hin; Rajadas, Jayakumar; Alavijeh, Mohammad S.; Seifalian, Alexander M.

    2013-01-01

    In situ endothelialization of cardiovascular implants has emerged in recent years as an attractive means of targeting the persistent problems of thrombosis and intimal hyperplasia. This study aimed to investigate the efficacy of immobilizing anti-CD34 antibodies onto a POSS-PCU nanocomposite polymer surface to sequester endothelial progenitor cells (EPCs) from human blood, and to characterize the surface properties and hemocompatibility of this surface. Amine-functionalized fumed silica was used to covalently conjugate anti-CD34 to the polymer surface. Water contact angle, fluorescence microscopy, and scanning electron microscopy were used for surface characterization. Peripheral blood mononuclear cells (PBMCs) were seeded on modified and pristine POSS-PCU polymer films. After 7 days, adhered cells were immunostained for the expression of EPC and endothelial cell markers, and assessed for the formation of EPC colonies. Hemocompatibility was assessed by thromboelastography, and platelet activation and adhesion assays. The number of EPC colonies formed on anti-CD34-coated POSS-PCU surfaces was not significantly higher than that of POSS-PCU (5.0±1.0 vs. 1.7±0.6, p>0.05). However, antibody conjugation significantly improved hemocompatibility, as seen from the prolonged reaction and clotting times, decreased angle and maximum amplitude (p<0.05), as well as decreased platelet adhesion (76.8±7.8 vs. 8.4±0.7, p<0.05) and activation. Here, we demonstrate that POSS-PCU surface immobilized anti-CD34 antibodies selectively captured CD34+ cells from peripheral blood, although only a minority of these were EPCs. Nevertheless, antibody conjugation significantly improves the hemocompatibility of POSS-PCU, and should therefore continue to be explored in combination with other strategies to improve the specificity of EPC capture to promote in situ endothelialization. PMID:24116210

  14. Ballistic performance of polyurea-coated armor grade ceramic tiles

    NASA Astrophysics Data System (ADS)

    Samiee, Ahsan; Isaacs, Jon; Nemat-Nasser, Sia

    2010-04-01

    The use of ceramics as energy absorbents has been studied by many researchers and some improvements in the ballistic performance of ceramic tiles have been made by coating them with different classes of materials (e.g. E-glass/epoxy, carbon-fiber/epoxy, etc.). Using ceramics for energy absorbing applications leads to a significant weight reduction of the system. Therefore, any modification to the ceramic configuration in the system which leads to more energy absorption with the same or less areal density is significant. On the other hand, polyurea has been proved to be an excellent energy dissipating agent in many applications. Inspired by this, we are studying the effect of coating ceramics with polyurea and other materials, on the energy absorption and ballistic performance of the resulting ceramic-based composites. In this study, we investigate the effect of polyurea on ballistic efficiency of ceramic tiles. To this end, we have performed a set of penetration tests on polyurea-ceramic composites. In our experiments, a high velocity projectile is propelled to impact and perforate the ceramic-polyurea composite. The velocity and mass of the projectile are measured before and after the penetration. The change in the kinetic energy of the projectile is evaluated and compared for different polyurea-ceramic configurations (e.g., polyurea on front face, polyurea on back face, polyurea between two ceramic tiles, etc.). The experimental results suggest that polyurea is not as effective as other restraining materials such as E-glass/epoxy and carbon-fiber/epoxy.

  15. Processing of functionally graded tungsten carbide-cobalt-diamond composites

    NASA Astrophysics Data System (ADS)

    Jain, Mohit

    Polycrystalline diamond compacts (PDCs) are widely used as drill bit cutters in rock drilling and as tool bits in machining non-ferrous materials. A typical PDC comprises a thin layer of sintered polycrystalline diamond bonded to a tungsten carbide-cobalt substrate. A well recognized failure mechanism is delamination at the interface between diamond and cemented carbide. High stresses at the diamond/carbide interface, due to thermal expansion and modulus mismatch, are the primary cause of in-service failure under impact loading conditions. This work was undertaken to develop a tungsten carbide-cobalt-diamond composite, which has a continuously graded interface between the diamond and tungsten carbide. The process developed comprised the following steps: (i) generation of a pore size gradient by electrochemical etching of cobalt from the surface of a partially sintered tungsten carbide-cobalt preform; (ii) chemical vapor infiltration of the porous preform with carbon by catalytic decomposition of a methane/hydrogen mixture, resulting in a graded carbon concentration; and (iii) consolidation of the carbon infiltrated preforms at 8GPa/1500°C to complete densification and to transform the carbon into diamond. Thus, the final product consists of a functionally graded WC-Co-diamond composite, with controlled distribution of the constituent phases. Tungsten carbide-cobalt powders with mean tungsten carbide particle size of 0.8mum(micro-grain) and 100 nm(nano-grain) were used as starting materials. Processing conditions were adjusted to obtain an optimal distribution of carbon in porous preforms. After high pressure/high temperature consolidation, both micro- and nano-composites showed a diffused interface between inner and outer regions of the fully dense materials. A micro-composite showed columnar-like tungsten carbide grains and faceted diamond grains in the outer region of the sintered material. The grain size of the diamond in this region was ˜2mum, and the

  16. Developing food-grade coatings for dry-cured hams to protect against ham mite infestation.

    PubMed

    Zhao, Y; Abbar, S; Phillips, T W; Williams, J B; Smith, B S; Schilling, M W

    2016-03-01

    Dry-cured hams may become infested with ham mites, Tyrophagus putrescentiae, during the aging process. Methyl bromide is the only known available fumigant pesticide that is effective at controlling ham mite infestations in dry cured ham plants. However, methyl bromide will be phased out of all industries as early as 2015 due to its status as an ozone-depleting substance. Research was conducted to develop and evaluate the potential of using food-grade film coatings to control mite infestations, without affecting the aging process and sensory properties of the dry-cured hams. Cubes coated with xanthan gum+20% propylene glycol and carrageenan/propylene glycol alginate+10% propylene glycol were effective at controlling mite infestations under laboratory conditions. Water vapor permeability was measured to estimate the impact of coatings during the aging process. It was evident that carrageenan/propylene glycol alginate coatings were permeable to moisture, which potentially makes them usable during aging. PMID:26624793

  17. Strontium and zoledronate hydroxyapatites graded composite coatings for bone prostheses.

    PubMed

    Boanini, Elisa; Torricelli, Paola; Sima, Felix; Axente, Emanuel; Fini, Milena; Mihailescu, Ion N; Bigi, Adriana

    2015-06-15

    Both strontium and zoledronate (ZOL) are known to be useful for the treatment of bone diseases associated to the loss of bone substance. In this work, we applied an innovative technique, Combinatorial Matrix-Assisted Pulsed Laser Evaporation (C-MAPLE), to deposit gradient thin films with variable compositions of Sr-substituted hydroxyapatite (SrHA) and ZOL modified hydroxyapatite (ZOLHA) on Titanium substrates. Compositional gradients were obtained by simultaneous laser vaporization of the two distinct material targets. The coatings display good crystallinity and granular morphology, which do not vary with composition. Osteoblast-like MG63 cells and human osteoclasts were co-cultured on the thin films up to 21 days. The results show that Sr counteracts the negative effect of relatively high concentration of ZOL on osteoblast viability, whereas both Sr and ZOL enhance extracellular matrix deposition. In particular, ZOL promotes type I collagen production, whereas Sr increases the production of alkaline phosphatase. Moreover, ZOL exerts a greater effect than Sr on osteoprotegerin/RANKL ratio and, as a consequence, on the reduction of osteoclast proliferation and activity. The deposition method allows to modulate the composition of the thin films and hence the promotion of bone growth and the inhibition of bone resorption. PMID:25706198

  18. Large deflection of flexible tapered functionally graded beam

    NASA Astrophysics Data System (ADS)

    Davoodinik, A. R.; Rahimi, G. H.

    2011-10-01

    In this paper the semi-analytical analyses of the flexible cantilever tapered functionally graded beam under combined inclined end loading and intermediate loading are studied. In order to derive the fully non-linear equations governing the non-linear deformation, a curvilinear coordinate system is introduced. A general non-linear second order differential equation that governs the shape of a deflected beam is derived based on the geometric nonlinearities, infinitesimal local displacements and local rotation concepts with remarkable physical properties of functionally graded materials. The solutions obtained from semi-analytical methods are numerically compared with the existing elliptic integral solution for the case of a flexible uniform cantilever functionally graded beam. The effects of taper ratio, inclined end load angle and material property gradient on large deflection of the beam are evaluated. The Adomian decomposition method will be useful toward the design of tapered functionally graded compliant mechanisms driven by smart actuators.

  19. Impact Energy of Functionally Graded Steels in Crack Arrester Configuration

    NASA Astrophysics Data System (ADS)

    Nazari, A.; Aghazadeh Mohandesi, J.

    2010-10-01

    Charpy impact energy of functionally graded steels produced by electroslag remelting composed of graded ferrite and austenite layers together with bainite or martensite intermediate layer in the form of crack arrester configuration has been investigated. The results obtained in the present study indicate that the notch tip position with respect to bainite or martensite layer significantly affects the impact energy. The closer the notch tip to the tougher layer, the higher the impact energy of the composite due to increment of energy absorbed by plastic deformation zone ahead of the notch and vice versa. Empirical relationships have been determined to correlate the impact energy of functionally graded steels to the morphology of layers.

  20. Gastro-resistant characteristics of GRAS-grade enteric coatings for pharmaceutical and nutraceutical products.

    PubMed

    Czarnocka, Justyna K; Alhnan, Mohamed A

    2015-01-01

    The use of naturally derived excipients to develop enteric coatings offers significant advantages over conventional synthetic polymers. Unlike synthetic polymers, they are biodegradable, relatively abundant, have no daily intake limits or restrictions on use for dietary and nutraceutical products. However, little information is available on their dissolution properties under different gastrointestinal conditions and in comparison to each other. This work investigated the gastric resistance properties of commercially available GRAS-based coating technologies. Three coating systems were evaluated: ethyl cellulose+carboxymethyl cellulose (EC-CMC), ethyl cellulose+sodium alginate (EC-Alg) and shellac+sodium alginate (Sh-Alg) combinations. The minimum coating levels were optimized to meet USP pharmacopoeial criteria for delayed release formulations (<10% release after 2h in pH 1.2 followed by >80% release after 45 min of pH change). Theophylline 150 mg tablets were coated with 6.5%, 7%, and 2.75% coating levels of formulations EC-CMC, EC-Alg and Sh-Alg, respectively. In vitro dissolution test revealed a fast release in pH 6.8 for ethyl cellulose based coatings: t80% value of 65 and 45 min for EC-CMC and EC-Alg respectively, while a prolonged drug release from Sh-Alg coating was observed in both pH 6.8 and 7.4 phosphate buffers. However, when more biologically relevant bicarbonate buffer was used, all coatings showed slower drug release. Disintegration test, carried out in both simulated gastric and intestinal fluid, confirmed good mechanical resistance of EC-CMC and EC-Alg coating, and revealed poor durability of the thinner Sh-Alg. Under elevated gastric pH conditions (pH 2, 3 and 4), EC-CMC and EC-Alg coatings were broken after 70, 30, 55 min and after 30, 15, 15 min, respectively, while Sh-Alg coated tablets demonstrated gastric resistance at all pH values. In conclusion, none of the GRAS-grade coatings fully complied with the different biological demands of delayed

  1. Compositionally Graded Thermal Barrier Coating by Hybrid Thermal Spraying Route and its Non-isothermal Oxidation Behavior

    NASA Astrophysics Data System (ADS)

    Nath, Subhasisa; Manna, Indranil; Dutta Majumdar, Jyotsna

    2013-08-01

    The present study concerns a detailed investigation of the characteristics and oxidation resistance property of a duplex and compositionally graded thermal barrier coating on Inconel 718. The duplex coating consists of a CoNiCrAlY bond coat layer sprayed on to sand-blasted Inconel 718 substrate (by high velocity oxy-fuel spraying) followed by deposition of a yttria-stabilized zirconia (YSZ) top coat by plasma spraying. The compositionally graded coating consists of several layers deposited by plasma spraying of pre-mixed CoNiCrAlY and YSZ powders in the weight ratios of 70:30, 50:50, 30:70, and 0:100 varying from the bond coat to the top surface, respectively. A detailed investigation of the microstructure, composition, and phases in the coating and its non-isothermal oxidation behavior from room temperature to 1250°C was performed. Oxidation proceeds by three stages in the as-received Inconel 718 and the compositionally graded coating, but by two stages in the duplex coating with a maximum activation energy for oxidation in the compositionally graded coating at high temperature (stage III). The kinetics and mechanism of oxidation were established.

  2. Method of making a functionally graded material

    DOEpatents

    Lauf, Robert J.; Menchhofer, Paul A.; Walls, Claudia A.; Moorhead, Arthur J.

    2002-01-01

    A gelcasting method of making an internally graded article alternatively includes the steps of: preparing a slurry including a least two different phases suspended in a gelcasting solution, the phases characterized by having different settling characteristics; casting the slurry into a mold having a selected shape; allowing the slurry to stand for a sufficient period of time to permit desired gravitational fractionation in order to achieve a vertical compositional gradient in the molded slurry; gelling the slurry to form a solid gel while preserving the vertical compositional gradient in the molded slurry; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying along the vertical direction because of the compositional gradient in the molded slurry.

  3. Method of making a functionally graded material

    DOEpatents

    Lauf, Robert J.; Menchhofer, Paul A.; Walls, Claudia A.

    2001-01-01

    A gelcasting method of making an internally graded article includes the steps of: preparing at least two slurries, each of the slurries including a different gelcastable powder suspended in a gelcasting solution, the slurries characterized by having comparable shrinkage upon drying and sintering thereof; casting the slurries into a mold having a selected shape, wherein relative proportions of the slurries is varied in at least one direction within the selected shape; gelling the slurries to form a solid gel while preserving the variation in relative proportions of the slurries; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying because of the variation in relative proportions of the starting slurries. A gelcasting method of making an internally graded article alternatively includes the steps of: preparing a slurry including a least two different phases suspended in a gelcasting solution, the phases characterized by having different settling characteristics; casting the slurry into a mold having a selected shape; allowing the slurry to stand for a sufficient period of time to permit desired gravitational fractionation in order to achieve a vertical compositional gradient in the molded slurry; gelling the slurry to form a solid gel while preserving the vertical compositional gradient in the molded slurry; drying the gel to form a dried green body; and sintering the dry green body to form a solid object, at least one property thereof varying along the vertical direction because of the compositional gradient in the molded slurry.

  4. Ceramic/polymer functionally graded material (FGM) lightweight armor system

    SciTech Connect

    Petrovic, J.J.; McClellan, K.J.

    1998-12-31

    This is the final report of a two-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Functionally graded material is an enabling technology for lightweight body armor improvements. The objective was to demonstrate the ability to produce functionally graded ceramic-polymer and ceramic-metal lightweight armor materials. This objective involved two aspects. The first and key aspect was the development of graded-porosity boron-carbide ceramic microstructures. The second aspect was the development of techniques for liquid infiltration of lightweight metals and polymers into the graded-porosity ceramic. The authors were successful in synthesizing boron-carbide ceramic microstructures with graded porosity. These graded-porosity boron-carbide hot-pressed pieces were then successfully liquid-infiltrated in vacuum with molten aluminum at 1,300 C, and with liquid polymers at room temperature. Thus, they were able to demonstrate the feasibility of producing boron carbide-aluminum and boron carbide-polymer functionally graded materials.

  5. Green's function evaluation for three-dimensional exponentially graded elasticity

    SciTech Connect

    Criado Portero, Rafael M; Gray, Leonard J; Mantic, Vladislav; Paris, Federico

    2008-01-01

    The numerical implementation of the Green's function for an isotropic exponentially graded three dimensional elastic solid is reported. The formulas for the nonsingular {\\lq}grading term{\\rq} in this Green's function, originally deduced by Martin et al., \\emph{Proc. R. Soc. Lond. A, 458, 1931-1947, 2000}, are quite complicated, and a small error in one of the formulas is corrected. The evaluation of the fundamental solution is tested by employing indirect boundary integral formulation using a Galerkin approximation to solve several problems having analytic solutions. The numerical results indicate that the Green's function formulas, and their evaluation, are correct.

  6. Designing functionally graded materials with superior load-bearing properties

    PubMed Central

    Zhang, Yu; Sun, Ming-jie; Zhang, Denzil

    2011-01-01

    Ceramic prostheses often fail from fracture and wear. We hypothesize that these failures may be substantially mitigated by an appropriate grading of elastic modulus at the ceramic surface. In this study, we elucidate the effect of elastic modulus profile on the flexural damage resistance of functionally graded materials (FGMs), providing theoretical guidlines for designing FGM with superior load-bearing property. The Young's modulus of the graded structure is assumed to vary in a power-law relation with a scaling exponent n; this is in accordance with experimental observations from our laboratory and elsewhere. Based on the theory for bending of graded beams, we examine the effect of n value and bulk-to-surface modulus ratio (Eb/Es) on stress distribution through the graded layer. Theory predicts that a low exponent (0.15 < n < 0.5), coupled with a relatively small modulus ratio (3 < Eb/Es < 6), is most desirable for reducing the maximum stress and transferring it into the interior, while keeping the surface stress low. Experimentally, we demonstrate that elastically graded materials with various n values and Eb/Es ratios can be fabricated by infiltrating alumina and zirconia with a low-modulus glass. Flexural tests show that graded alumina and zirconia with suitable values of these parameters exhibit superior load-bearing capacity, 20% to 50% higher than their homogeneous counterparts. Improving load-bearing capacity of ceramic materials could have broad impacts on biomedical, civil, structural, and an array of other engineering applications. PMID:22178651

  7. Higher-Order Theory for Functionally Graded Materials

    NASA Technical Reports Server (NTRS)

    Aboudi, Jacob; Pindera, Marek-Jerzy; Arnold, Steven M.

    1999-01-01

    This paper presents the full generalization of the Cartesian coordinate-based higher-order theory for functionally graded materials developed by the authors during the past several years. This theory circumvents the problematic use of the standard micromechanical approach, based on the concept of a representative volume element, commonly employed in the analysis of functionally graded composites by explicitly coupling the local (microstructural) and global (macrostructural) responses. The theoretical framework is based on volumetric averaging of the various field quantities, together with imposition of boundary and interfacial conditions in an average sense between the subvolumes used to characterize the composite's functionally graded microstructure. The generalization outlined herein involves extension of the theoretical framework to enable the analysis of materials characterized by spatially variable microstructures in three directions. Specialization of the generalized theoretical framework to previously published versions of the higher-order theory for materials functionally graded in one and two directions is demonstrated. In the applications part of the paper we summarize the major findings obtained with the one-directional and two-directional versions of the higher-order theory. The results illustrate both the fundamental issues related to the influence of microstructure on microscopic and macroscopic quantities governing the response of composites and the technologically important applications. A major issue addressed herein is the applicability of the classical homogenization schemes in the analysis of functionally graded materials. The technologically important applications illustrate the utility of functionally graded microstructures in tailoring the response of structural components in a variety of applications involving uniform and gradient thermomechanical loading.

  8. Enhancing Coating Functionality Using Nanoscience and Nanotechnology

    SciTech Connect

    Baer, Donald R.; Burrows, Paul E.; El-Azab, Anter

    2003-09-17

    Nanoscience and nanotechnology offer a set of tools and new approaches for creating coating with enhanced and optimized properties. The ultimate impact of nanoscience and nanotechnology in many of the potential application areas will depend on our ability to direct the assembly of hierarchical systems that include nanostructures. Two fundamentally different approaches to direct self-assembly are discussed. One approach involves ordering existing identifiable components into the desired coating or structures. The second approach involves the formation of new structures during the coating process. Potential impacts of nanostructure properties on film characteristics and applications are discussed with a focus on coating reactivity, corrosion resistance, strength and durability.

  9. Describing Communicative Functions in a First Grade Classroom.

    ERIC Educational Resources Information Center

    Wrather, Nancy

    The purpose of this study was to synthesize a category system for observation of communicative functions in children's speech and to test that category system by recording observations of interactions within a first-grade classroom. The observation system which was designed attempts to account for all factors of a communication situation and to…

  10. FUNCTIONALY GRADED ALUMINA/MULLITE COATINGS FOR PROTECTION OF SILICON CARBIDE CERAMIC COMPONENTS FROM CORROSION

    SciTech Connect

    PROF. STRATIS V. SOTIRCHOS

    1998-10-01

    The main objective of this research project is the formulation of processes that can be used to prepare compositionally graded alumina/mullite coatings for protection from corrosion of silicon carbide components (monolithic or composite) used or proposed to be used in coal utilization systems (e.g., combustion chamber liners, heat exchanger tubes, particulate removal filters, and turbine components) and other energy-related applications. Mullite will be employed as the inner (base) layer and the composition of the film will be continuously changed to a layer of pure alumina, which will function as the actual protective coating of the component. Chemical vapor deposition reactions of silica, alumina, and aluminosilicates (mullite) through hydrolysis of aluminum and silicon chlorides in the presence of CO2 and H2 will be employed to deposit compositionally graded films of mullite and alumina. Our studies will include the kinetic investigation of the silica, alumina, and aluminosilicate deposition processes, characterization of the composition, microstructure, surface morphology, and mechanical behavior of the prepared films, and modeling of the various deposition processes. During this six-month reporting period, the experimental work on the investigation of the deposition of alumina, silica, and aluminosilicates from mixtures of methyltrichlorosilane (MTS), aluminum trichloride, carbon dioxide, and hydrogen was continued. Experiments were also conducted on the deposition processes of the simple oxides, alumina and silica, from mixtures containing only one chloride (AlCl3 and MTS, respectively). Deposition rate data were obtained in a relatively broad range of operating conditions: temperatures in the range 800-1000 o C, 100 Torr pressure, 0.006-0.015 AlCl3 feed mole fraction, 0.011- 0.027 CH3SiCl3 feed mole fraction, and 0.004-0.07 CO2 feed mole fraction, and various positions along the axis of the deposition reactor. Since the effect of temperature had been

  11. Functionally graded materials for orthopedic applications - an update on design and manufacturing.

    PubMed

    Sola, Antonella; Bellucci, Devis; Cannillo, Valeria

    2016-01-01

    Functionally graded materials (FGMs) are innovative materials whose composition and/or microstructure gradually vary in space according to a designed law. As a result, also the properties gradually vary in space, so as to meet specific non-homogeneous service requirements without any abrupt interface at the macroscale. FGMs are emerging materials for orthopedic prostheses, since the functional gradient can be adapted to reproduce the local properties of the original bone, which helps to minimize the stress shielding effect and, at the same time, to reduce the shear stress between the implant and the surrounding bone tissue, two critical prerequisites for a longer lifespan of the graft. After a brief introduction to the origin of the FGM concept, the review surveys some representative examples of graded systems which are present in nature and, in particular, in the human body, with a focus on bone tissue. Then the rationale for using FGMs in orthopedic devices is discussed more in detail, taking into account both biological and biomechanical requirements. The core of the paper is dedicated to two fundamental topics, which are essential to benefit from the use of FGMs for orthopedic applications, namely (1) the computational tools for materials design and geometry optimization, and (2) the manufacturing techniques currently available to produce FGM-based grafts. This second part, in its turn, is structured to consider the production of functionally graded coatings (FGCs), of functionally graded 3D parts, and of special devices with a gradient in porosity (functionally graded scaffolds). The inspection of the literature on the argument clearly shows that the integration of design and manufacturing remains a critical step to overpass in order to achieve effective FGM-based implants. PMID:26757264

  12. MODELING FUNCTIONALLY GRADED INTERPHASE REGIONS IN CARBON NANOTUBE REINFORCED COMPOSITES

    NASA Technical Reports Server (NTRS)

    Seidel, G. D.; Lagoudas, D. C.; Frankland, S. J. V.; Gates, T. S.

    2006-01-01

    A combination of micromechanics methods and molecular dynamics simulations are used to obtain the effective properties of the carbon nanotube reinforced composites with functionally graded interphase regions. The multilayer composite cylinders method accounts for the effects of non-perfect load transfer in carbon nanotube reinforced polymer matrix composites using a piecewise functionally graded interphase. The functional form of the properties in the interphase region, as well as the interphase thickness, is derived from molecular dynamics simulations of carbon nanotubes in a polymer matrix. Results indicate that the functional form of the interphase can have a significant effect on all the effective elastic constants except for the effective axial modulus for which no noticeable effects are evident.

  13. Carbon nanotube based functional superhydrophobic coatings

    NASA Astrophysics Data System (ADS)

    Sethi, Sunny

    The main objective of this dissertation is synthesis of carbon nanotube (CNT) based superhydrophobic materials. The materials were designed such that electrical and mechanical properties of CNTs could be combined with superhydrophobicity to create materials with unique properties, such as self-cleaning adhesives, miniature flotation devices, ice-repellant coatings, and coatings for heat transfer furnaces. The coatings were divided into two broad categories based on CNT structure: Vertically aligned CNT arrays (VA coatings) and mesh-like (non-aligned) carbon nanotube arrays (NA coatings). VA coatings were used to create self-cleaning adhesives and flexible field emission devices. Coatings with self cleaning property along with high adhesiveness were inspired from structure found on gecko foot. Gecko foot is covered with thousands of microscopic hairs called setae; these setae are further divided into hundreds of nanometer sized hairs called spatulas. When gecko presses its foot against any surface, these hairs bend and conform to the topology of the surface resulting into very large area of contact. Such large area of intimate contact allows geckos to adhere to surfaces using van der Waals (vdW) interactions alone. VA-CNTs adhere to a variety of surfaces using a similar mechanism. CNTs of suitable diameter could withstand four times higher adhesion force than gecko foot. We found that upon soiling these CNT based adhesives (gecko tape) could be cleaned using a water droplet (lotus effect) or by applying vibrations. These materials could be used for applications requiring reversible adhesion. VA coatings were also used for developing field emission devices. A single CNT can emit electrons at very low threshold voltages. Achieving efficient electron emission on large scale has a lot of challenges such as screening effect, pull-off and lower current efficiency. We have explored the use of polymer-CNT composite structures to overcome these challenges in this work. NA

  14. Bio-inspired Propulsion with Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Schleicher, William; Floryan, Daniel; van Buren, Tyler; Smits, Alexander; Moored, Keith; Lehigh University Team; Priceton University Team

    2015-11-01

    From an engineering perspective, biological swimmers are a composite material system with varying material properties across their propulsors. These material properties govern how the swimmer's structure interacts with its surrounding fluid. A two dimensional boundary element fluid solver is strongly coupled to a direct, implicit, geometrically non-linear structure solver to study the effects of functionally graded materials. A zeroth order functionally graded material approximation is used, where a rigid material abruptly meets a flexible material. Thrust, input power, and propulsive efficiency are studied as functions of non-dimensional frequency, reduced frequency, Strouhal number, flexion ratio, and effective stiffness. The numerical results are compared to experimental results for zero attack angle cases, building confidence in the numerical model. The results are further compared to structurally rigid materials. Supported by the Office of Naval Research under Program Director Dr. Bob Brizzolara, MURI grant number N00014-14-1-0533.

  15. Synthesis of Ti/TiN/TiCN coatings grown in graded form by sputtering dc

    NASA Astrophysics Data System (ADS)

    Agudelo, L. C.; Ospina, R.; Castillo, H. A.; Devia, A.

    2008-10-01

    Graded coatings have the advantage of having gradual properties such as thermal expansion coefficient and lattice parameter, avoiding adherence problems due to good match between their component materials. In this work, some properties of coatings grown in graded form are presented. The materials were produced using the sputtering dc technique because of its facility to control the deposition parameters and generate homogeneous growth. The target is a disc of titanium and the samples are made of stainless steel 304. The working gases are argon, nitrogen and methane, which are mixed according to the material to be produced. Titatnium (Ti) layer is grown with argon, the titanium nitride (TiN) film is produced with a mixture of argon and nitrogen, and the titanium nitride carbon (TiCN) material is obtained mixing argon (Ar), nitrogen (N2) and methane (CH4). These materials are characterized with scanning probe microscopy (SPM) in atomic force microscopy (AFM) mode in order to determine grain size and with x-ray photoelectron spectroscopy (XPS) studying the chemical composition and performing depth profiles.

  16. Enhancement of Functional Ceramic Coating Performance by Gas Tunnel Type Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Kobayashi, Akira

    2016-02-01

    A high-precision plasma system has been pursued for advanced thermal processing. The gas tunnel type plasma jet device developed by the author exhibits high energy density and also high efficiency. Among its various applications is the plasma spraying of ceramics such as Al2O3 and ZrO2. The performance of these ceramic coatings is superior to conventional ones. Properties such as the mechanical and chemical properties of the zirconia coatings were reported in previous studies. In this study, the enhancement of the performance of functional ceramic coatings by the gas tunnel type plasma spraying method was carried out using different powders. Results show that the alumina/zirconia composite system exhibited improvements of mechanical properties and corrosion resistance. The alumina/zirconia composite coating has the potential for use as a high functionally graded thermal barrier coating. Another application of the gas tunnel type plasma is for surface modification of metals. As an example, TiN films were formed in 5 s and, thick TiN coatings were easily obtained by gas tunnel type plasma reactive spraying.

  17. Functionalization, coordination, and coating of carbon nanomaterials

    NASA Astrophysics Data System (ADS)

    Hamilton, Christopher Eric

    Single-walled carbon nanotubes were covalently end-functionalized with various donor ligands in order to facilitate the coordination of metal catalyst nanoparticles. The purpose of this study was to optimize catalyst complexation to SWNT ends, allowing growth from preformed seeds (SWNT-cats). The "SWNT amplification" method is envisioned as a route to bulk single-chirality nanotube samples. Study by 31P MAS NMR was undertaken in order to characterize SWNT phosphine derivatives. The synthesis of new N-aryl dipyridylamines (dpas) and related compounds is reported. The products, chelating N-donor ligands, will be used to prepare copper complexes. Copper dpa complexes are able to discriminate between olefin isomers in simple mixtures. Similar triarylamines have been similarly prepared and characterized; these have been tested for their ability to separate SWNTs of particular diameters (or chiral angles) by selective pi-pi stacking interactions. This method is a possible route to single or few-chirality samples, which could then be subjected to SWNT amplification. A novel method for production of high-yield dispersions of single and few layer graphene is presented. o-Dichlorobenzene suspensions of graphene provide twice the yield of previous methods. Moreover, ODCB graphene dispersions form a convenient platform from which to pursue covalent derivatization of graphene in a nonpolar medium. ODCB dispersions have been used to covalently functionalize graphene with perfluoroalkyl groups by a free radical method. Initiation of radical reactions was achieved by both UV photolysis and thermal decomposition of peroxides. Perfluoroalkylated graphene is highly exfoliated and shows great promise for use in polymer composites, lubricants and coatings. Chemical bath deposition (CBD) of II-VI semiconductor materials on SWNT substrates is demonstrated. Bulk heterojunction photovoltaic devices have been prepared from these SWNT-semiconductor composites. The CBD process of depositing

  18. Dual-Functional Antifogging/Antimicrobial Polymer Coating.

    PubMed

    Zhao, Jie; Ma, Li; Millians, William; Wu, Tiehang; Ming, Weihua

    2016-04-01

    Dual-functional antifogging/antimicrobial polymer coatings were prepared by forming a semi-interpenetrating polymer network (SIPN) of partially quaternized poly(2-(dimethylamino)ethyl methacrylate-co-methyl methacrylate) and polymerized ethylene glycol dimethacrylate network. The excellent antifogging behavior of the smooth coating was mainly attributed to the hydrophilic/hydrophobic balance of the partially quaternized copolymer, while the covalently bonded, hydrophobic quaternary ammonium compound (5 mol % in the copolymer) rendered the coating strongly antimicrobial, as demonstrated by the total kill against both Gram-positive Staphylococcus epidermidis and Gram-negative Escherichia coli. The antimicrobial action of the SIPN coating was based on contact killing, without leaching of bactericidal species, as revealed by a zone-of-inhibition test. This type of dual-functional coating may find unique applications where both antimicrobial and antifogging properties are desired. PMID:26977525

  19. Fabrication of a Functionally Graded Copper-Zinc Sulfide Phosphor

    PubMed Central

    Park, Jehong; Park, Kwangwon; Kim, Jongsu; Jeong, Yongseok; Kawasaki, Akira; Kwon, Hansang

    2016-01-01

    Functionally graded materials (FGMs) are compositionally gradient materials. They can achieve the controlled distribution of the desired characteristics within the same bulk material. We describe a functionally graded (FG) metal-phosphor adapting the concept of the FGM; copper (Cu) is selected as a metal and Cu- and Cl-doped ZnS (ZnS:Cu,Cl) is selected as a phosphor and FG [Cu]-[ZnS:Cu,Cl] is fabricated by a very simple powder process. The FG [Cu]-[ZnS:Cu,Cl] reveals a dual-structured functional material composed of dense Cu and porous ZnS:Cu,Cl, which is completely combined through six graded mediating layers. The photoluminescence (PL) of FG [Cu]-[ZnS:Cu,Cl] is insensitive to temperature change. FG [Cu]-[ZnS:Cu,Cl] also exhibits diode characteristics and photo reactivity for 365 nm -UV light. Our FG metal-phosphor concept can pave the way to simplified manufacturing of low-cost and can be applied to various electronic devices. PMID:26972313

  20. Fabrication of a Functionally Graded Copper-Zinc Sulfide Phosphor.

    PubMed

    Park, Jehong; Park, Kwangwon; Kim, Jongsu; Jeong, Yongseok; Kawasaki, Akira; Kwon, Hansang

    2016-01-01

    Functionally graded materials (FGMs) are compositionally gradient materials. They can achieve the controlled distribution of the desired characteristics within the same bulk material. We describe a functionally graded (FG) metal-phosphor adapting the concept of the FGM; copper (Cu) is selected as a metal and Cu- and Cl-doped ZnS (ZnS:Cu,Cl) is selected as a phosphor and FG [Cu]-[ZnS:Cu,Cl] is fabricated by a very simple powder process. The FG [Cu]-[ZnS:Cu,Cl] reveals a dual-structured functional material composed of dense Cu and porous ZnS:Cu,Cl, which is completely combined through six graded mediating layers. The photoluminescence (PL) of FG [Cu]-[ZnS:Cu,Cl] is insensitive to temperature change. FG [Cu]-[ZnS:Cu,Cl] also exhibits diode characteristics and photo reactivity for 365 nm -UV light. Our FG metal-phosphor concept can pave the way to simplified manufacturing of low-cost and can be applied to various electronic devices. PMID:26972313

  1. Higher-Order Theory for Functionally Graded Materials

    NASA Technical Reports Server (NTRS)

    Aboudi, J.; Pindera, M. J.; Arnold, Steven M.

    2001-01-01

    Functionally graded materials (FGM's) are a new generation of engineered materials wherein the microstructural details are spatially varied through nonuniform distribution of the reinforcement phase(s). Engineers accomplish this by using reinforcements with different properties, sizes, and shapes, as well as by interchanging the roles of the reinforcement and matrix phases in a continuous manner (ref. 1). The result is a microstructure that produces continuously or discretely changing thermal and mechanical properties at the macroscopic or continuum scale. This new concept of engineering the material's microstructure marks the beginning of a revolution both in the materials science and mechanics of materials areas since it allows one, for the first time, to fully integrate the material and structural considerations into the final design of structural components. Functionally graded materials are ideal candidates for applications involving severe thermal gradients, ranging from thermal structures in advanced aircraft and aerospace engines to computer circuit boards. Owing to the many variables that control the design of functionally graded microstructures, full exploitation of the FGM's potential requires the development of appropriate modeling strategies for their response to combined thermomechanical loads. Previously, most computational strategies for the response of FGM's did not explicitly couple the material's heterogeneous microstructure with the structural global analysis. Rather, local effective or macroscopic properties at a given point within the FGM were first obtained through homogenization based on a chosen micromechanics scheme and then subsequently used in a global thermomechanical analysis.

  2. Fabrication of a Functionally Graded Copper-Zinc Sulfide Phosphor

    NASA Astrophysics Data System (ADS)

    Park, Jehong; Park, Kwangwon; Kim, Jongsu; Jeong, Yongseok; Kawasaki, Akira; Kwon, Hansang

    2016-03-01

    Functionally graded materials (FGMs) are compositionally gradient materials. They can achieve the controlled distribution of the desired characteristics within the same bulk material. We describe a functionally graded (FG) metal-phosphor adapting the concept of the FGM; copper (Cu) is selected as a metal and Cu- and Cl-doped ZnS (ZnS:Cu,Cl) is selected as a phosphor and FG [Cu]-[ZnS:Cu,Cl] is fabricated by a very simple powder process. The FG [Cu]-[ZnS:Cu,Cl] reveals a dual-structured functional material composed of dense Cu and porous ZnS:Cu,Cl, which is completely combined through six graded mediating layers. The photoluminescence (PL) of FG [Cu]-[ZnS:Cu,Cl] is insensitive to temperature change. FG [Cu]-[ZnS:Cu,Cl] also exhibits diode characteristics and photo reactivity for 365 nm -UV light. Our FG metal-phosphor concept can pave the way to simplified manufacturing of low-cost and can be applied to various electronic devices.

  3. Structural and Morphological Difference Between Ti/TiN/TiCN Coatings Grown in Multilayer and Graded Form

    SciTech Connect

    Restrepo, E.; Baena, A.; Agudelo, C.; Castillo, H.; Devia, A.; Marino, A.

    2006-12-04

    Thin films can be grown in super-lattice, multilayers and graded form, having each one advantages and disadvantages. The difference between multilayer and graded coatings is the interface. In multilayers the interface is abrupt and in graded coatings it is diffuse. The interface influences many chemical and physical properties of the materials, and its choice depends on the application. Graded coatings have the advantage of having gradual properties such as thermal expansion coefficient and lattice parameter, avoiding adherence problems due to good match between their component materials. In this work the comparison between some properties of coatings grown as multilayer and graded is performed. The materials are produced using the sputtering DC technique because of its facility to control the deposition parameters and generate a slow growth. The target is a disc of titanium and the samples are made of stainless steel 304. The working gases are argon, nitrogen and methane, which are mixed according to the material to be produced, i.e. Ti layer is grown with argon, the TiN film is produced with a mixture of argon and nitrogen, and the TiCN material is obtained mixing argon, nitrogen and methane. These materials are characterized with AFM in order to determine grain size and with XPS studying the chemical composition and performing depth profiles.

  4. Surface functionalization with strontium-containing nanocomposite coatings via EPD.

    PubMed

    Ma, Kena; Huang, Dan; Cai, Jing; Cai, Xinjie; Gong, Lingling; Huang, Pin; Wang, Yining; Jiang, Tao

    2016-10-01

    Metal orthopedic implants still face challenges in some compromised conditions, partly due to bio-inertness. The present study aimed to functionalize metallic implants with organic-inorganic nanocomposite (strontium-containing chitosan/gelatin) coatings through a simple single-step electrophoretic deposition under mild conditions. The surface characterization and in vitro cellular response were studied and compared with chitosan/gelatin (CS/G) coatings. SEM images suggested the inorganic nanoparticles may be encapsulated within or mixed with organic polymers. The XRD patterns showed that strontium carbonate was generated in the coatings. The TEM images revealed strontium-containing nanoparticles were released from the coatings in PBS. The continuous release after the initial burst release ensured the enduring effects of the functionalized surface. The tensile bond strength of the coatings to the substrates increased after the addition of strontium. In vitro cellular study confirmed that strontium-containing coatings supported the proliferation of MC3T3-E1 cells and exhibited excellent ability to enhance the differentiation of such pre-osteoblasts. Therefore, such organic-inorganic nanocomposite coatings are a promising candidate to functionalize orthopedic implant surfaces. PMID:27262259

  5. Analysis of the Elastic Field in Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Mohammadi, Mohsen

    In this thesis, the elastic field in circular beams and pipes made of functionally graded materials is considered. The following aspects are presented. First, the thermoelastic stress field in a functionally graded curved beam, where the elastic stiffness varies in the radial direction, is considered. An analytical solution is obtained where the radial variation of the stiffness is represented by a fairly general form. The stress fields corresponding to two different cases for the elastic properties are examined. The flexural stress in the curved beam is then compared with that of a ring. A relatively simple approximate solution is then developed and this is shown to be in good agreement with the analytical results. Secondly, the effect of a nonconstant Poisson's ratio upon the elastic field in functionally graded axisymmetric solids is analyzed. Both of the elastic coefficients, i.e. Young's modulus and Poisson's ratio, are permitted to vary in the radial direction. These elastic coefficients are considered to be functions of composition and are related on this basis. This allows a closed form solution for the stress function to be obtained. Two cases are discussed in this investigation: a) both Young's modulus and Poisson's ratio are allowed to vary across the radius and the effect of spatial variation of Poisson's ratio upon the maximum radial displacement is investigated; b) Young's modulus is taken as constant and the change in the maximum hoop stress resulting from a variable Poisson's ratio is calculated. Thirdly, the stress concentration factor around a circular hole in an infinite plate subjected to uniform biaxial tension and pure shear is considered. The plate is made of a functionally graded material where both Young's modulus and Poisson's ratio vary in the radial direction. For plane stress conditions, the governing differential equation for the stress function is derived and solved. A general form for the stress concentration factor in case of

  6. Fracture and fatigue analysis of functionally graded and homogeneous materials using singular integral equation approach

    NASA Astrophysics Data System (ADS)

    Zhao, Huaqing

    There are two major objectives of this thesis work. One is to study theoretically the fracture and fatigue behavior of both homogeneous and functionally graded materials, with or without crack bridging. The other is to further develop the singular integral equation approach in solving mixed boundary value problems. The newly developed functionally graded materials (FGMs) have attracted considerable research interests as candidate materials for structural applications ranging from aerospace to automobile to manufacturing. From the mechanics viewpoint, the unique feature of FGMs is that their resistance to deformation, fracture and damage varies spatially. In order to guide the microstructure selection and the design and performance assessment of components made of functionally graded materials, in this thesis work, a series of theoretical studies has been carried out on the mode I stress intensity factors and crack opening displacements for FGMs with different combinations of geometry and material under various loading conditions, including: (1) a functionally graded layer under uniform strain, far field pure bending and far field axial loading, (2) a functionally graded coating on an infinite substrate under uniform strain, and (3) a functionally graded coating on a finite substrate under uniform strain, far field pure bending and far field axial loading. In solving crack problems in homogeneous and non-homogeneous materials, a very powerful singular integral equation (SEE) method has been developed since 1960s by Erdogan and associates to solve mixed boundary value problems. However, some of the kernel functions developed earlier are incomplete and possibly erroneous. In this thesis work, mode I fracture problems in a homogeneous strip are reformulated and accurate singular Cauchy type kernels are derived. Very good convergence rates and consistency with standard data are achieved. Other kernel functions are subsequently developed for mode I fracture in

  7. Coated vesicles: a diversity of form and function.

    PubMed

    Schmid, S L; Damke, H

    1995-11-01

    In every well-characterized example, the small transport vesicles that mediate membrane trafficking between intracellular organelles are encased in a protein coat. In general, the coat proteins assemble from cytosolic pools onto the membrane and play a critical role in vesicle formation. Recent reviews have emphasized the clear similarities in the mechanisms that drive vesicle budding at distinct cellular locations. Here we focus on the diversity of solutions to an apparently related biological task. These mechanistic differences are likely to be physiologically important determinants of the diversity in form, and function of coated transport vesicles. PMID:7589986

  8. Effect of cellulose nanowhiskers functionalization with polyaniline for epoxy coatings

    NASA Astrophysics Data System (ADS)

    Borsoi, C.; Zattera, A. J.; Ferreira, C. A.

    2016-02-01

    Functionalization of cellulose nanowhiskers (CNW) was performed by means of chemical synthesis involving polymerization of polyaniline in emeraldine salt form (PAni SE) in the presence of CNW. Thermal, chemical and morphological samples properties were evaluated. Polymeric coatings were obtained with epoxy, aminopropyltriethoxysilane (APS), CNW and CNW/PAni SE applied on carbon steel with a conversion coating of zirconia (Zr) and the mechanical properties were evaluated. With regard to CNW functionalization the sample was encapsulated with PAni SE as observed by FTIR and morphologic analysis, with decreased thermal stability. Regarding the mechanical properties of CNW and CNW/PAni SE polymeric coatings, improvements in flexibility and hardness properties using the APS and Zr layer were observed. The adherence of polymer coatings improved by the incorporation of CNW and CNW/PAni SE. Through morphological analysis it was observed that CNW shows good dispersion in the polymer matrix without agglomerates formation.

  9. Functional Carbon Nanocomposite, Optoelectronic, and Catalytic Coatings

    NASA Astrophysics Data System (ADS)

    Liang, Yu Teng

    Over the past couple decades, fundamental research into carbon nanomaterials has produced a steady stream of groundbreaking physical science. Their record setting mechanical strength, chemical stability, and optoelectronic performance have fueled many optimistic claims regarding the breadth and pace of carbon nanotube and graphene integration. However, present synthetic, processing, and economic constraints have precluded these materials from many practical device applications. To overcome these limitations, novel synthetic techniques, processing methodologies, device geometries, and mechanistic insight were developed in this dissertation. The resulting advancements in material production and composite device performance have brought carbon nanomaterials ever closer to commercial implementation. For improved materials processing, vacuum co-deposition was first demonstrated as viable technique for forming carbon nanocomposite films without property distorting covalent modifications. Co-deposited nanoparticle, carbon nanotube, and graphene composite films enabled rapid device prototyping and compositional optimization. Cellulosic polymer stabilizers were then shown to be highly effective carbon nanomaterial dispersants, improving graphene production yields by two orders of magnitude in common organic solvents. By exploiting polarity interactions, iterative solvent exchange was used to further increase carbon nanomaterial dispersion concentrations by an additional order of magnitude, yielding concentrated inks. On top of their low causticity, these cellulosic nanomaterial inks have highly tunable viscosities, excellent film forming capacity, and outstanding thermal stability. These processing characteristics enable the efficient scaling of carbon nanomaterial coatings and device production using existing roll-to-roll fabrication techniques. Utilizing these process improvements, high-performance gas sensing, energy storage, transparent conductor, and photocatalytic

  10. Analytical Model for Thermal Elastoplastic Stresses of Functionally Graded Materials

    SciTech Connect

    Zhai, P. C.; Chen, G.; Liu, L. S.; Fang, C.; Zhang, Q. J.

    2008-02-15

    A modification analytical model is presented for the thermal elastoplastic stresses of functionally graded materials subjected to thermal loading. The presented model follows the analytical scheme presented by Y. L. Shen and S. Suresh [6]. In the present model, the functionally graded materials are considered as multilayered materials. Each layer consists of metal and ceramic with different volume fraction. The ceramic layer and the FGM interlayers are considered as elastic brittle materials. The metal layer is considered as elastic-perfectly plastic ductile materials. Closed-form solutions for different characteristic temperature for thermal loading are presented as a function of the structure geometries and the thermomechanical properties of the materials. A main advance of the present model is that the possibility of the initial and spread of plasticity from the two sides of the ductile layers taken into account. Comparing the analytical results with the results from the finite element analysis, the thermal stresses and deformation from the present model are in good agreement with the numerical ones.

  11. Crack propagation in functionally graded strip under thermal shock

    NASA Astrophysics Data System (ADS)

    Ivanov, I. V.; Sadowski, T.; Pietras, D.

    2013-09-01

    The thermal shock problem in a strip made of functionally graded composite with an interpenetrating network micro-structure of Al2O3 and Al is analysed numerically. The material considered here could be used in brake disks or cylinder liners. In both applications it is subjected to thermal shock. The description of the position-dependent properties of the considered functionally graded material are based on experimental data. Continuous functions were constructed for the Young's modulus, thermal expansion coefficient, thermal conductivity and thermal diffusivity and implemented as user-defined material properties in user-defined subroutines of the commercial finite element software ABAQUS™. The thermal stress and the residual stress of the manufacturing process distributions inside the strip are considered. The solution of the transient heat conduction problem for thermal shock is used for crack propagation simulation using the XFEM method. The crack length developed during the thermal shock is the criterion for crack resistance of the different graduation profiles as a step towards optimization of the composition gradient with respect to thermal shock sensitivity.

  12. Thermal Characterization of Functionally Graded Materials: Design of Optimum Experiments

    NASA Technical Reports Server (NTRS)

    Cole, Kevin D.

    2003-01-01

    This paper is a study of optimal experiment design applied to the measure of thermal properties in functionally graded materials. As a first step, a material with linearly-varying thermal properties is analyzed, and several different tran- sient experimental designs are discussed. An optimality criterion, based on sen- sitivity coefficients, is used to identify the best experimental design. Simulated experimental results are analyzed to verify that the identified best experiment design has the smallest errors in the estimated parameters. This procedure is general and can be applied to design of experiments for a variety of materials.

  13. Mechanical Properties of Double-Layer and Graded Composite Coatings of YSZ Obtained by Atmospheric Plasma Spraying

    NASA Astrophysics Data System (ADS)

    Carpio, Pablo; Rayón, Emilio; Salvador, María Dolores; Lusvarghi, Luca; Sánchez, Enrique

    2016-04-01

    Double-layer and graded composite coatings of yttria-stabilized zirconia were sprayed on metallic substrates by atmospheric plasma spray. The coating architecture was built up by combining two different feedstocks: one micro- and one nanostructured. Microstructural features and mechanical properties (hardness and elastic modulus) of the coatings were determined by FE-SEM microscopy and nanoindentation technique, respectively. Additional adherence and scratch tests were carried out in order to assess the failure mechanisms occurring between the layers comprising the composites. Microstructural inspection of the coatings confirms the two-zone microstructure. This bimodal microstructure which is exclusive of the layer obtained from the nanostructured feedstock negatively affects the mechanical properties of the whole composite. Nanoindentation tests suitably reproduce the evolution of mechanical properties through coatings thickness on the basis of the position and/or amount of nanostructured feedstock used in the depositing layer. Adhesion and scratch tests show the negative effect on the coating adhesion of layer obtained from the nanostructured feedstock when this layer is deposited on the bond coat. Thus, the poor integrity of this layer results in lower normal stresses required to delaminate the coating in the adhesion test as well as minor critical load registered by using the scratch test.

  14. Damage tolerant functionally graded materials for advanced wear and friction applications

    NASA Astrophysics Data System (ADS)

    Prchlik, Lubos

    The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to

  15. Research of functional properties of nitride ion-plasma coatings

    NASA Astrophysics Data System (ADS)

    Vaulina, O. Yu; Ovechkin, B. B.; Papchenko, A. V.; Shvagrukova, E. V.

    2016-02-01

    This paper considers the influence of ion-plasma coatings with the use of nitrogen (N), zirconium nitride (ZrN), titanium-aluminum nitride (Ti,Al)N and titanium nitride and zirconium nitride by-layer (TiN+ZrN - eight layers) on the properties of steel 65X13. The main functional properties of the coatings are determined: microhardness, nanohardness, Young's modulus and corrosion resistance. It is shown that all the types of coatings allow increasing the physical and mechanical characteristics of instrument steel 65X13. Hardness and wear-resistance, depending on the type of the deposited coating, increase from 1, 5 to 4 times, corrosion resistance increases by tens times.

  16. Cohesive fracture model for functionally graded fiber reinforced concrete

    SciTech Connect

    Park, Kyoungsoo; Paulino, Glaucio H.; Roesler, Jeffery

    2010-06-15

    A simple, effective, and practical constitutive model for cohesive fracture of fiber reinforced concrete is proposed by differentiating the aggregate bridging zone and the fiber bridging zone. The aggregate bridging zone is related to the total fracture energy of plain concrete, while the fiber bridging zone is associated with the difference between the total fracture energy of fiber reinforced concrete and the total fracture energy of plain concrete. The cohesive fracture model is defined by experimental fracture parameters, which are obtained through three-point bending and split tensile tests. As expected, the model describes fracture behavior of plain concrete beams. In addition, it predicts the fracture behavior of either fiber reinforced concrete beams or a combination of plain and fiber reinforced concrete functionally layered in a single beam specimen. The validated model is also applied to investigate continuously, functionally graded fiber reinforced concrete composites.

  17. Development status of the reusable high-performance engines with functionally graded materials

    NASA Astrophysics Data System (ADS)

    Moro, A.; Kuroda, Y.; Kusaka, K.

    2002-04-01

    The background of the development of the two kinds of reusable high-performance engine is described. One of these two is the regeneratively cooled 1200 N thrust engine composed of two kinds of ZrO 2/Ni functionally graded materials (FGMs) chambers. This engine is a promising candidate for the future Japanese orbiting maneuvering system (OMS) engine of the H-II orbiting plane (HOPE). The other one is the reaction control system (RCS) engine which may also be used compatibly with HOPE. Developed RCS chambers are made of carbon-fiber-reinforced carbon matrix (C/C) composites coated with SiC FGMs. In the first stage of the development of the ZrO 2/Ni FGMs chamber, durability tests using a ZrO 2 (24.5 vol%)/Ni (75.5 vol%) FGMs chamber were performed to inspect the damage of the thermal coating layer and to evaluate the engine performance after a total of 260 firing tests. In the second stage, a combustion chamber having a compositional profile of perfect ZrO 2/Ni FGMs was used in the high-altitude performance tests (HAPT). Firing tests for the C/C-SiC FGMs chamber developed in the first stage were performed at sea level. In this test series, microcracks and penetration of the combustion gases were observed especially at the surface of the nozzle throat section after 382 cycle tests. In the next stage of developing C/C-SiC FGMs chamber (expansion area ratio of 30:1), it was shown that coating with FGMs seemed to effectively prevent the delamination of the SiC coating after 693 cycles under the conditions of P c=1.0 MPa, MR=1.65 and with an injector film cooling rate of 17%, over a total firing time of 2000 s.

  18. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    SciTech Connect

    Lei Yang; Ze Liu; Shizhone Wang; Jaewung Lee; Meilin Liu

    2008-04-30

    The main objective of this DOE project is to demonstrate that the performance and long-term stability of the state-of-the-art LSCF cathode can be enhanced by a catalytically active coating (e.g., LSM or SSC). We have successfully developed a methodology for reliably evaluating the intrinsic surface catalytic properties of cathode materials. One of the key components of the test cell is a dense LSCF film, which will function as the current collector for the electrode material under evaluation to eliminate the effect of ionic and electronic transport. Since it is dense, the effect of geometry would be eliminated as well. From the dependence of the electrode polarization resistance on the thickness of a dense LSCF electrode and on partial pressure of oxygen, we have confirmed that the surface catalytic activity of LSCF limits the performances of LSCF-based cathodes. Further, we have demonstrated, using test cells of different configurations, that the performance of LSCF-based electrodes can be significantly enhanced by infiltration of a thin film of LSM or SSC. In addition, the stability of LSCF-based cathodes was also improved by infiltration of LSM or SSC. While the concept feasibility of the electrode architecture is demonstrated, many details are yet to be determined. For example, it is not clear how the surface morphology, composition, and thickness of the coatings change under operating conditions over time, how these changes influence the electrochemical behavior of the cathodes, and how to control the microscopic details of the coatings in order to optimize the performance. The selection of the catalytic materials as well as the detailed microstructures of the porous LSCF and the catalyst layer may critically impact the performance of the proposed cathodes. Further, other fundamental questions still remain; it is not clear why the degradation rates of LSCF cathodes are relatively high, why a LSM coating improves the stability of LSCF cathodes, which catalysts

  19. Immobilization of Amphiphilic Polycations by Catechol Functionality for Antimicrobial Coatings

    PubMed Central

    Han, Hua; Wu, Jianfeng; Avery, Christopher W.; Mizutani, Masato; Jiang, Xiaoming; Kamigaito, Masami; Chen, Zhan; Xi, Chuanwu; Kuroda, Kenichi

    2011-01-01

    A new strategy to prepare antimicrobial surfaces by a simple dip-coating procedure is reported. Amphiphilic polycations with different mole ratios of monomers containing dodecyl quaternary ammonium, methoxyethyl, and catechol groups were synthesized by free-radical polymerization. The polymer coatings were prepared by immersing glass slides into a polymer solution and subsequent drying and heating. The quaternary ammonium side chains endow the coatings with potent antibacterial activity, while the methoxyetyhyl side chains enable tuning the hydrophobic/hydrophilic balance and the catachol groups promote immobilization of the polymers into films. The polymer coated surfaces displayed bactericidal activity against Escherichia coli and Staphylococcus aureus in a dynamic contact assay and prevented accumulation of viable E. coli, S. aureus, and Acinetobacter baumannii for up to 96 hours. Atomic force microscopy (AFM) images of coating surfaces indicated that the surfaces exhibit virtually the same smoothness for all polymers except the most hydrophobic. The hydrophobic polymer without methoxyethyl side chains showed clear structuring into polymer domains, causing high surface roughness. Sum-frequency generation (SFG) vibrational spectroscopy characterization of the surface structures demonstrated that the dodecyl chains are predominantly localized at the surface-air interface of the coatings. SFG also showed that the phenyl groups of the catechols are oriented on the substrate surface. These results support our hypothesis that the adhesive or cross-linking functionality of catechol groups discourages leaching of polymers, allowing tuning of the amphiphilic balance by incorporating hydrophilic components into the polymer chains to gain potent biocidal activity. PMID:21391641

  20. Physical, metabolic and developmental functions of the seed coat

    PubMed Central

    Radchuk, Volodymyr; Borisjuk, Ljudmilla

    2014-01-01

    The conventional understanding of the role of the seed coat is that it provides a protective layer for the developing zygote. Recent data show that the picture is more nuanced. The seed coat certainly represents a first line of defense against adverse external factors, but it also acts as channel for transmitting environmental cues to the interior of the seed. The latter function primes the seed to adjust its metabolism in response to changes in its external environment. The purpose of this review is to provide the reader with a comprehensive view of the structure and functionality of the seed coat, and to expose its hidden interaction with both the endosperm and embryo. Any breeding and/or biotechnology intervention seeking to increase seed size or modify seed features will have to consider the implications on this tripartite interaction. PMID:25346737

  1. Fabricating functionally graded films with designed gradient profiles using pulsed laser deposition

    SciTech Connect

    Won, Yoo Jai; Ki, Hyungson

    2013-05-07

    A novel picosecond-laser pulsed laser deposition method has been developed for fabricating functionally graded films with pre-designed gradient profiles. Theoretically, the developed method is capable of precisely fabricating films with any thicknesses and any gradient profiles by controlling the laser beam powers for the two different targets based on the film composition profiles. As an implementation example, we have successfully constructed functionally graded diamond-like carbon films with six different gradient profiles: linear, quadratic, cubic, square root, cubic root, and sinusoidal. Energy dispersive X-ray spectroscopy is employed for investigating the chemical composition along the thickness of the film, and the deposition profile and thickness errors are found to be less than 3% and 1.04%, respectively. To the best of the authors' knowledge, this is the first method for fabricating films with designed gradient profiles and has huge potential in many areas of coatings and films, including multifunctional optical films. We believe that this method is not only limited to the example considered in this study, but also can be applied to all material combinations as long as they can be deposited using the pulsed laser deposition technique.

  2. Applications and functions of food-grade phosphates.

    PubMed

    Lampila, Lucina E

    2013-10-01

    Food-grade phosphates are used in the production of foods to function as buffers, sequestrants, acidulants, bases, flavors, cryoprotectants, gel accelerants, dispersants, nutrients, precipitants, and as free-flow (anticaking) or ion-exchange agents. The actions of phosphates affect the chemical leavening of cakes, cookies, pancakes, muffins, and doughnuts; the even melt of processed cheese; the structure of a frankfurter; the bind and hydration of delicatessen meats; the fluidity of evaporated milk; the distinctive flavor of cola beverages; the free flow of spice blends; the mineral content of isotonic beverages; and the light color of par-fried potato strips. In the United States, food-grade phosphates are generally recognized as safe, but use levels have been defined for some foods by the Code of Federal Regulations, specifically Titles 9 and 21 for foods regulated by the U.S. Department of Agriculture (USDA) and the U.S. Food and Drug Administration (FDA), respectively. Standards for food purity are defined nationally and internationally in sources such as the Food Chemicals Codex and the Joint Food and Agriculture Organization and World Health Organization (FAO/WHO) Expert Committee on Food Additives. PMID:24033359

  3. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Castillo, M.; Moore, J. J.; Schowengerdt, F. D.; Ayers, R. A.; Zhang, X.; Umakoshi, M.; Yi, H. C.; Guigne, J. Y.

    2003-07-01

    Combustion synthesis, or self-propagating, high temperature synthesis is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr 3C 2, MOSi 2-SiC, NiAl-TiB 2, to engineered porous composites, e.g., B 4C-Al 2O 3, Ti-TiB x, Ni-Ti, Ca 3(P0 4) 2 and glass-ceramic composites, e.g., CaO-SiO 2-BaO-Al 2O 3-TiB 2. The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3(PO 4) 2. Recent experiments on the NASA parabolic flight (KC-135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMS TM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  4. Effects of gravity on combustion synthesis of functionally graded biomaterials

    NASA Astrophysics Data System (ADS)

    Moore, J.; Schowengerdt, F.; Ayers, R.; Castillo, M.; Zhang, X.; Umakoshi, U.; Yi, C.; Guigne, J.

    Combustion synthesis, or self-propagating, high temperature synthesis (SHS) is currently being used at the Colorado School of Mines to produce advanced materials for biomedical applications. These biomaterials include ceramic, intermetallic, and metal-matrix composites for applications ranging from structural to oxidation- and wear-resistant materials, e.g., TiC-Ti, TiC-Cr3 C2 , MoSi2 - SiC, NiAl-TiB2 , to engineered porous composites, e.g., B4 C-A l2 O3 , Ti-TiBx , Ni-Ti, Ca 3 (PO4 )2 and glass- ceramic composites, e.g., CaO-SiO2 - B a O-A l2 O3 -T i B2 . The goal of the functionally graded biomaterials project is to develop new materials, graded in porosity and composition, which will combine the desirable mechanical properties of implant, e.g., NiTi, with the bone-growth enhancement properties of porous biodegradable ceramics, e.g., Ca 3 (PO4 )2 . Recent experiments on the NASA parabolic flight (KC- 135) aircraft have shown that gravity plays an important role in controlling the structure and properties of materials produced by combustion synthesis. The results of these studies, which will be presented at the conference, will provide valuable input to the design of experiments to be done in Space-DRUMSTM, a containerless materials processing facility scheduled to be placed on the International Space Station in 2003.

  5. Experimental Study of Functionally Graded Beam with Fly Ash

    NASA Astrophysics Data System (ADS)

    Bajaj, K.; Shrivastava, Y.; Dhoke, P.

    2013-11-01

    Generally, concrete used in the field suffers from lack of durability and homogeneity. As cement is the only binding material in concrete and due to hike in its price, researchers have been looking for apt substitutes. For the sake of economy, strength and anti-corrosion functionally graded beam (FGB) has developed having one layer of normal concrete and another of high volume fly-ash concrete (HVFAC). The flexural behavior FGB has analyzed experimentally in this work with variation in interface as 0, 25, 50, 75 and 100 from bottom. In this study, HVFAC has prepared with replacement of cement by 20, 35 and 55 % with fly ash for M20 and M30 grade of concrete. It has seemed that there is 12.86 and 3.56 % increase in compressive and flexural strength of FGB. The bond strength FGM cube is optimum at 50 mm depth. As FGM is economical, having more durability and strength, so its adoption enables more sustainability in concrete industry.

  6. Method and system using power modulation for maskless vapor deposition of spatially graded thin film and multilayer coatings with atomic-level precision and accuracy

    DOEpatents

    Montcalm, Claude; Folta, James Allen; Tan, Swie-In; Reiss, Ira

    2002-07-30

    A method and system for producing a film (preferably a thin film with highly uniform or highly accurate custom graded thickness) on a flat or graded substrate (such as concave or convex optics), by sweeping the substrate across a vapor deposition source operated with time-varying flux distribution. In preferred embodiments, the source is operated with time-varying power applied thereto during each sweep of the substrate to achieve the time-varying flux distribution as a function of time. A user selects a source flux modulation recipe for achieving a predetermined desired thickness profile of the deposited film. The method relies on precise modulation of the deposition flux to which a substrate is exposed to provide a desired coating thickness distribution.

  7. Fracture Analysis in a Functionally Graded Magnetoelectroelastic Plane by BIEM

    NASA Astrophysics Data System (ADS)

    Stoynov, Y. D.

    2011-11-01

    A functionally graded magnetoelectroelastic (MEE) plane with a finite crack is considered. The crack is impermeable and subjected to anti-plane mechanical and in-plane electric and magnetic load. The fundamental solutions of the coupled system of the governing equations are derived in a closed form by the Radon transform. They are implemented in a non-hypersingular traction boundary integral equation method (BIEM). A program code in Fortran, based on the BIEM, is created. Comparison with the results obtained by a different method is presented. The numerical examples show the dependence of the stress intensity factor (SIF) on the normalized frequency for different magnitude of the material inhomogeneity. Results for a non-straight crack are also given.

  8. Functionally graded composite cathodes for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Hart, N. T.; Brandon, N. P.; Day, M. J.; Lapeña-Rey, N.

    Functionally graded solid oxide fuel cell (SOFC) cathodes have been prepared from mixtures of strontium-doped lanthanum manganite (LSM) and gadolinia-doped ceria (CGO) using slurry spraying techniques. Similar samples were also prepared from mixtures of LSM and ytrria-stabilised zirconia (YSZ). A current collector comprising a mixture of LSM and strontium-doped lanthanum cobaltite (LSCO) was then applied to both cathode types. Samples were characterised using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). Characterisation using EIS techniques showed that cathodes incorporating CGO into the structure gave improved performance over those fabricated using YSZ. These performance gains were most noticeable as the temperature was decreased towards 700 °C, and were maintained during the testing of three cell membrane electrode assemblies fabricated to the Rolls-Royce design.

  9. Polysaccharides coatings on medical-grade PVC: a probe into surface characteristics and the extent of bacterial adhesion.

