WorldWideScience

Sample records for cell foam core

  1. Characterization of compressive and short beam shear strength of bamboo opened cell foam core sandwich composites

    Science.gov (United States)

    Setyawan, Paryanto Dwi; Sugiman, Saputra, Yudhi

    2016-03-01

    The paper presents the compressive and the short beam shear strength of a sandwich composite with opened cell foam made of bamboo fiber as the core and plywood as the skins. The core thickness was varied from 10 mm to 40 mm keeping the volume fraction of fiber constant. Several test s were carried out including the core density, flatwise compressive and the short beam shear testing in three point bending. The results show that the density of bamboo opened cell foam is comparable with commercial plastic foam, such as polyurethane foam. The compressive strength tends to increase linearly with increasing the core thickness. The short beam shear failure load of the sandwich composite increases with the increase of core thickness, however on the contrary, the short beam shear strength which tends to sharply decrease from the thickness of 10 mm to 30 mm and then becomes flat.

  2. Graded open-cell aluminium foam core sandwich beams

    International Nuclear Information System (INIS)

    We show that the replication process can be extended towards the production of functionally graded porous structures by fabricating and testing structures in which outer layers of dense metal encase a central part made of foam with graded porosity. Samples of this kind are produced by pressing individual layers of NaCl powder of granulometry 60-90 μm, and then stacking these layers between two skins of dense aluminium. The stacked preforms are then infiltrated with pure aluminium and solidified before dissolution of the salt in water. Specimens containing up to five layers of porous Al of different density between two dense outer skins of pure Al are produced; selected samples are tested in three-point bending. Data show good agreement with analysis based on sandwich beam theory and the Deshpande-Fleck yield criterion. Results of this work indicate that whereas lightweight graded metal/metal foam beams show little promise from the standpoint of stiffness-limited design, they may be of interest from the standpoint of load-limited design

  3. Thermal-mechanical behavior of sandwich panels with closed-cell foam core under intensive laser irradiation

    OpenAIRE

    Li Zhi-Qiang; Song Wei-Dong; Tang Hui-Ping; Wang Zhi-Hua; Zhao Long-Mao

    2014-01-01

    Temperature field and thermal deformation of sandwich panels with closed-cell aluminum alloy foam core and heat-protective layer, which are subjected to Gaussian laser beam intensively irradiating, are investigated numerically. In transient heat analysis models, the influence of thermal conductivity, specific heat, and thickness of heat-protective layer on the temperature rise of the sandwich panels is calculated. In stress analysis models, a sequence coupl...

  4. Rigid polyurethane and kenaf core composite foams

    Science.gov (United States)

    Rigid polyurethane foams are valuable in many construction applications. Kenaf is a bast fiber plant where the surface stem skin provides bast fibers whose strength-to-weight ratio competes with glass fiber. The higher volume product of the kenaf core is an under-investigated area in composite appli...

  5. Fatigue of closed cell foams

    OpenAIRE

    Zenkert, Dan; Shipsha, Andrey; Burman, Magnus

    2006-01-01

    The static properties of foams scale with relative density and scaling can be obtained through various static tests. The same scaling appears to be valid for both crack propagation rates and fatigue properties of the foams. This implies that, once the fatigue behavior of one relative density foam is established, one can predict the fatigue behavior of all other density foams within the same class of materials. This study deals with fatigue of closed cell foams. The main idea is to use a few s...

  6. Fatigue of closed cell foams

    OpenAIRE

    Zenkert, Dan; Shipsha, Andrey; Burman, Magnus

    2005-01-01

    This paper deals with fatigue of closed cell foams. The main idea is to use a few simple tests to predict the tension-tension fatigue properties of foams. The required testing consists of crack propagation rate measurements and one tension-tension fatigue test performed at yield stress for the foam. This data can then be combined to construct a synthetic S-N Curve for the foam. Tests on three densities of Divinycell H-grade foam are performed and the results Support this approach. Some prelim...

  7. Experimental study of the mechanical behaviour of pin reinforced foam core sandwich materials under shear load

    Science.gov (United States)

    Dimassi, M. A.; Brauner, C.; Herrmann, A. S.

    2016-03-01

    Sandwich structures with a lightweight closed cell hard foam core have the potential to be used in primary structures of commercial aircrafts. Compared to honeycomb core sandwich, the closed cell foam core sandwich overcomes the issue of moisture take up and makes the manufacturing of low priced and highly integrated structures possible. However, lightweight foam core sandwich materials are prone to failure by localised external loads like low velocity impacts. Invisible cracks could grow in the foam core and threaten the integrity of the structure. In order to enhance the out-of-plane properties of foam core sandwich structures and to improve the damage tolerance (DT) dry fibre bundles are inserted in the foam core. The pins are infused with resin and co-cured with the dry fabric face sheets in an out-of-autoclave process. This study presents the results obtained from shear tests following DIN 53294-standard, on flat sandwich panels. All panels were manufactured with pin-reinforcement manufactured with the Tied Foam Core Technology (TFC) developed by Airbus. The effects of pin material (CFRP and GFRP) and pin volume fraction on the shear properties of the sandwich structure and the crack propagation were investigated and compared to a not pinned reference. It has been concluded that the pin volume fraction has a remarkable effect on the shear properties and damage tolerance of the observed structure. Increasing the pin volume fraction makes the effect of crack redirection more obvious and conserves the integrity of the structure after crack occurrence.

  8. Performance evaluation of OpenFOAM on many-core architectures

    Energy Technology Data Exchange (ETDEWEB)

    Brzobohatý, Tomáš; Říha, Lubomír; Karásek, Tomáš, E-mail: tomas.karasek@vsb.cz; Kozubek, Tomáš [IT4Innovations National Supercomputing Center, VŠB-Technical University of Ostrava (Czech Republic)

    2015-03-10

    In this article application of Open Source Field Operation and Manipulation (OpenFOAM) C++ libraries for solving engineering problems on many-core architectures is presented. Objective of this article is to present scalability of OpenFOAM on parallel platforms solving real engineering problems of fluid dynamics. Scalability test of OpenFOAM is performed using various hardware and different implementation of standard PCG and PBiCG Krylov iterative methods. Speed up of various implementations of linear solvers using GPU and MIC accelerators are presented in this paper. Numerical experiments of 3D lid-driven cavity flow for several cases with various number of cells are presented.

  9. Performance evaluation of OpenFOAM on many-core architectures

    International Nuclear Information System (INIS)

    In this article application of Open Source Field Operation and Manipulation (OpenFOAM) C++ libraries for solving engineering problems on many-core architectures is presented. Objective of this article is to present scalability of OpenFOAM on parallel platforms solving real engineering problems of fluid dynamics. Scalability test of OpenFOAM is performed using various hardware and different implementation of standard PCG and PBiCG Krylov iterative methods. Speed up of various implementations of linear solvers using GPU and MIC accelerators are presented in this paper. Numerical experiments of 3D lid-driven cavity flow for several cases with various number of cells are presented

  10. Foam

    Science.gov (United States)

    Cornick, Marc

    Phenolic foam is a unique cellular material that can be utilized in either a fully open cell structure or a completely closed cell structure in a diversity of applications such as open cellular material for floral foam, soil propagation media and/or orthopedic use, and closed cell phenolic foam primarily for thermal insulation. Thus, phenolic foam is much more versatile than other competitive organic foams such as polystyrene and polyurethane with the latter materials being more heavily involved in thermal insulation. Foam processing can consider batch, semi-continuous, or continuous conditions, and the features and weaknesses of the appropriate processes are discussed along with continuous mix heads involving high and low pressure conditions.

  11. Hypervelocity Impact Evaluation of Metal Foam Core Sandwich Structures

    Science.gov (United States)

    Yasensky, John; Christiansen, Eric L.

    2007-01-01

    A series of hypervelocity impact (HVI) tests were conducted by the NASA Johnson Space Center (JSC) Hypervelocity Impact Technology Facility (HITF) [1], building 267 (Houston, Texas) between January 2003 and December 2005 to test the HVI performance of metal foams, as compared to the metal honeycomb panels currently in service. The HITF testing was conducted at the NASA JSC White Sands Testing Facility (WSTF) at Las Cruces, New Mexico. Eric L. Christiansen, Ph.D., and NASA Lead for Micro-Meteoroid Orbital Debris (MMOD) Protection requested these hypervelocity impact tests as part of shielding research conducted for the JSC Center Director Discretionary Fund (CDDF) project. The structure tested is a metal foam sandwich structure; a metal foam core between two metal facesheets. Aluminum and Titanium metals were tested for foam sandwich and honeycomb sandwich structures. Aluminum honeycomb core material is currently used in Orbiter Vehicle (OV) radiator panels and in other places in space structures. It has many desirable characteristics and performs well by many measures, especially when normalized by density. Aluminum honeycomb does not perform well in Hypervelocity Impact (HVI) Testing. This is a concern, as honeycomb panels are often exposed to space environments, and take on the role of Micrometeoroid / Orbital Debris (MMOD) shielding. Therefore, information on possible replacement core materials which perform adequately in all necessary functions of the material would be useful. In this report, HVI data is gathered for these two core materials in certain configurations and compared to gain understanding of the metal foam HVI performance.

  12. Spacecraft Shielding: An Experimental Comparison Between Open Cell Aluminium Foam Core Sandwich Panel Structures and Whipple Shielding.

    Science.gov (United States)

    Pasini, D. L. S.; Price, M. C.; Burchell, M. J.; Cole, M. J.

    2013-09-01

    Spacecraft shielding is generally provided by metallic plates in a Whipple shield type configuration [1] where possible. However, mission restrictions such as spacecraft payload mass, can prevent the inclusion of a dedicated protective structure for prevention against impact damage from micrometeoroids. Due to this, often the spacecraft's primary structure will act as the de facto shield. This is commonly an aluminium honeycomb backed with either glass fibre reinforced plastic (GFRP) or aluminium faceplates [2]. Such materials are strong, lightweight and relatively cheap due to their abundance used within the aerospace industry. However, these materials do not offer the best protection (per unit weight) against hypervelocity impact damage. A new material for shielding (porous aluminium foam [3]) is suggested for low risk space missions. Previous studies by NASA [4] have been performed to test this new material against hypervelocity impacts using spherical aluminium projectiles. This showed its potential for protection for satellites in Earth orbit, against metallic space debris. Here we demonstrate the material's protective capabilities against micrometeoroids, using soda-lime glass spheres as projectiles to accurately gauge its potential with relation to silicatious materials, such as micrometeoroids and natural solar system debris. This is useful for spacecraft missions beyond Earth orbit where solar system materials are the dominant threat (via hypervelocity impacts) to the spacecraft, rather than manmade debris.

  13. Mechanical behavior of open cell aluminum foams

    Science.gov (United States)

    Zhou, Jikou

    Open cell metallic foams are relatively new materials with increasingly applications due to their attractive combinations of physical, chemical, mechanical and optical properties. Since plastic deformation in the struts involves dislocation motion, dislocation slip bands are used to track the initiation/propagation and locations of plastic deformation in individual struts. We find that the onset of plastic deformation in struts is far beyond the observable strut/cell shape changes, and both plastic bending and buckling are strut deformation modes. To measure the strut mechanical properties, an existing micro-scale tensile tester was updated to test the individual struts extracted from foams using electro-discharged machining. The micro-tensile testing results show that the foam struts are typically more ductile and one time stronger than the corresponding fully dense alloy. To integrate the measured strut and foam properties, a four-strut structure unit is identified as a structural representative of the open cell foam structure. Based on the observed strut deformation modes, mechanics analysis is performed on the structure unit to predict the foam stiffness and strength. The predictions are in good agreement with the measured data, suggesting the significance of the studies on the foam strut properties and deformation. This model also predicts the bounds of the foam strengths. Under cyclic compression, foams fail due to damage accumulation in individual struts, in which surface cracks initiate and grow. At low stress levels, surface cracks are formed in multiple struts that are distributed across the foam block. This results in an abrupt strain jump due to the crush of foam block, upon foam failure. To meet applications requirements, open cell aluminum foams are usually annealed or strengthened. The studies are carried out in the foams in the as-fabricated (F), annealed (O) and T6-strengthed (T6) conditions. We find that annealing and T6 strengthening

  14. Impact performance of nanophased foam core sandwich composites

    International Nuclear Information System (INIS)

    In this study, sandwich panels were fabricated with neat and nanophased foam core and three-layered plain weave carbon fabric/Sc-15 epoxy composite face sheets. Neat and nanophased foam cores with Nanocor I-28E nanoclay at a loading of 0.5% and 1% by weight were prepared. Sandwich panels were then fabricated using co-injection resin transfer molding process. Samples of size 100 mm x 100 mm were then cut from the panels and subjected to low-velocity impact loading using an instrumented impact test setup. Impact response of the panels was recorded and analyzed in terms of peak load, absorbed energy, time and deflection at peak load. The tested samples were then sectioned into two halves and scanned using a scanner, optical and scanning electron microscopes to understand the failure patterns. Samples with nanophased foam sustained higher loads and had lower damage areas as compared with neat counterparts. Nanophased foam cores exhibited relatively more brittle fracture

  15. Impact performance of nanophased foam core sandwich composites

    Energy Technology Data Exchange (ETDEWEB)

    Hosur, M.V. [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States)], E-mail: mhosur@gmail.com; Mohammed, A.A.; Zainuddin, S.; Jeelani, S. [Center for Advanced Materials, Tuskegee University, Tuskegee, AL 36088 (United States)

    2008-12-20

    In this study, sandwich panels were fabricated with neat and nanophased foam core and three-layered plain weave carbon fabric/Sc-15 epoxy composite face sheets. Neat and nanophased foam cores with Nanocor I-28E nanoclay at a loading of 0.5% and 1% by weight were prepared. Sandwich panels were then fabricated using co-injection resin transfer molding process. Samples of size 100 mm x 100 mm were then cut from the panels and subjected to low-velocity impact loading using an instrumented impact test setup. Impact response of the panels was recorded and analyzed in terms of peak load, absorbed energy, time and deflection at peak load. The tested samples were then sectioned into two halves and scanned using a scanner, optical and scanning electron microscopes to understand the failure patterns. Samples with nanophased foam sustained higher loads and had lower damage areas as compared with neat counterparts. Nanophased foam cores exhibited relatively more brittle fracture.

  16. Thermomechanical interaction effects in polymer foam cored sandwich structure

    OpenAIRE

    Zhang, Shufeng

    2013-01-01

    Polymer foam cored sandwich structures are frequently exposed to elevated temperatures in the range of 50-100°C. Recent theoretical studies showed that elevated temperatures may shift the behaviour of sandwich structures from linear and stable to nonlinear and unstable. Although this prediction has not been experimentally validated, it has aroused concerns on the performance of sandwich structures at elevated temperatures. Thereby, a focused experimental study is required to confirm the therm...

  17. Open Cell Metal Foams for Beam Liners?

    OpenAIRE

    Croce, R. P.; Petracca, S.; Stabile, A.

    2013-01-01

    The possible use of open-cell metal foams for particle accelerator beam liners is considered. Available materials and modeling tools are reviewed, potential pros and cons are pointed out, and a study program is outlined.

  18. Damage tolerance of a composite sandwich with interleaved foam core

    Science.gov (United States)

    Ishai, Ori; Hiel, Clement

    1992-01-01

    A composite sandwich panel consisting of carbon fiber-reinforced plastic (CFRP) skins and a syntactic foam core was selected as an appropriate structural concept for the design of wind tunnel compressor blades. Interleaving of the core with tough interlayers was done to prevent core cracking and to improve damage tolerance of the sandwich. Simply supported sandwich beam specimens were subjected to low-velocity drop-weight impacts as well as high velocity ballistic impacts. The performance of the interleaved core sandwich panels was characterized by localized skin damage and minor cracking of the core. Residual compressive strength (RCS) of the skin, which was derived from flexural test, shows the expected trend of decreasing with increasing size of the damage, impact energy, and velocity. In the case of skin damage, RCS values of around 50 percent of the virgin interleaved reference were obtained at the upper impact energy range. Based on the similarity between low-velocity and ballistic-impact effects, it was concluded that impact energy is the main variable controlling damage and residual strength, where as velocity plays a minor role.

  19. Numerical modelling of foam-cored sandwich plates under high-velocity impact

    OpenAIRE

    Ivañez, Inés; Santuiste, Carlos; Barbero, Enrique; Sánchez-Sáez, Sonia

    2011-01-01

    This paper studies the high velocity impact response of sandwich plates, with E glass fibre/polyester face sheets and foam core, using finite element models developed in ABAQUS/explicit code. The failure of the face sheets was predicted by implementing Hou failure criteria and a procedure to degrade mate rial properties in a user subroutine (VUMAT). The foam core was modelled as a crushable foam material. The numerical models were validated with experimental data obtained from scientific lite...

  20. Residual dent in locally loaded foam core sandwich structures – Analysis and use for NDI

    NARCIS (Netherlands)

    Koissin, Vitaly; Shipsha, Andrey

    2008-01-01

    This paper addresses the residual denting in the face sheet and corresponding core damage in a locally loaded flat sandwich structure with foam core. The problem is analytically considered in the context of elastic bending of the face sheet accompanied by non-linear deformation of the crushed foam c

  1. Foam flow in low-permeability Berea Sandstone cores. A laboratory investigation

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, S. [Colorado School of Mines Abu Dhabi (United States); Talabani, S. [Baker Atlas, Abu Dhabi (United Arab Emirates); Saleh, S.T.; Islam, M.R. [Knowledge Systems, Houston, TX (United States)

    2002-12-01

    Foam flow in porous media has been a subject of extensive investigation for the last 37 years because of its application in enhanced oil recovery (EOR) and stimulation operations. In acidizing, foam is used to facilitate the diversion of acid into the low-permeability strata when multiple layers of contrasting permeabilities are present. Very little has been done to investigate the flow behavior of foam in low-permeability rocks (1-10 md), mainly because of equipment limitations caused by the very high pressure gradients encountered when foam is injected. This paper discusses the results of several single-core, constant-quality, steady-state foam flow experiments, using a 9-md fired Berea Sandstone core and a 3500 psi (24 MPa) rated coreflooding unit. Factors, such as surfactant type, foam quality, liquid and gas velocities, were varied to investigate their effect on foam mobility, mobility reduction factors, and pressure gradients. To simulate the post-foam acid stage used in acidizing, brine was injected following foam injection in each experiment and the residual permeability and foam stability were observed. The foam qualities used varied from 55% to 90%, and the injection rates varied from 5 to 25 ft/day (1.5-7.5 m/day). Significant reductions in mobilities were observed for all the cases during steady-state foam injection. A new parameter called the persistency index is proposed to quantify foam stability during the post-foam acid stage, which may prove to be critical to predicting the foam diversion behavior. Also, more consistent results were obtained when dimensionless parameters such as mobility reduction factors rather than mobilities were compared. Finally, low-permeability results were compared with those for the higher permeability to identify uniqueness of foam generation in low-permeability formations.

  2. An experimental investigation of the diversion characteristics of foam in Berea sandstone cores of contrasting permeabilities

    Energy Technology Data Exchange (ETDEWEB)

    Siddiqui, S. [Saudi Aramco RandD Center, P.O. Box 62, Dhahran 31311 (Saudi Arabia); Talabani, S. [Baker Atlas, Abu Dhabi (United Arab Emirates); Yang, J. [Independent Consultant, Calgary (Canada); Saleh, S.T. [Knowledge Systems Ltd., Houston, TX (United States); Islam, M.R. [Dalhousie University, Halifax, Nova Scotia (Canada)

    2003-02-01

    Foam has been used successfully in the field as a diverting agent for matrix acidizing when layers of contrasting permeabilities are present. However, the mechanisms governing the diversion performance of foam are still not properly understood and only a handful of foam diversion papers can be found in the literature. This paper discusses the results from several dual-core experiments using 11- and 22-in. (27.9 and 55.9 cm) long and 1.5-in. (3.8 cm) diameter fired Berea sandstone cores (permeability range: 10-1000 md) in which parameters such as foam quality, total injection rate, foam slug size, etc., are varied systematically for different permeability contrasts. Each experiment consists of a gas-free surfactant injection phase, followed by a foam injection phase, which is then followed by a brine injection phase simulating the post-foam acid injection stage. The pressure data along each core at four locations and the weight of the liquid effluents for each core are recorded continuously. An attempt is made to quantify the diversion performance by the introduction of various diversion factors. The effect of variables such as foam quality, injection rate, slug size, etc., on the diversion factors are then compared for different permeability contrasts. Results show strong dependence of the diversion performance on permeability contrast, foam quality and total flow rate. This study provides important guidelines for designing acid jobs for different permeability contrasts and ranges when foam is used as a diverting agent.

  3. Regulation of Foam Cells by Adenosine

    OpenAIRE

    Allison B. Reiss; Cronstein, Bruce N.

    2012-01-01

    Macrophages rely on reverse cholesterol transport mechanisms to rid themselves of excess cholesterol. By reducing accumulation of cholesterol in the artery wall, reverse cholesterol transport slows or prevents development of atherosclerosis. In stable macrophages, efflux mechanisms balance influx mechanisms and accumulating lipids do not overwhelm the cell. Under atherogenic conditions, inflow of cholesterol exceeds outflow and the cell is ultimately transformed into a foam cell, the prototyp...

  4. Thermoelastic properties of sandwich materials with pin-reinforced foam cores

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Pin-reinforced foam is a novel type of sandwich core materials formed by inserting pins(trusses) into a foam matrix to create a truss-like network reinforced foam core.Upon loading,the pins deform predominantly by local stretching whilst the deformation of foam is governed by local bending.This paper presents a theoretical study on the thermoelasticity of pin-reinforced foam sandwich cores.To calculate the effective thermoelastic properties of pin-reinforced foam cores,the energy-based homogenization approach is employed to develop a micromechanics-based model,calibrated by the existing experimental data.It is found that the stiffness of the sandwich core is mainly governed by pin reinforcements:the foam matrix contributes little to sandwich stiffness.Compared with traditional foam cores without pin reinforcements,the changes in inplane thermal expansion coefficients are not vigorous as a result of pin reinforcements,while the through-thickness thermal expansion coefficient changes significantly.It is also demonstrated that it is possible to design materials with zero or negative thermal expansion coefficients under such a context.

  5. Fatigue Characterization of Fire Resistant Syntactic Foam Core Material

    Science.gov (United States)

    Hossain, Mohammad Mynul

    Eco-Core is a fire resistant material for sandwich structural application; it was developed at NC A&T State University. The Eco-Core is made of very small amount of phenolic resin and large volume of flyash by a syntactic process. The process development, static mechanical and fracture, fire and toxicity safety and water absorption properties and the design of sandwich structural panels with Eco-Core material was established and published in the literature. One of the important properties that is needed for application in transportation vehicles is the fatigue performance under different stress states. Fatigue data are not available even for general syntactic foams. The objective of this research is to investigate the fatigue performance of Eco-Core under three types of stress states, namely, cyclic compression, shear and flexure, then document failure modes, and develop empherical equations for predicting fatigue life of Eco-Core under three stress states. Compression-Compression fatigue was performed directly on Eco-Core cylindrical specimen, whereas shear and flexure fatigue tests were performed using sandwich beam made of E glass-Vinyl Ester face sheet and Eco-Core material. Compression-compression fatigue test study was conducted at two values of stress ratios (R=10 and 5), for the maximum compression stress (sigmamin) range of 60% to 90% of compression strength (sigmac = 19.6 +/- 0.25 MPa) for R=10 and 95% to 80% of compression strength for R=5. The failure modes were characterized by the material compliance change: On-set (2% compliance change), propagation (5%) and ultimate failure (7%). The number of load cycles correspond to each of these three damages were characterized as on-set, propagation and total lives. A similar approach was used in shear and flexure fatigue tests with stress ratio of R=0.1. The fatigue stress-number of load cycles data followed the standard power law equation for all three stress states. The constant of the equation were

  6. Effects of glycosaminoglycan from scallop skirt on foam cell

    Institute of Scientific and Technical Information of China (English)

    Fu-shengSUN; SaiLIU

    2004-01-01

    AIM: To study effects of glycosaminoglycan from scallop skirt (SS-GAG) on NO production, antioxidative enzyme activity,and formation of macrophage-derived and smooth muscle cell-derived foam cell; to study the effects of SS-GAG on VEGF expression, intracellular Ca2~ level, and cytokines secretion of macrophage-derived foam cell. METHODS: Foam-like cells were generated by incubating the U937 cells or porcine artery smooth

  7. Neutrons attenuation on composite metal foams and hybrid open-cell Al foam

    International Nuclear Information System (INIS)

    A comprehensive investigation of monochromatic neutron attenuation effectiveness for close-cell composite metal foams (CMFs) and open-cell Al foam infiltrated with variety of second phase materials is presented using both experimental and theoretical methods. The experimental results indicated higher neutron flux reduction in open-cell Al foam with fillers compared to the close-cell CMFs due to their large percentage of low Z elements such as hydrogen, boron and carbon, with superior neutron attenuation performance, in their filler materials. The main factor controlling the shielding effectiveness of steel–steel CMFs is found to be the ratio of the thickness of the sphere wall to the sphere radius while the intermetallic phases in the matrix of Al–steel CMFs seem to have a major role on their shielding properties. Successful models that link the observed material properties and microstructure have been developed using Monte Carlo N-Particle Transport Code (MCNP) to verify the accuracy of the experimental results. Close-cell CMFs were proposed through three different sphere arrangements: simple cubic, body center cubic and face center cubic, whereas open-cell Al foam with fillers was represented by creating a three-dimensional structure using periodic unit cell through two approaches. The simulation results were found to be in good agreement with the experimental values. This research indicates the potential of utilizing light-weight close-cell CMFs and open-cell Al foam with fillers as nuclear shields replacing conventional materials to achieve a specified shielding level with additional benefits of excellent energy absorption and thermal isolation. - Highlights: • Close-cell metal foams were processed with various sphere sizes. • Open-cell foams were infiltrated with hydrogen-rich fillers. • Open-cell foams with fillers exhibit excellent neutron shielding efficiency. • Close-cell CMFs were modeled through simple, body center, and face center cubic

  8. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Core for Lightweight Fan Blade Design

    Science.gov (United States)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. The present study investigates the use of a sandwich foam fan blade mae up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The resulting structures possesses a high stiffness while being lighter than a similar solid construction. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of sandwich structure for a fan blade application. A vibration analysis for natural frequencies and a detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of kin thickness and core volume are presented with a comparison to a solid titanium blade.

  9. Experimental Cosserat elasticity in open-cell polymer foam

    Science.gov (United States)

    Rueger, Zach; Lakes, Roderic S.

    2016-01-01

    Reticulated open-cell polymer foams exhibit substantial size effects in torsion and bending: slender specimens are more rigid than anticipated via classical elasticity. Such size effects are predicted by Cosserat (micropolar) elasticity, which allows points to rotate as well as translate and incorporates distributed moments (couple stresses). The Cosserat characteristic length is larger than the cell size. The Cosserat coupling coefficient is larger than in dense closed-cell foams and approaches 1 for foam with 0.4 mm cells.

  10. PMI Foam Cored Sandwich Components Produced by Means of Different Manufacturing Methods

    Institute of Scientific and Technical Information of China (English)

    Leonhard Maier; HU Pei; Herman Seibert

    2006-01-01

    The paper introduced the structural applications with PMI (Polymethacrylimide) foams in sandwich components for rotor craft, launching vehicle and civil aircraft and discuss some typically used manufacturing methods, such as e. g.in-mould pressing, autoclave curing and resin infusion. The advantages of foam-cored sandwich design versus honeycombcored design will be discussed, focussing on manufacturing costs.

  11. Graphitic Carbon Foam Structural Cores and Multifunctional Applications Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Project will procure available graphite foam products in small quantities, perform testing, and build simple prototype designs. Several specific applications have...

  12. Sandwich Composite, Syntactic Foam Core Based, Application for Space Structures

    Science.gov (United States)

    Hodge, Andrew J.; Kaul, Raj K.; McMahon, William M.; Reinarts, Thomas

    2000-01-01

    The current Solid Rocket Booster (SRB) launch vehicle has several metal based components that require a Thermal Protective System (TPS) be applied to the exterior surface to ensure its structural integrity and to protect the interior hardware from aerodynamic heating. TPS materials have distinct disadvantages associated with their use. One disadvantage to the application of TPS is that it can act as a debris source to the Space Shuttle Orbiter during flight and it also adds weight to the system without directly contributing any structural strength. One of the specific areas examined under this program was to replace a metal/TPS system with polymer based composites. A polymer matrix based sandwich composite was developed which had both structural and insulative properties to meet the high aerodynamic structural and heating load survival requirements. The SRB Nose Cap was selected as a candidate for this application. The sandwich system being qualified for this application is a carbon/epoxy outer and inner skin with a high strength-low thermal conductivity syntactic foam core.

  13. Porous Media Approach for Modeling Closed Cell Foam

    Science.gov (United States)

    Ghosn, Louis J.; Sullivan, Roy M.

    2006-01-01

    In order to minimize boil off of the liquid oxygen and liquid hydrogen and to prevent the formation of ice on its exterior surface, the Space Shuttle External Tank (ET) is insulated using various low-density, closed-cell polymeric foams. Improved analysis methods for these foam materials are needed to predict the foam structural response and to help identify the foam fracture behavior in order to help minimize foam shedding occurrences. This presentation describes a continuum based approach to modeling the foam thermo-mechanical behavior that accounts for the cellular nature of the material and explicitly addresses the effect of the internal cell gas pressure. A porous media approach is implemented in a finite element frame work to model the mechanical behavior of the closed cell foam. The ABAQUS general purpose finite element program is used to simulate the continuum behavior of the foam. The soil mechanics element is implemented to account for the cell internal pressure and its effect on the stress and strain fields. The pressure variation inside the closed cells is calculated using the ideal gas laws. The soil mechanics element is compatible with an orthotropic materials model to capture the different behavior between the rise and in-plane directions of the foam. The porous media approach is applied to model the foam thermal strain and calculate the foam effective coefficient of thermal expansion. The calculated foam coefficients of thermal expansion were able to simulate the measured thermal strain during heat up from cryogenic temperature to room temperature in vacuum. The porous media approach was applied to an insulated substrate with one inch foam and compared to a simple elastic solution without pore pressure. The porous media approach is also applied to model the foam mechanical behavior during subscale laboratory experiments. In this test, a foam layer sprayed on a metal substrate is subjected to a temperature variation while the metal substrate is

  14. Behaviour of cellular foam core materials in GRP sandwich under fatigue

    Energy Technology Data Exchange (ETDEWEB)

    Aamlid, O.; Echtermeyer, A.T.; McGeorge, D.; Buene, L. [Det Norske Veritas Research AS, Hoevik (Norway)

    1993-12-31

    This paper concerns four point bend testing of sandwich beams with PVC foam cores, representative of hull panels in high speed light craft. The study focuses on the long term behavior of cellular foam core materials when the sandwich beam is subjected to fatigue loading until the specimen fails due to shear fracture or excessive shear deformations in the core. The core materials tested include the partially cross-linked PVC Divinycell H100 and H200 and the linear PVC Airex R63.80. Results from the program are presented and discussed.

  15. Deformation behavior of open-cell stainless steel foams

    International Nuclear Information System (INIS)

    This study presents the deformation and cell collapse behavior of open-cell stainless steel foams. 316L stainless-steel open-cell foams with two porosities (30 and 45 pores per inch, ppi) were produced with the pressureless powder metallurgical method, and tested in quasi-static compression. As a result of the manufacturing technique, 316L stainless steel open-cell foams have a high amount of microporosity. The deformation behavior was investigated on a macroscopic scale by digital image correlation (DIC) evaluation of light micrographs and on the microscopic scale by in situ loading of cells in the scanning electron microscope. The deformation behavior of the metal foams was highly affected by microstructural features, such as closed pores and their distribution throughout the foam specimen. Moreover, the closed pores made a contribution to the plateau stress of the foams through cell face stretching. Strut buckling and bending are the dominant mechanisms in cell collapse. Although there are edge defects on the struts, the struts have an enormous plastic deformation capability. The cell size of the steel foams had no significant effect on the mechanical properties. Due to the inhomogeneities in the microstructure, the measured plateau stresses of the foams showed about 20% scatter at the same relative density

  16. Heat Transfer and Acoustic Properties of Open Cell Aluminum Foams

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The aluminum open cell foams have been prepared by the conventional precision casting method to investigate the thermal and acoustic properties. A water heating system and silencers were organized as a first step for its applications. The temperature increase between the top and bottom of the foam became larger as the cell size increased in the heat transfer measurement. Sound absorption ratio of the close cell foams was 60%-100%,whereas the open cell aluminum foam showed only 10%-20% of sound absorption at low frequency. When the prototype electric water heater manufactured by combining aluminum open cell foam with a heater was heated to 100-400℃, the highest temperature of water was in the range of 16-46℃. This suggests that there could be potential for this type of heater to be used as a commercial electric water heater. Sound silencer made with the aluminum open cell foam was applied to exit of exhaustion side at air pressure line. Sound silencing effect of open-celled aluminum foam showed that the noise level went down by introducing smaller cell size foam.

  17. Bidirectional Thermo-Mechanical Properties of Foam Core Materials Using DIC

    OpenAIRE

    Taher, Siavash Talebi; Thomsen, Ole Thybo; M. Dulieu-Barton, Janice

    2011-01-01

    Polymer foam cored sandwich structures are often subjected to aggressive service conditions which may include elevated temperatures. A modified Arcan fixture (MAF) has been developed to characterize polymer foam materials with respect to their tensile, compressive, shear and bidirectional mechanical properties at room and at elevated temperatures. The MAF enables the realization of pure compression or high compression to shear bidirectional loading conditions that is not possible with convent...

  18. A PEM fuel cell with metal foam as flow distributor

    International Nuclear Information System (INIS)

    Highlights: ► Metal foams are used to replace conventional flow channels as the flow distributor. ► Cell with metal foam out-performs the conventional cell with flow channel plate. ► Mass transport limitation phenomenon is not as obvious as in conventional unit cell. ► This is due to metal foam’s high porosity plus convective flow through the foam. ► Even operated at 40 °C, the current density reaches 1870 mA cm−2 at 0.6 V. - Abstract: In this work, we report our experimental results of the PEM fuel cell with metal foam as flow distributor. These experimental results show the characteristics of the PEM fuel cell with the metal foam as flow distributor and extend our understanding of the relation between cell performance and mass transport properties into a region of parameters that the conventional PEM unit cell cannot provide. The comparison in polarization curve is made between the PEM unit cell with different metal-foam properties and the PEM unit cell with graphite flow channel plate as flow distributor. The experimental results show that the PEM fuel cell with metal foam as flow distributor possesses some unique characteristics compared with the conventional PEM unit cell with flow channel plate as flow distributor. The unique characteristics are listed in this paper with our preliminary analysis. Due to the high porosity of metal-foam (as high as 95%) plus convective flow through the metal-foam, mass transport limitation phenomenon is not as pronounced as in the case of conventional PEM unit cell with flow channel plate as flow distributor. Another interesting phenomenon is that electrical conductivity of metal-foam plays a significant role in performance, which is seldom the case in the conventional PEM unit cell with flow channel plate as flow distributor. Although there are several technical challenges to be overcome for the current form of metal-foam to replace flow channel plates, the unique mass-transport properties of metal foam plus its

  19. Novel Aluminum (Al)-Carbon Nanotube (CNT) Open-Cell Foams

    Science.gov (United States)

    Morsi, K.; Krommenhoek, Max; Shamma, Mohamed

    2016-06-01

    This paper presents for the first time the processing of aluminum (Al)-carbon nanotube (CNT) open-cell foams. Al-2wt pct CNT and Al foams were successfully produced using a spark plasma sintering and dissolution process. Al-CNT foams with porosity levels of ~78 pct were produced. The mechanical response of the open-cell foams reveals initial evidence of enhanced damage tolerance of Al-CNT foams over Al foams produced in this study.

  20. Dynamic properties of high structural integrity auxetic open cell foam

    Science.gov (United States)

    Scarpa, F.; Ciffo, L. G.; Yates, J. R.

    2004-02-01

    This paper illustrates various dynamic characteristics of open cell compliant polyurethane foam with auxetic (negative Poisson's ratio) behaviour. The foam is obtained from off-the-shelf open cell polyurethane grey foam with a manufacturing process based on mechanical deformation on a mould in a temperature-controlled oven. The Poisson's ratio is measured with an image processing technique based on edge detection with wavelet methods. Foam samples have been tested in a viscoelastic analyser tensile test machine to determine the Young's modulus and loss factor for small dynamic strains. The same samples have also been tested in an acoustic impedance tube to measure acoustic absorption and specific acoustic resistance and reactance with a transmissibility technique. Another set of tests has been set up on a cam plastometer machine for constant strain rate dynamic crushing analysis. All the tests have been carried out on auxetic and normal foam samples to provide a comparison between the two types of cellular solids. The results from the experimental tests are discussed and interpreted using microstructure models for cellular materials existing in the literature. The negative Poisson's ratio foam presented in this paper shows an overall superiority regarding damping and acoustic properties compared to the original conventional foam. Its dynamic crushing performance is also significantly superior to the normal foam, suggesting a possible use in structural integrity compliant elements.

  1. Closed-cell crystalline foams: self-assembling, resonant metamaterials.

    Science.gov (United States)

    Spadoni, Alessandro; Höhler, Reinhard; Cohen-Addad, Sylvie; Dorodnitsyn, Vladimir

    2014-04-01

    Internal degrees of freedom and periodic structure are critical requirements in the design of acoustic/elastic metamaterials since they can give rise to extraordinary properties like negative effective mass and stiffness. However, they are challenging to realize in three dimensions. Closed-cell, crystalline foams are a particularly advantageous basis to develop metamaterials as they intrinsically have a complex microstructure, exhibiting internal resonances. Recently self-assembly techniques have been implemented to produce such foams: a Kelvin (body centered cubic) foam, a face centered cubic foam, and a Weaire-Phelan structure. Numerical models are employed to demonstrate that such foams are superanisotropic, selectively behaving as a fluid or a solid, pentamode solids as a result of fluid-structure interaction, in addition to having regimes characterized by film resonances and high density of states. Microstructural deformations obtained from numerical models allow the derivation of equivalent mechanical models. PMID:25234969

  2. Fatigue of closed-cell foams in compression

    OpenAIRE

    Zenkert, Dan; Burman, Magnus

    2011-01-01

    This article deals with fatigue of closed-cell foams under compression loading. Testing is performed on three densities of Divinycell H-grade and three densities of Rohacell WF-grade foam under cyclic compression loading. The fatigue failure is in all cases described as localized crushing of cell layers. The two main observations from this are that the slopes of the stress-life curves are almost all different, both between the foam types and relative density. Secondly, the stress-life relatio...

  3. Open Cell Conducting Foams for High Synchrotron Radiation Beam Liners

    OpenAIRE

    Petracca, Stefania; Stabile, Arturo

    2014-01-01

    The possible use of open-cell conductive foams in high synchrotron radiation particle accelerator beam liners is considered. Available materials and modeling tools are reviewed, potential pros and cons are discussed, and preliminary conclusions are drawn.

  4. Acoustic absorption behaviour of an open-celled aluminium foam

    CERN Document Server

    Han Fu Sheng; Zhao Yu Yuan; Gibbs, B

    2003-01-01

    Metal foams, especially close-celled foams, are generally regarded as poor sound absorbers. This paper studies the sound absorption behaviour of the open-celled Al foams manufactured by the infiltration process, and the mechanisms involved. The foams show a significant improvement in sound absorption compared with close-celled Al foams, because of their high flow resistance. The absorption performance can be further enhanced, especially at low frequencies, if the foam panel is backed by an appropriate air gap. Increasing the air-gap depth usually increases both the height and the width of the absorption peak and shifts the peak towards lower frequencies. The foam samples with the smallest pore size exhibit the best absorption capacities when there is no air gap, whereas those with medium pore sizes have the best overall performance when there is an air gap. The typical maximum absorption coefficient, noise reduction coefficient and half-width of the absorption peak are 0.96-0.99, 0.44-0.62 and 1500-3500 Hz, r...

  5. Neutrons attenuation on composite metal foams and hybrid open-cell Al foam

    Science.gov (United States)

    Chen, Shuo; Bourham, Mohamed; Rabiei, Afsaneh

    2015-04-01

    A comprehensive investigation of monochromatic neutron attenuation effectiveness for close-cell composite metal foams (CMFs) and open-cell Al foam infiltrated with variety of second phase materials is presented using both experimental and theoretical methods. The experimental results indicated higher neutron flux reduction in open-cell Al foam with fillers compared to the close-cell CMFs due to their large percentage of low Z elements such as hydrogen, boron and carbon, with superior neutron attenuation performance, in their filler materials. The main factor controlling the shielding effectiveness of steel-steel CMFs is found to be the ratio of the thickness of the sphere wall to the sphere radius while the intermetallic phases in the matrix of Al-steel CMFs seem to have a major role on their shielding properties. Successful models that link the observed material properties and microstructure have been developed using Monte Carlo N-Particle Transport Code (MCNP) to verify the accuracy of the experimental results. Close-cell CMFs were proposed through three different sphere arrangements: simple cubic, body center cubic and face center cubic, whereas open-cell Al foam with fillers was represented by creating a three-dimensional structure using periodic unit cell through two approaches. The simulation results were found to be in good agreement with the experimental values. This research indicates the potential of utilizing light-weight close-cell CMFs and open-cell Al foam with fillers as nuclear shields replacing conventional materials to achieve a specified shielding level with additional benefits of excellent energy absorption and thermal isolation.

  6. Functional grading of metal foam cores for yield-limited lightweight sandwich beams

    International Nuclear Information System (INIS)

    We show that grading the porosity in a bent metal skin/metal foam core sandwich can generate significant weight savings in yield-limited design when, and only when, there is a gradient in the applied moment along the sandwich beam

  7. Examination of Cell Shape in Wall Thickness Direction for Foamed Polyurethane Resin

    Science.gov (United States)

    Kono, Tsutomu; Matsuoka, Shin-Ichi; Araki, Kuninari; Iseki, Takashi

    The foaming flow process of polyurethane resin is difficult because temperature, density and thermal conductivity are changed greatly by heat generation resulting from the mixing reaction of polyol and polyisocyanate resin. It is thought that thermal conductivity and strength are influenced by cell shape after the foaming process. In this study, we evaluate three-dimensional cell shapes by quantitatively observation of the ratio of the diameter of the parallel and the perpendicular section to flow direction, the ratio of the major axis and the minor axis, and direction of the major axis of cells for closed cell shapes in foamed polyurethane resin. It is thought that cell shapes are mainly deformed by shear stress and pressure of adjacent cells. It becomes obvious by cell shape evaluation that cells in the skin layer are compressed in the thickness direction by pressure of adjacent cells, cells between the skin layer and the core layer are stretched perpendicular to the flow direction by shear stress, and cells in the core layer are similar to the sphere shape.

  8. Hyperbolic prisms and foams in Hele-Shaw cells

    International Nuclear Information System (INIS)

    The propagation of light in foams creates patterns which are generated due to the reflection and refraction of light. One of these patterns is observed by the formation of multiple mirror images inside liquid bridges in a layer of bubbles in a Hele-Shaw cell. We are presenting the existence of these patterns in foams and their relation with hyperbolic geometry and Sierpinski gaskets using the Poincare disk model. The images obtained from the experiment in foams are compared to the case of hyperbolic optical elements. -- Highlights: → The chaotic scattering of light in foams generating deltoid patterns is based on hyperbolic geometry. → The deltoid patterns are obtained through the Plateau borders in a Hele-Shaw cell. → The Plateau borders act like hyperbolic prism. → Some effects of the refraction and reflection of the light rays were studied using a hyperbolic prism.

  9. Bidirectional Thermo-Mechanical Properties of Foam Core Materials Using DIC

    DEFF Research Database (Denmark)

    Taher, Siavash Talebi; Thomsen, Ole Thybo; M Dulieu-Barton, Janice

    2011-01-01

    Polymer foam cored sandwich structures are often subjected to aggressive service conditions which may include elevated temperatures. A modified Arcan fixture (MAF) has been developed to characterize polymer foam materials with respect to their tensile, compressive, shear and bidirectional...... mechanical properties at room and at elevated temperatures. The MAF enables the realization of pure compression or high compression to shear bidirectional loading conditions that is not possible with conventional Arcan fixtures. The MAF is attached to a standard universal test machine equiped with an...... environmental chamber using specially designed grips that allow the specimen to rotate, and hence reduces paristic effects due to misalignment. The objective is to measure the unidirectional and bidirectional mechanical properties of PVC foam materials at elevated tempreature using digital image correlation...

  10. The production and characterization of topologically and mechanically gradient open-cell thermoplastic foams

    International Nuclear Information System (INIS)

    The development of longitudinally and radially gradient open-cell polyurethane foams is reported. Local and global mechanical properties and pore structure have been characterized using video extensometry with x−y strain-mapping capability, and x-ray microtomography (CT) and scanning electron microscopy (SEM), respectively. The local axial Poisson’s ratio varies in a smoothly continuous manner along the length of the longitudinally gradient foam from large negative (auxetic), through zero, to positive (conventional) values. The production of radially gradient foams having a coaxial core–sheath structure is reported for the first time. Two radially gradient foams have been produced, each displaying similar global negative axial Poisson’s ratio responses but with markedly different local axial Poisson’s ratio and local axial Young’s modulus behaviours. One of the radially gradient foams displays a positive Poisson’s ratio core and an auxetic sheath resulting from conventional and higher density re-entrant open-cell pore structures, respectively. (paper)

  11. Defects in aluminum foam with superfine open-cell structure

    Institute of Scientific and Technical Information of China (English)

    Wang Fang; Zhang Zhimin; Li Baocheng; Wang Lucai

    2008-01-01

    The infiltration casting process for producing aluminum foam includes three steps: preparing precursor using NaCI particles, infiltrating molten aluminum and cleaning NaCI precursor. Defects occur during the preparation of aluminum foam with superfine open-cell structure, and influence the pore structure and performance of aluminum foam materials. The types of the defect and their forming mechanisms are analyzed in this paper. The defects include point defects and linear metal defects, and are caused by the defects in salt precursor and the insufficient infiltration of molten aluminum into precursor. With the choice of proper precursor preparation method and infiltration process parameters, the complete aluminum foam with superfine pores could be achieved.

  12. Rigid polyurethane foam – kenaf core composites for structural applications

    Science.gov (United States)

    Kenaf (Hibiscus cannabinus L.) is a fast growing summer annual crop with numerous commercial applications (fibers, biofuels, bioremediation, paper pulp, building materials, cover crops, and livestock forages). The stalks of the kenaf plants contain two distinct fiber types, bast and core fibers. The...

  13. Analysis of Sandwich Shells with Metallic Foam Cores based on the Uniaxial Tensile Test

    Science.gov (United States)

    Mata, H.; Santos, A.; Fernandes, A. A.; Valente, R. A. F.; Parente, M. P. L.; Jorge, R. Natal

    2011-05-01

    On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications, especially in automotive and aeronautical industries. This work is divided into two parts; in the first part the mathematical model used to describe the behavior of sandwich shells with metal cores form is presented and some numerical examples are presented. In the second part of this work, the numerical results are validated using the experimental results obtained from the mechanical experiments. Using the isotropic hardening crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Using this constitutive model, the uniaxial tensile test for this material was simulated, and a comparison with the experimental results was made.

  14. Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and an immobilized electrolyte allow for reversible operation as electrolysis cell or fuel...

  15. Foaming and cell flotation in suspended plant cell cultures and the effect of chemical antifoams.

    Science.gov (United States)

    Wongsamuth, R; Doran, P M

    1994-08-01

    Foam development and stability in Atropa belladonna suspensions were investigated as a function of culture conditions. Foaming was due mainly to properties of the cell-free broth and was correlated with protein content; effects due to presence of cells increased towards the end of batch culture. Highest foam levels were measured 11 days after inoculation. Air flow rate was of major importance in determining foam volume; foam volume and stability were also strongly dependent on pH. Foam flotation of plant cells was very effective. After 30 min foaming, ca. 55% of cells were found in the foam; this increased to ca. 75% after 90 min. Polypropylene glycol 1025 and 2025, Pluronic PE 6100, and Antifoam-C emulsion were tested as chemical antifoams. Polypropylene glycol 1025 and Antifoam C at concentrations up to 600 ppm had no adverse effect on growth in shake flasks; Pluronic PE 6100 has an inhibitory effect at all levels tested. Concentrations of polypropylene glycol 2025 and Pluronic PE 6100 as low as 20 ppm reduced foam volumes by a factor of ca. 10. Addition of antifoam reduced k(L)a values in bubble-column and stirred-tank bioreactors. After operation of a stirred reactor for 2 days using Antifoam C for foam control, cell production was limited by oxygen due to the effect of antifoam on mass transfer. Theoretical analysis showed that maximum cell concentrations and biomass levels decline with increasing reactors working volume due to greater consumption of antifoam to prevent foam overflow. The results indicate that when chemical foam control is used in plant cell cultures, head-space volume and tolerable foam levels must be considered to optimize biomass production. (c) 1994 John Wiley & Sons, Inc. PMID:18618782

  16. Properties of polyurethane foam/coconut coir fiber as a core material and as a sandwich composites component

    International Nuclear Information System (INIS)

    This research focuses on the fabrication and characterization of sandwich composite panels using glass fiber composite skin and polyurethane foam reinforced coconut coir fiber core. The main objectives are to characterize the physical and mechanical properties and to elucidate the effect of coconut coir fibers in polyurethane foam cores and sandwich composite panels. Coconut coir fibers were used as reinforcement in polyurethane foams in which later were applied as the core in sandwich composites ranged from 5 wt% to 20 wt%. The physical and mechanical properties found to be significant at 5 wt% coconut coir fiber in polyurethane foam cores as well as in sandwich composites. It was found that composites properties serve better in sandwich composites construction

  17. Properties of polyurethane foam/coconut coir fiber as a core material and as a sandwich composites component

    Science.gov (United States)

    Azmi, M. A.; Abdullah, H. Z.; Idris, M. I.

    2013-12-01

    This research focuses on the fabrication and characterization of sandwich composite panels using glass fiber composite skin and polyurethane foam reinforced coconut coir fiber core. The main objectives are to characterize the physical and mechanical properties and to elucidate the effect of coconut coir fibers in polyurethane foam cores and sandwich composite panels. Coconut coir fibers were used as reinforcement in polyurethane foams in which later were applied as the core in sandwich composites ranged from 5 wt% to 20 wt%. The physical and mechanical properties found to be significant at 5 wt% coconut coir fiber in polyurethane foam cores as well as in sandwich composites. It was found that composites properties serve better in sandwich composites construction.

  18. Preparation of open-cell metal foams by investment cast

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Metal foams are a new kind of materials with low densities and novel physical, mechanical, thermal, electrical and acoustic properties. They can be divided into closed and open cell structures. In this paper the open cell structures,called sponges, were treated. A new technique to manufacture sponges by plaster investment casting was described.Experimental results show that it is essential to make a sound plaster mould by casting plaster slurry into the polyurethane foams and infiltrate the open channels of the baked plaster mold by molten metal. The optimal processes include plaster slurry preparation, plaster mold baking, and molten metal infiltration. The sponge sample with porosity of 97% is presented.

  19. Study of Debond Fracture Toughness of Sandwich Composites with Metal Foam Core

    Institute of Scientific and Technical Information of China (English)

    Xinzhu Wang; Linzhi Wu; Shixun Wang

    2009-01-01

    Two types of experiments were designed and performed to evaluate the adhesive bond in metal foam composite sandwich structures. The tensile bond strength of face/core was determined through the flatwise tensile test (FWT). The test results show that the interfacial peel strength is lower than the interlaminar peel strength in FWT test. The mode I interfacial fracture toughness (GIC) of sandwich structures containing a pre-crack on the upper face/core interface is determined by modified cracked sandwich beam (MCSB) experiment. It is found that the crack propagates unsynchronously on the two side of the specimen and the propagation of interfacial debonding always stays on the face/core interface during the MCSB tests. In order to simulate the failure of metal foam composite sandwich structures, a computational model based on the Tsai-Hill failure criterion and cohesive zone model is used. By comparing with experiment results, it can be concluded that the computational model can validly simulate the interfacial failure of metal foam composite sandwich structures with reasonable accuracy.

  20. Tensile Properties of Open Cell Ceramic Foams

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Řehořek, Lukáš; Chlup, Zdeněk

    2009-01-01

    Roč. 409, - (2009), s. 168-175. ISSN 1013-9826. [Fractography of Advanced Ceramics /3./. Stará Lesná, 07.09.2008-10.09.2008] R&D Projects: GA ČR(CZ) GA106/06/0724; GA ČR GD106/05/H008 Institutional research plan: CEZ:AV0Z20410507 Keywords : tensile test * ceramics foam * open porosity * tensile strength Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  1. Tensile Behaviour of Open Cell Ceramic Foams

    Czech Academy of Sciences Publication Activity Database

    Řehořek, Lukáš; Dlouhý, Ivo; Chlup, Zdeněk

    2009-01-01

    Roč. 53, č. 4 (2009), s. 237-241. ISSN 0862-5468 R&D Projects: GA ČR GA101/09/1821; GA ČR GD106/09/H035 Institutional research plan: CEZ:AV0Z20410507 Keywords : Tensile test * Ceramics foam * Open porosity * Tensile strength Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.649, year: 2009

  2. CFD characterization of flow regimes inside open cell foam substrates

    International Nuclear Information System (INIS)

    Highlights: • We investigated the pressure drop in open-cell foams. • The study is based on a combination of micro-CT, image-based modeling and CFD tools. • Detailed CFD simulations were applied for the investigation of turbulent flow regimes. • The effects of geometrical parameters are studied by means of RANS CFD simulations. • Results are analyzed in terms of non-dimensional parameters. - Abstract: In this work a combination of micro-CT, image-based modeling and CFD has been applied to investigate the pressure drop in open-cell foams. The analysis covers a range of flow regimes and is aimed at determining the effects of important morphological parameters on the pressure drop. The adoption of micro-CT technology along with detailed CFD modeling allows the investigation of phenomena occurring in real foam micro-structures. Moreover, by means of image processing tools, the geometry can be artificially modified in order to investigate the effects of mathematical transformation of the geometrical parameters of a real foam, one parameter at a time, e.g. varying pore size without affecting the porosity. Non-dimensional coefficients have been defined for the analysis of the results, with the purpose of describing the pressure drop as a function of the Reynolds number. The proposed formulation allows us to relate the permeability properties of an open-cell foam to its morphology alone, without any dependence on the properties of the fluid adopted or on the effective characteristic dimension of the foam micro-structure (pore or cell size). Comparison with experimental results available in the literature is also provided for one of the cases studied

  3. Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

    Science.gov (United States)

    Ambur, Damodar R.; Dexter, Benson H.

    1996-01-01

    A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

  4. Transcriptional profiling of foam cells in response to hypercholesterolemia.

    Science.gov (United States)

    Goo, Young-Hwa; Yechoor, Vijay K; Paul, Antoni

    2016-09-01

    Hypercholesterolemia is a main risk factor for atherosclerosis development. Arterial macrophages, or foam cells, take-up and process lipoprotein particles deposited in arteries, and store much of the cholesterol carried by these particles in their cytoplasm. However, the effects of exposure to different cholesterol levels on foam cells remain poorly understood. Given the remarkable plasticity of macrophages in response to environmental variables, studies on macrophage biology should ideally be performed in the environment where they exert their physiological functions, namely atherosclerotic lesions in the case of foam cells. We used a mouse model of atherosclerosis, the apolipoprotein E-deficient mouse, to study in vivo the transcriptional response of foam cells to short- and long-term elevations in plasma cholesterol, induced by feeding mice a western type diet. The microarray data sets from this study have been deposited in NCBI's Gene Expression Omnibus under the accession number GSE70619. Here we provide detailed information on the experimental set-up, on the isolation of RNA by laser capture microdissection, and on the methodology used for RNA amplification and analysis by microarray and quantitative real-time PCR. PMID:27408807

  5. The dynamic mechanical properties study on the sandwich panel of different thickness steel plate-foam aluminum core

    Science.gov (United States)

    Chang, Zhongliang; Zou, Guangping; Zhao, Weiling; Xia, Peixiu

    2010-03-01

    The foam aluminum belongs to multi-cell materials, and it has good mechanical performance, such as large deformation capacity and good energy absorption, and usually used as core material of sandwich panel, now it is widely used in automotive, aviation, aerospace and other fields, particularly suitable for various anti-collision structure and buffer structure. In this article, based on an engineering background, the INSTRON4505 electronic universal testing machine and split Hopkinson pressure bar (SHPB) were used for testing the static and dynamic mechanical properties of sandwich panel with different thickness steel plate- foam aluminum core, from the results we can see that the steel plate thickness has big influence on the stress-strain curve of the sandwich panel, and also takes the sandwich panel with 1mm steel panel to study the material strain rate dependence which under different high shock wave stress loaded, the results show that the sandwich panel is strain rate dependence material. And also, in order to get good waveforms in the SHPB experiment, the waveform shaped technique is used in the dynamic experiments, and the study of this paper will good to sandwich panel used in the engineering.

  6. Failure analysis of bolted joints in foam-core sandwich composites

    DEFF Research Database (Denmark)

    Zabihpoor, M.; Moslemian, Ramin; Afshin, M.;

    2008-01-01

    This study represents an effort to predict the bearing strength, failure modes, and failure load of bolted joints in foam-core sandwich composites. The studied joints have been used in a light full composite airplane. By using solid laminates, a new design for the joint zone is developed. These...... using 3D FEM in ANSYS commercial code. Tsai-Wu failure criterion is used in the failure analysis. The results indicate that the most important parameter in the proposed joint zone design is the foam -solid laminate interface angle which plays an important role on the value of failure criterion (damage...... analysis, the increase of solid laminate size or interface angle could result in considerable higher buckling strength....

  7. Derivation of temperature dependent mechanical properties of polymer foam core materials using optical extensometry

    Directory of Open Access Journals (Sweden)

    Fruehmann R.K.

    2010-06-01

    Full Text Available A methodology for determining the temperature dependence of Young’s modulus and Poisson’s ratio of polymer foams core materials is presented. The design of the test specimen is described in detail, covering the parasitic effects resulting from departures from the uniform strain condition. The measurement approach is based on a non-contact technique so that the behaviour of the complaint foam is not modified by the attachment of strain gauges or extensometers. Firstly experiments are conducted at room temperature and then at elevated temperatures in a thermal chamber. Readings are taken through an optical window using a standard digital camera. Digital image correlation is used to obtain the strains.

  8. Lightweight Hybrid Ablator Incorporating Aerogel-Filled Open-Cell Foam Structural Insulator Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In previous work for NASA and DoD, Ultramet developed lightweight open-cell foam insulators composed of a carbon or ceramic structural foam skeleton filled with a...

  9. Lightweight Hybrid Ablator Incorporating Aerogel-Filled Open-Cell Foam Structural Insulator, Phase II Project

    Data.gov (United States)

    National Aeronautics and Space Administration — In previous work for NASA and DoD, Ultramet developed lightweight open-cell foam insulators composed of a carbon or ceramic structural foam skeleton filled with a...

  10. Open-celled polymeric foam monoliths for heavy metal separations study

    International Nuclear Information System (INIS)

    Open-celled polymeric foam monoliths prepared by high internal phase emulsion polymerization (HIPE) are being investigated as improved materials for separation of heavy metals. In column flow studies, the foam monoliths have high flow rates and are durable up to at least 40 psi. A 4-vinylpyridine functionality has been incorporated into vinylbenzylchloride/styrene copolymer foams by graft-polymerization of vinylpyridine. The open structure of the foam and the flexible graft-polymerized ion-exchange chains result in improved kinetics in metal uptake. Iron uptake kinetics were greatly increased in the grafted foams over resin beads of similar structure. Plutonium uptake kinetics were moderately increased in the foams. (author)

  11. Perforation of aluminium foam core sandwich panels under impact loading: A numerical and analytical study

    Directory of Open Access Journals (Sweden)

    Elnasri Ibrahim

    2015-01-01

    Full Text Available This paper reports the numerical results of the inversed perforation test instrumented with Split Hopkinson Pressure Bar SHPB with an instrumented pressure bar on the AlSi7Mg0.5 aluminium foam core sandwich panels with 0.8 mm thick 2024 T3 aluminium top and bottom skin. The numerical models are developed in order to understand the origin of the enhancement of the top skin loads found under impact loading (paper published by [1]. Numerical predicted piercing force vs displacement curves are compared with experimental measurements (tests at impact velocities at 27 and 44 m/s. The simulation catches all process of the perforation of the sandwich panels (top skin, foam core, and bottom skin. Within experimental scatter, there is a good agreement between numerical predictions and experimental measurements. Virtual tests with different impact velocities up 200 m/s are presented and showed a significant enhancement of the piercing force under impact loading (top skin peak and foam core plateau loads. In order to understand the origin of these force enhancements, any difference of detailed local information between static and dynamic loading is studied and showed that a shock front effect is responsible for the enhancement piercing force. An analytical model using an improved RPPL shock model based a power law densification assumption is proposed to calculate the top skin piercing force. The improved RPPL shock model agrees with the FE results for small velocities and gives better prediction of the piercing force than the RPPL shock model for large velocities (>100 m/s.

  12. Perforation of aluminium foam core sandwich panels under impact loading: A numerical and analytical study

    Science.gov (United States)

    Elnasri, Ibrahim; Zhao, Han

    2015-09-01

    This paper reports the numerical results of the inversed perforation test instrumented with Split Hopkinson Pressure Bar SHPB with an instrumented pressure bar on the AlSi7Mg0.5 aluminium foam core sandwich panels with 0.8 mm thick 2024 T3 aluminium top and bottom skin. The numerical models are developed in order to understand the origin of the enhancement of the top skin loads found under impact loading (paper published by [1]). Numerical predicted piercing force vs displacement curves are compared with experimental measurements (tests at impact velocities at 27 and 44 m/s). The simulation catches all process of the perforation of the sandwich panels (top skin, foam core, and bottom skin). Within experimental scatter, there is a good agreement between numerical predictions and experimental measurements. Virtual tests with different impact velocities up 200 m/s are presented and showed a significant enhancement of the piercing force under impact loading (top skin peak and foam core plateau loads). In order to understand the origin of these force enhancements, any difference of detailed local information between static and dynamic loading is studied and showed that a shock front effect is responsible for the enhancement piercing force. An analytical model using an improved RPPL shock model based a power law densification assumption is proposed to calculate the top skin piercing force. The improved RPPL shock model agrees with the FE results for small velocities and gives better prediction of the piercing force than the RPPL shock model for large velocities (>100 m/s).

  13. Monotonic shear and shear fatigue of foam-core composite sandwich structures

    Energy Technology Data Exchange (ETDEWEB)

    Liu, L.; Song, H.; Holmes, J.W. [Georgia Institute of Technology, School of Aerospace Eng., Materials and Advanced Structure Testing Lab., Atlanta, Georgia (United States)

    2006-07-01

    Details of a new test apparatus that allows direct shear testing of sandwich structures is discussed. In addition to monotonic and cyclic shear, the apparatus allows studying the shear-creep behavior of various sandwich structures and can be extended to investigate lap-joints and adhesive joints. The test apparatus can accommodate sandwich panels as large as 400 mm x 400 mm. In proof-of-concept experiments, the apparatus was used to investigate the effect of loading history on the ambient temperature monotonic shear and shear fatigue life of sandwich composites with a PVC foam core and fiberglass/epoxy face sheets. The fatigue experiments were performed at a loading frequency of 1 Hz and a stress ratio between 0.16 and 0.19. During fatigue, a progressive degradation in shear modulus occurs as well as considerable stress-strain hysteresis. Damage accumulated by the cycle-by-cycle extension of cracks along the face-sheet/core interface and shear-related damage to the PVC foam core. (au)

  14. Nonlinear Thermo-mechanical Finite Element Analysis of Polymer Foam Cored Sandwich Structures including Geometrical and Material Nonlinearity

    DEFF Research Database (Denmark)

    Palleti, Hara Naga Krishna Teja; Thomsen, Ole Thybo; Taher, Siavash Talebi;

    In this paper, polymer foam cored sandwich structures with fibre reinforced composite face sheets subjected to combined mechanical and thermal loads will be analysed using the commercial FE code ABAQUS® incorporating both material and geometrical nonlinearity. Large displacements and rotations are...... included in the analysis. The full nonlinear stress-strain curves up to failure will be considered for the polymer foams at different temperatures to study the effect of material nonlinearity in detail....

  15. Moisture absorption and mechanical degradation studies of PMI foam cored fiber/epoxy resin sandwich composites

    Directory of Open Access Journals (Sweden)

    Liang Yin

    2015-04-01

    Full Text Available The present paper explores the result of hygrothermic aging of polymethacrylimide (PMI foam core sandwich composites immersed in different temperature deionized (DI and sea waters. The prepared specimens were tested for moisture up-take behavior and the resulting property degradation in terms of flexural and flat wise compressive strength. The results indicate that the saturated hygroscopic time of specimens immersed in low temperature water and high temperature water is about 480h and 720h, respectively. Due to the presence of ionic in sea water, the specimens immersed in sea water have higher compressive and flexural strength than specimens immersed in DI water.

