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Sample records for resistant elastomeric compositions

  1. Development of high energy radiation resistant elastomeric composites

    International Nuclear Information System (INIS)

    Shah, C.; Patni, M.J.; Pandya, M.V.; Desai, M.R.

    1992-01-01

    Stabilizer formulations are developed for the elastomeric composites which can withstand high energy radiations to the total dose of 200 MRads. The elastomeric materials used are general purpose formulations based on Ethylene propylene diene (EPDM) and Chlorosulfonated polyethylene (CSP). The stabilizers are synthesized from highly aromatic ring compounds in the oligomeric and polymeric form, in the laboratory. The polymeric stabilizers are found to have better radiation resistance compared to the former one when the performance was evaluated using standard methodology. Dielectric analysis, FTIR and wide angle x-ray diffraction are used to follow the physico-chemical changes taking place in the bulk when subjected to the performance test

  2. Interesting green elastomeric composites: silk textile reinforced natural rubber

    OpenAIRE

    Smitthipong, Wirasak; Suethao, Sukontip; Shah, Darshil Upendra; Vollrath, Fritz

    2016-01-01

    © 2016 Elsevier LtdThe reinforcement of natural rubber (NR) with particles and fibres enables their use in even high performance applications, such as in road-racing bicycle tire casings. Here, for the first time, we examine the potential of silk textiles as reinforcements in NR to produce a fully-green, flexible yet strengthened elastomeric composite material. Various material properties were evaluated and compared with similar nylon textile reinforced NR composites. Two types of NR were use...

  3. Influence of dispersants on aging and frost elastomeric compositions based on butadiene acrylonitrile rubbers

    Directory of Open Access Journals (Sweden)

    R. M. Dolinskaya

    2016-01-01

    Full Text Available The possibility of use of dispergators of various nature for production of rubber technical products with expanded temperature conditions of operation is studied. It is investigated influences of dispergators of Dispergator FL and INT 159 on properties of rubber mixes for receiving products with high resistance to thermal aging or frost resistance. Research of influence of modifiers was conducted for rubber mixes on the basis of butadienenitrile rubbers synthetic (BNRS-18 and BNRS-28. I’s established that at addition of a dispergator of Dispergator FL the indicator of relative deformatstion of compression (RDC and respectively heat stability of rubbers increases. Introduction to structure of elastomeric composition of a dispergator of INT 159 practically doesn’t influence frost resistance, and Dispergator FL worsens her (the coefficient of frost resistance decreases by 15.4–17.8%. Possibly it is connected with the fact that at the lowered temperatures in the presence of Dispergator FL there is a bigger delay of relaxation processes and decrease in energy of the thermal movement of links of macromolecules of rubbers. It becomes insufficient for overcoming of intermolecular interaction in the modified system and commission of conformational transitions of macromolecules under the influence of external loading. Mechanical energy is to a large extent mentioned not on change of a form of macromolecules, and on their mechanodestruction. However, it increases heat stability since it that is higher, than molecular mobility is lower. INT 159 dispergator components, settling down on borders of supramolecular formations of elastomers, increase mobility of links of macromolecules of rubbers, weaken chemical bonds in them, reduce thermal stability, but at the same time INT 159 dispergator practically doesn’t reduce frost resistance therefore it is expedient to apply it when receiving frost-resistant elastomeric composition. Thus, when receiving

  4. Magnetoactive elastomeric composites: Cure, tensile, electrical and ...

    Indian Academy of Sciences (India)

    frequency is due to the hopping of charge carriers (Papa- thanassiou 2002). 5. Conclusions. Magnetoactive composites containing nickel in poly- chloroprene and nitrile matrices have been prepared. The cure characteristics reveal that the processability and flexibility of the matrix is not affected much even up to a maximum ...

  5. Mechanically programmed shape change in laminated elastomeric composites.

    Science.gov (United States)

    Robertson, Jaimee M; Torbati, Amir H; Rodriguez, Erika D; Mao, Yiqi; Baker, Richard M; Qi, H Jerry; Mather, Patrick T

    2015-07-28

    Soft, anisotropic materials, such as myocardium in the heart and the extracellular matrix surrounding cells, are commonly found in nature. This anisotropy leads to specialized responses and is imperative to material functionality, yet few soft materials exhibiting similar anisotropy have been developed. Our group introduced an anisotropic shape memory elastomeric composite (A-SMEC) composed of non-woven, aligned polymer fibers embedded in an elastomeric matrix. The composite exhibited shape memory (SM) behavior with significant anisotropy in room-temperature shape fixing. Here, we exploit this anisotropy by bonding together laminates with oblique anisotropy such that tensile deformation at room temperature - mechanical programming - results in coiling. This response is a breakthrough in mechanical programming, since non-affine shape change is achieved by simply stretching the layered A-SMECs at room temperature. We will show that pitch and curvature of curled geometries depend on fiber orientations and the degree of strain programmed into the material. To validate experimental results, a model was developed that captures the viscoplastic response of A-SMECs. Theoretical results correlated well with experimental data, supporting our conclusions and ensuring attainability of predictable curling geometries. We envision these smart, soft, shape changing materials will have aerospace and medical applications.

  6. Flexible Connection Elastomeric Rubber as a Pounding Resisting Element between Two Adjacent Buildings

    Directory of Open Access Journals (Sweden)

    Yuskar Lase

    2013-03-01

    Full Text Available To solve pounding problem of two adjacent buildings, structural designer usually employs a dilatation between the structures or make the two structures as a monolith structure. Other alternative is by using an elastomeric rubber as a pounding resisting element between the two structures. Effectiveness in applying elastomeric rubber component as flexible connection of two adjacent structures is the main focus of this paper. Various simulations such as structure models, earthquake excitations and openings in gap element are studied. Observation of maximum structural responses will be performed for structure model with elastomeric rubber in comparison with (1 monolith structure model and (2 structure model with rigid element (steel element. Simulation results show that application of elastomeric rubber component to prevent structures from pounding problem provides advantages especially in reducing internal forces in the shorter building. However, it slightly increases displacement of both structures.

  7. Static frictional resistance with the slide low-friction elastomeric ligature system.

    Science.gov (United States)

    Jones, Steven P; Ben Bihi, Saida

    2009-11-01

    This ex-vivo study compared the static frictional resistance of a low-friction ligation system against a conventional elastomeric module, and studied the effect of storage in a simulated oral environment on the static frictional resistance of both ligation systems. Eighty stainless steel brackets were tested by sliding along straight lengths of 0.018 inch round and 0.019 x 0.025 inch rectangular stainless steel wires ligated with either conventional elastomerics or the Slide system (Leone, Florence, Italy). During the tests the brackets and wires were lubricated with artificial saliva. A specially constructed jig assembly was used to hold the bracket and archwire securely. The jig was clamped in an Instron universal load testing machine. Crosshead speed was controlled via a microcomputer connected to the Instron machine. The static frictional forces at 0 degree bracket/wire angulation were measured for both systems, fresh from the pack and after storage in artificial saliva at 37 degrees C for 24 hours. The results of this investigation demonstrated that the Slide ligatures produced significantly lower static frictional resistance than conventional elastomeric modules in the fresh condition and after 24 hours of storage in a simulated oral environment (p static frictional resistance of conventional elastomeric modules and the Slide system (p = 0.525). The claim by the manufacturer that the Slide system produces lower frictional resistance than conventional elastomeric modules is upheld.

  8. Radiation resistance of elastomeric O-rings in mixed neutron and gamma fields: Testing methodology and experimental results

    Science.gov (United States)

    Zenoni, A.; Bignotti, F.; Donzella, A.; Donzella, G.; Ferrari, M.; Pandini, S.; Andrighetto, A.; Ballan, M.; Corradetti, S.; Manzolaro, M.; Monetti, A.; Rossignoli, M.; Scarpa, D.; Alloni, D.; Prata, M.; Salvini, A.; Zelaschi, F.

    2017-11-01

    Materials and components employed in the presence of intense neutron and gamma fields are expected to absorb high dose levels that may induce deep modifications of their physical and mechanical properties, possibly causing loss of their function. A protocol for irradiating elastomeric materials in reactor mixed neutron and gamma fields and for testing the evolution of their main mechanical and physical properties with absorbed dose has been developed. Four elastomeric compounds used for vacuum O-rings, one fluoroelastomer polymer (FPM) based and three ethylene propylene diene monomer rubber (EPDM) based, presently available on the market have been selected for the test. One EPDM is rated as radiation resistant in gamma fields, while the other elastomers are general purpose products. Particular care has been devoted to dosimetry calculations, since absorbed dose in neutron fields, unlike pure gamma fields, is strongly dependent on the material composition and, in particular, on the hydrogen content. The products have been tested up to about 2 MGy absorbed dose. The FPM based elastomer, in spite of its lower dose absorption in fast neutron fields, features the largest variations of properties, with a dramatic increase in stiffness and brittleness. Out of the three EPDM based compounds, one shows large and rapid changes in the main mechanical properties, whereas the other two feature more stable behaviors. The performance of the EPDM rated as radiation resistant in pure gamma fields does not appear significantly better than that of the standard product. The predictive capability of the accelerated irradiation tests performed as well as the applicable concepts of threshold of radiation damage is discussed in view of the use of the examined products in the selective production of exotic species facility, now under construction at the Legnaro National Laboratories of the Italian Istituto Nazionale di Fisica Nucleare. It results that a careful account of dose rate effects

  9. Frictional resistance of orthodontic wires tied with 3 types of elastomeric ligatures

    Directory of Open Access Journals (Sweden)

    Amanda Carneiro da Cunha

    2011-12-01

    Full Text Available The aims of this study were to determine and compare frictional resistance obtained by low-friction and conventional elastomeric ligatures in the presence of artificial saliva, and observe whether this variable changed after 21 days. Super Slick® low-friction elastomeric ligatures and conventional ligatures of the brands TP conventional® and Unitek® were placed on standard edgewise maxillary central incisor metal brackets, slot .022" × .028" tying rectangular orthodontic wires .018" × .025". Three experimental groups were arranged according to the type of ligature and a control group in which no wires were used. The friction values obtained between the bracket/wire/ligature set were measured using a Universal Test Machine at a speed of 20 mm/minute, at two experimental time intervals: T0 - immediately after specimen fabrication; and T1 - 21 days after fabrication and immersion in artificial saliva at 37 ºC. Conventional Unitek ligatures and the low-friction ligature (Super Slick showed the lowest friction values at T0. After 21 days (T1, however, conventional Unitek ligatures presented the lowest value. All groups assessed from T0 to T1 showed a numerical reduction in friction values, suggesting that time, heat and humidity may cause elastic degradation, however this was not verified statistically (P > 0.05.

  10. Influence of particle arrangement on the permittivity of an elastomeric composite

    Directory of Open Access Journals (Sweden)

    Peiying J. Tsai

    2017-01-01

    Full Text Available Elastomers are used as dielectric layers contained between the parallel conductive plates of capacitors. The introduction of filler particles into an elastomer changes its permittivity ε. When particle organization in a composite is intentionally varied, this alters its capacitance. Using numerical simulations, we examine how conductive particle chains introduced into polydimethylsiloxane (PDMS alter ε. The effects of filler volume fraction ψ, interparticle d and interchain spacing a, zigzag angle θ between adjacent particles and overall chain orientation, particle size r, and clearance h between particles and the conductive plates are characterized. When filler particles are organized into chainlike structures rather than being just randomly distributed in the elastomer matrix, ε increases by as much as 85%. When particles are organized into chainlike forms, ε increases with increasing ψ and a, but decreases with increasing d and θ. A composite containing smaller particles has a higher ε when ψ<9% while larger particles provide greater enhancement when ψ is larger than that value. To enhance ε, adjacent particles must be interconnected and the overall chain direction should be oriented perpendicular to the conductive plates. These results are useful for additive manufacturing on electrical applications of elastomeric composites.

  11. Elastomeric polypeptides.

    Science.gov (United States)

    van Eldijk, Mark B; McGann, Christopher L; Kiick, Kristi L; van Hest, Jan C M

    2012-01-01

    Elastomeric polypeptides are very interesting biopolymers and are characterized by rubber-like elasticity, large extensibility before rupture, reversible deformation without loss of energy, and high resilience upon stretching. Their useful properties have motivated their use in a wide variety of materials and biological applications. This chapter focuses on elastin and resilin - two elastomeric biopolymers - and the recombinant polypeptides derived from them (elastin-like polypeptides and resilin-like polypeptides). This chapter also discusses the applications of these recombinant polypeptides in the fields of purification, drug delivery, and tissue engineering.

  12. Comparison of frictional resistance between self-ligating and conventional brackets tied with elastomeric and metal ligature in orthodontic archwires

    Directory of Open Access Journals (Sweden)

    Vanessa Vieira Leite

    2014-06-01

    Full Text Available OBJECTIVE: To compare the frictional resistance between self-ligating and conventional brackets tied to different types of wire. MATERIAL AND METHODS : Abzil Kirium Capelozza (Pattern I and Easy Clip (Roth prescription incisor brackets were used. An elastomeric ligature or a ligating wire 0.10-in was used to ligate the wire to the Abzil bracket. Three types of orthodontic archwire alloys were assessed: 0.016-in NiTi wire, 0.016 x 0.021-in NiTi wire and 0.019 x 0.025-in steel wire. Ten observations were carried out for each bracket-archwire angulation combination. Brackets were mounted in a special appliance, positioned at 90 degrees in relation to the wire and tested in two angulations. Frictional test was performed in a Universal Testing Machine at 5 mm/min and 10 mm of displacement. The means (MPa were submitted to ANOVA and Tukey's test set at 5% of significance. The surfaces of wires and brackets were observed at SEM. RESULTS: Steel-tied brackets (16.48 ± 8.31 showed higher means of frictional resistance than elastomeric-tied brackets (4.29 ± 2.16 and self-ligating brackets (1.66 ± 1.57 (P 0.05. No statistical differences (P > 0.05 were found between zero (7.76 ± 8.46 and five-degree (7.19 ± 7.93 angulations. CONCLUSIONS: Friction was influenced not only by the type of bracket, but also by the ligating systems. Different morphological aspects were observed for the brackets and wires studied

  13. Tooling with reinforced elastomeric materials

    Science.gov (United States)

    Musch, G.; Bishop, W.

    During vacuum bag/autoclave processing of thermosetting advanced composite prepregs, problems often develop with the pressure distribution on the composite component. These problems can result in local variations in finished component thickness, shape, resin/fiber ratio and void content and lead to rejection of the part or make it necessary to carry out expensive and time consuming rework. These pressure distributions problems are discussed and the key difficulty of bridging of composite lay-ups in female corner zones is examined. Conventional, unreinforced elastomeric tooling concepts designed to overcome these pressure distribution problems are reviewed, and, working from the shortcomings associated with these techniques, a set of requirements is established for improved elastomeric tooling. Reinforced elastomeric tooling based on AIRPAD polyacrylic rubber is shown to meet these performance requirements and the overall concept is presented, together with a detailed examination of the key elements of this form of tooling. Basic design quidelines are given for reinforced elastomeric tooling, and tooling concepts for more complex applications are discussed. Finally, two practical applications of the reinforced elastomeric tooling concept are described and examined in detail to fully illustrate the techniques involved.

  14. Caracterisation de l'effet du vieillissement en milieu aqueux sur les proprietes mecaniques de composites a matrice elastomere

    Science.gov (United States)

    Favre, Audrey

    Rubber composites are widely used in several engineering fields, such as automotive, and more recently for inflatable dams and other innovative underwater applications. These rubber materials are composed by an elastomeric matrix while the reinforcing phase is a synthetic fabric. Since these components are expected to operate several years in water environment, their durability must be guaranteed. The use of rubber materials immersed in water is not new, in fact, these materials have been studied for almost one century. However, the knowledge on reinforced rubber composites immersed several years in water is still limited. In this work, investigations on reinforced rubbers were carried out in the framework of a research project in partnership with Alstom and Hydro-Quebec. The objective of this study was to identify rubber composites that could be used under water for long periods. Various rubber composites with ethylene-propylene-diene monomer (EPDM), silicone, EPDM/silicone and polychloroprene (Neoprene) matrices reinforced with E-glass fabric were studied. Thus, these materials were exposed to an accelerated ageing at 85 °C underwater for periods varying from 14 to 365 days. For comparison purposes, they were also immersed and aged one year at room temperature (21 °C). The impact of accelerated aging was estimated through three different characterization methods. Scanning electron microscopy (SEM) was first used to assess the quality of fiber-matrix interface. Then, water absorption tests were performed to quantify the rate of water absorption during immersion. Finally the evolution of the mechanical properties was followed by the determination of Young's modulus (E) and ultimate stress (sigmau) using a dedicated traction test. This analysis allowed to point out that the quality of the fiber-matrix interface was the main factor influencing the drop of the mechanical properties and their durability. Moreover, it was noticed that this interface could be improved

  15. Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior

    Energy Technology Data Exchange (ETDEWEB)

    Soreto Teixeira, S.; Graça, M. P. F.; Costa, L. C. [I3N and Physics Department, University of Aveiro, 3810-193 Aveiro (Portugal); Dionisio, M. [REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica (Portugal); Ilcíkova, M.; Mosnacek, J.; Spitalsky, Z. [Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava (Slovakia); Krupa, I. [Polymer Institute, Slovak Academy of Sciences, Dúbravská cesta 9, Bratislava (Slovakia); Center for Advanced Materials, Qatar University, P.O. Box 2713, Doha (Qatar)

    2014-12-14

    Lithium ferrite (LiFe{sub 5}O{sub 8}) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe{sub 5}O{sub 8} crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li{sub 2}O-Fe{sub 2}O{sub 3} powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer and of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between −73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10{sup −2}) that can be considered interesting for technological applications.

  16. Self-standing elastomeric composites based on lithium ferrites and their dielectric behavior

    Science.gov (United States)

    Soreto Teixeira, S.; Graça, M. P. F.; Dionisio, M.; Ilcíkova, M.; Mosnacek, J.; Spitalsky, Z.; Krupa, I.; Costa, L. C.

    2014-12-01

    Lithium ferrite (LiFe5O8) is an attractive material for technological applications due to its physical properties, which are significantly dependent on the preparation method and raw materials. In this work, LiFe5O8 crystallites were obtained by controlled heat-treatment process at 1100 °C, of a homogeneous mixture of Li2O-Fe2O3 powders, prepared by wet ball-milling and using lithium and iron nitrates as raw materials. The main goal was the preparation of a flexible and self-standing tick composite film by embedding lithium ferrite particles in a polymeric matrix, taking advantage of the good mechanical properties of the polymer and of the electrical and dielectric properties of the ferrite. The selected polymer matrix was styrene-b-isoprene-b-styrene copolymer. To prepare the composites, the lithium ferrite particles were chemically modified in order to functionalize their surface. To analyse the influence of the particles surface modification, different composites were made, with modified and unmodified particles. The structure of the obtained composites was studied by FTIR, XRD, TGA, and DSC techniques. The dielectric properties were analysed, in the frequency range between 10 Hz and 1 MHz and in function of temperature in the range between -73 °C and 127 °C. These properties were related with the structure and concentration of the particles in the matrix network. The composites with the modified particles present higher dielectric constant, maintaining values of loss tangent sufficiently low (<10-2) that can be considered interesting for technological applications.

  17. New approach to obtain elastomeric nano composites with clay from lattices

    International Nuclear Information System (INIS)

    Azeredo, Luciane K. de; Jacobi, Marly M.

    2009-01-01

    Rubber-Montmorillonite nanocomposites were prepared by Continuous Dynamic Latex Compounding (CDLC). This technique, recently developed in our laboratory, permits an intensive intercalation of the polymer at very small residence times in an elongational flow reactor. The processing conditions strongly affect the morphology of nanocomposites characterized by TEM and XRD. Clay-rubber nanocomposites were prepared from the mixture of NBR-, XNBR- and SBR-latex and aqueous suspensions of Na-montmorillonite. The polarity of rubbers influences the final properties of nanocomposites. The nanocomposites obtained by CDLC showed better reinforcement and permeation resistance at far less volume fractions than the obtained with carbon black or silica by conventional methods. (author)

  18. High friction on ice provided by elastomeric fiber composites with textured surfaces

    Science.gov (United States)

    Rizvi, R.; Naguib, H.; Fernie, G.; Dutta, T.

    2015-03-01

    Two main applications requiring high friction on ice are automobile tires and footwear. The main motivation behind the use of soft rubbers in these applications is the relatively high friction force generated between a smooth rubber contacting smooth ice. Unfortunately, the friction force between rubber and ice is very low at temperatures near the melting point of ice and as a result we still experience automobile accidents and pedestrian slips and falls in the winter. Here, we report on a class of compliant fiber-composite materials with textured surfaces that provide outstanding coefficients of friction on wet ice. The fibrous composites consist of a hard glass-fiber phase reinforcing a compliant thermoplastic polyurethane matrix. The glass-fiber phase is textured such that it is aligned transversally and protruding out of the elastomer surface. Our analysis indicates that the exposed fiber phase exhibits a "micro-cleat" effect, allowing for it to fracture the ice and increase the interfacial contact area thereby requiring a high force to shear the interface.

  19. Resistance to disinfection of a polymicrobial association contaminating the surface of elastomeric dental impressions.

    Science.gov (United States)

    Giammanco, Giovanni M; Melilli, Dario; Rallo, Antonio; Pecorella, Sonia; Mammina, Caterina; Pizzo, Giuseppe

    2009-04-01

    The aim of this study was to evaluate the ability to resist disinfection of a polymicrobial association contaminating the surface of dental impressions obtained with two different elastomers: a polyether (Impregum) and an addition-polymerized silicone (Elite). Impressions were contaminated with a mixture of three biofilm-forming microorganisms (Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans) and disinfected immediately after contamination, or after microbial layers were allowed to develop during a six-hour storage. Two commercial disinfectants were tested: MD 520 containing 0.5% glutaraldehyde and Sterigum Powder without glutaraldehyde. Residual contamination was recovered by mechanical rinsing immediately after disinfection and after a six-hour storage of disinfected impressions, and assessed by colony counting. Both disinfectants tested were shown to be effective in reducing the microbial presence on the impression materials, achieving at least a 102 reduction of microbial counts compared to water rinsing. However, Sterigum was generally less effective on the Elite elastomer and could not grant disinfection on six-hour aged P. aeruginosa and C. albicans microbial layers. The results of this study suggest that the materials used for the impressions influence the efficacy of disinfection. Disinfectants should be tested according to conditions encountered in everyday clinical practice and the need for immediate disinfection of impressions should be clearly indicated by manufacturers.

  20. Electrically conductive composites based on an elastomeric matrix filled with expanded graphite as a potential oil sensing material

    Science.gov (United States)

    Krupa, Igor; Prostredný, Martin; Špitalský, Zdenko; Krajči, Juraj; AlMaadeed, Mariam Ali S.

    2014-12-01

    The preparation and properties of electrically conductive polymeric composites based on an elastomer matrix (styrene-isoprene styrene block copolymer) filled with expanded graphite are reported in this paper. The developed materials were tested as oil sensors in various modes. The operation of this sensor is based on changes in the electrical resistance R of the composites when exposed to oil. This phenomenon involves both simple geometrical changes and changes in inherent material characteristics such as the specific electrical conductivity (resistivity). An original method for the improvement of the sensors’ response rate based on the application of stretched sensing films was developed. Slightly stretched films (by 4% of the original length) showed a response that was 12.5 times faster with respect to oil absorption than an un-stretched film. The specific electrical conductivity of a material strongly depends on the extent to which it is stretched. For a composite filled with 10 wt.% of the filler, it was found that the electrical conductivity remained constant up to 11% of the sample extension before sharply decreasing. It was also found that an increase in the filler content reduced the response rate of the sensors.

  1. Erosion-resistant composite material

    Science.gov (United States)

    Finch, C.B.; Tennery, V.J.; Curlee, R.M.

    A highly erosion-resistant composite material is formed of chemical vapor-deposited titanium diboride on a sintered titanium diboride-nickel substrate. This material may be suitable for use in cutting tools, coal liquefaction systems, etc.

  2. Radiation resistant ceramic matrix composites

    International Nuclear Information System (INIS)

    Jones, R.H.; Steiner, D.; Heinisch, H.L.; Newsome, G.A.; Kerch, H.M.

    1997-01-01

    Ceramic matrix composites are of interest for nuclear applications because of their high-temperature properties, corrosion resistance, fracture toughness relative to monolithic ceramics, and low neutron activation and after heat. Evaluations of the radiation resistance of commercially available SiC/SiC composites have revealed their promise for this application, but also the need for further development to achieve the desired performance. This paper summarizes the results of a workshop cosponsored by the Offices of Fusion Energy and Basic Energy Sciences of the US Department of Energy and Lockheed-Martin Corporation with forty attendees from national laboratories, universities and industry. A number of promising routes for optimizing the radiation stability of ceramic matrix composites were identified at this workshop. These routes included the newer, more stoichiometric fibers and alternate fiber/matrix interfaces and matrix processing routes. (orig.)

  3. Unvulcanized elastomeric waterproofing materials for construction application

    Directory of Open Access Journals (Sweden)

    O. V. Karmanova

    2016-01-01

    Full Text Available In the construction was widespread elastomer profiles, which have the ability to swell in water. Such products should have a high capacity for swelling, elasticity, resistance to weathering. At the present time for these purposes are used materials, mostly of foreign origin. With the increasing pace of construction in Russia the problem of replacement of imported materials is particularly relevant. The work was dedicated to the creation of water-swellable elastomer materials using bentonite powders and study of their properties. Сomparative testing of imported and domestic hydrophilic sealants were held. Rationale and choice of components for the cords of bentonite was conducted. Polymer base is saturated ethylene-propylene rubber. Bentonite from different manufacturers used to increase the swelling of the samples. Filler added in an amount of 50–100 phr. The elastomeric compositions were prepared using laboratory roller at a temperature of 60 ± 5° C. Profiling was performed on a syringe-machine at a temperature of 120° C. Extrusion indicator of the mixtures were evaluated on a 10-point scale (German-Russian system. It is found that high swelling products provided using field Azerbaijan bentonite. It is noted that the dosage of bentonite than 150 w.p. deteriorates technological properties of bentonite cords. It has been shown that activation of the bentonite and sodium carbonate chloride can significantly improve product swelling, wherein the bentonite content of the composition was 150–200 w.p.

  4. An Analysis of the Macroscopic Tensile Behavior of a Nonlinear Nylon Reinforced Elastomeric Composite System Using MAC/GMC

    Science.gov (United States)

    Assaad, Mahmoud; Arnold, Steven M.

    1999-01-01

    A special class of composite laminates composed of soft rubbery matrices and stiff reinforcements made of steel wires or synthetic fibers is examined, where each constituent behaves in a nonlinear fashion even in the small strain domain. Composite laminates made of piles stacked at alternating small orientation angles with respect to the applied axial strain are primarily dominated by the nonlinear behavior of the reinforcing fibers. However; composites with large ply orientations or those perpendicular to the loading axis, will approximate the behavior of the matrix phase and respond in even a more complex fashion for arbitrarily stacked piles. The geometric nonlinearity due to small cord rotations during loading was deemed here to have a second order effect and consequently dropped from any consideration. The user subroutine USRMAT within the Micromechanics Analysis Code with the Generalized Method of Cells (MAC/GMC), was utilized to introduce the constituent material nonlinear behavior. Stress-strain behavior at the macro level was experimentally generated for single and multi ply composites comprised of continuous Nylon-66 reinforcements embedded in a carbon black loaded rubbery matrix. Comparisons between the predicted macro composite behavior and experimental results are excellent when material nonlinearity is included in the analysis. In this paper, a brief review of GMC is provided, along with a description of the nonlinear behavior of the constituents and associated constituent constitutive relations, and the improved macro (or composite) behavior predictions are documented and illustrated.

  5. Elastomeric Conducting Polyaniline Formed Through Topological Control of Molecular Templates.

    Science.gov (United States)

    Ding, Hangjun; Zhong, Mingjiang; Wu, Haosheng; Park, Sangwoo; Mohin, Jacob W; Klosterman, Luke; Yang, Zhou; Yang, Huai; Matyjaszewski, Krzysztof; Bettinger, Christopher John

    2016-06-28

    A strategy for creating elastomeric conducting polyaniline networks is described. Simultaneous elastomeric mechanical properties (E 10 S cm(-1)) are achieved via molecular templating of conjugated polymer networks. Diblock copolymers with star topologies processed into self-assembled elastomeric thin films reduce the percolation threshold of polyaniline synthesized via in situ polymerization. Block copolymer templates with star topologies produce elastomeric conjugated polymer composites with Young's moduli ranging from 4 to 12 MPa, maximum elongations up to 90 ± 10%, and electrical conductivities of 30 ± 10 S cm(-1). Templated polyaniline films exhibit Young's moduli up to 3 orders of magnitude smaller compared to bulk polyaniline films while preserving comparable bulk electronic conductivity. Flexible conducting polymers have prospective applications in devices for energy storage and conversion, consumer electronics, and bioelectronics.

  6. Synthesis and characterizations of high permittivity ultraviolet cured soft elastomeric networks and composites applicable as dielectric electroactive polymer

    DEFF Research Database (Denmark)

    Goswami, Kaustav

    siloxane) (PDMS) and polyurethanes are designed with the requirements specific for DEAPs. Thus there is a need to develop elastomers with low elastic modulus, low viscous and dielectric losses and high relative permittivity. Interpenetrating networks and fumed silica reinforced composites of poly...... (propylene oxide) (PPO) were prepared which showed marked improvements in properties compared to the acrylic elastomers. But difficulties in curing by industrial processes and handling of these elastomers posed as limitations. So the focus was on optimizing UV induced thiol-ene reactions for curing...... commercially available PDMS. UV curing of PDMS was successfully established which eliminated the major drawbacks of widely used platinum catalyzed addition curing of PDMS. An advanced sequential curing used to form the PDMS networks showed low elastic modulus and low viscous losses than the former...

  7. Reactive bonding mediated high mass loading of individualized single-walled carbon nanotubes in an elastomeric polymer

    Science.gov (United States)

    Zhao, Liping; Li, Yongjin; Qiu, Jishan; You, Jichun; Dong, Wenyong; Cao, Xiaojun

    2012-09-01

    A reactive chemical bonding strategy was developed for the incorporation of a high mass loading of individual single-wall carbon nanotubes (SWCNTs) into an elastomeric matrix using a reactive ionic liquid as a linker. This method simultaneously prevented the agglomeration of SWCNTs and caused strong interfacial bonding, while the electronic properties of the SWCNTs remained intact. As a result, the high conductivity of the carbon nanotubes (CNTs) and the flexibility of the elastomeric matrix were retained, producing optimum electrical and mechanical properties. A composite material with a loading of 20 wt% SWCNTs was fabricated with excellent mechanical properties and a high conductivity (9500 S m-1). The method could be used to form transparent thin conductive films that could tolerate over 800 bend cycles at a bending angle of 180° while maintaining a constant sheet resistance.A reactive chemical bonding strategy was developed for the incorporation of a high mass loading of individual single-wall carbon nanotubes (SWCNTs) into an elastomeric matrix using a reactive ionic liquid as a linker. This method simultaneously prevented the agglomeration of SWCNTs and caused strong interfacial bonding, while the electronic properties of the SWCNTs remained intact. As a result, the high conductivity of the carbon nanotubes (CNTs) and the flexibility of the elastomeric matrix were retained, producing optimum electrical and mechanical properties. A composite material with a loading of 20 wt% SWCNTs was fabricated with excellent mechanical properties and a high conductivity (9500 S m-1). The method could be used to form transparent thin conductive films that could tolerate over 800 bend cycles at a bending angle of 180° while maintaining a constant sheet resistance. Electronic supplementary information (ESI) available: Conductivity test of the SEBS-SWCNTs film, transmission spectra and sheet resistance for the spin-coated SEBS-SWCNTs thin films on PET slides. See DOI: 10

  8. Fire resistance of structural composite lumber products

    Science.gov (United States)

    Robert H. White

    2006-01-01

    Use of structural composite lumber products is increasing. In applications requiring a fire resistance rating, calculation procedures are used to obtain the fire resistance rating of exposed structural wood products. A critical factor in the calculation procedures is char rate for ASTM E 119 fire exposure. In this study, we tested 14 structural composite lumber...

  9. Asbestos free friction composition for brake linings

    Indian Academy of Sciences (India)

    An asbestos free friction material composite for brake linings is synthesized containing fibrous reinforcing constituents, friction imparting and controlling additives, elastomeric additives, fire retarding components and a thermosetting resin. The composite shows exemplary friction characteristics and has great resistance to ...

  10. Thermal stability of the elastomeric anti-trauma pad

    Directory of Open Access Journals (Sweden)

    Olszewska Karolina

    2017-06-01

    Full Text Available The elastomeric anti-trauma pad (EA-TP based on shear thickening fluid (STF has been developed. Dynamic oscillatory shear experiment was conducted at constant strain amplitude of 5%. STF composed of 25% of volume fraction of 7 nm Fumed Silica, dispersed in polypropylene glycol with molar mass 400 gmol−1 shows elastic properties in entire investigated range of the frequency. Ballistic tests of EA-TP with 7.62 mm × 39 mm PS bullets were performed according to the PN-V-87000:2011 standard. The studies revealed about 60% reduction of the average backface signature depth (BSD for the EA-TP, when compared to the nowadays commonly used soft insert. The ATR-FTIR analysis confirmed slight impact of the elevated temperature and air (oxygen on the chemical degradation of the EA-TP surface. The UV-VIS spectroscopy has allowed to notice colour deviation of the aged samples towards green and yellow, as well as lack of dye resistance to accelerated aging process. Thermographic analysis has shown no visible changes of the EA-TP surface and sub-surface during accelerated aging process. The aforementioned small changes on the surface of EA-TP did not affect the ballistic properties of composite armour. EA-TP insert maintains ballistic properties after accelerated aging process which was simulating the period of 6 years according to ASTM F1980 – 07:2002 standard.

  11. Production of Elastomeric Polypeptides for Materials Characterizations

    National Research Council Canada - National Science Library

    Urry, Dan

    2004-01-01

    .... Specifically, this effort is to provide 100 gram quantities of six and 10 gram quantities of an additional nine elastomeric polypeptides for conventional and specialized materials characterizations...

  12. Effect of composition on the polarization and ohmic resistances of ...

    Indian Academy of Sciences (India)

    However, the ohmic resistance was highest for the same composition and amounted to 60% of the total resistance value. Compositional dependence of resistances has been explained based on the variations of the triple phase boundaries and width of the O 2 −ion migration path with the composition of the electrode.

  13. Innovative Elastomeric Element for Earthquake Isolation

    Directory of Open Access Journals (Sweden)

    Vasile Iancu

    2012-09-01

    Full Text Available A modern tool to study the behavior of elastomeric elements for earthquake isolation is the Finite Element Method. The results of the simulations obtained in this way provide a large series of data about the behavior of the elastomeric elements under different types of loads and help in taking right decisions regarding geometrical optimizations needed for improve such kind of devices.

  14. Magnetorheological Fluid and Elastomeric Lag Damper for Helicopter Stability Augmentation

    Science.gov (United States)

    Hu, Wei; Wereley, Norman M.

    The feasibility of utilizing a composite magnetorheological fluid plus elastomeric (MRFE) damper is assessed. To emulate the loading conditions for a helicopter lag damper, the MRFE damper emulation was subjected to single frequency (lag/rev) and dual frequency (lag/rev and 1/rev) sinusoidal loading, and equivalent viscous damping was used to compare the MRFE damping characteristics with a conventional elastomeric damper. The preliminary MRFE damper showed nonlinear behavior: damping was reduced as displacement amplitude increased. Upon application of a magnetic field, the damping level was controlled according to a specific damping objective as a function of the excitation amplitude. Under dual frequency conditions, damping degradation at lag frequency due to 1/rev motion was also mitigated by magnetic field input to the MR damper.

  15. Chemical Stability of Telavancin in Elastomeric Pumps.

    Science.gov (United States)

    Sand, Patrick; Aladeen, Traci; Kirkegaard, Paul; LaChance, Dennis; Slover, Christine

    2015-12-01

    VIBATIV is a once-daily, injectable lipoglycopeptide antibiotic approved in the U.S. for the treatment of hospital-acquired and ventilator-associated bacterial pneumonia (HABP/VABP) caused by susceptible isolates of Staphylococcus aureus when alternative treatments are not suitable. In addition, VIBATIV is approved in the U.S. for the treatment of adult patients with complicated skin & skin structure infections (cSSSI) caused by susceptible isolates of Gram-positive bacteria, including Staphylococcus aureus, both methicillin-susceptible (MSSA) and methicillin-resistant (MRSA) strains. To evaluate the chemical stability of telavancin (Vibativ; Theravance Biopharma US, Inc, Northbrook, Illinois), a lipoglycopeptide antibiotic with activity against methicillin-resistant Staphylococcus aureus, in 2 types of elastomeric pumps, the Intermate Infusion System (Baxter International Inc) and the Homepump Eclipse (I-Flow Corporation). Different sizes of the Baxter (Ontario, Canada) (105 mL and 275 mL) and I-Flow (Stoughton, Massachusetts) (100 mL and 250 mL) pumps were compared with glass controls. The telavancin drug product was reconstituted and diluted to concentrations of 0.6 mg/mL and 8.0 mg/mL using either 0.9% saline, 5% dextrose in water, or sterilized water for injection (0.6 mg/mL telavancin) or saline (8.0 mg/mL telavancin) followed by Ringer's Lactate solution. Pumps were filled and stored at 2°C to 8°C, protected from light. Aliquots from both pump types and for all telavancin reconstitution/dilution schemes and concentrations were taken over a period of 8 days and analyzed for appearance, pH, telavancin concentration and purity, and degradation products. The pH of all pump solutions remained consistent throughout the 8-day analysis period, within a range of 4.6 to 5.7 for the 0.6 mg/mL and 4.4 to 4.9 for the 8.0 mg/mL telavancin solutions. There was no significant change in the chromatographic purity for any of the pump solutions examined. All decreases in

  16. Blends of thermoplastic and elastomeric matrices with liquid crystalline polymers

    Energy Technology Data Exchange (ETDEWEB)

    Roggero, A.; Pedretti, U.; La Mantia, F.P. [Eniricerche, Milanese (Italy)

    1995-12-01

    Liquid crystalline polymers (LCPs) present a unique balance of properties and, when added to thermoplastic (TP) or elastomeric (EL) matrices, can impart to the relevant blends specific properties that can be utilized for specific applications. As regards TP/LCP blends, the proclivity of LCPs to form fibrous structures and their low melt viscositiy allowed to obtain blends reinforced and easier to process than the pure TPs: particularly, depending on the LCP-TP structures and on the processing parameters, materials with improved processability, high modulus, enhanced impact strength and creeping resistance were obtained. As regards EL/LCP blends, that based on fluoroelastomers were in depth investigated and offered outstanding properties.

  17. Structural studies of thermally stable, combustion-resistant polymer composites

    OpenAIRE

    Smith, G.N.; Hallett, J.E.; Joseph, P.; Tretsiakova-McNally, S.; Zhang, T.; Blum, F.D.; Eastoe, J.

    2017-01-01

    Composites of the industrially important polymer, poly(methyl methacrylate) (PMMA), were prepared by free-radical polymerization of MMA with varying amounts (1–30 wt. %) of sodium dioctylsulfosuccinate (Aerosol OT or AOT) surfactant added to the reaction mixture. The composites with AOT incorporated show enhanced resistance to thermal degradation compared to pure PMMA homopolymer, and micro-cone combustion calorimetry measurements also show that the composites are combustion-resistant. The ph...

  18. Resistivity of pristine and intercalated graphite fiber epoxy composites

    Science.gov (United States)

    Gaier, James R.; Hambourger, Paul D.; Slabe, Melissa E.

    1991-01-01

    Laminar composites were fabricated from pristine and bromine intercalated Amoco P-55, P-75, and P-100 graphite fibers and Hysol-Grafil EAG101-1 film epoxy. The thickness and r.f. eddy current resistivity of several samples were measured at grid points and averaged point by point to obtain final values. Although the values obtained this way have high precision (less than 3 percent deviation), the resistivity values appear to be 20 to 90 percent higher than resistivities measured on high aspect ratio samples using multi-point techniques, and by those predicted by theory. The temperature dependence of the resistivity indicates that the fibers are neither damaged nor deintercalated by the composite fabrication process. The resistivity of the composites is a function of sample thickness (i.e., resin content). Composite resistivity is dominated by fiber resistivity, so lowering the resistivity of the fibers, either through increased graphitization or intercalation, results in a lower composite resistivity. A modification of the simple rule of mixtures model appears to predict the conductivity of high aspect ratio samples measured along a fiber direction, but a directional dependence appears which is not predicted by the theory. The resistivity of these materials is clearly more complex than that of homogeneous materials.

  19. Is static friction affected by aging and amount of elastomeric ligatures in orthodontic sliding mechanics? An in-vitro investigation.

    Science.gov (United States)

    Lo Giudice, A; Portelli, M; Militi, A; Spinuzza, P; Bellocchio, A M; Nucera, R; Marcolina, M; Ghilardi, G; Manuelli, M; Lucchese, A

    2018-03-15

    In straight-wire mechanics, friction can significantly influence the forces expressed by wires. The aim of this study is to assess whether the aging and the sum of elastomeric ligatures affect the static friction during orthodontic space closure. A 0.017x 0.025-in SS was drawn throughout a 3-bracket experimental model and engaged with elastomeric ligatures. Before performing the test, the ligatures were soaked in artificial saliva for 48 hours (Group 1), 2 weeks (Group 2) and 4 weeks (Group 3); brand-new ligatures were also tested as control group (Group 4). The resistance to sliding (RS) was recorded at 3 different numerical configurations of ligatures using a customized testing machine and tests were repeated for ten times. Data of RS were statistically analysed by using two way analysis of variance (ANOVA) and Tukey’s multiple comparison tests. RS was found to increase systematically when more elastomeric ligatures were included in the wire engaging system. At two weeks of immersion in artificial saliva elastomeric ligatures showed the lowest values of RS while they became significantly more frictional after immersion for 4 weeks. The results of this study showed that in multi-bracket orthodontic therapy, the RS increases with the number of elastomeric ligatures involved for arch-wire engagement. Differently from the frictional behavior of elastomeric modules, the aging of these ligatures does not influence their incremental effect of frictional forces.

  20. Magnetoactive elastomeric composites: Cure, tensile, electrical and ...

    Indian Academy of Sciences (India)

    150°C. Mechanical properties like tensile strength, modulus and elongation at break are evaluated using universal testing machine. Tensile test was carried out according to the ASTM D 412 standard. For measuring the magnetic impedance an indigenous experimental set up was used. The samples were kept between the ...

  1. Evaluation of Force Degradation Pattern of Elastomeric Ligatures and Elastomeric Separators in Active Tieback State

    Directory of Open Access Journals (Sweden)

    Amir Mohammadi

    2015-12-01

    Full Text Available Background and aims. The purpose of this study was to evaluate initial force and force decay of commercially available elastomeric ligatures and elastomeric separators in active tieback state in a simulated oral environment. Materials and methods. A total of 288 elastomeric ligatures and elastomeric separators from three manufacturers (Dentaurum, RMO, 3M Unitek were stretched to 100% and 150% of their original inner diameter. Force levels were measured initially and at 3-minute, 24-hour, and 1-, 2-, 3- and 4-week intervals. Data were analyzed by univariate analysis of variance and a post hoc Tukey test. Results. The means of initial forces of elastomeric ligatures and separators from three above-mentioned companies, when stretched to 100% of their inner diameters, were 199, 305 and 284 g, and 330, 416, 330 g; when they were stretched to 150% of their inner diameters the values were 286, 422 and 375 g, and 433, 540 and 504 g, respectively. In active tieback state, 11‒18% of the initial force of the specimens was lost within the first 3 minutes and 29‒63% of the force decay occurred in the first 24 hours; then force decay rate decreased. 62‒81% of the initial force was lost in 4 weeks. Although force decay pattern was identical in all the products, the initial force and force decay of Dentaurum elastomeric products were less than the similar products of other companies (P<0.05. Under the same conditions, the force of elastomeric separators was greater than elastomeric ligatures of the same company. Conclusion. Regarding the force pattern of elastomeric ligatures and separators and optimal force for tooth movement, many of these products can be selected for applying orthodontic forces in active tieback state.

  2. Study on the heat-resistant EB curing composites

    International Nuclear Information System (INIS)

    Bao Jianwen; Li Yang; Li Fengmei

    2000-01-01

    There are many advantages in the EB-curing process of composites. Heat-resistant EB-curing composites could substitute for polyimide composites used in aeronautical engine. The effects of catalyst and dose on the cured resin were investigated. The heat-resistance of the resin cured by EB was evaluated by dynamic mechanical thermal analysis (DMTA). The experiment result shows that the mechanical property of the composites cured by EB could meet the needs of the aeronautical engine in 250degC. (author)

  3. Effect of composition on the polarization and ohmic resistances of ...

    Indian Academy of Sciences (India)

    2017-06-09

    % of the total resistance value. Compositional dependence of ..... C due to our experimental limitations. However, it would not have any ... TPB's are present) suggest the formation of face-to-face con- tacts between the cathode ...

  4. Effect of composition on the polarization and ohmic resistances of ...

    Indian Academy of Sciences (India)

    2017-06-09

    Jun 9, 2017 ... Keywords. Solid oxide fuel cell; composite cathodes; polarization resistance; ohmic resistance; impedance spectroscopy. 1. Introduction ... cathode electrode and increase in the number of TPB's. ORR in LSM or LSM/YSZ ...... participation of increased number of TPB's from the cathode. Increased number of ...

  5. Smart conducting polymer composites having zero temperature coefficient of resistance

    Science.gov (United States)

    Chu, Kunmo; Lee, Sung-Chul; Lee, Sangeui; Kim, Dongearn; Moon, Changyoul; Park, Sung-Hoon

    2014-12-01

    Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self-heating properties for thermal stability and reliable temperature control. The bi-layer composites consisted of a carbon nanotube (CNT)-based layer having an NTC of resistance and a carbon black (CB)-based layer having a PTC of resistance which was in direct contact with electrodes to stabilize the electrical resistance change during electric Joule heating. The composite showed nearly constant resistance values with less than 2% deviation of the normalized resistance until 200 °C. The CB layer worked both as a buffer and as a distributor layer against the current flow from an applied voltage. This behavior, which was confirmed both experimentally and theoretically, has been rarely reported for polymer-based composite systems.Zero temperature coefficient of resistance (TCR) is essential for the precise control of temperature in heating element and sensor applications. Many studies have focused on developing zero-TCR systems with inorganic compounds; however, very few have dealt with developing zero-TCR systems with polymeric materials. Composite systems with a polymer matrix and a conducting filler show either a negative (NTC) or a positive temperature coefficient (PTC) of resistance, depending on several factors, e.g., the polymer nature and the filler shape. In this study, we developed a hybrid conducting zero-TCR composite having self

  6. Elastomeric actuator devices for magnetic resonance imaging

    Science.gov (United States)

    Dubowsky, Steven (Inventor); Hafez, Moustapha (Inventor); Jolesz, Ferenc A. (Inventor); Kacher, Daniel F. (Inventor); Lichter, Matthew (Inventor); Weiss, Peter (Inventor); Wingert, Andreas (Inventor)

    2008-01-01

    The present invention is directed to devices and systems used in magnetic imaging environments that include an actuator device having an elastomeric dielectric film with at least two electrodes, and a frame attached to the actuator device. The frame can have a plurality of configurations including, such as, for example, at least two members that can be, but not limited to, curved beams, rods, plates, or parallel beams. These rigid members can be coupled to flexible members such as, for example, links wherein the frame provides an elastic restoring force. The frame preferably provides a linear actuation force characteristic over a displacement range. The linear actuation force characteristic is defined as .+-.20% and preferably 10% over a displacement range. The actuator further includes a passive element disposed between the flexible members to tune a stiffness characteristic of the actuator. The passive element can be a bi-stable element. The preferred embodiment actuator includes one or more layers of the elastomeric film integrated into the frame. The elastomeric film can be made of many elastomeric materials such as, for example, but not limited to, acrylic, silicone and latex.

  7. Effect of composition on the polarization and ohmic resistances of ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 40; Issue 3. Effect of composition on the polarization and ohmic resistances of LSM/YSZ composite cathodes in solid oxide fuel cell. B SHRI PRAKASH S SENTHIL KUMAR S T ARUNA. Volume 40 Issue 3 June 2017 pp 441-452 ...

  8. Irradiatable polymer composition with improved oxidation resistance

    International Nuclear Information System (INIS)

    Lyons, B.J.

    1977-01-01

    A method is described for the incorporation of a substantially insoluble organic phosphite into a polymer composition such as polyolefin polymers or ethylene copolymers to prevent oxidation of the polymer at elevated temperatures after radiation-induced crosslinking. The crosslinking is readily achieved without affecting the antioxidant properties of the organic phosphite. Particularly suitable organic compounds are derivatives of pentaerythritol, dipentaerythritol, and tripentaerythritol in cooncentrations of 1 to 3% of the mixture to be irradiated

  9. Hydraulic resistance in part-full pipes with composite roughness

    DEFF Research Database (Denmark)

    Perrusquia, G.; Petersen, O.; Larsen, Torben

    1994-01-01

    The paper discusses the boundary shear stresses and the hydraulic resistance in part-full sewer pipes with composite roughness. The discussion is based on a series of numerical experiments using a validated numerical turbulence model. The results from the numerical model are compared with the sid......The paper discusses the boundary shear stresses and the hydraulic resistance in part-full sewer pipes with composite roughness. The discussion is based on a series of numerical experiments using a validated numerical turbulence model. The results from the numerical model are compared...

  10. Wear and impact resistance of HVOF sprayedceramic matrix composites coating

    Science.gov (United States)

    Prawara, B.; Martides, E.; Priyono, B.; Ardy, H.; Rikardo, N.

    2016-02-01

    Ceramic coating has the mechanical properties of high hardness and it is well known for application on wear resistance, but on the other hand the resistance to impact load is low. Therefore its use is limited to applications that have no impact loading. The aim of this research was to obtain ceramic-metallic composite coating which has improved impact resistance compared to conventional ceramic coating. The high impact resistance of ceramic-metallic composite coating is obtained from dispersed metallic alloy phase in ceramic matrix. Ceramic Matrix Composites (CMC) powder with chrome carbide (Cr3C2) base and ceramic-metal NiAl-Al2O3 with various particle sizes as reinforced particle was deposited on mild steel substrate with High Velocity Oxygen Fuel (HVOF) thermal spray coating. Repeated impact test showed that reinforced metallic phase size influenced impact resistance of CMC coating. The ability of CMC coating to absorb impact energy has improved eight times and ten times compared with original Cr3C2 and hard chrome plating respectively. On the other hand the high temperature corrosion resistance of CMC coating showed up to 31 cycles of heating at 800°C and water quenching cooling.

  11. Tensile properties of orthodontic elastomeric ligatures.

    Science.gov (United States)

    Ahrari, F; Jalaly, T; Zebarjad, M

    2010-01-01

    Tensile properties of elastomeric ligatures become important when efficiency of orthodontic appliances is considered. The aim of this study was to compare tensile strength, extension to tensile strength, toughness and modulus of elasticity of elastomeric ligatures in both the as--received condition and after 28 days of immersion in the simulated oral environment. Furthermore, the changes that occurred in tensile properties of each brand of ligatures after 28 days were evaluated. Experimental-laboratory based. Elastomeric ligatures were obtained from different companies and their tensile properties were measured using Zwick testing machine in both the as-received condition and after 28 days of immersion in the simulated oral environment. The data were analyzed using independent sample t-tests, analysis of variance and Tukey tests. After 28 days, all the ligatures experienced a significant decrease in tensile strength, extension to tensile strength and toughness ( P tensile properties of different brands of ligatures in both conditions ( P tensile properties of different brands of ligatures, which should be considered during selection of these products.

  12. Common bunt resistant wheat composite cross populations

    DEFF Research Database (Denmark)

    Steffan, Philipp Matthias; Borgen, A.; Backes, Gunter Martin

    stability. However, a number of challenges must be met before diverse wheat populations can be introduced into commercial wheat production: one of these is the development of breeding technologies based on mass selection which enable breeders and farmers to improve specific traits in populations...... and maintain diversity at the same time. BIOBREED is a project which commenced in Denmark in 2011 to meet these challenges for wheat population breeding. The project focuses on the development of tools and methods for mass selection of traits relevant for organic and low input production, where it is expected...... that the highest benefits of utilizing diverse populations can be achieved. BIOBREED focuses on three main aspects of wheat population breeding for organic and low input production systems: i) common bunt (caused by Tilletia caries) resistance, ii) selection for improved protein content and iii) the influence...

  13. Seismic resistance of composite floor diaphragms

    Science.gov (United States)

    Porter, M. L.; Greimann, L. F.

    1980-05-01

    The behavioral and strength characteristics of composite steel deck floor slab diaphragms are reported. Principal characteristics investigated include maximum load, ductility, stiffness, and failure mode. The addition of studs increases the flexural load capacity of one-way steel deck reinforced slabs by 10 to 30 percent. Non-studded specimens ultimately fail because of loss of interfacial force in the shear span. Studded specimens ultimately fail due to tearing of the deck near the stud. Two analysis procedures were used, a contributing forces approach and a shear-bond approach. The former was found to be a potential analysis procedure, and results from the shear-bond increase approach demonstrated its feasibility for studded specimens.

  14. Model for the resistive critical current transition in composite superconductors

    International Nuclear Information System (INIS)

    Warnes, W.H.

    1988-01-01

    Much of the research investigating technological type-II superconducting composites relies on the measurement of the resistive critical current transition. We have developed a model for the resistive transition which improves on older models by allowing for the very different nature of monofilamentary and multifilamentary composite structures. The monofilamentary model allows for axial current flow around critical current weak links in the superconducting filament. The multifilamentary model incorporates an additional radial current transfer between neighboring filaments. The development of both models is presented. It is shown that the models are useful for extracting more information from the experimental data than was formerly possible. Specific information obtainable from the experimental voltage-current characteristic includes the distribution of critical currents in the composite, the average critical current of the distribution, the range of critical currents in the composite, the field and temperature dependence of the distribution, and the fraction of the composite dissipating energy in flux flow at any current. This additional information about the distribution of critical currents may be helpful in leading toward a better understanding of flux pinning in technological superconductors. Comparison of the models with several experiments is given and shown to be in reasonable agreement. Implications of the models for the measurement of critical currents in technological composites is presented and discussed with reference to basic flux pinning studies in such composites

  15. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... the produced carbon is responsible for low electrical specific resistance of the ceramic carbon composites. References. [1] Takahashi M, Adachi K, Menchavez R L and Fuji M 2006 J. Mater. Sci. 41 1965. [2] ShuKMandTuGC2003Int. J. Machine Tools Manufacture43. 845. [3] Mikeska K R 1997 United States ...

  16. Electrodeposition and Corrosion Resistance of Ni-Graphene Composite Coatings

    Science.gov (United States)

    Szeptycka, Benigna; Gajewska-Midzialek, Anna; Babul, Tomasz

    2016-08-01

    The research on the graphene application for the electrodeposition of nickel composite coatings was conducted. The study assessed an important role of graphene in an increased corrosion resistance of these coatings. Watts-type nickel plating bath with low concentration of nickel ions, organic addition agents, and graphene as dispersed particles were used for deposition of the composite coatings nickel-graphene. The results of investigations of composite coatings nickel-graphene deposited from the bath containing 0.33, 0.5, and 1 g/dm3 graphene and one surface-active substance were shown. The contents of particles in coatings, the surface morphology, the cross-sectional structures of the coated samples, and their thickness and the internal stresses were studied. Voltammetric method was used for examination of the corrosion resistance of samples of composite coatings in 0.5 M NaCl. The obtained results suggest that the content of incorporated graphene particles increases with an increasing amount of graphene in plating bath. The application of organic compounds was advantageous because it caused compressive stresses in the deposited coatings. All of the nickel-graphene composite layers had better corrosion resistance than the nickel coating.

  17. Frictional characteristics of the newer orthodontic elastomeric ligatures

    Directory of Open Access Journals (Sweden)

    A V Arun

    2011-01-01

    Full Text Available Introduction: Elastomeric ligatures reduce chairside time but increase friction. Polymeric coatings and 45° angulations have been introduced to the ligature modules to combat its disadvantages and reduce friction. This in vitro study compared the frictional characteristics of six different types of the most commonly used elastomeric modules. Materials and Methods: Thecoefficient of friction for six ligation methods: the non-coated Mini Stix† and coated Super Slick Mini Stix™ (TP Orthodontics, 45° angulated but non-coated Alastik Easy-To-Tie™ (3M Unitek elastomerics and non-angulated non-coated Alastik QuiK-StiK FNx01 , 0.110′- and 0.120′-diameter elastomerics™ (Reliance Orthodontics were measured in dry conditions utilizing a jig according to the protocol of Tidy. Results: A significant difference was observed between the various types of elastomeric ligatures (P<.01. Among the six types of elastomeric ligatures, the 45° angulated elastomeric ligatures produced the least friction, followed by the coated Super Slick† elastomers. No difference in the friction was noted when the diameter of the elastomeric ligatures was varied. Conclusions: Polymeric surface coatings and introduction of angulations into elastomeric ligatures reduce the friction during sliding; however, the diameter of the ligature made no difference to sliding friction.

  18. Water Resistant Cellulose - Titanium Dioxide Composites for Photocatalysis.

    Science.gov (United States)

    Garusinghe, Uthpala M; Raghuwanshi, Vikram S; Batchelor, Warren; Garnier, Gil

    2018-02-02

    Novel water resistant photocatalytic composites of microfibrillated cellulose (MFC)-polyamide-amine-epichlorohydrin (PAE)-TiO 2 nanoparticles (NPs) were prepared by a simple two-step mixing process. The composites produced are flexible, uniform, reproducible and reusable; they can readily be removed from the pollutant once used. Small amount of TiO 2 NPs are required for the loaded composites to exhibit a remarkable photocatalytic activity which is quantified here as achieving at least 95% of methyl orange degradation under 150 min of UV light irradiation for the composite with best combination. The cellulose network combined with PAE strongly retains NPs and hinders their release in the environment. PAE dosage (10 and 50 mg/g MFC) controls the NP retention in the cellulose fibrous matrix. As TiO 2 content increases, the photocatalytic activity of the composites levels off to a constant; this is reached at 2wt% TiO 2 NPs for 10 mg/g PAE and 20wt% for 50 mg/g PAE. SEM and SAXS analysis confirms the uniform distribution of NPs and their formation of aggregates in the cellulose fibre network. These economical and water resistant photocatalytic paper composites made by a simple, robust and easily scalable process are ideal for applications such as waste water treatment where efficiency, reusability and recyclability are important.

  19. Wear resistance and fracture mechanics of WC-Co composites

    Energy Technology Data Exchange (ETDEWEB)

    Kaytbay, Saleh [Benha Univ. (Egypt). Dept. of Mechanical Engineering; El-Hadek, Medhat [Port-Said Univ. (Egypt). Dept. of Production and Mechanical Design

    2014-06-15

    Manufacturing of WC-Co composites using the electroless precipitation method at different sintering temperatures of 1 100, 1 250, 1 350 and 1 500 C was successfully achieved. The chemical composition of the investigated materials was 90 wt.% WC with 10 wt.% Co, and 80 wt.% WC with 20 wt.% Co. The specific density, densification, and Vickers microhardness measurements were found to increase with increased sintering temperature for both the WC-Co compositions. The composites of tungsten carbide with 10 wt.% Co had a higher specific density and Vickers microhardness measurements than those for the composites of tungsten carbide with 20 wt.% Co. Composites with WC-10 wt.% Co had better wear resistance. The stress-strain and transverse rupture strength increased monotonically with the increase in sintering temperatures, agreeing with the material hardness and wear resistance behavior. Fractographical scanning electron microscopy analysis of the fracture surface demonstrated a rough characteristic conical shape failure in the direction of the maximum shear stress. A proposed mechanism for the formation of the conical fracture surface under compression testing is presented. (orig.)

  20. Evaluation of shear mounted elastomeric damper

    Science.gov (United States)

    Zorzi, E.; Walton, J.

    1982-01-01

    Viton-70 elastomeric shear mounted damper was built and tested on a T-55 power turbine spool in the rotor's high speed balancing rig. This application of a shear mounted elastomeric damper demonstrated for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear damper design was selected because it was compatible with actual gas turbine engine radial space constraints, could accommodate both the radial and axial thrust loads present in gas turbine engines, and was capable of controlled axial preload. The shear damper was interchangeable with the production T-55 power turbine roller bearing support so that a direct comparison between the shear damper and the production support structure could be made. Test results show that the Viton-70 elastomer damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing up to the maximum rotor speed of 16,000 rpm. Excellent correlation between the predicted and experienced critical speeds, mode shapes and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

  1. Fissure sealant materials: Wear resistance of flowable composite resins.

    Science.gov (United States)

    Asefi, Sohrab; Eskandarion, Solmaz; Hamidiaval, Shadi

    2016-01-01

    Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow), Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists). A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm(2) and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm(2)of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics.

  2. Fissure sealant materials: Wear resistance of flowable composite resins

    Directory of Open Access Journals (Sweden)

    Sohrab Asefi

    2016-08-01

    Full Text Available Background. Wear resistance of pit and fissure sealant materials can influence their retention. Wear characteristics of sealant materials may determine scheduling of check-up visits. The aim of this study was to compare wear resistance of two flowable composite resins with that of posterior composite resin materials. Methods. Thirty-five disk-shaped specimens were prepared in 5 groups, including two flowable composite resins (Estelite Flow Quick and Estelite Flow Quick High Flow, Filtek P90 and Filtek P60 and Tetric N-Ceram. The disk-shaped samples were prepared in 25-mm diameter by packing them into a two-piece aluminum mold and then light-cured. All the specimens were polished for 1minute using 600-grit sand paper. The samples were stored in distilled water at room temperature for 1 week and then worn by two-body abrasion test using "pin-on-disk" method (with distilled water under a 15-Nload at 0.05 m/s, for a distance of 100 meter with Steatite ceramic balls antagonists. A Profilometer was used for evaluating the surface wear. Data were analyzed with the one-way ANOVA. Results. Estelite Flow Quick exhibited 2708.9 ± 578.1 μm2 and Estelite Flow Quick High Flow exhibited 3206 ± 2445.1 μm2of wear but there were no significant differences between the groups. They demonstrated similar wear properties. Conclusion. Estelite flowable composite resins have wear resistance similar to nano- and micro-filled and micro-hybrid composite resins. Therefore, they can be recommended as pit and fissure sealant materials in the posterior region with appropriate mechanical characteristics.

  3. The effect of dietary pigmentation on the esthetic appearance of clear orthodontic elastomeric modules.

    Science.gov (United States)

    Talic, Nabeel F; Almudhi, Abdullazez A

    2016-01-01

    To compare the stain resistance of three types of clear elastomeric modules exposed to several common dietary substances through the assessment of the perception of a group of dentists to discoloration using visual analog scale (VAS). Elastomeric modules from Unitek (AU), Ormco (OR), and dentaurum (DE) were immersed in the following food substances: Coffee, black tea, chocolate, energy drink, ketchup, and Coca-Cola for 72 h. VAS was used to reflect the module staining severity. Significant difference was found among the three types of modules examined in this study. OR modules showed the least mean staining ratings by the examiners. There was no statistical difference in the staining properties between AU and DE modules. Coffee and tea showed higher staining potential as compared to all staining media. Furthermore, there was no difference in the staining characteristics of coffee and black tea. Coffee and tea are strong staining media that should be avoided by patients who opted to have esthetic appliances for their orthodontic treatment. Elastomeric modules manufactured by AU showed higher staining optical properties as compared to the other two companies, which could be related to the manufacturing processing of these modules.

  4. Fabrication of an Electrically-Resistive, Varistor-Polymer Composite

    Directory of Open Access Journals (Sweden)

    Sanaz A. Mohammadi

    2012-11-01

    Full Text Available This study focuses on the fabrication and electrical characterization of a polymer composite based on nano-sized varistor powder. The polymer composite was fabricated by the melt-blending method. The developed nano-composite was characterized by X-ray diffraction (XRD, transmission electron microscopy (TEM, field emission scanning electron microscopy (FeSEM, and energy-dispersive X-ray spectroscopy (EDAX. The XRD pattern revealed the crystallinity of the composite. The XRD study also showed the presence of secondary phases due to the substitution of zinc by other cations, such as bismuth and manganese. The TEM picture of the sample revealed the distribution of the spherical, nano-sized, filler particles throughout the matrix, which were in the 10–50 nm range with an average of approximately 11 nm. The presence of a bismuth-rich phase and a ZnO matrix phase in the ZnO-based varistor powder was confirmed by FeSEM images and EDX spectra. From the current-voltage curves, the non-linear coefficient of the varistor polymer composite with 70 wt% of nano filler was 3.57, and its electrical resistivity after the onset point was 861 KΩ. The non-linear coefficient was 1.11 in the sample with 100 wt% polymer content. Thus, it was concluded that the composites established a better electrical non-linearity at higher filler amounts due to the nano-metric structure and closer particle linkages.

  5. Investigation of the recycling of tires to elastomeric requirements by techniques of thermal compression

    Science.gov (United States)

    Nadal Gisbert, Antonio V.

    In this work is investigated the recycling of tires to elastomeric requirements by thermal compression. The production of recycled products is carried out starting from the powder, of elastomeric nature, coming from the grinding of used tires denominated GTR (Ground Tire Rubber) of different grain size, although the fundamental objective is the recycling of powder of 0,2mm grain size. The process of forming used for obtaining the recycled product is thermal compression, due to its simplicity and low cost. The composition of the powder has been analyzed and also the influence, on the elastomeric characteristics of the recycled product, of different parameters: Grain size, compact pressure, temperature, time, thickness of the recycled product and combination of sizes. At last we give an hypothesis that justifies the mechanism that gives cohesion to the powder GTR and allows their recycling. We also have carried out an analysis of the investigation lines, at the present, on the recycling of tires in general and an economic study of the viability of the recycled product in front of present products in the market, agglomerated with polyurethane, that have their application in using it in different types of floors.

  6. Imprint lithography with degradable elastomeric polyanhydrides.

    Science.gov (United States)

    Lou, Qin; Shipp, Devon A

    2012-09-26

    A photocurable, degradable polyanhydride cross-linked elastomer that can be used as a stamp in imprint lithography applications has been developed. The degradable stamp materials are based on polyanhydrides synthesized using thiol-ene polymerization. In this study, curing the monomers 4-pentenoic anhydride and pentaerythritol tetrakis(3-mercaptopropionate) on a master mold yields low modulus, elastomeric, degradable polyanhydride polymer stamps that are a negative of the master. These stamps can be then used as a sacrificial template during the fabrication of a replica of the master, and can be readily degraded away from the replica using water. The resultant imprinted materials exhibited excellent uniformity over a large area. Compared with other conventional imprint lithography stamp materials, the thiol-ene polymerized polyanhydrides are degradable, master mold safe, show great release properties, have fast cure rates, are relatively low cost, and can be fabricated onto variety of substrates and materials.

  7. Anisotropic dewetting on stretched elastomeric substrates.

    Science.gov (United States)

    Qiao, L; He, L H

    2008-08-01

    We study the instability of a very thin liquid film resting on a uniformly stretched soft elastomeric substrate driven by van der Waals forces. A linear stability analysis shows that the critical fluctuation wavelength in the tensile direction is larger than those in the other directions. The magnitudes of the critical wavelengths are adjustable in the sense that they depend on the principal stretch of the substrate. For example, when the principal stretch of the substrate varies from 1.0 (unstretched) to 3.0, the range of the critical wavelength in the tensile direction increases by 7.0% while that normal to the tensile direction decreases by 8.7%. Therefore, the phenomenon may find potential applications in creating tunable topographically patterned surfaces with nano- to microscale features.

  8. Kinetic analysis of elastomeric lag damper for helicopter rotors

    Science.gov (United States)

    Liu, Yafang; Wang, Jidong; Tong, Yan

    2018-02-01

    The elastomeric lag dampers suppress the ground resonance and air resonance that play a significant role in the stability of the helicopter. In this paper, elastomeric lag damper which is made from silicone rubber is built. And a series of experiments are conducted on this elastomeric lag damper. The stress-strain curves of elastomeric lag dampers employed shear forces at different frequency are obtained. And a finite element model is established based on Burgers model. The result of simulation and tests shows that the simple, linear model will yield good predictions of damper energy dissipation and it is adequate for predicting the stress-strain hysteresis loop within the operating frequency and a small-amplitude oscillation.