    PubMed

    Asadinezhad, Ahmad; Novák, Igor; Lehocký, Marián; Bílek, Frantisek; Vesel, Alenka; Junkar, Ita; Sáha, Petr; Popelka, Anton

    2010-02-01

    Medical-grade polyvinyl chloride was coated by polysaccharides through a novel physicochemical approach. An initial surface activation was performed foremost via diffuse coplanar surface barrier discharge plasma in air at ambient temperature and pressure. Then, radical graft copolymerization of acrylic acid through grafting-from pathway was directed to render a well-defined brush of high density, and finally a chitosan monolayer and chitosan/pectin alternating multilayer were bound onto the functionalized surfaces. Surface characteristics were systematically investigated using several probe techniques. In vitro bacterial adhesion and biofilm formation assays indicated that a single chitosan layer was incapable of hindering the adhesion of a Staphylococcus aureus bacterial strain, while up to 30% reduction was achieved by the chitosan/pectin layered assembly. On the other hand, chitosan and chitosan/pectin multilayer could retard Escherichia coli adhesion by 50% and 20%, respectively. Furthermore, plasma treated and graft copolymerized samples were also found effective to diminish the degree of adherence of Escherichia coli. PMID:20335959

  10. Functionalization of polydopamine coated magnetic nanoparticles with biological entities

    NASA Astrophysics Data System (ADS)

    Mǎgeruşan, Lidia; Mrówczyński, Radosław; Turcu, Rodica

    2015-12-01

    New hybrid materials, obtained through introduction of cysteine, lysine and folic acid as biological entities into polydopamine-coated magnetite nanoparticles, are reported. The syntheses are straight forward and various methods were applied for structural and morphological characterization of the resulting nanoparticles. XPS proved a very powerful tool for surface chemical analysis and it evidences the functionalization of polydopamine coated magnetite nanoparticles. The superparamagnetic behavior and the high values of saturation magnetization recommend all products for further application where magnetism is important for targeting, separation, or heating by alternative magnetic fields.

  11. Transition mode long period grating biosensor with functional multilayer coatings.

    PubMed

    Pilla, Pierluigi; Malachovská, Viera; Borriello, Anna; Buosciolo, Antonietta; Giordano, Michele; Ambrosio, Luigi; Cutolo, Antonello; Cusano, Andrea

    2011-01-17

    We report our latest research results concerning the development of a platform for label-free biosensing based on overlayered Long Period Gratings (LPGs) working in transition mode. The main novelty of this work lies in a multilayer design that allows to decouple the problem of an efficient surface functionalization from that of the tuning in transition region of the cladding modes. An innovative solvent/nonsolvent strategy for the dip-coating technique was developed in order to deposit on the LPG multiple layers of transparent polymers. In particular, a primary coating of atactic polystyrene was used as high refractive index layer to tune the working point of the device in the so-called transition region. In this way, state-of-the-art-competitive sensitivity to surrounding medium refractive index changes was achieved. An extremely thin secondary functional layer of poly(methyl methacrylate-co-methacrylic acid) was deposited onto the primary coating by means of an original identification of selective solvents. This approach allowed to obtain desired functional groups (carboxyls) on the surface of the device for a stable covalent attachment of bioreceptors and minimal perturbation of the optical design. Standard 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide / N-hydrosuccinimide (EDC / NHS) coupling chemistry was used to link streptavidin on the surface of the coated LPG. Highly sensitive real-time monitoring of multiple affinity assays between streptavidin and biotinylated bovine serum albumin was performed by following the shift of the LPGs attenuation bands. PMID:21263591

  12. Micromechanics Modeling of Functionally Graded Interphase Regions in Carbon Nanotube-Polymer Composites

    NASA Technical Reports Server (NTRS)

    Seidel, Gary D.; Lagoudas, Dimitris C.; Frankland, Sarah Jane V.; Gates, Thomas S.

    2006-01-01

    The effective elastic properties of a unidirectional carbon fiber/epoxy lamina in which the carbon fibers are coated with single-walled carbon nanotubes are modeled herein through the use of a multi-scale method involving the molecular dynamics/equivalent continuum and micromechanics methods. The specific lamina representative volume element studied consists of a carbon fiber surrounded by a region of epoxy containing a radially varying concentration of carbon nanotubes which is then embedded in the pure epoxy matrix. The variable concentration of carbon nanotubes surrounding the carbon fiber results in a functionally graded interphase region as the properties of the interphase region vary according to the carbon nanotube volume fraction. Molecular dynamics and equivalent continuum methods are used to assess the local effective properties of the carbon nanotube/epoxy comprising the interphase region. Micromechanics in the form of the Mori-Tanaka method are then applied to obtain the global effective properties of the graded interphase region wherein the carbon nanotubes are randomly oriented. Finally, the multi-layer composite cylinders micromechanics approach is used to obtain the effective lamina properties from the lamina representative volume element. It was found that even very small quantities of carbon nanotubes (0.36% of lamina by volume) coating the surface of the carbon fibers in the lamina can have a significant effect (8% increase) on the transverse properties of the lamina (E22, k23, G23 and G12) with almost no affect on the lamina properties in the fiber direction (E11 and v12).

  13. Milestones in Functional Titanium Dioxide Thermal Spray Coatings: A Review

    NASA Astrophysics Data System (ADS)

    Gardon, M.; Guilemany, J. M.

    2014-04-01

    Titanium dioxide has been the most investigated metal oxide due to its outstanding performance in a wide range of applications, chemical stability and low cost. Coating processes that can produce surfaces based on this material have been deeply studied. Nevertheless, the necessity of coating large areas by means of rapid manufacturing processes renders laboratory-scale techniques unsuitable, leading to a noteworthy interest from the thermal spray (TS) community in the development of significant intellectual property and a large number of scientific publications. This review unravels the relationship between titanium dioxide and TS technologies with the aim of providing detailed information related to the most significant achievements, lack of knowhow, and performance of TS TiO2 functional coatings in photocatalytic, biomedical, and other applications. The influence of thermally activated techniques such as atmospheric plasma spray and high-velocity oxygen fuel spray on TiO2 feedstock based on powders and suspensions is revised; the influence of spraying parameters on the microstructural and compositional changes and the final active behavior of the coating have been analyzed. Recent findings on titanium dioxide coatings deposited by cold gas spray and the capacity of this technology to prevent loss of the nanostructured anatase metastable phase are also reviewed.

  14. Formation and application of functional coatings on synthetic fibers

    NASA Astrophysics Data System (ADS)

    Goli, Kiran; Ozcam, Ali; Roskov, Kristen; Spontak, Richard; Rojas, Orlando; Genzer, Jan

    2011-03-01

    We present two simple methods for modifying synthetic fibers made of polypropylene (PP) and poly(ethylene terephthalate) (PET). Specifically, we alter the inert PP fiber mats by physisorbing denatured proteins, and cross-linking the protein layers using glutaraldehyde. The amino- and hydroxyl-functionalities present in the protein coatings serve as attachment points for polymerization initiators. In addition, PET fibers are modified chemically by amidation with 3-aminopropyltriethoxysilane (APTES), followed by hydrolysis, which yields silanol groups that permit surface attachment of the initiator molecules. ``Grafting from'' polymerization from such modified PP and PET surfaces is employed following the atom transfer radical polymerization protocol to form functional and responsive polymer coatings. These include arrays of poly(2-hydroxyethyl methacrylate) (PHEMA) as well as chemically-modified PHEMA layers. Selected applications of these functional fibers will be outlined briefly, including, capture of metals or other contaminants from waters, prevention of protein adsorption, and attachment of metallic nanoparticles.

  15. Dynamic fracture of functionally graded magnetoelectroelastic composite materials

    SciTech Connect

    Stoynov, Y.; Dineva, P.

    2014-11-12

    The stress, magnetic and electric field analysis of multifunctional composites, weakened by impermeable cracks, is of fundamental importance for their structural integrity and reliable service performance. The aim is to study dynamic behavior of a plane of functionally graded magnetoelectroelastic composite with more than one crack. The coupled material properties vary exponentially in an arbitrary direction. The plane is subjected to anti-plane mechanical and in-plane electric and magnetic load. The boundary value problem described by the partial differential equations with variable coefficients is reduced to a non-hypersingular traction boundary integral equation based on the appropriate functional transform and frequency-dependent fundamental solution derived in a closed form by Radon transform. Software code based on the boundary integral equation method (BIEM) is developed, validated and inserted in numerical simulations. The obtained results show the sensitivity of the dynamic stress, magnetic and electric field concentration in the cracked plane to the type and characteristics of the dynamic load, to the location and cracks disposition, to the wave-crack-crack interactions and to the magnitude and direction of the material gradient.

  16. Fabrication, Characterization and Modeling of Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Lee, Po-Hua

    In the past few decades, a number of theoretical and experimental studies for design, fabrication and performance analysis of solar panel systems (photovoltaic/thermal systems) have been documented. The existing literature shows that the use of solar energy provides a promising solution to alleviate the shortage of natural resources and the environmental pollution associated with electricity generation. A hybrid solar panel has been invented to integrate photovoltaic (PV) cells onto a substrate through a functionally graded material (FGM) with water tubes cast inside, through which water flow serves as both a heat sink and a solar heat collector. Due to the unique and graded material properties of FGMs, this novel design not only supplies efficient thermal harvest and electrical production, but also provides benefits such as structural integrity and material efficiency. In this work, a sedimentation method has been used to fabricate aluminum (Al) and high-density polyethylene (HDPE) FGMs. The size effect of aluminum powder on the material gradation along the depth direction is investigated. Aluminum powder or the mixture of Al and HDPE powder is thoroughly mixed and uniformly dispersed in ethanol and then subjected to sedimentation. During the sedimentation process, the concentration of Al and HDPE particles temporally and spatially changes in the depth direction due to the non-uniform motion of particles; this change further affects the effective viscosity of the suspension and thus changes the drag force of particles. A Stokes' law based model is developed to simulate the sedimentation process, demonstrate the effect of manufacturing parameters on sedimentation, and predict the graded microstructure of deposition in the depth direction. In order to improve the modeling for sedimentation behavior of particles, the Eshelby's equivalent inclusion method (EIM) is presented to determine the interaction between particles, which is not considered in a Stokes' law based

  17. Functional Characterization of Clostridium difficile Spore Coat Proteins

    PubMed Central

    Permpoonpattana, Patima; Phetcharaburanin, Jutarop; Mikelsone, Anna; Dembek, Marcin; Tan, Sisareuth; Brisson, Marie-Clémence; La Ragione, Roberto; Brisson, Alain R.; Fairweather, Neil; Hong, Huynh A.

    2013-01-01

    Spores of Clostridium difficile play a key role in the dissemination of this important human pathogen, and until recently little has been known of their functional characteristics. Genes encoding six spore coat proteins (cotA, cotB, cotCB, cotD, cotE, and sodA) were disrupted by ClosTron insertional mutagenesis. Mutation of one gene, cotA, presented a major structural defect in spore assembly, with a clear misassembly of the outermost layers of the spore coat. The CotA protein is most probably subject to posttranslational modification and could play a key role in stabilizing the spore coat. Surprisingly, mutation of the other spore coat genes did not affect the integrity of the spore, although for the cotD, cotE, and sodA mutants, enzyme activity was reduced or abolished. This could imply that these enzymatic proteins are located in the exosporium or alternatively that they are structurally redundant. Of the spore coat proteins predicted to carry enzymatic activity, three were confirmed to be enzymes using both in vivo and in vitro methods, the latter using recombinant expressed proteins. These were a manganese catalase, encoded by cotD, a superoxide dismutase (SOD), encoded by sodA, and a bifunctional enzyme with peroxiredoxin and chitinase activity, encoded by cotE. These enzymes being exposed on the spore surface would play a role in coat polymerization and detoxification of H2O2. Two additional proteins, CotF (a tyrosine-rich protein and potential substrate for SodA) and CotG (a putative manganese catalase) were shown to be located at the spore surface. PMID:23335421

  18. Instructional Quality as a Function of Locale, Grade, and Subject.

    ERIC Educational Resources Information Center

    Randhawa, Bikkar S.

    This study investigated the effect of locale, grade, and subject on instructional quality. Rural and urban teachers were observed teaching grades 4, 5, and 6 in social studies, mathematics, and language arts. It was hypothesized that teacher verbal behavior in a classroom predicated the quality and quantity of cognitive behavior of pupils. Rural…

  19. FUNCTIONALIZED LATERAL SURFACE COATED LASERS FOR CHEM-BIO DETECTION

    SciTech Connect

    Goddard, L L; Bond, T C; Cole, G D; Behymer, E M

    2007-07-05

    We present a class of compact, monolithic, photonic sensors consisting of multiple section edge emitting lasers with functionalized lateral surface coatings for low level detection of chemical or biological agents. Specifically, we discuss 8 {micro}m x 250 {micro}m Pd-coated H{sub 2} sensors and configurations to reduce the minimum detection limit from 138ppm for passive sensors to 1ppm for active sensors. Compared with conventional optical H{sub 2} sensors that use fiber gratings, surface plasmon resonances, or surface reflectance, our sensors offer the advantages of smaller size, wider dynamic range, monolithic integration of laser source and detector, and 2-D scalability to arrays of sensors that are functionalized to detect different agents.

  20. Transient Elastodynamic Crack Growth in Functionally Graded Materials

    SciTech Connect

    Chalivendra, Vijaya B.

    2008-02-15

    A generalized elastic solution for an arbitrarily propagating transient crack in Functionally Graded Materials (FGMs) is obtained through an asymptotic analysis. The shear modulus and mass density of the FGM are assumed to vary exponentially along the gradation direction. The mode-mixity due to the inclination of property gradient with respect to the propagating crack tip is accommodated in the analysis through superposition of the opening and shear modes. First three terms of out of plane displacement field and its gradients about the crack tip are obtained in powers of radial coordinates, with the coefficients depending on the time rate of change of crack tip speed and stress intensity factors. Using these displacement fields, the effect of transient stress intensity factors and acceleration on synthetic contours of constant out of plane displacement under both opening and mixed mode loading conditions has been studied. These contours show that the transient terms cause significant spatial variation on out of plane displacements around the crack tip. Therefore, in studying dynamic fracture of FGMs, it is appropriate to include the transient terms in the field equations for the situations of sudden variation of stress intensity factor or crack tip velocity.

  1. Functionally Graded Al Alloy Matrix In-Situ Composites

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.

    2010-01-01

    In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.

  2. Optimum weight design of functionally graded material gears

    NASA Astrophysics Data System (ADS)

    Jing, Shikai; Zhang, He; Zhou, Jingtao; Song, Guohua

    2015-11-01

    Traditional gear weight optimization methods consider gear tooth number, module, face width or other dimension parameters of gear as design variables. However, due to the complicated form and geometric features peculiar to the gear, there will be large amounts of design parameters in gear design, and the influences of gear parameters changing on gear trains, transmission system and the whole equipment have to be taken into account, which increases the complexity of optimization problem. This paper puts forward to apply functionally graded materials (FGMs) to gears and then conduct the optimization. According to the force situation of gears, the material distribution form of FGM gears is determined. Then based on the performance parameters analysis of FGMs and the practical working demands for gears, a multi-objective optimization model is formed. Finally by using the goal driven optimization (GDO) method, the optimal material distribution is achieved, which makes gear weight and the maximum deformation be minimum and the maximum bending stress do not exceed the allowable stress. As an example, the applying of FGM to automotive transmission gear is conducted to illustrate the optimization design process and the result shows that under the condition of keeping the normal working performance of gear, the method achieves in greatly reducing the gear weight. This research proposes a FGM gears design method that is able to largely reduce the weight of gears by optimizing the microscopic material parameters instead of changing the macroscopic dimension parameters of gears, which reduces the complexity of gear weight optimization problem.

  3. Dislocation punching from interfaces in functionally-graded materials

    SciTech Connect

    Taya, M.; Lee, J.K.; Mori, T.

    1997-06-01

    A new dislocation punching model for a functionally graded material (FGM) subjected to a temperature change is proposed, using Eshelby`s model. FGM, consisting of several layers, is deposited on a ceramic substrate. Two types of microstructures are examined for a layer: one consists of a metal matrix and ceramic particles and the other of a ceramic matrix and metal particles. An elastic energy is evaluated when plastic strain, in addition to thermal mismatch strain, is introduced in the metal phase. The work dissipated by the plastic deformation is also calculated. From the condition that the reduction in the elastic energy is larger than the work dissipated, a critical thermal mismatch strain to induce stress relaxation is determined. The magnitude of the plastic strain is also determined, when the relaxation occurs. The theory is applied to a model FGM consisting of mixtures of Pd and Al{sub 2}O{sub 3} on an Al{sub 2}O{sub 3} substrate.

  4. A micromechanical study of residual stresses in functionally graded materials

    SciTech Connect

    Dao, M.; Gu, P.; Maewal, A.; Asaro, R.J.

    1997-08-01

    A physically based computational micromechanics model is developed to study random and discrete microstructures in functionally graded materials (FGMs). The influences of discrete microstructure on residual stress distributions at grain size level are examined with respect to material gradient and FGM volume percentage (within a ceramic-FGM-metal three-layer structure). Both thermoelastic and thermoplastic deformation are considered, and the plastic behavior of metal grains is modeled at the single crystal level using crystal plasticity theory. The results are compared with those obtained using a continuous model which does not consider the microstructural randomness and discreteness. In an averaged sense both the micromechanics model and the continuous model give practically the same macroscopic stresses; whereas the discrete micromechanics model predicts fairly high residual stress concentrations at the grain size level (i.e., higher than 700 MPa in 5--6 vol% FGM grains) with only a 300 C temperature drop in a Ni-Al{sub 2}O{sub 3} FGM system. Statistical analysis shows that the residual stress concentrations are insensitive to material gradient and FGM volume percentage. The need to consider microstructural details in FGM microstructures is evident. The results obtained provide some insights for improving the reliability of FGMs against fracture and delamination.

  5. Multipurpose Polymeric Coating for Functionalizing Inert Polymer Surfaces.

    PubMed

    Özçam, A Evren; Efimenko, Kirill; Spontak, Richard J; Fischer, Daniel A; Genzer, Jan

    2016-03-01

    In this work, we report on the development of a highly functionalizable polymer coating prepared by the chemical coupling of trichlorosilane (TCS) to the vinyl groups of poly(vinylmethyl siloxane) (PVMS). The resultant PVMS-TCS copolymer can be coated as a functional organic primer layer on a variety of polymeric substrates, ranging from hydrophilic to hydrophobic. Several case studies demonstrating the remarkable and versatile properties of PVMS-TCS coatings are presented. In particular, PVMS-TCS is found to serve as a convenient precursor for the deposition of organosilanes and the subsequent growth of polymer brushes, even on hydrophobic surfaces, such as poly(ethylene terephthalate) and polypropylene. In this study, the physical and chemical characteristics of these versatile PVMS-TCS coatings are interrogated by an arsenal of experimental probes, including scanning electron microscopy, water contact-angle measurements, ellipsometry, Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and near-edge X-ray absorption fine structure spectroscopy. PMID:26814561

  6. Is the British Army medical grading functional assessment tool effective?

    PubMed

    Mackie, Isobel

    2015-12-01

    Decision Support Aids (DSAs) have been widely used throughout industry and one (known as Table 7) is available to support British Army Medical Officers (MOs) grade soldiers against the Joint Medical Employment Standards. It is unknown how useful this DSA is in practice. An electronic questionnaire was distributed to British Army MOs working within Defence Primary Care facilities enquiring about MOs views on the usefulness of the DSA. Although the response rate was low, informative data were obtained. Between a half and a third of respondents felt that their judgement was affected in the application of the grading system when there were career implications to the grading MOs felt that the DSA allowed subjectivity in the grading. The results of this research suggest that although minor changes to Table 7 may improve service provision, an improvement in training in the application of Table 7 would be of greater benefit to the quality of occupational health service provision in the British Army. PMID:26621810

  7. Nanocomposite coatings on biomedical grade stainless steel for improved corrosion resistance and biocompatibility.

    PubMed

    Nagarajan, Srinivasan; Mohana, Marimuthu; Sudhagar, Pitchaimuthu; Raman, Vedarajan; Nishimura, Toshiyasu; Kim, Sanghyo; Kang, Yong Soo; Rajendran, Nallaiyan

    2012-10-24

    The 316 L stainless steel is one of the most commonly available commercial implant materials with a few limitations in its ease of biocompatibility and long-standing performance. Hence, porous TiO(2)/ZrO(2) nanocomposite coated over 316 L stainless steels was studied for their enhanced performance in terms of its biocompatibility and corrosion resistance, following a sol-gel process via dip-coating technique. The surface composition and porosity texture was studied to be uniform on the substrate. Biocompatibility studies on the TiO(2)/ZrO(2) nanocomposite coatings were investigated by placing the coated substrate in a simulated body fluid (SBF). The immersion procedure resulted in the complete coverage of the TiO(2)/ZrO(2) nanocomposite (coated on the surface of 316 L stainless steel) with the growth of a one-dimensional (1D) rod-like carbonate-containing apatite. The TiO(2)/ZrO(2) nanocomposite coated specimens showed a higher corrosion resistance in the SBF solution with an enhanced biocompatibility, surpassing the performance of the pure oxide coatings. The cell viability of TiO(2)/ZrO(2) nanocomposite coated implant surface was examined under human dermal fibroblasts culture, and it was observed that the composite coating enhances the proliferation through effective cellular attachment compared to pristine 316 L SS surface. PMID:22967070

  8. Processing and optimization of functional ceramic coatings and inorganic nanomaterials

    NASA Astrophysics Data System (ADS)

    Nyutu, Edward Kennedy G.

    Processing of functional inorganic materials including zero (0-D) dimensional (e.g. nanoparticles), 1-D (nanorods, nanofibers), and 2-D (films/coating) structures is of fundamental and technological interest. This research will have two major sections. The first part of section one focuses on the deposition of silicon dioxide onto a pre-deposited molybdenum disilicide coating on molybdenum substrates for both high (>1000 °C) and moderate (500-600 °C) temperature oxidation protection. Chemical vapor deposition (CVD/MOCVD) techniques will be utilized to deposit the metal suicide and oxide coatings. The focus of this study will be to establish optimum deposition conditions and evaluate the metal oxide coating as oxidation - thermal barriers for Mo substrates under both isothermal (static) and cyclic oxidation conditions. The second part of this section will involve a systematic evaluation of a boron nitride (BN) interface coating prepared by chemical vapor deposition. Ceramic matrix composites (CMCs) are prospective candidates for high (>1000 °C) temperature applications and fiber- matrix interfaces are the dominant design parameters in ceramic matrix composites (CMCs). An important goal of the study is to determine a set of process parameters, which would define a boron nitride (BN) interface coating by a chemical vapor deposition (CVD) process with respect to coating. In the first part of the second section, we will investigate a new approach to synthesize ultrafine metal oxides that combines microwave heating and an in-situ ultrasonic mixing of two or more liquid precursors with a tubular flow reactor. Different metal oxides such as nickel ferrite and zinc aluminate spinels will be studied. The synthesis of metal oxides were investigated in order to study the effects of the nozzle and microwave (INM process) on the purity, composition, and particle size of the resulting powders. The second part of this research section involves a study of microwave frequency

  9. The Contribution of Executive Functions to Narrative Writing in Fourth Grade Children

    ERIC Educational Resources Information Center

    Drijbooms, Elise; Groen, Margriet A.; Verhoeven, Ludo

    2015-01-01

    The present study investigated the contribution of executive functions to narrative writing in fourth grade children, and evaluated to what extent executive functions contribute differentially to different levels of narrative composition. The written skills of 102 Dutch children in fourth grade were assessed using a narrative picture-elicitation…

  10. Optimal Design of Functionally Graded Metallic Foam Insulations

    NASA Technical Reports Server (NTRS)

    Haftka, Raphael T.; Sankar, Bhavani; Venkataraman, Satchi; Zhu, Huadong

    2002-01-01

    The focus of our work has been on developing an insight into the physics that govern the optimum design of thermal insulation for use in thermal protection systems of launch vehicle. Of particular interest was to obtain optimality criteria for designing foam insulations that have density (or porosity) distributions through the thickness for optimum thermal performance. We investigate the optimum design of functionally graded thermal insulation for steady state heat transfer through the foam. We showed that the heat transfer in the foam has competing modes, of radiation and conduction. The problem assumed a fixed inside temperature of 400 K and varied the aerodynamic surface heating on the outside surface from 0.2 to 1.0 MW/sq m. The thermal insulation develops a high temperature gradient through the thickness. Investigation of the model developed for heat conduction in foams showed that at high temperatures (as on outside wall) intracellular radiation dominates the heat transfer in the foam. Minimizing radiation requires reducing the pore size, which increases the density of the foam. At low temperatures (as on the inside wall), intracellular conduction (of the metal and air) dominates the heat transfer. Minimizing conduction requires increasing the pore size. This indicated that for every temperature there was an optimum value of density that minimized the heat transfer coefficient. Two optimization studies were performed. One was to minimize the heat transmitted though a fixed thickness insulation by varying density profiles. The second was to obtain the minimum mass insulation for specified thickness. Analytical optimality criteria were derived for the cases considered. The optimality condition for minimum heat transfer required that at each temperature we find the density that minimizes the heat transfer coefficient. Once a relationship between the optimum heat transfer coefficient and the temperature was found, the design problem reduced to the solution of a

  11. Technology Tips: Two Useful Functions for Excel Grade Books

    ERIC Educational Resources Information Center

    Lobo, Glen E.

    2006-01-01

    The topic of this month's department is writing macros in Excel. The examples given are of use to teachers who maintain their grade books in Excel, and show, for example, how to drop the lowest or choose the highest scores from a student's record. The Surfing Note cites a collection of online tools and resources for professional development…

  12. Instructional Quality as a Function of Locale, Grade, and Subject

    ERIC Educational Resources Information Center

    Randhawa, Bikkar S.

    1977-01-01

    Sixty urban and 57 rural elementary school classrooms were observed to document the effects of rural versus urban locale, grade level, and subject matter taught on instructional quality. Teachers' verbal behaviors were grouped into 16 process-by-substance categories. Results showed that all three main effects were significant. (Author/MV)

  13. Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications

    NASA Astrophysics Data System (ADS)

    Finšgar, Matjaž; Uzunalić, Amra Perva; Stergar, Janja; Gradišnik, Lidija; Maver, Uroš

    2016-05-01

    Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys.

  14. Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications

    PubMed Central

    Finšgar, Matjaž; Uzunalić, Amra Perva; Stergar, Janja; Gradišnik, Lidija; Maver, Uroš

    2016-01-01

    Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys. PMID:27215333

  15. Novel chitosan/diclofenac coatings on medical grade stainless steel for hip replacement applications.

    PubMed

    Finšgar, Matjaž; Uzunalić, Amra Perva; Stergar, Janja; Gradišnik, Lidija; Maver, Uroš

    2016-01-01

    Corrosion resistance, biocompatibility, improved osteointegration, as well the prevention of inflammation and pain are the most desired characteristics of hip replacement implants. In this study we introduce a novel multi-layered coating on AISI 316LVM stainless steel that shows promise with regard to all mentioned characteristics. The coating is prepared from alternating layers of the biocompatible polysaccharide chitosan and the non-steroid anti-inflammatory drug (NSAID), diclofenac. Electrochemical methods were employed to characterize the corrosion behavior of coated and uncoated samples in physiological solution. It is shown that these coatings improve corrosion resistance. It was also found that these coatings release the incorporated drug in controlled, multi-mechanism manner. Adding additional layers on top of the as-prepared samples, has potential for further tailoring of the release profile and increasing the drug dose. Biocompatibility was proven on human-derived osteoblasts in several experiments. Only viable cells were found on the sample surface after incubation of the samples with the same cell line. This novel coating could prove important for prolongation of the application potential of steel-based hip replacements, which are these days often replaced by more expensive ceramic or other metal alloys. PMID:27215333

  16. A self-cleaning coating based on commercial grade polyacrylic latex modified by TiO2/Ag-exchanged-zeolite-A nanocomposite

    NASA Astrophysics Data System (ADS)

    Nosrati, Rahimeh; Olad, Ali; Nofouzi, Katayoon

    2015-08-01

    The commercial grade polyacrylic latex was modified in order to prepare a self-cleaning coating. TiO2/Ag-exchanged-zeolite-A nanocomposite was prepared and used as additive in the matrix of polyacrylic latex to achieve a hydrophilic and photocatalytic coating. FTIR and UV-visible spectroscopy, X-ray diffraction patterns and FESEM were used to characterize the composition and structure of the nanocomposites and coatings. The acrylic coatings, were prepared by using of TiO2/Ag-exchanged-zeolite-A additive, had better UV and visible light absorption, hydrophilic, degradation of organic pollutants, stability in water and antimicrobial properties than pristine commercial grade polyacrylic latex coating. According to the results, the modified polyacrylic based coating containing 0.5 wt% of TiO2/Ag-exchanged-zeolite-A nanocomposite additive with TiO2 to Ag-exchanged-zeolite-A ratio of 1:2 was the best coating considering most of useful properties such as small band gap and low water contact angle. The water contact angle for unmodified polyacrylic latex coating was 68° which was decreased to less than 10° in modified coating after 24 h LED lamp illumination.

  17. Fabrication of Al2O3-W Functionally Graded Materials by Slipcasting Method

    NASA Astrophysics Data System (ADS)

    Katayama, Tomoyuki; Sukenaga, Sohei; Saito, Noritaka; Kagata, Hajime; Nakashima, Kunihiko

    2011-10-01

    We have successfully fabricated a functionally graded material (FGM) from tungsten and alumina powders by a slip-casting method. This FGM has applications as a sealing and conducting component for high-intensity discharge lamps (HiDLs) that have a translucent alumina envelope. Two types of W powder, with different oxidizing properties, were used as the raw powders for the Al2O3-W FGM. "Oxidized W" was prepared by heat-treatment at 200 °C for 180 min in air. Alumina and each of the W powders were mixed in ultrapure water by ultrasonic stirring. The slurry was then cast into a cylindrical acrylic mold, which had a base of porous alumina, under controlled pressure. The green compacts were subsequently dried, and then sintered using a vacuum furnace at 1600 °C for a fixed time. The microstructures of the FGMs were observed by scanning electron microscopy (SEM) of the polished section. The Al2O3-W FGM with the "oxidized W" powder resulted in a microscopic compositional gradient. However, the FGM with "as-received W" showed no compositional gradient. This result was mainly attributed to the difference between the ζ-potentials of the W powders with the different oxidizing conditions; basically "oxidized W" powder tends to disperse because of the larger ζ-potential of the oxide layer coated on the W powder core.

  18. Differential Item Functioning by Gender on a Large-Scale Science Performance Assessment: A Comparison across Grade Levels.

    ERIC Educational Resources Information Center

    Holweger, Nancy; Taylor, Grace

    The fifth-grade and eighth-grade science items on a state performance assessment were compared for differential item functioning (DIF) due to gender. The grade 5 sample consisted of 8,539 females and 8,029 males and the grade 8 sample consisted of 7,477 females and 7,891 males. A total of 30 fifth grade items and 26 eighth grade items were…

  19. Generalized Constitutive-Based Theoretical and Empirical Models for Hot Working Behavior of Functionally Graded Steels

    NASA Astrophysics Data System (ADS)

    Vanini, Seyed Ali Sadough; Abolghasemzadeh, Mohammad; Assadi, Abbas

    2013-07-01

    Functionally graded steels with graded ferritic and austenitic regions including bainite and martensite intermediate layers produced by electroslag remelting have attracted much attention in recent years. In this article, an empirical model based on the Zener-Hollomon (Z-H) constitutive equation with generalized material constants is presented to investigate the effects of temperature and strain rate on the hot working behavior of functionally graded steels. Next, a theoretical model, generalized by strain compensation, is developed for the flow stress estimation of functionally graded steels under hot compression based on the phase mixture rule and boundary layer characteristics. The model is used for different strains and grading configurations. Specifically, the results for αβγMγ steels from empirical and theoretical models showed excellent agreement with those of experiments of other references within acceptable error.

  20. A Facile Approach to Functionalize Cell Membrane-Coated Nanoparticles

    PubMed Central

    Zhou, Hao; Fan, Zhiyuan; Lemons, Pelin K.; Cheng, Hao

    2016-01-01

    Convenient strategies to provide cell membrane-coated nanoparticles (CM-NPs) with multi-functionalities beyond the natural function of cell membranes would dramatically expand the application of this emerging class of nanomaterials. We have developed a facile approach to functionalize CM-NPs by chemically modifying live cell membranes prior to CM-NP fabrication using a bifunctional linker, succinimidyl-[(N-maleimidopropionamido)-polyethyleneglycol] ester (NHS-PEG-Maleimide). This method is particularly suitable to conjugate large bioactive molecules such as proteins on cell membranes as it establishes a strong anchorage and enable the control of linker length, a critical parameter for maximizing the function of anchored proteins. As a proof of concept, we show the conjugation of human recombinant hyaluronidase, PH20 (rHuPH20) on red blood cell (RBC) membranes and demonstrate that long linker (MW: 3400) is superior to short linker (MW: 425) for maintaining enzyme activity, while minimizing the changes to cell membranes. When the modified membranes were fabricated into RBC membrane-coated nanoparticles (RBCM-NPs), the conjugated rHuPH20 can assist NP diffusion more efficiently than free rHuPH20 in matrix-mimicking gels and the pericellular hyaluronic acid matrix of PC3 prostate cancer cells. After quenching the unreacted chemical groups with polyethylene glycol, we demonstrated that the rHuPH20 modification does not reduce the ultra-long blood circulation time of RBCM-NPs. Therefore, this surface engineering approach provides a platform to functionlize CM-NPs without sacrificing the natural function of cell membranes. PMID:27217834

  1. Enhanced corrosion resistance of strontium hydroxyapatite coating on electron beam treated surgical grade stainless steel

    NASA Astrophysics Data System (ADS)

    Gopi, D.; Rajeswari, D.; Ramya, S.; Sekar, M.; R, Pramod; Dwivedi, Jishnu; Kavitha, L.; Ramaseshan, R.

    2013-12-01

    The surface of 316L stainless steel (316L SS) is irradiated by high energy low current DC electron beam (HELCDEB) with energy of 500 keV and beam current of 1.5 mA followed by the electrodeposition of strontium hydroxyapatite (Sr-HAp) to enhance its corrosion resistance in physiological fluid. The coatings were characterised by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and High resolution scanning electron microscopy (HRSEM). The Sr-HAp coating on HELCDEB treated 316L SS exhibits micro-flower structure. Electrochemical results show that the Sr-HAp coating on HELCDEB treated 316L SS possesses maximum corrosion resistance in Ringer's solution.

  2. Protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating characterized using quartz crystal microbalance

    NASA Astrophysics Data System (ADS)

    Vaidya, Shyam V.; Yuan, Min; Narváez, Alfredo R.; Daghfal, David; Mattzela, James; Smith, David

    2016-02-01

    The protein-resistant properties of a chemical vapor deposited alkyl-functional carboxysilane coating (Dursan®) were compared to that of an amorphous fluoropolymer (AF1600) coating and bare 316L grade stainless steel by studying non-specific adsorption of various proteins onto these surfaces using quartz crystal microbalance with dissipation monitoring (QCM-D). A wash solution with nonionic surfactant, polyoxyethyleneglycol dodecyl ether (or Brij 35), facilitated 100% removal of the adsorbed bovine serum albumin (BSA), mouse immunoglobulin G (IgG), and normal human plasma proteins from the Dursan surface and of the adsorbed normal human plasma proteins from the AF1600 surface, whereas these proteins remained adsorbed on the bare stainless steel surface. Mechanical stress in the form of sonication demonstrated durability of the Dursan coating to mechanical wear and showed no negative impact on the coating's ability to prevent adsorption of plasma proteins. Surface delamination was observed in case of the sonicated AF1600 coating, which further led to adsorption of normal human plasma proteins.

  3. A Review on the Finite Element Methods for Heat Conduction in Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Sharma, R.; Jadon, V. K.; Singh, B.

    2015-01-01

    The review presented in this paper focuses mainly on the application of finite element methods for investigating the effect of heat transfer, variation of temperature and other parameters in the functionally graded materials. Different methods have been investigated for thermal conduction in functionally graded materials. The use of FEM for steady state heat transfer has been addressed in this work. The authors have also discussed the utilization of FEM based shear deformation theories and FEM in combination with other methods for the problems involving complexity of the shape and geometry of functionally graded materials. Finite element methods proved to be effective for the solution of heat transfer problem in functionally graded materials. These methods can be used for steady state heat transfer and as well as for transient state.

  4. Modeling fracture toughness of functionally graded steels in crack divider configuration

    NASA Astrophysics Data System (ADS)

    Aghazadeh Mohandesi, J.; Nazari, A.; Vishkasogheh, Mehdi Hamid; Abedi, Mohammad

    2010-10-01

    Fracture toughness of functionally graded steels in crack divider configuration has been modeled. By utilizing plain carbon and austenitic stainless steel slices with various thicknesses and arrangements as electroslag remelting electrodes, functionally graded steels were produced. The fracture toughness of the functionally graded steels was found to depend on the type, volume fraction and position of the phases present. According to the area under the stress-strain curve of each layer in the functionally graded composites, a mathematical model has been presented for fracture toughness prediction using the rule of mixtures. In addition, the fracture toughness of the composites has been simulated by the 3D dynamic finite element method. There is good agreement between experimental results and those acquired from the numerical and mathematical models.

  5. Sound symbolic naming of novel objects is a graded function.

    PubMed

    Thompson, Patrick D; Estes, Zachary

    2011-12-01

    Although linguistic traditions of the last century assumed that there is no link between sound and meaning (i.e., arbitrariness), recent research has established a nonarbitrary relation between sound and meaning (i.e., sound symbolism). For example, some sounds (e.g., /u/ as in took) suggest bigness whereas others (e.g., /i/ as in tiny) suggest smallness. We tested whether sound symbolism only marks contrasts (e.g., small versus big things) or whether it marks object properties in a graded manner (e.g., small, medium, and large things). In two experiments, participants viewed novel objects (i.e., greebles) of varying size and chose the most appropriate name for each object from a list of visually or auditorily presented nonwords that varied incrementally in the number of "large" and "small" phonemes. For instance, "wodolo" contains all large-sounding phonemes, whereas "kitete" contains all small-sounding phonemes. Participants' choices revealed a graded relationship between sound and size: The size of the object linearly predicted the number of large-sounding phonemes in its preferred name. That is, small, medium, and large objects elicited names with increasing numbers of large-sounding phonemes. The results are discussed in relation to cross-modal processing, gesture, and vocal pitch. PMID:21895561

  6. Structurally Integrated, Damage Tolerant Thermal Spray Coatings: Processing Effects on Surface and System Functionalities

    NASA Astrophysics Data System (ADS)

    Vackel, Andrew

    Thermal Spray (TS) coatings have seen extensive application as protective surfaces to enhance the service life of substrates prone to damage in their operating environment (wear, corrosion, heat etc.). With the advent of high velocity TS processes, the ability to deposit highly dense (>99%) metallic and cermet coatings has further enhanced the protective ability of these coatings. In addition to surface functionality, the influence of the coating application on the mechanical performance of a coated component is of great concern when such a component will experience either static or cyclic loading during service. Using a process mapping methodology, the processing-property interplay between coating materials meant to provide damage tolerant surface or for structural restoration are explored in terms of relevant mechanical properties. Most importantly, the residual stresses inherent in TS deposited coatings are shown to play a significant role in the integrated mechanical performance of these coatings. Unique to high velocity TS processes is the ability to produce compressive stresses within the deposit from the cold working induced by the high kinetic energy particles upon impact. The extent of these formation stresses are explored with different coating materials, as well as processing influence. The ability of dense TS coatings to carry significant structural load and synergistically strengthen coated tensile specimens is demonstrated as a function of coating material, processing, and thickness. The sharing of load between the substrate and otherwise brittle coating enables higher loads before yield for the bi-material specimens, offering a methodology to improve the tensile performance of coated components for structural repair or multi-functionality (surface and structure). The concern of cyclic fatigue damage in coated components is explored, since the majority of service application are designed for loading to be well below the yield point. The role of

  7. Coatings.

    ERIC Educational Resources Information Center

    Anderson, Dennis G.

    1989-01-01

    This review covers analytical techniques applicable to the examination of coatings, raw materials, and substrates upon which coatings are placed. Techniques include chemical and electrochemical methods, chromatography, spectroscopy, thermal analysis, microscopy, and miscellaneous techniques. (MVL)

  8. Functionally graded porous scaffolds made of Ti-based agglomerates.

    PubMed

    Nazari, Keivan A; Hilditch, Tim; Dargusch, Matthew S; Nouri, Alireza

    2016-10-01

    Mono- and double-layer porous scaffolds were successfully fabricated using ball-milled agglomerates of Ti and Ti-10Nb-3Mo alloy. For selectively controlling the level of porosity and pore size, the agglomerates were sieved into two different size fractions of 100-300μm and 300-500μm. Compressive mechanical properties were measured on a series of cylindrical sintered compacts with different ratios of solid core diameter to porous layer width. The graded porous scaffolds exhibited stress-strain curves typical for metallic foams with a defined plateau region after yielding. The compressive strengths and elastic moduli ranged from 300 to 700MPa and 14 to 55GPa, respectively, depending on the core diameter and the material used. The obtained properties make these materials suitable for load-bearing implant applications. PMID:27389321

  9. Bio-functional nano-coatings on metallic biomaterials.

    PubMed

    Mahapatro, Anil

    2015-10-01

    Metals and their alloys have been widely used in all aspects of science, engineering and medicine. Metals in biomedical devices are used due to their inertness and structural functions. They are generally preferred over polymers or ceramics and are especially desirable in applications where the implants are subjected to static, dynamic or cyclic loads that require a combination of strength and ductility. In biomedicine, the choice of a specific biomaterial is governed by many factors that include biocompatibility, corrosion resistance, controlled degradability, modulus of elasticity, fatigue strength and many other application specific criterions. Nanotechnology is driving newer demands and requirements for better performance of existing materials and presents an opportunity for surface modification of metals in response to demands on the surface of metals for their biomedical applications. Self-assembled monolayers (SAMs) are nanosized coatings that present a flexible method of carrying out surface modification of biomaterials to tailor its surface properties for specific end applications. These nanocoatings can serve primary functions such as surface coverage, etch protection and anti-corrosion along with a host of other secondary chemical functions such as drug delivery and biocompatibility. We present a brief introduction to surface modification of biomaterials and their alloys followed by a detailed description of organic nanocoatings based on self-assembled monolayers and their biomedical applications including patterning techniques and biological applications of patterned SAMs. PMID:26117759

  10. Development of strontium and magnesium substituted porous hydroxyapatite/poly(3,4-ethylenedioxythiophene) coating on surgical grade stainless steel and its bioactivity on osteoblast cells.

    PubMed

    Gopi, D; Ramya, S; Rajeswari, D; Surendiran, M; Kavitha, L

    2014-02-01

    The present study deals with the successful development of bilayer coatings by electropolymerisation of poly(3,4-ethylenedioxythiophene) (PEDOT) on surgical grade stainless steel (316L SS) followed by the electrodeposition of strontium (Sr) and magnesium (Mg) substituted porous hydroxyapatite (Sr, Mg-HA). The bilayer coatings were characterised by Fourier transform infrared spectroscopy (FT-IR) and high resolution scanning electron microscopy (HRSEM). Corrosion resistance of the obtained coatings was investigated in Ringer's solution by electrochemical techniques and the results were in good agreement with those obtained from chemical analysis, namely inductively coupled plasma atomic emission spectrometry (ICP-AES). Also, the mechanical and biological properties of the bilayer coatings were analyzed. From the obtained results it was evident that the PEDOT/Sr, Mg-HA bilayer exhibited greater adhesion strength than the Sr, Mg-HA coated 316L SS. In vitro cell adhesion test of the Sr, Mg-HA coating on PEDOT coated specimen is found to be more bioactive compared to that of the single substituted hydroxyapatite (Sr or Mg-HA) on the PEDOT coated 316L SS. Thus, the PEDOT/Sr, Mg-HA bilayer coated 316L SS can serve as a prospective implant material for biomedical applications. PMID:24200951

  11. Functionally graded Ti6Al4V and Inconel 625 by Laser Metal Deposition

    NASA Astrophysics Data System (ADS)

    Pulugurtha, Syamala R.

    The objective of the current work was to fabricate a crack-free functionally graded Ti6Al4V and Inconel 625 thin wall structure by Laser Metal Deposition (LMD). One potential application for the current material system is the ability to fabricate a functionally graded alloy that can be used in a space heat exchanger. The two alloys, Inconel 625 and Ti6Al4V are currently used for aerospace applications. They were chosen as candidates for grading because functionally grading those combines the properties of high strength/weight ratio of Ti6Al4V and high temperature oxidation resistance of Inconel 625 into one multifunctional material for the end application. However, there were challenges associated with the presence of Ni-Ti intermetallic phases (IMPs). The study focused on several critical areas such as (1) understanding microstructural evolution, (2) reducing macroscopic cracking, and (3) reducing mixing between graded layers. Finite element analysis (FEA) was performed to understand the effect of process conditions on multilayer claddings for simplified material systems such as SS316L and Inconel 625 where complex microstructures did not form. The thermo-mechanical models were developed using Abaqus(TM) (and some of them experimentally verified) to predict temperature-gradients; remelt layer depths and residual stresses. Microstructure evolution along the functionally graded Ti6Al4V and Inconel 625 was studied under different processing and grading conditions. Thermodynamic modeling using Factsage (v 6.1) was used to construct phase diagrams and predict the possible equilibrium major/minor phases (verified experimentally by XRD) that may be present along the functionally graded Ti6Al4V and Inconel 625 thin wall structures.

  12. Functionally Graded Interfaces: Role and Origin of Internal Electric Field and Modulated Electrical Response.

    PubMed

    Maurya, Deepam; Zhou, Yuan; Chen, Bo; Kang, Min-Gyu; Nguyen, Peter; Hudait, Mantu K; Priya, Shashank

    2015-10-14

    We report the tunable electrical response in functionally graded interfaces in lead-free ferroelectric thin films. Multilayer thin film graded heterostructures were synthesized on platinized silicon substrate with oxide layers of varying thickness. Interestingly, the graded heterostructure thin films exhibited shift of the hysteresis loops on electric field and polarization axes depending upon the direction of an applied bias. A diode-like characteristics was observed in current-voltage behavior under forward and reverse bias. This modulated electrical behavior was attributed to the perturbed dynamics of charge carriers under internal bias (self-bias) generated due to the increased skewness of the potential wells. The cyclic sweeping of voltage further demonstrated memristor-like current-voltage behavior in functionally graded heterostructure devices. The presence of an internal bias assisted the generation of photocurrent by facilitating the separation of photogenerated charges. These novel findings provide opportunity to design new circuit components for the next generation of microelectronic device architectures. PMID:26378954

  13. Fabrication of Al/Diamond Particles Functionally Graded Materials by Centrifugal Sintered-Casting Method

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Shibuya, Masafumi; Sato, Hisashi

    2013-03-01

    The continuous graded structure of functionally graded materials (FGMs) can be created under a centrifugal force. Centrifugal sintered-casting (CSC) method, proposed by the authors, is one of the fabrication methods of FGM under centrifugal force. This method is a combination of the centrifugal sintering method and centrifugal casting method. In this study, Al/diamond particle FGM was fabricated by the proposed method.

  14. Fabrication and characterization of Mg-doped chitosan-gelatin nanocompound coatings for titanium surface functionalization.

    PubMed

    Cai, Xinjie; Cai, Jing; Ma, Kena; Huang, Pin; Gong, Lingling; Huang, Dan; Jiang, Tao; Wang, Yining

    2016-07-01

    Titanium and its alloys have been widely used in clinic and achieved great success. Due to the bio-inertness of titanium surface, challenges still exit in some compromised conditions. The present study aimed to functionalize titanium surface with magnesium (Mg)-doped chitosan/gelatin (CS/G) nanocompound coatings via electrophoretic deposition (EPD). CS/G coatings loaded with different amount of magnesium were successfully prepared on titanium substrate via EPD. Physicochemical characterization of the coatings confirmed that magnesium ions were loaded into the coatings in a dose-dependent manner. XRD results demonstrated that co-deposition of magnesium influenced the crystallinity of the coatings, and a new crystalline substance presented, namely hydrated basic magnesium carbonate. Mechanical tests showed improved tensile and shear bond strength of the magnesium-doped coatings, while the excessively high magnesium concentration could eventually decrease the bonding strength. Sustained release of magnesium ion was detected by ICP-OES within 28 days. TEM images also displayed that nanoparticles could be released from the coatings. In vitro cellular response assays demonstrated that the Mg-doped nanocompound coatings could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells compared to CS/G coatings. Therefore, it could be concluded that Mg-doped CS/G nanocompound coatings were successfully fabricated on titanium substrates via EPD. It would be a promising candidate to functionalize titanium surface with such organic-inorganic nanocompound coatings. PMID:27115206

  15. Finite element analysis of the dynamic behavior of radially polarized Functionally Graded Piezoelectric (FGP) structures

    NASA Astrophysics Data System (ADS)

    Kandasamy, Ramkumar; Cui, Fangsen

    2016-04-01

    In the traditional layered piezoelectric structures, high stress concentrations could cause the structural failure in interlayer surfaces due to repeated strain reversals. To overcome the performance limitations of these structures, the concept of Functionally Graded Materials (FGMs) has been introduced to improve the lifetime, integrity, and reliability of these structures. In this paper, the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders under different sets of loading are studied. Material properties such as piezoelectric, elastic and permittivity are assumed to change along its thickness, based on a specific gradation function. Four-parameter power law distribution is used to grade the volume fraction of the constituents comprising of PZT-5A and PZT-5H. Material property is assumed to be temperature dependent for a few numerical studies. The present modeling approach is validated by comparing the free and forced vibration of radially polarized Functionally Graded Piezoelectric (FGP) cylinders with those reported in the literature. The effects of material composition, loading and boundary conditions on the dynamic behavior of FGP cylinder are described. Since the modeling of functionally graded piezoelectric systems is challenging, the present study can help in the design and analysis of FGP cylinders.

  16. Functionally Graded Cathodes for Solid Oxide Fuel Cells

    SciTech Connect

    YongMan Choi; Meilin Liu

    2006-09-30

    This DOE SECA project focused on both experimental and theoretical understanding of oxygen reduction processes in a porous mixed-conducting cathode in a solid oxide fuel cell (SOFC). Elucidation of the detailed oxygen reduction mechanism, especially the rate-limiting step(s), is critical to the development of low-temperature SOFCs (400 C to 700 C) and to cost reduction since much less expensive materials may be used for cell components. However, cell performance at low temperatures is limited primarily by the interfacial polarization resistances, specifically by those associated with oxygen reduction at the cathode, including transport of oxygen gas through the porous cathode, the adsorption of oxygen onto the cathode surface, the reduction and dissociation of the oxygen molecule (O{sub 2}) into the oxygen ion (O{sup 2-}), and the incorporation of the oxygen ion into the electrolyte. In order to most effectively enhance the performance of the cathode at low temperatures, we must understand the mechanism and kinetics of the elementary processes at the interfaces. Under the support of this DOE SECA project, our accomplishments included: (1) Experimental determination of the rate-limiting step in the oxygen reduction mechanism at the cathode using in situ FTIR and Raman spectroscopy, including surface- and tip-enhanced Raman spectroscopy (SERS and TERS). (2) Fabrication and testing of micro-patterned cathodes to compare the relative activity of the TPB to the rest of the cathode surface. (3) Construction of a mathematical model to predict cathode performance based on different geometries and microstructures and analyze the kinetics of oxygen-reduction reactions occurring at charged mixed ionic-electronic conductors (MIECs) using two-dimensional finite volume models with ab initio calculations. (4) Fabrication of cathodes that are graded in composition and microstructure to generate large amounts of active surface area near the cathode/electrolyte interface using a

  17. Biological response of human mesenchymal stromal cells to titanium grade 4 implants coated with PCL/ZrO₂ hybrid materials synthesized by sol-gel route: in vitro evaluation.

    PubMed

    Catauro, M; Bollino, F; Papale, F; Mozetic, P; Rainer, A; Trombetta, M

    2014-12-01

    The surface modification of implantable materials in order to improve their biological proprieties, including tissue tolerance and osseointegration ability, by means of functional coating deposition is a promising strategy to provide a firm fixation of the implants. In this study, organic/inorganic hybrid materials consisting of an inorganic zirconia-based matrix, in which a biocompatible polymer, poly(ε-caprolactone) (PCL), has been incorporated at different percentages, have been synthesized via sol-gel route. Developed materials have been used to coat titanium grade 4 substrates by means of dip coating technique. Scanning electron microscopy (SEM) analysis of the obtained coatings has shown that films crack-free can be obtained for high levels of PCL. Chemical composition and interactions between organic and inorganic moieties have been studied by Attenuated Total Reflectance Fourier Transform InfraRed spectroscopy. The bone-bonding capability of the nanocomposite films has been evaluated in vitro by examining the appearance of an apatite layer on their surface when soaked in a simulated body fluid by means of SEM equipped with EDS microanalysis. In vitro biocompatibility assessment was performed in combination with human mesenchymal stromal cells (hMSCs). Materials were found to be non-toxic and supporting cell proliferation. Additionally, the coating material was not hampering the differentiation of hMSCs in an osteogenic medium. PMID:25491844

  18. Thermo-Elastic Analysis Of A Rotating Hollow Cylinder Made Of Arbitrary Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Arefi, Mohammad; Nahas, Iman; Abedi, Majid

    2015-12-01

    Thermo-mechanical analysis of the functionally graded orthotropic rotating hollow structures, subjected to thermo-mechanical loadings is studied in this paper. The relations were derived for both plane strain and plane stress conditions as a cylinder and disk, respectively. Non homogeneity was considered arbitrary through thickness direction for all mechanical and thermal properties. The responses of the system including temperature distribution, radial displacement and radial and circumferential stresses were derived in the general state. As case study, power law gradation was assumed for functionally graded cylinder and the mentioned results were evaluated in terms of parameters of the system such as non-homogeneous index and angular velocity.

  19. Thermoelastic Stress in a Functionally Graded Infinite Plate with Electromagnetic Wave Absorption

    NASA Astrophysics Data System (ADS)

    Tian, Hong-Yan; Wang, Xing-Zhe; Zhou, You-He

    2012-11-01

    We present an analysis of thermal and thermoelastic behaviors of a functionally graded infinite plate taking into account electromagnetic wave absorption. To treat with the inhomogeneity of functionally graded wave-absorbing (FGWA) materials, the plate is approximated by subdividing it into thin homogeneous layers to solve the governing equations together with proper boundary and connecting conditions. The results illustrate that the FGWA plate is a broadband type absorber with electromagnetic wave absorption. By choosing proper material gradation character and the thickness of the FGWA plate, it is possible to obtain a good performance of electromagnetic wave absorption and thermoelastic stress characteristics.

  20. Zwitteration: Coating Surfaces with Zwitterionic Functionality to Reduce Nonspecific Adsorption

    PubMed Central

    2015-01-01

    Coating surfaces with thin or thick films of zwitterionic material is an effective way to reduce or eliminate nonspecific adsorption to the solid/liquid interface. This review tracks the various approaches to zwitteration, such as monolayer assemblies and polymeric brush coatings, on micro- to macroscopic surfaces. A critical summary of the mechanisms responsible for antifouling shows how zwitterions are ideally suited to this task. PMID:24754399

  1. Determination of characteristics of erosion wear of grade 15Kh11MF steel with the Cr-CrC ion-plasma sprayed coating

    NASA Astrophysics Data System (ADS)

    Seleznev, L. I.; Mednikov, A. F.; Tkhabisimov, A. B.; Ryzhenkov, A. V.; Kachalin, G. V.; Zilova, O. S.

    2016-06-01

    Results of investigations of the influence of a Cr-CrC ion-plasma sprayed protective coating on characteristics and the intensity of erosion wear of grade 15Kh11MF steel at a gas-abrasive flow incidence angle of 30° and an experimental specimen (target) surface temperature of 550°C are presented. The Cr-CrC ion-plasma sprayed coating was formed in a Gefest vacuum installation by magnetron deposition. Investigations of the formed coating were carried out using a research and experimental facility complex that provided the study of the composition and structure of the coating, measurement of its thickness, roughness, microhardness, and determination of its relative resistance at the combined action of the gas-abrasive flow and high temperatures. The Cr-CrC coating with a thickness of 6.5 ± 0.3 μm has a finegrained structure with grains with dimensions of 20-40 nm and contains layers of chromium and chromium carbide. The main coating element is chromium. Its content in carbide layers is 89.4-91.9% at a carbon content of 6.8-9.5%. The coating microhardness is H 0.05 = 1350 ± 50 HV. The maximum wear of the 15Kh11MF steel target is observed at the angle of the gas-abrasive flow incidence that is close to 30° (30 7°). With this incidence angle and a target surface temperature of 550°C, the Cr-CrC coating extends the term to the surface failure and the appearance of a clear abrasive trace no less than four times. The coating failure has a local character, i.e., the target surface forms islands with the coating, between which the intensive wear of the base material occurs.

  2. Graphene Nanoplatelets Based Protective and Functionalizing Coating for Stainless Steel.

    PubMed

    Mondal, Jayanta; Kozlova, Jekaterina; Sammelselg, Väino

    2015-09-01

    Stainless steel is the most widely used alloy for many industrial and everyday applications, and protection of this alloy substrate against corrosion is an important industrial issue. Here we report a promising application of graphene oxide and graphene nanoplatelets as effective corrosion inhibitors for AISI type 304 stainless steel alloy. The graphene oxide and graphene coatings on the stainless steel substrates were prepared using spin coating techniques. Homogeneous and complete surface coverage by the graphene oxide and graphene nanoplatelets were observed with a high-resolution scanning electron microscope. The corrosion inhibition ability of these materials was investigated through measurement of open circuit potential and followed by potentiodymamic polarization analysis in aqueous sodium chloride solution before and after a month of immersion. Analyzed result exhibits effective corrosion inhibition for both substrates coated with graphene oxide or graphene nanoplatelets by increasing corrosion potential, pitting potential and decreasing passive current density. The corrosion inhibition ability of the coated substrates has not changed even after the long-term immersion. The result showed both graphene materials can be used as an effective corrosion inhibitor for the stainless steel substrates, which would certainly increase lifetime the substrate. However, long-term protection ability of the graphene coated susbtsrate showed somewhat better inhibition performance than the ones coated with graphene oxide. PMID:26716239

  3. Prediction of the adhesive behavior of bio-inspired functionally graded materials against rough surfaces

    NASA Astrophysics Data System (ADS)

    Peijian, Chen; Juan, Peng; Yucheng, Zhao; Feng, Gao

    2014-06-01

    Roughness effect and adhesion properties are important characteristics to be accessed in the development of functionally graded materials for biological and biomimetic applications, particularly for the hierarchical composition in biomimetic gecko robot. A multi-asperities adhesion model to predict the adhesive forces is presented in this work. The effect of surface roughness and graded material properties, which significantly alter the adhesive strength between contact bodies, can be simultaneously considered in the generalized model. It is found that proper interfacial strength can be controlled by adjusting surface roughness σ / R, graded exponent k and material parameter E*R / Δγ. The results should be helpful in the design of new biomimetic materials and useful in application of micro functional instruments.

  4. Nonlinear vibration of functionally graded circular cylindrical shells based on improved Donnell equations

    NASA Astrophysics Data System (ADS)

    Bich, Dao Huy; Xuan Nguyen, Nguyen

    2012-12-01

    In the present work, the study of the nonlinear vibration of a functionally graded cylindrical shell subjected to axial and transverse mechanical loads is presented. Material properties are graded in the thickness direction of the shell according to a simple power law distribution in terms of volume fractions of the material constituents. Governing equations are derived using improved Donnell shell theory ignoring the shallowness of cylindrical shells and kinematic nonlinearity is taken into consideration. One-term approximate solution is assumed to satisfy simply supported boundary conditions. The Galerkin method, the Volmir's assumption and fourth-order Runge-Kutta method are used for dynamical analysis of shells to give explicit expressions of natural frequencies, nonlinear frequency-amplitude relation and nonlinear dynamic responses. Numerical results show the effects of characteristics of functionally graded materials, pre-loaded axial compression and dimensional ratios on the dynamical behavior of shells. The proposed results are validated by comparing with those in the literature.

  5. Microstructure and work function of dispenser cathode coatings: Effects on thermionic emission

    NASA Astrophysics Data System (ADS)

    Swartzentruber, Phillip

    Dispenser cathodes emit electrons through thermionic emission and are a critical component of space-based and telecommunication devices. The emission of electrons is enhanced when coated with a refractory metal such as osmium (Os), osmium-ruthenium (Os-Ru), or iridium (Ir). In this work the microstructure, thermionic emission, and work function of thin film Os-Ru coatings were studied in order to relate microstructural properties and thermionic emission. Os-Ru thin film coatings were prepared through magnetron sputtering and substrate biasing to produce films with an array of preferred orientations, or texture. The effect of texture on thermionic emission was studied in detail through closely-spaced diode testing, SEM imaging, and x-ray diffraction. Results indicated that there was a strong correlation with emission behavior and specific preferred orientations. An ultra-high vacuum compatible Kelvin Probe was used to measure the work function of W-Os-Ru ternary alloy films to determine the effect W interdiffusion has on work function. The results indicated that a high work function alloy coating corresponded to low work function cathodes, as expected. It was inferred that a high work function alloy coating results in a low work function cathode because it aligns more closely with ionization energy of Ba. The results also proved that this method of evaluating dispenser cathode coatings can distinguish small variations in microstructure and composition and may be a beneficial tool in the development of improved dispenser cathode coatings. A novel experimental apparatus was constructed to measure the work function of dispenser cathode coatings in-vacuo using the ultra-high vacuum Kelvin Probe. The apparatus is capable of activating cathodes at high temperature and measuring the work function at elevated temperature. The design of this apparatus allows for more rapid evaluation of dispenser cathode coatings.

  6. The fabrication and material characterization of PZT based functionally graded piezoceramics

    NASA Astrophysics Data System (ADS)

    Alexander, Paul W.; Brei, Diann; Halloran, John W.

    2005-05-01

    Functionally Graded Piezoceramics (FGP) increase actuator lifetime and provide complex deformations; however, to reap these benefits sophisticated grading and fabrication techniques beyond the conventional layered bonding techniques are required. This paper introduces the Dual Electro/Piezo Property (DEPP) gradient technique via MicroFabrication through CoeXtrusion (MFCX). The Dual Electro/Piezo Property (DEPP) grading technique pairs a high displacement lead zirconate titanate (PZT) piezoceramic with a high permittivity barium titanate (BT) dielectric. These compatible materials act synergistically to form dramatic gradients in permittivity across the structure, concentrating the electric field in the more piezoelectrically active region leading to electrically-efficient, large-displacement actuators; with the benefit of increased reliability stemming from the continuous gradients and monolithic nature of the ceramic. The DEPP variation was first evaluated independently of the MFCX process through fabrication and experimental characterization of a powder pressed bimorph. While simple one-dimensionally graded FGPs can be realized by this process, MFCX is needed for any complex, multidimensional gradient. The MFCX process was adapted for DEPP grading and demonstrated by creating a more complex linearly-graded FGP. Both the bimorph and linearly graded specimens had good material quality and generated high displacements correlating well with published FGP theory; with the linear gradient reducing internal stress levels, extending actuator lifetime. This paper presents a general FGP methodology that couples grading and fabrication to generate high yield, low cost monolithic actuators with complicated one-dimensional gradients. Extension of this research will pave the way for more complicated gradients yielding such deformation capabilities as warping, twisting, rippling, and dimpling.

  7. Development of Functionally Graded Materials for Manufacturing Tools and Dies and Industrial Processing Equipment

    SciTech Connect

    Lherbier, Louis, W.; Novotnak, David, J.; Herling, Darrell, R.; Sears, James, W.

    2009-03-23

    Hot forming processes such as forging, die casting and glass forming require tooling that is subjected to high temperatures during the manufacturing of components. Current tooling is adversely affected by prolonged exposure at high temperatures. Initial studies were conducted to determine the root cause of tool failures in a number of applications. Results show that tool failures vary and depend on the operating environment under which they are used. Major root cause failures include (1) thermal softening, (2) fatigue and (3) tool erosion, all of which are affected by process boundary conditions such as lubrication, cooling, process speed, etc. While thermal management is a key to addressing tooling failures, it was clear that new tooling materials with superior high temperature strength could provide improved manufacturing efficiencies. These efficiencies are based on the use of functionally graded materials (FGM), a new subset of hybrid tools with customizable properties that can be fabricated using advanced powder metallurgy manufacturing technologies. Modeling studies of the various hot forming processes helped identify the effect of key variables such as stress, temperature and cooling rate and aid in the selection of tooling materials for specific applications. To address the problem of high temperature strength, several advanced powder metallurgy nickel and cobalt based alloys were selected for evaluation. These materials were manufactured into tooling using two relatively new consolidation processes. One process involved laser powder deposition (LPD) and the second involved a solid state dynamic powder consolidation (SSDPC) process. These processes made possible functionally graded materials (FGM) that resulted in shaped tooling that was monolithic, bi-metallic or substrate coated. Manufacturing of tooling with these processes was determined to be robust and consistent for a variety of materials. Prototype and production testing of FGM tooling showed the

  8. Fracture Analysis of a Functionally Graded Two-Layer Strip with a Surface Crack Intersecting the Interface

    SciTech Connect

    Guo Licheng; Noda, Naotake

    2008-02-15

    The crack problem for a functionally graded two-layer strip under an in-plane load is investigated. The functionally graded layer is assumed to contain a surface crack intersecting the interface. An auxiliary function related to two layers is used. By using integral transform methods, the singular integral equation is obtained. The parameter influences on the stress intensity factors (SIFs) are studied.