  16. Perforation of aluminium foam core sandwich panels under impact loading: A numerical and analytical study

    OpenAIRE

    Elnasri Ibrahim; Zhao Han

    2015-01-01

    This paper reports the numerical results of the inversed perforation test instrumented with Split Hopkinson Pressure Bar SHPB with an instrumented pressure bar on the AlSi7Mg0.5 aluminium foam core sandwich panels with 0.8 mm thick 2024 T3 aluminium top and bottom skin. The numerical models are developed in order to understand the origin of the enhancement of the top skin loads found under impact loading (paper published by [1]). Numerical predicted piercing force vs displacement curves are c...

  17. Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into chemical energy in the form of hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and a liquid immobilized electrolyte allow the operation of...... the newly designed electrolysis cell as a fuel cell, but condensation of steam may lead to blocked pores, thereby inhibiting gas diffusion and decreasing the performance of the cell. In the here presented work we present the application of a hydrophobic, porous, and electro-catalytically active layer...

  18. Structural foam-core panels in Northwest HUD-code manufactured housing: A preliminary assessment of opportunities and obstacles

    Energy Technology Data Exchange (ETDEWEB)

    Durfee, D.L.; Lee, A.D.; Onisko, S.A.

    1993-07-01

    This investigation of structural foam-core panels (foam panels) in manufactured housing was initiated during the Super Good Cents (SGC) program. The SGC program limited allowable glazing area because of the relatively high thermal losses associated with most windows. Due to their superior thermal performance, foam panels appeared to be a viable option to allow increased glazing area without compromising the thermal integrity of the wall. With the inception of the Manufactured-Housing Acquisition Program (MAP), however, the focus of this study has shifted. MAP permits unlimited glazing area if expensive, super-efficient, vinyl-framed, argon-gas-filled, low-emissivity coated windows are installed. Although MAP permits unlimited glazing area, a foam panel wall could allow the use of less expensive windows, larger window area, or less insulation and still provide the required thermal performance for the building. Bonneville contracted with the Pacific Northwest Laboratory (PNL) to investigate the feasibility of using foam panels in HUD-code manufactured housing. This study presents the results from a product and literature search. The potential barriers and benefits to the use of foam panels are determined from a regional survey of the HUD-code manufacturers and foam panel producers.

  19. Acoustic properties of sintered FeCrAlY foams with open cells (Ⅱ): Sound attenuation

    Institute of Scientific and Technical Information of China (English)

    LU TianJian; M.KEPETS; A.P.DOWLING

    2008-01-01

    Open-celled metal foams fabricated through metal sintering offers novel mechani-cal, thermal and acoustic properties. Previously, polymer foams were used as a means of absorbing acoustic energy. However, the structural applications of these foams are inherently limited. The metal sintering approach provides a cost-effective means for the mass-production of open-cell foams from a range of materials, in-cluding high-temperature steel alloys. The low Reynolds number fluid properties of sintered steel alloy (FeCrAIY) foams were investigated in a previous study. The static flow resistance of the foams was modeled based on s cylinder and s sphere arranged in a periodic lattice at general incidence to the flow, with the resulting predictions correlating well to measurements. The application of the flow resis-tance in an acoustic model is the primary focus of the present study. The predic-tions for the static flow resistance of the sintered foams are first used in a theo-retical model to determine the characteristic impedances, as well as the propaga-tion constants of the foams. Subsequently, the predicted acoustic performance of the foams is compared to experimental results. Finally, the design space for a simple acoustic absorber incorporating sintered foams is examined, with the ef-fects of absorber size, foam selection, and foam spacing explored.

  20. Acoustic properties of sintered FeCrAlY foams with open cells (Ⅱ): Sound attenuation

    Institute of Scientific and Technical Information of China (English)

    M.; KEPETS; A.; P.; DOWLING2

    2008-01-01

    Open-celled metal foams fabricated through metal sintering offers novel mechani- cal, thermal and acoustic properties. Previously, polymer foams were used as a means of absorbing acoustic energy. However, the structural applications of these foams are inherently limited. The metal sintering approach provides a cost-effective means for the mass-production of open-cell foams from a range of materials, in- cluding high-temperature steel alloys. The low Reynolds number fluid properties of sintered steel alloy (FeCrAlY) foams were investigated in a previous study. The static flow resistance of the foams was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow, with the resulting predictions correlating well to measurements. The application of the flow resis- tance in an acoustic model is the primary focus of the present study. The predic- tions for the static flow resistance of the sintered foams are first used in a theo- retical model to determine the characteristic impedances, as well as the propaga- tion constants of the foams. Subsequently, the predicted acoustic performance of the foams is compared to experimental results. Finally, the design space for a simple acoustic absorber incorporating sintered foams is examined, with the ef- fects of absorber size, foam selection, and foam spacing explored.

  1. Foam Based Gas Diffusion Electrodes for Reversible Alkaline Electrolysis Cells

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    Alkaline electrolysis cells operated at 250 °C and 40 bar have shown to be able to convert electrical energy into hydrogen at very high efficiencies and power densities. Foam based gas diffusion electrodes and an immobilized electrolyte allow for reversible operation as electrolysis cell or fuel...... cell. In the present work we demonstrate the application of hydrophobic, porous, and electro-catalytically active gas diffusion electrodes. PTFE particles and silver nanowires as electro-catalysts were used in the gas diffusion electrodes. Impedance spectroscopy and cyclic voltammetry were performed to...

  2. Effect of Porosity and Cell Size on the Dynamic Compressive Properties of Aluminum Alloy Foams

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The dynamic mechanical properties of open-cell aluminum alloy foams with different relative densities and cell sizeshave been investigated by compressive tests. The strain rates varied from 700 s-1 to 2600 s-1. The experimentalresults showed that the dynamic compressive stress-strain curves exhibited a typical three-stage behavior: elastic,plateau and densification. The dynamic compressive strength of foams is affected not only by the relative densitybut also by the strain rate and cell size. Aluminum alloy foams with higher relative density or smaller cell size aremore sensitive to the strain rate than foams with lower relative density or larger cell size.

  3. Impaired SIRT1 promotes the migration of vascular smooth muscle cell-derived foam cells.

    Science.gov (United States)

    Zhang, Ming-Jie; Zhou, Yi; Chen, Lei; Wang, Xu; Pi, Yan; Long, Chun-Yan; Sun, Meng-Jiao; Chen, Xue; Gao, Chang-Yue; Li, Jing-Cheng; Zhang, Li-Li

    2016-07-01

    The formation of fat-laden foam cells, contributing to the fatty streaks of the plaques of atheroma, is the critical early process in atherosclerosis. The previous study demonstrated that vascular smooth muscle cells (VSMCs) contain a much larger burden of the excess cholesterol in comparison with monocyte-derived macrophages in human coronary atherosclerosis, as the main origin of foam cells. It is noteworthy that VSMC-derived foam cells are deposited in subintima but not media, where VSMCs normally deposit in. Therefore, migration from media to intima is an indispensable step for a VSMC to accrue neutral lipids and form foam cell. Whether this migration occurs paralleled with or prior to the formation of foam cell is still unclear. Herein, the present study was designed to test the VSMC migratory capability in the process of foam cell formation induced by oxidized low-density lipoprotein (oxLDL). In conclusion, we provide evidence that oxLDL induces the VSMC-derived foam cells formation with increased migration ability and MMP-9 expression, which were partly attributed to the impaired SIRT1 and enhanced nuclear factor-kappa B (NF-κB) activity. As activation of transient receptor potential vanilloid type 1 (TRPV1) has been reported to have anti-atherosclerotic effects, we investigated its role in oxLDL-treated VSMC migration. It is found that activating TRPV1 by capsaicin inhibits VSMC foam cell formation and the accompanied migration through rescuing the SIRT1 and suppressing NF-κB signaling. The present study provides evidence that SIRT1 may be a promising intervention target of atherosclerosis, and raises the prospect of TRPV1 in prevention and treatment of atherosclerosis. PMID:26883442

  4. Experimental study of partially-cured Z-pins reinforced foam core composites: K-Cor sandwich structures

    Directory of Open Access Journals (Sweden)

    Zheng Yingying

    2014-02-01

    Full Text Available This paper presents an experimental study of a novel K-Cor sandwich structure reinforced with partially-cured Z-pins. The influence of pultrusion processing parameters on Z-pins characteristics was studied and the effect of Z-pins on mechanical properties was disclosed. Differential scanning calorimetry (DSC and optical microscopy (OM methods were employed to determine the curing degree of as-prepared Z-pins and observe the implanted Z-pins in the K-Cor structure. These partially-cured Z-pins were treated with a stronger bonding link between face sheets and the foam core by means of a hot-press process, thereby decreasing burrs and cracking defects when the Z-pins were implanted into the Rohacell foam core. The results of the out-of-plane tensile tests and the climbing drum peel (CDP tests showed that K-Cor structures exhibited superior mechanical performance as compared to X-Cor and blank foam core. The observed results of failure modes revealed that an effective bonding link between the foam core and face sheets that was provided from partially-cured Z-pins contributed to the enhanced mechanical performances of K-Cor sandwich structures.

  5. Experimental study of partially-cured Z-pins reinforced foam core composites:K-Cor sandwich structures

    Institute of Scientific and Technical Information of China (English)

    Zheng Yingying; Xiao Jun; Duan Mufeng; Li Yong

    2014-01-01

    This paper presents an experimental study of a novel K-Cor sandwich structure rein-forced with partially-cured Z-pins. The influence of pultrusion processing parameters on Z-pins characteristics was studied and the effect of Z-pins on mechanical properties was disclosed. Differential scanning calorimetry (DSC) and optical microscopy (OM) methods were employed to determine the curing degree of as-prepared Z-pins and observe the implanted Z-pins in the K-Cor structure. These partially-cured Z-pins were treated with a stronger bonding link between face sheets and the foam core by means of a hot-press process, thereby decreasing burrs and cracking defects when the Z-pins were implanted into the Rohacell foam core. The results of the out-of-plane tensile tests and the climbing drum peel (CDP) tests showed that K-Cor structures exhibited superior mechanical performance as compared to X-Cor and blank foam core. The observed results of failure modes revealed that an effective bonding link between the foam core and face sheets that was provided from partially-cured Z-pins contributed to the enhanced mechan-ical performances of K-Cor sandwich structures.

  6. Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core

    International Nuclear Information System (INIS)

    In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined and 3D confined) were employed in this paper. Up to seven impact–healing cycles were conducted. Macroscopic and microscopic damage–healing observation and analysis were implemented. Residual strength was evaluated using an anti-buckling compression test fixture. It was found that the healing efficiency was over 100% for almost all the impact–healing cycles; programming using 20% prestrain led to higher residual strength than that with 3% prestrain; 3D confined recovery resulted in higher residual strength than 2D confined recovery; and as the impact energy increased, the healing efficiency slightly decreased

  7. Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core

    Science.gov (United States)

    John, Manu; Li, Guoqiang

    2010-07-01

    In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined and 3D confined) were employed in this paper. Up to seven impact-healing cycles were conducted. Macroscopic and microscopic damage-healing observation and analysis were implemented. Residual strength was evaluated using an anti-buckling compression test fixture. It was found that the healing efficiency was over 100% for almost all the impact-healing cycles; programming using 20% prestrain led to higher residual strength than that with 3% prestrain; 3D confined recovery resulted in higher residual strength than 2D confined recovery; and as the impact energy increased, the healing efficiency slightly decreased.

  8. Vibration Characteristics Determined for Stainless Steel Sandwich Panels With a Metal Foam Core for Lightweight Fan Blade Design

    Science.gov (United States)

    Ghosn, Louis J.; Min, James B.; Raj, Sai V.; Lerch, Bradley A.; Holland, Frederic A., Jr.

    2004-01-01

    The goal of this project at the NASA Glenn Research Center is to provide fan materials that are safer, weigh less, and cost less than the currently used titanium alloy or polymer matrix composite fans. The proposed material system is a sandwich fan construction made up of thin solid face sheets and a lightweight metal foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by the foam layer. The resulting structure has a high stiffness and lighter weight in comparison to the solid facesheet material alone. The face sheets carry the applied in-plane and bending loads (ref. 1). The metal foam core must resist the transverse shear and transverse normal loads, as well as keep the facings supported and working as a single unit. Metal foams have ranges of mechanical properties, such as light weight, impact resistance, and vibration suppression (ref. 2), which makes them more suitable for use in lightweight fan structures. Metal foams have been available for decades (refs. 3 and 4), but the difficulties in the original processes and high costs have prevented their widespread use. However, advances in production techniques and cost reduction have created a new interest in this class of materials (ref. 5). The material chosen for the face sheet and the metal foam for this study was the aerospace-grade stainless steel 17-4PH. This steel was chosen because of its attractive mechanical properties and the ease with which it can be made through the powder metallurgy process (ref. 6). The advantages of a metal foam core, in comparison to a typical honeycomb core, are material isotropy and the ease of forming complex geometries, such as fan blades. A section of a 17-4PH sandwich structure is shown in the following photograph. Part of process of designing any blade is to determine the natural frequencies of the particular blade shape. A designer needs to predict the resonance frequencies of a new blade design to properly identify a useful

  9. Compressive properties of open-cell ceramic foams

    Institute of Scientific and Technical Information of China (English)

    ZHANG Jun-yan; FU Yi-ming; ZENG Xiao-ming

    2006-01-01

    The compressive experiments of two kinds of ceramic foams were completed. The results show that the behavior of ceramic foams made by organic filling method is anisotropic. The stress-strain responses of ceramic foams made by sponge-replication show isotropy and strain rate dependence. The struts brittle breaking of net structure of this ceramic foam arises at the weakest defects of framework or at the part of framework,which causes the initiation and expanding of cracks. The compressive strength of ceramic foam is dependent on the strut size and relative density of foams.

  10. Numerical Modeling of the Compression Process of Elastic Open-cell Foams

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The random models of open-cell foams that can reflect the actual cell geometrical properties are constructed with the Voronoi technique. The compression process of elastic open-cell foams is simulated with the nonlinear calculation module of finite element analysis program. In order to get the general results applicable to this kind of materials, the dimensionless compressive stress is used and the stress-strain curves of foam models with different geometrical properties are obtained. Then, the influences of open-cell geometrical properties, including the shape of strut cross section, relative density and cell shape irregularity, on the compressive nonlinear mechanical performance are analyzed. In addition, the numerical results are compared with the predicted results of cubic staggering model. Numerical results indicate that the simulated results reflect the compressive process of foams quite well and the geometrical properties of cell have significant influences on the nonlinear mechanical behavior of foams.

  11. Microcellular foam injection molding with cellulose nanofibers (CNFs)

    Science.gov (United States)

    Ohshima, Masahiro; Kubota, Masaya; Ishihara, Shota; Hikima, Yuta; Sato, Akihiro; Sekiguchi, Takafumi

    2016-03-01

    Cellulose nanofibers (CNFs) nanocomposites polypropylene foams are prepared by microcellular foam injection molding with core-back operation. The modified CNFs were blended with isotactic-polypropylene (i-PP) at different CNFs weight percentages and foamed to investigate the effect of CNFs on cell morphology. CNFs in i-PP increased the elastic modulus and induced a strain hardening behavior. CNFs also shifted the crystallization temperature of i-PP to higher temperature and enhanced crystallization. With these changes in rheological and thermal properties, CNFs could reduce the cell size and increase the cell density of the foams. By adjusting the core-back timing i.e., foaming temperature, the closed cell and the nano-fibrillated open cellular structure could be produced. The flexural modulus and bending strength of foams were measured by three point flexural tester. The flexural modulus and bending strength were increased as the CNFs content in i-PP was increased at any foam expansion ratio.

  12. Evaluation of Experimental Parameters in the Accelerated Aging of Closed-Cell Foam Insulation

    Energy Technology Data Exchange (ETDEWEB)

    Stovall, Therese K [ORNL; Vanderlan, Michael [ORNL; Atchley, Jerald Allen [ORNL

    2012-12-01

    The thermal conductivity of many closed-cell foam insulation products changes over time as production gases diffuse out of the cell matrix and atmospheric gases diffuse into the cells. Thin slicing has been shown to be an effective means of accelerating this process in such a way as to produce meaningful results. Efforts to produce a more prescriptive version of the ASTM C1303 standard test method led to the ruggedness test described here. This test program included the aging of full size insulation specimens for time periods of five years for direct comparison to the predicted results. Experimental parameters under investigation include: slice thickness, slice origin (at the surface or from the core of the slab), thin slice stack composition, product facings, original product thickness, product density, and product type. The test protocol has been completed and this report provides a detailed evaluation of the impact of the test parameters on the accuracy of the 5-year thermal conductivity prediction.

  13. Defects in aluminum foam with superfi ne open-cell structure

    OpenAIRE

    Wang Fang; Zhang Zhimin; Li Baocheng

    2008-01-01

    The infiltration casting process for producing aluminum foam includes three steps: preparing precursor using NaCl particles, infi ltrating molten aluminum and cleaning NaCl precursor. Defects occur during the preparation of aluminum foam with superfi ne open-cell structure, and infl uence the pore structure and performance of aluminum foam materials. The types of the defect and their forming mechanisms are analyzed in this paper. The defects include point defects and linear metal defects, and...

  14. Tensile property of Al-Si closed-cell aluminum foam

    Institute of Scientific and Technical Information of China (English)

    YU Hai-jun; YAO Guang-chun; LIU Yi-han

    2006-01-01

    Al-Si closed-cell aluminum foams of different densities were prepared by molten body transitional foaming process. The tensile behavior of Al-Si closed-cell aluminum foam was studied and the influence of relative densities on the tensile strength and elastic modulus was also researched. The results show that the fracture surfaces of Al-Si closed-cell aluminum foam display quasi-cleavage fiacture consisting of brittle cleavages and ductile dimples. The tensile strength and elastic modulus are strictly affected by the relative density of Al-Si closed-cell aluminum foam. With increasing relative density, the tensile strength increases and the strain at which the peak strength is measured also increases; in addition, the elastic modulus increases with increasing relative density.

  15. Influence of material non-linearity on the thermo-mechanical response of polymer foam cored sandwich structures - FE modelling and preliminary experiemntal results

    DEFF Research Database (Denmark)

    Palleti, Hara Naga Krishna Teja; Thomsen, Ole Thybo; Fruehmann, Richard.K;

    the model. The full stress-strain curves up to failure will be considered for the polymer foams at different temperatures in order to study the plasticity influence of polymer foam on the sandwich structures in detail. Due to stiff face sheets resting on the soft polymer core and the ratio of the...

  16. Geometric classification of open-cell metal foams using X-ray micro-computed tomography

    International Nuclear Information System (INIS)

    The geometry of foams has long been an area of interest, and a number of idealized geometric descriptions have been proposed. In order to acquire detailed, quantitative, geometric data for aluminum open-cell metal foams, X-ray μCT is employed. The X-ray μCT images are analyzed using specialized software, FoamView®, from which geometric information including strut length and pore shapes are extracted. The X-ray μCT analysis allows comparison of the ideal geometric models to the actual geometric characteristics of the metal foam samples. The results reveal a high variability in ligament length, as well as features supporting the ideal geometry known as the Weaire–Phelan unit cell. The geometric findings provide information useful for improving current models of open-cell metal foam. Applications can range from predicting heat transfer or load failure to predicting liquid retention. Highlights: ► Aluminum open-cell metal foams are geometrically classified ► X-ray micro-computed tomography and specialized software are used to gather geometric data ► The foams are shown to have a high variability in strut length ► The Weaire–Phelan unit cell is shown to be a better representative of these foams

  17. Data characterizing flexural properties of Al/Al2O3 syntactic foam core metal matrix sandwich

    Science.gov (United States)

    Omar, Mohammed Yaseer; Xiang, Chongchen; Gupta, Nikhil; Strbik, Oliver M.; Cho, Kyu

    2015-01-01

    Microstructural observations and flexural property datasets are provided for aluminum alloy matrix syntactic foam core sandwich composites. The tests are conducted in three-point bending configuration. The data supplied includes methods used for conducting microscopy and mechanical testing. Raw load–displacement data, which is used to plot stress–strain graphs, obtained during the flexural test is also included. Images from a DSLR camera are stitched together to form a detailed failure sequencing video. Failure of specimens is captured in sequential images using a digital camera. These images are stitched together to develop a video for visualization of failure mechanisms. Calculations are also included for a theoretical model that is used to estimate the flexural properties of the syntactic foam core sandwich. PMID:26958610

  18. Modeling hydrodynamic properties of open-cell metal foams

    International Nuclear Information System (INIS)

    Modeling the hydrodynamics of open-cell aluminum foam still is a challenging task because of the large range of length-scales, own to the physical phenomena which occur in the complex structure. Upscaling the classical conservation equations is a promising approach, but introduces the problem of modeling closure terms. This is dealt with via the well-known porous properties, i.e., permeability and inertial loss factor. Derivation of these properties is commonly done by linking pressure drop data to velocity via a second order interpolation. This, however, introduces significant deviation between the available data set, up to anorder of magnitude, which in turn results in difficulties to predict pressure drop during desing the desing phase of an applicaiton. As the closure terms have a well-defined physical meaning, it should be possible to compute them with better accuracy. This forms the topic of this paper.

  19. Analysis of Mixed Mode I/II/III Fracture in Foam Core Sandwich Structures Using Imposed Displacement Split Cantilever Beams

    Directory of Open Access Journals (Sweden)

    Rizov V.

    2015-09-01

    Full Text Available Static fracture in foam core sandwich structures under mixed mode I/II/III loading conditions was studied theoretically. In order to generate such loading conditions, a thread guide was used to impose in- plane displacements of the lower crack arm of a sandwich Split Cantilever Beam (SCB. The upper crack arm was loaded by a transverse force. A three-dimensional finite element model of the imposed displacement sandwich SCB configuration was developed. The fracture was studied applying the concepts of linear-elastic fracture mechanics. The strain energy release rate mode components distribution along the crack front was analyzed using the virtual crack closure technique. The influence of the imposed displacement magnitude and the crack length on the fracture was evaluated. The effect of the sandwich core material on the mixed-mode I/II/III fracture was studied. For this purpose, finite element simulations were carried-out assuming that the core is made by different rigid cellular foams. It was found that the strain energy release rate decreases when the foam density increases.

  20. Effects of everolimus on macrophage-derived foam cell behavior

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Steven, E-mail: steven.hsu@av.abbott.com [Abbott Vascular, 3200 Lakeside Drive, Santa Clara, CA 95054 (United States); Koren, Eugen; Chan, Yen; Koscec, Mirna; Sheehy, Alexander [Abbott Vascular, 3200 Lakeside Drive, Santa Clara, CA 95054 (United States); Kolodgie, Frank; Virmani, Renu [CVPath Institute, Inc., 19 Firstfield Road, Gaithersburg, MD 20878 (United States); Feder, Debra [Abbott Vascular, 3200 Lakeside Drive, Santa Clara, CA 95054 (United States)

    2014-07-15

    Purpose: The purpose of this study was to investigate the effects of everolimus on foam cell (FC) viability, mRNA levels, and inflammatory cytokine production to better understand its potential inhibitory effects on atheroma progression. Methods and materials: Human THP1 macrophage-derived FC were formed using acetylated LDL (acLDL, 100 μg/mL) for 72 hours, followed by everolimus treatment (10{sup -5}–10{sup -11} M) for 24 hours. FC viability was quantified using fluorescent calcein AM/DAPI staining. FC lysates and media supernatants were analyzed for apoptosis and necrosis using a Cell Death ELISA{sup PLUS} assay. FC lysates and media supernatants were also analyzed for inflammatory cytokine (IL1β, IL8, MCP1, TNFα) mRNA levels and protein expression using quantitative reverse transcription real-time polymerase chain reaction (QPCR) and a Procarta® immunoassay, respectively. mRNA levels of autophagy (MAP1LC3), apoptosis (survivin, clusterin), and matrix degradation (MMP1, MMP9) markers were evaluated by Quantigene® Plex assay and verified with QPCR. Additionally, hypercholesterolemic rabbits received everolimus-eluting stents (EES) for 28 or 60 days. RAM-11 immunohistochemical staining was performed to compare %RAM-11 positive area between stented sections and unstented proximal sections. Statistical significance was calculated using one-way ANOVA (p ≤ 0.05). Results: Calcein AM/DAPI staining showed that FC exposed to everolimus (10{sup -5} M) had significantly decreased viability compared to control. FC apoptosis was significantly increased at a high dose of everolimus (10{sup -5} M), with no necrotic effects at any dose tested. Everolimus did not affect endothelial (HUVEC) and smooth muscle (HCASMC) cell apoptosis or necrosis. Everolimus (10{sup -5} M) significantly increased MAP1LC3, caused an increased trend in clusterin (p = 0.10), and significantly decreased survivin and MMP1 mRNA levels in FC. MCP1 cytokine mRNA levels and secreted protein

  1. Effects of everolimus on macrophage-derived foam cell behavior

    International Nuclear Information System (INIS)

    Purpose: The purpose of this study was to investigate the effects of everolimus on foam cell (FC) viability, mRNA levels, and inflammatory cytokine production to better understand its potential inhibitory effects on atheroma progression. Methods and materials: Human THP1 macrophage-derived FC were formed using acetylated LDL (acLDL, 100 μg/mL) for 72 hours, followed by everolimus treatment (10-5–10-11 M) for 24 hours. FC viability was quantified using fluorescent calcein AM/DAPI staining. FC lysates and media supernatants were analyzed for apoptosis and necrosis using a Cell Death ELISAPLUS assay. FC lysates and media supernatants were also analyzed for inflammatory cytokine (IL1β, IL8, MCP1, TNFα) mRNA levels and protein expression using quantitative reverse transcription real-time polymerase chain reaction (QPCR) and a Procarta® immunoassay, respectively. mRNA levels of autophagy (MAP1LC3), apoptosis (survivin, clusterin), and matrix degradation (MMP1, MMP9) markers were evaluated by Quantigene® Plex assay and verified with QPCR. Additionally, hypercholesterolemic rabbits received everolimus-eluting stents (EES) for 28 or 60 days. RAM-11 immunohistochemical staining was performed to compare %RAM-11 positive area between stented sections and unstented proximal sections. Statistical significance was calculated using one-way ANOVA (p ≤ 0.05). Results: Calcein AM/DAPI staining showed that FC exposed to everolimus (10-5 M) had significantly decreased viability compared to control. FC apoptosis was significantly increased at a high dose of everolimus (10-5 M), with no necrotic effects at any dose tested. Everolimus did not affect endothelial (HUVEC) and smooth muscle (HCASMC) cell apoptosis or necrosis. Everolimus (10-5 M) significantly increased MAP1LC3, caused an increased trend in clusterin (p = 0.10), and significantly decreased survivin and MMP1 mRNA levels in FC. MCP1 cytokine mRNA levels and secreted protein expression was significantly decreased by

  2. Mechanical Properties of 3-D Printed Cellular Foams with triangular cells

    Science.gov (United States)

    Bunga, Pratap Kumar

    In the present work, poly lactic acid (PLA) is used as a model system to investigate the mechanical behavior of 3-D printed foams with triangular cells. Solid PLA tension and compression specimens and foams made of PLA were fabricated using fused deposition 3-D printing technique. The solid PLA tension specimens were characterized for their densities and found to be about 10% lower in density as compared to their bulk counter parts. The triangular foams had a relative density of about 64%. The relationships between the structure of the foams and its deformation behavior under compression along two in-plane directions were characterized. Furthermore, simple finite element models were developed to understand the observed deformation behavior of triangular foams.

  3. Insulin and glucose play a role in foam cell formation and function

    OpenAIRE

    Keller Susanna R; Huo Yuqing; Rissing Benjamin A; Miller Yury I; Jain Nitin; Shashkin Pavel N; Vandenhoff George E; Nadler Jerry L; McIntyre Thomas M

    2006-01-01

    Abstract Background Foam cell formation in diabetic patients often occurs in the presence of high insulin and glucose levels. To test whether hyperinsulinemic hyperglycemic conditions affect foam cell differentiation, we examined gene expression, cytokine production, and Akt phosphorylation in human monocyte-derived macrophages incubated with two types of oxidized low density lipoprotein (LDL), minimally modified LDL (mmLDL) and extensively oxidized LDL (OxLDL). Methods and results Using Affy...

  4. Fracture of Open-Cell Nickel Foams Under Quasi-Static Tensile Loading

    Science.gov (United States)

    Shehata Aly, Mohamed

    2010-12-01

    Open-cell nickel foams with average pore size of 600 μm have been subjected to room temperature tensile tests to explore their tensile properties. Using a state of the art extensometer of noncontact type, foam properties as ultimate tensile strength, yield strength, and the Young's modulus ( E) have been measured accurately. The reason behind the usage of this kind of extensometer is to avoid completely any minor deformation that might be caused by the attachment of conventional extensometer to the sample's surface prior to testing. The function of this extensometer is based on the usage of a laser (CCD) camera that detects and records the dimensional changes as soon as the load is applied. A series of cyclic loading-unloading tests was performed to determine the foam's Young's modulus. The fracture behavior of foam cells was observed to be ductile. Complete separation of struts or cell walls took place successively by necking.

  5. Inhibition of mast cell-dependent conversion of cultured macrophages into foam cells with antiallergic drugs.

    Science.gov (United States)

    Ma, H; Kovanen, P T

    2000-12-01

    Degranulation of isolated, rat peritoneal mast cells in the presence of low density lipoprotein (LDL) induces cholesteryl ester accumulation in cocultured macrophages with ensuing foam cell formation. This event occurs when the macrophages phagocytose LDL particles that have been bound to the heparin proteoglycans of exocytosed granules. In an attempt to inhibit such foam cell formation pharmacologically, rat peritoneal mast cells that had been passively sensitized with anti-ovalbumin-IgE were treated with 2 mast cell-stabilizing antianaphylactic drugs, MY-1250 or disodium cromoglycate (DSCG). Both drugs were found to inhibit antigen (ovalbumin)-triggered release of histamine from the mast cells, revealing mast cell stabilization. In cocultures of rat peritoneal macrophages and passively sensitized mast cells, addition of MY-1250 before addition of the antigen resulted in parallel reductions in histamine release from mast cells, uptake of [(14)C]sucrose-LDL, and accumulation of LDL-derived cholesteryl esters in the cocultured macrophages. Similarly, when passively sensitized mast cells were stimulated with antigen in the presence of DSCG and the preconditioned media containing all substances released from the drug-treated mast cells were collected and added to macrophages cultured in LDL-containing medium, uptake and esterification of LDL cholesterol by the macrophages were inhibited. The inhibitory effects of both drugs were mast cell-specific because neither drug inhibited the ability of macrophages to take up and esterify LDL cholesterol. Analysis of heparin proteoglycan contents of the incubation media revealed that both drugs had inhibited mast cells from expelling their granule remnants. Thus, both MY-1250 and DSCG prevent mast cells from releasing the heparin proteoglycan-containing vehicles that bind LDL and carry it into macrophages. This study suggests that antiallergic pharmacological agents could be used in animal models to prevent mast cell

  6. Combination nickel foam expanded nickel screen electrical connection supports for solid oxide fuel cells

    Science.gov (United States)

    Draper, Robert; Prevish, Thomas; Bronson, Angela; George, Raymond A.

    2007-01-02

    A solid oxide fuel assembly is made, wherein rows (14, 25) of fuel cells (17, 19, 21, 27, 29, 31), each having an outer interconnection (20) and an outer electrode (32), are disposed next to each other with corrugated, electrically conducting expanded metal mesh member (22) between each row of cells, the corrugated mesh (22) having top crown portions and bottom portions, where the top crown portion (40) have a top bonded open cell nickel foam (51) which contacts outer interconnections (20) of the fuel cells, said mesh and nickel foam electrically connecting each row of fuel cells, and where there are no more metal felt connections between any fuel cells.

  7. Metal Foam Shields

    Science.gov (United States)

    Christiansen, Eric L.

    2006-01-01

    This paper compares the ballistic performance of metallic foam sandwich structures with honeycomb structures. Honeycomb sandwich structures, consisting of metallic or composite facesheets and honeycomb cores, are often used in spacecraft construction due to their light-weight and structural stiffness. Honeycomb panels, however, are considered rather poor candidates for protection from micrometeoroid orbital debris (MMOD) particles because the honeycomb channels the debris cloud from MMOD impacts on outer facesheet causing a concentrated load on the second facesheet. Sandwich structures with light-weight, open-cell metallic cores and metal or composite facesheets provide improved MMOD protection because channeling does not occur and because the core is more effective at disrupting hypervelocity impacts then honeycomb. This paper describes hypervelocity impact tests on metallic foam sandwich structures (aluminum and titanium) with metallic facesheets, compare them to equivalent mass and thickness honeycomb panels, based on the results of hypervelocity impact tests.

  8. Material characterization of open-cell foams by finite element based micromechanics methods

    Science.gov (United States)

    Thiyagasundaram, Prasanna

    Finite element based micromechanics methods have been used for predicting elastic properties, failure strengths, mode-I, mode-II and mixed mode fracture toughness of open-cell foams. In predicting the orthotropic elastic properties, foams with both equisided and Kelvin-elongated tetrakaidecahedron unit cells are studied. Periodic Boundary Conditions (PBCs) exploiting the special repeating microstructural geometry for these materials have been derived and have been applied on the micromechanical model to calculate the elastic properties. It is shown that the results for the elastic constants from these finite element based models agree well with the available analytical models. Further studies such as effect of a varying strut cross-section over a uniform strut cross-section on the elastic properties are also done in the same context. Next, the procedures used for predicting the above elastic properties are extended to predict multi-axial failure strengths of these low density open cell foams with a microstructure made out of tetrakaidecahedral unit cells. Again, foams with both equisided tetrakaidecahedron and Kelvin-elongated tetrakaidecahedron as unit cells are studied. Failure strengths in different material directions are computed using direct Micromechanics based Methods (DMM). Further, the effect of a varying strut cross section over a uniform strut cross section on failure strengths is also presented. Bi-axial failure envelopes for foams with equisided tetrakaidecahedron unit cells are shown to take the shape of a regular hexagon in the hydrostatic plane. The tri-axial failure envelope for foams made out of equisided tetrakaidecahedron unit cells is shown to have a shape of a double hexagonal pyramid. The bi-axial and tri-axial failure envelopes of foams with elongated tetrakaidecahedron unit cells are also plotted and the effect of anisotropy in foams with these unit cells on the failure envelopes is also discussed. Next, global-local models are developed

  9. Suitability of LN2 impregnated Open-Cell Foam as Electric Insulant for Superconducting Power Equipment

    International Nuclear Information System (INIS)

    The suitability of an open-cell foam is investigated for the application as electric insulant in superconducting power equipment. The tested foam is made from melamine resin, a thermoset plastic from the aminoplastics group; it is a mechanical very flexible material with excellence compatibility to high and low temperature. The aim of these investigations was to test the aptitude of the liquid nitrogen impregnated open-cell foam with respect to the dielectric properties and the electric strength under different conditions. In this paper the results of permittivity measurements and ramp voltage tests are discussed and an outlook for future applications is given. The tests showed excellence mechanical and thermal characteristics for the application in LN2 vessels. The ACBV of the LN2 impregnated foam was 50 % less than the ACBV of pure LN2

  10. Data characterizing compressive properties of Al/Al2O3 syntactic foam core metal matrix sandwich

    Directory of Open Access Journals (Sweden)

    Mohammed Yaseer Omar

    2015-12-01

    Full Text Available Microstructural observations and compressive property datasets of metal matrix syntactic foam core sandwich composite at quasi-static and high strain rate (HSR conditions (525–845 s−1 are provided. The data supplied in this article includes sample preparation procedure prior to scanning electron and optical microscopy as well as the micrographs. The data used to construct the stress–strain curves and the derived compressive properties of all specimens in both quasi-static and HSR regions are included. Videos of quasi-static compressive failure and that obtained by a high speed image acquisition system during deformation and failure of HSR specimen are also included.

  11. Fatigue characterization of Poly Vinyl Chloride (PVC) foam core sandwich composite using the G-control method

    DEFF Research Database (Denmark)

    Manca, Marcello; Berggreen, Christian; Carlsson, Leif A.;

    2016-01-01

    , compression and shear to determine in-plane and out-of-plane mechanical properties, such as Young’s modulus, Poisson’s ratio and shear modulus. These properties were then used in an analytical model of the mixed-mode bending sandwich specimen to calculate compliance and energy release rate. Finite element...... analysis was used to determine the mode-mixity of the crack loading. Experimental crack growth cyclic tests were carried out on pre-cracked mixed-mode bending sandwich specimens with H45, H100 and H160 PVC foam cores under two mode-mixities (mode I and mode II dominant). Post-mortem analysis was performed...

  12. Closed-Cell Aluminum Foam of Improved Sound Absorption Ability: Manufacture and Properties

    OpenAIRE

    Alexandra Byakova; Svyatoslav Gnyloskurenko; Yuriy Bezimyanniy; Takashi Nakamura

    2014-01-01

    The paper presents a new method for the production of the closed-cell Al foams of improved sound absorbing ability. Final heat treatment procedure including heating below the solidus temperature followed by water quenching is proposed as an alternative method to machining, which is used commonly for improvement of the sound absorption coefficient. Several kinds of foams based on AlZnMg-alloys comprising brittle eutectic domains of interdendritic redundant phase have been produced by the Alpor...

  13. Parameters estimation of sandwich beam model with rigid polyurethane foam core

    Science.gov (United States)

    Barbieri, Nilson; Barbieri, Renato; Winikes, Luiz Carlos

    2010-02-01

    In this work, the physical parameters of sandwich beams made with the association of hot-rolled steel, Polyurethane rigid foam and High Impact Polystyrene, used for the assembly of household refrigerators and food freezers are estimated using measured and numeric frequency response functions (FRFs). The mathematical models are obtained using the finite element method (FEM) and the Timoshenko beam theory. The physical parameters are estimated using the amplitude correlation coefficient and genetic algorithm (GA). The experimental data are obtained using the impact hammer and four accelerometers displaced along the sample (cantilevered beam). The parameters estimated are Young's modulus and the loss factor of the Polyurethane rigid foam and the High Impact Polystyrene.

  14. Effect of TiH2 on preparation of closed-cell aluminum foam and its compressive behavior

    Institute of Scientific and Technical Information of China (English)

    YANG Guo-jun; YU Hai-jun; YAO Guang-chun

    2006-01-01

    The vesicant problem during the process of preparing closed-cell aluminum foam by molten body transitional foaming process was discussed and the effect of granularity and addition of TiH2 on porosity of closed-cell aluminum foam was investigated.The static compressive behavior of closed-cell aluminum foam and the influence of porosity on static compressive property of closed-cell aluminum foam were researched as well. The results show that with increasing granularity of TiH2, the porosity of closed-cell aluminum foam firstly increases and then decreases gradually, the granularity should be controlled in the range of 38-74 μm which can result in higher porosity. The porosity of closed-cell aluminum foam increases with the increasing addition of TiH2,and the addition of TiH2 should be controlled from 1.5% to 2.5% which can result in homogeneous cell and moderate strength of closed-cell aluminum foam. The compressive process of closed-cell aluminum foam obviously displays linear elastic phase, plastic collapse phase, and densification phase, and the compressive strength grows with decreasing porosity.

  15. Mipu1 Overexpression Protects Macrophages from oxLDL-Induced Foam Cell Formation and Cell Apoptosis

    OpenAIRE

    Qu, Shun-Lin; Fan, Wen-Jing; Zhang, Chi; Guo, Fang; Han, Dan; Pan, Wen-Jun; Li, Wei; Feng, Da-Ming; JIANG, ZHI-SHENG

    2014-01-01

    Mipu1 (myocardial ischemic preconditioning upregulated protein 1) is a novel N-terminal Kruppel-associated box (KRAB)/C2H2 zinc finger superfamily protein, that displays a powerful effect in protecting H9c2 cells from oxidative stress-induced cell apoptosis. The present study aims to investigate the effect of Mipu1 overexpression on oxidized low-density lipoprotein (oxLDL)-induced foam cell formation, cell apoptosis, and its possible mechanisms. New Zealand healthy rabbits were used to establ...

  16. How to Study Thermal Applications of Open-Cell Metal Foam: Experiments and Computational Fluid Dynamics

    Directory of Open Access Journals (Sweden)

    Sven De Schampheleire

    2016-02-01

    Full Text Available This paper reviews the available methods to study thermal applications with open-cell metal foam. Both experimental and numerical work are discussed. For experimental research, the focus of this review is on the repeatability of the results. This is a major concern, as most studies only report the dependence of thermal properties on porosity and a number of pores per linear inch (PPI-value. A different approach, which is studied in this paper, is to characterize the foam using micro tomography scans with small voxel sizes. The results of these scans are compared to correlations from the open literature. Large differences are observed. For the numerical work, the focus is on studies using computational fluid dynamics. A novel way of determining the closure terms is proposed in this work. This is done through a numerical foam model based on micro tomography scan data. With this foam model, the closure terms are determined numerically.

  17. Microtomography-based CFD analysis of transport in open-cell aluminum metal foams

    International Nuclear Information System (INIS)

    Nowadays, the need for developing more effective heat exchange technologies and innovative materials, capable of increasing performances while keeping power consumption, size and cost at reasonable levels, is well recognized. Under this perspective, metal foams have a great potential for enhancing the thermal efficiency of heat transfer devices, while allowing for the use of smaller and lighter equipments. However, for practical applications, it is necessary to compromise between the augmented heat transfer rate and the increased pressure drop induced by the tortuous flow passages. For design purposes, the estimation of the flow permeability and the thermal conductivity of the foam is fundamental, but far from simple. From this perspective, besides classical transport models and correlations, computational fluid dynamics (CFD) at the pore scale, although challenging, is becoming a promising approach, especially if coupled with a realistic description of the foam structure. For precisely recovering the microstructure of the foams, a 3D X-ray computed microtomography (μ-CT) can be adopted. In this work, the results of μ-CT-based CFD simulations performed on different open-cell aluminum foams samples, for laminar flow regime, will be discussed. The results demonstrate that open-cell aluminum foams are effective means for enhancing heat transfer.

  18. Ionizing Radiation Induces Macrophage Foam Cell Formation and Aggregation Through JNK-Dependent Activation of CD36 Scavenger Receptors

    International Nuclear Information System (INIS)

    Purpose: Irradiated arteries of cancer patients can be associated with atherosclerosis-like lesions containing cholesterol-laden macrophages (foam cells). Endothelial cell damage by irradiation does not completely explain the foam cell formation. We investigated the possible underlying mechanisms for ionizing radiation (IR)-induced foam cell formation. Methods and Materials: Human peripheral blood monocytes were activated by macrophage colony-stimulating factor and then treated with varying doses of IR in vitro in the absence of endothelial cells. Scavenger receptor expression and foam cell formation of IR-treated macrophages were investigated in the presence or absence of oxidized low-density lipoprotein. We also assessed the importance of mitogen-activated protein kinase activity in the macrophage colony-stimulating factor-activated human monocytes (macrophages) for the foam cell formation. Results: We found that IR treatment of macrophage colony-stimulating factor-activated human peripheral blood monocytes resulted in the enhanced expression of CD36 scavenger receptors and that cholesterol accumulated in the irradiated macrophages with resultant foam cell formation in the presence of oxidized low-density lipoprotein. Furthermore, when cultured on collagen gels, human macrophages formed large foam cell aggregates in response to IR. Antibodies against CD36 inhibited the IR-induced foam cell formation and aggregation, indicating that the IR-induced foam cell formation and the subsequent aggregation are dependent on functional CD36. In addition, we found that IR of human macrophages resulted in c-Jun N-terminal kinase activation and that c-Jun N-terminal kinase inhibition suppressed IR-induced CD36 expression and the subsequent foam cell formation and aggregation. Conclusion: Taken together, these results suggest that IR-induced foam cell formation is mediated by c-Jun N-terminal kinase-dependent CD36 activation

  19. A relative permeability model to derive fractional-flow functions of water-alternating-gas and surfactant-alternating-gas foam core-floods

    International Nuclear Information System (INIS)

    Foam is used in enhanced oil recovery to improve the sweep efficiency by controlling the gas mobility. The surfactant-alternating-gas (SAG) foam process is used as an alternative to the water-alternating-gas (WAG) injection. In the WAG technique, the high mobility and the low density of the gas lead the gas to flow in channels through the high permeability zones of the reservoir and to rise to the top of the reservoir by gravity segregation. As a result, the sweep efficiency decreases and there will be more residual oil in the reservoir. The foam can trap the gas in liquid films and reduces the gas mobility. The fractional-flow method describes the physics of immiscible displacements in porous media. Finding the water fractional flow theoretically or experimentally as a function of the water saturation represents the heart of this method. The relative permeability function is the conventional way to derive the fractional-flow function. This study presents an improved relative permeability model to derive the fractional-flow functions for WAG and SAG foam core-floods. The SAG flow regimes are characterized into weak foam, strong foam without a shock front and strong foam with a shock front. (paper)

  20. Phage display identification of CD100 in human atherosclerotic plaque macrophages and foam cells.

    Directory of Open Access Journals (Sweden)

    Maria Carolina Aquino Luque

    Full Text Available Atherosclerosis is a complex disease in which vessels develop plaques comprising dysfunctional endothelium, monocyte derived lipid laden foam cells and activated lymphocytes. Considering that humans and animal models of the disease develop quite distinct plaques, we used human plaques to search for proteins that could be used as markers of human atheromas. Phage display peptide libraries were probed to fresh human carotid plaques, and a bound phage homologous to plexin B1, a high affinity receptor for CD100, was identified. CD100 is a member of the semaphorin family expressed by most hematopoietic cells and particularly by activated T cells. CD100 expression was analyzed in human plaques and normal samples. CD100 mRNA and protein were analyzed in cultured monocytes, macrophages and foam cells. The effects of CD100 in oxLDL-induced foam cell formation and in CD36 mRNA abundance were evaluated. Human atherosclerotic plaques showed strong labeling of CD100/SEMA4D. CD100 expression was further demonstrated in peripheral blood monocytes and in in vitro differentiated macrophages and foam cells, with diminished CD100 transcript along the differentiation of these cells. Incubation of macrophages with CD100 led to a reduction in oxLDL-induced foam cell formation probably through a decrease of CD36 expression, suggesting for the first time an atheroprotective role for CD100 in the human disease. Given its differential expression in the numerous foam cells and macrophages of the plaques and its capacity to decrease oxLDL engulfment by macrophages we propose that CD100 may have a role in atherosclerotic plaque development, and may possibly be employed in targeted treatments of these atheromas.

  1. Behaviour of Open Cell Ceramic Foams in Tension

    Czech Academy of Sciences Publication Activity Database

    Dlouhý, Ivo; Řehořek, Lukáš; Chlup, Zdeněk

    Columbus, Ohio, 2011. s. 165-165. [Materials Science and Technology 2011. Conference and Exhibition. 16.10.2011-20.10.2011, Columbus, Ohio] R&D Projects: GA ČR GA101/09/1821 Institutional research plan: CEZ:AV0Z20410507 Keywords : foam ceramics * tensile test * damage quantification Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass

  2. Closed-cell polymeric foam for hydrogen separation and storage

    Czech Academy of Sciences Publication Activity Database

    Pientka, Zbyněk; Pokorný, P.; Bélafi-Bakó, K.

    2007-01-01

    Roč. 304, 1-2 (2007), s. 82-87. ISSN 0376-7388 R&D Projects: GA ČR GA203/06/1207 Institutional research plan: CEZ:AV0Z40500505 Keywords : polymeric foam * gas separation * hydrogen storage Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.432, year: 2007

  3. Antisense oligodeoxynucleotide inhibits vascular endothelial growth factor expression in U937 foam cells

    Institute of Scientific and Technical Information of China (English)

    YANGPeng-Yuan; RUIYao-Cheng; JINYou-Xin; LITie-Jun; QIUYan; ZHANGLi; WANGJie-Song

    2003-01-01

    AIM:To study the expression of vascular endothelial growth factor (VEGF) induced by oxidized low density liprotein (ox-LDL) and the inhibitory effects of antisense oligodeoxynucleotide (asODN) on the levels of VEGF protein and mRNA in the U937 foam cells. METHODS: U937 cells were incubated with ox-LDL 80 mg/L for 48h, then ,the foam cells were treated with asODN (0,5,10, and 20μmol/L). The VEGF concentration in the media was determined by ELISA. The VEGF protein expression level in cells was measured by immuohistochemistry; the positive ratio detected by a morphometrical analysis system was used as the amount of the VEGF expression level. The VEGF mRNA level was examined by Northern blotting. RESULTS: After U937 cells were incubated with ox-LDL, VEGF expression level increased greatly both in the cells and in the media. asODN markeldy inhibited the increase of VEGF. After treatment with asODN 20μmol/L, the VEGF protein concentration in the media decreased by 45.0%, the VEGF positive ratio detected by immuohistochemistry in cells decreased by 64.9%, and the VEGF mRNA level decreased by 47.1%. CONCLUSION: The expression of VEGF in U937 foam cells was strong. asODN inhibited VEGF expression significantly in U937 foam cells in vitro.

  4. Hybrid Parallel Computation of OpenFOAM Solver on Multi-Core Cluster Systems

    OpenAIRE

    Liu, Yuan

    2011-01-01

    OpenFOAM, an open source industrial Computational Fluid Dynamics (CFD) tool, which contains dozens of simulation application inside. A traditional approach to accelerate physical simulation process is to employ more powerful supercomputer. However, It is bound to expense large amount of hardware resources. In recent years, parallel and distributed computing is becoming an efficient way to solve such computational intensive application. This thesis pick up the most used compressible reacting s...

  5. Porous, Ventricular Extracellular Matrix-Derived Foams as a Platform for Cardiac Cell Culture.

    Science.gov (United States)

    Russo, Valerio; Omidi, Ehsan; Samani, Abbas; Hamilton, Andrew; Flynn, Lauren E

    2015-01-01

    To more closely mimic the native cellular microenvironment, 3D scaffolds derived from the extracellular matrix (ECM) are being developed as alternatives to conventional 2D culture systems. In the present study, we established methods to fabricate nonchemically cross-linked 3D porous foams derived entirely from decellularized porcine left ventricle (DLV) for use as an in vitro cardiac cell culture platform. Furthermore, we explored the effects of physically preprocessing the DLV through mechanical mincing versus cryomilling, as well as varying the ECM concentration on the structure, composition, and physical properties of the foams. Our results indicate that the less highly processed minced foams had a more cohesive and complex network of ECM components, enhanced mechanical properties, and improved stability under simulated culturing conditions. To validate the DLV foams, a proof-of-concept study was conducted to explore the early cardiomyogenic differentiation of pericardial fat adipose-derived stem/stromal cells (pfASCs) on the minced DLV foams relative to purified collagen I gel controls. Differentiation was induced using a modified cardiomyogenic medium (MCM) or through stimulation with 5-azacytidine (5-aza), and cardiomyocyte marker expression was characterized by immunohistochemistry and real-time reverse transcriptase-polymerase chain reaction. Our results indicate that early markers of cardiomyogenic differentiation were significantly enhanced on the DLV foams cultured in MCM, suggesting a synergistic effect of the cardiac ECM-derived scaffolds and the culture medium on the induction of pfASC differentiation. Furthermore, in analyzing the response in the noninduced control groups, the foams were observed to provide a mildly inductive microenvironment for pfASC cardiomyogenesis, supporting the rationale for using tissue-specific ECM as a substrate for cardiac cell culture applications. PMID:26487982

  6. Closed-Cell Aluminum Foam of Improved Sound Absorption Ability: Manufacture and Properties

    Directory of Open Access Journals (Sweden)

    Alexandra Byakova

    2014-08-01

    Full Text Available The paper presents a new method for the production of the closed-cell Al foams of improved sound absorbing ability. Final heat treatment procedure including heating below the solidus temperature followed by water quenching is proposed as an alternative method to machining, which is used commonly for improvement of the sound absorption coefficient. Several kinds of foams based on AlZnMg-alloys comprising brittle eutectic domains of interdendritic redundant phase have been produced by the Alporas-like melting process to realize the method above. Opening of the closed cell structure required for ensuring high sound absorption ability has been achieved by cracking the walls between neighboring cells, making them gas permeable. They ultimately looked like Helmholtz micro-perforated resonators. Processing parameters and other variables that are favorable both for foaming regime and for final heat treatment are discussed and specified.

  7. Characteristics of oscillating flow through a channel filled with open-cell metal foam

    International Nuclear Information System (INIS)

    An experimental study was performed to investigate the characteristics of oscillating flow through a channel filled with open-cell metal foam with a fully inter-connected pore structure. Detailed experimental data of oscillating flow pressure drops and velocities for a wide range of oscillatory frequency and the maximum flow displacement were presented. A correlation equation for the maximum friction factor of metal foams subject to oscillating flow was obtained and compared with the results for channels inserted with wire-screens obtained by other investigators. The results showed that oscillating flow characteristics in an open-cell metal foam are governed by a hydraulic ligament diameter based kinetic Reynolds number Re ω(Dh) and the dimensionless flow displacement amplitude A Dh. The effects of kinetic Reynolds number on the variations of pressure drop and flow velocity in metal foam are more significant than that of the dimensionless flow displacement amplitude. The maximum friction factor of oscillating flow in open-cell metal foams is much smaller than that of oscillating flow in wire-screens for large flow displacement amplitudes

  8. Serum amyloid A stimulates macrophage foam cell formation via lectin-like oxidized low-density lipoprotein receptor 1 upregulation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ha Young, E-mail: hayoung@skku.edu [Department of Biological Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Mitochondria Hub Regulation Center, Dong-A University, Busan 602-714 (Korea, Republic of); Kim, Sang Doo [Department of Biological Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Baek, Suk-Hwan [Department of Biochemistry and Molecular Biology, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Choi, Joon Hyuk [Department of Pathology, College of Medicine, Yeungnam University, Daegu 705-717 (Korea, Republic of); Cho, Kyung-Hyun [School of Biotechnology, Yeungnam University, Gyeongsan 712-749 (Korea, Republic of); Zabel, Brian A. [Palo Alto Institute for Research and Education, Veterans Affairs Hospital, Palo Alto, CA 94304 (United States); Bae, Yoe-Sik, E-mail: yoesik@skku.edu [Department of Biological Science, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Mitochondria Hub Regulation Center, Dong-A University, Busan 602-714 (Korea, Republic of); Samsung Advanced Institute for Health Sciences and Technology, Sungkyunkwan University, Seoul 135-710 (Korea, Republic of)

    2013-03-29

    Highlights: ► SAA induced macrophage foam cell formation. ► SAA stimulated upregulation of lectin-like oxidized low-density lipoprotein receptor 1 (LOX1). ► SAA-induced LOX1 expression and foam cell formation is mediated by JNK/NF-κB signaling. ► HDL-conjugated SAA also stimulates foam cell formation via LOX1 upregulation. ► The finding reveals a novel mechanism of action of SAA in the pathogenesis of atherosclerosis. -- Abstract: Elevated levels of serum amyloid A (SAA) is a risk factor for cardiovascular diseases, however, the role of SAA in the pathophysiology of atherosclerosis remains unclear. Here we show that SAA induced macrophage foam cell formation. SAA-stimulated foam cell formation was mediated by c-jun N-terminal kinase (JNK) signaling. Moreover, both SAA and SAA-conjugated high density lipoprotein stimulated the expression of the important scavenger receptor lectin-like oxidized low-density lipoprotein receptor 1 (LOX1) via nuclear factor-κB (NF-κB). A LOX1 antagonist carrageenan significantly blocked SAA-induced foam cell formation, indicating that SAA promotes foam cell formation via LOX1 expression. Our findings therefore suggest that SAA stimulates foam cell formation via LOX1 induction, and thus likely contributes to atherogenesis.

  9. Experimental, Theoretical and Numerical Investigation of the Flexural Behaviour of the Composite Sandwich Panels with PVC Foam Core

    Science.gov (United States)

    Mostafa, A.; Shankar, K.; Morozov, E. V.

    2014-08-01

    This study presents the main results of an experimental, theoretical and numerical investigation on the flexural behaviour and failure mode of composite sandwich panels primarily developed for marine applications. The face sheets of the sandwich panels are made up of glass fibre reinforced polymer (GFRP), while polyvinylchloride (PVC) foam was used as core material. Four-point bending test was carried out to investigate the flexural behaviour of the sandwich panel under quasi static load. The finite element (FE) analysis taking into account the cohesive nature of the skin-core interaction as well as the geometry and materials nonlinearity was performed, while a classical beam theory was used to estimate the flexural response. Although the FE results accurately represented the initial and post yield flexural response, the theoretical one restricted to the initial response of the sandwich panel due to the linearity assumptions. Core shear failure associate with skin-core debonding close to the loading points was the dominant failure mode observed experimentally and validated numerically and theoretically.

  10. Design of Mechanical Properties of Open-Cell Porous Materials Based on μCT Study of Commercial Foams

    OpenAIRE

    Skibinski Jakub; Cwieka Karol; Wejrzanowski Tomasz; Kurzydlowski Krzysztof J.

    2015-01-01

    In the present paper numerical design of mechanical properties of open-cell porous materials is addressed. A detailed knowledge of mechanisms and parameters determining mechanical properties (i.e. Young’s Modulus, Poisson’s Ratio) of foams is essential for applications such as energy absorbers or lightweight construction materials. The foam structures were designed using procedure based on Laguerre-Voronoi tessellations (LVT) with micro-computed tomography of commercial foams used as referenc...

  11. Buoyancy driven convection in open-cell metal foam using the volume averaging theory

    International Nuclear Information System (INIS)

    Heat sinks with open-cell aluminium foam are studied numerically in buoyancy driven convection with air as surrounding medium. Results from a 2D numerical model are compared to experiments for different foam heights. The numerical model is based on the volume averaging theory. If only convective heat transfer is taken into account in the numerical model, the relative differences between the numerical and experimental results are smaller than 29% for all foam heights studied. However, when the influence of radiation is included in the numerical model, it is shown that the numerical results differ less than 9% with the experimental ones. This clearly shows that it is necessary to properly model radiative heat transfer in numerical models of open-cell aluminium foam in buoyancy driven convection. Finally, a sensitivity study of ten main parameters of the volume averaged model (closure terms, effective properties) and the experimental setup (substrate temperature, dimensions of the heat sink) is performed. It is shown that the construction details and dimensions of the experimental setup have the largest impact on the heat transfer rate and not the convection coefficient, as is often assumed. - Highlights: • Heat sinks with metal foam are studied in buoyancy driven convection. • Study is done numerically based on VAT and comparison is made with experiments. • When only convection is taken into account: differences are smaller than 29%. • When radiative heat transfer is included: differences are smaller than 9%. • Sensitivity study shows that convection coefficient is not most important parameter

  12. Delamination detection in foam core composite structures using transient flexural wavefields

    Science.gov (United States)

    Lamboul, B.; Osmont, D.

    2016-03-01

    This paper investigates a health monitoring technique for foam sandwich structures based on flexural wavefields imaged by Laser Doppler vibrometry. A study of calibrated artificial defect responses in harmonic regime demonstrates that the use of a low frequency regime (below 30 kHz) makes it possible to excite defects in their first flexural resonance modes. The analysis performed in harmonic regime is used to interpret signature patterns obtained with accumulated energy maps from transient wavefield recordings. The potential of the technique is demonstrated on a real impact-induced defect. The robustness of the method relatively to the excitation center frequency selection and to the presence of wave reverberation is demonstrated.

  13. Thermo-mechanical interaction effects in foam cored sandwich panels-correlation between High-order models and Finite element analysis results

    DEFF Research Database (Denmark)

    Palleti, Hara Naga Krishna Teja; Santiuste, Carlos; Thomsen, Ole Thybo;

    2010-01-01

    Thermo-mechanical interaction effects including thermal material degradation in polymer foam cored sandwich structures is investigated using the commercial Finite Element Analysis (FEA) package ABAQUS/Standard. Sandwich panels with different boundary conditions in the form of simply supported or...

  14. Foam drainage

    Energy Technology Data Exchange (ETDEWEB)

    Kraynik, A.M.

    1983-11-01

    Transient drainage from a column of persistent foam has been analyzed theoretically. Gravity-driven flow was assumed to occur through an interconnected network of Plateau borders that define the edges of foam cells taken to be regular pentagonal dodecahedrons. A small liquid volume fraction and monodisperse cell size distribution were assumed. In the basic model, it is assumed that all liquid is contained in Plateau borders that are bounded by rigid gas-liquid interfaces. The predicted half life, the time required for one half of the liquid to drain from the foam, is inversely proportional to the square of the cell diameter, illustrating the importance of foam structure in drainage. Liquid hold up in the films separating adjacent cells, nonuniform initial liquid volume fraction distribution and interfacial mobility are explored. Border suction due to reduced pressure in the Plateau borders provides a mechanism for film drainage. Simultaneous film drainage and flow through the Plateau borders are analyzed. Sufficient conditions for neglecting film drainage kinetics are obtained. The results indicate that improved foam stability is related to small cells, liquid hold up in the films and slow film drainage kinetics.

  15. Ni foam cathode enables high volumetric H2 production in a microbial electrolysis cell

    NARCIS (Netherlands)

    Jeremiasse, A.W.; Hamelers, H.V.M.; Saakes, M.; Buisman, C.J.N.

    2010-01-01

    Valuable, “green” H2 can be produced with a microbial electrolysis cell (MEC). To achieve a high volumetric production rate of high purity H2, a continuous flow MEC with an anion exchange membrane, a flow through bioanode and a flow through Ni foam cathode was constructed. At an electrical energy in

  16. Acoustic properties of sintered FeCrAlY foams with open cells (Ⅰ): Static flow resistance

    Institute of Scientific and Technical Information of China (English)

    LU TianJian; M.KEPETS; A.P.DOWLING

    2008-01-01

    Open celled metal foams fabricated through the route of metal sintering are a new class of material that offers novel mechanical and acoustic properties. The metal sintering approach offers a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The mechanical properties of open-celled steel alloy (FeCrAIY) foams have been characterized in previous studies, with focus placed on the influence of processing defects on stiffness and strength. In this work, the low-Reynolds number fluid properties of FeCrAIY foams were investigated both theoretically and experimen-tally. Specifically, the static flow resistance of the sintered foams important for heat transfer, filtration and sound absorption was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow. Experimental measurements were subsequently carried out to validate theoretical predictions, with good agreement achieved.

  17. A simplistic analytical unit cell based model for the effective thermal conductivity of high porosity open-cell metal foams

    International Nuclear Information System (INIS)

    We present a simplistic yet accurate analytical model for the effective thermal conductivity of high porosity open-cell metal foams saturated in a low conducting fluid (air). The model is derived analytically based on a realistic representative unit cell (a tetrakaidecahedron) under the assumption of one-dimensional heat conduction along highly tortuous-conducting ligaments at high porosity ranges (ε ⩾ 0.9). Good agreement with existing experimental data suggests that heat conduction along highly conducting and tortuous ligaments predominantly defines the effective thermal conductivity of open-cell metal foams with negligible conduction in parallel through the fluid phase. (paper)

  18. Mechanical and Numerical Analysis Concerning Compressive Properties of Tin-Lead Open-Cell Foams

    Science.gov (United States)

    Belhadj, Abd-Elmouneïm; Gavrus, Adinel; Bernard, Fabrice; Azzaz, Mohammed

    2015-10-01

    The design of new or innovative materials has to meet two essential criteria: increased mechanical performance and minimization of the mass. This dual requirement leads to interest in the study of various classes of metallic foams. The actual research is focused on open-cell Tin-Lead foams manufactured by replication process using NaCl preform. A mechanical press equipped with a load cell and a local extensometer with a controlled deformation rate is used. Experimental tests were carried out in order to study the influences of both the cell size and of the relative density on the mechanical behavior during a compression deformation and to analyze the obtained properties variation within a new framework. This study has three main sections which start with the manufacturing description and mechanical characterization of the proposed metallic foams followed by the understanding and modeling of their response to a compression load via a Gibson-Ashby model, a Féret law, a proposed simple Avrami model, and a generalized Avrami model. Finally, an exposition of a numerical simulation analyzing the compression of the Sn-Pb foams concerning the variation of the relative densities with respect to the plastic strain is proposed.

  19. Performance analysis of a membrane humidifier containing porous metal foam as flow distributor in a PEM fuel cell system

    International Nuclear Information System (INIS)

    Highlights: • Three metal foam configurations for the membrane humidifier are introduced. • The performances of the humidifiers containing metal foam are investigated. • A 3D CFD model is developed to compare the introduced humidifiers with one another. • Using metal foam at dry side has no positive effect on the humidifier performance. - Abstract: Using metal foam as flow distributor in membrane humidifier for proton exchange membrane (PEM) fuel cell system has some unique characteristics like more water transfer, low manufacturing complexity and low cost compared to the conventional flow channel plate. Metal foam can be applied at wet side or dry side or both sides of a humidifier. The three-dimensional CFD models are developed to investigate the performance of the above mentioned meanwhile compare them with the conventional humidifier. This model consists of a set of coupled equations including conservations of mass, momentum, species and energy for all regions of the humidifier. The results indicate that with the metal foam installed at wet side and both sides, water recovery ratio and dew point at dry side outlet are more than that of the conventional humidifier, indicating a better humidifier performance; while using metal foam at dry side has no positive effect on humidifier performance. At dry side mass flow rates higher than 10 mgr/s pressure drop in humidifier containing metal foam at wet side is lower than that of the conventional humidifier. As the mass flow rate increases from 9 to 15 mgr/s humidifier containing metal foam at wet side has better performance, while at mass flow rates lower than 9 mgr/s, the humidifier containing metal foam at both sides has better performance. At dry side inlet temperatures lower than 303 K, humidifier containing metal foam at wet side has better performance and at temperatures higher than 303 K, humidifier containing metal foam at both sides has better performance

  20. Metallized polymeric foam material

    Science.gov (United States)

    Birnbaum, B. A.; Bilow, N.