  9. Method of making sulfur-resistant composite metal membranes

    Science.gov (United States)

    Way, J Douglas [Boulder, CO; Lusk, Mark [Golden, CO; Thoen, Paul [Littleton, CO

    2012-01-24

    The invention provides thin, hydrogen-permeable, sulfur-resistant membranes formed from palladium or palladium-alloy coatings on porous, ceramic or metal supports. Also disclosed are methods of making these membranes via sequential electroless plating techniques, wherein the method of making the membrane includes decomposing any organic ligands present on the substrate, reducing the palladium crystallites on the substrate to reduced palladium crystallites, depositing a film of palladium metal on the substrate and then depositing a second, gold film on the palladium film. These two metal films are then annealed at a temperature between about 200.degree. C. and about 1200.degree. C. to form a sulfur-resistant, composite PdAu alloy membrane.

  10. Metal-nanotube composites as radiation resistant materials

    Energy Technology Data Exchange (ETDEWEB)

    González, Rafael I.; Valencia, Felipe; Mella, José; Kiwi, Miguel, E-mail: m.kiwi.t@gmail.com [Departamento de Física, Facultad de Ciencias, CEDENNA, Universidad de Chile, Casilla 653, Santiago 7800024 (Chile); Duin, Adri C. T. van [Department of Mechanical and Nuclear Engineering, The Pennsylvania State University, University Park, Pennsylvania 16802 (United States); So, Kang Pyo; Li, Ju [Department of Nuclear Science and Engineering and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Bringa, Eduardo M. [CONICET and Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Cuyo, Mendoza 5500 (Argentina)

    2016-07-18

    The improvement of radiation resistance in nanocomposite materials is investigated by means of classical reactive molecular dynamics simulations. In particular, we study the influence of carbon nanotubes (CNTs) in an Ni matrix on the trapping and possible outgassing of He. When CNTs are defect-free, He atoms diffuse alongside CNT walls and, although there is He accumulation at the metal-CNT interface, no He trespassing of the CNT wall is observed, which is consistent with the lack of permeability of a perfect graphene sheet. However, when vacancies are introduced to mimic radiation-induced defects, He atoms penetrate CNTs, which play the role of nano-chimneys, allowing He atoms to escape the damaged zone and reduce bubble formation in the matrix. Consequently, composites made of CNTs inside metals are likely to display improved radiation resistance, particularly when radiation damage is related to swelling and He-induced embrittlement.

  11. Fracture resistance of teeth restored with packable and hybrid composites

    Directory of Open Access Journals (Sweden)

    Ghavam M

    2006-06-01

    Full Text Available Background and Aim: With recent introduction of packable composites, it is claimed that they apply less stress on tooth structure because of reduced polymerization shrinkage, and similarity of coefficient of thermal expansion to tooth structure. However, the high viscosity may in turn cause less adaptation, so it is not clearly known whether these materials strengthen tooth structure or not. The aim of this study was to evaluate fracture resistance of maxillary premolars, receiving hybrid or packable composite restorations with different methods of application and curing. Materials and Methods: In this experimental study, seventy five intact premolars were randomly assigned to five groups of 15 teeth each. One group was maintained intact as the control group. Similar MOD cavities were prepared in the other teeth. The teeth in group two were restored with Spectrum in incremental layers and light cured with 500 mw/cm2 intensity. The third group were filled with Surefil and cured with light intensity of 500 mw/cm2. The groups four and five were restored with Surefil in bulk technique with two different modes: 500 mw/cm2 intensity and a ramp mode (100-900 mw/cm2 respectively. After thermocycling, force to fracture was assessed and degree of conversion (DC at the bottom of cavities was evaluated for different modes and methods. The curing and placement methods in groups tested for DC (A to D were the same as fracture resistance groups (2 to 5. Data were analyzed using one way ANOVA and Tukey HSD tests with p<0.05 as the limit of significance. Results: All the restored groups showed significantly less fracture resistance than the control group, but had no significant difference among themselves. DC of Spectrum was higher than Surefil. Bulk method with 500 mw/cm2 light intensity, significantly decreased DC. DC in bulk method with high light intensity was not significantly different from incremental method with 500 mw/cm2 light intensity. Conclusion

  12. Laser cladding of wear resistant metal matrix composite coatings

    International Nuclear Information System (INIS)

    Yakovlev, A.; Bertrand, Ph.; Smurov, I.

    2004-01-01

    A number of coatings with wear-resistant properties as well as with a low friction coefficient are produced by laser cladding. The structure of these coatings is determined by required performance and realized as metal matrix composite (MMC), where solid lubricant serves as a ductile matrix (e.g. CuSn), reinforced by appropriate ceramic phase (e.g. WC/Co). One of the engineered coating with functionally graded material (FGM) structure has a dry friction coefficient 0.12. Coatings were produced by coaxial injection of powder blend into the zone of laser beam action. Metallographic and tribological examinations were carried out confirming the advanced performance of engineered coatings

  13. Self-healing epoxy composite with heat-resistant healant.

    Science.gov (United States)

    Yuan, Yan Chao; Ye, Xiao Ji; Rong, Min Zhi; Zhang, Ming Qiu; Yang, Gui Cheng; Zhao, Jian Qing

    2011-11-01

    To provide self-healing epoxy composite with adequate heat resistance for high-performance application, we developed a novel microencapsulated epoxy/mercaptan healing agent. The key measure lies in usage of diglycidyl ether of bisphenol A (EPON 828) as the polymerizable component and 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30) as the catalyst. Because of the higher thermal stability of EPON 828 and lower volatility of DMP-30, the healing agent and the self-healing composite not only survive high-temperature curing and thermal exposure, but also offer satisfactory capability of autonomous properties restoration, as characterized by both fracture mechanics and fatigue tests. Especially when the operation temperature is not higher than 200 °C, the performance of the healing system is nearly independent of thermal history.

  14. Composition of human faecal microbiota in resistance to Campylobacter infection.

    Science.gov (United States)

    Kampmann, C; Dicksved, J; Engstrand, L; Rautelin, H

    2016-01-01

    In mice, specific species composition of gut microbiota enhances susceptibility to Campylobacter jejuni but little is known about the specific composition of the human gut microbiota in providing protection from infections caused by enteropathogens. Healthy adult individuals, who travelled in groups from Sweden to destinations with an estimated high risk for acquisition of Campylobacter infection, were enrolled. Faecal samples, collected before travelling and after returning home, were cultured for bacterial enteropathogens, and analysed for Campylobacter by PCR and for the species composition of the microbiota by 16S amplicon massive parallel sequencing. The microbiota compositions were compared between persons who became infected during their travel and those who did not. A total of 63 participants completed the study; 14 became infected with Campylobacter, two with Salmonella and 47 remained negative for the enteropathogens tested. After exclusion of samples taken after antimicrobial treatment, 49 individuals were included in the final analyses. Intra-individual stability of the microbiota was demonstrated for samples taken before travelling. The original diversity of the faecal microbiota was significantly lower among individuals who later became infected compared with those who remained uninfected. The relative abundances of bacteria belonging to the family Lachnospiraceae, and more specifically its two genera Dorea and Coprococcus, were significantly higher among those who remained uninfected. The travel-related infection did not significantly modify the faecal microbiota composition. Species composition of human gut microbiota is important for colonization resistance to Campylobacter infection. Especially individuals with a lower diversity are more susceptible to Campylobacter infection. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  15. A Numerical Analysis of the Resistance and Stiffness of the Aluminium and Concrete Composite Beam

    Directory of Open Access Journals (Sweden)

    Polus Łukasz

    2015-03-01

    Full Text Available In this paper a numerical analysis of the resistance and stiffness of the aluminium and concrete composite beam is presented. Composite aluminium and concrete structures are quite new and they have not been thoroughly tested. Composite structures have a lot of advantages. The composite aluminium and concrete beam is more corrosion-resistant, fire-resistant and stiff than the aluminium beam. The contemporary idea of sustainable buildings relies on new solutions which are more environmentally friendly. Aluminium is lighter and more resistant to corrosion than steel, which is often used in composite structures.

  16. Aligned composite structures for mitigation of impact damage and resistance to wear in dynamic environments

    Science.gov (United States)

    Mulligan, Anthony C.; Rigali, Mark J.; Sutaria, Manish P.; Popovich, Dragan; Halloran, Joseph P.; Fulcher, Michael L.; Cook, Randy C.

    2009-04-14

    Fibrous monolith composites having architectures that provide increased flaw insensitivity, improved hardness, wear resistance and damage tolerance and methods of manufacture thereof are provided for use in dynamic environments to mitigate impact damage and increase wear resistance.

  17. Baxter elastomeric pumps: Feasibility of weight estimates.

    Science.gov (United States)

    Chambers, Carole R; Pabia, Mica; Sawyer, Michael; Tang, Patricia A

    2017-09-01

    Purpose Elastomeric pumps are used to infuse a 46-h fluorouracil protocol and patients are asked to visually inspect the pump daily. The pump has a variability of ±10% and there are additional patient variables that can increase this. The feasibility of weighing the pump rather than a visual inspection along with the secondary objective to confirm the pump's variability in real world conditions was undertaken. Methods Empty pumps were weighed using both pharmacy and kitchen scales. Pumps upon completion of the 46-h infusion were also weighed using both pharmacy and kitchen scales. Results The kitchen scale was as accurate as the pharmacy grade scale. Disconnected pumps showed the expected variability from using these infusor pumps along with a few showing greater variability likely due to patient variables. Conclusion Weighing pumps appears to be feasible both at the pharmacy and home level. Next steps would be to weigh pumps during the infusion to validate an alternate method to simple visual inspection for patients to confirm proper infusing of the pump at their home.

  18. Behaviour of elastomeric seals at low temperature

    International Nuclear Information System (INIS)

    Weise, H.P.; Kowalewsky, H.; Wenz, R.

    1993-01-01

    The properties of elastomer O-ring seals (Viton, silicone rubber, EPDM) at low temperature have been investigated by measuring the gas leakage rate and the sealing force during thermal cycling between +20degC and -70degC. For all materials it has been found that at a well defined (critical) temperature the leakage rate sharply rises from permeation level to a high value which is determined by gas streaming through the leak path between the O-ring and the flange surfaces arising from thermal contraction of the elastomer in the glassy state. At the critical temperature the sealing force has been found to be zero or even negative due to adhesion between the elastomer material and the flanges. For all seals the critical temperature is well below the glass transition of the elastomer and also significantly below the temperature where the compression set becomes 100 %. Warming up the sealing system restores leak tightness. Low temperature cycle of elastomeric seals have been found to be entirely reversible. (author)

  19. Sterilizing elastomeric chains without losing mechanical properties. Is it possible?

    Directory of Open Access Journals (Sweden)

    Matheus Melo Pithon

    2015-06-01

    Full Text Available OBJECTIVE: To investigate the effects of different sterilization/disinfection methods on the mechanical properties of orthodontic elastomeric chains. METHODS: Segments of elastomeric chains with 5 links each were sent for sterilization by cobalt 60 (Co60 (20 KGy gamma ray technology. After the procedure, the elastomeric chains were contaminated with clinical samples of Streptococcus mutans. Subsequently, the elastomeric chains were submitted to sterilization/disinfection tests carried out by means of different methods, forming six study groups, as follows: Group 1 (control - without contamination, Group 2 (70°GL alcohol, Group 3 (autoclave, Group 4 (ultraviolet, Group 5 (peracetic acid and Group 6 (glutaraldehyde. After sterilization/disinfection, the effectiveness of these methods, by Colony forming units per mL (CFU/mL, and the mechanical properties of the material were assessed. Student's t-test was used to assess the number of CFUs while ANOVA and Tukey's test were used to assess elastic strength. RESULTS: Ultraviolet treatment was not completely effective for sterilization. No loss of mechanical properties occurred with the use of the different sterilization methods (p > 0.05. CONCLUSION: Biological control of elastomeric chains does not affect their mechanical properties.

  20. Radiation crosslinked block copolymer blends with improved impact resistance

    International Nuclear Information System (INIS)

    Saunders, F.L.; Pelletier, R.R.

    1976-01-01

    Polymer blends having high impact resistance after mechanical working are produced by blending together a non-elastomeric monovinylidene aromatic polymer such as polystyrene with an elastomeric copolymer, such as a block copolymer of styrene and butadiene, in the form of crosslinked, colloidal size particles

  1. Enhancing retention of partial dentures using elastomeric retention rings

    Directory of Open Access Journals (Sweden)

    Kakkirala Revathi

    2015-01-01

    Full Text Available This report presents an alternative method for the retention of partial dentures that relies on the engagement of tooth undercuts by a lining material. The lab procedures are also presented. A new maxillary and mandibular acrylic partial dentures were fabricated using elastomeric retention technique for a partially dentate patient. A partially dentate man reported difficulty in retaining his upper removable partial denture (RPD. The maxillary RPD was designed utilizing elastomeric retention technique. During follow-up, it was necessary to replace the retention rings due to wear. The replacement of the retention rings, in this case, was done through a chairside reline technique. Elastomeric retention technique provides exceptionally good retention can be indicated to stabilize, cushion, splint periodontally involved teeth, no enough undercut for clasps, eliminate extractions, single or isolated teeth.

  2. Effect of composite/amalgam thickness on fracture resistance of maxillary premolar teeth, restored with combined amalgam-composite restorations.

    Science.gov (United States)

    Firouzmandi, Maryam; Doozandeh, Maryam; Jowkar, Zahra; Abbasi, Sanaz

    2016-07-01

    Combined amalgam-composite restorations have been used through many years to benefit from the advantages of both dental amalgam and composite resin. Two variations have been mentioned for this technique, this study investigated the fracture resistance of maxillary premolar teeth with extended mesio-occluso-distal (MOD) cavities, restored with the two variations of combined amalgam-composite restorations. Sixty intact extracted premolar teeth were randomly divided into 6 groups (G1-G6) of 10 teeth. G1; consisted of intact teeth and G2; consisted of teeth with MOD preparations were assigned as the positive and negative control groups respectively. Other experimental groups after MOD preparations were as follows: G3, amalgam restoration; G4, composite restoration; G5 combined amalgam-composite restoration with amalgam placement only on 1mm of the gingival floor of the proximal boxes; G6, combined amalgam-composite restoration with amalgam placement to the height of contact area of the proximal surface of the tooth. Fracture strength of the specimens was measured and the data were analyzed using one-way analysis of variance (ANOVA). The level of significance was Pamalgam-composite restoration was similar to that achieved with composite restoration alone and more than that of amalgam restoration alone. It can be concluded that the thickness of amalgam in combined amalgam-composite restorations did not affect fracture resistance of the teeth. Amalgam, composite, fracture resistance, restoration.

  3. Effect of composite/amalgam thickness on fracture resistance of maxillary premolar teeth, restored with combined amalgam-composite restorations

    OpenAIRE

    Firouzmandi, Maryam; Doozandeh, Maryam; Jowkar, Zahra; Abbasi, Sanaz

    2016-01-01

    Background Combined amalgam-composite restorations have been used through many years to benefit from the advantages of both dental amalgam and composite resin. Two variations have been mentioned for this technique, this study investigated the fracture resistance of maxillary premolar teeth with extended mesio-occluso-distal (MOD) cavities, restored with the two variations of combined amalgam-composite restorations. Material and Methods Sixty intact extracted premolar teeth were randomly divid...

  4. Low interfacial contact resistance of Al-graphene composites via interface engineering

    Science.gov (United States)

    Hahm, Myung Gwan; Nam, Jaewook; Choi, Minseok; Park, Chi-Dong; Cho, Byungjin; Kazunori, Sanada; Ahm Kim, Yoong; Kim, Dong Young; Endo, Morinobu; Kim, Dong-Ho; Vajtai, Robert; Ajayan, Pulickel M.; Moo Song, Sung

    2015-05-01

    Al-based composites incorporating multilayered graphene sheets were developed via a facile approach. The multilayered graphene sheets were fabricated from the expanded graphite via a simple mechanical exfoliation process. The facile extrusion molding process with Al powder and graphene sheets exfoliated from expended graphite afforded Al-based graphene composite rods. These composites showed enhanced thermal conductivity compared to the pristine Al rods. Moreover, the Al-based multilayered graphene sheet composites exhibited lower interfacial contact resistance between graphene-based electrodes than the pristine Al. With increasing degrees of dispersion, the number of exposed graphene sheets increases, thereby significantly decreasing the interfacial contact resistance between the composite and external graphite electrode.

  5. Effects of processing method and moisture history on laboratory fungal resistance of wood-HDPE composites.

    Science.gov (United States)

    Craig M. Clemons; Rebecca E. Ibach

    2004-01-01

    The purpose of this study was to clarify the effects of composite processing and moisture sorption on laboratory fungal resistance of wood-plastic composites. A 2-week water soaking or cyclic boiling-drying procedure was used to infuse moisture into composites made from high-density polyethylene filled with 50 percent wood flour and processed by extrusion, compression...

  6. Continuous monitoring of the composition of liquid Pb-17Li eutectic using electrical resistivity methods

    International Nuclear Information System (INIS)

    Hubberstey, P.; Sample, T.; Barker, M.G.

    1991-01-01

    The composition of liquid Pb-17Li alloys has been continously determined, using an electrical resistivity monitor, during their interaction with nitrogen, oxygen, hydrogen and water vapour. The operation of the monitor depends on the fact that the resistivity of liquid Pb-Li alloys is dependent on their composition. Accurate resistivity-composition isotherms have been derived from resistivity-temperature data for 15 Pb-Li alloys (0 Li -8 Ω m (mol% Li) -1 at 725 K) is such that a change of 0.05 mol% Li in the alloy composition can be measured. The addition of oxygen and water vapour resulted in a decrease in the resistivity of the liquid alloy. Neither nitrogen nor hydrogen had any effect. The observed changes were shown to be consistent with Li 2 O formation. (orig.)

  7. Fiber Finishes for Improving Galvanic Resistance of Imide-Based Composites

    National Research Council Canada - National Science Library

    Allred, R. E

    1998-01-01

    The objective of this program is the development and demonstration of galvanic corrosion resistant carbon/ BMI composites through the use of reactive finishes to form coatings that isolate the carbon...

  8. Wireless Damage Monitoring of Laminated CFRP Composites using Electrical Resistance Change

    National Research Council Canada - National Science Library

    Todoroki, Akira

    2007-01-01

    .... In this system, a tiny oscillation circuit is attached to the composite component. When delimitation of the component occurs, electrical resistance changes, which causes a change in the oscillating frequency of the circuit...

  9. Stab Resistance of Shear Thickening Fluid (STF)-Kevlar Composites for Body Armor Applications

    National Research Council Canada - National Science Library

    Egres Jr., R. G; Decker, M. J; Halbach, C. J; Lee, Y. S; Kirkwood, J. E; Kirwood, K. M; Wagner, N. J; Wetzel, E. D

    2004-01-01

    The stab resistance of shear thickening fluid (STF)-Kevlar and STF-Nylon fabric composites are investigated and found to exhibit significant improvements over neat fabric targets of equivalent areal density...

  10. Low-Cost Repairable Oxidation Resistant Coatings for Carbon-Carbon Composites via CCVD

    National Research Council Canada - National Science Library

    Hendrick, Michelle

    2000-01-01

    ...) thin film process to yield oxidation resistant coatings on carbon-carbon (C-C) composites. Work was on simple coatings at this preliminary stage of investigation, including silicon dioxide, platinum and aluminum oxide...

  11. In situ studies of strain dependent transport properties of conducting polymers on elastomeric substrates

    Science.gov (United States)

    Vijay, Venugopalan; Rao, Arun D.; Narayan, K. S.

    2011-04-01

    We report the changes in the surface electrical resistance, R, of conducting polymer, Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) films coated on appropriate flexible substrates in stretched conditions. These studies are important in the context of flexible organic electronic applications. In situ conductivity measurements on pristine PEDOT:PSS thin films on elastomeric substrates upon stretching reveal a minima in R as a function of strain, x, prior to the expected increase at higher strain levels. The studies emphasize (i) role of substrates, (ii) stress-induced anisotropic features, and temperature dependence of R (iii) in comparison of R(x) in polymer films to that of conventional metal films. The stress induced changes is modeled in terms of effective medium approximation.

  12. Effects of composite scale on high temperature oxidation resistance of Fe-Cr-Ni heat resistant alloy

    Directory of Open Access Journals (Sweden)

    Wang Haitao

    2009-05-01

    Full Text Available Fe-Cr-Ni heat resistant alloys with aluminum and silicon addition, alone and in combination, were melted using an intermediate frequency induction furnace with a non-oxidation method. By the oxidation weight gain method, the oxidation resistances of the test alloys were determined at 1,200 ìC for 500 hours. According to the oxidation weight gains, the oxidation kinetic curves were plotted and the functions were regressed by the least squares method. The results show that the oxidation kinetic curves follow the power function of y = axb (a>0, 0compositions on oxidation resistance were studied further by analyses using X-ray diffraction (XRD and scanning electron microscope (SEM. It is found that the composite scale compounds of Cr2O3, メ-Al2O3, SiO2 and FeCr2O4, with compact structure and tiny grains, shows complete oxidation resistance at 1,200 ìC. When the composite scale lacks メ-Al2O3 or SiO2, it becomes weak in oxidation resistance with a loose structure. By the criterion of standard Gibbs formation free energy, the model of the nucleation and growth of the composite scale is established. The forming of the composite scale is the result of the competition of being oxidized and reduced between aluminum, silicon and the matrix metal elements of iron, chromium and nickel. The protection of the composite scale is analyzed essentially by electrical conductivity and strength properties.

  13. Pressure and temperature induced electrical resistance change in nano-carbon/epoxy composites

    NARCIS (Netherlands)

    Shen, J. T.; Buschhorn, S. T.; De Hosson, J. Th. M.; Schulte, K.; Fiedler, B.

    2015-01-01

    In this study, we investigate the changes of electrical resistance of the carbon black (CB) and carbon nanotube (CNT) filled epoxy composites upon compression, swelling and temperature variation. For all samples we observe a decrease of electrical resistance under compression, while an increase of

  14. Resistance Welding of Thermoplastic Composites : Process and Performance

    NARCIS (Netherlands)

    Shi, H.

    2014-01-01

    Compared to thermoset composites, thermoplastic composites are drawing more and more attention by aircraft industries not only due to their excellent material properties but also due to their potentials to reduce cycle time and structure cost by using low-cost manufacturing technologies such as

  15. Fatigue resistance of CAD/CAM resin composite molar crowns.

    NARCIS (Netherlands)

    Shembish, F.A.; Tong, H.; Kaizer, M.; Janal, M.N.; Thompson, V.P.; Opdam, N.J.M.; Zhang, Y.

    2016-01-01

    OBJECTIVE: To demonstrate the fatigue behavior of CAD/CAM resin composite molar crowns using a mouth-motion step-stress fatigue test. Monolithic leucite-reinforced glass-ceramic crowns were used as a reference. METHODS: Fully anatomically shaped monolithic resin composite molar crowns (Lava

  16. Active shape-morphing elastomeric colloids in short-pitch cholesteric liquid crystals.

    Science.gov (United States)

    Evans, Julian S; Sun, Yaoran; Senyuk, Bohdan; Keller, Patrick; Pergamenshchik, Victor M; Lee, Taewoo; Smalyukh, Ivan I

    2013-05-03

    Active elastomeric liquid crystal particles with initial cylindrical shapes are obtained by means of soft lithography and polymerization in a strong magnetic field. Gold nanocrystals infiltrated into these particles mediate energy transfer from laser light to heat, so that the inherent coupling between the temperature-dependent order and shape allows for dynamic morphing of these particles and well-controlled stable shapes. Continuous changes of particle shapes are followed by their spontaneous realignment and transformations of director structures in the surrounding cholesteric host, as well as locomotion in the case of a nonreciprocal shape morphing. These findings bridge the fields of liquid crystal solids and active colloids, may enable shape-controlled self-assembly of adaptive composites and light-driven micromachines, and can be understood by employing simple symmetry considerations along with electrostatic analogies.

  17. Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

    NARCIS (Netherlands)

    Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

    The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

  18. OPTIMIZATION OF THE COMPOSITION AND TECHNOLOGY OF THE ABRASION-RESISTANT CAST-IRONS MELTING

    Directory of Open Access Journals (Sweden)

    A. I. Garost

    2004-01-01

    Full Text Available Тhе methods of the service durability increase of wear resistant cast irons are analyzed. There are developed the compositions of economically-alloyed cast irons with low content of nickel and other deficient elements, being exploited both in cast and in thermotreated state. The composition of antifriction gray cast iron with increased exploitation characteristics is offered.

  19. Fracture strength and fatigue resistance of dental resin-based composites

    NARCIS (Netherlands)

    Keulemans, F.; Palav, P.; Aboushelib, M.M.N.; van Dalen, A.; Kleverlaan, C.J.; Feilzer, A.J.

    2009-01-01

    Objectives: The aim of this study was to evaluate in vitro the influence of fiber-reinforcement on the fracture strength and fatigue resistance of resin-based composites. Methods: One hundred rectangular bar-shaped specimens (2 mm × 2 mm × 25 mm) made of resin-based composite were prepared in a

  20. Fracture resistance of reattached incisor fragments with mini fibre-reinforced composite anchors.

    NARCIS (Netherlands)

    Fennis, W.M.M.; Kreulen, C.M.; Wolke, J.G.C.; Fokkinga, W.A.; Machado, C.; Creugers, N.H.J.

    2009-01-01

    OBJECTIVES: Fractured coronal fragments of incisors can be adhered to the remaining tooth with resin composite, but are prone to failure. This study explores whether mini fibre-reinforced composite (FRC) anchors increase fracture resistance of reattached fragments. METHODS: Forty-five extracted

  1. Hybrid magnetorheological fluid elastomeric lag dampers for helicopter stability augmentation

    Science.gov (United States)

    Hu, Wei; Wereley, Norman M.

    2008-08-01

    A laboratory demonstration of a hybrid magnetorheological fluid-elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e. controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid

  2. Effects of oxygen plasma treatment power on Aramid fiber III/BMI composite humidity resistance properties

    Science.gov (United States)

    Wang, Jing; Shi, Chen; Feng, Jiayue; Long, Xi; Meng, Lingzhi; Ren, Hang

    2018-01-01

    The effects of oxygen plasma treatment power on Aramid Fiber III chemical structure and its reinforced bismaleimides (BMI) composite humidity resistance properties were investigated in this work. The aramid fiber III chemical structure under different plasma treatment power were measured by FTIR. The composite bending strength and interlinear shear strength with different plasma treatment power before and after absorption water were tested respectively. The composite rupture morphology was observed by SEM. The FTIR results showed that oxygen plasma treatment do not change the fiber bulk chemical structure. The composite humidity resistance of bending strength and interlinear shear strength are similar for untreated and plasma treated samples. The retention rate of composite bending strength and interlinear shear strength are about 75% and 94%, respectively. The composite rupture mode turns to be the fiber failure after water absorption.

  3. WEAR-RESISTANCE OF CHROMIC CAST IRONS OF EUTECTIC COMPOSITION

    Directory of Open Access Journals (Sweden)

    K. E. Baranovskij

    2009-01-01

    Full Text Available Casting of wear-resistant chrome cast irons in combined molds and iron chills is studied. Application of these ways of casting results in blending of carbides and increasing of hardness of castings.

  4. Increased corrosion resistance of basalt reinforced cement compositions with nanosilica

    Directory of Open Access Journals (Sweden)

    URKHANOVA Larisa Alekseevna

    2014-08-01

    Full Text Available Disperse fiber reinforcement is used to improve deformation and shrinkage characteristics, flexural strength of concrete. Basalt roving and thin staple fiber are often used as mineral fibers. The paper considers the problems of using thin basalt fiber produced by centrifugal-blow method. Evaluation of the corrosion resistance of basalt fiber as part of the cement matrix was performed. Nanodispersed silica produced by electron beam accelerator was used to increase corrosion resistance of basalt fiber.

  5. Effect of nanofiller on wear resistance and surface roughness of resin composites.

    Science.gov (United States)

    Han, Jian Min; Lin, Hong; Zheng, Gang; Shinya, Akiyoshi; Gomi, Harunori; Shinya, Akikazu; Lin, Jie

    2012-01-01

    To compare the wear resistance and surface roughness of nanofiller-containing composites and microhybrid composites after simulated wear. Five microhybrid composites and five nanofiller-containing resin composites were included in the study. Six cylindrical specimens with a diameter of 10 mm and a thickness of 6 mm for each material were prepared. The volume loss, vertical loss and the surface roughness (Ra) were determined after 800 cycles of simulated chewing motion. One specimen of each material was analysed by scanning electron microscopy (SEM) to compare the morphology of the wear surfaces. The microhybrid composites group and nanofiller-containing composites group were tested using the Mann-Whitney U test with a significance level of α = 0.05. For all microhybrid composites, the average wear volume loss and vertical loss were 56.44 mm3 and 730.6 µm, respectively, while the average wear losses of nanofiller-containing composites were 40.15 mm3 and 528.17 µm, respectively. The nanofiller containing composite GNH400N showed the least roughness (Ra = 0.346 ± 0.076 µm), while the conventional microhybrid composite Ceramage showed the highest roughness (Ra = 0.699 ± 0.214 µm). However, wear resistance and surface roughness for the two groups showed no statistical difference. SEM micrographs of the nanofiller-containing composites after wear testing showed smoother and more uniform wear surfaces than for the microhybrid composites. Nanofillers did not significantly influence the wear resistance of resin composites, but might improve the surface roughness of resin composites.

  6. The importance of interfacial resistance on the thermal behavior of carbon nanofiber/epoxy composites

    Science.gov (United States)

    Gardea, Frank; Naraghi, Mohammad; Lagoudas, Dimitris C.

    2014-04-01

    This research addresses the thermal transport in carbon nanofiber (CNF)/epoxy composites via finite element modeling. The effects of nanofiber orientation on thermal transport are investigated through Fourier's Law of heat conduction and through simulation of a high magnitude, short heat pulse. The effect of interface thermal resistance on the effective composite thermal conductivity is also quantified. In addition, a simplified lightning strike simulation is modeled in order to analyze the effect of interfacial thermal resistance on composite behavior when subjected to multiple short heat pulses.

  7. Influence of Heat Treatment on Abrasive Wear Resistance of Silumin Matrix Composite Castings

    Directory of Open Access Journals (Sweden)

    Gawdzińska K.

    2016-03-01

    Full Text Available The authors attempted at examining the effect of heat treatment on abrasive wear resistance of metal composite castings. Metal matrix composites were made by infiltrating preforms created from unordered short fibers (graphite or silumin with liquid aluminium alloy AlSi12(b. Thus prepared composites were subject to solution heat treatment at a temperature of 520°C for four hours, then aging at a temperature of 220°C for four hours. Abrasion resistance of the material was tested before and after thermal treatment.

  8. Whole-body vibration augments resistance training effects on body composition in postmenopausal women.

    Science.gov (United States)

    Fjeldstad, Cecilie; Palmer, Ian J; Bemben, Michael G; Bemben, Debra A

    2009-05-20

    Age-related changes in body composition are well-documented with a decrease in lean body mass and a redistribution of body fat generally observed. Resistance training alone has been shown to have positive effects on body composition, however, these benefits may be enhanced by the addition of a vibration stimulus. The purpose of this study was to determine the effects of 8 months of resistance training with and without whole-body vibration (WBV) on body composition in sedentary postmenopausal women. Fifty-five women were assigned to resistance only (RG, n=22), vibration plus resistance (VR, n=21) or non-exercising control (CG, n=12) groups. Resistance training (3 sets 10 repetitions 80% strength) was performed using isotonic weight training equipment and whole-body vibration was done with the use of the power plate (Northbrooke, IL) vibration platform for three times per week for 8 months. Total and regional body composition was assessed from the total body DXA scans at baseline (pre) and after 8 months (post) of training. In the VR group, total % body fat decreased from pre- to post-time points (pbody fat (ptraining groups exhibited significant increases in bone free lean tissue mass for the total body, arm and trunk regions from pre to post (ptraining alone and with whole-body vibration resulted in positive body composition changes by increasing lean tissue. However, only the combination of resistance training and whole-body vibration was effective for decreasing percent body fat.

  9. Propolis chemical composition and honeybee resistance against Varroa destructor.

    Science.gov (United States)

    Popova, M; Reyes, M; Le Conte, Y; Bankova, V

    2014-01-01

    Propolis is known as honeybee chemical defence against infections and parasites. Its chemical composition is variable and depends on the specificity of the local flora. However, there are no data concerning the relationship between propolis chemical composition and honeybee colony health. We tried to answer this question, studying the chemical composition of propolis of bee colonies from an apiary near Avignon, which are tolerant to Varroa destructor, comparing it with colonies from the same apiary which are non-tolerant to the mites. The results indicated that non-tolerant colonies collected more resin than the tolerant ones. The percentage of four biologically active compounds - caffeic acid and pentenyl caffeates - was higher in propolis from tolerant colonies. The results of this study pave the way to understanding the effect of propolis in individual and social immunity of the honeybees. Further studies are needed to clarify the relationship between propolis chemical composition and honeybee colony health.

  10. Radiolucent Composites Providing High Resistance against Sterilization Decomposition

    Czech Academy of Sciences Publication Activity Database

    Suchý, Tomáš; Balík, Karel; Sedláček, R.; Sucharda, Zbyněk; Sochor, M.; Prokop, J.; Beneš, J.; Křena, J.

    2011-01-01

    Roč. 55, č. 4 (2011), s. 401-409 ISSN 0862-5468 R&D Projects: GA ČR(CZ) GAP108/10/1457 Institutional research plan: CEZ:AV0Z30460519 Keywords : composite material * polymer matrix * radiolucency Subject RIV: JI - Composite Materials Impact factor: 0.382, year: 2011 http://www.ceramics-silikaty.cz/2011/2011_04_401.htm

  11. Comparative Study of Wear Resistance of the Composite with Microhybrid Structure and Nanocomposite

    Directory of Open Access Journals (Sweden)

    Pieniak Daniel

    2016-12-01

    Full Text Available The aim of the study was to compare microhardness and wear resistance of ceramic-polymer composites with micro and nano-hybrid structure. For the studies commercial composites were used, containing filler particles of the same type but different sizes, nano-sized (Filtek Ultimate and micro-sized (Filtek Z250 composites. Tribological testing was conducted using ball-on-disc micro-tribometer. Vickers testing method was applied for microhardness studies with the use of Futertech FM 700 device. It has been demonstrated that the wear of Filtek Ultimate is almost twice lower in comparison to wear of Filtek Z250 composite. It has been concluded that the use of filler nanoparticles significantly increased wear resistance of the material. Additionally, lack of correlation between material microhardness and wear resistance has been demonstrated.

  12. Erosion resistance and adhesion of composite metal/ceramic coatings produced by plasma spraying

    International Nuclear Information System (INIS)

    Ramm, D.A.J.; Hutchings, I.M.; Clyne, T.W.

    1993-01-01

    Ceramic coatings can exhibit greater erosion resistance than most metallic coatings. Such coatings are conveniently produced by thermal spraying. Unfortunately, thermally sprayed ceramic coatings often exhibit poor adhesion, partly as a consequence of the development of residual stresses during spraying and subsequent cooling. Composite coatings have been studied using aluminium/alumina deposits on steel substrates. The incorporation of ceramics within a ductile matrix has potential for sharply reducing the erosive wear at high erodent impact angles, whilst retaining the good erosion resistance of ceramics at low angles. It is shown that the proportion of metal and ceramic at the free surface can be specified so as to optimise the erosion resistance. Experiments have also been carried out on the resistance of the coatings to debonding during four-point bending of the coated substrate. Progress is being made towards the tailoring of composition profiles in graded coatings so as to optimise the combination of erosion resistance and adhesion. (orig.)

  13. Radiation-resistant composite for biological shield of personnel

    Science.gov (United States)

    Barabash, D. E.; Barabash, A. D.; Potapov, Yu B.; Panfilov, D. V.; Perekalskiy, O. E.

    2017-10-01

    This article presents the results of theoretical and practical justification for the use of polymer concrete based on nonisocyanate polyurethanes in biological shield structures. We have identified the impact of ratio: polymer - radiation-resistant filling compound on the durability and protection properties of polymer concrete. The article expounds regression dependence of the change of basic properties of the aforementioned polymer concrete on the absorbed radiation dose rate. Synergy effect in attenuation of radioactivity release in case of conjoint use of hydrogenous polymer base and radiation-resistant powder is also addressed herein.

  14. Fracture resistance of premolar teeth restored with silorane-based or dimethacrylate-based composite resins.

    Science.gov (United States)

    Akbarian, Golsa; Ameri, Hamideh; Chasteen, Joseph E; Ghavamnasiri, Marjaneh

    2014-01-01

    To restore posterior teeth using low-shrinkage composite to minimize microleakage. To compare the fracture resistance of mesio-occlusal-distal (MOD) cavity preparations restored with either low-shrinkage composite or with dimethacrylate-based composite in conjunction with cavity liners and without them. The null hypothesis of the study is that there are no differences in either fracture resistance or fracture mode between the silorane group and dimethacrylate groups with and without the use of cavity liners. Sixty maxillary premolars were divided into six groups of 10. MOD cavities were prepared in four groups: F: posterior composite (Filtek P60); GF: 0.5-mm Glass Ionomer (Fuji LC) + posterior composite; FF: 0.5-mm flowable composite (Filtek Supreme XT) + posterior composite; and S: low-shrinkage composite (Filtek P90). Negative (N) and positive (P) control groups consisted of unrestored and sound teeth, respectively. The specimens were thermocycled and loaded. Data were analyzed using analysis of variance, Tukey, and chi-square tests (α = 0.05). Groups FF (1643.09 ± 187/80 N) and GF (1596.80 ± 163/93 N) (p = 0.06 > 0.05) were statistically identical, although less than group P (1742/33 ± 110/08 N), but still demonstrated greater fracture resistance than the other groups. The fracture resistance of group S (1434/69 ± 107/62 N) was identical to GF and FF (p = 0.06 > 0.05). The fracture resistance of F (1353/19 ± 233/90 N) was less than GF and FF, and statistically identical to S (p = 0.87 > 0.05). Silorane-based composite showed a resistance to fracture similar to methacrylate-based composite restorations regardless of whether cavity liners were used. The findings of this study support the selection of silorane-based composite for the restoration of maxillary premolars with standardized Class II cavity preparations in order to strengthen the resistance to fracture to the same extent as do dimethacrylate

  15. Effect of different glass and zeolite A compositions on the leach resistance of ceramic waste forms

    International Nuclear Information System (INIS)

    Lewis, M.A.; Hash, M.; Glandorf, D.

    1996-01-01

    A ceramic waste form is being developed for waste generated during electrometallurgical treatment of spent nuclear fuel. The waste is generated when fission products are removed from the electrolyte, LiCl-KCl eutectic. The waste form is a composite fabricated by hot isostatic pressing a mixture of glass frit and zeolite occluded with fission products and salt. Normalized release rate is less than 1 g/m 2 d for all elements in MCC-1 leach test run for 28 days in deionized water at 90 C. This leach resistance is comparable to that of early Savannah River glasses. We are investigating how leach resistance is affected by changes in cationic form of zeolite and in glass composition. Composites were made with 3 forms of zeolite A and 6 glasses. We used 3-day ASTM C1220-92 (formerly MCC-1) leach tests to screen samples for development purposes only. The leach test results show that the glass composites of zeolites 5A and 4A retain fission products equally well. Loss of Cs is small (0.1-0.5 wt%), while the loss of divalent and trivalent fission products is one or more orders of magnitude smaller. Composites of 5A retain chloride ion better in these short-term screens than 4A and 3A. The more leach resistant composites were made with durable glasses rich in silica and poor in alkaline earth oxides. XRD show that a salt phase was absent in the leach resistant composites of 5A and the better glasses but was present in the other composites with poorer leach performance. Thus, absence of salt phase corresponds to improved leach resistance. Interactions between zeolite and glass depend on composition of both

  16. Impact resistance of uncoated SiC/SiC composites

    International Nuclear Information System (INIS)

    Bhatt, Ramakrishna T.; Choi, Sung R.; Cosgriff, Laura M.; Fox, Dennis S.; Lee, Kang N.

    2008-01-01

    Two-dimensional woven SiC/SiC composites fabricated by melt infiltration method were impact tested at room temperature and at 1316 deg. C in air using 1.59-mm diameter steel-ball projectiles at velocities ranging from 115 to 400 m/s. The extent of substrate damage with increasing projectile velocity was imaged and analyzed using optical and scanning electron microscopy, and non-destructive evaluation (NDE) methods such as pulsed thermography, and computed tomography. The impacted specimens were tensile tested at room temperature to determine their residual mechanical properties. Results indicate that at 115 m/s projectile velocity, the composite showed no noticeable surface or internal damage and retained its as-fabricated mechanical properties. As the projectile velocity increased above this value, the internal damage increased and mechanical properties degraded. At velocities >300 m/s, the projectile penetrated through the composite, but the composite retained ∼50% of the ultimate tensile strength of the as-fabricated composite and exhibited non-brittle failure. Predominant internal damages are delamination of fiber plies, fiber fracture and matrix shearing

  17. Fracture resistance curves and toughening mechanisms in polymer based dental composites

    DEFF Research Database (Denmark)

    De Souza, J.A.; Goutianos, Stergios; Skovgaard, M.

    2011-01-01

    The fracture resistance (R-curve behaviour) of two commercial dental composites (Filtek Z350® and Concept Advanced®) were studied using Double Cantilever Beam sandwich specimens loaded with pure bending moments to obtain stable crack growth. The experiments were conducted in an environmental...... displayed distinctly different R-curve behaviours. The difference was related to different toughening mechanisms as the two composites had markedly different microstructures. Contrary to common experience, the composite with the finer microstructure (smaller particles), the Concept Advanced®, showed...... significantly higher fracture resistance than the composite with the coarser microstructure. The fracture properties were related to the flexural strength of the dental composites. The method, thus, can provide useful insight into how the microstructure enhances toughness, which is necessary for the future...

  18. B4C-MODIFIED SiO2-PHENOLIC Composites for Enhanced Ablation Resistance

    Science.gov (United States)

    Li, Maoyuan; Lu, Lin; Dai, Zhen; Hong, Yiqiang; Chen, Weiwei; Zhang, Yuping; Qiao, Yingjie

    In the present paper, the silica-phenolic composite (S-Ph) composites with different amount of B4C were prepared, and the ablation tests of these composites were carried out using oxygen-acetylene jet. The ablation process was systematically investigated. The addition of B4C with appropriate amount can efficiently improve the ablation resistance of S-Ph. The results showed that S-Ph containing B4C powder of 2wt.% exhibited the lowest linear and mass ablation rate. The influence mechanism for the results was analyzed deeply. The surface morphologies, phase composition, density and thermal conductivity of composites were characterized using a scanning electron microscope (SEM), X-Ray Diffraction (XRD), Archimedes method, and thermal conductivity meter, respectively. The present investigation will provide a theoretical basis for the preparation of the ablation resistant material.

  19. Development of in-situ ZrC reinforced iron based composites for wear resistance applications

    International Nuclear Information System (INIS)

    Bandyopadhyay, T.K.; Das, K.

    2002-01-01

    A common objective behind the processing of iron-based composites is to improve the wear resistance of steels by incorporating some reinforcing phases, e.g., carbides and oxides. In the present investigation, iron-based zirconium carbide reinforced composite is produced by the aluminothermic reduction of zircon sand (ZrSiO 4 ) and blue dust (Fe 2 O 3 ) in the presence of carbon. Aluminothermic reduction of blue dust and zircon sand, being highly exothermic in nature, essentially leads to a self-propagating high-temperature synthesis (SHS) of the Fe-ZrC composite. The as-cast composite is characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties of the composite and the effect of heat treatment on the microstructure are evaluated. The composite possess sufficient hardness and promising abrasive wear resistance property. The abrasive wear resistance property of the Fe-ZrC composite is compared with that of a M2 grade tool material and it is found to be better than the tool material. The composite also possess good high temperature stability. (author)

  20. Fracture resistance of endodontically treated teeth restored with a bulkfill flowable material and a resin composite.

    Science.gov (United States)

    Isufi, Almira; Plotino, Gianluca; Grande, Nicola Maria; Ioppolo, Pietro; Testarelli, Luca; Bedini, Rossella; Al-Sudani, Dina; Gambarini, Gianluca

    2016-01-01

    To determine and compare the fracture resistance of endodontically treated teeth restored with a bulk fill flowable material (SDR) and a traditional resin composite. Thirty maxillary and 30 mandibular first molars were selected based on similar dimensions. After cleaning, shaping and filling of the root canals and adhesive procedures, specimens were assigned to 3 subgroups for each tooth type (n=10): Group A: control group, including intact teeth; Group B: access cavities were restored with a traditional resin composite (EsthetX; Dentsply-Italy, Rome, Italy); Group C: access cavities were restored with a bulk fill flowable composite (SDR; Dentsply-Italy), except 1.5 mm layer of the occlusal surface that was restored with the same resin composite as Group B. The specimens were subjected to compressive force in a material static-testing machine until fracture occurred, the maximum fracture load of the specimens was measured (N) and the type of fracture was recorded as favorable or unfavorable. Data were statistically analyzed with one-way analysis of variance (ANOVA) and Bonferroni tests (Presin composite and with a bulk fill flowable composite (SDR) was similar in both maxillary and mandibular molars and showed no significant decrease in fracture resistance compared to intact specimens. No significant difference was observed in the mechanical fracture resistance of endodontically treated molars restored with traditional resin composite restorations compared to bulk fill flowable composite restorations.

  1. An electrical resistivity monitor for the detection of composition changes in Pb-17Li

    International Nuclear Information System (INIS)

    Hubberstey, P.; Barker, M.G.; Sample, T.

    1991-01-01

    An electrical resistivity monitor for the detection of composition changes in the lithium-lead eutectic alloy, Pb-17Li, has been developed. A miniature electromagnetic pump is used to sample alloy continuously from a pool or loop system and force it through a capillary section, within which the necessary resistance measurements are made, prior to its return to the bulk source. To calibrate the monitor, detailed resistivity-temperature and resistivity-composition data have been determined for Pb-Li alloys at temperatures from 600 to 800K and compositions from 0 to 20.5 at% Li. The resistivity increases with both temperature and composition; for Pb-17li at 723 K, dρ/dT=0.054x10 -8 ΩmK -1 , and dρ/d[Li]=1.27x10 -8 Ωm(at% Li) -1 . The sensitivity of the monitor is such that changes in composition of as little as ±0.05 at% Li can be detected and its response time is limited soley by the rate of sampling. (orig.)

  2. Specific features in the behavior of electrical resistivity of the pine biocarbon preform/copper composite

    Science.gov (United States)

    Burkov, A. T.; Orlova, T. S.; Smirnov, B. I.; Smirnov, I. A.; Misiorek, H.; Jezowski, A.

    2010-11-01

    The electrical resistivity ρ( T) of the novel type of composites prepared by infiltrating melted copper in vacuum in empty sap channels of white pine high-porosity biocarbon preforms has been measured in the temperature range 5-300 K. Biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two carbonization temperatures, 1000 and 2400°C. The electrical resistivity of the composites has been found to vary relatively weakly with temperature and to pass through a characteristic minimum near 40-50 K, which can be ascribed to iron and manganese impurities penetrating into copper from the carbon preform when liquid copper is infiltrated into it. It has been shown that the electrical resistivity ρ( T) of the composites is governed primarily by the specific microstructure of the preform, which is made up of parallel channels with an average diameter of about 50 μm interrupted by systems of thin capillaries. The small cross section of the copper-filled capillaries accounts for these regions providing the major contribution to the electrical resistivity of the composites. An increase in the wood carbonization temperature brings about a noticeable increase in the effective capillary cross section and a decrease in the electrical resistivity ρ( T) of the composite.

  3. Fabrication of low specific resistance ceramic carbon composites by ...

    Indian Academy of Sciences (India)

    2017-09-07

    Sep 7, 2017 ... C showing resistor behaviour even at low carbon content (1 wt%). In this work, ceramic carbon composites were fabricated using alumina–clay slurries with addition of glucose as a soluble carbon source. Morphology of the sintered samples was characterized by field emission gun (FEG) electron ...

  4. Thermal Cyclic Resistance Polyester Resin Composites Reinforce Fiber Nut Shell

    Science.gov (United States)

    Fahmi, Hendriwan

    2017-12-01

    The purpose of study is to determine the effect of fiber length and thermal cyclic of the bending strength of polyester resin composite reinforced by fibers nut shell. The materials used in this study is a nut shell fibers with fiber length of 1 cm, 2 cm and 3 cm and polyester resin with composition 70-30%wt. Fiber nut shell treated soaking in NaOH 30% for 30 minutes, then rinse with clean water so that the fiber free of alkali and then dried. Furthermore, the composite is heated in an oven to a temperature of 100°C for 1 hour and then cooled in the open with a variety of thermal cyclic 30, 40, and 50 times. Bending properties of composites known through the testing process using a three-point bending test equipment universal testing machine. The test results show that the bending strength bending highest in fiber length of 3 cm with 30 treatment cycles of thermal to the value of 53.325 MPa, while the lowest occurred in bending strength fiber length of 1 cm with no cycles of thermal treatment to the value of 30.675 MPa.

  5. Strain-dependent electrical resistance of multi-walled carbon nanotube/polymer composite films

    International Nuclear Information System (INIS)

    Park, Myounggu; Kim, Hyonny; Youngblood, Jeffrey P

    2008-01-01

    The strain-dependent electrical resistance characteristics of multi-walled carbon nanotube (MWCNT)/polymer composite films were investigated. In this research, polyethylene oxide (PEO) is used as the polymer matrix. Two representative volume fractions of MWCNT/PEO composite films were selected: 0.56 vol% (near the percolation threshold) and 1.44 vol% (away from the percolation threshold) of MWCNT. An experimental setup which can measure electrical resistance and strain simultaneously and continuously has been developed. Unique and repeatable relationships in resistance versus strain were obtained for multiple specimens with different volume fractions of MWCNT. The overall pattern of electrical resistance change versus strain for the specimens tested consists of linear and nonlinear regions. A resistance change model to describe the combination of linear and nonlinear modes of electrical resistance change as a function of strain is suggested. The unique characteristics in electrical resistance change for different volume fractions imply that MWCNT/PEO composite films can be used as tunable strain sensors and for application into embedded sensor systems in structures

  6. Fatigue resistance of CAD/CAM resin composite molar crowns.

    Science.gov (United States)

    Shembish, Fatma A; Tong, Hui; Kaizer, Marina; Janal, Malvin N; Thompson, Van P; Opdam, Niek J; Zhang, Yu

    2016-04-01

    To demonstrate the fatigue behavior of CAD/CAM resin composite molar crowns using a mouth-motion step-stress fatigue test. Monolithic leucite-reinforced glass-ceramic crowns were used as a reference. Fully anatomically shaped monolithic resin composite molar crowns (Lava Ultimate, n=24) and leucite reinforced glass-ceramic crowns (IPS Empress CAD, n=24) were fabricated using CAD/CAM systems. Crowns were cemented on aged dentin-like resin composite tooth replicas (Filtek Z100) with resin-based cements (RelyX Ultimate for Lava Ultimate or Multilink Automix for IPS Empress). Three step-stress profiles (aggressive, moderate and mild) were employed for the accelerated sliding-contact mouth-motion fatigue test. Twenty one crowns from each group were randomly distributed among these three profiles (1:2:4). Failure was designated as chip-off or bulk fracture. Optical and electron microscopes were used to examine the occlusal surface and subsurface damages, as well as the material microstructures. The resin composite crowns showed only minor occlusal damage during mouth-motion step-stress fatigue loading up to 1700N. Cross-sectional views revealed contact-induced cone cracks in all specimens, and flexural radial cracks in 2 crowns. Both cone and radial cracks were relatively small compared to the crown thickness. Extending these cracks to the threshold for catastrophic failure would require much higher indentation loads or more loading cycles. In contrast, all of the glass-ceramic crowns fractured, starting at loads of approximately 450N. Monolithic CAD/CAM resin composite crowns endure, with only superficial damage, fatigue loads 3-4 times higher than those causing catastrophic failure in glass-ceramic CAD crowns. Copyright © 2015 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  7. Fatigue Resistance of CAD/CAM Resin Composite Molar Crowns

    Science.gov (United States)

    Shembish, Fatma A.; Tong, Hui; Kaizer, Marina; Janal, Malvin N.; Thompson, Van P.; Opdam, Niek J.; Zhang, Yu

    2016-01-01

    Objective To demonstrate the fatigue behavior of CAD/CAM resin composite molar crowns using a mouth-motion step-stress fatigue test. Monolithic leucite-reinforced glass-ceramic crowns were used as a reference. Methods Fully anatomically shaped monolithic resin composite molar crowns (Lava Ultimate, n = 24) and leucite reinforced glass-ceramic crowns (IPS Empress CAD, n = 24) were fabricated using CAD/CAM systems. Crowns were cemented on aged dentin-like resin composite tooth replicas (Filtek Z100) with resin-based cements (RelyX Ultimate for Lava Ultimate or Multilink Automix for IPS Empress). Three step-stress profiles (aggressive, moderate and mild) were employed for the accelerated sliding-contact mouth-motion fatigue test. Twenty one crowns from each group were randomly distributed among these three profiles (1:2:4). Failure was designated as chip-off or bulk fracture. Optical and electronic microscopes were used to examine the occlusal surface and subsurface damages, as well as the material microstructures. Results The resin composite crowns showed only minor occlusal damage during mouth-motion step-stress fatigue loading up to 1700 N. Cross-sectional views revealed contact-induced cone cracks in all specimens, and flexural radial cracks in 2 crowns. Both cone and radial cracks were relatively small compared to the crown thickness. Extending these cracks to the threshold for catastrophic failure would require much higher indentation loads or more loading cycles. In contrast, all of the glass-ceramic crowns fractured, starting at loads of approximately 450 N. Significance Monolithic CAD/CAM resin composite crowns endure, with only superficial damage, fatigue loads 3 – 4 times higher than those causing catastrophic failure in glass-ceramic CAD crowns. PMID:26777092

  8. Equivalent network for resistance and temperature coefficient of resistance versus temperature and composition of thick resistive films

    International Nuclear Information System (INIS)

    Kusy, A.

    1987-01-01

    Two types of elementary resistances in thick resistive films have been considered: (i) constriction resistance R/sub C/ determined by the bulk properties of conducting material and by the geometry of constriction, and (ii) barrier resistance R/sub B/ determined by the parameters of a thermally activated type of tunneling process and by the geometry of the metal-insulator-metal unit. On this basis a resistance network composed of a large number of the two types of resistances has been defined. The network has been considered as being equivalent to thick resistive film (TRF) from the point of view of the resistance and temperature coefficient of resistance (TCR). The parameters of this network have been evaluated by the computer-aided approximation of the experimental data found for RuO 2 -based TRFs. On the basis of the equations derived for the network as well as the results of the approximation process, it can be concluded that the small values of the network TCR result from the superposition of the TCR of the conducting component β/sub C/ and of the temperature coefficient of barrier resistance α/sub B/. In this superposition β/sub C/ is attenuated (by 1--2 orders of magnitude), while α/sub B/ is attenuated by only few percentages. The network has been found to be strongly barrier dominated

  9. Performance testing of elastomeric seal materials under low and high temperature conditions: Final report

    Energy Technology Data Exchange (ETDEWEB)

    BRONOWSKI,DAVID R.

    2000-06-01

    The US Department of Energy Offices of Defense Programs and Civilian Radioactive Waste Management jointly sponsored a program to evaluate elastomeric O-ring seal materials for radioactive material shipping containers. The report presents the results of low- and high-temperature tests conducted on 27 common elastomeric compounds.

  10. 40 CFR 427.40 - Applicability; description of the asbestos paper (elastomeric binder) subcategory.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 29 2010-07-01 2010-07-01 false Applicability; description of the asbestos paper (elastomeric binder) subcategory. 427.40 Section 427.40 Protection of Environment... SOURCE CATEGORY Asbestos Paper (Elastomeric Binder) Subcategory § 427.40 Applicability; description of...

  11. Lateral Response Comparison of Unbonded Elastomeric Bearings Reinforced with Carbon Fiber Mesh and Steel

    Directory of Open Access Journals (Sweden)

    Ali Karimzadeh Naghshineh

    2015-01-01

    Full Text Available The vertical and horizontal stiffness used in design of bearings have been established in the last few decades. At the meantime, applicability of the theoretical approach developed to estimate vertical stiffness of the fiber-reinforced bearings has been verified in different academic studies. The suitability of conventional horizontal stiffness equation developed for elastomeric material, mainly for steel-reinforced elastomeric bearings, has not been tested in detail for use of fiber-reinforced elastomeric bearings. In this research, lateral response of fiber mesh-reinforced elastomeric bearings has been determined through experimental tests and the results have been compared by corresponding values pertaining to the steel-reinforced bearings. Within the test program, eight pairs of fiber mesh-reinforced bearings and eight pairs of steel-reinforced bearings are subjected to different levels of compressive stress and cyclic shear strains. Fiber-reinforced elastomeric bearings may be more favorable to be used in seismic regions due to lower horizontal stiffness that can result in mitigation of seismic forces for levels of 100% shear strain. Damping properties of these types of fiber mesh-reinforced bearings depend mostly on the selection of elastomeric material compounds. Suggestions have been made for the lateral response of fiber-reinforced elastomeric bearings. It has also been determined that the classical equation for lateral stiffness based on linear elastic behavior assumptions developed for elastomeric bearings does not always apply to the fiber-reinforced ones.

  12. Role of certain cellular composition in radio-resistant fungi

    International Nuclear Information System (INIS)

    Shahin, A.A.M.; Hammad, A.A.I.; Hazaa, M.M.; Swelim, M.A.; Mohamed, Y.A.

    2007-01-01

    Fifty three fungal isolates of genera Curvularia, Alternaria and Fusarium were isolated from different sources included crops, vegetables, fruits in addition to bread, chicken feed soil and air. Five isolates were selected from each genus according to the difference in the morphological characters and its source. The fifteen isolates were exposed to increasing doses of gamma rays from 0.5 to 10.0 I 10 values when irradiated in saline solution were found to be 1.92,1.25, 1.47,0.47,1.31 and 0.70 respectively while their D 10 values were 2.25, 1.56, 1.70, 1.30, 1.83 and 1.23 as the irradiation process was done in their natural sources. The values of total protein, total lipids and total nucleic acids either RNA or DNA were relatively higher in radio-resistant strains than sensitive ones. Amino acids containing sulfur (cysteine, methionine) or double bonds (histidine) and the percentage of unsaturated fatty acids were also higher in resistant strains than the sensitive ones. Exposing the six selected strains to dose level 4 kGy obviously decreased each of total protein, total amino acids and total nucleic acids especially DNA and the values of decreases were found to be higher in sensitive than the resistant strains. Dose level 12.5 kGy was quiet enough to eliminate the radioresistant fungi from the contaminated food whatever the level of contamination is

  13. Elastomeric contractile actuators for hand rehabilitation splints

    Science.gov (United States)

    Carpi, Federico; Mannini, Andrea; De Rossi, Danilo

    2008-03-01

    The significant electromechanical performances typically shown by dielectric elastomer actuators make this polymer technology particularly attractive for possible active orthoses for rehabilitation. Folded contractile actuators made of dielectric elastomers were recently described as a simple configuration, suitable to easily implement linear contractile devices. This paper describes an application of folded actuators for so-called hand splints: they consist of orthotic systems for hand rehabilitation. The dynamic versions of the state-of-the-art splints typically include elastic bands, which exert a passive elastic resistance to voluntary elongations of one or more fingers. In order to provide such splints with the possibility of electrically modulating the compliance of the resistive elements, the substitution of the passive elastic bands with the contractile actuators is here described. The electrical activation of the actuators is used to vary the compliance of the system; this enables modulations of the force that acts as an antagonist to voluntary finger movements, according to programmable rehabilitation exercises. The paper reports results obtained from the first prototype implementations of such a type of system.

  14. Thickness effect on electric resistivity on polystyrene and carbon black- based composites

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Lopez, S; Vigueras-Santiago, E [Laboratorio de Investigacion y Desarrollo de Materiales Avanzados (LIDMA) Facultad de Quimica, Paseo Colon Esquina con Paseo Tollocan, s/n, CP 50000, Toluca (Mexico); Mayorga-Rojas, M; Reyes-Contreras, D, E-mail: eviguerass@uaemex.m [Facultad de Ciencias, Universidad Autonoma del Estado de Mexico. Av. Instituto Literario 100 Ote. C. P. 50000, Toluca (Mexico)

    2009-05-01

    Changes on electrical resistivity were experimentally studied for polystyrene and carbon black-based composites respect to the temperature. 22% w/w carbon black composite films at 30{mu}m, 2mm y 1cm thick were submitted to thermal heating-cooling cycles from room temperature to 100 deg. C, slightly up to T{sub g} of the composite. For each cycle changes on electrical resistivity constituent a hysteresis loop that depends on the sample thickness. The changes during the heating stage could be explained as a consequence of the thermal expansion and mobility of the polymer chains at T{sub g}, producing a disconnecting of the electrical contacts among carbon black particles and an important increasing (200%) of the electrical resistivity. For each cycle, the hysteresis loop was observed in thicker samples, whereas for 30 mu m thickness sample the hysteresis loop was lost after four cycles.

  15. Development of impact resistant boron/aluminum composites for turbojet engine fan blades

    Science.gov (United States)

    Melnyk, P.; Toth, I. J.

    1975-01-01

    Composite fabrication was performed by vacuum press diffusion bonding by both the foil-filament array and preconsolidated monotape methods. The effect of matrix material, fiber diameter, matrix enhancement, fiber volume reinforcement, test temperature, angle-plying, notch, impact orientation, processing variables and fabrication methods on tensile strength and Charpy impact resistance are evaluated. Root attachment concepts, were evaluated by room and elevated temperature tensile testing, as well as by pendulum-Izod and ballistic impact testing. Composite resistance to foreign object damage was also evaluated by ballistic impacting of panels using projectiles of gelatin, RTV rubber and steel at various velocities, and impingement angles. A significant improvement in the pendulum impact resistance of B-Al composites was achieved.

  16. Thickness effect on electric resistivity on polystyrene and carbon black- based composites

    International Nuclear Information System (INIS)

    Hernandez-Lopez, S; Vigueras-Santiago, E; Mayorga-Rojas, M; Reyes-Contreras, D

    2009-01-01

    Changes on electrical resistivity were experimentally studied for polystyrene and carbon black-based composites respect to the temperature. 22% w/w carbon black composite films at 30 μm, 2mm y 1cm thick were submitted to thermal heating-cooling cycles from room temperature to 100 deg. C, slightly up to T g of the composite. For each cycle changes on electrical resistivity constituent a hysteresis loop that depends on the sample thickness. The changes during the heating stage could be explained as a consequence of the thermal expansion and mobility of the polymer chains at T g , producing a disconnecting of the electrical contacts among carbon black particles and an important increasing (200%) of the electrical resistivity. For each cycle, the hysteresis loop was observed in thicker samples, whereas for 30 μ m thickness sample the hysteresis loop was lost after four cycles.

  17. Thermal Shock Resistance of Cordierite-Mullite Refractory Composites

    Czech Academy of Sciences Publication Activity Database

    Chlup, Zdeněk; Dlouhý, Ivo; Boccaccini, A. R.; Boccaccini, D. N.; Leonelli, C.; Romagnoli, M.

    2005-01-01

    Roč. 290, - (2005), s. 260-263 ISSN 1013-9826. [Fractography of Advanced Ceramics /2./. Stará Lesná, 03.10.2004-06.10.2004] R&D Projects: GA AV ČR(CZ) IAA2041003 Keywords : cordierite-mullite composite * refractory materials * chevron notch Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.224, year: 2005

  18. Fracture Resistance Evaluation of Fibre Reinforced Brittle Matrix Composites

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Chlup, Zdeněk

    2005-01-01

    Roč. 290, - (2005), s. 167-174 ISSN 1013-9826. [Fractography of Advanced Ceramic s /2./. Stará Lesná, 03.10.2004-06.10.2004] R&D Projects: GA AV ČR(CZ) IAA2041003; GA ČR(CZ) GA101/02/0683 Keywords : fibre-reinforced ceramic s * glass matrix composites * chevron notch Subject RIV: JL - Materials Fatigue, Friction Mechanics Impact factor: 0.224, year: 2005

  19. Delamination Detection in Carbon Fibre Reinforced Composites Using Electrical Resistance Measurement

    International Nuclear Information System (INIS)

    Kovalovs, A; Rucevskis, S; Kulakov, V; Aniskevich, A

    2016-01-01

    In the present study 2-D numerical analysis of strip-type laminated composite specimens with and without damage is considered and numerical investigation is carried out by using a finite element method. The surface and oblique resistances are numerically calculated according to the two-probe and four-probe methods. The electrical conductivity of the composite laminate in the longitudinal direction is constant, while the electrical conductivity in the through-thickness direction is used as a variable in the parametric study. The resistance change due to delamination for each case is estimated by comparing the obtained resistance with the corresponding resistance of the specimen without delamination. Applicability and effectiveness of the proposed method are investigated by using various lengths of a delaminated crack in the specimen. (paper)

  20. Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

    OpenAIRE

    Alsadon, O.; Patrick, D.; Johnson, A.; Pollington, S.; Wood, D.

    2017-01-01

    The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create ...

  1. Fracture resistance of endodontically treated teeth restored with combined composite-amalgam restorations.

    Science.gov (United States)

    Geiger, Selly; Paikin, Lev; Gorfil, Colin; Gordon, Moshe

    2008-02-01

    To evaluate the resistance to fracture of endodontically treated teeth restored with combined composite-amalgam restorations in comparison to all-amalgam restorations. Forty-eight human premolar teeth were equally divided into 4 groups. Mesio-occlusodistal (MOD) cavities were prepared in 3 groups, and in the fourth group, a modified MOD preparation was designed with an additional buccolingual groove. All teeth were endodontically treated and restored using 1 of several restorative modalities: all amalgam (AM), all amalgam plus dentin adhesive (ADA), amalgam plus dentin adhesive plus composite resin (ADAC), and amalgam plus dentin adhesive plus composite resin with a modified preparation design (ADACM). Specimens were tested in a universal testing machine (Instron). The load (in kilonewtons) at fracture was recorded and statistically analyzed using a Bonferroni one-way statistical analysis (significance: Pcomposite-amalgam restoration were significantly more resistant to fracture ( Pamalgam alone. The modification with an additional horizontal buccolingual cavity preparation groove did not significantly increase resistance to fracture, nor did the addition of a bonding material to the amalgam restorations. Mean resistance to fracture (in kilonewtons) of each group was as follows: group AM, 0.31; group ADA, 0.34; group ADAC, 0.45; and group ADACM, 0.47. Restoration of endodontically treated teeth with combined composite-amalgam materials increased tooth resistance to fracture up to 51% when compared to teeth restored with amalgam alone.

  2. FIRE-RESISTANCE PROPERTIES RESEARCH OF “WATER GLASS - GRAPHITE MICROPARTICLES” COMPOSITE MATERIAL

    Directory of Open Access Journals (Sweden)

    E. A. Pitukhin

    2016-03-01

    Full Text Available Subject of Research. Research results of the fire-resistance for “water glass - graphite microparticles” composite material (CM are given. The method for fire-resistance test of the micro composition is suggested in order to determine the limit state of the experimental samples under hightemperature action. Method. Test-benchequipment being used for research includes metering devices of temperature and time, as well as laboratory electric furnace PL20 with a maximum temperature in the chamber up to 1250ºC. Fire-resistance limit for the test samples of composite material is determined by the loss of insulating ability (I. For that purpose, the time is obtained from the test beginning with the standard temperature mode up to a limiting condition. Main Results. In accordance with the requirements of regulatory documents fire-resistance limit I15 has been obtained equal to 15 minutes. The qualitative and quantitative phase analysis of the CM structure has been done. By the study of samples by X-ray diffraction and electron microscopy we have determined that the material retains the same chemical structure with a monotonic heating above 700° C. Practical Relevance. The composite material with obtained characteristics can be used as a protective coating for building constructions with the aim of fire-resistance enhancement and fuel hazard reduction.