  9. New platforms for multi-functional ocular lenses: engineering double-sided functionalized nano-coatings.

    PubMed

    Mehta, Prina; Justo, Lucas; Walsh, Susannah; Arshad, Muhammad S; Wilson, Clive G; O'Sullivan, Ciara K; Moghimi, Seyed M; Vizirianakis, Ioannis S; Avgoustakis, Konstantinos; Fatouros, Dimitris G; Ahmad, Zeeshan

    2015-05-01

    A scalable platform to prepare multi-functional ocular lenses is demonstrated. Using rapidly dissolving polyvinylpyrrolidone (PVP) as the active stabilizing matrix, both sides of ocular lenses were coated using a modified scaled-up masking electrohydrodynamic atomization (EHDA) technique (flow rates variable between 5 and 10 µL/min, applied voltage 4-11 kV). Each side was coated (using a specially designed flip-able well) selectively with a pre-determined morphology and model drug substance. PVP nanoparticles (inner side, to be in contact with the cornea, mean size functional polymers/excipients and advanced controlled release strategies) suggests several therapeutic platforms for ocular lenses can be further developed at ambient temperature and pressure. These provide multi-functional properties (in personalized delivery, nanomedicine and nanosensors) from a single drug delivery device. PMID:25582133

  10. Functionally Graded Designer Viscoelastic Materials Tailored to Perform Prescribed Tasks with Probabilistic Failures and Lifetimes

    SciTech Connect

    Hilton, Harry H.

    2008-02-15

    Protocols are developed for formulating optimal viscoelastic designer functionally graded materials tailored to best respond to prescribed loading and boundary conditions. In essence, an inverse approach is adopted where material properties instead of structures per se are designed and then distributed throughout structural elements. The final measure of viscoelastic material efficacy is expressed in terms of failure probabilities vs. survival time000.

  11. Eighth Grade In-Service Teachers' Knowledge of Proportional Reasoning and Functions: A Secondary Data Analysis

    ERIC Educational Resources Information Center

    Masters, Jessica

    2012-01-01

    A secondary data analysis was conducted using a large dataset from a study related to online professional development for eighth grade teachers of mathematics. Using this data, the paper provides a snapshot of the current state of teachers' knowledge related to proportional reasoning and functions. The paper also considers how teachers' knowledge…

  12. Algebraic Reasoning: Professor Arbegla Introduces Variables and Functions. GEMS Teacher's Guide for Grades 3-5.

    ERIC Educational Resources Information Center

    Kopp, Jaine; Bergman, Lincoln

    This teacher guide helps build a solid foundation in algebra for students in grades 3-5 in which students gain essential understanding of properties of numbers, variables, functions, equations, and formulas. Throughout the problem solving activities, students use computational skills and gain a deeper understanding of the number system. Students…

  13. Sub-stoichiometric functionally graded titania fibres for water-splitting applications

    NASA Astrophysics Data System (ADS)

    Adamaki, Vaia; Sergejevs, A.; Clarke, C.; Clemens, F.; Marken, F.; Bowen, C. R.

    2015-06-01

    The photo-electro-chemical (PEC) splitting of water requires semiconductor materials with a minimum energy gap of 1.23 eV along with conduction and valence bands overlapping the oxidation of H2O and reduction of H+ respectively. This work overcomes the limitations of stoichiometric titania by manufacturing fine scale fibres that exhibit a compositional gradient of oxygen vacancies across the fibre length. In such a fibre configuration the fibre end that is chemically reduced to a relatively small extent performs as the photoanode and the oxygen vacancies enhance the absorption of light. The fibre end that is reduced the most consists of Magnéli phases and exhibits metallic electrical conductivity that enhances the electron-hole separation. The structure and composition of the functionally graded fibres, which were manufactured through extrusion, pressureless sintering and carbo-thermal reduction, are studied using XRD and electron microscopy. Electrochemical impedance spectroscopy measurements were performed in a three-electrode electrochemical system and showed that the oxygen vacancies in the functionally graded fibres affect the flat band potential and have increased carrier density. The efficiency of the system was evaluated with PEC measurements that shows higher efficiency for the functionally graded fibres compared to homogeneous TiO2 or Magnéli phase fibres. The functionally graded and fine scale fibres have the potential to be used as an array of active fibres for water splitting applications.

  14. An Analysis of Schooling, Literacy and Functional Literacy of Urban and Suburban Eighth Grade Students.

    ERIC Educational Resources Information Center

    Lathen, Levi

    Through the administration of standardized tests, questionnaires, and an inventory of educational progress designed to assess the application of skills, an effort is made to analyze the literacy, functional literacy, and factors related to achievement in a population of 181 eighth-grade students selected from an inner-city population and a…

  15. Mother-Child Planning, Child Emotional Functioning, and Children's Transition to First Grade

    ERIC Educational Resources Information Center

    Perez, Susan M.; Gauvain, Mary

    2009-01-01

    Mother-child planning was examined in relation to child emotional functioning and first-grade school performance. Ninety dyads were randomly assigned to the explicit-goal condition (emphasized accuracy and preparation for a child-only posttest) or the no-explicit-goal condition (dyads just asked to work together). In the no-explicit-goal condition…

  16. Assessment of S-phase coated medical grade stainless steel (Ortron 90) for use in the human joint replacement corrosion wear environment

    NASA Astrophysics Data System (ADS)

    Dearnley, P. A.; Figueiredo Pina, C. G.; Fisher, J.

    2008-05-01

    Hard and corrosion resistant coating materials such as S-phase, a nitrogen supersaturated Fe-Ni-Cr-Mo phase, have the potential to limit the corrosion-wear (tribo-corrosion) damage that can affect the metallic bearing surfaces of joint replacement devices in vivo, but hitherto have not been much investigated. To test their suitability, a range of S-phase coatings (with five nitrogen concentrations [N]) was applied to several polished Ortron 90 (biomedical grade austenitic stainless steel) test pieces via magnetron sputter deposition. Crevice attack, via intergranular corrosion, was found to be worse for most S-phase coated and uncoated Ortron 90 materials when tested in bovine serum compared with testing in 0.89% NaCl solution. Measurements of the breakdown potentials and the anodic passive current density, for a given test solution, revealed the crevice corrosion response of uncoated Ortron 90 to be more severe than the S-phase coated materials, although this was not unequivocally supported by 2D profilometry measurements. Corrosion-wear tests made using a sliding contact Al2O3 counterface showed the surface degradation to be more aggressive in saline solution than in bovine serum. All S-phase coatings were very effective in mitigating corrosion-wear of Ortron 90 in bovine serum solution, but only one S-phase coating composition, containing 21 at% N, gave improved resistance when tested in 0.89% NaCl solution.

  17. Direct writing of bio-functional coatings for cardiovascular applications.

    PubMed

    Perkins, Jessica; Hong, Yi; Ye, Sang-Ho; Wagner, William R; Desai, Salil

    2014-12-01

    The surface modification of metallic biomaterials is of critical importance to enhance the biocompatibility of surgical implant materials and devices. This article investigates the use of a direct-write inkjet technique for multilayer coatings of a biodegradable polymer (polyester urethane urea (PEUU)) embedded with an anti-proliferation drug paclitaxel (Taxol). The direct-write inkjet technique provides selective patterning capability for depositing multimaterial coatings on three-dimensional implant devices such as pins, screws, and stents for orthopedic and vascular applications. Drug release profiles were studied to observe the influence of drug loading and coating thickness for obtaining tunable release kinetics. Platelet deposition studies were conducted following ovine blood contact and significant reduction in platelet deposition was observed on the Taxol loaded PEUU substrate compared with the unloaded control. Rat smooth muscle cells were used for cell proliferation studies. Significant reduction in cell growth was observed following the release of anti-proliferative drug from the biopolymer thin film. This research provides a basis for developing anti-proliferative biocompatible coatings for different biomedical device applications. PMID:24497436

  18. Free-edge stress analysis of functionally graded material layered biocomposite laminates.

    PubMed

    Huang, Bin; Kim, Heung Soo

    2014-10-01

    A stress function based theory is proposed to obtain free-edge stress distributions for three-dimensional, orthotropic, linearly elastic rectangular biocomposite laminates with surface-bonded functionally graded materials (FGM). The assumed stress fields automatically satisfy the pointwise equilibrium equation, as well as traction-free and free edge boundary conditions. The complementary virtual work principle, followed by the general eigenvalue solution procedure, is used to obtain 3-D free edge stress states. A typical stacking sequence of composite laminate is used as numerical investigation with surface bonded FGMs. It is shown that with proper exponential factor of FGMs, the interlaminar stresses at the FGM layer interface can be reduced significantly, in return to prevent debonding of FGM layers. This approach can be useful in the design of functionally graded material layered biocomposite structures. PMID:25942808

  19. Vibration analysis and transient response of a functionally graded piezoelectric curved beam with general boundary conditions

    NASA Astrophysics Data System (ADS)

    Su, Zhu; Jin, Guoyong; Ye, Tiangui

    2016-06-01

    The paper presents a unified solution for free and transient vibration analyses of a functionally graded piezoelectric curved beam with general boundary conditions within the framework of Timoshenko beam theory. The formulation is derived by means of the variational principle in conjunction with a modified Fourier series which consists of standard Fourier cosine series and supplemented functions. The mechanical and electrical properties of functionally graded piezoelectric materials (FGPMs) are assumed to vary continuously in the thickness direction and are estimated by Voigt’s rule of mixture. The convergence, accuracy and reliability of the present formulation are demonstrated by comparing the present solutions with those from the literature and finite element analysis. Numerous results for FGPM beams with different boundary conditions, geometrical parameters as well as material distributions are given. Moreover, forced vibration of the FGPM beams subjected to dynamic loads and general boundary conditions are also investigated.

  20. Low-Velocity Impact Response of Sandwich Beams with Functionally Graded Core

    NASA Technical Reports Server (NTRS)

    Apetre, N. A.; Sankar, B. V.; Ambur, D. R.

    2006-01-01

    The problem of low-speed impact of a one-dimensional sandwich panel by a rigid cylindrical projectile is considered. The core of the sandwich panel is functionally graded such that the density, and hence its stiffness, vary through the thickness. The problem is a combination of static contact problem and dynamic response of the sandwich panel obtained via a simple nonlinear spring-mass model (quasi-static approximation). The variation of core Young's modulus is represented by a polynomial in the thickness coordinate, but the Poisson's ratio is kept constant. The two-dimensional elasticity equations for the plane sandwich structure are solved using a combination of Fourier series and Galerkin method. The contact problem is solved using the assumed contact stress distribution method. For the impact problem we used a simple dynamic model based on quasi-static behavior of the panel - the sandwich beam was modeled as a combination of two springs, a linear spring to account for the global deflection and a nonlinear spring to represent the local indentation effects. Results indicate that the contact stiffness of thc beam with graded core Increases causing the contact stresses and other stress components in the vicinity of contact to increase. However, the values of maximum strains corresponding to the maximum impact load arc reduced considerably due to grading of thc core properties. For a better comparison, the thickness of the functionally graded cores was chosen such that the flexural stiffness was equal to that of a beam with homogeneous core. The results indicate that functionally graded cores can be used effectively to mitigate or completely prevent impact damage in sandwich composites.

  1. A simple and accurate grading system for orthoiodohippurate renal scans in the assessment of post-transplant renal function

    SciTech Connect

    Zaki, S.K.; Bretan, P.N.; Go, R.T.; Rehm, P.K.; Streem, S.B.; Novick, A.C. )

    1990-06-01

    Orthoiodohippurate renal scanning has proved to be a reliable, noninvasive method for the evaluation and followup of renal allograft function. However, a standardized system for grading renal function with this test is not available. We propose a simple grading system to distinguish the different functional phases of hippurate scanning in renal transplant recipients. This grading system was studied in 138 patients who were evaluated 1 week after renal transplantation. There was a significant correlation between the isotope renographic functional grade and clinical correlates of allograft function such as the serum creatinine level (p = 0.0001), blood urea nitrogen level (p = 0.0001), urine output (p = 0.005) and need for hemodialysis (p = 0.007). We recommend this grading system as a simple and accurate method to interpret orthoiodohippurate renal scans in the evaluation and followup of renal allograft recipients.

  2. Smart Surfaces: New Coatings & Paints with Radiation Detection Functionality

    SciTech Connect

    Farmer, J; Choi, J

    2007-03-12

    Paints are being developed and tested that might ultimately be able to detect radiological agents in the environment by incorporating special pigments into an organic polymeric binder that can be applied as a paint or coatings. These paints detect radioactive sources and contaminants with inorganic or organic scintillation or thermo-luminescent pigments, which are selected based upon the radiation ({alpha}, {beta}, {gamma} or n) to be detected, and are shown in Figure 1.

  3. Micromechanics and Structural Response of Functionally Graded, Particulate-Matrix, Fiber-Reinforced Composites

    PubMed Central

    Genin, Guy M.; Birman, Victor

    2009-01-01

    Reinforcement of fibrous composites by stiff particles embedded in the matrix offers the potential for simple, economical functional grading, enhanced response to mechanical loads, and improved functioning at high temperatures. Here, we consider laminated plates made of such a material, with spherical reinforcement tailored by layer. The moduli for this material lie within relatively narrow bounds. Two separate moduli estimates are considered: a “two-step” approach in which fibers are embedded in a homogenized particulate matrix, and the Kanaun-Jeulin (2001) approach, which we re-derive in a simple way using the Benveniste (1988) method. Optimal tailoring of a plate is explored, and functional grading is shown to improve the performance of the structures considered. In the example of a square, simply supported, cross-ply laminated panel subjected to uniform transverse pressure, a modest functional grading offers significant improvement in performance. A second example suggests superior blast resistance of the panel achieved at the expense of only a small increase in weight. PMID:23874001

  4. Methods of electrophoretic deposition for functionally graded porous nanostructures and systems thereof

    DOEpatents

    Worsley, Marcus A; Baumann, Theodore F; Satcher, Joe H; Olson, Tammy Y; Kuntz, Joshua D; Rose, Klint A

    2015-03-03

    In one embodiment, an aerogel includes a layer of shaped particles having a particle packing density gradient in a thickness direction of the layer, wherein the shaped particles are characterized by being formed in an electrophoretic deposition (EPD) process using an impurity. In another embodiment, a method for forming a functionally graded porous nanostructure includes adding particles of an impurity and a solution to an EPD chamber, applying a voltage difference across the two electrodes of the EPD chamber to create an electric field in the EPD chamber, and depositing the material onto surfaces of the particles of the impurity to form shaped particles of the material. Other functionally graded materials and methods are described according to more embodiments.

  5. Effect of partial elastic foundation on free vibration of fluid-filled functionally graded cylindrical shells

    NASA Astrophysics Data System (ADS)

    Kim, Young-Wann

    2015-12-01

    The free vibration characteristics of fluid-filled functionally graded cylindrical shells buried partially in elastic foundations are investigated by an analytical method. The elastic foundation of partial axial and angular dimensions is represented by the Pasternak model. The motion of the shells is represented by the first-order shear deformation theory to account for rotary inertia and transverse shear strains. The functionally graded cylindrical shells are composed of stainless steel and silicon nitride. Material properties vary continuously through the thickness according to a power law distribution in terms of the volume fraction of the constituents. The governing equation is obtained using the Rayleigh-Ritz method and a variation approach. The fluid is described by the classical potential flow theory. Numerical examples are presented and compared with existing available results to validate the present method.

  6. Mothers' depressive symptoms and children's cognitive and social agency: Predicting first-grade cognitive functioning.

    PubMed

    Yan, Ni; Dix, Theodore

    2016-08-01

    Using data from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (N = 1,364), the present study supports an agentic perspective; it demonstrates that mothers' depressive symptoms in infancy predict children's poor first-grade cognitive functioning because depressive symptoms predict children's low social and cognitive agency-low motivation to initiate social interaction and actively engage in activities. When mothers' depressive symptoms were high in infancy, children displayed poor first-grade cognitive functioning due to (a) tendencies to become socially withdrawn by 36 months and low in mastery motivation by 54 months and (b) tendencies for children's low agency to predict declines in mothers' sensitivity and cognitive stimulation. Findings suggest that mothers' depressive symptoms undermine cognitive development through bidirectional processes centered on children's low motivation to engage in social interaction and initiate and persist at everyday tasks. (PsycINFO Database Record PMID:27389834

  7. Multiscale Structured and Functionally Graded Gas Diffusion Electrodes for PEM-Fuel Cells and Electrodialysis

    NASA Astrophysics Data System (ADS)

    Wolf, H.; Franz, M.; Bienhüls, C.; Willert-Porada, M.

    2008-02-01

    In the presented work, different methods of preparation of functionally graded gas diffusion electrodes (GDE) for fuel cell and electrodialysis application were investigated. High electrochemical performance with a low platinum catalyst content of only 0.1 mg/cm2 was achieved. The new GDEs are superior to commercial ones with five times higher platinum content, due to their optimized pore structure and improved distribution of catalyst and ion conductive polymer.

  8. Prediction of acoustic radiation from functionally graded shells of revolution in light and heavy fluids

    NASA Astrophysics Data System (ADS)

    Qu, Yegao; Meng, Guang

    2016-08-01

    This paper presents a semi-analytical method for the vibro-acoustic analysis of a functionally graded shell of revolution immersed in an infinite light or heavy fluid. The structural model of the shell is formulated on the basis of a modified variational method combined with a multi-segment technique, whereas a spectral Kirchhoff-Helmholtz integral formulation is employed to model the exterior fluid field. The material properties of the shell are estimated by using the Voigt's rule of mixture and the Mori-Tanaka's homogenization scheme. Displacement and sound pressure variables of each segment are expanded in the form of a mixed series using Fourier series and Chebyshev orthogonal polynomials. A set of collocation nodes distributed over the roots of Chebyshev polynomials are employed to establish the algebraic system of the acoustic integral equations, and the non-uniqueness solution is eliminated using a combined Helmholtz integral equation formulation. Loosely and strongly coupled schemes are implemented for the structure-acoustic interaction problem of a functionally graded shell immersed in a light and heavy fluid, respectively. The present method provides a flexible way to account for the individual contributions of circumferential wave modes to the vibration and acoustic responses of functionally graded shells of revolution in an analytical manner. Numerical tests are presented for sound radiation problems of spherical, cylindrical, conical and coupled shells. The individual contributions of the circumferential modes to the radiated sound pressure and sound power of functionally graded shells are observed. Effects of the material profile on the sound radiation of the shells are also investigated.

  9. Method and apparatus for determination of mechanical properties of functionally-graded materials

    DOEpatents

    Giannakopoulos, Antonios E.; Suresh, Subra

    1999-01-01

    Techniques for the determination of mechanical properties of homogenous or functionally-graded materials from indentation testing are presented. The technique is applicable to indentation on the nano-scale through the macro-scale including the geological scale. The technique involves creating a predictive load/depth relationship for a sample, providing an experimental load/depth relationship, comparing the experimental data to the predictive data, and determining a physical characteristic from the comparison.

  10. Analysis of stress singularities at singular points of elastic solids made of functionally graded materials

    NASA Astrophysics Data System (ADS)

    Matveenko, V. P.; Fedorov, A. Yu.; Shardakov, I. N.

    2016-01-01

    The results of analytical and numerical investigations on estimating the character of the singularity of stresses in a vicinity of different variants of special points of the 2D elastic solids made of functionally graded materials (FGMs) are presented. The variant of construction by analytical methods in the polar system of coordinates is considered for eigensolutions in the flat wedges made of the FGM, the elastic properties of which are represented as power series in terms of the radial coordinate.

  11. Large current difference in Au-coated vertical silicon nanowire electrode array with functionalization of peptides

    PubMed Central

    2013-01-01

    Au-coated vertical silicon nanowire electrode array (VSNEA) was fabricated using a combination of bottom-up and top-down approaches by chemical vapor deposition and complementary metal-oxide-semiconductor process for biomolecule sensing. To verify the feasibility for the detection of biomolecules, Au-coated VSNEA was functionalized using peptides having a fluorescent probe. Cyclic voltammograms of the peptide-functionalized Au-coated VSNEA show a steady-state electrochemical current behavior. Because of the critically small dimension and vertically aligned nature of VSNEA, the current density of Au-coated VSNEA was dramatically higher than that of Au film electrodes. Au-coated VSNEA further showed a large current difference with and without peptides that was nine times more than that of Au film electrodes. These results indicate that Au-coated VSENA is highly effective device to detect peptides compared to conventional thin-film electrodes. Au-coated VSNEA can also be used as a divergent biosensor platform in many applications. PMID:24279451

  12. Large current difference in Au-coated vertical silicon nanowire electrode array with functionalization of peptides

    NASA Astrophysics Data System (ADS)

    Kim, Ilsoo; Kim, So-Eun; Han, Sanghun; Kim, Hyungsuk; Lee, Jaehyung; Jeong, Du-Won; Kim, Ju-Jin; Lim, Yong-beom; Choi, Heon-Jin

    2013-11-01

    Au-coated vertical silicon nanowire electrode array (VSNEA) was fabricated using a combination of bottom-up and top-down approaches by chemical vapor deposition and complementary metal-oxide-semiconductor process for biomolecule sensing. To verify the feasibility for the detection of biomolecules, Au-coated VSNEA was functionalized using peptides having a fluorescent probe. Cyclic voltammograms of the peptide-functionalized Au-coated VSNEA show a steady-state electrochemical current behavior. Because of the critically small dimension and vertically aligned nature of VSNEA, the current density of Au-coated VSNEA was dramatically higher than that of Au film electrodes. Au-coated VSNEA further showed a large current difference with and without peptides that was nine times more than that of Au film electrodes. These results indicate that Au-coated VSENA is highly effective device to detect peptides compared to conventional thin-film electrodes. Au-coated VSNEA can also be used as a divergent biosensor platform in many applications.

  13. Electrophoretic deposition of tetracycline modified silk fibroin coatings for functionalization of titanium surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen; Qu, Yinying; Li, Xiaoshuang; Zhang, Sheng; Wei, Qingsong; Shi, Yusheng; Chen, Lili

    2014-06-01

    Electrophoretic deposition has been widely used for the fabrication of functional coatings onto metal implant. A characteristic feature of this process is that positively charged materials migrate toward the cathode and can deposit on it. In this study, silk fibroin was decorated with tetracycline in aqueous solution to impart positive charge, and then deposited on negatively titanium cathode under certain electric field. The characterization of the obtained coatings indicated that the intermolecular hydrogen bonds formed between the backbone of silk fibroin and tetracycline molecular. In vitro biological tests demonstrated that osteoblast-like cells achieved acceptable cell affinity on the tetracycline cross-linked silk fibroin coatings, although greater cell viability was seen on pure silk fibroin coatings. The cationic silk fibroin coatings showed remarkable antibacterial activity against gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria. Therefore, we concluded that electrophoretic deposition was an effective and efficient technique to prepare cationic silk fibroin coatings on the titanium surface and that cationic silk fibroin coatings with acceptable biocompatibility and antibacterial property were promising candidates for further loading of functional agents.

  14. Mechanical and biological properties of the micro-/nano-grain functionally graded hydroxyapatite bioceramics for bone tissue engineering.

    PubMed

    Zhou, Changchun; Deng, Congying; Chen, Xuening; Zhao, Xiufen; Chen, Ying; Fan, Yujiang; Zhang, Xingdong

    2015-08-01

    Functionally graded materials (FGM) open the promising approach for bone tissue repair. In this study, a novel functionally graded hydroxyapatite (HA) bioceramic with micrograin and nanograin structure was fabricated. Its mechanical properties were tailored by composition of micrograin and nanograin. The dynamic mechanical analysis (DMA) indicated that the graded HA ceramics had similar mechanical property compared to natural bones. Their cytocompatibility was evaluated via fluorescent microscopy and MTT colorimetric assay. The viability and proliferation of rabbit bone marrow mesenchymal stem cells (BMSCs) on ceramics indicated that this functionally graded HA ceramic had better cytocompatibility than conventional HA ceramic. This study demonstrated that functionally graded HA ceramics create suitable structures to satisfy both the mechanical and biological requirements of bone tissues. PMID:25910818

  15. In vitro corrosion testing of PVD coatings applied to a surgical grade Co-Cr-Mo alloy.

    PubMed

    Bolton, J; Hu, X

    2002-06-01

    Toxic effects and biological reaction of metallic corrosion and wear products are an important concern for metal on metal artificial joints. Corrosion tests were conducted to study the susceptibility to pitting and localized corrosion, with three coatings, CrN, TiN and DLC, applied to a wrought high carbon Co-Cr-Mo alloy substrate material. Corrosion testing involved the measurement of potential time transients during immersion in a physiological solution and cyclic polarization of specimen potentials into the transpassive range followed by reversal of the potential to scan in the cathodic direction to regain the rest potential E(rest). Resistance to pitting and localized corrosion was assessed by determining the transpassive breakdown potential E(bd) and if any hysteresis generated during the reverse cyclic scan may have caused crossover with the original anodic scan. Three different surface coating conditions were tested namely: (1) as-coated, (2) polished, and (3) indented to penetrate the coating by diamond pyramid hardness indentor. Results showed that all three coatings produced significant improvements in corrosion resistance compared to performance of the wrought cobalt alloy but that some corrosive attack to both the CrN and TiN coatings occurred and some risk of attack to the cobalt alloy substrate existed due to coating defects or when damage to the coating occurred. TiN coatings were highly effective in preventing corrosion provided they were thick enough to produce complete coverage. Thin TiN coatings displayed some tendency to encourage localized attack of the cobalt alloy at coating defects or where the coating suffered mechanical damage. CrN coatings underwent transpassive breakdown more easily and some degree of pitting at defects within the coating was observed, especially when the CrN coating was polished before the test. No corrosive attack of the cobalt alloy substrate was observed when the CrN coating was mechanically damaged by indentation

  16. Investigating the Force Production of Functionally-Graded Flexible Wings in Flapping Wing Flight

    NASA Astrophysics Data System (ADS)

    Mudbhari, Durlav; Erdogan, Malcolm; He, Kai; Bateman, Daniel; Lipkis, Rory; Moored, Keith

    2015-11-01

    Birds, insects and bats oscillate their wings to propel themselves over long distances and to maneuver with unprecedented agility. A key element to achieve their impressive aerodynamic performance is the flexibility of their wings. Numerous studies have shown that homogeneously flexible wings can enhance force production, propulsive efficiency and lift efficiency. Yet, animal wings are not homogenously flexible, but instead have varying material properties. The aim of this study is to characterize the force production and energetics of functionally-graded flexible wings. A partially-flexible wing composed of a rigid section and a flexible section is used as a first-order model of functionally-graded materials. The flexion occurs in the spanwise direction and it is affected by the spanwise flexion ratio, that is, the ratio of the length of the rigid section compared to the total span length. By varying the flexion ratio as well as the material properties of the flexible section, the study aims to examine the force production and energetics of flapping flight with functionally-graded flexible wings. Supported by the Office of Naval Research under Program Director Dr. Bob Brizzolara, MURI grant number N00014-14-1-0533.

  17. Finite element analysis on longitudinal and radial functionally graded femoral prosthesis.

    PubMed

    Oshkour, Azim Ataollahi; Abu Osman, N A; Davoodi, M M; Yau, Y H; Tarlochan, F; Wan Abas, W A B; Bayat, M

    2013-12-01

    This study focused on developing a 3D finite element model of functionally graded femoral prostheses to decrease stress shielding and to improve total hip replacement performance. The mechanical properties of the modeled functionally graded femoral prostheses were adjusted in the sagittal and transverse planes by changing the volume fraction gradient exponent. Prostheses with material changes in the sagittal and transverse planes were considered longitudinal and radial prostheses, respectively. The effects of cemented and noncemented implantation methods were also considered in this study. Strain energy and von Mises stresses were determined at the femoral proximal metaphysis and interfaces of the implanted femur components, respectively. Results demonstrated that the strain energy increased proportionally with increasing volume fraction gradient exponent, whereas the interface stresses decreased on the prostheses surfaces. A limited increase was also observed at the surfaces of the bone and cement. The periprosthetic femur with a noncemented prosthesis exhibited higher strain energy than with a cemented prosthesis. Radial prostheses implantation displayed more strain energy than longitudinal prostheses implantation in the femoral proximal part. Functionally graded materials also increased strain energy and exhibited promising potentials as substitutes of conventional materials to decrease stress shielding and to enhance total hip replacement lifespan. PMID:23922316

  18. Physical activity levels and functional performance in the Osteoarthritis Initiative: a graded relationship

    PubMed Central

    Dunlop, Dorothy D.; Song, Jing; Semanik, Pamela A.; Sharma, Leena; Chang, Rowland W.

    2010-01-01

    Objective Physical activity improves function for adults with arthritis, but it is unknown if there is a graded relationship with functional benefit. We examine the cross-sectional and longitudinal relationship between self-reported physical activity and observed functional performance in adults with knee osteoarthritis. Methods The Osteoarthritis Initiative cohort included 2589 persons with knee osteoarthritis (2301 having longitudinal follow-up) aged 45 to 79 years at baseline. Two years of prospective annual functional performance was assessed from timed 20 meter walk tests. We used linear regression to estimate differences across physical activity quartiles in subsequent function (baseline and 1-year activity predicts 1- and 2-year function, respectively) adjusted for demographics (age, gender, race/ethnicity, education, marital status) and health factors (osteoarthritis severity, knee symptoms, knee pain, knee injury, body mass index, comorbidity, depression, smoking, alcohol use, other joint pain). Results Increasing physical activity levels had a significant graded relationship with functional performance. Adults in physical activity quartile groups, from least to most active, had average gait speed of 4.0, 4.2, 4.3, 4.5 feet/second respectively at baseline (p-value for trend <.001) and 4.1, 4.2, 4.3, 4.5 feet/second after one year (p-value for trend <.001); increasing trends remained significant after adjusting for covariates. Findings were similar within gender and age groups. Conclusion These prospective data showed a consistent graded relationship between physical activity level and better performance in adults with knee osteoarthritis. These findings support guidelines that encourage persons with arthritis who cannot attain minimum recommended physical activity to be as active as possible. PMID:20862681

  19. Asphalt pavement aging and temperature dependent properties using functionally graded viscoelastic model

    NASA Astrophysics Data System (ADS)

    Dave, Eshan V.

    Asphalt concrete pavements are inherently graded viscoelastic structures. Oxidative aging of asphalt binder and temperature cycling due to climatic conditions being the major cause of non-homogeneity. Current pavement analysis and simulation procedures dwell on the use of layered approach to account for these non-homogeneities. The conventional finite-element modeling (FEM) technique discretizes the problem domain into smaller elements, each with a unique constitutive property. However the assignment of unique material property description to an element in the FEM approach makes it an unattractive choice for simulation of problems with material non-homogeneities. Specialized elements such as "graded elements" allow for non-homogenous material property definitions within an element. This dissertation describes the development of graded viscoelastic finite element analysis method and its application for analysis of asphalt concrete pavements. Results show that the present research improves efficiency and accuracy of simulations for asphalt pavement systems. Some of the practical implications of this work include the new technique's capability for accurate analysis and design of asphalt pavements and overlay systems and for the determination of pavement performance with varying climatic conditions and amount of in-service age. Other application areas include simulation of functionally graded fiber-reinforced concrete, geotechnical materials, metal and metal composites at high temperatures, polymers, and several other naturally existing and engineered materials.

  20. The narwhal (Monodon monoceros) cementum-dentin junction: a functionally graded biointerphase.

    PubMed

    Grandfield, Kathryn; Chattah, Netta Lev-Tov; Djomehri, Sabra; Eidelmann, Naomi; Eichmiller, Frederick C; Webb, Samuel; Schuck, P James; Nweeia, Martin; Ho, Sunita P

    2014-08-01

    In nature, an interface between dissimilar tissues is often bridged by a graded zone, and provides functional properties at a whole organ level. A perfect example is a "biological interphase" between stratified cementum and dentin of a narwhal tooth. This study highlights the graded structural, mechanical, and chemical natural characteristics of a biological interphase known as the cementum-dentin junction layer and their effect in resisting mechanical loads. From a structural perspective, light and electron microscopy techniques illustrated the layer as a wide 1000-2000 μm graded zone consisting of higher density continuous collagen fiber bundles from the surface of cementum to dentin, that parallels hygroscopic 50-100 μm wide collagenous region in human teeth. The role of collagen fibers was evident under compression testing during which the layer deformed more compared to cementum and dentin. This behavior is reflected through site-specific nanoindentation indicating a lower elastic modulus of 2.2 ± 0.5 GPa for collagen fiber bundle compared to 3 ± 0.4 GPa for mineralized regions in the layer. Similarly, microindentation technique illustrated lower hardness values of 0.36 ± 0.05 GPa, 0.33 ± 0.03 GPa, and 0.3 ± 0.07 GPa for cementum, dentin, and cementum-dentin layer, respectively. Biochemical analyses including Raman spectroscopy and synchrotron-source microprobe X-ray fluorescence demonstrated a graded composition across the interface, including a decrease in mineral-to-matrix and phosphate-to-carbonate ratios, as well as the presence of tidemark-like bands with Zn. Understanding the structure-function relationships of wider tissue interfaces can provide insights into natural tissue and organ function. PMID:25205746

  1. Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

    PubMed

    Sengupta, Pranesh; Rogalla, Detlef; Becker, Hans Werner; Dey, Gautam Kumar; Chakraborty, Sumit

    2011-08-15

    Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt. PMID:21684682

  2. Electrical Properties of Conductive Cotton Yarn Coated with Eosin Y Functionalized Reduced Graphene Oxide.

    PubMed

    Kim, Eunju; Arul, Narayanasamy Sabari; Han, Jeong In

    2016-06-01

    This study reports the fabrication and investigation of the electrical properties of two types of conductive cotton yarns coated with eosin Y or eosin B functionalized reduced graphene (RGO) and bare graphene oxide (GO) using dip-coating method. The surface morphology of the conductive cotton yarn coated with reduced graphene oxide was observed by Scanning Electron Microscope (SEM). Due to the strong electrostatic attractive forces, the negatively charged surface such as the eosin Y functionalized reduced graphene oxide or bare GO can be easily coated to the positively charged polyethyleneimine (PEI) treated cotton yarn. The maximum current for the conductive cotton yarn coated with eosin Y functionalized RGO and bare GO with 20 cycles repetition of (5D + R) process was found to be 793.8 μA and 3482.8 μA. Our results showed that the electrical conductivity of bare GO coated conductive cotton yarn increased by approximately four orders of magnitude with the increase in the dipping cycle of (5D+R) process. PMID:27427672

  3. Determination and modeling of residual stress in functionally graded WC-Co

    NASA Astrophysics Data System (ADS)

    Tahvilian, Leila

    Gradual variations in composition and/or structure through the volume of functionally graded materials (FGMs) generally result in corresponding continuous spatial variations in mechanical/physical properties, and often in significant residual stresses that develop during processing. Due to inhomogeneous properties in these materials, residual stress measurement in FGMs can be a very challenging problem. In this study, residual stresses in functionally graded cemented tungsten carbide (FG-WC-Co) were investigated by numerical, analytical and experimental approaches by means of a layer removal technique. The numerical method consisted of finite element analysis (FEA) modeling for the FGM plate, in order to calculate residual stress distribution over the volume and to develop a method for predicting residual stress levels in closely related materials. The analytical procedure embodied a mathematical approach to determine residual stress distributions, and analytically determined values are compared with those obtained from FEA modeling and experimental results. The experimental approach consisted of fabricating and heat treating FG-WC-Co flat samples, then measuring strain changes by strain gauge after each sequential layer removal from the opposite side of the specimen from the graded region. Good agreement was found between analytical, numerical and experimental results. Furthermore, thermal residual stress distribution in FG-WC-Co hollow cylinder was examined with an emphasis on the effects of key variables, the gradient profile and the gradient thickness, on the magnitude and distribution of the stress field. An analytical direct solution based on solving the governing equations of a cylinder composed of a uniform inner core and a functionally graded outer shell was developed. The cylindrical compound was considered as two separate elements: homogeneous cylinder and functionally graded shell. Material properties, such as the elastic modulus and the coefficient of

  4. One-Dimensional Solutions for Transient Thermal Stresses in Functionally Graded Hollow Cylinders and Hollow Spheres

    NASA Astrophysics Data System (ADS)

    Ootao, Yoshihiro; Tanigawa, Yoshinobu

    2008-02-01

    This paper is concerned with the theoretical treatment of transient thermoelastic problems involving functionally graded hollow cylinders and hollow spheres due to uniform heat supply. The thermal and thermoelastic coefficients of the hollow cylinders and hollow spheres are expressed as power functions of the radial coordinate. The one-dimensional solutions for the temperature changes in a transient state and the thermoelastic response are obtained herein. Some numerical results are shown in figures. Furthermore, the influence of the material nonhomogeneity on the temperature change, displacements and stresses is investigated.

  5. Assessment of Preoperative Liver Function in Patients with Hepatocellular Carcinoma – The Albumin-Indocyanine Green Evaluation (ALICE) Grade

    PubMed Central

    Kokudo, Takashi; Hasegawa, Kiyoshi; Amikura, Katsumi; Uldry, Emilie; Shirata, Chikara; Yamaguchi, Takamune; Arita, Junichi; Kaneko, Junichi; Akamatsu, Nobuhisa; Sakamoto, Yoshihiro; Takahashi, Amane; Sakamoto, Hirohiko; Makuuchi, Masatoshi; Matsuyama, Yutaka; Demartines, Nicolas; Malagó, Massimo; Kokudo, Norihiro; Halkic, Nermin

    2016-01-01

    Background Most patients with hepatocellular carcinoma (HCC) have underlying liver disease, therefore, precise preoperative evaluation of the patient’s liver function is essential for surgical decision making. Methods We developed a grading system incorporating only two variables, namely, the serum albumin level and the indocyanine green retention rate at 15 minutes (ICG R15), to assess the preoperative liver function, based on the overall survival of 1868 patients with HCC who underwent liver resection. We then tested the model in a European cohort (n = 70) and analyzed the predictive power for the postoperative short-term outcome. Results The Albumin-Indocyanine Green Evaluation (ALICE) grading system was developed in a randomly assigned training cohort: linear predictor = 0.663 × log10ICG R15 (%)−0.0718 × albumin (g/L) (cut-off value: -2.20 and -1.39). This new grading system showed a predictive power for the overall survival similar to the Child-Pugh grading system in the validation cohort. Determination of the ALICE grade in Child-Pugh A patients allowed further stratification of the postoperative prognosis. This result was reproducible in the European cohort. Determination of the ALICE grade allowed better prediction of the risk of postoperative liver failure and mortality (ascites: grade 1, 2.1%; grade 2, 6.5%; grade 3, 16.0%; mortality: grade 1, 0%; grade 2, 1.3%; grade 3, 5.3%) than the previously reported model based on the presence/absence of portal hypertension. Conclusions This new grading system is a simple method for prediction of the postoperative long-term and short-term outcomes. PMID:27434062

  6. A new design of cemented stem using functionally graded materials (FGM).

    PubMed

    Hedia, H S; Aldousari, S M; Abdellatif, A K; Fouda, N

    2014-01-01

    One of the most frequent complications of total hip replacement (THR) is aseptic loosening of femoral component which is primarily due to changes of post-operative stress distribution pattern with respect to intact femur. Stress shielding of the femur is known to be a principal factor in aseptic loosening of hip replacements. Many designers show that a stiff stem shields the surrounding bone from mechanical loading causing stress shielding. Others show that reducing stem stiffness promotes higher proximal interface shear stress which increases the risk of proximal interface failure. Therefore, the task of this investigation is to solve these conflicting problems appeared in the cemented total hip replacement. The finite element method and optimization technique are used in order to find the optimal stem material which gives the optimal available stress distribution between the proximal medial femoral bone and the cement mantle interfaces. The stem is designed using the concept of functionally graded material (FGM) instead of using the conventional most common used stem material. The results showed that there are four feasible solutions from the optimization runs. The best of these designs is to use a cemented stem graded from titanium at the upper stem layer to collagen at the lower stem layer. This new cemented stem design completely eliminates the stress shielding problem at the proximal medial femoral region. The stress shielding using the cemented functionally graded stem is reduced by 98% compared to titanium stem. PMID:24840196

  7. On the nonlinear axisymmetric dynamic buckling behavior of clamped functionally graded spherical caps

    NASA Astrophysics Data System (ADS)

    Prakash, T.; Sundararajan, N.; Ganapathi, M.

    2007-01-01

    Here, the dynamic thermal buckling behavior of functionally graded spherical caps is studied considering geometric nonlinearity based on von Karman's assumptions. The formulation is based on first-order shear deformation theory and it includes the in-plane and rotary inertia effects. The material properties are graded in the thickness direction according to the power-law distribution in terms of volume fractions of the material constituents. The effective material properties are evaluated using homogenization method. The governing equations obtained using finite element approach are solved employing the Newmark's integration technique coupled with a modified Newton-Raphson iteration scheme. The pressure load corresponding to a sudden jump in the maximum average displacement in the time history of the shell structure is taken as the dynamic buckling load. The present model is validated against the available isotropic case. A detailed numerical study is carried out to highlight the influences of shell geometries, power law index of functional graded material and boundary conditions on the dynamic buckling load of shallow spherical shells.

  8. Surface functionalization for tailoring the aggregation and magnetic behaviour of silica-coated iron oxide nanostructures

    NASA Astrophysics Data System (ADS)

    Roca, A. G.; Carmona, D.; Miguel-Sancho, N.; Bomatí-Miguel, O.; Balas, F.; Piquer, C.; Santamaría, J.

    2012-04-01

    We report here a detailed structural and magnetic study of different silica nanocapsules containing uniform and highly crystalline maghemite nanoparticles. The magnetic phase consists of 5 nm triethylene glycol (TREG)- or dimercaptosuccinic acid (DMSA)-coated maghemite particles. TREG-coated nanoparticles were synthesized by thermal decomposition. In a second step, TREG ligands were exchanged by DMSA. After the ligand exchange, the ζ potential of the particles changed from - 10 to - 40 mV, whereas the hydrodynamic size remained constant at around 15 nm. Particles coated by TREG and DMSA were encapsulated in silica following a sol-gel procedure. The encapsulation of TREG-coated nanoparticles led to large magnetic aggregates, which were embedded in coalesced silica structures. However, DMSA-coated nanoparticles led to small magnetic clusters inserted in silica spheres of around 100 nm. The final nanostructures can be described as the result of several competing factors at play. Magnetic measurements indicate that in the TREG-coated nanoparticles the interparticle magnetic interaction scenario has not dramatically changed after the silica encapsulation, whereas in the DMSA-coated nanoparticles, the magnetic interactions were screened due to the function of the silica template. Moreover, the analysis of the AC susceptibility suggests that our systems essentially behave as cluster spin glass systems.

  9. Effects of functionally graded materials on dynamics of molecular bond clusters

    NASA Astrophysics Data System (ADS)

    Zhang, WenLiang; Qian, Jin; Yao, HaiMin; Chen, WeiQiu; Gao, HuaJian

    2012-06-01

    Unlike nonspecific adhesion of conventional hard materials in engineering commonly described by JKR and DMT type models, the molecular adhesion via specific receptor-ligand bonds is stochastic by nature and has the feature that its strength strongly depends on the medium stiffness surrounding the adhesion. In this paper, we demonstrate in a stochastic-elasticity framework that a type of materials with linearly graded elastic modulus can be designed to achieve "equal load sharing" and enhanced cooperative rebinding among interfacial molecular bonds. Upon modulus gradation, multiple molecular bonds can be elastically decoupled but statistically cooperative. In general, uniform molecular adhesion can be accomplished by two strategies: homogeneous materials with sufficient stiffness higher than a threshold or heterogeneous materials satisfying the criterion on modulus gradation. These results not only provide a theoretical principle for possible applications of functionally graded materials in quantitatively controlling cell-matrix adhesion, but also have general implications on adhesion between soft materials mediated by specific molecular binding.

  10. The role of the executive functions in school achievement at the end of Grade 1.

    PubMed

    Monette, Sebastien; Bigras, Marc; Guay, Marie-Claude

    2011-06-01

    The aim of this study was to determine the role of executive functions (EFs) in early school achievement when a variety of potential confounding factors were controlled. Measures of EF (inhibition, flexibility, and working memory) and school readiness were administered to a sample of 85 kindergartners (39 boys and 46 girls, 5-6years old). School achievement was then assessed at the end of Grade 1. Results show math and reading/writing skills at the end of Grade 1 to be associated with kindergarten EFs. Only working memory contributed uniquely to the variance in school achievement after all covariates (preacademic abilities, affective variables, and family variables) were controlled and, even then, only with respect to math skills. On the other hand, working memory and inhibition had an indirect effect on reading/writing skills via anger-aggression. EF implication in school achievement is discussed in terms of task demands and child age. PMID:21349537

  11. Research on Recent Processing Technologies for Functionally Graded Materials in China

    NASA Astrophysics Data System (ADS)

    Ge, C. C.; Song, S. X.; Zhou, Z. J.; Shen, W. P.; Du, J.; Cong, W. W.

    2008-02-01

    Functionally graded materials (FGMs) are attracting more and more attentions of materials scientists, because their composition, structures and properties vary gradually and continuously from one material to another along one or more direction, which satisfy the demands of the advanced materials. The studies on FGMs have been performed for nearly 20 years around the world. In China, the related research also has been carried out for more than 10 years and some notable progress is noted. This paper presents an overview on emerging technologies for FGMs in China, including ultra-high consolidation with graded sintering, spark plasma sintering (SPS), self-propagating high-temperature synthesis (SHS), thermal spraying, chemical vapor deposition, physical vapor deposition, laser cladding and so on. In addition, various applications of these technologies are presented and some new technologies to the next level are also discussed.

  12. Electro-magneto-thermo-elastic response of infinite functionally graded cylinders without energy dissipation

    NASA Astrophysics Data System (ADS)

    Zenkour, Ashraf M.; Abbas, Ibrahim A.

    2015-12-01

    The electro-magneto-thermo-elastic analysis problem of an infinite functionally graded (FG) hollow cylinder is studied in the context of Green-Naghdi's (G-N) generalized thermoelasticity theory (without energy dissipation). Material properties are assumed to be graded in the radial direction according to a novel power-law distribution in terms of the volume fractions of the metal and ceramic constituents. The inner surface of the FG cylinder is pure metal whereas the outer surface is pure ceramic. The equations of motion and the heat-conduction equation are used to derive the governing second-order differential equations. A finite element scheme is presented for the numerical purpose. The system of differential equations is solved numerically and some plots for displacement, radial and electromagnetic stresses, and temperature are presented. The radial displacement, mechanical stresses and temperature as well as the electromagnetic stress are all investigated along the radial direction of the infinite cylinder.

  13. Processing, microstructure and mechanics of functionally graded Al A359/SiC(p) composite

    NASA Astrophysics Data System (ADS)

    Rodriguez-Castro, Ramon

    2000-11-01

    Metal matrix composites (MMCs) have great promise for high temperature, high strength, wear resistant applications. However, their brittleness has limited their use in load bearing applications. Functionally graded MMCs with a reinforcement concentration higher on the surface than in the interior offer new opportunities, as these materials will have high surface hardness as well as high resistance to crack growth towards the interior. In this dissertation the processing and mechanical properties of a functionally graded MMC are investigated. Rectangular blocks (100 mmx60 mmx50 mm) of functionally graded SiC particulate reinforced aluminum A359 matrix composite were prepared by centrifugal casting techniques. The reinforcement volume fraction profiles varied as the centrifugal force was applied, owing to the different densities of Al and SiC. The casting at 1300 rpm (angular velocity) had a well-mixed, refined microstructure with the maximum SiC volume fraction of 44% near the outer surface of the blocks. This surface exhibited an elevated hardness. The effect of SiC particulate reinforcement on strengthening of A359 Al alloy was experimentally studied by tensile testing specimens prepared from the cast blocks. There was a continuous increase in tensile and yield strength with increasing SiC volume fractions in the range of 0.20 to 0.30. On the contrary, there was a reduction in tensile and yield strength for SiC concentrations in the range of 0.30 to 0.40. The elasticity modulus increased with increasing SiC volume fractions in the whole reinforcement range (0.20--0.40). Fractographic analysis by SEM revealed a ductile failure process of void growth in the matrix, but the amount of the void growth was less when the SiC concentration was higher. SEM also revealed SiC reinforcement fracture and decohesion, with the particle fracture increasing with the particle concentration. Appropriate flat specimens with a continuously graded microstructure for fracture mechanics

  14. Propagation of elastic waves in an anisotropic functionally graded hollow cylinder in vacuum.

    PubMed

    Baron, Cécile

    2011-02-01

    As a non-destructive, non-invasive and non-ionizing evaluation technique for heterogeneous media, the ultrasonic method is of major interest in industrial applications but especially in biomedical fields. Among the unidirectionally heterogeneous media, the continuously varying media are a particular but widespread case in natural materials. The first studies on laterally varying media were carried out by geophysicists on the Ocean, the atmosphere or the Earth, but the teeth, the bone, the shells and the insects wings are also functionally graded media. Some of them can be modeled as planar structures but a lot of them are curved media and need to be modeled as cylinders instead of plates. The present paper investigates the influence of the tubular geometry of a waveguide on the propagation of elastic waves. In this paper, the studied structure is an anisotropic hollow cylinder with elastic properties (stiffness coefficients c(ij) and mass density ρ) functionally varying in the radial direction. An original method is proposed to find the eigenmodes of this waveguide without using a multilayered model for the cylinder. This method is based on the sextic Stroh's formalism and an analytical solution, the matricant, explicitly expressed under the Peano series expansion form. This approach has already been validated for the study of an anisotropic laterally-graded plate (Baron et al., 2007; Baron and Naili, 2010) [6,5]. The dispersion curves obtained for the radially-graded cylinder are compared to the dispersion curves of a corresponding laterally-graded plate to evaluate the influence of the curvature. Preliminary results are presented for a tube of bone in vacuum modelling the in vitro conditions of bone strength evaluation. PMID:20692675

  15. Functionalized hexagonal boron nitride nano-coatings for protection of transparent plastics

    NASA Astrophysics Data System (ADS)

    Van Tran, Thu; Usta, Aybala; Asmatulu, Ramazan

    2016-04-01

    Nanocoating is the result of a coating application of nanomaterials to build a consistent network of molecules in a paint to protect the surfaces of various materials and devices. Hexagonal Boron Nitride (h-BN) is in two dimensional form with excellent thermal, mechanical and chemical properties. These BN nanocoatings are also a thermally insulating material for heat management. After adding functionalized h-BNs into paints or other coatings, they will absorb the harmful UV part of sunlight and prevent coating against the environmental degradations. The impacts of the environmental factors on the coatings can be substantially eliminated. In the present study, h-BNs were modified with [2-(2-Aminoethylamino) propyl] trimethoxysilane and uniformly dispersed into the polyurethane coatings with different amounts, such as 0.1, 0.2, 0.4, and 0.8wt% to increase hardness and water resistance, and decrease the UV degradation level of coatings and transparent plastics. The prepared samples were characterized by using Fourier Transform Infrared Spectroscopy (FTIR), UV-Vis Spectroscopy, Scanning Electron Microscope (SEM), Water Contact Angle, and Differential Scanning Calorimeter (DSC). The test results showed that the nanocoatings with functionalized h-BN provided excellent physical and chemical behaviors against the UV and other physical degradations on the substrates.

  16. Surface-Functionalization of Nanostructured Cellulose Aerogels by Solid State Eumelanin Coating.

    PubMed

    Panzella, Lucia; Melone, Lucio; Pezzella, Alessandro; Rossi, Bianca; Pastori, Nadia; Perfetti, Marco; D'Errico, Gerardino; Punta, Carlo; d'Ischia, Marco

    2016-02-01

    Bioinspired aerogel functionalization by surface modification and coating is in high demand for biomedical and technological applications. In this paper, we report an expedient three-step entry to all-natural surface-functionalized nanostructured aerogels based on (a) TEMPO/NaClO promoted synthesis of cellulose nanofibers (TOCNF); (b) freeze-drying for aerogel preparation; and (c) surface coating with a eumelanin thin film by ammonia-induced solid state polymerization (AISSP) of 5,6-dihydroxyindole (DHI) or 5,6-dihydroxyindole-2-carboxylic acid (DHICA) previously deposited from an organic solution. Scanning electron microscopy showed uniform deposition of the dark eumelanin coating on the template surface without affecting porosity, whereas solid state (13)C NMR and electron paramagnetic resonance (EPR) spectroscopy confirmed the eumelanin-type character of the coatings. DHI melanin coating was found to confer to TOCNF templates a potent antioxidant activity, as tested by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays as well as strong dye adsorption capacity, as tested on methylene blue. The unprecedented combination of nanostructured cellulose and eumelanin thin films disclosed herein implements an original all-natural multifunctional aerogel biomaterial realized via an innovative coating methodology. PMID:26734842

  17. AFM characterization of nonwoven material functionalized by ZnO sputter coating

    SciTech Connect

    Deng Bingyao; Yan Xiong; Wei Qufu Gao Weidong

    2007-10-15

    Sputter coatings provide new approaches to the surface functionalization of textile materials. In this study, polyethylene terephthalate (PET) nonwoven material was used as a substrate for creating functional nanostructures on the fiber surfaces. A magnetron sputter coating was used to deposit functional zinc oxide (ZnO) nanostructures onto the nonwoven substrate. The evolution of the surface morphology of the fibers in the nonwoven web was examined using atomic force microscopy (AFM). The AFM observations revealed a significant difference in the morphology of the fibers before and after the sputter coating. The AFM images also indicated the effect of the sputtering conditions on the surface morphology of the fibers. The increase in the sputtering time led to the growth of the ZnO grains on the fiber surfaces. The higher pressure in the sputtering chamber could cause the formation of larger grains on the fiber surfaces. The higher power used also generated larger grains on the fiber surfaces.

  18. Functionally strain-graded nanoscoops for high power Li-ion battery anodes.

    PubMed

    Krishnan, Rahul; Lu, Toh-Ming; Koratkar, Nikhil

    2011-02-01

    Lithium-ion batteries show poor performance for high power applications involving ultrafast charging/discharging rates. Here we report a functionally strain-graded carbon-aluminum-silicon anode architecture that overcomes this drawback. It consists of an array of nanostructures each comprising an amorphous carbon nanorod with an intermediate layer of aluminum that is finally capped by a silicon nanoscoop on the very top. The gradation in strain arises from graded levels of volumetric expansion in these three materials on alloying with lithium. The introduction of aluminum as an intermediate layer enables the gradual transition of strain from carbon to silicon, thereby minimizing the mismatch at interfaces between differentially strained materials and enabling stable operation of the electrode under high-rate charge/discharge conditions. At an accelerated current density of ∼51.2 A/g (i.e., charge/discharge rate of ∼40C), the strain-graded carbon-aluminum-silicon nanoscoop anode provides average capacities of ∼412 mAh/g with a power output of ∼100 kW/kg(electrode) continuously over 100 charge/discharge cycles. PMID:21192713

  19. Preparation and analysis of chemically gradient functional bioceramic coating formed by pulsed laser deposition.

    PubMed

    Rajesh, P; Muraleedharan, C V; Sureshbabu, S; Komath, Manoj; Varma, Harikrishna

    2012-02-01

    Bioactive ceramic coatings based on calcium phosphates yield better functionality in the human body for a variety of metallic implant devices including orthopaedic and dental prostheses. In the present study chemically and hence functionally gradient bioceramic coating was obtained by pulsed laser deposition method. Calcium phosphate bioactive ceramic coatings based on hydroxyapatite (HA) and tricalcium phosphate (TCP) were deposited over titanium substrate to produce gradation in physico-chemical characteristics and in vitro dissolution behaviour. Sintered targets of HA and α-TCP were deposited in a multi target laser deposition system. The obtained deposits were characterized by X-ray diffraction, fourier transform infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray analysis. Inductively coupled plasma spectroscopy was used to estimate the in vitro dissolution behaviour of coatings. The variation in mechanical property of the gradient layer was evaluated through scratch test and micro-indentation hardness. The bioactivity was examined in vitro with respect to the ability of HA layer to form on the surface as a result of contact with simulated body fluid. It could be inferred that chemically gradient functional bioceramic coating can be produced by laser deposition of multiple sintered targets with variable chemical composition. PMID:22105226

  20. Functional multilayer coated long period grating tuned in transition region for life science applications

    NASA Astrophysics Data System (ADS)

    Pilla, P.; Malachovská, V.; Borriello, A.; Giordano, M.; Ambrosio, L.; Cutolo, A.; Cusano, A.

    2010-09-01

    We report preliminary results on the development of multilayer coated long period gratings (LPGs) for life science applications. The dip-coating technique and a solvent/nonsolvent strategy were exploited to deposit double-layer polymeric film onto a LPG. A primary coating of atactic polystyrene was used as high refractive index layer to tune the working point of the device in the so-called transition region thus achieving remarkable surrounding medium refractive index sensitivity. A secondary layer of atactic poly(methyl methacrylate-co-methacrylic acid) containing functional carboxyl groups, characterized by a lower refractive index, was deposited onto the primary coating in order to have the desired functional groups on the surface of the device. Commonly used covalent immobilization procedure, NHS/EDC coupling method, was exploited to link streptavidin on the surface of the functionalized coated device. Finally, real-time detection of biotinylated bovine serum albumin affinity binding on immobilized streptavidin was performed by monitoring the shift of the LPG attenuation bands.

  1. Geometry Design Optimization of Functionally Graded Scaffolds for Bone Tissue Engineering: A Mechanobiological Approach

    PubMed Central

    Boccaccio, Antonio; Uva, Antonio Emmanuele; Fiorentino, Michele; Mori, Giorgio; Monno, Giuseppe

    2016-01-01

    Functionally Graded Scaffolds (FGSs) are porous biomaterials where porosity changes in space with a specific gradient. In spite of their wide use in bone tissue engineering, possible models that relate the scaffold gradient to the mechanical and biological requirements for the regeneration of the bony tissue are currently missing. In this study we attempt to bridge the gap by developing a mechanobiology-based optimization algorithm aimed to determine the optimal graded porosity distribution in FGSs. The algorithm combines the parametric finite element model of a FGS, a computational mechano-regulation model and a numerical optimization routine. For assigned boundary and loading conditions, the algorithm builds iteratively different scaffold geometry configurations with different porosity distributions until the best microstructure geometry is reached, i.e. the geometry that allows the amount of bone formation to be maximized. We tested different porosity distribution laws, loading conditions and scaffold Young’s modulus values. For each combination of these variables, the explicit equation of the porosity distribution law–i.e the law that describes the pore dimensions in function of the spatial coordinates–was determined that allows the highest amounts of bone to be generated. The results show that the loading conditions affect significantly the optimal porosity distribution. For a pure compression loading, it was found that the pore dimensions are almost constant throughout the entire scaffold and using a FGS allows the formation of amounts of bone slightly larger than those obtainable with a homogeneous porosity scaffold. For a pure shear loading, instead, FGSs allow to significantly increase the bone formation compared to a homogeneous porosity scaffolds. Although experimental data is still necessary to properly relate the mechanical/biological environment to the scaffold microstructure, this model represents an important step towards optimizing geometry

  2. Prediction of Dynamic Response for Ti/TiB Functionally Graded Beams

    SciTech Connect

    Tuegel, Eric J.; Byrd, Larry W.; Beberniss, Timothy J.

    2008-02-15

    Functionally graded ceramic-metal materials are candidates for use in aerospace structures that are exposed to high temperatures. These structures will experience other demands such as significant pressure fluctuations that will cause panels to vibrate at high frequencies. These materials must be engineered for specific applications. Standard engineering methods were used to predict the response of Ti/TiB cantilever beams to quasi-static and dynamic loadings. Experiments were performed and compared to the predictions. The predictions and experiments did not agree due to significant uncertainty about the elastic modulus of TiB.

  3. Microstructure and properties of multiphase and functionally graded materials prepared by chemical vapor deposition

    SciTech Connect

    Lee, W.Y.

    1996-05-01

    The synthesis of multiphase and functionally graded materials by chemical vapor deposition is discussed from a perspective of controlling their composition and microstructure at a nano-scale level, and ultimately, tailoring their material properties. Prior research is briefly reviewed to address the current state of this novel material concept. Recent experimental results relating to controlling the selected properties of two multiphase systems, TiN + MoS{sub 2} and NiAl + Al{sub 2}O{sub 3}, are described to illustrate this concept`s potential merits and challenges for use in realistic applications.

  4. A Study on Propagation Characteristic of One-dimensional Stress Wave in Functionally Graded Armor Composites

    NASA Astrophysics Data System (ADS)

    Yang, S. Y.; Liu, X.; Cao, D. F.; Mei, H.; Lei, Z. T.; Liu, L. S.

    2013-03-01

    The development of Functionally Graded Materials (FGM) for energy-absorbing applications requires understanding of stress wave propagation in these structures in order to optimize their resistance to failure. One-dimensional stress wave in FGM composites under elastic and plastic wave loading have been investigated. The stress distributions through the thickness and stress status have been analyzed and some comparisons have been done with the materials of sharp interfaces (two-layered material). The results demonstrate that the gradient structure design greatly decreases the severity of the stress concentrations at the interfaces and there are no clear differences in stress distribution in FGM composites under elastic and plastic wave loading.

  5. 2D analysis of functionally graded magneto-electro-elastic composite materials with cracks under SH waves

    NASA Astrophysics Data System (ADS)

    Stoynov, Yonko

    2015-11-01

    Functionally graded materials are composite materials with continuously variable material properties. They possess huge potential for applications in modern industry, because of their enhanced qualities: thermal barrier effects, protection from corrosion and oxidation, improved toughness and stress. In our research we consider functionally graded magneto-electro-elastic materials with cracks, subjected to anti-plane wave and evaluate stress concentration near the crack tips in this type of materials with respect to external loading for different material grading. Boundary integral equation method (BIEM) is used for the numerical solution. Numerical examples are presented to show the dependence between the stress intensity factors and the frequency of the applied dynamic load.

  6. Nitinol-based Nanotubular and Nanowell Coatings for the Modulation of Human Vascular Cell Functions

    NASA Astrophysics Data System (ADS)

    Lee, Phin Peng

    Current approaches to reducing restenosis do not balance the reduction of vascular smooth muscle cell proliferation with the increase in the healing of the endothelium. Here, I present my study on the synthesis and characterization of a nanotubular coating on Nitinol substrates. I found that the coating demonstrated 'pro-healing' properties by increasing primary human aortic endothelial cell spreading, migration and collagen and elastin production. Certain cellular functions such as collagen and elastin production were also found to be affected by changes in nanotube diameter. The coating also reduced the proliferation and mRNA expression of collagen I and MMP2 for primary human aortic smooth muscle cells. I will also demonstrate the synthesis of a nanowell coating on Nitinol stents as well as an additional poly(lactic-co-glycolic acid) coating on top of the nanowells that has the potential for controlling drug release. These findings demonstrate the potential for the coatings to aid in the prevention of restenosis and sets up future explorations of ex vivo and in vivo studies.

  7. Calcium-doped ceria/titanate tabular functional nanocomposite by layer-by-layer coating method

    SciTech Connect

    Liu, Xiang W.; Devaraju, M.K.; Yin, Shu; Sato, Tsugio

    2010-07-15

    Ca-doped ceria (CDC)/tabular titanate (K{sub 0.8}Li{sub 0.27}Ti{sub 1.73}O{sub 4}, TT) UV-shielding functional nanocomposite with fairly uniform CDC coating layers was prepared through a polyelectrolyte-associated layer-by-layer (LbL) coating method. TT with lepidocrocite-like layered structure was used as the substrate, poly (diallyldimethylammonium chloride) (PDDA) was used as a coupling agent, CDC nanoparticles were used as the main UV-shielding component. CDC/TT nanocomposites with various coating layers of CDC were obtained through a multistep coating process. The phases were studied by X-ray diffraction. The morphology and coating quality were studied by scanning electron microscopy and element mapping of energy dispersive X-ray analysis. The oxidation catalytic activity, UV-shielding ability and using comfort were characterized by Rancimat test, UV-vis spectra and dynamic friction test, respectively. CDC/TT nanocomposites with low oxidation catalytic activity, high UV-shielding ability and good using comfort were finally obtained. - Graphical abstract: Through the control of surface charge of particles calcium-doped ceria/titanate composites with low oxidation catalytic activity, higher UV-shielding ability and excellent comfort was obtained by a facile layer-by-layer coating method.

  8. Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols.

    PubMed

    Bakhshi, Hadi; Yeganeh, Hamid; Mehdipour-Ataei, Shahram; Shokrgozar, Mohammad Ali; Yari, Abbas; Saeedi-Eslami, Seyyed Nasirodin

    2013-01-01

    In this study, a simple and versatile synthetic approach was developed to prepare bactericidal polyurethane coatings. For this purpose, introduction of both quaternary ammonium salts (QASs), with well-known antibacterial activity, and reactive hydroxyl groups on to the backbone of soybean oil was considered. Epoxidized soybean oil was reacted with diethylamine and the intermediate tertiary amine containing polyol was reacted with two different alkylating agents, methyl iodide and benzyl chloride, to produce MQAP and BQAP, respectively. These functional polyols were reacted with different diisocyanate monomers to prepare polyurethane coatings. Depending on the structure of monomers used for the preparation of polyurethane coatings, initial modulus, tensile strength and elongation at break of samples were in the ranges of 122-339 MPa, 4.6-12.4 MPa and 8.4-46%, respectively. Polyurethane coatings based on isophorone diisocyanate showed proper mechanical properties and adhesion strength (0.41 MPa) for coating application. Study of fibroblast cells interaction with prepared polyurethanes showed promising cells viability in the range of 78-108%. Meanwhile, MQAP based samples with higher concentration of QASs showed better adhesion strength, surface hydrophilicity and antibacterial activity (about 95% bacterial reduction). Therefore, these materials can find applications as bactericidal coating for biomedical devices and implants. PMID:25428057

  9. Coating nanofiber scaffolds with beta cell membrane to promote cell proliferation and function

    NASA Astrophysics Data System (ADS)

    Chen, Wansong; Zhang, Qiangzhe; Luk, Brian T.; Fang, Ronnie H.; Liu, Younian; Gao, Weiwei; Zhang, Liangfang

    2016-05-01

    The cell membrane cloaking technique has emerged as an intriguing strategy in nanomaterial functionalization. Coating synthetic nanostructures with natural cell membranes bestows the nanostructures with unique cell surface antigens and functions. Previous studies have focused primarily on development of cell membrane-coated spherical nanoparticles and the uses thereof. Herein, we attempt to extend the cell membrane cloaking technique to nanofibers, a class of functional nanomaterials that are drastically different from nanoparticles in terms of dimensional and mechanophysical characteristics. Using pancreatic beta cells as a model cell line, we demonstrate successful preparation of cell membrane-coated nanofibers and validate that the modified nanofibers possess an antigenic exterior closely resembling that of the source beta cells. When such nanofiber scaffolds are used to culture beta cells, both cell proliferation rate and function are significantly enhanced. Specifically, glucose-dependent insulin secretion from the cells is increased by near five-fold compared with the same beta cells cultured in regular, unmodified nanofiber scaffolds. Overall, coating cell membranes onto nanofibers could add another dimension of flexibility and controllability in harnessing cell membrane functions and offer new opportunities for innovative applications.