    1974-01-01

    Open-celled polyurethane foams can be coated uniformly with thin film of metal by vapor deposition of aluminum or by sensitization of foam followed by electroless deposition of nickel or copper. Foam can be further processed to increase thickness of metal overcoat to impart rigidity or to provide inert surface with only modest increase in weight.

  1. Structural assessment of metal foam using combined NDE and FEA

    Science.gov (United States)

    Ghosn, Louis J.; Abdul-Aziz, Ali; Young, Philippe G.; Rauser, Richard W.

    2005-05-01

    Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a high fidelity finite element analysis is conducted on as fabricated metal foam microstructures, to compare the calculated mechanical properties with the idealized theory. The high fidelity geometric models for the FEA are generated using series of 2D CT scans of the foam structure to reconstruct the 3D metal foam geometry. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile, compressive, and shear mechanical properties are deduced from the FEA model and compared with the theoretical values. The combined NDE/FEA provided insight in the variability of the mechanical properties compared to idealized theory.

  2. Development of the smooth muscle foam cell: uptake of macrophage lipid inclusions.

    OpenAIRE

    Wolfbauer, G; Glick, J M; Minor, L K; Rothblat, G H

    1986-01-01

    A possible mechanism for the formation of smooth muscle foam cells in the atherosclerotic lesion was explored. Cultured macrophages (J774 cell line) were induced to form cytoplasmic cholesteryl ester inclusions by exposure to acetylated low density lipoprotein in the presence of cholesterol-rich phospholipid dispersions. The macrophages were disrupted by brief sonication, and the inclusions were isolated by flotation. When these inclusions were placed in direct contact with cultured smooth mu...

  3. Mechanical Properties of 17-4PH Stainless Steel Foam Panels

    Science.gov (United States)

    Raj, S. V.; Ghosn, L. J.; Lerch, B. a.; Hebsur, M.; Cosgriff, L. M.; Fedor, J.

    2007-01-01

    Rectangular 17-4PH stainless steel sandwiched foam panels were fabricated using a commercial manufacturing technique by brazing two sheets to a foam core. Microstructural observations and ultrasonic nondestructive evaluation of the panels revealed large variations in the quality of the brazed areas from one panel to the next as well as within the same panel. Shear tests conducted on specimens machined from the panels exhibited failures either in the brazed region or in the foam core for the poorly brazed and well-brazed samples, respectively. Compression tests were conducted on the foam cores to evaluate their elastic and plastic deformation behavior. These data were compared with published data on polymeric and metallic foams, and with theoretical deformation models proposed for open cell foams.

  4. Prevalence of Foam Cells and Helper-T cells in Atherosclerotic Plaques of Korean Patients with Carotid Atheroma

    OpenAIRE

    Lee, Won-Ha; Ko, Young-Hyeh; Kim, Dong-Ik; Lee, Byung-Boong; Park, Jeong-Euy

    2000-01-01

    Background Inflammation and activation of immune cells have important roles in the pathogenesis of atherosclerosis. We analyzed the involvement of various immune cells in the pathogenesis of atherosclerosis. Methods We investigated the presence of foam cells, lymphocytes and killer cells in 11 atherosclerotic plaque specimens removed from Korean patients who underwent carotid endoarterectomy. Atherosclerotic plaques were analyzed by immunohistochemistry using monoclonal antibody specific to f...

  5. On the random-based closed-cell metal foam modeling and its behavior in laser forming process

    Science.gov (United States)

    Roohi, Amir H.; Naeini, H. Moslemi; Gollo, M. Hoseinpour; Soltanpour, M.; Abbaszadeh, M.

    2015-09-01

    Metal foams are a new material category that, in the recent decade, are excessively used because of their good physical and mechanical properties such as low density and high stiffness. Regarding to their importance in engineering and other applications, modeling of metal foams are being studied and limited investigations have been carried out. The aim of this study is to develop a novel method to model the closed-cell metal foams. Closer modeling of foam sheets, which has an amorphous structure, are achieved by subtracting spheres with a random spatial position and random radius from an initial sheet rather than repeating a unit cell. In this article, the geometric properties of the closed-cell model is compared with the real foam. Also, finite element analysis of the laser forming process of the modeled foam is carried out. The effects of three geometrical parameters on bending angle is investigated. Both geometric comparison and FE validation shows a close agreement between numerical and actual results. Results show that relative density of the foam has the most effect and the mean cell size has the least effect on final bending angle.

  6. Effects of heat treatment on dynamic compressive properties and energy absorption characteristics of open-cell aluminum alloy foams

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The effects of heat treatment on the dynamic compressive properties and energy absorption characteristics of open cell aluminum alloy foams (Al-Mg-Si alloy foam and Al-Cu-Mg alloy foam) produced by infiltrating process were studied. Two kinds of heat treatment were exploited: age-hardening and solution heat treating plus age-hardening (T6). The split Hopkinson pressure bar (SHPB)was used for high strain rate compression test. The results show that both age-hardened and T6-strengthened foams exhibit improved compression strength and shortened plateau region compared with tnat of foams in as-fabricated state under high strain rate compression,and the energy absorption capacity is also influenced significantly by heat treatment. It is worthy to note that omitting the solution treating can also improve the strength and energy absorbed much.

  7. Mipu1 overexpression protects macrophages from oxLDL-induced foam cell formation and cell apoptosis.

    Science.gov (United States)

    Qu, Shun-Lin; Fan, Wen-Jing; Zhang, Chi; Guo, Fang; Han, Dan; Pan, Wen-Jun; Li, Wei; Feng, Da-Ming; Jiang, Zhi-Sheng

    2014-12-01

    Mipu1 (myocardial ischemic preconditioning upregulated protein 1) is a novel N-terminal Kruppel-associated box (KRAB)/C2H2 zinc finger superfamily protein, that displays a powerful effect in protecting H9c2 cells from oxidative stress-induced cell apoptosis. The present study aims to investigate the effect of Mipu1 overexpression on oxidized low-density lipoprotein (oxLDL)-induced foam cell formation, cell apoptosis, and its possible mechanisms. New Zealand healthy rabbits were used to establish atherosclerosis model, and serum levels of triglycerides, total cholesterol, high-density lipoprotein cholesterol, and low-density lipoprotein cholesterol were detected by an automatic biochemical analyzer. Sudan IV staining was used to detect atherosclerotic lesions. The RAW264.7 macrophage cell line was selected as the experimental material. Oil red O staining, high-performance liquid chromatography, and Dil-labeled lipoprotein were used to detect cholesterol accumulation qualitatively and quantitatively, respectively. Flow cytometry was used to determine cell apoptosis. Real-time quantitative polymerase chain reaction (PCR) was used to detect the mRNA expression of the main proteins that are associated with the transport of cholesterol, such as ABCA1, ABCG1, SR-BI, and CD36. Western blot analysis was used to detect the protein expression of Mipu1. There were atherosclerotic lesions in the high-fat diet group with Sudan IV staining. High-fat diet decreased Mipu1 expression and increased CD36 expression significantly at the 10th week compared with standard-diet rabbits. Mipu1 overexpression decreased oxLDL-induced cholesterol accumulation, oxLDL uptake, cell apoptosis, and cleaved caspase-3. Mipu1 overexpression inhibited the oxLDL-induced CD36 mRNA and protein expression, but it did not significantly inhibit the mRNA expression of ABCA1, ABCG1, and SR-BI. Mipu1 overexpression inhibits oxLDL-induced foam cell formation and cell apoptosis. Mipu1 overexpression reduces the

  8. microRNA-150 inhibits the formation of macrophage foam cells through targeting adiponectin receptor 2.

    Science.gov (United States)

    Li, Jing; Zhang, Suhua

    2016-08-01

    Transformation of macrophages into foam cells plays a critical role in the pathogenesis of atherosclerosis. The aim of this study was to determine the expression and biological roles of microRNA (miR)-150 in the formation of macrophage foam cells and to identify its functional target(s). Exposure to 50 μg/ml oxidized low-density lipoprotein (oxLDL) led to a significant upregulation of miR-150 in THP-1 macrophages. Overexpression of miR-150 inhibited oxLDL-induced lipid accumulation in THP-1 macrophages, while knockdown of miR-150 enhanced lipid accumulation. apoA-I- and HDL-mediated cholesterol efflux was increased by 66% and 43%, respectively, in miR-150-overexpressing macrophages relative to control cells. In contrast, downregulation of miR-150 significantly reduced cholesterol efflux from oxLDL-laden macrophages. Bioinformatic analysis and luciferase reporter assay revealed adiponectin receptor 2 (AdipoR2) as a direct target of miR-150. Small interfering RNA-mediated downregulation of AdipoR2 phenocopied the effects of miR-150 overexpression, reducing lipid accumulation and facilitating cholesterol efflux in oxLDL-treated THP-1 macrophages. Knockdown of AdipoR2 induced the expression of proliferator-activated receptor gamma (PPARγ), liver X receptor alpha (LXRα), ABCA1, and ABCG1. Moreover, pharmacological inhibition of PPARγ or LXRα impaired AdipoR2 silencing-induced upregulation of ABCA1 and ABCG1. Taken together, our results indicate that miR-150 can attenuate oxLDL-induced lipid accumulation in macrophages via promotion of cholesterol efflux. The suppressive effects of miR-150 on macrophage foam cell formation are mediated through targeting of AdipoR2. Delivery of miR-150 may represent a potential approach to prevent macrophage foam cell formation in atherosclerosis. PMID:27216461

  9. Zirconium oxide ceramic foam: a promising supporting biomaterial for massive production of glial cell line-derived neurotrophic factor*

    OpenAIRE

    Liu, Zhong-Wei; Li, Wen-qiang; Wang, Jun-kui; Ma, Xian-cang; Liang, Chen; Liu, Peng; Chu, Zheng; Dang, Yong-hui

    2014-01-01

    This study investigated the potential application of a zirconium oxide (ZrO2) ceramic foam culturing system to the production of glial cell line-derived neurotrophic factor (GDNF). Three sets of ZrO2 ceramic foams with different pore densities of 10, 20, and 30 pores per linear inch (PPI) were prepared to support a 3D culturing system. After primary astrocytes were cultured in these systems, production yields of GDNF were evaluated. The biomaterial biocompatibility, cell proliferation and act...

  10. C-Reactive Protein-Bound Enzymatically Modified Low-Density Lipoprotein Does Not Transform Macrophages into Foam Cells1

    OpenAIRE

    Singh, Sanjay K.; Suresh, Madathilparambil V.; Prayther, Deborah C; Moorman, Jonathan P.; Rusiñol, Antonio E.; Agrawal, Alok

    2008-01-01

    The formation of low-density lipoprotein (LDL) cholesterol-loaded macrophage foam cells contributes to the development of atherosclerosis. C-reactive protein (CRP) binds to atherogenic forms of LDL, but the role of CRP in foam cell formation is unclear. In this study, we first explored the binding site on CRP for enzymatically modified LDL (E-LDL), a model of atherogenic LDL to which CRP binds. As reported previously, phosphocholine (PCh) inhibited CRP-E-LDL interaction, indicating the involv...

  11. Paraoxonases 1, 2, and 3, oxidative stress, and macrophage foam cell formation during atherosclerosis development.

    Science.gov (United States)

    Aviram, Michael; Rosenblat, Mira

    2004-11-01

    Paraoxonases PON1 and PON3, which are both associated in serum with HDL, protect the serum lipids from oxidation, probably as a result of their ability to hydrolyze specific oxidized lipids. The activity of HDL-associated PON1 seems to involve an activity (phospholipase A2-like activity, peroxidase-like activity, lactonase activity) which produces LPC. To study the possible role of PON1 in macrophage foam cell formation and atherogenesis we used macrophages from control mice, from PON1 knockout mice, and from PON1 transgenic mice. Furthermore, we analyzed PON1-treated macrophages and PON1-transfected cells to demonstrate the contribution of PON1 to the attenuation of macrophage cholesterol and oxidized lipid accumulation and foam cell formation. PON1 was shown to inhibit cholesterol influx [by reducing the formation of oxidized LDL (Ox-LDL), increasing the breakdown of specific oxidized lipids in Ox-LDL, and decreasing macrophage uptake of Ox-LDL]. PON1 also inhibits cholesterol biosynthesis and stimulates HDL-mediated cholesterol efflux from macrophages. PON2 and PON3 protect against oxidative stress, with PON2 acting mainly at the cellular level. Whereas serum PON1 and PON3 were inactivated under oxidative stress, macrophage PON2 expression and activity were increased under oxidative stress, probably as a compensatory mechanism against oxidative stress. Intervention to increase the paraoxonases (cellular and humoral) by dietary or pharmacological means can reduce macrophage foam cell formation and attenuate atherosclerosis development. PMID:15454271

  12. Oleic acid induces smooth muscle foam cell formation and enhances atherosclerotic lesion development via CD36

    Directory of Open Access Journals (Sweden)

    Tang Bing

    2011-04-01

    Full Text Available Abstract Background Elevated plasma free fatty acid (FFA levels have been linked to the development of atherosclerosis. However, how FFA causes atherosclerosis has not been determined. Because fatty acid translocase (FAT/CD36 is responsible for the uptake of FFA, we hypothesized that the atherogenic effects of FFA may be mediated via CD36. Results We tested this hypothesis using cultured rat aortic smooth muscle cells (SMCs treated with oleic acid (OA. We found that OA induces lipid accumulation in SMCs in a dose dependent manner. Rat aortic SMCs treated for 48 hours with OA (250 μmol/L became foam cells based on morphological (Oil Red O staining and biochemical (5 times increase in cellular triglyceride criteria. Moreover, specific inhibition of CD36 by sulfo-N-succinimidyl oleate significantly attenuated OA induced lipid accumulation and foam cell formation. To confirm these results in vivo, we used ApoE-deficient mice fed with normal chow (NC, OA diet, NC plus lipolysis inhibitor acipimox or OA plus acipimox. OA-fed mice showed increased plasma FFA levels and enhanced atherosclerotic lesions in the aortic sinus compared to the NC group (both p 5 μm2 vs. OA plus acipimox: 2.60 ± 0.10 ×105 μm2, p p Conclusions These findings suggest that OA induces smooth muscle foam cell formation and enhances atherosclerotic lesions in part though CD36. Furthermore, these findings provide a novel model for the investigation of atherosclerosis.

  13. Growth and by-product profiles of Kluyveromyces marxianus cells immobilized in foamed alginate.

    Science.gov (United States)

    Wilkowska, Agnieszka; Kregiel, Dorota; Guneser, Onur; Karagul Yuceer, Yonca

    2015-01-01

    The aim of this research was to study how the yeast cell immobilization technique influences the growth and fermentation profiles of Kluyveromyces marxianus cultivated on apple/chokeberry and apple/cranberry pomaces. Encapsulation of the cells was performed by droplet formation from a foamed alginate solution. The growth and metabolic profiles were evaluated for both free and immobilized cells. Culture media with fruit waste produced good growth of free as well as immobilized yeast cells. The fermentation profiles of K. marxianus were different with each waste material. The most varied aroma profiles were noted for immobilized yeast cultivated on apple/chokeberry pomace. PMID:25277269

  14. Novel TRIP-steel/Mg-PSZ composite-open cell foam structures for energy absorption

    Energy Technology Data Exchange (ETDEWEB)

    Aneziris, Christos G.; Berek, Harry; Hasterok, Manuel [Institute of Ceramic, Glass and Construction Materials, Technische Universitaet Bergakademie Freiberg (Germany); Biermann, Horst; Wolf, Stefan; Krueger, Lutz [Institute of Materials Engineering, Technische Universitaet Bergakademie Freiberg (Germany)

    2010-03-15

    Porous materials have received extensive attention for energy absorption in the last years. In terms of this study austenitic TRIP-steel/Mg-PSZ composite-open cell foam structures are formed based on replicas using open-celled polyurethane foam as a skeleton with and without a supporting dense face (jacket) coating. Their compression strength as well as their specific energy absorption SEA has been registered as a function of the compressive strain. The zirconia addition has reinforced the composite material with the face coating up to a compressive strain of 50%. The stress-induced martensitic transformation of partially stabilized zirconia phases has been investigated as a function of the compressive strain by EBSD. The zirconia phase transformation is triggered already at low compressive strains below 2%. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  15. Human macrophage foam cells degrade atherosclerotic plaques through cathepsin K mediated processes

    DEFF Research Database (Denmark)

    Barascuk, Natasha; Skjøt-Arkil, Helene; Register, Thomas C; Larsen, Lise; Byrjalsen, Inger; Christiansen, Claus; Karsdal, Morten A

    2010-01-01

    BACKGROUND: Proteolytic degradation of Type I Collagen by proteases may play an important role in remodeling of atherosclerotic plaques, contributing to increased risk of plaque rupture.The aim of the current study was to investigate whether human macrophage foam cells degrade the extracellular...... matrix (ECM) of atherosclerotic plaques by cathepsin K mediated processes. METHODS: We 1) cultured human macrophages on ECM and measured cathepsin K generated fragments of type I collagen (C-terminal fragments of Type I collagen (CTX-I) 2) investigated the presence of CTX-I in human coronary arteries and......-I in areas of intimal hyperplasia and in shoulder regions of advanced plaques. Treatment of human monocytes with M-CSF or M-CSF+LDL generated macrophages and foam cells producing CTX-I when cultured on type I collagen enriched matrix. Circulating levels of CTX-I were not significantly different in...

  16. Manufacture of cordierite foams by direct foaming

    OpenAIRE

    Silva, Elisabete Ribeiro; N. Correia; Silva, J. M.; Oliveira, F. A. Costa; Ribeiro, F. R. M. C.; Bordalo, J. C.; Ribeiro, M.F.

    2007-01-01

    Open cell cordiereti fosms were prepared by a direct foaming two-component polyurethane (PUR)/ceramic system. Throught optimization of several experimental parameters such as contents of catalysts and ceramic cordiereti precursor, as well as plasticizer presence, foams with porosites 85-95&% and densities ranging from 130-410 kg/m3 were obtained. Thse foams characteristics make them attractive to be used as catalyst supports. The new two-component PUR/ceramics system developped allows the hig...

  17. Phage Display Identification of CD100 in Human Atherosclerotic Plaque Macrophages and Foam Cells

    OpenAIRE

    Luque, Maria Carolina Aquino; Gutierrez, Paulo Sampaio; Debbas, Victor; Martins, Waleska Kerllen; Puech-Leao, Pedro; Porto, Georgia; Coelho, Verônica; Boumsell, Laurence; Kalil, Jorge; Stolf, Beatriz

    2013-01-01

    Atherosclerosis is a complex disease in which vessels develop plaques comprising dysfunctional endothelium, monocyte derived lipid laden foam cells and activated lymphocytes. Considering that humans and animal models of the disease develop quite distinct plaques, we used human plaques to search for proteins that could be used as markers of human atheromas. Phage display peptide libraries were probed to fresh human carotid plaques, and a bound phage homologous to plexin B1, a high affinity rec...

  18. Porous, Ventricular Extracellular Matrix-Derived Foams as a Platform for Cardiac Cell Culture

    OpenAIRE

    Russo, Valerio; Omidi, Ehsan; Samani, Abbas; Hamilton, Andrew; Flynn, Lauren E.

    2015-01-01

    Abstract To more closely mimic the native cellular microenvironment, 3D scaffolds derived from the extracellular matrix (ECM) are being developed as alternatives to conventional 2D culture systems. In the present study, we established methods to fabricate nonchemically cross-linked 3D porous foams derived entirely from decellularized porcine left ventricle (DLV) for use as an in vitro cardiac cell culture platform. Furthermore, we explored the effects of physically preprocessing the DLV throu...

  19. Foam Micromechanics

    Energy Technology Data Exchange (ETDEWEB)

    Kraynik, A.M.; Neilsen, M.K.; Reinelt, D.A.; Warren, W.E.

    1998-11-03

    Foam evokes many different images: waves breaking at the seashore, the head on a pint of Guinness, an elegant dessert, shaving, the comfortable cushion on which you may be seated... From the mundane to the high tech, foams, emulsions, and cellular solids encompass a broad range of materials and applications. Soap suds, mayonnaise, and foamed polymers provide practical motivation and only hint at the variety of materials at issue. Typical of mukiphase materiaIs, the rheoIogy or mechanical behavior of foams is more complicated than that of the constituent phases alone, which may be gas, liquid, or solid. For example, a soap froth exhibits a static shear modulus-a hallmark of an elastic solid-even though it is composed primarily of two Newtonian fluids (water and air), which have no shear modulus. This apparent paradox is easily resolved. Soap froth contains a small amount of surfactant that stabilizes the delicate network of thin liq- uid films against rupture. The soap-film network deforms in response to a macroscopic strain; this increases interracial area and the corresponding sur- face energy, and provides the strain energy of classical elasticity theory [1]. This physical mechanism is easily imagined but very challenging to quantify for a realistic three-dimensional soap froth in view of its complex geome- try. Foam micromechanics addresses the connection between constituent properties, cell-level structure, and macroscopic mechanical behavior. This article is a survey of micromechanics applied to gas-liquid foams, liquid-liquid emulsions, and cellular solids. We will focus on static response where the foam deformation is very slow and rate-dependent phenomena such as viscous flow can be neglected. This includes nonlinear elasticity when deformations are large but reversible. We will also discuss elastic- plastic behavior, which involves yield phenomena. Foam structures based on polyhedra packed to fill space provide a unify- ing geometrical theme. Because a two

  20. Experimental Study on Sandwich Bridge Decks with GFRP Face Sheets and a Foam-Web Core Loaded under Two-Way Bending

    Directory of Open Access Journals (Sweden)

    Ruili Huo

    2015-01-01

    Full Text Available In recent years, the sandwich bridge decks with GFRP face sheets and light weight material core have been widely used in the world due to their advantages of low cost, high strength to weight ratios, and corrosion resisting. However, as the bridge decks, most of them are used in foot bridges rather than highway bridges because the ultimate bending strength and initial bending stiffness are relatively low. To address this issue and expand the scope of use, a simple and innovative sandwich bridge deck with GFRP face sheets and a foam-web core, manufactured by vacuum assisted resin infusion process, is developed. An experimental study was carried out to validate the effectiveness of this panel for increasing the ultimate bending strength and initial bending stiffness under two-way bending. The effects of face sheet thickness, foam density, web thickness, and web spacing on displacement ductility and energy dissipation were also investigated. Test results showed that, compared to the normal foam-core sandwich decks, an average approximately 657.1% increase in the ultimate bending strength can be achieved. Furthermore, the bending stiffness, displacement ductility, and energy dissipation can be enhanced by increasing web thickness, web height, and face sheet thickness or decreasing web spacing.

  1. Metal foams application to enhance cooling of open cathode polymer electrolyte membrane fuel cells

    Science.gov (United States)

    Sajid Hossain, Mohammad; Shabani, Bahman

    2015-11-01

    Conventional channel flow fields of open cathode Polymer Electrolyte Membrane Fuel Cells (PEMFCs) introduce some challenges linked to humidity, temperature, pressure and oxygen concentration gradients along the conventional flow fields that reduce the cell performance. According to previous experimental reports, with conventional air flow fields, hotspot formation due to water accumulation in Gas Diffusion Layer (GDL) is common. Unlike continuous long flow passages in conventional channels, metal foams provide randomly interrupted flow passages. Re-circulation of fluid, due to randomly distributed tortuous ligaments, enhances temperature and humidity uniformity in the fluid. Moreover, the higher electrical conductivity of metal foams compared to non-metal current collectors and their very low mass density compared to solid metal materials are expected to increase the electrical performance of the cell while significantly reducing its weight. This article reviews the existing cooling systems and identifies the important parameters on the basis of reported literature in the air cooling systems of PEMFCs. This is followed by investigating metal foams as a possible option to be used within the structure of such PEMFCs as an option that can potentially address cooling and flow distribution challenges associated with using conventional flow channels, especially in air-cooled PEMFCs.

  2. Novel technique for generating macrophage foam cells for in vitro reverse cholesterol transport studies.

    Science.gov (United States)

    Sengupta, Bhaswati; Narasimhulu, Chandrakala Aluganti; Parthasarathy, Sampath

    2013-12-01

    Generation of foam cells, an essential step for reverse cholesterol transport studies, uses the technique of receptor-dependent macrophage loading with radiolabeled acetylated LDL. In this study, we used the ability of a biologically relevant detergent molecule, lysophosphatidylcholine (lyso-PtdCho), to form mixed micelles with cholesterol or cholesteryl ester (CE) to generate macrophage foam cells. Fluorescent or radiolabeled cholesterol/lyso-PtdCho mixed micelles were prepared and incubated with RAW 264.7 or mouse peritoneal macrophages. Results showed that such micelles were quite stable at 4°C and retained the solubilized cholesterol during one month of storage. Macrophages incubated with cholesterol or CE (unlabeled, fluorescently labeled, or radiolabeled)/lyso-PtdCho mixed micelles accumulated CE as documented by microscopy, lipid staining, labeled oleate incorporation, and by TLC. Such foam cells unloaded cholesterol when incubated with HDL but not with oxidized HDL. We propose that stable cholesterol or CE/lyso-PtdCho micelles would offer advantages over existing methods. PMID:24115226

  3. Effective Thermal Conductivity of Open Cell Polyurethane Foam Based on the Fractal Theory

    Directory of Open Access Journals (Sweden)

    Kan Ankang

    2013-01-01

    Full Text Available Based on the fractal theory, the geometric structure inside an open cell polyurethane foam, which is widely used as adiabatic material, is illustrated. A simplified cell fractal model is created. In the model, the method of calculating the equivalent thermal conductivity of the porous foam is described and the fractal dimension is calculated. The mathematical formulas for the fractal equivalent thermal conductivity combined with gas and solid phase, for heat radiation equivalent thermal conductivity and for the total thermal conductivity, are deduced. However, the total effective heat flux is the summation of the heat conduction by the solid phase and the gas in pores, the radiation, and the convection between gas and solid phase. Fractal mathematical equation of effective thermal conductivity is derived with fractal dimension and vacancy porosity in the cell body. The calculated results have good agreement with the experimental data, and the difference is less than 5%. The main influencing factors are summarized. The research work is useful for the enhancement of adiabatic performance of foam materials and development of new materials.

  4. The influence of polyol type on cell geometry and the thermal stability of polyurethane foams

    Directory of Open Access Journals (Sweden)

    Prendžov Slobodan J.

    2006-01-01

    Full Text Available The aim of this study was to examine the influence of substituting defined amounts of polyol Voranol 3322 by polyol Voranol CP 1055 on the cell geometry and thermal stability of the synthesized flexible polyurethane foams. The influence of the amount of antipyrene on the cell geometry and their thermal stability was also investigated. The following components were used in the synthesis of the polyurethanes: a mixture of two polyols (Voranol 3322 with the hydroxyl number 47 mg KOH/g, mean molecular mass 3400 and Voranol CP 1055 with the hydroxyl number 156 mg KOH/g, mean molecular mass 1000, toluene discarnate as the isocyanate component, a combination of an organic-metallic compound and a tertiary amine as catalysts, surfactant and water as the coreactant. The thermal stability was determined by thermogravimetric analysis (in a nitrogen atmosphere. The cell geometry was analyzed by optical microscopy. Examination of the cell geometry revealed different cell shapes. The form factor as an indicator of cell deviation from spherical shape increased (more round forms were observed with increasing amount of Voranol CP 1055. The TG examination showed that specimens with 6 and 8 g of Voranol 3322 substituted by Voranol CP 1055 completely degraded at 350 °C, while foams with 10 and 12 g of Voranol 3322 substituted by Voranol CP 1055 displayed lower mass loss at higher temperatures and had residual masses of 46 % and 43 % at 600°C respectively. The addition of antipyrene in an amount of 1% (based on the amount of polyol contributed to improved thermal stability, no visible color change of the specimen tested at 210°C for 40 minutes, and to rounder cell forms. Considering the obtained results it can be concluded that an increase in the amount of Voranol CP 1055 yielded more spherically shaped cells and better thermal stability of the synthesized flexible polyurethane foams. The addition of antipyrene improves the thermal stability and the cell geometry.

  5. A constitutive model for the compressive response of metallic closed-cell foams including micro-inertia effects

    Science.gov (United States)

    Barthélémy, Romain; Jacques, Nicolas; Vermeersch, François; Kerampran, Steven

    2015-09-01

    Metallic foams have known a keen interest in the last decades. Their ability to undergo very large deformations while transmitting low stress levels make them capable of performing functions of protective layers against intense loadings and of energy absorbers, for instance. The behaviour of metal foams varies considerably between quasi-static and dynamic regimes. Those differences can be linked to the strain-rate sensitivity of the skeleton material and to micro-inertial effects (induced by the crushing of the foam cells). In the present work, a micromechanical model has been developed to take into account micro-inertia effects on the macroscopic behaviour of closed-cell foams under dynamic loading conditions. The proposed modelling is based on the dynamic homogenisation procedure introduced by Molinari and Mercier (J. Mech. Phys. Solids 49 (2001) 1497-1516). Within this framework, the macrostress is the sum of two terms. The first one is a static stress, that can be described with any existing model of metal foam. The second contribution is a dynamic stress related to micro-inertia effects. Considering an initially spherical shell as a Representative Volume Element (RVE) of the foam material, a closed-form expression of the dynamic stress was obtained. The proposed modelling was applied to shock propagation in aluminium foams (it should however be noted that the present theory is not restricted to uniaxial deformation but can be applied to arbitrary loadings). From experimental data of the literature, it is observed that incorporating micro-inertia effects allows one to achieve a better description of the foam shock response. This indicates that micro-inertia may have a significant influence on the dynamic behaviour of metallic foams.

  6. A constitutive model for the compressive response of metallic closed-cell foams including micro-inertia effects

    Directory of Open Access Journals (Sweden)

    Barthélémy Romain

    2015-01-01

    Full Text Available Metallic foams have known a keen interest in the last decades. Their ability to undergo very large deformations while transmitting low stress levels make them capable of performing functions of protective layers against intense loadings and of energy absorbers, for instance. The behaviour of metal foams varies considerably between quasi-static and dynamic regimes. Those differences can be linked to the strain-rate sensitivity of the skeleton material and to micro-inertial effects (induced by the crushing of the foam cells. In the present work, a micromechanical model has been developed to take into account micro-inertia effects on the macroscopic behaviour of closed-cell foams under dynamic loading conditions. The proposed modelling is based on the dynamic homogenisation procedure introduced by Molinari and Mercier (J. Mech. Phys. Solids 49 (2001 1497–1516. Within this framework, the macrostress is the sum of two terms. The first one is a static stress, that can be described with any existing model of metal foam. The second contribution is a dynamic stress related to micro-inertia effects. Considering an initially spherical shell as a Representative Volume Element (RVE of the foam material, a closed-form expression of the dynamic stress was obtained. The proposed modelling was applied to shock propagation in aluminium foams (it should however be noted that the present theory is not restricted to uniaxial deformation but can be applied to arbitrary loadings. From experimental data of the literature, it is observed that incorporating micro-inertia effects allows one to achieve a better description of the foam shock response. This indicates that micro-inertia may have a significant influence on the dynamic behaviour of metallic foams.

  7. Sound absorption and insulation property of closed-cell aluminum foam

    Institute of Scientific and Technical Information of China (English)

    YU Hai-jun; LI Bing; YAO Guang-chun; WANG Xiao-lin; LUO Hong-jie; LIU Yi-han

    2006-01-01

    The closed-cell aluminum foams (specimen p=0.31 g/cm3, diameter of 100 mm, and thickness of 20 mm for sound absorption testing; specimen p=0.51 g/cm3, length of 1 240 mm, width of 1 100 mm, and thickness of 30 mm for sound insulation testing) were prepared by the method of molten body transitional foaming process. Its sound absorption property under frequency of 160-2 000 Hz and the sound insulation property under frequency of 100-4 000 Hz were tested. The sound absorption results show that the sound absorption property is much better under middle frequencies than that under low and high frequencies. The sound absorption coefficient climbs when frequency increases from 160 Hz to 800 Hz and then drops when frequency is increased from 800 Hz to 2 000 Hz. The function of the sound absorption mainly depends on the Helmholtz resonator, the microphone as well as cracks of closed-cell aluminum foam. The sound insulation experiments show that the sound reduction index (R) is small under low frequencies, and large under high frequencies; the weighted sound reduction index (Rw) and the highest sound reduction index (R)can reach around 30.8 dB and 43 dB, respectively.

  8. Dynamic Crushing Response of Closed-cell Aluminium Foam at Variable Strain Rates

    Science.gov (United States)

    Islam, M. A.; Kader, M. A.; Escobedo, J. P.; Hazell, P. J.; Appleby-Thomas, G. J.; Quadir, M. Z.

    2015-06-01

    The impact response of aluminium foams is essential for assessing their crashworthiness and energy absorption capacity for potential applications. The dynamic compactions of closed-cell aluminium foams (CYMAT) have been tested at variable strain rates. Microstructural characterization has also been carried out. The low strain rate impact test has been carried out using drop weight experiments while the high strain compaction test has been carried out via plate impact experiments. The post impacted samples have been examined using optical and electron microscopy to observe the microstructural changes during dynamic loading. This combination of dynamic deformation during impact and post impact microstructural analysis helped to evaluate the pore collapse mechanism and impact energy absorption characteristics.

  9. A combined NDE/FEA approach to evaluate the structural response of a metal foam

    Science.gov (United States)

    Ghosn, Louis J.; Abdul-Aziz, Ali; Raj, Sai V.; Rauser, Richard W.

    2007-04-01

    Metal foams are expected to find use in structural applications where weight is of particular concern, such as space vehicles, rotorcraft blades, car bodies or portable electronic devices. The obvious structural application of metal foam is for light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The stiffness of the sandwich structure is increased by separating the two face sheets by a light weight metal foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. Since the face sheets carry the applied in-plane and bending loads, the sandwich architecture is a viable engineering concept. However, the metal foam core must resist transverse shear loads and compressive loads while remaining integral with the face sheets. Challenges relating to the fabrication and testing of these metal foam panels remain due to some mechanical properties falling short of their theoretical potential. Theoretical mechanical properties are based on an idealized foam microstructure and assumed cell geometry. But the actual testing is performed on as fabricated foam microstructure. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans. The series of the 2D images are assembled to construct a high precision solid model capturing all the fine details within the metal foam as detected by the CT scanning technique. Moreover, a finite element analysis is then performed on as fabricated metal foam microstructures, to calculate the foam mechanical properties with the idealized theory. The metal foam material is an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. Tensile and compressive mechanical properties are deduced from the FEA model and compared with the theoretical values for three different foam densities. The combined NDE/FEA provided insight in the variability of

  10. Nicotinate-Curcumin Impedes Foam Cell Formation from THP-1 Cells through Restoring Autophagy Flux.

    Science.gov (United States)

    Gu, Hong-Feng; Li, Hai-Zhe; Tang, Ya-Ling; Tang, Xiao-Qing; Zheng, Xi-Long; Liao, Duan-Fang

    2016-01-01

    Our previous studies have indicated that a novel curcumin derivate nicotinate-curcumin (NC) has beneficial effects on the prevention of atherosclerosis, but the precise mechanisms are not fully understood. Given that autophagy regulates lipid metabolism, the present study was designed to investigate whether NC decreases foam cell formation through restoring autophagy flux in oxidized low-density lipoprotein (ox-LDL)-treated THP-1 cells. Our results showed that ox-LDL (100 μg/ml) was accumulated in THP-1 cells and impaired autophagy flux. Ox-LDL-induced impairment of autophagy was enhanced by treatment with the autophagy inhibitor chloroquine (CQ) and rescued by the autophagy inducer rapamycin. The aggregation of ox-LDL was increased by CQ, but decreased by rapamycin. In addition, colocalization of lipid droplets with LC3-II was remarkably reduced in ox-LDL group. In contrast, NC (10 μM) rescued the impaired autophagy flux by significantly increasing level of LC3-II, the number of autophagolysosomes, and the degradation of p62 in ox-LDL-treated THP-1 cells. Inhibition of the PI3K-Akt-mTOR signaling was required for NC-rescued autophagy flux. Notably, our results showed that NC remarkably promoted the colocalization of lipid droplets with autophagolysosomes, increased efflux of cholesterol, and reduced ox-LDL accumulation in THP-1 cells. However, treatment with 3-methyladenine (3-MA) or CQ reduced the protective effects of NC on lipid accumulation. Collectively, the findings suggest that NC decreases lipid accumulation in THP-1 cells through restoring autophagy flux, and further implicate that NC may be a potential therapeutic reagent to reverse atherosclerosis. PMID:27128486

  11. Nicotinate-Curcumin Impedes Foam Cell Formation from THP-1 Cells through Restoring Autophagy Flux

    Science.gov (United States)

    Gu, Hong-Feng; Li, Hai-Zhe; Tang, Ya-Ling; Tang, Xiao-Qing; Zheng, Xi-Long; Liao, Duan-Fang

    2016-01-01

    Our previous studies have indicated that a novel curcumin derivate nicotinate-curcumin (NC) has beneficial effects on the prevention of atherosclerosis, but the precise mechanisms are not fully understood. Given that autophagy regulates lipid metabolism, the present study was designed to investigate whether NC decreases foam cell formation through restoring autophagy flux in oxidized low-density lipoprotein (ox-LDL)-treated THP-1 cells. Our results showed that ox-LDL (100 μg/ml) was accumulated in THP-1 cells and impaired autophagy flux. Ox-LDL-induced impairment of autophagy was enhanced by treatment with the autophagy inhibitor chloroquine (CQ) and rescued by the autophagy inducer rapamycin. The aggregation of ox-LDL was increased by CQ, but decreased by rapamycin. In addition, colocalization of lipid droplets with LC3-II was remarkably reduced in ox-LDL group. In contrast, NC (10 μM) rescued the impaired autophagy flux by significantly increasing level of LC3-II, the number of autophagolysosomes, and the degradation of p62 in ox-LDL-treated THP-1 cells. Inhibition of the PI3K-Akt-mTOR signaling was required for NC-rescued autophagy flux. Notably, our results showed that NC remarkably promoted the colocalization of lipid droplets with autophagolysosomes, increased efflux of cholesterol, and reduced ox-LDL accumulation in THP-1 cells. However, treatment with 3-methyladenine (3-MA) or CQ reduced the protective effects of NC on lipid accumulation. Collectively, the findings suggest that NC decreases lipid accumulation in THP-1 cells through restoring autophagy flux, and further implicate that NC may be a potential therapeutic reagent to reverse atherosclerosis. PMID:27128486

  12. Relationship between Microcellular Foaming Injection Molding Process Parameters and Cell Size

    Institute of Scientific and Technical Information of China (English)

    HU Guang-hong; JIANG Chao-dong; CUI Zhen-shan

    2008-01-01

    In order to study the relationship between the main process parameters and the cell size, the mathematical model of cell growth of microcellular foaming injection process is built. Then numeric simulation is employed as experimental method, and the Taguchi method is used to analyze significance of effect of process parameters on the cell size. At last the process parameters are focused on melt temperature, injection time, mold temperature and pre- filled volume. The significance order from big to small of the effect of each process parameters on cell size is melt temperature, pre-filled volume, injection time, and mold temperature. On the basis of above research, the effect of each process parameter on cell size is further researched.Appropriate reduction of the melt temperature and increase of the we-filled volume can optimize the cell size effectively, while the effects of injection time and mold temperature on cell size are less significant.

  13. Hierarchical ZnO@MnO2 Core-Shell Pillar Arrays on Ni Foam for Binder-Free Supercapacitor Electrodes

    KAUST Repository

    Huang, Ming

    2015-01-01

    © 2014 Elsevier Ltd. All rights reserved. Hierarchical ZnO@MnO2 core-shell pillar arrays on Ni foam have been fabricated by a facile two-step hydrothermal approach and further investigated as the binder-free electrode for supercapacitors. The core-shell hybrid nanostructure is achieved by decorating ultrathin self-standing MnO2 nanosheets on ZnO pillar arrays grown radically on Nickel foam. This unique well-designed binder-free electrode exhibits a high specific capacitance (423.5 F g-1 at a current density of 0.5 A g-1), and excellent cycling stability (92% capacitance retention after 3000 cycles). The improved electrochemical results show that the ZnO@MnO2 core-shell nanostructure electrode is promising for high-performance supercapacitors. The facile design of the unique core-shell array architectures provides a new and effective approach to fabricate high-performance binder-free electrode for supercapacitors.

  14. Development of a Hopkinson Bar Apparatus for Testing Soft Materials: Application to a Closed-Cell Aluminum Foam

    Directory of Open Access Journals (Sweden)

    Marco Peroni

    2016-01-01

    Full Text Available An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general “soft” materials exhibit a series of peculiarities that make difficult the adoption of standard testing techniques for their high strain-rate characterization. This paper presents an innovative apparatus, where high strain-rate tests of metal foams or other soft materials can be performed by exploiting the operating principle of the Hopkinson bar methods. Using the pre-stress method to generate directly a long compression pulse (compared with traditional SHPB, a displacement of about 20 mm can be applied to the specimen with a single propagating wave, suitable for evaluating the whole stress-strain curve of medium-sized cell foams (pores of about 1–2 mm. The potential of this testing rig is shown in the characterization of a closed-cell aluminum foam, where all the above features are amply demonstrated.

  15. On the crush behavior of an ultra light multi-cell foam-filled composite structures for energy absorption: Part 1-Experimental

    International Nuclear Information System (INIS)

    In this paper the experimental works pertaining to the crash behavior and crash worthiness characteristics of a novel multi-cell cost-effective crash worthy composite sandwich structure are presented. All samples are based on the concept of the triple-layered foam-filled block, for example three polyurethane foam core sheets which are wrapped by reinforcement fibreglass woven fabric, that acts as the reinforcement face and meanwhile tie the foam layers and faces together, thus preventing catastrophic collapse under axial loading. The design, manufacturing and crush testing of rectangular blocks fabricated with and without trigger mechanism are described. Particular attention is paid on the analysis of the mechanism of the block axial collapse, emphasizing on the mechanisms related to the crash energy absorption during the compression of the composite blocks with and without the use of two types of collapse trigger mechanism. Experimental results indicate an efficient progressive failure mechanism with high values of crush force efficiency (CFE) and specific energy absorption (SEA). (author)

  16. High Temperature Alkaline Electrolysis Cells with Metal Foam Based Gas Diffusion Electrodes

    DEFF Research Database (Denmark)

    Chatzichristodoulou, Christodoulos; Allebrod, Frank; Mogensen, Mogens Bjerg

    2016-01-01

    Alkaline electrolysis cells operating at 250°C and 40 bar are able to convert electrical energy into hydrogen at very high efficiencies and power densities. In the present work we demonstrate the application of a PTFE hydrophobic network and Ag nanowires as oxygen evolution electrocatalyst in the...... metal foam based gas diffusion electrodes. A novel cell production method, based on tape casting and hot pressing, was developed which allows to increase the cell size from lab scale (1 cm2) to areas of 25 cm2 or larger. The thickness of the electrolyte matrix could be adjusted to only 200 μm, achieving...... novel cell concept promises more than a 10-fold improvement in power density, compared to conventional alkaline electrolysis cells, and thereby equivalent reduction in stack size and cost....

  17. Development of the smooth muscle foam cell: uptake of macrophage lipid inclusions.

    Science.gov (United States)

    Wolfbauer, G; Glick, J M; Minor, L K; Rothblat, G H

    1986-10-01

    A possible mechanism for the formation of smooth muscle foam cells in the atherosclerotic lesion was explored. Cultured macrophages (J774 cell line) were induced to form cytoplasmic cholesteryl ester inclusions by exposure to acetylated low density lipoprotein in the presence of cholesterol-rich phospholipid dispersions. The macrophages were disrupted by brief sonication, and the inclusions were isolated by flotation. When these inclusions were placed in direct contact with cultured smooth muscle cells, cellular uptake of the inclusions in a time- and dose-dependent manner was observed. Light and electron microscopy indicated the presence of lipid inclusions throughout the cytoplasm of the cells. Uptake of inclusion lipid by the smooth muscle cells was inhibited by several metabolic inhibitors, indicating that the process is dependent on metabolic activity. A modest but significant hydrolysis of the cholesteryl ester was observed, showing that the stored cholesteryl esters are metabolically available. PMID:3020555

  18. Metal-air cells comprising collapsible foam members and means for minimizing internal pressure buildup

    Science.gov (United States)

    Woodruff, Glenn (Inventor); Putt, Ronald A. (Inventor)

    1994-01-01

    This invention provides a prismatic zinc-air cell including, in general, a prismatic container having therein an air cathode, a separator and a zinc anode. The container has one or more oxygen access openings, and the air cathode is disposed in the container in gaseous communication with the oxygen access openings so as to allow access of oxygen to the cathode. The separator has a first side in electrolytic communication with the air cathode and a second side in electrolytic communication with the zinc anode. The separator isolates the cathode and the zinc anode from direct electrical contact and allows passage of electrolyte therebetween. An expansion chamber adjacent to the zinc anode is provided which accommodates expansion of the zinc anode during discharge of the cell. A suitable collapsible foam member generally occupies the expansion space, providing sufficient resistance tending to oppose movement of the zinc anode away from the separator while collapsing upon expansion of the zinc anode during discharge of the cell. One or more vent openings disposed in the container are in gaseous communication with the expansion space, functioning to satisfactorily minimize the pressure buildup within the container by venting gasses expelled as the foam collapses during cell discharge.

  19. Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation[S

    Science.gov (United States)

    Haka, Abigail S.; Barbosa-Lorenzi, Valéria C.; Lee, Hyuek Jong; Falcone, Domenick J.; Hudis, Clifford A.; Dannenberg, Andrew J.

    2016-01-01

    Many types of apoptotic cells are phagocytosed and digested by macrophages. Adipocytes can be hundreds of times larger than macrophages, so they are too large to be digested by conventional phagocytic processes. The nature of the interaction between macrophages and apoptotic adipocytes has not been studied in detail. We describe a cellular process, termed exophagy, that is important for macrophage clearance of dead adipocytes and adipose tissue homeostasis. Using mouse models of obesity, human tissue, and a cell culture model, we show that macrophages form hydrolytic extracellular compartments at points of contact with dead adipocytes using local actin polymerization. These compartments are acidic and contain lysosomal enzymes delivered by exocytosis. Uptake and complete degradation of adipocyte fragments, which are released by extracellular hydrolysis, leads to macrophage foam cell formation. Exophagy-mediated foam cell formation is a highly efficient means by which macrophages internalize large amounts of lipid, which may ultimately overwhelm the metabolic capacity of the macrophage. This process provides a mechanism for degradation of objects, such as dead adipocytes, that are too large to be phagocytosed by macrophages. PMID:27044658

  20. Exocytosis of macrophage lysosomes leads to digestion of apoptotic adipocytes and foam cell formation.

    Science.gov (United States)

    Haka, Abigail S; Barbosa-Lorenzi, Valéria C; Lee, Hyuek Jong; Falcone, Domenick J; Hudis, Clifford A; Dannenberg, Andrew J; Maxfield, Frederick R

    2016-06-01

    Many types of apoptotic cells are phagocytosed and digested by macrophages. Adipocytes can be hundreds of times larger than macrophages, so they are too large to be digested by conventional phagocytic processes. The nature of the interaction between macrophages and apoptotic adipocytes has not been studied in detail. We describe a cellular process, termed exophagy, that is important for macrophage clearance of dead adipocytes and adipose tissue homeostasis. Using mouse models of obesity, human tissue, and a cell culture model, we show that macrophages form hydrolytic extracellular compartments at points of contact with dead adipocytes using local actin polymerization. These compartments are acidic and contain lysosomal enzymes delivered by exocytosis. Uptake and complete degradation of adipocyte fragments, which are released by extracellular hydrolysis, leads to macrophage foam cell formation. Exophagy-mediated foam cell formation is a highly efficient means by which macrophages internalize large amounts of lipid, which may ultimately overwhelm the metabolic capacity of the macrophage. This process provides a mechanism for degradation of objects, such as dead adipocytes, that are too large to be phagocytosed by macrophages. PMID:27044658

  1. Analysis of the cell walls of ceramic foams by X-ray microtomography

    International Nuclear Information System (INIS)

    Full text: Ceramic foams have a wide range of applications (heat exchangers, liquid metal filters, porous electrodes, composite of rocket nozzles, etc.) due its properties, such as high melt temperature, high porosity, low thermal conductivity and low weight. Since the mechanical resistance of this kind of material is linked to its cell walls features, this research analyzed the cell walls thickness of silicon carbide (SiC) ceramic foams by X-ray microtomography. This technique is a powerful non destructive way to analyze the internal structure of any object, generating images (cross sections) by attenuation of the X-ray beam. The analyses of these images allow us to determine the samples structural parameters through specific software. The samples have pore densities of 30, 60 and 100 pore per inch (ppi). A Skyscan-1172 microtomography, operated at 50 kV high tension and 200 μA current was utilized for the measurements. The spatial resolution obtained was 24.8 μm and the measurement time was around 30 minutes for each sample. The analyses show that the cell walls of the 30 ppi sample have micropores. These micropores were observed at same images of 60 ppi cross sections too, but they were not observed at 100 ppi sample. Its probable that the cell walls of 100 ppi sample have micropores smaller than the resolution achieved. (author)

  2. Transient Receptor Potential Ankyrin 1 Channel Involved in Atherosclerosis and Macrophage-Foam Cell Formation

    Science.gov (United States)

    Zhao, Jin-Feng; Shyue, Song-Kun; Kou, Yu Ru; Lu, Tse-Min; Lee, Tzong-Shyuan

    2016-01-01

    Transient receptor potential ankyrin 1 channel (TRPA1) plays an important role in the pathogenesis of inflammatory diseases, yet its role and the underlying mechanism in atherosclerosis remain unclear. We aimed to investigate the role of TRPA1 in atherosclerosis and foam-cell formation in vivo in mice and in vitro in mouse macrophages. Histopathology was examined by hematoxylin and eosin staining, levels of cytokines and lipid profile were evaluated by assay kits, and protein expression was determined by western blot analysis. TRPA1 expression was increased in macrophage foam cells in atherosclerotic aortas of apolipoprotein E-deficient (apoE-/-) mice. Atherosclerotic lesions, hyperlipidemia and systemic inflammation were worsened with chronic administration of the TRPA1 channel antagonist HC030031 or genetic ablation of TRPA1 (TRPA1-/-) in apoE-/- mice. Treatment with allyl isothiocyanate (AITC, a TRPA1 agonist) retarded the progression of atherosclerosis in apoE-/- mice but not apoE-/-TRPA1-/- mice. Mouse macrophages showed oxidized low-density lipoprotein (oxLDL) activated TRPA1 channels. OxLDL-induced lipid accumulation of macrophages was exacerbated by HC030031 or loss of function of TRPA1. Inhibition of TRPA1 activity did not alter oxLDL internalization but impaired cholesterol efflux by downregulating the ATP-binding cassette transporters. Furthermore, tumor necrosis factor-α-induced inflammatory response was attenuated in AITC-activated macrophages. TRPA1 may be a pivotal regulator in the pathogenesis of atherosclerosis and cholesterol metabolism of macrophage foam cells.

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

    Science.gov (United States)

    Sun, Yi

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

  4. Foaming Behaviour, Structure, and Properties of Polypropylene Nanocomposites Foams

    Directory of Open Access Journals (Sweden)

    M. Antunes

    2010-01-01

    Full Text Available This work presents the preparation and characterization of compression-moulded montmorillonite and carbon nanofibre-polypropylene foams. The influence of these nanofillers on the foaming behaviour was analyzed in terms of the foaming parameters and final cellular structure and morphology of the foams. Both nanofillers induced the formation of a more isometric-like cellular structure in the foams, mainly observed for the MMT-filled nanocomposite foams. Alongside their crystalline characteristics, the nanocomposite foams were also characterized and compared with the unfilled ones regarding their dynamic-mechanical thermal behaviour. The nanocomposite foams showed higher specific storage moduli due to the reinforcement effect of the nanofillers and higher cell density isometric cellular structure. Particularly, the carbon nanofibre foams showed an increasingly higher electrical conductivity with increasing the amount of nanofibres, thus showing promising results as to produce electrically improved lightweight materials for applications such as electrostatic painting.

  5. Simulation of a three-point bending test on the isolated cell wall of aluminium foam

    Czech Academy of Sciences Publication Activity Database

    Doktor, T.; Kytýř, Daniel; Zlámal, Petr; Fíla, Tomáš; Koudelka_ml., Petr; Jiroušek, Ondřej

    Kippen: Civil-Comp Press, 2013 - (Topping, B.; Iványi, P.). (Civil-Comp Proceedings. 102). ISBN 978-1-905088-57-7. ISSN 1759-3433. [International Conference on Civil, Structural and Environmental Engineering Computing /14./. Cagliari (IT), 03.09.2013-06.09.2013] R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : aluminium foam * material identification * inverse finite element modeling * isolated cell-wall Subject RIV: JI - Composite Materials

  6. Open-Cell Aluminium Foams with Graded Coatings as Passively Controllable Energy Absorbers

    OpenAIRE

    Jung, Anne; Beex, Lars; Diebels, Stefan; Bordas, Stéphane

    2015-01-01

    Compared to most bulk materials, open-cell aluminium (Al) foams (OCAFs) are light-weight and can absorb a significant amount of energy in compression, e.g. during impact.When coatedwith nickel (Ni), OCAFs can absorb even more energy, making them more appropriate for impacts at higher velocities than uncoated OCAFs. When Ni-coated OCAFs experience low-velocity impact however, the stopping distance during the impact is small compared to that of uncoated OCAFs and hence, deceleration occurs fast...

  7. Extraction of uranyl nitrate from aqueous nitrate solutions by open cell polyurethane foam sponge (OCPUFS)

    International Nuclear Information System (INIS)

    The extraction of uranyl nitrate into open cell polyurethane foam sponge (OCPUFS) from aqueous solution, in the presence of salting agents, was examined. The extraction efficiency was observed to depend on the concentration of uranyl and nitrate ions. The charge of the cation was also found to influence the distribution ratio. The effect of the change in temperature and pH was also studied. The results are interpreted in terms of OCPUFS acting as a viscous organic ether of moderate dielectric constant. (author) 14 refs.; 6 figs

  8. Berberine promotes the development of atherosclerosis and foam cell formation by inducing scavenger receptor A expression in macrophage

    Institute of Scientific and Technical Information of China (English)

    Ke Li; Wenqi Yao; Xiudan Zheng; Kan Liao

    2009-01-01

    Berberine is identified to lower the serum cholesterol level in human and hamster through the induction of low density lipoproteins (LDL) receptor in hepatic cells. To evaluate its potential in preventing atherosclerosis, the effect of berberine on atherosclerosis development in apolipoprotein E-deficient (apoE-/-) mice was investigated, in apoE-/-mice, berberine induced in vivo foam cell formation and promoted atherosclerosis development. The foam cell for-mation induced by berberine was also observed in mouse RAW264.7 cells, as well as in mouse and human primary macrophages. By inducing scavenger receptor A (SR-A) expression in macrophages, berberine increased the uptake of modified LDL (DiO-Ac-LDL). Berberine-induced SR-A expression was also observed in macrophage foam cells in vivo and in the cells at atherosclerotic lesion. Analysis in RAW264.7 cells indicated that berberine induced SR-A ex-pression by suppressing PTEN expression, which led to sustained Akt activation. Our results suggest that to evaluate the potential of a cholesterol-reducing compound in alleviating atherosclerosis, its effect on the cells involved in ath-erosclerosis development, such as macrophages, should also be considered. Promotion of foam cell formation could counter-balance the beneficial effect of lowering serum cholesterol.

  9. HIV-derived ssRNA binds to TLR8 to induce inflammation-driven macrophage foam cell formation.

    Directory of Open Access Journals (Sweden)

    Mark A Bernard

    Full Text Available Even though combined anti-retroviral therapy (cART dramatically improves patient survival, they remain at a higher risk of being afflicted with non-infectious complications such as cardiovascular disease (CVD. This increased risk is linked to persistent inflammation and chronic immune activation. In this study, we assessed whether this complication is related to HIV-derived ssRNAs inducing in macrophages increases in TNFα release through TLR8 activation leading to foam cell formation. HIV ssRNAs induced foam cell formation in monocyte-derived macrophages (MDMs in a dose-dependent manner. This response was reduced when either endocytosis or endosomal acidification was inhibited by dynasore or chloroquine, respectively. Using a flow cytometry FRET assay, we demonstrated that ssRNAs bind to TLR8 in HEK cells. In MDMs, ssRNAs triggered a TLR8-mediated inflammatory response that ultimately lead to foam cell formation. Targeted silencing of the TLR8 and MYD88 genes reduced foam cell formation. Furthermore, foam cell formation induced by these ssRNAs was blocked by an anti-TNFα neutralizing antibody. Taken together in MDMs, HIV ssRNAs are internalized; bind TLR8 in the endosome followed by endosomal acidification. TLR8 signaling then triggers TNFα release and ultimately leads to foam cell formation. As this response was inhibited by a blocking anti-TNFα antibody, drug targeting HIV ssRNA-driven TLR8 activation may serve as a potential therapeutic target to reduce chronic immune activation and inflammation leading to CVD in HIV+ patients.

  10. Polyethylene ionomer-based nano-composite foams prepared by a batch process and MuCell injection molding

    International Nuclear Information System (INIS)

    To understand the correlation between foamability and melt rheology of polyethylene-based ionomers having different degrees of the neutralization and corresponding nano-composites, we have conducted the foam processing via a batch process in an autoclave and microcellular foam injection molding (FIM) process using the MuCell technology. We have discussed the obtainable morphological properties in both foaming processes. All cellular structures were investigated by using field emission scanning electron microscopy. The competitive phenomenon between the cell nucleation and the cell growth including the coalescence of cell was discussed in light of the interfacial energy and the relaxation rate as revealed by the modified classical nucleation theory and rheological measurement, respectively. The FIM process led to the opposite behavior in the cell growth and coalescence of cell as compared with that of the batch process, where the ionic cross-linked structure has significant contribution to retard the cell growth and coalescence of cell. The mechanical properties of the structural foams obtained by FIM process were discussed.

  11. Polyethylene ionomer-based nano-composite foams prepared by a batch process and MuCell injection molding

    Energy Technology Data Exchange (ETDEWEB)

    Hayashi, Hidetomo; Mori, Tomoki [Advanced Polymeric Nanostructured Materials Engineering, Graduate School of Engineering, Toyota Technological Institute, Hisakata 2-12-1, Tempaku, Nagoya 468-8511 (Japan); Okamoto, Masami, E-mail: okamoto@toyota-ti.ac.jp [Advanced Polymeric Nanostructured Materials Engineering, Graduate School of Engineering, Toyota Technological Institute, Hisakata 2-12-1, Tempaku, Nagoya 468-8511 (Japan); Yamasaki, Satoshi; Hayami, Hiroshi [Polymer Materials Technology R and D Department Electronics and Materials R and D Laboratories, Sumitomo Electric Industries, Ltd., Shimaya, Konohana-ku, 1-1-3, Osaka, 554-0024 (Japan)

    2010-01-01

    To understand the correlation between foamability and melt rheology of polyethylene-based ionomers having different degrees of the neutralization and corresponding nano-composites, we have conducted the foam processing via a batch process in an autoclave and microcellular foam injection molding (FIM) process using the MuCell technology. We have discussed the obtainable morphological properties in both foaming processes. All cellular structures were investigated by using field emission scanning electron microscopy. The competitive phenomenon between the cell nucleation and the cell growth including the coalescence of cell was discussed in light of the interfacial energy and the relaxation rate as revealed by the modified classical nucleation theory and rheological measurement, respectively. The FIM process led to the opposite behavior in the cell growth and coalescence of cell as compared with that of the batch process, where the ionic cross-linked structure has significant contribution to retard the cell growth and coalescence of cell. The mechanical properties of the structural foams obtained by FIM process were discussed.

  12. Acoustic properties of sintered FeCrAlY foams with open cells (Ⅰ): Static flow resistance

    Institute of Scientific and Technical Information of China (English)

    M.; KEPETS; A.; P.; DOWLING

    2008-01-01

    Open celled metal foams fabricated through the route of metal sintering are a new class of material that offers novel mechanical and acoustic properties. The metal sintering approach offers a cost-effective means for the mass-production of open-cell foams from a range of materials, including high-temperature steel alloys. The mechanical properties of open-celled steel alloy (FeCrAlY) foams have been characterized in previous studies, with focus placed on the influence of processing defects on stiffness and strength. In this work, the low-Reynolds number fluid properties of FeCrAlY foams were investigated both theoretically and experimen- tally. Specifically, the static flow resistance of the sintered foams important for heat transfer, filtration and sound absorption was modeled based on a cylinder and a sphere arranged in a periodic lattice at general incidence to the flow. Experimental measurements were subsequently carried out to validate theoretical predictions, with good agreement achieved.

  13. Insulin and glucose play a role in foam cell formation and function

    Directory of Open Access Journals (Sweden)

    Keller Susanna R

    2006-06-01

    Full Text Available Abstract Background Foam cell formation in diabetic patients often occurs in the presence of high insulin and glucose levels. To test whether hyperinsulinemic hyperglycemic conditions affect foam cell differentiation, we examined gene expression, cytokine production, and Akt phosphorylation in human monocyte-derived macrophages incubated with two types of oxidized low density lipoprotein (LDL, minimally modified LDL (mmLDL and extensively oxidized LDL (OxLDL. Methods and results Using Affymetrix GeneChip® arrays, we found that several genes directly related to insulin signaling were changed. The insulin receptor and glucose-6-phosphate dehydrogenase were upregulated by mmLDL and OxLDL, whereas insulin-induced gene 1 was significantly down-regulated. In hyperinsulinemic hyperglycemic conditions, modified LDL upregulated Akt phosphorylation and expression of the insulin-regulated aminopeptidase. The level of proinflammatory cytokines, IL-lβ, IL-12, and IL-6, and of a 5-lipoxygenase eicosanoid, 5-hydroxyeicosatetraenoic acid (5-HETE, was also increased. Conclusion These results suggest that the exposure of macrophages to modified low density lipoproteins in hyperglycemic hyperinsulinemic conditions affects insulin signaling and promotes the release of proinflammatory stimuli, such as cytokines and eicosanoids. These in turn may contribute to the development of insulin resistance.

  14. Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

    International Nuclear Information System (INIS)

    Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO2 and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocyte chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO2 particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation. - Highlights: • Effects of metal oxide nanoparticles on foam cell formation were investigated. • Exposure to ZnO nanoparticles induced migration and adhesion of monocytes. • Exposure to ZnO nanoparticles increased macrophage cholesterol uptake. • Expression of membrane scavenger receptors of modified LDL was also increased. • These effects were not observed after exposure to TiO2 nanoparticles

  15. Zinc oxide nanoparticles induce migration and adhesion of monocytes to endothelial cells and accelerate foam cell formation

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, Yuka; Tada-Oikawa, Saeko [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan); Ichihara, Gaku [Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, Nagoya (Japan); Yabata, Masayuki; Izuoka, Kiyora [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan); Suzuki, Masako; Sakai, Kiyoshi [Nagoya City Public Health Research Institute, Nagoya (Japan); Ichihara, Sahoko, E-mail: saho@gene.mie-u.ac.jp [Graduate School of Regional Innovation Studies, Mie University, Tsu (Japan)

    2014-07-01

    Metal oxide nanoparticles are widely used in industry, cosmetics, and biomedicine. However, the effects of exposure to these nanoparticles on the cardiovascular system remain unknown. The present study investigated the effects of nanosized TiO{sub 2} and ZnO particles on the migration and adhesion of monocytes, which are essential processes in atherosclerogenesis, using an in vitro set-up of human umbilical vein endothelial cells (HUVECs) and human monocytic leukemia cells (THP-1). We also examined the effects of exposure to nanosized metal oxide particles on macrophage cholesterol uptake and foam cell formation. The 16-hour exposure to ZnO particles increased the level of monocyte chemotactic protein-1 (MCP-1) and induced the migration of THP-1 monocyte mediated by increased MCP-1. Exposure to ZnO particles also induced adhesion of THP-1 cells to HUVECs. Moreover, exposure to ZnO particles, but not TiO{sub 2} particles, upregulated the expression of membrane scavenger receptors of modified LDL and increased cholesterol uptake in THP-1 monocytes/macrophages. In the present study, we found that exposure to ZnO particles increased macrophage cholesterol uptake, which was mediated by an upregulation of membrane scavenger receptors of modified LDL. These results suggest that nanosized ZnO particles could potentially enhance atherosclerogenesis and accelerate foam cell formation. - Highlights: • Effects of metal oxide nanoparticles on foam cell formation were investigated. • Exposure to ZnO nanoparticles induced migration and adhesion of monocytes. • Exposure to ZnO nanoparticles increased macrophage cholesterol uptake. • Expression of membrane scavenger receptors of modified LDL was also increased. • These effects were not observed after exposure to TiO{sub 2} nanoparticles.

  16. Characterization of Solid Polymers, Ceramic Gap Filler, and Closed-Cell Polymer Foam Using Low-Load Test Methods

    Science.gov (United States)

    Herring, Helen M.