  3. Electrical resistance of CNT-PEEK composites under compression at different temperatures

    Directory of Open Access Journals (Sweden)

    Mohiuddin Mohammad

    2011-01-01

    Full Text Available Abstract Electrically conductive polymers reinforced with carbon nanotubes (CNTs have generated a great deal of scientific and industrial interest in the last few years. Advanced thermoplastic composites made of three different weight percentages (8%, 9%, and 10% of multiwalled CNTs and polyether ether ketone (PEEK were prepared by shear mixing process. The temperature- and pressure-dependent electrical resistance of these CNT-PEEK composites have been studied and presented in this paper. It has been found that electrical resistance decreases significantly with the application of heat and pressure.

  4. Carbon fiber polymer-matrix structural composites for electrical-resistance-based sensing

    Science.gov (United States)

    Wang, Daojun

    This dissertation has advanced the science and technology of electrical-resistance-based sensing of strain/stress and damage using continuous carbon fiber epoxy-matrix composites, which are widely used for aircraft structures. In particular, it has extended the technology of self-sensing of carbon fiber polymer-matrix composites from uniaxial longitudinal loading and flexural loading to uniaxial through-thickness loading and has extended the technology from structural composite self-sensing to the use of the composite (specifically a one-lamina composite) as an attached sensor. Through-thickness compression is encountered in the joining of composite components by fastening. Uniaxial through-thickness compression results in strain-induced reversible decreases in the through-thickness and longitudinal volume resistivities, due to increase in the fiber-fiber contact in the through-thickness direction, and minor-damage-induced irreversible changes in these resistivities. The Poisson effect plays a minor role. The effects in the longitudinal resistivity are small compared to those in the through-thickness direction, but longitudinal resistance measurement is more amenable to practical implementation in structures than through-thickness resistance measurement. The irreversible effects are associated with an increase in the through-thickness resistivity and a decrease in the longitudinal resistivity. The through-thickness gage factor is up to 5.1 and decreases with increasing compressive strain above 0.2%. The reversible fractional change in through-thickness resistivity per through-thickness strain is up to 4.0 and decreases with increasing compressive strain. The irreversible fractional change in through-thickness resistivity per unit through-thickness strain is around -1.1 and is independent of the strain. The sensing is feasible by measuring the resistance away from the stressed region, though the effectiveness is less than that at the stressed region. A one

  5. Energy dissipation in elastomeric isolators subjected to seismic forces

    International Nuclear Information System (INIS)

    Terhune, J.H.; Karim-Panahi, K.

    1996-01-01

    In this paper, a detailed analysis is presented to elucidate thermal effects in elastomeric seismic isolators. Using the material properties of elastomers and the time history of typical seismic events, it is shown that a properly designed base structure provides effective heat transfer and limits temperature rise in the elastomer. The frequency-dependent material properties are a key factor in designing the base structure for maximum effectiveness. When thermal effects are considered, the material properties of the elastomer(s) do not change with temperature. Thus, the isolator material do not degrade during a prolonged seismic event and effectiveness is thereby optimized

  6. Interaction of Reinforced Elastomeric Bearings in Bridge Construction

    Directory of Open Access Journals (Sweden)

    Nittmannová Ľubica

    2016-03-01

    Full Text Available The aim of this paper is to demonstrate the behavior of reinforced elastomeric bearings under various loads. They are made of special types of bearings. The experimental verification of these special bearings has been tested on various types of loading. The results of the experimental measurements are compared with the results of the numerical modeling and calculations according to the standard assumptions in STN EN 1337-3. In the conclusion, the results are summarized for the selected types of bearings.

  7. Preparation of electrodes on cfrp composites with low contact resistance comprising laser-based surface pre-treatment

    KAUST Repository

    Almuhammadi, Khaled Hamdan

    2016-12-29

    Various examples are provided related to the preparation of electrodes on carbon fiber reinforced polymer (CFRP) composites with low contact resistance. Laser-based surface preparation can be used for bonding to CFRP composites. In one example, a method includes preparing a pretreated target area on a CFRP composite surface using laser pulsed irradiation and bonding an electrode to exposed fibers in the pretreated target area. The surface preparation can allow the electrode to have a low contact resistance with the CFRP composite.

  8. Microstructure and wear resistance of in situ porous TiO/Cu composites

    Science.gov (United States)

    Qin, Qingdong; Huang, Bowei; Li, Wei

    2016-07-01

    An in situ porous TiO/Cu composite is successfully prepared using powder metallurgy by the reaction of Ti2CO and Cu powder. Morphological examination of the composite shows that the porosity of composites lies in the range between 10.2% and 35.2%. Dry sliding un-lubricated wear tests show that the wear resistance of the composite is higher than that of the Cu-Al alloy ingot. The coefficient of friction test shows that, as the volume fraction of the reinforced phase increases, the coefficient of friction decreases. The wear rate variation trend of the oil-lubricated wear test results is similar to that of the un-lubricated wear test results. The coefficient of friction for oil lubrication is similar for different volume fractions of the reinforced phase. The wear resistance of the composite at a sliding velocity of 200 rpm is slightly larger than that at 50 rpm. The porosity of the composites enhances the high-velocity oil-lubricated sliding wear resistance.

  9. Wear Resistance of TiC Reinforced Cast Steel Matrix Composite

    Directory of Open Access Journals (Sweden)

    Sobula S.

    2017-03-01

    Full Text Available Wear resistance of TiC-cast steel metal matrix composite has been investigated. Composites were obtained with SHSB method known as SHS synthesis during casting. It has been shown the differences in wear between composite and base cast steel. The Miller slurry machine test were used to determine wear loss of the specimens. The slurry was composed of SiC and water. The worn surface of specimens after test, were studied by SEM. Experimental observation has shown that surface of composite zone is not homogenous and consist the matrix lakes. Microscopic observations revealed the long grooves with SiC particles indented in the base alloy area, and spalling pits in the composite area. Due to the presence of TiC carbides on composite layer, specimens with TiC reinforced cast steel exhibited higher abrasion resistance. The wear of TiC reinforced cast steel mechanism was initially by wearing of soft matrix and in second stage by polishing and spalling of TiC. Summary weight loss after 16hr test was 0,14÷0,23 g for composite specimens and 0,90 g for base steel.

  10. Enhanced Strain-Dependent Electrical Resistance of Polyurethane Composites with Embedded Oxidized Multiwalled Carbon Nanotube Networks

    Directory of Open Access Journals (Sweden)

    R. Benlikaya

    2013-01-01

    Full Text Available The effect of different chemical oxidation of multiwalled carbon nanotubes with H2O2, HNO3, and KMnO4 on the change of electrical resistance of polyurethane composites with embedded oxidized nanotube networks subjected to elongation and bending has been studied. The testing has shown about twenty-fold increase in the electrical resistance for the composite prepared from KMnO4 oxidized nanotubes in comparison to the composites prepared from the pristine and other oxidized nanotubes. The evaluated sensitivity of KMnO4 treated composite in terms of the gauge factor increases with strain to nearly 175 at the strain 11%. This is a substantial increase, which ranks the composite prepared from KMnO4 oxidized nanotubes among materials as strain gauges with the highest electromechanical sensitivity. The observed differences in electromechanical properties of the composites are discussed on basis of their structure which is examined by the measurements of Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope. The possible practical use of the composites is demonstrated by monitoring of elbow joint flexion during two different physical exercises.

  11. Biodiversity increases functional and compositional resistance, but decreases resilience in phytoplankton communities.

    Science.gov (United States)

    Baert, Jan M; De Laender, Frederik; Sabbe, Koen; Janssen, Colin R

    2016-12-01

    There is now ample evidence that biodiversity stabilizes aggregated ecosystem functions, such as primary production, in changing environments. In primary producer systems, this stabilizing effect is found to be driven by higher functional resistance (i.e., reduced changes in functions by environmental changes) rather than through higher functional resilience (i.e., rapid recovery following environmental changes) in more diverse systems. The stability of aggregated ecosystem functions directly depends on changes in species composition and by consequence their functional contributions to ecosystem functions. Still, it remains only theoretically explored how biodiversity can stabilize ecosystem functions by affecting compositional stability. Here, we demonstrate how biodiversity effects on compositional stability drive biodiversity effects on functional stability in diatom communities. In a microcosm experiment, we exposed 39 communities of five different levels of species richness (1, 2, 4, 6, and 8 species) to three concentrations of a chemical stressor (0, 25, and 250 μg/L atrazine) for four weeks, after which all communities were transferred to atrazine-free medium for three more weeks. Biodiversity simultaneously increased, increasing functional and compositional resistance, but decreased functional and compositional resilience. These results confirm the theoretically proposed link between biodiversity effects on functional and compositional stability in primary producer systems, and provide a mechanistic underpinning for observed biodiversity-stability relationships. Finally, we discuss how higher compositional stability can be expected to become increasingly important in stabilizing ecosystem functions under field conditions when multiple environmental stressors fluctuate simultaneously. © 2016 by the Ecological Society of America.

  12. In vitro study of cytotoxicity of orthodontic elastomeric ligatures

    Directory of Open Access Journals (Sweden)

    Rogério Lacerda dos Santos

    2012-08-01

    Full Text Available This study investigated the cytotoxicity of crystal-coloured orthodontic elastomeric ligatures of polyurethane. Six ligatures from distinct manufactures were divided into 6 groups of 10 elastics each: Groups P1, P2, P3, P4, P5 and P6 (Polyurethane. The cytotoxicity essay was performed using L-929 line cells, which were submitted to the cell viability test with neutral red ("dye-uptake" at time intervals of 1, 2, 3, 7 and 28 days. Analysis of variance (ANOVA with multiple comparisons and Tukey's test were used (p < .05. There were statistical differences (p < .05 in cell viability between Groups P1, P4, P2 and P3, and Groups P5 and P6 at 1 and 2 days. All elastomeric ligatures were considered suitable for clinical use. The hypothesis was accepted, the P5 and P6 elastomers and the processing route of injection molding for these ligatures showed the lowest cell viability, due the temperature and pressure distinct in the processing of these elastomers.

  13. Adjustment of Part Properties for an Elastomeric Laser Sintering Material

    Science.gov (United States)

    Wegner, A.; Ünlü, T.

    2018-03-01

    Laser sintering of polymers is gaining more and more importance within the field of small series productions. Polyamide 12 is predominantly used, although a variety of other materials are also available for the laser sintering process. For example, elastomeric, rubberlike materials offer very different part property profiles. Those make the production of flexible parts like, e.g., sealings, flexible tubes or shoe soles possible because they offer high part ductility and low hardness. At the chair for manufacturing technology, a new elastomeric laser sintering material has been developed and then commercialized by a spin-off from university. The aim of the presented study was the analysis of the new material's properties. Proof was found that Shore hardness can be modified by varying the parameter settings. Therefore, the correlation between process parameters, energy input, Shore hardness and other part properties like mechanical properties were analyzed. Based on these results, suitable parameter settings were established which lead to the possibility of producing parts with different Shore hardnesses.

  14. Fatigue resistance of teeth restored with cuspal-coverage composite restorations.

    NARCIS (Netherlands)

    Fennis, W.M.M.; Kuijs, R.H.; Kreulen, C.M.; Verdonschot, N.J.J.; Creugers, N.H.J.

    2004-01-01

    PURPOSE: This study assessed the influence of palatal cuspal coverage on the in vitro fatigue resistance and failure mode of Class II resin composite restorations including replacement of the buccal cusp in premolars. MATERIALS AND METHODS: A master model was made of a maxillary premolar with an MOD

  15. In vitro fracture resistance of fiber reinforced cusp-replacing composite restorations.

    NARCIS (Netherlands)

    Fennis, W.M.M.; Tezvergil, A.; Kuijs, R.H.; Lassila, L.V.; Kreulen, C.M.; Creugers, N.H.J.; Vallittu, P.K.

    2005-01-01

    OBJECTIVES: To assess the fracture resistance and failure mode of fiber reinforced composite (FRC) cusp-replacing restorations in premolars. METHODS: Forty-five extracted sound upper premolars were randomly divided into three groups. Identical MOD cavities with simulated buccal cusp fracture and

  16. Study of the relation between hydrated portland cement composition and leaching resistance

    NARCIS (Netherlands)

    van Eijk, R.J.; Brouwers, Jos

    1998-01-01

    The present paper addresses cement compositions that have an optimal resistance against acid attack and hence, low leaching rates and optimal waste containment. To this end a shrinking core leaching model is used that describes the leaching of metals from a cement sample. This process is directly

  17. Decay resistance of wood-plastic composites reinforced with extracted or delignified wood flour

    Science.gov (United States)

    Rebecca E. Ibach; Yao Chen; Nicole M. Stark; Mandla A. Tshabalala; Yongming Fan; Jianmin Gao

    2014-01-01

    The moisture and decay resistance of wood-plastic composites (WPCs) reinforced with extracted or delignified wood flour (WF) was investigated. Three different extractions were preformed: toluene/ethanol (TE), acetone/water (AW), and hot water (HW). Delignification (DL) was performed using a sodium chlorite/acetic acid solution. All WPCs specimens were made with 50% by...

  18. Fatigue Resistant Bioinspired Composite from Synergistic Two-Dimensional Nanocomponents.

    Science.gov (United States)

    Wan, Sijie; Zhang, Qi; Zhou, Xiaohang; Li, Dechang; Ji, Baohua; Jiang, Lei; Cheng, Qunfeng

    2017-07-25

    Portable and wearable electronics require much more flexible graphene-based electrode with high fatigue life, which could repeatedly bend, fold, or stretch without sacrificing its mechanical properties and electrical conductivity. Herein, a kind of ultrahigh fatigue resistant graphene-based nanocomposite via tungsten disulfide (WS 2 ) nanosheets is synthesized by introducing a synergistic effect with covalently cross-linking inspired by the orderly layered structure and abundant interfacial interactions of nacre. The fatigue life of resultant graphene-based nanocomposites is more than one million times at the stress level of 270 MPa, and the electrical conductivity can be kept as high as 197.1 S/cm after 1.0 × 10 5 tensile testing cycles. These outstanding properties are attributed to the synergistic effect from lubrication of WS 2 nanosheets for deflecting crack propagation, and covalent bonding between adjacent GO nanosheets for bridging crack, which is verified by the molecular dynamics (MD) simulations. The WS 2 induced synergistic effect with covalent bonding offers a guidance for constructing graphene-based nanocomposites with high fatigue life, which have great potential for applications in flexible and wearable electronic devices, etc.

  19. "A New Class of Creep Resistant Oxide/Oxide Ceramic Matrix Composites"

    Energy Technology Data Exchange (ETDEWEB)

    Dr. Mohit Jain, Dr. Ganesh Skandan, Prof. Roger Cannon, Rutgers University

    2007-03-30

    Despite recent progress in the development of SiC-SiC ceramic matrix composites (CMCs), their application in industrial gas turbines for distributed energy (DE) systems has been limited. The poor oxidation resistance of the non-oxide ceramics warrants the use of envrionmental barrier coatings (EBCs), which in turn lead to issues pertaining to life expectancy of the coatings. On the other hand, oxide/oxide CMCs are potential replacements, but their use has been limited until now due to the poor creep resistance at high temperatures, particularly above 1200 oC: the lack of a creep resistant matrix has been a major limiting factor. Using yttrium aluminum garnet (YAG) as the matrix material system, we have advanced the state-of-the-art in oxide/oxide CMCs by introducing innovations in both the structure and composition of the matrix material, thereby leading to high temperature matrix creep properties not achieved until now. An array of YAG-based powders with a unique set of particle characteristics were produced in-house and sintered to full density and compressive creep data was obtained. Aided in part by the composition and the microstructure, the creep rates were found to be two orders of magnitude smaller than the most creep resistant oxide fiber available commercially. Even after accounting for porosity and a smaller matrix grain size in a practical CMC component, the YAG-based matrix material was found to creep slower than the most creep resistant oxide fiber available commercially.

  20. Resistance of Bonded Composite Restorations on Fractures of Endodontically Treated Teeth

    Directory of Open Access Journals (Sweden)

    AR Daneshkazemi

    2005-01-01

    Full Text Available Introduction: This study was performed to evaluate the effect of dentine bonding agents and Glass Ionomer cement beneath composite restorations and its resistance on fractures of endodontically treated teeth. Material and Methods: Forty sound maxillary teeth were selected; ten of them for positive control, and on the rest, RCT and MOD cavity preparations were done with standard methods. Then, the teeth were divided to four groups: 1-Sound teeth for positive control. 2-Prepared without any restoration for negative control. 3-Prepared and restored with Vitrabond(3M, USA, Single bond(3M, USA and Z100(3M, USA resin composite. 4-Prepared and restored by Single bond and Z100 resin composite. Specimens were subjected to compressive load by Instron 8502 until fracture occurred. Results: Group 1 showed the highest resistance to compressive forces followed by group 4,3&2 respectively. ANOVA, t test and Chi-square tests indicated significant difference between all the groups. Conclusion: Use of dentine bonding agents and resin composite increases resistance of endodontically treated teeth to fractures more than teeth restored with sandwich of glass ionomer cements, dentine bonding agents and resin composite.

  1. Improved Ablation Resistance of Silicone Rubber Composites by Introducing Montmorillonite and Silicon Carbide Whisker

    Directory of Open Access Journals (Sweden)

    Guangwu Zhang

    2016-08-01

    Full Text Available Montmorillonite (MMT was added to silicone rubber (SR to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite’s char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance.

  2. Evaluation of the Impact Resistance of Various Composite Sandwich Beams by Vibration Tests

    Directory of Open Access Journals (Sweden)

    Amir Shahdin

    2011-01-01

    Full Text Available Impact resistance of different types of composite sandwich beams is evaluated by studying vibration response changes (natural frequency and damping ratio. This experimental works will help aerospace structural engineer in assess structural integrity using classification of impact resistance of various composite sandwich beams (entangled carbon and glass fibers, honeycomb and foam cores. Low velocity impacts are done below the barely visible impact damage (BVID limit in order to detect damage by vibration testing that is hardly visible on the surface. Experimental tests are done using both burst random and sine dwell testing in order to have a better confidence level on the extracted modal parameters. Results show that the entangled sandwich beams have a better resistance against impact as compared to classical core materials.

  3. High compressive resistance drainage geo composites; Geocompuestos de drenaje de alta resistencia a compresion

    Energy Technology Data Exchange (ETDEWEB)

    Castelo Nolla, J.; Gutierrez Cuevas, J.

    2014-02-01

    There are several typologies of drainage geo composites available in the market which can be classified according to their structures as: cus pated, mono filaments, geo nets and those products formed by the combination of a draining blanket with a series of mini-pipes. Each one of them has its own range of compressive resistances. There are applications, such as are the new cells of landfills or mines and roads or railways over large embankments, where the pressure exerted on the geo composite exceeds the compressive resistance of the majority of these typologies. For all this applications, besides providing and adequate flow capacity, it must be ensured that the chosen typology is able to withstand the required loading without collapsing and guaranteeing an adequate factor of safety. This article will expose that, currently, the only typology of drainage geo composites that can bear these loadings while maintaining its drainage properties is the tri-planar geo net. (Author)

  4. A guide to the suitability of elastomeric seal materials for use in radioactive material transport packages

    International Nuclear Information System (INIS)

    Vince, D.J.

    2004-01-01

    Elastomeric seals are a frequently favoured method of sealing Radioactive Material Transport (RMT) packages. The sealing technology has been proven for many years in a wide range of industrial applications. The requirements of the RMT package applications, however, are significantly different from those commonly found in other industries. This guide outlines the Regulatory performance requirements placed on an RMT package sealing system by TS-R-1, and then summarises the material, environment and geometry characteristics of elastomeric seals relevant to RMT applications. Tables in the guide list typical material properties for a range of elastomeric materials commonly used in RMT packages

  5. Study of the effect of composition and construction of material on sub-bandage pressure during dynamic loading of a limb in vitro.

    Science.gov (United States)

    Kumar, Bipin; Das, Apurba; Alagirusamy, R

    2013-01-01

    Internal stress in a compression bandage wrapped over a limb in vitro is expected to reduce over time because of fatigue which may occur due to repetitive and prolonged variations in the extension of the bandage during posture change and exercise. This phenomenon may cause significant variation in the sub-bandage pressure over time. To examine the effect of composition and construction of material on the sub-bandage pressure variation over time in the dynamic state of a limb in the laboratory. Yarns comprising fibers of polyester, viscose, cotton and elastomeric yarn were used to prepare different knitted bandage samples having varying thread densities in the structure. A leg-segment prototype was used for the measurement of the interface pressure over a mannequin limb to analyse different bandages under similar dynamic conditions. The pressure drop in the dynamic state of the mannequin limb was greater than that in the static state. The mean pressure drop in 2 h in the dynamic state was greater by >30% for bandages made of pure cotton or viscose yarns than for bandages having elastomeric yarns in their structure. At the same applied tension, increasing the number of yarns per unit length in the bandage structure resulted in a smaller drop in pressure in the dynamic mode. Elastomeric yarn improves the elasticity and fatigue resistance of the bandage. Therefore, these yarns should be used in bandages to obtain sustained compression effects under dynamic conditions.

  6. The effect of mechanical stress on electric resistance of nanographite-epoxy composites

    Science.gov (United States)

    Vovchenko, L.; Lazarenko, A.; Matzui, L.; Zhuravkov, A.

    2012-03-01

    The in-plane electric resistance Ra of composite materials (CMs) thermoexfoliated graphite(TEG)-epoxy resin(ED) under compression along compacting C-axis has been investigated by four-probe method. TEG content was 5-75 wt%. It was shown that specimens prepared by cold pressing are denser and reveal lower values of electric resistivity in comparison with specimens prepared by pouring. It was found that compression of the specimens leads to plastic deformation of specimens (εpl) and essential irreversible decrease of electric resistance during the first cycle of loading (up to 50 MPa), especially for the poured specimens with low density. Within the proposed model the contact resistance Rk between graphite particles in CM has been evaluated and it was shown that it increased with the decrease in TEG content in CM and depends on compacting method of CMs and the dispersity of graphite filler.

  7. The Impact of Morphology and Composition on the Resistivity and Oxidation Resistance of Metal Nanostructure Films

    Science.gov (United States)

    Stewart, Ian Edward

    Printed electronics, including transparent conductors, currently rely on expensive materials to generate high conductivity devices. Conductive inks for thick film applications utilizing inkjet, aerosol, and screen printing technologies are often comprised of expensive and rare silver particles. Thin film applications such as organic light emitting diodes (OLEDs) and organic photovoltaics (OPVs) predominantly employ indium tin oxide (ITO) as the transparent conductive layer which requires expensive and wasteful vapor deposition techniques. Thus an alternative to silver and ITO with similar performance in printed electronics warrants considerable attention. Copper nanomaterials, being orders of magnitude cheaper and more abundant than silver or indium, solution-coatable, and exhibiting a bulk conductivity only 6 % less than silver, have emerged as a promising candidate for incorporation in printed electronics. First, we examine the effect of nanomaterial shape on the conductivity of thick films. The inks used in such films often require annealing at elevated temperature in order to sinter the silver nanoparticles together and obtain low resistivities. We explore the change in morphology and resistivity that occurs upon heating thick films of silver nanowires (of two different lengths, Ag NWs), nanoparticles (Ag NPs), and microflakes (Ag MFs) deposited from water at temperatures between 70 and 400 °C. At the lowest temperatures, longer Ag NWs exhibited the lowest resistivity (1.8 x 10-5 O cm), suggesting that the resistivity of thick films of silver nanostructures is dominated by the contact resistance between particles. This result supported previous research showing that junction resistance between Ag NWs in thin film conductors also dominates optoelectronic performance. Since the goal is to replace silver with copper, we perform a similar analysis by using a pseudo-2D rod network modeling approach that has been modified to include lognormal distributions in length

  8. Piezoelectric and mechanical properties of fatigue resistant, self-healing PZT–ionomer composites

    International Nuclear Information System (INIS)

    James, N K; Lafont, U; Van der Zwaag, S; Groen, W A

    2014-01-01

    Piezoelectric ceramic–polymer composites with 0–3 connectivity were fabricated using lead zirconium titanate (PZT) powder dispersed in an ionomer (Zn ionomer) and its reference ethylene methacrylic acid copolymer (EMAA) polymer matrix. The PZT–Zn ionomer and PZT–EMAA composites were prepared by melt extrusion followed by hot pressing. The effects of poling conditions such as temperature, time and electric field on the piezoelectric properties of the composites were investigated. The experimentally observed piezoelectric charge coefficient and dielectric constant of the composites were compared with theoretical models. The results show that PZT–Zn ionomer composites have better piezoelectric properties compared to PZT–EMAA composites. The static and fatigue properties of the composites were investigated. The PZT–Zn ionomer composites were found to have excellent fatigue resistance even at strain levels of 4%. Due to the self-healing capabilities of the ionomer matrix, the loss of piezoelectric properties after high strain tensile cyclic loading could be partially recovered by thermal healing. (paper)

  9. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites.

    Science.gov (United States)

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-12-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.It is established that the changes of the relative intensities of the bands in FTIR spectra indicate the destruction of the carboxyl group -COOH and group -OH. Electrical conductivity of composites has percolation character and graphite nanoplatelets (ultraviolet ozone treatment for 20 min) addition which leads to a decrease of percolation threshold 0.005 volume fraction and increase values of electrical conductivity (by 2-3 orders of magnitude) above the percolation threshold in comparison with composite materials-graphite nanoplatelets/epoxy resin. The changes of the value and behavior of temperature dependences of the electrical resistivity of epoxy composites with ultraviolet/ozone-treated graphite nanoparticles have been analyzed within the model of effective electrical conductivity. The model takes into account the own electrical conductivity of the filler and the value of contact electric resistance between the filler particles of the formation of continuous conductive pathways.

  10. Fracture Resistance of Premolars Restored by Various Types and Placement Techniques of Resin Composites

    Directory of Open Access Journals (Sweden)

    Horieh Moosavi

    2012-01-01

    Full Text Available To verify the fracture resistance of premolars with mesioocclusodistal preparations restored by different resin composites and placement techniques. Sixty premolars were randomly divided into two groups based on type of composite resin: Filtek P60 or Nulite F, and then each group was separated into three subgroups: bulk, centripetal, and fiber insert according to the type of placement method (n=10. Single-bond adhesive system was used as composite bonding according to the manufacturer's instructions. Specimens were restored in Groups 1, 2, and 3 with Filtek P60 and in Groups 4, 5, and 6 with Nulite F. After being stored 24 hours at 37∘C, a 4 mm diameter steel sphere in a universal testing machine was applied on tooth buccal and lingual cusps at a cross-head speed of 5 mm/min until fracture occurred. Groups 3 and 6 showed higher fracture resistance than Groups 1, 2, 4, and 5. Among the placement techniques, the fiber insert method had a significant effect, but the type of composite was ineffective. The insertion technique in contrast to the type of material had a significant influence on the fracture resistance of premolar teeth.

  11. Mechanical properties and environmental stress cracking resistance of rubber toughened polyester/kenaf composite

    Directory of Open Access Journals (Sweden)

    2010-02-01

    Full Text Available In this study rubber-toughened polyester-kenaf fibre composites were prepared by adding various percentages of kenaf fibre in unsaturated polyester resin and subsequently cross linked using a mixture of organic peroxide methyl ethyl ketone and cobalt octanoate. Three percent (3% of liquid natural rubber (LNR were added as a toughening agent. The mechanical properties of the composites were evaluated by impact and flexural testing. Environmental stress cracking resistance (ESCR of polyester-kenaf composite in acid and base medium was also studied. It was found that the addition of LNR increased impact strength by about 66% and flexural strength by 70%. Measurement of ESCR shows that the composite has the fastest diffusion rate in acid medium, followed by that in base medium and then without medium. Bonding mechanisms were assessed by scanning electron microscope and FTIR analysis.

  12. Fatigue resistance and failure mode of adhesively restored custom metal-composite resin premolar implant abutments.

    Science.gov (United States)

    Boff, Luís Leonildo; Oderich, Elisa; Cardoso, Antônio Carlos; Magne, Pascal

    2014-01-01

    To evaluate the fatigue resistance and failure mode of composite resin and porcelain onlays and crowns bonded to premolar custom metal-composite resin premolar implant abutments. Sixty composite resin mesostructures were fabricated with computer assistance with two preparation designs (crown vs onlay) and bonded to a metal implant abutment. Following insertion into an implant with a tapered abutment interface (Titamax CM), each metal-composite resin abutment was restored with either composite resin (Paradigm MZ100) or ceramic (Paradigm C) (n = 15) and attached with adhesive resin (Optibond FL) and a preheated light-curing composite resin (Filtek Z100). Cyclic isometric chewing (5 Hz) was then simulated, starting with 5,000 cycles at a load of 50 N, followed by stages of 200, 400, 600, 800, 1,000, 1,200, and 1,400 N (25,000 cycles each). Samples were loaded until fracture or to a maximum of 180,000 cycles. The four groups were compared using life table survival analysis (log-rank test). Previously published data using zirconia abutments of the same design were included for comparison. Paradigm C and MZ100 specimens fractured at average loads of 1,133 N and 1,266 N, respectively. Survival rates ranged from 20% to 33.3% (ceramic crowns and onlays) to 60% (composite resin crowns and onlays) and were significantly different (pooled data for restorative material). There were no restoration failures, but there were adhesive failures at the connection between the abutment and the mesostructure. The survival of the metal-composite resin premolar abutments was inferior to that of identical zirconia abutments from a previous study (pooled data for abutment material). Composite resin onlays/crowns bonded to metal-composite resin premolar implant abutments presented higher survival rates than comparable ceramic onlays/crowns. Zirconia abutments outperformed the metal-composite resin premolar abutments.

  13. Influence of aging solutions on wear resistance and hardness of selected resin-based dental composites.

    Science.gov (United States)

    Chladek, Grzegorz; Basa, Katarzyna; Żmudzki, Jarosław; Malara, Piotr; Nowak, Agnieszka J; Kasperski, Jacek

    2016-01-01

    The purpose of this study was to investigate the effect of different plasticizing aging solutions on wear resistance and hardness of selected universal resin-based dental composites. Three light cured (one nanofilled, two microhybride) and one hybride chemical cured composites were aged at 37 °C for 48 h in distillated water, ethyl alcohol solution or Listerine mouthwash. After aging the microhardness tests were carried out and then tribological tests were performed in the presence of aging solution at 37 °C. During wear testing coefficients of friction were determined. The maximal vertical loss in micrometers was determined with profilometer. Aging in all liquids resulted in a significant decrease in hardness of the test materials, with the largest values obtained successively in ethanol solution, mouthwash and water. The effect of the liquid was dependent on the particular material, but not the type of material (interpreted as the size of filler used). Introduction of mouthwash instead of water or ethanol solution resulted in a significant reduction in the coefficient of friction. The lowest wear resistance was registered after aging in ethanol and for the chemical cured hybrid composite, but the vertical loss was strongly material dependent. The effect of different aging solution, including commercial mouthrinse, on hardness and wear was material dependent, and cannot be deduced from their category or filler loading. There is no simple correlation between hardness of resin-based dental composites and their wear resistance, but softening of particular composites materials during aging leads to the reduction of its wear resistance.

  14. Effect of composition on corrosion resistance of high-alloy austenitic stainless steel weld metals

    International Nuclear Information System (INIS)

    Marshall, P.I.; Gooch, T.G.

    1993-01-01

    The corrosion resistance of stainless steel weld metal in the ranges of 17 to 28% chromium (Cr), 6 to 60% nickel (Ni), 0 to 9% molybdenum (Mo), and 0.0 to 0.37% nitrogen (N) was examined. Critical pitting temperatures were determined in ferric chloride (FeCl 3 ). Passive film breakdown potentials were assessed from potentiodynamic scans in 3% sodium chloride (NaCl) at 50 C. Potentiodynamic and potentiostatic tests were carried out in 30% sulfuric acid (H 2 SO 4 ) ar 25 C, which was representative of chloride-free acid media of low redox potential. Metallographic examination and microanalysis were conducted on the test welds. Because of segregation of alloying elements, weld metal pitting resistance always was lower than that of matching composition base steel. The difference increased with higher Cr, Mo, and N contents. Segregation also reduced resistance to general corrosion in H 2 SO 4 , but the effect relative to the base steel was less marked than with chloride pitting. Segregation of Cr, Mo, and N in fully austenitic deposits decreased as the Ni' eq- Cr' eq ratio increased. Over the compositional range studied, weld metal pitting resistance was dependent mainly on Mo content and segregation. N had less effect than in wrought alloys. Both Mo and N enhanced weld metal corrosion resistance in H 2 SO 4

  15. Co nanoparticles induced resistive switching and magnetism for the electrochemically deposited polypyrrole composite films.

    Science.gov (United States)

    Xu, Zedong; Gao, Min; Yu, Lina; Lu, Liying; Xu, Xiaoguang; Jiang, Yong

    2014-10-22

    The resistive switching behavior of Co-nanoparticle-dispersed polypyrrole (PPy) composite films is studied. A novel design method for resistive random access memory (ReRAM) is proposed. The conducting polymer films with metal nanocrystal (NC)-dispersed carbon chains induce the spontaneous oxidization of the conducting polymer at the surface. The resistive switching behavior is achieved by an electric field controlling the oxygen ion mobility between the metal electrode and the conducting polymer film to realize the mutual transition between intrinsic conduction (low resistive state) and oxidized layer conduction (high resistive state). Furthermore, the formation process of intrinsic conductive paths can be effectively controlled in the conducting polymer ReRAM using metal NCs in films because the inner metal NCs induce electric field lines converging around them and the intensity of the electric field at the tip of NCs can greatly exceed that of the other region. Metal NCs can also bring new characteristics for ReRAM, such as magnetism by dispersing magnetic metal NCs in polymer, to obtain multifunctional electronic devices or meet some special purpose in future applications. Our works will enrich the application fields of the electromagnetic PPy composite films and present a novel material for ReRAM devices.

  16. Wettability and interface considerations in advanced heat-resistant Ni-base composites

    International Nuclear Information System (INIS)

    Asthana, R.; Mileiko, S.T.; Sobczak, N.

    2006-01-01

    Oxide fiber-reinforced Ni-base composites have long been considered as attractive heat-resistant materials. After several decades of active research, however, interest in these materials began to decline around mid-1990's due chiefly to 1) a lack of manufacturing technology to grow inexpensive single-crystal oxide fibers to be used in structural composites, and 2) fiber strength loss during processing due to chemical interactions with reactive solutes in the matrix. The cost disadvantage has been mitigated to a large extent by the development of innovative fiber fabrication processes such as the Internal Crystallization Method (ICM) that produces monocrystalline oxide fibers in a cost-effective manner. Fiber strength loss has been an equally restrictive issue but recent work has shown that it may be possible to design creep-resistant composites even when fiber surface reconstruction from chemical interactions has degraded the strength of extracted fibers tested outside the matrix. The key issue is the optimization of the composite- and interface structure. Reaction-formed defects may be healed by the matrix (or a suitable coating material) so that the fiber residing in the matrix may exhibit diminished sensitivity to flaws as compared to fibers extracted from the matrix and tested in isolation of the matrix. Generally, the Ni-base/Al 2 O 3 composites exhibit acceptable levels of wettability and interface strength (further improved with the aid of reactive solutes), which are required for elevated-temperature creep-resistance. In order to harness the full potential of these composites, the quality of the interface as manifested in the fiber/matrix wettability, interface composition, interphase morphology, and interface strength must be designed. We identify key issues related to the measurement of contact angle, interface strength, and chemical and structural properties at the fiber/matrix interface in the Ni/alumina composites, and present the current state-of the

  17. Utilization of composite fecal samples for detection of anthelmintic resistance in gastrointestinal nematodes of cattle.

    Science.gov (United States)

    George, Melissa M; Paras, Kelsey L; Howell, Sue B; Kaplan, Ray M

    2017-06-15

    Recent reports indicate that anthelmintic resistance in gastrointestinal nematodes of cattle is becoming increasingly prevalent worldwide. Presently, the fecal egg count reduction test (FECRT) is the only means available for detection of resistance to anthelmintics in cattle herds at the farm level. However, the FECRT is labor and cost intensive, and consequently is only rarely performed on cattle farms unless for research purposes. If costs could be reduced, cattle producers might be more likely to pursue drug resistance testing on their farms. One approach to reducing the cost of the FECRT, is the use of composite fecal samples for performing fecal egg counts (FEC), rather than conducting FEC on fecal samples from 15 to 20 individual animals. In this study FECRT were performed on 14 groups of cattle using both individual and composite FEC methods To measure how well the results of composite sampling reproduce those of individual sampling, Lin's Concordance Correlation Coefficient was utilized to describe both the linear relationship between methods and the slope and y-intercept of the line relating the data sets. There was little difference between the approaches with 98% agreement in mean FEC found between methods Mean FEC based on individual counts ranged between 0 and 670.6 eggs per gram of feces, indicating that the results of this study are applicable to a wide range of FEC levels. Standard error of the mean FEC and range of FEC are reported for each group prior to and following treatment to describe the variability of the data set. There was greater than 95% agreement in drug efficacy between individual and composite sampling methods, demonstrating composite sampling is appropriate to evaluate drug efficacy. Notably, for all groups tested the efficacy calculated by composite sampling was within the 95% confidence interval for efficacy calculated using individual sampling. The use of composite samples was shown to reduce the number of FEC required by 79

  18. Seismic isolation of nuclear power plants using elastomeric bearings

    Science.gov (United States)

    Kumar, Manish

    Seismic isolation using low damping rubber (LDR) and lead-rubber (LR) bearings is a viable strategy for mitigating the effects of extreme earthquake shaking on safety-related nuclear structures. Although seismic isolation has been deployed in nuclear structures in France and South Africa, it has not seen widespread use because of limited new build nuclear construction in the past 30 years and a lack of guidelines, codes and standards for the analysis, design and construction of isolation systems specific to nuclear structures. The nuclear accident at Fukushima Daiichi in March 2011 has led the nuclear community to consider seismic isolation for new large light water and small modular reactors to withstand the effects of extreme earthquakes. The mechanical properties of LDR and LR bearings are not expected to change substantially in design basis shaking. However, under shaking more intense than design basis, the properties of the lead cores in lead-rubber bearings may degrade due to heating associated with energy dissipation, some bearings in an isolation system may experience net tension, and the compression and tension stiffness may be affected by the horizontal displacement of the isolation system. The effects of intra-earthquake changes in mechanical properties on the response of base-isolated nuclear power plants (NPPs) were investigated using an advanced numerical model of a lead-rubber bearing that has been verified and validated, and implemented in OpenSees and ABAQUS. A series of experiments were conducted at University at Buffalo to characterize the behavior of elastomeric bearings in tension. The test data was used to validate a phenomenological model of an elastomeric bearing in tension. The value of three times the shear modulus of rubber in elastomeric bearing was found to be a reasonable estimate of the cavitation stress of a bearing. The sequence of loading did not change the behavior of an elastomeric bearing under cyclic tension, and there was no

  19. Correlation between in vitro Elastomeric Force Degradation and Glass Transition Temperature determined by Dynamic Mechanical Analysis

    Directory of Open Access Journals (Sweden)

    Manu Krishnan

    2012-01-01

    Conclusion: Tg can be considered as a dependable parameter in envisaging the force properties of an elastomeric chain. Clinically, it suggested that a polymer with higher Tg can give higher or optimum levels of force for tooth movement.

  20. Hydraulic performance of elastomeric bonded permeable revetments and subsoil response to wave loads

    NARCIS (Netherlands)

    Oumeraci, H.; Staal, T.; Pfoertner, S.; Kudella, M.; Schimmels, S.; Verhagen, H.J.

    2010-01-01

    Elastomeric bonded permeable revetments, also called PBA (Polyurethane bonded aggregate) revetments, are highly porous structures made of mineral aggregates (e.g. crushed stones) which are durably and elastically bonded by polyurethane (PU). Despite their numerous advantages as compared to

  1. Wave propagation and instabilities in monolithic and periodically structured elastomeric materials undergoing large deformations

    NARCIS (Netherlands)

    Bertoldi, Katia; Boyce, M.C.

    2008-01-01

    Wave propagation in elastomeric materials undergoing large deformations is relevant in numerous application areas, including nondestructive testing of materials and ultrasound techniques, where finite deformations and corresponding stress states can influence wave propagation and hence

  2. Fracture resistance of zirconia-composite veneered crowns in comparison with zirconia-porcelain crowns.

    Science.gov (United States)

    Alsadon, Omar; Patrick, David; Johnson, Anthony; Pollington, Sarah; Wood, Duncan

    2017-05-31

    The objectives were to evaluate the fracture resistance and stress concentration in zirconia/composite veneered crowns in comparison to zirconia/porcelain crowns using occlusal fracture resistance and by stress analysis using finite element analysis method. Zirconia substructures were divided into two groups based on the veneering material. A static load was applied occlusally using a ball indenter and the load to fracture was recorded in Newtons (N). The same crown design was used to create 3D crown models and evaluated using FEA. The zirconia/composite crowns subjected to static occlusal load showed comparable results to the zirconia/porcelain crowns. Zirconia/composite crowns showed higher stress on the zirconia substructure at 63.6 and 50.9 MPa on the zirconia substructure veneered with porcelain. In conclusion, zirconia/composite crowns withstood high occlusal loads similar to zirconia/porcelain crowns with no significant difference. However, the zirconia/composite crowns showed higher stress values than the zirconia/porcelain crowns at the zirconia substructure.

  3. Production of Heat Resistant Composite based on Siloxane Elastomer and Multiwall Carbon Nanotubes

    Science.gov (United States)

    Bessonov, I. V.; Karelina, N. V.; Kopitsyna, M. N.; Morozov, A. S.; Reznik, S. V.; Skidchenko, V. Yu.

    2016-02-01

    Development of a new generation of composite with unique thermal properties is an important task in the fields of science and technology where material is operated at high temperatures and exposure to a short-wave radiation. Recent studies show that carbon nanomaterials (fullerenes and carbon nanotubes) could improve the thermal, radiation and thermal-oxidative stability of the polymer matrix. In this article the development of a new heat resistant composite based on elastomer and carbon nanotubes (CNT) was performed and physicochemical properties of final product were evaluated.

  4. Dependence of Seebeck coefficient on a load resistance and energy conversion efficiency in a thermoelectric composite

    International Nuclear Information System (INIS)

    Yamashita, Osamu; Odahara, Hirotaka; Ochi, Takahiro; Satou, Kouji

    2007-01-01

    The thermo-emf ΔV and current ΔI generated by imposing the alternating temperature gradients (ATG) at a period of T and the steady temperature gradient (STG) on a thermoelectric (TE) composite were measured as a function of t, where t is the lapsed time and T was varied from 60 to or ∞ s. The STG and ATG were produced by imposing steadily and alternatively a source voltage V in the range from 1.0 to 4.0 V on two Peltier modules sandwiching a composite. ΔT, ΔV, ΔI and V P oscillate at a period T and their waveforms vary significantly with a change of T, where ΔV and V P are the voltage drops in a load resistance R L and in resistance R P of two modules. The resultant Seebeck coefficient |α| = |ΔV|/ΔT of a composite under the STG was found to be expressed as |α| = |α 0 |(1 - R comp /R T ), where R T is the total resistance of a circuit for measuring the output signals and R comp is the resistance of a composite. The effective generating power ΔW eff has a local maximum at T = 960 s for the p-type composite and at T = 480 s for the n-type one. The maximum energy conversion efficiency η of the p- and n-type composites under the ATG produced by imposing a voltage of 4.0 V at an optimum period were 0.22 and 0.23% at ΔT eff = 50 K, respectively, which are 42 and 43% higher than those at ΔT = 42 K under the STG. These maximum η for a TE composite sandwiched between two Peltier modules, were found to be expressed theoretically in terms of R P , R T , R L , α P and α, where α P and α are the resultant Seebeck coefficients of Peltier modules and a TE composite

  5. A study on the resistance performance of epoxy nano-composites under the vacuum ultraviolet irradiation

    Science.gov (United States)

    Liu, Yang; Li, Guo-hui; Jiang, Li-xiang

    2008-12-01

    Irradiation damage effects of the epoxy resin 648 and epoxy nano-composites are studied by means of simulating the vacuum ultraviolet (VUV) irradiation whose wavelength ranges from 5 to 200 nm. Experimental results of the mass loss, SEM and XPS show that nano-TiO 2 particles exhibit better resistance performance under VUV. Comparing with epoxy resin, the epoxy nano-composite brings significantly less mass loss, slighter flexural strength variation and decreasing gas extraction with less gas component varieties after irradiation. What is more, no new carbon peak-value has been found and principle components of Ols peak-value remain unchanged on the surface.

  6. Cyrogenic and radiation resistant properties of three dimensional fabric reinforced composite materials

    International Nuclear Information System (INIS)

    Yasuda, J.; Hirodawa, T.; Uemura, T.; Iwasaki, Y.; Nishijima, S.; Okada, T.; Okuyama, H.; Wang, Y.A.

    1988-01-01

    The insulating and/or structural materials for the fusion superconducting magnets are used under such strict environments as the cryogenic temperatures, high stresses and radiation environments. It is recognized that the usual laminated composite materials reinforced by glass clothes (2D-GFRP) are difficult to be used in such strict conditions. The three dimensional glass fabric reinforced composite materials (3D-GFRP) have high interlaminar shear strength due to the fibers in thickness direction. The cryogenic and radiation resistance properties of 3D-GFRP had been measured and the results compared with those of the 2D-GFRP

  7. Muscle function and body composition profile in adolescents with restrictive anorexia nervosa: Does resistance training help?

    OpenAIRE

    Fernández del Valle, María; Larumbe Zabala, Eneko; Morandé Lavín, Gonzalo; Pérez Ruiz, Margarita

    2016-01-01

    The aim of this study was to analyze the effects of short-term resistance training on the body composition profile and muscle function in a group of Anorexia Nervosa restricting type (AN-R) patients. The sample consisted of AN-R female adolescents (12.8 ± 0.6 years) allocated into the control and intervention groups (n¼18 each). Body composition and relative strength were assessed at baseline, after 8 weeks and 4 weeks following the intervention. Body mass index (BMI) increased throughout...

  8. Thermal shock resistances of a bonding material of C/C composite and copper

    International Nuclear Information System (INIS)

    Kurumada, Akira; Oku, Tatsuo; Kawamata, Kiyohiro; Motojima, Osamu; Noda, Nobuaki; McEnaney, B.

    1997-01-01

    The purpose of this study is to contribute to the development and the safety design of plasma facing components for fusion reactor devices. We evaluated the thermal shock resistance and the thermal shock fracture toughness of a bonding material which was jointed a carbon-fiber-reinforced carbon composite (C/C composite) to oxygen-free copper. We also examined the microstructures of the bonding layers using a scanning electron microscope before and after thermal shock tests. The bonding material did not fracture during thermal shock tests. However, thermal cracks and delamination cracks were observed in the bonding layers. (author)

  9. Effect of Processing Conditions on Fracture Resistance and Cohesive Laws of Binderfree All-Cellulose Composites

    DEFF Research Database (Denmark)

    Goutianos, Stergios; Arévalo, R.; Sørensen, Bent F.

    2014-01-01

    method was first developed to obtain fracture resistance values from the DCB specimens taking into account the non-linear material response. The binderfree all-cellulose composites were prepared by a mechanical refinement process that allows the formation of intramolecular bonds between the cellulose...... molecules during the drying process. Defibrilation of the raw cellulose material is done in wet medium in a paper-like process. Panels with different refining time were tested and it was found than an increase in fibre fibrillation results in a lower fracture resistance. © 2014 Springer Science......The fracture properties of all-cellulose composites without matrix were studied using Double Cantilever Beam (DCB) sandwich specimens loaded with pure monotonically increasing bending moments, which give stable crack growth. The experiments were conducted in an environmental scanning electron...

  10. Effect of neutron irradiation on fracture resistance of advanced SiC/SiC composites

    Science.gov (United States)

    Ozawa, Kazumi; Katoh, Yutai; Nozawa, Takashi; Snead, Lance L.

    2011-10-01

    In order to identify the neutron irradiation effects on fracture resistance of advanced SiC/SiC composites, unloading-reloading single edge notched bend tests were conducted and an analytical model based on non-linear fracture mechanics was applied. As a result of the analysis, energy release rate contributed by macro-crack initiation of 3.1 kJ/m 2 for both unirradiated and irradiated advanced SiC/SiC composites (Hi-Nicalon Type-S (0°/90° plain woven)/multilayer/chemically vapor infiltration) is estimated. This result indicates no significant degradation in fracture resistance after neutron irradiation to 5.9 × 10 25 n/m 2 at 800 °C.

  11. Analysis of the Influence of Food Colorings in Esthetic Orthodontic Elastomeric Ligatures.

    Science.gov (United States)

    Dias da Silva, Vanessa; de Lima, Eduardo Martinelli S; Dias, Caroline; Osório, Leandro Berni

    2016-01-01

    The purpose of this study was to evaluate in vitro the color changes of esthetic orthodontic elastomeric ligatures of different shades when exposed to four food colorings commonly found in the diet of patients. The sample consisted of esthetic orthodontic elastomeric ligatures in the colors pearl, pearl blue, pearl white and colorless, which were immersed for 72 hours in five different solutions: distilled water (control group), coffee, tea, Coca-Cola ® and wine. The color changes of the esthetic orthodontic elastomeric ligatures were measured with the aid of a spectrophotometer, at T1 - as provided by the manufacturer; and T2 - after colorings process. The results indicated that the esthetic orthodontic elastomeric ligatures of all initial hues are susceptible to pigmentation. Among the evaluated colors, all changed the finished look and the color of the samples tested. In ascending order, the color of the samples was as follows: distilled water, Coca-Cola ® , black tea, wine and coffee. The substances that have a greater potential for pigmentation in esthetic orthodontic elastomeric ligatures were black tea, wine and coffee, respectively. All shades of esthetic orthodontic elastomeric ligatures are susceptible to color change.

  12. Erosion resistance and adhesion of composite metal/ceramic coatings produced by plasma spraying

    OpenAIRE

    Ramm , D.; Hutchings , I.; Clyne , T.

    1993-01-01

    Ceramic coatings can exhibit greater erosion resistance than most metallic coatings. Such coatings are conveniently produced by thermal spraying. Unfortunately, thermally sprayed ceramic coatings often exhibit poor adhesion, partly as a consequence of the development of residual stresses during spraying and subsequent cooling. Composite coatings have been studied using aluminium/alumina deposits on steel substrates. The incorporation of ceramics within a ductile matrix has potential for sharp...

  13. Static characterization of a soft elastomeric capacitor for non destructive evaluation applications

    International Nuclear Information System (INIS)

    Saleem, Hussam; Laflamme, Simon; Zhang, Huanhuan; Geiger, Randall; Kessler, Michael; Rajan, Krishna

    2014-01-01

    A large and flexible strain transducer consisting of a soft elastomeric capacitor (SEC) has been proposed by the authors. Arranged in a network setup, the sensing strategy offers tremendous potential at conducting non-destructive evaluation of large-scale surfaces. In prior work, the authors have demonstrated the performance of the sensor at tracking strain history, localizing cracks, and detecting vibration signatures. In this paper, we characterize the static performance of the proposed SEC. The characterization includes sensitivity of the signal, and temperature and humidity dependences. Tests are conducted on a simply supported aluminum beam subjected to bending as well as on a free standing sensor. The performance of the SEC is compared against off-the-shelf resistance-based strain gauges with resolution of 1 με. A sensitivity of 1190 pF/ε is obtained experimentally, in agreement with theory. Results also show the sensor linearity over the given level of strain, showing the promise of the SEC at monitoring of surface strain

  14. A Damage Resistance Comparison Between Candidate Polymer Matrix Composite Feedline Materials

    Science.gov (United States)

    Nettles, A. T

    2000-01-01

    As part of NASAs focused technology programs for future reusable launch vehicles, a task is underway to study the feasibility of using the polymer matrix composite feedlines instead of metal ones on propulsion systems. This is desirable to reduce weight and manufacturing costs. The task consists of comparing several prototype composite feedlines made by various methods. These methods are electron-beam curing, standard hand lay-up and autoclave cure, solvent assisted resin transfer molding, and thermoplastic tape laying. One of the critical technology drivers for composite components is resistance to foreign objects damage. This paper presents results of an experimental study of the damage resistance of the candidate materials that the prototype feedlines are manufactured from. The materials examined all have a 5-harness weave of IM7 as the fiber constituent (except for the thermoplastic, which is unidirectional tape laid up in a bidirectional configuration). The resin tested were 977-6, PR 520, SE-SA-1, RS-E3 (e-beam curable), Cycom 823 and PEEK. The results showed that the 977-6 and PEEK were the most damage resistant in all tested cases.

  15. Chemical resistance, void content and tensile properties of oil palm/jute fibre reinforced polymer hybrid composites

    International Nuclear Information System (INIS)

    Jawaid, M.; Khalil, H.P.S. Abdul; Bakar, A. Abu; Khanam, P. Noorunnisa

    2011-01-01

    Tri layer hybrid composites of oil palm empty fruit bunches (EFB) and jute fibres was prepared by keeping oil palm EFB as skin material and jute as the core material and vice versa. The chemical resistance, void content and tensile properties of oil palm EFB/Jute composites was investigated with reference to the relative weight of oil palm EFB/Jute, i.e. 4:1, the fibre loading was optimized and different layering pattern were investigated. It is found from the chemical resistance test that all the composites are resistant to various chemicals. It was observed that marked reduction in void content of hybrid composites in different layering pattern. From the different layering pattern, the tensile properties were slightly higher for the composite having jute as skin and oil palm EFB as core material. Scanning electron microscopy (SEM) was used to study tensile fracture surfaces of different composites.

  16. Towards mechanisms-guided resistivity-based monitoring of damage evolution in laminated composites

    KAUST Repository

    Lubineau, Gilles

    2013-04-05

    A convenient health monitoring technique for detecting degradation in laminated composite is to monitor the change of electrical resistance along multiple conduction paths within the structure. Yet, the relations between the global modification of resistivity and the exact underlying damage map is still unclear that makes diffcult to interpret these nondestructive-testing results. The challenge is then to be able to reconstruct from these global observation the underlying damage map. This is even more diffcult due to the numerous underlying damage mechanisms that can take place either at the inter laminar of intra laminar level. This paper intends to provide some preliminary insights about strategies to recover the damage state based only on global measurements. We focus here on transverse cracking detection. We introduce the homogenization process that defines at the meso scale an equivalent homogeneous ply that is energetically equivalent to the cracked one. This can be used as a first tool to reconstruct damage maps based on global resistivity measurements.

  17. Fracture resistance of composite and amalgam cores retained by pins coated with new adhesive resins.

    Science.gov (United States)

    Tjan, A H; Dunn, J R; Grant, B E

    1992-06-01

    This study determined the effects of coating pins with either Panavia EX or with 4-META (Cover-Up) materials on the fracture resistance of pin-retained amalgam and composite cores. Gold-plated stainless steel (TMS) and titanium (Filpin) self-threading pins were used. Findings of this study corroborated the findings of several other studies that the use of pins reduces the fracture resistance of restorations. However, coating the pins with adhesion promoters such as Panavia EX and 4-META materials has been found to be effective in improving the fracture resistance. Cross-preference was observed between TMS and Filpin pins; that is, Panavia material coating was more effective with TMS pins, while 4-META was more effective with Filpin pins.

  18. Effect of filler porosity on the abrasion resistance of nanoporous silica gel/polymer composites.

    Science.gov (United States)

    Luo, J; Lannutti, J J; Seghi, R R

    1998-01-01

    This laboratory study was designed to investigate the effect of controlled nanoporosity on the wear resistance of polymeric composites reinforced with silica gel powders and to determine the mechanisms controlling the abrasive wear properties of these unique nanostructured materials. Silica gels were prepared by hydrolysis and condensation of tetraethylorthosilicate (TEOS) using four different catalysts to modify the porous structure of the resulting polysilicate silanation, an organic monomer (TEGDMA) containing various initiators was introduced into the gel powders to form a paste. The various pastes were then polymerized inside a glass mold. A pin-on-disk apparatus was then used to record the specimen length and number of revolutions. Abrasive wear rates were determined by regression analysis and statistical differences were determined by analysis of variance and multiple comparisons. BET was used to characterize the filler pore structure and scanning electron microscopy was used used to visually examine the abraded surfaces. Significant differences (p particle pullout. Porous particles prepared via sol-gel show some promise as fillers that improve the wear resistance of photopolymerized resins. The wear resistance of the fillers appears to be directly related to nanoporous structure of the gel particles. Unlike conventional dental composites, these materials rely primarily on nanomechanical coupling for improved wear resistance. This new principle should benefit subsequent investigations.

  19. Resistance to maxillary premolar fractures after restoration of class II preparations with resin composite or ceromer.

    Science.gov (United States)

    de Freitas, Cláudia Regina Buainain; Miranda, Maria Isabel Serra; de Andrade, Marcelo Ferrarezi; Flores, Victor Humberto Orbegoso; Vaz, Luís Geraldo; Guimarães, Catanzaro

    2002-09-01

    The aim of this study was to evaluate the resistance to fracture of intact and restored human maxillary premolars. Thirty noncarious human maxillary premolars, divided into three groups of 10, were submitted to mechanical tests to evaluate their resistance to fracture. Group 1 consisted of intact teeth. Teeth in group 2 received mesio-occlusodistal cavity preparations and were restored with direct resin composite restorations. Teeth in group 3 received mesio-occlusodistal cavity preparations and were restored with ceromer inlays placed with the indirect technique. After restoration, teeth were stored at 37 degrees C for 24 hours and then thermocycled for 500 cycles at temperatures of 5 degrees C and 55 degrees C. Statistical analysis revealed that group 3 (178.765 kgf) had a significantly greater maximum rupture load than did group 1 (120.040 kgf). There was no statistically significant difference between groups 1 and 2 or between groups 2 and 3. Class II cavity preparations restored with indirect ceromer inlays offered greater resistance to fracture than did intact teeth. The fracture resistance of teeth restored with resin composite was not significantly different from that of either the ceromer or intact teeth.

  20. Wear Resistance of Sintered Composite Hardfacings under Different Abrasive Wear Conditions

    Directory of Open Access Journals (Sweden)

    Taavi SIMSON

    2017-08-01

    Full Text Available The article focuses on vacuum liquid phase sintered (PM composite hardfacings and their behaviour under different abrasive wear conditions. Hardfacings studied contained 30 – 50 vol % fine, coarse or multimodal (fine and coarse hardmetal reinforcement. For wear resistance studies, we used the Abrasive Rubber Wheel Wear (ARWW test as a three-body abrasive wear test, the Abrasive Wheel Wear (AWW test as a two-body abrasive wear test and the Abrasive-Impact Erosion wear (AIEW test as an abrasive-erosive wear test. Tested materials were compared to Hardox 400 steel and CDP112 wear plate (Castolin Eutectic® Ltd.. It was found that under three-body abrasion conditions (ARWW test hardfacings with high content of spehrical coarse reinforcement are suitable; their wear resistance is about two times higher than that of unreinforced hardfacings. Under two-body abrasive wear (AWW test, hardfacings with a high content of coarse reinforcement are recommended; their wear resistance is up to eight times higher than that of unreinforced hardfacings from the figures and graphs mentioned in the text. Under abrasive-erosive wear (AIEW test, unreinforced ductile materials are recommended; they have two to three times higher wear resistance than composite hardfacings reinforced with fine or multimodal reinforcement.DOI: http://dx.doi.org/10.5755/j01.ms.23.3.16323

  1. Electrical Resistance Based Damage Modeling of Multifunctional Carbon Fiber Reinforced Polymer Matrix Composites

    Science.gov (United States)

    Hart, Robert James

    In the current thesis, the 4-probe electrical resistance of carbon fiber-reinforced polymer (CFRP) composites is utilized as a metric for sensing low-velocity impact damage. A robust method has been developed for recovering the directionally dependent electrical resistivities using an experimental line-type 4-probe resistance method. Next, the concept of effective conducting thickness was uniquely applied in the development of a brand new point-type 4-probe method for applications with electrically anisotropic materials. An extensive experimental study was completed to characterize the 4-probe electrical resistance of CFRP specimens using both the traditional line-type and new point-type methods. Leveraging the concept of effective conducting thickness, a novel method was developed for building 4-probe electrical finite element (FE) models in COMSOL. The electrical models were validated against experimental resistance measurements and the FE models demonstrated predictive capabilities when applied to CFRP specimens with varying thickness and layup. These new models demonstrated a significant improvement in accuracy compared to previous literature and could provide a framework for future advancements in FE modeling of electrically anisotropic materials. FE models were then developed in ABAQUS for evaluating the influence of prescribed localized damage on the 4-probe resistance. Experimental data was compiled on the impact response of various CFRP laminates, and was used in the development of quasi- static FE models for predicting presence of impact-induced delamination. The simulation-based delamination predictions were then integrated into the electrical FE models for the purpose of studying the influence of realistic damage patterns on electrical resistance. When the size of the delamination damage was moderate compared to the electrode spacing, the electrical resistance increased by less than 1% due to the delamination damage. However, for a specimen with large

  2. Highly Magneto-Responsive Elastomeric Films Created by a Two-Step Fabrication Process

    KAUST Repository

    Marchi, Sophie

    2015-08-24

    An innovative method for the preparation of elastomeric magnetic films with increased magneto-responsivity is presented. Polymeric films containing aligned magnetic microchains throughout their thickness are formed upon the magnetophoretic transport and assembly of microparticles during polymer curing. The obtained films are subsequently magnetized at a high magnetic field of 3 T directed parallel to the orientation of the microchains. We prove that the combination of both alignment of the particles along a favorable direction during curing and the subsequent magnetization of the solid films induces an impressive increase of the films’ deflection. Specifically, the displacements reach few millimeters, up to 85 times higher than those of the nontreated films with the same particle concentration. Such a process can improve the performance of the magnetic films without increasing the amount of magnetic fillers and, thus, without compromising the mechanical properties of the resulting composites. The proposed method can be used for the fabrication of magnetic films suitable as components in systems in which large displacements at relatively low magnetic fields are required, such as sensors and drug delivery or microfluidic systems, especially where remote control of valves is requested to achieve appropriate flow and mixing of liquids.

  3. Antibiotics, Antibiotic Resistance Genes, and Bacterial Community Composition in Fresh Water Aquaculture Environment in China.

    Science.gov (United States)

    Xiong, Wenguang; Sun, Yongxue; Zhang, Tong; Ding, Xueyao; Li, Yafei; Wang, Mianzhi; Zeng, Zhenling

    2015-08-01

    Environmental antibiotic resistance has drawn increasing attention due to its great threat to human health. In this study, we investigated concentrations of antibiotics (tetracyclines, sulfonamides and (fluoro)quinolones) and abundances of antibiotic resistance genes (ARGs), including tetracycline resistance genes, sulfonamide resistance genes, and plasmid-mediated quinolone resistance genes, and analyzed bacterial community composition in aquaculture environment in Guangdong, China. The concentrations of sulfametoxydiazine, sulfamethazine, sulfamethoxazole, oxytetracycline, chlorotetracycline, doxycycline, ciprofloxacin, norfloxacin, and enrofloxacin were as high as 446 μg kg(-1) and 98.6 ng L(-1) in sediment and water samples, respectively. The relative abundances (ARG copies/16S ribosomal RNA (rRNA) gene copies) of ARGs (sul1, sul2, sul3, tetM, tetO, tetW, tetS, tetQ, tetX, tetB/P, qepA, oqxA, oqxB, aac(6')-Ib, and qnrS) were as high as 2.8 × 10(-2). The dominant phyla were Proteobacteria, Bacteroidetes, and Firmicutes in sediment samples and Proteobacteria, Actinobacteria and Bacteroidetes in water samples. The genera associated with pathogens were also observed, such as Acinetobacter, Arcobacter, and Clostridium. This study comprehensively investigated antibiotics, ARGs, and bacterial community composition in aquaculture environment in China. The results indicated that fish ponds are reservoirs of ARGs and the presence of potential resistant and pathogen-associated taxonomic groups in fish ponds might imply the potential risk to human health.

  4. Joining of the AMC Composites Reinforced with Ti3Al Intermetallic Particles by Resistance Butt Welding

    Directory of Open Access Journals (Sweden)

    Adamiak M.

    2016-06-01

    Full Text Available The introduction of new reinforcing materials continues to be investigated to improve the final behaviour of AMCs as well as to avoid some drawbacks of using ceramics as reinforcement. The present work investigates the structure, properties and ability of joining aluminium EN-AW 6061 matrix composite materials reinforced with Ti3Al particles by resistance butt welding as well as composite materials produced by mechanical milling, powder metallurgy and hot extrusion techniques. Mechanically milled and extruded composites show finer and better distribution of reinforcement particles, which leads to better mechanical properties of the obtained products. Finer microstructure improves mechanical properties of obtained composites. The hardness increases twice in the case of mechanically milled composites also, a higher reinforcement content results in higher particle dispersion hardening, for 15 wt.% of intermetallics reinforcement concentration composites reach about 400 MPa UTS. Investigation results of joints show that best hardness and tensile properties of joints can be achieved by altering soft conditions of butt welding process e.g. current flow time 1.2 s and current 1400 A. To improve mechanical properties of butt welding joints age hardening techniques can also be used.

  5. Development of HVOF Sprayed Erosion/Oxidation Resistant Coatings for Composite Structural Components in Propulsion Systems

    Science.gov (United States)

    Knight, R.; Ivosevic, M.; Twardowski, T. E.; Kalidindi, S. R.; Sutter, James K.; Kim, D. Y.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Thermally sprayed coatings are being studied and developed as methods of enabling lightweight composites to be used more extensively as structural components in propulsion applications in order to reduce costs and improve efficiency through weight reductions. The primary goal of this work is the development of functionally graded material [FGM] polymer/metal matrix composite coatings to provide improved erosion/oxidation resistance to polyimide-based polymer matrix composite [PMC] substrates. The goal is to grade the coating composition from pure polyimide, similar to the PMC substrate matrix on one side, to 100 % WC-Co on the other. Both step-wise and continuous gradation of the loading of the WC-Co reinforcing phase are being investigated. Details of the coating parameter development will be presented, specifically the high velocity oxy-fuel [HVOF] combustion spraying of pure PMR-11 matrix material and layers of various composition PMR-II/WC-Co blends onto steel and PMR-15 composite substrates. Results of the HVOF process optimization, microstructural characterization, and analysis will be presented. The sprayed coatings were evaluated using standard metallographic techniques - optical and scanning electron microscopy [SEM]. An SEM + electron dispersive spectroscopy [EDS] technique has also been used to confirm retention of the PMR-II component. Results of peel/butt adhesion testing to determine adhesion will also be presented.

  6. Scratch-resistant, highly conductive, and high-strength carbon nanotube-based composite yarns.

    Science.gov (United States)

    Liu, Kai; Sun, Yinghui; Lin, Xiaoyang; Zhou, Ruifeng; Wang, Jiaping; Fan, Shoushan; Jiang, Kaili

    2010-10-26

    High-strength and conductive carbon nanotube (CNT) yarns are very attractive in many potential applications. However, there is a difficulty when simultaneously enhancing the strength and conductivity of CNT yarns. Adding some polymers into CNT yarns to enhance their strength will decrease their conductivity, while treating them in acid or coating them with metal nanoparticles to enhance their conductivity will reduce their strength. To overcome this difficulty, here we report a method to make high-strength and highly conductive CNT-based composite yarns by using a continuous superaligned CNT (SACNT) yarn as a conductive framework and then inserting polyvinyl alcohol (PVA) into the intertube spaces of the framework through PVA/dimethyl sulphoxide solution to enhance the strength of yarns. The as-produced CNT/PVA composite yarns possess very high tensile strengths up to 2.0 GPa and Young's moduli more than 120 GPa, much higher than those of the CNT/PVA yarns reported. The electric conductivity of as-produced composite yarns is as high as 9.2 × 10(4) S/m, comparable to HNO(3)-treated or Au nanoparticle-coated CNT yarns. These composite yarns are flexible, lightweight, scratch-resistant, very stable in the lab environment, and resistant to extremely humid ambient and as a result can be woven into high-strength and heatable fabrics, showing potential applications in flexible heaters, bullet-proof vests, radiation protection suits, and spacesuits.