  10. Coating nanofiber scaffolds with beta cell membrane to promote cell proliferation and function.

    PubMed

    Chen, Wansong; Zhang, Qiangzhe; Luk, Brian T; Fang, Ronnie H; Liu, Younian; Gao, Weiwei; Zhang, Liangfang

    2016-05-21

    The cell membrane cloaking technique has emerged as an intriguing strategy in nanomaterial functionalization. Coating synthetic nanostructures with natural cell membranes bestows the nanostructures with unique cell surface antigens and functions. Previous studies have focused primarily on development of cell membrane-coated spherical nanoparticles and the uses thereof. Herein, we attempt to extend the cell membrane cloaking technique to nanofibers, a class of functional nanomaterials that are drastically different from nanoparticles in terms of dimensional and mechanophysical characteristics. Using pancreatic beta cells as a model cell line, we demonstrate successful preparation of cell membrane-coated nanofibers and validate that the modified nanofibers possess an antigenic exterior closely resembling that of the source beta cells. When such nanofiber scaffolds are used to culture beta cells, both cell proliferation rate and function are significantly enhanced. Specifically, glucose-dependent insulin secretion from the cells is increased by near five-fold compared with the same beta cells cultured in regular, unmodified nanofiber scaffolds. Overall, coating cell membranes onto nanofibers could add another dimension of flexibility and controllability in harnessing cell membrane functions and offer new opportunities for innovative applications. PMID:27139582

  11. Chemical tailoring of hybrid sol-gel thick coatings as hosting matrix for functional patterned microstructures.

    PubMed

    Falcaro, Paolo; Costacurta, Stefano; Malfatti, Luca; Buso, Dario; Patelli, Alessandro; Schiavuta, Piero; Piccinini, Massimo; Grenci, Gianluca; Marmiroli, Benedetta; Amenitsch, Heinz; Innocenzi, Plinio

    2011-02-01

    A phenyl-based hybrid organic - inorganic coating has been synthesized and processed by hard X-ray lithography. The overall lithography process is performed in a two-step process only (X-rays exposure and chemical etching). The patterns present high aspect ratio, sharp edges, and high homogeneity. The coating has been doped with a variety of polycyclic aromatic hydrocarbon functional molecules, such as anthracene, pentacene, and fullerene. For the first time, hard X-rays have been combined with thick hybrid functional coatings, using the sol-gel thick film directly as resist. A new technique based on a new material combined with hard X-rays is now available to fabricate optical devices. The effect due to the high-energy photon exposure has been investigated using FT-IR and Raman spectroscopy, laser scanner, optical profilometer, and confocal and electron microscope. High-quality thick hybrid fullerene-doped microstructures have been fabricated. PMID:21218788

  12. Use of Aloe vera gel coating preserves the functional properties of table grapes.

    PubMed

    Serrano, María; Valverde, Juan Miguel; Guillén, Fabian; Castillo, Salvador; Martínez-Romero, Domingo; Valero, Daniel

    2006-05-31

    Table grapes (Vitis vinifera L. cv. Crimson Seedless) were coated with Aloe vera gel according to our developed patent (SP Patent P200302937) and then stored for 35 days at 1 degrees C, and the subsequent shelf life (SL) was monitored at 20 degrees C. Uncoated clusters showed a rapid loss of functional compounds, such as total phenolics and ascorbic acid. These changes were accompanied by reduction of the total antioxidant activity (TAA) and increases in total anthocyanins, showing an accelerated ripening process. On the contrary, table grapes coated with Aloe vera gel significantly delayed the above changes, such as the retention of ascorbic acid during cold storage or SL. Consequently, Aloe vera gel coating, a simple and noncontaminating treatment, maintained the functional properties during postharvest storage of table grapes. PMID:16719510

  13. Dispersion relations of elastic waves in one-dimensional piezoelectric/piezomagnetic phononic crystal with functionally graded interlayers.

    PubMed

    Guo, Xiao; Wei, Peijun; Lan, Man; Li, Li

    2016-08-01

    The effects of functionally graded interlayers on dispersion relations of elastic waves in a one-dimensional piezoelectric/piezomagnetic phononic crystal are studied in this paper. First, the state transfer equation of the functionally graded interlayer is derived from the motion equation by the reduction of order (from second order to first order). The transfer matrix of the functionally graded interlayer is obtained by solving the state transfer equation with the spatial-varying coefficient. Based on the transfer matrixes of the piezoelectric slab, the piezomagnetic slab and the functionally graded interlayers, the total transfer matrix of a single cell is obtained. Further, the Bloch theorem is used to obtain the resultant dispersion equations of in-plane and anti-plane Bloch waves. The dispersion equations are solved numerically and the numerical results are shown graphically. Five kinds of profiles of functionally graded interlayers between a piezoelectric slab and a piezomagnetic slab are considered. It is shown that the functionally graded interlayers have evident influences on the dispersion curves and the band gaps. PMID:27179141

  14. Metal coated functionalized single-walled carbon nanotubes for composite applications

    NASA Astrophysics Data System (ADS)

    Zeng, Qiang

    This study is considered as a method for producing multifunctional composite materials by using metals coated Single-walled Carbon Nanotubes (SWCNTs). In this research, various metals (Ni, Cu, Ag) were successfully deposited onto the surface of SWCNTs. It has been found that homogenous dispersion and dense nucleation sites are the necessary conditions to form uniform coatings on SWCNTs. Functionalization has been applied to achieve considerable improvement in the dispersion of purified SWCNTs and creates more nucleation sites for subsequent metal deposition. A three-step electroless plating approach was used and the coating mechanism is described in the paper. The samples were characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA), Raman spectroscopy, fourier transform infrared spectroscopy (FTIR), and energy dispersive X-ray spectroscopy (EDX). Bulk copper/aluminum-SWNT composites were processed by powder metallurgy with wet mixing techniques. Coated SWCNTs were well dispersed in the metal matrix. Cold pressing followed by sintering was applied to control porosity. The relationships between hardness and SWCNTs addition were discussed. Ni-SWCNTs composite coatings were prepared by electro-composite deposition. SWCNTs were suspended in a Ni deposition electrolyte and deposited together with nickel during electrodeposition. SWCNTs concentrations in the coatings were found to be related to the SWCNTs concentration in the solution, current density and agitation rate. The microstructure of the coatings has been examined by electron microscopy. Ni coated SWCNTs were also incorporated into the high temperature Bismaleimide (BMI)/graphite composite to improve Electromagnetic Interference (EMI) shielding and surface conductivity. The vacuum assisted resin transfer molding (VARTM) was used to process these composites. Surface and volume resistivity and EMI shielding effectiveness of the composites

  15. Optically transparent and environmentally durable superhydrophobic coating based on functionalized SiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Schaeffer, Daniel A.; Polizos, Georgios; Barton Smith, D.; Lee, Dominic F.; Hunter, Scott R.; Datskos, Panos G.

    2015-02-01

    Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a ‘self-cleaning’ effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 160°-175°. This result is remarkable because such behavior cannot be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, they exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the CA and optical transmission between 190 and 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents, while the binder used was a polyurethane clearcoat. This solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 min, these coatings exhibited superhydrophobic behavior with a static CA ≥ 160°.

  16. Optically transparent and environmentally durable superhydrophobic coating based on functionalized SiO₂ nanoparticles.

    PubMed

    Schaeffer, Daniel A; Polizos, Georgios; Smith, D Barton; Lee, Dominic F; Hunter, Scott R; Datskos, Panos G

    2015-02-01

    Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a 'self-cleaning' effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 160°-175°. This result is remarkable because such behavior cannot be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, they exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the CA and optical transmission between 190 and 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents, while the binder used was a polyurethane clearcoat. This solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 min, these coatings exhibited superhydrophobic behavior with a static CA ≥ 160°. PMID:25573924

  17. Sodium functionalized graphene oxide coated titanium plates for improved corrosion resistance and cell viability

    NASA Astrophysics Data System (ADS)

    Marimuthu, Mohana; Veerapandian, Murugan; Ramasundaram, Subramaniyan; Hong, Seok Won; Sudhagar, P.; Nagarajan, Srinivasan; Raman, V.; Ito, Eisuke; Kim, Sanghyo; Yun, Kyusik; Kang, Yong Soo

    2014-02-01

    Surface functionalization is an important process that has been adopted to well explore the applications of nanomaterials. In this context, we demonstrate the sodium functionalized graphene oxide (NaGO) as an excellent candidate for increasing the life time of titanium (Ti) based ortho-implants. As-prepared aqueous dispersion of NaGO was used to assemble NaGO sheets on commercially pure Ti (CpTi) plates by heat controlled spin coating. The resulting wrinkled NaGO sheets play a dual role in implant material, i.e., passive layer against corrosion and biocompatible scaffold for cell viability. The preparation, physicochemical properties, and biocompatibility of NaGO coatings formed on CpTi were reported. The electrochemical polarization studies demonstrate the relative susceptibility of control GO and NaGO coatings to corrosion, which outline that the NaGO coating act as a geometric blocking layer and hence prevent the implant surface from contacting corrosive media. The immunofluorescence and cell proliferation studies performed using human dermal fibroblasts cells showed that NaGO coatings significantly (P < 0.05) enhanced the cellular viability for longer in vitro culture period (15 days) than control GO and pristine CpTi.

  18. Optically transparent and environmentally durable superhydrophobic coating based on functionalized SiO2 nanoparticles

    DOE PAGESBeta

    Schaeffer, Daniel A.; Polizos, Georgios; Smith, D. Barton; Lee, Dominic F.; Hunter, Scott R.; Datskos, Panos G.

    2015-01-09

    Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a self-cleaning effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 16≥0° to 175°. This result is remarkable because such behavior cannotmore » be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, surfaces exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the contact angle and optical transmission between 190 to 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents isopropyl alcohol and 4-chlorobenzotrifluoride (PCBTF) and a proprietary ceramic binder (Cerakote ). Finally, this solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 minutes, these coatings exhibited superhydrophobic behavior with a static CA ≥160°.« less

  19. Copper Ferrocyanide-Functionalized Magnetic Adsorbents Using Polyethyleneimine Coated Fe3O4 Nanoparticles for the Removal of Radioactive Cesium.

    PubMed

    Yang, Hee-Man; Hong, Sang Bum; Cho, Yong Suk; Lee, Kune-Woo; Seo, Bum-Kyoung; Moon, Jei-Kwon

    2016-03-01

    Copper ferrocyanide-functionalized magnetic nano-adsorbents were successfully synthesized by electrostatic coating of citric acid coated Fe3O4 nanoparticles with polyethyleneimine, and immobilizing copper and ferrocyanide on the surfaces of polyethyleneimine-coated nanoparticles. Radioactive cesium (Cs) adsorption tests were conducted to investigate the effectiveness of the copper ferrocyanide-functionalized magnetic nano-adsorbents toward the removal of radioactive Cs. PMID:27455762

  20. Fretting contact of a functionally graded piezoelectric layered half-plane under a conducting punch

    NASA Astrophysics Data System (ADS)

    Su, Jie; Ke, Liao-Liang; Wang, Yue-Sheng

    2016-02-01

    This paper investigates the fretting contact between a functionally graded piezoelectric layered half-plane and a rigid cylindrical punch. The electro-elastic properties of functionally graded piezoelectric materials (FGPMs) vary exponentially along the thickness direction. It is assumed that the punch is a perfect conductor with a constant electric potential within the contact region. The two bodies are brought into contact first by a monotonically increasing normal load, and then by a cyclic tangential load which is less than that necessary to cause complete sliding. The whole contact region is composed of an inner stick region and two outer slip regions in which Coulomb’s friction law is assumed. The problem is reduced to a set of coupled Cauchy singular integral equations by using the Fourier integral transform technique and the superposition theorem. An iterative method is used to determine the unknown stick/slip region, normal contact pressure, electric charge and tangential traction. The effects of the resultant electric charge and gradient index on the surface electromechanical fields are discussed during different loading phases. It is found that FGPMs could potentially be applied to improve fretting contact damage in smart devices.

  1. Comparison of Physicochemical and Functional Traits of Hanwoo Steer Beef by the Quality Grade

    PubMed Central

    Lim, Dong-Gyun; Jo, Cheorun; Lee, Kyung Haeng; Kim, Jong-Ju

    2014-01-01

    The physicochemical and functional traits for loin muscles of Hanwoo steers were compared by quality grade (QG). A total of 500 Hanwoo steers were slaughtered, their carcasses were categorized into four groups (QG 1++, 1+, 1, and 2), and the longissimus dorsi muscles were analyzed. QG 1++ group had the highest fat and lowest moisture content (p<0.05). QG 1++ showed higher L* and b* color values, higher cooking loss, and lower shear force values, compared with the other groups (p<0.05). The flavor, tenderness, juiciness, and preference scores by sensory evaluation were highly ranked for premium QG groups (1++ and 1+). Regarding the micro compounds, QG 1 and QG 2 had greater amounts of inosine monophosphate, and QG 2 had greater amounts of anserine, carnosine, and creatine, than QG 1++ (p<0.05). QG 1++ and 1+ had higher percentages of oleic acid (C18:1) than QG 2 (p<0.05). Within premium QG 1++ and 1+, the results of the nucleotides, free amino acids, dipeptides, and fatty acids did not show any distinctive differences. Hanwoo beef as determined by the current grading system was not significantly different in terms of functional components; the only significant difference was in intramuscular fat content. PMID:26761169

  2. Dynamic stability of functionally graded cantilever cylindrical shells under distributed axial follower forces

    NASA Astrophysics Data System (ADS)

    Torki, Mohammad Ebrahim; Kazemi, Mohammad Taghi; Reddy, Junuthula N.; Haddadpoud, Hassan; Mahmoudkhani, Saeid

    2014-02-01

    In this paper, flutter of functionally graded material (FGM) cylindrical shells under distributed axial follower forces is addressed. The first-order shear deformation theory is used to model the shell, and the material properties are assumed to be graded in the thickness direction according to a power law distribution using the properties of two base material phases. The solution is obtained by using the extended Galerkin's method, which accounts for the natural boundary conditions that are not satisfied by the assumed displacement functions. The effect of changing the concentrated (Beck's) follower force into the uniform (Leipholz's) and linear (Hauger's) distributed follower loads on the critical circumferential mode number and the minimum flutter load is investigated. As expected, the flutter load increases as the follower force changes from the so-called Beck's load into the so-called Leipholz's and Hauger's loadings. The increased flutter load was calculated for homogeneous shell with different mechanical properties, and it was found that the difference in elasticity moduli bears the most significant effect on the flutter load increase in short, thick shells. Also, for an FGM shell, the increase in the flutter load was calculated directly, and it was found that it can be derived from the simple power law when the corresponding increase for the two base phases are known.

  3. Buckling analysis of functionally graded nanobeams based on a nonlocal third-order shear deformation theory

    NASA Astrophysics Data System (ADS)

    Rahmani, O.; Jandaghian, A. A.

    2015-06-01

    In this paper, a general third-order beam theory that accounts for nanostructure-dependent size effects and two-constituent material variation through the nanobeam thickness, i.e., functionally graded material (FGM) beam is presented. The material properties of FG nanobeams are assumed to vary through the thickness according to the power law. A detailed derivation of the equations of motion based on Eringen nonlocal theory using Hamilton's principle is presented, and a closed-form solution is derived for buckling behavior of the new model with various boundary conditions. The nonlocal elasticity theory includes a material length scale parameter that can capture the size effect in a functionally graded material. The proposed model is efficient in predicting the shear effect in FG nanobeams by applying third-order shear deformation theory. The proposed approach is validated by comparing the obtained results with benchmark results available in the literature. In the following, a parametric study is conducted to investigate the influences of the length scale parameter, gradient index, and length-to-thickness ratio on the buckling of FG nanobeams and the improvement on nonlocal third-order shear deformation theory comparing with the classical (local) beam model has been shown. It is found out that length scale parameter is crucial in studying the stability behavior of the nanobeams.

  4. A study on the dynamics of rotating beams with functionally graded properties

    NASA Astrophysics Data System (ADS)

    Piovan, M. T.; Sampaio, R.

    2009-10-01

    The constant needs of the industry impel the engineering community in seeking of new concepts and new strategies in order to improve the structural response of structures as well as to enhance the endurance of materials. This is particularly true in the case of rotating blades that are subjected to severe environmental conditions such as high temperatures as well as mechanical conditions such as high rotating accelerations, centrifugal forces, geometric stiffening, among others. It is well known that flexible beams become stiffer when subjected to high speed rotations, because of the axial-bending coupling associated to the large displacements of the beam cross-section. This is called geometric stiffening effect and it was analyzed over the last decades in many beam applications from blade problems to drill-string modeling. In this paper a rotating nonlinear beam model accounting for arbitrary axial deformations is developed. The beam is made of functionally graded materials (FGM). This model is also employed to analyze other simplified models based on isotropic materials or composite materials, that are particular cases of the present formulation. The assumption of steady-state values of centrifugal loads is evaluated. It has to be said that there is a lack of information about modeling of beams made of functionally graded materials and this paper is intended to be a contribution on the subject.

  5. Synthesis of a Functionalized Polypyrrole Coated Electrotextile for Use in Biosensors

    PubMed Central

    McGraw, Shannon K.; Alocilja, Evangelyn; Senecal, Andre; Senecal, Kris

    2012-01-01

    An electrotextile with a biosensing focus composed of conductive polymer coated microfibers that contain functional attachment sites for biorecognition elements was developed. Experiments were conducted to select a compound with a pendant functional group for inclusion in the polymer, a fiber platform, and polymerization solvent. The effects of dopant inclusion and post-polymerization wash steps were also analyzed. Finally, the successful attachment of avidin, which was then used to capture biotin, to the electrotextile was achieved. The initial results show a nonwoven fiber matrix can be successfully coated in a conductive, functionalized polymer while still maintaining surface area and fiber durability. A polypropylene fiber platform with a conductive polypyrrole coating using iron (III) chloride as an oxidant, water as a solvent, and 5-sulfosalicylic acid as a dopant exhibited the best coating consistency, material durability, and lowest resistance. Biological attachment of avidin was achieved on the fibers through the inclusion of a carboxyl functional group via 3-thiopheneacetic acid in the monomer. The immobilized avidin was then successfully used to capture biotin. This was confirmed through the use of fluorescent quantum dots and confocal microscopy. A preliminary electrochemical experiment using avidin for biotin detection was conducted. This technology will be extremely useful in the formation of electrotextiles for use in biosensor systems. PMID:25586036

  6. An approximate solution to the stress and deformation states of functionally graded rotating disks

    NASA Astrophysics Data System (ADS)

    Sondhi, Lakshman; Sanyal, Shubhashis; Saha, Kashi Nath; Bhowmick, Shubhankar

    2016-07-01

    The present work employs variational principle to investigate the stress and deformation states and estimate the limit angular speed of functionally graded high-speed rotating annular disks of constant thickness. Assuming a series approximation following Galerkin's principle, the solution of the governing equation is obtained. In the present study, elasticity modulus and density of the disk material are taken as power function of radius with the gradient parameter ranging between 0.0 and 1.0. Results obtained from numerical solutions are validated with benchmark results and are found to be in good agreement. The results are reported in dimensional form and presented graphically. The results provide a substantial insight in understanding the behavior of FGM rotating disks with constant thickness and different gradient parameter. Furthermore, the stress and deformation state of the disk at constant angular speed and limit angular speed is investigated to explain the existence of optimum gradient parameters.

  7. Comparison of modeling of the rotating tapered axially functionally graded Timoshenko and Euler-Bernoulli microbeams

    NASA Astrophysics Data System (ADS)

    Shafiei, Navvab; Kazemi, Mohammad; Ghadiri, Majid

    2016-09-01

    The target of this paper is to present an exhaustive study on the small scale effect on vibrational behavior of a rotary tapered axially functionally graded (AFG) microbeam on the basis of Timoshenko and Euler-Bernoulli beam and modified couple stress theories. The variation of the material properties and cross section along the longitudinal direction of the microbeam are taken into consideration as a linear function. Hamilton's principle is used to derive the equations for cantilever and propped cantilever boundary conditions and the generalized differential quadrature method (GDQM) is employed to solve the equations. By parametric study, the effects of small-scale parameter, rates of cross section change of the microbeam and angular velocity on the fundamental and second frequencies of the microbeam are studied. Also, comparison between the frequencies of Timoshenko and Euler-Bernoulli microbeams are presented. The results can be used in many applications such as micro-robots and biomedical microsystems.

  8. Modeling the absorption behavior of solar thermal collector coatings utilizing graded alpha-C:H/TiC layers.

    PubMed

    Gruber, D P; Engel, G; Sormann, H; Schüler, A; Papousek, W

    2009-03-10

    Wavelength selective coatings are of common use in order to enhance the efficiency of devices heated by radiation such as solar thermal collectors. The use of suitable materials and the optimization of coating layer thicknesses are advisable ways to maximize the absorption. Further improvement is achievable by embedding particles in certain layers in order to modify material properties. We focus on optimizing the absorption behavior of a solar collector setup using copper as substrate, a layer of amorphous hydrogenated carbon with embedded titanium carbide particles (a-C:H/TiC), and an antireflection coating of amorphous silicon dioxide (aSiO(2)). For the setup utilizing homogeneous particle distribution, a relative absorption of 90.98% was found, while inhomogeneous particle embedding yielded 98.29%. These results are particularly interesting since until now, absorption of more than 95% was found only by using embedded Cr but not by using the more biocompatible Ti. PMID:19277084

  9. Experimental and numerical analysis concerning the behaviour of OL50 steel grade specimens coated with polyurea layer under dynamics loadings

    NASA Astrophysics Data System (ADS)

    Bucur, Florina; Trana, Eugen; Rotariu, Adrian; Gavrus, Adinel; Barbu, Cristian; Guines, Dominique

    2015-09-01

    This study refers to an experimental and numerical evaluation of a polyurea coating layer influence on the dynamic behaviour of OL50 specimens. Mechanical quasi-static and dynamic tensile tests were performed in axial loading conditions, for 2 mm steel plate specimens. Several metallic specimens have been previously coated with 1.5 mm and 3 mm respectively thickness polyurea layer and tested in traction. The findings results indicate that the presence of polyurea changes the loading pattern of metallic material in the necking area. In terms of polyurea coated metal specimens fracture, there was clearly observed a change of fracture limit. One possible explanation of this phenomenon is the modification of triaxiality state in the necking zone, fact proven by the numerical simulations. Test results indicate that the presence of polyurea layer delays the necking onset phenomenon which precedes the OL50 metallic specimen fracture.

  10. Development of a catheter functionalized by a polydopamine peptide coating with antimicrobial and antibiofilm properties.

    PubMed

    Lim, Kaiyang; Chua, Ray Rong Yuan; Bow, Ho; Tambyah, Paul Anantharajah; Hadinoto, Kunn; Leong, Susanna Su Jan

    2015-03-01

    Catheter-associated urinary tract infections (CAUTIs) are the most common hospital-acquired infections worldwide, aggravating the problem of antimicrobial resistance and patient morbidity. There is a need for a potent and robust antimicrobial coating for catheters to prevent these infections. An ideal coating agent should possess high antimicrobial efficacy and be easily and economically conjugated to the catheter surface. In this study, we report a simple yet effective immobilization strategy to tether a potent synthetic antimicrobial peptide, CWR11, onto catheter-relevant surfaces. Polydopamine (PD) was deposited as a thin adherent film onto a polydimethylsiloxane (PDMS) surface to facilitate attachment of CWR11 onto the PD-functionalized polymer. Surface characterization of the CWR11-tethered surfaces confirmed the successful immobilization of peptides onto the PD-coated PDMS. The CWR11-immobilized PDMS slides displayed excellent antimicrobial (significant inhibition of 5×10(4) colony-forming units of CAUTI-relevant microbes) and antibiofilm (∼92% enhanced antibacterial adherence) properties. To assess its clinical relevance, the PD-based immobilization platform was translated onto commercial silicone-coated Foley catheters. The CWR11-impregnated catheter displayed potent bactericidal properties against both Gram-positive and Gram-negative bacteria, and retained its antimicrobial functionality for at least 21days, showing negligible cytotoxicity against human erythrocyte and uroepithelial cells. The outcome of this study demonstrates the proof-of-concept potential of a polydopamine-CWR11-functionalized catheter to combat CAUTIs. PMID:25541344

  11. Novel Active Surface Prepared by Embedded Functionalized Clays in an Acrylate Coating.

    PubMed

    Xia, Yining; Ghasemlou, Mehran; Rubino, Maria; Auras, Rafael; Baghdachi, Jamil

    2015-11-11

    The research on a self-decontaminating surface has received significant attention because of the growth of pathogenic microorganisms on surfaces. In this study, a novel and simple technique for producing an active surface with antimicrobial functionality is demonstrated. A tethering platform was developed by grafting the biocide ampicillin (Amp) to a nanoclay and dispersing the nanoclay in a UV-curable acrylate coating applied on polypropylene films as the substrate. A coupling agent, [3-(glycidyloxy)propyl]trimethoxysilane, was used as a linker between the nanoclay and Amp. The Amp-functionalized clay was further modified with an organic surfactant to improve the compatibility with the coating. Several characterization assays, such as Fourier infrared transform analysis, thermogravimetric analysis, and X-ray diffraction, were conducted to confirm the presence of Amp in the nanoclay. Transmission electron microscopy images revealed that the clay particles were well dispersed in the coating and had a partial exfoliated morphology. The active coating surface was effective in inhibiting the growth of Gram-positive Listeria monocytogenes and Gram-negative Salmonella Typhimurium via contact. These findings suggest the potential for the development of active surfaces with the implementation of nanotechnology to achieve diverse functionalities. PMID:26488557

  12. Application of metal coatings for functionalization of technical fibers and fabrics

    NASA Astrophysics Data System (ADS)

    Lusis, A.; Pentjuss, E.; Balodis, J.; Janeliukštis, R.; Zandersons, J.

    2011-12-01

    The metal coatings in combination with sonochemical and leaching processes are used for nanostructuring and functionalization of glass, flax and hemp fabrics. The leaching is used for nanostructuring sodium alumosilicate K-glass fabrics to obtained silica like fibre with nanoporous structure on surface and in volume. The natural fibres as well as fabrics themselves are porous media. The porous media adsorbs water and content of moisture in fabrics have to be controlled. The metal-coated fabric characterization is an actual problem. Application of metal coatings for the functionalization of technical fibres and fabrics faced with influence of moisture on functional properties, e.g., the impedance of the metal coated K-glass and flax and hemp fabrics have strong dependence of content absorbed water or moisture. Presented studies are on the moisture content determination methodology based on fhermogravimetric analyses and impedance spectroscopy. The leached K-glass fibres have three absorption sites with different kinetic and desorption heat. The flax has more complicated distribution of sorption/desorption sites. The water desorption heatl,3 kJ/g for both type of fabrics in temperature range 30-150 0C is comparable to the water evaporation heat 2,3 kJ/g at 100 0C. For leached K-glass fibre from the isothermal nitrogen sorption/desorption plot the pore volume is up to 7.5 cm3/g. and pore sizes are in range 2-100 nm.

  13. Fabrication of functionally gradient nanocomposite coatings by plasma electrolytic oxidation based on variable duty cycle

    NASA Astrophysics Data System (ADS)

    Aliofkhazraei, M.; Rouhaghdam, A. Sabour

    2012-01-01

    Plasma electrolytic oxidation (PEO) was applied on the surface of commercially pure titanium substrates in a mixed aluminate-phosphate electrolyte in the presence of silicon nitride nanoparticles as suspension in the electrolyte in order to fabricate nanocomposite coatings. Pulsed current was applied based on variable duty cycle in order to synthesize functionally gradient coatings (FGC). Different rates of variable duty cycle (3, 1.5 and 1%/min), applied current densities (0.06-0.14 A/cm2) and concentrations of nanoparticles in the electrolyte (2, 4, 6, 8 and 10 g l-1) were investigated. The nanopowder and coated samples were analyzed by atomic force microscope, scanning electron microscope and transmission electron microscope. The influence of different rates of variable duty cycle (or treatment times) on the growth rate of nanocomposite coatings and their microhardness values was investigated. The experimental results revealed that the content of Si3N4 nanoparticulates in the layer increases with the increase of its concentration in the plasma electrolysis bath. Nanocomposite coatings fabricated with lower rate of variable duty cycle have higher microhardness with smoother microhardness profile.

  14. Convenient surface functionalization of whole-Teflon chips with polydopamine coating

    PubMed Central

    Shen, Bo; Xiong, Bin; Wu, Hongkai

    2015-01-01

    This paper presents a convenient strategy to modify the surface of whole-Teflon microfluidic chips by coating the channel walls with a thin layer of polydopamine (PDA) film, which is formed by oxidation-induced self-polymerization of dopamine in alkaline solution. Two coating strategies, static incubation and dynamic flow, are demonstrated and used for tuning the physical and chemical properties of the coated channel walls. The functionalized surfaces were investigated with the contact angle, X-ray photoelectron spectroscopy, and atomic force microscopy measurements. The coating time was optimized according to the fluorescent intensity of the green fluorescent protein immobilized on the modified surface. Applications of the PDA-modified Teflon microchips in bioanalysis were demonstrated with a typical sandwich immunoassay. Moreover, long-term cell culture experiments on modified and native Teflon chips revealed that the chip biocompatibility can be greatly improved with PDA coating. The results indicate that the surface properties of the Teflon can be easily controlled by the PDA modification, thus greatly expanding the application scope of whole-Teflon chips for various chemical and biological research fields. PMID:26339312

  15. Biological response on a titanium implant-grade surface functionalized with modular peptides☆

    PubMed Central

    Yazici, H.; Fong, H.; Wilson, B.; Oren, E.E.; Amos, F.A.; Zhang, H.; Evans, J.S.; Snead, M.L.; Sarikaya, M.; Tamerler, C.

    2015-01-01

    Titanium (Ti) and its alloys are among the most successful implantable materials for dental and orthopedic applications. The combination of excellent mechanical and corrosion resistance properties makes them highly desirable as endosseous implants that can withstand a demanding biomechanical environment. Yet, the success of the implant depends on its osteointegration, which is modulated by the biological reactions occurring at the interface of the implant. A recent development for improving biological responses on the Ti-implant surface has been the realization that bifunctional peptides can impart material binding specificity not only because of their molecular recognition of the inorganic material surface, but also through their self-assembly and ease of biological conjugation properties. To assess peptide-based functionalization on bioactivity, the present authors generated a set of peptides for implant-grade Ti, using cell surface display methods. Out of 60 unique peptides selected by this method, two of the strongest titanium binding peptides, TiBP1 and TiBP2, were further characterized for molecular structure and adsorption properties. These two peptides demonstrated unique, but similar molecular conformations different from that of a weak binder peptide, TiBP60. Adsorption measurements on a Ti surface revealed that their disassociation constants were 15-fold less than TiBP60. Their flexible and modular use in biological surface functionalization were demonstrated by conjugating them with an integrin recognizing peptide motif, RGDS. The functionalization of the Ti surface by the selected peptides significantly enhanced the bioactivity of osteoblast and fibroblast cells on implant-grade materials. PMID:23159566

  16. Influence of Functionalization of Nanocontainers on Self-Healing Anticorrosive Coatings.

    PubMed

    Zheng, Zhaoliang; Schenderlein, Matthias; Huang, Xing; Brownbill, Nick J; Blanc, Frédéric; Shchukin, Dmitry

    2015-10-21

    Feedback coating based on pH-induced release of inhibitor from organosilyl-functionalized containers is considered as a compelling candidate to achieve smart self-healing corrosion protection. Four key factors that determine the overall coating performance include (1) the uptake and release capacity of containers, (2) prevention of the premature leakage, (3) compatibility of containers in coating matrix, and (4) cost and procedure simplicity consideration. The critical influence introduced by organosilyl-functionalization of containers is systematically demonstrated by investigating MCM-41 silica nanoparticles modified with ethylenediamine (en), en-4-oxobutanoic acid salt (en-COO(-)), and en-triacetate (en-(COO(-))3) with higher and lower organic contents. The properties of the modified silica nanoparticles as containers were mainly characterized by solid-state (13)C nuclear magnetic resonance, scanning and transmission electron microscopy, N2 sorption, thermogravimetric analysis, small-angle X-ray scattering, dynamic light scattering, and UV-vis spectroscopy. Finally, the self-healing ability and anticorrosive performances of hybrid coatings were examined through scanning vibrating electrode technique (SVET) and electrochemical impedance spectroscopy (EIS). We found that en-(COO(-))3-type functionalization with content of only 0.23 mmol/g performed the best as a candidate for establishing pH-induced release system because the resulting capped and loaded (C-L) functionalized silica nanocontainers (FSNs) exhibit high loading (26 wt %) and release (80%) capacities for inhibitor, prevention of premature leakage (less than 2%), good dispersibility in coating matrix, and cost effectiveness. PMID:26393678

  17. Mouse low-grade gliomas contain cancer stem cells with unique molecular and functional properties.

    PubMed

    Chen, Yi-Hsien; McGowan, Lucy D'Agostino; Cimino, Patrick J; Dahiya, Sonika; Leonard, Jeffrey R; Lee, Da Yong; Gutmann, David H

    2015-03-24

    The availability of adult malignant glioma stem cells (GSCs) has provided unprecedented opportunities to identify the mechanisms underlying treatment resistance. Unfortunately, there is a lack of comparable reagents for the study of pediatric low-grade glioma (LGG). Leveraging a neurofibromatosis 1 (Nf1) genetically engineered mouse LGG model, we report the isolation of CD133(+) multi-potent low-grade glioma stem cells (LG-GSCs), which generate glioma-like lesions histologically similar to the parent tumor following injection into immunocompetent hosts. In addition, we demonstrate that these LG-GSCs harbor selective resistance to currently employed conventional and biologically targeted anti-cancer agents, which reflect the acquisition of new targetable signaling pathway abnormalities. Using transcriptomic analysis to identify additional molecular properties, we discovered that mouse and human LG-GSCs harbor high levels of Abcg1 expression critical for protecting against ER-stress-induced mouse LG-GSC apoptosis. Collectively, these findings establish that LGG cancer stem cells have unique molecular and functional properties relevant to brain cancer treatment. PMID:25772366

  18. Design of capillary flows with functionally graded porous titanium oxide films fabricated by anodization instability.

    PubMed

    Joung, Young Soo; Figliuzzi, Bruno Michel; Buie, Cullen R

    2014-06-01

    We have developed an electrochemical fabrication method utilizing breakdown anodization (BDA) to yield capillary flows that can be expressed as functions of capillary height. This method uses anodization instability with high electric potentials and mildly acidic electrolytes that are maintained at low temperature. BDA produces highly porous micro- and nano-structured surfaces composed of amorphous titanium oxide on titanium substrates, resulting in high capillary pressure and capillary diffusivity. With this fabrication technique the capillary flow properties can be controlled by varying the applied electric field and electrolyte temperature. Furthermore, they can be expressed as functions of capillary height when customized electric fields are used in BDA. To predict capillary flows on BDA surfaces, we developed a conceptual model of highly wettable porous films, which are modeled as multiple layers of capillary tubes oriented in the flow direction. From the model, we derived a general capillary flow equation of motion in terms of capillary pressure and capillary diffusivity, both of which can be expressed as functions of capillary height. The theoretical model was verified by comparisons with experimental capillary flows, showing good agreement. From investigation of the surface morphology we found that the surface structures were also functionally graded with respect to the capillary height (i.e. applied electric field). The suggested fabrication method and the theoretical model offer novel design methodologies for microscale liquid transport devices requiring control over propagation speed. PMID:24703679

  19. Silicone foul release coatings: effect of the interaction of oil and coating functionalities on the magnitude of macrofouling attachment strengths.

    PubMed

    Stein, Judith; Truby, Kathryn; Wood, Christina Darkangelo; Stein, Jeff; Gardner, Martha; Swain, Geoffrey; Kavanagh, Christopher; Kovach, Brett; Schultz, Michael; Wiebe, Deborah; Holm, Eric; Montemarano, Jean; Wendt, Dean; Smith, Celia; Meyer, Anne

    2003-04-01

    Silicone biofouling release coatings have been shown to be an effective method of combating fouling. Nearly all silicone foul release coatings are augmented with an oil additive to decrease macrofouling attachment strength. This paper addresses the effect of the type of oil that is incorporated into the silicone coating and the type of silicone coating itself (silica vs calcium carbonate filled) on macrofouling adhesion strengths to the coating. It was found that not only are the main effects of oil type and silicone coating type important in determining the magnitude of the attachment strength of the organism, but the interaction term (oil type crossed with coating type) is highly significant for all organisms studied, except oysters at the University of Hawaii test site (Oahu, Hawaii) which has a significance level of alpha = 0.1. Each of the organisms exhibited a unique response to the various silicone fouling release coatings. Thus, in order to predict the effectives of foul release coatings, the composition variables of the coatings and the type of target organisms must be considered. PMID:14618707

  20. The Development of Writing Proficiency as a Function of Grade Level: A Linguistic Analysis

    ERIC Educational Resources Information Center

    Crossley, Scott A.; Weston, Jennifer L.; McLain Sullivan, Susan T.; McNamara, Danielle S.

    2011-01-01

    In this study, a corpus of essays stratified by level (9th grade, 11th grade, and college freshman) are analyzed computationally to discriminate differences between the linguistic features produced in essays by adolescents and young adults. The automated tool Coh-Metrix is used to examine to what degree essays written at various grade levels can…

  1. Osteogenic Surface Modification Based on Functionalized Poly-P-Xylylene Coating

    PubMed Central

    Chang, Chih-Hao; Chen, Chia-Jie; Su, Chiao-Tzu; Lin, Yen-Ting; Liu, Chien-Lin; Chen, Hsien-Yeh

    2015-01-01

    The biotechnology to immobilize biomolecules on material surfaces has been developed vigorously due to its high potentials in medical applications. In this study, a simple and effective method was designed to immobilize biomolecules via amine-N-hydroxysuccinimide (NHS) ester conjugation reaction using functionalized poly-p-xylylene coating on material surfaces. The NHS ester functionalized coating is synthesized via chemical vapor deposition, a facile and solvent-less method, creating a surface which is ready to perform a one-step conjugation reaction. Bone morphogenetic protein 2 (BMP-2) is immobilized onto material surfaces by this coating method, forming an osteogenic environment. The immobilization process is controlled at a low temperature which does not damage proteins. This modified surface induces differentiation of preosteoblast into osteoblast, manifested by alkaline phosphatase (ALP) activity assay, Alizarin Red S (ARS) staining and the expression of osteogenic gene markers, Alpl and Bglap3. With this coating technology, immobilization of growth factors onto material surface can be achieved more simply and more effectively. PMID:26379273

  2. SYNTHESIS AND CHARACTERIZATION OF SMART FUNCTIONAL COATINGS BY CHEMICAL SOLUTION DEPOSITION METHODS

    SciTech Connect

    Mendez-Torres, A.

    2011-07-19

    New coating technology enables the fabrication of low cost structural health monitoring (SHM) and tamper indication devices that can be employed to strengthen national and international safeguards objectives. In particular, such innovations could serve the safeguards community by improving both the timeliness of detection and confidence in verification and monitoring. This work investigates the synthesis of functional surface coatings using chemical solutions deposition methods. Chemical solution deposition has recently received attention in the materials research community due to its unique advantages such as low temperature processing, high homogeneity of final products and the ability to fabricate materials with controlled surface properties and pore structures. The synthesis of functional coatings aimed at modifying the materials conductivity and optical properties was investigated by the incorporation of transition element (e.g. Cr{sup +3}) and rare earth (e.g. Er{sup +3}) serving as dopants in a polymer or gel matrix. The structural and morphological investigation of the as-deposited films was carried out using UV/Vis and photoluminescence (PL) spectroscopy. The as deposited coating was further investigated by scanning electron microscopy and energy dispersive x-ray microscopy.

  3. Numerical Analysis of Stress Intensity Factors in Three-Dimensional Functionally Graded Materials

    SciTech Connect

    Guo Licheng; Wu Linzhi; Yu Hongjun

    2008-02-15

    In this paper, a finite element method based on nonhomogeneous elements is used to study crack problems in three-dimensional (3D) functionally graded materials (FGMs). Since the actual material properties at each integral point are employed in the integration during formation of the element stiffness matrix, each element can have nonhomogeneous material properties. By this method, the number of elements is reduced and the meshing effort for the structure is simplified. Therefore, the modeling process for numerical simulation of fracture behavior in 3D FGMs is greatly simplified. The crack front characteristics of Mode-I edge penetrable crack in 3D FGM specimens are studied under uniform tension loading. The influence of material nonhomogeneity constant and geometric parameters on the stress intensity factors (SIFs) of the 3D FGM specimens are investigated.

  4. Nonlinear frequency response of parametrically excited functionally graded Timoshenko beams with a crack

    NASA Astrophysics Data System (ADS)

    Yang, J.; Yan, T.

    2010-06-01

    This paper investigates the nonlinear dynamic frequency response of a Timoshenko beam made of functionally graded materials (FGMs) with an open edge crack. The beam is clamped and subjected to an axial parametric excitation consisting of a static compressive force and a harmonic excitation force. Theoretical formulations are based on Timoshenko shear deformable beam theory, von Karman type geometric nonlinearity and rotational spring model. Hamilton's principle is used to derive the nonlinear partial differential equations which are transformed into nonlinear ordinary differential equation by using the Least Squares method and Galerkin technique. The nonlinear natural frequencies and excitation frequency-amplitude response curves are obtained by employing Runge-Kutta method and multiple scale method, respectively. A parametric study is conducted to study the effects of material property distribution, crack depth, crack location, excitation frequency, and slenderness ratio on the nonlinear dynamic characteristics of parametrically excited, cracked FGM Timoshenko beams.

  5. The beam-mode stability of periodic functionally-graded-material shells conveying fluid

    NASA Astrophysics Data System (ADS)

    Shen, Huijie; Païdoussis, Michael P.; Wen, Jihong; Yu, Dianlong; Wen, Xisen

    2014-05-01

    The characteristics of beam-mode stability of fluid-conveying shell systems are investigated in this paper for shells with clamped-free (cantilevered) boundary conditions. An FEM algorithm is developed to conduct the investigation. A periodic shell structure of functionally graded material (FGM), termed as PFGM shell here, is designed so as to enhance the stability for the shell system, and to eliminate the stress concentration problems that exist in periodic structures. Results show that by the introduction of periodic design the critical velocities can be raised over several desired ranges of the dimensionless fluid density β, and the stress concentration is effectively reduced in the PFGM shell. Finally, the effects of the geometric shape, material parameters and spring supports on the dynamical stability are probed.

  6. Electromechanical buckling of functionally graded electrostatic nanobridges using strain gradient theory

    NASA Astrophysics Data System (ADS)

    Shojaeian, Milad; Beni, Yaghoub Tadi; Ataei, Hossein

    2016-01-01

    Electromechanical buckling (EMB) of beam-type nanoelectromechanical systems (NEMSs) is investigated based on modified strain gradient theory. The system is modeled as a clamped-guided nanobeam which is under compressive or tensile axial loads as well as the effect of nonlinear electrostatic and van der Waals symmetric transverse forces. In addition, the beam is considered to be made of axially and transverse functionally graded materials. Here, FGM is Poly-SiGe, of which the general properties change gradually from silicon to germanium based on a simple power-law method. Considering the Euler-Bernoulli beam theory and using the principle of minimum potential energy, the governing equations and corresponding boundary conditions are established. After validation of results, the effects of power law index, variation of size effect parameters, length-thickness ratio and the distance between the two fixed and movable electrodes on the buckling response of the system are discussed.

  7. A drop-on-demand ink-jet printer for combinatorial libraries and functionally graded ceramics.

    PubMed

    Mohebi, Mohammad Masoud; Evans, Julian R G

    2002-01-01

    A printer has been designed and built for the preparation of combinatorial libraries of ceramics and for solid freeforming of functionally graded ceramics with three-dimensionally programmable spatial variation in composition. Several ceramic suspensions (as inks) can be subjected to micromixing behind the nozzle and printed at precise positions. Both mixing and positioning are computer-controlled. The machine consists of an XY table to control the geometry, a set of electromagnetic valves that manage the mixing, a combined electromagnetic valve and sapphire nozzle that form the print head, and a computer that controls the whole system. The mixing valves can eject as little as 1 mg/s ink into the mixing chamber. The printer has been controlled, run, calibrated and tested; the composition and geometry of printed mixtures can be controlled precisely. This method for the controlled mixing of powders facilitates the advance of combinatorial methods within the materials sciences. PMID:12099843

  8. Optimum gradient material for a functionally graded dental implant using metaheuristic algorithms.

    PubMed

    Sadollah, Ali; Bahreininejad, Ardeshir

    2011-10-01

    Despite dental implantation being a great success, one of the key issues facing it is a mismatch of mechanical properties between engineered and native biomaterials, which makes osseointegration and bone remodeling problematical. Functionally graded material (FGM) has been proposed as a potential upgrade to some conventional implant materials such as titanium for selection in prosthetic dentistry. The idea of an FGM dental implant is that the property would vary in a certain pattern to match the biomechanical characteristics required at different regions in the hosting bone. However, matching the properties does not necessarily guarantee the best osseointegration and bone remodeling. Little existing research has been reported on developing an optimal design of an FGM dental implant for promoting long-term success. Based upon remodeling results, metaheuristic algorithms such as the genetic algorithms (GAs) and simulated annealing (SA) have been adopted to develop a multi-objective optimal design for FGM implantation design. The results are compared with those in literature. PMID:21783149

  9. Low speed centrifugal casting of Functionally Graded solid cast ingot by anomalous particle distribution

    NASA Astrophysics Data System (ADS)

    Mer, K. K. S.; Ray, S.

    2011-12-01

    Functionally graded cylindrical ingot of Al-Al2O3 composite synthesized by centrifugal casting shows particle distribution and hardness decreasing radially from the outer radius to inner radius. The progressive decrease in alumina content and hardness from the outer radius towards the center may be attributed to higher centrifugal force acting on relatively denser alumina particles during rotation, as compared to that acting on lighter alloy melt. It is also observed, as one moves down from the top to the bottom of cast ingot the alumina content decreases. This is surprising in view of higher density of alumina particles relative to the melt. The particle settling should have resulted at more particles towards the bottom, but distribution observed is in contradiction.

  10. Recent development in modeling and analysis of functionally graded materials and structures

    NASA Astrophysics Data System (ADS)

    Gupta, Ankit; Talha, Mohammad

    2015-11-01

    In this article, an extensive review related to the structural response of the functionally graded materials (FGMs) and structures have been presented. These are high technology materials developed by a group scientist in the late 1980's in Japan. The emphasis has been made here, to present the structural characteristics of FGMs plates/shells under thermo-electro-mechanical loadings under various boundary and environmental conditions. This paper also provides an overview of different fabrication procedures and the future research directions which is required to implement these materials in the design and analysis appropriately. The expected outcome of present review can be treated as milestone for future studies in the area of high technology materials and structures, and would be definitely advantageous for the researchers, scientists, and designers working in this field.

  11. Functional Grammar and Teaching of Reading--A Pedagogy Based on Graded Teaching of College English in China

    ERIC Educational Resources Information Center

    Xu, Tuo; Zhang, Beili

    2015-01-01

    This article discusses the importance of functional grammar and demonstrates its application to the teaching of reading among graded college students. Functional grammar holds that a discourse is composed of two levels: the interior level and the exterior level. Therefore, reading activities involve both linguistic elements and contexts.…

  12. Changes in left ventricular structure and function in patients with white coat hypertension: cross sectional survey

    PubMed Central

    Muscholl, Michael W; Hense, Hans-W; Bröckel, Ulrich; Döring, Angela; Riegger, Günter A J; Schunkert, Heribert

    1998-01-01

    Objectives: To assess the relation between white coat hypertension and alterations of left ventricular structure and function. Design: Cross sectional survey. Setting: Augsburg, Germany. Subjects: 1677 subjects, aged 25 to 74 years, who participated in an echocardiographic substudy of the monitoring of trends and determinants in cardiovascular disease Augsburg study during 1994-5. Outcome measures: Blood pressure measurements and M mode, two dimensional, and Doppler echocardiography. After at least 30 minutes’ rest blood pressure was measured three times by a technician, and once by a physician after echocardiography. Subjects were classified as normotensive (technician <140/90 mm Hg, physician <160/95 mm Hg; n=849), white coat hypertensive (technician <140/90 mm Hg, physician ⩾160/95 mm Hg; n=160), mildly hypertensive (technician ⩾140/90 mm Hg, physician <160/95 mm Hg; n=129), and sustained hypertensive (taking antihypertensive drugs or blood pressure measured by a technican ⩾140/90 mm Hg, and physician ⩾160/95 mm Hg; n=538). Results: White coat hypertension was more common in men than women (10.9% versus 8.2% respectively) and positively related to age and body mass index. After adjustment for these variables, white coat hypertension was associated with an increase in left ventricular mass and an increased prevalence of left ventricular hypertrophy (odds ratio 1.9, 95% confidence interval 1.2 to 3.2; P=0.009) compared with normotensive patients. The increase in left ventricular mass was secondary to significantly increased septal and posterior wall thicknesses whereas end diastolic diameters were similar in both groups with white coat hypertension or normotension. Additionally, the systolic white coat effect (difference between blood pressures recorded by a technician and physician) was associated with increased left ventricular mass and increased prevalence of left ventricular hypertrophy (P<0.05 each). Values for systolic left

  13. Functionalization of a membrane sublayer using reverse filtration of enzymes and dopamine coating.

    PubMed

    Luo, Jianquan; Meyer, Anne S; Mateiu, R V; Kalyani, Dayanand; Pinelo, Manuel

    2014-12-24

    High permeability, high enzyme loading, and strong antifouling ability are the desired features for a biocatalytic membrane to be used in an enzymatic membrane reactor (EMR). To achieve these goals, the membrane sublayer was enriched with laccase by reverse filtration in this case, and the resulting enzyme-loaded sublayer was covered with a dopamine coating. After membrane reversal, the virgin membrane skin layer was facing the feed and the enzymes were entrapped by a polydopamine network in the membrane sublayer. Thus, the membrane sublayer was functionalized as a catalytically active layer. The effects of the original membrane properties (i.e., materials, pore size, and structure), enzyme type (i.e., laccase and alcohol dehydrogenase), and coating conditions (i.e., time and pH) on the resulting biocatalytic membrane permeability, enzyme loading, and activity were investigated. Using a RC10 kDa membrane with sponge-like sublayer to immobilize laccase with dopamine coating, the trade-off between permeability and enzyme loading was broken, and enzyme loading reached 44.5% without any permeability loss. After 85 days of storage and reuse 14 times, more than 80% of the immobilized laccase activity was retained for the membrane with a dopamine coating, while the relative activity was less than 40% without the coating. The resistance to high temperature and acidic/alkaline pH was also improved by the dopamine coating for the immobilized laccase. Moreover, this biocatalytic membrane could resist mild hydrodynamic cleaning (e.g., back-flushing), but the catalytic ability was reduced by chemical cleaning at extreme pH (e.g., 1.5 and 11.5). Since the immobilized enzyme is not directly facing the bulk of EMRs and the substrate can be specifically selected by the separation skin layer, this biocatalytic membrane is promising for cascade catalytic reactions. PMID:25420028

  14. Biomimetically-mineralized composite coatings on titanium functionalized with gelatin methacrylate hydrogels

    NASA Astrophysics Data System (ADS)

    Tan, Guoxin; Zhou, Lei; Ning, Chengyun; Tan, Ying; Ni, Guoxin; Liao, Jingwen; Yu, Peng; Chen, Xiaofeng

    2013-08-01

    Immobilizing organic-inorganic hybrid composites onto the implant surface is a promising strategy to improve host acceptance of the implant. The objective of this present study was to obtain a unique macroporous titanium-surface with the organic-mineral composite coatings consisting of gelatin methacrylate hydrogel (GelMA) and hydroxyapatite (HA). A 3-(trimethoxysilyl) propyl methacrylate (TMSPMA) layer was first coated onto the titanium surface, and surface was then covalently functionalized with GelMA using a photochemical method. Mineralization of the GelMA coating on the titanium surface was subsequently carried out by a biomimetic method. After 3-day mineralization, a large number of mineral phases comprising spherical amorphous nanoparticles were found randomly deposited inside GelMA matrix. The resulting mineralized hydrogel composites exhibited a unique rough surface of macroporous structure. The structure of the prepared GelMA/HA composite coating was studied by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectra (EDS), attenuated total refraction Fourier transform infrared spectroscopy (ATR-FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). Water contact angle measurement revealed the hydrophilicity properties of composite coatings. GelMA/HA on titanium after the TMSPMA treatment is very stable when tested in vitro with a PBS solution at 37 °C, due to the role of TMSPMA as a molecular bridge. It was expected that the macroporous GelMA/HA composite coatings might potentially promote and accelerate titanium (Ti)-based implants osseointegration for bone repair and regeneration.

  15. Improvement of Mechanical Properties in the Functionally Graded Aluminum Matrix Nanocomposites Fabricated via a Novel Multistep Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Salehi, Mojtaba; Farnoush, Hamidreza; Heydarian, Arash; Aghazadeh Mohandesi, Jamshid

    2015-02-01

    In the present study, the functionally graded bulk Al-SiC nanocomposites were successfully fabricated by applying a novel multistep friction stir processing. Microstructural observations by scanning electron microscope indicated a proper distribution of SiC nanoparticles in the Al 6061 matrix. Microhardness profiles descended to 50 from 160 Hv due to the formation of compositionally gradient of SiC nanoparticles along the thickness. The tensile behavior of graded samples revealed a simultaneous enhancement of ultimate tensile strength (44 pct), strain at maximum stress (244 pct), and work of fracture (492 pct) with respect to the homogeneous sample. Furthermore, the graded samples sustained up to 4 pct strain after initiation of primary cracking, while the catastrophic fracture occurred instantly after cracking in the homogenous sample. A dimple-like ductile fracture surface was observed for the graded layers in which an increase in the SiC particle content will result in smaller dimple size.

  16. Improvement of Mechanical Properties in the Functionally Graded Aluminum Matrix Nanocomposites Fabricated via a Novel Multistep Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Salehi, Mojtaba; Farnoush, Hamidreza; Heydarian, Arash; Aghazadeh Mohandesi, Jamshid

    2014-09-01

    In the present study, the functionally graded bulk Al-SiC nanocomposites were successfully fabricated by applying a novel multistep friction stir processing. Microstructural observations by scanning electron microscope indicated a proper distribution of SiC nanoparticles in the Al 6061 matrix. Microhardness profiles descended to 50 from 160 Hv due to the formation of compositionally gradient of SiC nanoparticles along the thickness. The tensile behavior of graded samples revealed a simultaneous enhancement of ultimate tensile strength (44 pct), strain at maximum stress (244 pct), and work of fracture (492 pct) with respect to the homogeneous sample. Furthermore, the graded samples sustained up to 4 pct strain after initiation of primary cracking, while the catastrophic fracture occurred instantly after cracking in the homogenous sample. A dimple-like ductile fracture surface was observed for the graded layers in which an increase in the SiC particle content will result in smaller dimple size.

  17. Biocompatible polymers coated on carboxylated nanotubes functionalized with betulinic acid for effective drug delivery.

    PubMed

    Tan, Julia M; Karthivashan, Govindarajan; Abd Gani, Shafinaz; Fakurazi, Sharida; Hussein, Mohd Zobir

    2016-02-01

    Chemically functionalized carbon nanotubes are highly suitable and promising materials for potential biomedical applications like drug delivery due to their distinct physico-chemical characteristics and unique architecture. However, they are often associated with problems like insoluble in physiological environment and cytotoxicity issue due to impurities and catalyst residues contained in the nanotubes. On the other hand, surface coating agents play an essential role in preventing the nanoparticles from excessive agglomeration as well as providing good water dispersibility by replacing the hydrophobic surfaces of nanoparticles with hydrophilic moieties. Therefore, we have prepared four types of biopolymer-coated single walled carbon nanotubes systems functionalized with anticancer drug, betulinic acid in the presence of Tween 20, Tween 80, polyethylene glycol and chitosan as a comparative study. The Fourier transform infrared spectroscopy studies confirm the bonding of the coating molecules with the SWBA and these results were further supported by Raman spectroscopy. All chemically coated samples were found to release the drug in a slow, sustained and prolonged fashion compared to the uncoated ones, with the best fit to pseudo-second order kinetic model. The cytotoxic effects of the synthesized samples were evaluated in mouse embryonic fibroblast cells (3T3) at 24, 48 and 72 h. The in vitro results reveal that the cytotoxicity of the samples were dependent upon the drug release profiles as well as the chemical components of the surface coating agents. In general, the initial burst, drug release pattern and cytotoxicity could be well-controlled by carefully selecting the desired materials to suit different therapeutic applications. PMID:26704543

  18. Longitudinal Investigation of Adaptive Functioning following Conformal Irradiation for Pediatric Craniopharyngioma and Low-Grade Glioma

    PubMed Central

    Netson, Kelli L.; Conklin, Heather M.; Wu, Shengjie; Xiong, Xiaoping; Merchant, Thomas E.

    2013-01-01

    Purpose Children treated for brain tumors with conformal radiation therapy experience preserved cognitive outcomes. Early evidence suggests that adaptive functions or independent living skills may be spared. This longitudinal investigation prospectively examined intellectual and adaptive functioning during the first 5 years following irradiation for childhood craniopharyngioma and low-grade glioma (LGG). The effect of visual impairment on adaptive outcomes was investigated. Methods and Materials Children with craniopharyngioma (n=62) and LGG (n=77) were treated using conformal or intensity-modulated radiation therapy. The median age was 8.05 years (3.21 years –17.64 years) and 8.09 years (2.20 years–19.27 years), respectively. Serial cognitive evaluations including measures of intelligence quotient (IQ) and the Vineland Adaptive Behavior Scales (VABS) were conducted at pre-irradiation baseline, 6 months after treatment, and annually through 5 years. A total of 588 evaluations were completed during the follow-up period. Results Baseline assessment revealed no deficits in IQ and VABS indices for children with craniopharyngioma, with significant (p < .05) longitudinal decline in VABS Communication and Socialization indices. Clinical factors associated with more rapid decline included females and pre-irradiation chemotherapy (interferon). The only change in VABS Daily Living Skills correlated with IQ change (r = .34; p = .01) in children with craniopharyngioma. Children with LGG performed below population norms (p < .05) at baseline on VABS Communication, Daily Living Indices, and the Adaptive Behavior Composite, with significant (p < .05) longitudinal decline limited to VABS Communication. Older age at irradiation was a protective factor against longitudinal decline. Severe visual impairment did not independently correlate with poorer adaptive outcomes for either tumor group. Conclusions There was relative sparing of post-irradiation functional outcomes over time

  19. Longitudinal Investigation of Adaptive Functioning Following Conformal Irradiation for Pediatric Craniopharyngioma and Low-Grade Glioma

    SciTech Connect

    Netson, Kelli L.; Conklin, Heather M.; Wu, Shengjie; Xiong, Xiaoping; Merchant, Thomas E.

    2013-04-01

    Purpose: Children treated for brain tumors with conformal radiation therapy experience preserved cognitive outcomes. Early evidence suggests that adaptive functions or independent-living skills may be spared. This longitudinal investigation prospectively examined intellectual and adaptive functioning during the first 5 years following irradiation for childhood craniopharyngioma and low-grade glioma (LGG). The effect of visual impairment on adaptive outcomes was investigated. Methods and Materials: Children with craniopharyngioma (n=62) and LGG (n=77) were treated using conformal or intensity modulated radiation therapy. The median age was 8.05 years (3.21-17.64 years) and 8.09 years (2.20-19.27 years), respectively. Serial cognitive evaluations including measures of intelligence quotient (IQ) and the Vineland Adaptive Behavior Scales (VABS) were conducted at preirradiation baseline, 6 months after treatment, and annually through 5 years. Five hundred eighty-eight evaluations were completed during the follow-up period. Results: Baseline assessment revealed no deficits in IQ and VABS indices for children with craniopharyngioma, with significant (P<.05) longitudinal decline in VABS Communication and Socialization indices. Clinical factors associated with more rapid decline included females and preirradiation chemotherapy (interferon). The only change in VABS Daily Living Skills correlated with IQ change (r=0.34; P=.01) in children with craniopharyngioma. Children with LGG performed below population norms (P<.05) at baseline on VABS Communication, Daily Living Indices, and the Adaptive Behavior Composite, with significant (P<.05) longitudinal decline limited to VABS Communication. Older age at irradiation was a protective factor against longitudinal decline. Severe visual impairment did not independently correlate with poorer adaptive outcomes for either tumor group. Conclusions: There was relative sparing of postirradiation functional outcomes over time in this sample

  20. Structure-function relationships in Macadamia integrifolia seed coats--fundamentals of the hierarchical microstructure.

    PubMed

    Schüler, Paul; Speck, Thomas; Bührig-Polaczek, Andreas; Fleck, Claudia

    2014-01-01

    The shells/coats of nuts and seeds are often very hard to crack. This is particularly the case with Macadamia seed coats, known to exhibit astoundingly high strength and toughness. We performed an extensive materials science characterization of the complex hierarchical structure of these coats, using light and scanning electron microscopy in 2D as well as microCT for 3D characterization. We differentiate nine hierarchical levels that characterize the structure ranging from the whole fruit on the macroscopic scale down to the molecular scale. From a biological viewpoint, understanding the hierarchical structure may elucidate why it is advantageous for these seed coats to be so difficult to break. From an engineering viewpoint, microstructure characterization is important for identifying features that contribute to the high strength and cracking resistance of these objects. This is essential for revealing the underlying structure-function-relationships. Such information will help us develop engineering materials and lightweight-structures with improved fracture and puncture resistance. PMID:25102155

  1. Spherical and polygonal shape of Au nanoparticles coated functionalized polymer microspheres

    NASA Astrophysics Data System (ADS)

    Xu, Ting; Li, Yingzhi; Zhang, Junxian; Qi, Yalong; Zhao, Xin; Zhang, Qinghua

    2015-08-01

    Uniform polystyrene (PS)/polypyrrole (PPy) composite microspheres with well-defined core/shell structures are synthesized by chemical oxidative polymerization. Gold nanoparticles (Au NPs) are successfully coated on the surface of PS/PPy microspheres by means of electrostatic interactions due to the functionalized PPy coatings supplying sufficient amino groups and the additive of mercapto acetic acid. Furthermore, the as-prepared PS/PPy/Au microspheres serving as seeds facilitate Au NPs further growth by in situ reduction in HAuCl4 solution to obtain PS/PPy/Au spheres with the core/shell/shell structure. Morphology observation demonstrates that the monodisperse PS/PPy/Au microspheres compose of uniform cores and the compact coatings containing distinct two layers. X-ray diffraction and X-ray photoelectron spectroscope confirm the existence of PPy and Au on the surface of the composite spheres. This facile approach to preparing metal-coated polymer spheres supplies the potential applications in biosensors, electronics and medical diagnosis.

  2. Coating fabrics with gold nanorods for colouring, UV-protection, and antibacterial functions

    NASA Astrophysics Data System (ADS)

    Zheng, Yidan; Xiao, Manda; Jiang, Shouxiang; Ding, Feng; Wang, Jianfang

    2012-12-01

    Gold nanorods exhibit rich colours owing to the nearly linear dependence of the longitudinal plasmon resonance wavelength on the length-to-diameter aspect ratio. This property of Au nanorods has been utilized in this work for dyeing fabrics. Au nanorods of different aspect ratios were deposited on both cotton and silk fabrics by immersing them in Au nanorod solutions. The coating of Au nanorods makes the fabrics exhibit a broad range of colours varying from brownish red through green to purplish red, which are essentially determined by the longitudinal plasmon wavelength of the deposited Au nanorods. The colorimetric values of the coated fabrics were carefully measured for examining the colouring effects. The nanorod-coated cotton fabrics were found to be commercially acceptable in washing fastness to laundering tests and colour fastness to dry cleaning tests. Moreover, the nanorod-coated cotton and silk fabrics show significant improvements on both UV-protection and antibacterial functions. Our study therefore points out a promising approach for the use of noble metal nanocrystals as dyeing materials for textile applications on the basis of their inherent localized plasmon resonance properties.

