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Sample records for carbide composite bodies

  1. Composite materials and bodies including silicon carbide and titanium diboride and methods of forming same

    DOEpatents

    Lillo, Thomas M.; Chu, Henry S.; Harrison, William M.; Bailey, Derek

    2013-01-22

    Methods of forming composite materials include coating particles of titanium dioxide with a substance including boron (e.g., boron carbide) and a substance including carbon, and reacting the titanium dioxide with the substance including boron and the substance including carbon to form titanium diboride. The methods may be used to form ceramic composite bodies and materials, such as, for example, a ceramic composite body or material including silicon carbide and titanium diboride. Such bodies and materials may be used as armor bodies and armor materials. Such methods may include forming a green body and sintering the green body to a desirable final density. Green bodies formed in accordance with such methods may include particles comprising titanium dioxide and a coating at least partially covering exterior surfaces thereof, the coating comprising a substance including boron (e.g., boron carbide) and a substance including carbon.

  2. Silicon nitride/silicon carbide composite powders

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-06-11

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  3. Silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salvatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    2001-01-01

    This invention relates to a process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  4. Joining of porous silicon carbide bodies

    DOEpatents

    Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

    1990-05-01

    A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

  5. Composition Comprising Silicon Carbide

    NASA Technical Reports Server (NTRS)

    Mehregany, Mehran (Inventor); Zorman, Christian A. (Inventor); Fu, Xiao-An (Inventor); Dunning, Jeremy L. (Inventor)

    2012-01-01

    A method of depositing a ceramic film, particularly a silicon carbide film, on a substrate is disclosed in which the residual stress, residual stress gradient, and resistivity are controlled. Also disclosed are substrates having a deposited film with these controlled properties and devices, particularly MEMS and NEMS devices, having substrates with films having these properties.

  6. Diamond-silicon carbide composite

    DOEpatents

    Qian, Jiang; Zhao, Yusheng

    2006-06-13

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5–8 GPa, T=1400K–2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.dot.m1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  7. Silicon nitride/silicon carbide composite densified materials prepared using composite powders

    DOEpatents

    Dunmead, S.D.; Weimer, A.W.; Carroll, D.F.; Eisman, G.A.; Cochran, G.A.; Susnitzky, D.W.; Beaman, D.R.; Nilsen, K.J.

    1997-07-01

    Prepare silicon nitride-silicon carbide composite powders by carbothermal reduction of crystalline silica powder, carbon powder and, optionally, crystalline silicon nitride powder. The crystalline silicon carbide portion of the composite powders has a mean number diameter less than about 700 nanometers and contains nitrogen. The composite powders may be used to prepare sintered ceramic bodies and self-reinforced silicon nitride ceramic bodies.

  8. Process for making silicon carbide reinforced silicon carbide composite

    NASA Technical Reports Server (NTRS)

    Lau, Sai-Kwing (Inventor); Calandra, Salavatore J. (Inventor); Ohnsorg, Roger W. (Inventor)

    1998-01-01

    A process comprising the steps of: a) providing a fiber preform comprising a non-oxide ceramic fiber with at least one coating, the coating comprising a coating element selected from the group consisting of carbon, nitrogen, aluminum and titanium, and the fiber having a degradation temperature of between 1400.degree. C. and 1450.degree. C., b) impregnating the preform with a slurry comprising silicon carbide particles and between 0.1 wt % and 3 wt % added carbon c) providing a cover mix comprising: i) an alloy comprising a metallic infiltrant and the coating element, and ii) a resin, d) placing the cover mix on at least a portion of the surface of the porous silicon carbide body, e) heating the cover mix to a temperature between 1410.degree. C. and 1450.degree. C. to melt the alloy, and f) infiltrating the fiber preform with the melted alloy for a time period of between 15 minutes and 240 minutes, to produce a ceramic fiber reinforced ceramic composite.

  9. Body Composition.

    ERIC Educational Resources Information Center

    Mayhew, Jerry L.

    1981-01-01

    Body composition refers to the types and amounts of tissues which make up the body. The most acceptable method for assessing body composition is underwater weighing. A subcutaneous skinfold provides a quantitative measurement of fat below the skin. The skinfold technique permits a valid estimate of the body's total fat content. (JN)

  10. Body Composition.

    ERIC Educational Resources Information Center

    Mayhew, Jerry L.

    1981-01-01

    Body composition refers to the types and amounts of tissues which make up the body. The most acceptable method for assessing body composition is underwater weighing. A subcutaneous skinfold provides a quantitative measurement of fat below the skin. The skinfold technique permits a valid estimate of the body's total fat content. (JN)

  11. Diamond-silicon carbide composite and method

    DOEpatents

    Zhao, Yusheng

    2011-06-14

    Uniformly dense, diamond-silicon carbide composites having high hardness, high fracture toughness, and high thermal stability are prepared by consolidating a powder mixture of diamond and amorphous silicon. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPam.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness.

  12. Carbides composite surface layers produced by (PTA)

    SciTech Connect

    Tajoure, Meloud; Tajouri, Ali E-mail: dr.mokhtarphd@yahoo.com; Abuzriba, Mokhtar E-mail: dr.mokhtarphd@yahoo.com; Akreem, Mosbah

    2013-12-16

    The plasma transferred arc technique was applied to deposit a composite layer of nickel base with tungsten carbide in powder form on to surface of low alloy steel 18G2A type according to polish standard. Results showed that, plasma transferred arc hard facing process was successfully conducted by using Deloro alloy 22 plus tungsten carbide powders. Maximum hardness of 1489 HV and minimum dilution of 8.4 % were achieved by using an arc current of 60 A. However, when the current was further increased to 120 A and the dilution increases with current increase while the hardness decreases. Microstructure of the nickel base deposit with tungsten carbide features uniform distribution of reinforcement particles with regular grain shape half - dissolved in the matrix.

  13. Silicon carbide/SRBSN composites

    SciTech Connect

    Razzell, A.G.; Lewis, M.H.

    1991-08-01

    Ceramic matrix composites have been produced using unidirectionally aligned Textron SCS-6 fibers in a sintered reaction bonded silicon nitride (SRBSN) matrix. A tape casting technique was used to produce a prepreg sheet that could be cut and stacked to form a layup. Sintering aids were MgO, Al2O3, and Y2O3 either singly or in combination, final sintering being carried out under pressure at temperatures up to 1750 C. The three-point bend strength of the material varied between 448 and 513 MPa and showed no variation with oxidation time at 1000 C up to 25 hours. Interfacial shear strength measured by indentation was 4 MPa; some samples had a reaction layer at the interface and a shear strength of greater than MPa. Within sections 6 mm from exposed fiber ends, the interfacial carbon layers were partially removed, and the interfacial shear strength was reduced with increasing oxidation time. 4 refs.

  14. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, John J.

    1995-01-01

    Compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  15. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    DOEpatents

    Petrovic, J.J.

    1995-01-17

    Compositions are disclosed consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia.

  16. Molybdenum disilicide composites reinforced with zirconia and silicon carbide

    SciTech Connect

    Petrovic, J.J.

    1992-12-31

    This patent pertains to compositions consisting essentially of molybdenum disilicide, silicon carbide, and a zirconium oxide component. The silicon carbide used in the compositions is in whisker or powder form. The zirconium oxide component is pure zirconia or partially stabilized zirconia or fully stabilized zirconia. Fabrication, fracture toughness, and bend strength are covered.

  17. Method for producing silicon nitride/silicon carbide composite

    DOEpatents

    Dunmead, Stephen D.; Weimer, Alan W.; Carroll, Daniel F.; Eisman, Glenn A.; Cochran, Gene A.; Susnitzky, David W.; Beaman, Donald R.; Nilsen, Kevin J.