    2008-01-01

    Various solid polymers, polymer-based composites, and closed-cell polymer foam are being characterized to determine their mechanical properties, using low-load test methods. The residual mechanical properties of these materials after environmental exposure or extreme usage conditions determines their value in aerospace structural applications. In this experimental study, four separate polymers were evaluated to measure their individual mechanical responses after thermal aging and moisture exposure by dynamic mechanical analysis. A ceramic gap filler, used in the gaps between the tiles on the Space Shuttle, was also tested, using dynamic mechanical analysis to determine material property limits during flight. Closed-cell polymer foam, used for the Space Shuttle External Tank insulation, was tested under low load levels to evaluate how the foam's mechanical properties are affected by various loading and unloading scenarios.

  17. Highly porous open cell Ti-foam using NaCl as temporary space holder through powder metallurgy route

    International Nuclear Information System (INIS)

    Highlights: ► NaCl crystals has been used as space holder. ► Variation of NaCl:Ti ratio varies porosity (65–80%). ► NaCl is cubic but the cells are spherical. ► Two types of pores: micro and macro pores are obtained. ► Foams are suitable for bones scaffolds and engineering applications. - Abstract: Open cell Titanium-foam (Ti-foam) with varying porosities (65–80%) was prepared using sodium chloride (NaCl) particles as space holder through powder metallurgy route. In order to ensure sufficient handling strength in cold compacted pallets, 2 wt.% polyvinyl alcohol (PVA) solutions (5 wt.% PVA in water) was mixed with the mixture of Ti and NaCl powders prior to cold compaction. After sintering, NaCl salt was removed by dissolving it in hot water. Detailed Energy dispersive X-ray (EDX) analysis and X-ray diffraction studies of the prepared Ti-foams were conducted to examine any physical and chemical changes in the phase constituents. The micro-architectural characteristics, density vis-a-vis porosity, and compressive deformation behavior of the synthesized foams were evaluated to examine their suitability as biomaterial and engineering applications

  18. Micromodel foam flow study

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, K.T.; Radke, C.J.

    1990-10-01

    Foams are often utilized as part of enhanced oil recovery techniques. This report presents the results of a micromodel foam flow study. Micromodels are valuable tools in uncovering capillary phenomena responsible for lamellae generation and coalescence during foam flow in porous media. Among the mechanisms observed are snap-off, weeping-flow breakup, and lamella division and leave behind. Coalescence mechanisms include dynamic capillary-pressure-induced lamella drainage and gas diffusion. These phenomena are sensitive to the mode of injection, the local capillary environment, and the geometry of the pore structure. An important consideration in presenting a tractable model of foam flow behavior is the ability to identify the pore-level mechanisms having the greatest impact on foam texture. The predominant mechanisms will vary depending upon the application for foam as an enhanced oil recovery (EOR) fluid. Both simultaneous gas and surfactant injection and surfactant alternating with gas injection (SAG) have been used to create foam for mobility control in EOR projects. The model developed is based on simultaneous gas and surfactant injection during steady-state conditions into a Berea sandstone core. The lamellae generation and coalescence mechanisms included in this model are snap-off, lamella division, and dynamic capillary-pressure-induced lamella drainage. This simplified steady-state model serves as a foundation for developing more complete rate expressions and for extending the population balance to handle transient foam flow behavior. 70 refs., 30 figs.

  19. Synthesis and characterisation of closed cells aluminium foams containing dolomite powder as foaming agent: Priprava in karakterizacija aluminijskih pen z zaprto poroznostjo, izdelanih z dolomitnim prahom kot sredstvom za penjenje:

    OpenAIRE

    JENKO, Monika; Kevorkijan, Varužan; Paulin, Irena; Škapin, Srečo D.; Šuštaršič, Borivoj

    2010-01-01

    In this work, the viability of dolomite powder as cost-effective alternative to TiHsub2 foaming agent was investigated. Closed cells aluminium foam samples were prepared starts from solid, foamable precursors synthesized by powder metallurgy and melt route. Precursors obtained by melt route were machined and additional cold isostatic pressed in order to improve their density. In allcases, the resulted precursors consisted of an aluminium matrix containing various mass fractions of uniformly d...

  20. Characterization of the cell structure of metallic foams; Charakterisierung der Zellstruktur von metallischen Schaeumen

    Energy Technology Data Exchange (ETDEWEB)

    Kriszt, B.; Faure, K. [Inst. fuer Werkstoffkunde und Materialpruefung, TU-Wien, Wien (Austria)

    2003-11-01

    The structure of metallic foams is described mainly in terms density distribution and porosity characteristics. Because of the lengthy, difficult preparation and image analysis of such specimens, the architecture of the metallic network has not been the subject of many investigations. This article thus describes the methods of preparation and automatic image analysis which can be used for cellular structures and discusses the results obtained with reference to a number of chosen examples. The methods of image analysis used to separate the metallic structure into cell edges and nodes are demonstrated on Alporas and metal foams which were manufactured using the powder compacting process (PCP). (orig.) [German] Die Beschreibung der Struktur von metallischen Schaeumen stuetzt sich vorwiegend auf die Dichteverteilung und die Porencharakteristik. Der Aufbau des metallischen Netzwerkes ist aufgrund der aufwaendigen und schwierigen Probenpraeparation und Bildbearbeitung nicht so gut untersucht. Dieser Beitrag verfolgt daher die Zielsetzung, Methoden der Praeparation und automatischen Bildbearbeitung von zellularen Strukturen aufzuzeigen und an ausgewaehlten Beispielen die Ergebnisse zu diskutieren. Die Bildprozessroutinen zur Trennung der metallischen Struktur in Zellstege und Knoten werden auf Alporasschaeume und Metallschaeume, die nach dem Pulverkompaktierungsprozess (PKV) hergestellt worden sind, angewendet. (orig.)

  1. NF-kB activity-dependent P-selectin involved in ox-LDL-induced foam cell formation in U937 cell

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yi, E-mail: wangyi2004a@126.com [Department of Cardiology, Shanghai First People' s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200080 (China); Wang, Xiang; Sun, Minghui; Zhang, Zhenyu; Cao, Heng; Chen, Xiaoqing [Department of Cardiology, Shanghai First People' s Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai 200080 (China)

    2011-08-05

    Highlights: {yields} Ox-LDL induced foam cell formation in the human U937 promonocytic cell line in a dose- and time-dependent manner. {yields} Ox-LDL induced expression of P-selectin through degradation of IkBa and augment of NF-kB activity and protein level during macrophage-derived foam cell formation. {yields} P-selectin and NF-kB may be identified as pivotal regulators of ox-LDL-induced foam cell formation. {yields} Therapy based on the inhibition of P-selectin and NF-kB may complement conventional treatments to prevent atherosclerosis. -- Abstract: Oxidized low-density lipoprotein (ox-LDL) plays a critical role in regulation of atherosclerosis. However, little is known about the role of Nuclear factor kB (NF-kB) activity-dependent P-selectin in ox-LDL-induced foam cell formation during atherosclerosis. In this study, we first investigated ox-LDL induced foam cell formation in the human U937 promonocytic cell line in a dose- and time-dependent manner. Treatment of U937 cells with ox-LDL increased lipid accumulation as well as intracellular cholesterol content. Next, a comparative analysis of gene expression profiling using cDNA microarray and Real-time-PCR indicated that ox-LDL exposure induced, in three treated groups, an extremely marked increase in the mRNA level of P-selectin. Protein levels of P-selectin and its upstream regulators IkBa and NF-kB showed that NF-kB pathway is involved in the ox-LDL-induced foam cell formation. Finally, overexpression of NF-kB significantly accelerated, whereas, inhibition of NF-kB with siRNA remarkably attenuated ox-LDL-induced macrophage-derived foam cell formation. It was concluded that the activity of NF-kB is augmented during macrophage-derived foam cell formation. Activation of NF-kB increased, whereas, inhibition of NF-kB decreased ox-LDL-induced P-selectin expression and lipid accumulation in macrophages, suggesting ox-LDL induced expression of P-selectin through degradation of IkBa and activation of NF-kB in the

  2. NF-kB activity-dependent P-selectin involved in ox-LDL-induced foam cell formation in U937 cell

    International Nuclear Information System (INIS)

    Highlights: → Ox-LDL induced foam cell formation in the human U937 promonocytic cell line in a dose- and time-dependent manner. → Ox-LDL induced expression of P-selectin through degradation of IkBa and augment of NF-kB activity and protein level during macrophage-derived foam cell formation. → P-selectin and NF-kB may be identified as pivotal regulators of ox-LDL-induced foam cell formation. → Therapy based on the inhibition of P-selectin and NF-kB may complement conventional treatments to prevent atherosclerosis. -- Abstract: Oxidized low-density lipoprotein (ox-LDL) plays a critical role in regulation of atherosclerosis. However, little is known about the role of Nuclear factor kB (NF-kB) activity-dependent P-selectin in ox-LDL-induced foam cell formation during atherosclerosis. In this study, we first investigated ox-LDL induced foam cell formation in the human U937 promonocytic cell line in a dose- and time-dependent manner. Treatment of U937 cells with ox-LDL increased lipid accumulation as well as intracellular cholesterol content. Next, a comparative analysis of gene expression profiling using cDNA microarray and Real-time-PCR indicated that ox-LDL exposure induced, in three treated groups, an extremely marked increase in the mRNA level of P-selectin. Protein levels of P-selectin and its upstream regulators IkBa and NF-kB showed that NF-kB pathway is involved in the ox-LDL-induced foam cell formation. Finally, overexpression of NF-kB significantly accelerated, whereas, inhibition of NF-kB with siRNA remarkably attenuated ox-LDL-induced macrophage-derived foam cell formation. It was concluded that the activity of NF-kB is augmented during macrophage-derived foam cell formation. Activation of NF-kB increased, whereas, inhibition of NF-kB decreased ox-LDL-induced P-selectin expression and lipid accumulation in macrophages, suggesting ox-LDL induced expression of P-selectin through degradation of IkBa and activation of NF-kB in the regulation of foam

  3. Pulsating column separation and preconcentration of radioiodine on hydrophobic organic reagent loaded resilient open-cell polyurethane foam

    International Nuclear Information System (INIS)

    The method is based on the resiliency of the open-cell polyurethane foam filling used in a pulsing bed column. A liquid anion exchanger containing I2 has been used as a hydrophobic organic phase immobilized in the polyurethane foam matrix. Forced flow of the mobile phase during successive pulsing of the column bed results in high preconcentration factors with practically quantitative separation yields. The pulsated column technique may also be conveniently automated. It can be utilized most advantageously for the rapid determination of low activity radioiodine in environmental waters mainly in routine field analysis. (author)

  4. In Situ Observation of Plastic Foaming under Static Condition, Extensional Flow and Shear Flow

    Science.gov (United States)

    Wong, Anson Sze Tat

    Traditional blowing agents (e.g., hydrochlorofluorocarbons) in plastic foaming processes has been phasing out due to environmental regulations. Plastic foaming industry is forced to employ greener alternatives (e.g., carbon dioxide, nitrogen), but their foaming processes are technologically challenging. Moreover, to improve the competitiveness of the foaming industry, it is imperative to develop a new generation of value-added plastic foams with cell structures that can be tailored to different applications. In this context, the objective of this thesis is to achieve a thorough understanding on cell nucleation and growth phenomena that determine cell structures in plastic foaming processes. The core research strategy is to develop innovative visualization systems to capture and study these phenomena. A system with accurate heating and cooling control has been developed to observe and study crystallization-induced foaming behaviors of polymers under static conditions. The cell nucleation and initial growth behavior of polymers blown with different blowing agents (nitrogen, argon and helium, and carbon dioxide-nitrogen mixtures) have also been investigated in great detail. Furthermore, two innovative systems have been developed to simulate the dynamic conditions in industrial foaming processes: one system captures a foaming process under an easily adjustable and uniform extensional strain in a high temperature and pressure environment, while the other achieves the same target, but with shear strain. Using these systems, the extensional and shear effects on bubble nucleation and initial growth processes has been investigated independently in an isolated manner, which has never been achieved previously. The effectiveness of cell nucleating agents has also been evaluated under dynamic conditions, which have led to the identification of new foaming mechanisms based on polymer-chain alignment and generation of microvoids under stress. Knowledge generated from these

  5. Numerical Study of Liquid Sloshing on Anti-sloshing Device Using Open Cell Metal Foams in Oil Tank

    Science.gov (United States)

    Zhang, Y.; Qu, Z. G.; Tao, W. Q.; Lu, T. J.

    2010-03-01

    A new baffle structure design named open-cell metal foams baffle for anti-sloshing device in oil tank is presented in this study. Numerical simulation study on the liquid sloshing with various baffles is carried out using FLUENT with the volume-of-fluid (VOF) model. Four types of baffles were studied, namely non-baffle (type A), conventional parallel-baffle (type B), cross-baffle (type C) and open- cell metal foams baffles (type D). The oil velocity distribution, centroid and oil occupancy in the sloshing process is revealed in the case of vehicle speeding up and turning respectively. It is found that type D reduce velocity of oil, increase the value of oil occupancy in the suction pipe entrance of the oil tank and lower the centroid of oil obviously comparing with the other types. As for the same open-cell metal foam pore density, lower open-cell metal foam porosity has much better effect of inhibition of liquid sloshing, but there is little deviation among different porosity for the absolute value. Moreover, according to the same porosity, the oil centroid can be lowered obviously with the increase of pore density. The results of type D show practical significance and referable guideline for baffles design to improve the safety and stability of vehicle.

  6. On the load-bearing efficiency of open-cell foams: A comparison of two architectures related to two processes

    International Nuclear Information System (INIS)

    Graphical abstract: -- Abstract: Using a simple beam element, this study estimates the elastic stiffness of two isotropic open-cell foam architectures that approximate, respectively, the space between tightly packed fluid bubbles and that defined between densified solid particles, and finds little difference between the two microstructures above a relative density of a few per cent.

  7. Compressive properties of a closed-cell aluminum foam as a function of strain-rate and temperature

    Energy Technology Data Exchange (ETDEWEB)

    Cady, Carl M [Los Alamos National Laboratory; Gray, Ill, George T [Los Alamos National Laboratory; Liu, Cheng [Los Alamos National Laboratory; Lovato, Manuel L [Los Alamos National Laboratory; Mukai, T [JAPAN

    2008-01-01

    The compressive constitutive behavior of a closed-cell aluminum foam (ALPORAS) manufactured by Shinko Wire Co. in Japan was evaluated under static and dynamic loading conditions as a function of temperature. High-strain-rate tests (1000-2000 s{sup -1}) were conducted using a split-Hopkinson pressure bar (SHPB). Quasi-static and intermediate-strain-rate tests were conducted on a hydraulic load frame. A small but discernable change in the flow stress behavior as a function of strain rate was measured. The deformation behavior of the Al-foam was however found to be strongly temperature dependent under both quasi-static and dynamic loading. Localized deformation and stress state instability during testing of metal foams is discussed in detail since the mechanical behavior over the entire range of strain rates indicates non-uniform deformation. Additionally, investigation of the effect of residual stresses created during manufacturing on the mechanical behavior was investigated.

  8. Thermal Conductivity of Foam Glass

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    Due to the increased focus on energy savings and waste recycling foam glass materials have gained increased attention. The production process of foam glass is a potential low-cost recycle option for challenging waste, e.g. CRT glass and industrial waste (fly ash and slags). Foam glass is used as...... only closed pores and its overall thermal conductivity will be much lower than that of the foam glass with open pores. In this work we have prepared foam glass using different types of recycled glasses and different kinds of foaming agents. This enabled the formation of foam glasses having gas cells...... glass types could have a significant advantage for getting low thermal conductivity when recycled for thermal insulation applications. The impact of crystallisation on the thermal conductivity of foam glasses is also discussed....

  9. X-ray and finite element analysis of deformation response of closed-cell metal foam subjected to compressive loading

    International Nuclear Information System (INIS)

    Time-lapse X-ray computed microtomography was employed to quantify the deformation behaviour of closed-cell aluminium foam. The specimen was incrementally loaded and tomographically scanned using a custom X-ray tomographic device to capture the deforming microstructure. Because of the very small thickness of the cell walls and the high ratio between pore size and cell wall thickness cone-beam reconstruction procedure was applied. A finite element (FE) model was developed based on the reconstructed three-dimensional data. The FE model was used for two purposes: i) the nodal points were used for tracking the displacements of the deforming structure, ii) verification of the material model for description of the foam's deformational behaviour. Digital volumetric correlation (DVC) algorithm was used on data obtained from the time-lapse tomography to provide a detailed description of the evolution of deformation in the complex structure of aluminium foam. The results from DVC demonstrate the possibility to use the complex microstructure of the aluminium foam as a random pattern for the correlation algorithm. The underlying FE model enables easy comparison between experimental results and results obtained from numerical simulations used for evaluation of proposed constitutive models.

  10. Anti-atherosclerotic potential of gossypetin via inhibiting LDL oxidation and foam cell formation

    International Nuclear Information System (INIS)

    Gossypetin, a flavone originally isolated from Hibiscus species, has been shown to possess antioxidant, antimicrobial, and antimutagenic activities. Here, we investigated the mechanism(s) underlying the anti-atherosclerotic potential of gossypetin. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) scavenging activity assay showed that the addition of > 50 μM of gossypetin could scavenge over 50% of DPPH radicals. The inhibitory effects of gossypetin on the lipid and protein oxidation of LDL were defined by thiobarbituric acid reactive substance (TBARS) assay, the relative electrophoretic mobility (REM) of oxidized LDL (ox-LDL), and fragmentation of apoB in the Cu2+-induced oxidation of LDL. Gossypetin showed potential in reducing ox-LDL-induced foam cell formation and intracellular lipid accumulation, and uptake ability of macrophages under non-cytotoxic concentrations. Molecular data showed that these influences of gossypetin might be mediated via peroxisome proliferator-activated receptor α (PPARα)/liver-X receptor α (LXRα)/ATP-binding cassette transporter A1 (ABCA1) and PPARγ/scavenger receptor CD36 pathways, as demonstrated by the transfection of PPARα siRNA or PPARγ expression vector. Our data implied that gossypetin regulated the PPAR signals, which in turn led to stimulation of cholesterol removal from macrophages and delay atherosclerosis. These results suggested that gossypetin potentially could be developed as an anti-atherosclerotic agent. - Highlights: • The anti-atherosclerotic effect of gossypetin in vitro was examined. • Gossypetin inhibited LDL oxidation. • Gossypetin showed potential in reducing on the formation of foam cells. • Gossypetin functions against ox-LDL through PPARa activation and PPARγ depression

  11. Anti-atherosclerotic potential of gossypetin via inhibiting LDL oxidation and foam cell formation

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing-Hsien [School of Nutrition, Chung Shan Medical University, Taichung, Taiwan (China); Department of Medical Research, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Tsai, Chia-Wen [Department of Nutrition, China Medical University, Taichung, Taiwan (China); Wang, Chi-Ping [Department of Clinical Laboratory, Chung Shan Medical University Hospital, Taichung, Taiwan (China); Lin, Hui-Hsuan, E-mail: linhh@csmu.edu.tw [Department of Medical Research, Chung Shan Medical University Hospital, Taichung, Taiwan (China); School of Medical Laboratory and Biotechnology, Chung Shan Medical University, Taichung, Taiwan (China)

    2013-10-15

    Gossypetin, a flavone originally isolated from Hibiscus species, has been shown to possess antioxidant, antimicrobial, and antimutagenic activities. Here, we investigated the mechanism(s) underlying the anti-atherosclerotic potential of gossypetin. 1,1-Diphenyl-2-picrylhydrazyl (DPPH) scavenging activity assay showed that the addition of > 50 μM of gossypetin could scavenge over 50% of DPPH radicals. The inhibitory effects of gossypetin on the lipid and protein oxidation of LDL were defined by thiobarbituric acid reactive substance (TBARS) assay, the relative electrophoretic mobility (REM) of oxidized LDL (ox-LDL), and fragmentation of apoB in the Cu{sup 2+}-induced oxidation of LDL. Gossypetin showed potential in reducing ox-LDL-induced foam cell formation and intracellular lipid accumulation, and uptake ability of macrophages under non-cytotoxic concentrations. Molecular data showed that these influences of gossypetin might be mediated via peroxisome proliferator-activated receptor α (PPARα)/liver-X receptor α (LXRα)/ATP-binding cassette transporter A1 (ABCA1) and PPARγ/scavenger receptor CD36 pathways, as demonstrated by the transfection of PPARα siRNA or PPARγ expression vector. Our data implied that gossypetin regulated the PPAR signals, which in turn led to stimulation of cholesterol removal from macrophages and delay atherosclerosis. These results suggested that gossypetin potentially could be developed as an anti-atherosclerotic agent. - Highlights: • The anti-atherosclerotic effect of gossypetin in vitro was examined. • Gossypetin inhibited LDL oxidation. • Gossypetin showed potential in reducing on the formation of foam cells. • Gossypetin functions against ox-LDL through PPARa activation and PPARγ depression.

  12. Aerogels and opened-cell structures: two examples of carbon foams; Les aerogels et les structures alveolaires. Deux exemples de mousses de carbone

    Energy Technology Data Exchange (ETDEWEB)

    Kocon, L.; Piquero, Th. [CEA Centre d' Etudes du Ripault, Dept. des Materiaux, Service Recherche Ceramiques et Composites, 37 - Tours (France)

    2006-03-15

    Two examples of carbon foams are exposed herein. They are very lightweight materials with an exceptionally open porosity high volume. Cells size varies from nanometer to micrometer for aerogels, and from micrometer to millimeter for opened cell carbon foams. Elaboration process conditions allow to adjust pore sizes as well as micro-textural characteristics and macroscopical mechanical properties. Carbon aerogels are synthesized by organic aerogels pyrolysis leading to a large variety of micro-textures. Opened cell carbon foams present an original mechanical behavior, brittle type, which can be enhanced by CVD or calefaction pyrocarbon reinforcement. (authors)

  13. Foam clogging

    OpenAIRE

    ROUYER, Florence; Haffner, Benjamin; Louvet, Nicolas; Khidas, Yacine; Pitois, Olivier

    2014-01-01

    To what extent are aqueous foams prone to clogging? Foam permeability is measured as a function of particulate loading (trapped hydrophilic particles) under conditions where the particle to bubble size ratio is allowed to increase when the number of particles per bubble is fixed. In addition to experiments performed on the foam scale, we investigated experimentally and numerically the hydrodynamic resistance of a single foam node loaded with one particle. It is shown that, with respect to sol...

  14. Thermo-fluid dynamic characterization and technical optimization of structured open-cell metal foams by means of numerical simulation

    OpenAIRE

    Horneber, Tobias

    2015-01-01

    The present contribution provides a fluid dynamic and thermal characterization of structured representatives of open-cell foams. Geometric and analytic methods as well as numeric simulations serve as tools for technical optimization. Three different types of structures are analyzed: a simple cubic structure, a Kelvin cell structure, and a diamond structure. These structures are used as carrier structures in catalysis and make up the inner part of a reactor which is built in its entirety u...

  15. Negative pressure wound therapy with reticulated open cell foam in children: an overview.

    Science.gov (United States)

    Contractor, Dhruti; Amling, June; Brandoli, Cinzia; Tosi, Laura L

    2008-01-01

    This article summarizes the results of a comprehensive review of the literature on the use of negative pressure wound therapy with reticulated open cell foam (NPWT/ROCF) as delivered by V.A.C.(R) Therapy (KCI, San Antonio, TX) in pediatric patients. A review of the literature revealed 20 articles that discussed the use of NPWT/ROCF in exclusively pediatric patients. Nine articles were retrospective reviews, and 11 were case studies. This review discusses the insights from these articles. This review discusses the versatility of NPWT/ROCF for use with pediatric patients with infected wounds; full-thickness burns; open fractures; large soft tissue wounds; surgical wounds of the chest, abdomen, and spine; pilonidal disease; and pressure ulcers. NPWT/ROCF has been used in children as young as a few weeks of age, and in children with comorbidities such as congenital heart disease, immunosuppression, and spina bifida. Wound healing in children can be delayed by impaired perfusion, infection, edema, and poor nutrition. Clinical considerations for using NPWT/ROCF in children can include differences in healing due to higher granulation rates requiring more frequent dressing changes, poor nutritional status, small size, and low weight. With pediatric patients, there is no consensus on foam (white or black) selection, optimum amount of negative pressure, frequency of NPWT/ROCF dressing changes, and interposing contact layer selection. Randomized prospective studies are needed to make recommendations for safe and efficacious clinical practice. Research regarding the effects of dressing types, adjunctive treatment, and wound healing in neonates and children is needed. PMID:19034165

  16. An experimental study of natural convection in open-cell aluminum foam

    Science.gov (United States)

    De Jaeger, P.; Reynders, R.; De Schampheleire, S.; T'Joen, C.; Huisseune, H.; Amee, B.; De Paepe, M.

    2012-11-01

    Natural convecton n air-saturated alumnum foam has been measured. A carefully designed experimental setup is built for his ask. The calibraton is done by comparing he results of a flat plate wh literature data, revealing excellent agreement. The nvestigated foams have a pore densiy of 10 and 20 PPI. The bondng of the foam is performed via brazing, or by applying a single epoxy which is enriched wh highly conductve alumna particles. The Rayleigh number is varied between 2500 and 6000, wh he rato of he surface area o he perimeter of he substrate as characteristc length. The foam height is varied between 12 and 25.4 mm. A major difference between both he bondng methods is observed. The brazed samples showed a beter heat ransfer n all cases. Furthermore, when ncreasing he foam height, a clear augmentaton of he heat ransfer is observed. Based on hese results, a correlaton is presented.

  17. Failure mechanisms of closed-cell aluminum foam under monotonic and cyclic loading

    International Nuclear Information System (INIS)

    This paper concentrates on the differences in failure mechanisms of Alporas closed-cell aluminum foam under either monotonic or cyclic loading. The emphasis lies on aspects of crack nucleation and crack propagation in relation to the microstructure. The cell wall material consists of Al dendrites and an interdendritic network of Al4Ca and Al22CaTi2 precipitates. In situ scanning electron microscopy monotonic tensile tests were performed on small samples to study crack nucleation and propagation. Digital image correlation was employed to map the strain in the cell wall on the characteristic microstructural length scale. Monotonic tensile tests and tension-tension fatigue tests were performed on larger samples to observe the overall fracture behavior and crack path in monotonic and cyclic loading. The crack nucleation and propagation path in both loading conditions are revealed and it can be concluded that during monotonic tension cracks nucleate in and propagate partly through the Al4Ca interdendritic network, whereas under cyclic loading cracks nucleate and propagate through the Al dendrites

  18. Development of a biaxial compression device for biological samples: preliminary experimental results for a closed cell foam.

    Science.gov (United States)

    Little, J P; Tevelen, G; Adam, C J; Evans, J H; Pearcy, M J

    2009-07-01

    Biological tissues are subjected to complex loading states in vivo and in order to define constitutive equations that effectively simulate their mechanical behaviour under these loads, it is necessary to obtain data on the tissue's response to multiaxial loading. Single axis and shear testing of biological tissues is often carried out, but biaxial testing is less common. We sought to design and commission a biaxial compression testing device, capable of obtaining repeatable data for biological samples. The apparatus comprised a sealed stainless steel pressure vessel specifically designed such that a state of hydrostatic compression could be created on the test specimen while simultaneously unloading the sample along one axis with an equilibrating tensile pressure. Thus a state of equibiaxial compression was created perpendicular to the long axis of a rectangular sample. For the purpose of calibration and commissioning of the vessel, rectangular samples of closed cell ethylene vinyl acetate (EVA) foam were tested. Each sample was subjected to repeated loading, and nine separate biaxial experiments were carried out to a maximum pressure of 204 kPa (30 psi), with a relaxation time of two hours between them. Calibration testing demonstrated the force applied to the samples had a maximum error of 0.026 N (0.423% of maximum applied force). Under repeated loading, the foam sample demonstrated lower stiffness during the first load cycle. Following this cycle, an increased stiffness, repeatable response was observed with successive loading. While the experimental protocol was developed for EVA foam, preliminary results on this material suggest that this device may be capable of providing test data for biological tissue samples. The load response of the foam was characteristic of closed cell foams, with consolidation during the early loading cycles, then a repeatable load-displacement response upon repeated loading. The repeatability of the test results demonstrated the

  19. Structural evaluation of a nickel base super alloy metal foam via NDE and finite element

    Science.gov (United States)

    Abdul-Aziz, Ali; Abumeri, G.; Garg, Mohit; Young, P. G.

    2008-03-01

    Cellular materials are known to be useful in the application of designing light but stiff structures. This applies to various components used in various industries such as rotorcraft blades, car bodies or portable electronic devices. Structural application of the metal foam is typically confined to light weight sandwich panels, made up of thin solid face sheets and a metallic foam core. The resulting high-stiffness structure is lighter than that constructed only out of the solid metal material. The face sheets carry the applied in-plane and bending loads and the role of the foam core is separate the face sheets to carry some of the shear stresses, while remaining integral with the face sheet. Many challenges relating to the fabrication and testing of these metal foam panels continue to exist due to some mechanical properties falling short of their theoretical potential. Hence in this study, a detailed three dimensional foam structure is generated using series of 2D Computer Tomography (CT) scans, on Haynes 25 metal foam. Series of the 2D images are utilized to construct a high precision solid model including all the fine details within the metal foam as detected by the CT scanning technique. Subsequently, a finite element analysis is then performed on an as fabricated metal foam microstructures to evaluate the foam structural durability and behavior under tensile and compressive loading conditions. The analysis includes a progressive failure analysis (PFA) using GENOA code to further assess the damage initiation, propagation, and failure. The open cell metal foam material is a cobalt-nickel-chromium-tungsten alloy that combines excellent high-temperature strength with good resistance to oxidizing environments up to 1800 °F (980 °C) for prolonged exposures. The foam is formed by a powder metallurgy process with an approximate 100 pores per inch (PPI).

  20. Chondrogenesis of human bone marrow mesenchymal stromal cells in highly porous alginate-foams supplemented with chondroitin sulfate

    International Nuclear Information System (INIS)

    To overcome the limited intrinsic cartilage repair, autologous chondrocyte or bone-marrow-derived mesenchymal stromal cell (BM-MSC) was implanted into cartilage defects. For this purpose suitable biocompatible scaffolds are needed to provide cell retention, chondrogenesis and initial mechanical stability. The present study should indicate whether a recently developed highly porous alginate (Alg) foam scaffold supplemented with chondroitin sulfate (CS) allows the attachment, survival and chondrogenesis of BM-MSCs and articular chondrocytes. The foams were prepared using a freeze-drying method; some of them were supplemented with CS and subsequently characterized for porosity, biodegradation and mechanical profile. BM-MSCs were cultured for 1–2 weeks on the scaffold either under chondrogenic or maintenance conditions. Cell vitality assays, histology, glycosaminoglycan (sGAG) assay, and type II and I collagen immunolabelings were performed to monitor cell growth and extracellular matrix (ECM) synthesis in the scaffolds. Scaffolds had a high porosity ~ 93–95% with a mean pore sizes of 237 ± 48 μm (Alg) and 197 ± 61 μm (Alg/CS). Incorporation of CS increased mechanical strength of the foams providing gradually CS release over 7 days. Most of the cells survived in the scaffolds. BM-MSCs and articular chondrocytes formed rounded clusters within the scaffold pores. The BM-MSCs, irrespective of whether cultured under non/chondrogenic conditions and chondrocytes produced an ECM containing sGAGs, and types II and I collagen. Total collagen and sGAG contents were higher in differentiated BM-MSC cultures supplemented with CS than in CS-free foams after 14 days. The cell cluster formation induced by the scaffolds might stimulate chondrogenesis via initial intense cell–cell contacts. - Highlights: • Alginate foam scaffolds revealed a high porosity and mean pore size of 197–237 μm. • Chondroitin sulfate was released over 14 days by the scaffolds. • Chondrocytes

  1. Chondrogenesis of human bone marrow mesenchymal stromal cells in highly porous alginate-foams supplemented with chondroitin sulfate

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Zhao [Department of Orthopaedic, Trauma and Reconstructive Surgery, Charité-Universitätsmedizin-Berlin Campus Benjamin Franklin, Berlin (Germany); Nooeaid, Patcharakamon [Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg (Germany); Kohl, Benjamin [Department of Orthopaedic, Trauma and Reconstructive Surgery, Charité-Universitätsmedizin-Berlin Campus Benjamin Franklin, Berlin (Germany); Roether, Judith A.; Schubert, Dirk W. [Institute of Polymer Materials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg (Germany); Meier, Carola [Department of Orthopaedic, Trauma and Reconstructive Surgery, Charité-Universitätsmedizin-Berlin Campus Benjamin Franklin, Berlin (Germany); Boccaccini, Aldo R. [Institute of Biomaterials, Department of Materials Science and Engineering, University of Erlangen-Nuremberg (Germany); Godkin, Owen; Ertel, Wolfgang; Arens, Stephan [Department of Orthopaedic, Trauma and Reconstructive Surgery, Charité-Universitätsmedizin-Berlin Campus Benjamin Franklin, Berlin (Germany); Schulze-Tanzil, Gundula, E-mail: gundula.schulze@pmu.ac.at [Department of Orthopaedic, Trauma and Reconstructive Surgery, Charité-Universitätsmedizin-Berlin Campus Benjamin Franklin, Berlin (Germany); Institute of Anatomy, Paracelsus Medical University, Nuremberg (Germany)

    2015-05-01

    To overcome the limited intrinsic cartilage repair, autologous chondrocyte or bone-marrow-derived mesenchymal stromal cell (BM-MSC) was implanted into cartilage defects. For this purpose suitable biocompatible scaffolds are needed to provide cell retention, chondrogenesis and initial mechanical stability. The present study should indicate whether a recently developed highly porous alginate (Alg) foam scaffold supplemented with chondroitin sulfate (CS) allows the attachment, survival and chondrogenesis of BM-MSCs and articular chondrocytes. The foams were prepared using a freeze-drying method; some of them were supplemented with CS and subsequently characterized for porosity, biodegradation and mechanical profile. BM-MSCs were cultured for 1–2 weeks on the scaffold either under chondrogenic or maintenance conditions. Cell vitality assays, histology, glycosaminoglycan (sGAG) assay, and type II and I collagen immunolabelings were performed to monitor cell growth and extracellular matrix (ECM) synthesis in the scaffolds. Scaffolds had a high porosity ~ 93–95% with a mean pore sizes of 237 ± 48 μm (Alg) and 197 ± 61 μm (Alg/CS). Incorporation of CS increased mechanical strength of the foams providing gradually CS release over 7 days. Most of the cells survived in the scaffolds. BM-MSCs and articular chondrocytes formed rounded clusters within the scaffold pores. The BM-MSCs, irrespective of whether cultured under non/chondrogenic conditions and chondrocytes produced an ECM containing sGAGs, and types II and I collagen. Total collagen and sGAG contents were higher in differentiated BM-MSC cultures supplemented with CS than in CS-free foams after 14 days. The cell cluster formation induced by the scaffolds might stimulate chondrogenesis via initial intense cell–cell contacts. - Highlights: • Alginate foam scaffolds revealed a high porosity and mean pore size of 197–237 μm. • Chondroitin sulfate was released over 14 days by the scaffolds. • Chondrocytes

  2. The effects on tensile, shear, and adhesive mechanical properties when recycled epoxy/fiberglass is used as an alternative for glass microballoons in fiberglass foam core sandwiches

    Science.gov (United States)

    Wilson, Dru Matthew

    The problem of this study was to determine whether fiberglass foam core sandwiches made with recycled epoxy/fiberglass have equal or better flatwise tension, shear, and peel (adhesion) mechanical properties when compared with composite sandwiches made with industry standard glass microballoons. Recycling epoxy/fiberglass could save money by: (1) reusing cured composite materials, (2) consuming less virgin composite materials, (3) spending less on transportation and disposing of unusable composites, and (4) possibly enabling companies to sell their recycled composite powder to other manufacturers. This study used three mechanical property tests, which included: flatwise tensile test, shear test, and peel (adhesion) test. Each test used 300 samples for a combined total of 900 sandwich test samples for this study. A factorial design with three independent variables was used. The first variable, filler type, had three levels: no filler, microballoon filler, and recycled epoxy/fiberglass filler. The second variable, foam density, had four levels: 3 lb/ft³, 4 lb/ft³, 5 lb/ft³, and 6 lb/ft³. The third variable, filler percentage ratio, had eight levels: 0%, 10%, 20%, 30%, 40%, 50%, 60%, and 70%. The results of this study revealed two primary conclusions. The first conclusion was that sandwich test panels produced with recycled epoxy/fiberglass powder were equal or significantly better in tensile, shear, and peel (adhesion) strength than sandwiches produced with hollow glass microballoons. The second conclusion was that sandwich test panels produced with recycled epoxy/fiberglass powder were equal or significantly lighter in weight than sandwiches produced with hollow glass microballoons.

  3. Memorizing and detecting an arrested crack in a foam-core sandwich structure using embedded plastic materials and fiber-optic sensors

    International Nuclear Information System (INIS)

    The authors recently established the ‘smart crack arrester’ concept to improve the damage tolerance of composite foam-core sandwich structures. The smart crack arrester can simultaneously arrest and detect a crack propagating along the interface between the facesheet and the core. Two fiber Bragg grating (FBG) sensors are embedded at both edges of the arrester to monitor the internal strain change induced by crack propagation. However, since the developed detection technique utilized transient elastic strain change during high-speed crack propagation, the system required a high-cost measurement system and could fail to detect a fatal interface crack in a practical noisy environment. Thus, this study advances the previous approach. Metal wires are additionally embedded alongside the FBG sensors, resulting in a more easily applicable and reliable crack-detection system with a new technical concept. Specifically, the characteristic strain state induced by arresting the interface crack is first ‘memorized’ by plastic deformation of the metal wire, and the consequent residual strain is then ‘statically’ picked up by the FBG sensor as a damage signal. This study begins by simulating deformation of the metal wires and the sensors to evaluate the feasibility of the proposed technique. The significant advantage of adding the metal wires is then demonstrated by comparing data from the new and previous approaches. Finally, a verification test is conducted to confirm that an FBG spectral shape statically obtained after unloading can indicate the propagation direction and tip location of an arrested crack. (paper)

  4. Carbon foam anode modified by urea and its higher electrochemical performance in marine benthic microbial fuel cell

    Science.gov (United States)

    Fu, Yubin; Lu, Zhikai; Zai, Xuerong; Wang, Jian

    2015-08-01

    Electrode materials have an important effect on the property of microbial fuel cell (MFC). Carbon foam is utilized as an anode and further modified by urea to improve its performance in marine benthic microbial fuel cell (BMFC) with higher voltage and output power. The electrochemical properties of plain carbon foam (PC) and urea-modified carbon foam (UC) are measured respectively. Results show that the UC obtains better wettability after its modification and higher anti-polarization ability than the PC. A novel phenomenon has been found that the electrical potential of the modified UC anode is nearly 100 mV lower than that of the PC, reaching -570 ±10 mV ( vs. SCE), and that it also has a much higher electron transfer kinetic activity, reaching 9399.4 mW m-2, which is 566.2-fold higher than that from plain graphite anode (PG). The fuel cell containing the UC anode has the maximum power density (256.0 mW m-2) among the three different BMFCs. Urea would enhance the bacteria biofilm formation with a more diverse microbial community and maintain more electrons, leading to a lower anodic redox potential and higher power output. The paper primarily analyzes why the electrical potential of the modified anode becomes much lower than that of others after urea modification. These results can be utilized to construct a novel BMFC with higher output power and to design the conditioner of voltage booster with a higher conversion ratio. Finally, the carbon foam with a bigger pore size would be a potential anodic material in conventional MFC.

  5. Correlation between Molding Conditions and Foam Morphology in Microcellular Injection Molding

    Science.gov (United States)

    Yamada, Takehiro; Murata, Yasuhiko; Yokoi, Hidetoshi

    In this study, a quantitative analysis of foam cell distribution at the cross section of products in microcellular injection molding was conducted concerning the relationship between the mold conditions and laminar morphology. The following results were obtained; (1) The morphology consists of a surface layer (Skin layer I) with silver streaks, a layer (Skin layer II) with no cells inside, and a foam layer (Core layers I, II, III) with many cells of different size. (2) The morphology changes depending on the molding conditions and cavity position. (3) The core layer domain decreases from the gate to the distal end. (4) Injection conditions greatly affect the thickness of Skin layer II. (5) Maximum filling pressure in the mold affects mainly the core layer of the foam morphology.

  6. Tuning the spectral emittance of α-SiC open-cell foams up to 1300 K with their macro porosity

    Directory of Open Access Journals (Sweden)

    B. Rousseau

    2016-06-01

    Full Text Available A simple and robust analytical model is used to finely predict the spectral emittance under air up to 1300 K of α-SiC open-cell foams constituted of optically thick struts. The model integrates both the chemical composition and the macro-porosity and is valid only if foams have volumes higher than their Representative Elementary Volumes required for determining their emittance. Infrared emission spectroscopy carried out on a doped silicon carbide single crystal associated to homemade numerical tools based on 3D meshed images (Monte Carlo Ray Tracing code, foam generator make possible to understand the exact role of the cell network in emittance. Finally, one can tune the spectral emittance of α-SiC foams up to 1300 K by simply changing their porosity.

  7. Effect of Bath ph on Electroless Ni-P Coating Deposited on Open-Cell Aluminum Foams

    Science.gov (United States)

    Liu, Jiaan; Si, Fujian; Li, Dong; Liu, Yan; Cao, Zheng; Wang, Guoyong

    2015-09-01

    Different electroless Ni-P coatings were deposited on open-cell aluminum foams at various bath pH. The effect of bath pH on the morphology, structure, components, phases and corrosion resistance of the Ni-P coating was studied by scanning electron microscopy (SEM), confocal laser scanning microscope (CLSM), energy-dispersive spectroscopy (EDS), X-ray diffraction (XRD), immersion test and electrochemical polarization measurement, respectively. The experimental results show that the bath pH not only changed the reactivity of the bath, but also had a influence on the microstructure and anticorrosive property of electroless Ni-P coating. The high pH bath raises the thickness of Ni-P coating but decreases the content of phosphorus element in the Ni-P coating. The corrosion resistance of the coated aluminum foams increases when the bath pH rises.

  8. Effect of aluminum closed-cell foam filling on the quasi-static axial crush performance of glass fiber reinforced polyester composite and aluminum/composite hybrid tubes

    OpenAIRE

    Güden, Mustafa; YÜKSEL, Sinan; Taşdemirci, Alper; Tanoğlu, Metin

    2007-01-01

    The effect of Al closed-cell foam filling on the quasi-static crushing behavior of an E-glass woven fabric polyester composite tube and thin-walled Al/polyester composite hybrid tube was experimentally investigated. For comparison, empty Al, empty composite and empty hybrid tubes were also tested. Empty composite and empty hybrid tubes crushed predominantly in progressive crushing mode, without applying any triggering mechanism. Foam filling was found to be ineffective in increasing the crush...

  9. Dual-energy X-ray micro-CT imaging of hybrid Ni/Al open-cell foam

    Science.gov (United States)

    Fíla, T.; Kumpová, I.; Koudelka, P.; Zlámal, P.; Vavřík, D.; Jiroušek, O.; Jung, A.

    2016-01-01

    In this paper, we employ dual-energy X-ray microfocus tomography (DECT) measurement to develop high-resolution finite element (FE) models that can be used for the numerical assessment of the deformation behaviour of hybrid Ni/Al foam subjected to both quasi-static and dynamic compressive loading. Cubic samples of hybrid Ni/Al open-cell foam with an edge length of [15]mm were investigated by the DECT measurement. The material was prepared using AlSi7Mg0.3 aluminium foam with a mean pore size of [0.85]mm, coated with nanocrystalline nickel (crystallite size of approx. [50]nm) to form a surface layer with a theoretical thickness of [0.075]mm. CT imaging was carried out using state-of-the-art DSCT/DECT X-ray scanner developed at Centre of Excellence Telč. The device consists of a modular orthogonal assembly of two tube-detector imaging pairs, with an independent geometry setting and shared rotational stage mounted on a complex 16-axis CNC positioning system to enable unprecedented measurement variability for highly-detailed tomographical measurements. A sample of the metal foam was simultaneously irradiated using an XWT-240-SE reflection type X-ray tube and an XWT-160-TCHR transmission type X-ray tube. An enhanced dual-source sampling strategy was used for data acquisition. X-ray images were taken using XRD1622 large area GOS scintillator flat panel detectors with an active area of [410 × 410]mm and resolution [2048 × 2048]pixels. Tomographic scanning was performed in 1,200 projections with a 0.3 degree angular step to improve the accuracy of the generated models due to the very complex microstructure and high attenuation of the investigated material. Reconstructed data was processed using a dual-energy algorithm, and was used for the development of a 3D model and voxel model of the foam. The selected parameters of the models were compared with nominal parameters of the actual foam and showed good correlation.

  10. Dual-energy X-ray micro-CT imaging of hybrid Ni/Al open-cell foam

    International Nuclear Information System (INIS)

    In this paper, we employ dual-energy X-ray microfocus tomography (DECT) measurement to develop high-resolution finite element (FE) models that can be used for the numerical assessment of the deformation behaviour of hybrid Ni/Al foam subjected to both quasi-static and dynamic compressive loading. Cubic samples of hybrid Ni/Al open-cell foam with an edge length of [15]mm were investigated by the DECT measurement. The material was prepared using AlSi7Mg0.3 aluminium foam with a mean pore size of [0.85]mm, coated with nanocrystalline nickel (crystallite size of approx. [50]nm) to form a surface layer with a theoretical thickness of [0.075]mm. CT imaging was carried out using state-of-the-art DSCT/DECT X-ray scanner developed at Centre of Excellence Telč. The device consists of a modular orthogonal assembly of two tube-detector imaging pairs, with an independent geometry setting and shared rotational stage mounted on a complex 16-axis CNC positioning system to enable unprecedented measurement variability for highly-detailed tomographical measurements. A sample of the metal foam was simultaneously irradiated using an XWT-240-SE reflection type X-ray tube and an XWT-160-TCHR transmission type X-ray tube. An enhanced dual-source sampling strategy was used for data acquisition. X-ray images were taken using XRD1622 large area GOS scintillator flat panel detectors with an active area of [410 × 410]mm and resolution [2048 × 2048]pixels. Tomographic scanning was performed in 1,200 projections with a 0.3 degree angular step to improve the accuracy of the generated models due to the very complex microstructure and high attenuation of the investigated material. Reconstructed data was processed using a dual-energy algorithm, and was used for the development of a 3D model and voxel model of the foam. The selected parameters of the models were compared with nominal parameters of the actual foam and showed good correlation

  11. New Approaches to Aluminum Integral Foam Production with Casting Methods

    OpenAIRE

    Ahmet Güner; Mustafa Merih Arıkan; Mehmet Nebioglu

    2015-01-01

    Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and a foam core. Producing near-net shape reduces production expenses. Insurance companies nowadays want the automotive industry to use metallic foam parts because of their higher impact energy absorption properties. In this paper, m...

  12. THE STRUCTURE CONTROL OF ALUMINUM FOAMS PRODUCED BY POWDER COMPACTED FOAMING PROCESS

    Institute of Scientific and Technical Information of China (English)

    X.H. You; F. Wang; L.C. Wang

    2004-01-01

    A new technique, powder compact foaming process for the production of aluminum foams has been studied in this article. According to this method, the aluminum powder is mixed with a powder foaming agent (TiH2). Subsequent to mixing, the powder blend is hot compacted to obtain a dense semi-finished product. Upon heating to temperatures within the range of the melting point, the foaming agent decomposes to evolve gas and the semi-finished product expands into a porous cellular aluminum. Foaming process is the key in this method. Based on experiments, the foaming characteristics were mainly analyzed and discussed. Experiments show that the aluminum-foam with closed pores and a uniform cell structure of high porosity can be obtained using this method by adjusting the foaming parameters: the content of foaming agent and foaming temperature.

  13. Effects of hydrothermal condition on properties of polymethacrylimide(PMI) foam cored sandwich structure%湿热环境对PMI泡沫夹芯复合材料性能的影响

    Institute of Scientific and Technical Information of China (English)

    董安琪; 段跃新; 肇研; 蔡吉喆

    2012-01-01

    采用聚甲基丙烯酰亚胺(PMI)泡沫、碳纤维增强环氧树脂(EW220/5258)复合材料面板制备了PMI泡沫夹芯复合材料,研究了PMI泡沫夹芯复合材料、EW220/5258复合材料面板及PMI泡沫芯材的吸湿特性,并讨论了湿热对PMI泡沫夹芯复合材料的压缩性能及介电性能的影响。结果发现:PMI泡沫夹芯复合材料的饱和吸湿时间为96h,饱和吸湿率为1.7%,EW220/5258复合材料面板会对PMI泡沫芯材起到一定的保护作用,阻止水汽进入泡沫,提高PMI泡沫夹芯复合材料的耐湿热性;由于水分子的增塑作用,湿热处理后PMI泡沫夹芯复合材料的压缩强度有所下降,强度保持率约为65.87%,湿热处理初期对其影响较大;湿热处理后,在7~18GHz的测试范围内,PMI泡沫夹芯复合材料的损耗角正切从0.008上升到0.012,介电常数几乎不变。%The polymethacrylimide(PMI) foam cored sandwich structure was prepared by using PMI foam,carbon fiber/epoxy resin(EW220/5258)composites panel.The absorption curves of PMI foam cored sandwich structure,EW220/5258 composite panel and PMI foam were investigated,and the effect of the hydrothermal condition on the compressive and dielectric properties of the PMI foam cored sandwich structure was also determined.The results indicate that the saturated hygroscopic time of the PMI foam cored sandwich structure is 96 hours and its absorption ratio is 1.7%,the EW220/5258 composite panel can protect its PMI foam from water to improve its hydrothermal resistance.Due to the plasticization of water,the compressive strength of the PMI foam cored sandwich structure decreases in hydrothermal environment with the retention ratio of 65.87%.Additionally,the initial stage has more influences on the properties than other stages of hydrothermal treatment.After hydrothermal treatment,the loss tangent of the PMI foam cored sandwich structure increases from 0.008 to 0.012 within the range of 7~18 GHz,while the

  14. Aspects of cell calculations in deterministic reactor core analysis

    Energy Technology Data Exchange (ETDEWEB)

    Varvayanni, M. [NCSR ' DEMOKRITOS' , PoB 60228, 15310 Aghia Paraskevi (Greece); Savva, P., E-mail: savvapan@ipta.demokritos.gr [NCSR ' DEMOKRITOS' , PoB 60228, 15310 Aghia Paraskevi (Greece); Catsaros, N. [NCSR ' DEMOKRITOS' , PoB 60228, 15310 Aghia Paraskevi (Greece)

    2011-02-15

    {Tau}he capability of achieving optimum utilization of the deterministic neutronic codes is very important, since, although elaborate tools, they are still widely used for nuclear reactor core analyses, due to specific advantages that they present compared to Monte Carlo codes. The user of a deterministic neutronic code system has to make some significant physical assumptions if correct results are to be obtained. A decisive first step at which such assumptions are required is the one-dimensional cell calculations, which provide the neutronic properties of the homogenized core cells and collapse the cross sections into user-defined energy groups. One of the most crucial determinations required at the above stage and significantly influencing the subsequent three-dimensional calculations of reactivity, concerns the transverse leakages, associated to each one-dimensional, user-defined core cell. For the appropriate definition of the transverse leakages several parameters concerning the core configuration must be taken into account. Moreover, the suitability of the assumptions made for the transverse cell leakages, depends on earlier user decisions, such as those made for the core partition into homogeneous cells. In the present work, the sensitivity of the calculated core reactivity to the determined leakages of the individual cells constituting the core, is studied. Moreover, appropriate assumptions concerning the transverse leakages in the one-dimensional cell calculations are searched out. The study is performed examining also the influence of the core size and the reflector existence, while the effect of the decisions made for the core partition into homogenous cells is investigated. In addition, the effect of broadened moderator channels formed within the core (e.g. by removing fuel plates to create space for control rod hosting) is also examined. Since the study required a large number of conceptual core configurations, experimental data could not be available

  15. Enhanced hydrogen production in microbial electrolysis cell with 3D self-assembly nickel foam-graphene cathode.

    Science.gov (United States)

    Cai, Weiwei; Liu, Wenzong; Han, Jinglong; Wang, Aijie

    2016-06-15

    In comparison to precious metal catalyst especially Platinum (Pt), nickel foam (NF) owned cheap cost and unique three-dimensional (3D) structure, however, it was scarcely applied as cathode material in microbial electrolysis cell (MEC) as the intrinsic laggard electrochemical activity for hydrogen recovery. In this study, a self-assembly 3D nickel foam-graphene (NF-G) cathode was fabricated by facile hydrothermal approach for hydrogen evolution in MECs. Electrochemical analysis (linear scan voltammetry and electrochemical impedance spectroscopy) revealed the improved electrochemical activity and effective mass diffusion after coating with graphene. NF-G as cathode in MEC showed a significant enhancement in hydrogen production rate compared with nickel foam at a variety of biases. Noticeably, NF-G showed a comparable averaged hydrogen production rate (1.31±0.07mL H2mL(-1) reactord(-1)) to Platinum/carbon (Pt/C) (1.32±0.07mL H2mL(-1) reactord(-1)) at 0.8V. Profitable energy recovery could be achieved by NF-G cathode at higher applied voltage, which performed the best hydrogen yield of 3.27±0.16mol H2mol(-1) acetate at 0.8V and highest energy efficiency of 185.92±6.48% at 0.6V. PMID:26807526

  16. Combination of spices and herbal extract restores macrophage foam cell migration and abrogates the athero-inflammatory signalling cascade of atherogenesis.

    Science.gov (United States)

    Nimgulkar, Chetan; Ghosh, Sudip; Sankar, Anand B; Uday, Kumar P; Surekha, M V; Madhusudhanachary, P; Annapurna, B R; Raghu, P; Bharatraj, Dinesh Kumar

    2015-09-01

    The trapping of lipid-laden macrophages in the arterial intima is a critical but reversible step in atherogenesis. However, information about possible treatments for this condition is lacking. Here, we hypothesized that combining the polyphenol-rich fractions (PHC) of commonly consumed spices (Allium sativum L (Liliaceae), Zingiber officinale R (Zingiberaceae), Curcuma longa L (Zingiberaceae)) and herbs (Terminalia arjuna (R) W & A (Combretaceae) and Cyperus rotundus L (Cyperaceae)) prevents foam cell formation and atherogenesis. Using an in vitro foam cell formation assay, we found that PHC significantly inhibited lipid-laden macrophage foam cell formation compared to the depleted polyphenol fraction of PHC (F-PHC). We further observed that PHC attenuated the LDL and LPS induced CD36, p-FAK and PPAR-γ protein expression in macrophages and increased their migration. NK-κB-DNA interaction, TNF-α, ROS generation, and MMP9 and MMP2 protein expression were suppressed in PHC-treated macrophages. The anti-atherosclerotic activity of PHC was investigated in a high fat- and cholesterol-fed rabbit model. The inhibition of foam cell deposition within the aortic intima and atheroma formation confirmed the atheroprotective activity of PHC. Therefore, we conclude that the armoury of polyphenols in PHC attenuates the CD36 signalling cascade-mediated foam cell formation, enhances the migration of these cells and prevents atherogenesis. PMID:25869517

  17. Demonstration of neutron detection utilizing open cell foam and noble gas scintillation

    Energy Technology Data Exchange (ETDEWEB)

    Lavelle, C. M., E-mail: christopher.lavelle@jhuapl.edu; Miller, E. C. [The Johns Hopkins University Applied Physics Laboratory, Asymmetric Operations Department, Laurel, Maryland 20723 (United States); Coplan, M. [Institute for Physical Science and Technology, University of Maryland College Park, Maryland 20142 (United States); Thompson, Alan K.; Vest, Robert E.; Yue, A. T. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Kowler, A. L. [Department of Chemical Physics, University of Maryland, College Park, Maryland 20142 (United States); Koeth, T. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20142 (United States); Al-Sheikhly, M. [Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742 (United States); Clark, Charles W. [Institute for Physical Science and Technology, University of Maryland College Park, Maryland 20142 (United States); National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Joint Quantum Institute, National Institute of Standards and Technology and University of Maryland, Gaithersburg, Maryland 20899 (United States)

    2015-03-02

    We present results demonstrating neutron detection via a closely spaced converter structure coupled to low pressure noble gas scintillation instrumented by a single photo-multiplier tube (PMT). The converter is dispersed throughout the gas volume using a reticulated vitreous carbon foam coated with boron carbide (B{sub 4}C). A calibrated cold neutron beam is used to measure the neutron detection properties, using a thin film of enriched {sup 10}B as a reference standard. Monte Carlo computations of the ion energy deposition are discussed, including treatment of the foam random network. Results from this study indicate that the foam shadows a significant portion of the scintillation light from the PMT. The high scintillation yield of Xe appears to overcome the light loss, facilitating neutron detection and presenting interesting opportunities for neutron detector design.

  18. A simplified analytical model of radiative heat transfer in open cell foams

    International Nuclear Information System (INIS)

    A simplified one-dimensional analytical model of radiative heat transfer in foams is presented, based on the idea of dividing the porous material into layers at the pore level and then modeling each layer of the porous material as an equivalent semi-transparent, absorbing and reflecting plane. Compared to existing models, the model proposed in this paper has the advantage of explicitly accounting for the geometry of the foam and the radiative energy fluxes, at the same time ensuring self-consistency and offering the computational lightness of analytical models, without sacrificing the mathematical simplicity of the formulation. Using a regular cubic lattice representation and assuming diffuse radiation, straightforward analytical correlations are derived to evaluate the characteristics both of single layers of foam and of finite thickness samples, accounting for various boundary conditions. The predictions of the model are in good agreement with experimental data taken from the literature

  19. Serially connected solid oxide fuel cells having monolithic cores

    Science.gov (United States)

    Herceg, Joseph E.

    1987-01-01

    A solid oxide fuel cell for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of cell segments electrically serially connected in the flow direction, each segment consisting of electrolyte walls and interconnect that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageways; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte composite materials is of the order of 0.002-0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002-0.05 cm thick. Between 2 and 50 cell segments may be connected in series.

  20. Low-density carbonized resorcinol-formaldehyde foams

    International Nuclear Information System (INIS)

    This report documents research and development on resorcinol- formaldehyde-based foam materials conducted between 1986 and June 1990, when the effort was discontinued. The foams discussed are resorcinol-formaldehyde (RF) foam, carbonized RF (CRF) foam, and two composite foams, a polystyrene/RF (PS/RF) foam and its carbonized derivative (CPR). The RF foams are synthesized by the polycondensation of resorcinol with formaldehyde in a slightly basic solution. Their structure and density depend strongly on the concentration of the sodium carbonate catalyst. The have an interconnected bead structure similar to that of silica aerogels; bead sizes range from 30 to 130 Angstrom, and cell sizes are less than 0.1 μm. We have achieved densities of 16 to 200 mg/cm3. The RF foams can be pyrolyzed in an inert atmosphere to form a vitreous carbon foam (CRF), which has a similar microstructure but much higher mechanical strength. The PS/RF foams are obtained by filling the 2- to 3-μm cells of PS foam (a low-density hydrocarbon foam we have developed) with RF. The resultant foams have the outstanding handling and machinability of the PS foam matrix and the small cell size of RF. Pyrolyzing PS/RF foams causes depolymerization and loss of the PS; the resulting CPR foams have a structure similar to the PS foams in which CRF both replicates and fills the PS cells

  1. SoftCell: Taking Control of Cellular Core Networks

    OpenAIRE

    Jin, Xin; Li, Li Erran; Vanbever, Laurent; Rexford, Jennifer

    2013-01-01

    Existing cellular networks suffer from inflexible and expensive equipment, and complex control-plane protocols. To address these challenges, we present SoftCell, a scalable architecture for supporting fine-grained policies for mobile devices in cellular core networks. The SoftCell controller realizes high-level service polices by directing traffic over paths that traverse a sequence of middleboxes, optimized to the network conditions and user locations. To ensure scalability, the core switche...

  2. Composite and Nanocomposite Metal Foams

    OpenAIRE

    Isabel Duarte; José M. F. Ferreira

    2016-01-01

    Open-cell and closed-cell metal foams have been reinforced with different kinds of micro- and nano-sized reinforcements to enhance their mechanical properties of the metallic matrix. The idea behind this is that the reinforcement will strengthen the matrix of the cell edges and cell walls and provide high strength and stiffness. This manuscript provides an updated overview of the different manufacturing processes of composite and nanocomposite metal foams.

  3. Low-density, salt-loaded foams

    International Nuclear Information System (INIS)

    An experiment was conducted at LLL that required low-density, fine-celled foams uniformly loaded with rubidium. Foams meeting these requirements were produced by impregnating foams made from polyacrylonitrile with rubidium fluoride. Foams with densities from 0.025 to 0.4 g/cm3 were prepared and loaded with 0.002 to 0.20 g/cm3 of rubidium fluoride

  4. Foam injection moulding of a TPO/TPC-blend and the effect of different nucleating agents on the resulting foam structure

    Science.gov (United States)

    Mueller, J.; Spoerrer, A.; Altstaedt, V.

    2014-05-01

    The manufacturing of car interior parts with a soft touch surface is possible in a one-step injection moulding process, in which an injection moulded carrier is overmoulded with a compatible foamed thermoplastic elastomer (TPE). In contrast to the complex conventional process the structural foaming of the TPE component allows a saving of one material component as it combines a compact skin and a foamed core. Furthermore the manufacturing process can be achieved on a two component injection moulding machine which offers a much higher economic efficiency. One approach to reach an adhesion between a reinforced PP carrier and the foamed TPE component including good surface resistance is the use of an olefinic-/polyester-based TPE blend (TPO/TPC-blend). This paper is going to show the possibility to process a TPO/TPC-blend system by foam injection moulding with MuCell® and how the resulting foam structure can be influenced by various nucleating agents. For this purpose particles which differ in type, form and size were added in various concentrations to the TPE-blend. Before the structure elucidation of the foamed samples the particle dispersion and their effects on the polymers rheological properties were investigated. Finally abrasion tests were performed to investigate the influence of the particles on the performance characteristics of the foamed blend system. The results showed that the foam structure as well as the surface quality of the foamed TPO/TPC-blend can be improved with the use of suitable nucleating agents. Furthermore the abrasion properties can be advanced with appropriate additives in the right dosage.

  5. Effective Elastic Moduli of Closed-cell Aluminium Foams - Homogenization Method

    Czech Academy of Sciences Publication Activity Database

    Koudelka, P.; Doktor, T.; Valach, J.; Kytýř, Daniel; Jiroušek, Ondřej

    2013-01-01

    Roč. 75, č. 1 (2013), s. 161-170. ISSN 1454-2358 R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : homogenization * metal foam * micromechanical properties Subject RIV: JJ - Other Materials http://www.scientificbulletin.upb.ro/rev_docs_arhiva/full61d_730795.pdf

  6. Indirect Determination of Material Properties of Closed-Cell Metal Foam: Comparison of Voxel and Tetrahedral Finite Element Models

    Czech Academy of Sciences Publication Activity Database

    Jiroušek, Ondřej; Koudelka_ml., Petr; Zlámal, Petr

    Stirlingshire: Civil-Comp Press, 2012 - (Topping, B.), s. 243-253 ISBN 978-1-905088-55-3. [Engineering Computational Technology 2012 /8./. Dubrovník (HR), 04.09.2012-07.09.2012] Grant ostatní: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : metal foam * closed-cell material * orthotropic material properties * indirect methods * micro-CT * voxel models * tetrahedral models Subject RIV: JI - Composite Materials http://www.ctresources.info/ccp/pdf.html?id=7235

  7. μ-CT-based finite element analysis on imperfections in open-celled metal foam: Mechanical properties

    International Nuclear Information System (INIS)

    This study digitally identifies and repairs defects produced in the manufacturing of an open-cell metal foam for the first time. Finite element calculations are based on microcomputed tomography data of actual samples. The effective Young’s modulus and 0.2% offset yield strength are calculated and equivalent plastic strain is used to identify weakness within the material. In areas of high plastic deformation, the structure is digitally repaired locally and the calculations are repeated in order to quantify the change in material properties.