  3. Structure-Function Relationships in Macadamia integrifolia Seed Coats – Fundamentals of the Hierarchical Microstructure

    PubMed Central

    Schüler, Paul; Speck, Thomas; Bührig-Polaczek, Andreas; Fleck, Claudia

    2014-01-01

    The shells/coats of nuts and seeds are often very hard to crack. This is particularly the case with Macadamia seed coats, known to exhibit astoundingly high strength and toughness. We performed an extensive materials science characterization of the complex hierarchical structure of these coats, using light and scanning electron microscopy in 2D as well as microCT for 3D characterization. We differentiate nine hierarchical levels that characterize the structure ranging from the whole fruit on the macroscopic scale down to the molecular scale. From a biological viewpoint, understanding the hierarchical structure may elucidate why it is advantageous for these seed coats to be so difficult to break. From an engineering viewpoint, microstructure characterization is important for identifying features that contribute to the high strength and cracking resistance of these objects. This is essential for revealing the underlying structure-function-relationships. Such information will help us develop engineering materials and lightweight-structures with improved fracture and puncture resistance. PMID:25102155

  4. Bio-functionalized star PEG-coated PVDF surfaces for cytocompatibility-improved implant components.

    PubMed

    Heuts, Jean; Salber, Jochen; Goldyn, Alexandra M; Janser, Romy; Möller, Martin; Klee, Doris

    2010-03-15

    Unmodified and GRGDS peptide-modified six arm PEG star based hydrogels (Star PEG) have been applied as a multifunctional, easy to handle coating system for textile polyvinylidene fluoride (PVDF) structures, which prevent unspecific protein and cell adsorption and control-specific cell adhesion. The reactive isocyanate-terminated Star PEG has been successfully applied to ammonia-plasma treated two- and three-dimensional PVDF surfaces. Easy modification of the surface hydrogel by mixing in of GRGDS peptide during the coating step or subsequent coupling of GRGDS was determined by TOF-SIMS. Unmodified and GRGDS-functionalized hydrogel surfaces show distinct protein repellency, as demonstrated by fluorescence microscopy after incubation with fluorescent labeled proteins and Surface MALDI-TOF-Mass Spectroscopy. Cell culture experiments with primary human dermal fibroblasts, primary fetal rat fibroblasts, and human osteoblasts on GRGDS and/or KRSR Star PEG-modified two- and three-dimensional substrates show advancement in cell adhesion and proliferation compared with untreated PVDF surfaces, whereas pure star PEG-coated surfaces show no cell adhesion. The combination of protein and cell repellent properties with specific biofunctionality and easy application of the coatings will enable their application for 3D-scaffolds. PMID:19431207

  5. Bone-like apatite coating on functionalized poly(etheretherketone) surface via tailored silanization layers technique.

    PubMed

    Zheng, Yanyan; Xiong, Chengdong; Zhang, Shenglan; Li, Xiaoyu; Zhang, Lifang

    2015-10-01

    Poly(etheretherketone) (PEEK) is a rigid semi-crystalline polymer with outstanding mechanical properties, bone-like stiffness and suitable biocompatibility that has attracted much interest as a biomaterial for orthopedic and dental implants. However, the bio-inert surface of PEEK limits its biomedical applications when direct osteointegration between the implants and the host tissue is desired. In this work, -PO4H2, -COOH and -OH groups were introduced on the PEEK surface by further chemical treatments of the vinyl-terminated silanization layers formed on the hydroxylation-pretreated PEEK surface. Both the surface-functionalized and pristine specimens were characterized by X-ray photoelectron spectroscopy (XPS), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy and water contact angle measurements. When placed in 1.5 strength simulated body fluid (SBF) solution, apatite was observed to form uniformly on the functionalized PEEK surface and firmly attach to the substrate. The characterized results demonstrated that the coating was constituted by poorly crystallized bone-like apatite and the effect of surface functional groups on coating formation was also discussed in detail. In addition, in vitro biocompatibility of PEEK, in terms of pre-osteoblast cell (MC3T3-E1) attachment, spreading and proliferation, was remarkably enhanced by the bone-like apatite coating. Thus, this study provides a method to enhance the bioactivity of PEEK and expand its applications in orthopedic and dental implants. PMID:26117784

  6. Simultaneous Formation of a Self-Wrinkled Surface and Silver Nanoparticles on a Functional Photocuring Coating.

    PubMed

    Lin, Hongbo; Wang, Yuanlong; Gan, Yanchang; Hou, Honghao; Yin, Jie; Jiang, Xuesong

    2015-11-01

    Bioinspired functional surface with micro/nanostructures are particularly attractive because of the potential for outstanding characteristics, such as self-cleaning, self-replenishing and antibiosis. Here, we presented a facile approach to fabricate a functional photocuring coating with both a self-wrinkling patterned surface and incorporated silver nanoparticles (Ag NPs). Fluorinated polymeric photoinitiator (FPPI) and silver precursor (TFAAg) can self-assemble together on the air/acrylate interface to form a top layer of photocuring liquid resin. Under UV irradiation, a wrinkled pattern was formed as a result of the mismatch in shrinkage caused by photopolymerization between the top layer and the bulk layer. Simultaneously, Ag NPs with sizes of 15 ± 8 nm in diameter were in situ generated in the photocuring coating through the photoreduction of TFAAg. Their number density is higher in the top layer than in the bulk. Scanning electron microscope (SEM) and atomic force microscope (AFM) measurements revealed that the characteristic wavelength (λ) and amplitude (A) of the wrinkled morphology increased with growing concentration of FPPI, and that the generation of Ag NPs led to the wrinkle-to-fold transition. Furthermore, the obtained functional coatings possess a low surface energy and self-replenishing and antibiosis capabilities as a result of the synergistic effect of the wrinkled surface covered by FPPI and Ag NPs. PMID:26471347

  7. PREFACE: 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM 2012)

    NASA Astrophysics Data System (ADS)

    Zhou, Zhangjian; Li, Jingfeng; Zhang, Lianmeng; Ge, Changchun

    2013-03-01

    The 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM-2012) was held in Beijing, China, from 22-36 October 2012. This was part of a series of conferences organized every two years endorsed by International Advisory Committee for FGM's, which serves as a forum for scientists, educators, engineers and young students interested in the development of functionally graded materials (FGM). The series continues from the previous international symposium on FGM held in Sendai, Japan (1990), San Francisco, USA (1992), Lausanne, Switzerland (1994), Tsukuba, Japan (1996), Dresden, Germany (1998), Estes Park, USA (2000), Beijing, China (2002), Leuven, Belgium (2004), Hawaii, USA (2006), Sendai, Japan (2008) and Guimaraes, Portugal (2010). Functionally graded materials are non-uniform materials which are designed with embodied continuous spatial variations in composition and microstructure for the specific purpose of adjusting their thermal, structural, mechanical, biological or functional response to specific application conditions. Such multi-phase materials cover a range of space and time scales, and are best understood by means of a comprehensive multiscale, multiphysics approach. These kinds of materials are presently in the forefront of materials research, receiving worldwide attention. They have a broad range of applications including for example, biomedical, biomechanical, automotive, aerospace, mechanical, civil, nuclear, and naval engineering. New applications are continuously being discovered and developed. The objective of the FGM-2012 intends to provide opportunities for exchanging ideas and discussing state-of-the-art theories, techniques and applications in the fields of multiscale, multifunctional and FGM, through invited lectures, oral and poster presentations. FGM-2012 was organized and hosted by University of Science and Technology Beijing, China, together with Tsing-hua University and Wuhan University of

  8. PREFACE: 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM 2012)

    NASA Astrophysics Data System (ADS)

    Zhou, Zhangjian; Li, Jingfeng; Zhang, Lianmeng; Ge, Changchun

    2013-03-01

    The 12th International Symposium on Multiscale, Multifunctional and Functionally Graded Materials (FGM-2012) was held in Beijing, China, from 22-36 October 2012. This was part of a series of conferences organized every two years endorsed by International Advisory Committee for FGM's, which serves as a forum for scientists, educators, engineers and young students interested in the development of functionally graded materials (FGM). The series continues from the previous international symposium on FGM held in Sendai, Japan (1990), San Francisco, USA (1992), Lausanne, Switzerland (1994), Tsukuba, Japan (1996), Dresden, Germany (1998), Estes Park, USA (2000), Beijing, China (2002), Leuven, Belgium (2004), Hawaii, USA (2006), Sendai, Japan (2008) and Guimaraes, Portugal (2010). Functionally graded materials are non-uniform materials which are designed with embodied continuous spatial variations in composition and microstructure for the specific purpose of adjusting their thermal, structural, mechanical, biological or functional response to specific application conditions. Such multi-phase materials cover a range of space and time scales, and are best understood by means of a comprehensive multiscale, multiphysics approach. These kinds of materials are presently in the forefront of materials research, receiving worldwide attention. They have a broad range of applications including for example, biomedical, biomechanical, automotive, aerospace, mechanical, civil, nuclear, and naval engineering. New applications are continuously being discovered and developed. The objective of the FGM-2012 intends to provide opportunities for exchanging ideas and discussing state-of-the-art theories, techniques and applications in the fields of multiscale, multifunctional and FGM, through invited lectures, oral and poster presentations. FGM-2012 was organized and hosted by University of Science and Technology Beijing, China, together with Tsing-hua University and Wuhan University of

  9. Functionalized antibiofilm thin coatings based on PLA-PVA microspheres loaded with usnic acid natural compounds fabricated by MAPLE

    NASA Astrophysics Data System (ADS)

    Grumezescu, Valentina; Socol, Gabriel; Grumezescu, Alexandru Mihai; Holban, Alina Maria; Ficai, Anton; Truşcǎ, Roxana; Bleotu, Coralia; Balaure, Paul Cǎtǎlin; Cristescu, Rodica; Chifiriuc, Mariana Carmen

    2014-05-01

    We report the fabrication of thin coatings of PLA-PVA microspheres loaded with usnic acid by matrix assisted pulsed laser evaporation (MAPLE) onto Ti substrate. The obtained coatings have been physico-chemically characterized by scanning electron microscopy (SEM) and infrared microscopy (IRM). In vitro biological assays have been performed in order to evaluate the influence of fabricated microsphere thin coatings on the Staphylococcus aureus biofilm development as well as their biocompatibility. SEM micrographs have revealed a uniform morphology of thin coatings, while IRM investigations have proved both the homogeneity and functional groups integrity of prepared thin coatings. The obtained microsphere-based thin coatings have proved to be efficient vehicles for usnic acid natural compound with antibiofilm activity, as demonstrated by the inhibitory activity on S. aureus mature biofilm development, opening new perspectives for the prevention and therapy associated to biofilm related infections.

  10. Diamond-like carbon coatings for orthopedic applications: Tribological behaviors of vacuum arc diamond-like carbon-coated titanium alloy against medical-grade ultra-high molecular weight polyethylene

    NASA Astrophysics Data System (ADS)

    Xu, Tianzong

    An extensive and detailed investigation of tribological behaviors of vacuum arc carbon coated Ti6Al4V against medical grade ultra high molecular weight polyethylene were conducted in this work in order to investigate the potential use of diamond-like carbon coatings for orthopedic applications. Further, the gas plasma sterilization and surface modification technique were evaluated as an alternative to the currently used gamma-radiation technique which has previously shown degradation effects on the mechanical properties of the UHMWPE. In addition, an emerging polymer surface modification technique using high-energy ion-implantation is explored to modify the surface of the UHMWPE for improved wear performance. The experiments were performed using a standard pin-on-disk wear tester under both dry and distilled water lubricated condition. The evolution of friction and wear processes are interpreted in the context of in situ recorded coefficient of friction and microscopic images of worn surfaces. Sliding wear tests demonstrated the existence of two distinct friction and wear regimes which comprise physically different dominant mechanisms: an adhesive and abrasive mechanism activated early in the run-in stage, followed by fatigue processes which developed later microscopically in the (quasi) steady-state sliding stage. The effects of surface roughness, distilled water lubricant, coating structure, polymer sterilization and surface modification on the tribological behaviors are presented and discussed in light of these results. Explanations based on theories of sliding contact stress fields, temperature profiles, as well as lubrication and coating fracture mechanics are presented to discuss and support the experimental results. It is revealed that, largely depending on material structures and surface roughness of both articulating components, significantly improved friction and wear performance can be achieved by optimal design of their process

  11. Probabilistic Fracture Analysis of Functionally Graded Materials--Part I: Uncertainty and Probabilistic Analysis Method

    SciTech Connect

    Song, Junho; Nguyen, Tam H.; Paulino, Glaucio H.

    2008-02-15

    Probabilistic fracture analysis is performed for predicting uncertain fracture responses of Functionally Graded Material (FGM) structures. The uncertainties in material properties including Young's modulus and fracture toughness are considered. The limit state function for a crack initiation event is defined in terms of the J-integral for FGMs. The First-Order-Reliability-Method (FORM) is used in conjunction with a finite element code that computes the J-integral with high accuracy. A two-step probabilistic analysis procedure is proposed to investigate the effects of the uncertainties in the spatial distribution of Young's modulus on the probability of crack initiation in FGMs. First, we investigate the effects of the uncertainties in the shape of the spatial distribution by considering the slope and the location of the inflection point of a spatial distribution profile as random quantities. Second, we investigate the effects of the spatial fluctuations of Young's modulus by making use of a discretized random field. The companion paper (Part II) implements this method into a finite element fracture analysis code and presents numerical examples.

  12. Numerical modeling of wave propagation in functionally graded materials using time-domain spectral Chebyshev elements

    NASA Astrophysics Data System (ADS)

    Hedayatrasa, Saeid; Bui, Tinh Quoc; Zhang, Chuanzeng; Lim, Chee Wah

    2014-02-01

    Numerical modeling of the Lamb wave propagation in functionally graded materials (FGMs) by a two-dimensional time-domain spectral finite element method (SpFEM) is presented. The high-order Chebyshev polynomials as approximation functions are used in the present formulation, which provides the capability to take into account the through thickness variation of the material properties. The efficiency and accuracy of the present model with one and two layers of 5th order spectral elements in modeling wave propagation in FGM plates are analyzed. Different excitation frequencies in a wide range of 28-350 kHz are investigated, and the dispersion properties obtained by the present model are verified by reference results. The through thickness wave structure of two principal Lamb modes are extracted and analyzed by the symmetry and relative amplitude of the vertical and horizontal oscillations. The differences with respect to Lamb modes generated in homogeneous plates are explained. Zero-crossing and wavelet signal processing-spectrum decomposition procedures are implemented to obtain phase and group velocities and their dispersion properties. So it is attested how this approach can be practically employed for simulation, calibration and optimization of Lamb wave based nondestructive evaluation techniques for the FGMs. The capability of modeling stress wave propagation through the thickness of an FGM specimen subjected to impact load is also investigated, which shows that the present method is highly accurate as compared with other existing reference data.

  13. Fracture Behavior and Properties of Functionally Graded Fiber-Reinforced Concrete

    SciTech Connect

    Roesler, Jeffery; Bordelon, Amanda; Gaedicke, Cristian; Park, Kyoungsoo; Paulino, Glaucio

    2008-02-15

    In concrete pavements, a single concrete mixture design is selected to resist mechanical loading without attempting to adversely affect the concrete pavement shrinkage, ride quality, or noise attenuation. An alternative approach is to design distinct layers within the concrete pavement surface which have specific functions thus achieving higher performance at a lower cost. The objective of this research was to address the structural benefits of functionally graded concrete materials (FGCM) for rigid pavements by testing and modeling the fracture behavior of different combinations of layered plain and synthetic fiber-reinforced concrete materials. Fracture parameters and the post-peak softening behavior were obtained for each FGCM beam configuration by the three point bending beam test. The peak loads and initial fracture energy between the plain, fiber-reinforced, and FGCM signified similar crack initiation. The total fracture energy indicated improvements in fracture behavior of FGCM relative to full-depth plain concrete. The fracture behavior of FGCM depended on the position of the fiber-reinforced layer relative to the starter notch. The fracture parameters of both fiber-reinforced and plain concrete were embedded into a finite element-based cohesive zone model. The model successfully captured the experimental behavior of the FGCMs and predicted the fracture behavior of proposed FGCM configurations and structures. This integrated approach (testing and modeling) demonstrates the viability of FGCM for designing layered concrete pavements system.

  14. Management of Grade III Mobile Anterior Tooth in Function Using Endostabilizer – A Case Report

    PubMed Central

    Patil, Swapnil N

    2014-01-01

    Impact of implant dentistry is such that today very few dentists think about saving grade III mobile anterior teeth. A patient with grade III mobility of central incisor due to apical root resorption was treated by using 80 no.stainless steel ‘H’ file as endostabiliser and one year follow up was done. Endostabiliser reduced the mobility of grade III mobile teeth drastically, immediately after its placement. Tooth was absolutely asymptomatic throughout one year follow up. PMID:25654043

  15. Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

    SciTech Connect

    Hopmann, Ch.; Weber, M.; Schöngart, M.; Schäfer, C.; Bobzin, K.; Bagcivan, N.; Brögelmann, T.; Theiß, S.; Münstermann, T.; Steger, M.

    2015-05-22

    Micro structured optical plastics components are intensively used i. e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting or laser technology. Injection moulding has proven to be successful for the large-scale production of those parts. However, the production of those parts still causes difficulties due to challenges in the moulding and demoulding of plastics parts created with laser structured mould inserts. A complete moulding of the structures often leads to increased demoulding forces, which then cause a breaking of the structures and a clogging of the mould. An innovative approach is to combine PVD-coated (physical vapour deposition), laser structured inserts and a variothermal moulding process to create functional mic8iüro structures in a one-step process. Therefore, a PVD-coating is applied after the laser structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of moulding trials with polycarbonate (PC) and polymethylmethacrylate (PMMA) using different coated moulds, the mould temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the moulded parts is evaluated by digital 3D laser-scanning microscopy. The influence of the moulding parameters and the coating of the mould insert on the moulding accuracy and the demoulding behaviour are being analysed. It is shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal moulding process. Due to the mould coating, significant improvements could be achieved in producing micro structured optical plastics components.

  16. Injection moulding of optical functional micro structures using laser structured, PVD-coated mould inserts

    NASA Astrophysics Data System (ADS)

    Hopmann, Ch.; Weber, M.; Schöngart, M.; Schäfer, C.; Bobzin, K.; Bagcivan, N.; Brögelmann, T.; Theiß, S.; Münstermann, T.; Steger, M.

    2015-05-01

    Micro structured optical plastics components are intensively used i. e. in consumer electronics, for optical sensors in metrology, innovative LED-lighting or laser technology. Injection moulding has proven to be successful for the large-scale production of those parts. However, the production of those parts still causes difficulties due to challenges in the moulding and demoulding of plastics parts created with laser structured mould inserts. A complete moulding of the structures often leads to increased demoulding forces, which then cause a breaking of the structures and a clogging of the mould. An innovative approach is to combine PVD-coated (physical vapour deposition), laser structured inserts and a variothermal moulding process to create functional mic8iüro structures in a one-step process. Therefore, a PVD-coating is applied after the laser structuring process in order to improve the wear resistance and the anti-adhesive properties against the plastics melt. In a series of moulding trials with polycarbonate (PC) and polymethylmethacrylate (PMMA) using different coated moulds, the mould temperature during injection was varied in the range of the glass transition and the melt temperature of the polymers. Subsequently, the surface topography of the moulded parts is evaluated by digital 3D laser-scanning microscopy. The influence of the moulding parameters and the coating of the mould insert on the moulding accuracy and the demoulding behaviour are being analysed. It is shown that micro structures created by ultra-short pulse laser ablation can be successfully replicated in a variothermal moulding process. Due to the mould coating, significant improvements could be achieved in producing micro structured optical plastics components.

  17. Cognitive functioning in long-term survivors of high-grade glioma.

    PubMed

    Archibald, Y M; Lunn, D; Ruttan, L A; Macdonald, D R; Del Maestro, R F; Barr, H W; Pexman, J H; Fisher, B J; Gaspar, L E; Cairncross, J G

    1994-02-01

    In a pilot study, two groups of patients with malignant glioma underwent sequential neuropsychological evaluations after successful tumor treatment. Group 1 included nine patients treated from 1981 to 1985; all patients received irradiation and eight underwent chemotherapy. The baseline neuropsychological assessment was performed 1 to 63 months after tumor diagnosis, with follow-up evaluations at irregular intervals over the next 3 to 7 years. Six patients in Group 1 exhibited impairment on most measures at baseline; subsequently, two patients developed profound cognitive impairment. Initially, three patients functioned in the average range on most tasks; thereafter, two deteriorated on one measure each. Group 2 was ascertained prospectively and included 16 patients treated from 1985 to 1987, all of whom received irradiation and chemotherapy. The first evaluation was performed 18 months after diagnosis, then every 6 months for 2 years, and then yearly. Compared to a control group, those in Group 2 had significant cognitive impairment at baseline. Cognitive performance did not change over the next 12 months in 10 patients who remained free of tumor, but within 2 years of baseline testing, deterioration on specific tasks was evident in two of seven disease-free survivors. When last tested, five of six disease-free survivors had deteriorated on one or more measures. Unlike Group 1, severe global cognitive impairment was not seen, perhaps because Group 2 was followed for a shorter time. Verbal and nonverbal composite scores derived from intelligence quotient (IQ) tests showed less impairment at baseline than did other measures and were more likely to remain stable subsequently. Verbal memory and sustained attention were the most impaired at baseline, and verbal learning and flexibility in thinking showed the greatest tendency to decline over time. Cognitive functioning in survivors of high-grade glioma is best measured and monitored by tests that probe a broader

  18. Membranes for periodontal regeneration: From commercially available to spatially designed and functionally graded materials

    NASA Astrophysics Data System (ADS)

    Bottino, Marco Cicero

    The aging of the global population will lead to a considerable increase in the number of surgical and restorative procedures related to oral rehabilitation or periodontal regeneration. Periodontitis is one of the most aggressive pathologies that concern the integrity of the periodontal system that can lead to the destruction of the periodontium. Guided tissue and guided bone regeneration (GTR/GBR) have been used for the repair and regeneration of periodontal tissues by utilizing an occlusive membrane. The goal of this dissertation is to advance the knowledge in the area of periodontal regeneration by investigating the properties of a commercially available freeze-dried collagen-based graft (AlloDermRTM) and by designing/fabricating a functionally graded membrane (FGM) via multilayer electrospinning. The effects of different rehydration times and of a simultaneous rehydration/crosslinking procedure on the biomechanical properties and matrix stability of the commercially available membrane were investigated. The results revealed that there are significant changes on the biomechanical properties of the graft as rehydration time increases. Moreover, it was demonstrated that the simultaneous rehydration/crosslinking protocol has a synergistic effect in terms of enhancing biomechanical properties. A FGM consisting of a core-layer (CL) and two functional surface-layers (SL) was fabricated via sequential electrospinning. Hydroxyapatite nanoparticles (n-HAp) were incorporated to enhance bone formation (SL facing bone defect), and metronidazole benzoate (MET) was added to prevent bacterial colonization (SL facing the epithelial tissue). Degradation studies performed on both the CL and the FGM confirmed that the design holds promise in terms of providing the required mechanical stability to avoid membrane collapse and, therefore, enhance bone regeneration. Finally, it was demonstrated that MET incorporation into the SL that would face epithelial tissue is effective in

  19. Cytotoxicity of protein-carbon nanotubes on J774 macrophages is a functionalization grade-dependent effect.

    PubMed

    Montes-Fonseca, Silvia Lorena; Sánchez-Ramírez, Blanca; Luna-Velasco, Antonia; Arzate-Quintana, Carlos; Silva-Cazares, Macrina Beatriz; González Horta, Carmen; Orrantia-Borunda, Erasmo

    2015-01-01

    Carbon nanotubes (CNTs) are used as carriers in medicine due to their ability to be functionalized with chemical substances. However, cytotoxicity analysis is required prior to use for in vivo models. The aim of this study was to evaluate the cytotoxic effect of CNTs functionalized with a 46 kDa surface protein from Entamoeba histolytica (P46-CNTs) on J774A macrophages. With this purpose, CNTs were synthesized by spray pyrolysis and purified (P-CNTs) using sonication for 48 h. A 46 kDa protein, with a 4.6-5.4 pI range, was isolated from E. histolytica HM1:IMSS strain trophozoites using an OFFGEL system. The P-CNTs were functionalized with the purified 46 kDa protein, classified according to their degree of functionalization, and characterized by Raman and Infrared spectroscopy. In vitro cytotoxicity was evaluated by MTT, apoptosis, and morphological assays. The results demonstrated that P46-CNTs exhibited cytotoxicity dependent upon the functionalized grade. Contrary to what was expected, P46-CNTs with a high grade of functionalization were more toxic to J774 macrophages than P46-CNTs with a low grade of functionalization, than P-CNTs, and had a similar level of toxicity as UP-CNT. This suggests that the nature of the functionalized protein plays a key role in the cytotoxicity of these nanoparticles. PMID:26075262

  20. Cytotoxicity of Protein-Carbon Nanotubes on J774 Macrophages Is a Functionalization Grade-Dependent Effect

    PubMed Central

    Montes-Fonseca, Silvia Lorena; Sánchez-Ramírez, Blanca; Luna-Velasco, Antonia; Arzate-Quintana, Carlos; Silva-Cazares, Macrina Beatriz; González Horta, Carmen

    2015-01-01

    Carbon nanotubes (CNTs) are used as carriers in medicine due to their ability to be functionalized with chemical substances. However, cytotoxicity analysis is required prior to use for in vivo models. The aim of this study was to evaluate the cytotoxic effect of CNTs functionalized with a 46 kDa surface protein from Entamoeba histolytica (P46-CNTs) on J774A macrophages. With this purpose, CNTs were synthesized by spray pyrolysis and purified (P-CNTs) using sonication for 48 h. A 46 kDa protein, with a 4.6–5.4 pI range, was isolated from E. histolytica HM1:IMSS strain trophozoites using an OFFGEL system. The P-CNTs were functionalized with the purified 46 kDa protein, classified according to their degree of functionalization, and characterized by Raman and Infrared spectroscopy. In vitro cytotoxicity was evaluated by MTT, apoptosis, and morphological assays. The results demonstrated that P46-CNTs exhibited cytotoxicity dependent upon the functionalized grade. Contrary to what was expected, P46-CNTs with a high grade of functionalization were more toxic to J774 macrophages than P46-CNTs with a low grade of functionalization, than P-CNTs, and had a similar level of toxicity as UP-CNT. This suggests that the nature of the functionalized protein plays a key role in the cytotoxicity of these nanoparticles. PMID:26075262

  1. Surface functionalization of carbon nanofibers by sol gel coating of zinc oxide

    NASA Astrophysics Data System (ADS)

    Shao, Dongfeng; Wei, Qufu; Zhang, Liwei; Cai, Yibing; Jiang, Shudong

    2008-08-01

    In this paper the functional carbon nanofibers were prepared by the carbonization of ZnO coated PAN nanofibers to expand the potential applications of carbon nanofibers. Polyacrylonitrile (PAN) nanofibers were obtained by electrospinning. The electrospun PAN nanofibers were then used as substrates for depositing the functional layer of zinc oxide (ZnO) on the PAN nanofiber surfaces by sol-gel technique. The effects of coating, pre-oxidation and carbonization on the surface morphology and structures of the nanofibers were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Scanning electron microscopy (SEM), respectively. The results of SEM showed a significant increase of the size of ZnO nanograins on the surface of nanofibers after the treatments of coating, pre-oxidation and carbonization. The observations by SEM also revealed that ZnO nanoclusters were firmly and clearly distributed on the surface of the carbon nanofibers. FTIR examination also confirmed the deposition of ZnO on the surface of carbon nanofibers. The XRD analysis indicated that the crystal structure of ZnO nanograins on the surface of carbon nanofibers.

  2. Functional metal oxide coatings by molecule-based thermal and plasma chemical vapor deposition techniques.

    PubMed

    Mathur, S; Ruegamer, T; Donia, N; Shen, H

    2008-05-01

    Deposition of thin films through vaccum processes plays an important role in industrial processing of decorative and functional coatings. Many metal oxides have been prepared as thin films using different techniques, however obtaining compositionally uniform phases with a control over grain size and distribution remains an enduring challenge. The difficulties are largely related to complex compositions of functional oxide materials, which makes a control over kinetics of nucleation and growth processes rather difficult to control thus resulting in non-uniform material and inhomogeneous grain size distribution. Application of tailor-made molecular precursors in low pressure or plasma-enhanced chemical vapor deposition (CVD) techniques offers a viable solution for overcoming thermodynamic impediments involved in thin film growth. In this paper molecule-based CVD of functional coatings is demonstrated for iron oxide (Fe2O3, Fe3O4), vanadium oxide (V2O5, VO2) and hafnium oxide (HfO2) phases followed by the characterization of their microstructural, compositional and functional properties which support the advantages of chemical design in simplifying deposition processes and optimizing functional behavior. PMID:18572690

  3. School Grades and Responsibility for Younger Siblings: An Empirical Study of the "Teaching Function."

    ERIC Educational Resources Information Center

    Smith, Thomas Ewin

    1984-01-01

    A study based on the confluence model of family effects upon intellectual growth found a negative relationship between grades and the number of older siblings for Whites but not for Blacks and a negative relationship between the grades of Blacks and responsibility for younger siblings. (CMG)

  4. Probabilistic Fracture Analysis of Functionally Graded Materials--Part II: Implementation and Numerical Examples

    SciTech Connect

    Nguyen, Tam H.; Song, Junho; Paulino, Glaucio H.

    2008-02-15

    Probabilistic fracture analyses are performed for investigating uncertain fracture response of Functionally Graded Material (FGM) structures. The First-Order-Reliability-Method (FORM) is implemented into an existing Finite Element code for FGM (FE-FGM), which was previously developed at the University of Illinois at Urbana-Champaign. The computational simulation will be used in order to estimate the probability of crack initiation with uncertainties in the material properties only. The two-step probability analysis method proposed in the companion paper is illustrated by a numerical example of a composite strip with an edge crack. First, the reliability index of a crack initiation event is estimated as we vary the mean and standard deviation of the slope and the location of the inflection point of the spatial profile of Young's modulus. Secondly, the reliability index is estimated as we vary the standard deviation and the correlation length of the random field that characterize the random spatial fluctuation of Young's modulus. Also investigated is the relative importance of the uncertainties in the toughness compared to those in Young's modulus.

  5. Rigorous buckling analysis of size-dependent functionally graded cylindrical nanoshells

    NASA Astrophysics Data System (ADS)

    Sun, Jiabin; Lim, C. W.; Zhou, Zhenhuan; Xu, Xinsheng; Sun, Wei

    2016-06-01

    This paper presents new analytical solutions for buckling of carbon nanotubes (CNTs) and functionally graded (FG) cylindrical nanoshells subjected to compressive and thermal loads. The model applies Eringen's nonlocal differential constitutive relation to describe the size-dependence of nanoshells. Based on Reddy's higher-order shear deformation theory, governing equations are established and solved by separating the variables. The analysis first re-examines the classical buckling of single-walled CNTs. Accurate solutions are established, and it is found that the buckling stress decreases drastically when the nonlocal parameter reaches a certain value. For CNTs with constant wall-thickness, the buckling stress eventually decreases with enhanced size effect. By comparing with CNTs molecular dynamic simulations, the obtained nonlocal parameters are much smaller than those proposed previously. Subsequently, FG cylindrical nanoshells are analyzed, and it is concluded that similar behavior that has been observed for CNTs is also valid for FG cylindrical nanoshells. The paper further discusses in detail the effects of different geometric parameters, material distribution, and temperature field.

  6. Comparison of Various Functionally Graded Femoral Prostheses by Finite Element Analysis

    PubMed Central

    Seyed Shirazi, Seyed Farid; Bayat, Mehdi; Yau, Yat Huang; Tarlochan, Faris; Abu Osman, Noor Azuan

    2014-01-01

    This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent. PMID:25302331

  7. Functionally Graded Aluminum Foam Fabricated by Friction Powder Sintering Process with Traversing Tool

    NASA Astrophysics Data System (ADS)

    Hangai, Yoshihiko; Morita, Tomoaki; Koyama, Shinji; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

    2016-07-01

    Functionally graded aluminum foam (FG Al foam) is a new class of Al foam in which the pore structure varies over the foam, resulting in corresponding variations in the mechanical properties of the foam. In this study, FG Al foam plates were fabricated by a friction powder sintering (FPS) process with a traversing tool that is based on a previously developed sintering and dissolution process. The variation of the mechanical properties was realized by setting the volume fraction φ of NaCl in the mixture to 60, 70, and 80%. Long FG Al foam plates were fabricated with a length equal to the tool traversing length with φ varying in the tool traversing direction. From x-ray computed tomography observation, it was shown that the density of the Al foam decreased with increasing φ. In contrast, almost uniform pore structures were obtained in each area. According to the results of compression tests on each area, the plateau stress and energy absorption tended to decrease with increasing φ. Therefore, it was shown that FG Al foam plates with varying mechanical properties can be fabricated by the FPS process with the traversing tool.

  8. Free vibration of functionally graded carbon-nanotube-reinforced composite plates with cutout

    PubMed Central

    Mirzaei, Mostafa

    2016-01-01

    Summary During the past five years, it has been shown that carbon nanotubes act as an exceptional reinforcement for composites. For this reason, a large number of investigations have been devoted to analysis of fundamental, structural behavior of solid structures made of carbon-nanotube-reinforced composites (CNTRC). The present research, as an extension of the available works on the vibration analysis of CNTRC structures, examines the free vibration characteristics of plates containing a cutout that are reinforced with uniform or nonuniform distribution of carbon nanotubes. The first-order shear deformation plate theory is used to estimate the kinematics of the plate. The solution method is based on the Ritz method with Chebyshev basis polynomials. Such a solution method is suitable for arbitrary in-plane and out-of-plane boundary conditions of the plate. It is shown that through a functionally graded distribution of carbon nanotubes across the thickness of the plate, the fundamental frequency of a rectangular plate with or without a cutout may be enhanced. Furthermore, the frequencies are highly dependent on the volume fraction of carbon nanotubes and may be increased upon using more carbon nanotubes as reinforcement. PMID:27335742

  9. Nonlocal thermo-mechanical vibration analysis of functionally graded nanobeams in thermal environment

    NASA Astrophysics Data System (ADS)

    Ebrahimi, Farzad; Salari, Erfan

    2015-08-01

    In this paper, the thermal effect on free vibration characteristics of functionally graded (FG) size-dependent nanobeams subjected to various types of thermal loading is investigated by presenting a Navier type solution and employing a semi analytical differential transform method (DTM) for the first time. Two kinds of thermal loading, namely, linear temperature rise and nonlinear temperature rise are studied. Material properties of FG nanobeam are supposed to vary continuously along the thickness according to the power-law form and the material properties are assumed to be temperature-dependent. The small scale effect is taken into consideration based on nonlocal elasticity theory of Eringen. The nonlocal equations of motion are derived through Hamilton's principle and they are solved applying DTM. According to the numerical results, it is revealed that the proposed modeling and semi analytical approach can provide accurate frequency results of the FG nanobeams as compared to analytical results and also some cases in the literature. The detailed mathematical derivations are presented and numerical investigations are performed while the emphasis is placed on investigating the effect of the several parameters such as thermal effect, material distribution profile, small scale effects, mode number and boundary conditions on the normalized natural frequencies of the temperature-dependent FG nanobeams in detail. It is explicitly shown that the vibration behaviour of a FG nanobeams is significantly influenced by these effects. Numerical results are presented to serve as benchmarks for future analyses of FG nanobeams.

  10. Forced vibration analysis of functionally graded carbon nanotube-reinforced composite plates using a numerical strategy

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Hasrati, E.; Faghih Shojaei, M.; Gholami, R.; Shahabodini, A.

    2015-05-01

    In this paper, the nonlinear forced vibration behavior of composite plates reinforced by carbon nanotubes is investigated by a numerical approach. The reinforcement is considered to be functionally graded (FG) in the thickness direction according to a micromechanical model. The first-order shear deformation theory and von Kármán-type kinematic relations are employed. The governing equations and the corresponding boundary conditions are derived with the use of Hamilton's principle. The generalized differential quadrature (GDQ) method is utilized to achieve a discretized set of nonlinear governing equations. A Galerkin-based scheme is then applied to obtain a time-varying set of ordinary differential equations of Duffing-type. Subsequently, a time periodic discretization is done and the frequency response of plates is determined via the pseudo-arc length continuation method. Selected numerical results are given for the effects of different parameters on the nonlinear forced vibration characteristics of uniformly distributed carbon nanotube- and FG carbon nanotube-reinforced composite plates. It is found that with the increase of CNT volume fraction, the flexural stiffness of plate increases; and hence its natural frequency gets larger. Moreover, it is observed that the distribution type of CNTs significantly affects the vibrational behavior of plate. The results also show that when the mid-plane of plate is CNT-rich, the natural frequency takes its minimum value and the hardening-type response of plate is intensified.

  11. Effect of anisotropy on creep behavior in a functionally graded material disc of variable thickness

    NASA Astrophysics Data System (ADS)

    Gupta, Vandana; Singh, S. B.

    2014-09-01

    In this paper, an effort has been made to study the effect of anisotropy on the steady state creep behavior in the functionally graded material disc with hyperbolic thickness made of Al-SiC (particle). The content of silicon carbide particles in the disc is assumed to decrease linearly from the inner to the outer radius of the disc. The creep behavior of the disc under stresses developing due to rotation at 15,000 rpm has been determined by Sherby's law. The creep parameters of the FGM disc vary along the radial distance due to varying composition and this variation has been estimated by regression fit of the available experimental data. The creep response of rotating disc is expressed by a threshold stress with value of stress exponent as 8. The study reveals that the anisotropy has a significant effect on the steady state creep response of rotating FGM disc. Thus, the care to introduce anisotropy should be taken for the safe design of the rotating FGM disc with hyperbolic thickness.

  12. Synthesis and microwave absorbing characteristics of functionally graded carbonyl iron/polyurethane composites

    NASA Astrophysics Data System (ADS)

    Yang, R. B.; Liang, W. F.; Wu, C. H.; Chen, C. C.

    2016-05-01

    Radar absorbing materials (RAMs) also known as microwave absorbers, which can absorb and dissipate incident electromagnetic wave, are widely used in the fields of radar-cross section reduction, electromagnetic interference (EMI) reduction and human health protection. In this study, the synthesis of functionally graded material (FGM) (CI/Polyurethane composites), which is fabricated with semi-sequentially varied composition along the thickness, is implemented with a genetic algorithm (GA) to optimize the microwave absorption efficiency and bandwidth of FGM. For impedance matching and broad-band design, the original 8-layered FGM was obtained by the GA method to calculate the thickness of each layer for a sequential stacking of FGM from 20, 30, 40, 50, 60, 65, 70 and 75 wt% of CI fillers. The reflection loss of the original 8-layered FGM below -10 dB can be obtained in the frequency range of 5.12˜18 GHz with a total thickness of 9.66 mm. Further optimization reduces the number of the layers and the stacking sequence of the optimized 4-layered FGM is 20, 30, 65, 75 wt% with thickness of 0.8, 1.6, 0.6 and 1.0 mm, respectively. The synthesis and measurement of the optimized 4-layered FGM with a thickness of 4 mm reveal a minimum reflection loss of -25.2 dB at 6.64 GHz and its bandwidth below - 10 dB is larger than 12.8 GHz.

  13. Nonlinear dynamics of initially imperfect functionally graded circular cylindrical shell under complex loads

    NASA Astrophysics Data System (ADS)

    Liu, Y. Z.; Hao, Y. X.; Zhang, W.; Chen, J.; Li, S. B.

    2015-07-01

    The nonlinear vibration of a simply supported FGM cylindrical shell with small initial geometric imperfection under complex loads is studied. The effects of radial harmonic excitation, compressive in-plane force combined with supersonic aerodynamic and thermal loads are considered. The small initial geometric imperfection of the cylindrical shell is characterized in the form of the sine-type trigonometric functions. The effective material properties of this FGM cylindrical shell are graded in the radial direction according to a simple power law in terms of the volume fractions. Based on Reddy's third-order shear deformation theory, von Karman-type nonlinear kinematics and Hamilton's principle, the nonlinear partial differential equation that controls the shell dynamics is derived. Both axial symmetric and driven modes of the cylindrical shell deflection pattern are included. Furthermore, the equations of motion can be reduced into a set of coupled nonlinear ordinary differential equations by applying Galerkin's method. In the study of the nonlinear dynamics responses of small initial geometric imperfect FGM cylindrical shell under complex loads, the 4th order Runge-Kutta method is used to obtain time history, phase portraits, bifurcation diagrams and Poincare maps with different parameters. The effects of external loads, geometric imperfections and volume fractions on the nonlinear dynamics of the system are discussed.

  14. Spin-polarized Wide Electron Slabs in Functionally Graded Polar Oxide Heterostructures

    PubMed Central

    Ye, Jiandong; Ter Lim, Sze; Bosman, Michel; Gu, Shulin; Zheng, Youdou; Tan, Hark Hoe; Jagadish, Chennupati; Sun, Xiaowei; Teo, Kie Leong

    2012-01-01

    We report on the high mobility wide electron slabs with enhanced correlation effects by tailoring the polarization effects in a functionally graded ZnMgO/ZnO heterostructures. The characteristics of three-dimensional (3D) spreading electrons are evidenced by the capacitance-voltage profiling and the quantization of 3D Fermi surface in magneto-transport measurements. Despite the weak spin-orbit interaction, such electron slabs are spin-polarized with a large zero-field spin splitting energy, which is induced by the carrier-mediated ferromagnetism. Our results suggest that the vast majority of electrons are localized at the surface magnetic moment which does not allow spin manipulations, and only in the region visited by the itinerant carriers that the ferromagnetic exchange interactions via coupling to the surface local moments contribute to the spin transport. The host ferromagnetism is likely due to the formation of Zn cation vacancies on the surface regime induced by the stabilization mechanism and strain-relaxation in ZnMgO polar ionic surface. PMID:22833785

  15. 3D-FE analysis of functionally graded structured dental posts.

    PubMed

    Abu Kasim, Noor H; Madfa, Ahmed A; Hamdi, Mohd; Rahbari, Ghahnavyeh R

    2011-01-01

    This study aimed to compare the biomechanical behaviour of functionally graded structured posts (FGSPs) and homogenous-type posts in simulated models of a maxillary central incisor. Two models of FGSPs consisting of a multilayer xTi-yHA composite design, where zirconia and alumina was added as the first layer for models A and B respectively were compared to homogenous zirconia post (model C) and a titanium post (model D). The amount of Ti and HA in the FGSP models was varied in gradations. 3D-FEA was performed on all models and stress distributions were investigated along the dental post. In addition, interface stresses between the posts and their surrounding structures were investigated under vertical, oblique, and horizontal loadings. Strain distribution along the post-dentine interface was also investigated. The results showed that FGSPs models, A and B demonstrated better stress distribution than models C and D, indicating that dental posts with multilayered structure dissipate localized and interfacial stress and strain more efficiently than homogenous-type posts. PMID:22123011

  16. Enhanced thermal stability of functionally graded sandwich cylindrical shells by shape memory alloys

    NASA Astrophysics Data System (ADS)

    Asadi, H.; Akbarzadeh, A. H.; Chen, Z. T.; Aghdam, M. M.

    2015-04-01

    The present paper deals with the nonlinear thermal instability of geometrically imperfect sandwich cylindrical shells under uniform heating. The sandwich shells are made of a shape memory alloy (SMA)-fiber-reinforced composite and functionally graded (FG) face sheets (FG/SMA/FG). The Brinson phenomenological model is used to express the constitutive characteristics of SMA fibers. The governing equations are established within the framework of the third-order shear deformation shell theory by taking into account the von Karman geometrical nonlinearity and initial imperfection. The material properties of constituents are assumed to be temperature dependent. The Galerkin technique is utilized to derive expressions of the bifurcation points and bifurcation paths of the sandwich cylindrical shells. Using the developed closed-form solutions, extensive numerical results are presented to provide an insight into the influence of the SMA fiber volume fraction, SMA pre-strain, core thickness, non-homogeneity index, geometrical imperfection, geometry parameters of sandwich shells and temperature dependency of materials on the stability of shells. The results reveal that proper application of SMA fibers postpones the thermal bifurcation point and dramatically decreases thermal post-buckling deflection. Moreover, the induced tensile recovery stress of SMA fibers could also stabilize the geometrically imperfect shells during the inverse martensite phase transformation.

  17. Hot Deformation Characteristics of Functionally Graded Steels Produced by Electroslag Remelting

    NASA Astrophysics Data System (ADS)

    Naderi, B.; Aghazadeh Mohandesi, J.

    2011-08-01

    In this work, a hot compression test was carried out at 1173 K to 1473 K (900°C to 1200 °C), with a strain rate of 0.01 to 1 s-1 up to ~50 pct height reduction on functionally graded steel (FGS) specimens comprised of ferritic, bainitic, austenitic, and martensitic layers ( αβγM γ). The stress-strain curves are strongly dependent on temperature and strain rate. Compressive flow stress varied from 40 to 105 MPa depending on the applied temperature and strain rates. Variation in steady-state flow stress with temperature and strain rates was studied. The strain-rate-sensitivity exponent ( m) and deformation activation energy ( Q) for the αβγM γ composite under studied condition were 0.106 and 354.8 KJ mol-1, respectively, which are within the values of boundary layers of ferrite (304.9 KJ mol-1) and austenite (454.8 KJ mol-1) layers. Given the alternative microstructure of the αβγM γ FGS, a range of deformation mechanisms from dynamic recovery to dynamic recrystallization maybe prevails, where the intensity of each mechanism depends on temperature and strain rates. In accordance with the experimental results, an empirical power-law equation was developed over the range of temperatures and strain rates investigated. The equation accurately describes temperature and strain-rate dependence of the flow stress.

  18. Free vibration of functionally graded carbon-nanotube-reinforced composite plates with cutout.

    PubMed

    Mirzaei, Mostafa; Kiani, Yaser

    2016-01-01

    During the past five years, it has been shown that carbon nanotubes act as an exceptional reinforcement for composites. For this reason, a large number of investigations have been devoted to analysis of fundamental, structural behavior of solid structures made of carbon-nanotube-reinforced composites (CNTRC). The present research, as an extension of the available works on the vibration analysis of CNTRC structures, examines the free vibration characteristics of plates containing a cutout that are reinforced with uniform or nonuniform distribution of carbon nanotubes. The first-order shear deformation plate theory is used to estimate the kinematics of the plate. The solution method is based on the Ritz method with Chebyshev basis polynomials. Such a solution method is suitable for arbitrary in-plane and out-of-plane boundary conditions of the plate. It is shown that through a functionally graded distribution of carbon nanotubes across the thickness of the plate, the fundamental frequency of a rectangular plate with or without a cutout may be enhanced. Furthermore, the frequencies are highly dependent on the volume fraction of carbon nanotubes and may be increased upon using more carbon nanotubes as reinforcement. PMID:27335742

  19. 2-D differential quadrature solution for vibration analysis of functionally graded conical, cylindrical shell and annular plate structures

    NASA Astrophysics Data System (ADS)

    Tornabene, Francesco; Viola, Erasmo; Inman, Daniel J.

    2009-12-01

    This paper focuses on the dynamic behavior of functionally graded conical, cylindrical shells and annular plates. The last two structures are obtained as special cases of the conical shell formulation. The first-order shear deformation theory (FSDT) is used to analyze the above moderately thick structural elements. The treatment is developed within the theory of linear elasticity, when materials are assumed to be isotropic and inhomogeneous through the thickness direction. The two-constituent functionally graded shell consists of ceramic and metal that are graded through the thickness, from one surface of the shell to the other. Two different power-law distributions are considered for the ceramic volume fraction. The homogeneous isotropic material is inferred as a special case of functionally graded materials (FGM). The governing equations of motion, expressed as functions of five kinematic parameters, are discretized by means of the generalized differential quadrature (GDQ) method. The discretization of the system leads to a standard linear eigenvalue problem, where two independent variables are involved without using the Fourier modal expansion methodology. For the homogeneous isotropic special case, numerical solutions are compared with the ones obtained using commercial programs such as Abaqus, Ansys, Nastran, Straus, Pro/Mechanica. Very good agreement is observed. Furthermore, the convergence rate of natural frequencies is shown to be very fast and the stability of the numerical methodology is very good. Different typologies of non-uniform grid point distributions are considered. Finally, for the functionally graded material case numerical results illustrate the influence of the power-law exponent and of the power-law distribution choice on the mechanical behavior of shell structures.

  20. Ion-assisted functional monolayer coating of nanorod arrays in hydrogen plasmas

    SciTech Connect

    Tam, E.; Levchenko, I.; Ostrikov, K.; Keidar, M.; Xu, S.

    2007-02-15

    Uniformity of postprocessing of large-area, dense nanostructure arrays is currently one of the greatest challenges in nanoscience and nanofabrication. One of the major issues is to achieve a high level of control in specie fluxes to specific surface areas of the nanostructures. As suggested by the numerical experiments in this work, this goal can be achieved by manipulating microscopic ion fluxes by varying the plasma sheath and nanorod array parameters. The dynamics of ion-assisted deposition of functional monolayer coatings onto two-dimensional carbon nanorod arrays in a hydrogen plasma is simulated by using a multiscale hybrid numerical simulation. The numerical results show evidence of a strong correlation between the aspect ratios and nanopattern positioning of the nanorods, plasma sheath width, and densities and distributions of microscopic ion fluxes. When the spacing between the nanorods and/or their aspect ratios are larger, and/or the plasma sheath is wider, the density of microscopic ion current flowing to each of the individual nanorods increases, thus reducing the time required to apply a functional monolayer coating down to 11 s for a 7-{mu}m-wide sheath, and to 5 s for a 50-{mu}m-wide sheath. The computed monolayer coating development time is consistent with previous experimental reports on plasma-assisted functionalization of related carbon nanostructures [B. N. Khare et al., Appl. Phys. Lett. 81, 5237 (2002)]. The results are generic in that they can be applied to a broader range of plasma-based processes and nanostructures, and contribute to the development of deterministic strategies of postprocessing and functionalization of various nanoarrays for nanoelectronic, biomedical, and other emerging applications.

  1. Ion-assisted functional monolayer coating of nanorod arrays in hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Tam, E.; Levchenko, I.; Ostrikov, K.; Keidar, M.; Xu, S.

    2007-02-01

    Uniformity of postprocessing of large-area, dense nanostructure arrays is currently one of the greatest challenges in nanoscience and nanofabrication. One of the major issues is to achieve a high level of control in specie fluxes to specific surface areas of the nanostructures. As suggested by the numerical experiments in this work, this goal can be achieved by manipulating microscopic ion fluxes by varying the plasma sheath and nanorod array parameters. The dynamics of ion-assisted deposition of functional monolayer coatings onto two-dimensional carbon nanorod arrays in a hydrogen plasma is simulated by using a multiscale hybrid numerical simulation. The numerical results show evidence of a strong correlation between the aspect ratios and nanopattern positioning of the nanorods, plasma sheath width, and densities and distributions of microscopic ion fluxes. When the spacing between the nanorods and/or their aspect ratios are larger, and/or the plasma sheath is wider, the density of microscopic ion current flowing to each of the individual nanorods increases, thus reducing the time required to apply a functional monolayer coating down to 11 s for a 7-μm-wide sheath, and to 5 s for a 50-μm-wide sheath. The computed monolayer coating development time is consistent with previous experimental reports on plasma-assisted functionalization of related carbon nanostructures [B. N. Khare et al., Appl. Phys. Lett. 81, 5237 (2002)]. The results are generic in that they can be applied to a broader range of plasma-based processes and nanostructures, and contribute to the development of deterministic strategies of postprocessing and functionalization of various nanoarrays for nanoelectronic, biomedical, and other emerging applications.

  2. Ion-assisted functional monolayer coating of nanorod arrays in hydrogen plasmas

    NASA Astrophysics Data System (ADS)

    Tam, E.; Levchenko, I.; Ostrikov, K.; Keidar, M.; Xu, S.

    2007-03-01

    Uniformity of postprocessing of large-area, dense nanostructure arrays is currently one of the greatest challenges in nanoscience and nanofabrication. One of the major issues is to achieve a high level of control in specie fluxes to specific surface areas of the nanostructures. As suggested by the numerical experiments in this work, this goal can be achieved by manipulating microscopic ion fluxes by varying the plasma sheath and nanorod array parameters. The dynamics of ion-assisted deposition of functional monolayer coatings onto two-dimensional carbon nanorod arrays in a hydrogen plasma is simulated by using a multiscale hybrid numerical simulation. The numerical results show evidence of a strong correlation between the aspect ratios and nanopattern positioning of the nanorods, plasma sheath width, and densities and distributions of microscopic ion fluxes. When the spacing between the nanorods and/or their aspect ratios are larger, and/or the plasma sheath is wider, the density of microscopic ion current flowing to each of the individual nanorods increases, thus reducing the time required to apply a functional monolayer coating down to 11s for a 7-μm-wide sheath, and to 5s for a 50-μm-wide sheath. The computed monolayer coating development time is consistent with previous experimental reports on plasma-assisted functionalization of related carbon nanostructures [B. N. Khare et al., Appl. Phys. Lett. 81, 5237 (2002)]. The results are generic in that they can be applied to a broader range of plasma-based processes and nanostructures, and contribute to the development of deterministic strategies of postprocessing and functionalization of various nanoarrays for nanoelectronic, biomedical, and other emerging applications.

  3. Functional and electrophysiological changes after graded traumatic spinal cord injury in adult rat.

    PubMed

    Cao, Qilin; Zhang, Yi Ping; Iannotti, Christopher; DeVries, William H; Xu, Xiao-Ming; Shields, Christopher B; Whittemore, Scott R

    2005-02-01

    A graded contusion spinal cord injury (SCI) was created in the adult rat spinal cord using the Infinite Horizons (IH) impactor to study the correlation between injury severity and anatomical, behavioral, and electrophysiological outcomes. Adult Fisher rats were equally divided into five groups and received contusion injuries at the ninth thoracic level (T9) with 100, 125, 150, 175, or 200 kdyn impact forces, respectively. Transcranial magnetic motor-evoked potentials (tcMMEPs) and BBB open-field locomotor analyses were performed weekly for 4 weeks postinjury. Our results demonstrated that hindlimb locomotor function decreased in accordance with an increase in injury severity. The locomotor deficits were proportional to the amount of damage to the ventral and lateral white matter (WM). Locomotor function was strongly correlated to the amount of spared WM, which contains the reticulospinal and propriospinal tracts. Normal tcMMEP latencies were recorded in control, all of 100-kdyn-injured and half of 125-kdyn-injured animals. Delayed latency responses were recorded in some of 125-kdyn-injured and all of 150-kdyn-injured animals. No tcMMEP responses were recorded in 175- and 200-kdyn-injured animals. Comparison of tcMMEP responses with areas of WM loss or demyelination identified the medial ventrolateral funiculus (VLF) as the location of the tcMMEP pathway. Immunohistochemical and electromicroscopic (EM) analyses showed the presence of demyelinated axons in WM tracts surrounding the lesion cavities at 28 days postinjury. These data support the notion that widespread WM damage in the ventral and lateral funiculi may be a major cause for locomotor deficits and lack of tcMMEP responses after SCI. PMID:15629760

  4. Functionalization and Characterization of Metal Oxide Coatings of Stainless Steel and Silica Nanoparticles

    NASA Astrophysics Data System (ADS)

    Slaney, Anne Margaret

    The development of tolerogens, fabricated devices eliciting tolerance toward incompatible donor ABO antigens in implant patients, is the ultimate goal of this project. This would permit ABO incompatible organ transplants, increase the donor pool for patients, increase efficiency in the use of available organs, reduce waitlist times and reduce mortality rates of patients. Stainless steel stents and silica nanoparticles were chosen as platforms for the stationary and circulating tolerogens. Stainless steel was coated with silica by solgel dip-coating, electrodeposition, and atomic layer deposition (ALD). The coatings were evaluated by CV, EIS, SEM, AFM, VASE, FTIR, XPS, and AES. Of the silica films, those deposited by ALD provided superior insulating, conformal, and thin coatings. These silica ALD films outperformed even titania ALD films upon stressing. Silica ALD films were subsequently functionalized with mixtures of silane derivatives of poly(ethylene glycol) (PEG), to prevent nonspecific protein binding, and monosaccharides (MS) or trisaccharide and tetrasaccharide (TS) antigens. Functionalizations were characterized by FTIR, XPS and UV-Vis following enzyme-linked lectin assays (ELLAs) or enzyme-linked immunosorbent assays (ELISAs). Effective functionalization allowing biological availability and activity even after incubation in blood plasma was confirmed. Microarray microscope slides were similarly developed with all ABO antigen subtypes, characterized by ToF-SIMS and ELISA, and proved useful in detecting antibodies in human blood samples. Silica nanoparticles, including fluorescent and magnetic varieties, in a range of sizes were prepared by sol-gel synthesis. The nanoparticles were evaluated by SEM, DLS, zeta potential measurements, fluorescence imaging, flow cytometry, two-photon excitation fluorescence correlation spectroscopy and TEM. Different dye incorporation methods were used for effective detection of NPs, and additional silica layers improved

  5. Calcium as a superior coating metal in functionalization of carbon fullerenes for high-capacity hydrogen storage

    SciTech Connect

    Yoon, Mina; Yang, Shenyuan; Hicke, Christian; Wang, Enge; Geohegan, David B; Zhang, Zhenyu

    2008-01-01

    We explore theoretically the feasibility of functionalizing carbon nanostructures for hydrogen storage, focusing on the coating of C60 fullerenes with light alkaline-earth metals. Our first-principles density functional theory studies show that both Ca and Sr can bind strongly to the C60 surface, and highly prefer monolayer coating, thereby explaining existing experimental observations. The strong binding is attributed to an intriguing charge transfer mechanism involving the empty d levels of the metal elements. The charge redistribution, in turn, gives rise to electric fields surrounding the coated fullerenes, which can now function as ideal attractors upon molecular hydrogen adsorption with binding strengths strong enough for potential room temperature applications but weak enough to avoid H2 dissociation. With a hydrogen uptake of >8.4wt% on Ca32C60, Ca is superior to all the recently suggested metal coating elements.

  6. Hydroxyapatite nanocrystals functionalized with alendronate as bioactive components for bone implant coatings to decrease osteoclastic activity

    NASA Astrophysics Data System (ADS)

    Bosco, Ruggero; Iafisco, Michele; Tampieri, Anna; Jansen, John A.; Leeuwenburgh, Sander C. G.; van den Beucken, Jeroen J. J. P.

    2015-02-01

    The integration of bone implants within native bone tissue depends on periprosthetic bone quality, which is severely decreased in osteoporotic patients. In this work, we have synthesized bone-like hydroxyapatite nanocrystals (nHA) using an acid-base neutralization reaction and analysed their physicochemical properties. Subsequently, we have functionalized the nHA with alendronate (nHAALE), a well-known bisphosphonate drug used for the treatment of osteoporosis. An in vitro osteoclastogenesis test was carried out to evaluate the effect of nHAALE on the formation of osteoclast-like cells from monocytic precursor cells (i.e. RAW264.7 cell line) showing that nHAALE significantly promoted apoptosis of osteoclast-like cells. Subsequently, nHA and nHAALE were deposited on titanium disks using electrospray deposition (ESD), for which characterisation of the deposited coatings confirmed the presence of alendronate in nHAALE coatings with nanoscale thickness of about 700 nm. These results indicate that alendronate linked to hydroxyapatite nanocrystals has therapeutic potential and nHAALE can be considered as an appealing coating constituent material for orthopaedic and oral implants for application in osteoporotic patients.

  7. Controlled Design of Functional Nano-Coatings: Reduction of Loss Mechanisms in Photoelectrochemical Water Splitting.

    PubMed

    Landsmann, Steve; Surace, Yuri; Trottmann, Matthias; Dilger, Stefan; Weidenkaff, Anke; Pokrant, Simone

    2016-05-18

    Efficient water splitting with photoelectrodes requires highly performing and stable photoactive materials. Since there is no material known which fulfills all these requirements because of various loss mechanisms, we present a strategy for efficiency enhancement of photoanodes via deposition of functional coatings in the nanometer range. Origins of performance losses in particle-based oxynitride photoanodes were identified and specifically designed coatings were deposited to address each loss mechanism individually. Amorphous TiO2 located at interparticle boundaries enables high electron conductivity. A thin layer of amorphous Ta2O5 can be used as protection layer for photoanodes because of its hole conductivity and thermal and chemical stability. An amorphous layer of NiOx and Co(OH)2 reduces photocorrosion or increases water oxidation kinetics because they act as a hole-capture material or water oxidation catalyst, respectively. Crystalline CoOx nanoparticles increase photocurrent and reduce the onset potential due to enhanced charge separation. The combination of all coatings deposited by a scalable, mild, and reproducible step-by-step approach leads to high-performance oxynitride-based photoanodes providing a maximum photocurrent of 2.52 mA/cm(2) at 1.23 VRHE under AM1.5G illumination. PMID:27159411

  8. How preschool executive functioning predicts several aspects of math achievement in Grades 1 and 3: A longitudinal study.

    PubMed

    Viterbori, Paola; Usai, M Carmen; Traverso, Laura; De Franchis, Valentina

    2015-12-01

    This longitudinal study analyzes whether selected components of executive function (EF) measured during the preschool period predict several indices of math achievement in primary school. Six EF measures were assessed in a sample of 5-year-old children (N = 175). The math achievement of the same children was then tested in Grades 1 and 3 using both a composite math score and three single indices of written calculation, arithmetical facts, and problem solving. Using previous results obtained from the same sample of children, a confirmatory factor analysis examining the latent EF structure in kindergarten indicated that a two-factor model provided the best fit for the data. In this model, inhibition and working memory (WM)-flexibility were separate dimensions. A full structural equation model was then used to test the hypothesis that math achievement (the composite math score and single math scores) in Grades 1 and 3 could be explained by the two EF components comprising the kindergarten model. The results indicate that the WM-flexibility component measured during the preschool period substantially predicts mathematical achievement, especially in Grade 3. The math composite scores were predicted by the WM-flexibility factor at both grade levels. In Grade 3, both problem solving and arithmetical facts were predicted by the WM-flexibility component. The results empirically support interventions that target EF as an important component of early childhood mathematics education. PMID:26218333

  9. Promoting effects of an extended photoperiod treatment on the condition of hair coats and gonadal function in Thoroughbred weanlings

    PubMed Central

    HARADA, Takehiro; NAMBO, Yasuo; ISHIMARU, Mutsuki; SATO, Fumio; NAGAOKA, Kentaro; WATANABE, Gen; TAYA, Kazuyoshi

    2016-01-01

    ABSTRACT The effects of an extended photoperiod (EP) treatment (14.5 hr light, 9.5 hr dark) on Thoroughbred colts and fillies from December 25 at 7–9 months old to the following May at 12–14 months old on coat condition and gonadal functions were investigated. Coat condition was evaluated in April. The colts and fillies in the EP treatment group changed from winter to summer coats (molting of winter coats), whereas those in the control group did not. To determine the day of first ovulation, the plasma concentrations of progesterone were measured once a month in fillies. The day of first ovulation was advanced in the EP treatment fillies compared with the control fillies. The present study clearly demonstrated that the EP treatment advanced the molting of winter coats and advanced ovulation in fillies, even in weanlings. PMID:26858581

  10. Promoting effects of an extended photoperiod treatment on the condition of hair coats and gonadal function in Thoroughbred weanlings.

    PubMed

    Harada, Takehiro; Nambo, Yasuo; Ishimaru, Mutsuki; Sato, Fumio; Nagaoka, Kentaro; Watanabe, Gen; Taya, Kazuyoshi

    2015-01-01

    The effects of an extended photoperiod (EP) treatment (14.5 hr light, 9.5 hr dark) on Thoroughbred colts and fillies from December 25 at 7-9 months old to the following May at 12-14 months old on coat condition and gonadal functions were investigated. Coat condition was evaluated in April. The colts and fillies in the EP treatment group changed from winter to summer coats (molting of winter coats), whereas those in the control group did not. To determine the day of first ovulation, the plasma concentrations of progesterone were measured once a month in fillies. The day of first ovulation was advanced in the EP treatment fillies compared with the control fillies. The present study clearly demonstrated that the EP treatment advanced the molting of winter coats and advanced ovulation in fillies, even in weanlings. PMID:26858581

  11. Focusing X-rays to a 1-{mu}m spot using elastically bent, graded multilayer coated mirrors

    SciTech Connect

    Underwood, J.H.; Thompson, A.C.; Kortright, J.B.

    1997-04-01

    In the x-ray fluorescent microprobe at beamline 10.3.1, the ALS bending magnet source is demagnified by a factor of several hundred using a pair of mirrors arranged in the Kirkpatrick-Baez (K-B) configuration. These are coated with multilayers to increase reflectivity and limit the pass band of the x-rays striking the sample. The x-rays excite characteristic fluorescent x-rays of elements in the sample, which are analyzed by an energy dispersive Si-Li detector, for a sensitive assay of the elemental content. By scanning the focal spot the spatial distribution of the elements is determined; the spatial resolution depends on the size of this spot. When spherical mirrors are used, the spatial resolution is limited by aberrations to 5 or 10 {mu}m. This has been improved to 1 {mu}m through the use of an elliptical mirror formed by elastically bending a plane mirror of uniform width and thickness with the optimum combination of end couples.

  12. Surface modification of ultrafiltration membranes by grafting glycine-functionalized PVA based on polydopamine coatings

    NASA Astrophysics Data System (ADS)

    Li, Fang; Ye, Jianfeng; Yang, Linming; Deng, Chunhua; Tian, Qing; Yang, Bo

    2015-08-01

    Due to the ease of processing and stability during filtration, polydopamine (PD) coatings with grafted hydrophilic polymers have recently received significant attention. In this study, glycine-functionalized PVA was synthesized and grafted to a PD-coated ultrafiltration (UF) membrane to improve its performance during wastewater filtration. The membranes were modified by grafting PD with glycine-functionalized PVA (PD-g-PVA), and the resultant materials were characterized using surface morphology analyses, contact angle measurements, flux, oil/water emulsion separation tests, and grafted layer stability tests. The performance of the PD-g-PVA membrane was compared to that of the membrane modified with PD-g-polyethylene glycol (PEG). After grafting the PD-g-PVA, the surface roughness of the membranes decreased significantly. The grafted PVA layer, which was stable under acidic and alkaline conditions, protected the PD layer. The filtration experiments with an oil/water emulsion indicated that modifying the glycine-functionalized PVA by grafting can significantly improve the antifouling ability of membranes.

  13. Surface roughness of anodized titanium coatings.

    SciTech Connect

    Dugger, Michael Thomas; Chinn, Douglas Alan

    2010-10-01

    Samples of grade five 6Al4V titanium alloy were coated with two commercial fluoropolymer anodizations (Tiodize and Canadize) and compared. Neither coating demonstrates significant outgassing. The coatings show very similar elemental analysis, except for the presence of lead in the Canadize coating, which may account for its lower surface friction in humid environments. Surface roughness has been compared by SEM, contact profilometry, optical profilometry, power spectral density and bidirectional scattering distribution function (BSDF). The Tiodize film is slightly smoother by all measurement methods, but the Canadize film shows slightly less scatter at all angles of incidence. Both films exhibited initial friction coefficients of 0.2 to 0.4, increasing to 0.4 to 0.8 after 1000 cycles of sliding due to wear of the coating and ball. The coatings are very similar and should behave identically in most applications.