    1996-07-23

    Silicon carbide/silicon nitride composites are prepared by carbothermal reduction of crystalline silica powder, carbon powder and optionally crsytalline silicon nitride powder. The crystalline silicon carbide portion of the composite has a mean number diameter less than about 700 nanometers and contains nitrogen.

  18. Carbide coated fibers in graphite-aluminum composites

    NASA Technical Reports Server (NTRS)

    Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

    1975-01-01

    The study of protective-coupling layers of refractory metal carbides on the graphite fibers prior to their incorporation into composites is presented. Such layers should be directly wettable by liquid aluminum and should act as diffusion barriers to prevent the formation of aluminum carbide. Chemical vapor deposition was used to uniformly deposit thin, smooth, continuous coats of ZrC on the carbon fibers of tows derived from both rayon and polyacrylonitrile. A wet chemical coating of the fibers, followed by high-temperature treatment, was used, and showed promise as an alternative coating method. Experiments were performed to demonstrate the ability of aluminum alloys to wet carbide surfaces. Titanium carbide, zirconium carbide and carbide-coated graphite surfaces were successfully wetted. Results indicate that initial attempts to wet surfaces of ZrC-coated carbon fibers appear successful.

  19. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  20. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  1. Silicon carbide sintered body manufactured from silicon carbide powder containing boron, silicon and carbonaceous additive

    NASA Technical Reports Server (NTRS)

    Tanaka, Hidehiko

    1987-01-01

    A silicon carbide powder of a 5-micron grain size is mixed with 0.15 to 0.60 wt% mixture of a boron compound, i.e., boric acid, boron carbide (B4C), silicon boride (SiB4 or SiB6), aluminum boride, etc., and an aluminum compound, i.e., aluminum, aluminum oxide, aluminum hydroxide, aluminum carbide, etc., or aluminum boride (AlB2) alone, in such a proportion that the boron/aluminum atomic ratio in the sintered body becomes 0.05 to 0.25 wt% and 0.05 to 0.40 wt%, respectively, together with a carbonaceous additive to supply enough carbon to convert oxygen accompanying raw materials and additives into carbon monoxide.

  2. Sintered silicon carbide molded body and method for its production

    NASA Technical Reports Server (NTRS)

    Omori, M.; Sendai, M.; Ohira, K.

    1984-01-01

    Sintered silicon carbide shapes are described. They are produced by using a composition containing an oxide of at least one element chosen from the group: Li, Be, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Nb, Mo, Ba, Tc, Ta, W and Th as a supplement to known sintering aids.

  3. Carbide-reinforced metal matrix composite by direct metal deposition

    NASA Astrophysics Data System (ADS)

    Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

    Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.

  4. Evaluation of Neutron Irradiated Silicon Carbide and Silicon Carbide Composites

    SciTech Connect

    Newsome G, Snead L, Hinoki T, Katoh Y, Peters D

    2007-03-26

    The effects of fast neutron irradiation on SiC and SiC composites have been studied. The materials used were chemical vapor deposition (CVD) SiC and SiC/SiC composites reinforced with either Hi-Nicalon{trademark} Type-S, Hi-Nicalon{trademark} or Sylramic{trademark} fibers fabricated by chemical vapor infiltration. Statistically significant numbers of flexural samples were irradiated up to 4.6 x 10{sup 25} n/m{sup 2} (E>0.1 MeV) at 300, 500 and 800 C in the High Flux Isotope Reactor at Oak Ridge National Laboratory. Dimensions and weights of the flexural bars were measured before and after the neutron irradiation. Mechanical properties were evaluated by four point flexural testing. Volume increase was seen for all bend bars following neutron irradiation. Magnitude of swelling depended on irradiation temperature and material, while it was nearly independent of irradiation fluence over the fluence range studied. Flexural strength of CVD SiC increased following irradiation depending on irradiation temperature. Over the temperature range studied, no significant degradation in mechanical properties was seen for composites fabricated with Hi-Nicalon{trademark} Type-S, while composites reinforced with Hi-Nicalon{trademark} or Sylramic fibers showed significant degradation. The effects of irradiation on the Weibull failure statistics are also presented suggesting a reduction in the Weibull modulus upon irradiation. The cause of this potential reduction is not known.

  5. Hot forging of graphite-carbide composites. Final report

    SciTech Connect

    Jenkins, G.M.; Holland, L.R.

    1998-07-15

    This project was aimed at hot shaping of titanium carbide/graphite and vanadium carbide/graphite composite materials by heating them to above 2000 degrees celsius and pressing into an electrographite die. The sample was to be a preformed cylinder of powdered graphite mixed with powdered titanium or vanadium, lightly sintered. The preform would be heated in a hot press and the titanium or vanadium would react with some of the graphite to form titanium or vanadium carbide. The remaining (excess) graphite would form a composite with the carbide, and this could then be deformed plastically at temperatures well below the onset of plasticity in pure graphite. There were to be two major thrusts in the research: In the first, an electron beam furnace at Sandia Laboratory was to be used for rapid heating of the sample, which would then be transferred into the press. The second thrust was to be entirely at Alabama A and M University, and here they intended to use a heated, controlled atmosphere press to forge the graphite/carbide preforms at a steady temperature and measure their viscosity as a function of temperature. This report discusses the progress made on this project.

  6. Evaluation of silicon carbide fiber/titanium composites

    NASA Technical Reports Server (NTRS)

    Jech, R. W.; Signorelli, R. A.

    1979-01-01

    Izod impact, tensile, and modulus of elasticity were determined for silicon carbide fiber/titanium composites to evaluate their potential usefulness as substitutes for titanium alloys or stainless steel in stiffness critical applications for aircraft turbine engines. Variations in processing conditions and matrix ductility were examined to produce composites having good impact strength in both the as-fabricated condition and after air exposure at elevated temperature. The impact strengths of composites containing 36 volume percent silicon carbide (SiC) fiber in an unalloyed (A-40) titanium matrix were found to be equal to unreinforced titanium-6 aluminum-4 vanadium alloy; the tensile strengths of the composites were marginally better than the unreinforced unalloyed (A-70) matrix at elevated temperature, though not at room temperature. At room temperature the modulus of elasticity of the composites was 48 percent higher than titanium or its alloys and 40 percent higher than that of stainless steel.

  7. Carbide/fluoride/silver self-lubricating composite

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E. (Inventor)

    1988-01-01

    A self-lubricating, friction and wear reducing composite material for use over a wide temperature spectrum from cryogenic temperature to about 900.degree. C. in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.

  8. Carbide-fluoride-silver self-lubricating composite

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E. (Inventor)

    1987-01-01

    A self-lubricating, friction and wear reducing composite material is described for use over a wide temperature spectrum from cryogenic temperature to about 900 C in a chemically reactive environment comprising silver, barium fluoride/calcium fluoride eutectic, and metal bonded chromium carbide.

  9. Method of preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals

    DOEpatents

    Peng, Yu-Min; Wang, Jih-Wen; Liue, Chun-Ying; Yeh, Shinn-Horng

    1994-01-01

    A method for preparing silicon carbide particles dispersed in an electrolytic bath for composite electroplating of metals includes the steps of washing the silicon carbide particles with an organic solvent; washing the silicon carbide particles with an inorganic acid; grinding the silicon carbide particles; and heating the silicon carbide particles in a nickel-containing solution at a boiling temperature for a predetermined period of time.