  8. Growth of MRSA and Pseudomonas aeruginosa in a fine-celled foam model containing sessile commensal skin bacteria.

    Science.gov (United States)

    Oates, Angela; McBain, Andrew J

    2016-01-01

    Sessile cultures of the skin bacteria Staphylococcus saprophyticus and Corynebacterium xerosis were grown using novel fine-celled foam substrata to test the outcome of challenge by methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa under three growth medium regimens (simulated sweat, simulated serum or simulated sweat substituted with simulated serum during the microbial challenge). S. saprophyticus and C. xerosis significantly limited MRSA and P. aeruginosa immigration respectively, under the simulated sweat and serum medium regimes. Under the substitution medium regime however, MRSA and P. aeruginosa integrated into pre-established biofilms to a significantly greater extent, attaining cell densities similar to the axenic controls. The outcome of challenge was influenced by the medium composition and test organism but could not be predicted based on planktonic competition assays or growth dynamics. Interactions between skin and wound isolates could be modelled using the fine-celled foam-based system. This model could be used to further investigate interactions and also in preclinical studies of antimicrobial wound care regimens. PMID:26727101

  9. Continuous production of microcellular foams

    Science.gov (United States)

    Han, Xiangmin

    Continuous production of microcellular foams, characterized by cell size smaller than 10 mum and cell density larger than 109 cells/cm 3, was studied using supercritical carbon dioxide (CO2) as the foaming agent. Microcellular foams of polystyrene and polystyrene nanocomposites were successfully produced on a two-stage single screw extruder. The contraction flow in the extrusion die was simulated with the FLUENT fluid dynamics computational code to predict profiles of pressure, temperature, viscosity, and velocity. The nucleation onset was determined based on the pressure profile and equilibrium solubility. It was shown that a high CO 2 concentration or a high foaming temperature induces an earlier nucleation near the die entrance. The pressure profile and the position of nucleation onset were correlated to cell nucleation and growth, which helps understand the effects of operating conditions on cell structure. To perform the simulation, viscosity and solubility of the CO2/polystyrene system were characterized. Sanchez-Lacombe equation of state was applied to represent the phase equilibrium. Effects of temperature, pressure, and CO 2 content on the shear viscosity were explained using the free volume theory. Systematic experiments were performed to verify effects of three key operating conditions: CO2 content, pressure drop or pressure drop rate, and foaming temperature, on the foam cell structure. Experimental results were compared with simulations to gain insight into the foaming process. Studies exhibit that a higher pressure drop or pressure drop rate results in smaller cells and greater cell density. Below the CO2 solubility, cell size decreases and cell density increases with an increase of CO2 concentration. A high CO2 concentration favors producing open cell foams. Die temperature affects both cell size and cell structure (open or closed). Combining nano-clay compounding with supercritical CO2 foaming provides a new technique for the design and control of

  10. Foam Microrheology

    International Nuclear Information System (INIS)

    The microrheology of liquid foams is discussed for two different regimes: static equilibrium where the capillary number Ca is zero, and the viscous regime where viscosity and surface tension are important and Ca is finite. The Surface Evolver is used to calculate the equilibrium structure of wet Kelvin foams and dry soap froths with random structure, i.e., topological disorder. The distributions of polyhedra and faces are compared with the experimental data of Matzke. Simple shearing flow of a random foam under quasistatic conditions is also described. Viscous phenomena are explored in the context of uniform expansion of 2D and 3D foams at low Reynolds number. Boundary integral methods are used to calculate the influence of Ca on the evolution of foam microstructure, which includes bubble shape and the distribution of liquid between films, Plateau borders, and (in 3D) the nodes where Plateau borders meet. The micromechanical point of view guides the development of structure-property-processing relationships for foams

  11. Foam Microrheology

    Energy Technology Data Exchange (ETDEWEB)

    KRAYNIK,ANDREW M.; LOEWENBERG,MICHAEL; REINELT,DOUGLAS A.

    1999-09-01

    The microrheology of liquid foams is discussed for two different regimes: static equilibrium where the capillary number Ca is zero, and the viscous regime where viscosity and surface tension are important and Ca is finite. The Surface Evolver is used to calculate the equilibrium structure of wet Kelvin foams and dry soap froths with random structure, i.e., topological disorder. The distributions of polyhedra and faces are compared with the experimental data of Matzke. Simple shearing flow of a random foam under quasistatic conditions is also described. Viscous phenomena are explored in the context of uniform expansion of 2D and 3D foams at low Reynolds number. Boundary integral methods are used to calculate the influence of Ca on the evolution of foam microstructure, which includes bubble shape and the distribution of liquid between films, Plateau borders, and (in 3D) the nodes where Plateau borders meet. The micromechanical point of view guides the development of structure-property-processing relationships for foams.

  12. Fabrication and electromagnetic interference shielding performance of open-cell foam of a Cu–Ni alloy integrated with CNTs

    Energy Technology Data Exchange (ETDEWEB)

    Ji, Keju; Zhao, Huihui; Zhang, Jun; Chen, Jia; Dai, Zhendong, E-mail: zddai@nuaa.edu.cn

    2014-08-30

    Highlights: • Cu–Ni alloy open-cell foam integrated with CNTs was used for EMI shielding. • The composite was prepared by electroless, electro-, and electrophoretic deposition. • The main shielding mechanism was multiple reflections and absorptions of microwaves. • The composite had a porous structure, large surface area, and inherent permeability. - Abstract: A lightweight multi-layered electromagnetic interference (EMI) shielding material made of open-cell foam of a Cu–Ni alloy integrated with carbon nanotubes (CNTs) was prepared by electroless copper plating, then nickel electroplating, and finally electrophoretic deposition of CNTs. The foamed Cu–Ni–CNT composite comprises, from inside to outside, Cu, Ni, and CNT layers. Scanning electron microscopy, energy dispersive spectroscopy, and EMI tests were employed to characterize the morphology, composition, and EMI performance of the composite, respectively. The results indicated that the shielding effectiveness (SE) of the composite increased with increasing pore density (indicated as pores per inch (PPI)) and increasing thickness. A specimen with a PPI of 110 and a 1.5-mm thickness had a maximum SE of up to 54.6 dB, and a SE as high as 47.5 dB on average in the 8–12 GHz range. Integrating the inherent superiority of Cu, Ni, and CNTs, the porous structure of the composite can attenuate the incident electromagnetic microwaves by reflecting, scattering, and absorbing them between the metallic skeleton and the CNT layer. The multiple reflections and absorptions make it difficult for the microwaves to escape from the composite before being absorbed, thereby making the composite a potential shielding material.

  13. Cobalt and molybdenum activated electrodes in foam based alkaline electrolysis cells at 150-250 °C and 40 bar

    DEFF Research Database (Denmark)

    Allebrod, Frank; Chatzichristodoulou, Christodoulos; Mogensen, Mogens Bjerg

    2014-01-01

    A new type of alkaline electrolysis cells with nickel foam based gas diffusion electrodes and KOH (aq) immobilized in mesoporous SrTiO3 has been developed and tested at temperatures of 150 C, 200 C and 250 C at a pressure of 40 bar. Two cells have been characterized during the 270 h long test...

  14. Graded porous polyurethane foam: A potential scaffold for oro-maxillary bone regeneration

    International Nuclear Information System (INIS)

    Bone tissue engineering applications demand for biomaterials offering a substrate for cell adhesion, migration, and proliferation, while inferring suitable mechanical properties to the construct. In the present study, polyurethane (PU) foams were synthesized to develop a graded porous material—characterized by a dense shell and a porous core—for the treatment of oro-maxillary bone defects. Foam was synthesized via a one-pot reaction starting from a polyisocyanate and a biocompatible polyester diol, using water as a foaming agent. Different foaming conditions were examined, with the aim of creating a dense/porous functional graded material that would perform at the same time as an osteoconductive scaffold for bone defect regeneration and as a membrane-barrier to gingival tissue ingrowth. The obtained PU was characterized in terms of morphological and mechanical properties. Biocompatibility assessment was performed in combination with bone-marrow-derived human mesenchymal stromal cells (hBMSCs). Our findings confirm that the material is potentially suitable for guided bone regeneration applications. - Highlights: • Graded porous polyurethane foams were synthesized via a one-pot foaming reaction. • The inner porous core might act as a scaffold for guided bone regeneration. • A dense outer shell was introduced to act as a barrier to gingival tissue ingrowth. • The synthesized foams were non-toxic and supportive of hBMSC adhesion

  15. Graded porous polyurethane foam: A potential scaffold for oro-maxillary bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Giannitelli, S.M. [Department of Engineering, Tissue Engineering Unit, Università Campus Bio-Medico di Roma, Rome (Italy); Basoli, F. [Department of Chemical Science and Technology, University of Rome “Tor Vergata”, Rome (Italy); Mozetic, P. [Department of Engineering, Tissue Engineering Unit, Università Campus Bio-Medico di Roma, Rome (Italy); Piva, P.; Bartuli, F.N.; Luciani, F. [University of Rome “Tor Vergata”, Rome (Italy); Arcuri, C. [Department of Periodontics, University of Rome “Tor Vergata”, Rome (Italy); U.O.C.C. Odontostomatology, “S. Giovanni Calibita, Fatebenefratelli” Hospital, Rome (Italy); Trombetta, M. [Department of Engineering, Tissue Engineering Unit, Università Campus Bio-Medico di Roma, Rome (Italy); Rainer, A., E-mail: a.rainer@unicampus.it [Department of Engineering, Tissue Engineering Unit, Università Campus Bio-Medico di Roma, Rome (Italy); Licoccia, S. [Department of Chemical Science and Technology, University of Rome “Tor Vergata”, Rome (Italy)

    2015-06-01

    Bone tissue engineering applications demand for biomaterials offering a substrate for cell adhesion, migration, and proliferation, while inferring suitable mechanical properties to the construct. In the present study, polyurethane (PU) foams were synthesized to develop a graded porous material—characterized by a dense shell and a porous core—for the treatment of oro-maxillary bone defects. Foam was synthesized via a one-pot reaction starting from a polyisocyanate and a biocompatible polyester diol, using water as a foaming agent. Different foaming conditions were examined, with the aim of creating a dense/porous functional graded material that would perform at the same time as an osteoconductive scaffold for bone defect regeneration and as a membrane-barrier to gingival tissue ingrowth. The obtained PU was characterized in terms of morphological and mechanical properties. Biocompatibility assessment was performed in combination with bone-marrow-derived human mesenchymal stromal cells (hBMSCs). Our findings confirm that the material is potentially suitable for guided bone regeneration applications. - Highlights: • Graded porous polyurethane foams were synthesized via a one-pot foaming reaction. • The inner porous core might act as a scaffold for guided bone regeneration. • A dense outer shell was introduced to act as a barrier to gingival tissue ingrowth. • The synthesized foams were non-toxic and supportive of hBMSC adhesion.

  16. Analysis of anisotropy and strain rate sensitivity of open-cell metal foam

    International Nuclear Information System (INIS)

    Highlights: ► Numerical analysis of m.pore® aluminium foam based on micro-computed tomography data. ► Additional experimental testing – excellent agreement with numerical data. ► Analysis of strain rate sensitivity. ► Analysis of material anisotropy. ► Detailed analysis of micro-inertia and strain rate sensitivity. - Abstract: This paper addresses numerical and experimental analysis of the m.pore® aluminium foam. Numerical models are based on computed tomography data in order to capture the complex material meso-structure. Uni-axial experimental tests were performed for quasi-static loading and an excellent agreement with numerical results has been obtained. Numerical analyses were extended for characteristic strain rates in order to analyse the strain rate sensitivity and anisotropy. Both, the micro-inertia and the base material strain rate sensitivity have an influence on the dynamic behaviour of the cellular metal

  17. Endothelial cell death and intimal foam cell accumulation in the coronary artery of infected hypercholesterolemic minipigs

    DEFF Research Database (Denmark)

    Birck, Malene Muusfeldt; Saraste, Antti; Hyttel, Poul;

    2013-01-01

    Apoptosis of endothelial cells (ECs) has been suggested to play a role in atherosclerosis. We studied the synergism of hypercholesterolemia with Chlamydia pneumoniae and influenza virus infections on EC morphology and intimal changes in a minipig model. The coronary artery was excised at euthanasia...

  18. Evaluation of core-debris accommodation within inner containment cell

    International Nuclear Information System (INIS)

    A reactor cell concept for permanent retention has been developed based on evaluations of core debris melt penetration into containment structures, material interactions, pressure buildup and hydrogen concentration in the containment. The selected reactor cell concept includes a protective layer of MgO on the reactor cell floor, a graphite layer as the cell wall liner protection, and insulating firebrick to keep the cell concrete structures at an acceptable temperature level. To determine the feasibility of long-term/permanent retention of core debris, parametric studies were performed with the modified GROWS-2 code and the CACECO code to assess the range of debris penetration, containment responses and cooling requirements. Debris penetration into a MgO delay bed was shown to be very sensitive to the initial debris layer thickness. Long-term debris retention capability can be enhanced by preventing early sodium boil-off from the reactor cell

  19. Amorphous Fe-based metal foam

    International Nuclear Information System (INIS)

    A foam synthesis method that takes advantage of the viscous high-temperature liquid state of Fe-based bulk glass-forming alloys to produce amorphous steel foam is introduced. Zirconium hydride is utilized as a foaming agent taking advantage of the low hydrogen solubility of these glass-forming alloys. Amorphous foams with porosities up to 65% were produced having homogenous cellular morphologies that exhibit cell-size uniformity. Even though intracellular solid regions as thin as a few micrometers are detected, on a global scale the cellular structure is determined to be incapable of alleviating the foam from the brittle nature of the monolithic glass

  20. New Approaches to Aluminum Integral Foam Production with Casting Methods

    Directory of Open Access Journals (Sweden)

    Ahmet Güner

    2015-08-01

    Full Text Available Integral foam has been used in the production of polymer materials for a long time. Metal integral foam casting systems are obtained by transferring and adapting polymer injection technology. Metal integral foam produced by casting has a solid skin at the surface and a foam core. Producing near-net shape reduces production expenses. Insurance companies nowadays want the automotive industry to use metallic foam parts because of their higher impact energy absorption properties. In this paper, manufacturing processes of aluminum integral foam with casting methods will be discussed.

  1. Fabrication and electromagnetic interference shielding performance of open-cell foam of a Cu-Ni alloy integrated with CNTs

    Science.gov (United States)

    Ji, Keju; Zhao, Huihui; Zhang, Jun; Chen, Jia; Dai, Zhendong

    2014-08-01

    A lightweight multi-layered electromagnetic interference (EMI) shielding material made of open-cell foam of a Cu-Ni alloy integrated with carbon nanotubes (CNTs) was prepared by electroless copper plating, then nickel electroplating, and finally electrophoretic deposition of CNTs. The foamed Cu-Ni-CNT composite comprises, from inside to outside, Cu, Ni, and CNT layers. Scanning electron microscopy, energy dispersive spectroscopy, and EMI tests were employed to characterize the morphology, composition, and EMI performance of the composite, respectively. The results indicated that the shielding effectiveness (SE) of the composite increased with increasing pore density (indicated as pores per inch (PPI)) and increasing thickness. A specimen with a PPI of 110 and a 1.5-mm thickness had a maximum SE of up to 54.6 dB, and a SE as high as 47.5 dB on average in the 8-12 GHz range. Integrating the inherent superiority of Cu, Ni, and CNTs, the porous structure of the composite can attenuate the incident electromagnetic microwaves by reflecting, scattering, and absorbing them between the metallic skeleton and the CNT layer. The multiple reflections and absorptions make it difficult for the microwaves to escape from the composite before being absorbed, thereby making the composite a potential shielding material.

  2. Plasma-Spray Metal Coating On Foam

    Science.gov (United States)

    Cranston, J.

    1994-01-01

    Molds, forms, and other substrates made of foams coated with metals by plasma spraying. Foam might be ceramic, carbon, metallic, organic, or inorganic. After coat applied by plasma spraying, foam left intact or removed by acid leaching, conventional machining, water-jet cutting, or another suitable technique. Cores or vessels made of various foam materials plasma-coated with metals according to method useful as thermally insulating containers for foods, liquids, or gases, or as mandrels for making composite-material (matrix/fiber) parts, or making thermally insulating firewalls in automobiles.

  3. Metal Foaming Investigated by X-ray Radioscopy

    Directory of Open Access Journals (Sweden)

    Catalina Jiménez

    2011-12-01

    Full Text Available The use of X-ray radioscopy for in-situ studies of metal foam formation and evolution is reviewed. Selected results demonstrate the power of X-ray radioscopy as diagnostic tool for metal foaming. Qualitative analyses of foam nucleation and evolution, drainage development, issues of thermal contact, mold filling, cell wall rupture and more are given. Additionally, quantitative analyses based on series of images of foam expansion yielding coalescence rates, density distributions, etc., are performed by dedicated software. These techniques help us to understand the foaming behavior of metals and to improve both foaming methods and foam quality.

  4. Identification of stress-strain relation of aluminium foam cell wall by spherical nanoindentation

    Czech Academy of Sciences Publication Activity Database

    Králík, V.; Němeček, J.; Koudelka_ml., Petr

    Vol. 606. Durnten-Zurich : Trans Tech Publications, 2014 - (Haušild, P.), s. 11-14 ISBN 978-3-03835-062-0. ISSN 1013-9826. [Local Mechanical Properties /10./. Kutná Hora (CZ), 06.11.2013-08.11.2013] R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : aluminium foam * spherical nanoindentation * micromechanical properties * plastic properties Subject RIV: JI - Composite Materials http://www. scientific .net/KEM.606.11

  5. Effective elastic moduli of closed-cell aluminium foams - homogenization method

    Czech Academy of Sciences Publication Activity Database

    Koudelka_ml., Petr; Doktor, Tomáš; Valach, Jaroslav; Kytýř, Daniel; Jiroušek, Ondřej

    Brašov : Civil Engineering Faculty,Transilvania University of Brašov, 2012 - (Tuns, I.; Szava, I.; Ungureanu, V.), s. 244-250 ISBN 978-606-19-0078-7. [Youth Symposium on Experimental Solid Mechanics /11./. Brašov (RO), 30.05.2012-02.06.2012] Grant ostatní: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : metal foam * micromechanical properties * homogenization Subject RIV: JI - Composite Materials http://ysesm2012.comyr.com/text/Proceedings_11th_YSESM_FINAL.pdf

  6. Low density polycarbonate-graphene nanocomposite foams produced by supercritical carbon dioxide two-step foaming. Thermal stability

    OpenAIRE

    Gedler, Gabriel; Antunes, Marcelo de Sousa Pais; Velasco Perero, José Ignacio

    2016-01-01

    The thermal stability of low density polycarbonate-graphene nanocomposite foams prepared by supercritical carbon dioxide two-step foaming was investigated. Unfilled polycarbonate foams showed improved thermal stabilities when compared to the unfoamed polycarbonate, as the cellular structure of foams effectively slowed down the heat transfer process. Comparatively, polycarbonate foams with larger cells exhibited the highest delays in the early stage of thermal decomposition. Low density polyca...

  7. Corticotropin-Releasing Hormone (CRH) Promotes Macrophage Foam Cell Formation via Reduced Expression of ATP Binding Cassette Transporter-1 (ABCA1)

    OpenAIRE

    Cho, Wonkyoung; Kang, Jihee Lee; Park, Young Mi

    2015-01-01

    Atherosclerosis, the major pathology of cardiovascular disease, is caused by multiple factors involving psychological stress. Corticotropin-releasing hormone (CRH), which is released by neurosecretory cells in the hypothalamus, peripheral nerve terminals and epithelial cells, regulates various stress-related responses. Our current study aimed to verify the role of CRH in macrophage foam cell formation, the initial critical stage of atherosclerosis. Our quantitative real-time reverse transcrip...

  8. Enhancement of human ACAT1 gene expression to promote the macrophage-derived foam cell formation by dexamethasone

    Institute of Scientific and Technical Information of China (English)

    Li YANG; Ta Yuan CHANG; Bo Liang LI; Jin Bo YANG; Jia CHEN; Guang Yao YU; Pei ZHOU; Lei LEI; Zhen Zhen WANG; Catherine CY CHANG; XinYing YANG

    2004-01-01

    In macrophages, the accumulation of cholesteryl esters synthesized by the activated acyl-coenzyme A:cholesterol acyltransferase-1 (ACAT1) results in the foam cell formation, a hallmark of early atherosclerotic lesions. In this study,with the treatment of a glucocorticoid hormone dexamethasone (Dex), lipid staining results clearly showed the large accumulation of lipid droplets containing cholesteryl esters in THP- 1-derived macrophages exposed to lower concentration of the oxidized low-density lipoprotein (ox-LDL). More notably, when treated together with specific anti-ACAT inhibitors, the abundant cholesteryl ester accumulation was markedly diminished in THP-l-derived macrophages, confirming that ACAT is the key enzyme responsible for intracellular cholesteryl ester synthesis. RT-PCR and Western blot results indicated that Dex caused up-regulation of human ACAT1 expression at both the mRNA and protein levels in THP-1 and THP- 1-derived macrophages. The luciferase activity assay demonstrated that Dex could enhance the activity of human ACAT1 gene P1 promoter, a major factor leading to the ACAT1 activation, in a cell-specific manner.Further experimental evidences showed that a glucocorticoid response element (GRE) located within human ACAT1gene P1 promoter to response to the elevation of human ACAT1 gene expression by Dex could be functionally bound with glucocorticoid receptor (GR) proteins. These data supported the hypothesis that the clinical treatment with Dex,which increased the incidence of atherosclerosis, may in part due to enhancing the ACAT1 expression to promote the accumulation of cholesteryl esters during the macrophage-derived foam cell formation, an early stage of atherosclerosis.

  9. Interference Cancellation for Hollow-Core Fiber Reference Cells

    DEFF Research Database (Denmark)

    Seppä, Jeremias; Merimaa, Mikko; Manninen, Albert;

    2015-01-01

    Doppler-free saturated absorption spectroscopy of gases in hollow-core fiber (HCF)-based cells can be used for realizing new compact, robust, and portable frequency standards. In this paper, methods for cancelling interferences resulting from the optical connections between standard fiber and HCF...

  10. Fabrication of Gold Nanoparticles Doped DVB Foams

    International Nuclear Information System (INIS)

    The fabrication of gold nanoparticles doped low density DVB foams was researched, which can be used as ICF target materials. By high internal phase emulsion (HIPE) method, gold nanoparticles doped low density DVB foams were prepared, with gold nanoparticles dissolved in inner phase. The results show that the content of Au in the gold nanoparticles doped DVB foam is 3. 19%, the axial direction density of the foam is uniform which indicates none evident settlement of gold nanoparticles. SEM tests show that the gold doped DVB polymer foams have open-celled structure and very uniform aperture, and the average pore size is about 1 μm, which is much smaller than that of pure DVB foams. EDX test shows that Au disperses uniformly in the foams. (authors)

  11. Solid oxide fuel cell having a monolithic core

    International Nuclear Information System (INIS)

    A solid oxide fuel cell for electrochemically combining fuel and oxidant for generating galvanic output, wherein the cell core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support. Instead, the core is monolithic, where each electrolyte wall consists of thin layers of cathode and anode materials sandwiching a thin layer of electrolyte material therebetween, and each interconnect wall consists of thin layers of the cathode and anode materials sandwiching a thin layer of interconnect material therebetween. The electrolyte walls are arranged and backfolded between adjacent interconnect walls operable to define a plurality of core passageways alternately arranged where the inside faces thereof have only the anode material or only the cathode material exposed. Means direct the fuel to the anode-exposed core passageways and means direct the oxidant to the cathode-exposed core passageway; and means also direct the galvanic output to an exterior circuit. Each layer of the electrolyte and interconnect materials is of the order of 0.002-0.01 cm thick; and each layer of the cathode and anode materials is of the order of 0.002-0.05 cm thick

  12. Experimental study of foam flow through Berea Sandstone with applications to foam diversion in matrix acidizing

    Energy Technology Data Exchange (ETDEWEB)

    Parlar, M.; Parris, M.D.; Jasinski, R.J.; Robert, J.A.

    1995-12-31

    The results of a series of dual (diversion) and single core foam experiments followed by liquid injection in unfired Berea sandstone cores are reported at high rates relevant to matrix acidizing. The sensitivity of the results to surfactant type and concentration, foam and post-foam liquid injection rates, permeability, temperature and presence of oil are discussed. Surfactant type, preflush and foam slug sites are identified as critical parameters for subsequent liquid diversion into low-permeability regions. In contrast to EOR processes, surfactant adsorption is shown to be beneficial for diversion. At low liquid rates and high foam qualities relevant to EOR, foam at steady-state is found to behave as a Newtonian fluid with respect to liquid rate provided that the gas rate is above a critical rate. At high liquid rates and low qualities a shear-thinning behavior is observed. Pressure gradient during post-foam liquid injection is found to be independent of both foam and subsequent liquid rates, and to depend only on permeability for fixed surfactant chemistry. The entrance effects noted in foam literature are found to be more pronounced at high permeabilities and intermediate injection rates. Potential mechanisms as to why foam diversion in matrix acidizing works in the field are also discussed.

  13. Development of a Hopkinson Bar Apparatus for Testing Soft Materials: Application to a Closed-Cell Aluminum Foam

    OpenAIRE

    Marco Peroni; George Solomos; Norbert Babcsan

    2016-01-01

    An increasing interest in lightweight metallic foams for automotive, aerospace, and other applications has been observed in recent years. This is mainly due to the weight reduction that can be achieved using foams and for their mechanical energy absorption and acoustic damping capabilities. An accurate knowledge of the mechanical behavior of these materials, especially under dynamic loadings, is thus necessary. Unfortunately, metal foams and in general “soft” materials exhibit a series of pec...

  14. Human hepatoma cell lines on gas foaming templated alginate scaffolds for in vitro drug-drug interaction and metabolism studies.

    Science.gov (United States)

    Stampella, A; Rizzitelli, G; Donati, F; Mazzarino, M; de la Torre, X; Botrè, F; Giardi, M F; Dentini, M; Barbetta, A; Massimi, M

    2015-12-25

    Liver in vitro systems that allow reliable prediction of major human in vivo metabolic pathways have a significant impact in drug screening and drug metabolism research. In the present study, a novel porous scaffold composed of alginate was prepared by employing a gas-in-liquid foaming approach. Galactose residues were introduced on scaffold surfaces to promote cell adhesion and to enhance liver specific functions of the entrapped HepG2/C3A cells. Hepatoma cells in the gal-alginate scaffold showed higher levels of liver specific products (albumin and urea) and were more responsive to specific inducers (e.g. dexamethasone) and inhibitors (e.g. ketoconazole) of the CYP3A4 system than in conventional monolayer culture. HepG2/C3A cells were also more efficient in terms of rapid elimination of testosterone, used as a model substance, at rates comparable to those of in vivo excretion. In addition, an improvement in metabolism of testosterone, in terms of phase II metabolite formation, was also observed when the more differentiated HepaRG cells were used. Together the data suggest that hepatocyte/gas templated alginate-systems provide an innovative high throughput platform for in vitro drug metabolism and drug-drug interaction studies, with broad fields of application, and might provide a valid tool for minimizing animal use in preclinical testing of human relevance. PMID:26456671

  15. Foam Transport in Porous Media - A Review

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Z. F.; Freedman, Vicky L.; Zhong, Lirong

    2009-11-11

    Amendment solutions with or without surfactants have been used to remove contaminants from soil. However, it has drawbacks such that the amendment solution often mobilizes the plume, and its movement is controlled by gravity and preferential flow paths. Foam is an emulsion-like, two-phase system in which gas cells are dispersed in a liquid and separated by thin liquid films called lamellae. Potential advantages of using foams in sub-surface remediation include providing better control on the volume of fluids injected, uniformity of contact, and the ability to contain the migration of contaminant laden liquids. It is expected that foam can serve as a carrier of amendments for vadose zone remediation, e.g., at the Hanford Site. As part of the U.S. Department of Energy’s EM-20 program, a numerical simulation capability will be added to the Subsurface Transport Over Multiple Phases (STOMP) flow simulator. The primary purpose of this document is to review the modeling approaches of foam transport in porous media. However, as an aid to understanding the simulation approaches, some experiments under unsaturated conditions and the processes of foam transport are also reviewed. Foam may be formed when the surfactant concentration is above the critical micelle concentration. There are two main types of foams – the ball foam (microfoam) and the polyhedral foam. The characteristics of bulk foam are described by the properties such as foam quality, texture, stability, density, surface tension, disjoining pressure, etc. Foam has been used to flush contaminants such as metals, organics, and nonaqueous phase liquids from unsaturated soil. Ball foam, or colloidal gas aphrons, reportedly have been used for soil flushing in contaminated site remediation and was found to be more efficient than surfactant solutions on the basis of weight of contaminant removed per gram of surfactant. Experiments also indicate that the polyhedral foam can be used to enhance soil remediation. The

  16. Plane-compression properties of microcellular injected polypropylene using gas counter pressure and core-back expansion process

    OpenAIRE

    Reglero Ruiz, José Antonio; VINCENT, Michel; Billon, Noëlle

    2015-01-01

    Microcellular Polypropylene (PP) was obtained using Chemical Blowing Agents (CBA) in a injection process combined with Gas Counter Pressure (GCP) and core-back expansion molding. Two different types of PP, neat and charged, were mixed with a fixed proportion of CBA and injected into a plate, obtaining structural foams with a foamed core and solid outer skins. After, the plate morphology is analyzed to evaluate the main morphological parameters, such as cell size and thickness of the outer ski...

  17. Defect generation during solidification of aluminium foams

    International Nuclear Information System (INIS)

    The reason for the frequent occurrence of cell wall defects in metal foams was investigated. Aluminium foams often expand during solidification, a process which is referred as solidification expansion (SE). The effect of SE on the structure of aluminium foams was studied in situ by X-ray radioscopy and ex situ by X-ray tomography. A direct correlation between the magnitude of SE and the number of cell wall ruptures during SE and finally the number of defects in the solidified foams was found.

  18. Effect of crystals and fibrous network polymer additives on cellular morphology of microcellular foams

    Science.gov (United States)

    Miyamoto, Ryoma; Utano, Tatsumi; Yasuhara, Shunya; Ishihara, Shota; Ohshima, Masahiro

    2015-05-01

    In this study, the core-back foam injection molding was used for preparing microcelluar polypropylene (PP) foam with either a 1,3:2,4 bis-O-(4-methylbenzylidene)-D-sorbitol gelling agent (Gel-all MD) or a fibros network polymer additive (Metablen 3000). Both agent and addiive could effectively control the celluar morphology in foams but somehow different ways. In course of cooling the polymer with Gel-all MD in the mold caity, the agent enhanced the crystal nucleation and resulted in the large number of small crystals. The crystals acted as effective bubble nucleation agent in foaming process. Thus, the agent reduced the cell size and increased the cell density, drastically. Furthermore, the small crystals provided an inhomogenuity to the expanding cell wall and produced the high open cell content with nano-scale fibril structure. Gell-all as well as Metablene 3000 formed a gel-like fibrous network in melt. The network increased the elongational viscosity and tended to prevent the cell wall from breaking up. The foaming temperature window was widened by the presence of the network. Especially, the temperature window where the macro-fibrous structure was formed was expanded to the higher temperature. The effects of crystal nucleating agent and PTFE on crystals' size and number, viscoelsticity, rheological propreties of PP and cellular morphology were compared and thorougly investigated.

  19. Microcellular foams via phase separation

    International Nuclear Information System (INIS)

    A study of wide variety of processes for making plastic foams shows that phase separation processes for polymers from solutions offers the most viable methods for obtaining rigid plastic foams which met the physical requirements for fusion target designs. Four general phase separation methods have been shown to give polymer foams with densities less than 0.1 g/cm3 and cell sizes of 30μm or less. These methods involve the utilization of non-solvent, chemical or thermal cooling processes to achieve a controlled phase separation wherein either two distinct phases are obtained where the polymer phase is a continuous phase or two bicontinuous phases are obtained where both the polymer and solvent are interpenetrating, continuous, labyrinthine phases. Subsequent removal of the solvent gives the final foam structure

  20. Chemokine Signaling Enhances CD36 Responsiveness toward Oxidized Low-Density Lipoproteins and Accelerates Foam Cell Formation

    Directory of Open Access Journals (Sweden)

    Harikesh S. Wong

    2016-03-01

    Full Text Available Excessive uptake of oxidized low-density lipoproteins (oxLDL by macrophages is a fundamental characteristic of atherosclerosis. However, signals regulating the engagement of these ligands remain elusive. Using single-molecule imaging, we discovered a mechanism whereby chemokine signaling enhanced binding of oxLDL to the scavenger receptor, CD36. By activating the Rap1-GTPase, chemokines promoted integrin-mediated adhesion of macrophages to the substratum. As a result, cells exhibited pronounced remodeling of the cortical actin cytoskeleton that increased CD36 clustering. Remarkably, CD36 clusters formed predominantly within actin-poor regions of the cortex, and these regions were primed to engage oxLDL. In accordance with enhanced ligand engagement, prolonged exposure of macrophages to chemokines amplified the accumulation of esterified cholesterol, thereby accentuating the foam cell phenotype. These findings imply that the activation of integrins by chemokine signaling exerts feedforward control over receptor clustering and effectively alters the threshold for cells to engage ligands.

  1. Corticotropin-Releasing Hormone (CRH Promotes Macrophage Foam Cell Formation via Reduced Expression of ATP Binding Cassette Transporter-1 (ABCA1.

    Directory of Open Access Journals (Sweden)

    Wonkyoung Cho

    Full Text Available Atherosclerosis, the major pathology of cardiovascular disease, is caused by multiple factors involving psychological stress. Corticotropin-releasing hormone (CRH, which is released by neurosecretory cells in the hypothalamus, peripheral nerve terminals and epithelial cells, regulates various stress-related responses. Our current study aimed to verify the role of CRH in macrophage foam cell formation, the initial critical stage of atherosclerosis. Our quantitative real-time reverse transcriptase PCR (qRT-PCR, semi-quantitative reverse transcriptase PCR, and Western blot results indicate that CRH down-regulates ATP-binding cassette transporter-1 (ABCA1 and liver X receptor (LXR-α, a transcription factor for ABCA1, in murine peritoneal macrophages and human monocyte-derived macrophages. Oil-red O (ORO staining and intracellular cholesterol measurement of macrophages treated with or without oxidized LDL (oxLDL and with or without CRH (10 nM in the presence of apolipoprotein A1 (apoA1 revealed that CRH treatment promotes macrophage foam cell formation. The boron-dipyrromethene (BODIPY-conjugated cholesterol efflux assay showed that CRH treatment reduces macrophage cholesterol efflux. Western blot analysis showed that CRH-induced down-regulation of ABCA1 is dependent on phosphorylation of Akt (Ser473 induced by interaction between CRH and CRH receptor 1(CRHR1. We conclude that activation of this pathway by CRH accelerates macrophage foam cell formation and may promote stress-related atherosclerosis.

  2. Tumor Necrosis Factor-Alpha and Receptor Activator of Nuclear Factor-κB Ligand Augment Human Macrophage Foam-Cell Destruction of Extracellular Matrix Through Protease-Mediated Processes

    DEFF Research Database (Denmark)

    Skjøt-Arkil, Helene; Barascuk, Natasha; Larsen, Lise Korsager; Dziegiel, Morten; Henriksen, Kim; Karsdal, Morten A

    2012-01-01

    Abstract By secreting proteases such as cathepsins and matrix metalloproteinases (MMPs), macrophage foam cells may be a major cause of ruptured atherosclerotic plaques. The aims of the present study were to investigate in vitro role of human macrophage foam cells in degrading type I collagen, a...... into macrophage foam cells and cultured on a type I collagen matrix in the presence of TNF-alpha and RANK-L. Matrix degradation was measured by the cathepsin K-generated C-terminal cross-linked telopeptide of type I collagen (CTX-I) and the MMP-generated carboxyterminal telopeptide of type I collagen...... (ICTP) in supernatants showing that macrophage foam cells secrete MMPs and cathepsin K, resulting in release of ICTP and CTX-I. Stimulation with TNF-alpha increased CTX-I and ICTP dose dependently, with ICTP levels increasing by 59% and CTX-I levels increasing by 43%. RANK-L enhanced the release of CTX...

  3. A novel technique for making open-cell Al2O3-ZrO2 ceramic foam with plant seed template

    Directory of Open Access Journals (Sweden)

    Yu Jingyuan

    2010-08-01

    Full Text Available The aim of the present research is to provide a technique for preparing open-cell Al2O3-ZrO2 ceramic foams with uniform cell size. This technique used plant seeds to array templates and centrifugal slip casting to obtain cell struts with high packing density. Aqueous Al2O3-ZrO2 slurries with up to 50 vol.% solid contents were prepared and the rheological characteristic of the slurries was investigated. Consolidation was performed at an acceleration of 2,860 g for 60 min. The effect of the characteristic of plant seeds on the drying behavior of Al2O3-ZrO2 green compact was analyzed. The effects of the solid contents of slurries on segregation phenomena of Al2O3 and ZrO2 particles and green compact uniformity were investigated. The compressive stress-strain curve and deformation behavior of Al2O3-ZrO2 ceramic foams prepared using plant seed template were analyzed. The results showed segregation phenomenon is negligible for highly stable slurry with 50 vol.% solid loading. The prepared cell struts of Al2O3-ZrO2 foams have high green density (61.9% TD, sintered density (99.1% TD and homogeneous microstructure. When sintered at 1,550 篊 for 2 h, the cell size of Al2O3-ZrO2 foam is approximately uniform and the diameter is about 1.1 mm. The porosity and compressive strength of sintered products is 66.2% and 5.86 MPa, respectively.

  4. Washcoat Deposition of Ni- and Co-ZrO2 Low Surface Area Powders onto Ceramic Open-Cell Foams: Influence of Slurry Formulation and Rheology

    Directory of Open Access Journals (Sweden)

    Riccardo Balzarotti

    2015-12-01

    Full Text Available The effect of formulations and procedures to deposit thin active layers based on low surface area powders on complex geometry substrates (open-cell foams was experimentally assessed. An acid-free liquid medium based on water, glycerol, and polyvinyl alcohol was used for powder dispersion, while a dip-coating technique was chosen for washcoat deposition on 30 PPI ceramic open-cell foams. The rheological behavior was explained on the bases of both porosity and actual powder density. It was proved that the use of multiple dippings fulfills flexibility requirements for washcoat load management. Multiple depositions with intermediate flash drying steps at 350 °C were carried out. Washcoat loads in the 2.5 to 22 wt. % range were obtained. Pore clogging was seldom observed in a limited extent in samples with high loading (>20 wt. %. Adhesion, evaluated by means of accelerated stress test in ultrasound bath, pointed out good results of all the deposited layers.

  5. Facile Fabrication of Graphene-Containing Foam as a High-Performance Anode for Microbial Fuel Cells.

    Science.gov (United States)

    Yang, Lu; Wang, Shuqin; Peng, Shuqin; Jiang, Hongmei; Zhang, Youming; Deng, Wenfang; Tan, Yueming; Ma, Ming; Xie, Qingji

    2015-07-20

    Facile fabrication of novel three-dimensional anode materials to increase the bacterial loading capacity and improve substrate transport in microbial fuel cells (MFCs) is of great interest and importance. Herein, a novel graphene-containing foam (GCF) was fabricated easily by freeze-drying and pyrolysis of a graphene oxide-agarose gel. Owing to the involvement of graphene and stainless-steel mesh in the GCF, the GCF shows high electrical conductivity, enabling the GCF to be a conductive electrode for MFC applications. With the aid of agarose, the GCF electrode possesses a supermacroporous structure with pore sizes ranging from 100-200 μm and a high surface area, which greatly increase the bacterial loading capacity. Cell viability measurements indicate that the GCF possesses excellent biocompatibility. The MFC, equipped with a 0.4 mm-thick GCF anode, shows a maximum area power density of 786 mW m(-2) , which is 4.1 times that of a MFC equipped with a commercial carbon cloth anode. The simple fabrication route in combination with the outstanding electrochemical performance of the GCF indicates a promising anode for MFC applications. PMID:26095648

  6. Effect of composites based nickel foam anode in microbial fuel cell using Acetobacter aceti and Gluconobacter roseus as a biocatalysts.

    Science.gov (United States)

    Karthikeyan, Rengasamy; Krishnaraj, Navanietha; Selvam, Ammaiyappan; Wong, Jonathan Woon-Chung; Lee, Patrick K H; Leung, Michael K H; Berchmans, Sheela

    2016-10-01

    This study explores the use of materials such as chitosan (chit), polyaniline (PANI) and titanium carbide (TC) as anode materials for microbial fuel cells. Nickel foam (NF) was used as the base anode substrate. Four different types of anodes (NF, NF/PANI, NF/PANI/TC, NF/PANI/TC/Chit) are thus prepared and used in batch type microbial fuel cells operated with a mixed consortium of Acetobacter aceti and Gluconobacter roseus as the biocatalysts and bad wine as a feedstock. A maximum power density of 18.8Wm(-3) (≈2.3 times higher than NF) was obtained in the case of the anode modified with a composite of PANI/TC/Chit. The MFCs running under a constant external resistance of (50Ω) yielded 14.7% coulombic efficiency with a maximum chemical oxygen demand (COD) removal of 87-93%. The overall results suggest that the catalytic materials embedded in the chitosan matrix show the best performance and have potentials for further development. PMID:26970695

  7. Crosslinked polyethylene foams, via eb radiation

    International Nuclear Information System (INIS)

    Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to these foams, imparts optimum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine; building and insulation; packaging; domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203 degree sign C as the right blowing agent decomposition temperature. At a 22.7 kGys/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time

  8. Crosslinked polyethylene foams, via EB radiation

    Science.gov (United States)

    Cardoso, E. C. L.; Lugão, A. B.; Andrade E. Silva, L. G.

    1998-06-01

    Polyethylene foams, produced by radio-induced crosslinking, show a smooth and homogeneous surface, when compared to chemical crosslinking method using peroxide as crosslinking agent. This process fosters excellent adhesive and printability properties. Besides that, closed cells, intrinsic to theses foams, imparts opitmum mechanical, shocks and insulation resistance, indicating these foams to some markets segments as: automotive and transport; buoyancy, flotation and marine: building and insulation: packaging: domestic sports and leisure goods. We were in search of an ideal foam, by adding 5 to 15% of blowing agent in LDPE. A series of preliminary trials defined 203° C as the right blowing agent decomposition temperature. At a 22.7 kGy/dose ratio, the lowest dose for providing an efficient foam was 30 kGy, for a formulation comprising 10% of azodicarbonamide in LDPE, within a 10 minutes foaming time.

  9. Macrophage PPAR gamma Co-activator-1 alpha participates in repressing foam cell formation and atherosclerosis in response to conjugated linoleic acid

    OpenAIRE

    McCarthy, Cathal; Lieggi, Nora T; Barry, Denis; Mooney, Declan; de Gaetano, Monica; James, William G; McClelland, Sarah; Barry, Mary C; Escoubet-Lozach, Laure; Li, Andrew C.; Glass, Christopher K.; Fitzgerald, Desmond J.; Belton, Orina

    2013-01-01

    Conjugated linoleic acid (CLA) has the unique property of inducing regression of pre-established murine atherosclerosis. Understanding the mechanism(s) involved may help identify endogenous pathways that reverse human atherosclerosis. Here, we provide evidence that CLA inhibits foam cell formation via regulation of the nuclear receptor coactivator, peroxisome proliferator-activated receptor (PPAR)-γ coactivator (PGC)-1α, and that macrophage PGC-1α plays a role in atheroprotection in vivo. PGC...

  10. miR-155 acts as an anti-inflammatory factor in atherosclerosis-associated foam cell formation by repressing calcium-regulated heat stable protein 1

    OpenAIRE

    Xiaoyi Li; Deyong Kong; Heming Chen; Shuiyi Liu; Hui Hu; Tangwei Wu; Jing Wang; Weiqun Chen; Yong Ning; Yong Li; Zhongxin Lu

    2016-01-01

    Atherosclerosis (AS) is chronic inflammation in response to lipid accumulation. MicroRNA-155 (miR-155) is being increasingly studied to evaluate its potential as diagnostic biomarkers and therapeutic targets in many diseases. However, delineating the role of miR-155 in AS remains difficult. Here, we detected constitutive expression of several microRNAs (miRNAs) possibly associated with cardiovascular disease in foam cells and clinical specimens from patients with AS. Among them, we found that...

  11. Thermal Expansion of Polyurethane Foam

    Science.gov (United States)

    Lerch, Bradley A.; Sullivan, Roy M.

    2006-01-01

    Closed cell foams are often used for thermal insulation. In the case of the Space Shuttle, the External Tank uses several thermal protection systems to maintain the temperature of the cryogenic fuels. A few of these systems are polyurethane, closed cell foams. In an attempt to better understand the foam behavior on the tank, we are in the process of developing and improving thermal-mechanical models for the foams. These models will start at the microstructural level and progress to the overall structural behavior of the foams on the tank. One of the key properties for model characterization and verification is thermal expansion. Since the foam is not a material, but a structure, the modeling of the expansion is complex. It is also exacerbated by the anisoptropy of the material. During the spraying and foaming process, the cells become elongated in the rise direction and this imparts different properties in the rise direction than in the transverse directions. Our approach is to treat the foam as a two part structure consisting of the polymeric cell structure and the gas inside the cells. The polymeric skeleton has a thermal expansion of its own which is derived from the basic polymer chemistry. However, a major contributor to the thermal expansion is the volume change associated with the gas inside of the closed cells. As this gas expands it exerts pressure on the cell walls and changes the shape and size of the cells. The amount that this occurs depends on the elastic and viscoplastic properties of the polymer skeleton. The more compliant the polymeric skeleton, the more influence the gas pressure has on the expansion. An additional influence on the expansion process is that the polymeric skeleton begins to breakdown at elevated temperatures and releases additional gas species into the cell interiors, adding to the gas pressure. The fact that this is such a complex process makes thermal expansion ideal for testing the models. This report focuses on the thermal

  12. miR-155 acts as an anti-inflammatory factor in atherosclerosis-associated foam cell formation by repressing calcium-regulated heat stable protein 1.

    Science.gov (United States)

    Li, Xiaoyi; Kong, Deyong; Chen, Heming; Liu, Shuiyi; Hu, Hui; Wu, Tangwei; Wang, Jing; Chen, Weiqun; Ning, Yong; Li, Yong; Lu, Zhongxin

    2016-01-01

    Atherosclerosis (AS) is chronic inflammation in response to lipid accumulation. MicroRNA-155 (miR-155) is being increasingly studied to evaluate its potential as diagnostic biomarkers and therapeutic targets in many diseases. However, delineating the role of miR-155 in AS remains difficult. Here, we detected constitutive expression of several microRNAs (miRNAs) possibly associated with cardiovascular disease in foam cells and clinical specimens from patients with AS. Among them, we found that the level of miR-155 in foam cells was the most significantly elevated in a dose- and time-dependent manner. In addition, the expression of miR-155 was elevated in the plasma and plaque of patients with AS. We also reported for the first time that miR-155 targets calcium-regulated heat stable protein 1 (CARHSP1), which regulates the stability of tumor necrosis factor alpha (TNF-α) mRNA. Furthermore, we investigated the mechanism by which the miR-155 level is elevated. miR-155 upregulation is due to transcriptional regulation by nuclear factor (NF)-κB, which is activated by the inflammatory factor TNF-α. In summary, increased miR-155 relieves chronic inflammation by a negative feedback loop and plays a protective role during atherosclerosis-associated foam cell formation by signaling through the miR-155-CARHSP1-TNF-α pathway. PMID:26899994

  13. Influence of Orientation and Radiative Heat Transfer on Aluminum Foams in Buoyancy-Induced Convection

    Directory of Open Access Journals (Sweden)

    Marijn Billiet

    2015-10-01

    Full Text Available Two differently-produced open-cell aluminum foams were compared to a commercially available finned heat sink. Further, an aluminum plate and block were tested as a reference. All heat sinks have the same base plate dimensions of four by six inches. The first foam was made by investment casting of a polyurethane preform and has a porosity of 0.946 and a pore density of 10 pores per linear inch. The second foam is manufactured by casting over a solvable core and has a porosity of 0.85 and a pore density of 2.5 pores per linear inch. The effects of orientation and radiative heat transfer are experimentally investigated. The heat sinks are tested in a vertical and horizontal orientation. The effect of radiative heat transfer is investigated by comparing a painted/anodized heat sink with an untreated one. The heat flux through the heat sink for a certain temperature difference between the environment and the heat sink’s base plate is used as the performance indicator. For temperature differences larger than 30 °C, the finned heat sink outperforms the in-house-made aluminum foam heat sink on average by 17%. Furthermore, the in-house-made aluminum foam dissipates on average 12% less heat than the other aluminum foam for a temperature difference larger than 40 °C. By painting/anodizing the heat sinks, the heat transfer rate increased on average by 10% to 50%. Finally, the thermal performance of the horizontal in-house-made aluminum foam heat sink is up to 18% larger than the one of the vertical aluminum foam heat sink.

  14. Brazing open cell reticulated copper foam to stainless steel tubing with vacuum furnace brazed gold/indium alloy plating

    Science.gov (United States)

    Howard, Stanley R.; Korinko, Paul S.

    2008-05-27

    A method of fabricating a heat exchanger includes brush electroplating plated layers for a brazing alloy onto a stainless steel tube in thin layers, over a nickel strike having a 1.3 .mu.m thickness. The resultant Au-18 In composition may be applied as a first layer of indium, 1.47 .mu.m thick, and a second layer of gold, 2.54 .mu.m thick. The order of plating helps control brazing erosion. Excessive amounts of brazing material are avoided by controlling the electroplating process. The reticulated copper foam rings are interference fit to the stainless steel tube, and in contact with the plated layers. The copper foam rings, the plated layers for brazing alloy, and the stainless steel tube are heated and cooled in a vacuum furnace at controlled rates, forming a bond of the copper foam rings to the stainless steel tube that improves heat transfer between the tube and the copper foam.

  15. Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

    International Nuclear Information System (INIS)

    Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO2 balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry), melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength)

  16. Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

    Science.gov (United States)

    Rapp, F.; Schneider, A.; Elsner, P.

    2014-05-01

    Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO2 balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry), melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength).

  17. Biopolymer foams - Relationship between material characteristics and foaming behavior of cellulose based foams

    Energy Technology Data Exchange (ETDEWEB)

    Rapp, F., E-mail: florian.rapp@ict.fraunhofer.de, E-mail: anja.schneider@ict.fraunhofer.de; Schneider, A., E-mail: florian.rapp@ict.fraunhofer.de, E-mail: anja.schneider@ict.fraunhofer.de [Fraunhofer Institute for Chemical Technology ICT (Germany); Elsner, P., E-mail: peter.elsner@ict.fraunhofer.de [Fraunhofer Institute for Chemical Technology ICT, Germany and Karlsruhe Institute of Technology KIT (Germany)

    2014-05-15

    Biopolymers are becoming increasingly important to both industry and consumers. With regard to waste management, CO{sub 2} balance and the conservation of petrochemical resources, increasing efforts are being made to replace standard plastics with bio-based polymers. Nowadays biopolymers can be built for example of cellulose, lactic acid, starch, lignin or bio mass. The paper will present material properties of selected cellulose based polymers (cellulose propionate [CP], cellulose acetate butyrate [CAB]) and corresponding processing conditions for particle foams as well as characterization of produced parts. Special focus is given to the raw material properties by analyzing thermal behavior (differential scanning calorimetry), melt strength (Rheotens test) and molecular weight distribution (gel-permeation chromatography). These results will be correlated with the foaming behavior in a continuous extrusion process with physical blowing agents and underwater pelletizer. Process set-up regarding particle foam technology, including extrusion foaming and pre-foaming, will be shown. The characteristics of the resulting foam beads will be analyzed regarding part density, cell morphology and geometry. The molded parts will be tested on thermal conductivity as well as compression behavior (E-modulus, compression strength)

  18. Co-doped titanium oxide foam and water disinfection device

    Energy Technology Data Exchange (ETDEWEB)

    Shang, Jian-Ku; Wu, Pinggui; Xie, Rong-Cai

    2016-01-26

    A quaternary oxide foam, comprises an open-cell foam containing (a) a dopant metal, (b) a dopant nonmetal, (c) titanium, and (d) oxygen. The foam has the advantages of a high surface area and a low back pressure during dynamic flow applications. The inactivation of Escherichia coli (E. coli) was demonstrated in a simple photoreactor.

  19. GABA and Topiramate Inhibit the Formation of Human Macrophage-Derived Foam Cells by Modulating Cholesterol-Metabolism-Associated Molecules

    Directory of Open Access Journals (Sweden)

    Ying Yang

    2014-04-01

    Full Text Available Aims: γ-aminobutyric acid (GABA, the principal inhibitory neurotransmitter, acts on GABA receptors to play an important role in the modulation of macrophage functions. The present study examined the effects of GABA and a GABA receptor agonist on modulating cholesterol-metabolism-associated molecules in human monocyte-derived macrophages (HMDMs. Methods: ORO stain, HPLC, qRT-PCR, Western blot and EMSA were carried out using HMDMs exposed to ox-LDL with or without GABAergic agents as the experimental model. Results: GABA and topiramate reduced the percentage of cholesterol ester in lipid-laden HMDMs by down-regulating SR-A, CD36 and LOX-1 expression and up-regulating ABCA1, ABCG1 and SR-BI expression in lipid-laden HMDMs. The production of TNF-a was decreased in GABA-and topiramate-treated lipid-laden HMDMs, and levels of interleukin (IL-6 did not change. The activation of two signaling pathways, p38MAPK and NF-γB, was repressed by GABA and topiramate in lipid-laden HMDMs. Conclusion: GABA and topiramate inhibit the formation of human macrophage-derived foam cells and may be a possibility for macrophage targeted therapy of atherosclerotic lesions.

  20. FeS/nickel foam as stable and efficient counter electrode material for quantum dot sensitized solar cells

    Science.gov (United States)

    Geng, Huifang; Zhu, Liqun; Li, Weiping; Liu, Huicong; Quan, Linlin; Xi, Fanxing; Su, Xunwen

    2015-05-01

    A stable and efficient FeS/nickel foam (NF) counter electrode for quantum dots-sensitized solar cells (QDSCs) is first fabricated by electrochemistry deposition and characterized with scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), current voltage and impedance spectroscopy. The QDSC based on FeS/NF CE achieves a power conversion efficiency (PCE) of 4.39% attributing to the high fill factor (FF) of 0.58, and the PCE is much higher than that of based on FeS/FTO CE (2.76%) and other reported FeS CEs (1.76% and 3.34%). The phenomenon that the electrode can transform between FeS/NF (in the polysulfide electrolyte) and Fe2O3/NF (in the air) spontaneously is first reported. And the excellent stability in photoelectric performance of the CE is also demonstrated in the present work. Therefore, the FeS/NF is very promising as a stable and efficient CE for QDSCs.

  1. CARBONIZED STARCH MICROCELLULAR FOAM-CELLULOSE FIBER COMPOSITE STRUCTURES

    OpenAIRE

    Andrew R. Rutledge; Richard A. Venditti; Joel J. Pawlak; Sameer Patel; Janderson L. Cibils

    2008-01-01

    The production of microporous carbon foams from renewable starch microcellular foam-fiber (SMCF-Fiber) composites is described. Carbon foams are used in applications such as thermal insulation, battery electrodes, filters, fuel cells, and medical devices. SMCF-Fiber compos-ites were created from an aquagel. The water in the aquagel was exchanged with ethanol and then dried and carbonized. Higher amylose content starches and fiber contents of up to 4% improved the processability of the foam. ...

  2. Low-density, salt-loaded foams. [RbF

    Energy Technology Data Exchange (ETDEWEB)

    Rinde, J.A.

    1979-01-10

    An experiment was conducted at LLL that required low-density, fine-celled foams uniformly loaded with rubidium. Foams meeting these requirements were produced by impregnating foams made from polyacrylonitrile with rubidium fluoride. Foams with densities from 0.025 to 0.4 g/cm/sup 3/ were prepared and loaded with 0.002 to 0.20 g/cm/sup 3/ of rubidium fluoride.

  3. Foam stability in microgravity

    Science.gov (United States)

    Vandewalle, N.; Caps, H.; Delon, G.; Saint-Jalmes, A.; Rio, E.; Saulnier, L.; Adler, M.; Biance, A. L.; Pitois, O.; Cohen Addad, S.; Hohler, R.; Weaire, D.; Hutzler, S.; Langevin, D.

    2011-12-01

    Within the context of the ESA FOAM project, we have studied the stability of aqueous and non-aqueous foams both on Earth and in microgravity. Foams are dispersions of gas into liquid or solid. On Earth, the lifetime of a foam is limited by the free drainage. By drainage, we are referring to the irreversible flow of liquid through the foam (leading to the accumulation of liquid at the foam bottom, and to a global liquid content decreases within the foam). When the liquid films become thinner, they eventually break, and the foam collapses. In microgravity, this process is no more present and foams containing large amounts of liquid can be studied for longer time. While the difference between foaming and not-foaming solutions is clear, the case of slightly-foaming solutions is more complicated. On Earth, such mixtures are observed to produce unstable froth for a couple of seconds. However, these latter solutions may produce foam in microgravity. We have studied both configurations for different solutions composed of common surfactant, proteins, anti-foaming agents or silicon oil. Surprising results have been obtained, emphasizing the role played by gravity on the foam stabilization process.

  4. Foam stability in microgravity

    International Nuclear Information System (INIS)

    Within the context of the ESA FOAM project, we have studied the stability of aqueous and non-aqueous foams both on Earth and in microgravity. Foams are dispersions of gas into liquid or solid. On Earth, the lifetime of a foam is limited by the free drainage. By drainage, we are referring to the irreversible flow of liquid through the foam (leading to the accumulation of liquid at the foam bottom, and to a global liquid content decreases within the foam). When the liquid films become thinner, they eventually break, and the foam collapses. In microgravity, this process is no more present and foams containing large amounts of liquid can be studied for longer time. While the difference between foaming and not-foaming solutions is clear, the case of slightly-foaming solutions is more complicated. On Earth, such mixtures are observed to produce unstable froth for a couple of seconds. However, these latter solutions may produce foam in microgravity. We have studied both configurations for different solutions composed of common surfactant, proteins, anti-foaming agents or silicon oil. Surprising results have been obtained, emphasizing the role played by gravity on the foam stabilization process.

  5. CORE

    DEFF Research Database (Denmark)

    Krigslund, Jeppe; Hansen, Jonas; Hundebøll, Martin;

    2013-01-01

    different flows. Instead of maintaining these approaches separate, we propose a protocol (CORE) that brings together these coding mechanisms. Our protocol uses random linear network coding (RLNC) for intra- session coding but allows nodes in the network to setup inter- session coding regions where flows...... increase the benefits of XORing by exploiting the underlying RLNC structure of individual flows. This goes beyond providing additional reliability to each individual session and beyond exploiting coding opportunistically. Our numerical results show that CORE outperforms both forwarding and COPE......-like schemes in general. More importantly, we show gains of up to 4 fold over COPE-like schemes in terms of transmissions per packet in one of the investigated topologies....

  6. Expanded polylactide bead foaming - A new technology

    Science.gov (United States)

    Nofar, M.; Ameli, A.; Park, C. B.

    2015-05-01

    Bead foaming technology with double crystal melting peak structure has been recognized as a promising method to produce low-density foams with complex geometries. During the molding stage of the bead foams, the double peak structure generates a strong bead-to-bead sintering and maintains the overall foam structure. During recent years, polylactide (PLA) bead foaming has been of the great interest of researchers due to its origin from renewable resources and biodegradability. However, due to the PLA's low melt strength and slow crystallization kinetics, the attempts have been limited to the manufacturing methods used for expanded polystyrene. In this study, for the first time, we developed microcellular PLA bead foams with double crystal melting peak structure. Microcellular PLA bead foams were produced with expansion ratios and average cell sizes ranging from 3 to 30-times and 350 nm to 15 µm, respectively. The generated high melting temperature crystals during the saturation significantly affected the expansion ratio and cell density of the PLA bead foams by enhancing the PLA's poor melt strength and promoting heterogeneous cell nucleation around the crystals.

  7. Method of Preventing Shrinkage of Aluminum Foam Using Carbonates

    Directory of Open Access Journals (Sweden)

    Takashi Nakamura

    2011-12-01

    Full Text Available Metallic foams are commonly produced using titanium hydride as a foaming agent. Carbonates produce aluminum foam with a fine and homogenous cell structure. However, foams produced using carbonates show marked shrinkage, which is clearly different from those produced using titanium hydride. It is essential for practical applications to clarify foam shrinkage and establish a method of preventing it. In this research, cell structures were observed to study the shrinkage of aluminum foam produced using carbonates. The cells of foam produced using dolomite as a foaming agent connected to each other with maximum expansion. It was estimated that foaming gas was released through connected cells to the outside. It was assumed that cell formation at different sites is effective in preventing shrinkage induced by cell connection. The multiple additions of dolomite and magnesium carbonate, which have different decomposition temperatures, were applied. The foam in the case with multiple additions maintained a density of 0.66 up to 973 K, at which the foam produced using dolomite shrank. It was verified that the multiple additions of carbonates are effective in preventing shrinkage.

  8. Local buckling strength of steel foam sandwich panels

    OpenAIRE

    Szyniszewski, S; Schafer, BW; Smith, BH; Arwade, SR; Hajjar, JF

    2012-01-01

    The objective of this paper is to provide and verify a new design method for the in-plane compressive strength of steel sandwich panels comprised of steel face sheets and foamed steel cores. Foamed steel, literally steel with internal voids, provides enhanced bending rigidity, exceptional energy dissipation, and the potential to mitigate local instability. In this work, Winters effective width expression is generalized to the case of steel foam sandwich panels. The generalization requires mod...

  9. Nanoparticle-stabilized CO₂ foam for CO₂ EOR application

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Ning [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Lee, Robert [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Yu, Jianjia [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Li, Liangxiong [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Bustamante, Elizabeth [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Khalil, Munawar [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Mo, Di [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Jia, Bao [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); Wang, Sai [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); San, Jingshan [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States); An, Cheng [New Mexico Petroleum Recovery Research Center, Socorro, NM (United States)

    2015-01-31

    The purpose of this project was to develop nanoparticle-stabilized CO₂ foam for CO₂ -EOR application, in which nanoparticles instead of surfactants are used for stabilizing CO₂ foam to improve the CO₂ sweep efficiency and increase oil recovery. The studies included: (1) investigation of CO₂ foam generation nanoparticles, such as silica nanoparticles, and the effects of particle concentration and surface properties, CO₂/brine ratio, brine salinity, pressure, and temperature on foam generation and foam stability; (2) coreflooding tests to understand the nanoparticle-stabilized CO₂ foam for waterflooded residual oil recovery, which include: oil-free coreflooding experiments with nanoparticle-stabilized CO₂ foam to understand the transportation of nanoparticles through the core; measurements of foam stability and CO₂ sweep efficiency under reservoir conditions to investigate temperature and pressure effects on the foam performance and oil recovery as well as the sweep efficiency in different core samples with different rock properties; and (3) long-term coreflooding experiments with the nanoparticle- stabilized CO₂ foam for residual oil recovery. Finally, the technical and economical feasibility of this technology was evaluated.

  10. Foams theory, measurements, and applications

    CERN Document Server

    Khan, Saad A

    1996-01-01

    This volume discusses the physics and physical processes of foam and foaming. It delineates various measurement techniques for characterizing foams and foam properties as well as the chemistry and application of foams. The use of foams in the textile industry, personal care products, enhanced oil recovery, firefighting and mineral floatation are highlighted, and the connection between the microstructure and physical properties of foam are detailed. Coverage includes nonaqueous foams and silicone antifoams, and more.