  14. Functioning mechanism of AlF3 coating on the Li- and Mn-rich cathode materials

    SciTech Connect

    Zheng, Jianming; Gu, Meng; Xiao, Jie; Polzin, Bryant; Yan, Pengfei; Chen, Xilin; Wang, Chong M.; Zhang, Jiguang

    2014-11-25

    Li- and Mn-rich (LMR) material is a very promising cathode for lithium ion batteries because of their high theoretical energy density (~900 Wh kg-1) and low cost. However, their poor long-term cycling stability, voltage fade, and low rate capability are significant barriers hindered their practical applications. Surface coating, e.g. AlF3 coating, can significantly improve the capacity retention and enhance the rate capability. However, the fundamental mechanism of this improvement and the microstructural evolution related to the surface coating is still not well understood. Here, we report systematic studies of the microstructural changes of uncoated and AlF3-coated materials before and after cycling using aberration-corrected scanning/transmission electron microscopy and electron energy loss spectroscopy. The results reveal that surface coating can reduce the oxidation of electrolyte at high voltage, thus suppressing the accumulation of SEI layer on electrode particle surface. Surface coating also enhances structural stability of the surface region (especially the electrochemically transformed spinel-like phase), and protects the electrode from severe etching/corrosion by the acidic species in the electrolyte, therefore limiting the degradation of the material. Moreover, surface coating can alleviate the undesirable voltage fade by minimize layered-spinel phase transformation in the bulk region of the materials. These fundamental findings may also be widely applied to explain the functioning mechanism of other surface coatings used in a broad range of electrode materials.

  15. Nonlinear analysis of thermally and electrically actuated functionally graded material microbeam

    PubMed Central

    Li, Yingli; Meguid, S. A.; Fu, Yiming; Xu, Daolin

    2014-01-01

    In this paper, we provide a unified and self-consistent treatment of a functionally graded material (FGM) microbeam with varying thermal conductivity subjected to non-uniform or uniform temperature field. Specifically, it is our objective to determine the effect of the microscopic size of the beam, the electrostatic gap, the temperature field and material property on the pull-in voltage of the microbeam under different boundary conditions. The non-uniform temperature field is obtained by integrating the steady-state heat conduction equation. The governing equations account for the microbeam size by introducing an internal material length-scale parameter that is based on the modified couple stress theory. Furthermore, it takes into account Casimir and van der Waals forces, and the associated electrostatic force with the first-order fringing field effects. The resulting nonlinear differential equations were converted to a coupled system of algebraic equations using the differential quadrature method. The outcome of our work shows the dramatic effect and dependence of the pull-in voltage of the FGM microbeam upon the temperature field, its gradient for a given boundary condition. Specifically, both uniform and non-uniform thermal loading can actuate the FGM microbeam even without an applied voltage. Our work also reveals that the non-uniform temperature field is more effective than the uniform temperature field in actuating a FGM cantilever-type microbeam. For the clamped-clamped case, care must be taken to account for the effective use of thermal loading in the design of microbeams. It is also observed that uniform thermal loading will lead to a reduction in the pull-in voltage of a FGM microbeam for all the three boundary conditions considered. PMID:24511250

  16. Vibro-acoustic response and sound transmission loss analysis of functionally graded plates

    NASA Astrophysics Data System (ADS)

    Chandra, N.; Raja, S.; Nagendra Gopal, K. V.

    2014-10-01

    This paper presents analytical studies on the vibro-acoustic and sound transmission loss characteristics of functionally graded material (FGM) plates using a simple first-order shear deformation theory. The material properties of the plate are assumed to vary according to power law distribution of the constituent materials in terms of volume fraction. The sound radiation due to sinusoidally varying point load, uniformly distributed load and obliquely incident sound wave is computed by solving the Rayleigh integral with a primitive numerical scheme. Displacement, velocity, acceleration, radiated sound power level, radiated sound pressure level and radiation efficiency of FGM plate for varying power law index are examined. The sound transmission loss of the FGM plate for several incidence angles and varying power law index is studied in detail. It has been found that, for the plate being considered, the sound power level increases monotonically with increase in power law index at lower frequency range (0-500 Hz) and a non-monotonic trend is appeared towards higher frequencies for both point and distributed force excitations. Increased vibration and acoustic response is observed for ceramic-rich FGM plate at higher frequency band; whereas a similar trend is seen for metal-rich FGM plate at lower frequency band. The dBA values are found to be decreasing with increase in power law index. The radiation efficiency of ceramic-rich FGM plate is noticed to be higher than that of metal and metal-rich FGM plates. The transmission loss below the first resonance frequency is high for ceramic-rich FGM plate and low for metal-rich FGM plate and further depends on the specific material property. The study has found that increased transmission loss can be achieved at higher frequencies with metal-rich FGM plates.

  17. Fast plasma sintering delivers functional graded materials components with macroporous structures and osseointegration properties.

    PubMed

    Godoy, R F; Coathup, M J; Blunn, G W; Alves, A L; Robotti, P; Goodship, A E

    2016-01-01

    We explored the osseointegration potential of two macroporous titanium surfaces obtained using fast plasma sintering (FPS): Ti macroporous structures with 400-600 µmØ pores (TiMac400) and 850-1000 µmØ pores (TiMac850). They were compared against two surfaces currently in clinical use: Ti-Growth® and air plasma spray (Ti-Y367). Each surface was tested, once placed over a Ti-alloy and once onto a CoCr bulk substrate. Implants were placed in medial femoral condyles in 24 sheep. Samples were explanted at four and eight weeks after surgery. Push-out loads were measured using a material-testing system. Bone contact and ingrowth were assessed by histomorphometry and SEM and EDX analyses. Histology showed early osseointegration for all the surfaces tested. At 8 weeks, TiMac400, TiMac850 and Ti-Growth® showed deep bone ingrowth and extended colonisation with newly formed bone. The mechanical push-out force was equal in all tested surfaces. Plasma spray surfaces showed greater bone-implant contact and higher level of pores colonisation with new bone than FPS produced surfaces. However, the void pore area in FPS specimens was significantly higher, yet the FPS porous surfaces allowed a deeper osseointegration of bone to implant. FPS manufactured specimens showed similar osseointegration potential to the plasma spray surfaces for orthopaedic implants. FPS is a useful technology for manufacturing macroporous titanium surfaces. Furthermore, its capability to combine two implantable materials, using bulk CoCr with macroporous titanium surfaces, could be of interest as it enables designers to conceive and manufacture innovative components. FPS delivers functional graded materials components with macroporous structures optimised for osseointegration. PMID:27071735

  18. Nonlinear analysis of thermally and electrically actuated functionally graded material microbeam.

    PubMed

    Li, Yingli; Meguid, S A; Fu, Yiming; Xu, Daolin

    2014-02-01

    In this paper, we provide a unified and self-consistent treatment of a functionally graded material (FGM) microbeam with varying thermal conductivity subjected to non-uniform or uniform temperature field. Specifically, it is our objective to determine the effect of the microscopic size of the beam, the electrostatic gap, the temperature field and material property on the pull-in voltage of the microbeam under different boundary conditions. The non-uniform temperature field is obtained by integrating the steady-state heat conduction equation. The governing equations account for the microbeam size by introducing an internal material length-scale parameter that is based on the modified couple stress theory. Furthermore, it takes into account Casimir and van der Waals forces, and the associated electrostatic force with the first-order fringing field effects. The resulting nonlinear differential equations were converted to a coupled system of algebraic equations using the differential quadrature method. The outcome of our work shows the dramatic effect and dependence of the pull-in voltage of the FGM microbeam upon the temperature field, its gradient for a given boundary condition. Specifically, both uniform and non-uniform thermal loading can actuate the FGM microbeam even without an applied voltage. Our work also reveals that the non-uniform temperature field is more effective than the uniform temperature field in actuating a FGM cantilever-type microbeam. For the clamped-clamped case, care must be taken to account for the effective use of thermal loading in the design of microbeams. It is also observed that uniform thermal loading will lead to a reduction in the pull-in voltage of a FGM microbeam for all the three boundary conditions considered. PMID:24511250

  19. Inkjet printing of Chitlac-nanosilver--a method to create functional coatings for non-metallic bone implants.

    PubMed

    Nganga, Sara; Moritz, Niko; Kolakovic, Ruzica; Jakobsson, Kristina; Nyman, Johan O; Borgogna, Massimiliano; Travan, Andrea; Crosera, Matteo; Donati, Ivan; Vallittu, Pekka K; Sandler, Niklas

    2014-12-01

    Biostable fiber-reinforced composites, based on bisphenol-A-dimethacrylate and triethyleneglycoldimethacrylate thermoset polymer matrix reinforced with E-glass fibers have been successfully used in cranial reconstructions and the material has been approved for clinical use. As a further refinement of these implants, antimicrobial, non-cytotoxic coatings on the composites were created by an immersion procedure driven by strong electrostatic interactions. Silver nanoparticles (nAg) were immobilized in lactose-modified chitosan (Chitlac) to prepare the bacteriostatic coatings. Herein, we report the use of inkjet technology (a drop-on-demand inkjet printer) to deposit functional Chitlac-nAg coatings on the thermoset substrates. Characterization methods included scanning electron microscopy, scanning white light interferometry and electro-thermal atomic absorption spectroscopy. Inkjet printing enabled the fast and flexible functionalization of the thermoset surfaces with controlled coating patterns. The coatings were not impaired by the printing process: the kinetics of silver release from the coatings created by inkjet printing and conventional immersion technique was similar. Further research is foreseen to optimize printing parameters and to tailor the characteristics of the coatings for specific clinical applications. PMID:25336511

  20. Two-dimensional thermoelastic analysis of a functionally graded cylinder for different functionalities by using the higher-order shear deformation theory

    NASA Astrophysics Data System (ADS)

    Arefi, M.

    2015-05-01

    The present paper addresses application of the general shear deformation theory for the thermoelastic analysis of a functionally graded cylindrical shell subjected to inner and outer loads. The shear deformation theory and the energy method are employed for this purpose. This method presents the final relations by using a set of second-order differential equations in terms of the integral of material properties over the shell thickness. The obtained formulation can be solved for two well-known functionalities.

  1. Adsorption and functionality of fibrinogen on triblock copolymer-coated surfaces

    NASA Astrophysics Data System (ADS)

    O'Connor, Stephen Moss

    To assess the influence of the surface microenvironment on the adsorption and biologic activity of fibrinogen, a series of poly(ethylene oxide)/poly(propylene oxide) triblock copolymers were adsorbed to solid, hydrophobic polystyrene-divinylbenzene beads. The copolymers, which were of the form PEOsb{b}PPOsb{a}PEOsb{b}, varied in their hydrophile/lipophile balances (HLB) due only to differences in their PEO chain length (5 to 129 EO units) as the hydrophobic PPO core segment was of fixed length (56 or 69 PO units). The surface coverage of copolymers was determined first and after exposing the beads to fibrinogen or to human plasma, the total amount of protein adsorbed to their surface was measured. The functionality of fibrinogen bound to copolymer-modified beads was assessed in terms of fibrin clot formation and by the adherence of macrophages (THP-1 tumor cells). Enzymatic processing was used to probe the surface orientation of fibrinogen. The copolymers appear to adsorb in an expanded fashion, a conclusion supported by surface pressure-area isotherms of the copolymers spread at the air-water interface. As compared to copolymer-free surfaces, protein adsorption decreases by up to 90% as the PEO chain length of the copolymers increases. The copolymer coatings appear to lower fibrinogen adsorption by limiting the available surface area. On surfaces coated with the hydrophobic versions of the copolymers, the biologic assays demonstrate that fibrinogen is as reactive/coagulable as for surfaces with saturated coverages of fibrin despite that these copolymer-coated surfaces have 60% less fibrinogen adsorbed to them. When adsorbed at the same low surface concentration in the absence of copolymer, fibrinogen is not active. Enzymatic processing of bound fibrinogen suggests that the presence of the copolymers promote the adsorption of the protein in end-on fashion. It is proposed here, that when adsorbed end-on, fibrinogen is functional because its reactive sites are

  2. Core-shell structured carbonyl iron microspheres prepared via dual-step functionality coatings and their magnetorheological response.

    PubMed

    Fang, Fei Fei; Liu, Ying Dan; Choi, Hyoung Jin; Seo, Yongsok

    2011-09-01

    The dispersion stability of soft magnetic carbonyl iron (CI)-based magnetorheological (MR) fluids was improved by applying a unique functional coating composed of a conducting polyaniline layer and a multiwalled carbon nanotube nest to the surfaces of the CI particles via conventional dispersion polymerization, followed by facile solvent casting. The coating morphology and thickness were analyzed by SEM and TEM imaging. Chemical composition of the polyaniline layer was detected by Raman spectroscope, which also confirmed the coating performance successfully. The influence of the functional coating on the magnetic properties was investigated by measuring the MR performance and sedimentation properties using a vibrating sample magnetometer, rotational rheometer, and Turbiscan apparatus. Improved dispersion characteristics of the MR fluid were observed. PMID:21815626

  3. The Development and Production of a Functionally Graded Composite for Pb-Bi Service

    SciTech Connect

    Ballinger, Ronald G

    2011-08-01

    A material that resists lead-bismuth eutectic (LBE) attack and retains its strength at 700°C would be an enabling technology for LBE-cooled reactors. No single alloy currently exists that can economically meet the required performance criteria of high strength and corrosion resistance. A Functionally Graded Composite (FGC) was developed with layers engineered to perform these functions. F91 was chosen as the structural layer of the composite for its strength and radiation resistance. Fe-12Cr-2Si, an alloy developed from previous work in the Fe-Cr-Si system, was chosen as the corrosion-resistant cladding layer because of its chemical similarity to F91 and its superior corrosion resistance in both oxidizing and reducing environments. Fe-12Cr-2Si experienced minimal corrosion due to its self-passivation in oxidizing and reducing environments. Extrapolated corrosion rates are below one micron per year at 700ï°C. Corrosion of F91 was faster, but predictable and manageable. Diffusion studies showed that 17 microns of the cladding layer will be diffusionally diluted during the three year life of fuel cladding. 33 microns must be accounted for during the sixty year life of coolant piping. 5 cm coolant piping and 6.35 mm fuel cladding preforms were produced on a commercial scale by weld-overlaying Fe-12Cr-2Si onto F91 billets and co-extruding them. An ASME certified weld was performed followed by the prescribed quench-and-tempering heat treatment for F91. A minimal heat affected zone was observed, demonstrating field weldability. Finally, corrosion tests were performed on the fabricated FGC at 700ï°C after completely breaching the cladding in a small area to induce galvanic corrosion at the interface. None was observed. This FGC has significant impacts on LBE reactor design. The increases in outlet temperature and coolant velocity allow a large increase in power density, leading to either a smaller core for the same power rating or more power output for the same size

  4. Coated zinc oxide improves intestinal immunity function and regulates microbiota composition in weaned piglets.

    PubMed

    Shen, Junhua; Chen, Yan; Wang, Zhisheng; Zhou, Anguo; He, Miao; Mao, Lei; Zou, Huawei; Peng, Quanhui; Xue, Bai; Wang, Lizhi; Zhang, Xiangfei; Wu, Shilin; Lv, Yong

    2014-06-28

    The present study was conducted to test the hypothesis that low concentrations of coated ZnO, as a substitute for a high concentration of ZnO (2250 mg Zn/kg), could improve intestinal immunity function and regulate microbiota composition, thus alleviating the incidence of diarrhoea in weaned piglets. A total of eighty-four cross-bred piglets, weaned at an age of 28 (SEM 1) d, were allocated randomly, on the basis of average initial body weight (7·72 (SEM 0·65) kg), to seven treatment groups as follows: a 250 mg Zn (ZnO)/kg group (low Zn; LZ) and a 2250 mg Zn (ZnO)/kg group (high Zn; HZ) that were offered diets containing ZnO at 250 and 2250 mg Zn/kg, respectively; and five experimental groups in which coated ZnO was added at 250, 380, 570, 760 and 1140 mg Zn/kg basal diet, respectively. The trial lasted 2 weeks. The results indicated that, compared with LZ treatment, supplementation with coated ZnO at 380 or 570 mg Zn/kg reduced (P< 0·05) diarrhoea index, increased (P< 0·05) duodenal villus height and the ratio of villus height:crypt depth, up-regulated (P< 0·05) the gene expression of insulin-like growth factor 1, zonula occludens protein-1, occludin, IL-10 and transforming growth factor β1, and elevated (P< 0·05) secretory IgA concentration in the jejunal mucosa. Microbiota richness and the Shannon diversity index were also decreased (P< 0·05). Furthermore, piglets in the group fed coated ZnO at 380 or 570 mg Zn/kg did not differ from those in the HZ-fed group in relation to the aforementioned parameters. Collectively, a low concentration of coated ZnO (380 or 570 mg Zn/kg) can alleviate the incidence of diarrhoea by promoting intestinal development, protecting the intestinal mucosal barrier from damage, stimulating the mucosal immune system and regulating the microbiota composition. PMID:24606984

  5. Characterization and selection of suitable grades of lactose as functional fillers for capsule filling: part 1.

    PubMed

    Moolchandani, Vikas; Augsburger, Larry L; Gupta, Abhay; Khan, Mansoor; Langridge, John; Hoag, Stephen W

    2015-01-01

    The purpose of this work is to characterize thermal, physical and mechanical properties of different grades of lactose and better understand the relationships between these properties and capsule filling performance. Eight grades of commercially available lactose were evaluated: Pharmatose 110 M, 125 M, 150 M, 200 M, 350 M (α-lactose monohydrate), AL (anhydrous lactose containing ∼80% β-AL), DCL11 (spray dried α-lactose monohydrate containing ∼15% amorphous lactose) and DCL15 (granulated α-lactose monohydrate containing ∼12% β-AL). In this study, different lactose grades were characterized by thermal, solid state, physical and mechanical properties and later evaluated using principal component analysis (PCA) to assess the inter-relationships among some of these properties. The lactose grades were characterized by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-ray diffraction (XRD), moisture sorption/desorption isotherms, particle size distribution; the flow was characterized by Carr Index (CI), critical orifice diameter (COD) and angle of friction. Plug mechanical strength was estimated from its diametric crushing strength. The first and second principal components (PC) captured 47.6% and 27.4% of variation in the physical and mechanical property data, respectively. The PCA plot grouped together 110 M, AL, DCL11 and DCL15 on the one side of plot which possessed superior properties for capsule formulation and these grades were selected for future formulation development studies (part II of this work). PMID:25212639

  6. [Grading of the functional sport shoe parameter "cushioning" and "forefoot flexibility" on running shoes].

    PubMed

    Kleindienst, F I; Krabbe, B; Walther, M; Brüggemann, G-P

    2006-03-01

    On nearly every running event a heterogeneous structure of participants regarding body height and body weight can be observed. This study should figure out whether the running shoe manufacturers will consider this anthropometric variability. Moreover it should be investigated the runners needs based on different anthropometrics regarding preferred cushioning and forefoot flexibility properties. In order to check whether the running shoe manufacturers will apply a grading pattern, a dynamic material study with conventional running shoes in different sizes was conducted. In a second step a field study in Middle Europe and North America with 244 female and 227 male runners was organized. Every subject had to run and evaluate 7 different shoe modifications. Based on the material study it is to state, that the running shoe manufacturers currently do not consider a systematic grading of cushioning and forefoot flexibility properties. In contrast to this, the field study reveals the necessity to grade these properties. A shoe size dependent and a geographic grading concept are suggested. It is supposed, that the application of these grading concepts do not only provide a comfort improvement, but they also contribute to a reduction of joint loads of the lower extremities and consequently to a prevention of overuse injuries. PMID:16544212

  7. PREFACE: Low temperature Plasma in the Processes of Functional Coating Preparation

    NASA Astrophysics Data System (ADS)

    Gali Yunusovich, Dautov; Kashapov Faikovich, Nail; Larionov, Viktor; Gerfanovich Zaripov, Renat; Galyautdinov Tagirovich, Raphael; Ilnaz, Fayrushin; Ramil Nailevich, Kashapov

    2013-12-01

    In November 2013 the V Republican Scientific Technical Conference 'Low-temperature plasma during the deposition of functional coatings' was held in Kazan. The Conference took place from 4-7 November at the Academy of Sciences of the Republic of Tatarstan and Kazan Federal University chaired by a member of the Academy of Sciences of the Republic of Tatarstan Nail Kashapov, Professor, Doctor of Technical Science, and a member of the Scientific and Technical Council of the Ministry of Economy of the Republic of Tatarstan. At the conference, the participants were offered a wide range of issues affecting the theoretical and computational aspects of the research problems in the physics and technology of low-temperature plasma. There was also a whole series of works devoted to the study of thin films, obtained by low-temperature plasma. For the second year at this conference, work dedicated to the related field of pulsation combustion and low- temperature plasma was considered. In addition much interest is devoted to reports on the exploration of gas discharges with liquid electrolytic electron trodes and the study of dusty plasmas. The VI All-Russian Conference 'Low-temperature plasma during the deposition of functional coatings', an extended version with international participation, is scheduled to take place in November 2014. Nail Kashapov Editor

  8. ENHANCED SAFEGUARDS: THE ROLE OF SMART FUNCTIONAL COATINGS FOR TAMPER INDICATION

    SciTech Connect

    Mendez-Torres, A.; Martinez-Rodriguez, M.; Brinkman, K.; Krementz, D.

    2012-02-24

    This work investigates the synthesis of smart functional coatings (SFC) using chemical solution deposition methods. Chemical solution deposition methods have recently received attention in the materials research community due to several unique advantages that include low temperature processing, high homogeneity of final products, the ability to fabricate materials with controlled surface properties and pore structures, and the ease of dopant incorporation in controlled concentrations. The optical properties of thin films were investigated using UV-Vis spectroscopy, Raman, SEM and EDS, with the aim of developing a protective transparent coating for a ceramic surface as a first line of defense for tamper indication. The signature produced by the addition of rare earth dopants will be employed as an additional tamper indicating feature. The integration of SFC's as part of a broader verification system such as an electronic seals can provide additional functionality and defense in depth. SFC's can improve the timeliness of detection by providing a robust, in-situ verifiable tamper indication framework.

  9. Note: Automatic layer-by-layer spraying system for functional thin film coatings

    NASA Astrophysics Data System (ADS)

    Seo, Seongmin; Lee, Sangmin; Park, Yong Tae

    2016-03-01

    In this study, we have constructed an automatic spray machine for producing polyelectrolyte multilayer films containing various functional materials on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits advantages in terms of automation, process speed, and versatility. Furthermore, it has several features that allow a fully automated spraying operation, such as various two-dimensional spraying paths, control of the flow rate and operating speed, air-assist fan-shaped twin-fluid nozzles, and an optical display. The robot uniformly sprays aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species onto a large-area substrate. Between each deposition of opposite species, samples are spray-rinsed with deionized water and blow-dried with air. The spraying, rinsing, and drying areas and times are adjustable by a computer program. Twenty-bilayer flame-retardant thin films were prepared in order to compare the performance of the spray-assisted LbL assembly with a sample produced by conventional dipping. The spray-coated film exhibited a reduction of afterglow time in vertical flame tests, indicating that the spray-LbL technique is a simple method to produce functional thin film coatings.

  10. Magnetic nanoparticles coated with maltose-functionalized polyethyleneimine for highly efficient enrichment of N-glycopeptides.

    PubMed

    Li, Jinan; Wang, Fangjun; Wan, Hao; Liu, Jing; Liu, Zheyi; Cheng, Kai; Zou, Hanfa

    2015-12-18

    Hydrophilic interaction chromatography (HILIC) adsorbents have drawn increasing attention in recent years due to their high efficiency in N-glycopeptides enrichment. The hydrophilicity and binding capacity of HILIC adsorbents are crucial to the enrichment efficiency and mass spectrometry (MS) detection sensitivity of N-glycopeptides. Herein, magnetic nanoparticles coated with maltose-functionalized polyethyleneimine (Fe3O4-PEI-Maltose MNPs) were prepared by one-pot solvothermal reaction coupled with "click chemistry" and utilized for N-glycopeptides enrichment. Owing to the presence of hydrophilic and branched polyethyleneimine, the amount of immobilized disaccharide units was improved about four times. The N-glycopeptides capturing capacity was about 150mg/g (IgG/MNPs) and the MS detection limitation as low as 0.5fmol for IgG and 85% average enrichment recovery were feasibly achieved by using this hybrid magnetic adsorbent. Finally, 1237 unique N-glycosylation sites and 1567 unique N-glycopeptides from 684 N-glycoproteins were reliably characterized from 60μg protein sample extracted from mouse liver. Therefore, this maltose-functionalized polyethyleneimine coated adsorbent can play a promising role in highly efficient N-glycopeptides enrichment for glycoproteomic analyses of complex protein samples. PMID:26607318

  11. Diversity and function of maize pollen coat proteins: from biochemistry to proteomics

    PubMed Central

    Gong, Fangping; Wu, Xiaolin

    2015-01-01

    Maize (Zea mays L.) is globally cultivated as one of the most important grain crops. As a wind-pollinated species, maize produces a large quantity of pollen grains that heavier and larger compared to Arabidopsis. Maize is an important model plant in pollen biology of monocots. The pollen coat, the outermost layer of pollen, plays a vital role in pollen–stigma interactions and successful fertilization. Pollen coat proteins (PCPs), which confer species specificity, are required for pollen adhesion, recognition, hydration, and germination on the stigma. Thus, PCPs have attracted intensive research efforts in plant science for decades. However, only a few PCPs in maize have been characterized to date, whereas the functions of most maize PCPs remain unclear. In this review, we summarize the current knowledge of maize PCPs with regard to protein constituents, synthesis and transport, and functions by comparison with the model plant Arabidopsis thaliana and Brassica plants. An understanding of the comprehensive knowledge of maize PCPs will help to illuminate the mechanism by which PCPs are involved in pollen–stigma interactions in maize and other crop plants. PMID:25870606

  12. Surface functionalization of silica-coated magnetic nanoparticles for covalent attachment of cholesterol oxidase

    NASA Astrophysics Data System (ADS)

    Šulek, Franja; Drofenik, Miha; Habulin, Maja; Knez, Željko

    2010-01-01

    A systematic approach towards the fabrication of highly functionalized silica shell magnetic nanoparticles, presently used for enzyme immobilization, is herein fully presented. The synthesis of bare maghemite (γ-Fe 2O 3) nanoparticles was accomplished by thermal co-precipitation of iron ions in ammonia alkaline solution at harsh reaction conditions, respectively. Primary surface engineering of maghemite nanoparticles was successfully performed by the proper deposition of silica onto nanoparticles surface under strictly regulated reaction conditions. Next, the secondary surface functionalization of the particles was achieved by coating the particles with organosilane followed by glutaraldehyde activation in order to enhance protein immobilization. Covalent immobilization of cholesterol oxidase was attempted afterwards. The structural and magnetic properties of magnetic silica nanocomposites were characterized by TEM and vibrating sample magnetometer (VSM) instruments. X-ray diffraction measurements confirmed the spinel structure and average size of uncoated maghemite nanoparticles to be around 20 nm in diameter. SEM-EDS spectra indicated a strong signal for Si, implying the coating procedure of silica onto the particles surface to be successfully accomplished. Fourier transform infrared (FT-IR) spectra analysis confirmed the binding of amino silane molecules onto the surface of the maghemite nanoparticles mediated Si-O-Si chemical bonds. Compared to the free enzyme, the covalently bound cholesterol oxidase retained 50% of its activity. Binding of enzyme onto chemically modified magnetic nanoparticles via glutaraldehyde activation is a promising method for developing biosensing components in biomedicine.

  13. Succinate Functionalization of Hyperbranched Polyglycerol-Coated Magnetic Nanoparticles as a Draw Solute During Forward Osmosis.

    PubMed

    Yang, Hee-Man; Choi, Hye Min; Jang, Sung-Chan; Han, Myeong Jin; Seo, Bum-Kyoung; Moon, Jei-Kwon; Lee, Kune-Woo

    2015-10-01

    Hyperbranched polyglycerol-coated magnetic nanoparticles (SHPG-MNPs) were functionalized with succinate groups to form a draw solute for use in a forward osmosis (FO). After the one-step synthesis of hyperbranched polyglycerol-coated magnetic nanoparticles (HPG-MNPs), the polyglycerol groups on the surfaces of the HPG-MNPs were functionalized with succinic anhydride moieties. The resulting SHPG-MNPs showed no change of size and magnetic property compared with HPG-MNPs and displayed excellent dispersibility in water up to the concentration of 400 g/L. SHPG-MNPs solution showed higher osmotic pressure than that of HPG-MNPs solution due to the presence of surface carboxyl groups in SHPG-MNPs and could draw water from a feed solution across an FO membrane without any reverse draw solute leakage during FO process. Moreover, the water flux remained nearly constant over several SHPG-MNP darw solute regeneration cycles applied to the ultrafiltration (UF) process. The SHPG-MNPs demonstrate strong potential for use as a draw solute in FO processes. PMID:26726503

  14. New biobased high functionality polyols and their use in polyurethane coatings.

    PubMed

    Pan, Xiao; Webster, Dean C

    2012-02-13

    High-functionality polyols for application in polyurethanes (PUs) were prepared by epoxide ring-opening reactions from epoxidized sucrose esters of soybean oil-epoxidized sucrose soyates-in which secondary hydroxyl groups were generated from epoxides on fatty acid chains. Ester polyols were prepared by using a base-catalyzed acid-epoxy reaction with carboxylic acids (e.g., acetic acid); ether polyols were prepared by using an acid-catalyzed alcohol-epoxy reaction with monoalcohols (e.g., methanol). The polyols were characterized by using gel permeation chromatography, FTIR spectroscopy, (1)H NMR spectroscopy, differential scanning calorimetry (DSC), and viscosity measurements. PU thermosets were prepared by using aliphatic polyisocyanates based on isophorone diisocyanate and hexamethylene diisocyanate. The properties of the PUs were studied by performing tensile testing, dynamic mechanical analysis, DSC, and thermogravimetric analysis. The properties of PU coatings on steel substrates were evaluated by using ASTM methods to determine coating hardness, adhesion, solvent resistance, and ductility. Compared to a soy triglyceride polyol, sucrose soyate polyols provide greater hardness and range of cross-link density to PU thermosets because of the unique structure of these macromolecules: well-defined compact structures with a rigid sucrose core coupled with high hydroxyl group functionality. PMID:22271418

  15. A photoemission model for low work function coated metal surfaces and its experimental validation

    NASA Astrophysics Data System (ADS)

    Jensen, Kevin L.; Feldman, Donald W.; Moody, Nathan A.; O'Shea, Patrick G.

    2006-06-01

    Photocathodes are a critical component many linear accelerator based light sources. The development of a custom-engineered photocathode based on low work function coatings requires an experimentally validated photoemission model that accounts the complexity of the emission process. We have developed a time-dependent model accounting for the effects of laser heating and thermal propagation on photoemission. It accounts for surface conditions (coating, field enhancement, and reflectivity), laser parameters (duration, intensity, and wavelength), and material characteristics (reflectivity, laser penetration depth, and scattering rates) to predict current distribution and quantum efficiency (QE) as a function of wavelength. The model is validated by (i) experimental measurements of the QE of cesiated surfaces, (ii) the QE and performance of commercial dispenser cathodes (B, M, and scandate), and (iii) comparison to QE values reported in the literature for bare metals and B-type dispenser cathodes, all for various wavelengths. Of particular note is that the highest QE for a commercial (M-type) dispenser cathode found here was measured to be 0.22% at 266 nm, and is projected to be 3.5 times larger for a 5 ps pulse delivering 0.6 mJ/cm2 under a 50 MV/m field.

  16. Functional separator consisted of polyimide nonwoven fabrics and polyethylene coating layer for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Shi, Chuan; Zhang, Peng; Huang, Shaohua; He, Xinyi; Yang, Pingting; Wu, Dezhi; Sun, Daoheng; Zhao, Jinbao

    2015-12-01

    In this paper, a composite membrane with nonwoven polyimide (PI) membrane as structural support and polyethylene (PE) particles coating layer as a thermal shutdown layer, is fabricated as the separator for lithium-ion battery. Different from PI nonwoven membrane, the PE coating PI nonwoven composite membrane (PE-PI-S) not only shows excellent thermal shutdown function, similar to traditional multilayer PP/PE/PP separator, but also exhibits much higher thermal stability, better wettability to the polar electrolyte and lower internal resistance than the PP/PE/PP separator. The electrolyte uptake and ionic conductivity of PE-PI-S increase from 58%, 0.84 mS cm-1 to 400%, 1.34 mS cm-1, respectively. Furthermore, the thermal shutdown function of PE-PI-S can be controlled widely in the temperature range from 120 °C to more than 200 °C while the multilayer PP/PE/PP separator only with a shutdown temperature range from 130 °C to 160 °C. Lithium ion battery with PE-PI-S nonwoven separator also shows excellent stable cycling and good rate performance.

  17. Note: Automatic layer-by-layer spraying system for functional thin film coatings.

    PubMed

    Seo, Seongmin; Lee, Sangmin; Park, Yong Tae

    2016-03-01

    In this study, we have constructed an automatic spray machine for producing polyelectrolyte multilayer films containing various functional materials on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits advantages in terms of automation, process speed, and versatility. Furthermore, it has several features that allow a fully automated spraying operation, such as various two-dimensional spraying paths, control of the flow rate and operating speed, air-assist fan-shaped twin-fluid nozzles, and an optical display. The robot uniformly sprays aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species onto a large-area substrate. Between each deposition of opposite species, samples are spray-rinsed with deionized water and blow-dried with air. The spraying, rinsing, and drying areas and times are adjustable by a computer program. Twenty-bilayer flame-retardant thin films were prepared in order to compare the performance of the spray-assisted LbL assembly with a sample produced by conventional dipping. The spray-coated film exhibited a reduction of afterglow time in vertical flame tests, indicating that the spray-LbL technique is a simple method to produce functional thin film coatings. PMID:27036843

  18. "A New Class od Functionally Graded Cearamic-Metal Composites for Next Generation Very High Temperature Reactors"

    SciTech Connect

    Dr. Mohit Jain; Dr. Ganesh Skandan; Dr. Gordon E. Khose; Mrs. Judith Maro, Nuclear Reactor Laboratory, MIT

    2008-05-01

    Generation IV Very High Temperature power generating nuclear reactors will operate at temperatures greater than 900 oC. At these temperatures, the components operating in these reactors need to be fabricated from materials with excellent thermo-mechanical properties. Conventional pure or composite materials have fallen short in delivering the desired performance. New materials, or conventional materials with new microstructures, and associated processing technologies are needed to meet these materials challenges. Using the concept of functionally graded materials, we have fabricated a composite material which has taken advantages of the mechanical and thermal properties of ceramic and metals. Functionally-graded composite samples with various microstructures were fabricated. It was demonstrated that the composition and spatial variation in the composition of the composite can be controlled. Some of the samples were tested for irradiation resistance to neutrons. The samples did not degrade during initial neutron irradiation testing.

  19. Transglutaminase 2 Expression Is Increased as a Function of Malignancy Grade and Negatively Regulates Cell Growth in Meningioma

    PubMed Central

    Huang, Yin-Cheng; Wei, Kuo-Chen; Chang, Chen-Nen; Chen, Pin-Yuan; Hsu, Peng-Wei; Chen, Carl P.; Lu, Chin-Song; Wang, Hung-Li; Gutmann, David H.; Yeh, Tu-Hsueh

    2014-01-01

    Most meningiomas are benign, but some clinical-aggressive tumors exhibit brain invasion and cannot be resected without significant complications. To identify molecular markers for these clinically-aggressive meningiomas, we performed microarray analyses on 24 primary cultures from 21 meningiomas and 3 arachnoid membranes. Using this approach, increased transglutaminase 2 (TGM2) expression was observed, which was subsequently validated in an independent set of 82 meningiomas by immunohistochemistry. Importantly, the TGM2 expression level was associated with increasing WHO malignancy grade as well as meningioma recurrence. Inhibition of TGM2 function by siRNA or cystamine induced meningioma cell death, which was associated with reduced AKT phosphorylation and caspase-3 activation. Collectively, these findings suggest that TGM2 expression increases as a function of malignancy grade and tumor recurrence and that inhibition of TGM2 reduces meningioma cell growth. PMID:25247996

  20. Improve the performance of coated cemented hip stem through the advanced composite materials.

    PubMed

    Hedia, H S; Fouda, N

    2015-01-01

    Design of hip joint implant using functionally graded material (FGM) (advanced composite material) has been used before through few researches. It gives great results regarding the stress distribution along the implant and bone interfaces. However, coating of orthopaedic implants has been widely investigated through many researches. The effect of using advanced composite stem material, which mean by functionally graded stem material, in the total hip replacement coated with the most common coated materials has not been studied yet. Therefore, this study investigates the effect of utilizing these two concepts together; FGM and coating, in designing new stem material. It is concluded that the optimal FGM cemented stem is consisting from titanium at the upper stem layers graded to collagen at a lower stem layers. This optimal graded stem coated with hydroxyapatite found to reduce stress shielding by 57% compared to homogenous titanium stem coated with hydroxyapatite. However, the optimal functionally graded stem coated with collagen reduced the stress shielding by 51% compared to homogenous titanium stem coated with collagen. PMID:26407117

  1. Neurotransmitter Specific, Cellular-Resolution Functional Brain Mapping Using Receptor Coated Nanoparticles: Assessment of the Possibility

    PubMed Central

    Forati, Ebrahim; Sabouni, Abas; Ray, Supriyo; Head, Brian; Schoen, Christian; Sievenpiper, Dan

    2015-01-01

    Receptor coated resonant nanoparticles and quantum dots are proposed to provide a cellular-level resolution image of neural activities inside the brain. The functionalized nanoparticles and quantum dots in this approach will selectively bind to different neurotransmitters in the extra-synaptic regions of neurons. This allows us to detect neural activities in real time by monitoring the nanoparticles and quantum dots optically. Gold nanoparticles (GNPs) with two different geometries (sphere and rod) and quantum dots (QDs) with different sizes were studied along with three different neurotransmitters: dopamine, gamma-Aminobutyric acid (GABA), and glycine. The absorption/emission spectra of GNPs and QDs before and after binding of neurotransmitters and their corresponding receptors are reported. The results using QDs and nanorods with diameter 25nm and aspect rations larger than three were promising for the development of the proposed functional brain mapping approach. PMID:26717196

  2. An Overview of Micromechanics-Based Techniques for the Analysis of Microstructural Randomness in Functionally Graded Materials

    SciTech Connect

    Ferrante, Fernando J.; Brady, Lori L. Graham; Acton, Katherine; Arwade, Sanjay R.

    2008-02-15

    A review of current research efforts to develop micromechanics-based techniques for the study of microstructural randomness of functionally graded materials is presented, along with a framework developed by the authors of this paper that includes stochastic simulation of statistically inhomogeneous samples and a windowing technique coupled with a micromechanical homogenization technique. The methodology is illustrated through the analysis of one sample coupled with finite element modeling.

  3. Carbohydrate coated, folate functionalized colloidal graphene as a nanocarrier for both hydrophobic and hydrophilic drugs

    NASA Astrophysics Data System (ADS)

    Maity, Amit Ranjan; Chakraborty, Atanu; Mondal, Avijit; Jana, Nikhil R.

    2014-02-01

    Although graphene based drug delivery has gained significant recent interest, the synthesis of colloidal graphene based nanocarriers with high drug loading capacities and with targeting ligands at the outer surface is a challenging issue. We have synthesized carbohydrate coated and folate functionalized colloidal graphene which can be used as a nanocarrier for a wide variety of hydrophobic and hydrophilic drugs. The synthesized colloidal graphene is loaded with paclitaxol, camptothecin, doxorubicin, curcumin and used for their targeted delivery to cancer cells. We demonstrate that this drug loaded functional graphene nanocarrier can successfully deliver drugs into target cells and offers an enhanced therapeutic performance. The reported approach can be extended to the cellular delivery of other hydrophobic and hydrophilic drugs and the simultaneous delivery of multiple drugs.Although graphene based drug delivery has gained significant recent interest, the synthesis of colloidal graphene based nanocarriers with high drug loading capacities and with targeting ligands at the outer surface is a challenging issue. We have synthesized carbohydrate coated and folate functionalized colloidal graphene which can be used as a nanocarrier for a wide variety of hydrophobic and hydrophilic drugs. The synthesized colloidal graphene is loaded with paclitaxol, camptothecin, doxorubicin, curcumin and used for their targeted delivery to cancer cells. We demonstrate that this drug loaded functional graphene nanocarrier can successfully deliver drugs into target cells and offers an enhanced therapeutic performance. The reported approach can be extended to the cellular delivery of other hydrophobic and hydrophilic drugs and the simultaneous delivery of multiple drugs. Electronic supplementary information (ESI) available: Details of the characterisation of carbohydrate functionalisation, images of different drug/dye loaded graphene nanocarriers at 3 hours incubation time, controlled cell

  4. HOTCFGM-1D: A Coupled Higher-Order Theory for Cylindrical Structural Components with Through-Thickness Functionally Graded Microstructures

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Aboudi, Jacob

    1998-01-01

    The objective of this three-year project was to develop and deliver to NASA Lewis one-dimensional and two-dimensional higher-order theories, and related computer codes, for the analysis, optimization and design of cylindrical functionally graded materials/structural components for use in advanced aircraft engines (e.g., combustor linings, rotor disks, heat shields, blisk blades). To satisfy this objective, a quasi one-dimensional version of the higher-order theory, HOTCFGM-1D, and four computer codes based on this theory, for the analysis, design and optimization of cylindrical structural components functionally graded in the radial direction were developed. The theory is applicable to thin multi-phased composite shell/cylinders subjected to macroscopically axisymmetric thermomechanical and inertial loading applied uniformly along the axial direction such that the overall deformation is characterized by a constant average axial strain. The reinforcement phases are uniformly distributed in the axial and circumferential directions, and arbitrarily distributed in the radial direction, thereby allowing functional grading of the internal reinforcement in this direction.

  5. A single-step enzyme immunoassay capillary sensor composed of functional multilayer coatings for the diagnosis of marker proteins.

    PubMed

    Funano, Shun-ichi; Sugahara, Masato; Henares, Terence G; Sueyoshi, Kenji; Endo, Tatsuro; Hisamoto, Hideaki

    2015-03-01

    A single-step, easy-to-use enzyme immunoassay capillary sensor, composed of functional multilayer coatings, was developed in this study. The coatings were composed of substrate-immobilized hydrophobic coating, hydrogel coating, and soluble coating containing an enzyme-labeled antibody. The response mechanism involved a spontaneous immunoreaction triggered by capillary action-mediated introduction of a sample antigen solution and subsequent separation of unreacted enzyme-labeled antibodies and antigen-enzyme-labeled antibody complexes by the molecular sieving effect of the hydrogel. An enzyme reaction at the substrate-immobilized hydrophobic coating/hydrogel coating interface resulted in a protein-selective fluorescence response. An antigen concentration-dependent response was obtained for diagnostic marker protein samples (hemoglobin A1c (HbA1c), 7.14-16.7 mg mL(-1); alpha-fetoprotein (AFP), 1.4-140 ng mL(-1); C-reactive protein (CRP), 0.5-10 μg mL(-1)) that cover a clinically important concentration range. The successful measurement of CRP in diluted serum samples demonstrated the application of this capillary sensor. PMID:25599100

  6. Asphalt Pavement Aging and Temperature Dependent Properties Using Functionally Graded Viscoelastic Model

    ERIC Educational Resources Information Center

    Dave, Eshan V.

    2009-01-01

    Asphalt concrete pavements are inherently graded viscoelastic structures. Oxidative aging of asphalt binder and temperature cycling due to climatic conditions being the major cause of non-homogeneity. Current pavement analysis and simulation procedures dwell on the use of layered approach to account for these non-homogeneities. The conventional…

  7. Prevalence, Stability, and Functionality of Achievement Goal Profiles in Mathematics from Third to Seventh Grade

    ERIC Educational Resources Information Center

    Schwinger, Malte; Wild, Elke

    2012-01-01

    This study examined the longitudinal trajectories of achievement goal profiles in mathematics from third to seventh grade in a sample of 302 German students. Latent profile analyses were conducted separately for each school year and revealed three subgroups of students with distinct goal profiles labeled high multiple goals, moderate multiple…

  8. Children's Singing Accuracy as a Function of Grade Level, Gender, and Individual versus Union Singing.

    ERIC Educational Resources Information Center

    Cooper, Nancy A.

    1995-01-01

    Examines the relationship between vocal pitch accuracy and gender, grade level, and the presence or absence of an accompanying unison voice. Reveals no significant differences between unison or individual singing or for gender. Fourth and fifth graders exhibited significant differences. (MJP)

  9. Is Mentoring throughout the Fourth and Fifth Grades Associated with Improved Psychosocial Functioning in Children?

    ERIC Educational Resources Information Center

    Schmidt, Michelle E.; McVaugh, Brittany; Jacobi, Jennifer

    2007-01-01

    This study examined whether mentoring influenced children's self-concept, anxiety, depression, and relationships with parents and peers over an 18-month period. We examined 31 mentored children (50% female) and a comparison group of 22 nonmentored children (50% female) at the beginning of a mentoring program in the fall of the fourth-grade year…

  10. Self-Esteem of Black and White Fifth Grade Pupils as a Function of Demographic Categorization.

    ERIC Educational Resources Information Center

    Beers, Joan S.

    Do varying racial and social school mixtures significantly relate to self-esteem of black and white fifth-grade pupils? The purpose of the present study was to examine several facets of this question. Interrelationships were studied among pupil's self-esteem and the following demographic variables: school's racial composition, pupil's sex, pupil's…

  11. Mussel-inspired functionalization of PEO/PCL composite coating on a biodegradable AZ31 magnesium alloy.

    PubMed

    Tian, Peng; Xu, Demin; Liu, Xuanyong

    2016-05-01

    The rapid degradation of magnesium-based implants in physiological environments in vivo not only will quickly deteriorate their mechanical strengths but will also lead to a severe change of the micro-environment around the implants, which may cause the final failure of magnesium-based implants. In this work, a polycaprolactone (PCL) layer was prepared to seal the plasma electrolytic oxidization coating (PEO) to form a PEO/PCL composite coating on a biodegradable AZ31 magnesium alloy, followed by further surface functionalization with polydopamine. The in vitro degradation behaviors of the bare AZ31 alloy and coated samples were evaluated in a simulated body fluid (SBF) using the potentiodynamic polarization curve test and the static immersion test. The bioactivity of the samples was investigated using the SBF soaking test. The cytocompatibility of all samples was evaluated using the cytotoxicity test and analysis of the adhesion and proliferation of osteoblast cells (MC3T3-E1) directly cultivated on the sample surface. The results showed that the PCL layer successfully sealed the pores of the PEO coating, and then the polydopamine layer formed on its surface. The in vitro degradation tests showed that the PEO/PCL composite coating improved the corrosion resistance of the AZ31 alloy in SBF with a more positive corrosion potential and a lower corrosion current density. Due to the protection of the PEO/PCL composite coating, the surrounding environment showed nearly no influence on the degradation of the coated sample, which led to no obvious local alkalization and hydrogen evolution. Moreover, compared with the AZ31 alloy and PEO coating, the PEO/PCL composite coating was more suitable for cell adhesion and proliferation. After further surface functionalization by polydopamine, the corrosion resistance of the composite coating was maintained, while its bioactivity was significantly enhanced with a large amount of hydroxyapatite (HA) formed on its surface after

  12. Yeast Gga coat proteins function with clathrin in Golgi to endosome transport.

    PubMed

    Costaguta, G; Stefan, C J; Bensen, E S; Emr, S D; Payne, G S

    2001-06-01

    Gga proteins represent a newly recognized, evolutionarily conserved protein family with homology to the "ear" domain of the clathrin adaptor AP-1 gamma subunit. Yeast cells contain two Gga proteins, Gga1p and Gga2p, that have been proposed to act in transport between the trans-Golgi network and endosomes. Here we provide genetic and physical evidence that yeast Gga proteins function in trans-Golgi network clathrin coats. Deletion of Gga2p (gga2Delta), the major Gga protein, accentuates growth and alpha-factor maturation defects in cells carrying a temperature-sensitive allele of the clathrin heavy chain gene. Cells carrying either gga2Delta or a deletion of the AP-1 beta subunit gene (apl2Delta) alone are phenotypically normal, but cells carrying both gga2Delta and apl2Delta are defective in growth, alpha-factor maturation, and transport of carboxypeptidase S to the vacuole. Disruption of both GGA genes and APL2 results in cells so severely compromised in growth that they form only microcolonies. Gga proteins can bind clathrin in vitro and cofractionate with clathrin-coated vesicles. Our results indicate that yeast Gga proteins play an important role in cargo-selective clathrin-mediated protein traffic from the trans-Golgi network to endosomes. PMID:11408593

  13. Improved wear resistance of functional diamond like carbon coated Ti-6Al-4V alloys in an edge loading conditions.

    PubMed

    Choudhury, Dipankar; Lackner, Jürgen M; Major, Lukasz; Morita, Takehiro; Sawae, Yoshinori; Bin Mamat, Azuddin; Stavness, Ian; Roy, Chanchal K; Krupka, Ivan

    2016-06-01

    This study investigates the durability of functional diamond-like carbon (DLC) coated titanium alloy (Ti-6Al-4V) under edge loading conditions for application in artificial hip joints. The multilayered (ML) functional DLC coatings consist of three key layers, each of these layers were designed for specific functions such as increasing fracture strength, adapting stress generation and enhancing wear resistance. A 'ball-on-disk' multi-directional wear tester was used in the durability test. Prior to the wear testing, surface hardness, modulus elasticity and Raman intensity were measured. The results revealed a significant wear reduction to the DLC coated Ti-6Al-4V disks compared to that of non-coated Ti-6Al-4V disks. Remarkably, the counterpart Silicon Nitride (Si3N4) balls also yielded lowered specific wear rate while rubbed against the coated disks. Hence, the pairing of a functional multilayered DLC and Si3N4 could be a potential candidate to orthopedics implants, which would perform a longer life-cycle against wear caused by edge loading. PMID:27085502

  14. Analytical performance characteristics of nanoelectrospray emitters as a function of conductive coating.

    PubMed

    Smith, Douglas R; Moy, Marie A; Dolan, Anthony R; Wood, Troy D

    2006-04-01

    As miniaturization of electrospray continues to become more prevalent in the mass spectrometry arsenal, numerous types of conductive coatings have been developed with miniaturized electrospray emitters. Different conductive coatings have different properties that may lead to differences in analytical performance. This paper investigates and compares the analytical properties of a series of applied conductive coatings for low-flow electrospray ionization developed in this laboratory vs. commercially-available types. Evaporated graphite is thoroughly compared with commercially available polyaniline (PANI) coated emitters and metal coated emitters. Each set of emitters was investigated to determine various performance characteristics, including susceptibility to electrical discharge in both positive and negative ionization modes, as well as emitter reproducibility and generation of a standard curve to determine each emitter coating's limit of detection and limit of quantitation. Furthermore, evaporated graphite and polyaniline coated fused silica capillaries were investigated to determine which coating is more stable over long-term analyses and during electrical discharge. PMID:16568172

  15. Fabrication of Fe-FeAl Functionally Graded Material Using the Wire-Arc Additive Manufacturing Process

    NASA Astrophysics Data System (ADS)

    Shen, Chen; Pan, Zengxi; Cuiuri, Dominic; Roberts, Jon; Li, Huijun

    2016-02-01

    A functionally gradient iron-aluminum wall structure with aluminum composition gradient from 0 at. pct to over 50 at. pct is fabricated using a wire-arc additive manufacturing (WAAM) system. The as-fabricated alloy is investigated using optical microstructure analysis, hardness testing, tensile testing, X-ray diffraction phase characterization, and electron-dispersive spectrometry. The comprehensive analysis of the experimental samples has shown that the WAAM system can be used for manufacturing iron aluminide functionally graded material with full density, desired composition, and reasonable mechanical properties.

  16. Investigation of non-isocyanate urethane functional latexes and carbon nanofiller/epoxy coatings

    NASA Astrophysics Data System (ADS)

    Meng, Lei

    This dissertation consists of two parts. In the first part, a new class of non-isocyanate urethane methacrylates was synthesized and the effect of the new monomers on the urethane functional latex was investigated. The second part focused on a comparison of carbon nanofillers in inorganic/organic epoxy coating system for anticorrosive applications. A new class of non-isocyanate urethane methacrylates (UMAs) monomers was synthesized through an environmentally friendly non-isocyanate pathway. The kinetics of seeded semibatch emulsion polymerization of UMAs with methyl methacrylate (MMA) and butyl acrylate (BA) was monitored. The particle size and morphology were investigated by dynamic light scattering (DLS), ultrasound acoustic attenuation spectroscopy (UAAS) and transmission electron microscopy (TEM). The minimum film formation temperature (MFFT), mechanical and viscoelastic properties were studied. It was found that the emulsion polymerization processes all proceeded via Smith-Ewart control, leading to the uniform morphology and particle size. The glass transition temperature (Tg) and the mechanical properties of poly(MMA/BA/UMA) decreased with the increasing chain length of urethane methacrylate monomers due to the increasing flexibility of side chains. Without the effect of Tg, lower MFFT and improved mechanical properties were observed from urethane functional latexes. The improved mechanical properties were due to the increasing particle interaction by forming hydrogen bonding. Furthermore, the effect of urethane functionality in terms of the polymer composition, the location and the concentration was investigated by the batch, single-stage and two-stage semibatch polymerization of 2-[(butylcarbamoyl)oxy]ethyl methacrylate (BEM) with MMA and BA. The core-shell and homogeneous structures were evaluated by TEM, differential scanning calorimetry (DSC), and solid state nuclear magnetic resonance (SS-NMR). The compositional drift was observed from the batch

  17. Sugar‐coated sperm: Unraveling the functions of the mammalian sperm glycocalyx

    PubMed Central

    Tecle, Eillen

    2015-01-01

    SUMMARY Mammalian spermatozoa are coated with a thick glycocalyx that is assembled during sperm development, maturation, and upon contact with seminal fluid. The sperm glycocalyx is critical for sperm survival in the female reproductive tract and is modified during capacitation. The complex interplay among the various glycoconjugates generates numerous signaling motifs that may regulate sperm function and, as a result, fertility. Nascent spermatozoa assemble their own glycans while the cells still possess a functional endoplasmic reticulum and Golgi in the seminiferous tubule, but once spermatogenesis is complete, they lose the capacity to produce glycoconjugates de novo. Sperm glycans continue to be modified, during epididymal transit by extracellular glycosidases and glycosyltransferases. Furthermore, epididymal cells secrete glycoconjugates (glycophosphatidylinositol‐anchored glycoproteins and glycolipids) and glycan‐rich microvesicles that can fuse with the maturing sperm membrane. The sperm glycocalyx mediates numerous functions in the female reproductive tract, including the following: inhibition of premature capacitation; passage through the cervical mucus; protection from innate and adaptive female immunity; formation of the sperm reservoir; and masking sperm proteins involved in fertilization. The immense diversity in sperm‐associated glycans within and between species forms a remarkable challenge to our understanding of essential sperm glycan functions. Mol. Reprod. Dev. 82: 635–650, 2015. © 2015 The Authors. Molecular Reproduction and Development published by Wiley Periodicals, Inc. PMID:26061344

  18. Sugar-coated sperm: Unraveling the functions of the mammalian sperm glycocalyx.

    PubMed

    Tecle, Eillen; Gagneux, Pascal

    2015-09-01

    Mammalian spermatozoa are coated with a thick glycocalyx that is assembled during sperm development, maturation, and upon contact with seminal fluid. The sperm glycocalyx is critical for sperm survival in the female reproductive tract and is modified during capacitation. The complex interplay among the various glycoconjugates generates numerous signaling motifs that may regulate sperm function and, as a result, fertility. Nascent spermatozoa assemble their own glycans while the cells still possess a functional endoplasmic reticulum and Golgi in the seminiferous tubule, but once spermatogenesis is complete, they lose the capacity to produce glycoconjugates de novo. Sperm glycans continue to be modified, during epididymal transit by extracellular glycosidases and glycosyltransferases. Furthermore, epididymal cells secrete glycoconjugates (glycophosphatidylinositol-anchored glycoproteins and glycolipids) and glycan-rich microvesicles that can fuse with the maturing sperm membrane. The sperm glycocalyx mediates numerous functions in the female reproductive tract, including the following: inhibition of premature capacitation; passage through the cervical mucus; protection from innate and adaptive female immunity; formation of the sperm reservoir; and masking sperm proteins involved in fertilization. The immense diversity in sperm-associated glycans within and between species forms a remarkable challenge to our understanding of essential sperm glycan functions. PMID:26061344

  19. Investigation of static and dynamic behavior of functionally graded piezoelectric actuated Poly-Si micro cantilever probe

    NASA Astrophysics Data System (ADS)

    Pandey, Vibhuti Bhushan; Parashar, Sandeep Kumar

    2016-04-01

    In the present paper a novel functionally graded piezoelectric (FGP) actuated Poly-Si micro cantilever probe is proposed for atomic force microscope. The shear piezoelectric coefficient d15 has much higher value than coupling coefficients d31 and d33, hence in the present work the micro cantilever beam actuated by d15 effect is utilized. The material properties are graded in the thickness direction of actuator by a simple power law. A three dimensional finite element analysis has been performed using COMSOL Multiphysics® (version 4.2) software. Tip deflection and free vibration analysis for the micro cantilever probe has been done. The results presented in the paper shall be useful in the design of micro cantilever probe and their subsequent utilization in atomic force microscopes.

  20. Functionally graded beta-TCP/PCL nanocomposite scaffolds: in vitro evaluation with human fetal osteoblast cells for bone tissue engineering.

    PubMed

    Ozkan, Seher; Kalyon, Dilhan M; Yu, Xiaojun

    2010-03-01

    The engineering of biomimetic tissue relies on the ability to develop biodegradable scaffolds with functionally graded physical and chemical properties. In this study, a twin-screw-extrusion/spiral winding (TSESW) process was developed to enable the radial grading of porous scaffolds (discrete and continuous gradations) that were composed of polycaprolactone (PCL), beta-tricalciumphosphate (beta-TCP) nanoparticles, and salt porogens. Scaffolds with interconnected porosity, exhibiting myriad radial porosity, pore-size distributions, and beta-TCP nanoparticle concentration could be obtained. The results of the characterization of their compressive properties and in vitro cell proliferation studies using human fetal osteoblast cells suggest the promising nature of such scaffolds. The significant degree of freedom offered by the TSESW process should be an additional enabler in the quest toward the mimicry of the complex elegance of the native tissues. PMID:19296543

  1. Versatile Method for Coating Surfaces with Functional and Responsive Polymer-Based Films.

    PubMed

    Zhang, Qiang Matthew; Serpe, Michael J

    2015-12-16

    A versatile surface modification technique was developed to yield poly(N-isopropylacrylamide) (pNIPAm) microgel-based thin films on a variety of substrates, e.g., metals, nonmetals, and polymers. Because the chemistry, and hence functionality and responsivity, of the pNIPAm-based microgels is easily tuned, multifunctional and responsive thin films could be generated on many different surfaces without varying the coating conditions. In one case, we showed that fluorescent/light emitting thin films could be generated using crystal violet-modified microgels. Antibacterial films could be obtained using silver nanoparticle-modified pNIPAm-based microgels. Finally, we show that thin films fabricated via the methods here could be used as a component in optical sensors. Although we show only a few examples of the utility of this approach, we feel that the apparent universality of the technique can be extended to countless other applications. PMID:26640982

  2. Functionalized zinc oxide nanorod with ionophore-membrane coating as an intracellular Ca2+ selective sensor

    NASA Astrophysics Data System (ADS)

    Asif, M. H.; Fulati, A.; Nur, O.; Willander, M.; Brännmark, Cecilia; Strâlfors, Peter; Börjesson, Sara I.; Elinder, Fredrik

    2009-07-01

    The tip of a borosilicate glass capillary with functionalized hexagonal ZnO nanorods was used to make a sensitive electrochemical intracellular Ca2+ sensor. To adjust the sensor for Ca2+ measurements with sufficient selectivity and stability, polyvinylchloride membrane containing Ca2+ ionophores were coated on the surface. The membrane covered ZnO nanorods exhibited a Ca2+-dependent electrochemical potential difference versus an Ag/AgCl reference electrode. The potential difference was linear over a large concentration range (100 nM-10 mM). The measurements of Ca2+ concentrations using our ZnO nanorods sensor in human fat cells or in frog egg cells were consistent with values of Ca2+ concentrations reported in the literature. This nanoelectrode device paves the way to measurements of intracellular biochemical species in specific locations within single living cells.

  3. Preparation, Functionality, and Application of Metal Oxide-coated Noble Metal Nanoparticles.

    PubMed

    Liu, Shuhua; Regulacio, Michelle D; Tee, Si Yin; Khin, Yin Win; Teng, Choon Peng; Koh, Leng Duei; Guan, Guijian; Han, Ming-Yong

    2016-08-01

    With their remarkable properties and wide-ranging applications, nanostructures of noble metals and metal oxides have been receiving significantly increased attention in recent years. The desire to combine the properties of these two functional materials for specific applications has naturally prompted research in the design and synthesis of novel nanocomposites, consisting of both noble metal and metal-oxide components. In this review, particular attention is given to core-shell type metal oxide-coated noble metal nanostructures (i.e., metal@oxide), which display potential utility in applications, including photothermal therapy, catalytic conversions, photocatalysis, molecular sensing, and photovoltaics. Emerging research directions and areas are envisioned at the end to solicit more attention and work in this regard. PMID:27291595

  4. Health Sensing Functions in Thermal Barrier Coatings Incorporating Rare-Earth-Doped Luminescent Sublayers

    NASA Technical Reports Server (NTRS)

    Eldridge, J. I.; Singh, J.; Wolfe, D. E.

    2004-01-01

    Great effort has been directed towards developing techniques to monitor the health of thermal barrier coatings (TBCs) that would detect the approach of safety-threatening conditions. An unconventional approach is presented here where health sensing functionality is integrated into the TBC itself by the incorporation of rare-earth-doped luminescent sublayers to monitor erosion as well as whether the TBC is maintaining the underlying substrate at a sufficiently low temperature. Erosion indication is demonstrated in electron-beam physical vapor deposited (EB-PVD) TBCs consisting of 7wt% yttria-stabilized zirconia (7YSZ) with europium-doped and terbium-doped sublayers. Multiple ingot deposition produced sharp boundaries between the doped sublayers without interrupting the columnar growth of the TBC. The TBC-coated specimens were subjected to alumina particle jet erosion, and the erosion depth was then indicated under ultraviolet illumination that excited easily visible luminescence characteristic of sublayer that was exposed by erosion. In addition, temperature measurements from a bottom-lying europium-doped sublayer in a TBC produced by multiple ingot EB-PVD were accomplished by measuring the temperature-dependent decay time from the 606 nm wavelength emission excited in that sublayer with a 532 nm wavelength laser that was selected for its close match to one of the europium excitation wavelengths as well as being at a wavelength where the TBC is relatively transparent. It is proposed the low dopant levels and absence of interruption of the TBC columnar growth allow the addition of the erosion and temperature sensing functions with minimal effects on TBC performance.

  5. Functionalization of PDMS modified and plasma activated two-component polyurethane coatings by surface attachment of enzymes

    NASA Astrophysics Data System (ADS)

    Kreider, Alexej; Richter, Katharina; Sell, Stephan; Fenske, Mandus; Tornow, Christian; Stenzel, Volkmar; Grunwald, Ingo

    2013-05-01

    This article describes a new strategy for coupling the enzyme horseradish peroxidase to a two-component polyurethane (2C-PUR) coating. A stable polymer conjugate was achieved by combining the enzyme and the 2C-PUR coating which was modified with poly(dimethylsiloxane) (PDMS), located at the surface. An atmospheric pressure plasma jet system was used to convert alkyl groups from the PDMS into polar silanol functionalities. This conversion was proven by X-ray photoelectron spectroscopy and dynamic contact angle measurements. In addition, the stability of the activated 2C-PUR surface containing silanol groups was determined by measuring the contact angle as a function of time. Compared to the non-modified 2C-PUR systems the one with PDMS displayed a higher stability over a time period over 28 h. In a silanization process the coating was treated with (3-aminopropyl) trimethoxysilane and the enzyme was subsequently immobilized to the coating via the cross linker glutaraldehyde to receive new biomimetic catalytic/enzymatic functions. The chemical immobilization (chemisorption) of the enzyme to the surface showed statistically significant higher biological activity as compared to references samples without using a cross linker (physisorption). The presented technique offers the opportunity to design new and smart multifunctional surface coatings which employ biomimetic capabilities.

  6. Factors controlling the multi-functional corrosion properties of pulsed thermal sprayed Aluminum-Cobalt -Cerium coatings

    NASA Astrophysics Data System (ADS)

    Tailleart, Nicole R.