  10. Fabrication of Carbon Nanotube - Chromium Carbide Composite Through Laser Sintering

    NASA Astrophysics Data System (ADS)

    Liu, Ze; Gao, Yibo; Liang, Fei; Wu, Benxin; Gou, Jihua; Detrois, Martin; Tin, Sammy; Yin, Ming; Nash, Philip; Tang, Xiaoduan; Wang, Xinwei

    2016-03-01

    Ceramics often have high hardness and strength, and good wear and corrosion resistance, and hence have many important applications, which, however, are often limited by their poor fracture toughness. Carbon nanotubes (CNTs) may enhance ceramic fracture toughness, but hot pressing (which is one typical approach of fabricating CNT-ceramic composites) is difficult to apply for applications that require localized heat input, such as fabricating composites as surface coatings. Laser beam may realize localized material sintering with little thermal effect on the surrounding regions. However, for the typical ceramics for hard coating applications (as listed in Ref.[1]), previous work on laser sintering of CNT-ceramic composites with mechanical property characterizations has been very limited. In this paper, research work has been reported on the fabrication and characterization of CNT-ceramic composites through laser sintering of mixtures of CNTs and chromium carbide powders. Under the studied conditions, it has been found that laser-sintered composites have a much higher hardness than that for plasma-sprayed composites reported in the literature. It has also been found that the composites obtained by laser sintering of CNTs and chromium carbide powder mixtures have a fracture toughness that is ~23 % higher than the material obtained by laser sintering of chromium carbide powders without CNTs.

  11. Ceramic composites reinforced with modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1990-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  12. Protective coating for alumina-silicon carbide whisker composites

    DOEpatents

    Tiegs, Terry N.

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  13. Diamond-Silicon Carbide Composite And Method For Preparation Thereof

    DOEpatents

    Qian, Jiang; Zhao, Yusheng

    2005-09-06

    Fully dense, diamond-silicon carbide composites are prepared from ball-milled microcrystalline diamond/amorphous silicon powder mixture. The ball-milled powder is sintered (P=5-8 GPa, T=1400K-2300K) to form composites having high fracture toughness. A composite made at 5 GPa/1673K had a measured fracture toughness of 12 MPa.multidot.m.sup.1/2. By contrast, liquid infiltration of silicon into diamond powder at 5 GPa/1673K produces a composite with higher hardness but lower fracture toughness. X-ray diffraction patterns and Raman spectra indicate that amorphous silicon is partially transformed into nanocrystalline silicon at 5 GPa/873K, and nanocrystalline silicon carbide forms at higher temperatures.

  14. Method for Forming Fiber Reinforced Composite Bodies with Graded Composition and Stress Zones

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay (Inventor); Levine, Stanley R. (Inventor); Smialek, James A. (Inventor)

    1999-01-01

    A near-net, complex shaped ceramic fiber reinforced silicon carbide based composite bodies with graded compositions and stress zones is disclosed. To provide the composite a fiber preform is first fabricated and an interphase is applied by chemical vapor infiltration, sol-gel or polymer processes. This first body is further infiltrated with a polymer mixture containing carbon, and/or silicon carbide, and additional oxide, carbide, or nitride phases forming a second body. One side of the second body is spray coated or infiltrated with slurries containing high thermal expansion and oxidation resistant. crack sealant phases and the other side of this second body is coated with low expansion phase materials to form a third body. This third body consisting of porous carbonaceous matrix surrounding the previously applied interphase materials, is then infiltrated with molten silicon or molten silicon-refractory metal alloys to form a fourth body. The resulting fourth body comprises dense composites consisting of fibers with the desired interphase which are surrounded by silicon carbide and other second phases materials at the outer and inner surfaces comprising material of silicon, germanium, refractory metal suicides, borides, carbides, oxides, and combinations thereof The resulting composite fourth body has different compositional patterns from one side to the other.

  15. Method for making hot-pressed fiber-reinforced carbide-graphite composite

    DOEpatents

    Riley, Robert E.; Wallace Sr., Terry C.

    1979-01-01

    A method for the chemical vapor deposition of a uniform coating of tantalum metal on fibers of a woven graphite cloth is described. Several layers of the coated cloth are hot pressed to produce a tantalum carbide-graphite composite having a uniformly dispersed, fine grained tantalum carbide in graphite with compositions in the range of 15 to 40 volume percent tantalum carbide.

  16. Method of making carbide/fluoride/silver composites

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E. (Inventor); Dellacorte, Christopher (Inventor)

    1991-01-01

    A composition containing 30 to 70 percent chromium carbide, 5 to 20 percent soft noble metal, 5 to 20 percent metal fluorides, and 20 to 60 percent metal binder is used in a powdered metallurgy process for the production of self-lubricating components, such as bearings. The use of the material allows the self-lubricating bearing to maintain its low friction properties over an extended range of operating temperatures.

  17. Fatigue of alumina-based ceramics and chrome carbide composites

    NASA Astrophysics Data System (ADS)

    Kireitseu, Maksim V.; Yerakhavets, Liudmila; Nemerenco, Ion; Basenuk, Vladimir L.

    2003-10-01

    The paper was revealed a fatigue in the alumina-chrome carbide composite. The trapped crack front resembles a collinear array of microcracks interspersed by grains rich in transformable precipitates. This micromechanical model provides a reasonable explanation for the observed fatigue crack growth. A numerical procedure similar to the one used in the analysis of the array of collinear cracks, based on complex potentials and dislocation formalism is also used to simulate fatigue of composite coatings based on oxide ceramics and chrome carbide. Assuming power-law crack growth, it is found that the crack growth rate decreases with the applied stress intensity factor in the initial stage of fatigue crack growth. Depending on the applied load and the amount of transformation, the growth rate either goes through a minimum before increasing to the normal crack regime, or the rate continues to decrease until the crack is arrested. A detailed parametric study of the phenomenon of fatigue crack arrest in composite coatings based on oxide ceramics and chrome carbide reveals that the combination of transformation strength parameter and applied load determines whether or not crack arrest will occur, irrespective of the initial crack length. Based on the parametric study a simple linear relationship between the applied load and the minimum transformation strength parameter necessary to cause crack arrest has been developed. it will be found useful in the design against fatigue by predicting the maximum toad at which crack arrest can be expected.

  18. Thermal properties of wood-derived silicon carbide and copper-silicon carbide composites

    NASA Astrophysics Data System (ADS)

    Pappecena, Kristen E.

    Wood-derived ceramics and composites have been of interest in recent years due to their unique microstructures, which lead to tailorable properties. The porosity and pore size distribution of each wood type is different, which yields variations in properties in the resultant materials. The thermal properties of silicon carbide ceramics and copper-silicon carbide composites derived from wood were studied as a function of their pore structures. Wood was pyrolyzed at temperatures ranging from 300-2400°C to yield porous carbon. The progression toward long-range order was studied as a function of pyrolyzation temperature. Biomorphic silicon carbide (bioSiC) is a porous ceramic material resulting from silicon melt infiltration of these porous carbon materials. BioSiC has potential applicability in many high temperature environments, particularly those in which rapid temperature changes occur. To understand the behavior of bioSiC at elevated temperatures, the thermal and thermo-mechanical properties were studied. The thermal conductivity of bioSiC from five precursors was determined using flash diffusivity at temperatures up to 1100°C. Thermal conductivity results varied with porosity, temperature and orientation, and decreased from 42-13 W/mK for porosities of 43-69%, respectively, at room temperature. The results were compared with to object-oriented finite-element analysis (OOF). OOF was also used to model and understand the heat-flow paths through the complex bioSiC microstructures. The thermal shock resistance of bioSiC was also studied, and no bioSiC sample was found to fail catastrophically after up to five thermal shock cycles from 1400°C to room temperature oil. Copper-silicon carbide composites have potential uses in thermal management applications due to the high thermal conductivity of each phase. Cu-bioSiC composites were created by electrodeposition of copper into bioSiC pores. The detrimental Cu-SiC reaction was avoided by using this room temperature

  19. Body of Knowledge for Silicon Carbide Power Electronics

    NASA Technical Reports Server (NTRS)

    Boomer, Kristen; Lauenstein, Jean-Marie; Hammoud, Ahmad

    2016-01-01

    Wide band gap semiconductors, such as silicon carbide (SiC), have emerged as very promising materials for future electronic components due to the tremendous advantages they offer in terms of power capability, extreme temperature tolerance, and high frequency operation. This report documents some issues pertaining to SiC technology and its application in the area of power electronics, in particular those geared for space missions. It also serves as a body of knowledge (BOK) in reference to the development and status of this technology obtained via literature and industry survey as well as providing a listing of the major manufacturers and their capabilities. Finally, issues relevant to the reliability of SiC-based electronic parts are addressed and limitations affecting the full utilization of this technology are identified.