  7. Gut microbiota composition and its effects on obesity and insulin resistance.

    Science.gov (United States)

    Caricilli, Andrea M; Saad, Mario J A

    2014-07-01

    Rising evidence suggest that variation in the gut microbiome at gene and species levels defines subsets of individuals who have increased risk of obesity-related metabolic disorders, including insulin resistance and type 2 diabetes, which is influenced by diet and genetic profile of the host. Our goal in this review is gathering the newest findings concerning gut microbiota composition and effects on host's metabolism. Dietary changes have been shown as the most prominent shaper of gut microbiota composition, reflecting major phenotypes, which can also be transmitted to other individuals, in spite of genetic variances. Gut microbiota composition has also been presented as diversity, which may have important implications in metabolite production and consequent interference with inflammatory activation, insulin resistance, and obesity. Specific approaches made it possible to comprehend some of the interactions between certain bacterial strains and their host, and how their metabolites may interfere with host's cell signaling, changing its metabolic profile. Herein, we discuss some of the mechanisms by which alterations in the gut microbiota composition may contribute to the pathophysiology of obesity and its related comorbidities.

  8. Insulin resistance, exercise capacity and body composition in subjects with two hypertensive parents

    DEFF Research Database (Denmark)

    Andersen, U B; Dige-Petersen, H; Ibsen, H

    1999-01-01

    -ray absorptiometry; (4) an exercise test with gas exchange analysis; and (5) investigation of composition of usual diet by diet registration for 5 days. RESULTS: The 24-h diastolic blood pressure was higher in subjects predisposed to hypertension compared with the controls: 78.1 versus 74.0 mmHg (confidence interval......OBJECTIVE: To study insulin resistance in subjects with strong genetic predisposition to essential hypertension, compared with non-disposed subjects. SUBJECTS: Thirty normotensive subjects aged 18-35 years whose parents both had essential hypertension, and 30 age- and sex matched subjects whose...... for the difference between the means; -0.5; -7.9), but the insulin sensitivity index was similar: 312 versus 362 I(2) min(-1) pmol(-1) kg(-1) (28; -129). The two groups were similar in terms of body composition, exercise capacity and composition of usual diet. Resting and 24-h diastolic blood pressures were...

  9. In vitro fracture resistance of composite-resin-veneered zirconia crowns.

    Science.gov (United States)

    Peampring, Chaimongkon; Aksornmuang, Juthatip; Sanohkan, Sasiwimol

    2017-01-01

    The aim of this study is to investigate the fracture load to failure and damage mode of the composite resin-veneered zirconia crowns preparing with two different zirconia surface treatments compared conventional porcelain-veneered zirconia crowns. Metallic molar-shape dies prepared with 10° convergence angle a 1.5 mm deep chamfer finish line were used. Two groups of composite-resin-veneered zirconia crowns were prepared using different surface treatment (Group A - sandblasting and Group B - glaze-on technique). Group C (conventional porcelain-veneered zirconia crowns) was served as control. Load to failure test was performed to evaluate the fracture resistance of the crowns using a universal testing machine. One-way ANOVA was used to evaluate the differences of mean values ( P zirconia coping exposed. Group B and C showed significant higher load to failure than Group A. Four specimens of Group A revealed the delamination of composite resin veneering.

  10. Fabrication of Environmentally Resistant NITE-SiC/SiC Composites

    Energy Technology Data Exchange (ETDEWEB)

    Park, J S; Jung, H C [Muroran Establishment, IEST Co., Ltd., 27-1 Mizumoto-cho, Muroran 050-8585 (Japan); Ooi, Y; Kishimoto, K; Kohyama, A, E-mail: jspark@iest.jp [OASIS, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran 050-8585 (Japan)

    2011-10-29

    NITE-SiC, SiC/SiC qualification of environmental resistance in various conditions is on-going toward early utilization in advanced energy and aero-space systems. Multi-layered SiC/SiC composites for preventing environmental attacks to pyrocarbon interphase was provided. Thermal exposure test in air and liquid metal(Pb and Li-Pb) compatibility test were carried out. It was confirmed the significant loss of PyC interphase in SiC/SiC composites. In case of Li-Pb-layered SiC/SiC composites, an attack of air and liquid metal has been sucessfuly supressed by surface SiC layer

  11. The correlation of low-velocity impact resistance of graphite-fiber-reinforced composites with matrix properties

    Science.gov (United States)

    Bowles, Kenneth J.

    1988-01-01

    Summarized are basic studies that were conducted to correlate the impact resistance of graphite-fiber-reinforced composites with polymer matrix properties. Three crosslinked epoxy resins and a linear polysulfone were selected as composite matrices. As a group, these resins possess a significantly large range of mechanical properties. The mechanical properties of the resins and their respective composites were measured. Neat resin specimens and unidirectional and crossply composite specimens were impact tested with an instrumented dropweight tester. Impact resistances of the specimens were assesseed on the basis of loading capability, energy absorption, and extent of damage.

  12. Fracture resistance of endodontically treated molars restored with extensive composite resin restorations.

    Science.gov (United States)

    Plotino, Gianluca; Buono, Laura; Grande, Nicola M; Lamorgese, Vincenzo; Somma, Francesco

    2008-03-01

    When cuspal coverage is required, there is no evidence that indirect composite resin restorations are superior to direct restorations in terms of biomechanical behavior. The purpose of this in vitro study was to compare the fracture resistance of cusp-replacing direct and indirect composite resin restorations in endodontically treated molars. Forty-five human mandibular molars were selected and divided into 3 groups (n=15): DIR specimens, restored with direct composite resin (Estelite Sigma) restorations; IND specimens, restored with indirect composite resin (Estelite Sigma) restorations, and control specimens, which remained intact. Endodontic treatment was performed using NiTi ProTaper rotary instruments, and teeth were filled using lateral condensation of gutta-percha and sealer. Extensive Class II MO cavities were prepared, and the 2 mesial cusps were reduced, allowing a 2-mm layer of composite resin. All teeth were prepared to the same dimensions, considering reasonable human variation. Specimens were loaded to failure and the fracture loads were recorded (N). The mode of fracture was determined using a stereomicroscope and classified as favorable or unfavorable failure. The data were subjected to a Kruskal-Wallis test, multiple-comparison Mann-Whitney test, and a chi-square test (alpha=.05). Significant differences (P<.001) were observed between the control group and both DIR and IND groups. However, no significant difference was found between the DIR and IND groups. The chi-square test did not show a significant difference in the frequencies of favorable/unfavorable failure modes among the 3 groups (P=.981). No significant difference was observed in the fracture resistance of endodontically treated molars restored to original contours with an extensive cusp-replacing direct or indirect composite resin restoration.

  13. Wear Resistance Properties Reinforcement Using Nano-Al/Cu Composite Coating in Sliding Bearing Maintenance.

    Science.gov (United States)

    Liu, Hongtao; Li, Zhixiong; Wang, Jianmei; Sheng, Chenxing; Liu, Wanli

    2018-03-01

    Sliding bearing maintenance is crucial for reducing the cost and extending the service life. An efficient and practical solution is to coat a restorative agent onto the worn/damaged bearings. Traditional pure-copper (Cu) coating results in a soft surface and poor abrasion resistance. To address this issue, this paper presents a nano-composite repairing coating method. A series of nano-Al/Cu coatings were prepared on the surface of 45 steel by composite electro-brush plating (EBP). Their micro-hardness was examined by a MHV-2000 Vickers hardness tester, and tribological properties by a UMT-2M Micro-friction tester, 3D profiler and SEM. Then, the influence of processing parameters such as nano-particle concentration and coating thickness on the micro-hardness of nano-Al/Cu coating was analyzed. The experimental analysis results demonstrate that, when the nano-Al particle concentration in electrolyte was 10 g/L, the micro-hardness of the composite coating was 1.1 times as much as that of pure-Cu coating. When the Al nano-particle concentration in electrolyte was 20 g/L, the micro-hardness of the composite coating reached its maximum value (i.e., 231.6 HV). Compared with the pure-Cu coating, the hardness and wear resistance of the nano-composite coating were increased, and the friction coefficient and wear volume were decreased, because of the grain strengthening and dispersion strengthening. The development in this work may provide a feasible and effective nano-composite EBP method for sliding bearing repair.

  14. The comparative evaluation of fracture resistance and microleakage in bonded amalgam, amalgam, and composite resins in primary molars

    Directory of Open Access Journals (Sweden)

    H S Vanishree

    2015-01-01

    Conclusions: Bonded amalgam appears to be comparable to amalgam when microleakage is considered and to composite resin when fracture resistance is considered; hence, bonded amalgam can also be an alternative material to amalgam in primary molars.

  15. Fatigue resistance and microleakage of CAD/CAM ceramic and composite molar crowns.

    Science.gov (United States)

    Kassem, Amr S; Atta, Osama; El-Mowafy, Omar

    2012-01-01

    The aim of this study was to determine effect of compressive cyclic loading on fatigue resistance and microleakage of monolithic CAD/CAM molar ceramic and composite crowns. Thirty-two extracted molars were prepared to receive CEREC crowns according to manufacturer's guidelines using a special paralleling device (Parallel-A-Prep). Sixteen feldspathic ceramic crowns (VITABLOCS Mark II) (VMII) and 16 resin-composite crowns (Paradigm-MZ100 blocks) (PMZ) were milled using a CEREC-3D machine. Eight crowns of each group were cemented to their respective teeth using self-etching resin cement (Panavia-F-2.0) (PAN), and eight were cemented using self-adhesive resin cement (RelyX-Unicem-Clicker) (RXU). Following storage for 1 week in water, specimens were subjected to uniaxial compressive cyclic loading in an Instron testing machine at 12 Hz for 1,000,000 cycles. Load was applied at the central fossa, and the cycle range was 60-600 N. Specimens were then subjected to microleakage testing. Data were statistically analyzed using factorial ANOVA and Post Hoc (Tukey HSD) tests. All composite crowns survived compressive cyclic loading without fracture, while three ceramic crowns from the subgroup cemented with RXU developed surface cracks at the center of occlusal surfaces, extending laterally. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other three subgroups (p crowns were more fatigue-resistant than VMII ceramic crowns. Cement type had a significant effect on fatigue resistance of the ceramic crowns but not the composite ones. Microleakage scores of ceramic crowns cemented with PAN were significantly lower than those of the other subgroups (p < 0.05). © 2011 by The American College of Prosthodontists.

  16. Comparative analysis of the water resistance of glass composites and homogeneous glass matrices for immobilization of radioactive wastes

    International Nuclear Information System (INIS)

    Karlina, O.K.; Ozhovan, M.I.; Popov, M.V.

    1994-01-01

    The reliability of immobilizing radioactive wastes in glass composites as compared to homogeneous glasses containing the same amount of radioactive components is evaluated. The resistance criterion of the glass composites is defined as the condition where their water resistance is no worse than that of a homogeneous glass of the same composition without unexpected sample decompositions. The water resistance of the glass composites and the homogeneous matrices in addition to its change after induced sample fragmentation are experimentally studied. The limit is found for the maximal particle size of the dispersed radioactive phase in the glass composites. The maximal achievable size of the radioactive inclusions depends on the properties of the glass matrix used and the distribution coefficient of the radionuclides between the additive and the matrix

  17. Fatigue resistance and stiffness of glass fiber-reinforced urethane dimethacrylate composite.

    Science.gov (United States)

    Narva, Katja K; Lassila, Lippo V J; Vallittu, Pekka K

    2004-02-01

    Retentive properties of cast metal clasps decrease over time because of metal fatigue. Novel fiber-reinforced composite materials are purported to have increased fatigue resistance compared with metals and may offer a solution to the problem of metal fatigue. The aim of this study was to investigate the fatigue resistance and stiffness of E-glass fiber-reinforced composite. Twelve cylindrical fiber-reinforced composite test cylinders (2 mm in diameter and 60 mm in length) were made from light-polymerized urethane dimethacrylate monomer with unidirectional, single-stranded, polymer preimpregnated E-glass fiber reinforcement. Six cylinders were stored in dry conditions and 6 in distilled water for 30 days before testing. Fatigue resistance was measured by a constant-deflection fatigue test with 1 mm of deflection across a specimen span of 11 mm for a maximum of 150,000 loading cycles. The resistance of the cylinder against deflection was measured (N) and the mean values of the force were compared by 1-way analysis of variance (alpha = .05). The flexural modulus (GPa) was calculated for the dry and water-stored cylinders for the first loading cycle. Scanning electron microscopy was used to assess the distribution of the fibers, and the volume percent of fibers and polymer were assessed by combustion analysis. The test cylinders did not fracture due to fatigue following 150,000 loading cycles. Flexural modulus at the first loading cycle was 18.9 (+/- 2.9) GPa and 17.5 (+/- 1.7) GPa for the dry and water-stored cylinders, respectively. The mean force required to cause the first 1-mm deflection was 33.5 (+/- 5.2) N and 37.7 (+/- 3.6) N for the dry and water stored cylinders, respectively; however, the differences were not significant. After 150,000 cycles the mean force to cause 1-mm deflection was significantly reduced to 23.4 (+/- 8.5) N and 13.1 (+/- 3.5) N, respectively (P fiber- and polymer-rich areas within the specimens and indicated that individual fibers were

  18. Relationship of margin design for fiber-reinforced composite crowns to compressive fracture resistance.

    Science.gov (United States)

    Maghrabi, Abdulhamaid A; Ayad, Mohamed F; Garcia-Godoy, Franklin

    2011-07-01

    Fiber-reinforced composite restorations provide excellent esthetics; however, little is known regarding the influence of margin design on marginal fit and fracture resistance for this type of crown. This study evaluated the effect of variations in tooth-preparation design on the marginal fit and compressive fracture resistance of fiber-reinforced composite crowns. Three metal dies with a total convergence of 5° and different margin designs (0.5-mm light chamfer, 1.0-mm deep chamfer, and 1.0-mm shoulder) were prepared. Sixty standardized crowns (FibreKor) were made on duplicated base metal alloy dies (n = 20 for each margin design). Marginal fit was stereoscopically evaluated by measuring the distances between each of the four pairs of indentations on the crowns and on the dies. The specimens were then subjected to a compressive fracture-loading test using a universal testing machine. The data were analyzed with one-way analysis of variance (ANOVA) followed by Ryan-Einot-Gabriel-Welsch multiple-range test (α = 0.05). Analysis of marginal fit and fracture resistance disclosed a statistically significant difference for tooth-preparation design (p crowns was adversely affected by tooth-preparation design. The marginal gaps were greater for the shoulder margin specimens than in the light or deep chamfer margin specimens; however, the fracture strength of the chamfer margin specimens was greater than that of the shoulder margin specimens. © 2011 by the American College of Prosthodontists.

  19. Effect of Fiber Layers on the Fracture Resistance of Fiber Reinforced Composite Bridges

    Directory of Open Access Journals (Sweden)

    A Fazel

    2011-08-01

    Full Text Available Introduction: The purpose of this in vitro study was to introduce the fiber reinforced composite bridges and evaluate the most suitable site and position for placement of fibers in order to get maximum strength. Methods: The study included 20 second premolars and 20 second molars selected for fabricating twenty fiber reinforced composite bridges. Twenty specimens were selected for one fiber layer and the remaining teeth for two fiber layers. In the first group, fibers were placed in the inferior third and in the second group, fibers were placed in both the middle and inferior third region. After tooth preparation, the restorations were fabricated, thermocycled and then loaded with universal testing machine in the middle of the pontics with crosshead speed of 1mm/min. Data was analyzed by Kolmogorov-Smirnov test, Independent sample t test and Kaplan-Meier test. Mode of failure was evaluated using stereomicroscope. Results: Mean fracture resistance for the first and second groups was 1416±467N and 1349±397N, respectively. No significant differences were observed between the groups (P>0.05.In the first group, 5 specimens had delamintation and 5 specimens had detachment between fibers and resin composite. In the second group, there were 4 and 6 delaminations and detachments, respectively. There was no fracture within the fiber. Conclusion: In the fiber reinforced fixed partial dentures, fibers reinforce the tensile side of the connectors but placement of additional fibers at other sites does not increase the fracture resistance of the restoration.

  20. Comparison of fracture resistance of teeth restored with ceramic inlay and resin composite: An in vitro study

    Directory of Open Access Journals (Sweden)

    Priti D Desai

    2011-01-01

    Conclusion: The fracture resistant strength of teeth restored with ceramic inlay was comparable to that of the normal intact teeth or slightly higher, while teeth restored with direct composite resin restoration showed less fracture resistant strength than that of the normal teeth.

  1. Diffusion of nanoparticles in solution through elastomeric membrane

    Science.gov (United States)

    Zemzem, Mohamed; Vinches, Ludwig; Hallé, Stéphane

    2017-04-01

    Diffusion phenomena encountered in mass transfer of liquids play an important role in many technological processes of polymer manufacturing and use. In addition and alongside the notable growth of nanoparticles use, particularly when in suspension in liquid solutions, it has become important to pay some attention to their interactions with polymeric structures. The aim of this work is to evaluate some diffusion parameters of gold nanoparticle solutions as well as of their liquid carrier (water) through elastomeric membranes. Gravimetric method was chosen as the main technique to quantify swelling phenomena and to assess kinetic properties. The dynamic liquid uptake measurements were conducted on gold nanoparticles (5 nm and 50 nm in diameter) in aqueous solutions when brought into contact with two types of nitrile material samples. Results showed that diffusion mechanism of the liquids lies between Fickian and sub-Fickian modes. Slight deviations were noticed with the gold nanoparticle solutions. A growth in liquid interaction with the rubbery structure in presence of the nanoparticles was also observed from comparison of K factor (characteristic of the elastomer-liquid interaction). Difference between the characteristics of the two membranes was also reported using this parameter. Besides, diffusion coefficients testified the impact of the membrane thickness on the penetration process, while no significant effect of the nature of the nanoparticle solution can be seen on this coefficient.

  2. Unification of reactor elastomeric sealing based on material

    International Nuclear Information System (INIS)

    Sinha, N.K.; Raj, Baldev

    2012-01-01

    The unification of elastomeric sealing applications of Indian nuclear reactors based on a few qualified fluoroelastomer/perfluoroelastomer compounds and standardized approaches for finite element analysis (FEA) based design, manufacturing process and antifriction coatings is discussed. It is shown that the advance polymer architecture based Viton ® formulation developed for inflatable seals of 500 MWe Prototype Fast Breeder Reactor (PFBR) and its four basic variations can encompass other sealing applications of PFBR with minimum additional efforts on development and validation. Changing the blend ratio of Viton ® GBL 200S and 600S in inflatable seal formulation could extend its use to Pressurized Heavy Water Reactors (PHWRs). The higher operating temperature of Advanced Heavy Water Reactor (AHWR) seals expands the choice to perfluoroelastomers. FEA based on plane-strain/axisymmetric modeling (with Mooney–Rivlin as the basic constitutive model), seal manufacture by cold feed extrusion and injection molding as well as plasma Teflon-like coating belonging to two variations obtained from the development of inflatable seals provide the necessary standardization for unification. The gains in simplification of design, development and operation of seals along with the enhancements of safety and reliability are expected to be substantial.

  3. A method for nanofluidic device prototyping using elastomeric collapse

    Science.gov (United States)

    Park, Seung-min; Huh, Yun Suk; Craighead, Harold G.; Erickson, David

    2009-01-01

    Nanofluidics represents a promising solution to problems in fields ranging from biomolecular analysis to optical property tuning. Recently a number of simple nanofluidic fabrication techniques have been introduced that exploit the deformability of elastomeric materials like polydimethylsiloxane (PDMS). These techniques are limited by the complexity of the devices that can be fabricated, which can only create straight or irregular channels normal to the direction of an applied strain. Here, we report a technique for nanofluidic fabrication based on the controlled collapse of microchannel structures. As is demonstrated, this method converts the easy to control vertical dimension of a PDMS mold to the lateral dimension of a nanochannel. We demonstrate here the creation of complex nanochannel structures as small as 60 nm and provide simple design rules for determining the conditions under which nanochannel formation will occur. The applicability of the technique to biomolecular analysis is demonstrated by showing DNA elongation in a nanochannel and a technique for optofluidic surface enhanced Raman detection of nucleic acids. PMID:19717418

  4. Improvement of Strength and Oxidation Resistance for SiC/graphite Composites by SiC coating

    Science.gov (United States)

    Yang, Wanli; Shi, Zhongqi; Li, Hongwei; Li, Zhen; Jin, Zhihao; Qiao, Guanjun

    2011-03-01

    SiC/graphite composites with exelent machinable properties and thermal shock behaviour were successfully fabricated by pressureless sintering at 1700°C in nitrogen atmosphere. A dipping infiltration process was applied to improve the strength and oxidation resistance of the composites. Dense SiC coating was covered on the composites' surface by heat-treating at 1400°C in nitrogen atmosphere with dipping infiltration of silica sol and phenolic resin solutions. The flexural strength of the SiC coated composites were improved from 60 MPa to 140 MPa obviously, and the weight loss of the SiC coated composites was reduced more than 20 % comparing with the uncoated composites by oxidation resistance testing at 1000 °C for 24 h in air. SEM micrographs shows that SiC coating was surrounded the surface of pores and XRD pattern revealed that the new layer was SiC.

  5. Fatty acid composition analyses of the DCMU resistant mutants of Nannochloropsis oculata (eustigmatophyceae)

    Science.gov (United States)

    Jimin, Zhang; Shuang, Liu; Xue, Sun; Guanpin, Yang; Xuecheng, Zhang; Zhenhui, Gao

    2003-04-01

    Ultraviolet mutagenesis was applied to Nannochloropsis oculata and three mutants resistant to 3-(3, 4-dichlorophenyl)-1,1-dimethylurea (DCMU) were isolated. The cellular chlorophyll a and total lipid content of the wild are higher in the medium supplemented with DCMU than in the control without DCMU. Without DCMU, the growth rates and chlorophyll a contents of the mutants are similar to those of the wild. Significant changes of fatty acid content and composition have occurred in DCMU-resistant mutants growing in the medium supplemented with DCMU. The total lipid, palmitic acid (16:0), palmitoleic acid (16:1ω9) and oleic (18:1ω9) contents decrease significantly, while the vaccenic acid (18:1ω11) increases significantly and the EPA content of dried powder increases slightly in the mutants. The study may provide a basis to improve EPA content in Nannochloropsis oculata in the future.

  6. Chemical composition and antibacterial activity of Lavandula coronopifolia essential oil against antibiotic-resistant bacteria.

    Science.gov (United States)

    Ait Said, L; Zahlane, K; Ghalbane, I; El Messoussi, S; Romane, A; Cavaleiro, C; Salgueiro, L

    2015-01-01

    The aim of this study was to analyse the composition of the essential oil (EO) of Lavandula coronopifolia from Morocco and to evaluate its in vitro antibacterial activity against antibiotic-resistant bacteria isolated from clinical infections. The antimicrobial activity was assessed by a broth micro-well dilution method using multiresistant clinical isolates of 11 pathogenic bacteria: Klebsiella pneumoniae subsp. pneumoniae, Klebsiella ornithinolytica, Escherichia coli, Enterobacter cloacae, Enterobacter aerogenes, Providencia rettgeri, Citrobacter freundii, Hafnia alvei, Salmonella spp., Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus. The main compounds of the oil were carvacrol (48.9%), E-caryophyllene (10.8%) and caryophyllene oxide (7.7%). The oil showed activity against all tested strains with minimal inhibitory concentration (MIC) values ranging between 1% and 4%. For most of the strains, the MIC value was equivalent to the minimal bactericidal concentration value, indicating a clear bactericidal effect of L. coronopifolia EO.

  7. Microstructure and Corrosion Resistance of Aluminium and Copper Composite Coatings Deposited by LPCS Method

    Directory of Open Access Journals (Sweden)

    Winnicki M.

    2016-12-01

    Full Text Available The paper presents the study of microstructure and corrosion resistance of composite coatings (Al+Al2O3 and Cu+Al2O3 deposited by Low Pressure Cold Spraying method (LPCS. The atmospheric corrosion resistance was examined by subjecting the samples to cyclic salt spray and Kesternich test chambers, with NaCl and SO2 atmospheres, respectively. The selected tests allowed reflecting the actual working conditions of the coatings. The analysis showed very satisfactory results for copper coatings. After eighteen cycles, with a total time of 432 hours, the samples show little signs of corrosion. Due to their greater susceptibility to chloride ions, aluminium coatings have significant corrosion losses.

  8. Effect of fiber diameter and matrix alloys on impact-resistant boron/aluminum composites

    Science.gov (United States)

    Mcdanels, D. L.; Signorelli, R. A.

    1976-01-01

    Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Nonstandard thin-sheet charpy and Izod impact tests and standard full-size Charpy impact tests were conducted on composites containing unidirectional 0.10mm, 0.14mm, and 0.20mm diameter boron fibers in 1100, 2024, 5052, and 6061 Al matrices. Impact failure modes of B/Al are proposed in an attempt to describe the mechanisms involved and to provide insight for maximizing impact resistance. The impact strength of B/Al was significantly increased by proper selection of materials and processing. The use of a ductile matrix and large diameter boron fibers gave the highest impact strengths. This combination resulted in improved energy absorption through matrix shear deformation and multiple fiber breakage.

  9. Force decay of elastomeric chains - a mechanical design and product comparison study.

    Science.gov (United States)

    Balhoff, David A; Shuldberg, Matthew; Hagan, Joseph L; Ballard, Richard W; Armbruster, Paul C

    2011-03-01

    To evaluate the percentage force decay of elastomeric chain products utilizing three different design mechanisms simulating canine retraction; and to evaluate the percentage force decay of elastomeric chain products from four different companies. In vitro, laboratory study. LSUHSC Dental School, New Orleans, LA, USA. Closed (non-spaced), grey elastomeric chains from four companies were selected for the study. Three acrylic resin jigs were constructed to provide a framework for three simulated space closure mechanisms. The 6-5-3, the chain loop, and the 6-3 were the configuration mechanisms used in the study. An electronic force gauge was used to measure the percentage force decay associated with each elastomeric chain over 28 days at preselected times. There was a significant difference in the mean percentage force decay for the three different mechanisms (P mechanical design had the smallest mean percentage force decay. There was a significant difference in the mean percentage force decay for the different companies (P mechanisms, Ormco had the smallest percentage force decay while Unitek had the highest percentage force decay. The significant difference in the mean percentage force decay for the different mechanisms suggests that the 6-3 design is a more efficient means of closing extraction spaces utilizing elastomeric chains.

  10. The role of elastomeric pumps in postoperative analgesia in orthopaedics and factors affecting their flow rate.

    Science.gov (United States)

    Theodorides, Anthony Andreas

    2017-12-01

    Elastomeric pumps are mechanical devices composed of an elastomeric balloon reservoir into which the drug to be infused is stored, a protective casing (used by some manufacturers), a flow controller and a wound catheter. In orthopaedics they are used to provide continuous local infiltration analgesia. In this way patients rely less on other routes of analgesia and thus avoid their systemic side effects. Studies have shown good response to analgesia with these pumps for the first 24 hours but their benefit is not as clear at 48 and 72 hours. There are numerous factors that affect the flow rate of elastomeric pumps. Some are inherent to all elastomeric pumps such as: the pressure exerted by the elastomeric balloon, catheter size, the vertical height of the pump in relation to the wound, viscosity and partial filling. There are also other factors which vary according to the manufacturer such as: the optimal temperature to obtain the desired flow rate as this directly affects viscosity, the dialysate that the analgesic drug is mixed with (ie normal saline or 5% dextrose), and the storage conditions of the fluid to be infused. It is thus essential to follow the clinical guidelines provided by the manufacturer in order to obtain the desired flow rate. Copyright the Association for Perioperative Practice.

  11. Body composition using deuterated water, index of insulin resistance and cortisol levels in Costa Rican school in the metropolitan area

    International Nuclear Information System (INIS)

    Valverde Vindas, Allan Ignacio

    2014-01-01

    Body composition in the Costa Rican child population is evaluated and analyzed to determine the relationship with the index of insulin resistance and serum cortisol levels. 113 children in the metropolitan area were studied using deuterium isotope techniques as reference method for overweight and obesity. Morning cortisol levels were determined by immunoassay techniques (ELISA). The insulin resistance index of 113 Costa Rican boys and girls is obtained by the homeostatic method and the relationship between body composition with index of insulin resistance or levels of cortisol [es

  12. Wear Resistance of Sintered Composite Hardfacings under Different Abrasive Wear Conditions

    OpenAIRE

    SIMSON, Taavi; KULU, Priit; SURŽENKOV, Andrei; TARBE, Riho; GOLJANDIN, Dmitri; TARRASTE, Marek; VILJUS, Mart; TRAKSMAA, Rainer

    2017-01-01

    The article focuses on vacuum liquid phase sintered (PM) composite hardfacings and their behaviour under different abrasive wear conditions. Hardfacings studied contained 30 – 50 vol % fine, coarse or multimodal (fine and coarse) hardmetal reinforcement. For wear resistance studies, we used the Abrasive Rubber Wheel Wear (ARWW) test as a three-body abrasive wear test, the Abrasive Wheel Wear (AWW) test as a two-body abrasive wear test and the Abrasive-Impact Erosion wear (AIEW) test as an abr...

  13. Influence of Ultraviolet/Ozonolysis Treatment of Nanocarbon Filler on the Electrical Resistivity of Epoxy Composites

    Science.gov (United States)

    Perets, Yulia; Matzui, Lyudmila; Vovchenko, Lyudmila; Ovsiienko, Irina; Yakovenko, Olena; Lazarenko, Oleksandra; Zhuravkov, Alexander; Brusylovets, Oleksii

    2016-08-01

    In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.

  14. Effects of pulp capping materials on fracture resistance of Class II composite restorations

    OpenAIRE

    Kucukyilmaz, Ebru; Yasa, Bilal; Akcay, Merve; Savas, Selcuk; Kavrik, Fevzi

    2015-01-01

    Objective: The aim of this study was to investigate the effect of cavity design and the type of pulp capping materials on the fracture resistance of Class II composite restorations. Materials and Methods: Sixty freshly extracted, sound molar teeth were selected for the study. A dovetail cavity on the mesio-occlusal and a slot cavity on disto-occlusal surfaces of each tooth were prepared, and the teeth were divided 4 groups which one of them as a control group. The pulp capping materials (Ther...

  15. Insulin resistance, exercise capacity and body composition in subjects with two hypertensive parents

    DEFF Research Database (Denmark)

    Andersen, U B; Dige-Petersen, H; Ibsen, H

    1999-01-01

    OBJECTIVE: To study insulin resistance in subjects with strong genetic predisposition to essential hypertension, compared with non-disposed subjects. SUBJECTS: Thirty normotensive subjects aged 18-35 years whose parents both had essential hypertension, and 30 age- and sex matched subjects whose...... parents were both normotensive, were studied. Subjects or parents with diabetes and morbid obesity were excluded. METHODS: The study comprised (1) a frequent sampling oral glucose tolerance test; (2) an isoglycemic hyperinsulinemic clamp study; (3) an analysis of body composition by dual-energy X...

  16. Effect of angleplying and matrix enhancement on impact-resistant boron/aluminum composites

    Science.gov (United States)

    Mcdanels, D. L.; Signorelli, R. A.

    1976-01-01

    Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Tensile and dynamic modulus tests, thin sheet Charpy and Izod impact tests, and standard full size Charpy impact tests were conducted on 0.20 mm (8 mil) diameter-B/1100 Al matrix composites. Angleplies ranged from unidirectional to + or - 30 deg. The best compromise between reduced longitudinal properties and increased transverse properties was obtained with + or - 15 deg angleply. The pendulum impact strengths of improved B/Al were higher than that of notched titanium and appear to be enough to warrant consideration of B/Cl for application to fan blades in aircraft gas turbine engines.

  17. Assessment of Erosion Resistance of Coated Polymer Matrix Composites for Propulsion Applications

    Science.gov (United States)

    Miyoshi, Kazuhisa; Sutter, James K.; Horan, Richard A.; Naik, Subhash K.; Cupp, Randall J.

    2004-01-01

    The erosion behavior of tungsten carbide-cobalt (WC-Co) coated and uncoated polymer matrix composites (PMCs) was examined with solid particle impingement using air jets. Erosion tests were conducted with Arizona road dust impinging at 20 degrees, 60 degrees, and 90 degrees angles at a velocity of 229 meters per second at both 294 and 366 K. Noncontact optical profilometry was used to measure the wear volume loss. Results indicate that the WC-Co coating enhanced erosion resistance and reduced erosion wear volume loss by a factor of nearly 2. This should contribute to longer wear lives, reduced related breakdowns, decreased maintenance costs, and increased product reliability.

  18. Insulin resistance, exercise capacity and body composition in subjects with two hypertensive parents

    DEFF Research Database (Denmark)

    Andersen, U B; Dige-Petersen, H; Ibsen, H

    1999-01-01

    OBJECTIVE: To study insulin resistance in subjects with strong genetic predisposition to essential hypertension, compared with non-disposed subjects. SUBJECTS: Thirty normotensive subjects aged 18-35 years whose parents both had essential hypertension, and 30 age- and sex matched subjects whose...... parents were both normotensive, were studied. Subjects or parents with diabetes and morbid obesity were excluded. METHODS: The study comprised (1) a frequent sampling oral glucose tolerance test; (2) an isoglycemic hyperinsulinemic clamp study; (3) an analysis of body composition by dual-energy X......-ray absorptiometry; (4) an exercise test with gas exchange analysis; and (5) investigation of composition of usual diet by diet registration for 5 days. RESULTS: The 24-h diastolic blood pressure was higher in subjects predisposed to hypertension compared with the controls: 78.1 versus 74.0 mmHg (confidence interval...

  19. Examining of abrasion resistance of hybrid composites reinforced with SiC and Cgr particles

    Directory of Open Access Journals (Sweden)

    M. Łągiewka

    2008-08-01

    Full Text Available The presented work discusses the influence of the type and volume percentage of particulate reinforcement consisting of mixed silicon carbide and graphite on the abrasion wear of hybrid composites with AlMg10 matrix. Also the macro photos of frictional surfaces have been shown and the results of hardness measurements have been presented. The performed examinations have allowed for stating that the mixture of SiC and Cgr particles changes in favour the tribological properties of the matrix alloy. It has been also proved that introducing hard reinforcing particles along with soft lubricating ones allows for achieving the material exhibiting high abrasion resistance, and moreover, the graphite particles protect the abraded surface from the destructive action of silicon carbide particles. Also hardness measurements have been performed and the resulting conclusion is that the composite hardness increases with an increase in volume fraction of the reinforcing particles.

  20. Composition and adaptation of human myotendinous junction and neighboring muscle fibers to heavy resistance training

    DEFF Research Database (Denmark)

    Jakobsen, Johannes; Mackey, A L; Knudsen, A B

    2017-01-01

    The myotendinous junction (MTJ) is a common site of strain injury and yet understanding of its composition and ability to adapt to loading is poor. The main aims of this study were to determine the profile of selected collagens and macrophage density in human MTJ and adjoining muscle fibers......, and to investigate whether heavy exercise loading would alter this profile. Fifteen individuals scheduled for anterior cruciate ligament repair surgery were randomized into three groups: control, acute or 4 weeks heavy resistance training. MTJ samples were collected from the semitendinosus and gracilis muscles...... collagens were abundant at the MTJ and in muscle perimysium or endomysium. The endomysial content of collagen XIV, macrophages and Tenascin-C increased following 4 weeks of training. These findings illustrate the heterogeneity of collagen type composition of human MTJ. The increase in collagen XIV following...

  1. Radiation resistance of the carbon fiber reinforced composite material with PEEK as the matrix resin

    International Nuclear Information System (INIS)

    Sasuga, Tsuneo; Seguchi, Tadao; Sakai, Hideo; Nakakura, Toshiyuki; Masutani, Masahiro.

    1987-01-01

    In the fast breeder reactor etc. the structural materials are exposed to various environment, i.e., repeated high and low temperature, stress, etc. Irradiation effect (electron radiation) in the mechanical characteristic at low and high temperature has been studied in the PEEK-CF, polyarylether · ether · ketone - carbon fiber composite. Following are the results. (1) Radiation resistance of PEEK-CF is higher than that of PEEK-PES-CF, PEEK - polyethersulfone surface treated CF composite. In PEEK-PES-CF, PES is deteriorated by irradiation so the adhesive power lowers. (2) In the unirradiated PEEK-CF, its mechanical characteristic decreases beyond 140 deg C. With increase of the radiation dose, however, the characteristic rises. (3) Mechanical characteristic of PEEK-CF thus little drops by the heat treatment after the irradiation. (Mori, K.)

  2. Wear resistance analysis of the aluminum 7075 alloy and the nanostructured aluminum 7075 - silver nanoparticles composites

    Directory of Open Access Journals (Sweden)

    Estrada-Ruiz R.H.

    2016-01-01

    Full Text Available Nanostructured composites of the aluminum 7075 alloy and carbon-coated silver nanoparticles were synthetized by the mechanical milling technique using a high-energy mill SPEX 8000M; the powders generated were compacted, sintered and hot-extruded to produce 1 cm-diameter bars. The composites were then subjected to a wear test using a pin-on-disc device to validate the hypothesis that second phase-ductile nanometric particles homogenously distributed throughout the metalmatrix improve the wear resistance of the material. It was found that silver nanoparticles prevent the wear of the material by acting as an obstacle to dislocations movement during the plastic deformation of the contact surface, as well as a solid lubricant when these are separated from the metal-matrix.

  3. Resistance of composite and amalgam core foundations retained with and without pins and bonding agents.

    Science.gov (United States)

    Imbery, Terence A; Swigert, Ryan; Richman, Brian; Sawicki, Vincent; Pace, Lauren; Moon, Peter C

    2010-01-01

    To compare the resistance of different amalgam and composite core foundations retained by pins, bonding agents, or both, 100 molars were mounted in acrylic resin and their occlusal surfaces were reduced to expose dentin. Pins were inserted at the four line angles of the teeth and matrices were placed. Bonding agents were applied according to the manufacturers' instructions. Amalgam was handcondensed and composite was incrementally added and photocured. Restorations were adjusted to produce specimens (n = 10) 5 mm in height with a 1 mm bevel at the axial-occlusal surface. After immersion in deionized water for 24 hours, specimens were loaded at a 45 degree angle on their beveled surfaces in a Universal Testing Machine at a crosshead speed of 0.02 in./minute. ANOVA and Tukey's tests indicated that FluoroCore 2 (with or without pins) was statistically stronger than all other combinations (p < 0.05).

  4. A Numerical Analysis of the Resistance and Stiffness of the Timber and Concrete Composite Beam

    Directory of Open Access Journals (Sweden)

    Szumigała Ewa

    2015-03-01

    Full Text Available The article presents the results of a numerical analysis of the load capacity and stiffness of the composite timber and concrete beam. Timber and concrete structures are relatively new, they have not been thoroughly tested and they are rarely used because of technological constraints. One of the obstacles to using them is difficulty with finding a method which would allow successful cooperation between concrete and timber, which has been proposed by the authors of the present article. The modern idea of sustainable construction design requires the use of new more environmentally-friendly solutions. Wood as an ecological material is easily accessible, less energy-consuming, and under certain conditions more corrosion-resistant than steel. The analysis presented in the article showed that cooperation between a wooden beam and a concrete slab on profiled steel sheeting is possible. The analysed composite beam has a greater load capacity and stiffness than the wooden beam.

  5. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts

    OpenAIRE

    PANITIWAT, Prapaporn; SALIMEE, Prarom

    2017-01-01

    Abstract Objective This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC), MultiCore Flow (MCF), and LuxaCore Z-Dual (LCZ)), and a nanohybrid composite, (Tetric N-Ceram (TNC)). Material and Methods Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post) cemented with resin cement (Panavia F2...

  6. The Effects of Hygrothermal Aging on the Impact Penetration Resistance of Triaxially Braided Composites

    Science.gov (United States)

    Pereira, J. Michael; Revilock, Duane M.; Ruggeri, Charles R.; Roberts, Gary D.; Kohlman, Lee W.; Miller, Sandi G.

    2016-01-01

    An experimental study was conducted to measure the effects of long term hygrothermal aging on the impact penetration resistance of triaxially braided polymer composites. Flat panels of three different materials were subjected to repeated cycles of high and low temperature and high and low humidity for two years. Samples of the panels were periodically tested under impact loading during the two year time period. The purpose of the study was to identify and quantify any degradation in impact penetration resistance of these composites under cyclic temperature and humidity conditions experienced by materials in the fan section of commercial gas turbine engines for a representative aircraft flight cycle. The materials tested consisted of Toray ® T700S carbon fibers in a 2D triaxial braid with three different resins, Cycom® PR520, a toughened resin, Hercules® 3502, an untoughened resin and EPON 862, intermediate between the two. The fiber preforms consisted of a quasi-isotropic 0/+60/-60 braid with 24K tows in the axial direction and 12K tows in the bias directions. The composite panels were manufactured using a resin transfer molding process producing panels with a thickness of 0.125 inches. The materials were tested in their as-processed condition and again after one year and two years of aging (1.6 years in the case of E862). The aging process involved subjecting the test panels to two cycles per day of high and low temperature and high and low humidity. A temperature range of -60degF to 250degF and a humidity range of 0 to 85% rh was used to simulate extreme conditions for composite components in the fan section of a commercial gas turbine engine. Additional testing was conducted on the as-processed PR520 composite under cryogenic conditions. After aging there was some change in the failure pattern, but there was no reduction in impact penetration threshold for any of the three systems, and in the case of the 3502 system, a significant increase in penetration

  7. Highly improved Uv resistance and composite interfacial properties of aramid fiber via iron (III) coordination

    Science.gov (United States)

    Cheng, Zheng; Hong, Dawei; Dai, Yu; Jiang, Chan; Meng, Chenbo; Luo, Longbo; Liu, Xiangyang

    2018-03-01

    The poor Uv stability and weak interfacial adhesion are considered as the bottleneck problems for further application of aramid fiber. Herein, a new strategy, Fe3+ coordination, was reported for aramid fiber to simultaneous improve its Uv resistance and composite interfacial shear strength. Fe3+ was introduced onto aramid fiber by coordinating with benzimidazole unit of fiber structure. It can reach a doping capacity of as high as 1516ug/g fiber, and the fiber surface is saturatedly covered with Fe3+. The chemical structure of Fe3+-benzimidazole brings about strong metal-enhanced fluorescence emission effect, which, in turn, greatly raises its Uv stability. Owing to the Fe3+ coordination, the tensile strength of Fe-coordinated fiber could preserve as high as 96% after Uv irradiation, compared with 73% of untreated fiber. Meanwhile, the introduction of Fe3+ improves the surface polarity of aramid fiber and consequently leads to the increase of the composite interfacial shear strength by 39%. It is believed that the Fe-coordinated fiber integrates the advantages of easy production, cost-effective and increased Uv stability, as well as high composite interfacial adhesion, and can be used as promising enhancement for the advanced composite material in harsh environment.

  8. Wear resistance of laser-deposited boride reinforced Ti-Nb-Zr-Ta alloy composites for orthopedic implants

    International Nuclear Information System (INIS)

    Samuel, Sonia; Nag, Soumya; Scharf, Thomas W.; Banerjee, Rajarshi

    2008-01-01

    The inherently poor wear resistance of titanium alloys limits their application as femoral heads in femoral (hip) implants. Reinforcing the soft matrix of titanium alloys (including new generation β-Ti alloys) with hard ceramic precipitates such as borides offers the possibility of substantially enhancing the wear resistance of these composites. The present study discusses the microstructure and wear resistance of laser-deposited boride reinforced composites based on Ti-Nb-Zr-Ta alloys. These composites have been deposited using the LENS TM process from a blend of elemental Ti, Nb, Zr, Ta, and boron powders and consist of complex borides dispersed in a matrix of β-Ti. The wear resistance of these composites has been compared with that of Ti-6Al-4V ELI, the current material of choice for orthopedic femoral implants, against two types of counterfaces, hard Si 3 N 4 and softer SS440C stainless steel. Results suggest a substantial improvement in the wear resistance of the boride reinforced Ti-Nb-Zr-Ta alloys as compared with Ti-6Al-4V ELI against the softer counterface of SS440. The presence of an oxide layer on the surface of these alloys and composites also appears to have a substantial effect in terms of enhanced wear resistance

  9. In Situ Synthesis of Reduced Graphene Oxide-Reinforced Silicone-Acrylate Resin Composite Films Applied in Erosion Resistance

    Directory of Open Access Journals (Sweden)

    Yang Cao

    2015-01-01

    Full Text Available The reduced graphene oxide reinforced silicone-acrylate resin composite films (rGO/SAR composite films were prepared by in situ synthesis method. The structure of rGO/SAR composite films was characterized by Raman spectrum, atomic force microscope, scanning electron microscopy, and thermogravimetric analyzer. The results showed that the rGO were uniformly dispersed in silicone-acrylate resin matrix. Furthermore, the effect of rGO loading on mechanical properties of composite films was investigated by bulge test. A significant enhancement (ca. 290% and 320% in Young’s modulus and yield stress was obtained by adding the rGO to silicone-acrylate resin. At the same time, the adhesive energy between the composite films and metal substrate was also improved to be about 200%. Moreover, the erosion resistance of the composite films was also investigated as function of rGO loading. The rGO had great effect on the erosion resistance of the composite films, in which the Rcorr (ca. 0.8 mm/year of composite film was far lower than that (28.7 mm/year of pure silicone-acrylate resin film. Thus, this approach provides a novel route to investigate mechanical stability of polymer composite films and improve erosion resistance of polymer coating, which are very important to be used in mechanical-corrosion coupling environments.

  10. Study on dry friction and wear resistance of a WC-Co particle reinforced iron matrix composite material

    Directory of Open Access Journals (Sweden)

    Zhang Peng

    2013-05-01

    Full Text Available In order to select a suitable material for the rolling mill guide application, the dry sliding friction and wear resistance of a tungsten carbide combining cobalt (WC-Co particle reinforced chromium cast iron composite material were studied. In particular, the wear resistance was discussed in detail. The results showed that the composite material demonstrates 25 times the wear resistance of high Cr cast iron, and 9 times the wear resistance of heat resistant steel. However, the average friction factor in the stable friction stage showed a relationship of μComposites/45 # steel > μHigh chromium cast iron/45 # steel > μHeat resistant steel/45 # steel. The wear resistance mechanism of the composite material was associated with the reinforcing particles, which protruded from the worn surface to bear the friction load when the matrix material surface was worn, thereby reducing the abrasive and adhesive wear. In addition, the matrix material possessed suitable hardness and toughness, providing a support to the reinforcements.

  11. The inaccuracy of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional composite walls

    International Nuclear Information System (INIS)

    Wong, K.-L.; Hsien, T.-L.; Hsiao, M.-C.; Chen, W.-L.; Lin, K.-C.

    2008-01-01

    This investigation is to show that two-dimensional steady state heat transfer problems of composite walls should not be solved by the conventionally one-dimensional parallel thermal resistance circuits (PTRC) model because the interface temperatures are not unique. Thus PTRC model cannot be used like its conventional recognized analogy, parallel electrical resistance circuits (PERC) model which has the unique node electric voltage. Two typical composite wall examples, solved by CFD software, are used to demonstrate the incorrectness. The numerical results are compared with those obtained by PTRC model, and very large differences are observed between their results. This proves that the application of conventional heat transfer PTRC model to two-dimensional composite walls, introduced in most heat transfer text book, is totally incorrect. An alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to the two-dimensional composite walls with isothermal boundaries. Results with acceptable accuracy can be obtained by the new model

  12. Incorrectness of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional circular composite pipes

    International Nuclear Information System (INIS)

    Wong, K.-L.; Hsien, T.-L.; Chen, W.-L.; Yu, S.-J.

    2008-01-01

    This study is to prove that two-dimensional steady state heat transfer problems of composite circular pipes cannot be appropriately solved by the conventional one-dimensional parallel thermal resistance circuits (PTRC) model because its interface temperatures are not unique. Thus, the PTRC model is definitely different from its conventional recognized analogy, parallel electrical resistance circuits (PERC) model, which has unique node electric voltages. Two typical composite circular pipe examples are solved by CFD software, and the numerical results are compared with those obtained by the PTRC model. This shows that the PTRC model generates large error. Thus, this conventional model, introduced in most heat transfer text books, cannot be applied to two-dimensional composite circular pipes. On the contrary, an alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to a two-dimensional composite circular pipe with isothermal boundaries, and acceptable results are returned

  13. Cotton fabric with plasma pretreatment and ZnO/Carboxymethyl chitosan composite finishing for durable UV resistance and antibacterial property.

    Science.gov (United States)

    Wang, Chunxia; Lv, Jingchun; Ren, Yu; Zhou, Qingqing; Chen, Jiayi; Zhi, Tian; Lu, Zhenqian; Gao, Dawei; Ma, Zhipeng; Jin, Limin

    2016-03-15

    ZnO/carboxymethyl chitosan (ZnO/CMCS) composite was prepared and confirmed by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Ultraviolet-visible (UV-vis) spectroscopy, Scanning electron microscope (SEM), Transmission electron microscope (TEM). The combination of plasma pretreatment and ZnO/CMCS composite finishing was applied to provide durable UV resistance and antibacterial activity for cotton fabric. Cotton fabric was pretreated by cold oxygen plasma and the ZnO/CMCS composite finishing was carried out by pad-dry-cure. Cotton fabric was characterized by SEM, FTIR, UV resistance, antibacterial activity and Thermogravimetry (TG). SEM and FTIR analysis demonstrated the presence of ZnO/CMCS composite on cotton fabric and the increasing loading efficiency of ZnO/CMCS composite owing to plasma treatment. UV resistance and antibacterial activity of the finished cotton fabric were greatly improved, which increased with the increasing concentration of ZnO/CMCS composite. TG analysis indicated that the combined finishing of cotton fabric with plasma pretreatment and ZnO/CMCS composite could improve its thermal property. The finished cotton fabric exhibited an excellent laundering durability in UV resistance and antibacterial activity. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Spatio-Temporal Variation in Landscape Composition May Speed Resistance Evolution of Pests to Bt Crops.

    Directory of Open Access Journals (Sweden)

    Anthony R Ives

    Full Text Available Transgenic crops that express insecticide genes from Bacillus thuringiensis (Bt are used worldwide against moth and beetle pests. Because these engineered plants can kill over 95% of susceptible larvae, they can rapidly select for resistance. Here, we use a model for a pyramid two-toxin Bt crop to explore the consequences of spatio-temporal variation in the area of Bt crop and non-Bt refuge habitat. We show that variability over time in the proportion of suitable non-Bt breeding habitat, Q, or in the total area of Bt and suitable non-Bt habitat, K, can increase the overall rate of resistance evolution by causing short-term surges of intense selection. These surges can be exacerbated when temporal variation in Q and/or K cause high larval densities in refuges that increase density-dependent mortality; this will give resistant larvae in Bt fields a relative advantage over susceptible larvae that largely depend on refuges. We address the effects of spatio-temporal variation in a management setting for two bollworm pests of cotton, Helicoverpa armigera and H. punctigera, and field data on landscape crop distributions from Australia. Even a small proportion of Bt fields available to egg-laying females when refuges are sparse may result in high exposure to Bt for just a single generation per year and cause a surge in selection. Therefore, rapid resistance evolution can occur when Bt crops are rare rather than common in the landscape. These results highlight the need to understand spatio-temporal fluctuations in the landscape composition of Bt crops and non-Bt habitats in order to design effective resistance management strategies.

  15. Resistance of Phosphogypsum Cement Pozzolanic Compositions against the Influence of Water

    Directory of Open Access Journals (Sweden)

    Sergejus GAIDUČIS

    2011-09-01

    Full Text Available The reprocessing of freshly removed extractive hemihydrate phosphogypsum into hydraulic composite phosphogypsum cement pozzolana (PGCP binder using mechanical activation is analyzed in this work. In order to increase the effectiveness of the dealing with phosphogypsum reprocessing problem and to lower the energy consumption required for the production of binding materials from phosphogypsum, physical mechanical and water resistance properties of the PGCP binder with less amount (10 % of cement (PGCP(10 were analyzed and compared with the properties of conventional PGCP binder, where the amount of cement is 20 % (PGCP(20. The PGCP binder with pozzolana additives of two types - carbonate opoka and microsilica are analysed. Fresh wet hemihydrate phosphogypsum, cement and pozzolana additive were mechanically activated together and from resulting mixture the samples were formed by vibrating. Compressive strength of PGCP(10 samples after 28 days was 26 MPa - 29 MPa, after 4 months - 30 MPa - 32 MPa, PGCP(20 - 32 MPa - 35 MPa and 36 MPa - 42 MPa accordingly. It is found, that hardened PGCP(10 are also quite resistant to short-term (2 days impact of water (softening coefficient was 0.91 - 0.94, however, its resistance to long-term impact of water is significantly less than PGCP(20. PGCP with microsilica is more strength and more resistant to impact of water than PGCP with opoka. Both, PGCP with opoka, as well as the ones with microsilica, are resistant to the formation of ettringite. However, the primary ettringite and high amount of carbonates, found in the PGCP with opoka, stimulates the formation of thaumasite at low positive temperature and humidity.http://dx.doi.org/10.5755/j01.ms.17.3.599

  16. TiO2-TiO2 composite resistive humidity sensor: ethanol crosssensitivity

    International Nuclear Information System (INIS)

    Ghalamboran, Milad; Saedi, Yasin

    2016-01-01

    The fabrication method and characterization results of a TiO 2 -TiO 2 composite bead used for humidity sensing along with its negative cross-sensitivity to ethanol vapor are reported. The bead shaped resistive sample sensors are fabricated by the drop-casting of a TiO 2 slurry on two Pt wire segments. The dried bead is pre-fired at 750°C and subsequently impregnated with a Ti-based sol. The sample is ready for characterization after a thermal annealing at 600°C in air. Structurally, the bead is a composite of the micron-sized TiO 2 crystallites embedded in a matrix of nanometric TiO 2 particle aggregates. The performance of the beads as resistive humidity sensors is recorded at room temperature in standard humidity level chambers. Results evince the wide dynamic range of the sensors fabricated in the low relative humidity range. While the sensor conductance is not sensitive to ethanol vapor in dry air, in humid air, sensor's responses are negatively affected by the contaminant. (paper)

  17. Resistivity and low-frequency noise characteristics of epoxy-carbon composites

    Science.gov (United States)

    PralgauskaitÄ--, Sandra; Matukas, Jonas; Tretjak, Marina; Macutkevic, Jan; Banys, Juras; Selskis, Algirdas; Cataldo, Antonino; Micciulla, Federico; Bellucci, Stefano; Fierro, Vanessa; Celzard, Alain

    2017-03-01

    Noise and electrical transport properties of composites based on epoxy resin filled with various carbon inclusions (single-walled carbon nanotubes, high surface area carbon black, and exfoliated graphite) were investigated in depth. The temperature dependence of resistivity shows that Mott's hopping and tunneling between conductive carbon particles dominate the charge carrier transport at low temperature, whereas a positive temperature coefficient effect occurs at higher temperature. Low-frequency noise spectra of the investigated materials comprise 1/fα type components. The noise level is the highest for composites close to the percolation threshold. The percolation threshold value of the system also strongly impacts both the temperature dependence of the noise level and the resistivity. Close to the percolation threshold, the noise level increases due to the carrier tunneling throughout the polymer matrix and decreases due to the rapid expansion of the polymer matrix. In contrast, the latter has almost no influence on the noise level far above the percolation threshold, and the small kink in the temperature dependence of the noise level indicates a crossover between tunneling and thermally activated electron transport mechanisms.

  18. Muscle function and body composition profile in adolescents with restrictive anorexia nervosa: does resistance training help?

    Science.gov (United States)

    Fernández-del-Valle, Maria; Larumbe-Zabala, Eneko; Morande-Lavin, Gonzalo; Perez Ruiz, Margarita

    2016-01-01

    The aim of this study was to analyze the effects of short-term resistance training on the body composition profile and muscle function in a group of Anorexia Nervosa restricting type (AN-R) patients. The sample consisted of AN-R female adolescents (12.8 ± 0.6 years) allocated into the control and intervention groups (n = 18 each). Body composition and relative strength were assessed at baseline, after 8 weeks and 4 weeks following the intervention. Body mass index (BMI) increased throughout the study (p = 0.011). Significant skeletal muscle mass (SMM) gains were found in the intervention group (p = 0.045, d = 0.6) that correlated to the change in BMI (r = 0.51, p  0.60) with change in BMI in both the groups. Significant relative strength increases (p Anorexia Nervosa Restricting Type (AN-R) AN-R is a psychiatric disorder that has a major impact on muscle mass content and function. However, little or no attention has been paid to muscle recovery. High intensity resistance training is safe for AN-R after hospitalization and enhances the force generating capacity as well as muscle mass gains. Skeletal muscle mass content and muscular function improvements are partially maintained for a short period of time when the exercise program ceases.

  19. Non-Magnetic, Tough, Corrosion- and Wear-Resistant Knives From Bulk Metallic Glasses and Composites

    Science.gov (United States)

    Hoffman, Douglas C.; Potter, Benjamin

    2013-01-01

    Quality knives are typically fabricated from high-strength steel alloys. Depending on the application, there are different requirements for mechanical and physical properties that cause problems for steel alloys. For example, diver's knives are generally used in salt water, which causes rust in steel knives. Titanium diver's knives are a popular alternative due to their salt water corrosion resistance, but are too soft to maintain a sharp cutting edge. Steel knives are also magnetic, which is undesirable for military applications where the knives are used as a tactical tool for diffusing magnetic mines. Steel is also significantly denser than titanium (8 g/cu cm vs. 4.5 g/cu cm), which results in heavier knives for the same size. Steel is hard and wear-resistant, compared with titanium, and can keep a sharp edge during service. A major drawback of both steel and titanium knives is that they must be ground or machined into the final knife shape from a billet. Since most knives have a mirrored surface and a complex shape, manufacturing them is complex. It would be more desirable if the knife could be cast into a net or near-net shape in a single step. The solution to the deficiencies of titanium, steel, and ceramic knives is to fabricate them using bulk metallic glasses (or composites). These alloys can be cast into net or near-net shaped knives with a combination of properties that exceed both titanium and steel. A commercially viable BMG (bulk metallic glass) or composite knife is one that exhibits one or all of the following properties: It is based on titanium, has a self-sharpening edge, can retain an edge during service, is hard, is non-magnetic, is corrosion-resistant against a variety of corrosive environments, is tough (to allow for prying), can be cast into a net-shape with a mirror finish and a complex shape, has excellent wear resistance, and is low-density. These properties can be achieved in BMG and composites through alloy chemistry and processing. For

  20. Adequate plasma drug concentrations suggest that amoxicillin can be administered by continuous infusion using elastomeric pumps.

    Science.gov (United States)

    Arensdorff, Lyne; Boillat-Blanco, Noémie; Decosterd, Laurent; Buclin, Thierry; de Vallière, Serge

    2017-09-01

    Elastomeric pumps can be useful for the administration of antibiotics in the outpatient setting. To determine amoxicillin degradation in elastomeric pumps, as well as the effectiveness of amoxicillin treatment administered by elastomeric pumps. Antibiotic degradation was measured in elastomeric pumps filled with 6 g of amoxicillin in 240 mL of NaCl 0.9% by drawing samples at 12 h intervals when stored in the fridge for 48 h and when worn around the waist for 24 h. Subsequently nine patients were treated with continuous infusions of 8 or 12 g of amoxicillin per day. Plasma amoxicillin concentrations were measured on each visit to the outpatient parenteral antibiotic therapy unit. Clinical outcome was verified 3 months after the end of treatment. Amoxicillin degradation in elastomeric pumps reached 10% after 48 h in the fridge and an additional 30% when worn around the waist for 24 h. Mean plasma drug concentrations achieved with 12 g of amoxicillin per day were 18.5 mg/L (95% CI 13.5-23.5), which is largely above the MIC of amoxicillin-susceptible bacteria. Nine patients treated for various complicated infections were cured and had no unexpected adverse effects. Adequate plasma drug concentrations and favourable clinical outcomes suggest that amoxicillin can be administered by continuous infusion using elastomeric pumps. This treatment modality does not fulfil formal requirements regarding pharmaceutical stability, but the resulting safety impact in patients is probably limited. Therapeutic drug monitoring and a close clinical follow-up are recommended if this route of administration is chosen. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  1. Effect of Different Liners on Fracture Resistance of Premolars Restored with Conventional and Short Fiber-Reinforced Composite Resins.

    Science.gov (United States)

    Shafiei, Fereshteh; Doozandeh, Maryam; Ghaffaripour, Dordaneh

    2018-01-11

    To see whether applying four different liners under short fiber-reinforced composite (SFRC), everX Posterior, compared to conventional composite resin, Z250, affected their strengthening property in premolar MOD cavities. Mesio-occluso-distal (MOD) cavities were prepared in 120 sound maxillary premolars divided into 10 groups (n = 12) in terms of two composite resin types and 4 liners or no liner. For each composite resin, in 5 groups no liner, resin-modified glass ionomer (RMGI), conventional flowable composite (COFL), self-adhesive flowable composite resin (SAFL), and self-adhesive resin cement (SARC) were applied prior to restoring incrementally. After water storage and thermocycling, static fracture resistance was tested. Data (in Newtons) were analyzed using two-way ANOVA (α = 0.05). Fracture resistance was significantly affected by composite resin type (p = 0.02), but not by the liner (p > 0.05). The interaction of the two factors was not statistically significant (p > 0.05). SFRC exhibited higher fracture strength (1470 ± 200 N) compared to conventional composite resin (1350 ± 290), irrespective of the application of liners. Application of SARC and SAFL liners led to a higher number of restorable fractures for both composite resins. The four liners can be used without interfering with the higher efficacy of SFRC, compared to conventional composite resins, to improve the fracture strength of premolar MOD cavities. © 2018 by the American College of Prosthodontists.

  2. Effect of protein source and resistance training on body composition and sex hormones

    Directory of Open Access Journals (Sweden)

    Krieger Diane R

    2007-07-01

    Full Text Available Abstract Background Evidence suggests an inverse relationship between soy protein intake and serum concentrations of male sex hormones. Anecdotal evidence indicates that these alterations in serum sex hormones may attenuate changes in lean body mass following resistance training. However, little empirical data exists regarding the effects of soy and milk-based proteins on circulating androgens and exercise induced body composition changes. Methods For 12 weeks 20 subjects were supplemented with 50 g per day of one of four different protein sources (Soy concentrate; Soy isolate; Soy isolate and whey blend, and Whey blend only in combination with a resistance-training program. Body composition, testosterone, estradiol and sex hormone binding globulin (SHBG were measured at baseline and week 12. Results Protein supplementation resulted in a significant increase in lean body mass independent of protein source (0.5 ± 1.1 and 0.9 ± 1.4 kg, p = 0.006, p = 0.007. No significant differences were observed between groups for total and free testosterone, SHBG, percentage body fat, BMI or body weight. The Testosterone/Estradiol ratio increased across all groups (+13.4, p = 0.005 and estradiol decreased (p = 0.002. Within group analysis showed significant increases in the Testosterone/Estradiol ratio in soy isolate + whey blend group (+16.3, p = 0.030. Estradiol was significantly lower in the whey blend group (-9.1 ± 8.7 pg/ml, p = 0.033. Conclusion This investigation shows that 12 week supplementation with soy protein does not decrease serum testosterone or inhibit lean body mass changes in subjects engaged in a resistance exercise program.

  3. Leptin, visfatin, insulin resistance, and body composition change in chronic obstructive pulmonary disease.

    Science.gov (United States)

    Eker, Suzan; Ayaz, Lokman; Tamer, Lulufer; Ulubas, Bahar

    2010-02-01

    The aim of the study was to compare endocrine parameters such as leptin, visfatin, insulin resistance, exercise capacity and body composition change, the pulmonary functions test (PFT) and arterial blood gases (ABG) parameters of chronic obstructive pulmonary disease (COPD) patients and in healthy controls. Fifty-five patients with COPD and without malnutrition and 25 healthy controls were included in our study. The serum leptin, visfatin, tumor necrosis factor alpha (TNF-alpha) and insulin resistance, body fat-free mass (FFM) and fat mass (FM) were measured in the groups. Additionally, body mass index (BMI) was calculated and the 6-minute walk test (6MWT), PFT and ABG analyses were performed in all of the cases. No difference in BMI between the COPD group and controls was determined. Serum leptin and visfatin levels, FFM and 6MWT distance were significantly lower in the patients with COPD (p leptin levels and BMI (r = 0.333, p = 0.027), and with FM (r = 0.365, p = 0.029). Serum visfatin level was correlated with the percentage of forced expiratory volume in the first second in the patients with COPD (r = 0.371, p = 0.013). HOMA-IR (Homeostasis model assessment of insulin resistance) and serum TNF-alpha levels in the patients with COPD were found to be significantly higher than controls (p = 0.001, p COPD. Evaluating the patients not only with the pulmonary function and also systemically, contributes to minimizing the mortality and morbidity.

  4. Rhodium and Hafnium Influence on the Microstructure, Phase Composition, and Oxidation Resistance of Aluminide Coatings

    Directory of Open Access Journals (Sweden)

    Maryana Zagula-Yavorska

    2017-12-01

    Full Text Available A 0.5 μm thick layer of rhodium was deposited on the CMSX 4 superalloy by the electroplating method. The rhodium-coated superalloy was hafnized and aluminized or only aluminized using the Chemical vapour deposition method. A comparison was made of the microstructure, phase composition, and oxidation resistance of three aluminide coatings: nonmodified (a, rhodium-modified (b, and rhodium- and hafnium-modified (c. All three coatings consisted of two layers: the additive layer and the interdiffusion layer. Rhodium-doped (rhodium- and hafnium-doped β-NiAl phase was found in the additive layer of the rhodium-modified (rhodium- and hafnium-modified aluminide coating. Topologically Closed-Pack (μ and σ phases precipitated in the matrix of the interdiffusion layer. Rhodium also dissolved in the β-NiAl phase between the additive and interdiffusion layers, whereas Hf-rich particles precipitated in the (Ni,RhAl phase at the additive/interdiffusion layer interface in the rhodium- and hafnium-modified coating (c. The rhodium-modified aluminide coating (b has better oxidation resistance than the nonmodified one (a, whereas the rhodium- and hafnium-modified aluminide coating (c has better oxidation resistance than the rhodium-modified (b and nonmodified (a ones.

  5. Effect of combined aerobic and resistance training in body composition of obese postmenopausal women

    Directory of Open Access Journals (Sweden)

    Fabrício E. Rossi

    2015-03-01

    Full Text Available The aim of this study was to investigate the effects of a 16-week program of combined aerobic and resistance training on the body composition of postmenopausal women who are obese. The participants were divided into two groups: training group (TG, n = 37 and non-trained control group (CG, n = 18. The trunk fat, fat mass, percentage of fat mass and fat-free mass were estimated using DXA. Three nonconsecutive 24-hour dietary recalls were conducted. The training protocol consisted of 50 minutes of resistance training followed by 30 minutes of aerobic training. After the 16-week training program, differences were observed in trunk fat (CG= 0.064 x TG= -0.571 Kg; p-value = .020, fat mass (CG= -0.088 x TG= -1.037 Kg; p-value = .020 and fat-free mass (CG= -0.388 x TG= 1.049 Kg; p = .001. Therefore, a 16-week program of systematic combined aerobic and resistance training in obese postmenopausal women was effective in improving fat-free mass and decreasing both whole and abdominal adiposity.

  6. Mutations in PMR5 result in powdery mildew resistance and altered cell wall composition.

    Science.gov (United States)

    Vogel, John P; Raab, Theodore K; Somerville, Chris R; Somerville, Shauna C

    2004-12-01

    Powdery mildews and other obligate biotrophic pathogens are highly adapted to their hosts and often show limited host ranges. One facet of such host specialization is likely to be penetration of the host cell wall, a major barrier to infection. A mutation in the pmr5 gene rendered Arabidopsis resistant to the powdery mildew species Erysiphe cichoracearum and Erysiphe orontii, but not to the unrelated pathogens Pseudomonas syringae or Peronospora parasitica. PMR5 belongs to a large family of plant-specific genes of unknown function. pmr5-mediated resistance did not require signaling through either the salicylic acid or jasmonic acid/ethylene defense pathways, suggesting resistance in this mutant may be due either to the loss of a susceptibility factor or to the activation of a novel form of defense. Based on Fourier transform infrared analysis, the pmr5 cell walls were enriched in pectin and exhibited a reduced degree of pectin modification relative to wild-type cell walls. In addition, the mutant had smaller cells, suggesting a defect in cell expansion. A double mutant with pmr6 (defective in a glycosylphosphatidylinositol-anchored pectate lyase-like gene) exhibited a strong increase in total uronic acid content and a more severe reduction in size, relative to the single mutants, suggesting that the two genes affect pectin composition, either directly or indirectly, via different mechanisms. These two mutants highlight the importance of the host cell wall in plant-microbe interactions.