    High density, low porosity Al-Co-Ce metallic coatings have been successfully applied to precipitation age hardened aerospace structural alloy AA 2024-T351 substrates using a pulsed thermal spray (PTS) process. The three proposed modes of corrosion protection were brought about by the metallurgical and physical attributes of the coating. These include formation of a localized corrosion barrier, a sacrificial anode to enable cathodic protection of any exposed AA 2024-T351, and a source of an active inhibitor. The inhibitor (e.g., cerium and cobalt cations) can be released by various chemical triggers, such as chloride and pH. These functions were verified for the first time in this study on Al-Co-Ce PTS coated substrates and were found to function simultaneously in dilute chloride solutions. However, the localized corrosion properties of the PTS applied coating samples were not equal to fully amorphous, melt spun ribbon variants of the same alloy composition when ribbons were produced from feedstock powders. The goal of this research was to elucidate the critical attributes that govern the ability of the Al-Co-Ce coatings to perform each of these three functions. A structure-property paradigm describing relationships between composition, structure, as well as physical attributes and resulting coating corrosion properties, was explored. The effects of various metallurgical, physical, and geometric characteristics of the coating, such as structure, composition, morphology, porosity, and thickness were investigated. The main emphasis was placed on the localized corrosion barrier properties. The inferior behavior of the PTS coatings was traced to various microstructural and physical defects (i.e., chiefly the formation of intermetallic particles as well as crystalline, a non-amorphous structures with chemical non-uniformities). However, this inferior behavior cannot be attributed to feedstock powder composition since melt spun ribbons were successfully made from

  7. Late evaluation of the relationship between morphological and functional renal changes and hypertension after non-operative treatment of high-grade renal injuries

    PubMed Central

    2012-01-01

    Objective To evaluate the anatomical and functional renal alterations and the association with post-traumatic arterial hypertension. Methods The studied population included patients who sustained high grades renal injury (grades III to V) successfully non-operative management after staging by computed tomography over a 16-year period. Beyond the review of medical records, these patients were invited to the following protocol: clinical and laboratory evaluation, abdominal computed tomography, magnetic resonance angiography, DMSA renal scintigraphy, and ambulatory blood pressure monitoring. The hypertensive patients also were submitted to dynamic renal scintigraphy (99mTc EC), using captopril stimulation to verify renal vascular etiology. Results Of the 31 patients, there were thirteen grade III, sixteen grade IV (nine lacerations, and seven vascular lesions), and two grade V injuries. All the patients were asymptomatic and an average follow up post-injury of 6.4 years. None had abnormal BUN or seric creatinine. The percentage of renal volume reduction correlates with the severity as defined by OIS. There was no evidence of renal artery stenosis in Magnetic Resonance angiography (MRA). DMSA scanning demonstrated a decline in percentage of total renal function corresponding to injury severity (42.2 ± 5.5% for grade III, 35.3 ± 12.8% for grade IV, 13.5 ± 19.1 for grade V). Six patients (19.4%) had severe compromised function (< 30%). There was statistically significant difference in the decrease in renal function between parenchymal and vascular causes for grade IV injuries (p < 0.001). The 24-hour ambulatory blood pressure monitoring detected nine patients (29%) with post-traumatic hypertension. All the patients were male, mean 35.6 years, 77.8 % had a familial history of arterial hypertension, 66.7% had grade III renal injury, and average post-injury time was 7.8 years. Seven patients had negative captopril renography. Conclusions Late

  8. Fabrication and in vitro evaluation of the collagen/hyaluronic acid PEM coating crosslinked with functionalized RGD peptide on titanium.

    PubMed

    Huang, Ying; Luo, Qiaojie; Li, Xiaodong; Zhang, Feng; Zhao, Shifang

    2012-02-01

    Surface modification of titanium (Ti) using biomolecules has attracted much attention recently. In this study, a new strategy has been employed to construct a stable and bioactive coating on Ti. To this end, a derivative of hyaluronic acid (HA), i.e. HA-GRGDSPC-(SH), was synthesized. The disulfide-crosslinked Arg-Gly-Asp (RGD)-containing collagen/hyaluronic acid polyelectrolyte membrane (PEM) coating was then fabricated on Ti through the alternate deposition of collagen and HA-GRGDSPC-(SH) with five assembly cycles and subsequent crosslinking via converting free sulphydryl groups into disulfide linkages (RGD-CHC-Ti group). The assembly processes for PEM coating and the physicochemical properties of the coating were carefully characterized. The stability of PEM coating in phosphate-buffered saline solution could be adjusted by the crosslinking degree, while its degradation behaviors in the presence of glutathione were glutathione concentration dependent. The adhesion and proliferation of MC3T3-E1 cells were significantly enhanced in the RGD-CHC-Ti group. Up-regulated bone specific genes, enhanced alkaline phosphatase activity and osteocalcin production, the increased areas of mineralization were also observed in the RGD-CHC-Ti group. These results indicate that the strategy employed herein may function as an effective way to construct stable, RGD-containing bioactive coatings on Ti. PMID:22040683

  9. The use of a dual PEDOT and RGD-functionalized alginate hydrogel coating to provide sustained drug delivery and improved cochlear implant function

    PubMed Central

    Chikar, JA; Hendricks, JL; Richardson-Burns, SM; Raphael, Y; Pfingst, BE; Martin, DC

    2011-01-01

    Cochlear implants provide hearing by electrically stimulating the auditory nerve. Implant function can be hindered by device design variables, including electrode size and electrode-to-nerve distance, and cochlear environment variables, including the degeneration of the auditory nerve following hair cell loss. We have developed a dual component cochlear implant coating to improve both the electrical function of the implant and the biological stability of the inner ear, thereby facilitating the long-term perception of sound through a cochlear implant. This coating is a combination of an arginine-glycine-aspartic acid (RGD)-functionalized alginate hydrogel and the conducting polymer poly(3, 4-ethylenedioxythiophene) (PEDOT). Both in vitro and in vivo assays on the effects of these electrode coatings demonstrated improvements in device performance. We found that the coating reduced electrode impedance, improved charge delivery, and locally released significant levels of a trophic factor into cochlear fluids. This coating is non-cytotoxic, clinically relevant, and has the potential to significantly improve the cochlear implant user’s experience. PMID:22182748

  10. Microstructure, Mechanical, and Scratch Resistance Properties of TiAlCrNbN-Graded Composite Coating Deposited on AISI H13 Steel Substrate with Pulsed DC Closed Field Unbalanced Magnetron Sputtering Method

    NASA Astrophysics Data System (ADS)

    Kara, Levent; Küçükömeroğlu, Tevfik; Baran, Özlem; Efeoğlu, İhsan; Yamamoto, Kenji

    2014-04-01

    Structure and adhesion properties of TiAlCrNbN coatings were investigated. These coatings were deposited onto AISI H13 steel substrate using pulsed dc closed field unbalanced magnetron sputtering at different deposition parameters including duty cycle, bias voltage, and working pressure. The coatings have been characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The TiAlCrNbN-graded composite coatings have a dense and columnar structure. The X-ray diffraction patterns of coatings exhibited predominantly c-TiAlCrN, h-NbN, and h-TiAlN reflections. Scratch resistance test showed that the highest adhesion strength was attained as 68 N at 2.5 μs duty time, 100 V bias voltages, and 3 × 10-3 Torr deposition parameters. The lowest adhesion strength was obtained as 55 N at 0.5 μs duty time, 50V bias voltage, and 2 × 10-3 Torr deposition parameters.

  11. Functionally graded scaffolds for the engineering of interface tissues using hybrid twin screw extrusion/electrospinning technology

    NASA Astrophysics Data System (ADS)

    Erisken, Cevat

    Tissue engineering is the application of the principles of engineering and life sciences for the development of biological alternatives for improvement or regeneration of native tissues. Native tissues are complex structures with functions and properties changing spatially and temporally, and engineering of such structures requires functionally graded scaffolds with composition and properties changing systematically along various directions. Utilization of a new hybrid technology integrating the controlled feeding, compounding, dispersion, deaeration, and pressurization capabilities of extrusion process with electrospinning allows incorporation of liquids and solid particles/nanoparticles into polymeric fibers/nanofibers for fabrication of functionally graded non-woven meshes to be used as scaffolds in engineering of tissues. The capabilities of the hybrid technology were demonstrated with a series of scaffold fabrication and cell culturing studies along with characterization of biomechanical properties. In the first study, the hybrid technology was employed to generate concentration gradations of beta-tricalcium phosphate (beta-TCP) nanoparticles in a polycaprolactone (PCL) binder, between two surfaces of nanofibrous scaffolds. These scaffolds were seeded with pre-osteoblastic cell line (MC3T3-E1) to attempt to engineer cartilage-bone interface, and after four weeks, the tissue constructs revealed formation of continuous gradations in extracellular matrix akin to cartilage-bone interface in terms of distributions of mineral concentrations and biomechanical properties. In a second demonstration of the hybrid technology, graded differentiation of stem cells was attempted by using insulin, a known stimulator of chondrogenic differentiation, and beta-glycerol phosphate (beta-GP), for mineralization. Concentrations of insulin and beta-GP in PCL were controlled to monotonically increase and decrease, respectively, along the length of scaffolds, which were then seeded

  12. Free vibration analysis of a rotating hub-functionally graded material beam system with the dynamic stiffening effect

    NASA Astrophysics Data System (ADS)

    Li, L.; Zhang, D. G.; Zhu, W. D.

    2014-02-01

    A comprehensive dynamic model of a rotating hub-functionally graded material (FGM) beam system is developed based on a rigid-flexible coupled dynamics theory to study its free vibration characteristics. The rigid-flexible coupled dynamic equations of the system are derived using the method of assumed modes and Lagrange's equations of the second kind. The dynamic stiffening effect of the rotating hub-FGM beam system is captured by a second-order coupling term that represents longitudinal shrinking of the beam caused by the transverse displacement. The natural frequencies and mode shapes of the system with the chordwise bending and stretching (B-S) coupling effect are calculated and compared with those with the coupling effect neglected. When the B-S coupling effect is included, interesting frequency veering and mode shift phenomena are observed. A two-mode model is introduced to accurately predict the most obvious frequency veering behavior between two adjacent modes associated with a chordwise bending and a stretching mode. The critical veering angular velocities of the FGM beam that are analytically determined from the two-mode model are in excellent agreement with those from the comprehensive dynamic model. The effects of material inhomogeneity and graded properties of FGM beams on their dynamic characteristics are investigated. The comprehensive dynamic model developed here can be used in graded material design of FGM beams for achieving specified dynamic characteristics.

  13. Bimolecular integrin–ligand interactions quantified using peptide-functionalized dextran-coated microparticles

    PubMed Central

    Sun, Jessie E. P.; Vranic, Justin; Composto, Russell J.; Streu, Craig; Billings, Paul C.; Bennett, Joel S.; Weisel, John W.

    2012-01-01

    Integrins play a key role in cell–cell and cell–matrix interactions. Artificial surfaces grafted with integrin ligands, mimicking natural interfaces, have been used to study integrin-mediated cell adhesion. Here we report the use of a new chemical engineering technology in combination with single-molecule nanomechanical measurements to quantify peptide binding to integrins. We prepared latex beads with covalently-attached dextran. The beads were then functionalized with the bioactive peptides, cyclic RGDFK (cRGD) and the fibrinogen γC-dodecapeptide (H12), corresponding to the active sites for fibrinogen binding to the platelet integrin αIIbβ3. Using optical tweezers-based force spectroscopy to measure non-specific protein–protein interactions, we found the dextran-coated beads nonreactive towards fibrinogen, thus providing an inert platform for biospecific modifications. Using periodate oxidation followed by reductive amination, we functionalized the bead-attached dextran with either cRGD or H12 and used the peptide-grafted beads to measure single-molecule interactions with the purified αIIbβ3. Bimolecular force spectroscopy revealed that the peptide-functionalized beads were highly and specifically reactive with the immobilized αIIbβ3. Further, the cRGD- and H12-functionalized beads displayed a remarkable interaction profile with a bimodal force distribution up to 90 pN. The cRGD–αIIbβ3 interactions had greater binding strength than that of H12–αIIbβ3, indicating that they are more stable and resistant mechanically, consistent with the platelet reactivity of RGD-containing ligands. Thus, the results reported here describe the mechanistic characteristics of αIIbβ3–ligand interactions, confirming the utility of peptide-functionalized latex beads for the quantitative analysis of molecular recognition. PMID:22120019

  14. Effects of the DICOM grayscale standard display function on the accuracy of medical-grade grayscale and consumer-grade color displays for telemammography screening

    NASA Astrophysics Data System (ADS)

    Salazar, Antonio J.; Romero, Javier; Bernal, Oscar; Moreno, Angela; Velasco, Sofía.; Díaz, Xavier

    2013-11-01

    The aim of this study was to compare the diagnostic accuracy of the consumer-grade and medical-grade monitors —with very different costs— in breast cancer detection, when using with and without Digital Imaging and Communication in Medicine (DICOM) standard calibration. This was a retrospective study with factorial design and repeated measures, using 70 digital mammograms (40 benign or normal cases and 30 malignant cases), four radiologists, and three displays, with and without display calibration. Film mammograms were also included. Readings were classified according to the Breast Imaging Reporting and Data System. One medical-grade grayscale display and two consumer-grade displays were compared. Receiver operating characteristics curves were plotted for nodules, micro calcifications and the degree of malignancy. The diagnostic accuracy for each device was calculated as the area under these curves and accuracies were compared using analysis of variance.

  15. Optically transparent and environmentally durable superhydrophobic coating based on functionalized SiO2 nanoparticles

    SciTech Connect

    Schaeffer, Daniel A.; Polizos, Georgios; Smith, D. Barton; Lee, Dominic F.; Hunter, Scott R.; Datskos, Panos G.

    2015-01-09

    Optical surfaces such as mirrors and windows that are exposed to outdoor environmental conditions are susceptible to dust buildup and water condensation. The application of transparent superhydrophobic coatings on optical surfaces can improve outdoor performance via a self-cleaning effect similar to the Lotus effect. The contact angle (CA) of water droplets on a typical hydrophobic flat surface varies from 100° to 120°. Adding roughness or microtexture to a hydrophobic surface leads to an enhancement of hydrophobicity and the CA can be increased to a value in the range of 16≥0° to 175°. This result is remarkable because such behavior cannot be explained using surface chemistry alone. When surface features are on the order of 100 nm or smaller, surfaces exhibit superhydrophobic behavior and maintain their optical transparency. In this work we discuss our results on transparent superhydrophobic coatings that can be applied across large surface areas. We have used functionalized silica nanoparticles to coat various optical elements and have measured the contact angle and optical transmission between 190 to 1100 nm on these elements. The functionalized silica nanoparticles were dissolved in a solution of the solvents isopropyl alcohol and 4-chlorobenzotrifluoride (PCBTF) and a proprietary ceramic binder (Cerakote ). Finally, this solution was spin-coated onto a variety of test glass substrates, and following a curing period of about 30 minutes, these coatings exhibited superhydrophobic behavior with a static CA ≥160°.

  16. Safety Analysis Using Lebesgue Strain Measure of Thick-Walled Cylinder for Functionally Graded Material under Internal and External Pressure

    PubMed Central

    Aggarwal, A. K.; Sharma, Richa; Sharma, Sanjeev

    2013-01-01

    Safety analysis has been done for thick-walled circular cylinder under internal and external pressure using transition theory which is based on the concept of generalized principal Lebesgue strain measure. Results have been analyzed theoretically and discussed numerically. From the analysis, it can be concluded that circular cylinder made of functionally graded material is on the safer side of the design as compared to homogeneous cylinder with internal and external pressure, which leads to the idea of “stress saving” that minimizes the possibility of fracture of cylinder. PMID:24089605

  17. Analysis of a Generally Oriented Crack in a Functionally Graded Strip Sandwiched Between Two Homogeneous Half Planes

    NASA Technical Reports Server (NTRS)

    Shbeeb, N.; Binienda, W. K.; Kreider, K.

    1999-01-01

    The driving forces for a generally oriented crack embedded in a Functionally Graded strip sandwiched between two half planes are analyzed using singular integral equations with Cauchy kernels, and integrated using Lobatto-Chebyshev collocation. Mixed-mode Stress Intensity Factors (SIF) and Strain Energy Release Rates (SERR) are calculated. The Stress Intensity Factors are compared for accuracy with previously published results. Parametric studies are conducted for various nonhomogeneity ratios, crack lengths. crack orientation and thickness of the strip. It is shown that the SERR is more complete and should be used for crack propagation analysis.

  18. Free Vibration of Size-Dependent Functionally Graded Microbeams Based on the Strain Gradient Reddy Beam Theory

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Gholami, R.; Sahmani, S.

    2014-09-01

    The microscale vibration characteristics of microbeams made of functionally graded materials (FGMs) are investigated based on the strain gradient Reddy beam theory capable of capturing the size effect. The non-classical governing differential equations, together with the corresponding boundary conditions, are obtained using Hamilton's principle. Then, the free vibration problem of simply supported FGM microbeams is solved using the Navier solution. The natural frequencies of FGM microbeams are calculated corresponding to a wide range of dimensionless length scale parameters, material property gradient indices, and aspect ratios to illustrate the influences of size effect on the vibrational response of FGM microbeams.

  19. Piezoelectricity above the Curie temperature? Combining flexoelectricity and functional grading to enable high-temperature electromechanical coupling

    SciTech Connect

    Mbarki, R.; Baccam, N.; Dayal, Kaushik; Sharma, P.

    2014-03-24

    Most technologically relevant ferroelectrics typically lose piezoelectricity above the Curie temperature. This limits their use to relatively low temperatures. In this Letter, exploiting a combination of flexoelectricity and simple functional grading, we propose a strategy for high-temperature electromechanical coupling in a standard thin film configuration. We use continuum modeling to quantitatively demonstrate the possibility of achieving apparent piezoelectric materials with large and temperature-stable electromechanical coupling across a wide temperature range that extends significantly above the Curie temperature. With Barium and Strontium Titanate, as example materials, a significant electromechanical coupling that is potentially temperature-stable up to 900 °C is possible.

  20. Nonlinear Dynamic Behavior of Functionally Graded Truncated Conical Shell Under Complex Loads

    NASA Astrophysics Data System (ADS)

    Yang, S. W.; Hao, Y. X.; Zhang, W.; Li, S. B.

    Nonlinear dynamic behaviors of ceramic-metal graded truncated conical shell subjected to complex loads are investigated. The shell is modeled by first-order shear deformation theory. The nonlinear partial differential governing equation in terms of transverse displacements of the FGM truncated conical shell is derived from the Hamilton's principle. Galerkin's method is then utilized to discretize the partial governing equations to a two-degree-of-freedom nonlinear ordinary differential equation. The temperature-dependent materials properties of the constituents are graded in the radial direction in accordance with a power-law distribution. The aerodynamic pressure can be calculated by using the first-order piston theory. The temperature field is assumed to be a steady-state constant-temperature distribution. Bifurcation diagrams, the maximum Lyapunov exponents, wave forms and phase portraits are obtained by numerical simulation to demonstrate the complex nonlinear dynamics response of the FGM truncated conical shell. The influences of the semi-vertex angle, the material gradient index, in-plane and aerodynamic load on the nonlinear dynamics are studied.

  1. Synergistic Ultrathin Functional Polymer-Coated Carbon Nanotube Interlayer for High Performance Lithium-Sulfur Batteries.

    PubMed

    Kim, Joo Hyun; Seo, Jihoon; Choi, Junghyun; Shin, Donghyeok; Carter, Marcus; Jeon, Yeryung; Wang, Chengwei; Hu, Liangbing; Paik, Ungyu

    2016-08-10

    Lithium-sulfur (Li-S) batteries have been intensively investigated as a next-generation rechargeable battery due to their high energy density of 2600 W·h kg(-1) and low cost. However, the systemic issues of Li-S batteries, such as the polysulfide shuttling effect and low Coulombic efficiency, hinder the practical use in commercial rechargeable batteries. The introduction of a conductive interlayer between the sulfur cathode and separator is a promising approach that has shown the dramatic improvements in Li-S batteries. The previous interlayer work mainly focused on the physical confinement of polysulfides within the cathode part, without considering the further entrapment of the dissolved polysulfides. Here, we designed an ultrathin poly(acrylic acid) coated single-walled carbon nanotube (PAA-SWNT) film as a synergic functional interlayer to address the issues mentioned above. The designed interlayer not only lowers the charge transfer resistance by the support of the upper current collector but also localizes the dissolved polysulfides within the cathode part by the aid of a physical blocking and chemical bonding. With the synergic combination of PAA and SWNT, the sulfur cathode with a PAA-SWNT interlayer maintained higher capacity retention over 200 cycles and achieved better rate retention than the sulfur cathode with a SWNT interlayer. The proposed approach of combining a functional polymer and conductive support material can provide an optimiztic strategy to overcome the fundamental challenges underlying in Li-S batteries. PMID:27437758

  2. (99m) Tc radiolabeling and biological evaluation of nanoparticles functionalized with a versatile coating ligand.

    PubMed

    Felber, Michael; Bauwens, Matthias; Mateos, José M; Imstepf, Sebastian; Mottaghy, Felix M; Alberto, Roger

    2015-04-13

    Radiolabeling allows noninvasive imaging by single photon emission computed tomography (SPECT) or positron emission tomography (PET) for assessing the biodistribution of nanostructures. Herein, the synthesis of a new coating ligand for gold nanoparticles (AuNPs) and quantum dots (QDs) is reported. This ligand is multifunctional; it combines the metal chelate with conjugating functions to biological vectors. The concept allows the coupling of any targeting function to the chelator; an example for the prostate specific membrane antigen is given. Derivatized NPs can directly be labeled in one step with [(99m) Tc(OH2 )3 (CO)3 ](+) . AuNPs in particular are highly stable, a prerequisite for in vivo studies excluding misinterpretation of the biodistribution data. AuNPs with differing sizes (7 and 14 nm core diameter) were administered intravenously into nude NMRI mice bearing LNCaP xenografts. MicroSPECT images show for both probes rapid clearance from the blood pool through the hepatobiliary pathway. The 7 nm AuNPs revealed a significantly higher bone uptake than the 14 nm AuNPs. The high affinity towards bone mineral is further confirmed in vitro with hydroxyapatite. PMID:25765900

  3. Two of Everything: Developing Functional Thinking in the Primary Grades through Children's Literature

    ERIC Educational Resources Information Center

    Muir, Tracey; Bragg, Leicha A.; Livy, Sharyn

    2015-01-01

    The concept of functional thinking as a foundational idea associated with algebraic thinking is explored by Tracey Muir, Leicha Bragg and Sharyn Livy. They provide ideas for using children's literature as a context to promote functional thinking

  4. Developing Essential Understanding of Functions for Teaching Mathematics in Grades 9-12

    ERIC Educational Resources Information Center

    Lloyd, Gwendolyn; Beckmann, Sybilla; Zbiek, Rose Mary; Cooney, Thomas

    2010-01-01

    Are sequences functions? What can't the popular "vertical line test" be applied in some cases to determine if a relation is a function? How does the idea of rate of change connect with simpler ideas about proportionality as well as more advanced topics in calculus? Helping high school students develop a robust understanding of functions requires…

  5. Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

    NASA Astrophysics Data System (ADS)

    Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

    2016-08-01

    Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

  6. Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

    NASA Astrophysics Data System (ADS)

    Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

    2016-06-01

    Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

  7. Long-term survival and functional status of patients with low-grade astrocytoma of spinal cord

    SciTech Connect

    Robinson, Clifford G.; Prayson, Richard A.; Hahn, Joseph F.; Kalfas, Iain H.; Whitfield, Melvin D.; Lee, S.-Y.; Suh, John H. . E-mail: suhj@ccf.org

    2005-09-01

    Purpose: To determine survival and changes in neurologic function and Karnofsky performance status (KPS) in a series of patients treated for low-grade astrocytoma of the spinal cord during the past two decades. Methods: This study consisted of 14 patients with pathologically confirmed low-grade astrocytoma of the spinal cord who were treated between 1980 and 2003. All patients underwent decompressive laminectomy followed by biopsy (n = 7), subtotal resection (n = 6), or gross total resection (n = 1). Ten patients underwent postoperative radiotherapy (median total dose 50 Gy in 28 fractions). The overall survival, progression-free survival, and changes in neurologic function and KPS were measured. Results: The overall survival rate at 5, 10, and 20 years was 100%, 75%, and 60%, respectively. The progression-free survival rate at 5, 10, and 20 years was 93%, 80%, and 60%, respectively. Neither overall survival nor progression-free survival was clearly correlated with any patient, tumor, or treatment factors. Neurologic function and KPS worsened after surgery in 8 (57%) of 14 and 9 (69%) of 13 patients, respectively. At a mean follow-up of 10.2 years, neurologic function had stabilized or improved in 8 (73%) of 11 remaining patients, but the KPS had worsened in 5 (50%) of 10. Most patients who were employed before surgery were working at last follow-up. Conclusion: Patients who undergo gross total resection of their tumor may be followed closely. Patients who undergo limited resection should continue to receive postoperative RT (50.4 Gy in 1.8-Gy fractions). The functional measures should be routinely evaluated to appreciate the treatment outcomes.

  8. Design of a W/steel functionally graded material for plasma facing components of DEMO

    NASA Astrophysics Data System (ADS)

    Missiaen, J. M.; Raharijaona, J. J.; Antoni, A.; Pascal, C.; Richou, M.; Magaud, P.

    2011-09-01

    The design of a graded transition between tungsten and steel for plasma facing components of a nuclear fusion reactor is proposed and the interest of such a transition is demonstrated by FEM calculations of the thermo-mechanical behaviour in the operating conditions of the DEMO reactor. The transition consists in stacked layers of W-WC and WC-Fe between W and Eurofer steel. The maximum surface temperature of the structural component could be maintained below 1300 °C for a very simple multilayer geometry, from FEM calculations. The maximum strains and equivalent elastic stresses could be reduced by a factor of about 3 as compared to a direct W/steel joint. Considerations about processing techniques of such a component are discussed, based on the literature background and a few preliminary tests.

  9. An evaluation of a coupled microstructural approach for the analysis of functionally graded composites via the finite-element method

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Dunn, Patrick

    1995-01-01

    A comparison is presented between the predictions of the finite-element analysis and a recently developed higher-order theory for functionally graded materials subjected to a thorough-thickness temperature gradient. In contrast to existing micromechanical theories that utilize classical (i.e., uncoupled) homogenization schemes to calculate micro-level and macro-level stress and displacement fields in materials with uniform or nonuniform fiber spacing (i.e., functionally graded materials), the new theory explicitly couples the microstructural details with the macrostructure of the composite. Previous thermo-elastic analysis has demonstrated that such coupling is necessary when: the temperature gradient is large with respect to the dimension of the reinforcement; the characteristic dimension of the reinforcement is large relative to the global dimensions of the composite and the number of reinforcing fibers or inclusions is small. In these circumstances, the standard micromechanical analyses based on the concept of the representative volume element used to determine average composite properties produce questionable results. The comparison between the predictions of the finite-element method and the higher-order theory presented herein establish the theory's accuracy in predicting thermal and stress fields within composites with a finite number of fibers in the thickness direction subjected to a thorough-thickness thermal gradient.

  10. DEVELOPMENT OF ADVANCED DRILL COMPONENTS FOR BHA USING MICROWAVE TECHNOLOGY INCORPORATING CARBIDE, DIAMOND COMPOSITES AND FUNCTIONALLY GRADED MATERIALS

    SciTech Connect

    Dinesh Agrawal; Rustum Roy

    2003-01-01

    The microwave processing of materials is a new emerging technology with many attractive advantages over the conventional methods. The advantages of microwave technology for various ceramic systems has already been demonstrated and proven. The recent developments at Penn State have succeeded in applying the microwave technology for the commercialization of WC/Co and diamond based cutting and drilling tools, effectively sintering of metallic materials, and fabrication of transparent ceramics for advanced applications. In recent years, the Microwave Processing and Engineering Center at Penn State University in collaboration with our industrial partner, Dennis Tool Co. has succeeded in commercializing the developed microwave technology partially funded by DOE for WC/Co and diamond based cutting and drilling tools for gas and oil exploration operations. In this program we have further developed this technology to make diamond-carbide composites and metal-carbide-diamond functionally graded materials. Several actual product of diamond-carbide composites have been processed in microwave with better performance than the conventional product. The functionally graded composites with diamond as one of the components has been for the first time successfully developed. These are the highlights of the project.

  11. Vibration and buckling characteristics of functionally graded nanoplates subjected to thermal loading based on surface elasticity theory

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Ashrafi, M. A.; Pourashraf, T.; Sahmani, S.

    2015-04-01

    The buckling and vibration responses of nanoplates made of functionally graded materials (FGMs) subjected to thermal loading are studied in prebuckling domain with considering the effect of surface stress. To accomplish this purpose, Gurtin-Murdoch elasticity theory is incorporated into the classical plate theory to develop a non-classical plate model including the surface effects. The material properties of FGM nanoplate are considered to be graded in the thickness direction on the basis of the power law function. Hamilton's principle is utilized to derive size-dependent governing differential equations of motion and associated boundary conditions. Selected numerical results are presented to indicate the importance of surface stress effect. It is revealed that in the presence of surface stress effect, the influence of material property gradient index on the critical thermal buckling load is more prominent for FGM nanoplates with lower length-to-thickness ratios. Also, by increasing the natural frequency of FGM nanoplate, the role of surface stress effect in the value of critical thermal buckling load is more prominent.

  12. PLASMA SPRAYED FUNCTIONALLY GRADED AND LAYERED MoSi2-A1203 COMPOSITES FOR HIGH TEMPERATURE SENSOR SHEATH APPLICATION

    SciTech Connect

    R. VAIDYA; ET AL

    2001-01-01

    Protective sensor sheaths are required in the glass industry for sensors that are used to measure various properties of the melt. Molten glass presents an extremely corrosive elevated temperature environment, in which only a few types of materials can survive. Molybdenum disilicide (MoSi{sub 2}) has been shown to possess excellent corrosion resistance in molten glass, and is thus a candidate material for advanced sensor sheath applications. Plasma spray-forming techniques were developed to fabricate molybdenum dilicide-alumina (Al{sub 2}O{sub 3}) laminate and functionally graded composite tubes with mechanical properties suitable for sensor sheath applications. These functionally graded materials (FGMs) were achieved by manipulating the powder hoppers and plasma torch translation via in-house created computer software. Molybdenum disilicide and alumina are thermodynamically stable elevated temperature materials with closely matching thermal expansion coefficients. Proper tailoring of the microstructure of these MoSi{sub 2}-Al{sub 2}O{sub 3} composites can result in improved strength, toughness, and thermal shock resistance. This study focuses on the mechanical performance of these composite microstructures.

  13. Cognitive function after radiotherapy for supratentorial low-grade glioma: A North Central Cancer Treatment Group prospective study

    SciTech Connect

    Laack, Nadia N.; Brown, Paul D. . E-mail: brown.paul@mayo.edu; Ivnik, Robert J.; Furth, Alfred F. M.S.; Ballman, Karla V.; Hammack, Julie E.; Arusell, Robert M.; Shaw, Edward G.; Buckner, Jan C.

    2005-11-15

    Purpose: To evaluate the effects of cranial radiotherapy (RT) on cognitive function in patients with supratentorial low-grade glioma. Methods and Materials: Twenty adult patients with supratentorial low-grade glioma were treated with 50.4 Gy (10 patients) or 64.8 Gy (10 patients) localized RT. The patients then were evaluated with an extensive battery of psychometric tests at baseline (before RT) and at approximately 18-month intervals for as long as 5 years after completing RT. To allow patients to serve as their own controls, cognitive performance was evaluated as change in scores over time. All patients underwent at least two evaluations. Results: Baseline test scores were below average compared with age-specific norms. At the second evaluation, the groups' mean test scores were higher than their initial performances on all psychometric measures, although the improvement was not statistically significant. No changes in cognitive performance were seen during the evaluation period when test scores were analyzed by age, treatment, tumor location, tumor type, or extent of resection. Conclusions: Cognitive function was stable after RT in these patients evaluated prospectively during 3 years of follow-up. Slight improvements in some cognitive areas are consistent with practice effects attributable to increased familiarity with test procedures and content.

  14. Thermoelastic Theory for the Response of Materials Functionally Graded in Two Directions with Applications to the Free-Edge Problem

    NASA Technical Reports Server (NTRS)

    Aboudi, Jacob; Pindera, Marek-Jerzy; Arnold, Steven M.

    1995-01-01

    A recently developed micromechanical theory for the thermoelastic response of functionally graded composites with nonuniform fiber spacing in the through-thickness direction is further extended to enable analysis of material architectures characterized by arbitrarily nonuniform fiber spacing in two directions. In contrast to currently employed micromechanical approaches applied to functionally graded materials, which decouple the local and global effects by assuming the existence of a representative volume element at every point within the composite, the new theory explicitly couples the local and global effects. The analytical development is based on volumetric averaging of the various field quantities, together with imposition of boundary and interfacial conditions in an average sense. Results are presented that illustrate the capability of the derived theory to capture local stress gradients at the free edge of a laminated composite plate due to the application of a uniform temperature change. It is further shown that it is possible to reduce the magnitude of these stress concentrations by a proper management of the microstructure of the composite plies near the free edge. Thus by an appropriate tailoring of the microstructure it is possible to reduce or prevent the likelihood of delamination at free edges of standard composite laminates.

  15. Novel functionally graded acicular electrode for solid oxide cells fabricated by the freeze-tape-casting process

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Bunch, Jacob; Li, Tingshuai; Mao, Zhengping; Chen, Fanglin

    2012-09-01

    The performance of electrode supported solid oxide cells is often limited by gas transport in the thick electrode support. In this study, a novel functionally graded acicular hydrogen electrode microstructure has been fabricated by the freeze-tape-casting method. The effects of freeze-tape-casting processing parameters such as solid loading, freezing bed temperature and tape pulling rate on the morphology of the hydrogen electrode support have been investigated. The electrochemical performance of the cells having the novel functionally graded acicular hydrogen electrode has been significantly improved. In the fuel cell mode, a high power output of 1.28 W cm-2 and a low polarization resistance of 0.166 Ω cm2 have been achieved at 800 °C with H2 as fuel and ambient air as oxidant using nickel-yttria-stabilized zirconia (YSZ) as the hydrogen electrode, YSZ as the electrolyte, and (La0.75Sr0.25)0.95MnO3-YSZ as the oxygen electrode. In the electrolysis mode, a high current density of 2.3 A cm-2 with 30 vol% absolute humidity in the hydrogen electrode at 800 °C has been achieved with an applied cell voltage of 1.6 V. It has been revealed that the novel acicular hydrogen electrode decreases the gas diffusion resistance, thus enhancing the cell performance.

  16. Functionally gradient materials for thermal barrier coatings in advanced gas turbine systems

    SciTech Connect

    Banovic, S.W.; Barmak, K.; Chan, H.M.

    1995-10-01

    New designs for advanced gas turbine engines for power production are required to have higher operating temperatures in order to increase efficiency. However, elevated temperatures will increase the magnitude and severity of environmental degradation of critical turbine components (e.g. combustor parts, turbine blades, etc{hor_ellipsis}). To offset this problem, the usage of thermal barrier coatings (TBCs) has become popular by allowing an increase in maximum inlet temperatures for an operating engine. Although thermal barrier technology is over thirty years old, the principle failure mechanism is the spallation of the ceramic coating at or near the ceramic/bond coat interface. Therefore, it is desirable to develop a coating that combines the thermal barrier qualities of the ceramic layer and the corrosion protection by the metallic bond coat without the detrimental effects associated with the localization of the ceramic/metal interface to a single plane.

  17. Application of the Reverberation-Ray Matrix to the Non-Fourier Heat Conduction in Functionally Graded Materials

    NASA Astrophysics Data System (ADS)

    Zhou, Feng-xi

    2016-02-01

    The method of the reverberation-ray matrix has been developed and successfully applied to analyse the wave propagation in a multibranched framed structure or in a layered medium. However, the method is confined to the case of mechanical loads applied at the medium until now. This paper aims to extend the formulation of the reverberation-ray matrix to cases of thermal propagation and diffusion. The thermal response in functionally graded materials (FGM) with the non-Fourier heat conduction model is analysed. In the present work, it is assumed that the material properties of an FG plate vary only in the thickness direction by following the power law function. The effect of non-Fourier and material inhomogeneity in the plate subjected to a periodic thermal disturbance is investigated. The present approach is validated by comparing it with the solutions obtained by other methods.

  18. Fabrication of Minerals Substituted Porous Hydroxyapaptite/Poly(3,4-ethylenedioxy pyrrole-co-3,4-ethylenedioxythiophene) Bilayer Coatings on Surgical Grade Stainless Steel and Its Antibacterial and Biological Activities for Orthopedic Applications.

    PubMed

    Subramani, Ramya; Elangomannan, Shinyjoy; Louis, Kavitha; Kannan, Soundarapandian; Gopi, Dhanaraj

    2016-05-18

    Current strategies of bilayer technology have been aimed mainly at the enhancement of bioactivity, mechanical property and corrosion resistance. In the present investigation, the electropolymerization of poly(3,4-ethylenedioxypyrrole-co-3,4-ethylenedioxythiophene) (P(EDOP-co-EDOT)) with various feed ratios of EDOP/EDOT on surgical grade stainless steel (316L SS) and the successive electrodeposition of strontium (Sr(2+)), magnesium (Mg(2+)) and cerium (Ce(3+)) (with 0.05, 0.075 and 0.1 M Ce(3+)) substituted porous hydroxyapatite (M-HA) are successfully combined to produce the bioactive and corrosion resistance P(EDOP-co-EDOT)/M-HA bilayer coatings for orthopedic applications. The existence of as-developed coatings was confirmed by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), proton nuclear magnetic resonance spectroscopy ((1)H NMR), high resolution scanning electron microscopy (HRSEM), energy dispersive X-ray analysis (EDAX) and atomic force microscopy (AFM). Also, the mechanical and thermal behavior of the bilayer coatings were analyzed. The corrosion resistance of the as-developed coatings and also the influence of copolymer (EDOP:EDOT) feed ratio were studied in Ringer's solution by electrochemical techniques. The as-obtained results are in accord with those obtained from the chemical analysis using inductively coupled plasma atomic emission spectrometry (ICP-AES). In addition, the antibacterial activity, in vitro bioactivity, cell viability and cell adhesion tests were performed to substantiate the biocompatibility of P(EDOP-co-EDOT)/M-HA bilayer coatings. On account of these investigations, it is proved that the as-developed bilayer coatings exhibit superior bioactivity and improved corrosion resistance over 316L SS, which is potential for orthopedic applications. PMID:27128574

  19. PREFACE: VI Scientific Technical Conference on "Low-temperature plasma during the deposition of functional coatings"

    NASA Astrophysics Data System (ADS)

    2014-11-01

    The VI Republican Scientific Technical Conference "Low-temperature plasma during the deposition of functional coatings" took place from 4 to 7 November 2014 at the Academy of Sciences of the Republic of Tatarstan and the Kazan Federal University. The conference was chaired by a Member of the Academy of Sciences of the Republic of Tatarstan Nail Kashapov -Professor, Doctor of Technical Sciences- a member of the Scientific and Technical Council of the Ministry of Economy of the Republic of Tatarstan. At the conference, the participants discussed a wide range of issues affecting the theoretical and computational aspects of research problems in the physics and technology of low-temperature plasma. A series of works were devoted to the study of thin films obtained by low-temperature plasma. This year work dedicated to the related field of heat mass transfer in multiphase media and low-temperature plasma was also presented. Of special interest were reports on the exploration of gas discharges with liquid electrolytic electrotrodes and the study of dusty plasmas. Kashapov Nail, D.Sc., Professor (Kazan Federal University)

  20. PREFACE: VII Conference on Low Temperature Plasma in the Processes of Functional Coating Preparation

    NASA Astrophysics Data System (ADS)

    Nail, Kashapov

    2016-01-01

    The VII All-Russian (with international participation) Scientific Technical Conference "Low-temperature plasma during the deposition of functional coatings" took place from 4-7 November 2015 at the Academy of Sciences of the Republic of Tatarstan and the Kazan Federal University. The conference was attended by over 150 people from Russia and abroad. The participants proposed a wide range of issues affecting the theoretical and experimental aspects of the problems of the physics of low-temperature plasma. We heard the reports of experts from leading universities and research organizations in the field of plasma physics: Moscow State University, St. Petersburg State University, MEPhI, Tomsk Polytechnic University, Institute of High Current Electronics SB RAS, etc. A series of works were devoted to the study of thin films obtained by low-temperature plasma. This year, work dedicated to the related field of heat mass transfer in multiphase media and low-temperature plasma was also presented. Of special interest were reports on the exploration of gas discharges with liquid electrolytic electrodes and the study of dusty plasmas. Kashapov Nail, D.Sc., professor (Kazan Federal University)

  1. Ultrathin coatings of nanoporous materials as property enhancements for advanced functional materials.

    SciTech Connect

    Coker, Eric Nicholas

    2010-11-01

    This report summarizes the findings of a five-month LDRD project funded through Sandia's NTM Investment Area. The project was aimed at providing the foundation for the development of advanced functional materials through the application of ultrathin coatings of microporous or mesoporous materials onto the surface of substrates such as silicon wafers. Prior art teaches that layers of microporous materials such as zeolites may be applied as, e.g., sensor platforms or gas separation membranes. These layers, however, are typically several microns to several hundred microns thick. For many potential applications, vast improvements in the response of a device could be realized if the thickness of the porous layer were reduced to tens of nanometers. However, a basic understanding of how to synthesize or fabricate such ultra-thin layers is lacking. This report describes traditional and novel approaches to the growth of layers of microporous materials on silicon wafers. The novel approaches include reduction of the quantity of nutrients available to grow the zeolite layer through minimization of solution volume, and reaction of organic base (template) with thermally-oxidized silicon wafers under a steam atmosphere to generate ultra-thin layers of zeolite MFI.

  2. Remediation of mercury contaminated saltwater with functionalized silica coated magnetite nanoparticles.

    PubMed

    Mohmood, Iram; Lopes, Cláudia B; Lopes, Isabel; Tavares, Daniela S; Soares, Amadeu M V M; Duarte, Armando C; Trindade, Tito; Ahmad, Iqbal; Pereira, Eduarda

    2016-07-01

    The study aimed to evaluate the efficiency of dithiocarbamate functionalized silica coated magnetite nanoparticles (NPs) for Hg decontamination of saltwater either contaminated with Hg alone or with As and Cd. For this, the residual levels of Hg in seawater were assessed and Hg-contaminated or Hg+As+Cd-contaminated seawater toxicity to aquatic biota, before and after the sorption process, was compared. The results showed that under highly competitive conditions (water salts, Cd and As), the removal of Hg from seawater, by using these magnetic NPs, for the lowest concentration (50μg/L) was superior to 98% and for the highest concentration (500μg/L) ranged between 61% to 67%. Despite the great affinity of the magnetic NPs for Hg, they were not effective at removing As and Cd from seawater. In relation to the ecotoxicity endpoints after remediation, the mixture with lower Hg concentration exhibited no toxicity to rotifer Brachionus plicatilis and bacteria Vibrio fischeri ; however, the mixture with higher concentration revealed toxicity. In addition, the toxicity of bacteria V. fischeri, rotifer B. plicatilis and algae Phaeodactylum tricornutum, whose responses where inhibited during its exposure to the non-remediate sample was considerably reduced after treatment with NPs. Furthermore, microalgae P. tricornutum appears to be most sensitive species while Artemia franciscana showed no toxic effects to the tested solutions. Both chemical and ecotoxicological approaches revealed a high efficiency for the remediation of Hg-contaminated saltwater. PMID:27039062

  3. Starting times of school: effects on daytime functioning of fifth-grade children in Israel.

    PubMed

    Epstein, R; Chillag, N; Lavie, P

    1998-05-01

    In the present study we investigated the effects of school starting time on daytime behavior and sleep. Eight-hundred and eleven 5th grade pupils (10-12 years old) from 28 classes in 18 schools throughout Israel were divided into "early risers" (N = 232) who started school at 07:10 (42%) at least 2 times a week, and "regular risers" (N = 340) who always started school at 08:00 (58%). The remaining 239 pupils started school between 7:20 and 07:55 (and also after 08:00), and were not included in the study. Self-administered questionnaires concerning sleep habits during school days, weekends, and holidays, daytime fatigue, sleepiness, and difficulties concentrating and paying attention in school were completed by all children. Mean sleep time of the "early risers" was significantly shorter than that of the "regular risers." Early risers complained significantly more about daytime fatigue and sleepiness, and about attention and concentration difficulties in school. Their complaints were independent of the reported hours of sleep. We conclude that early starting of school negatively affects total sleep time and, as a consequence, has a negative effect on daytime behavior. The implications of these findings to the ongoing controversy concerning sleep need in contemporary society are discussed. PMID:9595603

  4. Exact analytical solution of shear-induced flexural vibration of functionally graded piezoelectric beam

    NASA Astrophysics Data System (ADS)

    Sharma, Pankaj; Parashar, Sandeep Kumar

    2016-05-01

    The priority of this paper is to obtain the exact analytical solution for free flexural vibration of FGPM beam actuated using the d15 effect. In piezoelectric actuators, the potential use of d15 effect has been of particular interest for engineering applications since shear piezoelectric coefficient d15 is much higher than the other piezoelectric coupling constants d31 and d33. The applications of shear actuators are to induce and control the flexural vibrations of beams and plates. In this study, a modified Timoshenko beam theory is used where electric potential is assumed to vary sinusoidaly along the thickness direction. The material properties are assumed to be graded across the thickness in accordance with power law distribution. Hamilton`s principle is employed to obtain the equations of motion along with the associated boundary conditions for FGPM beams. Exact analytical solution is derived thus obtained equations of motion. Results for clamped-clamped and clamped-free boundary conditions are presented. The presented result and method shell serve as benchmark for comparing the results obtained from the other approximate methods.

  5. The influence of sol-gel-derived silica coatings functionalized with betamethasone on adipose-derived stem cells (ASCs).

    PubMed

    Donesz-Sikorska, Anna; Grzesiak, Jakub; Smieszeka, Agnieszk; Krzak, Justyna; Marycz, Krzysztof

    2014-09-01

    Silica-based sol-gel coatings have gained attention in bone therapies and orthopedic applications, due to the biocompatibility and bioactivity, including a high potential for the controlled release both in vitro and in vivo. Bioactive materials are created to facilitate the biocompatibility of orthopedic implants. One of the promising alternatives is biomaterials with immobilized drugs. In this study we demonstrated for the first time novel sol-gel-derived silica coatings with active amino groups (SiO2(NH2)) functionalized with a steroid drug-betamethasone, applied to a substrate 316 L using dip coating technique. The presence of betamethasone in functionalized coatings was directly confirmed by Raman spectroscopy and energy-dispersive X-ray spectroscopic analysis. The wettability was evaluated by the sessile drop method, while the surface free energy was estimated based on the contact angles measured. Our results showed a shift in surface properties from hydrophobic to hydrophilic after application of the coatings. We have investigated the morphology, proliferation factor, and the population doubling time of adipose-derived stem cells for biological purposes. Moreover, the analysis of the distribution and localization of cellular microvesicles was performed to evaluate the influence of functionalized surfaces on cellular cytophysiological activity. Increased proliferation and activation of cells, determined by the observations of microvesicles shedding processes, provided evidence of the availability of the drug. Therefore, we conclude that the sol-gel synthesis proposed here allows to improve the metal substrates and can be successfully used for immobilization of betamethasone. This in turn enables the direct delivery of the drug with implanted material into the wound site, and to stimulate the activity of cells to enhance tissue regeneration. PMID:24825759

  6. Culture of human vascular endothelial cells on an RGD-containing synthetic peptide attached to a starch-coated polystyrene surface: comparison with fibronectin-coated tissue grade polystyrene.

    PubMed

    Holland, J; Hersh, L; Bryhan, M; Onyiriuka, E; Ziegler, L

    1996-11-01

    A synthetic peptide, Gly-Arg-Gly-Asp-Ser-Pro-Lys (GRGDSPK), which includes the cell-adhesive region of fibronectin, Arg-Gly-Asp (RGD), was covalently bound to a dialdehyde starch (DAS) coating on a polymer surface by reductive amination. The GRGDSPK/DAS-coated surface was characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). AFM and SEM revealed a uniform, roughened, textured surface, much more so than standard polymer or adhesive protein-coated polymer surfaces. XPS showed that GRGDSPK binding to DAS occurred in dose-dependent fashion in the 0-200 micrograms ml-1 GRGDSPK concentration range, with a plateau happening in the 200-400 micrograms ml-1 range. AFM revealed a uniform peptide layer on the DAS surface with a maximum separation distance of 50 nm between peptides. Angle-dependent XPS showed that the peptide is present in nearly constant amounts to at least 10 nm depth of the DAS coating. The attachment, spreading and growth properties of anchorage-dependent human umbilical vein endothelial cells (EC) on the GRGDSPK/DAS-coated polystyrene surface were compared with a standard fibronectin-coated polystyrene surface. EC adhesion, spreading and growth properties were similar for cells plated on polystyrene surfaces coated with fibronectin (5 micrograms cm-2) and GRGDSPK (25-50 micrograms ml-1)/DAS. In contrast, EC adhesion, spreading and growth performance significantly increased for cells plated on GRGDSPK (100-200 micrograms ml-1)/DAS compared with the fibronectin-coated surface. These findings support the conclusion that the GRGDSPK/DAS-coated surface can be substituted for an adhesive protein-coated surface in the culture of anchorage-dependent cells. PMID:8922600

  7. High-gravity-assisted pulsed laser ablation system for the fabrication of functionally graded material thin film.

    PubMed

    Nishiyama, T; Morinaga, S; Nagayama, K

    2009-03-01

    This paper describes a novel method for the fabrication of a thin film deposited on an appropriate substrate having a continuous composition gradient. The composition gradient was achieved by a combination of pulsed laser ablation (PLA) of the target material with a very strong acceleration field generated on a moving disk rotating at a very high speed. The PLA process was used to produce a cloud of high-energy particles of the target material that will be deposited on a substrate placed on the rotating disk. After deposition, the particles will diffuse on the surface of the thin film under a strong acceleration field. The high energy of the particles and their diffusion on the substrate surface in a high-vacuum environment produces a macroscopic composition distribution in the thin film. We have constructed an experimental apparatus consisting of a vacuum chamber in which a circular disk made of titanium is driven by a high-frequency inductive motor. An acceleration field of up to 10,000 G can be generated by this apparatus. Functionally graded material thin films of FeSi(2) with a continuous concentration gradient were successfully fabricated by this method under a gravity field of 5400 G. A significant advantage of this method is that it allows us to fabricate graded thin films with a very smooth surface covered by few droplets. PMID:19334931

  8. Rapid coating of surfaces with functionalized nanoparticles for regulation of cell behavior.

    PubMed

    Tang, Rui; Moyano, Daniel F; Subramani, Chandramouleeswaran; Yan, Bo; Jeoung, Eunhee; Tonga, Gülen Yesilbag; Duncan, Bradley; Yeh, Yi-Cheun; Jiang, Ziwen; Kim, Chaekyu; Rotello, Vincent M

    2014-05-28

    A robust monolayer of nanoparticles is formed via dip-coating of cell culture plates. These surfaces provide cell type-specific modulation of growth behavior without the uptake of nanoparticles. PMID:24677290

  9. Histopathology of a well-functioning hydroxyapatite-coated femoral prosthesis after 52 months.

    PubMed

    Hardy, D C; Frayssinet, P; Krallis, P; Descamps, P Y; Fabeck, L; Delplancke, J L; Delince, P E

    1999-03-01

    A fully hydroxyapatite-coated femoral implant was retrieved during autopsy. This component, provided with a bipolar femoral head, had been inserted for a displaced fracture of the femoral neck 52 months before. Osseointegration of the implant was evident, without any formation of fibrous tissue :39.9% of the perimeter of the prosthesis at the level of its proximal third was interfaced with bone (62.8% at the mid-third and 65.2% at the distal third). Remodeling of bone had ensued. Deposition of bone was most prominent in the calcar zone, along the medial and lateral aspects and around the tip. Proximally, cortical porosity was found to be increased by 73%, whereas medullary bone porosity was increased by a factor of 2. Cell-mediated resorption of the coating was systematically present in these bone remodeling areas. The average thickness of the coating was respectively 10.8, 50.2 and 151.2 microns in the proximal, mid- and distal thirds of the implant. Formation of new bone was often coupled with resorption. No debris from the coating was found in the joint tissues or in the articulating surface of the polyethylene insert. These overall histopathological features support mechanical stability of the implant and active remodelling of bone along with focal removal of HA coating associated with osteoclastic activity. No side effects from coating degradation could be demonstrated. PMID:10217005

  10. A static analysis of three-dimensional functionally graded beams through hierarchical one-dimensional finite elements

    SciTech Connect

    Giunta, G.; Belouettar, S.

    2015-03-10

    In this paper, the static response of three-dimensional beams made of functionally graded materials is investigated through a family of hierarchical one-dimensional finite elements. A wide variety of elements is proposed differing by the kinematic formulation and the number of nodes per elements along the beam axis. Elements’ stiffness matrix and load vector are derived in a unified nuclear form that does not depend upon the a priori expansion order over the cross-section nor the finite element approximation along the beam axis. Results are validated towards three-dimensional finite element models as well as equivalent Navier-type analytical solutions. The numerical investigations show that accurate and efficient solutions (when compared with full three-dimensional FEM solutions) can be obtained by the proposed family of hierarchical one-dimensional elements’ family.

  11. Wear Properties of Intermetallic Compound Reinforced Functionally Graded Materials Fabricated by Centrifugal Solid-particle and In-Situ Methods

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Sato, Hisashi; Fukui, Yasuyoshi

    One of the functionally graded material (FGM) fabrication methods is a centrifugal method, which is an application of the centrifugal casting technique. The centrifugal force applied to a homogeneous molten composite assists the formation of the desired gradation. In this paper, the wear properties of two kinds of Al base FGMs, namely Al-Al3Ti FGM and Al-Al3Ni FGM, are reported. The former and the latter hold the oriented intermetallic compound platelets and the particle size gradient, respectively. Here, volume fraction, size, shape and orientation of the reinforcements in the composite play an important role in improving the mechanical properties of the materials, whereby FGMs with oriented platelets or particle size gradient may have special mechanical properties such as increased wear resistance. Based on the experimental results, the origin of anisotropic wear resistance and the effect of particle size on the wear properties are discussed.

  12. Fast fabrication of W-Cu functionally graded material by high-gravity combustion synthesis and melt-infiltration

    NASA Astrophysics Data System (ADS)

    Zhao, P.; Guo, S. B.; Liu, G. H.; Chen, Y. X.; Li, J. T.

    2014-02-01

    W-Cu functionally graded material (FGM, 75 wt% W + 25 wt% Cu-40 wt% W + 60 wt% Cu) has been prepared by a method of high-gravity combustion synthesis and melt-infiltration in a short time (∼5 min). The infiltration mechanism in the high-gravity field was investigated. The W-Cu FGM showed an overall relative density of ∼97% and gradually-varying properties in terms of density, micro hardness, coefficient of thermal expansion. Especially, the W-Cu FGM exhibited a coefficient of thermal expansion between those of W and Cu, and thus could be used as a transition layer between W and Cu to relax the thermal stresses.

  13. Functionally graded polymeric materials: A brif review of current fabrication methods and introduction of a novel fabrication method.

    PubMed

    Almasi, Davood; Sadeghi, Maliheh; Lau, Woei Jye; Roozbahani, Fatemeh; Iqbal, Nida

    2016-07-01

    The present work reviews the current fabrication methods of the functionally graded polymeric material (FGPM) and introduces a novel fabrication method that is versatile in applications as compared to those of existing used methods. For the first time electrophoresis was used to control the distribution of the tetracycline hydrochloride (TC) in a film made of polylactic acid (PLA), aiming to induce antimicrobial effect on the film prepared. The elemental analysis on the film surface showed that by employing electrophoresis force, higher amount of TC was detected near the top surface of the film. Results also showed that the FGPM samples with higher percentage of the TC on the film surface were highly effective to minimize the growth of Escherichia coli. These findings are useful and important to improve dispersion quality of the particles in the composite material and further enhance its antibacterial property. PMID:27127033

  14. Impact of Writing Interventions Informed by Systemic Functional Linguistics with a Focus on Tenor, on Sixth, Seventh and Eighth Grade English Language Learners

    ERIC Educational Resources Information Center

    Holmgren, Katherine Hayes

    2012-01-01

    This action research study examines the impact instruction informed by Systemic Functional Linguistics (SFL) with a particular focus on tenor and socio-cultural theory has on sixth, seventh and eighth grade English language learners in an urban school. Over the course of seven and 1/2 months I used Systemic Functional Linguistics with a focus on…

  15. Children's Monetary Evaluations of Body Parts as a Function of Sex, Grade, and Race.

    ERIC Educational Resources Information Center

    Vaughan, Sandra L.; And Others

    The present study reports ratings of seven body parts as a function of sex, age, and race of child. Subjects were 320 public school children. They were given a sheet of paper with pictures of seven different body parts, and were asked to select from a list of numbers a dollar value for each body part. The instructions suggested that they imagine a…

  16. School-Based Functional Assessments for Children with Physical Disabilities in Grades K-12

    ERIC Educational Resources Information Center

    Johnson, Richard W.

    2012-01-01

    The purpose of this study was to develop three school-based assessments and determine the content validity for each assessment. The School Activities and Participation Analysis-Elementary (SAPA-E) measures functional movement performance in children with physical disability attending the elementary school, and the School Activities and…

  17. The Role of the Executive Functions in School Achievement at the End of Grade 1

    ERIC Educational Resources Information Center

    Monette, Sebastien; Bigras, Marc; Guay, Marie-Claude

    2011-01-01

    The aim of this study was to determine the role of executive functions (EFs) in early school achievement when a variety of potential confounding factors were controlled. Measures of EF (inhibition, flexibility, and working memory) and school readiness were administered to a sample of 85 kindergartners (39 boys and 46 girls, 5-6 years old). School…

  18. Synthesis and evaluation of antibacterial polyurethane coatings made from soybean oil functionalized with dimethylphenylammonium iodide and hydroxyl groups.

    PubMed

    Bakhshi, Hadi; Yeganeh, Hamid; Mehdipour-Ataei, Shahram

    2013-06-01

    Preparation of antibacterial polyurethane coatings from novel functional soybean oil was considered in this work. First, epoxidized soybean oil (ESBO) as a low price and widely available renewable resource raw material was subjected to the reaction with aniline using an ionic liquid as a green catalyst. The intermediate phenylamine containing polyol (SAP) was then methylated by reaction with methyl iodide to produce a polyol (QAP) with pendant dimethylphenylammonium iodide groups. To regulate the physical and mechanical properties as well as biological characteristics of final coatings, QAP was mixed with different portions of a similar soybean oil-based polyol (MSP) without quaternary ammonium groups. The mixtures were reacted with isophorone diisocyanate to produce crosslinked polyurethane coatings. Evaluation of viscoelastic properties by DMA method revealed single phase structure with Tg in the range of 50-82°C. Stress-strain analysis of the prepared polyurethanes showed initial modulus, tensile strength, and elongation at break in the ranges of 13-299 MPa, 4.5-13.8 MPa, and 16-109%, respectively. Additionally, the coatings showed good adherence to aluminum and PVC substrates. The solvent extracted samples showed excellent biocompatibility as determined by monitoring L929 fibroblast cells morphology and MTT assay. Meanwhile, very promising antibacterial properties against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria with bacterial reduction in the range of 83-100% was observed. PMID:23172859

  19. Fabrication and properties of functionally graded NiAl/Al2O3 composites

    NASA Technical Reports Server (NTRS)

    Miller, D. P.; Lannutti, J. J.; Noebe, R. D.

    1993-01-01

    A modified sedimentation process was used in the production of a functionally gradient material (FGM), NiAl/Al2O3. A simple finite element model was used to guide our design and fabrication efforts by estimating residual stress states as a function of composite structure. This approach could lead to tailored designs that enhance or avoid specific residual stress states. Thermal cycling tests were factored into the model to predict time dependent or steady-state internal temperature and stress profiles. Four-point bend tests were conducted to establish the mechanical load-displacement behavior of a single interlayer FGM at room temperature, 800 and 1000 K. Room temperature bend strength of the FGM was 3-4 times that of the base NiAl. At elevated temperatures, composite fracture occurred in a gradual, noncatastrophic mode involving NiAl retardation of a succession of cracks originating in the alumina face.

  20. Poly (3, 4-ethylenedioxythiophene)-ionic liquid coating improves neural recording and stimulation functionality of MEAs

    PubMed Central

    Du, Zhanhong Jeff; Luo, Xiliang; Weaver, Cassandra

    2015-01-01

    In vivo multi-electrode arrays (MEAs) can sense electrical signals from a small set of neurons or modulate neural activity through micro-stimulation. Electrode's geometric surface area (GSA) and impedance are important for both unit recording and neural stimulation. Smaller GSA is preferred due to enhanced selectivity of neural signal, but it tends to increase electrode impedance. Higher impedance leads to increased electrical noise and signal loss in single unit neural recording. It also yields a smaller charge injection window for safe neural stimulation. To address these issues, poly (3, 4-ethylenedioxythiophene) - ionic liquid (PEDOT-IL) conducting polymers were electrochemically polymerized on the surface of the microelectrodes. The PEDOT-IL coating reduced the electrode impedance modulus by over 35 times at 1 kHz. It also exhibited compelling nanostructure in surface morphology and significant impedance reduction in other physiologically relevant range (100Hz-1000Hz). PEDOT-IL coated electrodes exhibited a Charge Storage Capacity (CSC) that was about 20 times larger than that of bare electrodes. The neural recording performance of PEDOT-IL coated electrodes was also compared with uncoated electrodes and PEDOT-poly (styrenesulfonate) (PSS) coated electrodes in rat barrel cortex (SI). Spontaneous neural activity and sensory evoked neural response were utilized for characterizing the electrode performance. The PEDOT-IL electrodes exhibited a higher unit yield and signal-to-noise ratio (SNR) in vivo. The local field potential recording was benefited from the low impedance PEDOT-IL coating in noise and artifact reduction as well. Moreover, cell culture on PEDOT-IL coating demonstrated that the material is safe for neural tissue and reduces astrocyte fouling. Taken together, PEDOT-IL coating has the potential to benefit neural recording and stimulation electrodes, especially when integrated with novel small GSA electrode arrays designed for high recording density

  1. Influence of biodegradable polymer coatings on corrosion, cytocompatibility and cell functionality of Mg-2.0Zn-0.98Mn magnesium alloy.

    PubMed

    Witecka, Agnieszka; Yamamoto, Akiko; Idaszek, Joanna; Chlanda, Adrian; Święszkowski, Wojciech

    2016-08-01

    Four kinds of biodegradable polymers were employed to prepare bioresorbable coatings on Mg-2.0Zn-0.98Mn (ZM21) alloy to understand the relationship between polymer characteristics, protective effects on substrate corrosion, cytocompatibility and cell functionality. Poly-l-lactide (PLLA), poly(3-hydroxybutyrate) (PHB), poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) or poly(lactic-co-glycolic) acid (PLGA) was spin-coated on ZM21, obtaining a smooth, non-porous coating less than 0.5μm in thickness. Polymer coating characterization, a degradation study, and biocompatibility evaluations were performed. After 4 w of immersion into cell culture medium, degradation of PLGA and PLLA coatings were confirmed by ATR-FTIR observation. The coatings of PLLA, PHB and PHBV, which have lower water permeability and slower degradation than PLGA, provide better suppression of initial ZM21 degradation and faster promotion of human osteosarcoma cell growth and differentiation. PMID:27100855

  2. Anatomical and Functional Outcomes following a Precise, Graded, Dorsal Laceration Spinal Cord Injury in C57BL/6 Mice

    PubMed Central

    Hill, Rachel L.; Zhang, Yi Ping; Burke, Darlene A.; DeVries, William H.; Zhang, Yongjie; Magnuson, David S.K.; Whittemore, Scott R.

    2009-01-01

    Abstract To study the pathophysiology of spinal cord injury (SCI), we used the LISA-Vibraknife to generate a precise and reproducible dorsal laceration SCI in the mouse. The surgical procedure involved a T9 laminectomy, dural resection, and a spinal cord laceration to a precisely controlled depth. Four dorsal hemisection injuries with lesion depths of 0.5, 0.8, 1.1, and 1.4 mm, as well as normal, sham (laminectomy and dural removal only), and transection controls were examined. Assessments including the Basso Mouse Scale (BMS), footprint analysis, beam walk, toe spread reflex, Hargreaves' test, and transcranial magnetic motor-evoked potential (tcMMEP) analysis were performed to assess motor, sensorimotor, and sensory function. These outcome measures demonstrated significant increases in functional deficits as the depth of the lesion increased, and significant behavioral recovery was observed in the groups over time. Quantitative histological examination showed significant differences between the injury groups and insignificant lesion depth variance within each of the groups. Statistically significant differences were additionally found in the amount of ventral spared tissue at the lesion site between the injury groups. This novel, graded, reproducible laceration SCI model can be used in future studies to look more closely at underlying mechanisms that lead to functional deficits following SCI, as well as to determine the efficacy of therapeutic intervention strategies in the injury and recovery processes following SCI. PMID:19196178

  3. Anatomical and functional outcomes following a precise, graded, dorsal laceration spinal cord injury in C57BL/6 mice.

    PubMed

    Hill, Rachel L; Zhang, Yi Ping; Burke, Darlene A; Devries, William H; Zhang, Yongjie; Magnuson, David S K; Whittemore, Scott R; Shields, Christopher B

    2009-01-01

    To study the pathophysiology of spinal cord injury (SCI), we used the LISA-Vibraknife to generate a precise and reproducible dorsal laceration SCI in the mouse. The surgical procedure involved a T9 laminectomy, dural resection, and a spinal cord laceration to a precisely controlled depth. Four dorsal hemisection injuries with lesion depths of 0.5, 0.8, 1.1, and 1.4 mm, as well as normal, sham (laminectomy and dural removal only), and transection controls were examined. Assessments including the Basso Mouse Scale (BMS), footprint analysis, beam walk, toe spread reflex, Hargreaves' test, and transcranial magnetic motor-evoked potential (tcMMEP) analysis were performed to assess motor, sensorimotor, and sensory function. These outcome measures demonstrated significant increases in functional deficits as the depth of the lesion increased, and significant behavioral recovery was observed in the groups over time. Quantitative histological examination showed significant differences between the injury groups and insignificant lesion depth variance within each of the groups. Statistically significant differences were additionally found in the amount of ventral spared tissue at the lesion site between the injury groups. This novel, graded, reproducible laceration SCI model can be used in future studies to look more closely at underlying mechanisms that lead to functional deficits following SCI, as well as to determine the efficacy of therapeutic intervention strategies in the injury and recovery processes following SCI. PMID:19196178

  4. Grade 3 open tibial shaft fractures treated with a circular frame, functional outcome and systematic review of literature.