  20. Status of silicon carbide composites for fusion

    SciTech Connect

    Snead, L.L.; Jones, R.H.; Kohyama, A.

    1996-04-01

    An effort is now underway to design an irradiation creep experiment involving SiC composites and SiC fibers. In order to successfully design such an experiment, it is necessary to review and assess the available data for monolithic SiC to establish the possible bounds of creep behavior for the composite. The data available show that monolithic SiC will indeed creep at a higher rate under irradiation compared to that of thermal creep, and surprisingly, it will do so in a temperature-dependant manner that is typical of metals.

  1. Carbide coated fibers in graphite-aluminum composites

    NASA Technical Reports Server (NTRS)

    Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

    1975-01-01

    The NASA-supported program at the Los Alamos Scientific Laboratory (LASL) to develop carbon fiber-aluminum matrix composites is described. Chemical vapor deposition (CVD) was used to uniformly deposit thin, smooth, continuous coats of TiC on the fibers of graphite tows. Wet chemical coating of fibers, followed by high-temperature treatment, was also used, but showed little promise as an alternative coating method. Strength measurements on CVD coated fiber tows showed that thin carbide coats can add to fiber strength. The ability of aluminum alloys to wet TiC was successfully demonstrated using TiC-coated graphite surfaces. Pressure-infiltration of TiC- and ZrC-coated fiber tows with aluminum alloys was only partially successful. Experiments were performed to evaluate the effectiveness of carbide coats on carbon as barriers to prevent reaction between alluminum alloys and carbon. Initial results indicate that composites of aluminum and carbide-coated graphite are stable for long periods of time at temperatures near the alloy solidus.

  2. Dynamic consolidation of aluminum-silicon carbide composites

    SciTech Connect

    Rabin, B.H.; Korth, G.E.; Williamson, R.L.

    1990-01-01

    Dynamic consolidation was investigated as a potential method for producing P/M metal matrix composites. In this study, 2124 aluminum powders were mixed with silicon carbide particulate and consolidated using explosives. Numerical simulations were performed to provide insight into the consolidation process and to aid in the selection of experimental conditions. The microstructure of the as-consolidated product was dependent upon processing variables. Careful control of the shock parameters allowed full density, crack free composites to be achieved in cylindrical geometries. Although full density was obtained, low fracture strengths suggested a lack of interparticle bonding, probably resulting from the limited ability to redistribute surface oxides during consolidation. 10 refs., 9 figs.

  3. Carbide coated fibers in graphite-aluminum composites

    NASA Technical Reports Server (NTRS)

    Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

    1975-01-01

    Thin, uniform coats of titanium carbide, deposited on graphite fibers by chemical vapor deposition with thicknesses up to approximately 0.1 microns were shown to improve fiber strength significantly. For greater thicknesses, strength was degraded. The coats promote wetting of the fibers and infiltration of the fiber yarns with aluminum alloys, and act as protective barriers to inhibit reaction between the fibers and the alloys. Chemical vapor deposition was used to produce silicon carbide coats on graphite fibers. In general, the coats were nonuniform and were characterized by numerous surface irregularities. Despite these irregularities, infiltration of these fibers with aluminum alloys was good. Small graphite-aluminum composite samples were produced by vacuum hot-pressing of aluminum-infiltrated graphite yarn at temperatures above the metal liquidus.

  4. Silicon carbide-silicon composite having improved oxidation resistance and method of making

    NASA Technical Reports Server (NTRS)

    Luthra, Krishan Lal (Inventor); Wang, Hongyu (Inventor)

    1999-01-01

    A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.

  5. Method of making silicon carbide-silicon composite having improved oxidation resistance

    NASA Technical Reports Server (NTRS)

    Luthra, Krishan Lal (Inventor); Wang, Hongyu (Inventor)

    2002-01-01

    A Silicon carbide-silicon matrix composite having improved oxidation resistance at high temperatures in dry or water-containing environments is provided. A method is given for sealing matrix cracks in situ in melt infiltrated silicon carbide-silicon matrix composites. The composite cracks are sealed by the addition of various additives, such as boron compounds, into the melt infiltrated silicon carbide-silicon matrix.

  6. Microstructural Evolution of Chloride-Cleaned Silicon Carbide Aluminum Composites

    NASA Astrophysics Data System (ADS)

    Adeosun, S. O.; Akpan, E. I.; Gbenebor, O. P.; Balogun, S. A.

    2016-02-01

    This study examines the synergy between reinforcement surface modifications on the evolution of microstructures of AA6011-silicon carbide particle (SiCp) composites in multidirectional solidification. Silicon carbide particles (SiCp) were cleaned with ammonium chloride, tin(II) chloride, sodium chloride, and palladium(II) chloride and used as reinforcement to cast AA6011-SiCp composites by applying the stir casting method. A scanning electron microscope and x-ray diffractometer were used to investigate the morphology and phases present, respectively, in the composite material. Results show that wetting agents were effective as they inhibited the formation of Al4C3 in all modified composites. The modified SiCp was found to have varying effects on the morphology, dendrite arm size and direction, size and configuration of AlFeSi, and the amount of eutectic silicon depending on the concentration of the reagent and cleaning time. The highest effect was shown by the use of 40 g/L of tin(II) chloride. The composites had short dendritic arms, good interfacial interaction, and only a few crystals of AlFeSi.

  7. Iron aluminide-titanium carbide composites: Microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.; Alexander, K.B.

    1996-09-01

    Composites of intermetallics and carbides (with binder contents less that 50 vol.%) are considered as potential candidates for applications requiring high wear resistance in corrosive environments. Intermetallics, especially aluminides, provide the corrosion resistance, and the high hardness of the carbide phase contributes to increased wear resistance of the composites. In this study, cost effective and simple processing techniques to obtain FeAl-TiC composites, over a wide range of binder volume fractions, are demonstrated. Binder volume fractions range from 0.15 to 0.7 (18 to 75 wt. % binder). Two techniques - liquid phase sintering of mixed powders and pressureless melt infiltration of TiC preforms was found to be very successful for obtaining fully dense composites with binder volume fractions from 0.15 to 0.3 (18 to 34 wt. %), whereas for higher binder contents liquid phase sintering of mixed powders was the best approach. Mechanical properties of these composites including the 3-point bend strength, fracture toughness and hardness are presented.

  8. Oxidation Behavior of Carbon Fiber Reinforced Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    Valentin, Victor M.

    1995-01-01

    Carbon fiber reinforced Silicon Carbide (C-SiC) composites offer high strength at high temperatures and good oxidation resistance. However, these composites present some matrix microcracks which allow the path of oxygen to the fiber. The aim of this research was to study the effectiveness of a new Silicon Carbide (SiC) coating developed by DUPONT-LANXIDE to enhance the oxidation resistance of C-SiC composites. A thermogravimetric analysis was used to determine the oxidation rate of the samples at different temperatures and pressures. The Dupont coat proved to be a good protection for the SiC matrix at temperatures lower than 1240 C at low and high pressures. On the other hand, at temperatures above 1340 C the Dupont coat did not seem to give good protection to the composite fiber and matrix. Even though some results of the tests have been discussed, because of time restraints, only a small portion of the desired tests could be completed. Therefore, no major conclusions or results about the effectiveness of the coat are available at this time.