  11. Numerical modeling of foam flows

    International Nuclear Information System (INIS)

    Liquid foam flows are involved in numerous applications, e.g. food and cosmetics industries, oil extraction, nuclear decontamination. Moreover, their study leads to fundamental knowledge: as it is easier to manipulate and analyse, foam is used as a model material to understand the flow of emulsions, polymers, pastes, or cell aggregates, all of which display both solid and liquid behaviour. Systematic experiments performed by Francois Graner et al. provide precise data that emphasize the non Newtonian properties of the foam. Meanwhile, Pierre Saramito proposed a visco-elasto-plastic continuous tensorial model, akin to predict the behaviour of the foam. The goal of this thesis is to understand this complex behaviour, using these two elements. We have built and validated a resolution algorithm based on a bidimensional finite elements methods. The numerical solutions are in excellent agreement with the spatial distribution of all measured quantities, and confirm the predictive capabilities of the model. The dominant parameters have been identified and we evidenced the fact that the viscous, elastic, and plastic contributions to the flow have to be treated simultaneously in a tensorial formalism. We provide a substantial contribution to the understanding of foams and open the path to realistic simulations of complex VEP flows for industrial applications. (author)

  12. Three-dimensional graphene foams loaded with bone marrow derived mesenchymal stem cells promote skin wound healing with reduced scarring

    International Nuclear Information System (INIS)

    The regeneration of functional skin remains elusive, due to poor engraftment, deficient vascularization, and excessive scar formation. Aiming to overcome these issues, the present study proposed the combination of a three-dimensional graphene foam (GF) scaffold loaded with bone marrow derived mesenchymal stem cells (MSCs) to improve skin wound healing. The GFs demonstrated good biocompatibility and promoted the growth and proliferation of MSCs. Meanwhile, the GFs loaded with MSCs obviously facilitated wound closure in animal model. The dermis formed in the presence of the GF structure loaded with MSCs was thicker and possessed a more complex structure at day 14 post-surgery. The transplanted MSCs correlated with upregulation of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), which may lead to neo-vascularization. Additionally, an anti-scarring effect was observed in the presence of the 3D-GF scaffold and MSCs, as evidenced by a downregulation of transforming growth factor-beta 1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) together with an increase of TGF-β3. Altogether, the GF scaffold could guide the wound healing process with reduced scarring, and the MSCs were crucial to enhance vascularization and provided a better quality neo-skin. The GF scaffold loaded with MSCs possesses necessary bioactive cues to improve wound healing with reduced scarring, which may be of great clinical significance for skin wound healing. - Highlights: • The GFs promoted the growth and proliferation of MSCs. • The GFs loaded with MSCs obviously facilitated wound closure in the animal model. • An anti-scarring effect was observed in the presence of 3D-GF scaffold and MSCs. • The GF scaffold loaded with MSCs has great effect on skin wound healing

  13. Three-dimensional graphene foams loaded with bone marrow derived mesenchymal stem cells promote skin wound healing with reduced scarring

    Energy Technology Data Exchange (ETDEWEB)

    Li, Zhonghua [Department of Burn and Plastic Surgery, Provincial Hospital Affiliated to Shandong University, Jinan 250021 (China); Department of Burn and Plastic Surgery, The Fourth People' s Hospital Of Jinan, Jinan 250031 (China); Wang, Haiqin [Department of Obstetrics and Gynecology, The Fifth People' s Hospital Of Jinan, Jinan 250022 (China); Yang, Bo; Sun, Yukai [Department of Burn and Plastic Surgery, The Fourth People' s Hospital Of Jinan, Jinan 250031 (China); Huo, Ran, E-mail: rhuo12@163.com [Department of Burn and Plastic Surgery, Provincial Hospital Affiliated to Shandong University, Jinan 250021 (China)

    2015-12-01

    The regeneration of functional skin remains elusive, due to poor engraftment, deficient vascularization, and excessive scar formation. Aiming to overcome these issues, the present study proposed the combination of a three-dimensional graphene foam (GF) scaffold loaded with bone marrow derived mesenchymal stem cells (MSCs) to improve skin wound healing. The GFs demonstrated good biocompatibility and promoted the growth and proliferation of MSCs. Meanwhile, the GFs loaded with MSCs obviously facilitated wound closure in animal model. The dermis formed in the presence of the GF structure loaded with MSCs was thicker and possessed a more complex structure at day 14 post-surgery. The transplanted MSCs correlated with upregulation of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF), which may lead to neo-vascularization. Additionally, an anti-scarring effect was observed in the presence of the 3D-GF scaffold and MSCs, as evidenced by a downregulation of transforming growth factor-beta 1 (TGF-β1) and alpha-smooth muscle actin (α-SMA) together with an increase of TGF-β3. Altogether, the GF scaffold could guide the wound healing process with reduced scarring, and the MSCs were crucial to enhance vascularization and provided a better quality neo-skin. The GF scaffold loaded with MSCs possesses necessary bioactive cues to improve wound healing with reduced scarring, which may be of great clinical significance for skin wound healing. - Highlights: • The GFs promoted the growth and proliferation of MSCs. • The GFs loaded with MSCs obviously facilitated wound closure in the animal model. • An anti-scarring effect was observed in the presence of 3D-GF scaffold and MSCs. • The GF scaffold loaded with MSCs has great effect on skin wound healing.

  14. The role of negative pressure wound therapy with reticulated open cell foam in the treatment of war wounds.

    Science.gov (United States)

    Powell, Elisha T

    2008-01-01

    The treatment of war wounds poses many unique challenges to all healthcare providers (surgeons, flight medics, nurses, etc.), whether they are located at the far forward trauma hospitals located in or near areas of conflict, at regional hospitals such as Landstuhl Medical Center in Germany, or the larger military hospitals in the United States. These complex wounds often involve massive loss of soft tissue and bone, are contaminated, and are unlike most injuries seen at civilian hospitals. Treatment guidelines, or doctrine, are the result of lessons learned in conflicts over the past few centuries dating back to early 19th century Europe through the Vietnam and recent Persian Gulf war. Advances in surgical and medical treatment have resulted from the complex challenges presented to the war trauma surgeon. More than 1 million patients have been treated for chronic pressure ulcers, abdominal wounds, diabetic ulcers, and acute civilian trauma wounds with negative pressure wound therapy with reticulated open cell foam (NPWT/ROCF) as delivered by V.A.C.(R) Therapy (KCI, San Antonio, TX) for over the past decade. However, the use of NPWT/ROCF for the care of war wounds at battlefield trauma hospitals and/or in the aeromedical evacuation transport system aboard aircraft is a new application of this wound treatment not yet accepted as doctrine. Investigational studies are ongoing to study the safety and efficacy of the treatment of battlefield wounds with NPWT/ROCF both for those national citizens treated at the trauma hospitals in Iraq and Afghanistan and for those wounded American and coalition patients who are transported through the aeromedical transport system to medical centers in the United States. PMID:19034160

  15. Method to evaluate foaming in petroleum

    Energy Technology Data Exchange (ETDEWEB)

    Fraga, A.K.; Rezende, D.A.; Santos, R.F.; Mansur, C.R.E. [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Macromoleculas], e-mail: celias@ima.ufrj.br

    2011-01-15

    In oil fields, gravitational separation tanks are generally used to separate the oil, gas and water phases, remove emulsifying agents present at the interfaces and permit the coalescence of water droplets associated with the crude oil being pumped. The main problem that influences the performance of these separators is the formation of foam. In this work, a method was developed to evaluate foaming in crude oil in laboratory scale, reproducing the operation conditions in gas-oil separators in real fields. This method was employed with seven crude oil samples, and the performance of silicone anti foams with different molar masses could be tested. The results indicated that the method of evaluating the breakdown of foam in oil by using the Aging Cell apparatus in a roller oven proved to be suitable. It was observed that the oil viscosity is a determining factor in predicting whether or not foam will form. (author)

  16. Dynamic compressive behavior of foamed polyethylene film

    OpenAIRE

    Tateyama Kohei; Yamada Hiroyuki; Ogasawara Nagahisa; Okui Ryo; Ogawa Kinya

    2015-01-01

    The foamed film as the shock absorption material has attracted much attention because it is thin (100 μm ∼ 400 μm) and has a closed cell structure. However, the dynamic mechanical properties have not been reported in the foamed film. The purpose of this study is to elucidate the compressive behavior of the foamed polyethylene film at the wide strain rate range. First, the new compressive test apparatus for the dynamic strain rate, the drop-weight testing machine with opposed load cell, was de...

  17. RIP140 contributes to foam cell formation and atherosclerosis by regulating cholesterol homeostasis in macrophages

    OpenAIRE

    Lin, Yi-Wei; Liu, Pu-Ste; Adhikari, Neeta; Jennifer L Hall; Wei, Li-Na

    2014-01-01

    Atherosclerosis, a syndrome with abnormal arterial walls, is one of the major causes that lead to the development of various cardiovascular diseases. The key initiator of atherosclerosis is cholesterol accumulation. The uncontrolled cholesterol deposition, mainly involving low-density lipoprotein (LDL), causes atheroma plaque formation, which initiates chronic inflammation due to the recruitment of inflammatory cells such as macrophages. Macrophages scavenge excess peripheral cholesterol and ...

  18. Oleic acid induces smooth muscle foam cell formation and enhances atherosclerotic lesion development via CD36

    OpenAIRE

    Tang Bing; Li; Yang Dachun; Ma Shuangtao; Yang Yongjian

    2011-01-01

    Abstract Background Elevated plasma free fatty acid (FFA) levels have been linked to the development of atherosclerosis. However, how FFA causes atherosclerosis has not been determined. Because fatty acid translocase (FAT/CD36) is responsible for the uptake of FFA, we hypothesized that the atherogenic effects of FFA may be mediated via CD36. Results We tested this hypothesis using cultured rat aortic smooth muscle cells (SMCs) treated with oleic acid (OA). We found that OA induces lipid accum...

  19. Hybrid Deployable Foam Antennas and Reflectors

    Science.gov (United States)

    Rivellini, Tommaso; Willis, Paul; Hodges, Richard; Spitz, Suzanne

    2006-01-01

    Hybrid deployable radio antennas and reflectors of a proposed type would feature rigid narrower apertures plus wider adjoining apertures comprising reflective surfaces supported by open-cell polymeric foam structures (see figure). The open-cell foam structure of such an antenna would be compressed for compact stowage during transport. To initiate deployment of the antenna, the foam structure would simply be released from its stowage mechanical restraint. The elasticity of the foam would drive the expansion of the foam structure to its full size and shape. There are several alternatives for fabricating a reflective surface supported by a polymeric foam structure. One approach would be to coat the foam with a metal. Another approach would be to attach a metal film or a metal-coated polymeric membrane to the foam. Yet another approach would be to attach a metal mesh to the foam. The hybrid antenna design and deployment concept as proposed offers significant advantages over other concepts for deployable antennas: 1) In the unlikely event of failure to deploy, the rigid narrow portion of the antenna would still function, providing a minimum level of assured performance. In contrast, most other concepts for deploying a large antenna from compact stowage are of an "all or nothing" nature: the antenna is not useful at all until and unless it is fully deployed. 2) Stowage and deployment would not depend on complex mechanisms or actuators, nor would it involve the use of inflatable structures. Therefore, relative to antennas deployed by use of mechanisms, actuators, or inflation systems, this antenna could be lighter, cheaper, amenable to stowage in a smaller volume, and more reliable. An open-cell polymeric (e.g., polyurethane) foam offers several advantages for use as a compressible/expandable structural material to support a large antenna or reflector aperture. A few of these advantages are the following: 3) The open cellular structure is amenable to compression to a very

  20. Polyurethane-Foam Maskant

    Science.gov (United States)

    Bodemeijer, R.

    1985-01-01

    Brown wax previously used to mask hardware replaced with polyurethane foam in electroplating and electroforming operations. Foam easier to apply and remove than wax and does not contaminate electrolytes.

  1. Mechanical Characterization of PVC Foam Using Digital Image Correlation and Nonlinear FE Analysis

    OpenAIRE

    Taher, Siavash Talebi; Thomsen, Ole Thybo; M. Dulieu-Barton, Janice

    2011-01-01

    olymer foam cored sandwich structures are often subjected to aggressive service conditions which may include elevated temperatures. The mechanical properties of polymer foam cores degrade significantly with elevated temperatures, and significant changes in the properties may occur well within the operating range of temperatures. The material properties of foam cored sandwich structures depend on the temperature field imposed, and this is usually ignored in engineering analysis and design. As ...

  2. Tailoring properties of reticulated vitreous carbon foams with tunable density

    Science.gov (United States)

    Smorygo, Oleg; Marukovich, Alexander; Mikutski, Vitali; Stathopoulos, Vassilis; Hryhoryeu, Siarhei; Sadykov, Vladislav

    2016-06-01

    Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09-0.42 g/cm3 were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.

  3. Tailoring properties of reticulated vitreous carbon foams with tunable density

    Science.gov (United States)

    Smorygo, Oleg; Marukovich, Alexander; Mikutski, Vitali; Stathopoulos, Vassilis; Hryhoryeu, Siarhei; Sadykov, Vladislav

    2016-04-01

    Reticulated vitreous carbon (RVC) foams were manufactured by multiple replications of a polyurethane foam template structure using ethanolic solutions of phenolic resin. The aims were to create an algorithm of fine tuning the precursor foam density and ensure an open-cell reticulated porous structure in a wide density range. The precursor foams were pyrolyzed in inert atmospheres at 700°C, 1100°C and 2000°C, and RVC foams with fully open cells and tunable bulk densities within 0.09-0.42 g/cm3 were synthesized. The foams were characterized in terms of porous structure, carbon lattice parameters, mechanical properties, thermal conductivity, electric conductivity, and corrosive resistance. The reported manufacturing approach is suitable for designing the foam microstructure, including the strut design with a graded microstructure.

  4. Modulation Peroxisome Proliferators Activated Receptor alpha (PPAR α and Acyl Coenzyme A: Cholesterol Acyltransferase1 (ACAT1 Gene expression by Fatty Acids in Foam cell

    Directory of Open Access Journals (Sweden)

    Mojarrad Majed

    2009-09-01

    Full Text Available Abstract Background One of the most important factors in the initiation and progression of atherosclerosis is the default in macrophage cholesterol homeostasis. Many genes and transcription factors such as Peroxisome Proliferators Activated Receptors (PPARs and Acyl Coenzyme A: Cholesterol Acyltransferase1 (ACAT1 are involved in cholesterol homeostasis. Fatty Acids are important ligands of PPARα and the concentration of them can effect expression of ACAT1. So this study designed to clarified on the role of these genes and fatty acids on the lipid metabolism in foam cells. Methods This study examined effects of c9, t11-Conjugated Linoleic Acid(c9, t11-CLA, Alpha Linolenic Acid (LA, Eicosapentaenoic Acid (EPA on the PPARα and ACAT1 genes expression by using Real time PCR and cholesterol homeostasis in THP-1 macrophages derived foam cells. Results Incubation of c9, t11-CLA, LA cause a significant reduction in intracellular Total Cholesterol, Free Cholesterol, cellular and Estrified Cholesterol concentrations (P ≤ 0.05. CLA and LA had no significant effect on the mRNA levels of ACAT1, but EPA increased ACAT1 mRNA expression (P = 0.003. Treatment with EPA increased PPARα mRNA levels (P ≤ 0.001, although CLA, LA had no significant effect on PPARα mRNA expression. Conclusion In conclusion, it seems that different fatty acids have different effects on gene expression and lipid metabolism and for complete conception study of the genes involved in lipid metabolism in foam cell all at once maybe is benefit.

  5. NiCo2S4@Co(OH)2 core-shell nanotube arrays in situ grown on Ni foam for high performances asymmetric supercapacitors

    Science.gov (United States)

    Li, Rui; Wang, Senlin; Huang, Zongchuan; Lu, Fengxia; He, Taobin

    2016-04-01

    In this paper, hierarchical NiCo2S4@Co(OH)2 nanotube arrays supported on Ni foam have been synthesised though a facile and commendable method. The smart combination of NiCo2S4 nanotubes and Co(OH)2 nanosheets exhibits brilliant synergistic effect for supercapacitors with significantly enhanced performances. The NiCo2S4@Co(OH)2 electrode shows a relatively high area capacitance of 9.6 F cm-2 at 2 mA cm-2 (almost 2 times as high as that of bare NiCo2S4 electrode), even at 32 mA cm-2, the area capacitance is maintained at 6.4 F cm-2. Moreover, an asymmetric supercapacitor is successfully assembled by using NiCo2S4@Co(OH)2 nanotubes as the positive electrode and active carbon (AC) as the negative electrode. The NiCo2S4@Co(OH)2//AC device achieves a relatively high energy density of 35.89 Wh kg-1 at a power density of 0.4 kW kg-1 with excellent cycling performance(70.01% capacitance retention over 5000 cycles). Such unique NiCo2S4@Co(OH)2 nanotube arrays not only demonstrate promising applications in energy storage but also remind researchers of the unlimited potential of heterostructured materials.

  6. Foam engineering fundamentals and applications

    CERN Document Server

    2012-01-01

    Containing contributions from leading academic and industrial researchers, this book provides a much needed update of foam science research. The first section of the book presents an accessible summary of the theory and fundamentals of foams. This includes chapters on morphology, drainage, Ostwald ripening, coalescence, rheology, and pneumatic foams. The second section demonstrates how this theory is used in a wide range of industrial applications, including foam fractionation, froth flotation and foam mitigation. It includes chapters on suprafroths, flotation of oil sands, foams in enhancing petroleum recovery, Gas-liquid Mass Transfer in foam, foams in glass manufacturing, fire-fighting foam technology and consumer product foams.

  7. Gamma-irradiated cross-linked LDPE foams: Characteristics and properties

    Science.gov (United States)

    Cardoso, E. C. L.; Scagliusi, S. R.; Parra, D. F.; Lugão, A. B.

    2013-03-01

    Foamed polymers are future materials, as they are increasingly considered "green materials" due to their interesting properties at very low consumption of raw materials. They can be used to improve appearance of insulation structures, thermal and acoustic insulation, core materials for sandwich panels, fabrication of furniture and flotation materials or to reduce costs involving materials. Low-density polyethylene is widely used because of its excellent properties, such as softness, elasticity, processibility and insulation. In general, cross-linking is often applied to improve the thermal and mechanical properties of polyethylene products, due to the formation of a three-dimensional network. In particular for the production of PE foams, cross-linking is applied prior the expansion to control bubble formation, cell characteristics and final properties of the foam. However, the usual production process of PE foams is a process in which a gaseous blowing agent is injected into a melted thermoplastic polymer, under pressure, to form a solution between blowing agent and melted polymer. An extrusion system is provided for foaming the polymer, supplied to an extruder and moving through a rotating screw. The pressure must be high enough to keep the gas blowing agent (or foaming agent) in the solution with the melt. The foaming agent is then diffused and dissolved in the molten material to form a single-phase solution. In the present work carbon dioxide was used as the bowing agent, a chemically stable and non-toxic gas, with good diffusion coefficient; gas pressure used varied within a 20-40 bar range. Some requirements for physical foaming are required, as low friction heat generation, homogeneous melt temperature distribution, melt temperature at die exit just above crystallization temperature (die) and high melt strength during expansion. This work studied foams properties gamma-irradiated within 0, 10, 15, 20, 25, and 30 kGy, from a LDPE exhibiting 2.6 g/10 min Melt

  8. The two steps thermal decomposition of titanium hydride and two steps foaming of Al alloy

    Institute of Scientific and Technical Information of China (English)

    SHANG; Jintang; HE; Deping

    2005-01-01

    Two steps foaming (TSF) technique was proposed to prepare shaped Al alloy foam. Based on the thermal decomposition kinetics equation of titanium hydride, the relationship between two steps thermal decomposition kinetics of titanium hydride and two steps foaming Al alloy melt was studied. Two steps thermal decomposition curve of titanium hydride under increasing and constant temperature was calculated respectively. The hydrogen mass needed in the second foaming step was also calculated. Results showed that the hydrogen mass of the second thermal decomposition of titanium hydride is enough for the second foaming step in the condition of as-received Al melt foaming. Experimental and theoretical results indicate that two steps foaming technique can be used to prepare Al alloy foam with high porosity, shaped components and sandwich with Al alloy foam core.

  9. Improving the mechanical performance of wood fiber reinforced bio-based polyurethane foam

    Science.gov (United States)

    Chang, Li-Chi

    Because of the environmental impact of fossil fuel consumption, soybean-based polyurethane (PU) foam has been developed as an alternative to be used as the core in structural insulated panels (SIPs). Wood fibers can be added to enhance the resistance of foam against bending and buckling in compression. The goal of this work is to study the effect of three modifications: fiber surface treatment, catalyst choice, and mixing method on the compression performance of wood fiber-reinforced PU foam. Foams were made with a free-rising process. The compression performance of the foams was measured and the foams were characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray computed tomography (CT). The foam reinforced with alkali-treated fibers had improved compression performance. The foams made with various catalysts shared similar performance. The foam made using a mechanical stirrer contained well-dispersed fibers but the reinforcing capability of the fibers was reduced.

  10. A Successful Industrial Academic Cooperation, Development of Closed-cell Metallic Foams

    Directory of Open Access Journals (Sweden)

    Sheng-Chung Tzeng

    2005-01-01

    Full Text Available This investigation proposes a successful case of industrial-academic cooperation between the Chienkuo Technology University and J. King Aluminum Inc. This study was proposed by the rotating machinery and heat transfer laboratory. They studied the optimal heat transfer and structural strength of closed-cell aluminum porous material. The cooperation involved the exchange of technical skills; the determination of policies and methods for establishing a lasting relationship, to ensure mutual trust between the parties involved and the elucidation of the benefits enjoyed by both sides. This study seeks to provide a good example to local technical industrial institutions of successful industrial-academic cooperation to promote academic professional research and the establishment of empirical formulae from relevant experimental data. The results of the example are useful in designing an electronic package and cooling device will lead to the novel material applications and reduce the cost of research in related industries, improving global production and marketing, also motivates students to combine academic skills and industrial practice as part of a professional education.

  11. Hibiscus sabdariffa leaf polyphenolic extract inhibits LDL oxidation and foam cell formation involving up-regulation of LXRα/ABCA1 pathway.

    Science.gov (United States)

    Chen, Jing-Hsien; Wang, Chau-Jong; Wang, Chi-Ping; Sheu, Jenn-Yuan; Lin, Chia-Liang; Lin, Hui-Hsuan

    2013-11-01

    The oxidative modification of low-density lipoprotein (LDL) is involved in the pathogenesis of atherosclerotic lesions through the formation of macrophage-derived foam cells. In the present study, we aimed to investigate the anti-atherosclerotic effect of Hibiscus sabdariffa leaf polyphenolic extract (HLP), which is rich in flavonoid. The inhibitory effect of HLP on oxidation and lipid peroxidation of LDL was defined in vitro. HLP showed potential in reducing foam cell formation and intracellular lipid accumulation in oxidised-LDL (ox-LDL)-induced macrophage J774A.1 cells under non-cytotoxic concentrations. Molecular data showed these influences of HLP might be mediated via liver-X receptor α (LXRα)/ATP-binding cassette transporter A1 (ABCA1) pathway, as demonstrated by the transfection of LXRα siRNA. Our data implied that HLP up-regulated the LXRα/ABCA1 pathway, which in turn led to stimulation of cholesterol removal from macrophages and delay atherosclerosis. These results suggested that HLP potentially could be developed as an anti-atherosclerotic agent. PMID:23768373

  12. Starch-lignin foams

    Directory of Open Access Journals (Sweden)

    2010-05-01

    Full Text Available Although starch foams are well known as biodegradable alternatives to foamed polystyrene, starch-lignin foams have not previously been reported. Lignin is an abundant byproduct of paper manufacture usually burned as fuel for lack of higher-value uses. We have prepared novel starch-kraft lignin foams with a known technique similar to compression molding. Replacing 20% of the starch with lignin has no deleterious effect on density or morphology as indicated by scanning electron microscopy: a thin outer layer of approximately 100 µm encloses a region of cellular structure containing 100–200 µm voids, with the major internal region of the foam consisting of large voids of up to 1 mm in size. Powder X-ray diffraction shows residual structure in both starch and starch-lignin foams. Differential scanning calorimetry displays endothermic transitions in the starch foam but not in the starch-lignin foam, indicating that lignin stabilizes the residual starch structure. Lignin decreases water absorption; diffusion constants for the starch and starch-lignin foams are 2.68•10–6 and 0.80•10–6 cm2/sec, respectively. The flexural strength of the starch-lignin foam is similar to that of foamed polystyrene, the strain at maximum stress is smaller, and the modulus of elasticity is larger.

  13. Foam process models.

    Energy Technology Data Exchange (ETDEWEB)

    Moffat, Harry K.; Noble, David R.; Baer, Thomas A. (Procter & Gamble Co., West Chester, OH); Adolf, Douglas Brian; Rao, Rekha Ranjana; Mondy, Lisa Ann

    2008-09-01

    In this report, we summarize our work on developing a production level foam processing computational model suitable for predicting the self-expansion of foam in complex geometries. The model is based on a finite element representation of the equations of motion, with the movement of the free surface represented using the level set method, and has been implemented in SIERRA/ARIA. An empirically based time- and temperature-dependent density model is used to encapsulate the complex physics of foam nucleation and growth in a numerically tractable model. The change in density with time is at the heart of the foam self-expansion as it creates the motion of the foam. This continuum-level model uses an homogenized description of foam, which does not include the gas explicitly. Results from the model are compared to temperature-instrumented flow visualization experiments giving the location of the foam front as a function of time for our EFAR model system.

  14. Foam decontamination containing silica nanoparticles of various structures

    International Nuclear Information System (INIS)

    A process is needed to decrease the amounts of chemical reagents and secondary waste produced during the decontamination process. Decontamination foam is a non-stable, two-phase fluid with aqueous and gas phases representing not more than 10% and 90% of the total volume, respectively. The application of foam allows for remote decontamination processing using only an injection nozzle and the equipment to generate the decontamination foam, which reduces operator exposure to high radioactivity. Solid colloidal particles increase the foam stability in the foam formulation. These particles can be specifically hydrophobized for optimal adsorption at the liquid/gas interface, which creates armor for the bubbles and prevents coalescence by reducing the internal gas transfer. Conversely, hydrophilic particles remain confined in the liquid phase, and to enhance the foam stability. In addition, the silica nanoparticles (NPs) were synthesized with various structures and used for the stabilizer of decontamination foam. In this study, we aimed to synthesize silica nanoparticles (NPs) with various structures such as porous, core-shell, and non-porous using methods proposed in previous literatures. We also investigated the effect of silica NPs with various structures for the foam stability and oxide dissolution rate with chemical reagents. This study showed the effect of the silica NPs with various structures on the decontamination foam. The result indicates that porous NPs have a significant effect on the foam stability and oxide dissolution rate because of lower density and smaller size owing to high specific surface area, large pore volume, and porosity

  15. Foam decontamination containing silica nanoparticles of various structures

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Inho; Kim, Chorong; Jung, Chonghun; Yang, Hanbeom; Park, Sang Yoon; Moon, Jeikwon; Choi, Wangkyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Yoon, Suk Bon [Korea Hydro and Nuclear Power Co., Ltd., Daejeon (Korea, Republic of)

    2014-05-15

    A process is needed to decrease the amounts of chemical reagents and secondary waste produced during the decontamination process. Decontamination foam is a non-stable, two-phase fluid with aqueous and gas phases representing not more than 10% and 90% of the total volume, respectively. The application of foam allows for remote decontamination processing using only an injection nozzle and the equipment to generate the decontamination foam, which reduces operator exposure to high radioactivity. Solid colloidal particles increase the foam stability in the foam formulation. These particles can be specifically hydrophobized for optimal adsorption at the liquid/gas interface, which creates armor for the bubbles and prevents coalescence by reducing the internal gas transfer. Conversely, hydrophilic particles remain confined in the liquid phase, and to enhance the foam stability. In addition, the silica nanoparticles (NPs) were synthesized with various structures and used for the stabilizer of decontamination foam. In this study, we aimed to synthesize silica nanoparticles (NPs) with various structures such as porous, core-shell, and non-porous using methods proposed in previous literatures. We also investigated the effect of silica NPs with various structures for the foam stability and oxide dissolution rate with chemical reagents. This study showed the effect of the silica NPs with various structures on the decontamination foam. The result indicates that porous NPs have a significant effect on the foam stability and oxide dissolution rate because of lower density and smaller size owing to high specific surface area, large pore volume, and porosity.

  16. Plastic Foam Withstands Greater Temperatures And Pressures

    Science.gov (United States)

    Cranston, John A.; Macarthur, Doug

    1993-01-01

    Improved plastic foam suitable for use in foam-core laminated composite parts and in tooling for making fiber/matrix-composite parts. Stronger at high temperatures, more thermally and dimensionally stable, machinable, resistant to chemical degradation, and less expensive. Compatible with variety of matrix resins. Made of polyisocyanurate blown with carbon dioxide and has density of 12 to 15 pounds per cubic feet. Does not contibute to depletion of ozone from atmosphere. Improved foam used in cores of composite panels in such diverse products as aircraft, automobiles, railroad cars, boats, and sporting equipment like surfboards, skis, and skateboards. Also used in thermally stable flotation devices in submersible vehicles. Machined into mandrels upon which filaments wound to make shells.

  17. Ultrasonic Measurement of Elastic Modulus of Kelvin Foam

    Directory of Open Access Journals (Sweden)

    Oh Sukwon

    2016-01-01

    Full Text Available Elastic modulus of 3D-printed Kelvin foam plate is investigated by measuring the acoustic wave velocity of 1 MHz ultrasound. An isotropic tetrakaidecahedron foam of 3 mm unit cell is designed and printed layer upon layer to fablicate a Kelvin foam plate of 14mm thickness by 3D CAD/printer using ABS plastic. The Kelvin foam plate is filled completely with paraffin wax for impedance matching, so that acoustic wave may propagate through the porous foam plate. The acoustic wave velocity of the foam plate is measured using the time-of-flight (TOF method to calculate the elastic modulus of the Kelvin foam plate based on acousto-elasticity.

  18. Strain-rate dependence for Ni/Al hybrid foams

    OpenAIRE

    Jung Anne; Larcher Martin; Jirousek Ondrej; Koudelka Petr; Solomos George

    2015-01-01

    Shock absorption often needs stiff but lightweight materials that exhibit a large kinetic energy absorption capability. Open-cell metal foams are artificial structures, which due to their plateau stress, including a strong hysteresis, can in principle absorb large amounts of energy. However, their plateau stress is too low for many applications. In this study, we use highly novel and promising Ni/Al hybrid foams which consist of standard, open-cell aluminium foams, where nanocrystalline nicke...

  19. Investigation of foam flotation and phase partitioning techniques

    Science.gov (United States)

    Currin, B. L.

    1985-01-01

    The present status of foam flotation as a separation process is evaluated and limitations for cells and proteins are determined. Possible applications of foam flotation to separations in microgravity are discussed. Application of the fluid mechanical aspects of foam separation techniques is made to phase partitioning in order to investigate the viscous drag forces that may effect the partitioning of cells in a two phase poly(ethylene glycol) and dextran system.

  20. Foam Glass for Construction Materials: Foaming Mechanism and Thermal Conductivity

    DEFF Research Database (Denmark)

    Petersen, Rasmus Rosenlund

    2016-01-01

    in a solid foam glass. The foam glass industry employs a range of different melt precursors and foaming agents. Recycle glass is key melt precursors. Many parameters influence the foaming process and optimising the foaming conditions is very time consuming. The most challenging and attractive goal is...

  1. Compact and Robust Refilling and Connectorization of Hollow Core Photonic Crystal Fiber Gas Reference Cells

    Science.gov (United States)

    Poberezhskiy, Ilya Y.; Meras, Patrick; Chang, Daniel H.; Spiers, Gary D.

    2007-01-01

    This slide presentation reviews a method for refilling and connectorization of hollow core photonic crystal fiber gas reference cells. Thees hollow-core photonic crystal fiber allow optical propagation in air or vacuum and are for use as gas reference cell is proposed and demonstrated. It relies on torch-sealing a quartz filling tube connected to a mechanical splice between regular and hollow-core fibers.

  2. The Role of Foaming Agent and Processing Route in the Mechanical Performance of Fabricated Aluminum Foams

    Directory of Open Access Journals (Sweden)

    Takashi Nakamura

    2012-05-01

    Full Text Available The results of the present study highlight the role of foaming agent and processing route in influencing the contamination of cell wall material by side products, which, in turn, affect the macroscopic mechanical response of closed-cell Al-foams. Several kinds of Al-foams have been produced with pure Al by the Alporas melt process and powder metallurgical technique, all performed either with conventional TiH2 foaming agent or CaCO3 as an alternative. Mechanical characteristics of contaminating products induced by processing additives, all of which were presented in one or another kind of Al-foam, have been determined in indentation experiments. Damage behavior of these contaminations affects the micro-mechanism of deformation and favors either plastic buckling or brittle failure of the cell walls. It is justified that there is no discrepancy between experimental values of compressive strengths for Al-foams comprising ductile Al + Al4Ca eutectic domains and those prescribed by theoretical models for closed-cell structure. However, the presence of low ductile Al + Al3Ti + Al4Ca eutectic domains and brittle particles/layers of Al3Ti, fine CaCO3/CaO particles, Al2O3 oxide network, and, especially, residues of partially reacted TiH2, results in reducing the compressive strength to values close to or even below those of open-cell foams of the same relative density.

  3. Urotensin II increases foam cell formation by repressing ABCA1 expression through the ERK/NF-κB pathway in THP-1 macrophages

    International Nuclear Information System (INIS)

    Highlights: • U II reduces cholesterol efflux in THP-1 macrophages. • U II decreases the expression of ABCA1. • Inhibition of the ERK/NF-κB pathway reduces U II effects on ABCA1 expression and cholesterol efflux. - Abstract: Objective: Foam cell formation in the arterial wall plays a key role in the development of atherosclerosis. Recent studies showed that Urotensin II (U II) is involved in the pathogenesis of atherosclerosis. Here we examined the effects of human U II on ATP-binding cassette transporter A1 (ABCA1) expression and the underlying mechanism in THP-1 macrophages. Methods and results: Cultured THP-1 macrophages were treated with U II, followed by measuring the intracellular lipid contents, cholesterol efflux and ABCA1 levels. The results showed that U II dramatically decreased ABCA1 levels and impaired cholesterol efflux. However, the effects of U II on ABCA1 protein expression and cellular cholesterol efflux were partially reversed by inhibition of extracellular signal regulated kinase 1/2 (ERK1/2) and nuclear factor kappa B (NF-κB) activity, suggesting the potential roles of ERK1/2 and NF-κB in ABCA1 expression, respectively. Conclusion: Our current data indicate that U II may have promoting effects on the progression of atherosclerosis, likely through suppressing ABCA1 expression via activation of the ERK/NF-κB pathway and reducing cholesterol efflux to promote macrophage foam cell formation

  4. Urotensin II increases foam cell formation by repressing ABCA1 expression through the ERK/NF-κB pathway in THP-1 macrophages

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yan [Department of Anesthesiology, The Second Affiliated Hospital of University of South China, Hengyang 421001, Hunan (China); Wu, Jian-Feng [Department of Cardiovascular Medicine, The Second Affiliated Hospital of University of South China, Hengyang 421001, Hunan (China); Tang, Yan-Yan; Zhang, Min; Li, Yuan [Institute of Cardiovascular Research, Key Laboratory for Atherosclerology of Hunan Province, University of South China, Hengyang 421001, Hunan (China); Chen, Kong; Zeng, Meng-Ya [Department of Cardiovascular Medicine, The Second Affiliated Hospital of University of South China, Hengyang 421001, Hunan (China); Yao, Feng; Xie, Wei [Institute of Cardiovascular Research, Key Laboratory for Atherosclerology of Hunan Province, University of South China, Hengyang 421001, Hunan (China); Zheng, Xi-Long [Department of Biochemistry and Molecular Biology, Libin Cardiovascular Institute of Alberta, University of Calgary, Health Sciences Center, 3330 Hospital Dr NW, Calgary, Alberta T2N 4N1 (Canada); Zeng, Gao-Feng, E-mail: qichingnudou@tom.com [Department of Cardiovascular Medicine, The Second Affiliated Hospital of University of South China, Hengyang 421001, Hunan (China); Tang, Chao-Ke, E-mail: tangchaoke@qq.com [Institute of Cardiovascular Research, Key Laboratory for Atherosclerology of Hunan Province, University of South China, Hengyang 421001, Hunan (China)

    2014-10-03

    Highlights: • U II reduces cholesterol efflux in THP-1 macrophages. • U II decreases the expression of ABCA1. • Inhibition of the ERK/NF-κB pathway reduces U II effects on ABCA1 expression and cholesterol efflux. - Abstract: Objective: Foam cell formation in the arterial wall plays a key role in the development of atherosclerosis. Recent studies showed that Urotensin II (U II) is involved in the pathogenesis of atherosclerosis. Here we examined the effects of human U II on ATP-binding cassette transporter A1 (ABCA1) expression and the underlying mechanism in THP-1 macrophages. Methods and results: Cultured THP-1 macrophages were treated with U II, followed by measuring the intracellular lipid contents, cholesterol efflux and ABCA1 levels. The results showed that U II dramatically decreased ABCA1 levels and impaired cholesterol efflux. However, the effects of U II on ABCA1 protein expression and cellular cholesterol efflux were partially reversed by inhibition of extracellular signal regulated kinase 1/2 (ERK1/2) and nuclear factor kappa B (NF-κB) activity, suggesting the potential roles of ERK1/2 and NF-κB in ABCA1 expression, respectively. Conclusion: Our current data indicate that U II may have promoting effects on the progression of atherosclerosis, likely through suppressing ABCA1 expression via activation of the ERK/NF-κB pathway and reducing cholesterol efflux to promote macrophage foam cell formation.

  5. Experimental study on size effect in quasi-static compressive behavior of closed-cell aluminium foams

    Czech Academy of Sciences Publication Activity Database

    Koudelka_ml., Petr; Zlámal, Petr; Kytýř, Daniel; Fíla, Tomáš; Jiroušek, Ondřej

    Prague: Czech Technical University in Prague, Faculty of Transportation Sciences, 2012 - (Jiroušek, O.; Kytýř, D.), s. 115-118 ISBN 978-80-01-05062-0. [Bilateral Czech/German Symposium /13./. Telč (CZ), 05.06.2012-08.06.2012] Grant ostatní: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : metal foam * compressive behaviour * size effect Subject RIV: JI - Composite Materials

  6. Operator spin foam models

    Energy Technology Data Exchange (ETDEWEB)

    Bahr, Benjamin [DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge CB3 0WA (United Kingdom); Hellmann, Frank; Kaminski, Wojciech; Kisielowski, Marcin; Lewandowski, Jerzy [Instytut Fizyki Teoretycznej, Uniwersytet Warszawski, ul. Hoza 69, 00-681 Warszawa (Warsaw), Polska. Poland (Poland)

    2011-05-21

    The goal of this paper is to introduce a systematic approach to spin foams. We define operator spin foams, that is foams labelled by group representations and operators, as our main tool. A set of moves we define in the set of the operator spin foams (among other operations) allows us to split the faces and the edges of the foams. We assign to each operator spin foam a contracted operator, by using the contractions at the vertices and suitably adjusted face amplitudes. The emergence of the face amplitudes is the consequence of assuming the invariance of the contracted operator with respect to the moves. Next, we define spin foam models and consider the class of models assumed to be symmetric with respect to the moves we have introduced, and assuming their partition functions (state sums) are defined by the contracted operators. Briefly speaking, those operator spin foam models are invariant with respect to the cellular decomposition, and are sensitive only to the topology and colouring of the foam. Imposing an extra symmetry leads to a family we call natural operator spin foam models. This symmetry, combined with assumed invariance with respect to the edge splitting move, determines a complete characterization of a general natural model. It can be obtained by applying arbitrary (quantum) constraints on an arbitrary BF spin foam model. In particular, imposing suitable constraints on a spin(4) BF spin foam model is exactly the way we tend to view 4D quantum gravity, starting with the BC model and continuing with the Engle-Pereira-Rovelli-Livine (EPRL) or Freidel-Krasnov (FK) models. That makes our framework directly applicable to those models. Specifically, our operator spin foam framework can be translated into the language of spin foams and partition functions. Among our natural spin foam models there are the BF spin foam model, the BC model, and a model corresponding to the EPRL intertwiners. Our operator spin foam framework can also be used for more general spin

  7. Inhibiting NF-K B increases cholesterol efflux from THP-1 derived- foam cells treated with Angll via up-regulating the expression of ATP-binding cassette transporter A1

    Institute of Scientific and Technical Information of China (English)

    Kun Liu; Yanfu Wang; Zhijian Chen; Yuhua Liao; Xiang Gao; Jian Chen

    2008-01-01

    Objective:To study the role of nuclear factor-kappa B(NF- K B) in cholesterol efflux from THP-I derived-foam cells treated with Angiotensin Ⅱ (Ang Ⅱ ). Methods:Cultured THP-l derived-foam cells were treated with Ang Ⅱ or preincubated with tosyl-phenylalan inechloromethyl-ketone(TPCK) NF-K B inhibitor. The levels of activated NF-K B in the cells were examined by sandwich ELISA. Cellular cholesterol content was studied by electron microscopy scanning and zymochemistry via fluorospectrophotometer and cholesterol efflux was detected by scintillation counting technique. ABCAI mRNA and protein were quantified by RT-PCR and Western blotting. Results:Addition of TPCK to the cells before Ang Ⅱ stimulation attenuated the response of NF- K B p65 nuclear translocation induced by Ang Ⅱ and showed no peak in foam cells group and caused a reduction in cholesterol content and an increase in cholesterol effiux by 24.1%(P < 0.05) and 41.1%(P < 0.05) respectively, when compared with Ang Ⅱ group. In accordance, the ABCAl mRNA and protein were increased by 30% and 19%(P< 0.05) respectively, when compared with Ang Ⅱ group. Conclusion:Ang Ⅱ can down- regulate ABCAI in THP-l derived-foam cells via NF- K B, which leads to less cholesterol effiux and the increase of cholesterol content with the consequence of the promotion of atherosclerosis.

  8. Foam Decontamination of Metals

    International Nuclear Information System (INIS)

    The foam decontamination is quite promising method for purifying radioactive contaminated surfaces. Foam decontamination solutions allow creating the necessary volume of deactivating medium and forming a relatively small amount of secondary liquid waste so that this method may be applicable to bulky objects. Also it should be noted that foam compositions can be effective for objects with a complex geometry. Despite the numerous advantages the well known foam decontamination methods are unpopular today due to their low efficiency and difficulties of recycling waste decontamination solutions. We have made some attempts to improve the attractiveness of foam decontamination process. Currently two compositions (acidic and alkaline) for foam decontamination have been tested. The main advantage of both tested compositions is that they are based on easily degradable surfactants. At the same time the acidic composition has a very low salt content. The preliminary results of tests carried out in real production conditions showed that such approach for metal decontamination was very promising. Metal decontamination factors over 2500 were achieved for consequent treating of metal surfaces with acidic and alkali foam solutions in industrial conditions. The total flow rate of foam generating solutions was 1 L/m2 and processing time was 1 hour. Presently we are trying to modify the foam physical properties to improve the process of decontamination of vertical, inclined and inverted surfaces. Also methods and scheme of spent foam generating solutions treatment are under development. (authors)

  9. Behaviour of Metal Foam Sandwich Panels

    DEFF Research Database (Denmark)

    Alkhudery, Hayder; Virdi, Kuldeep

    Sandwich panels as used in structures comprise of a foam core enclosed by thin high strength steel faces. This paper discusses currently design formulae of local buckling behaviour of such panels using the finite element method. Multiple wave finite element models were adopted to investigate and...

  10. Dynamic compressive behavior of foamed polyethylene film

    Directory of Open Access Journals (Sweden)

    Tateyama Kohei

    2015-01-01

    Full Text Available The foamed film as the shock absorption material has attracted much attention because it is thin (100 μm ∼ 400 μm and has a closed cell structure. However, the dynamic mechanical properties have not been reported in the foamed film. The purpose of this study is to elucidate the compressive behavior of the foamed polyethylene film at the wide strain rate range. First, the new compressive test apparatus for the dynamic strain rate, the drop-weight testing machine with opposed load cell, was developed, which can be also evaluated the dynamic stress equilibrium of the specimen. It is confirmed that the compressive flow stress increased with increasing the strain rate, regardless of the film thickness. The foamed polyethylene film has the high strain rate sensitivity in the quasi-static deformation. On the other hand, there is almost no change of the strain rate sensitivity in the dynamic and the impact deformation. In order to investigate the mechanism of strain rate dependence, the foamed polyethylene film was observed by X-ray computed tomography scanner before and after compressive test. The fracture of the closed cell only occurred in the quasi-static deformation. It was clarified that the strain rate sensitivity of the foamed film depends strongly on that of the construction material, polyethylene.

  11. Superhydrophobic graphene foams.

    Science.gov (United States)

    Singh, Eklavya; Chen, Zongping; Houshmand, Farzad; Ren, Wencai; Peles, Yoav; Cheng, Hui-Ming; Koratkar, Nikhil

    2013-01-14

    The static and dynamic wetting properties of a 3D graphene foam network are reported. The foam is synthesized using template-directed chemical vapor deposition and contains pores several hundred micrometers in dimension while the walls of the foam comprise few-layer graphene sheets that are coated with Teflon. Water contact angle measurements reveal that the foam is superhydrophobic with an advancing contact angle of ∼163 degrees while the receding contact angle is ∼143 degrees. The extremely water repellent nature of the foam is also confirmed when impacting water droplets are able to completely rebound from the surface. Such superhydrophobic graphene foams show potential in a variety of applications ranging from anti-sticking and self-cleaning to anti-corrosion and low-friction coatings. PMID:22911509

  12. Composite carbon foam electrode

    Science.gov (United States)

    Mayer, S.T.; Pekala, R.W.; Kaschmitter, J.L.

    1997-05-06

    Carbon aerogels used as a binder for granulated materials, including other forms of carbon and metal additives, are cast onto carbon or metal fiber substrates to form composite carbon thin film sheets. The thin film sheets are utilized in electrochemical energy storage applications, such as electrochemical double layer capacitors (aerocapacitors), lithium based battery insertion electrodes, fuel cell electrodes, and electrocapacitive deionization electrodes. The composite carbon foam may be formed by prior known processes, but with the solid particles being added during the liquid phase of the process, i.e. prior to gelation. The other forms of carbon may include carbon microspheres, carbon powder, carbon aerogel powder or particles, graphite carbons. Metal and/or carbon fibers may be added for increased conductivity. The choice of materials and fibers will depend on the electrolyte used and the relative trade off of system resistivity and power to system energy. 1 fig.

  13. Doping of carbon foams for use in energy storage devices

    Science.gov (United States)

    Mayer, Steven T.; Pekala, Richard W.; Morrison, Robert L.; Kaschmitter, James L.

    1994-01-01

    A polymeric foam precursor, wetted with phosphoric acid, is pyrolyzed in an inert atmosphere to produce an open-cell doped carbon foam, which is utilized as a lithium intercalation anode in a secondary, organic electrolyte battery. Tests were conducted in a cell containing an organic electrolyte and using lithium metal counter and reference electrodes, with the anode located therebetween. Results after charge and discharge cycling, for a total of 6 cycles, indicated a substantial increase in the energy storage capability of the phosphorus doped carbon foam relative to the undoped carbon foam, when used as a rechargeable lithium ion battery.

  14. Fire-retardant foams

    Science.gov (United States)

    Gagliani, J.

    1978-01-01

    Family of polyimide resins are being developed as foams with exceptional fire-retardant properties. Foams are potentially useful for seat cushions in aircraft and ground vehicles and for applications such as home furnishings and building-construction materials. Basic formulations can be modified with reinforcing fibers or fillers to produce celular materials for variety of applications. By selecting reactants, polymer structure can be modified to give foams with properties ranging from high resiliency and flexibility to brittleness and rigidity.

  15. Structure and distribution of oxides in aluminium foam

    International Nuclear Information System (INIS)

    Foaming of aluminium is investigated under oxidizing and non-oxidizing gas atmospheres. Foams were prepared by mixing and pressing Al99.95 and TiH2 powders and foaming the pressed material in a gas-tight X-ray transparent furnace while following the process by X-ray radioscopy. The structure and distribution of the oxides present in the powders, precursors and foams were studied by light microscopy, scanning and transmission electron microscopy. Sequential focused ion beam slicing was used to obtain tomographic images of oxide and micropore distributions within the individual cell walls of the foams. A complex hierarchical structure of the oxides is found. Oxides reside in the bulk of the cell walls without a pronounced segregation to the gas/metal interfaces. The presence of air retards foaming due to oxidation of the outer surface

  16. Tough graphene-polymer microcellular foams for electromagnetic interference shielding.

    Science.gov (United States)

    Zhang, Hao-Bin; Yan, Qing; Zheng, Wen-Ge; He, Zhixian; Yu, Zhong-Zhen

    2011-03-01

    Functional polymethylmethacrylate (PMMA)/graphene nanocomposite microcellular foams were prepared by blending of PMMA with graphene sheets followed by foaming with subcritical CO(2) as an environmentally benign foaming agent. The addition of graphene sheets endows the insulating PMMA foams with high electrical conductivity and improved electromagnetic interference (EMI) shielding efficiency with microwave absorption as the dominant EMI shielding mechanism. Interestingly, because of the presence of the numerous microcellular cells, the graphene-PMMA foam exhibits greatly improved ductility and tensile toughness compared to its bulk counterpart. This work provides a promising methodology to fabricate tough and lightweight graphene-PMMA nanocomposite microcellular foams with superior electrical and EMI shielding properties by simultaneously combining the functionality and reinforcement of the graphene sheets and the toughening effect of the microcellular cells. PMID:21366239

  17. Shape memory polymer foams

    Science.gov (United States)

    Santo, Loredana

    2016-02-01

    Recent advances in shape memory polymer (SMP) foam research are reviewed. The SMPs belong to a new class of smart polymers which can have interesting applications in microelectromechanical systems, actuators and biomedical devices. They can respond to specific external stimulus changing their configuration and then remember the original shape. In the form of foams, the shape memory behaviour can be enhanced because they generally have higher compressibility. Considering also the low weight, and recovery force, the SMP foams are expected to have great potential applications primarily in aerospace. This review highlights the recent progress in characterization, evaluation, and proposed applications of SMP foams mainly for aerospace applications.

  18. Ultralight metal foams

    Science.gov (United States)

    Jiang, Bin; He, Chunnian; Zhao, Naiqin; Nash, Philip; Shi, Chunsheng; Wang, Zejun

    2015-09-01

    Ultralight (silver mirror reaction and electroless plating. We have produced ultralight monolithic metal foams, such as silver, nickel, cobalt, and copper via this method. The resultant ultralight monolithic metal foams have remarkably low densities down to 7.4 mg/cm3 or 99.9% porosity. The metal foams have a long flat stress-train curve in compression tests and the densification strain ɛD of the Ni/Ag foam with a porosity of 99.8% can reach 82%. The plateau stress σpl was measured and found to be in agreement with the value predicted by the cellular solids theory.

  19. Foam height effects on heat transfer performance of 20 ppi aluminum foams

    International Nuclear Information System (INIS)

    This paper investigates the heat transfer performance of two 20 PPI (pores per linear inch) aluminum foams with constant porosity (around 0.93) and different foam core height (20 mm and 40 mm). The aluminum foams are cellular structure materials that present a stochastic interconnected pores distribution mostly uniform in size and shape. Most commercially available metal foams are based on aluminum, copper, nickel and metal alloys. Metal foams have considerable applications in multifunctional heat exchangers, cryogenics, combustion chambers, cladding on buildings, strain isolation, petroleum reservoirs, compact heat exchangers for airborne equipment, air cooled condensers and compact heat sinks for power electronics. The experimental measurements of the heat transfer coefficient and pressure drop have been carried out in a test apparatus built at Dipartimento di Fisica Tecnica of the Università di Padova. The foam core height effects on the heat transfer performance have been studied imposing three constant specific heat fluxes at the bottom of the samples: 25.0, 32.5 and 40.0 kW m−2 and varying the frontal air velocity between 2.0 and 5.0 m s−1. The experimental heat transfer coefficients and pressure gradients have been compared against the predictions obtained from two models recently suggested by present authors. - Highlights: ► Foam height effects on the heat transfer performance of 20 PPI foams are investigated. ► Heat transfer coefficients and pressure drops during air flow are presented. ► Two models suggested by the authors are compared with present experimental data.

  20. Metal Foam Analysis: Improving Sandwich Structure Technology for Engine Fan and Propeller Blades

    Science.gov (United States)

    Fedor, Jessica L.

    2004-01-01

    The Life Prediction Branch of the NASA Glenn Research Center is searching for ways to construct aircraft and rotorcraft engine fan and propeller blades that are lighter and less costly. One possible design is to create a sandwich structure composed of two metal faces sheets and a metal foam core. The face sheets would carry the bending loads and the foam core would have to resist the transverse shear loads. Metal foam is ideal because of its low density and energy absorption capabilities, making the structure lighter, yet still stiff. The material chosen for the face sheets and core was 17-4PH stainless steel, which is easy to make and has appealing mechanical properties. This material can be made inexpensively compared to titanium and polymer matrix composites, the two current fan blade alternatives. Initial tests were performed on design models, including vibration and stress analysis. These tests revealed that the design is competitive with existing designs; however, some problems were apparent that must be addressed before it can be implemented in new technology. The foam did not hold up as well as expected under stress. This could be due to a number of issues, but was most likely a result of a large number of pores within the steel that weakened the structure. The brazing between the face sheets and the foam was also identified as a concern. The braze did not hold up well under shear stress causing the foam to break away from the face sheets. My role in this project was to analyze different options for improving the design. I primarily spent my time examining various foam samples, created with different sintering conditions, to see which exhibited the most favorable characteristics for our purpose. Methods of analysis that I employed included examining strut integrity under a microscope, counting the number of cells per inch, measuring the density, testing the microhardness, and testing the strength under compression. Shear testing will also be done to examine

  1. Piezoresistive Foam Sensor Arrays for Marine Applications

    CERN Document Server

    Dusek, Jeff E; Lang, Jeffrey H

    2016-01-01

    Spatially-dense pressure measurements are needed on curved surfaces in marine environments to provide marine vehicles with the detailed, real-time measurements of the near-field flow necessary to improve performance through flow control. To address this challenge, a waterproof and conformal pressure sensor array comprising carbon black-doped-silicone closed-cell foam (CBPDMS foam) was developed for use in marine applications. The response of the CBPDMS foam sensor arrays was characterized using periodic hydrodynamic pressure stimuli from vertical plunging, from which a piecewise polynomial calibration was developed to describe the sensor response. Inspired by the distributed pressure and velocity sensing capabilities of the fish lateral line, the CBPDMS foam sensor arrays have significant advantages over existing commercial sensors for distributed flow reconstruction and control. Experimental results have shown the sensor arrays to have sensitivity on the order of 5 Pascal, dynamic range of 50-500 Pascal; are...

  2. On the modelling of compressive response of closed-cell aluminium foams under high-strain rate loading

    Czech Academy of Sciences Publication Activity Database

    Koudelka_ml., P.; Zlámal, Petr; Fíla, Tomáš

    Praha : Czech Technical University in Prague, Faculty of Transportation Sciences, 2014 - (Kytýř, D.; Zlámal, P.; Růžička, M.), s. 61-65 ISBN 978-80-01-05556-4. [Youth symposium on experimental solid mechanics /13./. Děčín (CZ), 29.06.2014-02.07.2014] R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : aluminium foam * high strain-rate compression * finite element modelling Subject RIV: JI - Composite Materials http://www.itam.cas.cz/ysesm2014/proceedings/id_4_ysesm2014_proceedings.pdf

  3. Al-TiH2 Composite Foams Magnesium Alloy

    Science.gov (United States)

    Prasada Rao, A. K.; Oh, Y. S.; Ain, W. Q.; A, Azhari; Basri, S. N.; Kim, N. J.

    2016-02-01

    The work presented here in describes the synthesis of aluminum based titanium-hydride particulate composite by casting method and its foaming behavior of magnesium alloy. Results obtained indicate that the Al-10TiH2 composite can be synthesized successfully by casting method. Further, results also reveal that closed-cell magnesium alloy foam can be synthesized by using Al-10TiH2 composite as a foaming agent.

  4. Optimisation of Sintering Factors of Titanium Foams Using Taguchi Method

    OpenAIRE

    Ahmad, S.; Muhamad, N; J. Sahari; K. R. Jamaludin

    2010-01-01

    Metal foams have the potential to be used in the production of bipolar plates in Polymer Electron Membrane Fuel Cells (PEMFC). In this paper, pure titanium was used to prepare titanium foam using the slurry method. The electrical conductivity is the most important parameter to be considered in the production of good bipolar plates. To achieve a high conductivity of the titanium foam, the effects of various parameters including temperature, time profile and composition have to be characterised...

  5. Role of Silicone Surfactant in Flexible Polyurethane Foam.

    Science.gov (United States)

    Zhang; Macosko; Davis; Nikolov; Wasan

    1999-07-15

    Grafted copolymers which consist of a polydimethylsiloxane backbone and polyethylene oxide-co-propylene oxide pendant groups are used as surfactants to stabilize the foam cells in the flexible polyurethane foaming process. The mechanical properties of the cured polyurethane foam such as air permeability and foam cell size are affected significantly by the structure of the silicone surfactant used in the formulation. It is shown that silicone surfactant has an important impact on both the bubble generation and the cell window stabilization stage. A series of silicone surfactants with different structures was tested. Surfactants with higher silicone content will provide lower surface tension and thus help increase the number of air bubbles introduced during mixing. These air bubbles serve as the starting point for foam cell growth. As a result, the cured polyurethane foam made with higher silicone content surfactant has a smaller bubble size. It is also shown that silicone surfactant can reduce the cell window drainage rate due to the surface tension gradient along the cell window. The Gibbs film elasticity, the dynamic film elasticity, and the film drainage rate were measured for the first time versus surfactant composition. Surfactants with longer siloxane backbones are shown to give higher film elasticity. Using the vertical film drainage and foam column tests, it is shown that surfactants with higher film elasticity will yield slower drainage rate and better foam cell stability. Copyright 1999 Academic Press. PMID:10419661

  6. Expression of core clock genes in colorectal tumour cells compared with normal mucosa

    DEFF Research Database (Denmark)

    Fonnes, S; Donatsky, A M; Gögenur, I

    2015-01-01

    AIM: Experimental studies have shown that some circadian core clock genes may act as tumour suppressors and have an important role in the response to oncological treatment. This study investigated the evidence regarding modified expression of core clock genes in colorectal cancer and its...... expression of colorectal cancer cells compared with healthy mucosa cells from specimens analysed by real-time or quantitative real-time polymer chain reaction. The expression of the core clock genes Period, Cryptochrome, Bmal1 and Clock in colorectal tumours were compared with healthy mucosa and correlated...... of Clock. Other core clock genes did not appear to be differentially expressed. Decreased Period gene expression was correlated to some clinicopathological features. CONCLUSION: The Period genes seemed to be modified in colorectal tumour cells compared with normal mucosa. Core clock genes might be...

  7. Ultra-low density microcellular foams

    International Nuclear Information System (INIS)

    Ultra-low density (<6.0 mg/cc) microcellular foams (cell size less than 20 μmeters) have been developed to support the NARYA pulsed-power-driven X-ray laser program. Other pulsed power targets using these foams are anticipated. Because of the extreme fragility of these foams emphasis was placed on molding to shape to avoid machining. The foams are made by a thermally induced phase separation process from solutions of water soluble polymers. In practice the solutions are rapidly frozen to induce the phase separation, and they are then freeze dried to remove the solvent without destroying the foam's structure. A number of water soluble polymers have proven capable of meeting the density and cell size requirements. However, polyacrylic acid was used in most of our work because of its low shrinkage during molding and its purity. These foams have been molded into rods (1, 2, and 3 mm dia.), half rods, half annuli, and most recently full annuli with 3.0 mm outside diameter and 2.0 mm inside diameter. The molding techniques have varied with the various shapes. The rods were molded by freezing the solution in thin walled silicone rubber molds, extracting the frozen preform from the mold, and then freeze drying. Metal molds were used to make all other shapes. Rapid surface melting, followed by rapid refreezing, was used to remove the more complex shapes from their molds. In the case of the foam annuli, a pin with a very small taper was used to form the inner diameter. The foam rods have been successfully used in gas-puff implosion experiments on the PROTO-II accelerator. 3 refs., 4 figs., 1 tab

  8. Ultra-low density microcellular foams

    Energy Technology Data Exchange (ETDEWEB)

    Rand, P.B.

    1986-01-01

    Ultra-low density (<6.0 mg/cc) microcellular foams (cell size less than 20 ..mu..meters) have been developed to support the NARYA pulsed-power-driven X-ray laser program. Other pulsed power targets using these foams are anticipated. Because of the extreme fragility of these foams emphasis was placed on molding to shape to avoid machining. The foams are made by a thermally induced phase separation process from solutions of water soluble polymers. In practice the solutions are rapidly frozen to induce the phase separation, and they are then freeze dried to remove the solvent without destroying the foam's structure. A number of water soluble polymers have proven capable of meeting the density and cell size requirements. However, polyacrylic acid was used in most of our work because of its low shrinkage during molding and its purity. These foams have been molded into rods (1, 2, and 3 mm dia.), half rods, half annuli, and most recently full annuli with 3.0 mm outside diameter and 2.0 mm inside diameter. The molding techniques have varied with the various shapes. The rods were molded by freezing the solution in thin walled silicone rubber molds, extracting the frozen preform from the mold, and then freeze drying. Metal molds were used to make all other shapes. Rapid surface melting, followed by rapid refreezing, was used to remove the more complex shapes from their molds. In the case of the foam annuli, a pin with a very small taper was used to form the inner diameter. The foam rods have been successfully used in gas-puff implosion experiments on the PROTO-II accelerator. 3 refs., 4 figs., 1 tab.

  9. Synthesis of Various Silica Nanoparticles for Foam Stability

    International Nuclear Information System (INIS)

    The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles

  10. Synthesis of Various Silica Nanoparticles for Foam Stability

    Energy Technology Data Exchange (ETDEWEB)

    Yoon, Suk Bon; Yoon, Inho; Jung, Chonghun; Kim, Chorong; Choi, Wangkyu; Moon, Jeikwon [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2013-05-15

    The synthesis of the non-porous silica nanoparticles with uniform sizes has been reported through the Sto ber method, the synthesis of meso porous silica nanoparticles with a specific morphology such as core-shell, rod-like, and hexagonal shapes is not so common. As a synthetic strategy for controlling the particle size, shape, and porosity, the synthesis of core-shell silicas with meso porous shells formed on silica particle cores through the self-assembly of silica precursor and organic templates or spherical meso porous silicas using modified Sto ber method was also reported. Recently, in an effort to reduce the amount of radioactive waste and enhance the decontamination efficiency during the decontamination process of nuclear facilities contaminated with radionuclides, a few research for the preparation of the decontamination foam containing solid nanoparticles has been reported. In this work, the silica nanoparticles with various sizes, shapes, and structures were synthesized based on the previous literatures. The resulting silica nanoparticles were used to investigate the effect of the nanoparticles on the foam stability. In a study on the foam stability using various silica nanoparticles, the results showed that the foam volume and liquid volume in foam was enhanced when using a smaller size and lower density of the silica nanoparticles. Silica nanoparticles with various sizes, shapes, and structures such as a non-porous, meso porous core-shell, and meso porous silica were synthesized to investigate the effect of the foam stability. The sizes and structural properties of the silica nanoparticles were easily controlled by varying the amount of silica precursor, surfactant, and ammonia solution as a basic catalyst. The foam prepared using various silica nanoparticles showed that foam the volume and liquid volume in the foam were enhanced when using a smaller size and lower density of the silica nanoparticles.

  11. Enhancement of canonical Wnt/β-catenin signaling activity by HCV core protein promotes cell growth of hepatocellular carcinoma cells.

    Directory of Open Access Journals (Sweden)

    Jiao Liu

    Full Text Available BACKGROUND: The Hepatitis C virus (HCV core protein has been implicated as a potential oncogene or a cofactor in HCV-related hepatocellular carcinoma (HCC, but the underlying mechanisms are unknown. Overactivation of the Wnt/β-catenin signaling is a major factor in oncogenesis of HCC. However, the pathogenesis of HCV core-associated Wnt/β-catenin activation remains to be further characterized. Therefore, we attempted to determine whether HCV core protein plays an important role in regulating Wnt/β-catenin signaling in HCC cells. METHODOLOGY: Wnt/β-catenin signaling activity was investigated in core-expressing hepatoma cells. Protein and gene expression were examined by Western blot, immunofluorescence staining, RT-qPCR, and reporter assay. PRINCIPAL FINDINGS: HCV core protein significantly enhances Tcf-dependent transcriptional activity induced by Wnt3A in HCC cell lines. Additionally, core protein increases and stabilizes β-catenin levels in hepatoma cell line Huh7 through inactivation of GSK-3β, which contributes to the up-regulation of downstream target genes, such as c-Myc, cyclin D1, WISP2 and CTGF. Also, core protein increases cell proliferation rate and promotes Wnt3A-induced tumor growth in the xenograft tumor model of human HCC. CONCLUSIONS/SIGNIFICANCE: HCV core protein enhances Wnt/β-catenin signaling activity, hence playing an important role in HCV-associated carcinogenesis.

  12. Bonding Low-density Nanoporous Metal Foams Using Sputtered Solder

    Energy Technology Data Exchange (ETDEWEB)

    Bono, M; Cervantes, O; Akaba, C; Hamza, A; Foreman, R; Teslich, N

    2007-08-21

    A method has been developed for bonding low-density nanoporous metal foam components to a substrate using solder that is sputtered onto the surfaces. Metal foams have unusual properties that make them excellent choices for many applications, and as technologies for processing these materials are evolving, their use in industry is increasing dramatically. Metal foams are lightweight and have advantageous dynamic properties, which make them excellent choices for many structural applications. They also provide good acoustic damping, low thermal conductivity, and excellent energy absorption characteristics. Therefore, these materials are commonly used in the automotive, aerospace, construction, and biomedical industries. The synthesis of nanoporous metal foams with a cell size of less then 1 {micro}m is an emerging technology that is expected to lead to widespread application of metal foams in microdevices, such as sensors and actuators. One of the challenges to manufacturing components from metal foams is that they can be difficult to attach to other structures without degrading their properties. For example, traditional liquid adhesives cannot be used because they are absorbed into foams. The problem of bonding or joining can be particularly difficult for small-scale devices made from nanoporous foam, due to the requirement for a thin bond layer. The current study addresses this problem and develops a method of soldering a nanoporous metal foam to a substrate with a bond thickness of less than 2 {micro}m. There are many applications that require micro-scale metal foams precisely bonded to substrates. This study was motivated by a physics experiment that used a laser to drive a shock wave through an aluminum foil and into a copper foam, in order to determine the speed of the shock in the copper foam. To avoid disturbing the shock, the interface between the copper foam and the aluminum substrate had to be as thin as possible. There are many other applications that

  13. Chronicles of foam films.

    Science.gov (United States)

    Gochev, G; Platikanov, D; Miller, R

    2016-07-01

    The history of the scientific research on foam films, traditionally known as soap films, dates back to as early as the late 17th century when Boyle and Hooke paid special attention to the colours of soap bubbles. Their inspiration was transferred to Newton, who began systematic study of the science of foam films. Over the next centuries, a number of scientists dealt with the open questions of the drainage, stability and thickness of foam films. The significant contributions of Plateau and Gibbs in the middle/late 19th century are particularly recognized. After the "colours" method of Newton, Reinold and Rücker as well as Johhonnot developed optical methods for measuring the thickness of the thinner "non-colour" films (first order black) that are still in use today. At the beginning of the 20th century, various aspects of the foam film science were elucidated by the works of Dewar and Perrin and later by Mysels. Undoubtedly, the introduction of the disjoining pressure by Derjaguin and the manifestation of the DLVO theory in describing the film stability are considered as milestones in the theoretical development of foam films. The study of foam films gained momentum with the introduction of the microscopic foam film methodology by Scheludko and Exerowa, which is widely used today. This historical perspective serves as a guide through the chronological development of knowledge on foam films achieved over several centuries. PMID:26361708

  14. Metal foams: A survey

    Institute of Scientific and Technical Information of China (English)

    Michael; F.; Ashby; LU; Tianjian(卢天健)

    2003-01-01

    The current state-of-the-art in the development of cellular metal foams is reviewed, with focus on their fabrication, mechanical/thermal/acoustic properties, and potential applications as lightweight panels, energy absorbers, heat exchangers, and acoustic liners. Foam property charts with scaling relations are presented, allowing scoping and selection through the use of material indices.