    PubMed

    Dickson, D R; Moulder, E; Hadland, Y; Giannoudis, P V; Sharma, H K

    2015-04-01

    We report on the surgical and functional outcome of 22 patients with Grade 3 open tibial fractures treated with circular frame. All cases united and there were no re-fractures or amputations. All patients were assessed at a minimum of 1-year post frame removal. Assessment included clinical examination, IOWA ankle and knee scores, Olerud and Molander ankle score and EuroQol EQ-5D. Clinical scores were either good or excellent in over half of the patients in all knee and ankle scores. There was a significant positive correlation between functional outcomes and the EQ-5D score. The EQ-5D mean health state visual analogue score was comparable to the general UK population despite patients scoring less than the average UK population in three of the five domains. 36% reported some difficulties in walking and 41% had problems with pain. 14% had difficulties with self-care and 46% had difficulties with their usual activities. 14% had problems with anxiety or depression. Systematic review of the literature suggests, in the management of open tibial fractures, circular frames provide equivalent or superior surgical outcomes in comparison with other techniques. Our study finds the application of a circular frame also results in a good functional outcome in the majority of cases. PMID:25648287

  5. Nanoscale Graphene Disk: A Natural Functionally Graded Material-How is Fourier's Law Violated along Radius Direction of 2D Disk.

    PubMed

    Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

    2015-01-01

    In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier's law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs' thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity. PMID:26443206

  6. Nanoscale Graphene Disk: A Natural Functionally Graded Material-How is Fourier’s Law Violated along Radius Direction of 2D Disk

    NASA Astrophysics Data System (ADS)

    Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

    2015-10-01

    In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier’s law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs’ thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity.

  7. Nanoscale Graphene Disk: A Natural Functionally Graded Material–How is Fourier’s Law Violated along Radius Direction of 2D Disk

    PubMed Central

    Yang, Nuo; Hu, Shiqian; Ma, Dengke; Lu, Tingyu; Li, Baowen

    2015-01-01

    In this Paper, we investigate numerically and analytically the thermal conductivity of nanoscale graphene disks (NGDs), and discussed the possibility to realize functionally graded material (FGM) with only one material, NGDs. Different from previous studies on divergence/non-diffusive of thermal conductivity in nano-structures with different size, we found a novel non-homogeneous (graded) thermal conductivity along the radius direction in a single nano-disk structure. We found that, instead of a constant value, the NGD has a graded thermal conductivity along the radius direction. That is, Fourier’s law of heat conduction is not valid in two dimensional graphene disk structures Moreover, we show the dependent of NGDs’ thermal conductivity on radius and temperature. Our study might inspire experimentalists to develop NGD based versatile FGMs, improve understanding of the heat removal of hot spots on chips, and enhance thermoelectric energy conversion efficiency by two dimensional disk with a graded thermal conductivity. PMID:26443206

  8. Extended Functionality of Environmentally-Resistant Mo-Si-B-Based Coatings

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.; Sakidja, R.

    2013-02-01

    Multiphase Mo-Si-B alloys with compositions which yield the ternary intermetallic Mo5SiB2 (T2) phase as a key microstructure constituent together with the Mo and Mo3Si phases, offer an attractive balance of high melting temperature, oxidation resistance, and mechanical properties. The investigation of reaction kinetics involving the T2 phase enables the analysis of oxidation in terms of diffusion pathways and the design of effective coatings. From this basis, kinetic biasing is used together with pack cementation to develop Mo-Si-B-based multilayered coatings with an aluminoborosilica surface and in situ diffusion barriers with self-healing characteristics for enhanced oxidation resistance. While a combustion environment contains water vapor that can accelerate an attack of silica-based coatings, the Mo-Si-B-based coatings provide oxidation resistance in water vapor up to at least 1,500°C. An exposure to hot ionized gas species generated in an arc jet confirms the robust coating performance in extreme environments. To extend the application beyond Mo-based systems, a two-stage process has been implemented to provide effective oxidation resistance for refractory metal cermets, SiC and ZrB2 ultra-high-temperature composites.

  9. Coated platelets function in platelet-dependent fibrin formation via integrin αIIbβ3 and transglutaminase factor XIII

    PubMed Central

    Mattheij, Nadine J.A.; Swieringa, Frauke; Mastenbroek, Tom G.; Berny-Lang, Michelle A.; May, Frauke; Baaten, Constance C.F.M.J.; van der Meijden, Paola E.J.; Henskens, Yvonne M.C.; Beckers, Erik A.M.; Suylen, Dennis P.L.; Nolte, Marc W.; Hackeng, Tilman M.; McCarty, Owen J.T.; Heemskerk, Johan W.M.; Cosemans, Judith M.E.M.

    2016-01-01

    Coated platelets, formed by collagen and thrombin activation, have been characterized in different ways: i) by the formation of a protein coat of α-granular proteins; ii) by exposure of procoagulant phosphatidylserine; or iii) by high fibrinogen binding. Yet, their functional role has remained unclear. Here we used a novel transglutaminase probe, Rhod-A14, to identify a subpopulation of platelets with a cross-linked protein coat, and compared this with other platelet subpopulations using a panel of functional assays. Platelet stimulation with convulxin/thrombin resulted in initial integrin αIIbβ3 activation, the appearance of a platelet population with high fibrinogen binding, (independently of active integrins, but dependent on the presence of thrombin) followed by phosphatidylserine exposure and binding of coagulation factors Va and Xa. A subpopulation of phosphatidylserine-exposing platelets bound Rhod-A14 both in suspension and in thrombi generated on a collagen surface. In suspension, high fibrinogen and Rhod-A14 binding were antagonized by combined inhibition of transglutaminase activity and integrin αIIbβ3. Markedly, in thrombi from mice deficient in transglutaminase factor XIII, platelet-driven fibrin formation and Rhod-A14 binding were abolished by blockage of integrin αIIbβ3. Vice versa, star-like fibrin formation from platelets of a patient with deficiency in αIIbβ3 (Glanzmann thrombasthenia) was abolished upon blockage of transglutaminase activity. We conclude that coated platelets, with initial αIIbβ3 activation and high fibrinogen binding, form a subpopulation of phosphatidylserine-exposing platelets, and function in platelet-dependent star-like fibrin fiber formation via transglutaminase factor XIII and integrin αIIbβ3. PMID:26721892

  10. Bi-Functionalization of a Calcium Phosphate-Coated Titanium Surface with Slow-Release Simvastatin and Metronidazole to Provide Antibacterial Activities and Pro-Osteodifferentiation Capabilities

    PubMed Central

    Liu, Yang; Jin, Xiaoxiao; Fan, Cong; Ye, Hongqiang; Ou, Meng’en; Lv, Longwei; Wu, Gang; Zhou, Yongsheng

    2014-01-01

    Coating the surface of titanium implants or other bone graft substitute materials with calcium phosphate (Ca-P) crystals is an effective way to enhance the osteoconduction of the implants. Ca-P coating alone cannot confer pro-osteodifferentiation and antibacterial capabilities on implants; however, it can serve as a carrier for biological agents which could improve the performance of implants and bone substitutes. Here, we constructed a novel, bi-functional Ca-P coating with combined pro-osteodifferentiation and antibacterial capabilities. Different concentrations of metronidazole (MNZ) and simvastatin (SIM) were integrated into biomimetic Ca-P coatings on the surface of titanium disks. The biological effects of this bi-functional biomimetic coating on human bone marrow mesenchymal stem cells (hBMMSCs), human adipose derived stromal cells (hASCs), and Porphyromonas gingivalis were assessed in vitro. We observed that Ca-P coatings loaded with both SIM and MNZ display favorable release kinetics without affecting cell proliferation or attachment. In the inhibition zone test, we found that the bi-functional coating showed lasting antibacterial effects when incubated with Porphyromonas gingivalis for 2 and 4 days. Moreover, the osteodifferentiation of hBMMSCs and hASCs were increased when cultured on this bi-functional coating for 7 and 14 days. Both drugs were loaded onto the Ca-P coating at specific concentrations (10−5 M SIM; 10−2 M MNZ) to achieve optimal release kinetics. Considering the safety, stability and low cost of SIM and MNZ, this novel bi-functional Ca-P coating technique represents a promising method to improve the performance of metal implants or other bone substitute materials, and can theoretically be easily translated to clinical applications. PMID:24844416

  11. Resecting diffuse low-grade gliomas to the boundaries of brain functions: a new concept in surgical neuro-oncology.

    PubMed

    Duffau, H

    2015-12-01

    The traditional dilemma making surgery for diffuse low-grade gliomas (DLGGs) challenging is underlain by the need to optimize tumor resection in order to significantly increase survival versus the risk of permanent neurological morbidity. Development of neuroimaging led neurosurgeons to achieve tumorectomy according to the oncological limits provided by preoperative or intraoperative structural and metabolic imaging. However, this principle is not coherent, neither with the infiltrative nature of DLGGs nor with the limited resolution of current neuroimaging. Indeed, despite technical advances, MRI still underestimates the actual spatial extent of gliomas, since tumoral cells are present several millimeters to centimeters beyond the area of signal abnormalities. Furthermore, cortical and subcortical structures may be still crucial for brain functions despite their invasion by this diffuse tumoral disease. Finally, the lack of reliability of functional MRI has also been demonstrated. Therefore, to talk about "maximal safe resection" based upon neuroimaging is a non-sense, because oncological MRI does not show the tumor and functional MRI does not show critical neural pathways. This review proposes an original concept in neuro-oncological surgery, i.e. to resect DLGG to the boundaries of brain functions, thanks to intraoperative electrical mapping performed in awake patients. This paradigmatic shift from image-guided resection to functional mapping-guided resection, based upon an accurate study of brain connectomics and neuroplasticity in each patient throughout tumor removal has permitted to solve the classical dilemma, by increasing both survival and quality of life in DLGG patients. With this in mind, brain surgeons should also be neuroscientists. PMID:25907410

  12. Functional reorganization of the attentional networks in low-grade glioma patients: a longitudinal study.

    PubMed

    Charras, Pom; Herbet, Guillaume; Deverdun, Jérémy; de Champfleur, Nicolas M; Duffau, Hugues; Bartolomeo, Paolo; Bonnetblanc, François

    2015-02-01

    Right brain damage often provokes deficits of visuospatial attention. Although the spatial attention networks have been widely investigated in stroke patients as well as in the healthy brain, little is known about the impact of slow growing lesions in the right hemisphere. We here present a longitudinal study of 20 patients who have been undergoing awake brain surgery with per-operative line bisection testing. Our aim was to investigate the impact of tumour presence and of tumour resection on the functional (re)organization of the attention networks. We assessed patients' performance on lateralized target detection, visual exploration and line bisection before surgery, and in the acute and post-acute operative phases after surgery. Clear evidence for transient neglect signs was observed in the acute post-operative phase, although full recovery had invariably occurred in all patients. The resection of the right angular gyrus was associated with transient neglect-like symptoms in all tasks, whereas resection of more anterior regions correlated with transient deficits only in visual exploration or detection (but not in line bisection). The attentional networks showed substantial functional recovery. This impressive pattern of recovery is discussed in terms of involvement of the contralateral left hemisphere and of preservation of long-range white matter pathways within the right hemisphere. PMID:25241396

  13. Hippocampal Dosimetry Predicts Neurocognitive Function Impairment After Fractionated Stereotactic Radiotherapy for Benign or Low-Grade Adult Brain Tumors

    SciTech Connect

    Gondi, Vinai; Hermann, Bruce P.; Mehta, Minesh P.; Tome, Wolfgang A.

    2012-07-15

    Purpose: To prospectively evaluate the association between hippocampal dose and long-term neurocognitive function (NCF) impairment for benign or low-grade adult brain tumors treated with fractionated stereotactic radiotherapy (FSRT). Methods and Materials: Adult patients with benign or low-grade adult brain tumors were treated with FSRT per institutional practice. No attempt was made to spare the hippocampus. NCF testing was conducted at baseline and 18 months follow-up, on a prospective clinical trial. Regression-based standardized z scores were calculated by using similar healthy control individuals evaluated at the same test-retest interval. NCF impairment was defined as a z score {<=}-1.5. After delineation of the bilateral hippocampi according to the Radiation Therapy Oncology Group contouring atlas, dose-volume histograms were generated for the left and right hippocampi and for the composite pair. Biologically equivalent doses in 2-Gy fractions (EQD{sub 2}) assuming an {alpha}/{beta} ratio of 2 Gy were computed. Fisher's exact test and binary logistic regression were used for univariate and multivariate analyses, respectively. Dose-response data were fit to a nonlinear model. Results: Of 29 patients enrolled in this trial, 18 completed both baseline and 18-month NCF testing. An EQD{sub 2} to 40% of the bilateral hippocampi >7.3 Gy was associated with impairment in Wechsler Memory Scale-III Word List (WMS-WL) delayed recall (odds ratio [OR] 19.3; p = 0.043). The association between WMS-WL delayed recall and EQD{sub 2} to 100% of the bilateral hippocampi >0.0 Gy trended to significance (OR 14.8; p = 0.068). Conclusion: EQD{sub 2} to 40% of the bilateral hippocampi greater than 7.3 Gy is associated with long-term impairment in list-learning delayed recall after FSRT for benign or low-grade adult brain tumors. Given that modern intensity-modulated radiotherapy techniques can reduce the dose to the bilateral hippocampi below this dosimetric threshold, patients

  14. Hippocampal Dosimetry Predicts Neurocognitive Function Impairment After Fractionated Stereotactic Radiotherapy for Benign or Low-Grade Adult Brain Tumors

    SciTech Connect

    Gondi, Vinai; Hermann, Bruce P.; Mehta, Minesh P.; Tome, Wolfgang A.

    2013-02-01

    Purpose: To prospectively evaluate the association between hippocampal dose and long-term neurocognitive function (NCF) impairment for benign or low-grade adult brain tumors treated with fractionated stereotactic radiotherapy (FSRT). Methods and Materials: Adult patients with benign or low-grade adult brain tumors were treated with FSRT per institutional practice. No attempt was made to spare the hippocampus. NCF testing was conducted at baseline and 18 months follow-up, on a prospective clinical trial. Regression-based standardized z scores were calculated by using similar healthy control individuals evaluated at the same test-retest interval. NCF impairment was defined as a z score {<=}-1.5. After delineation of the bilateral hippocampi according to the Radiation Therapy Oncology Group contouring atlas, dose-volume histograms were generated for the left and right hippocampi and for the composite pair. Biologically equivalent doses in 2-Gy fractions (EQD{sub 2}) assuming an {alpha}/{beta} ratio of 2 Gy were computed. Fisher's exact test and binary logistic regression were used for univariate and multivariate analyses, respectively. Dose-response data were fit to a nonlinear model. Results: Of 29 patients enrolled in this trial, 18 completed both baseline and 18-month NCF testing. An EQD{sub 2} to 40% of the bilateral hippocampi >7.3 Gy was associated with impairment in Wechsler Memory Scale-III Word List (WMS-WL) delayed recall (odds ratio [OR] 19.3; p = 0.043). The association between WMS-WL delayed recall and EQD{sub 2} to 100% of the bilateral hippocampi >0.0 Gy trended to significance (OR 14.8; p = 0.068). Conclusion: EQD{sub 2} to 40% of the bilateral hippocampi greater than 7.3 Gy is associated with long-term impairment in list-learning delayed recall after FSRT for benign or low-grade adult brain tumors. Given that modern intensity-modulated radiotherapy techniques can reduce the dose to the bilateral hippocampi below this dosimetric threshold, patients

  15. Meshless Local Petrov-Galerkin Method for Shallow Shells with Functionally Graded and Orthotropic Material Properties

    NASA Astrophysics Data System (ADS)

    Sladek, J.; Sladek, V.; Zhang, Ch.

    2008-02-01

    A meshless local Petrov-Galerkin (MLPG) formulation is presented for analysis of shear deformable shallow shells with orthotropic material properties and continuously varying material properties through the shell thickness. Shear deformation of shells described by the Reissner theory is considered. Analyses of shells under static and dynamic loads are given here. For transient elastodynamic case the Laplace-transform is used to eliminate the time dependence of the field variables. A weak formulation with a unit test function transforms the set of the governing equations into local integral equations on local subdomains in the plane domain of the shell. The meshless approximation based on the Moving Least-Squares (MLS) method is employed for the implementation.

  16. Intumescent Coatings as Fire Retardants

    NASA Technical Reports Server (NTRS)

    Parker, J. A.; Fohlen, G. M.; Sawko, P. M.; Fish, R. H.

    1970-01-01

    The development of fire-retardant coatings to protect surfaces which may be exposed to fire or extreme heat is a subject of intense interest to many industries. A fire-retardant paint has been developed which represents a new chemical approach for preparing intumescent coatings, and potentially, is very important to fire-prevention authorities. The requirements for a superior coating include ease of application, suitability to a wide variety of surfaces and finishes, and stability over an extended period of time within a broad range of ambient temperature and humidity conditions. These innovative coatings, when activated by the heat of a fire, react to form a thick, low-density, polymeric coating or char layer. Water vapor and sulphur dioxide are released during the intumescent reaction. Two fire-protection mechanisms thus become available: (1) the char layer retards the flow of heat, due to the extremely low thermal conductivity; and (2) water vapor and sulfur dioxide are released, providing fire quenching properties. Still another mechanism functions in cases where the char, by virtue of its high oxidation resistance and low thermal conductivity, reaches a sufficiently high temperature to re-radiate much of the incident heat load. The coatings consist of dispersions of selective salts of a nitro-amino-arornatic compound. Specifically, para-nitroaniline bisulfate and the ammonium salt of para-nitroaniline-ortho sulphuric acid (2-amino-5-nitrobenzenesulphuric acid) are used. Suitable vehicles are cellulose nitrate of lacquer grade, a nitrite-phenolic modified rubber, or epoxy-polysulfide copolymer. Three separate formulations have been developed. A solvent is usually employed, such as methylethyl ketone, butyl acetate, or toluene, which renders the coatings suitably thin and which evaporates after the coatings are applied. Generally, the intumescent material is treated as insoluble in the vehicle, and is ground and dispersed in the vehicle and solvent like an

  17. Quinone-rich polydopamine functionalization of yttria stabilized zirconia for apatite biomineralization: The effects of coating temperature

    NASA Astrophysics Data System (ADS)

    Zain, Norhidayu Muhamad; Hussain, Rafaqat; Abdul Kadir, Mohammed Rafiq

    2015-08-01

    The use of yttria stabilized zirconia (YSZ) as biomedical implants is often offset by its bioinert nature that prevents its osseointegration to occur. Therefore, the functionalization of YSZ surface by polydopamine to facilitate the biomineralization of apatite layer on top of the coated film has incessantly been studied. In this study YSZ discs were first immersed in 2 mg/mL of stirred dopamine solution at coating temperatures between 25 and 80 °C. The specimens were then incubated for 7d in 1.5 SBF. The effect of coating temperature on the properties (chemical compositions and wettability) and the apatite mineralization on top of the generated films was investigated. It was found that at 50 °C, the specimen displayed the highest intensity of Ca 2p peak (1.55 ± 0.42 cps) with Ca/P ratio of 1.67 due to the presence of abundant quinone groups (Cdbnd O). However, the hydrophilicity (40.9 ± 01.7°) was greatly improved at 60 °C accompanied by the highest film thickness of 306 nm. Therefore, it was concluded that the presence of high intensity of quinone groups (Cdbnd O) in polydopamine film at elevated temperature affects the chelation of Ca2+ ions and thus enhance the growth of apatite layer on top of the functionalized YSZ surface.

  18. Thermoelastic Analysis of a Functionally Graded Rotating Thick-Walled Tube Subjected to Mechanical and Thermal Loads

    NASA Astrophysics Data System (ADS)

    Xin, Libiao; Yang, Shengyou; Ma, Baoyu; Dui, Guansuo

    2015-11-01

    A thermoelastic solution for the functionally graded rotating thick-walled tube subjected to axisymmetric mechanical and thermal loads is given in terms of volume fractions of constituents. We assume that the tube consists of two linear elastic constituents and the volume fraction of one phase is a power function varied in the radial direction. By using the assumption of a uniform strain field within the representative volume element, the theoretical solutions of the displacement and the stresses are presented. Based on the relation of the volume average stresses of constituents and the macroscopic stresses of the composite material in micromechanics, the present method can avoid the assumption of the distribution regularities of unknown overall material parameters appeared in existing papers, such as Young's modulus, thermal expansion coefficient, thermal conductivity, and density. The effects of the angular velocity, the volume fraction, the ratio of two thermal expansion coefficients, the ratio of two thermal conductivities, and the ratio of two densities on the displacement and stresses are systematically studied, which should help structural engineers and material scientists optimally design thick-walled tube comprised inhomogeneous materials.

  19. Thermal analysis of a functionally graded material subject to a thermal gradient using the boundary element method

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Hopkins, Dale A.

    1994-01-01

    The boundary element method is utilized in this study to conduct thermal analysis of functionally graded composites, materials in which the internal microstructure or properties are explicitly tailored in order to obtain an optimal response, on the micromechanical (constituent) scale. A unique feature of the boundary element formulations used here is the use of circular shape functions to convert the two-dimensional integrations of the composite fibers to one dimensional integrations. Using the computer code BEST-CMS, the through the thickness temperature profiles are computed for a representative material with varying numbers of fibers and fiber spacing in the thickness direction. The computed temperature profiles are compared to those obtained using an alternate analytical theory which explicitly couples the heterogeneous microstructure to the global analysis. The boundary element results compared favorably to the analytical calculations, with discrepancies that are explainable based on the boundary element formulation. The results serve both to demonstrate the ability of the boundary element method to analyze these types of materials, and to verify the accuracy of the analytical theory.

  20. STRUCTURE AND FUNCTION OF PROTEIN-BASED EDIBLE FILMS AND COATINGS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Research and development on films and coatings made from various agricultural proteins has been conducted over the past 20 years but recently has been of heightened interest because of the demand for environmentally friendly, renewable replacements for petroleum-based polymeric materials and plastic...

  1. Niobium oxide-polydimethylsiloxane hybrid composite coatings for tuning primary fibroblast functions.

    PubMed

    Young, Matthew D; Tran, Nhiem; Tran, Phong A; Jarrell, John D; Hayda, Roman A; Born, Chistopher T

    2014-05-01

    This study evaluates the potential of niobium oxide-polydimethylsiloxane (PDMS) composites for tuning cellular response of fibroblasts, a key cell type of soft tissue/implant interfaces. In this study, various hybrid coatings of niobium oxide and PDMS with different niobium oxide concentrations were synthesized and characterized using scanning electron microscopy, X-ray photoelectron spectrometry (XPS), and contact angle goniometry. The coatings were then applied to 96-well plates, on which primary fibroblasts were seeded. Fibroblast viability, proliferation, and morphology were assessed after 1, 2, and 3 days of incubation using WST-1 and calcein AM assays along with fluorescent microscopy. The results showed that the prepared coatings had distinct surface features with submicron spherical composites covered in a polymeric layer. The water contact angle measurement demonstrated that the hybrid surfaces were much more hydrophobic than the original pure niobium oxide and PDMS. The combination of surface roughness and chemistry resulted in a biphasic cellular response with maximum fibroblast density on substrate with 40 wt % of niobium oxide. The results of the current study indicate that by adjusting the concentration of niobium oxide in the coating, a desirable cell response can be achieved to improve tissue/implant interfaces. PMID:23776075

  2. Lolium latent virus (Alphaflexiviridae) coat proteins: expression and functions in infected plant tissue

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Lolium latent virus (LoLV, Lolavirus, Alphaflexiviridae) viral genome is encapsidated by two carboxy-coterminal coat protein (CP) variants (about 28 and 33 kDa), in equimolar proportion. The CP ORF contains two 5'-proximal AUGs, encoding Met 1 and Met 49, respectively promoting translation of th...

  3. Investigation of enhanced hemocompatibility and tissue compatibility associated with multi-functional coating based on hyaluronic acid and Type IV collagen.

    PubMed

    Li, Jingan; Zhang, Kun; Ma, Wenyong; Wu, Feng; Yang, Ping; He, Zikun; Huang, Nan

    2016-09-01

    The biocompatibility of cardiovascular devices has always been considered crucial for their clinical efficacy. Therefore, a biofunctional coating composed of Type IV collagen (CoIV) and hyaluronan (HA) was previously fabricated onto the titanium (Ti) substrate for the application of promoting vascular smooth muscle cell contractile phenotype and improving surface endothelialization. However, the anti-inflammation property, blood compatibility and in vivo tissue compatibility of the HA/CoIV coating, as paramount consideration of cardiovascular materials surface coating, have not been investigated. Thus, in this study, the three crucial properties of the HA/CoIV coating were tested. The platelet adhesion/activation test and the dynamic whole blood experiment implied that the HA/CoIV coating had better blood compatibility compared with Ti substrate and pure CoIV coating. The macrophage adhesion/activation and inflammatory cytokine release (tumor necrosis factor-alpha and interleukin-1) results indicated that the HA/CoIV coating could significantly improve the anti-inflammation property of the Ti substrate. The in vivo implantation of SD rats for 3 weeks' results demonstrated that the HA/CoIV coating caused milder tissue response. All these results suggested that the multi-functional HA/CoIV coating possessed good biocompatibility. This research is anticipated to be potentially applied for the surface modification of cardiovascular stents. PMID:27252884

  4. RGDS-functionalized polyethylene glycol hydrogel-coated magnetic iron oxide nanoparticles enhance specific intracellular uptake by HeLa cells

    PubMed Central

    Nazli, Caner; Ergenc, Tugba Ipek; Yar, Yasemin; Acar, Havva Yagci; Kizilel, Seda

    2012-01-01

    The objective of this study was to develop thin, biocompatible, and biofunctional hydrogel-coated small-sized nanoparticles that exhibit favorable stability, viability, and specific cellular uptake. This article reports the coating of magnetic iron oxide nanoparticles (MIONPs) with covalently cross-linked biofunctional polyethylene glycol (PEG) hydrogel. Silanized MIONPs were derivatized with eosin Y, and the covalently cross-linked biofunctional PEG hydrogel coating was achieved via surface-initiated photopolymerization of PEG diacrylate in aqueous solution. The thickness of the PEG hydrogel coating, between 23 and 126 nm, was tuned with laser exposure time. PEG hydrogel-coated MIONPs were further functionalized with the fibronectin-derived arginine-glycine-aspartic acid-serine (RGDS) sequence, in order to achieve a biofunctional PEG hydrogel layer around the nanoparticles. RGDS-bound PEG hydrogel-coated MIONPs showed a 17-fold higher uptake by the human cervical cancer HeLa cell line than that of amine-coated MIONPs. This novel method allows for the coating of MIONPs with nano-thin biofunctional hydrogel layers that may prevent undesirable cell and protein adhesion and may allow for cellular uptake in target tissues in a specific manner. These findings indicate that the further biofunctional PEG hydrogel coating of MIONPs is a promising platform for enhanced specific cell targeting in biomedical imaging and cancer therapy. PMID:22619531

  5. Investigation of enhanced hemocompatibility and tissue compatibility associated with multi-functional coating based on hyaluronic acid and Type IV collagen

    PubMed Central

    Li, Jingan; Zhang, Kun; Ma, Wenyong; Wu, Feng; Yang, Ping; He, Zikun; Huang, Nan

    2016-01-01

    The biocompatibility of cardiovascular devices has always been considered crucial for their clinical efficacy. Therefore, a biofunctional coating composed of Type IV collagen (CoIV) and hyaluronan (HA) was previously fabricated onto the titanium (Ti) substrate for the application of promoting vascular smooth muscle cell contractile phenotype and improving surface endothelialization. However, the anti-inflammation property, blood compatibility and in vivo tissue compatibility of the HA/CoIV coating, as paramount consideration of cardiovascular materials surface coating, have not been investigated. Thus, in this study, the three crucial properties of the HA/CoIV coating were tested. The platelet adhesion/activation test and the dynamic whole blood experiment implied that the HA/CoIV coating had better blood compatibility compared with Ti substrate and pure CoIV coating. The macrophage adhesion/activation and inflammatory cytokine release (tumor necrosis factor-alpha and interleukin-1) results indicated that the HA/CoIV coating could significantly improve the anti-inflammation property of the Ti substrate. The in vivo implantation of SD rats for 3 weeks’ results demonstrated that the HA/CoIV coating caused milder tissue response. All these results suggested that the multi-functional HA/CoIV coating possessed good biocompatibility. This research is anticipated to be potentially applied for the surface modification of cardiovascular stents. PMID:27252884

  6. Propagation of Surface Waves in a Homogeneous Layer of Finite Thickness over an Initially Stressed Functionally Graded Magnetic-Electric-Elastic Half-Space

    NASA Astrophysics Data System (ADS)

    Li, Li; Wei, P. J.

    2015-03-01

    The propagation behaviour of Love wave in an initially stressed functionally graded magnetic-electric-elastic half-space carrying a homogeneous layer is investigated. The material parameters in the substrate are assumed to vary exponentially along the thickness direction only. The velocity equations of Love wave are derived on the electrically or magnetically open circuit and short circuit boundary conditions, based on the equations of motion of the graded magnetic-electric-elastic mate- rial with the initial stresses and the free traction boundary conditions of surface and the continuous boundary conditions of interface. The dispersive curves are obtained numerically and the influences of the initial stresses and the material gradient index on the dispersive curves are dis- cussed. The investigation provides a basis for the development of new functionally graded magneto-electro-elastic surface wave devices.

  7. Markers of T Cell Infiltration and Function Associate with Favorable Outcome in Vascularized High-Grade Serous Ovarian Carcinoma

    PubMed Central

    Townsend, Katelin N.; Spowart, Jaeline E.; Huwait, Hassan; Eshragh, Sima; West, Nathan R.; Elrick, Mary A.; Kalloger, Steve E.; Anglesio, Michael; Watson, Peter H.; Huntsman, David G.; Lum, Julian J.

    2013-01-01

    Background When T cells infiltrate the tumor environment they encounter a myriad of metabolic stressors including hypoxia. Overcoming the limitations imposed by an inadequate tumor vasculature that contributes to these stressors may be a crucial step to immune cells mounting an effective anti-tumor response. We sought to determine whether the functional capacity of tumor infiltrating lymphocytes (TIL) could be influenced by the tumor vasculature and correlated this with survival in patients with ovarian cancer. Methodology and Principal Findings In 196 high-grade serous ovarian tumors, we confirmed that the tumor vascularity as measured by the marker CD31 was associated with improved patient disease-specific survival. We also found that tumors positive for markers of TIL (CD8, CD4 and forkhead box P3 (FoxP3)) and T cell function (granzyme B and T-cell restricted intracellular antigen-1 (TIA-1)) correlated significantly with elevated vascularity. In vitro, hypoxic CD8 T cells showed reduced cytolytic activity, secreted less effector cytokines and upregulated autophagy. Survival analysis revealed that patients had a significant improvement in disease-specific survival when FoxP3 expressing cells were present in CD31-high tumors compared to patients with FoxP3 expressing cells in CD31-low tumors [HR: 2.314 (95% CI 1.049–5.106); p = 0.0377]. Patients with high vascular endothelial growth factor (VEGF) expressing tumors containing granzyme B positive cells had improved survival compared to patients with granzyme B positive cells in VEGF-low tumors [HR: 2.522 (95% CI 1.097–5.799); p = 0.0294]. Significance Overall, this data provides a rationale for developing strategies aimed at improving the adaptability and function of TIL to hypoxic tumor conditions. PMID:24376535

  8. Effects of an extended photoperiod on gonadal function and condition of hair coats in Thoroughbred colts and fillies

    PubMed Central

    KUNII, Hirokazu; NAMBO, Yasuo; OKANO, Atsushi; MATSUI, Akira; ISHIMARU, Mutsuki; ASAI, Yo; SATO, Fumio; FUJII, Kazuki; NAGAOKA, Kentaro; WATANABE, Gen; TAYA, Kazuyoshi

    2015-01-01

    ABSTRACT The effects of an extended photoperiod (EP) in Thoroughbreds colts and fillies from winter at one year old to spring at two years old on the gonadal functions, coat condition, and endocrine changes were investigated. Sixty-two Thoroughbreds (31 colts and 31 fillies) reared in the Hidaka Training and Research Center (Hidaka), Japan Racing Association were used. Thirty of them (15 colts and 15 fillies) were reared under EP conditions from December 20 to April 10, and the remaining 32 horses were reared under natural light alone as a control group. For EP, a 100-watt white bulb was set near the ceilings of stalls, and lighting conditions of 14.5-hr light and 9.5-hr dark periods were established. Blood was collected from the jugular vein once a month from October at one year old to February at two years old in both colts and fillies, and then twice a month in colts and weekly in fillies after March, and the coat condition was evaluated in January and April in 56 horses. To investigate endocrine changes, the plasma concentrations of prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), immunoreactive (ir-) inhibin, testosterone, estradiol-17β and progesterone were measured. No significant difference was noted in the coat condition between the two groups in January, but they changed from winter to summer coats (molting of winter coats) in April in the EP group compared with the control group. Regarding endocrine changes, the plasma concentrations of prolactin, FSH, ir-inhibin and testosterone were significantly higher in the EP colts than in the control group from January to April. The plasma concentrations of LH tended to rise in the EP colts from January to April compared with the control group. In the EP fillies, the plasma concentrations of prolactin, LH, ir-inhibin, estradiol-17β and progesterone were significantly higher during January and April, but a significantly high level of FSH was noted in the control than EP group in January

  9. Effects of an extended photoperiod on gonadal function and condition of hair coats in Thoroughbred colts and fillies.

    PubMed

    Kunii, Hirokazu; Nambo, Yasuo; Okano, Atsushi; Matsui, Akira; Ishimaru, Mutsuki; Asai, Yo; Sato, Fumio; Fujii, Kazuki; Nagaoka, Kentaro; Watanabe, Gen; Taya, Kazuyoshi

    2015-01-01

    The effects of an extended photoperiod (EP) in Thoroughbreds colts and fillies from winter at one year old to spring at two years old on the gonadal functions, coat condition, and endocrine changes were investigated. Sixty-two Thoroughbreds (31 colts and 31 fillies) reared in the Hidaka Training and Research Center (Hidaka), Japan Racing Association were used. Thirty of them (15 colts and 15 fillies) were reared under EP conditions from December 20 to April 10, and the remaining 32 horses were reared under natural light alone as a control group. For EP, a 100-watt white bulb was set near the ceilings of stalls, and lighting conditions of 14.5-hr light and 9.5-hr dark periods were established. Blood was collected from the jugular vein once a month from October at one year old to February at two years old in both colts and fillies, and then twice a month in colts and weekly in fillies after March, and the coat condition was evaluated in January and April in 56 horses. To investigate endocrine changes, the plasma concentrations of prolactin, luteinizing hormone (LH), follicle-stimulating hormone (FSH), immunoreactive (ir-) inhibin, testosterone, estradiol-17β and progesterone were measured. No significant difference was noted in the coat condition between the two groups in January, but they changed from winter to summer coats (molting of winter coats) in April in the EP group compared with the control group. Regarding endocrine changes, the plasma concentrations of prolactin, FSH, ir-inhibin and testosterone were significantly higher in the EP colts than in the control group from January to April. The plasma concentrations of LH tended to rise in the EP colts from January to April compared with the control group. In the EP fillies, the plasma concentrations of prolactin, LH, ir-inhibin, estradiol-17β and progesterone were significantly higher during January and April, but a significantly high level of FSH was noted in the control than EP group in January. The

  10. The Effects of Contingent Praise Upon the Achievement of a Deficit Junior High School Student in Oral Reading Accuracy in Probes Above Her Functional Grade Level.

    ERIC Educational Resources Information Center

    Proe, Susan; Wade, David

    Evaluated was the effectiveness of three training procedures (imitation training, imitation training with praise, and imitation training with points for an art supply contingency) in improving the oral reading accuracy and reading comprehension of a 13-year-old girl whose functional reading was at the second grade level. The procedures were…

  11. A Function-Based Intervention to Increase a Second-Grade Student's On-Task Behavior in a General Education Classroom

    ERIC Educational Resources Information Center

    Germer, Kathryn A.; Kaplan, Lauren M.; Giroux, Lindsay N.; Markham, Elizabeth H.; Ferris, Geoffrey J.; Oakes, Wendy P.; Lane, Kathleen Lynne

    2011-01-01

    A functional assessment-based intervention (FABI) was designed and implemented to increase the on-task behavior of David, a second-grade student in a general education classroom. David attended an elementary school that used a comprehensive, integrated, three-tiered (CI3T) model of prevention. The school's principal nominated David for Project…

  12. Power and Type I Error of the Mean and Covariance Structure Analysis Model for Detecting Differential Item Functioning in Graded Response Items

    ERIC Educational Resources Information Center

    Gonzalez-Roma, Vicente; Hernandez, Ana; Gomez-Benito, Juana

    2006-01-01

    In this simulation study, we investigate the power and Type I error rate of a procedure based on the mean and covariance structure analysis (MACS) model in detecting differential item functioning (DIF) of graded response items with five response categories. The following factors were manipulated: type of DIF (uniform and non-uniform), DIF…

  13. o-Vanillin functionalized mesoporous silica - coated magnetite nanoparticles for efficient removal of Pb(II) from water

    NASA Astrophysics Data System (ADS)

    Culita, Daniela C.; Simonescu, Claudia Maria; Patescu, Rodica-Elena; Dragne, Mioara; Stanica, Nicolae; Oprea, Ovidiu

    2016-06-01

    o-Vanillin functionalized mesoporous silica - coated magnetite (Fe3O4@MCM-41-N-oVan) was synthesized and fully characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, N2 adsorption-desorption technique and magnetic measurements. The capacity of Fe3O4@MCM-41-N-oVan to adsorb Pb(II) from aqueous solutions was evaluated in comparison with raw mesoporous silica - coated magnetite (Fe3O4@MCM-41) and amino - modified mesoporous silica coated magnetite (Fe3O4@MCM-41-NH2). The effect of adsorption process parameters such us pH, contact time, initial Pb(II) concentration was also investigated. The adsorption data were successfully fitted with the Langmuir model, exhibiting a maximum adsorption capacity of 155.71 mg/g at pH=4.4 and T=298 K. The results revealed that the adsorption rate was very high at the beginning of the adsorption process, 80-90% of the total amount of Pb(II) being removed within the first 60 min, depending on the initial concentration. The results of the present work suggest that Fe3O4@MCM-41-N-oVan is a suitable candidate for the separation of Pb(II) from contaminated water.

  14. Optical detection of glucose and glycated hemoglobin using etched fiber Bragg gratings coated with functionalized reduced graphene oxide.

    PubMed

    Sridevi, S; Vasu, K S; Sampath, S; Asokan, S; Sood, A K

    2016-07-01

    An enhanced optical detection of D-glucose and glycated hemoglobin (HbA1c ) has been established in this study using etched fiber Bragg gratings (eFBG) coated with aminophenylboronic acid (APBA)-functionalized reduced graphene oxide (RGO). The read out, namely the shift in Bragg wavelength (ΔλB ) is highly sensitive to changes that occur due to the adsorption of glucose (or HbA1c ) molecules on the eFBG sensor coated with APBA-RGO complex through a five-membered cyclic ester bond formation between glucose and APBA molecules. A limit of detection of 1 nM is achieved with a linear range of detection from 1 nM to 10 mM in the case of D-glucose detection experiments. For HbA1c , a linear range of detection varying from 86 nM to 0.23 mM is achieved. The observation of only 4 pm (picometer) change in ΔλB even for the 10 mM lactose solution confirms the specificity of the APBA-RGO complex coated eFBG sensors to glucose molecules. PMID:26266873

  15. Utilization of wheat straw for the preparation of coated controlled-release fertilizer with the function of water retention.

    PubMed

    Xie, Lihua; Liu, Mingzhu; Ni, Boli; Wang, Yanfang

    2012-07-18

    With the aim of improving fertilizer use efficiency and minimizing the negative impact on the environment, a new coated controlled-release fertilizer with the function of water retention was prepared. A novel low water solubility macromolecular fertilizer, poly(dimethylourea phosphate) (PDUP), was "designed" and formulated from N,N'-dimethylolurea (DMU) and potassium dihydrogen phosphate. Simultaneously, an eco-friendly superabsorbent composite based on wheat straw (WS), acrylic acid (AA), 2-acryloylamino-2-methyl-1-propanesulfonic acid (AMPS), and N-hydroxymethyl acrylamide (NHMAAm) was synthesized and used as the coating to control the release of nutrient. The nitrogen release profile and water retention capacity of the product were also investigated. The degradation of the coating material in soil solution was studied. Meanwhile, the impact of the content of N-hydroxymethyl acrylamide on the degradation extent was examined. The experimental data showed that the product with good water retention and controlled-release capacities, being economical and eco-friendly, could be promising for applications in agriculture and horticulture. PMID:22730900

  16. Analysis of Plasma-Sprayed Thermal Barrier Coatings With Homogeneous and Heterogeneous Bond Coats Under Spatially Uniform Cyclic Thermal Loading

    NASA Technical Reports Server (NTRS)

    Arnold, Steven M.; Pindera, Marek-Jerzy; Aboudi, Jacob

    2003-01-01

    This report summarizes the results of a numerical investigation into the spallation mechanism in plasma-sprayed thermal barrier coatings observed under spatially-uniform cyclic thermal loading. The analysis focuses on the evolution of local stress and inelastic strain fields in the vicinity of the rough top/bond coat interface during thermal cycling, and how these fields are influenced by the presence of an oxide film and spatially uniform and graded distributions of alumina particles in the metallic bond coat aimed at reducing the top/bond coat thermal expansion mismatch. The impact of these factors on the potential growth of a local horizontal delamination at the rough interface's crest is included. The analysis is conducted using the Higher-Order Theory for Functionally Graded Materials with creep/relaxation constituent modeling capabilities. For two-phase bond coat microstructures, both the actual and homogenized properties are employed in the analysis. The results reveal the important contributions of both the normal and shear stress components to the delamination growth potential in the presence of an oxide film, and suggest mixed-mode crack propagation. The use of bond coats with uniform or graded microstructures is shown to increase the potential for delamination growth by increasing the magnitude of the crack-tip shear stress component.

  17. Microelectrode Arrays and the Use of PEG-Functionalized Diblock Copolymer Coatings

    PubMed Central

    Uppal, Sakshi; Graaf, Matthew D.; Moeller, Kevin D.

    2014-01-01

    PEG-modified diblock copolymer surfaces have been examined for their compatibility with microelectrode array based analytical methods. The use of PEG-modified polymer surfaces on the arrays was initially problematic because the redox couples used in the experiments were adsorbed by the polymer. This led the current measured by cyclic voltammetry for the redox couple to be unstable and increase with time. However, two key findings allow the experiments to be successful. First, after multiple cyclic voltammograms the current associated with the redox couple does stabilize so that a good baseline current can be established. Second, the rate at which the current stabilizes is consistent every time a particular coated array is used. Hence, multiple analytical experiments can be conducted on an array coated with a PEG-modified diblock copolymer and the data obtained is comparable as long as the data for each experiment is collected at a consistent time point. PMID:25587425

  18. Love-type waves in functionally graded piezoelectric material (FGPM) sandwiched between initially stressed layer and elastic substrate

    NASA Astrophysics Data System (ADS)

    Saroj, Pradeep K.; Sahu, S. A.; Chaudhary, S.; Chattopadhyay, A.

    2015-10-01

    This paper investigates the propagation behavior of Love-type surface waves in three-layered composite structure with initial stress. The composite structure has been taken in such a way that a functionally graded piezoelectric material (FGPM) layer is bonded between initially stressed piezoelectric upper layer and an elastic substrate. Using the method of separation of variables, frequency equation for the considered wave has been established in the form of determinant for electrical open and short cases on free surface. The bisection method iteration technique has been used to find the roots of the dispersion relations which give the modes for electrical open and short cases. The effects of gradient variation of material constant and initial stress on the phase velocity of surface waves are discussed. Dependence of thickness on each parameter of the study has been shown explicitly. Study has been also done to show the existence of cut-off frequency. Graphical representation has been done to exhibit the findings. The obtained results are significant for the investigation and characterization of Love-type waves in FGPM-layered media.

  19. Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer

    PubMed Central

    Lawrenson, Kate; Li, Qiyuan; Kar, Siddhartha; Seo, Ji-Heui; Tyrer, Jonathan; Spindler, Tassja J.; Lee, Janet; Chen, Yibu; Karst, Alison; Drapkin, Ronny; Aben, Katja K. H.; Anton-Culver, Hoda; Antonenkova, Natalia; Bowtell, David; Webb, Penelope M.; deFazio, Anna; Baker, Helen; Bandera, Elisa V.; Bean, Yukie; Beckmann, Matthias W.; Berchuck, Andrew; Bisogna, Maria; Bjorge, Line; Bogdanova, Natalia; Brinton, Louise A.; Brooks-Wilson, Angela; Bruinsma, Fiona; Butzow, Ralf; Campbell, Ian G.; Carty, Karen; Chang-Claude, Jenny; Chenevix-Trench, Georgia; Chen, Anne; Chen, Zhihua; Cook, Linda S.; Cramer, Daniel W.; Cunningham, Julie M.; Cybulski, Cezary; Dansonka-Mieszkowska, Agnieszka; Dennis, Joe; Dicks, Ed; Doherty, Jennifer A.; Dörk, Thilo; du Bois, Andreas; Dürst, Matthias; Eccles, Diana; Easton, Douglas T.; Edwards, Robert P.; Eilber, Ursula; Ekici, Arif B.; Fasching, Peter A.; Fridley, Brooke L.; Gao, Yu-Tang; Gentry-Maharaj, Aleksandra; Giles, Graham G.; Glasspool, Rosalind; Goode, Ellen L.; Goodman, Marc T.; Grownwald, Jacek; Harrington, Patricia; Harter, Philipp; Hasmad, Hanis Nazihah; Hein, Alexander; Heitz, Florian; Hildebrandt, Michelle A. T.; Hillemanns, Peter; Hogdall, Estrid; Hogdall, Claus; Hosono, Satoyo; Iversen, Edwin S.; Jakubowska, Anna; James, Paul; Jensen, Allan; Ji, Bu-Tian; Karlan, Beth Y.; Kruger Kjaer, Susanne; Kelemen, Linda E.; Kellar, Melissa; Kelley, Joseph L.; Kiemeney, Lambertus A.; Krakstad, Camilla; Kupryjanczyk, Jolanta; Lambrechts, Diether; Lambrechts, Sandrina; Le, Nhu D.; Lee, Alice W.; Lele, Shashi; Leminen, Arto; Lester, Jenny; Levine, Douglas A.; Liang, Dong; Lissowska, Jolanta; Lu, Karen; Lubinski, Jan; Lundvall, Lene; Massuger, Leon F. A. G.; Matsuo, Keitaro; McGuire, Valerie; McLaughlin, John R.; Nevanlinna, Heli; McNeish, Ian; Menon, Usha; Modugno, Francesmary; Moysich, Kirsten B.; Narod, Steven A.; Nedergaard, Lotte; Ness, Roberta B.; Azmi, Mat Adenan Noor; Odunsi, Kunle; Olson, Sara H.; Orlow, Irene; Orsulic, Sandra; Weber, Rachel Palmieri; Pearce, Celeste L.; Pejovic, Tanja; Pelttari, Liisa M.; Permuth-Wey, Jennifer; Phelan, Catherine M.; Pike, Malcolm C.; Poole, Elizabeth M.; Ramus, Susan J.; Risch, Harvey A.; Rosen, Barry; Rossing, Mary Anne; Rothstein, Joseph H.; Rudolph, Anja; Runnebaum, Ingo B.; Rzepecka, Iwona K.; Salvesen, Helga B.; Schildkraut, Joellen M.; Schwaab, Ira; Sellers, Thomas A.; Shu, Xiao-Ou; Shvetsov, Yurii B.; Siddiqui, Nadeem; Sieh, Weiva; Song, Honglin; Southey, Melissa C.; Sucheston, Lara; Tangen, Ingvild L.; Teo, Soo-Hwang; Terry, Kathryn L.; Thompson, Pamela J.; Timorek, Agnieszka; Tsai, Ya-Yu; Tworoger, Shelley S.; van Altena, Anne M.; Van Nieuwenhuysen, Els; Vergote, Ignace; Vierkant, Robert A.; Wang-Gohrke, Shan; Walsh, Christine; Wentzensen, Nicolas; Whittemore, Alice S.; Wicklund, Kristine G.; Wilkens, Lynne R.; Woo, Yin-Ling; Wu, Xifeng; Wu, Anna H.; Yang, Hannah; Zheng, Wei; Ziogas, Argyrios; Monteiro, Alvaro; Pharoah, Paul D.; Gayther, Simon A.; Freedman, Matthew L.

    2015-01-01

    Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions associated with HGSOC risk (P≤10−5). For three cis-eQTL associations (P<1.4 × 10−3, FDR<0.05) at 1p36 (CDC42), 1p34 (CDCA8) and 2q31 (HOXD9), we evaluate the functional role of each candidate by perturbing expression of each gene in HGSOC precursor cells. Overexpression of HOXD9 increases anchorage-independent growth, shortens population-doubling time and reduces contact inhibition. Chromosome conformation capture identifies an interaction between rs2857532 and the HOXD9 promoter, suggesting this SNP is a leading causal variant. Transcriptomic profiling after HOXD9 overexpression reveals enrichment of HGSOC risk variants within HOXD9 target genes (P=6 × 10−10 for risk variants (P<10−4) within 10 kb of a HOXD9 target gene in ovarian cells), suggesting a broader role for this network in genetic susceptibility to HGSOC. PMID:26391404

  20. Cis-eQTL analysis and functional validation of candidate susceptibility genes for high-grade serous ovarian cancer.

    PubMed

    Lawrenson, Kate; Li, Qiyuan; Kar, Siddhartha; Seo, Ji-Heui; Tyrer, Jonathan; Spindler, Tassja J; Lee, Janet; Chen, Yibu; Karst, Alison; Drapkin, Ronny; Aben, Katja K H; Anton-Culver, Hoda; Antonenkova, Natalia; Baker, Helen; Bandera, Elisa V; Bean, Yukie; Beckmann, Matthias W; Berchuck, Andrew; Bisogna, Maria; Bjorge, Line; Bogdanova, Natalia; Brinton, Louise A; Brooks-Wilson, Angela; Bruinsma, Fiona; Butzow, Ralf; Campbell, Ian G; Carty, Karen; Chang-Claude, Jenny; Chenevix-Trench, Georgia; Chen, Anne; Chen, Zhihua; Cook, Linda S; Cramer, Daniel W; Cunningham, Julie M; Cybulski, Cezary; Dansonka-Mieszkowska, Agnieszka; Dennis, Joe; Dicks, Ed; Doherty, Jennifer A; Dörk, Thilo; du Bois, Andreas; Dürst, Matthias; Eccles, Diana; Easton, Douglas T; Edwards, Robert P; Eilber, Ursula; Ekici, Arif B; Fasching, Peter A; Fridley, Brooke L; Gao, Yu-Tang; Gentry-Maharaj, Aleksandra; Giles, Graham G; Glasspool, Rosalind; Goode, Ellen L; Goodman, Marc T; Grownwald, Jacek; Harrington, Patricia; Harter, Philipp; Hasmad, Hanis Nazihah; Hein, Alexander; Heitz, Florian; Hildebrandt, Michelle A T; Hillemanns, Peter; Hogdall, Estrid; Hogdall, Claus; Hosono, Satoyo; Iversen, Edwin S; Jakubowska, Anna; James, Paul; Jensen, Allan; Ji, Bu-Tian; Karlan, Beth Y; Kruger Kjaer, Susanne; Kelemen, Linda E; Kellar, Melissa; Kelley, Joseph L; Kiemeney, Lambertus A; Krakstad, Camilla; Kupryjanczyk, Jolanta; Lambrechts, Diether; Lambrechts, Sandrina; Le, Nhu D; Lee, Alice W; Lele, Shashi; Leminen, Arto; Lester, Jenny; Levine, Douglas A; Liang, Dong; Lissowska, Jolanta; Lu, Karen; Lubinski, Jan; Lundvall, Lene; Massuger, Leon F A G; Matsuo, Keitaro; McGuire, Valerie; McLaughlin, John R; Nevanlinna, Heli; McNeish, Ian; Menon, Usha; Modugno, Francesmary; Moysich, Kirsten B; Narod, Steven A; Nedergaard, Lotte; Ness, Roberta B; Azmi, Mat Adenan Noor; Odunsi, Kunle; Olson, Sara H; Orlow, Irene; Orsulic, Sandra; Weber, Rachel Palmieri; Pearce, Celeste L; Pejovic, Tanja; Pelttari, Liisa M; Permuth-Wey, Jennifer; Phelan, Catherine M; Pike, Malcolm C; Poole, Elizabeth M; Ramus, Susan J; Risch, Harvey A; Rosen, Barry; Rossing, Mary Anne; Rothstein, Joseph H; Rudolph, Anja; Runnebaum, Ingo B; Rzepecka, Iwona K; Salvesen, Helga B; Schildkraut, Joellen M; Schwaab, Ira; Sellers, Thomas A; Shu, Xiao-Ou; Shvetsov, Yurii B; Siddiqui, Nadeem; Sieh, Weiva; Song, Honglin; Southey, Melissa C; Sucheston, Lara; Tangen, Ingvild L; Teo, Soo-Hwang; Terry, Kathryn L; Thompson, Pamela J; Timorek, Agnieszka; Tsai, Ya-Yu; Tworoger, Shelley S; van Altena, Anne M; Van Nieuwenhuysen, Els; Vergote, Ignace; Vierkant, Robert A; Wang-Gohrke, Shan; Walsh, Christine; Wentzensen, Nicolas; Whittemore, Alice S; Wicklund, Kristine G; Wilkens, Lynne R; Woo, Yin-Ling; Wu, Xifeng; Wu, Anna H; Yang, Hannah; Zheng, Wei; Ziogas, Argyrios; Monteiro, Alvaro; Pharoah, Paul D; Gayther, Simon A; Freedman, Matthew L

    2015-01-01

    Genome-wide association studies have reported 11 regions conferring risk of high-grade serous epithelial ovarian cancer (HGSOC). Expression quantitative trait locus (eQTL) analyses can identify candidate susceptibility genes at risk loci. Here we evaluate cis-eQTL associations at 47 regions associated with HGSOC risk (P≤10(-5)). For three cis-eQTL associations (P<1.4 × 10(-3), FDR<0.05) at 1p36 (CDC42), 1p34 (CDCA8) and 2q31 (HOXD9), we evaluate the functional role of each candidate by perturbing expression of each gene in HGSOC precursor cells. Overexpression of HOXD9 increases anchorage-independent growth, shortens population-doubling time and reduces contact inhibition. Chromosome conformation capture identifies an interaction between rs2857532 and the HOXD9 promoter, suggesting this SNP is a leading causal variant. Transcriptomic profiling after HOXD9 overexpression reveals enrichment of HGSOC risk variants within HOXD9 target genes (P=6 × 10(-10) for risk variants (P<10(-4)) within 10 kb of a HOXD9 target gene in ovarian cells), suggesting a broader role for this network in genetic susceptibility to HGSOC. PMID:26391404

  1. Vibration analysis of rotating functionally graded Timoshenko microbeam based on modified couple stress theory under different temperature distributions

    NASA Astrophysics Data System (ADS)

    Ghadiri, Majid; Shafiei, Navvab

    2016-04-01

    In this study, thermal vibration of rotary functionally graded Timoshenko microbeam has been analyzed based on modified couple stress theory considering temperature change in four types of temperature distribution on thermal environment. Material properties of FG microbeam are supposed to be temperature dependent and vary continuously along the thickness according to the power-law form. The axial forces are also included in the model as the thermal and true spatial variation due to the rotation. Governing equations and boundary conditions have been derived by employing Hamiltonian's principle. The differential quadrature method is employed to solve the governing equations for cantilever and propped cantilever boundary conditions. Validations are done by comparing available literatures and obtained results which indicate accuracy of applied method. Results represent effects of temperature changes, different boundary conditions, nondimensional angular velocity, length scale parameter, different boundary conditions, FG index and beam thickness on fundamental, second and third nondimensional frequencies. Results determine critical values of temperature changes and other essential parameters which can be applicable to design micromachines like micromotor and microturbine.

  2. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    NASA Astrophysics Data System (ADS)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-04-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  3. Investigation on 316L/W functionally graded materials fabricated by mechanical alloying and spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Tan, Chao; Wang, Guoyu; Ji, Lina; Tong, Yangang; Duan, Xuan-Ming

    2016-02-01

    316L-W (Tungsten) composite materials were fabricated by spark plasma sintering (SPS) of mechanically alloyed 316L-W powders for the development of functionally graded materials (FGMs). The effect of milling parameters on the morphology of the blended 316L/W powders and its subsequent effect on the transition between 316L and W particles during the SPS process were investigated. Samples were characterized by SEM, EDS and XRD analyses. The results so obtained show that with the increase of milling time, the mechanically activated W powder particles become thinner and smoother, with some broken fragments aggregated or inserted in the severely deformed 316L particles. A further SPS process under the conditions of 1050 °C × 45.5 MPa × 5 min leads to the densification of the powder compact and the formation of a distinguishable gray belt surrounding the retained W particles. Such a belt, which has a width of about 2-8 μm depending on different milling parameters and mainly contains Fe7W6, Fe3W3C and Fe2W phases, is bound to be a transitional region between the retained W particles and the 316L matrix. This favorable behavior with regards to the formation of a transitional belt, is accompanied by a substantial increase in the hardness values of the composite.

  4. Fabrication of Al/Al3Ti Functionally Graded Materials by Reaction Centrifugal Mixed-Powder Method

    NASA Astrophysics Data System (ADS)

    El-Hadad, Shimaa; Sato, Hisashi; Miura-Fujiwara, Eri; Watanabe, Yoshimi

    2011-01-01

    Formation of compositional gradient in Al/Al3Ti Functionally graded materials (FGMs) fabricated by the centrifugal method (CM) depends mainly on the centrifugal force and the processing temperature. In this study, a novel centrifugal method, reaction centrifugal mixed-powder method (RCMPM), was proposed to fabricate Al/Al3Ti FGMs under fixed centrifugal force (G=80). The effects of RCMPM processing temperature on the formation of Al3Ti intermetallics, its morphology and its distribution in the fabricated Al/Al3Ti FGMs have been investigated. Fine granular Al3Ti were observed at relatively lower processing temperature while the known coarse platelet-like particles of Al3Ti could be achieved at higher casting temperatures. Moreover, Ti3Al intermetallics compound and unreacted Ti phases are also observed along with Al3Ti particles. In addition, distribution of Al3Ti intermetallics size and their volume fraction showed a significant change when the Al/Al3Ti FGMs processed at different temperatures relative to the liquidus temperature of the master alloy.

  5. Nonlocal three-dimensional theory of elasticity with application to free vibration of functionally graded nanoplates on elastic foundations

    NASA Astrophysics Data System (ADS)

    Ansari, R.; Shahabodini, A.; Faghih Shojaei, M.

    2016-02-01

    In the present work, a three-dimensional (3D) elastic plate model capturing the small scale effects is developed for the free vibration of functionally graded (FG) nanoplates resting on elastic foundations. The theoretical model is formulated employing the nonlocal differential constitutive relations of Eringen in conjunction with the 3D equations of motion of elasticity.The material properties are assumed to vary continuously along the thickness of the nanoplate in accordance with the power law formulation. Through extending the generalized differential quadrature (GDQ) method to the three-dimensional case, the governing equations are simultaneously discretized in every three coordinate directions and are then recast to the standard form of an eigen value problem. Solving the acquired problem, the natural frequencies of the nanoplates with different boundary conditions are calculated. The convergence behavior of the numerical results is checked out and comparison studies are conducted to make sure of the accuracy and reliability of the present model. Finally, the dependence of the vibration behavior of the nanoplate on edge conditions, elastic coefficients of the foundation, scale coefficient, mode number, material and geometric parameters are discussed.

  6. Fracture problem for an external circumferential crack in a functionally graded superconducting cylinder subjected to a parallel magnetic field

    NASA Astrophysics Data System (ADS)

    Yan, Z.; Gao, S. W.; Feng, W. J.

    2016-02-01

    In this study, the multiple isoparametric finite element method (MIFEM) is used to investigate external circumferential crack problem of a functionally graded superconducting cylinder subjected to electromagnetic forces. The superconducting cylinder is composed by Bi2223/Ag composite with material parameters varying. A crack reference region is defined to reflect the effects of crack on flux and current densities, and the magnetically impermeable crack surface condition and the generalized Irie-Yamafuji critical state model outside the crack region are adopted. The distributions of magnetic flux density in the superconducting cylinder are obtained analytically for both the zero-field cooling (ZFC) and the field cooling (FC) activation processes. Based on the MIFEM, the stress intensity factors (SIFs) at crack fronts in the process of field ascent and/or descent are then numerically calculated. It is interesting to note from numerical results that for the present crack model in the ZFC activation process, the crack is easily propagate and grow with the applied field increases, and that in the field descent process of either the ZFC case or FC case, the crack generally does not propagate. In addition, in the field ascent process of the ZFC case, the SIFs depend on not only the crack depths and model parameters but also the applied field. The present study should be helpful to the design and application of high-temperature superconductors with external edge cracks.

  7. Studies on Interfacial Phenomena in Titanium Carbide/Liquid Steel Systems for Development of Functionally Graded Material

    NASA Astrophysics Data System (ADS)

    Kiviö, Miia; Holappa, Lauri; Louhenkilpi, Seppo; Nakamoto, Masashi; Tanaka, Toshihiro

    2016-08-01

    In modern materials' applications, versatile, often contradictory requirements are set for properties like high strength, hardness, and toughness. However, e.g., in steel castings, typically only certain surfaces should be hard and wear resistant, whereas the other "bulk" might have only standard properties. Then the critical parts of the surface should be "locally reinforced" to get functionally graded material. Expensive alloying elements are saved, and manufacturing stages are minimized. Titanium carbide is an extremely hard material widely applied in carbide tools. It could be used to reinforce steel castings. When TiC particles are added to liquid steel, wettability, stability, and dissolution are key phenomena that should be understood to better design and control manufacturing processes. In this work, the interfacial phenomena and reactions between TiC and iron/steel melts were examined by wetting experiments with special emphasis on the influence of Cr, Ni, and Mo. No significant effect on wettability was observed by Ni or Mo. High Cr melts showed somewhat higher contact angles. Partial penetration of liquid metal took place in the substrate along the grain boundaries. Ni seemed to promote penetration. During longer experiments, re-precipitation of carbides occurred on the liquid droplet influencing the apparent wetting angle. Cr and Mo promoted carbide formation.

  8. Tribological performance of hybrid filtered arc-magnetron coatings - Part I: Coating deposition process and basic coating properties characterization

    SciTech Connect

    Gorokhovsky, Vladimir; Bowman, C.; Gannon, Paul E.; VanVorous, D.; Voevodin, A. A.; Rutkowski, A.; Muratore, C.; Smith, Richard J.; Kayani, Asghar N.; Gelles, David S.; Shutthanandan, V.; Trusov, B. G.

    2006-12-04

    Aircraft propulsion applications require low-friction and wear resistant surfaces that operate under high contact loads in severe environments. Recent research on supertough and low friction nanocomposite coatings produced with hybrid plasma deposition processes was demonstrated to have a high potential for such demanding applications. However, industrially scalable hybrid plasma technologies are needed for their commercial realization. The Large area Filtered Arc Deposition (LAFAD) process provides atomically smooth coatings at high deposition rates over large surface areas. The LAFAD technology allows functionally graded, multilayer, super-lattice and nanocomposite architectures of multi-elemental coatings via electro-magnetic mixing of two plasma flows composed of different metal ion vapors. Further advancement can be realized through a combinatorial process using a hybrid filtered arc-magnetron deposition system. In the present study, multilayer and nanostructured TiCrCN/TiCr +TiBC composite cermet coatings were deposited by the hybrid filtered arc-magnetron process. Filtered plasma streams from arc evaporated Ti and Cr targets, and two unbalanced magnetron sputtered B4C targets, were directed to the substrates in the presence of reactive gases. A multiphase nanocomposite coating architecture was designed to provide the optimal combination of corrosion and wear resistance of advanced steels (Pyrowear 675) used in aerospace bearing and gear applications. Coatings were characterized using SEM/EDS, XPS and RBS for morphology and chemistry, XRD and TEM for structural analyses, wafer curvature and nanoindentation for stress and mechanical properties, and Rockwell and scratch indentions for adhesion. Coating properties were evaluated for a variety of coating architectures. Thermodynamic modeling was used for estimation of phase composition of the top TiBC coating segment. Correlations between coating chemistry, structure and mechanical properties are discussed.

  9. Deposition of Functional Coatings from an Acetylene-Containing Plasma at Atmospheric Pressure

    NASA Astrophysics Data System (ADS)

    Plevako, F. V.; Gorbatov, S. V.; Davidovich, P. A.; Prikhod‧ko, E. M.; Shushkov, S. V.; Krul‧, L. P.; Butovskaya, G. V.; Shakhno, O. V.; Gusakova, S. V.; Korolik, O. V.; Mazanik, A. V.

    2016-03-01

    Properties of thin coatings formed on polymer and glass substrates by plasma-enhanced chemical vapor deposition from a mixture of nitrogen with acetylene at atmospheric pressure were investigated. It was established that chemically stable transparent films with a mass ratio of fixed carbon and nitrogen C:N ~ 2:1 are formed on the surface of these substrates. When the deposition time was increased, arrays of dendrite-like structures were formed on the substrates.

  10. Biotransformation of magnetic nanoparticles as a function of coating in a rat model

    NASA Astrophysics Data System (ADS)

    Ruiz, A.; Gutiérrez, L.; Cáceres-Vélez, P. R.; Santos, D.; Chaves, S. B.; Fascineli, M. L.; Garcia, M. P.; Azevedo, R. B.; Morales, M. P.

    2015-10-01

    Long-term in vivo studies in murine models have shown that DMSA-coated nanoparticles accumulate in spleen, liver and lung tissues during extended periods