  9. Titanium-silicon carbide composite lattice structures

    NASA Astrophysics Data System (ADS)

    Moongkhamklang, Pimsiree

    Sandwich panel structures with stiff, strong face sheets and lightweight cellular cores are widely used for weight sensitive, bending dominated loading applications. The flexural stiffness and strength of a sandwich panel is determined by the stiffness, strength, thickness, and separation of the face sheets, and by the compressive and shear stiffness and strength of the cellular core. Panel performance can be therefore optimized using cores with high specific stiffness and strength. The specific stiffness and strength of all cellular materials depends upon the specific elastic modulus and strength of the material used to make the structure. The stiffest and strongest cores for ambient temperature applications utilize carbon fiber reinforced polymer (CFRP) honeycombs and lattice structures. Few options exist for lightweight sandwich panels intended for high temperature uses. High temperature alloys such as Ti-6A1-4V can be applied to SiC monofilaments to create very high specific modulus and strength fibers. These are interesting candidates for the cores of elevated temperature sandwich structures such as the skins of hypersonic vehicles. This dissertation explores the potential of sandwich panel concepts that utilize millimeter scale titanium matrix composite (TMC) lattice structures. A method has been developed for fabricating millimeter cell size cellular lattice structures with the square or diamond collinear truss topologies from 240 mum diameter Ti-6A1-4V coated SiC monofilaments (TMC monofilaments). Lattices with relative densities in the range 10% to 20% were manufactured and tested in compression and shear. Given the very high compressive strength of the TMC monofilaments, the compressive strengths of both the square and diamond lattices were dominated by elastic buckling of the constituent struts. However, under shear loading, some of the constituent struts of the lattices are subjected to tensile stresses and failure is then set by tensile failure of the

  10. Shock response of boron carbide based composites infiltrated with magnesium

    NASA Astrophysics Data System (ADS)

    Kafri, Mathan; Dariel, Moshe P.; Frage, Naum; Zaretsky, Eugene

    2012-03-01

    The fully dense composites were obtained by vacuum infiltrating boron carbide compacts (80% green density) with molten AZ91 magnesium alloy (850°C) and with the melt of a 50/50 AZ91- silicon mixture (1050°C). The densities composites were, 2.44 g/cm3 and 2.54 g/cm3, respectively. The impact response of the composites was studied in a series of VISAR -instrumented planar impact experiments with velocities of W and Cu impactors ranging from 100 to 1000 m/s. The velocity history recorded for the composites produced by infiltration with the Mg-Si alloy contains a distinct elastic precursor front followed by a plastic ramp. In contrast, the velocity history of the composite infiltrated with AZ91 does not display any step-like front; the amplitude of the elastic wave grows gradually from zero level and transforms smoothly into the plastic front. The influence of the composites microstructure on their compressive and tensile behavior is discussed.

  11. Rapid Fabrication of Carbide Matrix/Carbon Fiber Composites

    NASA Technical Reports Server (NTRS)

    Williams, Brian E.; Bernander, Robert E.

    2007-01-01

    Composites of zirconium carbide matrix material reinforced with carbon fibers can be fabricated relatively rapidly in a process that includes a melt infiltration step. Heretofore, these and other ceramic matrix composites have been made in a chemical vapor infiltration (CVI) process that takes months. The finished products of the CVI process are highly porous and cannot withstand temperatures above 3,000 F (approx.1,600 C). In contrast, the melt-infiltration-based process takes only a few days, and the composite products are more nearly fully dense and have withstood temperatures as high as 4,350 F (approx.2,400 C) in a highly oxidizing thrust chamber environment. Moreover, because the melt- infiltration-based process takes much less time, the finished products are expected to cost much less. Fabrication begins with the preparation of a carbon fiber preform that, typically, is of the size and shape of a part to be fabricated. By use of low-temperature ultraviolet-enhanced chemical vapor deposition, the carbon fibers in the preform are coated with one or more interfacial material(s), which could include oxides. The interfacial material helps to protect the fibers against chemical attack during the remainder of the fabrication process and against oxidation during subsequent use; it also enables slippage between the fibers and the matrix material, thereby helping to deflect cracks and distribute loads. Once the fibers have been coated with the interfacial material, the fiber preform is further infiltrated with a controlled amount of additional carbon, which serves as a reactant for the formation of the carbide matrix material. The next step is melt infiltration. The preform is exposed to molten zirconium, which wicks into the preform, drawn by capillary action. The molten metal fills most of the interstices of the preform and reacts with the added carbon to form the zirconium carbide matrix material. The zirconium does not react with the underlying fibers because they

  12. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    NASA Astrophysics Data System (ADS)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  13. Thermal stress analysis of a silicon carbide/aluminum composite

    NASA Technical Reports Server (NTRS)

    Gdoutos, E. E.; Karalekas, D.; Daniel, I. M.

    1991-01-01

    Thermal deformations and stresses were studied in a silicon-carbide/aluminum filamentary composite at temperatures up to 370 C (700 F). Longitudinal and transverse thermal strains were measured with strain gages and a dilatometer. An elastoplastic micromechanical analysis based on a one-dimensional rule-of-mixtures model and an axisymmetric two-material composite cylinder model was performed. It was established that beyond a critical temperature thermal strains become nonlinear with decreasing longitudinal and increasing transverse thermal-expansion coefficients. This behavior was attributed to the plastic stresses in the aluminum matrix above the critical temperature. An elastoplastic analysis of both micromechanical models was performed to determine the stress distributions and thermal deformation in the fiber and matrix of the composite. While only axial stresses can be determined by the rule-of-mixtures model, the complete triaxial state of stress is established by the composite cylinder model. Theoretical predictions for the two thermal-expansion coefficients were in satisfactory agreement with experimental results.

  14. Advanced Measurements of Silicon Carbide Ceramic Matrix Composites

    SciTech Connect

    Farhad Farzbod; Stephen J. Reese; Zilong Hua; Marat Khafizov; David H. Hurley

    2012-08-01

    Silicon carbide (SiC) is being considered as a fuel cladding material for accident tolerant fuel under the Light Water Reactor Sustainability (LWRS) Program sponsored by the Nuclear Energy Division of the Department of Energy. Silicon carbide has many potential advantages over traditional zirconium based cladding systems. These include high melting point, low susceptibility to corrosion, and low degradation of mechanical properties under neutron irradiation. In addition, ceramic matrix composites (CMCs) made from SiC have high mechanical toughness enabling these materials to withstand thermal and mechanical shock loading. However, many of the fundamental mechanical and thermal properties of SiC CMCs depend strongly on the fabrication process. As a result, extrapolating current materials science databases for these materials to nuclear applications is not possible. The “Advanced Measurements” work package under the LWRS fuels pathway is tasked with the development of measurement techniques that can characterize fundamental thermal and mechanical properties of SiC CMCs. An emphasis is being placed on development of characterization tools that can used for examination of fresh as well as irradiated samples. The work discuss in this report can be divided into two broad categories. The first involves the development of laser ultrasonic techniques to measure the elastic and yield properties and the second involves the development of laser-based techniques to measurement thermal transport properties. Emphasis has been placed on understanding the anisotropic and heterogeneous nature of SiC CMCs in regards to thermal and mechanical properties. The material properties characterized within this work package will be used as validation of advanced materials physics models of SiC CMCs developed under the LWRS fuels pathway. In addition, it is envisioned that similar measurement techniques can be used to provide process control and quality assurance as well as measurement of