  15. Vegetable-origin foam employed in dye extraction in tanning and leather processing facilities

    Directory of Open Access Journals (Sweden)

    José M. Cangemi

    2009-01-01

    Full Text Available This study addressed the use of conventional and vegetable origin polyurethane foams to extract C. I. Acid Orange 61 dye. The quantitative determination of the residual dye was carried out with an UV/Vis absorption spectrophotometer. The extraction of the dye was found to depend on various factors such as pH of the solution, foam cell structure, contact time and dye and foam interactions. After 45 days, better results were obtained for conventional foam when compared to vegetable foam. Despite presenting a lower percentage of extraction, vegetable foam is advantageous as it is considered a polymer with biodegradable characteristics.

  16. Electrical properties of foamed polypropylene/carbon black composites

    Science.gov (United States)

    Iliev, M.; Kotzev, G.; Vulchev, V.

    2016-02-01

    Polypropylene composites containing carbon black fillers were produced by vibration assisted extrusion process. Solid (unfoamed) composite samples were molded by conventional injection molding method, while structural foams were molded by a low pressure process. The foamed samples were evidenced to have a solid skin-foamed core structure which main parameters were found to depend on the quantity of material injected in the mold. The average bubbles' sizes and their distribution were investigated by scanning electron microscopy. It is established that the conductivity of the foamed samples gradually decreases when reducing the sample density. Nevertheless, the conductivity is found to be lower than the conductivity of the unfoamed samples both being of the same order. The flexural properties of the composites were studied and the results were discussed in the context of the structure parameters of the foamed samples.

  17. Endurance of Damping Properties of Foam-Filled Tubes

    Directory of Open Access Journals (Sweden)

    Matteo Strano

    2015-07-01

    Full Text Available The favorable energy-absorption properties of metal foams have been frequently proposed for damping or anti-crash applications. The aim of this paper is to investigate the endurance of these properties for composite structures, made by a metal or a hybrid metal-polymeric foam used as the core filling of a tubular metal case. The results of experimental tests are shown, run with two types of structures: 1 square steel tubes filled with aluminum or with hybrid aluminum-polymer foams; 2 round titanium tubes filled with aluminum foams. The paper shows that the damping properties of a foam-filled tube change (improve with the number of cycles, while all other dynamic properties are nearly constant. This result is very important for several potential applications where damping is crucial, e.g., for machine tools.

  18. Aluminium foam sandwich panels: manufacture, metallurgy and applications

    Energy Technology Data Exchange (ETDEWEB)

    Banhart, J. [Hahn-Meitner-Institut, TU Berlin (Germany); Seeliger, H.W. [Alm GmbH, Saarbruecken (Germany)

    2008-09-15

    Sandwich panels consisting of a highly porous aluminium foam core and aluminium alloy face sheets are manufactured by roll-bonding aluminium alloy sheets to a densified mixture of metal powders - usually Al-Si or Al-Si-Cu alloys with 6-8% Si and 3-10% Cu - and titanium hydride, and foaming the resulting three-layer structure by a thermal treatment. We review the various processing steps of aluminium foam sandwich (AFS) and the metallurgical processes during foaming, compare the process to alternative ways to manufacture AFS, e.g. by adhesive bonding, and give an overview of the available literature. Two ways to treat AFS after foaming are presented, namely forging and age-hardening. Some current and potential applications are described and the market potential of AFS is assessed. (Abstract Copyright [2008], Wiley Periodicals, Inc.)

  19. Shock Wave Attenuation Using Foam Obstacles: Does Geometry Matter?

    Directory of Open Access Journals (Sweden)

    Hongjoo Jeon

    2015-06-01

    Full Text Available A shock wave impact study on open and closed cell foam obstacles was completed to assess attenuation effects with respect to different front face geometries of the foam obstacles. Five different types of geometries were investigated, while keeping the mass of the foam obstacle constant. The front face, i.e., the side where the incident shock wave impacts, were cut in geometries with one, two, three or four convergent shapes, and the results were compared to a foam block with a flat front face. Results were obtained by pressure sensors located upstream and downstream of the foam obstacle, in addition to high-speed schlieren photography. Results from the experiments show no significant difference between the five geometries, nor the two types of foam.

  20. An Unusual Complication of Foam Sclerotherapy: Acute Kidney Injury

    Directory of Open Access Journals (Sweden)

    Müge EREK

    2014-09-01

    Full Text Available Sclerotherapy, in which an irritant solution is administered, is a method used to treat venous failure that results in complete venous destruction due to endothelial reaction and fibrosis. In recent years, foam sclerotherapy, in which a sclerosing agent (aethyl sclerole and air are mixed until they turn into foam and the resultant mixture is injected into noticeable veins directly and into other veins under ultrasonography in doses depending on the diameters of the varices, has been introduced. The drugs or gases used in foam sclerotherapy can cause local or systemic complications. Foam affects vessel endothelial cells and causes severe spasm in the vessel. It has been reported that endothelin-1 levels are high after foam sclerotherapy compared to the initial levels and that neurological complications vary with the endothelin levels. In this report, we present a case of acute kidney injury due to acute tubular necrosis probably caused by endothelin release following foam sclerotherapy.

  1. Investigation into stress wave propagation in metal foams

    Science.gov (United States)

    Li, Lang; Xue, Pu; Chen, Yue

    2015-09-01

    The aim of this study is to investigate stress wave propagation in metal foams under high-speed impact loading. Three-dimensional Voronoi model is established to represent real closed-cell foam. Based on the one-dimensional stress wave theory and Voronoi model, a numerical model is developed to calculate the velocity of elastic wave and shock wave in metal foam. The effects of impact velocity and relative density of metal foam on the stress wave propagation in metal foams are explored respectively. The results show that both elastic wave and shock wave propagate faster in metal foams with larger relative density; with increasing the impact velocity, the shock wave propagation velocity increase, but the elastic wave propagation is not sensitive to the impact velocity.

  2. An assessment on forced convection in metal foams

    International Nuclear Information System (INIS)

    Metal foams are a class of cellular structured materials with open cells randomly oriented and mostly homogeneous in size and shape. In the last decade, several authors have discussed the interesting heat transfer capabilities of these materials as enhanced surfaces for air conditioning, refrigeration, and electronic cooling applications. This paper reports an assessment on the forced convection through metal foams presenting experimental and analytical results carried out during air heat transfer through twelve aluminum foam samples and nine copper foam samples. The metal foam samples present different numbers of pores per linear inch (PPI), which vary between 5 and 40 with a porosity ranging between 0.896–0.956; samples of different heights have been studied. From the experimental measurements two correlations for the heat transfer coefficient and pressure drop calculations have been developed. These models can be successfully used to optimize different foam heat exchangers for any given application.

  3. Investigation into stress wave propagation in metal foams

    Directory of Open Access Journals (Sweden)

    Li Lang

    2015-01-01

    Full Text Available The aim of this study is to investigate stress wave propagation in metal foams under high-speed impact loading. Three-dimensional Voronoi model is established to represent real closed-cell foam. Based on the one-dimensional stress wave theory and Voronoi model, a numerical model is developed to calculate the velocity of elastic wave and shock wave in metal foam. The effects of impact velocity and relative density of metal foam on the stress wave propagation in metal foams are explored respectively. The results show that both elastic wave and shock wave propagate faster in metal foams with larger relative density; with increasing the impact velocity, the shock wave propagation velocity increase, but the elastic wave propagation is not sensitive to the impact velocity.

  4. Calculation of the elastic properties of a triangular cell core for lightweight composite mirrors

    Science.gov (United States)

    Penado, F. Ernesto; Clark, James H., III; Walton, Joshua P.; Romeo, Robert C.; Martin, Robert N.

    2007-09-01

    The use of composite materials in the fabrication of optical telescope mirrors offers many advantages over conventional methods, including lightweight, portability and the potential for lower manufacturing costs. In the construction of the substrate for these mirrors, sandwich construction offers the advantage of even lower weight and higher stiffness. Generally, an aluminum or Nomex honeycomb core is used in composite applications requiring sandwich construction. However, the use of a composite core offers the potential for increased stiffness and strength, low thermal distortion compatible with that of the facesheets, the absence of galvanic corrosion and the ability to readily modify the core properties. In order to design, analyze and optimize these mirrors, knowledge of the mechanical properties of the core is essential. In this paper, the mechanical properties of a composite triangular cell core (often referred to as isogrid) are determined using finite element analysis of a representative unit cell. The core studied offers many advantages over conventional cores including increased thermal and dimensional stability, as well as low weight. Results are provided for the engineering elastic moduli of cores made of high stiffness composite material as a function of the ply layup and cell size. Finally, in order to illustrate the use of these properties in a typical application, a 1.4-m diameter composite mirror is analyzed using the finite element method, and the resulting stiffness and natural frequencies are presented.

  5. Diverting acid into low permeability reservoir using foam for stimulation

    Energy Technology Data Exchange (ETDEWEB)

    Talabani, S.; Islam, M.R.

    1999-07-01

    A very difficult problem in oil well recovery is the displacement of oil in the low permeability zones in a heterogeneous reservoir. The presence of foam helps reduce the liquid mobility in the high permeability layers. The reduction in mobility causes the diversion of most of the liquid to low permeability layers. There are three factors that characterize a surfactant's ability to divert acid into the low permeability layers: the true mobility reduction factor, the foam injectivity index, and the early diversion factor. They are very practical to use in the field, and some surfactants destabilize the clays in the core that might swell. Other surfactants displace most of the oil in the core, hence generating a more stable foam later. Because most of the oil stays in the low permeability core, it will later cause the distraction of the foam in the core if it is generated. Surfactants that cause the wash of oil in the high permeability core will later generate a stable foam, which produces acid diversion into the lower permeability core. 8 refs., 10 figs.

  6. Properties of baked foams from citric acid modified cassava starch and native cassava starch blends.

    Science.gov (United States)

    Pornsuksomboon, Kanlaya; Holló, Berta Barta; Szécsényi, Katalin Mészáros; Kaewtatip, Kaewta

    2016-01-20

    Starch foams from native cassava starch (NS) and citric acid modified cassava starch (CNS) were prepared using baking processes with blend ratios of 80/20, 60/40, 50/50, 40/60 and 20/80. The density, thickness, morphology, thermal stability and water absorption of the NS, CNS and blended starch foams were determined. The ratio of the two starch components had a significant influence on the density and thickness of the blended starch foams. All blended starch foams showed good water resistance. Moreover, the morphology of the blended starch foam with the NS/CNS ratio of 50/50 showed a more ordered distribution of cell sizes with thicker cell walls than for the NS and CNS foams. The thermal stability of the blended starch foams was somewhat lower than the stability of the NS foam but not to the extent that it affected any potential practical applications. PMID:26572335

  7. Method and apparatus for producing a carbon based foam article having a desired thermal-conductivity gradient

    Science.gov (United States)

    Klett, James W. [Knoxville, TN; Cameron, Christopher Stan [Sanford, NC

    2010-03-02

    A carbon based foam article is made by heating the surface of a carbon foam block to a temperature above its graphitizing temperature, which is the temperature sufficient to graphitize the carbon foam. In one embodiment, the surface is heated with infrared pulses until heat is transferred from the surface into the core of the foam article such that the graphitizing temperature penetrates into the core to a desired depth below the surface. The graphitizing temperature is maintained for a time sufficient to substantially entirely graphitize the portion of the foam article from the surface to the desired depth below the surface. Thus, the foam article is an integral monolithic material that has a desired conductivity gradient with a relatively high thermal conductivity in the portion of the core that was graphitized and a relatively low thermal conductivity in the remaining portion of the foam article.

  8. Modeling of Sandwich Sheets with Metallic Foam

    Science.gov (United States)

    Mata, H.; Jorge, R. Natal; Santos, A.; Fernandes, A. A.; Valente, R. A. F.; Parente, M. P. L.

    2011-08-01

    World-wide vehicles safety experts agree that significant further reductions in fatalities and injuries can be achieved as a result of the use of new lightweight and energy absorbing materials. On this work, the authors present the development and evaluation of an innovative system able to perform reliable panels of sandwich sheets with metallic foam cores for industrial applications. The mathematical model used to describe the behavior of sandwich shells with metal cores foam is presented and some numerical examples are presented. In order to validate those results mechanical experiments are carried out. Using the crushable foam constitutive model, available on ABAQUS, a set of different mechanical tests were simulated. There are two variants of this model available on ABAQUS: the volumetric hardening model and the isotropic hardening model. As a first approximation we chose the isotropic hardening variant. The isotropic hardening model available uses a yield surface that is an ellipse centered at the origin in the p-q stress plane. Based on this constitutive model for the foam, numerical simulations of the tensile and bulge test will be conducted. The numerical results will be validated using the data obtained from the experimental results.

  9. Properties of Starch Based Foams Made by Thermal Pressure Forming

    Directory of Open Access Journals (Sweden)

    J. Štancl

    2008-01-01

    Full Text Available Packaging materials based on expanded polystyrene can be substituted by biodegradable foam, manufactured by direct or indirect electrical heating of a potato starch suspension in a closed mold. This paper deals with an experimental evaluation of selected properties of potato starch and starch foam related to this technology: density, specific heat capacity and specific electrical conductivity of a water suspension of potato starch within the temperature range up to 100 °C, and mass fraction from 5 to 65 %. The electric conductivity and heat capacity changes were observed during direct ohmic heating of a starch suspension between electrodes in a closed cell (feeding voltage 100 V, frequency 50 Hz. Specific electric conductivity increases with temperature, with the exception of the gelatinization region at 60 to 70 °C, and decreases with increasing concentration of starch (the temperature and concentration dependencies were approximated using the Lorentz equation. Direct ohmic heating is restricted by a significant decrease in effective electrical conductivity above a temperature of 100 °C, when evaporated steam worsens the contact with the electrodes. Experiments show that when direct ohmic heating is not combined with indirect contact heating, only 20 % of the water can be evaporated from manufactured samples and the starch foam is not fully formed. This is manifested by only a slight expansion of the heated sample. Only the indirect contact heating from the walls of the mold, with the wall temperature above 180 °C, forms a fixed porous structure (expansion of about 300 % and a crust, ensuring suitable mechanical and thermal insulation properties of the manufactured product. The effective thermal conductivity of the foamed product (sandwich plates with a porous core and a compact crust was determined by the heated wire method, while the porosity of the foam and the thickness of the crust were evaluated by image analysis of colored cross

  10. 3-dimensional shaped aluminium foam sandwiches

    Energy Technology Data Exchange (ETDEWEB)

    Baumeister, J. [Fraunhofer-Institut fuer Fertigungstechnik und Angewandte Materialforschung, Bremen (Germany); Baumgaertner, F. [Schunk Sintermetalltechnik, Giessen (Germany); Gers, H. [Honsel AG, Meschede (Germany); Seeliger, W. [Wilhelm Karmann GmbH, Osnabrueck (Germany)

    2000-07-01

    3-dimensional shaped sandwich panels with a very high stiffness can be produced in an elegant way by combining aluminium face sheets with an aluminium foam core. For this, a mixture of aluminium powder and a foaming agent is compressed to a semi-finished product of nearly vanishing porosity by extrusion, powder rolling or hot isostatic pressing. The resulting foamable semi-finished aluminium material is roll clad with sheets of conventional sheet or aluminium. As a result a precursor material is obtained consisting of two face sheets which are metallurgically bonded to the foamable core layer. This sandwich precursor material can be shaped into a 3-dimensional part by conventional techniques, e.g. by stamping or deep drawing. In a final step the foamable precursor material is heated up to the melting point of the core layer thus initiating its expansion into the desired 3-dimensional shaped sandwich structure. The porosity of the foamed core layer is in the range from 80-90% so that the integral density of the sandwich structure can be as low as 0,7 g/cm{sup 3}. The sandwich materials combine the low weight and high bending stiffness with the advantages of the face sheets, i.e. the high strength and weldability. The manufacturing process will be described in detail and the material properties will be shown. Current and future possible applications will be outlined as well as concrete parts produced up to date. (orig.)

  11. Foam coating of filtration media

    OpenAIRE

    Johansson, Mirva

    2015-01-01

    The objective of this thesis was to find out if foam coating could be applied to non-woven filtration media. The goal was to increase collection efficiency without significantly decreasing air permeability. In the theoretical part, foams and their characteristics were the centre of attention. Coating in general and, of course, foam coating were also studied. The empirical part consisted of series of foaming experiments and pilot scale coating experiments. In the foaming experiments differ...

  12. Innovative Technologies to Manufacture Hybrid Metal Foam/Composite Components

    International Nuclear Information System (INIS)

    The aim of this paper is to verify the technological feasibility to realize hybrid metal-foam/composite component and the mechanical performances of the final structure. The hybrid component is composed by a cylindrical core in aluminum foam, the most used between those commercially available, and an outer layer in epoxy/S2-glass, manufactured by filament winding technology.A set of experimental tests have been carried out, to the aim to estimate the improvement of the hybrid component characteristics, compared to the sum of the single components (metal foam cylinder and epoxy/S2-glass tube).

  13. Rheology of liquid foam

    International Nuclear Information System (INIS)

    Liquid foams can behave like solids or liquids, depending on the applied stress and on the experimental timescale. Understanding the origin of this complex rheology which gives rise to many applications and which resembles that of many other forms of soft condensed matter made of closely packed soft units requires challenging theoretical questions to be solved. We briefly recall the basic physics and physicochemistry of foams and review the experiments, numerical simulations and theoretical models concerning foam rheology published in recent years. (topical review)

  14. The foaming of lavas

    Science.gov (United States)

    Okeefe, J. A.; Walton, W.

    1976-01-01

    Foaming is of great practical and theoretical significance for volcanic processes on the earth, the moon, and perhaps the meteorite parent bodies. The theory of foams agrees with steelmaking experience to indicate that their presence depends on the existence of solutes in the lavas which reduce the surface tension, and are not saturated. These solutes concentrate at the surface, and are called surfactants. The surfactant responsible for the formation of volcanic ash was not identified; it appears to be related to the oxygen partial pressure above the lava. This fact may explain why lunar and meteoritic melts are not observed to foam. Experimental studies are needed to clarify the process.

  15. Effect of process and compound formulation variables on properties of extruded EPDM foam

    OpenAIRE

    Chonlada K. Lewis; Bunreang Misaen; Sarote Changchum

    1999-01-01

    The effects of extruded EPDM foam tube compound formulations and process conditions on foam properties were investigated. The objective was to obtain a fine close cell structure with low density foam indication better insulation properties. A cold feed extruder was used to prepare extruded tubes where foaming and vulcanizing took place in a circulationg hot air oven. Five grades of EPDM rubber base were compounded with a formula that gave good surface quality extrudates. The viscosity and die...

  16. Both core and F proteins of hepatitis C virus could enhance cell proliferation in transgenic mice

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Wen-Ta [Graduate Institute of Medical Biotechnology, Tzu Chi University, Hualien, Taiwan (China); Li, Hui-Chun [Department of Biochemistry, Tzu Chi University, Hualien, Taiwan (China); Lee, Shen-Kao; Ma, Hsin-Chieh; Yang, Chee-Hing; Chen, Hung-Ling [Graduate Institute of Medical Biotechnology, Tzu Chi University, Hualien, Taiwan (China); Lo, Shih-Yen, E-mail: losylo@mail.tcu.edu.tw [Graduate Institute of Medical Biotechnology, Tzu Chi University, Hualien, Taiwan (China); Department of Laboratory Medicine, Buddhist Tzu Chi General Hospital, Hualien, Taiwan (China)

    2013-05-24

    Highlights: •HCV core and F proteins could induce hepatocyte proliferation in the transgenic mice. •β-Catenin signaling pathway was activated by core protein in the transgenic mice. •β-Catenin signaling pathway was activated by myc-F protein in the transgenic mice. •Expression of SMA protein was enhanced by core but not myc-F protein. -- Abstract: The role of the protein encoded by the alternative open reading frame (ARF/F/core+1) of the Hepatitis C virus (HCV) genome in viral pathogenesis remains unknown. The different forms of ARF/F/core+1 protein were labile in cultured cells, a myc-tag fused at the N-terminus of the F protein made it more stable. To determine the role of core and F proteins in HCV pathogenesis, transgenic mice with either protein expression under the control of Albumin promoter were generated. Expression of core protein and F protein with myc tag (myc-F) could be detected by Western blotting analysis in the livers of these mice. The ratio of liver to body weight is increased for both core and myc-F transgenic mice compared to that of wild type mice. Indeed, the proliferating cell nuclear antigen protein, a proliferation marker, was up-regulated in the transgenic mice with core or myc-F protein. Further analyses by microarray and Western blotting suggested that β-catenin signaling pathway was activated by either core or myc-F protein in the transgenic mice. These transgenic mice were further treated with either Diethynitrosamine (a tumor initiator) or Phenobarbital (a tumor promoter). Phenobarbital but not Diethynitrosamine treatment could increase the liver/body weight ratio of these mice. However, no tumor formation was observed in these mice. In conclusion, HCV core and myc-F proteins could induce hepatocyte proliferation in the transgenic mice possibly through β-catenin signaling pathway.

  17. Both core and F proteins of hepatitis C virus could enhance cell proliferation in transgenic mice

    International Nuclear Information System (INIS)

    Highlights: •HCV core and F proteins could induce hepatocyte proliferation in the transgenic mice. •β-Catenin signaling pathway was activated by core protein in the transgenic mice. •β-Catenin signaling pathway was activated by myc-F protein in the transgenic mice. •Expression of SMA protein was enhanced by core but not myc-F protein. -- Abstract: The role of the protein encoded by the alternative open reading frame (ARF/F/core+1) of the Hepatitis C virus (HCV) genome in viral pathogenesis remains unknown. The different forms of ARF/F/core+1 protein were labile in cultured cells, a myc-tag fused at the N-terminus of the F protein made it more stable. To determine the role of core and F proteins in HCV pathogenesis, transgenic mice with either protein expression under the control of Albumin promoter were generated. Expression of core protein and F protein with myc tag (myc-F) could be detected by Western blotting analysis in the livers of these mice. The ratio of liver to body weight is increased for both core and myc-F transgenic mice compared to that of wild type mice. Indeed, the proliferating cell nuclear antigen protein, a proliferation marker, was up-regulated in the transgenic mice with core or myc-F protein. Further analyses by microarray and Western blotting suggested that β-catenin signaling pathway was activated by either core or myc-F protein in the transgenic mice. These transgenic mice were further treated with either Diethynitrosamine (a tumor initiator) or Phenobarbital (a tumor promoter). Phenobarbital but not Diethynitrosamine treatment could increase the liver/body weight ratio of these mice. However, no tumor formation was observed in these mice. In conclusion, HCV core and myc-F proteins could induce hepatocyte proliferation in the transgenic mice possibly through β-catenin signaling pathway

  18. Insights on the effective incorporation of a foam-based methanol reformer in a high temperature polymer electrolyte membrane fuel cell

    Science.gov (United States)

    Avgouropoulos, George; Papavasiliou, Joan; Ioannides, Theophilos; Neophytides, Stylianos

    2015-11-01

    Highly active Al-doped CuMnOx catalyst supported on metallic copper foam was prepared via the combustion method and placed adjacent to the anode electrocatalyst of a high temperature PEM fuel cell operating at 200-210 °C. The addition of aluminum oxide in the catalyst composition enhanced the specific surface area (19.1 vs. 8.6 m2 g-1) and the reducibility of the Cu-Mn spinel oxide. Accordingly, the catalytic performance of CuMnOx was also improved. The doped sample is up to 2.5 times more active than the undoped sample at 200 °C, depending on the methanol concentration at the inlet, while CO selectivity is less than 0.8% in all cases. A membrane-electrode assembly comprising the ADVENT cross-linked TPS® high-temperature polymer electrolyte was integrated with the Cu-based methanol reformer in an Internal Reforming Methanol Fuel Cell (IRMFC). In order to avoid extensive poisoning of the reforming catalyst by H3PO4, a thin separation plate was placed between the reforming catalyst and the electrooxidation catalyst. Preliminary results obtained from a single-cell laboratory prototype demonstrated the improved functionality of the unit. Indeed, promising electrochemical performance was obtained during the first 24 h, during which the required H2 for achieving 580 mV at 0.2 A cm-2, was supplied from the reformer.

  19. CARBONIZED STARCH MICROCELLULAR FOAM-CELLULOSE FIBER COMPOSITE STRUCTURES

    Directory of Open Access Journals (Sweden)

    Andrew R. Rutledge

    2008-11-01

    Full Text Available The production of microporous carbon foams from renewable starch microcellular foam-fiber (SMCF-Fiber composites is described. Carbon foams are used in applications such as thermal insulation, battery electrodes, filters, fuel cells, and medical devices. SMCF-Fiber compos-ites were created from an aquagel. The water in the aquagel was exchanged with ethanol and then dried and carbonized. Higher amylose content starches and fiber contents of up to 4% improved the processability of the foam. The SMCF structure revealed agglomerates of swollen starch granules connected by a web of starch with pores in the 50-200 nanometer range. Heating the SMCF-fiber in a nitrogen atmosphere to temperatures between 350-700˚C produced carbon foams with a three-dimensional closed cell foam structure with cell diameters around 50 microns and pore walls around 1-3 microns. The stress versus strain compression data for carbonized samples displayed a linear elastic region and a plateau indicative of brittle crushing, typical of an elastic-brittle foam. The carbon foam products from these renew-able precursors are promising carbon structures with moderate strength and low density.

  20. High Strain Rate Response of Sandwich Composites with Nanophased Cores

    Science.gov (United States)

    Mahfuz, Hassan; Uddin, Mohammed F.; Rangari, Vijaya K.; Saha, Mrinal C.; Zainuddin, Shaik; Jeelani, Shaik

    2005-05-01

    Polyurethane foam materials have been used as core materials in a sandwich construction with S2-Glass/SC-15 facings. The foam material has been manufactured from liquid polymer precursors of polyurethane. The precursors are made of two components; part-A (diphenylmethane diisocyanate) and part-B (polyol). In one set of experiments, part-A was mixed with part-B to manufacture the foam. In another set, TiO2 nanoparticles have been dispersed in part-A through ultrasonic cavitation technique. The loading of nanoparticles was 3% by weight of the total polymer precursor. The TiO2 nanoparticles were spherical in shape, and were about 29 nm in diameter. Sonic cavitation was carried out with a vibrasound liquid processor at 20 kHz frequency with a power intensity of about 100 kW/m2. The two categories of foams manufactured in this manner were termed as neat and nanophased. Sandwich composites were then fabricated using these two categories of core materials using a co-injection resin transfer molding (CIRTM) technique. Test samples extracted from the panel were subjected to quasi-static as well as high strain rate loadings. Rate of loading varied from 0.002 s-1 to around 1300 s-1. It has been observed that infusion of nanoparticles had a direct correlation with the cell geometry. The cell dimensions increased by about 46% with particle infusion suggesting that nanoparticles might have worked as catalysts during the foaming process. Correspondingly, enhancement in thermal properties was also noticed especially in the TGA experiments. There was also a significant improvement in mechanical properties due to nanoparticle infusion. Average increase in sandwich strength and energy absorption with nanophased cores was between 40 60% over their neat counterparts. Details of manufacturing and analyses of thermal and mechanical tests are presented in this paper.

  1. Dynamics of poroelastic foams

    Science.gov (United States)

    Forterre, Yoel; Sobac, Benjamin

    2010-11-01

    Soft poroelastic structures are widespread in biological tissues such as cartilaginous joints in bones, blood-filled placentae or plant organs. Here we investigate the dynamics of open elastic foams immersed in viscous fluids, as model soft poroelastic materials. The experiment consists in slowly compacting blocs of polyurethane solid foam embedded in silicon oil-tanks and studying their relaxation to equilibrium when the confining stress is suddenly released. Measurements of the local fluid pressure and foam velocity field are compared with a simple two-phase flow approach. For small initial compactions, the results show quantitative agreement with the classical diffusion theory of soil consolidation (Terzaghi, Biot). On the other hand, for large initial compactions, the dynamics exhibits long relaxation times and decompaction fronts, which are mainly controlled by the highly non-linear mechanical response of the foam. The analogy between this process and the evaporation of a polymer melt close to the glass transition will be briefly discussed.

  2. Inhibition of LDL oxidation and oxidized LDL-induced foam cell formation in RAW 264.7 cells show anti-atherogenic properties of a foliar methanol extract of Scoparia dulcis

    Directory of Open Access Journals (Sweden)

    Sinjitha S. Nambiar

    2014-01-01

    Full Text Available Background: Oxidation of low density lipoproteins and their further uptake by macrophages is known to result in the formation of foam cells, which are critical in the initiation of atherosclerosis through activation of inflammatory signalling cascades. Thus, powerful dietary antioxidants are receiving attention for the reversal of such pathological states. Materials and Methods: Extracts of Scoparia dulcis have been used as tea and health drinks with various health promoting effects. In the present study, we examined the reactive oxygen scavenging potential as well as anti-inflammatory and anti-atherogenic efficacies, using leaf extracts obtained after successive extraction with various solvents. Results: A methanol extract showed potent antioxidant activity with an IC 50 value of 570 μg/ml, caused hydrogen peroxide scavenging (28.9 µg/ml and anti-inflammatory effects by improving human erythrocyte membrane stabilisation (about 86%. The methanol extract also efficiently inhibited lipid peroxidation and oxidation of low density lipoproteins, thus preventing foam cell formation in cultured RAW 264.7 cells. Furthermore, phytochemical screening of the extracts showed high accumulation of flavonoids. Conclusions: The foliar methanol extract of Scoparia dulcis has a strong anti-atherogenic potential and this property could be attributed maybe due to presence of flavonoids since HPLC analysis showed high concentrations of myricetin and rutin in the methanol extract.

  3. Foaming in stout beers

    OpenAIRE

    Lee, W T; Devereux, M. G.

    2011-01-01

    We review the differences between bubble formation in champagne and other carbonated drinks, and stout beers which contain a mixture of dissolved nitrogen and carbon dioxide. The presence of dissolved nitrogen in stout beers gives them a number of properties of interest to connoisseurs and physicists. These remarkable properties come at a price: stout beers do not foam spontaneously and special technology, such as the widgets used in cans, is needed to promote foaming. Nevertheless the same m...

  4. New View to Obtain Dryer Food Foams with Different Polysaccharides and Soy Protein by High Ultrasound

    Directory of Open Access Journals (Sweden)

    Karina D. Martínez

    2014-01-01

    Full Text Available The objective of this work was to determine the effects of high intensity ultrasound application on the foaming properties of soy protein-polysaccharides mixed solutions. To this end, foaming parameters during foam formation were analyzed. The samples were sonicated for 20 min using ultrasonic processor Vibra Cell Sonics, and model VCX 750 at a frequency of 20 kHz and an amplitude of 20%. The foams were produced by a Foamscan instrument. The evolution of the bubble size change in the foam was also determined by a second CCD camera. For all foamed systems, at two pHs 3 and 7, Foam expansion and Relative Foam Conductivity showed a great increase after ultrasonic treatment. Other parameters studied did not show difference. On the other hand, Final Time of Foaming and the Total Gas Volume incorporation for foams formation were correlated with the Relative Foam Conductivity decrease and the Foam Expansion increase when HIUS were applied in every system. Comparative bubble size and shape during the foam formation according to the treatments and pH used confirmed the parameters results.

  5. Responsive foams for nanoparticle delivery.

    Science.gov (United States)

    Tang, Christina; Xiao, Edward; Sinko, Patrick J; Szekely, Zoltan; Prud'homme, Robert K

    2015-09-01

    We have developed responsive foam systems for nanoparticle delivery. The foams are easy to make, stable at room temperature, and can be engineered to break in response to temperature or moisture. Temperature-responsive foams are based on the phase transition of long chain alcohols and could be produced using medical grade nitrous oxide as a propellant. These temperature-sensitive foams could be used for polyacrylic acid (PAA)-based nanoparticle delivery. We also discuss moisture-responsive foams made with soap pump dispensers. Polyethylene glycol (PEG)-based nanoparticles or PMMA latex nanoparticles were loaded into Tween 20 foams and the particle size was not affected by the foam formulation or foam break. Using biocompatible detergents, we anticipate this will be a versatile and simple approach to producing foams for nanoparticle delivery with many potential pharmaceutical and personal care applications. PMID:26091943

  6. Material characterization of rigid foam insulation at low temperature

    Science.gov (United States)

    Barrios, Matthew

    foam, containing cells about 10 times smaller than those that make up the bulk of the foam). The 100 kN mechanical testing system at the NHMFL was used to measure the ultimate tensile strength of the foam. The number of samples available limited the amount of measurements, but the data show that the orientation of the foam (parallel or perpendicular to the knit lines) has a greater effect on the tensile strength than does the moisture absorption or exposure to cryogenic temperature.

  7. Covalent binding of a nerve agent hydrolyzing enzyme within polyurethane foams.

    Science.gov (United States)

    Lejeune, K E; Russell, A J

    1996-08-20

    A phosphotriesterase preparation, extracted from Escherichia coli DH5alpha cells, was immobilized within a polyurethane foam matrix during polymer synthesis. The enzyme-foam interaction was shown to be covalent and analysis of the hydrolysis of paraoxon in aqueous solution demonstrated that more than 50% of the initial enzyme specific activity was retained after immobilization in the foam. Factors affecting the rate of paraoxon degradation include foam hydrophobicity, the degree of mixing applied to initiate polymerization, and foam pretreatment prior to use in substrate hydrolysis. The storage stability of the foam is significant, with phosphotriesterase-foam activity profiles exhibiting a three month half-life. Foams are currently being developed for biocatalytic air filtering, in which gaseous substrates will be simultaneously adsorbed and degraded by the immobilized enzyme system. (c) 1996 John Wiley & Sons, Inc. PMID:18629797

  8. Development of a phenomenological constitutive model for polyurethane foams

    International Nuclear Information System (INIS)

    Rigid, closed-cell, polyurethane foam is used in impact limiters in nuclear waste transport containers. During a hypothetical nuclear waste transport accident, the foam is expected to absorb a significant amount of impact energy by undergoing large inelastic volume reductions. Consequently, the crushing of polyurethane foams must be well characterized and accurately modeled to properly analyze a transport container accident. At the request of Sandia National Laboratories, a series of uniaxial, hydrostatic and triaxial compression tests on polyurethane foams were performed by the New Mexico Engineering Research Institute (NMERI). The combination of hydrostatic and triaxial tests was chosen to provide sufficient data to characterize both the volumetric and deviatoric behaviors of the foams and the coupling between the two responses. Typical results from the NMERI tests are included in this paper. A complete description of these tests can be found in Neilsen et al., 1987. Constitutive models that have been used in the past to model foam did not capture some important foam behaviors observed in the NMERI tests. Therefore, a new constitutive model for rigid, closed-cell, polyurethane foams was developed and implemented in two finite element codes. Development of the new model is discussed in this paper. Also, results from analyses with the new model and other constitutive models are presented to demonstrate differences between the various models. 4 refs., 6 figs., 1 tab

  9. Development of a phenomenological constitutive model for polyurethane foams

    International Nuclear Information System (INIS)

    Rigid, closed-cell, polyurethane foam is used in impact limiters in nuclear waste transport containers. During a hypothetical nuclear waste transport accident, the foam is expected to absorb a significant amount of impact energy by undergoing large inelastic volume reductions. Consequently, the crushing of polyurethane foams must be well characterized and accurately modeled to properly analyze a transport container accident. At the request of Sandia National Laboratories, a series of uniaxial, hydrostatic and triaxial compression tests on polyurethane foams were performed by the New Mexico Engineering Research Institute (NMERI). The combination of hydrostatic and triaxial tests was chosen to provide sufficient data to characterize both the volumetric and deviatoric behaviors of the foams and the coupling between the two responses. Typical results from the NMERI tests are included in this paper. Constitutive models that have been used in the past to model foam did not capture some important foam behaviors observed in the NMERI tests. Therefore, a new constitutive model for rigid, closed-cell, polyurethane foams was developed and implemented in two finite element codes. Development of the new model is discussed in this paper. Also, results from analyses with the new model and other constitutive models are presented to demonstrate differences between the various models

  10. Fabrication of Aluminum Tubes Filled with Aluminum Alloy Foam by Friction Welding

    Directory of Open Access Journals (Sweden)

    Yoshihiko Hangai

    2015-10-01

    Full Text Available Aluminum foam is usually used as the core of composite materials by combining it with dense materials, such as in Al foam core sandwich panels and Al-foam-filled tubes, owing to its low tensile and bending strengths. In this study, all-Al foam-filled tubes consisting of ADC12 Al-Si-Cu die-cast aluminum alloy foam and a dense A1050 commercially pure Al tube with metal bonding were fabricated by friction welding. First, it was found that the ADC12 precursor was firmly bonded throughout the inner wall of the A1050 tube without a gap between the precursor and the tube by friction welding. No deformation of the tube or foaming of the precursor was observed during the friction welding. Next, it was shown that by heat treatment of an ADC12-precursor-bonded A1050 tube, gases generated by the decomposition of the blowing agent expand the softened ADC12 to produce the ADC12 foam interior of the dense A1050 tube. A holding time during the foaming process of approximately tH = 8.5 min with a holding temperature of 948 K was found to be suitable for obtaining a sound ADC12-foam-filled A1050 tube with sufficient foaming, almost uniform pore structures over the entire specimen, and no deformation or reduction in the thickness of the tube.

  11. In Silico Identification of Co-transcribed Core Cell Cycle Regulators and Transcription Factors in Arabidopsis

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Regulatory networks involving transcription factors and core cell cycle regulators are expected to play crucial roles in plant growth and development. In this report, we describe the identification of two groups of co-transcribed core cell cycle regulators and transcription factors via a two-step in silico screening. The core cell cycle regulators include TARDY ASYNCHRONOUS MEIOSIS (CYCA1;2), CYCB1;1, CYCB2;1, CDKB1;2, and CDKB2;2 while the transcription factors include CURLY LEAF, AINTEGUMENTA, a MYB protein, two Forkhead-associated domain proteins, and a SCARECROW family protein. Promoter analysis revealed a potential web of cross- and self-regulations among the identified proteins. Because one criterion for screening for these genes is that they are predominantly transcribed in young organs but not in mature organs, these genes are likely to be particularly involved in Arabidopsis organ growth.

  12. 巨噬细胞源性泡沫细胞胆固醇代谢与动脉粥样硬化%Cholesterol metabolism of macrophage foam cells and atherosclerosis

    Institute of Scientific and Technical Information of China (English)

    徐艳杰; 程晓曙

    2013-01-01

    巨噬细胞源性泡沫细胞的形成是动脉粥样硬化形成和发展中的早期变化.巨噬细胞向泡沫细胞的转变与巨噬细胞清道夫受体介导脂蛋白的吸收,ATP结合盒转运子介导胆固醇的流出及细胞内胆固醇的代谢机制相关.对巨噬细胞源性泡沫细胞胆固醇代谢的研究,将为防治动脉粥样硬化寻找新的突破口.%Foam cells is formed in early stage of atherosclerosis. The transformation of macrophage foam cell involves the disruption of a homeostatic mechanism that controls the uptake, intracellular metabolism and efflux of cholesterol by macrophages. The research of the mechanism of foam cells has a great significance for the prevention and the treatment for the atherosclerosis.

  13. Core/Shell heterojunction nanowire solar cell fabricated by lithographically patterned nanowire electrodeposition method

    OpenAIRE

    Ghosh, Somnath

    2012-01-01

    Lithographically Patterned NW Electrodeposition (LPNE) is a new technique for preparing NWs that was developed by Prof. Erik Menke while he was doing his research in Penner group in 2006. Here, we discuss some of the common problems in state of the art solar cell technology and how we can effectively use LPNE to make next generation Core/Shell NW based solar cells and NIR photodetectors. The first step in the process is the synthesis of Au/PbSe and Au/copper indium diselenide (CIS) core/shell...

  14. Development of rubidium and niobium containing plastic foams. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Botham, R.A.; McClung, C.E.; Schwendeman, J.I.

    1978-07-26

    Rubidium fluoride and niobium metal-containing foam samples (rods and sheets) were prepared using two foam sytems: (1) hydrophilic polyurethanes prepared from W.R. Grace Co.'s Hypol prepolymers and (2) polyimides prepared from Monsanto Company's Skybond polyimide resin. The first system was used only for preparation of rubidium fluoride-containing foams while the second was used for both rubidium fluoride and niobium-containing foams. The niobium metal could readily be incorporated into the polyimide foam during molding, to produce foam sheets of the required dimensions and density. The rubidium fluoride-containing polyimide foams were preferably prepared by first rendering the molded polyimide foam hydrophilic with a postcuring treatment, then absorbing the rubidium fluoride from water solution. Similarly, rubidium fluoride was absorbed into the hydrophilic polyurethanes from water solution. Since the high reactive rubidium metal could not be employed, rubidium fluoride, which is very hygroscopic, was used instead, primarily because of its high rubidium content (approximately 82 weight percent). This was important in view of the low total densities and the high weight percentage rubidium required in the foam samples. In addition, at the later request of LLL, a block of rigid Hypol hydrophilic polyurethane foam (with a density of approximately 0.04 g/cm/sup 3/ and cell sizes = or <0.2 mm) was prepared without any metal or metal compounds in it. Two shipments of foam samples, which met or closely approximated the project specifications, were submitted to LLL during the course of this project. Information on these samples is contained in Table 1. A complete description of their preparation is given in the Experimental Results and Discussion Section.

  15. Development of rubidium and niobium containing plastic foams. Final report

    International Nuclear Information System (INIS)

    Rubidium fluoride and niobium metal-containing foam samples (rods and sheets) were prepared using two foam sytems: (1) hydrophilic polyurethanes prepared from W.R. Grace Co.'s Hypol prepolymers and (2) polyimides prepared from Monsanto Company's Skybond polyimide resin. The first system was used only for preparation of rubidium fluoride-containing foams while the second was used for both rubidium fluoride and niobium-containing foams. The niobium metal could readily be incorporated into the polyimide foam during molding, to produce foam sheets of the required dimensions and density. The rubidium fluoride-containing polyimide foams were preferably prepared by first rendering the molded polyimide foam hydrophilic with a postcuring treatment, then absorbing the rubidium fluoride from water solution. Similarly, rubidium fluoride was absorbed into the hydrophilic polyurethanes from water solution. Since the high reactive rubidium metal could not be employed, rubidium fluoride, which is very hygroscopic, was used instead, primarily because of its high rubidium content (approximately 82 weight percent). This was important in view of the low total densities and the high weight percentage rubidium required in the foam samples. In addition, at the later request of LLL, a block of rigid Hypol hydrophilic polyurethane foam (with a density of approximately 0.04 g/cm3 and cell sizes = or <0.2 mm) was prepared without any metal or metal compounds in it. Two shipments of foam samples, which met or closely approximated the project specifications, were submitted to LLL during the course of this project. Information on these samples is contained in Table 1. A complete description of their preparation is given in the Experimental Results and Discussion Section

  16. Nano-Aramid Fiber Reinforced Polyurethane Foam

    Science.gov (United States)

    Semmes, Edmund B.; Frances, Arnold

    2008-01-01

    Closed cell polyurethane and, particularly, polyisocyanurate foams are a large family of flexible and rigid products the result of a reactive two part process wherein a urethane based polyol is combined with a foaming or "blowing" agent to create a cellular solid at room temperature. The ratio of reactive components, the constituency of the base materials, temperature, humidity, molding, pouring, spraying and many other processing techniques vary greatly. However, there is no known process for incorporating reinforcing fibers small enough to be integrally dispersed within the cell walls resulting in superior final products. The key differentiating aspect from the current state of art resides in the many processing technologies to be fully developed from the novel concept of milled nano pulp aramid fibers and their enabling entanglement capability fully enclosed within the cell walls of these closed cell urethane foams. The authors present the results of research and development of reinforced foam processing, equipment development, strength characteristics and the evolution of its many applications.

  17. Corrigendum to "Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams"

    Science.gov (United States)

    Raj. Sai V.

    2011-01-01

    Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use an idealized three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15% and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50-57% of the cell faces were pentagonal while 24-28% were quadrilateral and 15-22% were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with 3 quadrilateral, 6 pentagonal faces and 2 hexagonal faces consistent with the 3-6-2 Matzke cell

  18. Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams

    Science.gov (United States)

    Raj, S. V.

    2010-01-01

    Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use the three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15 percent and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50 to 57 percent of the cell faces were pentagonal while 24 to 28 percent were quadrilateral and 15 to 22 percent were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with 3 quadrilateral, 6 pentagonal faces and 2 hexagonal faces consistent with the 3-6-2 cell.

  19. High Heat Flux Testing of a Helium-Cooled Tungsten Tube with Porous Foam

    International Nuclear Information System (INIS)

    Utramet, Inc. fabricated refractory heat exchanger tubes of chemical vapor deposited (CVD) tungsten with an integrally bonded core of open-cell CVD tungsten foam. The 10 pores-per-inch, 20% dense foam is very open (80% porous) with a structure of joined ligaments that combines a relatively low resistance to flow and a large area for heat transfer. Sandia National Laboratories tested the helium-cooled tungsten foam tubes in Sandia's Electron Beam Test Stand (EBTS), a 30 kW electron beam high heat flux facility that includes a closed helium cooling loop. The specimens were 12.7 mm ID x 16.2 mm OD W tubes with W foam centered along 38 mm of the axial length. CVD niobium coating of the ends of the tubes permitted the use of compression fittings to join the specimens to the piping of the helium loop. The fabrication and testing of the specimens were funded through a Phase I grant by the US Department of Energy's Small Business Innovation Research Program. We also tested an open CVD tungsten tube without the porous foam for comparison. Tests were performed in EBTS at progressively higher heat loads. With the foam sample, the maximum absorbed heat load was ∼ 22 MW/m2 with helium at 4 MPa, flowing at 27 g/s and with inlet and outlet temperatures of 40 oC and 91 oC and a pressure drop of ∼ 92 kPa. The helium removed over 7100 W steady state from the part at the highest heat flux. The part failed and fragmented during the cool down after exposure to this heat load. While the fragmentation of the sample indicates that development of more robust W or Mo alloy components will ultimately be required, which are feasible via CVD and part of proposed Phase II work, the very high heat load obtained in these tests is an impressive result for the potential of helium-cooled refractory systems for plasma facing components in fusion devices. The paper reports details of the test, including the surface temperature distributions indicated by an infrared camera and pyrometers, the

  20. Foamed Antenna Support for Very Large Apertures Project

    Data.gov (United States)

    National Aeronautics and Space Administration — The proposed Phase I program will demonstrate the feasibility of the in-space production of large aperture antenna structures. The use of a novel open cell foam,...

  1. Low density metal hydride foams

    International Nuclear Information System (INIS)

    Disclosed is a low density foam having a porosity of from 0 to 98% and a density less than about 0.67 gm/cc, prepared by heating a mixture of powered lithium hydride and beryllium hydride in an inert atmosphere at a temperature ranging from about 455 to about 490 K for a period of time sufficient to cause foaming of said mixture, and cooling the foam thus produced. Also disclosed is the process of making the foam. 6 figures

  2. Foam injection molding of elastomers with iron microparticles

    Science.gov (United States)

    Volpe, Valentina; D'Auria, Marco; Sorrentino, Luigi; Davino, Daniele; Pantani, Roberto

    2015-12-01

    In this work, a preliminary study of foam injection molding of a thermoplastic elastomer, Engage 8445, and its microcomposite loaded with iron particles was carried out, in order to evaluate the effect of the iron microparticles on the foaming process. In particular, reinforced samples have been prepared by using nanoparticles at 2% by volume. Nitrogen has been used as physical blowing agent. Foamed specimens consisting of neat and filled elastomer were characterized by density measurements and morphological analysis. While neat Engage has shown a well developed cellular morphology far from the injection point, the addition of iron microparticles considerably increased the homogeneity of the cellular morphology. Engage/iron foamed samples exhibited a reduction in density greater than 32%, with a good and homogeneous cellular morphology, both in the transition and in the core zones, starting from small distances from the injection point.

  3. Effect of adhesive on the strengthening of aluminum foam-filled circular tubes

    OpenAIRE

    Toksoy, Ahmet Kaan; Tanoğlu, Metin; Güden, Mustafa; Hall, Ian W.

    2004-01-01

    Studies of the crushing behavior of closed-cell, aluminum foam-filled aluminum and steel tubes have shown an interaction effect between tubewall and foam filler [1, 2, 3]. The crushing loads of foam-filled tubes are, therefore, found to be higher than the sum of the crushing loads of foam (alone) and tube (alone) mainly due to this effect. Santosa et al. [1], based on FEM results, proposed the following equation for the average crushing load of foam-filled square tubes of length b,

  4. A smart core-sheath nanofiber that captures and releases red blood cells from the blood

    Science.gov (United States)

    Shi, Q.; Hou, J.; Zhao, C.; Xin, Z.; Jin, J.; Li, C.; Wong, S.-C.; Yin, J.

    2016-01-01

    A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from the blood above phase-transition temperature of PNIPAAm. Meanwhile, the captured RBCs are readily released from the nanofibers with temperature stimuli in an undamaged manner. The release efficiency of up to 100% is obtained while maintaining cellular integrity and function. This work presents promising nanofibers to effectively capture non-adherent cells and release for subsequent molecular analysis and diagnosis of single cells.A smart core-sheath nanofiber for non-adherent cell capture and release is demonstrated. The nanofibers are fabricated by single-spinneret electrospinning of poly(N-isopropylacrylamide) (PNIPAAm), polycaprolactone (PCL) and nattokinase (NK) solution blends. The self-assembly of PNIPAAm and PCL blends during the electrospinning generates the core-sheath PCL/PNIPAAm nanofibers with PNIPAAm as the sheath. The PNIPAAm-based core-sheath nanofibers are switchable between hydrophobicity and hydrophilicity with temperature change and enhance stability in the blood. When the nanofibers come in contact with blood, the NK is released from the nanofibers to resist platelet adhesion on the nanofiber surface, facilitating the direct capture and isolation of red blood cells (RBCs) from

  5. Inverted heterojunction solar cells incorporating fullerene/polythiophene composite core/shell nanorod arrays

    International Nuclear Information System (INIS)

    We have fabricated inverted heterojunction solar cell devices incorporating [6,6]-phenyl-C61-butyric acid methyl ester/poly(3-hexylthiophene) core/shell nanorod arrays by using an anodic alumina oxide template. The internal quantum efficiencies and external quantum efficiencies of these core/shell nanorod inverted solar cells were higher than those of the corresponding conventional inverted bulk heterojunction device. The optimized nanorod array structure had a high hole mobility that was over one order magnitude greater than that of the conventional bulk heterojunction structure, as determined by fitting the dark J-V curves into the space charge limited current model. The more efficient carrier transport of the device incorporating the core/shell nanorod arrays provided it with both a higher short-circuit current density and power conversion efficiency.

  6. Foaming in stout beers

    Science.gov (United States)

    Lee, W. T.; Devereux, M. G.

    2011-10-01

    We review the differences between bubble formation in champagne and other carbonated drinks, and stout beers which contain a mixture of dissolved nitrogen and carbon dioxide. The presence of dissolved nitrogen in stout beers gives them several properties of interest to connoisseurs and physicists. These remarkable properties come at a price: stout beers do not foam spontaneously and special technology, such as the widgets used in cans, is needed to promote foaming. Nevertheless, the same mechanism, nucleation by gas pockets trapped in cellulose fibers, responsible for foaming in carbonated drinks is active in stout beers, but at an impractically slow rate. This gentle rate of bubble nucleation makes stout beers an excellent model system for investigating the nucleation of gas bubbles. The equipment needed is modest, putting such experiments within reach of undergraduate laboratories. We also consider the suggestion that a widget could be constructed by coating the inside of a beer can with cellulose fibers.

  7. Foaming in stout beers

    CERN Document Server

    Lee, W T

    2011-01-01

    We review the differences between bubble formation in champagne and other carbonated drinks, and stout beers which contain a mixture of dissolved nitrogen and carbon dioxide. The presence of dissolved nitrogen in stout beers gives them a number of properties of interest to connoisseurs and physicists. These remarkable properties come at a price: stout beers do not foam spontaneously and special technology, such as the widgets used in cans, is needed to promote foaming. Nevertheless the same mechanism, nucleation by gas pockets trapped in cellulose fibres, responsible for foaming in carbonated drinks is active in stout beers, but at an impractically slow rate. This gentle rate of bubble nucleation makes stout beers an excellent model system for the scientific investigation of the nucleation of gas bubbles. The equipment needed is very modest, putting such experiments within reach of undergraduate laboratories. Finally we consider the suggestion that a widget could be constructed by coating the inside of a beer...

  8. Foams in porous media

    Energy Technology Data Exchange (ETDEWEB)

    Marsden, S.S.

    1986-07-01

    In 1978 a literature search on selective blocking of fluid flow in porous media was done by Professor S.S. Marsden and two of his graduate students, Tom Elson and Kern Huppy. This was presented as SUPRI Report No. TR-3 entitled ''Literature Preview of the Selected Blockage of Fluids in Thermal Recovery Projects.'' Since then a lot of research on foam in porous media has been done on the SUPRI project and a great deal of new information has appeared in the literature. Therefore we believed that a new, up-to-date search should be done on foam alone, one which would be helpful to our students and perhaps of interest to others. This is a chronological survey showing the development of foam flow, blockage and use in porous media, starting with laboratory studies and eventually getting into field tests and demonstrations. It is arbitrarily divided into five-year time periods. 81 refs.

  9. LFT foam - Lightweight potential for semi-structural components through the use of long-glass-fiber-reinforced thermoplastic foams

    Science.gov (United States)

    Roch, A.; Huber, T.; Henning, F.; Elsner, P.

    2014-05-01

    Investigations on PP-LGF30 foam sandwiches have been carried out using different manufacturing processes: standard injection molding, MuCell® and LFT-D foam. Both chemical and physical blowing agents were applied. Precision mold opening (breathing mold technology) was selected for the foaming process. The integral foam design, which can be conceived as a sandwich structure, helps to save material in the neutral axis area and maintains a distance between load-bearing, unfoamed skin layers. The experiments showed that, at a constant mass per unit area, integral foams have a significantly higher flexural rigidity than compact components, due to their greater area moment of inertia after foaming: with an increase of the wall thickness from 3.6 mm to 4.4 mm compared to compact construction, the flexural rigidity increased by 75 %. With a final wall thickness of 5.8 mm an increase of 300 % was measured. Compared to non-reinforced components that show significant embrittlement during foaming, the energy absorption capacity (impact strength) of LFT foam components remains almost constant.

  10. Space Time Foam

    Science.gov (United States)

    Garattini, Remo

    In the context of a model of space-time foam, made by N wormholes we discuss the possibility of having a foam formed by different configurations. An equivalence between Schwarzschild and Schwarzschild-Anti-de Sitter wormholes in terms of Casimir energy is shown. An argument to discriminate which configuration could represent a foamy vacuum coming from Schwarzschild black hole transition frequencies is used. The case of a positive cosmological constant is also discussed. Finally, a discussion involving charged wormholes leads to the conclusion that they cannot be used to represent a ground state of the foamy type.

  11. Long lasting decontamination foam

    Science.gov (United States)

    Demmer, Ricky L.; Peterman, Dean R.; Tripp, Julia L.; Cooper, David C.; Wright, Karen E.

    2010-12-07

    Compositions and methods for decontaminating surfaces are disclosed. More specifically, compositions and methods for decontamination using a composition capable of generating a long lasting foam are disclosed. Compositions may include a surfactant and gelatin and have a pH of less than about 6. Such compositions may further include affinity-shifting chemicals. Methods may include decontaminating a contaminated surface with a composition or a foam that may include a surfactant and gelatin and have a pH of less than about 6.

  12. Materials Applications for Non-Lethal: Aqueous Foams

    Energy Technology Data Exchange (ETDEWEB)

    GOOLSBY,TOMMY D.; SCOTT,STEVEN H.

    1999-09-15

    High expansion aqueous foam is an aggregation of bubbles that has the appearance of soap suds and is used to isolate individuals both visually and acoustically. It was developed in the 1920's in England to fight coal mine fires and has been widely used since for fire fighting and dust suppression. It was developed at Sandia National Laboratories (SNL) in the 1970's for nuclear safeguards and security applications. In the mid-1990s, the National Institute of Justice (NIJ), the research arm of the Department of Justice, began a project with SNL to determine the applicability of high expansion aqueous foam for correctional applications. NIJ funded the project as part of its search for new and better less-than-lethal weapons for responding to violent and dangerous individuals, where other means of force could lead to serious injuries. The phase one objectives of the project were to select a low-to-no toxicity foam concentrate (foaming agent) with physical characteristics suited for use in a single cell or large prison disturbances, and to determine if the selected foam concentrate could serve as a carrier for Oleoresin Capsicum (OC) irritant. The phase two objectives were to conduct an extensive toxicology review of the selected foam concentrate and OC irritant, and to conduct respiration simulation experiments in the selected high expansion aqueous foam. The phase three objectives were to build a prototype individual cell aqueous foam system and to study the feasibility of aqueous foams for large prison facility disturbances. The phase four and five objectives were to use the prototype system to do large scale foam physical characteristics testing of the selected foam concentrate, and to have the prototype single cell system further evaluated by correctional representatives. Prison rather than street scenarios were evaluated as the first and most likely place for using the aqueous foam since prisons have recurrent incidents where officers and inmates might

  13. Materials Applications for Non-Lethal: Aqueous Foams

    International Nuclear Information System (INIS)

    High expansion aqueous foam is an aggregation of bubbles that has the appearance of soap suds and is used to isolate individuals both visually and acoustically. It was developed in the 1920's in England to fight coal mine fires and has been widely used since for fire fighting and dust suppression. It was developed at Sandia National Laboratories (SNL) in the 1970's for nuclear safeguards and security applications. In the mid-1990s, the National Institute of Justice (NIJ), the research arm of the Department of Justice, began a project with SNL to determine the applicability of high expansion aqueous foam for correctional applications. NIJ funded the project as part of its search for new and better less-than-lethal weapons for responding to violent and dangerous individuals, where other means of force could lead to serious injuries. The phase one objectives of the project were to select a low-to-no toxicity foam concentrate (foaming agent) with physical characteristics suited for use in a single cell or large prison disturbances, and to determine if the selected foam concentrate could serve as a carrier for Oleoresin Capsicum (OC) irritant. The phase two objectives were to conduct an extensive toxicology review of the selected foam concentrate and OC irritant, and to conduct respiration simulation experiments in the selected high expansion aqueous foam. The phase three objectives were to build a prototype individual cell aqueous foam system and to study the feasibility of aqueous foams for large prison facility disturbances. The phase four and five objectives were to use the prototype system to do large scale foam physical characteristics testing of the selected foam concentrate, and to have the prototype single cell system further evaluated by correctional representatives. Prison rather than street scenarios were evaluated as the first and most likely place for using the aqueous foam since prisons have recurrent incidents where officers and inmates might be

  14. Molded ultra-low density microcellular foams

    International Nuclear Information System (INIS)

    Ultra-low density (< 0.01 g/cc) microcellular foams were required for the NARYA pulsed-power-driven x-ray laser development program. Because of their extreme fragility, molded pieces would be necessary to successfully field these foams in the pulsed power accelerator. All of the foams evaluated were made by the thermally induced phase separation technique from solutions of water soluble polymers. The process involved rapidly freezing the solution to induce the phase separation, and then freeze drying to remove the water without destroying the foam's structure. More than sixty water soluble polymers were evaluated by attempting to make their solutions into foams. The foams were evaluated for shrinkage, density, and microstructure to determine their suitability for molding and meeting the required density and cell size requirements of 5.0 mg/cc and less than twenty μmeters. Several promising water soluble polymers were identified including the polyactylic acids, guar gums, polyactylamide, and polyethylene oxide. Because of thier purity, structure, and low shrinkage, the polyacrylic acids were chosen to develop molding processes. The initial requirements were for 2.0 cm. long molded rods with diameters of 1.0, 2.0. and 3.0 mm. These rods were made by freezing the solution in thin walled silicon rubber molds, extracting the frozen preform from the mold, and then freeze drying. Requirements for half rods and half annuli necessitated using aluminum molds. Again we successfully molded these shapes. Our best efforts to date involve molding annuli with 3.0 mm outside diameters and 2.0 mm inside diameters

  15. Molded ultra-low density microcellular foams

    Energy Technology Data Exchange (ETDEWEB)

    Rand, P.B.; Montoya, O.J.

    1986-07-01

    Ultra-low density (< 0.01 g/cc) microcellular foams were required for the NARYA pulsed-power-driven x-ray laser development program. Because of their extreme fragility, molded pieces would be necessary to successfully field these foams in the pulsed power accelerator. All of the foams evaluated were made by the thermally induced phase separation technique from solutions of water soluble polymers. The process involved rapidly freezing the solution to induce the phase separation, and then freeze drying to remove the water without destroying the foam's structure. More than sixty water soluble polymers were evaluated by attempting to make their solutions into foams. The foams were evaluated for shrinkage, density, and microstructure to determine their suitability for molding and meeting the required density and cell size requirements of 5.0 mg/cc and less than twenty ..mu..meters. Several promising water soluble polymers were identified including the polyactylic acids, guar gums, polyactylamide, and polyethylene oxide. Because of thier purity, structure, and low shrinkage, the polyacrylic acids were chosen to develop molding processes. The initial requirements were for 2.0 cm. long molded rods with diameters of 1.0, 2.0. and 3.0 mm. These rods were made by freezing the solution in thin walled silicon rubber molds, extracting the frozen preform from the mold, and then freeze drying. Requirements for half rods and half annuli necessitated using aluminum molds. Again we successfully molded these shapes. Our best efforts to date involve molding annuli with 3.0 mm outside diameters and 2.0 mm inside diameters.

  16. Daintain/AIF-1 Plays Roles in Coronary Heart Disease via Affecting the Blood Composition and Promoting Macrophage Uptake and Foam Cell Formation

    Directory of Open Access Journals (Sweden)

    Junhan Wang

    2013-07-01

    Full Text Available Background: Daintain/AIF-1 is an inflammatory polypeptide factor/allograft inflammatory factor 1 derived from macrophages. It is characterized in APOE-/- mice as a novel inflammatory factor associated with atherosclerosis. The purpose of this study was to characterize its function in human atherosclerosis. Methods: Immunohistochemistry was used to identify the expression of daintain/AIF-1 in vessel segments within and far from atherosclerotic plaques; High-performance liquid chromatography (HPLC was used to display the effects of daintain/AIF-1 on C-reactive protein (CRP, oxidative capacity and superoxide dismutase (SOD in vivo; Oil Red O Staining was used to show the effects of daintain/AIF-1 on uptake of oxidized low density lipoprotein (ox-LDL into U937 cells, a macrophage line; Western Blot was used to test scavenger receptor A (SRA expression. Results: A high density of daintain/AIF-1 was observed in the tunica intima and media of coronary artery with atherosclerotic plaque, and fewer daintain/AIF-1 in the vessels without atherosclerotic plaque; Daintain/AIF-1 injected intravenously into BALB/c mice boosted oxidative capacity, significantly impaired SOD activities and augmented the CRP level in blood. According to the oil red O test, daintain/AIF-1 profoundly facilitated the uptake of ox-LDL in U937 macrophages and formation of foam cells in the endothelium. We also found that the molecular mechanisms are effective by promoting overexpression of SRA on macrophages. Conclusion: These findings implicate that the inflammatory factor daintain/AIF-1 is closely associated with atherogenesis, and could be further characterized as a novel risk factor for atherosclerosis

  17. Walnut oil increases cholesterol efflux through inhibition of stearoyl CoA desaturase 1 in THP-1 macrophage-derived foam cells

    Directory of Open Access Journals (Sweden)

    Gillies Peter J

    2011-08-01

    Full Text Available Abstract Background Walnuts significantly decrease total and low-density lipoprotein cholesterol in normo- and hypercholesterolemic individuals. No study to date has evaluated the effects of walnuts on cholesterol efflux, the initial step in reverse cholesterol transport, in macrophage-derived foam cells (MDFC. The present study was conducted to investigate the mechanisms by which walnut oil affects cholesterol efflux. Methods The extract of English walnuts (walnut oil was dissolved in DMSO and applied to cultured THP-1 MDFC cells (0.5 mg/mL. THP-1 MDFC also were treated with human sera (10%, v:v taken from subjects in a walnut feeding study. Cholesterol efflux was examined by liquid scintillation counting. Changes in gene expression were quantified by real time PCR. Results Walnut oil treatment significantly increased cholesterol efflux through decreasing the expression of the lipogenic enzyme stearoyl CoA desaturase 1 (SCD1 in MDFC. Alpha-linolenic acid (ALA, the major n-3 polyunsaturated fatty acids found in walnuts, recaptured SCD1 reduction in MDFC, a mechanism mediated through activation of nuclear receptor farnesoid-X-receptor (FXR. Postprandial serum treatment also increased cholesterol efflux in MDFC. When categorized by baseline C-reactive protein (CRP; cut point of 2 mg/L, subjects in the lower CRP sub-group benefited more from dietary intervention, including a more increase in cholesterol efflux, a greater reduction in SCD1, and a blunted postprandial lipemia. Conclusion In conclusion, walnut oil contains bioactive molecules that significantly improve cholesterol efflux in MDFC. However, the beneficial effects of walnut intake may be reduced by the presence of a pro-inflammatory state. Trial Registration ClinicalTrials.gov: NCT00938340

  18. A V2O5/conductive-polymer core/shell nanobelt array on three-dimensional graphite foam: a high-rate, ultrastable, and freestanding cathode for lithium-ion batteries.