  7. Effect of storage period on the accuracy of elastomeric impressions

    Directory of Open Access Journals (Sweden)

    Eduardo Batista Franco

    2007-06-01

    Full Text Available AIMS: To investigate the effect of the storage period on the accuracy of recently developed elastomeric materials. METHODS: Simultaneous impressions of a steel die were taken using a polyether (I: Impregum Soft Heavy and Light body, 3M ESPE and vinyl polysiloxane (P: Perfectim Blue Velvet and Flexi-Velvet, J.Morita. The trays were loaded with the heavy-bodied impression materials while the light-bodied impression materials were simultaneously spread on the steel die. The impressions were poured after 2 hours, 24 hours, and 7 days. Impressions were stored at approximately 55% relative humidity and room temperature. Ten replicas were produced for each experimental condition (n=60. Accuracy of the stone dies was assessed with a depth-measuring microscope. The difference in height between the surface of the stone die and a standard metallic ring was recorded in micrometers at four demarcated points, by two independent examiners. Data were submitted to two-way ANOVA and Tukey test (a = 0.05. RESULTS: Significant differences were found among the groups. Smaller discrepancies were observed when pouring was performed up to 24 hours (I-2h= 65.0 ± 15.68 µm; I-24h= 81.6 ± 11.13 µm for the polyether, and up to 7 days for the vinyl polysiloxane (P-2h= 79.1 ± 13.82 µm; P-24h= 96.8 ± 6.02 µm; P-7d= 81.4 ± 4.3 µm. Significant dimensional discrepancies, however, were observed when polyether was stored for 7 days (I-7d= 295.3 ± 17.4 µm. CONCLUSION: Storage may significantly affect the dimensional accuracy of impressions and, thus, a maximum period and storage condition should be specified for the recently developed materials.

  8. Baxter elastomeric pumps: Weighing as an alternative to visual inspection.

    Science.gov (United States)

    Cusano, Ellen L; Ali, Raafi; Sawyer, Michael B; Chambers, Carole R; Tang, Patricia A

    2018-04-01

    Purpose Elastomeric pumps are used to administer 46-hour infusions of 5-fluorouracil (5FU). Baxter suggests patients visually monitor their pumps to ensure that infusions are proceeding correctly. This can be confusing and lead to concerns about under- or over-dosing. Baxter has not considered weighing pumps as a validated method for monitoring. This study aims to validate weighing as a more accurate method for patients and healthcare professionals, and describe real life Baxter Infusor™ variability. Methods Patients who had been started on a 46-hour 5FU infusion returned to the clinic approximately 24 h after starting treatment. The pump was weighed on a StarFrit kitchen scale, and date, time, and weights recorded. Patients were asked if they had a preference for weighing or visually inspecting their pump. Results Pumps ( n = 103) were weighed between 17.25 and 27.5 h after connection. The average weight of a pump was 189 g. Of 103 pumps weighed, 99 weighed less than expected, corresponding to average flow rates of 5.69 mL/h over the elapsed time. The expected flow rate is 5 mL/h with 10% variability. Average flow rates within the 17.25- to 27.5-hour window were 4.561 mL/h, which is 8.78% slower than expected, but within the 10% known variability. Forty-seven percent of patients didn't have a preference for either method, but for those who did have a preference, more than twice as many preferred weighing. Conclusion With proper education, weighing Baxter Infusors at home with kitchen scales can be an accepted and objective alternative to the current recommendation of visual inspection.

  9. Are linear elastic material properties relevant predictors of the cyclic fatigue resistance of dental resin composites?

    Science.gov (United States)

    Belli, Renan; Petschelt, Anselm; Lohbauer, Ulrich

    2014-04-01

    The aim of this study was to measure the linear elastic material properties of direct dental resin composites and correlate them with their fatigue strength under cyclic loading. Bar specimens of twelve resin composites were produced according to ISO 4049 and tested for elastic modulus (Emod) in 3-point bending (n=10), flexural strength (FS) (n=15) and single-edge-notch-beam fracture toughness (FT) (n=15), both in 4-point bending. Using the same specimen geometry, the flexural fatigue strength (FFS) was determined using the staircase approach after 10(4) cycles at 0.5 Hz in 4-point bending (n=25). The observation of the fracture surface and fracture profiles was conducted using a scanning electron microscope in order to evaluate the respective fracture mechanisms according to the two different loading conditions. Materials were ranked differently according to the tested parameters. Only weak correlations were found between any of the initial properties and FFS or strength loss. The best correlation to FFS was found to be the Emod (r(2)=0.679), although only slightly. Crack path in both loading conditions was mainly interparticle, with the crack propagating mainly within the matrix phase for fatigued specimens and eventually through the filler/matrix interface for statically loaded specimens. Fracture of large particles or prepolymerized fillers was only observed in specimens of FS and FT. Initial properties were better associated with microstructural features, whereas the fatigue resistance showed to be more dependent on aspects relating to the matrix phase. Our results show that linear elastic properties such as elastic modulus, flexural strength and fracture toughness are not good descriptors of the fatigue resistance of dental resin composite under cyclic bending, and may therefore have limited clinical relevance. Copyright © 2014 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  10. Fracture Resistance of Endodontically Treated Teeth Restored with 2 Different Fiber-reinforced Composite and 2 Conventional Composite Resin Core Buildup Materials: An In Vitro Study.

    Science.gov (United States)

    Eapen, Ashly Mary; Amirtharaj, L Vijay; Sanjeev, Kavitha; Mahalaxmi, Sekar

    2017-09-01

    The purpose of this in vitro study was to comparatively evaluate the fracture resistance of endodontically treated teeth restored with 2 fiber-reinforced composite resins and 2 conventional composite resin core buildup materials. Sixty noncarious unrestored human maxillary premolars were collected, endodontically treated (except group 1, negative control), and randomly divided into 5 groups (n = 10). Group 2 was the positive control. The remaining 40 prepared teeth were restored with various direct core buildup materials as follows: group 3 teeth were restored with dual-cure composite resin, group 4 with posterior composite resin, group 5 with fiber-reinforced composite resin, and group 6 with short fiber-reinforced composite resin. Fracture strength testing was performed using a universal testing machine. The results were statistically analyzed by 1-way analysis of variance and the post hoc Tukey test. Fracture patterns for each sample were also examined under a light microscope to determine the level of fractures. The mean fracture resistance values (in newtons) were obtained as group 1 > group 6 > group 4 > group 3 > group 5 > group 2. Group 6 showed the highest mean fracture resistance value, which was significantly higher than the other experimental groups, and all the fractures occurred at the level of enamel. Within the limitations of this study, a short fiber-reinforced composite can be used as a direct core buildup material that can effectively resist heavy occlusal forces against fracture and may reinforce the remaining tooth structure in endodontically treated teeth. Copyright © 2017 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  11. Renewable and superior thermal-resistant cellulose-based composite nonwoven as lithium-ion battery separator.

    Science.gov (United States)

    Zhang, Jianjun; Liu, Zhihong; Kong, Qingshan; Zhang, Chuanjian; Pang, Shuping; Yue, Liping; Wang, Xuejiang; Yao, Jianhua; Cui, Guanglei

    2013-01-01

    A renewable and superior thermal-resistant cellulose-based composite nonwoven was explored as lithium-ion battery separator via an electrospinning technique followed by a dip-coating process. It was demonstrated that such nanofibrous composite nonwoven possessed good electrolyte wettability, excellent heat tolerance, and high ionic conductivity. The cells using the composite separator displayed better rate capability and enhanced capacity retention, when compared to those of commercialized polypropylene separator under the same conditions. These fascinating characteristics would endow this renewable composite nonwoven a promising separator for high-power lithium-ion battery.

  12. Effect of the fatty acid composition of acclimated oenological Lactobacillus plantarum on the resistance to ethanol.

    Science.gov (United States)

    Bravo-Ferrada, B M; Gómez-Zavaglia, A; Semorile, L; Tymczyszyn, E E

    2015-02-01

    The aim of this work was to evaluate the changes due to acclimation to ethanol on the fatty acid composition of three oenological Lactobacillus plantarum strains and their effect on the resistance to ethanol and malic acid consumption (MAC). Lactobacillus plantarum UNQLp 133, UNQLp 65.3 and UNQLp 155 were acclimated in the presence of 6 or 10% v/v ethanol, for 48 h at 28°C. Lipids were extracted to obtain fatty acid methyl esters and analysed by gas chromatography interfaced with mass spectroscopy. The influence of change in fatty acid composition on the viability and MAC in synthetic wine was analysed by determining the Pearson correlation coefficient. Acclimated strains showed a significant change in the fatty composition with regard to the nonacclimated strains. Adaptation to ethanol led to a decrease in the unsaturated/saturated ratio, mainly resulting from an increase in the contribution of short-length fatty acid C12:0 and a decrease of C18:1. The content of C12:0 was related to a higher viability after inoculation of synthetic wine. The MAC increased at higher contents in saturated fatty acid, but its efficiency was strain dependent. © 2014 The Society for Applied Microbiology.

  13. The Formation Mechanism and Corrosion Resistance of a Composite Phosphate Conversion Film on AM60 Alloy.

    Science.gov (United States)

    Chen, Jun; Lan, Xiangna; Wang, Chao; Zhang, Qinyong

    2018-03-08

    Magnesium alloy AM60 has high duc and toughness, which is expected to increase in demand for automotive applications. However, it is too active, and coatings have been extensively studied to prevent corrosion. In this work, a Ba-containing composite phosphate film has been prepared on the surface of AM60. The composition and formation mechanism of the film have been investigated using a scanning electronic microscope equipped with energy dispersive X-ray spectroscopy, Fourier transform infrared, X-ray photoelectron spectroscopy, and X-ray diffractometry tests. The corrosion resistance of the film has been measured by electrochemical and immersion tests. The results show that the deposition film has fully covered the substrate but there are some micro-cracks. The structure of the film is complex, and consists of MgHPO₄·3H₂O, MnHPO₄·2.25H₂O, BaHPO₄·3H₂O, BaMg₂(PO₄)₂, Mg₃(PO₄)₂·22H₂O, Ca₃(PO₄)₂·xH₂O, and some amorphous phases. The composite phosphate film has better anticorrosion performance than the AM60 and can protect the bare alloy from corrosion for more than 12 h in 0.6 M NaCl.

  14. Incremental dynamic analysis of concrete moment resisting frames reinforced with shape memory composite bars

    International Nuclear Information System (INIS)

    Zafar, Adeel; Andrawes, Bassem

    2012-01-01

    Fiber reinforced polymer (FRP) reinforcing bars have been used in concrete structures as an alternative to conventional steel reinforcement, in order to overcome corrosion problems. However, due to the linear behavior of the commonly used reinforcing fibers, they are not considered in structures which require ductility and damping characteristics. The use of superelastic shape memory alloy (SMA) fibers with their nonlinear elastic behavior as reinforcement in the composite could potentially provide a solution for this problem. Small diameter SMA wires are coupled with polymer matrix to produce SMA–FRP composite, which is sought in this research as reinforcing bars. SMA–FRP bars are sought in this study to enhance the seismic performance of reinforced concrete (RC) moment resisting frames (MRFs) in terms of reducing their residual inter-story drifts while still maintaining the elastic characteristics associated with conventional FRP. Three story one bay and six story two bay RC MRF prototype structures are designed with steel, SMA–FRP and glass–FRP reinforcement. The incremental dynamic analysis technique is used to investigate the behaviors of the two frames with the three different reinforcement types under a suite of ground motion records. It is found that the frames with SMA–FRP composite reinforcement exhibit higher performance levels including lower residual inter-story drifts, high energy dissipation and thus lower damage, which are important for structures in highly seismic zones. (paper)

  15. Corrosion resistance of Ni-Cr-Mo alloys. Chemical composition and metallurgical condition's effects

    International Nuclear Information System (INIS)

    Zadorozne, N.S.; Rebak, Raul B.

    2009-01-01

    P, may form if Ni-Cr-Mo alloys are exposed for tens of hours in the range of 600 C degrees to 1100 C degrees. These phases could have a detrimental effect upon corrosion resistance and cause a loss of mechanical ductility. The precipitation of TCP phases starts at grain boundaries and for long aging times it progresses to twins boundaries and then the grain bodies. TCP phases are rich in Mo and Cr. Zones in the matrix adjacent to the TCP precipitates may be depleted of Cr and Mo, and the alloy becomes sensitized.The aim of the present work was to compare the general corrosion rate and the crevice corrosion susceptibility of alloys C-22, C-22HS and HYBRID-BC1 in different metallurgical conditions when exposed to hot chloride solutions. The effects of the alloy composition and different heat treatments were assessed. (author)

  16. Resistivity and Its Anisotropy Characterization of 3D-Printed Acrylonitrile Butadiene Styrene Copolymer (ABS/Carbon Black (CB Composites

    Directory of Open Access Journals (Sweden)

    Jie Zhang

    2017-01-01

    Full Text Available The rapid printing of 3D parts with desired electrical properties enables numerous applications. Fused deposition modeling (FDM using conductive thermoplastic composites has been a valuable approach for such fabrication. The parts produced by FDM possess various controllable structural features, but the effects of the structural features on the electrical properties remain to be determined. This study investigated the effects of these features on the electrical resistivity and resistivity anisotropy of 3D-printed ABS/CB composites. The effects of the process parameters of FDM, including the layer thickness, raster width, and air gap, on the resistivity in both the vertical and horizontal directions for cubic samples were studied because the internal structure of the printed parts depended on those process parameters. The resistivities of printed parts in different parameter combinations were measured by an impedance analyzer and finite element models were created to investigate the relationship between the resistivity and the internal structure. The results indicated that the parameters remarkably affected the resistivity due to the influence of voids and the bonding condition between adjacent fibers. The resistivity in the vertical direction ranged from 70.40 ± 2.88 Ω·m to 180.33 ± 8.21 Ω·m, and the resistivity in the horizontal direction ranged from 41.91 ± 2.29 Ω·m to 58.35 ± 0.61 Ω·m at the frequency of 1 kHz. Moreover, by adjusting the resistivities in different directions, the resistivity anisotropy of the printed parts can be manipulated from 1.01 to 3.59. This research may serve as a reference to fabricate parts with sophisticated geometry with desired electrical resistivity and resistivity anisotropy.

  17. The comparative evaluation of fracture resistance and microleakage in bonded amalgam, amalgam, and composite resins in primary molars.

    Science.gov (United States)

    Vanishree, H S; Shanthala, B M; Bobby, W

    2015-01-01

    The intense development of adhesive restorative materials and parents' preferences for esthetic restorations prompt clinicians to use alternative restorative materials for primary molars. Amalgam, however, is the choice of material when it comes to occlusal stress bearing areas, either in primary or permanent molars. To overcome the drawbacks of amalgam and restorative adhesive materials, the bonded amalgam technique is employed. To evaluate microleakage and fracture resistance of bonded amalgam in primary molars, and compare it with the microleakage and fracture resistance of high-copper amalgam and composite resin materials. An in vitro study and 60 caries-free primary molars were used. A total of 60 samples were randomly divided into two equal groups for the evaluation of microleakage and fracture resistance. Class V cavities for microleakage study prepared on 30 samples and Class II mesio-occluso-distal cavities for fracture resistance study on other 30 samples were prepared and randomly divided into three equal groups. Group I received amalgam, Group II received bonded amalgam, and Group III received composite resins. The microleakage was viewed under a stereomicroscope. The fracture resistance was evaluated using a universal testing machine. Bonded amalgam exhibited minimum microleakage, when compared to amalgam and composite resin and was found to be statistically insignificant (P = 0.203), while amalgam showed better fracture resistance compared to bonded amalgam and composite resin. It was found to be statistically insignificant (P = 0.144). Bonded amalgam appears to be comparable to amalgam when microleakage is considered and to composite resin when fracture resistance is considered; hence, bonded amalgam can also be an alternative material to amalgam in primary molars.

  18. Improved Corrosion and Abrasion Resistance of Organic-Inorganic Composite Coated Electro-galvanized Steels for Digital TV Panels

    International Nuclear Information System (INIS)

    Jo, Du-Hwan; Noh, Sang-Geol; Park, Jong-Tae; Kang, Choon-Ho

    2015-01-01

    Recently, household electronic industries require environmentally-friendly and highly functional steels in order to enhance the quality of human life. Customers especially require both excellent corrosion and abrasion resistant anti-fingerprint steels for digital TV panels. Thus POSCO has developed new functional electro-galvanized steels, which have double coated layers with organic-inorganic composites on the zinc surface of the steel for usage as the bottom chassis panel of TVs. The inorganic solution for the bottom layer consists of inorganic phosphate, magnesium, and zirconium compounds with a small amount of epoxy binder, and affords both improved adhesion properties by chemical conversion reactions and corrosion resistance due to a self-healing effect. The composite solution for the top layer was prepared by fine dispersion of organic-inorganic ingredients that consist of a urethane modified polyacrylate polymer, hardener, silica sol and a titanium complex inhibitor in aqueous media. Both composite solutions were coated on the steel surface by using a roll coater and then cured through an induction furnace in the electro-galvanizing line. New anti-fingerprint steel was evaluated for quality performance through such procedures as the salt spray test for corrosion resistance, tribological test for abrasion resistance, and conductivity test for surface electric conductance regarding to both types of polymer resin and coating weight of composite solution. New composite coated anti-fingerprint steels afford both better corrosion resistance and abrasion properties compared to conventional anti-fingerprint steel that mainly consists of acrylate polymers. Detailed discussions of both composite solutions and experimental results suggest that urethane modifications of acrylate polymers of composite solutions play a key role in enhanced quality performances

  19. Contribution to the study of the influence of zinc bath composition on corrosion resistance of coatings obtained by galvanization

    International Nuclear Information System (INIS)

    Cabrillac, Claude

    1969-01-01

    This research thesis deals with the influence of zinc purity on the corrosion resistance of a coating obtained by galvanization, and on its effect on cathodic protection. This study therefore addresses methods and tests processes (notably salt spray test) aiming at assessing the efficiency of steel protection by hot galvanization, and aims at highlighting the influence of galvanization bath purity or composition on corrosion resistance of galvanized layers

  20. Data on post irradiation experiments of heat resistant ceramic composite materials. PIE for 97M-13A

    Energy Technology Data Exchange (ETDEWEB)

    Baba, Shin-ichi; Ishihara, Masahiro; Souzawa, Shizuo [Japan Atomic Energy Research Inst., Oarai, Ibaraki (Japan). Oarai Research Establishment; Sekino, Hajime [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

    2003-03-01

    The research on the radiation damage mechanism of heat resistant ceramic composite materials is one of the research subjects of the innovative basic research in the field of high temperature engineering, using the High Temperature engineering Test Reactor (HTTR). Three series of irradiation tests on the heat resistant ceramic composite materials, first to third irradiation test program, were carried out using the Japan Material Testing Reactor (JMTR). This is a summary report on the first irradiation test program; irradiation induced dimensional change, thermal expansion coefficient, X-ray diffraction and {gamma}-ray spectrum are reported. (author)

  1. Microstructure and wear resistance of a laser clad TiC reinforced nickel aluminides matrix composite coating

    International Nuclear Information System (INIS)

    Chen, Y.; Wang, H.M.

    2004-01-01

    Wear resistant TiC/(NiAl-Ni 3 Al) composite coating was fabricated on a substrate of electrolyzed nickel by laser cladding using Ni-Al-Ti-C alloy powders. The laser clad coating is metallurgically bonded to the substrate and has a homogenous fine microstructure consisting of the flower-like equiaxed TiC dendrite and the dual phase matrix of NiAl and Ni 3 Al. The intermetallic matrix composite coating exhibits excellent wear resistance under both room- and high-temperature sliding wear test conditions due to the high hardness of TiC coupled with the strong atomic bonds of intermetallic matrix

  2. Corrosion resistance of a composite polymeric coating applied on biodegradable AZ31 magnesium alloy.

    Science.gov (United States)

    Zomorodian, A; Garcia, M P; Moura e Silva, T; Fernandes, J C S; Fernandes, M H; Montemor, M F

    2013-11-01

    The high corrosion rate of magnesium alloys is the main drawback to their widespread use, especially in biomedical applications. There is a need for developing new coatings that provide simultaneously corrosion resistance and enhanced biocompatibility. In this work, a composite coating containing polyether imide, with several diethylene triamine and hydroxyapatite contents, was applied on AZ31 magnesium alloys pre-treated with hydrofluoric acid by dip coating. The coated samples were immersed in Hank's solution and the coating performance was studied by electrochemical impedance spectroscopy and scanning electron microscopy. In addition, the behavior of MG63 osteoblastic cells on coated samples was investigated. The results confirmed that the new coatings not only slow down the corrosion rate of AZ31 magnesium alloys in Hank's solution, but also enhance the adhesion and proliferation of MG63 osteoblastic cells, especially when hydroxyapatite nanoparticles were introduced in the coating formulation. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  3. Influence of electropolishing and anodic oxidation on morphology, chemical composition and corrosion resistance of niobium.

    Science.gov (United States)

    Sowa, Maciej; Greń, Katarzyna; Kukharenko, Andrey I; Korotin, Danila M; Michalska, Joanna; Szyk-Warszyńska, Lilianna; Mosiałek, Michał; Zak, Jerzy; Pamuła, Elżbieta; Kurmaev, Ernst Z; Cholakh, Seif O; Simka, Wojciech

    2014-09-01

    The work presents results of the studies performed on electropolishing of pure niobium in a bath that contained: sulphuric acid, hydrofluoric acid, ethylene glycol and acetanilide. After the electropolishing, the specimens were subjected to anodic passivation in a 1moldm(-3) phosphoric acid solution at various voltages. The surface morphology, thickness, roughness and chemical composition of the resulting oxide layers were analysed. Thusly prepared niobium samples were additionally investigated in terms of their corrosion resistance in Ringer's solution. The electropolished niobium surface was determined to be smooth and lustrous. The anodisation led to the growth of barrier-like oxide layers, which were enriched in phosphorus species. Copyright © 2014 Elsevier B.V. All rights reserved.

  4. Relationships between Composition of Major Fatty Acids and Fat Distribution and Insulin Resistance in Japanese.

    Science.gov (United States)

    Fujii, Chikako; Kawai, Toshihide; Azuma, Koichiro; Oguma, Yuko; Katsukawa, Fuminori; Hirose, Hiroshi; Tanaka, Kumiko; Meguro, Shu; Matsumoto, Hideo; Itoh, Hiroshi

    2017-01-01

    Objective . The aim of this study was to evaluate the relationships between the composition of free fatty acids (FFAs) and metabolic parameters, including body fat distribution, in Japanese. Methods . The study subjects were 111 Japanese patients (54 males, 57 females). Metabolic parameters and visceral and subcutaneous fat areas as determined by CT scanning at the umbilical level were measured. Glucose tolerance test (GTT) was performed by administering 75 g glucose orally. Results . The percentage of linoleic acid (C18:2), the greatest constituent among FFAs, was negatively correlated with visceral fat area ( r = -0.411, p acid percentage was also significantly negatively correlated with HOMA-IR ( r = -0.416, p acid in diabetic subjects was significantly lower than that in normal subjects. Conclusion . We conclude that serum linoleic acid level is negatively correlated with the accumulation of visceral fat in relation to a reduction of insulin resistance in Japanese subjects.

  5. Improved impact-resistant boron/aluminum composites for use as turbine engine fan blades

    Science.gov (United States)

    Mcdanels, D. L.; Signorelli, R. A.

    1976-01-01

    Thin-sheet Charpy and Izod impact tests and standard full-size Charpy impact tests were conducted on unidirectional and angleply composites containing 4, 5.6 and 8 mil boron in 1100, 2024, 5052 and 6061 Al matrices. Impact failure modes of B/Al are proposed to describe the mechanisms involved and to provide insight for maximizing impact resistance. The impact strength of B/Al was significantly increased by proper selection of materials and processing. The use of more ductile matrices and larger diameter boron fibers gave the highest impact strengths by allowing matrix shear deformation and multiple fiber breakage. Pendulum impact test results of improved B/Al were higher than notched titanium and indicate sufficient foreign object damage protection to warrant consideration of B/Al for application to fan blades in aircraft gas turbine engines.

  6. Altered skeletal muscle fiber composition and size precede whole-body insulin resistance in young men with low birth weight

    DEFF Research Database (Denmark)

    Jensen, Christine B; Storgaard, Heidi; Madsbad, Sten

    2007-01-01

    CONTEXT: Low birth weight (LBW), a surrogate marker of an adverse fetal milieu, is linked to muscle insulin resistance, impaired insulin-stimulated glycolysis, and future risk of type 2 diabetes. Skeletal muscle mass, fiber composition, and capillary density are important determinants of muscle f...... was not significantly different between groups. CONCLUSION: Alterations in fiber composition and size may contribute to development of type 2 diabetes in individuals with LBW....

  7. Role of polymeric binders on mechanical behavior and cracking resistance of silicon composite electrodes during electrochemical cycling

    Science.gov (United States)

    Li, Dawei; Wang, Yikai; Hu, Jiazhi; Lu, Bo; Dang, Dingying; Zhang, Junqian; Cheng, Yang-Tse

    2018-05-01

    This work focuses on understanding the role of various binders, including sodium alginate (SA), Nafion, and polyvinylidene fluoride (PVDF), on the mechanical behavior and cracking resistance of silicon composite electrodes during electrochemical cycling. In situ curvature measurement of bilayer electrodes, consisting of a silicon-binder-carbon black composite layer on a copper foil, is used to determine the effects of binders on bending deformation, elastic modulus, and stress on the composite electrodes. It is found that the lithiation induced curvature and the modulus of the silicon/SA electrodes are larger than those of electrodes with Nafion and PVDF as binders. Although the modulus of Nafion is smaller than that of PVDF, the curvature and the modulus of silicon/Nafion composite are larger than those of silicon/PVDF electrodes. The moduli of all three composites decrease not only during lithiation but also during delithiation. Based on the measured stress and scanning electron microscopy observations of cracking in the composite electrodes, we conclude that the stress required to crack the composite electrodes with SA and Nafion binders is considerably higher than that of the silicon/PVDF electrode during electrochemical cycling. Thus, the cracking resistance of silicon/SA and silicon/Nafion composite electrodes is higher than that of silicon/PVDF electrodes.

  8. Materials, Manufacturing, and Test Development of a Composite Fan Blade Leading Edge Subcomponent for Improved Impact Resistance

    Science.gov (United States)

    Miller, Sandi G.; Handschuh, Katherine; Sinnott, Matthew J.; Kohlman, Lee W.; Roberts, Gary D.; Martin, Richard E.; Ruggeri, Charles R.; Pereira, J. Michael

    2015-01-01

    Application of polymer matrix composite materials for jet engine fan blades is becoming attractive as an alternative to metallic blades; particularly for large engines where significant weight savings are recognized on moving to a composite structure. However, the weight benefit of the composite is offset by a reduction of aerodynamic efficiency resulting from a necessary increase in blade thickness; relative to the titanium blades. Blade dimensions are largely driven by resistance to damage on bird strike. Further development of the composite material is necessary to allow composite blade designs to approximate the dimensions of a metallic fan blade. The reduction in thickness over the state of the art composite blades is expected to translate into structural weight reduction, improved aerodynamic efficiency, and therefore reduced fuel consumption. This paper presents test article design, subcomponent blade leading edge fabrication, test method development, and initial results from ballistic impact of a gelatin projectile on the leading edge of composite fan blades. The simplified test article geometry was developed to realistically simulate a blade leading edge while decreasing fabrication complexity. Impact data is presented on baseline composite blades and toughened blades; where a considerable improvement to impact resistance was recorded.

  9. [The effect of C-SiO2composite films on corrosion resistance of dental Co-Cr alloy].

    Science.gov (United States)

    Huang, Yi; Hu, Jing-Yu; Liu, Yu-Pu; Zhao, Dong-Yuan; Yu, You-Cheng; Bi, Wei

    2016-10-01

    To study the effect of carbon-silica composite films on corrosion resistance of Co-Cr alloy in simulated oral environment and provide evidences for clinical application of this new material. Co-Cr alloy specimens were cut into appropriate size of 20 mm × 20 mm × 0.5 mm. Then, the carbon-silica composite films were spin-coated onto the specimens. Subsequently, ICP-AES was used to observe the Co, Cr, Mo ion concentrations. Finally, Tafel polarization curves of the specimens were used to measure the electrochemical corrosion resistance by electrochemical workstation. SAS8.0 software package was used for statistical analysis. The results of ICP-AES showed that the ion concentrations of Co, Cr, Mo of specimens coated with composite films in the testing liquid were significantly smaller than that of Co-Cr alloy specimens. Tafel polarization curves showed that in the specimens coated with composite films, the corrosion potential moved in the positive direction and increased from -0.261 V to -0.13 V. At the same time, the corrosion current density decreased from -5.0017μA/cm 2 to -5.3006 μA/cm 2 . Carbon-silica composite films (silica=61.71wt %) can reduce the release of metal ions significantly and improve the corrosion resistance of Co-Cr alloys effectively. Carbon-silica composite films may be a promising dental material.

  10. Oxidation resistance of YSZ-alumina composites compared to normal YSZ TBC coatings at 1100 deg. C

    Energy Technology Data Exchange (ETDEWEB)

    Keyvani, A., E-mail: akeyvani@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Saremi, M., E-mail: saremi@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of); Sohi, M. Heydarzadeh, E-mail: mhsohi@ut.ac.ir [School of Metallurgy and Materials, College of Engineering, University of Tehran, P.O. Box 11155-4563, Tehran (Iran, Islamic Republic of)

    2011-08-18

    Highlights: > This work aims to study the oxidation behavior of plasma sprayed YSZ-alumina composites coatings. > The composites TBC coatings of YSZ-alumina showed better oxidation resistance than normal YSZ. > The durability of composite coating with alumina is a novel method and has not been reported before. - Abstract: In the present work oxidation behavior of plasma sprayed YSZ-alumina composite TBC coatings on Ni-base (IN-738LC) super alloy substrate was studied and compared to normal YSZ. Cyclic oxidation process in 4 h intervals was performed in an air electrical furnace at 1100 deg. C and the specimens were cooled in the furnace during each cycle. Preliminary checking was done with naked eye and further investigation was achieved using scanning electron microscopy. If there were any cracks or spallation in the coating's edge, the tests were stopped, the time was recorded and coating microstructure was studied. YSZ-alumina composites were made by applying alumina layer at the top of YSZ or mixed with YSZ as a TBC layer on the bond coat. Composite coatings of YSZ-alumina having alumina as a top coat and the mixed YSZ-alumina layer, showed better resistance than normal YSZ in oxidation test. It was observed that alumina overlay on YSZ has promoted the oxidation resistance of the coatings for longer times by preventing infiltration of oxygen through YSZ layer.

  11. Evaluating the thermal damage resistance of graphene/carbon nanotube hybrid composite coatings

    Science.gov (United States)

    David, L.; Feldman, A.; Mansfield, E.; Lehman, J.; Singh, G.

    2014-03-01

    We study laser irradiation behavior of multiwalled carbon nanotubes (MWCNT) and chemically modified graphene (rGO)-composite spray coatings for use as a thermal absorber material for high-power laser calorimeters. Spray coatings on aluminum test coupon were exposed to increasing laser irradiance for extended exposure times to quantify their damage threshold and optical absorbance. The coatings, prepared at varying mass % of MWCNTs in rGO, demonstrated significantly higher damage threshold values at 2.5 kW laser power at 10.6 μm wavelength than carbon paint or MWCNTs alone. Electron microscopy and Raman spectroscopy of irradiated specimens show that the coating prepared at 50% CNT loading endure at least 2 kW.cm-2 for 10 seconds without significant damage. The improved damage resistance is attributed to the unique structure of the composite in which the MWCNTs act as an efficient absorber of laser light while the much larger rGO sheets surrounding them, dissipate the heat over a wider area.

  12. The effect of N-stearoylethanolamine on plasma lipid composition in rats with experimental insulin resistance

    Directory of Open Access Journals (Sweden)

    O. V. Onopchenko

    2015-02-01

    Full Text Available A model of insulin resistance (IR, induced by prolonged high fat diet with high content of saturated fats was used to investigate the effect of N-stearoylethanolamine (NSE on the composition of free fatty acids (FFA, plasma lipoprotein spectrum and content of proinflammatory cytokine TNFα in rats. The results of this work showed a rise in the content of monounsaturated fatty acids (18:1 n-9 and a reduction in the level of polyunsaturated fatty acids (20:4 n-6 in plasma of rats with experimental IR. These findings are accompanied by the increased TNFα production and significant changes in plasma lipoprotein profile of rats with the fat overload. Particularly, a decreased high-density lipoprotein (HDL cholesterol level and increased low-density (LDL and very low-density lipoprotein (VLDL cholesterol level were detected. The NSE administration to obese rats with IR restored the content of mono- and polyunsaturated FFA, increased HDL cholesterol content and reduced LDL cholesterol level. In addition, the IR rats treated with NSE showed normalization in the serum TNFα level. Our results showed the restoration of plasma lipid profile under NSE administration in rats with obesity-induced IR. Considering the fact that plasma lipid composition displays the lipid metabolism in general, the NSE actions may play a significant role in the prevention of IR-associated complications.

  13. Fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar restorations.

    Science.gov (United States)

    Taguchi, Kohei; Komine, Futoshi; Fushiki, Ryosuke; Blatz, Markus B; Kamio, Shingo; Matsumura, Hideo

    2014-08-01

    This study evaluated the fracture resistance of single-tooth implant-supported zirconia-based indirect composite-layered molar restorations. Forty-four titanium abutments (GingiHue Post) were placed on dental implants (Osseotite Implant). Standardized single-tooth cement-retained implant-supported mandibular molar restorations were fabricated for each of four test groups (n = 11) as follows: porcelain-fused-to-metal crowns (PFM), zirconia-based all-ceramic crowns (ZAC), zirconia-based indirect composite-layered crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E), and zirconia-based indirect composite-layered crowns (ZIC). The crowns were luted with a glass-ionomer cement (Ketac Cem Easymix). Fracture resistance (N) was determined by force application of a perpendicular load to the crowns with a universal testing machine. One-way analysis of variance (ANOVA) and the Tukey's HSD test were used to assess differences in fracture resistance values (α = 0.05). Mean fracture resistances (SD) were 3.09 (0.22) kN, 3.11 (0.34) kN, 2.84 (0.21) kN, and 2.50 (0.36) kN for the PFM, ZAC, ZIC-E, and ZIC groups, respectively. Fracture resistance in the ZIC specimens was significantly lower (P zirconia-based indirect composite-layered molar crowns primed with Estenia Opaque Primer for zirconia frameworks (ZIC-E) is comparable to that of porcelain-fused-to-metal (PFM) and zirconia-based all-ceramic (ZAC) restorations. Application of Estenia Opaque Primer to zirconia ceramic framework provides superior fracture resistance in implant-supported zirconia-based indirect composite-layered molar crowns. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  14. Comparison of fracture resistance of teeth restored with ceramic inlay and resin composite: an in vitro study.

    Science.gov (United States)

    Desai, Priti D; Das, Utapal Kumar

    2011-01-01

    The aim of this study was to evaluate the in vitro fracture resistance of teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal tooth. This study evaluated the fracture strength of the teeth restored with bonded ceramic inlay and direct composite resin restoration in comparison to the normal teeth. Thirty intact human maxillary first premolars were assigned to three groups: Group 1 - comprising sound/unprepared teeth (control). Group 2 - comprising of Class-II direct composite resin restored teeth and Group 3 - comprising Class-II ceramic inlay restored teeth. Cavities were prepared with occlusal width of 1/3 intercuspal distance and 2 mm deep pulpally. Group 2 teeth were restored with hybrid composite resin (Z350 3M ESPE, USA) and group 3 teeth were restored with Vitadur Alpha alumina (Ivoclare Vivadent, Liechtenstein, Europe). Ceramic inlay was bonded with adhesive cement (rely X resin cement of 3MESPE, USA). The specimens were subjected to a compressive load until they fractured. Data were analyzed statistically by unpaired Student's t test. The fracture resistant strength, expressed as kilonewton (KN), was group 1 - 1.51 KN, group 2 - 1.25 KN, and group 3 - 1.58 KN. Statistically, group III had highest fracture resistance followed by group I, while group II had the lowest average fracture resistance. The fracture resistant strength of teeth restored with ceramic inlay was comparable to that of the normal intact teeth or slightly higher, while teeth restored with direct composite resin restoration showed less fracture resistant strength than that of the normal teeth.

  15. Resistance exercise dosage in older adults: single- versus multiset effects on physical performance and body composition.

    Science.gov (United States)

    Galvão, Daniel A; Taaffe, Dennis R

    2005-12-01

    To determine whether variation in resistance exercise volume affects muscle function and physical performance response in older adults. A randomized trial with subjects assigned to a single-set (1-SET) or three-set (3-SET) exercise group. An exercise facility at the University of Queensland. Twenty-eight community-dwelling men and women aged 65 to 78. Progressive resistance training consisting of seven exercises targeting the major muscle groups of the upper and lower body performed on exercise machines twice weekly for 20 weeks at eight-repetition maximum (RM) intensity. Muscle function included isotonic muscle strength (1-RM) of the seven exercises, isokinetic and isometric knee extensor strength, and muscle endurance for the chest press and leg press exercises. Physical performance included timed chair rise, usual and fast 6-m walk, 6-m backwards walk, 400-m walk, floor rise to standing, and stair climbing ability. In addition, body composition was determined using dual energy x-ray absorptiometry. Isotonic muscle strength increased in both exercise groups for all seven exercises (P<.01), with the gain in the 3-SET group greater (P<.05) for the seated row, triceps extension, and knee extension (analysis of covariance). Similarly, muscle endurance gains were greater for the 3-SET than the 1-SET group (P<.01), with no significant difference between groups for isokinetic and isometric knee extensor strength. Both groups improved (P<.05) in the chair rise (1-SET, 10.1%; 3-SET, 13.6%), 6-m backwards walk (1-SET, 14.3%; 3-SET, 14.8%), 400-m walk (1-SET, 3.8%; 3-SET, 7.4%), and stair climbing test (1-SET, 7.7%; 3-SET, 6.4%), with the only difference between groups for the 400-m walk (P<.05). There was no difference between groups for change in body composition. Resistance training consisting of only single-set exercises is sufficient to significantly enhance muscle function and physical performance, although muscle strength and endurance gains are greater with higher

  16. The flow Rate Accuracy of Elastomeric Infusion Pumps After Repeated Filling.

    Science.gov (United States)

    Mohseni, Masood; Ebneshahidi, Amin

    2014-05-01

    One of the frequent applications of elastomeric infusion pumps is postoperative pain management. In daily practice, the disposable pumps get refilled with modified medication combinations in the successive days; although, the accuracy of infusion rates is unknown to clinicians. Our aim was to evaluate the effect of repeated filling on the delivery rate accuracy of an elastomeric pump available in our market. We examined 10 elastomeric infusion pumps (BOT-802, Nanchang Biotek Medical Device Company, China) with 100 mL capacity and nominal flow of 5 mL/h. Each pump was filled for three times, accounting for 30 series of experiments. A microset scaled in mL was used to measure the pump deliveries. Flow profile and reliability of infusion rate were analyzed after repeated use. The mean flow rate in the three series of measurements showed a gradual increase; however, the difference was not statistically significant (5.01 ± 0.07 vs. 5.03 ± 0.06 vs. 5.06 ± 0.08 mL/h; P = 0.81). The percentage of the flow rate error (deviation from 5 mL/h ± 15%) was 100% in the first and second hours of infusion, 96% in the third hour, 60% in the 20th hour and zero percent in the rest of the infusion time. This study indicated that the delivery rate accuracy of elastomeric infusion pumps is preserved after repeated usage. These laboratory findings suggested that elastomeric pumps could be safely refilled in the successive days to provide postoperative analgesia.

  17. Fracture resistance of endodontically treated teeth restored with fiber-reinforced composite posts and composite core with varying remaining coronal tooth structure.

    Science.gov (United States)

    Ananviriyaporn, Sirirat; Jitarmat, Piyabhorn; Chairat, Surachara; Ranchan, Atchariyaporn

    2012-01-01

    Endodontically treated teeth often have a varying remaining coronal tooth structure, is an important factor in the successful of post-core with crown restoration. This study compared the fracture resistance of pulpless teeth with variable amounts of remaining coronal tooth structure restored with fiber-reinforced composite posts and composite core. Fifty extracted human premolars were endodontically treated and divided into 5 groups of 10 teeth each. Four groups were prepared having axial wall heights of 4 mm around the preparation circumferences. In 3 of the groups with axial tooth structure, mesial axial tooth structure was removed, mesial and lingual axial tooth structure were removed, mesial-lingual and distal axial tooth structure were removed. For the fifth group, all axial tooth structure was removed to the level of the prepared finish line. All 50 prepared teeth were restored with fiber-reinforced composite posts (FRC Postec Plus) and composite resin cores (Multicore Flow). Testing was conducted with a universal testing machine with the application of a static load to the lingual incline plane of buccal cusp at a crosshead speed of 5 mm/min at 45 degrees to the long axis of the tooth. The load at failure was recorded. The data were subjected to 1-way analysis of variance. The mean value + standard deviation for the failure load of group 1 to 5 were 237.48 +/- 81.87, 242.97 +/- 66.80, 257.67 +/- 70.42, 239.56 +/- 70.42 and 297.70 +/- 99.42 (N), respectively There were no significant differences in the fracture resistance (p structure of endodontically treated tooth had no influenced on the fracture resistance when restored with fiber-reinforced composite posts and composite core.

  18. Fracture resistance of cuspal coverage of endodontically treated maxillary premolars with combined composite-amalgam compared to other techniques.

    Science.gov (United States)

    Shafiei, F; Memarpour, M; Karimi, F

    2011-01-01

    This in vitro study investigated the fracture resistance of teeth restored with combined composite-amalgam for cuspal coverage compared to direct coverage with composite (with or without an amalgam base) and composite onlay. Seventy-two intact maxillary premolars were randomly divided into six groups (n=12). The two control groups were G1, intact teeth (negative control), and G2, mesio-occlusodistal preparation only (positive control). Each of the four experimental groups used a different type of restoration for the prepared teeth: G3, direct composite cusp coverage; G4, composite onlay; G5, direct composite coverage with an amalgam base; and G6, combined composite-amalgam cuspal coverage. After thermocycling, fracture strength was tested. The data were analyzed with analysis of variance and the least significant differences post hoc tests (α=0.05). Mean fracture resistance in the six groups (in N) were G1, 1101 ±1 86; G2, 228 ± 38; G2, 699 ± 161; G4, 953 ± 185; G5, 859 ± 146; and G6, 772 ± 154. There were significant differences between G1 and all the other groups except for G4 and between G2 and all the other groups. Fracture strength in G3 also differed significantly compared to G4 and G5. The difference between G4 and G6 was statistically significant (p0.05).

  19. Thermal Shock Resistance of Si3N4/h -BN Composites Prepared via Catalytic Reaction-Bonding Route

    Science.gov (United States)

    Yang, Wanli; Peng, Zhigang; Dai, Lina; Shi, Zhongqi; Jin, Zhihao

    2017-09-01

    Si3N4/h-BN ceramic matrix composites were prepared via a catalytic reaction-bonding route by using ZrO2 as nitridation catalyst, and the water quenching (fast cooling) and molten aluminum quenching tests (fast heating) were carried out to evaluate the thermal shock resistance of the composites. The results showed that the thermal shock resistance was improved obviously with the increase in h-BN content, and the critical thermal shock temperature difference (Δ T c) reaches as high as 780 °C when the h-BN content was 30 wt.%. The improvement of thermal shock resistance of the composites was mainly due to the crack tending to quasi static propagating at weak bonding interface between Si3N4 and h-BN with the increase in h-BN content. For the molten aluminum quenching test, the residual strength showed no obvious decrease compared with water quenching test, which could be caused by the mild stress condition on the surface. In addition, a calculated parameter, volumetric crack density ( N f), was presented to quantitative evaluating the thermal shock resistance of the composites in contrast to the conventional R parameter.

  20. Biological degradation of wood-plastic composites (WPC) and strategies for improving the resistance of WPC against biological decay

    Science.gov (United States)

    Anke Schirp; Rebecca E. Ibach; David E. Pendleton; Michael P. Wolcott

    2008-01-01

    Much of the research on wood-plastic composites (WPC) has focused on formulation development and processing while high biological durability of the material was assumed. The gap between assumption and knowledge in biodeterioration of WPC needs to be reduced. Although some information on the short-term resistance of WPC against biological degradation is available, long-...

  1. Ex vivo fracture resistance of direct resin composite complete crowns with and without posts on maxillary premolars.

    NARCIS (Netherlands)

    Fokkinga, W.A.; Bell, A.M. Le; Kreulen, C.M.; Lassila, L.V.; Vallittu, P.K.; Creugers, N.H.J.

    2005-01-01

    AIM: To investigate ex vivo the fracture resistance and failure mode of direct resin composite complete crowns with and without various root canal posts made on maxillary premolars. METHODOLOGY: The clinical crowns of 40 human extracted single-rooted maxillary premolars were sectioned at the

  2. Oxygen plasma treatment and deposition of CNx on a fluorinated polymer matrix composite for improved erosion resistance

    International Nuclear Information System (INIS)

    Muratore, C.; Korenyi-Both, A.; Bultman, J. E.; Waite, A. R.; Jones, J. G.; Storage, T. M.; Voevodin, A. A.

    2007-01-01

    The use of polymer matrix composites in aerospace propulsion applications is currently limited by insufficient resistance to erosion by abrasive media. Erosion resistant coatings may provide necessary protection; however, adhesion to many high temperature polymer matrix composite (PMC) materials is poor. A low pressure oxygen plasma treatment process was developed to improve adhesion of CN x coatings to a carbon reinforced, fluorinated polymer matrix composite. Fullerene-like CN x was selected as an erosion resistant coating for its high hardness-to-elastic modulus ratio and elastic resilience which were expected to reduce erosion from media incident at different angles (normal or glancing) relative to the surface. In situ x-ray photoelectron spectroscopy was used to evaluate the effect of the plasma treatment on surface chemistry, and electron microscopy was used to identify changes in the surface morphology of the PMC substrate after plasma exposure. The fluorine concentration at the surface was significantly reduced and the carbon fibers were exposed after plasma treatment. CN x coatings were then deposited on oxygen treated PMC substrates. Qualitative tests demonstrated that plasma treatment improved coating adhesion resulting in an erosion resistance improvement of a factor of 2 compared to untreated coated composite substrates. The combination of PMC pretreatment and coating with CN x reduced the erosion rate by an order of magnitude for normally incident particles

  3. Thermally Bonded PET–Basalt Sandwich Composites for Heat Pipeline Protection: Preparation, Stab Resisting, and Thermal-Insulating Properties

    Directory of Open Access Journals (Sweden)

    Ting-Ting Li

    2018-03-01

    Full Text Available In order to solve the cost and bulky problems of buried thermal pipeline insulating materials, this study adopts basalt fabric and low-melting PET nonwoven to construct low-cost and light-weight pipeline thermal-insulating composites after needle punching and thermal bonding processes. Research result shows that thermal-bonded temperature affected the stab resistance and burst energy more significantly. As thermal-bonded temperature increased, knife resistance and spike resistance presented the upward and then downward trends, but the burst energy gradually decreased. Yarn pull-out result shows that the enhancement of stab resistance of intra-/inter-thermal-bonded structure resulted from the increment in the coefficient of friction between yarns. When PET–basalt sandwich composites were thermal-bonded at 140 °C for 5 min, the maximum knife and spike resistance were 147.00 N (1.99 J and 196.30 N (1.11 J, respectively, and burst energy was 4.79 J, thermal conductivity reduced to 0.0073 W/(m∙K. The resultant thermally bonded sandwich composites can be used as thermal-insulating protection for buried thermal pipeline.

  4. Analysis of the Effect of Surface Modification on Polyimide Composites Coated with Erosion Resistant Materials

    Science.gov (United States)

    Ndalama, Tchinga; Hirschfeld, Deidre; Sutter, James K. (Technical Monitor)

    2003-01-01

    The aim of this research is to enhance performance of composite coatings through modification of graphite-reinforced polyimide composite surfaces prior to metal bond coat/ hard topcoat application for use in the erosive and/or oxidative environments of advanced engines. Graphite reinforced polyimide composites, PMR-15 and PMR-II-50, formed by sheet molding and pre-pregging will be surface treated, overlaid with a bond coat and then coated with WC-Co. The surface treatment will include cleaning, RF plasma or ultraviolet light- ozone etching, and deposition of SiO(x) groups. These surface treatments will be studied in order to investigate and improve adhesion and oxidation resistance. The following panels were provided by NASA-Glenn Research Center(NASA-GRC): Eight compression molded PMR-II-50; 6 x 6 x 0.125 in. Two vacuum-bagged PMR-II-50; 12 x 12 x 0.125 in. Eight compression molded PMR-15; 6 x 6 x 0.125 in. One vacuum-bagged PMR-15; 12 x 12 x 0.125 in. All panels were made using a 12 x 12 in. T650-35 8HS (3K-tow) graphite fabric. A diamond-wafering blade, with deionized water as a cutting fluid, was used to cut PMR-II-50 and PMR-15 panels into 1 x 1 in. pieces for surface tests. The panel edges exhibiting delamination were used for the preliminary surface preparation tests as these would be unsuitable for strength and erosion testing. PMR-15 neat resin samples were also provided by NASA GRC. Surface profiles of the as-received samples were determined using a Dektak III Surface profile measuring system. Two samples of compression molded PMR-II-50 and PMR-15, vacuum-bagged PMR-II-50 and PMR-15 were randomly chosen for surface profile measurement according to ANSI/ASME B46.1. Prior to each measurement, the samples were blasted with compressed air to remove any artifacts. Five 10 mm-long scans were made on each sample. The short and long wavelength cutoff filter values were set at 100 and 1000 m, diamond stylus radius was 12.5 microns. Table 1 is a summary of the

  5. Assessment of peanut quality and compositional characteristics among transgenic sclerotinia blight-resistant and non-transgenic susceptible cultivars.

    Science.gov (United States)

    Hu, Jiahuai; Telenko, Darcy E P; Phipps, Patrick M; Grabau, Elizabeth A

    2014-08-06

    This study presents the results of a comparison that includes an analysis of variance and a canonical discriminant analysis to determine compositional equivalence and similarity between transgenic, sclerotinia blight-resistant and non-transgenic, susceptible cultivars of peanut in 3 years of field trials. Three Virginia-type cultivars (NC 7, Wilson, and Perry) and their corresponding transgenic lines (N70, W73, and P39) with a barley oxalate oxidase gene were analyzed for differences in key mineral nutrients, fatty acid components, hay constituents, and grade characteristics. Results from both analyses demonstrated that transgenic lines were compositionally similar to their non-transgenic parent cultivar in all factors as well as market-grade characteristics and nutritional value. Transgenic lines expressing oxalate oxidase for resistance to sclerotinia blight were substantially equivalent to their non-transgenic parent cultivar in quality and compositional characteristics.

  6. Fracture resistance of computer-aided design/computer-aided manufacturing-generated composite resin-based molar crowns.

    Science.gov (United States)

    Harada, Akio; Nakamura, Keisuke; Kanno, Taro; Inagaki, Ryoichi; Örtengren, Ulf; Niwano, Yoshimi; Sasaki, Keiichi; Egusa, Hiroshi

    2015-04-01

    The aim of this study was to investigate whether different fabrication processes, such as the computer-aided design/computer-aided manufacturing (CAD/CAM) system or the manual build-up technique, affect the fracture resistance of composite resin-based crowns. Lava Ultimate (LU), Estenia C&B (EC&B), and lithium disilicate glass-ceramic IPS e.max press (EMP) were used. Four types of molar crowns were fabricated: CAD/CAM-generated composite resin-based crowns (LU crowns); manually built-up monolayer composite resin-based crowns (EC&B-monolayer crowns); manually built-up layered composite resin-based crowns (EC&B-layered crowns); and EMP crowns. Each type of crown was cemented to dies and the fracture resistance was tested. EC&B-layered crowns showed significantly lower fracture resistance compared with LU and EMP crowns, although there was no significant difference in flexural strength or fracture toughness between LU and EC&B materials. Micro-computed tomography and fractographic analysis showed that decreased strength probably resulted from internal voids in the EC&B-layered crowns introduced by the layering process. There was no significant difference in fracture resistance among LU, EC&B-monolayer, and EMP crowns. Both types of composite resin-based crowns showed fracture loads of >2000 N, which is higher than the molar bite force. Therefore, CAD/CAM-generated crowns, without internal defects, may be applied to molar regions with sufficient fracture resistance. © 2015 Eur J Oral Sci.

  7. Changes in muscle size and MHC composition in response to resistance exercise with heavy and light loading intensity

    DEFF Research Database (Denmark)

    Holm, Lars; Reitelseder, Søren; Pedersen, T.G.

    2008-01-01

    Muscle mass accretion is accomplished by heavy-load resistance training. The effect of light-load resistance exercise has been far more sparsely investigated with regard to potential effect on muscle size and contractile strength. We applied a resistance exercise protocol in which the same indivi...... in healthy young men. However, LL resistance training was inferior to HL training in evoking adaptive changes in muscle size and contractile strength and was insufficient to induce changes in MHC composition.......Muscle mass accretion is accomplished by heavy-load resistance training. The effect of light-load resistance exercise has been far more sparsely investigated with regard to potential effect on muscle size and contractile strength. We applied a resistance exercise protocol in which the same.......05) in HL but remained unchanged in LL (4 +/- 5%, not significant). Finally, MHC IIX protein expression was decreased with HL but not LL, despite identical total workload in HL and LL. Our main finding was that LL resistance training was sufficient to induce a small but significant muscle hypertrophy...

  8. Fracture Resistance of Composite Fixed Partial Dentures Reinforced with Pre-impregnated and Non-impregnated Fibers

    Directory of Open Access Journals (Sweden)

    Ramin Mosharraf

    2012-02-01

    Full Text Available Background and aims. The mechanical properties of fiber-reinforced composite fixed partial dentures (FPDs are affected by fiber impregnation. The aim of this in vitro study was to compare the fracture resistance of composite fixed partial dentures reinforced with pre-impregnated and non-impregnated fibers. Materials and methods. Groups (n=5 of three-unit fiber-reinforced composite FPDs (23 mm in length from maxillary second premolar to maxillary second molar were fabricated on two abutments with pontic width of 12 mm. One group was fabricated as the control group with composite (Gradia and the other two groups were fabricated with composite (Gradia reinforced with pre-impregnated fiber (Fibrex ribbon and non-impregnated fiber (Fiber braid, respectively. The specimens were stored in distilled water for one week at 37°C and then tested in a universal testing machine by means of a three-point bending test. Statistical analysis consisted of one-way ANOVA and a post hoc Scheffé’s test for the test groups (α=0.05. Results. Fracture resistance (N differed significantly between the control group and the other two groups (P<0.001, but there were no statistically significant differences between the pre-impregnated and non-impregnated groups (P=0.565. The degree of deflection measured (mm did not differ significantly between the three groups (P=0.397, yet the mean deflection measured in pre-impregnated group was twice as that in the other two groups. Conclusion. Reinforcement of composite with fiber might considerably increase the fracture resistance of FPDs; however, the type of the fiber used resulted in no significant difference in fracture resistance of FPD specimens.

  9. Correlation of gut microbiota composition with resistance to experimental autoimmune encephalomyelitis in rats

    Directory of Open Access Journals (Sweden)

    Suzana Stanisavljevic

    2016-12-01

    Full Text Available Multiple sclerosis is a chronic inflammatory disease of the central nervous system (CNS. It is widely accepted that autoimmune response against the antigens of the CNS is the essential pathogenic force in the disease. It has recently become increasingly appreciated that activated encephalitogenic cells tend to migrate towards gut associated lymphoid tissues (GALT and that interrupted balance between regulatory and inflammatory immunity within the GALT might have decisive role in the initiation and propagation of the CNS autoimmunity. Gut microbiota composition and function has the major impact on the balance in the GALT. Thus, our aim was to perform analyses of gut microbiota in experimental autoimmune encephalomyelitis (EAE, an animal model of multiple sclerosis. Albino Oxford (AO rats that are highly resistant to EAE induction and Dark Agouti (DA rats that develop EAE after mild immunization were compared for gut microbiota composition in different phases after EAE induction. Microbial analyses of the genus Lactobacillus and related lactic acid bacteria showed higher diversity of Lactobacillus spp. in EAE-resistant AO rats, while some members of Firmicutes and Proteobacteria (Undibacterium oligocarboniphilum were detected only in faeces of DA rats at the peak of the disease (between 13 and 16 days after induction. Interestingly, Turicibacter sp. that was found exclusively in non-immunized AO, but not in DA rats in our previous study was detected in DA rats that remained healthy 16 days after induction. Similar observation was obtained for the members of Lachnospiraceae. As dominant presence of the members of Lachnospiraceae family in gut microbial community has been linked with mild symptoms of various diseases, it is tempting to assume that Turicibacter sp. and Lachnospiraceae contribute to the prevention of EAE development and the alleviation of the disease symptoms. Further, production of a typical regulatory cytokine interleukin-10 was

  10. Low-level laser therapy effects on pain perception related to the use of orthodontic elastomeric separators

    OpenAIRE

    Furquim, Rachel D'Aurea; Pascotto, Renata Correa; Rino, Jos?; Cardoso, Jefferson Rosa; Ramos, Adilson Luiz

    2015-01-01

    INTRODUCTION: Some patients refer to pre-banding orthodontic separation as a painful orthodontic procedure. Low-level laser therapy (LLLT) has been reported to have local analgesic effect. OBJECTIVE: The aim of this single-blind study was to investigate the perception of pain caused by orthodontic elastomeric separators with and without a single LLLT application (6J). METHODS: The sample comprised 79 individuals aged between 13 and 34 years old at orthodontic treatment onset. Elastomeric sepa...

  11. Temperature Dependence of Electrical Resistance of Woven Melt-Infiltrated SiCf/SiC Ceramic Matrix Composites

    Science.gov (United States)

    Appleby, Matthew P.; Morscher, Gregory N.; Zhu, Dongming

    2016-01-01

    Recent studies have successfully shown the use of electrical resistance (ER)measurements to monitor room temperature damage accumulation in SiC fiber reinforced SiC matrix composites (SiCf/SiC) Ceramic Matrix Composites (CMCs). In order to determine the feasibility of resistance monitoring at elevated temperatures, the present work investigates the temperature dependent electrical response of various MI (Melt Infiltrated)-CVI (Chemical Vapor Infiltrated) SiC/SiC composites containing Hi-Nicalon Type S, Tyranno ZMI and SA reinforcing fibers. Test were conducted using a commercially available isothermal testing apparatus as well as a novel, laser-based heating approach developed to more accurately simulate thermomechanical testing of CMCs. Secondly, a post-test inspection technique is demonstrated to show the effect of high-temperature exposure on electrical properties. Analysis was performed to determine the respective contribution of the fiber and matrix to the overall composite conductivity at elevated temperatures. It was concluded that because the silicon-rich matrix material dominates the electrical response at high temperature, ER monitoring would continue to be a feasible method for monitoring stress dependent matrix cracking of melt-infiltrated SiC/SiC composites under high temperature mechanical testing conditions. Finally, the effect of thermal gradients generated during localized heating of tensile coupons on overall electrical response of the composite is determined.

  12. Electrostatic Assembly Preparation of High-Toughness Zirconium Diboride-Based Ceramic Composites with Enhanced Thermal Shock Resistance Performance.

    Science.gov (United States)

    Zhang, Baoxi; Zhang, Xinghong; Hong, Changqing; Qiu, Yunfeng; Zhang, Jia; Han, Jiecai; Hu, PingAn

    2016-05-11

    The central problem of using ceramic as a structural material is its brittleness, which associated with rigid covalent or ionic bonds. Whiskers or fibers of strong ceramics such as silicon carbide (SiC) or silicon nitride (Si3N4) are widely embedded in a ceramic matrix to improve the strength and toughness. The incorporation of these insulating fillers can impede the thermal flow in ceramic matrix, thus decrease its thermal shock resistance that is required in some practical applications. Here we demonstrate that the toughness and thermal shock resistance of zirconium diboride (ZrB2)/SiC composites can be improved simultaneously by introducing graphene into composites via electrostatic assembly and subsequent sintering treatment. The incorporated graphene creates weak interfaces of grain boundaries (GBs) and optimal thermal conductance paths inside composites. In comparison to pristine ZrB2-SiC composites, the toughness of (2.0%) ZrB2-SiC/graphene composites exhibited a 61% increasing (from 4.3 to 6.93 MPa·m(1/2)) after spark plasma sintering (SPS); the retained strength after thermal shock increased as high as 74.8% at 400 °C and 304.4% at 500 °C. Present work presents an important guideline for producing high-toughness ceramic-based composites with enhanced thermal shock properties.

  13. Chemical Resistance of Glass Composite Materials Made From Incinerated Scheduled Waste Slag and SLS Waste Glass

    Directory of Open Access Journals (Sweden)

    Juoi Jariah Mohamad

    2018-01-01

    Full Text Available Incineration of scheduled waste and landfilling of the incineration residue (Bottom Slag is extensively practised in Malaysia as a treatment method for scheduled waste. Land site disposal of Bottom Slag (BS may lead to environmental health issues and reduces the availability of land to sustain the nation’s development. This research aims in producing Glass Composite Material (GCM incorporating BS and Soda Lime Silicate (SLS waste glass as an alternative method for land site disposal and as an effort for recycling SLS waste glass. SLS waste glass originates from the urban waste has been a waste stream in most of the nation whereby the necessity for recycling is in high priority. Batches of powder mixture is formulated with 30 wt. % to 70 wt. % of BS powder and SLS waste glass powder for GCM sintering. The powder mixtures of BS and SLS waste glass is compacted by uniaxial pressing and sintered at 800°C with heating rate of 2°C/min and 1 hour soaking time into tiles of 18mm×18mm. The GCM porosity and water absorption increases as the BS waste loading increases. Meanwhile, its bulk density increases as the BS waste loading decreases. The GCM tiles made from BS 30 wt. % and 70 wt. % SLS waste glass are determined to have the lowest water absorption of 1.17 % and porosity percentage of 2.2 % with the highest bulk density of 1.88 g/cm3. It was also found is found that the chemical resistance of these GCM tiles is classified as ULA (No visible Effect and UHA (No visible Effect after 5 day immersions in low and high concentration of acid and alkali solution; respectively (determined using MS ISO10545-13:2001(Ceramic Tile: Determination of chemical resistance test. However, the chemical resistance is weak upon increased duration of 12 immersion days where severe corrosion effects on both surface tiles in low and high concentration chemical solutions. The penetration of chemical in attacking the samples are related to the presence of pores. Hence

  14. Electrical Resistivity, Tribological Behaviour of Multiwalled Carbon Nanotubes and Nanoboron Carbide Particles Reinforced Copper Hybrid Composites for Pantograph Application

    Directory of Open Access Journals (Sweden)

    N. Selvakumar

    2016-01-01

    Full Text Available This work focuses on the influence and contribution of multiwalled carbon-nanotube (MWCNT–boron carbide (B4C to the mechanical and tribological properties of copper matrix composites. Different weight fractions of nano- B4C-containing fixed-weight fractions of MWCNT-reinforced copper composites were prepared using the entrenched cold-press sintering method of powder metallurgy. The wear losses of sintered Cu–MWCNT–B4C composites were investigated by conducting sliding tests in a pin-on-disc apparatus. The addition of reinforcements showed enhancements in the hardness and wear properties of the composites due to the uniform dispersion of the secondary reinforcement in the copper matrix and the self-lubricating effect of the MWCNTs. The effects of the nanoparticle distribution in the matrix, the worn surface morphology, and the elemental composition of the composites were characterized using high-resolution scanning electron microscopy and X-ray diffraction analysis. The electrical resistivity of the fabricated copper hybrid composite preforms was evaluated using a four-point probe tester. Our results highlight the use of experiential reinforcing limits of B4C on the wear and electrical and mechanical behaviour of copper composites.

  15. Composite plasma electrolytic oxidation to improve the thermal radiation performance and corrosion resistance on an Al substrate

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Donghyun [Department of Materials Science and Engineering, Pusan National University, Busan 46241 (Korea, Republic of); Sung, Dahye [Department of Materials Science and Engineering, Pusan National University, Busan 46241 (Korea, Republic of); Korea Institute of Industrial Technology (KITECH), Busan 46742 (Korea, Republic of); Lee, Junghoon [Department of Mechanical Engineering, Stevens Institute of Technology, Hoboken, NJ 07030 (United States); Kim, Yonghwan [Korea Institute of Industrial Technology (KITECH), Busan 46742 (Korea, Republic of); Chung, Wonsub, E-mail: wschung1@pusan.ac.kr [Department of Materials Science and Engineering, Pusan National University, Busan 46241 (Korea, Republic of)

    2015-12-01

    Highlights: • Composite plasma electrolytic oxidation was performed using dispersed CuO particles in convectional PEO electrolyte. • Thermal radiation performance and corrosion resistance were examined by FT-IR spectroscopy and electrochemical methods, respectively. • Deposited copper oxide on the surface of the Al substrate was enhanced the corrosion resistance and the emissivity compared with the conventional PEO. - Abstract: A composite plasma electrolytic oxidation (PEO) was performed for enhancing the thermal radiation performance and corrosion resistance on an Al alloy by dispersing cupric oxide (CuO) particles in a conventional PEO electrolyte. Cu-based oxides (CuO and Cu{sub 2}O) formed by composite PEO increased the emissivity of the substrate to 0.892, and made the surface being dark color, similar to a black body, i.e., an ideal radiator. In addition, the corrosion resistance was analyzed using potentio-dynamic polarization and electrochemical impedance spectroscopy tests in 3.5 wt.% NaCl aqueous solution. An optimum condition of 10 ampere per square decimeter (ASD) current density and 30 min processing time produced appropriate surface morphologies and coating thicknesses, as well as dense Cu- and Al-based oxides that constituted the coating layers.

  16. Effect of resistance training on body composition, self-efficacy, depression, and activity in postpartum women.

    Science.gov (United States)

    LeCheminant, J D; Hinman, T; Pratt, K B; Earl, N; Bailey, B W; Thackeray, R; Tucker, L A

    2014-04-01

    This study assessed the effect of resistance training (RT) in 60 healthy postpartum women. Participants were randomized to 18 weeks of RT or an active comparison group (flexibility training). RT and flexibility training (FT) exercises were completed twice-weekly based on the American College of Sports Medicine recommendations. Study outcomes included muscular strength, body composition (dual-energy x-ray absorptiometry), exercise self-efficacy, depressive symptoms [Center for Epidemiological Studies Depression Scale (CES-D)], and physical activity (accelerometery). For completers (n = 44), the RT group showed greater strength gains than the FT group, respectively (bench press: +36% vs +8%, P self-efficacy (F = 5.33, P = 0.026). For CES-D score, the RT group decreased (F = 4.61, P = 0.016), while the FT group did not; however, the group × time interaction in CES-D score was not significant (F = 1.33, P = 0.255). Sedentary time decreased (F = 5.27, P = 0.027) and light-intensity activity time increased (F = 5.55, P = 0.023) more in the RT than FT group. Intent-to-treat analyses did not alter the results. Twice-weekly RT increases strength and may be associated with better exercise self-efficacy and improved physical activity outcomes compared with FT in postpartum women. © 2012 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  17. Ni-W coatings electrodeposited on carbon steel: Chemical composition, mechanical properties and corrosion resistance

    Energy Technology Data Exchange (ETDEWEB)

    Arganaraz, M.P. Quiroga; Ribotta, S.B. [INQUINOA-CONICET, Instituto de Quimica Fisica, Facultad de Bioquimica, Quimica y Farmacia, Universidad Nacional de Tucuman, Ayacucho 471, (4000) San Miguel de Tucuman (Argentina); Folquer, M.E., E-mail: mefolquer@fbqf.unt.edu.ar [INQUINOA-CONICET, Instituto de Quimica Fisica, Facultad de Bioquimica, Quimica y Farmacia, Universidad Nacional de Tucuman, Ayacucho 471, (4000) San Miguel de Tucuman (Argentina); Gassa, L.M.; Benitez, G.; Vela, M.E.; Salvarezza, R.C. [Instituto de Investigaciones Fisicoquimicas Teoricas y Aplicadas (INIFTA), Universidad Nacional de La Plata-CONICET, Suc. 4, C.C. 16, (1900) La Plata (Argentina)

    2011-07-01

    Highlights: > Hard, ductile and adherent nanostructured Ni-W coatings on carbon steel. > New procedures for achieving deposits by current pulse techniques. > Current pulse frequency was the dominant factor to define coating characteristics. > Ni-W coatings protect the carbon steel from corrosion induced by sulphate anions. - Abstract: Hard, ductile and adherent nanostructured Ni-W coatings were electrodeposited on carbon steel from electrolyte solutions containing sodium tungstate, nickel sulfate and sodium citrate, using different current pulse programs. Current pulse frequency was the dominant factor to define chemical composition, grain size, thickness and hardness. According to the electrodeposition conditions the deposited coatings showed 15-30 at% W, the grain size ranged from 65 to 140 nm, and the hardness varied from 650 to 850 Hv. Tungsten carbide also present in the coating contributed to its hardness. The corrosion resistance of the Ni-W coated steel was tested by potentiodynamic polarization in a neutral medium containing sulphate ions. The Ni-W coating protected the carbon steel from localized corrosion induced by sulphate anions.