  15. Ultrafine-grained Aluminm and Boron Carbide Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Vogt, Rustin

    Cryomilling is a processing technique used to generate homogenously distributed boron carbide (B4C) particulate reinforcement within an ultrafine-grained aluminum matrix. The motivation behind characterizing a composite consisting of cryomilled aluminum B4C metal matrix composite is to design and develop a high-strength, lightweight aluminum composite for structural and high strain rate applications. Cryomilled Al 5083 and B4C powders were synthesized into bulk composite by various thermomechanical processing methods to form plate and extruded geometries. The effects of processing method on microstructure and mechanical behavior for the final consolidated composite were investigated. Cryomilling for extended periods of time in liquid nitrogen has shown to increase strength and thermal stability. The effects associated with cryomilling with stearic acid additions (as a process-control agent) on the degassing behavior of Al powders is investigated and results show that the liberation of compounds associated with stearic acid were suppressed in cryomilled Al powders. The effect of thermal expansion mismatch strain on strengthening due to geometrically necessary dislocations resulting from quenching is investigated and found not to occur in bulk cryomilled Al 5083 and B 4C composites. Previous cryomilled Al 5083 and B4C composites have exhibited ultrahigh strength associated with considerable strain-to-failure (>14 pct.) at high strain rates (>103/s) during mechanical testing, but only limited strain-to-failure (˜0.75 pct.) at quasi-static strain rates (10-3/s). The increased strain to failure at high strain rates is attributed to micro-flaw developments, including kinking, extensive axial splitting, and grain growth were observed after high strain rate deformation, and the significance of these mechanisms is considered.

  16. Affordable Fabrication and Properties of Silicon Carbide-Based Interpenetrating Phase Composites

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay

    1998-01-01

    An affordable processing technique for the fabrication of silicon carbide-based interpenetrating phase composites (IPCs) is presented. This process consists of the production of microporous carbon preforms and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture for which methods to control pore volume and pore size have been established. The process gives good control of microstructure and morphology of silicon carbide-based composite materials. Room and high temperature mechanical properties (flexural strength, compressive strength, and flexural creep) of low and high silicon-silicon carbide composites will be discussed.

  17. Silicon carbide nanowires and composites obtained from carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Wang, Yuejian

    In this dissertation a simple route has been developed to synthesize Silicon Carbide (beta-SiC) nanothreads and C-SiC coaxial nanotubes by solid/liquid-state reaction between multiwall carbon nanotubes and silicon conducted at 1473 K and 1723 K, respectively. Through the kinetics study of SiC formation from carbon nanotubes and Si, our results demonstrated that carbon nanotubes may have higher chemical reactivity than other forms of elemental Carbon. Based on the above investigation, CNT/SiC and diamond/CNT/SiC were manufactured. Key factors influencing the mechanical properties of final products, such as phase composition, grain size, stress-strain, sintering time, and sintering temperature were thoroughly studied with Raman spectroscopy, x-ray diffraction, SEM and TEM techniques. Taking advantage of high elasticity of Carbon nanotube and its ability to block the microcrack propagation and dislocation movement, both composites showed enhanced fracture toughness. Carbon nanotubes composites trigger a new field in fundamental science and manifest potential application in multiple industries.

  18. Modal acoustic emission source determination in silicon carbide matrix composites

    NASA Astrophysics Data System (ADS)

    Morscher, G. N.

    2000-05-01

    Modal acoustic emission has been used to monitor damage accumulation in woven silicon carbide (SiC) fiber reinforced SiC matrix composites during tensile testing. There are several potential sources of damage in these systems including transverse matrix cracking, fiber/matrix interphase debonding and sliding, longitudinal cracks in between plies, and fiber breakage. In the past, it has been shown that modal AE is excellent at detecting when damage occurs and subsides, where the damage occurs along the length of the sample, and the loss in material stiffness as a consequence of damage accumulation. The next step is to determine the extent that modal AE can be used to identify specific physical sources. This study will discuss the status of this aim for this composite system. Individual events were analyzed and correlated to specific sources based on the characteristics of the received waveforms, e.g., frequency spectrum and energy, and when the event occurred during the stress-history of the tensile test. Post-test microstructural examination of the test specimens enabled some correlation between specific types of AE events and damage sources.

  19. Phase diagram of boron carbide with variable carbon composition

    NASA Astrophysics Data System (ADS)

    Yao, Sanxi; Gao, Qin; Widom, Michael

    2017-02-01

    Boron carbide exhibits intrinsic substitutional disorder over a broad composition range. The structure consists of 12-atom icosahedra placed at the vertices of a rhombohedral lattice, together with a 3-atom chain along the threefold axis. In the high-carbon limit, one or two carbon atoms can replace boron atoms on the icosahedra while the chains are primarily of type C-B-C. We fit an interatomic pair interaction model to density-functional-theory total energies to investigate the substitutional carbon disorder. Monte Carlo simulations with sampling improved by replica exchange and augmented by two-dimensional multiple histogram analysis predict three phases. The low-temperature, high-carbon-composition monoclinic C m structure disorders through a pair of phase transitions, first via an Ising-like transition to a monoclinic centrosymmetric state with space group C 2 /m , then via a first-order three-state Potts-like transition to the experimentally observed rhombohedral R 3 ¯m symmetry.

  20. Interfacial preferential dissolution on silicon carbide particulate/aluminum composites

    SciTech Connect

    Yao, H.Y.; Zhu, R.Z.

    1998-07-01

    Previous studies on corrosion of discontinuously reinforced aluminum alloy composites have assumed that the role of the reinforcement-matrix interface is merely as a preferable site for pitting. In this work, the interfacial preferential dissolution (IPD) occurring on silicon carbide particulate/aluminum (SiC{sub p}/Al) composites in a medium of aqueous sodium chloride (NaCl) solution was studied. IPD was quite distinct from pitting. IPD occurred on the composites with either a pure aluminum matrix or an aluminum alloy Al 2024 (UNS A92024) matrix, whether they were fabricated by a cast process or by a powder metallurgy process. In the light of elastoplastic mechanics, the width of the plastically deformed zone around SiC particles (created by the contraction misfit between SiC particles and the matrix during quenching) was deduced to be 0.5 D, where D is the diameter of the SiC particles. This was in agreement with the measured width of the IPD region (0.3 D to 0.4 D). It was concluded that IPD was caused by the poor integrity of the surface oxide film upon the plastically deformed zone near the interface and was independent of the chemical, metallurgical, and galvanic coupling factors around the interface, if any. A copper-deposition experiment indicated this poor integrity. IPD caused increased dissolution at SiC clusters and uniform corrosion for the composites with high SiC content. Moreover, IPD and pitting suppressed each other by a means of cathodic protection.

  1. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    NASA Astrophysics Data System (ADS)

    Ponomarev, V. I.; Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

    2015-09-01

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide В15- х С х , (1.5 ≤ x ≤ 3) and its magnesium derivative C4B25Mg1.42. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from В12.9С2.1 to В12.4С2.6.

  2. Low Cost Fabrication of Silicon Carbide Based Ceramics and Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Levine, S. R.

    1995-01-01

    A low cost processing technique called reaction forming for the fabrication of near-net and complex shaped components of silicon carbide based ceramics and composites is presented. This process consists of the production of a microporous carbon preform and subsequent infiltration with liquid silicon or silicon-refractory metal alloys. The microporous preforms are made by the pyrolysis of a polymerized resin mixture with very good control of pore volume and pore size thereby yielding materials with tailorable microstructure and composition. Mechanical properties (elastic modulus, flexural strength, and fracture toughness) of reaction-formed silicon carbide ceramics are presented. This processing approach is suitable for various kinds of reinforcements such as whiskers, particulates, fibers (tows, weaves, and filaments), and 3-D architectures. This approach has also been used to fabricate continuous silicon carbide fiber reinforced ceramic composites (CFCC's) with silicon carbide based matrices. Strong and tough composites with tailorable matrix microstructure and composition have been obtained. Microstructure and thermomechanical properties of a silicon carbide (SCS-6) fiber reinforced reaction-formed silicon carbide matrix composites are discussed.