    Science.gov (United States)

    Chao, Dongliang; Xia, Xinhui; Liu, Jilei; Fan, Zhanxi; Ng, Chin Fan; Lin, Jianyi; Zhang, Hua; Shen, Ze Xiang; Fan, Hong Jin

    2014-09-01

    A thin polymer shell helps V2O5 a lot. Short V2O5 nanobelts are grown directly on 3D graphite foam as a lithium-ion battery (LIB) cathode material. A further coating of a poly(3,4-ethylenedioxythiophene) (PEDOT) thin shell is the key to the high performance. An excellent high-rate capability and ultrastable cycling up to 1000 cycles are demonstrated. PMID:24888872

  19. THE STUDY OF CORE SAND MIXTURES BASED ON POLYMERIC BINDERS

    Directory of Open Access Journals (Sweden)

    Ms. Natalia V. Zakharova

    2016-06-01

    Full Text Available The possibility of using foamed polystyrene waste as the binder in manufacturing core sand mixtures. The article provides experimental data obtained by studying the core sand mixtures properties depending on the methods of addition, foamed polystyrene solution amount, its viscosity and the method of drying. The author investigates the ways of using foamed polystyrene as the binder and as the polymeric additive.

  20. Preparation of precursor for stainless steel foam

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xiang-yang; LI Shan-ni; LI Jie; LIU Ye-xiang

    2008-01-01

    The effects of polyurethane sponge pretreatment and slurry compositions on the slurry loading in precursor were discussed, and the,performances of stainless steel foams prepared from precursors with different slurry loadings and different particle sizes of the stainless steel powder were also investigated. The experimental results show that the pretreatment of sponge with alkaline solution is effective to reduce the jam of cells in precursor and ensure the slurry to uniformly distribute in sponge, and it is also an effective method for increasing the slurry loading in precursor; the mass fraction of additive A and solid content in slurry greatly affect the slurry loading in precursor, when they are kept in 9%-13% and 52%-75%, respectively, the stainless steel foam may hold excellent 3D open-cell network structure and uniform muscles; the particle size of the stainless steel powder and the slurry loading in precursor have great effects on the bending strength, apparent density and open porosity of stainless steel foam; when the stainless steel powder with particle size of 44 tan and slurry loading of 0.5 g/cm3 in precursor are used, a stainless steel foam can be obtained, which has open porosity of 81.2%, bending strength of about 51.76 MPa and apparent density of about 1.0 g/cm3.

  1. Sensory and Foaming Properties of Sparkling Cider

    OpenAIRE

    Picinelli, A.M. (Anna); Fernández, Norman; Rodríguez, Roberto; Suárez, Belén

    2012-01-01

    The effect of yeast strain and aging time on the chemical composition, analytical, and sensory foam properties of sparkling ciders has been studied. The analytical foam parameters (foamability, HM; Bikerman coefficient, ∑; and foam stability time, Ts) were significantly influenced by aging and yeast strain. The sensory attributes (initial foam, foam area persistence, bubble size, foam collar, and overall foam quality) improved with aging time. Likewise, the yeast strain positively influenced ...

  2. Morphological Study of Directionally Freeze-Cast Nickel Foams

    Science.gov (United States)

    Jo, Hyungyung; Kim, Min Jeong; Choi, Hyelim; Sung, Yung-Eun; Choe, Heeman; Dunand, David C.

    2016-03-01

    Nickel foams, consisting of 51 to 62 pct aligned, elongated pores surrounded by a network of Ni walls, were fabricated by reduction and sintering of directionally cast suspensions of nanometric NiO powders in water. Use of dispersant in the slurry considerably affected the foam morphology and microstructure at both the micro- and macro-scale, most likely by modifying ice solidification into dendrites (creating the aligned, elongated macro-pores) and NiO powder accumulation in the inter-dendritic space (creating the Ni walls with micro-pores). The mean width of the Ni walls, in foams solidified with and without dispersant, was 21 ± 5 and 75 ± 13 µm, respectively. Additionally, the foams with the dispersant showed less dense walls and rougher surfaces than those without the dispersant. Moreover, the fraction of closed pores present in the foam walls with the dispersant was higher than that of the samples without dispersant. We finally verified the potential energy application of the Ni foam produced in this study by carrying out a preliminary single-cell performance test with the Ni foam sample as the gas diffusion layer on the anode side of a polymer electrolyte membrane fuel cell.

  3. Quasi-one-dimensional foam drainage

    Science.gov (United States)

    Grassia, P.; Cilliers, J. J.; Neethling, S. J.; Ventura-Medina, E.

    Foam drainage is considered in a froth flotation cell. Air flow through the foam is described by a simple two-dimensional deceleration flow, modelling the foam spilling over a weir. Foam microstructure is given in terms of the number of channels (Plateau borders) per unit area, which scales as the inverse square of bubble size. The Plateau border number density decreases with height in the foam, and also decreases horizontally as the weir is approached. Foam drainage equations, applicable in the dry foam limit, are described. These can be used to determine the average cross-sectional area of a Plateau border, denoted A, as a function of position in the foam. Quasi-one-dimensional solutions are available in which A only varies vertically, in spite of the two-dimensional nature of the air flow and Plateau border number density fields. For such situations the liquid drainage relative to the air flow is purely vertical. The parametric behaviour of the system is investigated with respect to a number of dimensionless parameters: K (the strength of capillary suction relative to gravity), α (the deceleration of the air flow), and n and h (respectively, the horizontal and vertical variations of the Plateau border number density). The parameter K is small, implying the existence of boundary layer solutions: capillary suction is negligible except in thin layers near the bottom boundary. The boundary layer thickness (when converted back to dimensional variables) is independent of the height of the foam. The deceleration parameter α affects the Plateau border area on the top boundary: weaker decelerations give larger Plateau border areas at the surface. For weak decelerations, there is rapid convergence of the boundary layer solutions at the bottom onto ones with negligible capillary suction higher up. For strong decelerations, two branches of solutions for A are possible in the K=0 limit: one is smooth, and the other has a distinct kink. The full system, with small but non

  4. Foaming in manure based digesters

    DEFF Research Database (Denmark)

    Kougias, Panagiotis; Boe, Kanokwan; Angelidaki, Irini

    2012-01-01

    Anaerobic digestion foaming is one of the major problems that occasionally occurred in the Danish full-scale biogas plants, affecting negatively the overall digestion process. The foam is typically formatted in the main biogas reactor or in the pre-storage tank and the entrapped solids in the foam....... Moreover, foaming presents adverse environmental impacts owing to the overflowing of the pre-storage or digester tanks. So far, there has never been thoroughly investigation of foaming problem in manure-based digester, which is the main anaerobic digestion applied in Denmark. The purpose of the present...... study was to identify potential causes of foaming in manure based digesters. Moreover, it was also an aim to investigate possible solutions to counteract foam formation with the use of antifoam agents. Thus, the impact of organic loading rate and content of feeding substrate on anaerobic digestion...

  5. Cells Cultured on Core-Shell Photonic Crystal Barcodes for Drug Screening.

    Science.gov (United States)

    Fu, Fanfan; Shang, Luoran; Zheng, Fuyin; Chen, Zhuoyue; Wang, Huan; Wang, Jie; Gu, Zhongze; Zhao, Yuanjin

    2016-06-01

    The development of effective drug screening platforms is an important task for biomedical engineering. Here, a novel methacrylated gelatin (GelMA) hydrogel-encapsulated core-shell photonic crystal (PhC) barcode particle was developed for three-dimensional cell aggregation culture and drug screening. The GelMA shells of the barcode particles enable creation of a three-dimensional extracellular matrix (ECM) microenvironment for cell adhesion and growth, while the PhC cores of the barcode particles provide stable diffraction peaks that can encode different cell spheroids during culture and distinguish their biological response during drug testing. The applicability of this cell spheroids-on-barcodes platform was investigated by testing the cytotoxic effect of tegafur (TF), a prodrug of 5-fluorouracil (5-FU), on barcode particle-loaded liver HepG2 and HCT-116 colonic tumor cell spheroids. The cytotoxicity of TF against the HCT-116 tumor cell spheroids was enhanced in systems using cocultures of HepG2 and NIH-3T3 cells, indicating the effectiveness of this multiple cell spheroids-on-barcodes platform for drug screening. PMID:27214156

  6. Behavior of Metallic Foam under Shock Wave Loading

    Directory of Open Access Journals (Sweden)

    Zoran Ren

    2012-08-01

    Full Text Available In this manuscript, the behavior of metallic foam under impact loading and shock wave propagation has been observed. The goal of this research was to investigate the material and structural properties of submerged open-cell aluminum foam under impact loading conditions with particular interest in shock wave propagation and its effects on cellular material deformation. For this purpose experimental tests and dynamic computational simulations of aluminum foam specimens inside a water tank subjected to explosive charge have been performed. Comparison of the results shows a good correlation between the experimental and simulation results.

  7. Cosserat elasticity of negative Poisson’s ratio foam: experiment

    Science.gov (United States)

    Rueger, Zach; Lakes, Roderic S.

    2016-05-01

    Negative Poisson’s ratio polymer foams derived from reticulated open cell foams exhibit large size effects in torsion and bending. Effective moduli increase as diameter decreases in contrast to the prediction of classical elasticity. Size effects of this sort are predicted by Cosserat (micropolar) elasticity in which points can rotate as well as translate and distributed moments are incorporated. The Cosserat coupling number N was about twice as large as that of as-received foam, leading to strong effects. The torsion characteristic length {{\\ell }}{{t}} was similar. Cosserat effects are known to enhance toughness and immunity from stress concentration.

  8. Z向增强泡沫夹芯复合材料冲击损伤及冲击后压缩性能%Impact damage characteristics and post-impact compressive properties of Z-reinforcement foam core sandwich composites

    Institute of Scientific and Technical Information of China (English)

    段友社; 郭书良; 吴刚; 侯军生

    2012-01-01

    基于热压罐成型工艺,选择了树脂柱Z向增强泡沫芯材、碳纤维Z向增强泡沫芯材、Kevlar纤维缝纫增强泡沫芯材3种Z向增强复合材料结构,对夹芯结构进行了低速冲击损伤和冲击后压缩(CAI)性能研究,考察了不同Z向增强方式对冲击损伤面积和破坏模式的影响。结果表明,Z向增强对泡沫芯材产生了初始损伤,其冲击后损伤面积大于未增强泡沫夹芯结构;但Z向增强改变了夹芯结构的压缩破坏机制。通过选用合适的Z向增强材料和Z向增强参数,能够提高夹芯结构的压缩强度和CAI强度。其中当增强材料为碳纤维,增强参数为10mm×10mm时,压缩强度提高了13%,CAI强度提高超过40%。%Resin column reinforced,carbon fiber prepreg bar reinforced and kevlar fiber stitched reinforced foam core sandwich composites were produced using the same face sheets based on the autoclave manufacturing technology.The prepared sandwich structures were tested under low-velocity impact and post-impact compression.The post-impact damage characteristics and damage modes were also studied.The results indicate that initial damage of foam-core is caused by the Z-reinforcement,and the post-impact damage area increases compared with that of the unreinforced one,while the compressive failure mechanism of foam core sandwich composites is changed by the Z-reinforcement.The compressive strength and the CAI strength can be improved by choosing the right Z-reinforcement material and parameter,which increase by 13% and more than 40% respectively with carbon fiber prepreg bar reinforced at 10 mm×10 mm Z-reinforcement parameters.

  9. Method of fabricating a monolithic core for a solid oxide fuel cell

    International Nuclear Information System (INIS)

    A method is disclosed for forming a core for use in a solid oxide fuel cell that electrochemically combines fuel and oxidant for generating galvanic output. The core has an array of electrolyte and interconnect walls that are substantially devoid of any composite inert materials for support consisting instead only of the active anode, cathode, electrolyte and interconnect materials. Each electrolyte wall consists of cathode and anode materials sandwiching electrolyte material therebetween, and each interconnect wall consists of the cathode and anode materials sandwiching interconnect material therebetween. The electrolyte and interconnect walls define a plurality of substantially parallel core passageways alternately having respectively the inside faces thereof with only the anode material or with only the cathode material exposed. In the wall structure, the electrolyte and interconnect materials are only 0.002-0.01 cm thick; and the cathode and anode materials are only 0.002-0.05 cm thick. The method consists of building up the electrolyte and interconnect walls by depositing each material on individually and endwise of the wall itself, where each material deposit is sequentially applied for one cycle; and where the depositing cycle is repeated many times until the material buildup is sufficient to formulate the core. The core is heat cured to become dimensionally and structurally stable

  10. Characterization of Ti-6Al-4V open cellular foams fabricated by additive manufacturing using electron beam melting

    International Nuclear Information System (INIS)

    Ti-6Al-4V open cellular foams were fabricated by additive manufacturing using electron beam melting (EBM). Foam models were developed from CT-scans of aluminum open cellular foams and embedded in CAD for EBM. These foams were fabricated with solid cell structures as well as hollow cell structures and exhibit tailorable stiffness and strength. The strength in proportion to the measured microindentation hardness is as much as 40% higher for hollow cell (wall) structures in contrast to solid, fully dense EBM fabricated components. Plots of relative stiffness versus relative density were in good agreement with the Gibson-Ashby model for open cellular foam materials. Stiffness or Young's modulus values measured using a resonant frequency-damping analysis technique were found to vary inversely with porosity especially for solid cell wall, open cellular structure foams. These foams exhibit the potential for novel biomedical, aeronautics, and automotive applications.

  11. Design and optimization of Ag-dielectric core-shell nanostructures for silicon solar cells

    Directory of Open Access Journals (Sweden)

    Feng-Xiang Chen

    2015-09-01

    Full Text Available Metal-dielectric core-shell nanostructures have been proposed as a light trapping scheme for enhancing the optical absorption of silicon solar cells. As a potential application of such enhanced effects, the scattering efficiencies of three core-shell structures (Ag@SiO2, Ag@TiO2, and Ag@ZrO2 are discussed using the Mie Scattering theory. For compatibility with experiment results, the core diameter and shell thickness are limited to 100 and 30 nm, respectively, and a weighted scattering efficiency is introduced to evaluate the scattering abilities of different nanoparticles under the solar spectrum AM 1.5. The simulated results indicate that the shell material and thickness are two key parameters affecting the weighted scattering efficiency. The SiO2 is found to be an unsuitable shell medium because of its low refractive index. However, using the high refractive index mediumTiO2 in Ag@TiO2 nanoparticles, only the thicker shell (30 nm is more beneficial for light scattering. The ZrO2 is an intermediate refractive index material, so Ag@ZrO2 nanoparticles are the most effective core-shell nanostructures in these silicon solar cells applications.

  12. NDE of Fiber Reinforced Foam Composite Structures for Future Aerospace Vehicles

    Science.gov (United States)

    Walker, james; Roth, Don; Hopkins, Dale

    2010-01-01

    This slide presentation reviews the complexities of non-destructive evaluation (NDE) of fiber reinforced foam composite structures to be used for aerospace vehicles in the future.Various views of fiber reinforced foam materials are shown and described. Conventional methods of NDE for composites are reviewed such as Micro-computed X-Ray Tomography, Thermography, Shearography, and Phased Array Ultrasonics (PAUT). These meth0ods appear to work well on the face sheet and face sheet ot core bond, they do not provide adequate coverage for the webs. There is a need for additional methods that will examine the webs and web to foam core bond.

  13. Core-Shell Nanopillar Array Solar Cells using Cadmium Sulfide Coating on Indium Phosphide Nanopillars

    OpenAIRE

    Tu, Bor-An Clayton

    2013-01-01

    This thesis presents a new strategy to fabricate nanostructured indium phosphide and cadmium sulfide photovoltaics. The cells are formed by chemical bath deposition (electroless deposition) of cadmium sulfide onto indium phosphide nanopillar arrays grown by selective-area metalorganic chemical vapor deposition. Characterizations through electrical and optical measurements show that the devices consisting of p-InP core and CdS shell have a conversion efficiency, open circuit voltage, short cir...

  14. Foam Experiment Hardware are Flown on Microgravity Rocket MAXUS 4

    Science.gov (United States)

    Lockowandt, C.; Löth, K.; Jansson, O.; Holm, P.; Lundin, M.; Schneider, H.; Larsson, B.

    2002-01-01

    The Foam module was developed by Swedish Space Corporation and was used for performing foam experiments on the sounding rocket MAXUS 4 launched from Esrange 29 April 2001. The development and launch of the module has been financed by ESA. Four different foam experiments were performed, two aqueous foams by Doctor Michele Adler from LPMDI, University of Marne la Vallée, Paris and two non aqueous foams by Doctor Bengt Kronberg from YKI, Institute for Surface Chemistry, Stockholm. The foam was generated in four separate foam systems and monitored in microgravity with CCD cameras. The purpose of the experiment was to generate and study the foam in microgravity. Due to loss of gravity there is no drainage in the foam and the reactions in the foam can be studied without drainage. Four solutions with various stabilities were investigated. The aqueous solutions contained water, SDS (Sodium Dodecyl Sulphate) and dodecanol. The organic solutions contained ethylene glycol a cationic surfactant, cetyl trimethyl ammonium bromide (CTAB) and decanol. Carbon dioxide was used to generate the aqueous foam and nitrogen was used to generate the organic foam. The experiment system comprised four complete independent systems with injection unit, experiment chamber and gas system. The main part in the experiment system is the experiment chamber where the foam is generated and monitored. The chamber inner dimensions are 50x50x50 mm and it has front and back wall made of glass. The front window is used for monitoring the foam and the back window is used for back illumination. The front glass has etched crosses on the inside as reference points. In the bottom of the cell is a glass frit and at the top is a gas in/outlet. The foam was generated by injecting the experiment liquid in a glass frit in the bottom of the experiment chamber. Simultaneously gas was blown through the glass frit and a small amount of foam was generated. This procedure was performed at 10 bar. Then the pressure was

  15. Photophysical study on core-enlarged-rylendiimides and -anhydrides for dye sensitized solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Noelscher, Belinda; Meister, Michael; Howard, Ian; Battagliarin, Glauco; Li, Chen; Muellen, Klaus; Laquai, Frederic [Max-Planck-Institute for Polymer Research, Mainz (Germany)

    2011-07-01

    Dye Sensitized Solar Cells (DSSCs) are promising devices for light-weight and cheap photovoltaic energy conversion. Up to now many different dyes have been synthesized to improve the efficiency of these solar cells. Investigation of the relation between the photophysical properties of the dyes and their performance in solar cells is required for a better understanding of the working principle of DSSCs. In this contribution we present a photophysical study on novel core-enlarged perylene-iimides and -anhydrides. By changing the core size or expanding the bay-position the absorption maximum can be tuned and further shifted into the red part of the solar spectrum. We employ transient and steady-state photoinduced absorption as well as time-resolved photoluminescence spectroscopy to investigate the dynamics of charge generation and recombination of these dyes in solid-state DSSCs. Theoretically a higher efficiency of core-enlarged dyes due to increased photon harvesting can be expected, however, it appears that these dyes follow a different trend. Based on our results we draw conclusions for future material development of higher efficiency all-organic dyes for DSSCs.

  16. Method of making metal-doped organic foam products

    International Nuclear Information System (INIS)

    Organic foams having a low density and very small cell size and method for producing same in either a metal-loaded or unloaded (Nonmetal loaded) form are described. Metal-doped foams are produced by soaking a polymer gel in an aqueous solution of desired metal salt, soaking the gel successively in a solvent series of decreasing polarity to remove water from the gel and replace it with a solvent of lower polarity with each successive solvent in the series being miscible with the solvents on each side and being saturated with the desired metal salt, and removing the last of the solvents from the gel to produce the desired metal-doped foam having desired density cell size, and metal loading. The unloaded or metal-doped foams can be utilized in a variety of applications requiring low density, small cell size foam. For example, rubidium-doped foam made in accordance with the invention has utility in special applications, such as in x-ray lasers

  17. Shape memory polyurethane foams

    Directory of Open Access Journals (Sweden)

    B. K. Kim

    2012-01-01

    Full Text Available Molded flexible polyurethane (PU foams have been synthesized from polypropylene glycol (PPG with different molecular weights (Mw and functionalities (f, and 2,4/2,6-toluene diisocyanate (TDI-80 with water as blowing agent. It was found that the glassy state properties of the foam mainly depended on the urethane group content while the rubbery state properties on the crosslink density. That is, PPG of low MW and low f (more urethane groups provided superior glass state modulus, strength, density, shape fixity and glass transition temperature (Tg, while that of high Mw and high f (higher crosslink density showed high rubbery modulus and shape recovery. Consequently shape fixity of low Mw PPG decreased from 85 to 72% while shape recovery increased from 52 to 63% as the content of high Mw PPG increased from 0 to 40%.

  18. Shock Hugoniot Measurements in Foam

    Science.gov (United States)

    Petel, Oren; Ouellet, Simon; Frost, David; Higgins, Andrew

    2013-06-01

    Foams are found in a variety of protective equipment, including those used in applications involving high-speed impact and blast waves. Despite their exposure to shock wave loadings, there is a considerable lack of shock Hugoniot data for these materials. Typical characterizations of foams have involved the use of split-Hopkinson pressure bars or quasi-static compression machines to determine the stress-strain relationship in the foams. As such, the elastic-plastic response of foam at intermediate pressure ranges continues to be a source of confusion. In the present study, Photonic Doppler Velocimetry is used to measure the shock Hugoniot of a foam for a comparison to its quasi-static compression curves. The deviation of these two curves will be discussed and compared to common plasticity models used to describe dynamic foam behaviour in the literature.

  19. Langerhans Cell Histiocytosis Arising from the Mandible as Diagnosed by US-guided Core Biopsy

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Soo Jin [Center of Thyroid Cancer, National Cancer Center, Goyang (Korea, Republic of); Kim, Eun Kyung [Research Institute of Radiological Science, Yonsei University Heath System, Seoul (Korea, Republic of); Lee, Min Kyung [Eulji University College of Medicine, Eulji University Hospital, Daejeon (Korea, Republic of)

    2010-09-15

    Langerhans cell histiocytosis (LCH) is a clonal proliferative disorder of Langerhans cells. Although LCH is not considered a malignant disease, its appearance on radiographs may be similar to that of a malignant tumor. The diagnosis of LCH is usually made by a soft tissue biopsy, or by bone marrow aspiration or curettage. We present a patient with a mandibular mass confirmed to be LCH by US-guided core needle biopsy, and present a strategy for diagnosing localized LCH of the bone based on the usefulness and reliability of the percutaneous biopsy

  20. Langerhans Cell Histiocytosis Arising from the Mandible as Diagnosed by US-guided Core Biopsy

    International Nuclear Information System (INIS)

    Langerhans cell histiocytosis (LCH) is a clonal proliferative disorder of Langerhans cells. Although LCH is not considered a malignant disease, its appearance on radiographs may be similar to that of a malignant tumor. The diagnosis of LCH is usually made by a soft tissue biopsy, or by bone marrow aspiration or curettage. We present a patient with a mandibular mass confirmed to be LCH by US-guided core needle biopsy, and present a strategy for diagnosing localized LCH of the bone based on the usefulness and reliability of the percutaneous biopsy

  1. Characterization and Functional Applications of Nanoporous Ag Foams Prepared by Chemical Dealloying

    Science.gov (United States)

    Wu, T. Y.; Wang, X.; Huang, J. C.; Tsai, W. Y.; Chu, Y. Y.; Chen, S. Y.; Du, X. H.

    2015-10-01

    In this study, the pure Ag nanoporous foams, with open cell pore volume fractions 55 to 70 pct and pore sizes 100 to 400 nm, have been prepared by chemical dealloying. The Ag nanoporous foams possess favorable modulus (~0.7 GPa) and strength (~14 MPa), much higher than most of the polymers or ceramic foams. It is found that the Ag nanoporous foams are appropriate candidates for the catalytic and electrode applications. However, they do not exhibit efficient anti-bacterial effect, unless much smaller bacteria with cell sizes of 100 nm or less in the neighborhood are encountered.

  2. Photon Channelling in Foams

    OpenAIRE

    Schmiedeberg, Michael; Miri, MirFaez; Stark, Holger

    2005-01-01

    Experiments by Gittings, Bandyopadhyay, and Durian [Europhys. Lett.\\ \\textbf{65}, 414 (2004)] demonstrate that light possesses a higher probability to propagate in the liquid phase of a foam due to total reflection. The authors term this observation photon channelling which we investigate in this article theoretically. We first derive a central relation in the work of Gitting {\\em et al.} without any free parameters. It links the photon's path-length fraction $f$ in the liquid phase to the li...

  3. Creation of a gradient index structure inside foam material - Microwave application for a lens antenna at 60 GHz

    OpenAIRE

    Bor, Jonathan; Lafond, Olivier; Himdi, Mohamed

    2014-01-01

    — Creating a gradient index into a dielectric structure is a major issue nowadays for the design of microwave components and antennas, especially for inhomogeneous lenses as Luneburg, Fresnel and Maxwell Fish-eye. The use of a foam material and a simple technological process can allow this. Because a foam material is composed of air bubbles, and core materials (resin, PVC, …), removing the air will increase the density of the foam and so increase its dielectric constant. The authors present a...

  4. Aspiration tests in aqueous foam using a breathing simulator

    Energy Technology Data Exchange (ETDEWEB)

    Archuleta, M.M.

    1995-12-01

    Non-toxic aqueous foams are being developed by Sandia National Laboratories (SNL) for the National Institute of Justice (NIJ) for use in crowd control, cell extractions, and group disturbances in the criminal justice prison systems. The potential for aspiration of aqueous foam during its use and the resulting adverse effects associated with complete immersion in aqueous foam is of major concern to the NIJ when examining the effectiveness and safety of using this technology as a Less-Than-Lethal weapon. This preliminary study was designed to evaluate the maximum quantity of foam that might be aspirated by an individual following total immersion in an SNL-developed aqueous foam. A.T.W. Reed Breathing simulator equipped with a 622 Silverman cam was used to simulate the aspiration of an ammonium laureth sulfate aqueous foam developed by SNL and generated at expansion ratios in the range of 500:1 to 1000:1. Although the natural instinct of an individual immersed in foam is to cover their nose and mouth with a hand or cloth, thus breaking the bubbles and decreasing the potential for aspiration, this study was performed to examine a worst case scenario where mouth breathing only was examined, and no attempt was made to block foam entry into the breathing port. Two breathing rates were examined: one that simulated a sedentary individual with a mean breathing rate of 6.27 breaths/minute, and one that simulated an agitated or heavily breathing individual with a mean breathing rate of 23.7 breaths/minute. The results of this study indicate that, if breathing in aqueous foam without movement, an air pocket forms around the nose and mouth within one minute of immersion.

  5. Blending Novatein¯ thermoplastic protein with PLA for carbon dioxide assisted batch foaming

    Science.gov (United States)

    Walallavita, Anuradha; Verbeek, Casparus J. R.; Lay, Mark

    2016-03-01

    The convenience of polymeric foams has led to their widespread utilisation in everyday life. However, disposal of synthetic petroleum-derived foams has had a detrimental effect on the environment which needs to be addressed. This study uses a clean and sustainable approach to investigate the foaming capability of a blend of two biodegradable polymers, polylactic acid (PLA) and Novatein® Thermoplastic Protein (NTP). PLA, derived from corn starch, can successfully be foamed using a batch technique developed by the Biopolymer Network Ltd. NTP is a patented formulation of bloodmeal and chemical additives which can be extruded and injection moulded similar to other thermoplastics. However, foaming NTP is a new area of study and its interaction with blowing agents in the batch process is entirely unknown. Subcritical and supercritical carbon dioxide have been examined individually in two uniquely designed pressure vessels to foam various compositions of NTP-PLA blends. Foamed material were characterised in terms of expansion ratio, cell size, and cellular morphology in order to study how the composition of NTP-PLA affects foaming with carbon dioxide. It was found that blends with 5 wt. % NTP foamed using subcritical CO2 expanded up to 11 times due to heterogeneous nucleation. Morphology analysis using scanning electron microscopy showed that foams blown with supercritical CO2 had a finer cell structure with consistent cell size, whereas, foams blown with subcritical CO2 ranged in cell size and showed cell wall rupture. Ultimately, this research would contribute to the production of a biodegradable foam material to be used in packaging applications, thereby adding to the application potential of NTP.

  6. Complications of foam sclerotherapy.

    Science.gov (United States)

    Cavezzi, A; Parsi, K

    2012-03-01

    Foam sclerotherapy may result in drug and/or gas-related complications of a generalized or localized nature. Significant complications include anaphylactic/anaphylactoid reactions (very rare), deep vein thrombosis (1-3%), stroke (0.01%), superficial venous thrombosis (4.4%), tissue necrosis (variable frequency), oedema (0.5%) and nerve damage (0.2%). Cosmetic complications include telangiectatic matting (15-24%) and pigmentation (10-30%). Patent foramen ovale and other cardio-pulmonary right-to-left shunts seem to play a role in the systemic gas-related complications. In conclusion, foam sclerotherapy is characterized by an overall high degree of safety, though special attention should be given to the embolic and thrombotic complications. Good technique, adequate imaging, general precautions and compliance with post-treatment instructions may help avoid some of the adverse events and an appropriate early intervention may minimize possible sequelae. Higher volumes of sclerosant foam have been attributed to local and distant thrombotic complications and should be avoided. PMID:22312067

  7. Polyimide Foams Offer Superior Insulation

    Science.gov (United States)

    2012-01-01

    At Langley Research Center, Erik Weiser and his colleagues in the Advanced Materials and Processing Branch were working with a new substance for fabricating composites for use in supersonic aircraft. The team, however, was experiencing some frustration. Every time they tried to create a solid composite from the polyimide (an advanced polymer) material, it bubbled and foamed. It seemed like the team had reached a dead end in their research - until they had another idea. "We said, This isn t going to work for composites, but maybe we could make a foam out of it," Weiser says. "That was kind of our eureka moment, to see if we could go in a whole other direction. And it worked." Weiser and his colleagues invented a new kind of polyimide foam insulation they named TEEK. The innovation displayed a host of advantages over existing insulation options. Compared to other commercial foams, Weiser explains, polyimide foams perform well across a broad range of temperatures, noting that the NASA TEEK foams provide effective structural insulation up to 600 F and down to cryogenic temperatures. The foam does not burn or off-gas toxic fumes, and even at -423 F - the temperature of liquid hydrogen - the material stays flexible. The inventors could produce the TEEK foam at a range of densities, from 0.5 pounds per cubic foot up to 20 pounds per cubic foot, making the foam ideal for a range of applications, including as insulation for reusable launch vehicles and for cryogenic tanks and lines. They also developed a unique, friable balloon format for manufacturing the foam, producing it as hollow microspheres that allowed the foam to be molded and then cured into any desired shape - perfect for insulating pipes of different sizes and configurations. The team s originally unplanned invention won an "R&D 100" award, and a later form of the foam, called LaRC FPF-44 (Spinoff 2009), was named "NASA Invention of the Year" in 2007.

  8. Fracture Toughness Evaluation of Space Shuttle External Tank Thermal Protection System Polyurethane Foam Insulation Materials

    Science.gov (United States)

    McGill, Preston; Wells, Doug; Morgan, Kristin

    2006-01-01

    Experimental evaluation of the basic fracture properties of Thermal Protection System (TPS) polyurethane foam insulation materials was conducted to validate the methodology used in estimating critical defect sizes in TPS applications on the Space Shuttle External Fuel Tank. The polyurethane foam found on the External Tank (ET) is manufactured by mixing liquid constituents and allowing them to react and expand upwards - a process which creates component cells that are generally elongated in the foam rise direction and gives rise to mechanical anisotropy. Similarly, the application of successive foam layers to the ET produces cohesive foam interfaces (knitlines) which may lead to local variations in mechanical properties. This study reports the fracture toughness of BX-265, NCFI 24-124, and PDL-1034 closed-cell polyurethane foam as a function of ambient and cryogenic temperatures and knitline/cellular orientation at ambient pressure.

  9. Thermal Conductivity of Foam Glass

    OpenAIRE

    Petersen, Rasmus Rosenlund; König, Jakob; Yue, Yuanzheng

    2014-01-01

    Due to the increased focus on energy savings and waste recycling foam glass materials have gained increased attention. The production process of foam glass is a potential low-cost recycle option for challenging waste, e.g. CRT glass and industrial waste (fly ash and slags). Foam glass is used as thermal insulating material in building and chemical industry. The large volume of gas (porosity 90 – 95%) is the main reason of the low thermal conductivity of the foam glass. If gases with lower the...

  10. Polyurethane Foams with Pyrimidine Rings

    Directory of Open Access Journals (Sweden)

    Kania Ewelina

    2014-09-01

    Full Text Available Oligoetherols based on pyrimidine ring were obtained upon reaction of barbituric acid with glycidol and alkylene carbonates. These oligoetherols were then used to obtain polyurethane foams in the reaction of oligoetherols with isocyanates and water. The protocol of foam synthesis was optimized by the choice of proper kind of oligoetherol and synthetic composition. The thermal resistance was studied by dynamic and static methods with concomitant monitoring of compressive strength. The polyurethane foams have similar physical properties as the classic ones except their enhanced thermal resistance. They stand long-time heating even at 200°C. Moreover thermal exposition of foams results generally in increase of their compressive strength.

  11. Fiber reinforced hybrid phenolic foam

    Science.gov (United States)

    Desai, Amit

    Hybrid composites in recent times have been developed by using more than one type of fiber reinforcement to bestow synergistic properties of the chosen filler and matrix and also facilitating the design of materials with specific properties matched to end use. However, the studies for hybrid foams have been very limited because of problems related to fiber dispersion in matrix, non uniform mixing due to presence of more than one filler and partially cured foams. An effective approach to synthesize hybrid phenolic foam has been proposed and investigated here. Hybrid composite phenolic foams were reinforced with chopped glass and aramid fibers in varied proportions. On assessing mechanical properties in compression and shear several interesting facts surfaced but overall hybrid phenolic foams exhibited a more graceful failure, greater resistance to cracking and were significantly stiffer and stronger than foams with only glass and aramid fibers. The optimum fiber ratio for the reinforced hybrid phenolic foam system was found to be 1:1 ratio of glass to aramid fibers. Also, the properties of hybrid foam were found to deviate from rule of mixture (ROM) and thus the existing theories of fiber reinforcement fell short in explaining their complex behavior. In an attempt to describe and predict mechanical behavior of hybrid foams a statistical design tool using analysis of variance technique was employed. The utilization of a statistical model for predicting foam properties was found to be an appropriate tool that affords a global perspective of the influence of process variables such as fiber weight fraction, fiber length etc. on foam properties (elastic modulus and strength). Similar approach could be extended to study other fiber composite foam systems such as polyurethane, epoxy etc. and doing so will reduce the number of experimental iterations needed to optimize foam properties and identify critical process variables. Diffusivity, accelerated aging and flammability

  12. An examination of the mechanisms for stable foam formation in activated sludge systems.

    Science.gov (United States)

    Petrovski, Steve; Dyson, Zoe A; Quill, Eben S; McIlroy, Simon J; Tillett, Daniel; Seviour, Robert J

    2011-02-01

    Screening pure cultures of 65 mycolic acid producing bacteria (Mycolata) isolated mainly from activated sludge with a laboratory based foaming test revealed that not all foamed under the conditions used. However, for most, the data were generally consistent with the flotation theory as an explanation for foaming. Thus a stable foam required three components, air bubbles, surfactants and hydrophobic cells. With non-hydrophobic cells, an unstable foam was generated, and in the absence of surfactants, cells formed a greasy surface scum. Addition of surfactant converted a scumming population into one forming a stable foam. The ability to generate a foam depended on a threshold cell number, which varied between individual isolates and reduced markedly in the presence of surfactant. Consequently, the concept of a universal threshold applicable to all foaming Mycolata is not supported by these data. The role of surfactants in foaming is poorly understood, but evidence is presented for the first time that surfactin synthesised by Bacillus subtilis may be important. PMID:21239035

  13. Aluminium Foam and Magnesium Compound Casting Produced by High-Pressure Die Casting

    Directory of Open Access Journals (Sweden)

    Iban Vicario

    2016-01-01

    Full Text Available Nowadays, fuel consumption and carbon dioxide emissions are two of the main focal points in vehicle design, promoting the reduction in the weight of vehicles by using lighter materials. The aim of the work is to evaluate the influence of different aluminium foams and injection parameters in order to obtain compound castings with a compromise between the obtained properties and weight by high-pressure die cast (HPDC using aluminium foams as cores into a magnesium cast part. To evaluate the influence of the different aluminium foams and injection parameters on the final casting products quality, the type and density of the aluminium foam, metal temperature, plunger speed, and multiplication pressure have been varied within a range of suitable values. The obtained compound HPDC castings have been studied by performing visual and RX inspections, obtaining sound composite castings with aluminium foam cores. The presence of an external continuous layer on the foam surface and the correct placement of the foam to support injection conditions permit obtaining good quality parts. A HPDC processed magnesium-aluminium foam composite has been developed for a bicycle application obtaining a suitable combination of mechanical properties and, especially, a reduced weight in the demonstration part.

  14. The Anisotropy of Replicated Aluminum Foams

    OpenAIRE

    Furman, Eugeny L.; Arcady B. Finkelstein; Maxim L. Cherny

    2014-01-01

    The replication casting process gives the open-cell aluminum foams that can be used in many industrial applications as well as in filtering technology. The essential requirement for filters is the uniformity of filtering degree which is defined by the minimal pore size. However the structure of replication castings is often inhomogeneous and the minimal pore radius is decreasing in the direction of melt infiltration. The objective of this investigation is to study the dynamics of melt impregn...

  15. Assessing and improving steam-assisted gravity drainage: Reservoir heterogeneities, hydraulic fractures, and mobility control foams

    Science.gov (United States)

    Chen, Qing

    0.3 bbl oil/bbl CWE steam are achieved by adding a vertical fracture. The new concept of foam-assisted SAGD (FA-SAGD) is evaluated numerically with a foam simulator that incorporates the physical mechanisms of foam generation, destruction, and transport. To reduce computational costs, we develop a simplified foam model based on the assumption of local equilibrium of foam generation and coalescence at field scale. Foam displacements in a linear sandstone core are measured using pressure transducers, X-ray Computed Tomography (CT), and a visualization cell to quantify foam bubble texture. The local equilibrium approximation is validated, and good agreement between the experimental results and the predictions of the simplified model is found, with a minor mismatch in the entrance region. For the scenario under study, numerical simulation of the FA-SAGD process shows considerable improvement in the process efficiency over the conventional SAGD process. Live steam production is reduced by a factor of 5 for FA-SAGD compared to conventional SAGD. Consequently, cumulative oil production is increased by about 30% when production versus the volume of steam injected is compared for cases with and without foam.

  16. Fabrication of aluminum foam from aluminum scrap Hamza

    Directory of Open Access Journals (Sweden)

    O. A. Osman1 ,

    2015-02-01

    Full Text Available In this study the optimum parameters affecting the preparation of aluminum foam from recycled aluminum were studied, these parameters are: temperature, CaCO3 to aluminum scrap wt. ratio as foaming agent, Al2O3 to aluminum scrap wt. ratio as thickening agent, and stirring time. The results show that, the optimum parameters are the temperature ranged from 800 to 850oC, CaCO3 to aluminum scrap wt. ratio was 5%, Al2O3 to aluminum scrap wt. ratio was 3% and stirring time was 45 second with stirring speed 1200 rpm. The produced foam apparent densities ranged from 0.40-0.60 g/cm3. The microstructure of aluminum foam was examined by using SEM, EDX and XRD, the results show that, the aluminum pores were uniformly distributed along the all matrices and the cell walls covered by thin oxide film.

  17. High Strength Silicon Carbide Foams and Their Deformation Behavior

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Silicon carbide (SiC) foams with a continuously connected open-cell structure were prepared and characterized for their mechanical performance. The apparent densities of SiC foams were controlled between about 0.4 and 1.3 g/cm3, with corresponding compressive strengths ranging from about 13 to 60 MPa and flexural strengths from about 8 to 30 MPa. Compressive testing of the SiC foams yielded stress-strain curves with only one linear-elastic region, which is different from those reported on ceramic foams in literature. This can possibly be attributed to the existence of filaments with fine, dense and high strength microstructures. The SiC and the filaments respond homogeneously to applied loading.

  18. Low density, microcellular, dopable, agar/gelatin foams for pulsed power experiments

    Energy Technology Data Exchange (ETDEWEB)

    McNamara, W.F. [Orion International Technologies, Inc., Albuquerque, NM (United States); Aubert, J.H. [Sandia National Lab., Albuquerque, NM (United States)

    1997-04-01

    Low-density, microcellular foams prepared from the natural polymers agar and gelatin have been developed for pulsed-power physics experiments. Numerous experiments were supported with foams having densities at or below 10 mg/cm{sup 3}. For some of the experiments, the agar/gelatin foam was uniformly doped with metallic elements using soluble salts. Depending on the method of preparation, cell sizes were typically below 10 microns and for one process were below 1.0 micron.

  19. Use of the supercritical fluid technology to prepare efficient nanocomposite foams for environmental protection purpose

    OpenAIRE

    Urbanczyk, Laetitia; Thomassin, Jean-Michel; Huynen, Isabelle; Alexandre, Michaël; Jérôme, Christine

    2009-01-01

    This work reports on the preparation of novel nanocomposite foams that are efficient broadband microwave absorbers. Carbon nanotubes are first successfully dispersed into PCL and PMMA by melt blending. Then, foaming is promoted by supercritical CO2 by depressurization. Regular cellular structures are obtained in both cases with cells size around 10-50µm. The electromagnetic interference (EMI) shielding efficiency of these materials are then evaluated and compared to the non-foamed nanocomposi...

  20. Core-shell polymer nanoparticles for prevention of GSH drug detoxification and cisplatin delivery to breast cancer cells

    Science.gov (United States)

    Surnar, Bapurao; Sharma, Kavita; Jayakannan, Manickam

    2015-10-01

    detoxification. In vitro drug-release studies revealed that the core-shell nanoparticles were ruptured upon exposure to lysosomal enzymes like esterase at the intracellular compartments. Cytotoxicity studies were performed both in normal wild-type mouse embryonic fibroblast cells (Wt-MEFs), and breast cancer (MCF-7) and cervical cancer (HeLa) cell lines. Free cisplatin and polymer drug core-shell nanoparticles showed similar cytotoxicity effects in the HeLa cells. In MCF-7 cells, the free cisplatin drug exhibited 50% cell death whereas complete cell death (100%) was accomplished by the polymer-cisplatin core-shell nanoparticles. Confocal microscopic images confirmed that the core-shell nanoparticle

  1. Influence of polyamide-imide concentration on the cellular structure and thermo-mechanical properties of polyetherimide/polyamide-imide blend foams

    OpenAIRE

    Abbasi, Hooman; Antunes, Marcelo de Sousa Pais; Velasco Perero, José Ignacio

    2015-01-01

    The present work considers the preparation of medium-density polyetherimide (PEI)/polyamide-imide (PAI) blend foams by means of water vapor-induced phase separation (WVIPS) and their characterization. While pure polymer foams showed homogeneous cellular structures with average cell sizes of 10-12 µm, PEI/PAI blend foams presented two distinctive closed-cell structures depending on the composition of the blend. At the lowest concentration of PAI (25 wt%) foams showed a very fine homogeneous mi...

  2. Microwave Synthesis of Nearly Monodisperse Core/Multishell Quantum Dots with Cell Imaging Applications

    Science.gov (United States)

    Su, Huaipeng; Xu, Hengyi; Gao, Shuai; Dixon, John David; Aguilar, Zoraida P.; Wang, Andrew Y.; Xu, Jian; Wang, Jingkang

    2010-03-01

    We report in this article the microwave synthesis of relatively monodisperse, highly crystalline CdSe quantum dots (QDs) overcoated with Cd0.5Zn0.5S/ZnS multishells. The as-prepared QDs exhibited narrow photoluminescence bandwidth as the consequence of homogeneous size distribution and uniform crystallinity, which was confirmed by transmission electron microscopy. A high photoluminescence quantum yield up to 80% was measured for the core/multishell nanocrystals. Finally, the resulting CdSe/Cd0.5Zn0.5S/ZnS core/multishell QDs have been successfully applied to the labeling and imaging of breast cancer cells (SK-BR3).

  3. Microwave Synthesis of Nearly Monodisperse Core/Multishell Quantum Dots with Cell Imaging Applications

    Directory of Open Access Journals (Sweden)

    Xu Hengyi

    2010-01-01

    Full Text Available Abstract We report in this article the microwave synthesis of relatively monodisperse, highly crystalline CdSe quantum dots (QDs overcoated with Cd0.5Zn0.5S/ZnS multishells. The as-prepared QDs exhibited narrow photoluminescence bandwidth as the consequence of homogeneous size distribution and uniform crystallinity, which was confirmed by transmission electron microscopy. A high photoluminescence quantum yield up to 80% was measured for the core/multishell nanocrystals. Finally, the resulting CdSe/Cd0.5Zn0.5S/ZnS core/multishell QDs have been successfully applied to the labeling and imaging of breast cancer cells (SK-BR3.

  4. Kinetic parameters evaluation of PWRs using static cell and core calculation codes

    International Nuclear Information System (INIS)

    Highlights: ► In this study, we have calculated effective delayed neutron fraction and prompt neutron lifetime in PWRs. ► New software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. ► This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. ► The ratios ((βeff)i)/((βeff)core) , which are the important input data for the reactivity accident analysis, are also calculated. - Abstract: In this paper, evaluation of the kinetic parameters (effective delayed neutron fraction and prompt neutron lifetime) in PWRs, using static cell and core calculation codes, is reported. A new software has been developed to link the WIMS, BORGES and CITATION codes in Visual C computer programming language. Using the WIMS cell calculation code, multigroup microscopic cross-sections and number densities of different materials can be generated in a binary file. By the use of BORGES code, these binary-form cross-sections and number densities are converted to a format readable by the CITATION core calculation code, by which the kinetic parameters can be finally obtained. This software is used for calculation of the kinetic parameters in a typical VVER-1000 and NOK Beznau reactor. The ratios ((βeff)i)/((βeff)core) , which are the important input data for the reactivity accident analysis, are also calculated. Benchmarking of the results against the final safety analysis report (FSAR) of the aforementioned reactors shows very good agreements with these published documents.

  5. Simulated Tip Rub Testing of Low-Density Metal Foam

    Science.gov (United States)

    Bowman, Cheryl L.; Jones, Michael G.

    2009-01-01

    Preliminary acoustic studies have indicated that low-density, open-cell, metal foams may be suitable acoustic liner material for noise suppression in high by-pass engines. Metal foam response under simulated tip rub conditions was studied to assess whether its durability would be sufficient for the foam to serve both as a rub strip above the rotor as well as an acoustic treatment. Samples represented four metal alloys, nominal cell dimensions ranging from 60 to 120 cells per inch (cpi), and relative densities ranging from 3.4 to 10 percent. The resulting rubbed surfaces were relatively smooth and the open cell structure of the foam was not adversely affected. Sample relative density appeared to have significant influence on the forces induced by the rub event. Acoustic responses of various surface preparations were measured using a normal incidence tube. The results of this study indicate that the foam s open-cell structure was retained after rubbing and that the acoustic absorption spectra variation was minimal.

  6. Microstructural Characterization of Metal Foams: An Examination of the Applicability of the Theoretical Models for Modeling Foams. Revision 1

    Science.gov (United States)

    Raj, S. V.

    2011-01-01

    Establishing the geometry of foam cells is useful in developing microstructure-based acoustic and structural models. Since experimental data on the geometry of the foam cells are limited, most modeling efforts use an idealized three-dimensional, space-filling Kelvin tetrakaidecahedron. The validity of this assumption is investigated in the present paper. Several FeCrAlY foams with relative densities varying between 3 and 15 percent and cells per mm (c.p.mm.) varying between 0.2 and 3.9 c.p.mm. were microstructurally evaluated. The number of edges per face for each foam specimen was counted by approximating the cell faces by regular polygons, where the number of cell faces measured varied between 207 and 745. The present observations revealed that 50 to 57 percent of the cell faces were pentagonal while 24 to 28 percent were quadrilateral and 15 to 22 percent were hexagonal. The present measurements are shown to be in excellent agreement with literature data. It is demonstrated that the Kelvin model, as well as other proposed theoretical models, cannot accurately describe the FeCrAlY foam cell structure. Instead, it is suggested that the ideal foam cell geometry consists of 11 faces with three quadrilateral, six pentagonal faces and two hexagonal faces consistent with the 3-6-2 Matzke cell. A compilation of 90 years of experimental data reveals that the average number of cell faces decreases linearly with the increasing ratio of quadrilateral to pentagonal faces. It is concluded that the Kelvin model is not supported by these experimental data.

  7. Core-shell nanoparticle-based peptide therapeutics and combined hyperthermia for enhanced cancer cell apoptosis.

    Science.gov (United States)

    Shah, Birju P; Pasquale, Nicholas; De, Gejing; Tan, Tao; Ma, Jianjie; Lee, Ki-Bum

    2014-09-23

    Mitochondria-targeting peptides have garnered immense interest as potential chemotherapeutics in recent years. However, there is a clear need to develop strategies to overcome the critical limitations of peptides, such as poor solubility and the lack of target specificity, which impede their clinical applications. To this end, we report magnetic core-shell nanoparticle (MCNP)-mediated delivery of a mitochondria-targeting pro-apoptotic amphipathic tail-anchoring peptide (ATAP) to malignant brain and metastatic breast cancer cells. Conjugation of ATAP to the MCNPs significantly enhanced the chemotherapeutic efficacy of ATAP, while the presence of targeting ligands afforded selective delivery to cancer cells. Induction of MCNP-mediated hyperthermia further potentiated the efficacy of ATAP. In summary, a combination of MCNP-mediated ATAP delivery and subsequent hyperthermia resulted in an enhanced effect on mitochondrial dysfunction, thus resulting in increased cancer cell apoptosis. PMID:25133971

  8. A linear peristaltic MRF/foam actuator

    Science.gov (United States)

    Larsen, J. J.; Jenkins, C. H.; Korde, U. A.

    2007-04-01

    Magneto-rheological fluid (MRF) was first developed in the late 1940s. MRF consists of iron or other ferrous particles, typically on the order of 1 - 10 μm characteristic dimension, dispersed in a host carrier fluid, usually oil or water. In the presence of a magnetic field, the alignment of the iron particles along field lines results in the effective rheological properties of the composite fluid to be modified. In the "off" state (no field applied), the fluid has similar viscous properties to the host fluid. In the "on" state (field applied), the viscosity and yield stress can be significantly modified. Recently, MRF has been of interest in a number of novel devices, for example, for variable damping such as in automotive shock absorbers. In the present work, we briefly describe our initial investigations into variable damping MRF/foam devices. Open-cell polymer foam blocks were infused with commercial MRF and subjected to magnetic fields of various strengths. Drop tests were conducted by dropping a small indenter from a fixed platform and observing the rebound height as a function of applied field strength. The difference in rebound height can be directly related to loss of energy through damping. In the tests conducted, the energy absorbed by the MRF/foam increased from about 60% in the off-state device to over 90% in the on-state device. One of the difficulties encountered in performing the drop tests and providing credible data interpretation was that the MRF/foam itself changed dimensions under applied field. The iron particles in the fluid were attracted to the magnet and thus caused constriction of the foam block. Peristalsis is the process of involuntary and successive wave-like muscular contractions by which food is moved through the digestive tract. The esophagus, stomach, and intestines all move and/or mix food and liquid by peristalsis. Peristalsis is also used to move lymph through the lymphatic system. Inspired by biological peristalsis

  9. Determination of elastic-plastic properties of Alporas foam at the cell-wall level using microscale-cantilever bending tests

    Czech Academy of Sciences Publication Activity Database

    Doktor, Tomáš; Kytýř, Daniel; Koudelka_ml., Petr; Zlámal, Petr; Fíla, Tomáš; Jiroušek, Ondřej

    2015-01-01

    Roč. 49, č. 2 (2015), s. 203-206. ISSN 1580-2949 R&D Projects: GA ČR(CZ) GAP105/12/0824 Institutional support: RVO:68378297 Keywords : aluminium foam * cantilever bending * micromechanics * optical strain measurement Subject RIV: JI - Composite Materials Impact factor: 0.548, year: 2014 http://mit.imt.si/Revija/izvodi/mit152/doktor.pdf

  10. Recovery of proteins and microorganisms from cultivation media by foam flotation.

    Science.gov (United States)

    Schügerl, K

    2000-01-01

    Foaming is often present in aerated bioreactors. It is undesired, because it removes the cells and the cultivation medium from the reactor and blocks the sterile filter. However, it can be used for the recovery of proteins and microorganisms from the cultivation medium. The present review deals with the characterization of model protein foams and foams of various cultivation media. The suppression of foaming by antifoam agents and their effect on the oxygen transfer rate, microbial cell growth and product formation are discussed. The influence of process variables on the recovery of proteins by flotation without and with surfactants and mathematical models for protein flotation are presented. The effect of cultivation conditions, flotation equipment and operational parameters on foam flotation of microorganisms is reviewed. Floatable and non-floatable microorganisms are characterized by their surface envelope properties. A mathematical model for cell recovery by flotation is presented. Possible application areas of cell recovery by flotation are discussed. PMID:11036688

  11. Characterization of Polyimide Foams for Ultra-Lightweight Space Structures

    Science.gov (United States)

    Meador, Michael (Technical Monitor); Hillman, Keithan; Veazie, David R.

    2003-01-01

    Ultra-lightweight materials have played a significant role in nearly every area of human activity ranging from magnetic tapes and artificial organs to atmospheric balloons and space inflatables. The application range of ultra-lightweight materials in past decades has expanded dramatically due to their unsurpassed efficiency in terms of low weight and high compliance properties. A new generation of ultra-lightweight materials involving advanced polymeric materials, such as TEEK (TM) polyimide foams, is beginning to emerge to produce novel performance from ultra-lightweight systems for space applications. As a result, they require that special conditions be fulfilled to ensure adequate structural performance, shape retention, and thermal stability. It is therefore important and essential to develop methodologies for predicting the complex properties of ultra-lightweight foams. To support NASA programs such as the Reusable Launch Vehicle (RLV), Clark Atlanta University, along with SORDAL, Inc., has initiated projects for commercial process development of polyimide foams for the proposed cryogenic tank integrated structure (see figure 1). Fabrication and characterization of high temperature, advanced aerospace-grade polyimide foams and filled foam sandwich composites for specified lifetimes in NASA space applications, as well as quantifying the lifetime of components, are immensely attractive goals. In order to improve the development, durability, safety, and life cycle performance of ultra-lightweight polymeric foams, test methods for the properties are constant concerns in terms of timeliness, reliability, and cost. A major challenge is to identify the mechanisms of failures (i.e., core failure, interfacial debonding, and crack development) that are reflected in the measured properties. The long-term goal of the this research is to develop the tools and capabilities necessary to successfully engineer ultra-lightweight polymeric foams. The desire is to reduce density

  12. Sound Absorption Characteristics of Aluminum Foams Treated by Plasma Electrolytic Oxidation

    Directory of Open Access Journals (Sweden)

    Wei Jin

    2015-11-01

    Full Text Available Open-celled aluminum foams with different pore sizes were fabricated. A plasma electrolytic oxidation (PEO treatment was applied on the aluminum foams to create a layer of ceramic coating. The sound absorption coefficients of the foams were measured by an impedance tube and they were calculated by a transfer function method. The experimental results show that the sound absorption coefficient of the foam increases gradually with the decrease of pore size. Additionally, when the porosity of the foam increases, the sound absorption coefficient also increases. The PEO coating surface is rough and porous, which is beneficial for improvement in sound absorption. After PEO treatment, the maximum sound absorption of the foam is improved to some extent.

  13. Advanced Signal Processing Techniques Applied to Terahertz Inspections on Aerospace Foams

    Science.gov (United States)

    Trinh, Long Buu

    2009-01-01

    The space shuttle's external fuel tank is thermally insulated by the closed cell foams. However, natural voids composed of air and trapped gas are found as by-products when the foams are cured. Detection of foam voids and foam de-bonding is a formidable task owing to the small index of refraction contrast between foam and air (1.04:1). In the presence of a denser binding matrix agent that bonds two different foam materials, time-differentiation of filtered terahertz signals can be employed to magnify information prior to the main substrate reflections. In the absence of a matrix binder, de-convolution of the filtered time differential terahertz signals is performed to reduce the masking effects of antenna ringing. The goal is simply to increase probability of void detection through image enhancement and to determine the depth of the void.

  14. Identification of the SL3-3 virus enhancer core as a T-lymphoma cell-specific element.

    OpenAIRE

    Boral, A. L.; Okenquist, S A; Lenz, J.

    1989-01-01

    Transient expression assays were used to determine the sequences within the long terminal repeat (LTR) that define the high activity in T-lymphoma cells of the leukemogenic SL3-3 virus in comparison with that of the nonleukemogenic Akv virus. Each of these viruses contains sequences related to the consensus element, the enhancer core. The SL3-3 and Akv enhancer cores differ at a single base pair. Substitution of the Akv core element into the SL3-3 LTR decreased expression in T-lymphoma cells ...

  15. Determination of effective thermal conductivity for polyurethane foam by use of fractal method

    Institute of Scientific and Technical Information of China (English)

    SHI Mingheng; LI Xiaochuan; CHEN Yongping

    2006-01-01

    The microstructure of polyurethane foam is disordered, which influences the foam heat conduction process significantly. In this paper foam structure is described by using the local area fractal dimension in a certain small range of length scales. An equivalent element cell is constructed based on the local fractal dimensions along the directions parallel and transverse to the heat flux. By use of fractal void fraction a simplified heat conduction model is proposed to calculate the effective thermal conductivity of polyurethane foam. The predicted effective thermal conductivity agrees well with the experimental data.

  16. Analysis of Stainless Steel Sandwich Panels with a Metal Foam Care for Lightweight Fan Blade Design

    Science.gov (United States)

    Min, James B.; Ghosn, Louis J.; Lerch, Bradley A.; Raj, Sai V.; Holland, Frederic A., Jr.; Hebsur, Mohan G.

    2004-01-01

    The quest for cheap, low density and high performance materials in the design of aircraft and rotorcraft engine fan and propeller blades poses immense challenges to the materials and structural design engineers. Traditionally, these components have been fabricated using expensive materials such as light weight titanium alloys, polymeric composite materials and carbon-carbon composites. The present study investigates the use of P sandwich foam fan blade made up of solid face sheets and a metal foam core. The face sheets and the metal foam core material were an aerospace grade precipitation hardened 17-4 PH stainless steel with high strength and high toughness. The stiffness of the sandwich structure is increased by separating the two face sheets by a foam core. The resulting structure possesses a high stiffness while being lighter than a similar solid construction. Since the face sheets carry the applied bending loads, the sandwich architecture is a viable engineering concept. The material properties of 17-4 PH metal foam are reviewed briefly to describe the characteristics of the sandwich structure for a fan blade application. A vibration analysis for natural frequencies and P detailed stress analysis on the 17-4 PH sandwich foam blade design for different combinations of skin thickness and core volume %re presented with a comparison to a solid titanium blade.

  17. Development and Mechanical Behavior of FML/Aluminium Foam Sandwiches

    Science.gov (United States)

    Baştürk, S. B.; Tanoğlu, M.

    2013-10-01

    In this study, the Fiber-Metal Laminates (FMLs) containing glass fiber reinforced polypropylene (GFPP) and aluminum (Al) sheet were consolidated with Al foam cores for preparing the sandwich panels. The aim of this article is the comparison of the flexural properties of FML/Al foam sandwich panels bonded with various surface modification approaches (silane treatment and combination of silane treatment with polypropylene (PP) based film addition). The FML/foam sandwich systems were fabricated by laminating the components in a mould at 200 °C under 1.5 MPa pressure. The energy absorbtion capacities and flexural mechanical properties of the prepared sandwich systems were evaluated by mechanical tests. Experiments were performed on samples of varying foam thicknesses (8, 20 and 30 mm). The bonding among the sandwich components were achieved by various surface modification techniques. The Al sheet/Al foam sandwiches were also consolidated by bonding the components with an epoxy adhesive to reveal the effect of GFPP on the flexural performance of the sandwich structures.

  18. Permeability of Aluminium Foams Produced by Replication Casting

    Directory of Open Access Journals (Sweden)

    Maxim L. Cherny

    2012-12-01

    Full Text Available The replication casting process is used for manufacturing open-pore aluminum foams with advanced performances, such as stability and repeatability of foam structure with porosity over 60%. A simple foam structure model based on the interaction between sodium chloride solid particles poorly wetted by melted aluminum, which leads to the formation of air pockets (or “air collars”, is proposed for the permeability of porous material. The equation for the minimum pore radius of replicated aluminum foam is derived. According to the proposed model, the main assumption of the permeability model consists in a concentration of flow resistance in a circular aperture of radius rmin. The permeability of aluminum open-pore foams is measured using transformer oil as the fluid, changing the fractions of initial sodium chloride. Measured values of minimum pore size are close to theoretically predicted ones regardless of the particle shape. The expression for the permeability of replicated aluminum foam derived on the basis of the “bottleneck” model of porous media agrees well with the experimental data. The obtained data can be applied for commercial filter cells and pneumatic silencers.

  19. Foaming behaviour of Al-Si-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, A. [Kongju National University (Korea). Dept. of Mechanical Engineering; Cho, S.S. [Chungnam National University, Daejeon (Korea). School of Materials Engineering; Lee, H.J. [Hanbat National University, Daejeon (Korea). Dept. of Building Service Engineering

    2004-12-15

    The powder metallurgical route was utilised to obtain the Al-5Si-4Cu-4Mg (alloy 544) and Al-3Si-2Cu-2Mg (alloy 322) foams. Various steps such as centrifugal atomisation, mixing alloy powder and foaming agent (1 wt-%TiH{sub 2}), cold compaction of mixture, hot extrusion and foaming in a preheated furnace were performed. Foaming behaviour of the alloys was investigated by digital microscopy, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping in this study. It was found that alloy 544 takes a shorter period of time to initiate pore nucleation than alloy 322. Alloy 544 had a higher pore growth rate than alloy 322 at the same pre-set furnace temperature. In both alloys, crack-like pore nucleation occurred between aluminium alloy powders elongated in a direction parallel to the extrusion direction. Both alloys showed the same foaming sequence of crack-like pore nucleation, spherical pore growth, coalescence of neighbouring pores and collapse of pores adjacent to the free surface of specimen. The time required to start pore nucleation decreased with the increase of foaming temperature. The cell walls of both alloys consisted of {alpha}-Al phase and eutectic phase. (author)

  20. Thermo-mechanical behavior of epoxy shape memory polymer foams

    Science.gov (United States)

    Di Prima, M. A.; Lesniewski, M.; Gall, K.; McDowell, D. L.; Sanderson, T.; Campbell, D.

    2007-12-01

    Shape memory polymer foams have significant potential in biomedical and aerospace applications, but their thermo-mechanical behavior under relevant deformation conditions is not well understood. In this paper we examine the thermo-mechanical behavior of epoxy shape memory polymer foams with an average relative density of nearly 20%. These foams are deformed under conditions of varying stress, strain, and temperature. The glass transition temperature of the foam was measured to be approximately 90 °C and compression and tensile tests were performed at temperatures ranging from 25 to 125 °C. Various shape recovery tests were used to measure recovery properties under different thermo-mechanical conditions. Tensile strain to failure was measured as a function of temperature to probe the maximum recovery limits of the foam in both temperature and strain space. Compression tests were performed to examine compressibility of the material as a function of temperature; these foams can be compacted as much as 80% and still experience full strain recovery over multiple cycles. Furthermore, both tensile strain to failure tests and cyclic compression recovery tests revealed that deforming at a temperature of 80 °C maximizes macroscopic strain recovery. Deformation temperatures above or below this optimal value lead to lower failure strains in tension and the accumulation of non-recoverable strains in cyclic compression. Micro-computed tomography (micro-CT) scans of the foam at various compressed states were used to understand foam deformation mechanisms. The micro-CT studies revealed the bending, buckling, and collapse of cells with increasing compression, consistent with results from published numerical simulations.