  18. Dendrimeric Thin-Film Composite Membranes: Free Volume, Roughness, and Fouling Resistance

    KAUST Repository

    Phuoc, Duong

    2017-11-10

    Copolyamide films with a thickness from 50 to 780 nm were fabricated by interfacial polymerization between mixtures of m-phenylene diamine and primary amine-terminated polyamidoamine dendrimers (PAMAM) in the aqueous phase and trimesoyl chloride (TMC) in the organic phase. Different PAMAM generations (G0, d = 15 Å, Z = 4; G3, d = 36 Å, Z = 32; and G5, d = 54, Z = 128, where d is the measured diameter and Z is the number of terminal groups) and concentrations were used to obtain copolyamide films with different crosslinked structures. The influences of the concentration and degree of branching (PAMAM generation) on free volume were analysed via positon annihilation spectroscopy (PAS) and correlated with the separation properties of copolyamide films. Besides, surface and intrinsic properties of copolyamide films under different conditions were compared. The high hydrophilicity of PAMAM in the copolyamide network leads to the formation of a hydration layer on the copolyamide surface, which minimizes fouling. The separation performance of copolyamide membranes with various PAMAM networks was investigated in forward osmosis (FO) experiments. Understanding the correlation between the PAMAM structure/concentration, free volume, thickness, and surface intrinsic properties leads to the design of suitable fouling resistant thin-film composite membranes in a single interfacial polymerization process.

  19. A Resistive Humidity Sensor Based on Nanostructured WO3-ZnO Composites

    Directory of Open Access Journals (Sweden)

    Karunesh Tiwari

    2011-11-01

    Full Text Available Paper reports morphological and humidity sensing studies of WO3 and WO3-ZnO composite pellets prepared in the weight % ratio of 10:1, 4:1 and 2:1 by solid-state reaction route. The pellets have been annealed at temperatures of 300-500 °C. XRD pattern shows peaks of ZnWO4 formed due to solid state reaction between WO3 and ZnO. SEM micrographs show that the sensing elements manifest porous structure. Granulation and tendency to agglomerate seen in the SEM micrograph are due to the presence of zinc ions in ZnWO4. Nanoparticles are having their sizes in the range 37-182 nm. The average Kelvin radius at 20˚C room temperature is 27 Ả. Humidity sensing application of the pellets has been studied in a humidity control cabinet. It is observed that as relative humidity increases, there is decrease in the resistance of pellets in the range 10-85 % RH. Sensing element of WO3-ZnO in 2:1 weight % ratio shows best results in 10-85 % relative humidity range. The average sensitivity of this sample is 1.25 MΩ/%RH. This sensing element shows good reproducibility, low hysteresis and less effect of aging.

  20. Biodegradation Resistance and Bioactivity of Hydroxyapatite Enhanced Mg-Zn Composites via Selective Laser Melting

    Directory of Open Access Journals (Sweden)

    Cijun Shuai

    2017-03-01

    Full Text Available Mg-Zn alloys have attracted great attention as implant biomaterials due to their biodegradability and biomechanical compatibility. However, their clinical application was limited due to the too rapid degradation. In the study, hydroxyapatite (HA was incorporated into Mg-Zn alloy via selective laser melting. Results showed that the degradation rate slowed down due to the decrease of grain size and the formation of protective layer of bone-like apatite. Moreover, the grain size continually decreased with increasing HA content, which was attributed to the heterogeneous nucleation and increased number of nucleation particles in the process of solidification. At the same time, the amount of bone-like apatite increased because HA could provide favorable areas for apatite nucleation. Besides, HA also enhanced the hardness due to the fine grain strengthening and second phase strengthening. However, some pores occurred owing to the agglomerate of HA when its content was excessive, which decreased the biodegradation resistance. These results demonstrated that the Mg-Zn/HA composites were potential implant biomaterials.

  1. Biodegradation Resistance and Bioactivity of Hydroxyapatite Enhanced Mg-Zn Composites via Selective Laser Melting.

    Science.gov (United States)

    Shuai, Cijun; Zhou, Yuanzhuo; Yang, Youwen; Feng, Pei; Liu, Long; He, Chongxian; Zhao, Mingchun; Yang, Sheng; Gao, Chengde; Wu, Ping

    2017-03-17

    Mg-Zn alloys have attracted great attention as implant biomaterials due to their biodegradability and biomechanical compatibility. However, their clinical application was limited due to the too rapid degradation. In the study, hydroxyapatite (HA) was incorporated into Mg-Zn alloy via selective laser melting. Results showed that the degradation rate slowed down due to the decrease of grain size and the formation of protective layer of bone-like apatite. Moreover, the grain size continually decreased with increasing HA content, which was attributed to the heterogeneous nucleation and increased number of nucleation particles in the process of solidification. At the same time, the amount of bone-like apatite increased because HA could provide favorable areas for apatite nucleation. Besides, HA also enhanced the hardness due to the fine grain strengthening and second phase strengthening. However, some pores occurred owing to the agglomerate of HA when its content was excessive, which decreased the biodegradation resistance. These results demonstrated that the Mg-Zn/HA composites were potential implant biomaterials.

  2. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts.

    Science.gov (United States)

    Panitiwat, Prapaporn; Salimee, Prarom

    2017-01-01

    This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC), MultiCore Flow (MCF), and LuxaCore Z-Dual (LCZ)), and a nanohybrid composite, (Tetric N-Ceram (TNC)). Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post) cemented with resin cement (Panavia F2.0). Samples were randomly divided into four groups (n=10). Each group was built-up with one of the four core materials following its manufacturers' instructions. The teeth were embedded in acrylic resin blocks. Nickel-Chromium crowns were fixed on the specimens with resin cement. The fracture resistance was determined using a universal testing machine with a crosshead speed of 1 mm/min at 1350 to the tooth axis until failure occurred. All core materials used in the study were subjected to test for the flexural modulus according to ISO 4049:2009. One-way ANOVA and Bonferroni multiple comparisons test indicated that the fracture resistance was higher in the groups with CPC and MCF, which presented no statistically significant difference (p>0.05), but was significantly higher than in those with LCZ and TNC (paligned with the same tendency of fracture loads. Among the cores used in this study, the composite core with high filler content tended to enhance fracture thresholds of teeth restored with fiber posts more than others.

  3. Antimicrobial resistance and species composition of Enterococcus spp. isolated from waters and sands of marine recreational beaches in Southeastern Brazil.

    Science.gov (United States)

    de Oliveira, Ana Julia Fernandes Cardoso; Pinhata, Juliana Maira Watanabe

    2008-04-01

    Density, species composition and antimicrobial resistance in bacteria of the Enterococcus genus were evaluated in seawater and sands from 2 marine recreational beaches with different levels of pollution. The 2 beaches showed predominance of Enterococcus faecalis and Enterococcus faecium, in the water and the sand. Dry sand presented higher densities of Enterococcus sp. and higher frequency of resistant strains than wet sand and seawater. The beach with a higher degree of pollution presented higher percentages of resistant strains (66.7% and 61.5%, in sand and in water, respectively) and resistance to a larger number of antimicrobials compared with the less polluted beach, Ilha Porchat (35.7% and 31.25% of resistant strains in sand and water, respectively). In water samples, the highest frequencies of resistance were obtained against streptomycin (38.5%) and erythromycin (25%), whilst in sand, the highest frequencies were observed in relation to erythromycin and tetracycline (38.1% and 14.3%, respectively). These results show that water and sands from beaches with high indexes of faecal contamination of human origin may be potential sources of contamination by pathogens and contribute to the dissemination of bacterial resistance.

  4. Effect of length and diameter of fiber reinforced composite post (FRC on fracture resistance of remaining tooth structure

    Directory of Open Access Journals (Sweden)

    Mahdiyeh seifi

    2013-03-01

    Full Text Available Introduction: Post and core has been considered for endodontically treated tooth, especially in cases with severe damage crowns. Recently fiber reinforced composite posts (FRC post have been used in the treatment of endodontically treated teeth. Because the length and diameter of posts are effective in stress distribution, the purpose of this study is to evaluate the effect of length and diameter of FRC post on fracture resistance. Methods: In this experimental study, 36 glass fiber posts with combination of 7mm, 9mm, and 12mm length and 1.1mm, 1.3mm and 1.5mm diameter were divided into 9 groups of 4. These posts were cemented in root canals by Panavia. Samples were tested with 45° compressive forces for the evaluation of fracture resistance. Datas were analyzed using SPSS soft ware and One- way and Two-way ANOVA analyses. Results: Fracture resistance did not increase significantly with the effect of length and diameter simultaneously (P=0.85. Samples with 12mm length and 1.5mm diameter had the greatest fracture resistance (1023/33N±239/22. The minimum fracture resistance had occurred in post with 7mm length and 1.5mm diameter (503/13N ±69/18. Fracture resistance increased significantly by increasing the length and the same diameter. Conclusion: It can be concluded that fracture resistance is affected by the length and not the diameter of FRC post.

  5. Effect of Length and Diameter of Fiber Reinforced Composite Post on Fracture Resistance of Remaining Tooth Structure

    Directory of Open Access Journals (Sweden)

    Saeid Ebrahimzadeh

    2013-03-01

    Full Text Available Introduction: Post and core has been considered for endodontically treated tooth, especially in cases with severe damage crowns. Recently fiber reinforced composite posts (FRC post have been used in the treatment of endodontically treated teeth. Because the length and diameter of posts are effective in stress distribution, the purpose of this study is to evaluate the effect of length and diameter of FRC post on fracture resistance. Methods: In this experimental study, 36 glass fiber posts with combination of 7mm, 9mm, and 12mm length and 1.1mm, 1.3mm and 1.5mm diameter were divided into 9 groups of 4. These posts were cemented in root canals by Panavia. Samples were tested with 45° compressive forces for the evaluation of fracture resistance. Datas were analyzed using SPSS soft ware and One- way and Two-way ANOVA analyses. Results: Fracture resistance did not increase significantly with the effect of length and diameter simultaneously (P=0.85. Samples with 12mm length and 1.5mm diameter had the greatest fracture resistance (1023/33N±239/22. The minimum fracture resistance had occurred in post with 7mm length and 1.5mm diameter (503/13N ±69/18. Fracture resistance increased significantly by increasing the length and the same diameter. Conclusion: It can be concluded that fracture resistance is affected by the length and not the diameter of FRC post.

  6. Fluorine-containing composition for forming anti-reflection film on resist surface and pattern formation method

    Science.gov (United States)

    Nishi, Mineo; Makishima, Hideo

    1996-01-01

    A composition for forming anti-reflection film on resist surface which comprises an aqueous solution of a water soluble fluorine compound, and a pattern formation method which comprises the steps of coating a photoresist composition on a substrate; coating the above-mentioned composition for forming anti-reflection film; exposing the coated film to form a specific pattern; and developing the photoresist, are provided. Since the composition for forming anti-reflection film can be coated on the photoresist in the form of an aqueous solution, not only the anti-reflection film can be formed easily, but also, the film can be removed easily by rinsing with water or alkali development. Therefore, by the pattern formation method according to the present invention, it is possible to form a pattern easily with a high dimensional accuracy.

  7. Vapor Grown Carbon Fiber/Polydicyclopentadiene Composites: Shapeable Pastes to Make Composite Tooling and Plasma Erosion-Resistant Parts

    National Research Council Canada - National Science Library

    Pittman, Charles

    2002-01-01

    .... In addition to dicyclopentadiene, other liquid resins, including phenolic, epoxies and vinyl esters were also blended with these nanofibers and then cured to form organic matrix carbon fiber composites. When the wt...

  8. Study of rheological, viscoelastic and vulcanization behavior of sponge EPDM/NR blended nano- composites

    International Nuclear Information System (INIS)

    Bashir, M Arshad; Shahid, M; Ahmed, Riaz; Yahya, A G

    2014-01-01

    In this research paper the effect of blending ratio of natural rubber (NR) with Ethylene Propylene Diene Monomer (EPDM) were investigated. Different samples of EPDM/NR ratio were prepared to study the variation of NR in EPDM on rheology, curing characteristics, tangent δ, and viscosity variation during vulcanization of sponge nano composites.The main aim of present research is to develop elastomeric based sponge composites with the blending ratio of base elastomers along with the carbon nano particles for high energy absorbing and damping applications. The curing characteristics, rheology and viscoelastic nature of the composite is remarkably influenced with the progressive blending ratio of the base elastomeric matrix

  9. Study of rheological, viscoelastic and vulcanization behavior of sponge EPDM/NR blended nano-composites

    International Nuclear Information System (INIS)

    Bashir, M. A.; Shahid, M.; Ahmed, R.; Yahya, A. G.

    2013-01-01

    In this research paper the effect of blending ratio of natural rubber (NR) with Ethylene Propylene Diene Monomer (EPDM) were investigated. Different samples of EPDM/NR ratio were prepared to study the variation of NR in EPDM on rheology, curing characteristics, tangent d, and viscosity variation during vulcanization of sponge nano composites. The main aim of present research is to develop elastomeric based sponge composites with the blending ratio of base elastomers along with the carbon nano particles for high energy absorbing and damping applications. The curing characteristics, rheology and viscoelastic nature of the composite is remarkably influenced with the progressive blending ratio of the base elastomeric matrix. (author)

  10. Sensitivity improvement of a fibre Bragg grating pH sensor with elastomeric coating

    International Nuclear Information System (INIS)

    Yulianti, Ian; Supa'at, A S M; Idrus, Sevia M; Anwar, M R S; Kurdi, Ojo

    2012-01-01

    A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating

  11. Sensitivity improvement of a fibre Bragg grating pH sensor with elastomeric coating

    Science.gov (United States)

    Yulianti, Ian; Supa'at, A. S. M.; Idrus, Sevia M.; Kurdi, Ojo; Anwar, M. R. S.

    2012-01-01

    A new optical pH sensor based on fibre Bragg grating (FBG) is demonstrated. The sensor consists of a FBG coated with pH sensitive hydrogel. The sensing was performed through the detection of wavelength shifts resulting from the induced strain on the FBG due to mechanical expansion of the hydrogel. An elastomeric coating was applied before the hydrogel coating to improve the sensitivity. The sensor performance was investigated by simulating the hydrogel swelling and the strain induced on the FBG. The swelling of hydrogel due to pH change was modelled using a free-energy function and was solved using the finite element method. With silicone rubber as the elastomer material, the results show that the sensitivity was improved by up to 66% compared to that of the FBG pH sensor without elastomeric coating.

  12. Pattern transfer printing by kinetic control of adhesion to an elastomeric stamp

    Science.gov (United States)

    Nuzzo, Ralph G [Champaign, IL; Rogers, John A [Champaign, IL; Menard, Etienne [Urbana, IL; Lee, Keon Jae [Tokyo, JP; Khang, Dahl-Young [Urbana, IL; Sun, Yugang [Champaign, IL; Meitl, Matthew [Champaign, IL; Zhu, Zhengtao [Urbana, IL

    2011-05-17

    The present invention provides methods, systems and system components for transferring, assembling and integrating features and arrays of features having selected nanosized and/or microsized physical dimensions, shapes and spatial orientations. Methods of the present invention utilize principles of `soft adhesion` to guide the transfer, assembly and/or integration of features, such as printable semiconductor elements or other components of electronic devices. Methods of the present invention are useful for transferring features from a donor substrate to the transfer surface of an elastomeric transfer device and, optionally, from the transfer surface of an elastomeric transfer device to the receiving surface of a receiving substrate. The present methods and systems provide highly efficient, registered transfer of features and arrays of features, such as printable semiconductor element, in a concerted manner that maintains the relative spatial orientations of transferred features.

  13. Novel Stabilisers Acting Simultaneously as Molecular-Weight Regulators in Soluble Elastomeric Polyurethanes

    Czech Academy of Sciences Publication Activity Database

    Hetflejš, Jiří; Šabata, Stanislav; Podešva, Jiří; Kovářová, Jana; Prokůpek, L.; Netopilík, Miloš; Spěváček, Jiří; Sýkora, Jan

    2010-01-01

    Roč. 95, č. 4 (2010), s. 579-586 ISSN 0141-3910 R&D Projects: GA ČR GA203/07/0987; GA AV ČR IAA400720706 Institutional research plan: CEZ:AV0Z40720504; CEZ:AV0Z40500505 Keywords : stabilisers * molecular-weight regulators * elastomeric polyurethanes Subject RIV: CC - Organic Chemistry Impact factor: 2.594, year: 2010

  14. Friction produced by types of elastomeric ligatures in treatment mechanics with the preadjusted appliance.

    Science.gov (United States)

    Baccetti, Tiziano; Franchi, Lorenzo

    2006-03-01

    The objective was to compare the frictional forces generated by new nonconventional passive elastomeric ligatures (NCL) and conventional elastomeric ligatures (CL) under dry conditions. An experimental model reproducing the right buccal segment of the upper arch and consisting of five stainless steel 0.022-inch preadjusted brackets (from the second premolar through the central incisor) was used to assess both static and kinetic frictional forces produced by NCL and CL. The frictional forces generated by the 0.019 x 0.025-inch stainless steel wire with the two types of elastomeric ligatures were recorded by sliding the wire into the aligned brackets. The friction produced by the 0.014-inch superelastic nickel titanium wire was evaluated both in the presence of aligned brackets and of three-mm misaligned canine bracket. The amount of both static and kinetic frictions were minimal (<10 g) in the NCL group in the presence of aligned brackets with both types of wires, whereas it ranged from a minimum of 95.6 g for the 0.014-inch superelastic nickel titanium wire to a maximum of 590.7 g for the 0.019 x 0.025-inch stainless steel wire when using CL. The amount of both static and kinetic frictions in the presence of a misaligned canine bracket in the NCL group were less than half of that shown by the CL group. A recently developed passive ligature system is able to produce significantly lower levels of frictional forces in vitro when compared with conventional elastomeric modules.

  15. Evaluation of the effectiveness of elastomeric mount using vibration power flow and transmissibility methods

    Science.gov (United States)

    Arib Rejab, M. N.; Shukor, S. A. Abdul; Sofian, M. R. Mohd; Inayat-Hussain, J. I.; Nazirah, A.; Asyraf, I.

    2017-10-01

    This paper presents the results of an experimental work to determine the dynamic stiffness and loss factor of elastomeric mounts. It also presents the results of theoretical analysis to determine the transmissibility and vibration power flow of these mounts, which are associated with their contribution to structure-borne noise. Four types of elastomeric mounts were considered, where three of them were made from green natural rubber material (SMR CV60, Ekoprena and Pureprena) and one made from petroleum based synthetic rubber (EPDM). In order to determine the dynamic stiffness and loss factor of these elastomeric mounts, dynamic tests were conducted using MTS 830 Elastomer Test System. Dynamic stiffness and loss factor of these mounts were measured for a range of frequency between 5 Hz and 150 Hz, and with a dynamic amplitude of 0.2 mm (p-p). The transmissibility and vibration power flow were determined based on a simple 2-Degree-of-Freedom model representing a vibration isolation system with a flexible receiver. This model reprsents the three main parts of a vehicle, which are the powertrain and engine mounting, the flexible structure and the floor of the vehicle. The results revealed that synthetic rubber (EPDM) was only effective at high frequency region. Natural rubber (Ekoprena), on the other hand, was found to be effective at both low and high frequency regions due to its low transmissibility at resonant frequency and its ability to damp the resonance. The estimated structure-borne noise emission showed that Ekoprena has a lower contribution to structure-borne noise as compared to the other types of elastomeric mounts.

  16. Antibiotic stability related to temperature variations in elastomeric pumps used for outpatient parenteral antimicrobial therapy (OPAT).

    Science.gov (United States)

    Voumard, Rachel; Van Neyghem, Niklas; Cochet, Camille; Gardiol, Céline; Decosterd, Laurent; Buclin, Thierry; de Valliere, Serge

    2017-05-01

    Elastomeric pumps can be used for the continuous administration of antimicrobials in the outpatient setting. A potentially limiting factor in their use is the stability of antimicrobials. To investigate under real-life conditions the temperature variations of antibiotic solutions contained in elastomeric pumps, and to examine under such conditions the stability of five antibiotics. Healthy volunteers carried the elastomeric pumps in carry pouches during their daily activities. A thermologger measured the temperatures every 15 min over 24 h. Antibiotic concentrations were measured by HPLC coupled to tandem MS. During daytime, the temperature of solutions in the pumps increased steadily, warming to >30°C. During the night, when the pumps were kept attached to the waist, the temperatures reached up to 33°C. The use of white carry pouches avoided excessive temperature increases. Over seven experiments, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. Flucloxacillin showed a mean decrease in concentration of 11% ( P  = 0.001). Real-life situations can cause significant temperature rises in elastomeric pumps, thereby potentially increasing the risk of antibiotic degradation. Patients should be instructed to avoid situations causing excessive temperature increases. Despite these temperature variations, cefazolin, cefepime, piperacillin and tazobactam were found to be stable over 24 h. A moderate degradation was noticed for flucloxacillin, albeit most probably not to an extent that might impair anti-infective efficacy. © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  17. Assessment of Performance for Elastomeric Bearings Used on Bridges and Viaducts

    Science.gov (United States)

    Popa, Sorin Adrian

    2017-12-01

    The in service safety and reliability assurance of bridges and viaducts is determined by the choice of materials and products suitable for the design bearing solution of that construction structure. The paper proposes an operational solution for the performance characteristics assessment and verification of elastomeric bearings, which will be the basis for the consistent and coherent application of the requirements established by technical and legal regulations in the construction domain.

  18. Hybrid magnetorheological fluid–elastomeric lag dampers for helicopter stability augmentation

    International Nuclear Information System (INIS)

    Hu Wei; Wereley, Norman M

    2008-01-01

    A laboratory demonstration of a hybrid magnetorheological fluid–elastomeric (MRFE) damper is investigated for adjustable or programmable lag mode damping in helicopters, so that damping requirements can be varied as a function of different flight conditions. The laboratory demonstration of this hybrid MRFE lag damper consists of a double lap shear elastomeric damper in parallel with two magnetorheological (MR) flow mode dampers. This is compared to a damper where only elastomeric materials are implemented, i.e., a double lap shear specimen. The relationship between the output force and the quasi-steady harmonic displacement input to a flow mode MR damper is exploited, where the output force can be adjusted as a function of applied magnetic field. Equivalent viscous damping is used to compare the damping characteristics of the hybrid damper to a conventional elastomeric damper under steady-state sinusoidal displacement excitation. To demonstrate feasibility, a hybrid MRFE damper test setup is designed, and single frequency (lag frequency or rotor in-plane bending frequency) and dual frequency (lag frequency and rotor frequency) tests are conducted under different magnetic fields. The hybrid MRFE damper exhibits amplitude-dependent damping behavior. However, with application of a magnetic field, the damping level is controlled to a specific damping level objective as a function of displacement amplitude. Similarly, under dual frequency conditions, damping degradation at the lag frequency, because of lag motion at the rotor frequency, can also be recovered by increasing magnetic field. A time-domain analysis is developed to study the nonlinear dynamic behavior of the hybrid MRFE damper. Using rate-dependent elasto-slides, the amplitude-dependent behavior of the hybrid MRFE damper is accurately reconstructed using both constant and current-dependent (i.e. controllable) parameters. The analysis is physically motivated and can be applied to the elastomer and MR fluid

  19. Permeation of "Hydromer" Film: An Elastomeric Hydrogen-Capturing Biopolymer.

    Energy Technology Data Exchange (ETDEWEB)

    Karnesky, Richard A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Friddle, Raymond William [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Whaley, Josh A. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Smith, Geoffrey [New Mexico State Univ., Las Cruces, NM (United States)

    2015-12-01

    This report analyzes the permeation resistance of a novel and proprietary polymer coating for hydrogen isotope resistance that was developed by New Mexico State University. Thermal gravimetric analysis and thermal desoprtion spectroscopy show the polymer is stable thermally to approximately 250 deg C. Deuterium gas-driven permeation experiments were conducted at Sandia to explore early evidence (obtained using Brunauer - Emmett - Teller) of the polymer's strong resistance to hydrogen. With a relatively small amount of the polymer in solution (0.15%), a decrease in diffusion by a factor of 2 is observed at 100 and 150 deg C. While there was very little reduction in permeability, the preliminary findings reported here are meant to demonstrate the sensitivity of Sandia's permeation measurements and are intended to motivate the future exploration of thicker barriers with greater polymer coverage.

  20. Initial Tensile and Residual Forces of Pigmented Elastomeric Ligatures from Various Brands

    Science.gov (United States)

    Wichai, Wassana; Anuwongnukroh, Niwat; Dechkunakorn, Surachai; Kaypetch, Rattiporn; Tua-ngam, Peerapong

    2017-11-01

    This study aimed to investigate the initial tensile and residual forces of pigmented elastomeric ligatures (clear, pink, and metallic) from three commercial brands - Brand 1 (USA), Brand 2 (USA), and Brand 3(China). Twelve elastomeric ligatures of each brand and color were evaluated for initial tensile and residual forces after stretching for 28 days at 37°C by a Universal Testing Machine. The results showed that the highest initial tensile force was 14.78 N, 20.71 N, and 15.1 N for the metallic color of Brand-1, pink color of Brand -2, and metallic color of Brand -3, respectively. There were significant (pbrand, except clear and metallic color of Brand-1 & 3 and pink color of Brand-2 & 3. Similarly, among the pigmented ligatures from each brand, significant (pBrand-1 & 3. Brand-3 had the highest residual force after 28 days, whereas the loss of force was 80-90% in Brand-1 & 2 and 20-30% in Brand-3. There were also significant (pbrand, except metallic color of Brand-1. In conclusion, there were significant differences in the initial tensile and residual forces among the three pigmented elastomeric ligatures of the three commercial brands.

  1. Preliminary SEM Observations on the Surface of Elastomeric Impression Materials after Immersion or Ozone Disinfection

    Science.gov (United States)

    Prombonas, Anthony; Yannikakis, Stavros; Karampotsos, Thanasis; Katsarou, Martha-Spyridoula; Drakoulis, Nikolaos

    2016-01-01

    Introduction Surface integrity of dental elastomeric impression materials that are subjected to disinfection is of major importance for the quality of the final prosthetic restorations. Aim The aim of this qualitative Scanning Electronic Microscopy (SEM) study was to reveal the effects of immersion or ozone disinfection on the surface of four dental elastomeric impression materials. Materials and Methods Four dental elastomeric impression material brands were used (two vinyl polysiloxane silicones, one polyether, and one vinyl polyether silicone). Total of 32 specimens were fabricated, eight from each impression material. Specimens were immersion (0.525% sodium hypochlorite solution or 0.3% benzalkonium chloride solution) or ozone disinfected or served as controls and examined with SEM. Results Surface degradation was observed on several speci-mens disinfected with 0.525% sodium hypochlorite solution. Similar wavy-wrinkling surface structures were observed in almost all specimens, when treated either with 0.3% benzalkonium chloride solution or ozone. Conclusion The SEM images obtained from this study revealed that both immersion disinfectants and ozone show similar impression material surface alterations. Ozone seems to be non-inferior as compared to immersion disinfectants, but superior as to environmental protection. PMID:28208993

  2. Forces released during alignment with a preadjusted appliance with different types of elastomeric ligatures.

    Science.gov (United States)

    Franchi, Lorenzo; Baccetti, Tiziano

    2006-05-01

    The purpose of this in-vitro study was to compare the forces generated by new nonconventional elastomeric ligatures (NCEL) and conventional elastomeric ligatures (CEL) during leveling and aligning phases. The testing model consisted of 5 stainless steel 0.022-in preadjusted brackets for second premolar, first premolar, canine, lateral incisor, and central incisor. The canine bracket was welded to a sliding bar that allowed for different vertical positions. The forces generated by 3 sizes of wires (0.012-, 0.014-, and 0.016-in superelastic nickel-titanium) with the 2 types of elastomeric ligatures at different amounts of upward canine misalignment (1.5, 3, 4.5, and 6 mm) were recorded. Significant differences between CEL and NCEL were found for all tested variables (P <.01) with the exception of the 0.014- and 0.016-in wires at canine misalignment of 1.5 mm. A noticeable amount of force was generated with the NCEL at all 4 canine positions with all 3 wire sizes (from about 50 to about 150 g). With 4.5 mm of canine misalignment or more, the average amount of released force with the CEL was approximately zero.

  3. Puncture mechanics of soft elastomeric membrane with large deformation by rigid cylindrical indenter

    Science.gov (United States)

    Liu, Junjie; Chen, Zhe; Liang, Xueya; Huang, Xiaoqiang; Mao, Guoyong; Hong, Wei; Yu, Honghui; Qu, Shaoxing

    2018-03-01

    Soft elastomeric membrane structures are widely used and commonly found in engineering and biological applications. Puncture is one of the primary failure modes of soft elastomeric membrane at large deformation when indented by rigid objects. In order to investigate the puncture failure mechanism of soft elastomeric membrane with large deformation, we study the deformation and puncture failure of silicone rubber membrane that results from the continuous axisymmetric indentation by cylindrical steel indenters experimentally and analytically. In the experiment, effects of indenter size and the friction between the indenter and the membrane on the deformation and puncture failure of the membrane are investigated. In the analytical study, a model within the framework of nonlinear field theory is developed to describe the large local deformation around the punctured area, as well as to predict the puncture failure of the membrane. The deformed membrane is divided into three parts and the friction contact between the membrane and indenter is modeled by Coulomb friction law. The first invariant of the right Cauchy-Green deformation tensor I1 is adopted to predict the puncture failure of the membrane. The experimental and analytical results agree well. This work provides a guideline in designing reliable soft devices featured with membrane structures, which are present in a wide variety of applications.

  4. Dynamic force delivery and damping behavior of different brands of elastomeric chains using dynamic mechanical analysis

    Directory of Open Access Journals (Sweden)

    Vivek Mahajan

    2015-01-01

    Full Text Available Introduction: The ability to close space efficiently in orthodontic tooth movement is of major clinical importance. Elastomeric chains are extensively used as tooth moving mechanism in orthodontics. The objective of this study was to evaluate the dynamic force delivery and damping behaviour of different brands of elastomeric chains using Dynamic Mechanical Analysis. Materials and Methods: Five types of clear elastomeric chains were taken from the different manufacturers: GAC International (Sunburst TM Power Chain, 3M Unitek (AlastiK TM Power Chain, ROCKY MOUNTAIN ORTHODONTICS (Energy Chain TM , ORMCO Power Chain and LIBRAL (Rabbit Force. Dynamic Mechanical Analysis was performed at room temperature at eight defined frequencies (0.125, 0.25, 0.5, 1.0, 2.0, 4.0, 8.0, and 16.0 Hz in immediate succession from lowest to highest. Five variables (Dynamic force, loss Stiffness, Storage Stiffness, Tan Delta and Damping were analyzed using repeated measures analysis of variance and Post-Hoc test was done to evaluate the difference between the means at different frequencies. Results: Post-hoc tests compared all frequencies for each brand showing significant differences were found among the different types of brands. Significance was set at 0.05. Conclusion: GAC brand had higher dynamic, storage and loss stiffness values. GAC brand shows higher damping values at lower frequencies.

  5. Elastomeric impression as a diagnostic method of cavitation in proximal dentin caries in primary molars

    Directory of Open Access Journals (Sweden)

    Adriela Azevedo Souza Mariath

    2007-12-01

    Full Text Available The purpose of this study was to validate the elastomeric impression after temporary tooth separation as a method of cavitation detection in proximal caries lesions in primary molars with outer half dentin radiolucency. Fifty-one children (4-10 years old, presenting radiolucency in the outer half of the dentin at the proximal surfaces of primary molars and proximal anatomic contact with the adjacent tooth (without restoration/cavitated caries lesion were enrolled in the study. Temporary tooth separation was performed with an orthodontic rubber ring placed around the contact point during 2-3 days. Thereafter, impression of the proximal surfaces was made. The elastomeric impressions were classified as "non-cavitated" or "cavitated" surfaces. Visual inspection after tooth separation was considered as the gold standard. Examiner reliability of visual inspection after tooth separation was determined (kappa 0.92. Impression examination was repeated every 5 participants to evaluate the reproducibility of the method. The frequency of cavitated lesions was 65%, and 67% of those were inactive. Sensitivity, specificity, positive and negative predictive values were 0.88% (95%CI 0.73-0.95, 0.89% (95%CI 0.67-0.97, 0.94% (95%CI 0.79-0.98 and 0.80% (95%CI 0.58-0.92, respectively. Impression examination showed total agreement regarding cavitation. The evaluation of elastomeric impression after tooth separation is a useful clinical resource in cavitation detection for clinicians and researchers when visual inspection is doubtful.

  6. In silico simulation and in vitro evaluation of an elastomeric scaffold using ultrasonic shear wave imaging

    Science.gov (United States)

    Yu, Jiao; Nie, Erwei; Zhu, Yanying; Hong, Yi

    2018-03-01

    Biodegradable elastomeric scaffolds for soft tissue repair represent a growing area of biomaterials research. Mechanical strength is one of the key factors to consider in the evaluation of candidate materials and the designs for tissue scaffolds. It is desirable to develop non-invasive evaluation methods of the mechanical property of scaffolds which would provide options for monitoring temporal mechanical property changes in situ. In this paper, we conduct in silico simulation and in vitro evaluation of an elastomeric scaffold using a novel ultrasonic shear wave imaging (USWI). The scaffold is fabricated from a biodegradable elastomer, poly(carbonate urethane) urea using salt leaching method. A numerical simulation is performed to test the robustness of the developed inversion algorithm for the elasticity map reconstruction which will be implemented in the phantom experiment. The generation and propagation of shear waves in a homogeneous tissue-mimicking medium with a circular scaffold inclusion is simulated and the elasticity map is well reconstructed. A PVA phantom experiment is performed to test the ability of USWI combined with the inversion algorithm to non-invasively characterize the mechanical property of a porous, biodegradable elastomeric scaffold. The elastic properties of the tested scaffold can be easily differentiated from the surrounding medium in the reconstructed image. The ability of the developed method to identify the edge of the scaffold and characterize the elasticity distribution is demonstrated. Preliminary results in this pilot study support the idea of applying the USWI based method for non-invasive elasticity characterization of tissue scaffolds.

  7. High Kinetic Energy Penetrator Shielding and High Wear Resistance Materials Fabricated with Boron Nitride Nanotubes (BNNTS) and BNNT Polymer Composites

    Science.gov (United States)

    Kang, Jin Ho (Inventor); Park, Cheol (Inventor); Sauti, Godfrey (Inventor); Smith, Michael W. (Inventor); Jordan, Kevin C. (Inventor); Lowther, Sharon E. (Inventor); Bryant, Robert George (Inventor)

    2015-01-01

    Boron nitride nanotubes (BNNTs), boron nitride nanoparticles (BNNPs), carbon nanotubes (CNTs), graphites, or combinations, are incorporated into matrices of polymer, ceramic or metals. Fibers, yarns, and woven or nonwoven mats of BNNTs are used as toughening layers in penetration resistant materials to maximize energy absorption and/or high hardness layers to rebound or deform penetrators. They can be also used as reinforcing inclusions combining with other polymer matrices to create composite layers like typical reinforcing fibers such as Kevlar.RTM., Spectra.RTM., ceramics and metals. Enhanced wear resistance and usage time are achieved by adding boron nitride nanomaterials, increasing hardness and toughness. Such materials can be used in high temperature environments since the oxidation temperature of BNNTs exceeds 800.degree. C. in air. Boron nitride based composites are useful as strong structural materials for anti-micrometeorite layers for spacecraft and space suits, ultra strong tethers, protective gear, vehicles, helmets, shields and safety suits/helmets for industry.

  8. Effect of domain size and interface characteristics on the impact resistance of selected polymer composites

    Science.gov (United States)

    Viratyaporn, Wantinee

    Nanocomposite technology has advanced considerably in recent years and excellent engineering properties have been achieved in numerous systems. In multiphase materials the enhancement of properties relies heavily on the nature at the interphase region between polymer domains and nanoparticle reinforcements. Strong adhesion between the phases provides excellent load-transfer and good mechanical elastic modulus and strength, whereas weak interaction contributes to crack deflection mechanisms and toughness. Polymer molecules are large and the presence of comparably sized filler particles affects chain gyration, which in turn influences the conformation of the polymer and the properties of the composite. Nanoparticles were incorporated into a poly(methyl methacrylate) matrix by means of in situ free radical (bulk) polymerization. Aluminum oxide and zinc oxide nanoparticles were added to study the effects of particle chemistry and shape on selected mechanical properties such as impact resistance, which showed significant improvement at a certain loading of zinc oxide. The elongated shape of zinc oxide particles appears to promote crack deflection processes and to introduce a pull-out mechanism similar to that observed in fiber composite systems. Moreover, the thermal stability of PMMA was improved with the addition of nanoparticles, apparently by steric hindrance of polymer chain motion and a second mechanism related to the dipole inducing effect of the oxide particles. The sensitivity of infrared spectroscopy to changes in molecular dipoles was used to study the nature of the polymer/particle interface. The results revealed some interesting aspects of the secondary bonds between polymers and oxides. Raman spectroscopy was used to investigate the extent of polymerization and changes in polymer conformation. A degree of polymerization of 93% was achieved in neat PMMA, and even when 5.0 v/o of PGMEA was introduced into the system no monomer was detected. However, when

  9. Determining the fracture resistance of fibre-reinforced glass matrix composites by means of the chevron-notch flexural technique

    Czech Academy of Sciences Publication Activity Database

    Boccaccini, A. R.; Kern, H.; Dlouhý, Ivo

    2001-01-01

    Roč. 308, 1/2 (2001), s. 111-117 ISSN 0921-5093 R&D Projects: GA ČR GV101/96/K264 Institutional research plan: CEZ:AV0Z2041904 Keywords : glass matrix composites * fracture toughness * chevron notch test Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.978, year: 2001

  10. The culturable intestinal microbiota of triploid and diploid juvenile Atlantic salmon (Salmo salar) - a comparison of composition and drug resistance

    OpenAIRE

    Cantas, Leon; Fraser, Thomas W. K.; Fjelldal, Per Gunnar; Mayer, Ian; Sørum, Henning

    2011-01-01

    Abstract Background With the increased use of ploidy manipulation in aquaculture and fisheries management this investigation aimed to determine whether triploidy influences culturable intestinal microbiota composition and bacterial drug resistance in Atlantic salmon (Salmo salar). The results could provide answers to some of the physiological differences observed between triploid and diploid fish, especially in terms of fish health. Results No ploidy effect was observed in the bacterial speci...

  11. Effect of chemical composition on corrosion resistance of Zircaloy fuel cladding tube for BWR

    International Nuclear Information System (INIS)

    Inagaki, Masahisa; Akahori, Kimihiko; Kuniya, Jirou; Masaoka, Isao; Suwa, Masateru; Maru, Akira; Yasuda, Teturou; Maki, Hideo.

    1990-01-01

    Effects of Fe and Ni contents on nodular corrosion susceptibility and hydrogen pick-up of Zircaloy were investigated. Total number of 31 Zr alloys having different chemical compositions; five Zr-Sn-Fe-Cr alloys, eight Zr-Sn-Fe-Ni alloys and eighteen Zr-Sn-Fe-Ni-Cr alloys, were melted and processed to thin plates for the corrosion tests in the environments of a high temperature (510degC) steam and a high temperature (288degC) water. In addition, four 450 kg ingots of Zr-Sn-Fe-Ni-Cr alloys were industrially melted and BWR fuel cladding tubes were manufactured through a current material processing sequence to study their producibility, tensile properties and corrosion resistance. Nodular corrosion susceptibility decreased with increasing Fe and Ni contents of Zircaloys. It was seen that the improved Zircaloys having Fe and Ni contents in the range of 0.30 [Ni]+0.15[Fe]≥0.045 (w%) showed no susceptibility to nodular corrosion. An increase of Fe content resulted in a decrease of hydrogen pick-up fraction in both steam and water environments. An increase of Fe and Ni content of Zircaloys in the range of Fe≤0.25 w% and Ni≤0.1 w% did not cause the changes in tensile properties and fabricabilities of fuel cladding tube. The fuel cladding tube of improved Zircaloy, containing more amount of Fe and Ni than the upper limit of Zircaloy-2 specification showed no susceptibility to nodular corrosion even in the 530degC steam test. (author)

  12. Nanoscale characterization of the thermal interface resistance of a heat-sink composite material by in situ TEM

    Science.gov (United States)

    Kawamoto, Naoyuki; Kakefuda, Yohei; Mori, Takao; Hirose, Kenji; Mitome, Masanori; Bando, Yoshio; Golberg, Dmitri

    2015-11-01

    We developed an original method of in situ nanoscale characterization of thermal resistance utilizing a high-resolution transmission electron microscope (HRTEM). The focused electron beam of the HRTEM was used as a contact-free heat source and a piezo-movable nanothermocouple was developed as a thermal detector. This method has a high flexibility of supplying thermal-flux directions for nano/microscale thermal conductivity analysis, and is a powerful way to probe the thermal properties of complex or composite materials. Using this method we performed reproducible measurements of electron beam-induced temperature changes in pre-selected sections of a heat-sink α-Al2O3/epoxy-based resin composite. Observed linear behavior of the temperature change in a filler reveals that Fourier’s law holds even at such a mesoscopic scale. In addition, we successfully determined the thermal resistance of the nanoscale interfaces between neighboring α-Al2O3 fillers to be 1.16 × 10-8 m2K W-1, which is 35 times larger than that of the fillers themselves. This method that we have discovered enables evaluation of thermal resistivity of composites on the nanoscale, combined with the ultimate spatial localization and resolution sample analysis capabilities that TEM entails.

  13. Oxidation and Ablation Resistance of Low Pressure Plasma-Sprayed ZrB2-Si Composite Coating

    Science.gov (United States)

    Niu, Yaran; Wang, Hongyan; Huang, Liping; Li, Hong; Liu, Xuanyong; Zheng, Xuebin; Ding, Chuanxian

    2014-02-01

    In the present work, ZrB2-based coating containing Si additive was prepared by low pressure plasma spray process. The chemical composition and microstructure of the ZrB2-Si coating were characterized by XRD, EDS and SEM. The oxidation behavior of the coating was investigated in ambient air for different duration time. The ablation-resistant property of the coating was carried out using a plasma flame. The results obtained indicate that the ZrB2-Si composite coating exhibited compact lamellar microstructure with a porosity less than 5%. The silicon phase was uniformly distributed in the ZrB2 matrix. The composite coating presented excellent oxidation-resistance at high temperature of 1500 °C, which resulted from the formed continuous and dense glassy silicon oxide film on its surface. The ablation resistance of the ZrB2-Si coating has been proved to be excellent, which could withstand the plasma flame (above 2000 °C, atmosphere) for 10 min.

  14. Wear Resistant Thermal Sprayed Composite Coatings Based on Iron Self-Fluxing Alloy and Recycled Cermet Powders

    Directory of Open Access Journals (Sweden)

    Heikki SARJAS

    2012-03-01

    Full Text Available Thermal spray and WC-Co based coatings are widely used in areas subjected to abrasive wear. Commercial  cermet thermal spray powders for HVOF are relatively expensive. Therefore applying these powders in cost-sensitive areas like mining and agriculture are hindered. Nowadays, the use of cheap iron based self-fluxing alloy powders for thermal spray is limited. The aim of this research was to study properties of composite powders based on self-fluxing alloys and recycled cermets and to examine the properties of thermally sprayed (HVOF coatings from composite powders based on iron self-fluxing alloy and recycled cermet powders (Cr3C2-Ni and WC-Co. To estimate the properties of  recycled cermet powders, the sieving analysis, laser granulometry and morphology were conducted. For deposition of coatings High Velocity Oxy-Fuel spray was used. The structure and composition of powders and coatings were estimated by SEM and XRD methods. Abrasive wear performance of coatings was determined and compared with wear resistance of coatings from commercial powders. The wear resistance of thermal sprayed coatings from self-fluxing alloy and recycled cermet powders at abrasion is comparable with wear resistance of coatings from commercial expensive spray powders and may be an alternative in tribological applications in cost-sensitive areas.DOI: http://dx.doi.org/10.5755/j01.ms.18.1.1338

  15. Relationships of wear resistance to phase composition and mechanical properties of newly developed high-nitrogen iron-chromium alloys

    International Nuclear Information System (INIS)

    Bannykh, O.A.; Blinov, V.M.; Kosytina, M.V.; Filippov, M.A.; Khadyev, M.S.; Nemirovskij, Yu.R.; Belozerova, T.A.

    2000-01-01

    Comparative tests for resistance against abrasive wear are performed using newly developed high-nitrogen (0.424-1.281 % N) chromium (14.93-23.85 % Cr) laboratory steel melts and commercial steel 110G13L. A layer-by-layer analysis of phase composition in the steels being tested are carried out in the direction from the surface into the base metal. The abrasive wear resistance of all steels is shown to be dependent on the development of martensitic transformation in the layer contacting with abrasive particles, as well as on the degree of strain hardening of the austenite of the layer. The laboratory steels after hardening and tempering in a wide temperature range essentially surpasses the steel 110G13L in wear resistance. The results obtained confirm the possibility of the use of high-nitrogen chromium steels as substitutes for steel 110G13L [ru

  16. Thioridazine Induces Major Changes in Global Gene Expression and Cell Wall Composition in Methicillin-Resistant Staphylococcus aureus USA300

    DEFF Research Database (Denmark)

    Thorsing, Mette; Klitgaard, Janne Kudsk; Atilano, Magda L.

    2013-01-01

    Subinhibitory concentrations of the neuroleptic drug thioridazine (TDZ) are well-known to enhance the killing of methicillin-resistant Staphylococcus aureus (MRSA) by β-lactam antibiotics, however, the mechanism underlying the synergy between TDZ and β-lactams is not fully understood. In the pres......Subinhibitory concentrations of the neuroleptic drug thioridazine (TDZ) are well-known to enhance the killing of methicillin-resistant Staphylococcus aureus (MRSA) by β-lactam antibiotics, however, the mechanism underlying the synergy between TDZ and β-lactams is not fully understood....... In the present study, we have examined the effect of a subinhibitory concentration of TDZ on antimicrobial resistance, the global transcriptome, and the cell wall composition of MRSA USA300. We show that TDZ is able to sensitize the bacteria to several classes of antimicrobials targeting the late stages...

  17. Development of mathematical models and methods for calculation of rail steel deformation resistance of various chemical composition

    Science.gov (United States)

    Umansky, A. A.; Golovatenko, A. V.; Kadykov, V. N.; Dumova, L. V.

    2016-09-01

    Using the device of the complex “Gleeble System 3800” the physical experimental studies of deformation resistance of chrome rail steel at different thermo-mechanical deformation parameters were carried out. On the basis of mathematical processing of experimental data the statistical model of dependence of the rail steel deformation resistance on the simultaneous influence of deformation degree, rate and temperature, as well as the steel chemical composition, was developed. The nature of influence of deformation parameters and the content of chemical elements in steel on its resistance to plastic deformation is scientifically substantiated. Verification of the adequacy of the proposed model by the comparative analysis of the calculated and actual rolling forces during passes in the universal rail-and-structural steel mill JSC “EVRAZ Consolidated West Siberian Metallurgical Plant” (“EVRAZ ZSMK”) showed the possibility of its use for development and improvement of new modes of rails rolling.

  18. Abscisic acid deficiency causes changes in cuticle permeability and pectin composition that influence tomato resistance to Botrytis cinerea.

    Science.gov (United States)

    Curvers, Katrien; Seifi, Hamed; Mouille, Grégory; de Rycke, Riet; Asselbergh, Bob; Van Hecke, Annelies; Vanderschaeghe, Dieter; Höfte, Herman; Callewaert, Nico; Van Breusegem, Frank; Höfte, Monica

    2010-10-01

    A mutant of tomato (Solanum lycopersicum) with reduced abscisic acid (ABA) production (sitiens) exhibits increased resistance to the necrotrophic fungus Botrytis cinerea. This resistance is correlated with a rapid and strong hydrogen peroxide-driven cell wall fortification response in epidermis cells that is absent in tomato with normal ABA production. Moreover, basal expression of defense genes is higher in the mutant compared with the wild-type tomato. Given the importance of this fast response in sitiens resistance, we investigated cell wall and cuticle properties of the mutant at the chemical, histological, and ultrastructural levels. We demonstrate that ABA deficiency in the mutant leads to increased cuticle permeability, which is positively correlated with disease resistance. Furthermore, perturbation of ABA levels affects pectin composition. sitiens plants have a relatively higher degree of pectin methylesterification and release different oligosaccharides upon inoculation with B. cinerea. These results show that endogenous plant ABA levels affect the composition of the tomato cuticle and cell wall and demonstrate the importance of cuticle and cell wall chemistry in shaping the outcome of this plant-fungus interaction.

  19. Effect of Shear Resistance on Flexural Debonding Load-Carrying Capacity of RC Beams Strengthened with Externally Bonded FRP Composites

    Directory of Open Access Journals (Sweden)

    Guibing Li

    2014-05-01

    Full Text Available Debonding failure is the main failure mode in flexurally strengthened reinforced concrete beams by externally bonded or near surface mounted fibre reinforced polymer (FRP composites. It is believed that FRP debonding will be initiated if the shear stress on the concrete-FRP interface reaches the tensile strength of concrete. However, it was found through experimental and analytical studies that the debonding mechanism of FRP composites has the potential of shear failure in combination with debonding failure. Moreover, the shear failure probably influences the debonding failure. Presently, there are very little experimental and analytical studies to investigate the influence of shear resistance of reinforced concrete (RC beam on FRP debonding failure. The current study investigates and analyzes the effect of shear resistance on FRP debonding failure based on test results. The analytical results show that the shear resistance of RC beam has a great effect on flexural debonding load-carrying capacity of FRP-strengthened RC beam. The influence of shear resistance on flexural debonding load-carrying capacity must be fully considered in flexural strengthening design of RC beams.

  20. The Cryogenic Impact Resistant Evaluation of Filament Wound Materials for Use in Composite Pressure Vessels Project

    Data.gov (United States)

    National Aeronautics and Space Administration — HyPerComp Engineering Inc. (HEI) and Utah State University (USU) propose to develop technology for lightweight composite materials for use in composite structures...

  1. Impact-Resistant, Damage-Tolerant Composites with STF Energy Absorbing Layers, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — We propose an innovative hybrid composite that combines the smart energy-absorbing shear thickening fluids (STF) with validated hard upper torso composite materials...

  2. Development of a snubber type magnetorheological fluid elastomeric lag damper for helicopter stability augmentation

    Science.gov (United States)

    Ngatu, Grum T.

    Most advanced helicopter rotors are typically fitted with lag dampers, such as elastomeric or hybrid fluid-elastomeric (FE) lag dampers, which have lower parts counts, are lighter in weight, easier to maintain, and more reliable than conventional hydraulic dampers. However, the damping and stiffness properties of elastomeric and fluid elastomeric lag dampers are non-linear functions of lag/rev frequency, dynamic lag amplitude, and operating temperature. It has been shown that elastomeric damping and stiffness levels diminish markedly as amplitude of damper motion increases. Further, passive dampers tend to present severe damping losses as damper operating temperature increases either due to in-service self-heating or hot atmospheric conditions. Magnetorheological (MR) dampers have also been considered for application to helicopter rotor lag dampers to mitigate amplitude and frequency dependent damping behaviors. MR dampers present a controllable damping with little or no stiffness. Conventional MR dampers are similar in configuration to linear stroke hydraulic type dampers, which are heavier, occupy a larger space envelope, and are unidirectional. Hydraulic type dampers require dynamic seal to prevent leakage, and consequently, frequent inspections and maintenance are necessary to ensure the reliability of these dampers. Thus, to evaluate the potential of combining the simplicity and reliability of FE and smart MR technologies in augmenting helicopter lag mode stability, an adaptive magnetorheological fluid-elastomeric (MRFE) lag damper is developed in this thesis as a retrofit to an actual fluid-elastomeric (FE) lag damper. Consistent with the loading condition of a helicopter rotor system, single frequency (lag/rev) and dual frequency (lag/rev at 1/rev) sinusoidal loading were applied to the MRFE damper at varying temperature conditions. The complex modulus method was employed to linearly characterize and compare the performance of the MRFE damper with the

  3. Preparation and corrosion resistance of magnesium phytic acid/hydroxyapatite composite coatings on biodegradable AZ31 magnesium alloy.

    Science.gov (United States)

    Zhang, Min; Cai, Shu; Zhang, Feiyang; Xu, Guohua; Wang, Fengwu; Yu, Nian; Wu, Xiaodong

    2017-06-01

    In this work, a magnesium phytic acid/hydroxyapatite composite coating was successfully prepared on AZ31 magnesium alloy substrate by chemical conversion deposition technology with the aim of improving its corrosion resistance and bioactivity. The influence of hydroxyapatite (HA) content on the microstructure and corrosion resistance of the coatings was investigated. The results showed that with the increase of HA content in phytic acid solution, the cracks on the surface of the coatings gradually reduced, which subsequently improved the corrosion resistance of these coated magnesium alloy. Electrochemical measurements in simulated body fluid (SBF) revealed that the composite coating with 45 wt.% HA addition exhibited superior surface integrity and significantly improved corrosion resistance compared with the single phytic acid conversion coating. The results of the immersion test in SBF showed that the composite coating could provide more effective protection for magnesium alloy substrate than that of the single phytic acid coating and showed good bioactivity. Magnesium phytic acid/hydroxyapatite composite, with the desired bioactivity, can be synthesized through chemical conversion deposition technology as protective coatings for surface modification of the biodegradable magnesium alloy implants. The design idea of the new type of biomaterial is belong to the concept of "third generation biomaterial". Corrosion behavior and bioactivity of coated magnesium alloy are the key issues during implantation. In this study, preparation and corrosion behavior of magnesium phytic acid/hydroxyapatite composite coatings on magnesium alloy were studied. The basic findings and significance of this paper are as follows: 1. A novel environmentally friendly, homogenous and crack-free magnesium phytic acid/hydroxyapatite composite coating was fabricated on AZ31 magnesium alloy via chemical conversion deposition technology with the aim of enhancing its corrosion resistance and

  4. An evaluation of the effect of various gloves on polymerization inhibition of elastomeric impression materials: An In vitro study

    Directory of Open Access Journals (Sweden)

    Vinuta Hiremath

    2017-01-01

    Full Text Available Background: Latex protective barriers such as gloves and rubber dam material have been used widely in restorative procedures for crown and bridge. However, the chemical used during latex glove fabrication is thought to inhibit the polymerization of elastomeric impression materials used for impression making which has a detrimental effect on the dimensional accuracy and surface definition of resultant casts used for restorative procedures. The objectives of the study were to examine the surface of different elastomeric impressions on contact with various gloves. Materials and Methods: This clinical study included a total of eighty specimens of two types of the putty elastomeric impression material were hand manipulated by wearing three different gloves materials and is placed on a marked area of a clean and alcohol-treated glass slab at room temperature. The specimens examined for any signs of polymerization inhibition. The specimen will be rated as being “inhibited” if any residue remains on the glass slab and absence of the above will result as “no inhibition.” Results: The results showed no interference with the polymerization inhibition of the selected elastomers followed by the nitrile glove. The latex gloves showed inhibited set of the elastomeric impression material but set after sometime confirming time-dependent inhibition of the impression material. Conclusion: This study shows that the use of latex and sometime nitrile gloves during crown and bridge procedures should be contraindicated and the use of vinyl gloves should be stressed when working with elastomeric impression materials.

  5. An Evaluation of the Effect of Various Gloves on Polymerization Inhibition of Elastomeric Impression Materials: An In vitro Study.

    Science.gov (United States)

    Hiremath, Vinuta; Vinayakumar, G; Ragher, Mallikarjuna; Rayannavar, Sounyala; Bembalagi, Mahantesh; Ashwini, B L

    2017-11-01

    Latex protective barriers such as gloves and rubber dam material have been used widely in restorative procedures for crown and bridge. However, the chemical used during latex glove fabrication is thought to inhibit the polymerization of elastomeric impression materials used for impression making which has a detrimental effect on the dimensional accuracy and surface definition of resultant casts used for restorative procedures. The objectives of the study were to examine the surface of different elastomeric impressions on contact with various gloves. This clinical study included a total of eighty specimens of two types of the putty elastomeric impression material were hand manipulated by wearing three different gloves materials and is placed on a marked area of a clean and alcohol-treated glass slab at room temperature. The specimens examined for any signs of polymerization inhibition. The specimen will be rated as being "inhibited" if any residue remains on the glass slab and absence of the above will result as "no inhibition." The results showed no interference with the polymerization inhibition of the selected elastomers followed by the nitrile glove. The latex gloves showed inhibited set of the elastomeric impression material but set after sometime confirming time-dependent inhibition of the impression material. This study shows that the use of latex and sometime nitrile gloves during crown and bridge procedures should be contraindicated and the use of vinyl gloves should be stressed when working with elastomeric impression materials.

  6. Maxillomandibular relationship record for implant complete mouth rehabilitation with elastomeric material and facial surface index of existing denture

    Directory of Open Access Journals (Sweden)

    Pravinkumar G Patil

    2015-01-01

    Full Text Available Introduction: The maxillomandibular relationship (MMR record is a critical step to establish the new occlusion in implant supported complete mouth rehabilitation. Using patients existing denture for recording the MMR requires implant definitive cast to be modified extensively to completely seat the denture (with unaltered flanges on it. This may influence the correct seating of the denture on the implant definitive cast causing faulty recording of the MMR. Materials and Method: Elastomeric record bases, reinforced with the resin framework, are fabricated and relined with the light body elastomeric material when all the healing abutments are in place. The MMR is recorded with these elastomeric record bases using vacuum formed facial surface index of the occluded existing dentures as a guideline. Results: The elastomeric record bases with facial surface index of the existing dentures can allow clinicians to record MMR records without removing the healing abutments from the mouth with acceptable accuracy. This can save chair-side time of the procedure. The record of facial surfaces of existing complete denture in the form of vacuum formed sheet helps to set the occlusal vertical dimension. Conclusion: Use of facial surface index together with the elastomeric record bases can be the useful alternative technique to record the MMR in patients with implant supported full mouth rehabilitation. Further study is required to prove its routine clinical utility.

  7. Composites

    OpenAIRE

    Zhao, Hanqing; Guo, Yuanzheng

    2014-01-01

    This thesis was a literature study concerning composites. With composites becoming increasingly popular in various areas such as aerospace industry and construction, the research about composites has a significant meaning accordingly. This thesis was aim at introducing some basic information of polymer matrix composites including raw mate-rial, processing, testing, applications and recycling to make a rough understanding of this kind of material for readers. Polymeric matrices, fillers,...

  8. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2011-01-01

    Strategies are open compositions to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them in full...

  9. Composition

    DEFF Research Database (Denmark)

    2014-01-01

    Memory Pieces are open compositions to be realised solo by an improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound files will in some cases only provide a few minutes' sample. Please DOWNLOAD them to hear them...

  10. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2010-01-01

    New Year is an open composition to be realised by improvising musicians. It is included in "From the Danish Seasons" (see under this title). See more about my composition practise in the entry "Composition - General Introduction". This work is licensed under a Creative Commons "by-nc" License. You...

  11. Effect of different composite core materials on fracture resistance of endodontically treated teeth restored with FRC posts

    Directory of Open Access Journals (Sweden)

    Prapaporn PANITIWAT

    Full Text Available Abstract Objective This study evaluated the fracture resistance of endodontically treated teeth restored with fiber reinforced composite posts, using three resin composite core build-up materials, (Clearfil Photo Core (CPC, MultiCore Flow (MCF, and LuxaCore Z-Dual (LCZ, and a nanohybrid composite, (Tetric N-Ceram (TNC. Material and Methods Forty endodontically treated lower first premolars were restored with quartz fiber posts (D.T. Light-Post cemented with resin cement (Panavia F2.0. Samples were randomly divided into four groups (n=10. Each group was built-up with one of the four core materials following its manufacturers’ instructions. The teeth were embedded in acrylic resin blocks. Nickel-Chromium crowns were fixed on the specimens with resin cement. The fracture resistance was determined using a universal testing machine with a crosshead speed of 1 mm/min at 1350 to the tooth axis until failure occurred. All core materials used in the study were subjected to test for the flexural modulus according to ISO 4049:2009. Results One-way ANOVA and Bonferroni multiple comparisons test indicated that the fracture resistance was higher in the groups with CPC and MCF, which presented no statistically significant difference (p>0.05, but was significantly higher than in those with LCZ and TNC (p<0.05. In terms of the flexural modulus, the ranking from the highest values of the materials was aligned with the same tendency of fracture loads. Conclusion Among the cores used in this study, the composite core with high filler content tended to enhance fracture thresholds of teeth restored with fiber posts more than others.

  12. Study on Composition, Microstructure and Wear Behavior of Fe-B-C Wear-Resistant Surfacing Alloys

    Science.gov (United States)

    Zhuang, Minghui; Li, Muqin; Wang, Jun; Ma, Zhen; Yuan, Shidan

    2017-12-01

    Fe-B-C alloy layers with various microstructures were welded on Q235 steel plates using welding powders/H08Mn2Si and welding wires composite surfacing technology. The relationship existing between the chemical composition, microstructure and wear resistance of the surfacing alloy layers was investigated by scanning electron microscopy, x-ray diffraction, electron backscatter diffraction and wear tests. The results demonstrated that the volume fractions and morphologies of the microstructures in the surfacing alloy layers could be controlled by adjusting the boron and carbon contents in the welding powders, which could further regulate the wear resistance of the surfacing alloy layers. The typical microstructures of the Fe-B-C surfacing alloy layers included dendritic Fe, rod-like Fe2B, fishbone-like Fe2B and daisy-like Fe3(C, B). The wear resistance of the alloy layers with various morphologies differed. The wear resistance order of the different microstructures was: rod-like Fe2B > fishbone-like Fe2B > daisy-like Fe3(C, B) > dendritic Fe. A large number of rod-like Fe2B with high microhardness could be obtained at the boron content of 5.70 5.90 wt.% and the carbon content of 0.50 0.60wt.%. The highest wear resistance of the Fe-B-C alloy layers reached the value of 24.1 g-1, which demonstrates the main microscopic cutting wear mechanism of the Fe-B-C alloy layers.

  13. Mechanical behavior of composite based polypropylene: Recycling and strain rate effects

    Science.gov (United States)

    Bahlouli, N.; Pessey, D.; Ahzi, S.; Rémond, Y.

    2006-08-01

    Recycling effects on the dynamic response of composite based polypropylene is studied in this paper. Materials used here are filled and unfilled impact modified polypropylene. Nodules of EPDM represent the elastomeric phase for the filled composite based polypropylene. Fillers are particles of talc. For the unfilled polypropylene, the elastomeric phase is nodules of EPR. Different tensile tests, until rupture, were performed from quasi static to high strain rates. Virgin specimens were recycled in order to study the degradation due to the effect of recycling under dynamic loading. Thus microstructural effects due to dynamic loading and recycling were observed by SEM.

  14. Initial fracture resistance and curing temperature rise of ten contemporary resin-based composites with increasing radiant exposure.

    Science.gov (United States)

    Shortall, A; El-Mahy, W; Stewardson, D; Addison, O; Palin, W

    2013-05-01

    The principal objective of this study was to determine whether the bulk fracture resistance of ten light activated composites varied over a clinically realistic range of radiant exposures between 5 and 40 J/cm(2). Ten operators were tested for clinically simulated radiant exposure delivery from a Bluephase(®) (Ivoclar Vivadent, Schaan, Liechtenstein) LED light to an occlusal cavity floor in tooth 27 in a mannequin head using a MARC(®)-Patient Simulator (Bluelight Analytics Inc., Halifax, NS) device. Notch disc test samples were prepared to determine the torque resistance to fracture (T) of the composites. Samples were irradiated with the same monowave Bluephase(®) light for 10s, 20s or 40s at distances of 0mm or 7 mm. After 24h, storage samples were fractured in a universal testing machine and torque to failure was derived. Radiant exposure delivered in the clinical simulation ranged from 14.3% to 69.4% of maximum mean radiant exposure deliverable at 0mm in a MARC(®)-Resin Calibrator (Bluelight Analytics Inc., Halifax, NS) test device. Mean torque to failure increased significantly (Pradiant exposure for 8 out of 10 products. The micro-fine hybrid composite Gradia Direct anterior (GC) had the lowest mean (S.D.) T between 10.3 (1.8)N/mm and 13.7 (2.2)N/mm over the tested radiant exposure range. Three heavily filled materials Majesty Posterior, Clearfil APX and Clearfil Photo-Posterior (Kuraray) had mean T values in excess of 25 N/mm following 40 J/cm(2) radiant exposure. Mean T for Z100 (3MESPE) and Esthet-X (Dentsply) increased by 10% and 91% respectively over the tested range of radiant exposures. Individual products require different levels of radiant exposure to optimize their fracture resistance. Light activated composites vary in the rate at which they attain optimal fracture resistance. Unless the clinician accurately controls all the variables associated with energy delivery, there is no way of predicting that acceptable fracture resistance will be

  15. Fracture resistance of endodontically treated teeth restored with indirect composite inlay and onlay restorations – An in vitro study

    Science.gov (United States)

    Alshiddi, Ibraheem F.; Aljinbaz, Amjad

    2015-01-01

    Objective The purpose of this in vitro study was to evaluate and compare the fracture resistance and fracture mode of extensive indirect inlay and onlay composite resin restorations performed for endodontically treated premolars. Materials and methods A total of 55 extracted maxillary premolars were randomly divided into four groups. The first group (n = 15) remained untreated to serve as a positive control; the second group (n = 15) was endodontically treated with inlay cavities prepared and restored with indirect composite inlay restorations; the third group (n = 15) was also endodontically treated with onlay cavities prepared and restored with indirect composite onlay restorations; and the fourth group (n = 10) was endodontically treated with mesio-occlusodistal (MOD) cavities prepared and left unrestored to serve as negative controls. Dual cure indirect composite resin was used to fabricate the inlay and onlay restorations performed for the second and third groups, respectively. All teeth were subjected to compressive axial loading test using a metal ball (6 mm in diameter) in a universal testing machine (Instron 1195) with a cross-head speed of 0.5 mm/min until a fracture occurred. Statistical analysis of fracture resistance and fracture mode were performed with analysis of variance (ANOVA) (α = 0.05) and Kruskal–Wallis (α = 0.05) tests, respectively. Results For the four treatment groups, the mean fracture resistance values were 1326.9 N, 1500.1 N, 1006.1 N, and 702.7 N, respectively. Statistical analyses showed no significant differences between the mean fracture resistance of the intact tooth group and the inlay restoration group (p > 0.05), while significant differences were observed between the mean fracture resistance of all the other groups (p inlay and onlay restorations. However, the fractures that accompanied the inlay restorations were more severe and were unable to be restored. PMID:26792970

  16. HTSC-based composites as materials with high magnetic resistance in weak magnetic fields

    CERN Document Server

    Balaev, D A; Popkov, S I; Shajkhutdinov, K A; Petrov, M I

    2001-01-01

    The magnetoresistance of the composites on the HTSC-basis with the structure of 1-2-3- + dielectric and HTSC + normal metal are studied. The composite materials are characterized by high magnetoresistance effect in weak magnetic fields within the wide temperature range. Such a behavior is explained on the basis of the notions on the nonreversibility line in the HTSC and thermal fluctuations and in the net of the Josephson-type weak bonds realized in the HTSC-composites. The HTSC-based composites are characterized by high sensitivity to weak magnetic fields (up to 300 Oe) at the liquid nitrogen temperature

  17. Effect of resin cements and aging on cuspal deflection and fracture resistance of teeth restored with composite resin inlays.