  3. METHOD FOR FORMING A COATING OF MOLYBDENUM CARBIDE ON A CARBON BODY

    DOEpatents

    Simnad, M.T.

    1962-04-01

    A method is described for coating a carbon bodywith molybdenum carbide in such a manner that the carbon body is rendered less permeable to the flow of gases and has increased resistance to corrosion and erosion. The method includes coating a carbon body with molybdenum trioxide by contacting it at a temperature below the condensation temperature with molybdenum trioxide vapors and thereafter carburizing the molybdenum trioxide in situ in an inert atmosphere on the carhon body. (AEC)

  4. [Effects of silicon carbide on the cure depth, hardness and compressive strength of composite resin].

    PubMed

    Wang, Ke; Lin, Yi'na; Liu, Xiaoqing

    2009-08-01

    The hardness, compressive strength and cure depth are important indices of the composite resin. This investigation was made with regard to the effects of silicon carbide on the cure depth, hardness and compressive strength of the light-curing composite resin. Different amounts of silicon carbide were added to the light-curing composite resin, which accounted for 0 wt%, 1 wt%, 0.6 wt%, 0.3 wt%, 0.1 wt%, 0.05 wt% and 0.005 wt% of the composite resin, respectively. The hardness, compressive strength and cure depth of the six afore-mentioned groups of composite resin were measured by the vernier caliper, the vickers hardness tester and the tensile strength of machine, respectively. The results showed that silicon carbide improved the hardness and compressive strength of the light-curing composite resin,when the concentration was 0.05 wt%. And the cure depth was close to that of control.

  5. Investigation of Microstructural Factors that Cause Low Fracture Toughness in Silicon Carbide Whisker/Al Alloy Composites

    DTIC Science & Technology

    1988-10-01

    TOUGHNESS IN SILICON CARBIDE WHISKER/Al ALLOY COMPOSITES oSubmittLJ to: Office of Naval Research 800 N. Quincy Street Arlington, VA 22217-5000...September 30, 1988 INVESTIGATION OF MICROSTRUCTURAL FACTORS THAT CAUSE LOW FRACTURE TOUGHNESS IN SILICON CARBIDE WHISKER/Al ALLOY COMPOSITES Submitted...Investigation of Microstructural Factors that Cause Low Fracture Toughness in Silicon Carbide Whisker/Al Alloy Composites .12 PERSONAL AUTHOR(S) F. E. Wawner

  6. Evaluation of titanium carbide metal matrix composites deposited via laser cladding

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Daniel Thomas

    Metal matrix composites have been widely studied in terms of abrasion resistance, but a particular material system may behave differently as particle size, morphology, composition, and distribution of the hardening phase varies. The purpose of this thesis was to understand the mechanical and microstructural effects of combining titanium carbide with 431 series stainless steel to create a unique composite via laser cladding, particularly regarding wear properties. The most predominant effect in increasing abrasion resistance, measured via ASTM G65, was confirmed to be volume fraction of titanium carbide addition. Macrohardness was directly proportional to the amount of carbide, though there was an overall reduction in individual particle microhardness after cladding. The reduction in particle hardness was obscured by the effect of volume fraction carbide and did not substantially contribute to the wear resistance changes. A model evaluating effective mean free path of the titanium carbide particles was created and correlated to the measured data. The model proved successful in linking theoretical mean free path to overall abrasion resistance. The effects of the titanium carbide particle distributions were limited, while differences in particle size were noticeable. The mean free path model did not correlate well with the particle size, but it was shown that the fine carbides were completely removed by the coarse abrasive particles in the ASTM G65 test. The particle morphology showed indications of influencing the wear mode, but no statistical reduction was observed in the volume loss figures. Future studies may more specifically focus on particle morphology or compositional effects of the carbide particles.

  7. Characterization of SiC (SCS-6) Fiber Reinforced Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Dickerson, Robert M.

    1995-01-01

    Silicon carbide (SCS-6) fiber reinforced-reaction formed silicon carbide matrix composites were fabricated using NASA's reaction forming process. Silicon-2 at a percent of niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bi-modal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon and silicon. Fiber push-out tests on these composites determined a debond stress of approx. 67 MPa and a frictional stress of approx. 60 MPa. A typical four point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pull out.

  8. Characterization of SiC Fiber (SCS-6) Reinforced-Reaction-Formed Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Singh, M.; Dickerson, R. M.

    1996-01-01

    Silicon carbide fiber (SCS-6) reinforced-reaction-formed silicon carbide matrix composites were fabricated using a reaction-forming process. Silicon-2 at.% niobium alloy was used as an infiltrant instead of pure silicon to reduce the amount of free silicon in the matrix after reaction forming. The matrix primarily consists of silicon carbide with a bimodal grain size distribution. Minority phases dispersed within the matrix are niobium disilicide (NbSi2), carbon, and silicon. Fiber pushout tests on these composites determined a debond stress of approximately 67 MPa and a frictional stress of approximately 60 MPa. A typical four-point flexural strength of the composite is 297 MPa (43.1 KSi). This composite shows tough behavior through fiber pullout.

  9. Composition optimization of self-lubricating chromium-carbide-based composite coatings for use to 760 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Chris; Sliney, Harold E.

    1987-01-01

    This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a ternary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760 C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.

  10. Composition optimization of self-lubricating chromium carbide-based composite coatings for use to 760 deg C

    NASA Technical Reports Server (NTRS)

    Dellacorte, C.; Sliney, H. E.

    1986-01-01

    This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a ternary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760 C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.

  11. Composition optimization of self-lubricating chromium-carbide-based composite coatings for use to 760 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Chris; Sliney, Harold E.

    1987-01-01

    This paper describes new compositions of self-lubricating coatings that contain chromium carbide. A bonded chromium carbide was used as the base stock because of the known excellent wear resistance and the chemical stability of chromium carbide. Additives were silver and barium fluoride/calcium fluoride eutectic. The coating constituents were treated as a ternary system consisting of: (1) the bonded carbide base material, (2) silver, and (3) the eutectic. A study to determine the optimum amounts of each constituent was performed. The various compositions were prepared by powder blending. The blended powders were then plasma sprayed onto superalloy substrates and diamond ground to the desired coating thickness. Friction and wear studies were performed at temperatures from 25 to 760 C in helium and hydrogen. A variety of counterface materials were evaluated with the objective of discovering a satisfactory metal/coating sliding combination for potential applications such as piston ring/cylinder liner couples for Stirling engines.

  12. Changes in the phase composition, structure, and hardness of "titanium carbide-high-carbon steel" cermets under heat treatment

    NASA Astrophysics Data System (ADS)

    Frage, N.; Kaputkina, L. M.; Prokoshkina, V. G.; Kaputkin, D. E.; Sverdlova, N. R.

    2007-03-01

    Ceramic metals obtained by pressing and sintering of briquettes from titanium carbide powders with constant compositions (stoichiometric and with carbon deficit) followed by impregnation with steels U8, U10, and U12 are studied. The effects of the compositions of the metallic binder and of titanium carbide on the processes of austenization, dissolution, and segregation of carbides, martensitic transformation, and on the hardness of the cermets after subsequent heat treatment are determined.