    Science.gov (United States)

    Salaverry, Aurélio; Borges, Gilberto Antonio; Mota, Eduardo Gonçalves; Burnett Júnior, Luiz Henrique; Spohr, Ana Maria

    2013-12-01

    To evaluate the influence of resin cements and aging on cuspal deflection, fracture resistance, and mode of failure of endodontically treated teeth restored with composite resin inlays. Seventy-two maxillary premolars were divided into 6 groups: 1: sound teeth as control (C); 2: preparations without restoration (WR); 3: inlays luted with RelyX ARC (ARC); 4: inlays luted with RelyX Unicem (RLXU); 5: inlays luted with Maxcem Elite (MCE); 6: inlays luted with SeT (ST). Groups 2 to 6 received mesio-occlusal-distal preparations and endodontic treatment. Stone casts were made for groups 3 to 6. Composite resin inlays were built over each cast and luted with the resin cements. A 200-N load was applied on the occlusal aspect and the cuspal deflection was measured using a micrometer before and after 500,000 cycles of fatigue loading (200 N; 500,000 cycles). The specimens were then submitted to an axial load until failure. The median cuspal deflection (µm) and median fracture resistance (N) were calculated and statistically analyzed using Kruskal-Wallis and Mann-Whitney tests (p inlays luted with RelyX ARC maintained cuspal deflection stability and showed higher fracture resistance of the teeth than did inlays luted with the other cements tested.

  18. Development of polystyrene-geopolymer composite for thermal insulating material and its properties with special regards to flame resistance

    Science.gov (United States)

    Mucsi, G.; Szabó, R.; Nagy, S.; Bohács, K.; Gombkötő, I.; Debreczeni, Á.

    2017-10-01

    As a first part of the research, systematic experimental series were conducted in order to develop an appropriate fly ash-based geopolymer binder focusing on the workability of the paste. In these series, the NaOH molar ratio and water glass/NaOH ratio were investigated and the fineness of the fly ash was optimized presented in a recent paper. Based on these results the effect of metakaolin on the mechanical properties was studied. After developing the appropriate binder, experimental series were carried out using ground polystyrene as light aggregate in various concentration (from 30 V/V% up to 98 V/V%) and geopolymer as a binder in order to develop a heat insulating material. Compressive and flexural strength, specimen density, flammability, freeze-thaw resistance were determined in order to characterize the composite product. As a result of the experimental investigation, it was found that the flexural strength of the composite was found to be ~400 kPa which is as high as the original polystyrene heat insulating panel. Additionally, the flammability was much better than the original pure PS product, the sample was not ignited even at higher PS content (90%). Furthermore, the freeze-thaw resistance of the composite improved compared with the neat geopolymer.

  19. Effect of Si3N4 Addition on Oxidation Resistance of ZrB2-SiC Composites

    Directory of Open Access Journals (Sweden)

    Manab Mallik

    2017-06-01

    Full Text Available The oxidation behavior of ZrB2-20 vol % SiC and ZrB2-20 vol % SiC-5 vol % Si3N4 composites prepared by hot-pressing and subjected to isothermal exposure at 1200 or 1300 °C for durations of 24 or 100 h in air, as well as cyclic exposure at 1300 °C for 24 h, have been investigated. The oxidation resistance of the ZrB2-20 vol % SiC composite has been found to improve by around 20%–25% with addition of 5 vol % Si3N4 during isothermal or cyclic exposures at 1200 or 1300 °C. This improvement in oxidation resistance has been attributed to the formation of higher amounts of SiO2 and Si2N2O, as well as a greater amount of continuity in the oxide scale, because these phases assist in closing the pores and lower the severity of cracking by exhibiting self-healing type behavior. For both the composites, the mass changes are found to be higher during cyclic exposure at 1300 °C by about 2 times compared to that under isothermal conditions.

  20. Electromagnetic property of SiO2-coated carbonyl iron/polyimide composites as heat resistant microwave absorbing materials

    Science.gov (United States)

    Wang, Hongyu; Zhu, Dongmei; Zhou, Wancheng; Luo, Fa

    2015-02-01

    Heat resistant microwave absorbing materials were prepared by compression molding method, using polyimide resin as matrix and SiO2 coated carbonyl iron (CI) as filler. The SiO2 coated CI particles were prepared by Stober process. The microwave absorbing properties and the effect of heat treatment on the electromagnetic properties of SiO2 coated CI/polyimide composites were investigated. When the content of SiO2 coated CI is 60 wt%, the value of minimum reflection loss decreases from -25 dB to -33 dB with the thickness increases from 1.5 mm to 2.1 mm. According to the thermal-gravimetric analyses (TGA) curves, the polyimide matrix can be used at 300 °C for long time. The complex permittivity of the composites slightly increases while the complex permeability almost keeps constant after heat treatment at 300 °C for 10 h, which indicating that the composites can be used at elevated temperature as microwave absorbing materials at the same time have good heat resistance and microwave absorption.

  1. Development and optimization of manufacture process for heat resistant fibre reinforced ceramic matrix composites

    Czech Academy of Sciences Publication Activity Database

    Glogar, Petr; Hron, P.; Burian, M.; Balík, Karel; Černý, Martin; Sucharda, Zbyněk; Vymazalová, Z.; Červencl, J.; Pivoňka, M.

    -, č. 14 (2005), 25-32 ISSN 1214-9691 R&D Projects: GA ČR(CZ) GA106/02/0177 Institutional research plan: CEZ:AV0Z30460519 Keywords : polysiloxane resin * pyrolysis * ceramic matrix composite Subject RIV: JI - Composite Materials

  2. Effect of Translaminar Reinforcements and Hybridization on Damage Resistance and Tolerance of Composite Laminates

    Science.gov (United States)

    2012-01-01

    1 Various hybrid composite laminates and FGM ................................................... 98 5-2 Elastic properties for composite materials in...91 5-5 Shear stress profiles of homogeneous the FGMs ...the bending stiffness matrix in classical plate laminate theory. Substituting for p from Eq. (2-2) into Eq. (2-3), we obtain 4 4 s m m dd w EI bp

  3. Microstructure and mechanical properties of heat resistant composites reinforced with basalt fibres

    Czech Academy of Sciences Publication Activity Database

    Glogar, Petr; Sucharda, Zbyněk; Černý, Martin; Puchegger, S.; Peterlik, H.

    2007-01-01

    Roč. 51, č. 4 (2007), s. 190-197 ISSN 0862-5468 R&D Projects: GA ČR GA106/05/0817 Institutional research plan: CEZ:AV0Z30460519 Keywords : ceramic matrix composites * thermosetting resin * basalt fibre Subject RIV: JI - Composite Materials Impact factor: 0.488, year: 2007

  4. Modelling the influence of steel fibres on the electrical resistivity of cementitious composites

    DEFF Research Database (Denmark)

    Solgaard, Anders Ole Stubbe; Michel, Alexander; Stang, Henrik

    2009-01-01

    One of the governing factors on the corrosion of embedded reinforcement is the electrical resistivity of the concrete. The combination of steel fibres and conventional reinforcement bars has been used in a number of structures. However, the addition of electrical con-ductive fibres might influence...... of steel fibre reinforced concrete (SFRC). The parameters investigated in the following are the fibre geometry, the fibre volume and the transitional resistance. On basis of the experimental results, a model, taking the resistivity of the fibres and the concrete matrix into account is proposed....

  5. Characterization of Antibiotic Resistance Gene Abundance and Microbiota Composition in Feces of Organic and Conventional Pigs from Four EU Countries.

    Science.gov (United States)

    Gerzova, Lenka; Babak, Vladimir; Sedlar, Karel; Faldynova, Marcela; Videnska, Petra; Cejkova, Darina; Jensen, Annette Nygaard; Denis, Martine; Kerouanton, Annaelle; Ricci, Antonia; Cibin, Veronica; Österberg, Julia; Rychlik, Ivan

    2015-01-01

    One of the recent trends in animal production is the revival of interest in organic farming. The increased consumer interest in organic animal farming is mainly due to concerns about animal welfare and the use of antibiotics in conventional farming. On the other hand, providing animals with a more natural lifestyle implies their increased exposure to environmental sources of different microorganisms including pathogens. To address these concerns, we determined the abundance of antibiotic resistance and diversity within fecal microbiota in pigs kept under conventional and organic farming systems in Sweden, Denmark, France and Italy. The abundance of sul1, sul2, strA, tet(A), tet(B) and cat antibiotic resistance genes was determined in 468 samples by real-time PCR and the fecal microbiota diversity was characterized in 48 selected samples by pyrosequencing of V3/V4 regions of 16S rRNA. Contrary to our expectations, there were no extensive differences between the abundance of tested antibiotic resistance genes in microbiota originating from organic or conventionally housed pigs within individual countries. There were also no differences in the microbiota composition of organic and conventional pigs. The only significant difference was the difference in the abundance of antibiotic resistance genes in the samples from different countries. Fecal microbiota in the samples originating from southern European countries (Italy, France) exhibited significantly higher antibiotic resistance gene abundance than those from northern parts of Europe (Denmark, Sweden). Therefore, the geographical location of the herd influenced the antibiotic resistance in the fecal microbiota more than farm's status as organic or conventional.

  6. Quasi-Static Behavior of Palm-Based Elastomeric Polyurethane: For Strengthening Application of Structures under Impulsive Loadings

    Directory of Open Access Journals (Sweden)

    H. M. Chandima Chathuranga Somarathna

    2016-05-01

    Full Text Available In recent years, attention has been focused on elastomeric polymers as a potential retrofitting material considering their capability in contributing towards the impact resistance of various structural elements. A comprehensive understanding of the behavior and the morphology of this material are essential to propose an effective and feasible alternative to existing structural strengthening and retrofitting materials. This article presents the findings obtained from a series of experimental investigations to characterize the physical, mechanical, chemical and thermal behavior of eight types of palm-based polyurethane (PU elastomers, which were synthesized from the reaction between palm kernel oil-based monoester polyol (PKO-p and 4,4-diphenylmethane diisocyanate (MDI with polyethylene glycol (PEG as the plasticizer via pre-polymerization. Fourier transform infrared (FT-IR spectroscopy analysis was conducted to examine the functional groups in PU systems. Mechanical and physical behavior was studied with focus on elongation, stresses, modulus, energy absorption and dissipation, and load dispersion capacities by conducting hardness, tensile, flexural, Izod impact, and differential scanning calorimetry tests. Experimental results suggest that the palm-based PU has positive effects as a strengthening and retrofitting material against dynamic impulsive loadings both in terms of energy absorption and dissipation, and load dispersion. In addition, among all PUs with different plasticizer contents, PU2 to PU8 (which contain 2% to 8% (w/w PEG with respect to PKO-p content show the best correlation with mechanical response under quasi-static conditions focusing on energy absorption and dissipation and load dispersion characteristics.

  7. Insulin Resistance in Nondiabetic Peritoneal Dialysis Patients: Associations with Body Composition, Peritoneal Transport, and Peritoneal Glucose Absorption.

    Science.gov (United States)

    Bernardo, Ana Paula; Oliveira, Jose C; Santos, Olivia; Carvalho, Maria J; Cabrita, Antonio; Rodrigues, Anabela

    2015-12-07

    Insulin resistance has been associated with cardiovascular disease in peritoneal dialysis patients. Few studies have addressed the impact of fast transport status or dialysis prescription on insulin resistance. The aim of this study was to test whether insulin resistance is associated with obesity parameters, peritoneal transport rate, and glucose absorption. Insulin resistance was evaluated with homeostasis model assessment method (HOMA-IR), additionally corrected by adiponectin (HOMA-AD). Enrolled patients were prevalent nondiabetics attending at Santo António Hospital Peritoneal Dialysis Unit, who were free of hospitalization or infectious events in the previous 3 months (51 patients aged 50.4 ± 15.9 years, 59% women). Leptin, adiponectin, insulin-like growth factor-binding protein 1 (IGFBP-1), and daily glucose absorption were also measured. Lean tissue index, fat tissue index (FTI), and relative fat mass (rel.FM) were assessed using multifrequency bioimpedance. Patients were categorized according to dialysate to plasma creatinine ratio at 4 hours, 3.86% peritoneal equilibration test, and obesity parameters. Obesity was present in 49% of patients according to rel.FM. HOMA-IR correlated better with FTI than with body mass index. Significant correlations were found in obese, but not in nonobese patients, between HOMA-IR and leptin, leptin/adiponectin ratio (LAR), and IGFBP-1. HOMA-IR correlated with HOMA-AD, but did not correlate with glucose absorption or transport rate. There were no significant differences in insulin resistance indices, glucose absorption, and body composition parameters between fast and nonfast transporters. A total of 18 patients (35.3%) who had insulin resistance presented with higher LAR and rel.FM (7.3 [12.3, interquartile range] versus 0.7 [1.4, interquartile range], Pinsulin resistance. FTI and LAR were independent correlates of HOMA-IR in multivariate analysis adjusted for glucose absorption and small-solute transport (r=0

  8. The Composition and Spatial Patterns of Bacterial Virulence Factors and Antibiotic Resistance Genes in 19 Wastewater Treatment Plants.

    Science.gov (United States)

    Zhang, Bing; Xia, Yu; Wen, Xianghua; Wang, Xiaohui; Yang, Yunfeng; Zhou, Jizhong; Zhang, Yu

    2016-01-01

    Bacterial pathogenicity and antibiotic resistance are of concern for environmental safety and public health. Accumulating evidence suggests that wastewater treatment plants (WWTPs) are as an important sink and source of pathogens and antibiotic resistance genes (ARGs). Virulence genes (encoding virulence factors) are good indicators for bacterial pathogenic potentials. To achieve a comprehensive understanding of bacterial pathogenic potentials and antibiotic resistance in WWTPs, bacterial virulence genes and ARGs in 19 WWTPs covering a majority of latitudinal zones of China were surveyed by using GeoChip 4.2. A total of 1610 genes covering 13 virulence factors and 1903 genes belonging to 11 ARG families were detected respectively. The bacterial virulence genes exhibited significant spatial distribution patterns of a latitudinal biodiversity gradient and a distance-decay relationship across China. Moreover, virulence genes tended to coexist with ARGs as shown by their strongly positive associations. In addition, key environmental factors shaping the overall virulence gene structure were identified. This study profiles the occurrence, composition and distribution of virulence genes and ARGs in current WWTPs in China, and uncovers spatial patterns and important environmental variables shaping their structure, which may provide the basis for further studies of bacterial virulence factors and antibiotic resistance in WWTPs.

  9. Evaluation of contact resistance between carbon fiber/epoxy composite laminate and printed silver electrode for damage monitoring

    Energy Technology Data Exchange (ETDEWEB)

    Jeon, Eun Beom; Kim, Hak Sung [Dept. of Mechanical Convergence Engineering, Hanyang University, Seoul (Korea, Republic of); Takahashi, Kosuke [Dept. of Mechanical Sciences and Engineering, Tokyo Institute of Technology, Tokyo (Korea, Republic of)

    2014-10-15

    An addressable conducting network (ACN) makes it possible to monitor the condition of a structure using the electrical resistance between electrodes on the surface of a carbon fiber reinforced plastics (CFRP) structure. To improve the damage detection reliability of the ACN, the contact resistances between the electrodes and CFRP laminates needs to be minimized. In this study, silver nanoparticle electrodes were fabricated via printed electronics techniques on a CFRP composite. The contact resistance between the silver electrodes and CFRP were measured with respect to various fabrication conditions such as the sintering temperature of the silver nano-ink and the surface roughness of the CFRP laminates. The interfaces between the silver electrode and carbon fibers were observed using a scanning electron microscope (SEM). Based on this study, it was found that the lowest contact resistance of 0.3664Ω could be achieved when the sintering temperature of the silver nano-ink and surface roughness were 120 degree C and 0.230 a, respectively.

  10. Fabrication and characterization of a micromachined swirl-shaped ionic polymer metal composite actuator with electrodes exhibiting asymmetric resistance.

    Science.gov (United States)

    Feng, Guo-Hua; Liu, Kim-Min

    2014-05-12

    This paper presents a swirl-shaped microfeatured ionic polymer-metal composite (IPMC) actuator. A novel micromachining process was developed to fabricate an array of IPMC actuators on a glass substrate and to ensure that no shortcircuits occur between the electrodes of the actuator. We demonstrated a microfluidic scheme in which surface tension was used to construct swirl-shaped planar IPMC devices of microfeature size and investigated the flow velocity of Nafion solutions, which formed the backbone polymer of the actuator, within the microchannel. The unique fabrication process yielded top and bottom electrodes that exhibited asymmetric surface resistance. A tool for measuring surface resistance was developed and used to characterize the resistances of the electrodes for the fabricated IPMC device. The actuator, which featured asymmetric electrode resistance, caused a nonzero-bias current when the device was driven using a zero-bias square wave, and we propose a circuit model to describe this phenomenon. Moreover, we discovered and characterized a bending and rotating motion when the IPMC actuator was driven using a square wave. We observed a strain rate of 14.6% and a displacement of 700 μm in the direction perpendicular to the electrode surfaces during 4.5-V actuation.

  11. Characterization of microbiota composition and presence of selected antibiotic resistance genes in carriage water of ornamental fish.

    Science.gov (United States)

    Gerzova, Lenka; Videnska, Petra; Faldynova, Marcela; Sedlar, Karel; Provaznik, Ivo; Cizek, Alois; Rychlik, Ivan

    2014-01-01

    International trade with ornamental fish is gradually recognized as an important source of a wide range of different antibiotic resistant bacteria. In this study we therefore characterized the prevalence of selected antibiotic resistance genes in the microbiota found in the carriage water of ornamental fish originating from 3 different continents. Real-time PCR quantification showed that the sul1 gene was present in 11 out of 100 bacteria. tet(A) was present in 6 out of 100 bacteria and strA, tet(G), sul2 and aadA were present in 1-2 copies per 100 bacteria. Class I integrons were quite common in carriage water microbiota, however, pyrosequencing showed that only 12 different antibiotic gene cassettes were present in class I integrons. The microbiota characterized by pyrosequencing of the V3/V4 variable region of 16S rRNA genes consisted of Proteobacteria (48%), Bacteroidetes (29.5%), Firmicutes (17.8%), Actinobacteria (2.1%) and Fusobacteria (1.6%). Correlation analysis between antibiotic resistance gene prevalence and microbiota composition verified by bacterial culture showed that major reservoirs of sul1 sul2, tet(A), tet(B) tet(G), cat, cml, bla, strA, aacA, aph and aadA could be found among Alpha-, Beta- and Gammaproteobacteria with representatives of Enterobacteriaceae, Pseudomonadaceae, Rhizobiaceae and Comamonadaceae being those most positively associated with the tested antibiotic resistance genes.

  12. The culturable intestinal microbiota of triploid and diploid juvenile Atlantic salmon (Salmo salar) - a comparison of composition and drug resistance.

    Science.gov (United States)

    Cantas, Leon; Fraser, Thomas W K; Fjelldal, Per Gunnar; Mayer, Ian; Sørum, Henning

    2011-11-17

    With the increased use of ploidy manipulation in aquaculture and fisheries management this investigation aimed to determine whether triploidy influences culturable intestinal microbiota composition and bacterial drug resistance in Atlantic salmon (Salmo salar). The results could provide answers to some of the physiological differences observed between triploid and diploid fish, especially in terms of fish health. No ploidy effect was observed in the bacterial species isolated, however, triploids were found to contain a significant increase in total gut microbiota levels, with increases in Pseudomonas spp., Pectobacterium carotovorum, Psychrobacter spp., Bacillus spp., and Vibrio spp., (12, 42, 9, 10, and 11% more bacteria in triploids than diploids, respectively), whereas a decrease in Carnobacterium spp., within triploids compared to diploids was close to significant (8% more bacteria in diploids). With the exception of gentamicin, where no bacterial resistance was observed, bacterial isolates originating from triploid hosts displayed increased resistance to antibacterials, three of which were significant (tetracycline, trimethoprim, and sulphonamide). Results indicate that triploidy influences both the community and drug resistance of culturable intestinal microbiota in juvenile salmon. These results demonstrate differences that are likely to contribute to the health of triploid fish and have important ramifications on the use of antibacterial drugs within aquaculture.

  13. The culturable intestinal microbiota of triploid and diploid juvenile Atlantic salmon (Salmo salar - a comparison of composition and drug resistance

    Directory of Open Access Journals (Sweden)

    Cantas Leon

    2011-11-01

    Full Text Available Abstract Background With the increased use of ploidy manipulation in aquaculture and fisheries management this investigation aimed to determine whether triploidy influences culturable intestinal microbiota composition and bacterial drug resistance in Atlantic salmon (Salmo salar. The results could provide answers to some of the physiological differences observed between triploid and diploid fish, especially in terms of fish health. Results No ploidy effect was observed in the bacterial species isolated, however, triploids were found to contain a significant increase in total gut microbiota levels, with increases in Pseudomonas spp., Pectobacterium carotovorum, Psychrobacter spp., Bacillus spp., and Vibrio spp., (12, 42, 9, 10, and 11% more bacteria in triploids than diploids, respectively, whereas a decrease in Carnobacterium spp., within triploids compared to diploids was close to significant (8% more bacteria in diploids. With the exception of gentamicin, where no bacterial resistance was observed, bacterial isolates originating from triploid hosts displayed increased resistance to antibacterials, three of which were significant (tetracycline, trimethoprim, and sulphonamide. Conclusion Results indicate that triploidy influences both the community and drug resistance of culturable intestinal microbiota in juvenile salmon. These results demonstrate differences that are likely to contribute to the health of triploid fish and have important ramifications on the use of antibacterial drugs within aquaculture.

  14. Characterization of Antibiotic Resistance Gene Abundance and Microbiota Composition in Feces of Organic and Conventional Pigs from Four EU Countries

    DEFF Research Database (Denmark)

    Gerzova, Lenka; Babak, Vladimir; Sedlar, Karel

    2015-01-01

    One of the recent trends in animal production is the revival of interest in organic farming. The increased consumer interest in organic animal farming is mainly due to concerns about animal welfare and the use of antibiotics in conventional farming. On the other hand, providing animals with a more...... natural lifestyle implies their increased exposure to environmental sources of different microorganisms including pathogens. To address these concerns, we determined the abundance of antibiotic resistance and diversity within fecal microbiota in pigs kept under conventional and organic farming systems...... to our expectations, there were no extensive differences between the abundance of tested antibiotic resistance genes in microbiota originating from organic or conventionally housed pigs within individual countries. There were also no differences in the microbiota composition of organic and conventional...

  15. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    Science.gov (United States)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  16. The influence of calcium supplement on body composition, weight loss and insulin resistance in obese adults receiving low calorie diet

    Directory of Open Access Journals (Sweden)

    Maryam Shalileh

    2010-01-01

    Full Text Available Background: Obesity and diabetes are the most important problems of public health. Evidence from molecular animal research and epidemiologic investigations indicate that calcium intake may have an influence on body composition, weight and insulin resistance. The objective of this study was to determine the effects of calcium supplementation on body composition, weight, insulin resistance and blood pressure in the face of calorie restriction in obese adults. Methods: A double blind randomized placebo-controlled trial on 40 adults with Body Mass Index > 25kg/m2 was conducted. Subjects were maintained for 24 weeks on a balanced deficit diet (-500 kcal/d deficit and randomly assigned into two groups with 1000 mg ca/d as calcium carbonate or placebo. Results: There were no significant differences in variables at the 12th and 24th week between the two groups. The lean mass showed no significant increase in the calcium group at the 12th week compared to baseline and in placebo group at the 24th week compared to the 12th week. The insulin concentration showed a significant decrease in the calcium group at the 12th week compared to the baseline (p < 0.05. The diastolic blood pressure had a significant decrease at the 24th week compared to the 12th week in both groups (p = 0.013-0.009. Conclusions: Results from this study suggest that 24 weeks of supplementation with 1000 mg ca/d did not have any effect on weight, body composition, insulin resistance and blood pressure beyond what can be achieved in an energy restricted diet in obese adults.

  17. A review on the cords & plies reinforcement of elastomeric polymer matrix

    Science.gov (United States)

    Mahmood, S. S.; Husin, H.; Mat-Shayuti, M. S.; Hassan, Z.

    2016-06-01

    Steel, polyester, nylon and rayon are the main materials of cords & plies that have been reinforced in the natural rubber to produce quality tyres but there is few research reported on cord and plies reinforcement in silicone rubber. Taking the innovation of tyres as inspiration, this review's first objective is to compile the comprehensive studies about the cords & plies reinforcement in elastomeric polymer matrix. The second objective is to gather information about silicone rubber that has a high potential as a matrix phase for cords and plies reinforcement. All the tests and findings are gathered and compiled in sections namely processing preparation, curing, physical and mechanical properties, and adhesion between cords-polymer.

  18. Multiple refraction switches realized by stretching elastomeric scatterers in sonic crystals

    Directory of Open Access Journals (Sweden)

    Y. Huang

    2015-02-01

    Full Text Available The effect of out-of-plane pre-stretch on the 2D sonic crystal with stretchable elastomeric scatterers is explored. The hyperelastic scatterers are characterized by a compressible neo-Hookean model. The Dirichlet-to-Neumann (DtN map is adopted to obtain the band structure and equi-frequency contours. We focus on the first passband and find that a variety of switching functionalities for refraction behaviors can be realized in selected frequencies under a specific pre-stretch range. These refraction switches enable an active control of wave propagation and are applicable in advanced technologies where switchable and multifunctional sonic crystals are required.

  19. Elastomeric thermal interface materials with high through-plane thermal conductivity from carbon fiber fillers vertically aligned by electrostatic flocking.

    Science.gov (United States)

    Uetani, Kojiro; Ata, Seisuke; Tomonoh, Shigeki; Yamada, Takeo; Yumura, Motoo; Hata, Kenji

    2014-09-03

    Electrostatic flocking is applied to create an array of aligned carbon fibers from which an elastomeric thermal interface material (TIM) can be fabricated with a high through-plane thermal conductivity of 23.3 W/mK. A high thermal conductivity can be achieved with a significantly low filler level (13.2 wt%). As a result, this material retains the intrinsic properties of the matrix, i.e., elastomeric behavior. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Realization of resistive switching and magnetoresistance in ZnO/ZnO-Co composite materials

    Science.gov (United States)

    Li, Xiaoli; Jia, Juan; Li, Yanchun; Bai, Yuhao; Li, Jie; Shi, Yana; Wang, Lanfang; Xu, Xiaohong

    2016-09-01

    Combining resistive switching and magnetoresistance in a system exhibits great potential for application in multibit nonvolatile data storage. It is in significance and difficulty to seek a material with resistances that can be stably switched at different resistance states modulated by an electrical field and a magnetic field. In this paper, we propose a novel electrode/ZnO/ZnO-Co/electrode device in which the storage layer combines a nanostructured ZnO-Co layer and a ZnO layer. The device exhibits bipolar resistive switching characteristics, which can be explained by the accumulation of oxygen vacancies due to the migration of oxygen ions by external electrical stimuli and the contribution of Co particles in the ZnO-Co layer. Moreover, the magnetoresistance effect at room temperature can be observed in the device at high and low resistance states. Therefore, through electrical and magnetic control, four resistance states are achieved in this system, presenting a new possibility towards enhancing data densities by many folds.

  1. Mechanisms of charge transport and resistive switching in composite films of semiconducting polymers with nanoparticles of graphene and graphene oxide

    Science.gov (United States)

    Berestennikov, A. S.; Aleshin, A. N.

    2017-11-01

    We have investigated the effect of the resistive switching in the composite films based on polyfunctional polymers - PVK, PFD and PVC mixed with particles of Gr and GO with the concentration of ˜ 1 - 3 wt.%. We have developed the solution processed hybrid memory structures based on PVK and GO particles composite films. The effect of the resistive switching in Al/PVK(PFD; PVC):Gr(GO)/ITO/PET structures manifests itself as a sharp change of the electrical resistance from a low-conducting state to a relatively high-conducting state when applying a bias to Al-ITO electrodes of ˜ 0.2-0.4 V. It has been established that a sharp conductivity jump characterized by S-shaped current-voltage curves and the presence of their hysteresis occurs upon applying a voltage pulse to the Au/PVK(PFD; PVC):Gr(GO)/ITO/PET structures, with the switching time in the range from 1 to 30 μs. The mechanism of resistive switching associated with the processes of capture and accumulation of charge carriers by Gr(GO) particles introduced into the matrixes of the PVK polymer due to the reduction/oxidation processes. The possible mechanisms of energy transfer between organic and inorganic components in PVK(PFD; PVC):GO(Gr) films causes increase mobility are discussed. Incorporating of Gr (GO) particles into the polymer matrix is a promising route to enhance the performance of hybrid memory structures, as well as it is an effective medium for memory cells.

  2. Influence of immediate dentin sealing techniques on cuspal deflection and fracture resistance of teeth restored with composite resin inlays.

    Science.gov (United States)

    Oliveira, L; Mota, E G; Borges, G A; Burnett, L H; Spohr, A M

    2014-01-01

    SUMMARY This research evaluated the influence of immediate dentin sealing (IDS) techniques on cuspal deflection and fracture resistance of teeth restored with composite resin inlays. Forty-eight maxillary premolars were divided into four groups: G1, sound teeth (control); G2, without IDS; G3, IDS with Clearfil SE Bond (CSE); and G4, IDS with CSE and Protect Liner F. The teeth from groups 2, 3, and 4 received mesio-distal-occlusal preparations. The impressions were made with vinyl polysiloxane, followed by provisional restoration and storage in water for seven days. The impressions were poured using type IV die stone, and inlays with Filtek Z250 composite resin were built over each cast. The inlays were luted with Panavia F. After storage in water for 72 hours, a 200-N load was applied on the occlusal surface using a metal sphere connected to a universal testing machine, and the cuspal deflection was measured with a micrometer. The specimens were then submitted to an axial load until failure. The following mean cuspal deflection (μm) and mean fracture resistance (N) followed by the same lowercase letter represent no statistical difference by analysis of variance and Tukey (p<0.05): cuspal deflection: G1, 3.1 ± 1.5(a); G2, 10.3 ± 4.6(b); G3, 5.5 ± 1.8(ac); and G4, 7.7 ± 5.1(bc); fracture resistance: G1, 1974 ± 708(a); G2, 1162 ± 474(b); G3, 700 ± 280(b); and G4, 810 ± 343(b). IDS with CSE allowed cuspal deflection comparable with that associated with sound teeth. The application of Protect Liner F did not contribute to a decrease in cuspal deflection. The IDS techniques did not influence the fracture resistance of teeth.

  3. Epoxy-borax-coal tar composition for a radiation protective, burn resistant drum liner and centrifugal casting method

    International Nuclear Information System (INIS)

    Boyer, N.W.; Taylor, R.S.

    1980-01-01

    A boron containing burn resistant, low level radiation protection material useful, for example, as a liner for radioactive waste disposal and storage, a component for neutron absorber, and a shield for a neutron source. The material is basically composed of borax in the range of 25-50%, coal tar in the range of 25-37.5%, with the remainder being an epoxy resin mix. A preferred composition is 50% borax, 25% coal tar and 25% epoxy resin. The material is not susceptible to burning and is about 1/5 the cost of existing radiation protection material utilized in similar applications

  4. Fracture resistance of computer-aided design/computer-aided manufacturing-generated composite resin-based molar crowns

    OpenAIRE

    Harada, A; Nakamura, Keisuke; Kanno, Taro; Inagaki, R.; Ørtengren, Ulf Thore; Niwano, Y.; Sasaki, Keiichi; Egusa, Hiroshi

    2015-01-01

    Accepted manuscript version.Published version available at http://doi.org/10.1111/eos.12173 The aim of this study was to investigate whether different fabrication processes, such as the computer-aided design/computer-aided manufacturing (CAD/CAM) system or the manual build-up technique, affect the fracture resistance of composite resin-based crowns. Lava Ultimate (LU), Estenia C&B (EC&B), and lithium disilicate glass-ceramic IPS e.max press (EMP) were used. Four types of molar ...

  5. Influence of different composite materials and cavity preparation designs on the fracture resistance of mesio-occluso-distal inlay restoration.

    Science.gov (United States)

    Tekçe, Neslihan; Pala, Kansad; Demirci, Mustafa; Tuncer, Safa

    2016-01-01

    The aim of the study to evaluate the fracture resistance of a computer-aided design/computer-aided manufacturing (CAD/CAM) and three indirect composite materials for three different mesio-occluso-distal (MOD) inlay cavity designs. A total of 120 mandibular third molar were divided into three groups: (G1) non-proximal box, (G2) 2-mm proximal box, and (G3) 4-mm proximal box. Each cavity design received four composite materials: Estenia, Epricord (Kuraray, Japan), Tescera (Bisco, USA), and Cerasmart CAD/CAM blocks (GC, USA). The specimens were subjected to a compressive load at a crosshead speed of 1 mm/min. The data was analyzed using the two-way analysis of variance and Bonferroni post hoc test (pinlay restoration.

  6. Hexagonal Boron Nitride Impregnated Silane Composite Coating for Corrosion Resistance of Magnesium Alloys for Temporary Bioimplant Applications

    Directory of Open Access Journals (Sweden)

    Saad Al-Saadi

    2017-11-01

    Full Text Available Magnesium and its alloys are attractive potential materials for construction of biodegradable temporary implant devices. However, their rapid degradation in human body fluid before the desired service life is reached necessitate the application of suitable coatings. To this end, WZ21 magnesium alloy surface was modified by hexagonal boron nitride (hBN-impregnated silane coating. The coating was chemically characterised by Raman spectroscopy. Potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS of the coated alloy in Hanks’ solution showed a five-fold improvement in the corrosion resistance of the alloy due to the composite coating. Post-corrosion analyses corroborated the electrochemical data and provided a mechanistic insight of the improvement provided by the composite coating.

  7. In vitro evaluation of the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with composite fillings after cyclic loading

    OpenAIRE

    Sadighpour, Leyla; Geramipanah, Farideh; Allahyari, Somayeh; Fallahi Sichani, Babak; Kharazi Fard, Mohamd Javad

    2014-01-01

    PURPOSE There is insufficient data regarding the durability of porcelain laminate veneers bonded to existing composite fillings. The aim of the present study was to evaluate the fracture resistance and microleakage of porcelain laminate veneers bonded to teeth with existing composite fillings. MATERIALS AND METHODS Thirty maxillary central incisors were divided into three groups (for each group, n=10): intact teeth (NP), teeth with class III composite fillings (C3) and teeth with class IV cav...

  8. Accelerated Fatigue Resistance of Thick CAD/CAM Composite Resin Overlays Bonded with Light- and Dual-polymerizing Luting Resins.

    Science.gov (United States)

    Goldberg, Jack; Güth, Jan-Frederik; Magne, Pascal

    To evaluate the accelerated fatigue resistance of thick CAD/CAM composite resin overlays luted with three different bonding methods. Forty-five sound human second mandibular molars were organized and distributed into three experimental groups. All teeth were restored with a 5-mm-thick CAD/CAM composite resin overlay. Group A: immediate dentin sealing (IDS) with Optibond FL and luted with light-polymerizing composite (Herculite XRV). Group B: IDS with Optibond FL and luted with dual-polymerizing composite (Nexus 3). Group C: direct luting with Optibond FL and dual-polymerizing composite (Nexus 3). Masticatory forces at a frequency of 5 Hz were simulated using closed-loop servo-hydraulics and forces starting with a load of 200 N for 5000 cycles, followed by steps of 400, 600, 800, 1000, 1200 and 1400 N for a maximum of 30,000 cycles. Each step was applied through a flat steel cylinder at a 45-degree angle under submerged conditions. The fatigue test generated one failure in group A, three failures in group B, and no failures in group C. The survival table analysis for the fatigue test did not demonstrate any significant difference between the groups (p = 0.154). The specimens that survived the fatigue test were set up for the load-to-failure test with a limit of 4600 N. The survival table analysis for the load-to-failure test demonstrates an average failure load of 3495.20 N with survival of four specimens in group A, an average failure load of 4103.60 N with survival of six specimens in group B, and an average failure load of 4075.33 N with survival of nine specimens in group C. Pairwise comparisons revealed no significant differences (p composites in combination with IDS are not contraindicated with thick restorations.

  9. Development of an oxidation resistant glass-ceramic composite coating on Ti-47Al-2Cr-2Nb alloy

    Science.gov (United States)

    Li, Wenbo; Zhu, Shenglong; Chen, Minghui; Wang, Cheng; Wang, Fuhui

    2014-02-01

    Three glass-ceramic composite coatings were prepared on Ti-47Al-2Cr-2Nb alloy by air spraying technique and subsequent firing. The aim of this work is to study the reactions between glass matrix and inclusions and their effects on the oxidation resistance of the glass-ceramic composite coating. The powders of alumina, quartz, or both were added into the aqueous solution of potassium silicate (ASPS) to form slurries used as the starting materials for the composite coatings. The coating formed from an ASPS-alumina slurry was porous, because the reaction between alumina and potassium silicate glass resulted in the formation of leucite (KAlSi2O6), consuming substantive glass phase and hindering the densification of the composite coating. Cracks were observed in the coating prepared from an ASPS-quartz slurry due to the larger volume shrinkage of the coating than that of the alloy. In contrast, an intact and dense SiO2-Al2O3-glass coating was successfully prepared from an ASPS-alumina-silica slurry. The oxidation behavior of the SiO2-Al2O3-glass composite coating on Ti-47Al-2Cr-2Nb alloy was studied at 900 °C. The SiO2-Al2O3-glass composite coating acted as an oxygen diffusion barrier, and prevented the inward diffusion of the oxygen from the air to the coating/alloy interface, therefore, decreasing the oxidation rate of the Ti-47Al-2Cr-2Nb alloy significantly.

  10. Fracture Resistance of Endodontically Treated Teeth Restored with Biodentine, Resin Modified GIC and Hybrid Composite Resin as a Core Material.

    Science.gov (United States)

    Subash, Dayalan; Shoba, Krishnamma; Aman, Shibu; Bharkavi, Srinivasan Kumar Indu; Nimmi, Vijayan; Abhilash, Radhakrishnan

    2017-09-01

    The restoration of a severely damaged tooth usually needs a post and core as a part of treatment procedure to provide a corono - radicular stabilization. Biodentine is a class of dental material which possess high mechanical properties with excellent biocompatibility and bioactive behaviour. The sealing ability coupled with optimum physical properties could make Biodentine an excellent option as a core material. The aim of the study was to determine the fracture resistance of Biodentine as a core material in comparison with resin modified glass ionomer and composite resin. Freshly extracted 30 human permanent maxillary central incisors were selected. After endodontic treatment followed by post space preparation and luting of Glass fibre post (Reforpost, Angelus), the samples were divided in to three groups based on the type of core material. The core build-up used in Group I was Biodentine (Septodont, France), Group II was Resin-Modified Glass Ionomer Cement (GC, Japan) and Group III was Hybrid Composite Resin (TeEconom plus, Ivoclar vivadent). The specimens were subjected to fracture toughness using Universal testing machine (1474, Zwick/Roell, Germany) and results were compared using One-way analysis of variance with Tukey's Post hoc test. The results showed that there was significant difference between groups in terms of fracture load. Also, composite resin exhibited highest mean fracture load (1039.9 N), whereas teeth restored with Biodentine demonstrated the lowest mean fracture load (176.66 N). Resin modified glass ionomer exhibited intermediate fracture load (612.07 N). The primary mode of failure in Group I and Group II was favourable (100%) while unfavourable fracture was seen in Group III (30%). Biodentine, does not satisfy the requirements to be used as an ideal core material. The uses of RMGIC's as a core build-up material should be limited to non-stress bearing areas. Composite resin is still the best core build-up material owing to its high fracture

  11. Novel Elastomeric Closed Cell Foam - Nonwoven Fabric Composite Material (Phase III)

    Science.gov (United States)

    2008-10-01

    higher than target density (11 pounds per cubic foot [pcf] vs 6 pcf target). Efforts to optimize tensile/elongation properties with lower density...3M Company. The product, 9372W, was a 2 mil acrylic PSA. Rolls were sent to Haartz Corporation for testing. Haartz found the lamination with this...REFERENCES 1. ASTM D412, 2006. Standard Test Methods for Vulcanized Rubber and Thermoplastic Elastomers—Tension. 2. ASTM D1056, 2007. Standard Specification for Flexible Cellular Materials—Sponge or Expanded Rubber.

  12. The effect of N-stearoylethanolamine on liver phospholipid composition of rats with insulin resistance caused by alimentary obesity

    Directory of Open Access Journals (Sweden)

    O. V. Onopchenko

    2014-02-01

    Full Text Available We used alimentary obesity-induced insulin resistance (IR model in rats to investigate the influence of N-stearoylethanolamine on the content of phospholipids and their fatty acid composition. Our results show that prolonged high-fat diet triggers considerable aberrations in the composition of main phospholipids in the liver and can be one of the causes of IR in rats. In particular, the increase of phosphatidylcholine, phosphatidylethanolamine and significant decrease of other phospholipids: lysophosphatidylcholine, lysophosphatidylethanolamine, sphingomyelin, phosphatidylinositol, phosphatidylserine and diphosphaglicerol were observed. The levels of monounsaturated (erucic, nervonic, oleic and polyunsaturated (eicosatrienoic, docosatrienoic, arachidonic fatty acids were increased; meanwhile the content of diunsaturated acids was decreased. The NSE administration (50 mg/kg of body weight caused restoration of the phospholipids content in the liver of rats with diet-induced IR that highly correlated with the decrease in plasma insulin level and the improvement of insulin sensitivity. Moreover, the effect of NSE was accompanied by the normalization of fatty acids composition of phospholipids that could be related to modulating influen­ce of NSE on the activity of the main fatty acid desaturases. It is known that the imbalance in phospholipid composition of the rat liver causes substantial metabolic alterations that are associated with the development of IR. Accordingly, the compensations of the imbalance by NSE can help to restore insulin sensitivity, inhibit the development of obesity, IR and type 2 diabetes.

  13. Advanced SiC-Matrix Composites with Improved Oxidation Resistance and Life, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this proposed effort is to demonstrate the promise of advanced C/SiC and SiC/SiC composites having improved environmental durability and longer life...

  14. Toughened and corrosion- and wear-resistant composite structures and fabrication methods thereof

    Science.gov (United States)

    Seals, Roland D.; Ripley, Edward B.; Hallman, Russell L.

    2017-06-20

    Composite structures having a reinforced material interjoined with a substrate, wherein the reinforced material comprises a compound selected from the group consisting of titanium monoboride, titanium diboride, and combinations thereof.

  15. Novel Nonporous Fouling-Resistant Enzymatic Composite Membranes for Waste Water Treatment

    National Research Council Canada - National Science Library

    Freeman, Benny D

    2005-01-01

    .... Permeation properties of thin-films made of these gels is also reported. Approximately 20 m2 of chitosan composite membrane were prepared at our industrial partner, Membrane Technology and Research (MTR...

  16. Microcrack Resistant Matrix Materials for Out-of-Autoclave Processing of Composite Cryogenic Tanks, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — NASA is keen on advancing technologies for lightweight composite cryotanks for heavy lift vehicles for future NASA missions. Two primary challenges must be overcome...

  17. Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

    OpenAIRE

    Jeseung Yoo; Yongbeom Kim; Suyong Kwon; Joohyun Lee; Young-Soo Seo

    2015-01-01

    We developed polyesterimide (PEI) nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was co...

  18. Comparison of the abrasive wear resistance between amalgams, hybrid composite material and different dental cements.

    Science.gov (United States)

    Gil, F J; Espias, A; Sánchez, L A; Planell, J A

    1999-12-01

    This paper reports on the abrasion wear of various restorative dental materials (three amalgams and two dental cements and a hybrid composite material) commonly used in dentistry. The mechanical properties, surface roughness and the volume loss by abrasion were determined for the different materials studied. The results showed a better profile for the amalgams versus the composite materials due to the failure of the polymeric matrix of the latter materials. However, the amalgams exhibited corrosion observed by means of Scanning Electron Microscopy.

  19. APPLICATION OF FUNCTIONAL OLIGODIENES FOR MODIFICATION OF COMPOSITIONS BASED ON 1,4-CIS-ISOPRENE RUBBER SKI-5

    Directory of Open Access Journals (Sweden)

    N. A. Shabunina

    2013-01-01

    Full Text Available Application liquid oligodienes as a part of polymeric compositions on the basis of 1,4-cispolyisoprene SKI-5 rubber is investigated. Extent of influence of quantity of an entered oligomer and his functionality on rheological and elastic and strength properties of elastomeric compositions is established. Nature of dispersing action functional and nonfunctional oligodienes is defined.

  20. Electrical resistivity and ultrasonic measurements during sequential fracture test of cementitious composite

    Directory of Open Access Journals (Sweden)

    V. Veselý

    2014-10-01

    Full Text Available Cracks in cover of reinforced and pre-stressed concrete structures significantly influence the ingress of deleterious species causing decrease in durability of these structures. The paper is focused on the effect of fracture process on two selected physical parameters of concrete – the electrical resistivity and the ultrasonic pulse passing time – which might be employed as the quality indicator of concrete cover within (nondestructive procedure(s of assessment of the structural durability. The concrete electrical resistivity and ultrasonic passing time were investigated here with respect to two variants of treatment of the test specimens’ surface (the pre-dried surface and the wet surface. Test configuration of three-point bending of notched beam was utilized to control the crack propagation; the fracture process passed through several loading–unloading sequences between which the electrical resistivity and ultrasonic passing time readings over the fractured region were performed. Equivalent elastic crack model was used for estimation of the fracture advance (described via the effective crack length at the loading stages corresponding to the resistivity and ultrasonic measurements. Relationships between changes of both the concrete resistivity and ultrasonic pulse passing time and the effective crack length is determined and discussed.

  1. Composition

    DEFF Research Database (Denmark)

    Bergstrøm-Nielsen, Carl

    2014-01-01

    Cue Rondo is an open composition to be realised by improvising musicians. See more about my composition practise in the entry "Composition - General Introduction". Caution: streaming the sound/video files will in some cases only provide a few minutes' sample, or the visuals will not appear at all....... Please DOWNLOAD them to see/hear them in full length! This work is licensed under a Creative Commons "by-nc" License. You may for non-commercial purposes use and distribute it, performance instructions as well as specially designated recordings, as long as the author is mentioned. Please see http...

  2. METHOD FOR PROVIDING SHAPED BIODEGRADABLE AND ELASTOMERIC STRUCTURES OF (CO) POLYMERS OF 1,3-TRIMETHYLENE CARBONATE (TMC), SHAPED BIODEGRADABLE AND ELASTOMERIC STRUCTURES, AND THE USE OF THESE STRUCTURES

    NARCIS (Netherlands)

    Grijpma, D.W.; Pêgo, A.P.; Feijen, Jan

    2004-01-01

    The present invention relates to methods for providing shaped biodegradable and elastomeric structures of (co)polymers of 1,3­trimethylene carbonate (TMC) with improved (mechanical) properties which can be used for tissue or tissue component support, generation or regeneration. Such shaped

  3. Influence of high sintering pressure on the microhardness and wear resistance of diamond powder and silicon carbide-based composites

    Directory of Open Access Journals (Sweden)

    Osipov Oleksandr Sergueevitch

    2004-01-01

    Full Text Available The work reported on here involved the development of several samples of "diamond-SiC" composite produced under sintering pressures of up to 9.0 GPa at temperatures of up to 1973 7K. The average size of the diamond micropowder crystals used was 40/28 µm. The sintering process was carried out in a 2500-ton hydraulic press equipped with an anvil-type high-pressure device having a toroidal work surface and a central concavity diameter of 20 mm. The microhardness and wear resistance of the samples were found to be dependent on the sintering pressure. The experimental results indicated that the maximum microhardness and minimum wear resistance coefficients of each compact were attained when the pressure applied during sintering exceeded 6.5 GPa. Based on the established values of pressure, this study served to identify the types of devices applicable for the manufacture of composite material inserts for a variety of rock drilling applications.

  4. The Variations of Thermal Contact Resistance and Heat Transfer Rate of the AlN Film Compositing with PCM

    Directory of Open Access Journals (Sweden)

    Huann-Ming Chou

    2015-01-01

    Full Text Available The electrical industries have been fast developing over the past decades. Moreover, the trend of microelements and packed division multiplex is obviously for the electrical industry. Hence, the high heat dissipative and the electrical insulating device have been popular and necessary. The thermal conduct coefficient of aluminum nitride (i.e., AlN is many times larger than the other materials. Moreover, the green technology of composite with phase change materials (i.e., PCMs is worked as a constant temperature cooler. Therefore, PCMs have been used frequently for saving energy and the green environment. Based on the above statements, it does show great potential in heat dissipative for the AlN film compositing with PCM. Therefore, this paper is focused on the research of thermal contact resistance and heat transfer between the AlN/PCM pairs. According to the experimental results, the heat transfer decreases and the thermal contact resistance increases under the melting process of PCM. However, the suitable parameters such as contact pressures can be used to improve the above defects.

  5. Effects of single- vs. multiple-set resistance training on maximum strength and body composition in trained postmenopausal women.

    Science.gov (United States)

    Kemmler, Wolfgang K; Lauber, Dirk; Engelke, Klaus; Weineck, Juergen

    2004-11-01

    The purpose of this study was to examine the effect of a single- vs. a multiple-set resistance training protocol in well-trained early postmenopausal women. Subjects (N = 71) were randomly assigned to begin either with 12 weeks of the single-set or 12 weeks of the multiple-set protocol. After another 5 weeks of regenerational resistance training, the subgroup performing the single-set protocol during the first 12 weeks crossed over to the 12-week multiple-set protocol and vice versa. Neither exercise type nor exercise intensity, degree of fatigue, rest periods, speed of movement, training sessions per week, compliance and attendance, or periodization strategy differed between exercise protocols. Body mass, body composition, and 1 repetition maximum (1RM) values for leg press, bench press, rowing, and leg adduction were measured at baseline and after each period. Multiple-set training resulted in significant increases (3.5-5.5%) for all 4 strength measurements, whereas single-set training resulted in significant decreases (-1.1 to -2.0%). Body mass and body composition did not change during the study. The results show that, in pretrained subjects, multiple-set protocols are superior to single-set protocols in increasing maximum strength.

  6. Mechanochemical Kinetics in Elastomeric Polymer Networks: Heterogeneity of Local Forces Results in Nonexponential Kinetics.

    Science.gov (United States)

    Adhikari, Ramesh; Makarov, Dmitrii E

    2017-03-16

    A common approach to inducing selective mechanochemical transformations relies on embedding the target molecules (called mechanophores) within elastomeric polymer networks. Mechanical properties of such elastomers can also be modulated through the mechanochemical response of the constituent polymer chains. The inherent randomness in the molecular structure of such materials leads to heterogeneity of the local forces exerted on individual mechanophores. Here we use coarse-grained simulations to study the force distributions within random elastomeric networks and show that those distributions are close to exponential regardless of the applied macroscopic load, entanglement effects, or network parameters. Exponential form of the distribution allows one to completely characterize the mechanophore kinetics in terms of the mean value of the force. At the same time, heterogeneity of the local force affects the kinetics qualitatively: While a narrow force distribution around the mean would lead to exponential kinetics, exponential force distribution results in highly nonexponential kinetics, with a fast kinetic phase involving highly loaded molecules, followed by a slow phase dominated by unloaded molecules.

  7. A constrained maximization formulation to analyze deformation of fiber reinforced elastomeric actuators

    Science.gov (United States)

    Singh, Gaurav; Krishnan, Girish

    2017-06-01

    Fiber reinforced elastomeric enclosures (FREEs) are soft and smart pneumatic actuators that deform in a predetermined fashion upon inflation. This paper analyzes the deformation behavior of FREEs by formulating a simple calculus of variations problem that involves constrained maximization of the enclosed volume. The model accurately captures the deformed shape for FREEs with any general fiber angle orientation, and its relation with actuation pressure, material properties and applied load. First, the accuracy of the model is verified with existing literature and experiments for the popular McKibben pneumatic artificial muscle actuator with two equal and opposite families of helically wrapped fibers. Then, the model is used to predict and experimentally validate the deformation behavior of novel rotating-contracting FREEs, for which no prior literature exist. The generality of the model enables conceptualization of novel FREEs whose fiber orientations vary arbitrarily along the geometry. Furthermore, the model is deemed to be useful in the design synthesis of fiber reinforced elastomeric actuators for general axisymmetric desired motion and output force requirement.

  8. Applicability of base isolation made of elastomeric isolators for the protection of cultural heritage

    Directory of Open Access Journals (Sweden)

    Vojko Kilar

    2009-01-01

    Full Text Available This article briefly presents the applicability of base isolation made of elastomeric isolators for the protection of heritage architecture. The first part of the article gives an illustrative overview on the use of base isolation throughout the world, together with an analysis of guidelines for the protection and management of places of heritage architecture. The guidelines which are given through international agreements and resolutions on the conservation of monuments have to be considered when designing the base isolation of existing monuments. Generally, interventions into such structures should be minimal or visible as little as possible and should minimally affect the aesthetics and functionality of the object. In the second part of the article the general and some special requirements for base isolation design with elastomeric isolators are presented. The influence of the slenderness of the structure is analysed in more detail. The analysis is based on the corresponding rocking prevention criterion, upon the condition that the isolators cannot bear any tensile forces. The article concludes with a presentation of the maximum height-to-width ratios for objects that can be mounted on isolators, fulfilling the given rocking prevention criterion for different soil conditions. The maximum aspect ratios have also been determined by considering 5 appropriately scaled ground motions from the 1998 Posočje earthquake.

  9. Power turbine dynamics - An evaluation of a shear-mounted elastomeric damper

    Science.gov (United States)

    Zorzi, E. S.; Walton, J.; Cunningham, R.

    1983-01-01

    As an alternative to the more conventional squeeze-film bearing damper designs, a Viton-70 shear-mounted, elastomeric damper was built and tested in a T-55 power turbine high-speed balancing rig. This application demonstrated, for the first time, the feasibility of using elastomers as the primary rotor damping source in production turbine engine hardware. The shear-mounted damper design was selected because of its compatibility with actual gas turbine engine radial space constraints, its accommodation of both the radial and axial thrust loads present in gas turbine engines, and its capability of controlled axial preload. Test results showed that the Viton-70 elastomeric damper operated successfully and provided excellent control of both synchronous and nonsynchronous vibrations through all phases of testing to the maximum rotor speed of 1676 rad/s (16,000 rpm). Excellent correlation between the predicted and experienced critical speeds, mode shapes, and log decrements for the power turbine rotor and elastomer damper assembly was also achieved.

  10. Locally-tailored structure of an elastomeric substrate for stretchable circuits

    Science.gov (United States)

    Park, Chan Woo; Jung, Soon Won; Na, Bock Soon; Oh, Ji-Young; Park, Nae-Man; Lee, Sang Seok; Bon Koo, Jae

    2016-02-01

    We demonstrate a new process for fabricating a hybrid elastomeric polydimethylsiloxane (PDMS) substrate, which can provide a high ratio (as large as ∼50) of the elastic modulus between the active device region and the interconnect area, as well as a locally tailored surface profile for each region. For this process, a Si master mold with a dual surface profile is prepared, where locally flat regions are distributed within a wavy-surfaced area. The stiffer elastomeric islands for active devices are formed on the flat regions by photolithography of a photo-patternable and hard PDMS layer (E ∼ 160 MPa), over which a soft PDMS layer (E ∼ 2 to 3 MPa) is casted. By releasing the whole PDMS layer from the mold, a hybrid silicone substrate with stiff and flat islands embedded within a soft and wavy matrix is obtained. In this hybrid structure, active devices located on the stiff regions can provide high reliability under stretched conditions, while most strain is accommodated by wavy interconnects within the soft area. Such beneficial effects are demonstrated by organic thin film transistors produced on the hybrid substrate.

  11. Use of copper slag in glass-epoxy composites for improved wear resistance.

    Science.gov (United States)

    Biswas, Sandhyarani; Satapathy, Alok

    2010-07-01

    Copper slag is a by-product obtained during matte smelting and refining of copper. The common management options for copper slag are recycling, recovery of metal and production of value-added products. In the present study using copper slag as a filler in glass-epoxy composites, the tensile modulus increased from 8.77 GPa to 9.64 GPa when using up to 10 wt% of copper slag but on further addition of copper slag (up to 20 wt%), the tensile modulus started to decrease down to 7.11 GPa. Similar trends were observed in the case of flexural strength and interlaminar shear strength. With the incorporation of copper slag particles, the impact strength increased about 10-15%. This work includes the processing, characterization and study of the erosion behaviour of a class of such copper slag filled glass-epoxy composites based on Taguchi's experimental approach to characterise erosion behaviour. The results show that peak erosion takes place at an impingement angle of 60 degrees for the unfilled composites whereas for the copper slag filled glass-epoxy composites it occurs at a 45 degrees impingement angle. This paper considers the possible utilisation of copper slag as filler material for the preparation of composite materials and preparation of added-value products such as abrasive tools, cutting tools and railroad ballast.

  12. Carbon and nitrogen molecular composition of soil organic matter fractions resistant to oxidation

    Science.gov (United States)

    Katherine Heckman; Dorisel Torres; Christopher Swanston; Johannes Lehmann

    2017-01-01

    The methods used to isolate and characterise pyrogenic organic carbon (PyC) from soils vary widely, and there is little agreement in the literature as to which method truly isolates the most chemically recalcitrant (inferred from oxidative resistance) and persistent (inferred from radiocarbon abundance) fraction of soil organic matter. In addition, the roles of fire,...

  13. Diversity and community composition of tributyltin-resistant bacteria under different conditions

    International Nuclear Information System (INIS)

    Lee, Y. H.; Park, S.; Park, H.; Choi, Y

    2009-01-01

    Tributyltin (TBT) is an organometallic compound used as anti fouling agent in marine paints. this compound is toxic not only for eukaryotes, but also for bacteria. Based on the literature review, a few researchers have reported evidence for the presence of TBT-resistant bacteria in natural seawater and marine sediment. (Author)

  14. Application of laboratory fungal resistance tests to solid wood and wood-plastic composite

    Science.gov (United States)

    Craig Merrill Clemons; Rebecca E. Ibach

    2003-01-01

    The fungal resistance of high density polyethylene filled with 50% wood flour was investigated using laboratory soil block tests. Modifications to standard test methods were made to increase initial moisture content, increase exposure surface area, and track moisture content, mechanical properties, and weight loss over the exposure period. Mechanical properties...

  15. Multilayer sulfur-resistant composite metal membranes and methods of making and repairing the same

    Science.gov (United States)

    Way, J. Douglas; Hatlevik, Oyvind

    2014-07-15

    The invention relates to thin, hydrogen-permeable, sulfur-resistant membranes formed from multi-layers of palladium or palladium-alloy coatings on porous, ceramic or metal supports, methods of making these membranes, methods of repairing layers of these membranes and devices that incorporate these membranes.

  16. In vitro evaluation of fracture resistance of Fiber-Reinforced Composite inlay bridges in upper anterior and lower posterior teeth

    Directory of Open Access Journals (Sweden)

    Jalalian E.

    2007-07-01

    Full Text Available Background and Aim: Considering flexural strength of fiber-reinforced composites (FRC and also the role of conservative cavities in protecting sound tissue of abutments, the aim of this study was to evaluate the fracture resistance of these bridges by handmade samples in vitro.Materials and Methods: In this experimental in vitro study, 44 sound newly extracted teeth were used to make 22 fixed inlay bridges including 11 three unit anterior upper inlay bridges substituting clinical model of upper central and 11 three unit posterior lower inlay bridges substituting clinical model of lower first molar. Specimens were prepared with FRC and mounted with artificial PDL in acryl. Cases were exposed to final load by using Universal Testing Machine (Instron 1195 with the speed of 1 mm/min. Statistical analysis was performed by Kolmogorov- Smirnov, independent sample T and Kaplan-Meier tests with p<0.05 as the level of significance.Results: Based on the statistical tests, the 95% confidence interval of mean was 450-562 N in anterior and  1473- 1761 N in posterior area. Fracture strength was high in the studied groups. Fractures in both groups occurred on composite facing, and the framework remained intact. The highest percentage of fracture in posterior teeth was in the middle of pontic towards the distal connector and in the anterior teeth in the lateral connector, between central pontic and lateral abutment. Using the independent sample T  test a significant statistical difference was observed between two groups (P<0.001. The fracture resistance of anterior samples was lower than the posterior ones.Conclusion: Based on the results of this study regarding the high fracture resistance in both areas FRC inlay bridges could be recommended for upper anterior and lower posterior teeth in clinical dentistry certainly more studies are needed to ascertain this treatment option.

  17. Effect of protein source on resistive-training-induced changes in body composition and muscle size in older men123

    Science.gov (United States)

    Haub, Mark D; Wells, Amanda M; Tarnopolsky, Mark A; Campbell, Wayne W

    2008-01-01

    Background Aging is associated with reductions in muscle mass and strength, but nutrition and exercise interventions can delay this progression and enhance the quality of life. Objective We examined whether the predominant source of protein consumed by older men influenced measures of muscle size and strength, body composition, resting energy expenditure, and skeletal muscle creatine concentrations in response to 12 wk of resistive training. Design After consuming a lactoovovegetarian (LOV) diet for 2 wk, 21 men aged 65 ± 5 y were randomly assigned to either consume a beef-containing (BC) diet (n = 10) or to continue the LOV diet (n = 11) throughout resistive training. The BC diet included 0.6 g protein · kg−1 · d−1 from beef and the LOV diet included 0.6 g protein · kg−1 · d−1 from textured vegetable protein (soy) sources. The remaining protein in the diets came from self-selected LOV sources. Results The mean total protein intake for both groups ranged from 1.03 to 1.17 g · kg−1 · d−1 during the intervention. Men in both groups had improvements (14–38%) in maximal dynamic strength of all the muscle groups trained with no significant difference between groups. With resistive training, cross-sectional muscle area of the vastus lateralis increased in both groups (4.2 ± 3.0% and 6.0 ± 2.6% for the LOV and BC groups, respectively) with no significant difference between groups. Body composition, resting energy expenditure, and concentrations of muscle creatine, phosphocreatine, and total creatine did not differ significantly between groups or change over time. Conclusions These data suggest that increases in muscle strength and size were not influenced by the predominant source of protein consumed by older men with adequate total protein intake. PMID:12197993

  18. Creatine monohydrate and conjugated linoleic acid improve strength and body composition following resistance exercise in older adults.

    Directory of Open Access Journals (Sweden)

    Mark Tarnopolsky

    2007-10-01

    Full Text Available Aging is associated with lower muscle mass and an increase in body fat. We examined whether creatine monohydrate (CrM and conjugated linoleic acid (CLA could enhance strength gains and improve body composition (i.e., increase fat-free mass (FFM; decrease body fat following resistance exercise training in older adults (>65 y. Men (N = 19 and women (N = 20 completed six months of resistance exercise training with CrM (5g/d+CLA (6g/d or placebo with randomized, double blind, allocation. Outcomes included: strength and muscular endurance, functional tasks, body composition (DEXA scan, blood tests (lipids, liver function, CK, glucose, systemic inflammation markers (IL-6, C-reactive protein, urinary markers of compliance (creatine/creatinine, oxidative stress (8-OH-2dG, 8-isoP and bone resorption (Nu-telopeptides. Exercise training improved all measurements of functional capacity (P<0.05 and strength (P<0.001, with greater improvement for the CrM+CLA group in most measurements of muscular endurance, isokinetic knee extension strength, FFM, and lower fat mass (P<0.05. Plasma creatinine (P<0.05, but not creatinine clearance, increased for CrM+CLA, with no changes in serum CK activity or liver function tests. Together, this data confirms that supervised resistance exercise training is safe and effective for increasing strength in older adults and that a combination of CrM and CLA can enhance some of the beneficial effects of training over a six-month period. Trial Registration. ClinicalTrials.gov NCT00473902.

  19. Effect of fed- versus fasted state resistance training during Ramadan on body composition and selected metabolic parameters in bodybuilders

    Science.gov (United States)

    2013-01-01

    Background Muslim bodybuilders often continue training during Ramadan. However, the effect of resistance training in a fasted versus a fed state during Ramadan on body composition and metabolic parameters in bodybuilders is not well known. The aim of this study was to evaluate the effects of resistance training in a fasted versus a fed state during Ramadan on body composition and metabolic parameters in bodybuilders. Methods Sixteen men were allocated to two groups: Eight practicing resistance training in the late afternoon in a fasted state (FAST), and eight training in the late evening in an acutely fed state (FED) during Ramadan. All visited the laboratory in the morning two days before the start of Ramadan (Bef-R) and on the 29th day of Ramadan (End-R) for anthropometric measurement, completion of a dietary questionnaire, and provision of fasting blood and urine samples. Results Body mass and body fat percentage remained unchanged in FAST and FED during the whole period of the investigation. Both FAST and FED experienced an increase in the following parameters from Bef-R to End-R: urine specific gravity (1%; p = 0.028, p = 0.004 respectively), serum concentrations of urea (4%, p = 0.006; 7%, p = 0.004 respectively), creatinine (5%, p = 0.015; 6%, p = 0.04 respectively), uric acid (17%; p bodybuilders. Additionally, Ramadan fasting induced changes in urinary and some biochemical parameters, but these changes were not different according to when the training occurred. PMID:23617897

  20. Formation of structure, phase composition and properties of electro explosion resistant coatings using electron-beam processing

    International Nuclear Information System (INIS)

    Romanov, Denis A.; Sosnin, Kirill V.; Budovskikh, Evgenij A.; Gromov, Viktor E.; Semin, Alexander P.

    2014-01-01

    For the first time, the high intensity electron beam modification of electroexplosion composite coatings of MoCu, MoCCu, WCu, WCCu and TiB 2 Cu systems was done. The studies of phase and elemental composition, defective structure conditions of these coatings were carried out. The regimes of electron-beam processing making possible to form the dense, specular luster surface layers having a submicrocrystalline structure were revealed. It was established that electron-beam processing of elecroexplosion spraying of layer of elecroexplosion spraying carried out in the regime of melting results in the formation of structurally and contrationally homogeneous surface layer. Investigation of the effect of electron-beam processing of electroexplosion electroerosion resistant coatings on their tribological properties (wear resistanse and coefficient of friction) and electroerosion resistance was done. It was shown that all the examined costings demonstrate the increase of electroerosion resistance in spark erosion up to 10 times

  1. Effect of concurrent resistance and sprint training on body composition and cardiometabolic health indicators in masters cyclists.

    Science.gov (United States)

    Delvecchio, Luke; Reaburn, Peter; Trapp, Gail; Korhonen, Marko T

    2016-10-01

    In older previously sedentary individuals endurance training imposes a more effective stimulus to enhance cardiometabolic health compared with resistance or sprint training. We examined the effect of replacing a portion of endurance training with combined resistance and/or sprint training and how this influences cardiometabolic health indicators in masters endurance cyclists. Twenty-seven well-trained male road cyclists (53.7±8.2 years) were allocated to a resistance and track sprint-cycling training group (RTC, n=10), an endurance and track sprint-cycling group (ETC, n=7) or a control endurance group (CTRL, n=10). Both the RTC and ETC groups completed a 12-week intervention of specific training while the CTRL group maintained their endurance training load. Lower limb lean mass (LLM), trunk fat mass (TFM), fasting blood glucose (FBG), total cholesterol (TC), triglycerides (TG), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured before and after the intervention period. TFM decreased for all groups ( P training with 12 weeks of ETC or RTC training favourably affects body composition by lowering TFM and increasing LLM without negatively affecting cardiometabolic health indicators in well-trained masters endurance cyclists.

  2. Effect of concurrent resistance and sprint training on body composition and cardiometabolic health indicators in masters cyclists

    Science.gov (United States)

    Delvecchio, Luke; Reaburn, Peter; Trapp, Gail; Korhonen, Marko T.

    2016-01-01

    In older previously sedentary individuals endurance training imposes a more effective stimulus to enhance cardiometabolic health compared with resistance or sprint training. We examined the effect of replacing a portion of endurance training with combined resistance and/or sprint training and how this influences cardiometabolic health indicators in masters endurance cyclists. Twenty-seven well-trained male road cyclists (53.7±8.2 years) were allocated to a resistance and track sprint-cycling training group (RTC, n=10), an endurance and track sprint-cycling group (ETC, n=7) or a control endurance group (CTRL, n=10). Both the RTC and ETC groups completed a 12-week intervention of specific training while the CTRL group maintained their endurance training load. Lower limb lean mass (LLM), trunk fat mass (TFM), fasting blood glucose (FBG), total cholesterol (TC), triglycerides (TG), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured before and after the intervention period. TFM decreased for all groups (P<0.05) while LLM significantly increased for RTC and ETC groups (P<0.05). No significant between group or time effects were observed for FBG, TC, TG, SBP, or DBP. The results suggest that replacing a portion of endurance training with 12 weeks of ETC or RTC training favourably affects body composition by lowering TFM and increasing LLM without negatively affecting cardiometabolic health indicators in well-trained masters endurance cyclists. PMID:27807523

  3. The fabrication, nano/micro-structure, heat- and wear-resistance of the superhydrophobic PPS/PTFE composite coatings.

    Science.gov (United States)

    Wang, Huaiyuan; Zhao, Jingyan; Zhu, Youzhuang; Meng, Yang; Zhu, Yanji

    2013-07-15

    A simple engineering method was used to fabricate stability and wear-resistance of superhydrophobic PPS-based PPS/PTFE surfaces through nano/micro-structure design and modification of the lowest surface energy groups (-CF2-), which was inspired by the biomimic lotus leaves. The hydrophobic properties and wear-resistance of the coatings were measured by a contact angle meter and evaluated on a pin-on-disk friction and wear tester, respectively. Moreover, the surfaces of the PPS/PTFE composite coatings were investigated by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffractometry (XRD), and thermogravimetry (TG) analysis. Results showed that the highest contact angle of the PPS/PTFE surface, with papillae-like randomly distributed double-scale structure, could reach up to 162°. When 1 wt.% PDMS was added, the highest contact angle could hold is 172°. The coatings also retained superhydrophobicity, even under high temperature environment. The investigation also indicated that the coatings were not only superhydrophobic but also oleophobic behavior at room temperature, such as the crude oil, glycerol, and oil-water mixture. The PPS/45%PTFE coatings had more stable friction coefficient and excellent wear-resistance (331,407 cycles) compared with those with less than 45% of PTFE. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Environmental and Sustainable Technology Evaluation: Mold-Resistant Armacell Insulation--Armacell LLC, AP Armaflex Black

    Science.gov (United States)

    The ESTE test program measured the mold resistance of Armacell AP Armaflex Black insulation. Tests for emissions of VOCs and formaldehyde were also performed. AP Armaflex Roll Insulation is a black flexible closed-cell, fiber-free elastomeric thermal insulation. The expanded clos...

  5. Compositions of corrosion-resistant Fe-based amorphous metals suitable for producing thermal spray coatings

    Science.gov (United States)

    Farmer, Joseph C; Wong, Frank M.G.; Haslam, Jeffery J; Ji, Xiaoyan; Day, Sumner D; Blue, Craig A; Rivard, John D.K.; Aprigliano, Louis F; Kohler, Leslie K; Bayles, Robert; Lemieux, Edward J; Yang, Nancy; Perepezko, John H; Kaufman, Larry; Heuer, Arthur; Lavernia, Enrique J

    2013-09-03

    A method of coating a surface comprising providing a source of amorphous metal that contains manganese (1 to 3 atomic %), yttrium (0.1 to 10 atomic %), and silicon (0.3 to 3.1 atomic %) in the range of composition given in parentheses; and that contains the following elements in the specified range of composition given in parentheses: chromium (15 to 20 atomic %), molybdenum (2 to 15 atomic %), tungsten (1 to 3 atomic %), boron (5 to 16 atomic %), carbon (3 to 16 atomic %), and the balance iron; and applying said amorphous metal to the surface by a spray.

  6. Neuroendocrine Responses and Body Composition Changes Following Resistance Training Under Normobaric Hypoxia

    Directory of Open Access Journals (Sweden)

    Chycki Jakub

    2016-12-01

    Full Text Available The aim of the present study was to evaluate the effects of a 6 week resistance training protocol under hypoxic conditions (FiO2 = 12.9%, 4000 m on muscle hypertrophy. The project included 12 resistance trained male subjects, randomly divided into two experimental groups. Group 1 (n = 6; age 21 ± 2.4 years; body height [BH] 178.8 ± 7.3 cm; body mass [BM] 80.6 ± 12.3 kg and group 2 (n = 6; age 22 ± 1.5 years; BH 177.8 ± 3.7cm; BM 81.1 ± 7.5 kg. Each group performed resistance exercises alternately under normoxic and hypoxic conditions (4000 m for 6 weeks. All subjects followed a training protocol that comprised two training sessions per week at an exercise intensity of 70% of 1RM; each training session consisted of eight sets of 10 repetitions of the bench press and barbell squat, with 3 min rest periods. The results indicated that strength training in normobaric hypoxia caused a significant increase in BM (p < 0.01 and fat free mass (FFM (p < 0.05 in both groups. Additionally, a significant increase (p < 0.05 was observed in IGF-1 concentrations at rest after 6 weeks of hypoxic resistance training in both groups. The results of this study allow to conclude that resistance training (6 weeks under normobaric hypoxic conditions induces greater muscle hypertrophy compared to training in normoxic conditions.

  7. Fatigue resistance and crack propensity of large MOD composite resin restorations: direct versus CAD/CAM inlays.

    Science.gov (United States)

    Batalha-Silva, Silvana; de Andrada, Mauro Amaral Caldeira; Maia, Hamilton Pires; Magne, Pascal

    2013-03-01

    To assess the influence of material/technique selection (direct vs. CAD/CAM inlays) for large MOD composite adhesive restorations and its effect on the crack propensity and in vitro accelerated fatigue resistance. A standardized MOD slot-type tooth preparation was applied to 32 extracted maxillary molars (5mm depth and 5mm bucco-palatal width) including immediately sealed dentin for the inlay group. Fifteen teeth were restored with direct composite resin restoration (Miris2) and 17 teeth received milled inlays using Paradigm MZ100 block in the CEREC machine. All inlays were adhesively luted with a light curing composite resin (Filtek Z100). Enamel shrinkage-induced cracks were tracked with photography and transillumination. Cyclic isometric chewing (5 Hz) was simulated, starting with a load of 200 N (5000 cycles), followed by stages of 400, 600, 800, 1000, 1200 and 1400 N at a maximum of 30,000 cycles each. Samples were loaded until fracture or to a maximum of 185,000 cycles. Teeth restored with the direct technique fractured at an average load of 1213 N and two of them withstood all loading cycles (survival=13%); with inlays, the survival rate was 100%. Most failures with Miris2 occurred above the CEJ and were re-restorable (67%), but generated more shrinkage-induced cracks (47% of the specimen vs. 7% for inlays). CAD/CAM MZ100 inlays increased the accelerated fatigue resistance and decreased the crack propensity of large MOD restorations when compared to direct restorations. While both restorative techniques yielded excellent fatigue results at physiological masticatory loads, CAD/CAM inlays seem more indicated for high-load patients. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Effect of resistance training with elements of stretching on body composition and quality of life in postmenopausal women

    Directory of Open Access Journals (Sweden)

    Małgorzata Socha

    2016-03-01

    Full Text Available Introduction: Physical activity in elderly persons contributes to prevention and treatment of chronic disease and, through its influence on the musculoskeletal system, increases physical capability and improves mental function. Aim of the study was to assess the effect of resistance training with elements of stretching on body composition and quality of life in women of postmenopausal age. Material and methods : Thirty-eight postmenopausal women aged 62.5 ±5.8 years were randomly divided into two groups. One group participated in an 8-week training program (60 minutes, twice weekly; 4 MET [metabolic equivalent] 2 hours/week. The second group performed no training. A comparison was made of body composition and quality of life (SF-36 Health Survey prior to and after 8 weeks of training. Results: In the training group, after 8 weeks there was a significant reduction in body fat (in %; p = 0.028, and an increase in fat-free mass (in %; p = 0.025 and total body water (in %; p = 0.021, which indicates increased muscle mass. Furthermore, there were statistically significant differences in the assessment of quality of life in physical (role-physical [RP], bodily pain [BP], general health [GH] scales; p < 0.005 and mental health (vitality [VT] scale; p = 0.05. In the non-exercising group no changes were observed in features examined in the initial and final test. Conclusions : Resistance training with elements of stretching in postmenopausal women improved body composition to achieve a reduction in risk factors associated with excess fatty tissue and muscle mass deficiency. It raises the quality of life in terms of both physical and mental function.

  9. Biomimetic elastomeric, conductive and biodegradable polycitrate-based nanocomposites for guiding myogenic differentiation and skeletal muscle regeneration.

    Science.gov (United States)

    Du, Yuzhang; Ge, Juan; Li, Yannan; Ma, Peter X; Lei, Bo

    2018-03-01

    Artificial muscle-like biomaterials have gained tremendous interests owing to their broad applications in regenerative medicine, wearable devices, bioelectronics and artificial intelligence. Unfortunately, key challenges are still existed for current materials, including biomimetic viscoelasticity, biocompatibility and biodegradation, multifunctionality. Herein, for the first time, we develop highly elastomeric, conductive and biodegradable poly (citric acid-octanediol-polyethylene glycol)(PCE)-graphene (PCEG) nanocomposites, and demonstrate their applications in myogenic differentiation and guiding skeletal muscle tissue regeneration. In PCEG nanocomposites, PCE provides the biomimetic elastomeric behavior, and the addition of reduced graphene oxide (RGO) endows the enhanced mechanical strength and conductivity. The highly elastomeric behavior, significantly enhanced modulus (400%-800%), strength (200%-300%) of PCEG nanocomposites with controlled biodegradability and electrochemical conductivity were achieved. The myoblasts proliferation and myogenic differentiation were significantly improved by PCEG nanocomposite. Significantly high in vivo biocompatibility of PCEG nanocomposites was observed when implanted in the subcutaneous tissue for 4 weeks in rats. PCEG nanocomposites could significantly enhance the muscle fibers and blood vessels formation in vivo in a skeletal muscle lesion model of rat. This study may provide a novel strategy to develop multifunctional elastomeric nanocomposites with high biocompatibility for potential soft tissue regeneration and stretchable bioelectronic devices. Copyright © 2017 Elsevier Ltd. All rights reserved.

  10. Glass interface effect on high-strain-rate tensile response of a soft polyurethane elastomeric polymer material

    NARCIS (Netherlands)

    Fan, J.T.; Weerheijm, J.; Sluys, L.J.

    2015-01-01

    The glass interface effect on dynamic tensile response of a soft polyurethane elastomeric polymer material has been investigated by subjecting a glass-polymer system of this polymer material matrix embedded a single 3 mm-diameter glass particle to impact loading in a split Hopkinson tension bar

  11. Plaque accumulation and Streptococcus mutans levels around self-ligating bracket clips and elastomeric modules: A randomized controlled trial

    Directory of Open Access Journals (Sweden)

    Dhaval Fadia

    2015-01-01

    Full Text Available Aim: To determine the effect of two different ligating systems that is, elastomeric modules and self-ligating (SL bracket systems (Smartclip - 3M Unitek with respect to harboring bacterial plaque in fixed orthodontic treatment. Objectives: To assess, evaluate, and compare the amount of plaque accumulation and Streptococcus mutans colonization around elastomeric ligation and SL clips in the smart clip appliance. Materials and Methods: A total of 111 orthodontic patients scheduled for fixed orthodontic treatments were selected for this split maxillary arch study. All the patients were bonded with smart-clip (3M Unitek SL brackets, and the wire was placed into the bracket slots, on the randomly selected hemi arch, elastomeric modules were placed for the study to be conducted. Microbial and periodontal plaque accumulation was recorded at 3-time intervals post ligation. Plaque index-by Silness and Loe, modified Quigely Hein index, bleeding on probing were evaluated, and biofilm was collected from the tooth surface after 30 days and placed in petri dishes containing Mitis Salivarius agar for bacterial culturing. Result: It was observed that the side where ligation was done with elastomeric modules accumulated more plaque and increase in S. mutans colony forming units as compared to the side without external ligation (P < 0.05. Conclusion: Reduced bacterial colonization and better plaque control was seen with SL orthodontic bracket appliance system as compared to conventional ligation method.

  12. Preparation, characterization and wear resistance to ceramic composites Si C/Ti B{sub 2}; Elaboration, caracterisation et resistance a l`usure de composites ceramiques SiC/TiB{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Blanc, C.

    1997-12-18

    The composites Si C-Ti B{sub 2} (5,10,15% vol. Ti B{sub 2}) have been synthesized by natural and reactive sintering from Ti O{sub 2}, B{sub 4} C and phenolic resin used as carbon source, by the reaction: Ti O{sub 2} + 0.5 B{sub 4} C +1.5 C -> Ti B{sub 2} + 2 CO (1400 degrees Celsius). They have been characterized from a microstructural, mechanical and tribological point of view. The dispersion of Ti B{sub 2} particles is very homogeneous in optical microscopy and in scanning electron microscopy. The images analysis has showed that most of the particles have a size smaller than 1 {mu}m. The atomic force microscopy and the transmission electron microscopy have revealed the existence of nanometrical particles. Concerning the mechanical properties, the fracture toughness increases with the Ti B{sub 2} rate and the hardness decreases. By friction, the composite materials wear slowly than the monolithic SiC. The wear mechanisms are modified in air and in water. In air, a layer of oxidized scraps, protector if it is stable, are formed for composites while there is formation of rollers for SiC. In water, composites are polished while SiC wears by cleavages. The influence of the Ti B{sub 2} phase on the wear resistance is due to the tribo-oxidation: a lubrication can take place through the tribo-oxidation products. (O.M.) 64 refs.

  13. Study of wear resistance of diamond grinding tool, a layer which contains the dispersed abrasive powders of composite materials

    Directory of Open Access Journals (Sweden)

    V.І. Lavrinenko

    2017-12-01

    Full Text Available The results of the study opportunities of application compacted structured by nanocarbon bond dispersed powders of synthetic, natural diamond and boron carbide in the grinding wheels for the processing of cemented carbide. For this purpose were selected Diamond powders AC 6 125/100 and on their surface was damaged composite material based on sub-micron (3/0 fractions of natural diamond powders, as well as boron carbide micropowders, compacted carbon pile method physicochemical synthesis at a pressure lower than atmospheric pressure. In this paper, the main task was to compare features of the operational characteristics of the diamond community, primarily their durability when used in their working layer dispersed of abrasive powders of new composite materials based on natural diamond and boron carbide and set conditions for their effective application in grinding wheels. In this paper, the main task was to compare features of the operational characteristics of the diamond community, primarily their durability when used in their working layer dispersed of abrasive powders of new composite materials based on natural diamond and boron carbide and set conditions for their effective application in grinding wheels. It is shown that partial (50 % or total replacement of synthetic diamonds compacted powders that contain diamonds, surrounded by the original coating of mìcropowders natural diamond or boron carbide mìcropowders structured by nanocarbon bond, allows you to significantly increase wear resistance diamond grinding wheels.

  14. Hybrid carbon/glass fiber composites: Micromechanical analysis of structure–damage resistance relationships

    DEFF Research Database (Denmark)

    Mishnaevsky, Leon; Dai, Gaoming

    2014-01-01

    A computational study of the effect of microstructure of hybrid carbon/glass fiber composites on their strength is presented. Unit cells with hundreds of randomly located and misaligned fibers of various properties and arrangements are subject to tensile and compression loading, and the evolution...

  15. The Impact Resistance of Fiber-Reinforced Polymer Composites: A Review

    Directory of Open Access Journals (Sweden)

    Mahmood Mehrdad Shokrieh

    2012-12-01

    Full Text Available Fiber reinforced composites are widely used instead of traditional materials in various technological applications. Therefore, by considering the extensive applications of these materials, a proper knowledge of their impact behavior (from low- to high-velocity as well as their static behavior is necessary. In order to study the effects of strain rates on the behavior of these materials, special testing machines are needed. Most of the research efforts in this feld are focused on application of real loading and gripping boundary conditions on the testing specimens. In this paper, a detailed review of different types of impact testing techniques and the strain rate dependence of mechanical and strength properties of polymer composite materials  are presented. In this respect, an attempt is made to present and summarize the methods of impact tests and the strain rate effects on the tensile, compressive, shear and bending properties of the fber-reinforced polymer composite materials. Moreover, a classifcation of the state-of-the-art of the testing techniques to characterize composite material properties in a wide range of strain rates are also given.

  16. Factors influencing creep resistance in discontinuously reinforced magnesium metal matrix composites

    Czech Academy of Sciences Publication Activity Database

    Sklenička, Václav; Kuchařová, Květa; Kvapilová, Marie; Svoboda, Milan

    2015-01-01

    Roč. 53, č. 4 (2015), s. 221-229 ISSN 0023-432X R&D Projects: GA MŠk(CZ) ED1.1.00/02.0068 Institutional support: RVO:68081723 Keywords : magnesium alloys * composites * creep properties testing * structure * fibres * interfaces Subject RIV: JG - Metal lurgy Impact factor: 0.365, year: 2015

  17. Characterization of nano-composite PVD coatings for wear-resistant applications

    NARCIS (Netherlands)

    Galvan, D.; Pei, Y.T.; de Hosson, J.T.M.; DeHosson, JTM; Brebbia, CA; Nishida, SI

    2005-01-01

    Various methodologies for the characterization of nano-composite coatings are discussed, which consist TiC nano-particles distributed in an amorphous hydrocarbon (a-C:H) matrix. Complications that arise from the influence of coating roughness and underlying substrate on the properties are evaluated

  18. Sliding wear resistance of metal matrix composite layers prepared by high power laser

    NARCIS (Netherlands)

    Ocelik, Vaclav; Matthews, D; de Hosson, Jeff

    2005-01-01

    Two laser surface engineering techniques, Laser Cladding and Laser Melt Injection (LMI), were used to prepare three different metal matrix composite layers with a thickness of about 1 mm and approximately 25-30% volume fraction of ceramic particles. SiC/Al-8Si, WC/Ti-6Al-4V and TiB2/Ti-6Al-4V layers

  19. Toughened and corrosion- and wear-resistant composite structures and fabrication methods thereof

    Science.gov (United States)

    Seals, Roland D; Ripley, Edward B; Hallman, Russell L

    2014-04-08

    Composite structures having a reinforced material interjoined with a substrate and methods of creating a composite material interjoined with a substrate. In some embodiments the composite structure may be a line or a spot or formed by reinforced material interjoined with the substrate. The methods typically include disposing a precursor material comprising titanium diboride and/or titanium monoboride on at least a portion of the substrate and heating the precursor material and the at least a portion of the substrate in the presence of an oxidation preventative until at least a portion of the precursor material forms reinforced material interjoined with the substrate. The precursor material may be disposed on the substrate as a sheet or a tape or a slurry or a paste. Localized surface heating may be used to heat the precursor material. The reinforced material typically comprises a titanium boron compound, such as titanium monoboride, and preferably comprises .beta.-titanium. The substrate is typically titanium-bearing, iron-bearing, or aluminum-bearing. A welding rod is provided as an embodiment. The welding rod includes a metal electrode and a precursor material is disposed adjacent at least a portion of the metal electrode. A material for use in forming a composite structure is provided. The material typically includes a precursor material that includes one or more materials selected from the following group: titanium diboride and titanium monoboride. The material also typically includes a flux.

  20. Preparation of Silicon Rubber/2,2'-(3-methyl-4-dihydro-1,3,2-benzoxazinePropane Ablative-resistant Composites and Its Ablative Structure

    Directory of Open Access Journals (Sweden)

    DONG Yimin

    2017-10-01

    Full Text Available Benzoxazine resin is a new generation of anti-ablation resin with high char yield and high-temperature oxidation resistance. Using high temperature vulcanized silicon rubber as ablation resistance matrix and 2,2'-(3-methyl-4-dihydro-1,3,2-benzoxazinepropane as anti-ablation resin, silicon rubber/polybenzoxazine anti-ablation composite was prepared by blending method. The mechanical properties were tested,and the ablation structure and the composition of the composite were investigated by DSC,SEM,FT-IR and Raman.Experimental results show that the polybenzoxazine resin can improve the ablation resistance property of silicone rubber composite. The composite has good ablation resistance and mechanical property when the addition of polybenzoxazine resin reaches 20 phr. After ablated by oxygen acetylene flame,the ablation layer is divided into three obvious layers as surface ceramic layer,pyrolysis carbonization layer and base layer. The surface ceramic layer formed in the progress of ablation plays a positive role in the ablation property of the composite material.

  1. The effect of fibre content, fibre size and alkali treatment to Charpy impact resistance of Oil Palm fibre reinforced composite material

    Science.gov (United States)

    Fitri, Muhamad; Mahzan, Shahruddin

    2016-11-01

    In this research, the effect of fibre content, fibre size and alkali treatment to the impact resistance of the composite material have been investigated, The composite material employs oil palm fibre as the reinforcement material whereas the matrix used for the composite materials are polypropylene. The Oil Palm fibres are prepared for two conditions: alkali treated fibres and untreated fibres. The fibre sizes are varied in three sizes: 5mm, 7mm and 10mm. During the composite material preparation, the fibre contents also have been varied into 3 different percentages: 5%, 7% and 10%. The statistical approach is used to optimise the variation of specimen determined by using Taguchi method. The results were analyzed also by the Taguchi method and shows that the Oil Palm fibre content is significantly affect the impact resistance of the polymer matrix composite. However, the fibre size is moderately affecting the impact resistance, whereas the fibre treatment is insignificant to the impact resistance of the oil palm fibre reinforced polymer matrix composite.

  2. Effect of commonly used beverage, soft drink, and mouthwash on force delivered by elastomeric chain: a comparative in vitro study.

    Science.gov (United States)

    Kumar, Kiran; Shetty, Sharath; Krithika, M J; Cyriac, Bobby

    2014-06-01

    The objective was to evaluate and compare the effect of Coca-Cola®, tea, Listerine® mouthwash on the force delivered by elastomeric chain in vitro. Four specimen groups (distilled water, Coca-Cola®, tea, Listerine® mouthwash) with a total sample size of 480 specimens. A specimen is described as a four link grey close elastomeric chain. Jigs, each with a series of pins set 25 mm apart, was used to hold stretched elastomeric chains at a constant length. These jigs allowed for complete submersion of the elastomeric chain in a water bath throughout the test period, as well as the dipping of elastomeric chains in respective control and test solutions. For 60 s, twice a day, groups were exposed to the respective solutions, the two daily exposure was separated by 9 h and force measurements were taken at six time points during the experiment, that is, 1 h, 24 h, 7 days, 14 days, 21 days, and 28 days. Force measurements were made by Instron machine by a single blinded examiner with the help of a second examiner. It was found out that there was highly significant difference between groups control, Coca-Cola®, Listerine®, and tea as well as there was highly significant (p Coca-Cola® and the Listerine® group reached a plateau between 7 and 21 days then decrease between 21 and 28 days. The tea group showed plateau phase between 7 and 28 days. After 28 days in the control group, 25% force decay occurred while the test groups force decay of 30-50% occurred. Coca-Cola®, Listerine® mouthwash, and tea cause an increase in force decay of elastomeric chains over time. Tea caused highest force decay followed by Listerine® and Coca-Cola® when compared to control group. How to cite the article: Kumar K, Shetty S, Krithika MJ, Cyriac B. Effect of commonly used beverage, soft drink, and mouthwash on force delivered by elastomeric chain: A comparative in vitro study. J Int Oral Health 2014;6(3):7-10.

  3. Multi-Ferroic Polymer Nanoparticle Composites for Next Generation Metamaterials

    Science.gov (United States)

    2015-12-18

    electric circuits from a composite material of silver nanoparticles and elastomeric fibres. Nat Nanotechnol... Conductors Based on Block Copolymer Silver Nanoparticle Composites. Acs Nano 2015, 9 (1), 336-344. 2. (a) Yang, T. I.; Brown, R. N. C.; Kempel, L. C...Stretchable nanoparticle conductors with self-organized conductive pathways. Abstr Pap Am Chem S 2014, 248; (c) Balazs, A. C.; Emrick, T.;

  4. The Effect of 10 Weeks of Resistance Training on Serum Myostatin and Body Composition Levels in Obese Adolescents

    Directory of Open Access Journals (Sweden)

    Mohammad ebrahim Bahram

    2017-06-01

    Full Text Available Background and Objectives: Studies are indicative of negative regulatory role of myostatin in skeletal muscle growth. In the present study, the effect of 10 weeks of resistance training was investigated on serum level of myostatin and body composition in obese adolescents. Methods: In this quasi-experimental study, 16 students of Mohammad Naraghi Technical and Vocational Institute of Kashan with body mass index of 30-35, were purposefully selected and randomly divided into two groups of experimental and control. Resistance training program included 3 sets of 8-10 reps with 50-90% 1RM for 3 days a week. Before starting the training program and 48 h after the last training session, blood samples were taken from all participants. Before and after the training, plasma level of myostatin were measured. Data were analyzed using Kolmogorov-Smirnov, dependent t-, and independent t-tests at significance level of p<0.05. Results: In this study, 10 weeks of resistance training resulted in a significant decrease in serum level of myostatin (p=0.0001, weight (p=0.015, body mass index (p=0.02, and fat percentage (p=0.0001 in the experimental group as compared to the control group (p<0.05. Conclusion: According to the findings of the current study, it can be concluded that resistance training-induced changes reduce myostatin level and some anthropometric parameters related to obesity and overweight, which may be effective in the prevention of muscle atrophy and loss of muscle mass, and can play a role as an autocrine mechanism for guiding mechanical load stimuli in response to the growth of skeletal muscle.

  5. Blast-Resistant Improvement of Sandwich Armor Structure with Aluminum Foam Composite

    Directory of Open Access Journals (Sweden)

    Shu Yang

    2013-01-01

    Full Text Available Sandwich armor structures with aluminum foam can be utilized to protect a military vehicle from harmful blast load such as a landmine explosion. In this paper, a system-level dynamic finite element model is developed to simulate the blast event and to evaluate the blast-resistant performance of the sandwich armor structure. It is found that a sandwich armor structure with only aluminum foam is capable of mitigating crew injuries under a moderate blast load. However, a severe blast load causes force enhancement and results in much worse crew injury. An isolating layer between the aluminum foam and the vehicle floor is introduced to remediate this drawback. The results show that the blast-resistant capability of the innovative sandwich armor structure with the isolating layer increases remarkably.

  6. UV radiation resistant polyimide based composites reinforced with nanostructured titanate particles: preparation and properties

    OpenAIRE

    Harito, Christian

    2017-01-01

    Ultraviolet (UV) exposure is one of the most deleterious threats to polymers. UV light may alter chemical bonds, leading to discoloration of the polymer and even degradation of its properties. Polyimide (PI) is a well-known polymer in electronic devices, filtration and as components for spacecraft and satellites. PI has desirable properties as a lightweight material, which is flexible and resistant to heat and chemicals. This work is focused on protection of polyimide from UV damage by incor...

  7. Crack resistance curve in glass matrix composite reinforced by long SiC fibres

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Kotoul, M.; Vysloužil, T.; Chlup, Zdeněk; Boccaccini, A. R.

    2008-01-01

    Roč. 43, č. 13 (2008), s. 4022-4030 ISSN 0022-2461 R&D Projects: GA ČR(CZ) GA106/05/0495; GA ČR(CZ) GA106/06/0724 Institutional research plan: CEZ:AV0Z20410507 Keywords : glass matrix compositze * Nicalon fibres * fracture toughness * toughening prediction Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 1.181, year: 2008

  8. Demonstration of Corrosion-Resistant Hybrid Composite Bridge Beams for Structural Applications

    Science.gov (United States)

    2016-09-01

    severity. Although the steel coupon testing resulted in a C2 classification , the results were on the upper limit of the category. The potential for...suggest the Fort Knox Bridge #4 site is a Category 3 classification of atmospheric corrosion severity. Although the steel coupon testing re- sulted in a...result of corrosion of the steel support structures or the reinforcing bar in the concrete. The application of corrosion-resistant technology can

  9. Chemical composition and antibacterial activities of Illicium verum against antibiotic-resistant pathogens.

    Science.gov (United States)

    Yang, Jyh-Ferng; Yang, Cheng-Hong; Chang, Hsueh-Wei; Yang, Cheng-San; Wang, Shao-Ming; Hsieh, Ming-Che; Chuang, Li-Yeh

    2010-10-01

    In recent years, human pathogenic microorganisms have developed multiple drug resistance and caused serious nosocomial infections. In this study, we identified four new antimicrobial compounds from the Chinese herbal medicine Illicium verum and assessed their antibacterial efficacies. The supercritical CO₂ and ethanol extracts of Illicium verum showed substantial antibacterial activity against 67 clinical drug-resistant isolates, including 27 Acinetobacter baumannii, 20 Pseudomonas aeruginosa, and 20 methicillin-resistant Staphylococcus aureus. The diethyl ether (EE) fraction obtained from partition extraction and supercritical CO₂ extracts revealed an antibacterial activity with a minimum inhibitory concentration value of 0.15-0.70 mg/mL and 0.11 mg/mL, respectively. The EE fraction of I. verum showed synergetic effects with some commercial antibiotics. The antimicrobial mechanism was investigated with killing curves and scanning electron microscopy observation. The chemical components of the extracts were analyzed by spectrophotometry; (E)-anethole, anisyl acetone, anisyl alcohol, and anisyl aldehyde exhibited antibacterial activity against different clinical isolates. These extracts from I. verum can be further developed into antibiotic medicines due to their proven antibacterial activity.

  10. Toward advanced gamma rays radiation resistance and shielding efficiency with phthalonitrile resins and composites

    Science.gov (United States)

    Derradji, Mehdi; Zegaoui, Abdeldjalil; Xu, Yi-Le; Wang, An-ran; Dayo, Abdul Qadeer; Wang, Jun; Liu, Wen-bin; Liu, Yu-Guang; Khiari, Karim

    2018-04-01

    The phthalonitrile resins have claimed the leading place in the field of high performance polymers thanks to their combination of outstanding properties. The present work explores for the first time the gamma rays radiation resistance and shielding efficiency of the phthalonitrile resins and its related tungsten-reinforced nanocomposites. The primary goal of this research is to define the basic behavior of the phthalonitrile resins under highly ionizing gamma rays. The obtained results confirmed that the neat phthalonitrile resins can resist absorbed doses as high as 200 kGy. Meanwhile, the remarkable shielding efficiency of the phthalonitrile polymers was confirmed to be easily improved by preparing lead-free nanocomposites. In fact, the gamma rays screening ratio reached the exceptional value of 42% for the nanocomposites of 50 wt% of nano-tungsten loading. Thus, this study confirms that the remarkable performances of the phthalonitrile resins are not limited to the thermal and mechanical properties and can be extended to the gamma rays radiation and shielding resistances.

  11. Unidirectional fibers and polyurethane elastomer matrix based composites synthesis and properties. Ph.D. Thesis

    Science.gov (United States)

    Chakar, A.

    1984-01-01

    A study of the properties and manufacturing techniques for long-fiber reinforced elastomeric composites for flexible and damping structural materials is presented. Attention is given to the usage of polyurethane in the matrix to obtain plastic elastomeric matrices and vitreous transition temperatures which vary from -80 C to 10 C, as well as assure good fiber adhesion. Various polyurethane formulations synthesized from diisocyanate prepolymers are examined in terms of mechanical and thermal properties. The principal reinforcing fiber selected is a unidirectional glass cloth.

  12. A New Design of In Situ Ti(C,N) Reinforced Composite Coatings and Their Microstructures, Interfaces, and Wear Resistances.

    Science.gov (United States)

    Wang, Mingliang; Cui, Hongzhi; Wei, Na; Ding, Lei; Zhang, Xinjie; Zhao, Yong; Wang, Canming; Song, Qiang

    2018-01-31

    Here, a unique combination of a novel carbon-nitrogen source (g-C 3 N 4 ) with different mole ratios of Ti/g-C 3 N 4 has been utilized to fabricate iron matrix composite coatings by a synchronized powder feeding plasma transferred arc (PTA) cladding technology. The results show that submicron Ti(C,N) particles are successfully fabricated in situ on a Q235 low carbon steel substrate to reinforce the iron matrix composite coatings and exhibit dense microstructures and good metallurgical bonding between the coating and the substrate. The microstructure of the coating consists of an α-Fe matrix and Ti(C,N) particles when the mole ratio of Ti/g-C 3 N 4 is no more than 5:1. The microhardness and wear resistance of the coating gradually improve with increasing abundance of the in-situ-synthesized Ti(C,N) particles. Interestingly, for a Ti/g-C 3 N 4 mole ratio of 6:1, a fine lamellar eutectic Laves phase (Fe 2 Ti) appears, and this phase further improves the microhardness and wear resistance of the coating. The microhardness of the coating is 3.5 times greater than that of the Q235 substrate, and the wear resistance is enhanced 7.66 times over that of the substrate. The Ti(C,N)/Fe 2 Ti and Fe 2 Ti/α-Fe interfaces are very clean, and the crystallographic orientation relationships between the phases are analyzed by high-resolution transmission electron microscopy (HRTEM) and an edge-to-edge matching model. The theoretical predictions and the experimental results are in good agreement. Furthermore, based on the present study, for the solidification process near equilibrium, smaller interatomic spacing misfits and interplanar spacing d-value mismatches contribute to the formation of crystallographic orientation relationships between phases during the PTA cladding process. The existence of orientation relationships is beneficial for improving the properties of the coatings. This work not only expands the application fields of g-C 3 N 4 but also provides a new idea for the

  13. Fracture resistance of composite resin restorations and porcelain veneers in relation to residual tooth structure in fractured incisors.

    Science.gov (United States)

    Batalocco, Guido; Lee, Heeje; Ercoli, Carlo; Feng, Changyong; Malmstrom, Hans

    2012-02-01

    The aim of the present study was to investigate whether there is a direct correlation between the amount of residual tooth structure in a fractured maxillary incisor and the fracture resistance of composite resin restorations or porcelain veneers after cyclic loading. Sixty human-extracted maxillary central and lateral incisors were mounted in an acrylic block with the coronal aspect of the tooth protruding from the block surface. The teeth were assigned to two groups: 2-mm incisal fracture and 4-mm incisal fracture. Then, the teeth were further divided into two different restoration subgroups, porcelain laminate veneer and composite resin restoration, therefore obtaining four groups for the study (n=15). The specimens were subjected to 1000 cycles of thermocycling and were mechanically tested with a custom-designed cyclic loading apparatus for 2×106 cycles or until they failed. The specimens that survived the cyclic loading were loaded on the incisal edge along the long axis of the tooth with a flat stainless steel applicator until they fractured using a universal testing machine to measure the failure load. Two-way anova was used to assess the significance of restoration, amount of fracture, and interaction effect (α=0.05). During the cyclic loading, for the composite resin group, two specimens with 2-mm fracture and three specimens with 4-mm fracture failed. For the porcelain veneer group, two specimens with 2-mm fracture and one specimen with 4-mm fracture failed. The 2-way anova did not show statistical significance for restoration (P=0.584), amount of fracture (P=0.357), or interaction effect (P=0.212). A composite resin restoration and a porcelain veneer could perform similarly for replacing a fractured incisor edge up to 4mm. Other factors such as esthetic and/or cost would be considerations to indicate one treatment over the other. © 2011 John Wiley & Sons A/S.

  14. Surge-Resistant Nanocomposite Enameled Wire Using Silica Nanoparticles with Binary Chemical Compositions on the Surface

    Directory of Open Access Journals (Sweden)

    Jeseung Yoo

    2015-01-01

    Full Text Available We developed polyesterimide (PEI nanocomposite enameled wires using surface-modified silica nanoparticles with binary chemical compositions on the surface. The modification was done using silanes assisted by ultrasound, which facilitated high density modification. Two different trimethoxysilanes were chosen for the modification on the basis of resemblance of chemical compositions on the silica surface to PEI varnish. The surface-modified silica was well dispersed in PEI varnish, which was confirmed by optical observation and viscosity measurement. The glass transition temperature of the silica-PEI nanocomposite increased with the silica content. The silica-dispersed PEI varnish was then used for enameled wire fabrication. The silica-PEI nanocomposite enameled wire exhibited a much longer lifetime compared to that of neat PEI enameled wire in partial discharge conditions.

  15. Thermal shock resistance of ceramic fibre composites characterized by non-destructive methods

    Directory of Open Access Journals (Sweden)

    M. Dimitrijević

    2008-12-01

    Full Text Available Alumina based ceramic fibres and alumina based ceramic were used to produce composite material. Behaviour of composite ceramics after thermal shock treatments was investigated. Thermal shock of the samples was evaluated using water quench test. Surface deterioration level of samples was monitored by image analysis before and after a number of quenching cycles. Ultrasonic measurements were done on samples after quench tests. Dynamic Young modulus of elasticity and strength degradation were calculated using measured values of ultrasonic velocities. Strengths deterioration was calculated using the non-destructive measurements and correlated to degradation of surface area and number of quenches. The addition of small amount of ceramic fibres improves the strengths and diminishes the loss of mechanical properties of samples during thermal shock experiments.

  16. Physiochemical Control of Composition and Location for Fundamental Studies of Biofouling Resistant, High Fouling Release Surfaces

    Science.gov (United States)

    2016-06-22

    From - To) 06/22/2016 Final Technical Report 5/1/15- 3/31/2016 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Physiochemical Control of Composition and... brushes with chemically complex architectures. 1S. SUBJECT TERMS Polymer Brushes ; Lithography; Patterning; Photochemistry; Flow Chemistry; Anti-Fouling...preparing and testing polymers brush surfaces with amphiphilic structures. In this report, we summarize a pattern formation approach, based on surface

  17. Composition.

    Science.gov (United States)

    Communication: Journalism Education Today, 2002

    2002-01-01

    Considers how photography is more than just pointing a camera in the right direction. Explains that good pictures use elements of composition such as the Rule of Thirds, leading lines, framing and repetition of shapes. Presents 16 photographs from college and secondary school publications, and describes the techniques that makes them effective.…

  18. A Kinetics Study on Electrical Resistivity Transition of In Situ Polymer Aging Sensors Based on Carbon-Black-Filled Epoxy Conductive Polymeric Composites (CPCs)

    Science.gov (United States)

    Liang, Qizhen; Nyugen, Mark T.; Moon, Kyoung-Sik; Watkins, Ken; Morato, Lilian T.; Wong, Ching Ping

    2013-06-01

    Sensors based on carbon-black-filled bisphenol A-type epoxy conductive polymeric composites (CPCs) have been prepared and applied to monitor thermal oxidation aging of polymeric materials. Thermogravimetric analysis (TGA) is applied to characterize weight loss of epoxy resin in the aging process. By using a mathematical model based on the Boltzmann equation, a relationship between the electrical resistivity of the sensors based on epoxy/carbon black composites and aging time is established, making it possible to monitor and estimate the aging status of polymeric components in situ based on a fast and convenient electrical resistance measurement.

  19. A new discrete-element approach for the assessment of the seismic resistance of composite reinforced concrete-masonry buildings

    International Nuclear Information System (INIS)

    Calio, I.; Cannizzaro, F.; Marletta, M.; Panto, B.; D'Amore, E.

    2008-01-01

    In the present study a new discrete-element approach for the evaluation of the seismic resistance of composite reinforced concrete-masonry structures is presented. In the proposed model, unreinforced masonry panels are modelled by means of two-dimensional discrete-elements, conceived by the authors for modelling masonry structures, whereas the reinforced concrete elements are modelled by lumped plasticity elements interacting with the masonry panels through nonlinear interface elements. The proposed procedure was adopted for the assessment of the seismic response of a case study confined-masonry building which was conceived to be a typical representative of a wide class of residential buildings designed to the requirements of the 1909 issue of the Italian seismic code and widely adopted in the aftermath of the 1908 earthquake for the reconstruction of the cities of Messina and Reggio Calabria

  20. Multi-wall carbon nanotube-embedded lithium cobalt phosphate composites with reduced resistance for high-voltage lithium-ion batteries

    Science.gov (United States)

    Kim, Tae Kyoung; Rustomji, Cyrus S.; Cho, Hyung-Man; Chun, Dongwon; Jung, Jae-Young; Caldwell, Elizabeth; Kim, Youngjin; Han, Jun Hyun; Jin, Sungho

    2016-01-01

    Lithium cobalt phosphate (LCP) is a high-voltage cathode material used in highenergy- density lithium-ion batteries. With a novel composite synthesis method, multi-wall carbon nanotube (MWCNT)-embedded LCP nanocomposites (LCPCNT composites) are synthesized to enhance the electrical conductance of LCP particles, reducing charge-transfer resistance. The LCP-CNT composites with enhanced electrical conductance approximately doubled cell capacity compared to a cell with a bare LCP cathode. The crystal structure of LCP-CNT composite particles is characterized by X-ray diffraction; the microstructures of the embedded MWCNTs inside LCP particles are confirmed by transmission and scanning electron microscopy with focused ion beam procedures. Electrochemical impedance spectroscopy shows the charge-transfer resistance of the cell with the LCP-CNT composite (1.0 wt. % CNT) cathode decreases to ~80 Ω, much smaller than the ~150 Ω charge-transfer resistance of the bare-LCP cathode cell. Based on battery test and impedance analysis, the main factors affecting the capacity increment are the reduced charge transfer resistance and the uniform distribution of MWCNTs, which is formed during the gelation step of the LCP synthesis procedure. [Figure not available: see fulltext.

  1. Ultrastructure and lipid composition of detergent-resistant membranes derived from mammalian sperm and two types of epithelial cells.

    Science.gov (United States)

    van Gestel, Renske A; Brouwers, Jos F; Ultee, Anton; Helms, J Bernd; Gadella, Bart M

    2016-01-01

    Lipid rafts are micro-domains of ordered lipids (Lo phase) in biological membranes. The Lo phase of cellular membranes can be isolated from disordered lipids (Ld phase) after treatment with 1 % Triton  X-100 at 4 °C in which the Lo phase forms the detergent-resistant membrane (DRM) fraction. The lipid composition of DRM derived from Madin-Darby canine kidney (MDCK) cells, McArdle cells and porcine sperm is compared with that of the whole cell. Remarkably, the unsaturation and chain length degree of aliphatic chains attached to phospholipids is virtually the same between DRM and whole cells. Cholesterol and sphingomyelin were enriched in DRMs but to a cell-specific molar ratio. Sulfatides (sphingolipids from MDCK cells) were enriched in the DRM while a seminolipid (an alkylacylglycerolipid from sperm) was depleted from the DRM. Treatment with DRM without affecting the composition and amount of the phospholipid while higher levels disrupted the DRM. The substantial amount of (poly)unsaturated phospholipids in DRMs as well as a low stoichiometric amount of cholesterol suggest that lipid rafts in biological membranes are more fluid and dynamic than previously anticipated. Using negative staining, ultrastructural features of DRM were monitored and in all three cell types the DRMs appeared as multi-lamellar vesicular structures with a similar morphology. The detergent resistance is a result of protein-cholesterol and sphingolipid interactions allowing a relatively passive attraction of phospholipids to maintain the Lo phase. For this special issue, the relevance of our findings is discussed in a sperm physiological context.

  2. AS160 deficiency causes whole-body insulin resistance via composite effects in multiple tissues.

    Science.gov (United States)

    Wang, Hong Yu; Ducommun, Serge; Quan, Chao; Xie, Bingxian; Li, Min; Wasserman, David H; Sakamoto, Kei; Mackintosh, Carol; Chen, Shuai

    2013-01-15

    AS160 (Akt substrate of 160 kDa) is a Rab GTPase-activating protein implicated in insulin control of GLUT4 (glucose transporter 4) trafficking. In humans, a truncation mutation (R363X) in one allele of AS160 decreased the expression of the protein and caused severe postprandial hyperinsulinaemia during puberty. To complement the limited studies possible in humans, we generated an AS160-knockout mouse. In wild-type mice, AS160 expression is relatively high in adipose tissue and soleus muscle, low in EDL (extensor digitorum longus) muscle and detectable in liver only after enrichment. Despite having lower blood glucose levels under both fasted and random-fed conditions, the AS160-knockout mice exhibited insulin resistance in both muscle and liver in a euglycaemic clamp study. Consistent with this paradoxical phenotype, basal glucose uptake was higher in AS160-knockout primary adipocytes and normal in isolated soleus muscle, but their insulin-stimulated glucose uptake and overall GLUT4 levels were markedly decreased. In contrast, insulin-stimulated glucose uptake and GLUT4 levels were normal in EDL muscle. The liver also contributes to the AS160-knockout phenotype via hepatic insulin resistance, elevated hepatic expression of phosphoenolpyruvate carboxykinase isoforms and pyruvate intolerance, which are indicative of increased gluconeogenesis. Overall, as well as its catalytic function, AS160 influences expression of other proteins, and its loss deregulates basal and insulin-regulated glucose homoeostasis, not only in tissues that normally express AS160, but also by influencing liver function.

  3. Preparation of Fouling-Resistant Nanofibrous Composite Membranes for Separation of Oily Wastewater

    Directory of Open Access Journals (Sweden)

    Fatma Yalcinkaya

    2017-12-01

    Full Text Available A facile and low-cost method has been developed for separation of oily wastewater. Polyvinylidene fluoride/polyacrylonitrile (PVDF/PAN nanofibers laminated on a supporting layer were tested. In order to create highly permeable and fouling-resistant membranes, surface modifications of both fibers were conducted. The results of oily wastewater separation showed that, after low vacuum microwave plasma treatment with Argon (Ar and chemical modification with sodium hydroxide (NaOH, the membranes had excellent hydrophilicity, due to the formation of active carboxylic groups. However, the membrane performance failed during the cleaning procedures. Titanium dioxide (TiO2 was grafted onto the surface of membranes to give them highly permeable and fouling-resistance properties. The results of the self-cleaning experiment indicated that grafting of TiO2 on the surface of the membranes after their pre-treatment with Ar plasma and NaOH increased the permeability and the anti-fouling properties. A new surface modification method using a combination of plasma and chemical treatment was introduced.

  4. Effect of whey protein isolate on strength, body composition and muscle hypertrophy during resistance training.

    Science.gov (United States)

    Hayes, Alan; Cribb, Paul J

    2008-01-01

    Sarcopenia (skeletal muscle wasting with aging) is thought to underlie a number of serious age-related health issues. While it may be seen as inevitable, decreasing this gradual loss of muscle is vital for healthy aging. Thus, it is imperative to investigate exercise and nutrition-based strategies designed to build a reservoir of muscle mass as early as possible. Elderly individuals are still able to respond to both resistance training and the anabolic signals provided by protein ingestion, provided specific amino acids, such as leucine, are present. Whey proteins are a rich source of these essential amino acids and rapidly elevate plasma amino acids, thus providing the foundations for preservation of muscle mass. Several studies involving supplementation with whey protein have been shown to be effective in augmenting the effects of resistance exercise, particularly when supplementation occurs in the hours surrounding the exercise training. While further work is required, particularly in elderly people, simple dietary and exercise strategies that may improve the maintenance of skeletal muscle mass will likely result in a decrease in the overall burden of a number of diseases and improve the quality of life as we age.

  5. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system.

    Science.gov (United States)

    Montenegro, Alexandre Campos; do Couto, Cintia Fernandes; Ventura, Paulo Roberto Rezende; Gouvea, Cresus Vinicius Depes; Machado, Aldir Nascimento

    2010-01-01

    Restorative materials must be capable not only of restoring the patient's masticatory function, but also to rescue the self-esteem of those maculated by a disharmonious smile. Among the esthetic materials available on the market, the choice frequently lies between ceramic or indirect laboratory resin restorations. This study assessed the resistance to compression of two laboratory resins found on the market, namely Artglass and Targis, considering Omega 900 ceramic from Vita as control. With the aid of stainless steel matrices, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, being 5 of each material to be tested. The test specimens were kept in distilled water for 72 hours and submitted to an axial load by the action of a point with a rounded tip 2 mm in diameter, adapted to an EMIC 500 universal test machine. The compression speed was 0.5 mm/min, with a load cell capacity of 200 Kgf. The means of the results were calculated in kilogram-force (Kgf). The results found were treated by analysis of variance (ANOVA) and the differences found among the groups were identified by the Tukey test (5%). It was observed that the material Omega 900 (R) offered significantly greater resistance to compression than the other two materials, which did not present statistically significant difference between them.

  6. Abundance of antibiotics, antibiotic resistance genes and bacterial community composition in wastewater effluents from different Romanian hospitals.

    Science.gov (United States)

    Szekeres, Edina; Baricz, Andreea; Chiriac, Cecilia Maria; Farkas, Anca; Opris, Ocsana; Soran, Maria-Loredana; Andrei, Adrian-Stefan; Rudi, Knut; Balcázar, Jose Luis; Dragos, Nicolae; Coman, Cristian

    2017-06-01

    Antimicrobial resistance represents a growing and significant public health threat, which requires a global response to develop effective strategies and mitigate the emergence and spread of this phenomenon in clinical and environmental settings. We investigated, therefore, the occurrence and abundance of several antibiotics and antibiotic resistance genes (ARGs), as well as bacterial community composition in wastewater effluents from different hospitals located in the Cluj County, Romania. Antibiotic concentrations ranged between 3.67 and 53.05 μg L -1 , and the most abundant antibiotic classes were β-lactams, glycopeptides, and trimethoprim. Among the ARGs detected, 14 genes confer resistance to β-lactams, aminoglycosides, chloramphenicol, macrolide-lincosamide-streptogramin B (MLSB) antibiotics, sulfonamides, and tetracyclines. Genes encoding quaternary ammonium resistance and a transposon-related element were also detected. The sulI and qacEΔ1 genes, which confer resistance to sulfonamides and quaternary ammonium, had the highest relative abundance with values ranging from 5.33 × 10 -2 to 1.94 × 10 -1 and 1.94 × 10 -2 to 4.89 × 10 -2 copies/16 rRNA gene copies, respectively. The dominant phyla detected in the hospital wastewater samples were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. Among selected hospitals, one of them applied an activated sludge and chlorine disinfection process before releasing the effluent to the municipal collector. This conventional wastewater treatment showed moderate removal efficiency of the studied pollutants, with a 55-81% decrease in antibiotic concentrations, 1-3 order of magnitude lower relative abundance of ARGs, but with a slight increase of some potentially pathogenic bacteria. Given this, hospital wastewaters (raw or treated) may contribute to the spread of these emerging pollutants in the receiving environments. To the best of our knowledge, this study quantified for the first time the

  7. Diets high in resistent starch and arabinoxylan modulate digestion processes and SCFA pool size in the large intestine and faecal microbial composition in pigs

    DEFF Research Database (Denmark)

    Nielsen, Tina Skau; Lærke, Helle Nygaard; Theil, Peter Kappel

    2014-01-01

    The effects of a high level of dietary fibre (DF) either as arabinoxylan (AX) or resistant starch (RS) on digestion processes, SCFA concentration and pool size in various intestinal segments and on the microbial composition in the faeces were studied in a model experiment with pigs. A total...... resulted in a 3- to 5-fold higher pool size of butyrate compared with WSD feeding, with the RSD being intermediate (P microbial composition towards butyrogenic...

  8. Elastomeric friction

    Science.gov (United States)

    Vorvolakos, Katherine

    This dissertation examines the tribology of PDMS (polydimethylsiloxane) elastomers from a practical and a fundamental perspective. We examine the adhesive, energetic, and tribological properties of several commercial biofouling release coatings, and show that adhesive (and bioadhesive) release from an elastomer depends on the friction of its surface. Having shown that friction is an obstacle to release, we lubricate a model PDMS network by incorporating linear unreactive PDMS oils varying in molecular weight (0.8--423 kg/mol). Surface segregation upon curing depends on molecular weight and mass percentage. Atomic Force Microscopy (AFM) is used to detect the thickness of the lubricant layer. Surprisingly, high-viscosity oils lubricate better than low-viscosity oils, indicating a non-hydrodynamic lubrication. Applying this technology to a commercial elastomer, we see an improvement in bioadhesive release capabilities, as evidenced by a reduced tenacity of mussel adhesive protein. In comparing entangled polymer melts to crosslinked elastomers, we encountered an opportunity to study the tribology of the latter. We studied the effects of molecular weight, velocity, and temperature on the friction of crosslinked PDMS elastomers sliding against two model surfaces: a self-assembled monolayer (SAM) of n-hexadecylsilane, and a thin (˜100mum) film of polystyrene (PS). The change from smooth to stick-slip (unstable) interfacial sliding occurs at a distinct velocity on each surface, implying that it's not necessarily attributable to a bulk glass transition of the PDMS, as popularly believed. The peak shear stress attained immediately before stick-slip sliding is found to be linear with the shear modulus raised to an exponent n of ¾, in contrast with the predictions of Chernyak and Leonov ( n = 1). Low-velocity behavior differs greatly between the SAM and the PS, implying a mechanistic difference. Whereas on the SAM, sliding likely proceeds purely by stochastic adsorption and desorption of polymer chains, on the PS it may also proceed by disentanglement of PDMS from the PS. Temperature-variant measurements allow us to estimate the activation energy of sliding, implying strongly that the velocity of instability depends on the van der Waals interfacial interaction.

  9. Silicon micro-masonry using elastomeric stamps for three-dimensional microfabrication

    International Nuclear Information System (INIS)

    Keum, Hohyun; Eisenhaure, Jeffrey D; Kim, Seok; Carlson, Andrew; Ning, Hailong; Mihi, Agustin; Braun, Paul V; Rogers, John A

    2012-01-01

    We present a micromanufacturing method for constructing microsystems, which we term ‘micro-masonry’ based on individual manipulation, influenced by strategies for deterministic materials assembly using advanced forms of transfer printing. Analogous to masonry in construction sites, micro-masonry consists of the preparation, manipulation, and binding of microscale units to assemble microcomponents and microsystems. In this paper, for the purpose of demonstration, we used microtipped elastomeric stamps as manipulators and built three dimensional silicon microstructures. Silicon units of varied shapes were fabricated in a suspended format on donors, retrieved, delivered, and placed on a target location on a receiver using microtipped stamps. Annealing of the assembled silicon units permanently bound them and completed the micro-masonry procedure. (paper)

  10. Printing transferable components using microstructured elastomeric surfaces with pressure modulated reversible adhesion

    Energy Technology Data Exchange (ETDEWEB)

    Menard, Etienne; Rogers, John A.; Kim, Seok; Carlson, Andrew

    2016-08-09

    In a method of printing a transferable component, a stamp including an elastomeric post having three-dimensional relief features protruding from a surface thereof is pressed against a component on a donor substrate with a first pressure that is sufficient to mechanically deform the relief features and a region of the post between the relief features to contact the component over a first contact area. The stamp is retracted from the donor substrate such that the component is adhered to the stamp. The stamp including the component adhered thereto is pressed against a receiving substrate with a second pressure that is less than the first pressure to contact the component over a second contact area that is smaller than the first contact area. The stamp is then retracted from the receiving substrate to delaminate the component from the stamp and print the component onto the receiving substrate. Related apparatus and stamps are also discussed.

  11. Seismic response analyses of base isolated structures with high damping elastomeric bearings

    Energy Technology Data Exchange (ETDEWEB)

    Wang, C.Y.; Tang, Y.; Chang, Y.W.; Seidensticker, R.W. (Argonne National Lab., IL (USA)); Marchertas, A.H. (Northern Illinois Univ., De Kalb, IL (USA))

    1991-01-01

    Seismic response analysis of base-isolated structures with high damping elastomeric bearings is described. Emphasis is placed on the adaptation of a nonlinear constitutive model for the isolation bearing together with the treatment of foundation embedment for the soil-structure-interaction analysis. The constitutive model requires six input parameters derived from bearing experimental data under sinusoidal loading. The characteristic behavior of bearing, such as the variation of shear modulus and material damping with the change of maximum shear deformation, can be captured closely by the formulation. In the treatment of soil embedment a spring method is utilized to evaluate the foundation input motion as well as soil stiffness and damping. The above features have been incorporated into a three-dimensional system response program, SISEC, developed at Argonne National Laboratory. Sample problems are presented to illustrate the relative response of isolated and unisolated structures. 11 refs., 12 figs.

  12. Electrical Resistivity Correlation to Vadose Zone Sediment and Pore-Water Composition for the BC Cribs and Trenches Area

    Energy Technology Data Exchange (ETDEWEB)

    Serne, R. Jeffrey; Ward, Anderson L.; Um, Wooyong; Bjornstad, Bruce N.; Rucker, Dale F.; Lanigan, David C.; Benecke, Mark W.

    2009-06-01

    This technical report documents the results of geochemical and soil resistivity characterization of sediment obtained from four boreholes drilled in the BC Cribs and Trench area. Vadose zone sediment samples were obtained at a frequency of about every 2.5 ft from approximately 5 ft bgs to borehole total depth. In total, 505 grab samples and 39 six-inch long cores were obtained for characterization. The pore-water chemical composition data, laboratory-scale soil resistivity and other ancillary physical and hydrologic measurements and analyses described in this report are designed to provide a crucial link between direct measurements on sediments and the surface-based electrical-resistivity information obtained via field surveys. A second goal of the sediment characterization was to measure the total and water-leachable concentrations of key contaminants of concern as a function of depth and distance from the footprints of inactive disposal facilities. The total and water-leachable concentrations of key contaminants will be used to update contaminant distribution conceptual models and to provide more data for improving base-line risk predictions and remedial alternative selections. The ERC “ground truthing” exercise for the individual boreholes showed mixed results. In general, the high concentrations of dissolved salts in the pore waters of sediments from C5923, C5924 and C4191 produced a low resistivity “target” in the processed resistivity field surveys, and variability could be seen in the resistivity data that could relate to the variability in pore- water concentrations but the correlations (regression R2 were mediocre ranging from 0.2 to 0.7 at best; where perfect correlation is 1.0). The field-based geophysical data also seemed to suffer from a sort of vertigo, where looking down from the ground surface, the target (e.g., maximum pore-water salt concentration) depth was difficult to resolve. The best correlations between the field electrical

  13. Effects of oxalate desensitizer with different resin cement-retained indirect composite inlays on fracture resistance of teeth.

    Science.gov (United States)

    Shafiei, Fereshteh; Alavi, Ali Asghar; Karimi, Fatemeh; Ansarifard, Elham

    2013-06-01

    This study investigated whether the tubular occluding effect of oxalate desensitizer (OX) during adhesive cementation (three resin cements) influenced fracture resistance of teeth restored with adhesive inlays. Ninety intact maxillary premolars were randomly divided into 9 groups of 10 each. The two control groups were Gr 1, intact teeth and Gr 2, mesio-occlusodistal preparation only. In six experimental groups, the composite inlays were cemented with ED Primer II/Panavia F 2.0, Excite DSC/Variolink II, and One-Step Plus/Duolink according to manufacturers' instructions (Groups 3, 5, and 7, respectively) or with OX during cementation (Groups 4, 6, and 8, respectively). In Group 9, inlays were cemented with a resin cement without adhesive system. After thermocycling, fracture strength was tested. The data were analyzed using two-way and one-way ANOVA and LSD post hoc tests (α = 0.05). Fracture resistance of the six groups were significantly affected by OX (p = 0.002) but not by the resin cement type (p > 0.05). The interaction of the two factors was statistically significant (p = 0.052). A statistically significant difference between all groups was found (p inlay cemented with Panavia F2.0 and Variolink II, but it had no significant effect when cemented with Duolink. © 2012 by the American College of Prosthodontists.

  14. PRELIMINARY REPORT: EFFECTS OF IRRADIATION AND THERMAL EXPOSURE ON ELASTOMERIC SEALS FOR CASK TRANSPORTATION AND STORAGE

    Energy Technology Data Exchange (ETDEWEB)

    Verst, C.; Skidmore, E.; Daugherty, W.

    2014-05-30

    A testing and analysis approach to predict the sealing behavior of elastomeric seal materials in dry storage casks and evaluate their ability to maintain a seal under thermal and radiation exposure conditions of extended storage and beyond was developed, and initial tests have been conducted. The initial tests evaluate the aging response of EPDM elastomer O-ring seals. The thermal and radiation exposure conditions of the CASTOR® V/21 casks were selected for testing as this cask design is of interest due to its widespread use, and close proximity of the seals to the fuel compared to other cask designs leading to a relatively high temperature and dose under storage conditions. A novel test fixture was developed to enable compression stress relaxation measurements for the seal material at the thermal and radiation exposure conditions. A loss of compression stress of 90% is suggested as the threshold at which sealing ability of an elastomeric seal would be lost. Previous studies have shown this value to be conservative to actual leakage failure for most aging conditions. These initial results indicate that the seal would be expected to retain sealing ability throughout extended storage at the cask design conditions, though longer exposure times are needed to validate this assumption. The high constant dose rate used in the testing is not prototypic of the decreasingly low dose rate that would occur under extended storage. The primary degradation mechanism of oxidation of polymeric compounds is highly dependent on temperature and time of exposure, and with radiation expected to exacerbate the oxidation.

  15. A new UV-curing elastomeric substrate for rapid prototyping of microfluidic devices

    International Nuclear Information System (INIS)

    Alvankarian, Jafar; Majlis, Burhanuddin Yeop

    2012-01-01

    Rapid prototyping in the design cycle of new microfluidic devices is very important for shortening time-to-market. Researchers are facing the challenge to explore new and suitable substrates with simple and efficient microfabrication techniques. In this paper, we introduce and characterize a UV-curing elastomeric polyurethane methacrylate (PUMA) for rapid prototyping of microfluidic devices. The swelling and solubility of PUMA in different chemicals is determined. Time-dependent measurements of water contact angle show that the native PUMA is hydrophilic without surface treatment. The current monitoring method is used for measurement of the electroosmotic flow mobility in the microchannels made from PUMA. The optical, physical, thermal and mechanical properties of PUMA are evaluated. The UV-lithography and molding process is used for making micropillars and deep channel microfluidic structures integrated to the supporting base layer. Spin coating is characterized for producing different layer thicknesses of PUMA resin. A device is fabricated and tested for examining the strength of different bonding techniques such as conformal, corona treating and semi-curing of two PUMA layers in microfluidic application and the results show that the bonding strengths are comparable to that of PDMS. We also report fabrication and testing of a three-layer multi inlet/outlet microfluidic device including a very effective fluidic interconnect for application demonstration of PUMA as a promising new substrate. A simple micro-device is developed and employed for observing the pressure deflection of membrane made from PUMA as a very effective elastomeric valve in microfluidic devices. (paper)

  16. Three-Dimensional Elastomeric Scaffolds Designed with Cardiac-Mimetic Structural and Mechanical Features

    Science.gov (United States)

    Neal, Rebekah A.; Jean, Aurélie; Park, Hyoungshin; Wu, Patrick B.; Hsiao, James; Engelmayr, George C.; Langer, Robert

    2013-01-01

    Tissue-engineered constructs, at the interface of material science, biology, engineering, and medicine, have the capacity to improve outcomes for cardiac patients by providing living cells and degradable biomaterials that can regenerate the native myocardium. With an ultimate goal of both delivering cells and providing mechanical support to the healing heart, we designed three-dimensional (3D) elastomeric scaffolds with (1) stiffnesses and anisotropy mimicking explanted myocardial specimens as predicted by finite-element (FE) modeling, (2) systematically varied combinations of rectangular pore pattern, pore aspect ratio, and strut width, and (3) structural features approaching tissue scale. Based on predicted mechanical properties, three scaffold designs were selected from eight candidates for fabrication from poly(glycerol sebacate) by micromolding from silicon wafers. Large 20×20 mm scaffolds with high aspect ratio features (5:1 strut height:strut width) were reproducibly cast, cured, and demolded at a relatively high throughput. Empirically measured mechanical properties demonstrated that scaffolds were cardiac mimetic and validated FE model predictions. Two-layered scaffolds providing fully interconnected pore networks were fabricated by layer-by-layer assembly. C2C12 myoblasts cultured on one-layered scaffolds exhibited specific patterns of cell elongation and interconnectivity that appeared to be guided by the scaffold pore pattern. Neonatal rat heart cells cultured on two-layered scaffolds for 1 week were contractile, both spontaneously and in response to electrical stimulation, and expressed sarcomeric α-actinin, a cardiac biomarker. This work not only demonstrated several scaffold designs that promoted functional assembly of rat heart cells, but also provided the foundation for further computational and empirical investigations of 3D elastomeric scaffolds for cardiac tissue engineering. PMID:23190320

  17. Preparation of the CNC/Ag/beeswax composites for enhancing antibacterial and water resistance properties of paper.

    Science.gov (United States)

    Liu, Kai; Liang, Hunan; Nasrallah, Joseph; Chen, Lihui; Huang, Liulian; Ni, Yonghao

    2016-05-20

    An effective method of preparing composites containing inorganic (Ag) and organic (beeswax) particles was established in this study. Ag nanoparticles were first immobilized on the cellulose nanocrystals (CNC) during the reduction of AgNO3 in the presence of CNC, then mixed with beeswax by high speed stirring. Scanning transmission electron microscopy (STEM) images indicated that Ag and beeswax particles were uniformly dispersed and stable in the network structure formed by CNC. Upon coating on a paper surface, a layer of beeswax film was evident based on scanning electron microscopy (SEM) images. The dynamic contact angle and antibacterial activity tests indicated that the contact angle of coated paper reached 113.06° and the growth inhibition of Escherichia coli increased to 99.96%, respectively, at a coating amount of 21.53 g/m(2). When applied onto paper surface by coating, the CNC/Ag/beeswax composites can impact paper with antibacterial property and improved water resistance. Copyright © 2016 Elsevier Ltd. All rights reserved.

  18. The Combined Effects of Tai Chi, Resistance Training, and Diet on Physical Function and Body Composition in Obese Older Women

    Directory of Open Access Journals (Sweden)

    S. A. Maris

    2014-01-01

    Full Text Available Obesity is a major health problem in the USA, especially in minority populations over the age of 60 years, and the aging process can cause adverse effects on physical function. Previous research has shown that Tai Chi, resistance training (RT, and diet result in overall health improvements. However, the combination of these specific interventions has yet to be translated to obese older women in an urban setting. The purpose of this study was to examine a combined intervention on the primary outcomes of physical function and body composition. Using a nonrandomized design, 26 obese women (65.2±8.1 years completed a 12-week intervention; participants were assigned to an intervention (EXD group or a control (CON group. The EXD group (n=17 participated in Tai Chi, RT, and a dietary session. The CON group (n=9 was asked to continue their normal lifestyle. Timed up and go (TUG time was reduced by 0.64±2.1 seconds (P=0.04 in the EXD group while the CON group saw a borderline significant increase of 0.71 sec (P=0.051. The combined intervention helped improve performance on TUG time, but there were no significant increases in other body composition or function measures.

  19. Magnetocaloric effect and corrosion resistance of La(Fe, Si)13 composite plates bonded by different fraction of phenolic resin

    Science.gov (United States)

    Zhang, K. S.; Xue, J. N.; Wang, Y. X.; Sun, H.; Long, Y.

    2018-04-01

    La(Fe, Si)13-based composite plates were successfully fabricated using different amount of phenolic resin. The introduction of phenolic resin as binder increased the corrosion resistance and maintained giant magnetocaloric effect for La(Fe, Si)13-based composite plates. It was found that corroded spots were firstly observed on the boundaries between resin and La(Fe, Si)13 particles, rather than in La(Fe, Si)13-based particles, after being immersed in static distilled water. The corrosion rate decreased significantly with the increase of resin content. And the increase of the content of phenolic resin leads to the reduction of corrosion current density. Meanwhile, the volumetric magnetic entropy change ΔSM decreases slightly as the content of phenolic resin increases. The ΔSM of the plates with 3 wt.%, 5 wt.% and 8 wt.% resin are 63.1, 61.2 and 59.8 mJ/cm3 K under a low magnetic field change of 1 T, respectively.

  20. In vitro comparative analysis of resistance to compression of laboratory resin composites and a ceramic system

    Directory of Open Access Journals (Sweden)

    Montenegro Alexandre

    2010-01-01

    Full Text Available Background: Restorative materials must be capable not only of restoring the patient′s masticatory function, but also to rescue the self-esteem of those maculated by a disharmonious smile. Among the esthetic materials available on the market, the choice frequently lies between ceramic or indirect laboratory resin restorations. Aim: This study assessed the resistance to compression of two laboratory resins found on the market, namely Artglass ® and Targis ® , considering Omega 900 ® ceramic from Vita as control. Materials and Methods: With the aid of stainless steel matrices, with internal dimensions of 8.0 mm diameter at the base, 9.0 mm in the top portion and 4.0 mm height, 15 test specimens were made, being 5 of each material to be tested. The test specimens were kept in distilled water for 72 hours and submitted to an axial load by the action of a point with a rounded tip 2 mm in diameter, adapted to an EMIC 500 universal test machine. The compression speed was 0.5 mm/min, with a load cell capacity of 200 Kgf. Results: The means of the results were calculated in kilogram-force (Kgf. The results found were treated by analysis of variance (ANOVA and the differences found among the groups were identified by the Tukey test (5%. Conclusion: It was observed that the material Omega 900 ® offered significantly greater resistance to compression than the other two materials, which did not present statistically significant difference between them.