  13. Reactive infiltration in fabricating silicon carbide composites for electronic packaging

    NASA Astrophysics Data System (ADS)

    Xiao, Liming

    The silicon carbide (SiC) composite is a promising material to improve thermal dissipation and thermal expansion matching for electronic packaging, but its wide application has been greatly hindered by the high fabrication cost. To address this cost issue, two new reactive infiltration methods have been proposed and developed to fabricate SiC composite in a net-shape manner. They are Method 1--locally magnesium-enhanced infiltration and Method 2--globally carbon-enhanced infiltration. In Method 1, a magnesium wetting agent was strategically inserted at the interface between SiC powder and Al-Si alloy. The molten Al-Si alloy was assisted by chemical reaction to infiltrate into the porous SiC powder in an inert atmosphere sealed in a quartz tube or a steel cup. The infiltration kinetics was characterized by measuring the infiltration weight gain with respect to time. It was found that the infiltration kinetics could be divided into three stages: infiltration initiation, rapid infiltration, and slow infiltration, and most of the weight gain occurred in the rapid infiltration stage. The rapid infiltration was due to the magnesium-silicon oxide reaction and the magnesium accumulation at the infiltration front. Modeling of the infiltration kinetics showed the magnesium dilution increased the dynamic contact angle, which in turn decreased the infiltration rate. The SiC oxidation, Mg content and temperature were shown to be important factors affecting the infiltration. In Method 2, a carbon wetting agent is coated globally on every SiC particle. To accomplish this coating, a slip casting, drying, curing and carbonization process was developed. A crucibleless infiltration method was designed to fabricate SiC composites in an open atmosphere protected by nitrogen. The temperature change of SiC preform during infiltration was monitored to determine the infiltration kinetics. The silicon-carbon reaction was found to create a spontaneous infiltration of molten Si or molten Al

  14. Wear study of carbide reinforced P/M ferrous composites

    SciTech Connect

    Hawk, Jeffrey A.; Dogan, Omer N.; Wilson, Rick D.

    2000-10-01

    Ferrous alloys have been used for decades as wear resistant materials for applications where severe wear (primarily abrasion) has been a problem. Irons and steels have an advantage in these applications because they can be alloyed with various elements to create structures which are quite harder than the iron matrix. For example, martensitic matrices can be developed as well as carbide structures (consisting usually of Cr-, Nb- or V-based carbides or some other complex carbide structure). However, these materials are usually made through melt/solidification techniques which can sometimes limit the type, volume fraction, and morphology of the carbide. In P/M processing these factors can be ignored in most instances. This paper will discuss the abrasive and impact-abrasive wear behavior of one class of wear resistant materials based on TiC. The materials removal mechanisms will be discussed with emphasis on microstructure-wear interactions. The results will be compared to traditional wear resistant ferrous based alloys.

  15. The Effects of Carbide Characteristics on the Performance of Tungsten Carbide-Based Composite Overlays, Deposited by Plasma-Transferred Arc Welding

    NASA Astrophysics Data System (ADS)

    Fisher, G.; Wolfe, T.; Meszaros, K.

    2013-06-01

    In Alberta, there are huge quantities of ore processed to remove bitumen from oil sands deposits. The scale of production generates very aggressive tribocorrosive conditions during the mining, extraction, and upgrading processes. It is common to apply tungsten carbide-based composite overlays to improve the reliability and extend service lives of equipment and components. The performance of the applied overlays is largely dependent on the selection of the carbide type and the wear environment. This paper will evaluate overlays containing macrocrystalline, angular eutectic, and spherical eutectic tungsten carbides and discuss the performance of the overlays with a focus on carbide properties and the interactions between the service conditions and the composite material. This discussion will demonstrate how effective selection of protective materials can improve the reliability of oil sands equipment.

  16. Gonadotropin excretion and body composition.

    PubMed

    Penny, R; Goldstein, I P; Frasier, S D

    1978-02-01

    Urinary follicle stimulating hormone (FSH) and luteinizing hormone (LH) excretion was correlated with calculated total body water (TBW) and body fat (BF) in 140 normal girls and 142 normal boys, ages 3 to 16 years. In girls, there was a significant increase in gonadotropin excretion at the time of a significant increase in BF as a percent of body weight and decrease in TBW as a percent of body weight. Pubertal changes in body composition were seen in girls at the same chronological age and stage of puberty as increased gonadotropin excretion. Similar findings were observed in boys. Pubertal changes in body composition (an increase in TBW as a percent of body weight and decrease of BF as a percent of body weight) accompanied significantly increased gonadotropin excretion. Both developmental changes were seen at the same chronological age and stage of puberty. Our findings are consistent with the hypothesis that characteristic changes in body composition as well as the other hallmarks of puberty, including menarche in girls, result from increased gonadotropin and gonadal steroid secretion. They do not support the hypothesis that changes of body composition trigger increased hypothalamic function and hormone secretion leading to the subsequent events of puberty.

  17. Aluminum nitride-silicon carbide whisker composites: Processing, properties, and microstructural stability

    SciTech Connect

    Cross, M.T.

    1990-01-01

    Aluminum nitride -- silicon carbide whisker composites with up to 20 vol % whiskers were fabricated by pressureless sintering (1750{degree}--1800{degree}C) and by hot-pressing (1700{degree}--1800{degree}C). Silicon carbide whiskers were found to degrade depending on the type of protective powder bed used during sintering. Whiskers were found to degraded in high oxygen containing samples by reaction with sintering additives. Whisker degradation was also due to the formation of silicon carbide -- aluminum nitride solid solution. No whisker degradation was observed in hot-pressed samples. For these samples Young's modulus and fracture toughness were measured. A 33% increase in the fracture toughness was measured by the indentation technique for a 20 vol % whisker composite. Operative toughening mechanisms were investigated using scanning electron microscopy. Crack deflection and whisker bridging were the dominant mechanisms. It was also shown that load transfer from matrix to whiskers can be a contributing factor to toughening. 88 refs., 34 figs., 11 tabs.

  18. Priority compositions of boron carbide crystals obtained by self-propagating high-temperature synthesis

    SciTech Connect

    Ponomarev, V. I. Konovalikhin, S. V.; Kovalev, I. D.; Vershinnikov, V. I.

    2015-09-15

    Splitting of reflections from boron carbide has been found for the first time by an X-ray diffraction study of polycrystalline mixture of boron carbide B{sub 15–x}C{sub x}, (1.5 ≤ x ≤ 3) and its magnesium derivative C{sub 4}B{sub 25}Mg{sub 1.42}. An analysis of reflection profiles shows that this splitting is due to the presence of boron carbide phases of different compositions in the sample, which are formed during crystal growth. The composition changes from B{sub 12.9}C{sub 2.1} to B{sub 12.4}C{sub 2.6}.

  19. Silicon carbide whisker composites. (Latest citations from Engineered Materials abstracts). NewSearch

    SciTech Connect

    Not Available

    1994-11-01

    The bibliography contains citations concerning the manufacture and applications of silicon carbide whisker reinforced composites. Citations discuss the preparation of whiskers and the processing of composites containing the whiskers. Applications include aerospace engines, automotive components, engine components, and surgical implants. Physical properties such as bending strength, crack propagation, creep, fracture toughness, and stress strain curves are covered. Ceramic matrix, metal matrix, and carbon-carbon composites are examined. (Contains a minimum of 248 citations and includes a subject term index and title list.)

  20. Spray-Formed Stainless Steel Matrix Composites with Co-Injected Carbide Particles

    NASA Astrophysics Data System (ADS)

    Cui, Chengsong; Schulz, Alwin; Uhlenwinkel, Volker; Zoch, Hans-Werner

    2011-08-01

    In order to develop new types of wear-resistant and corrosion-resistant materials, TiC and VC particles were injected into martensitic stainless steel X46Cr13 during spray forming, respectively. The microstructures of the spray-formed steel matrix composites under different processing conditions were investigated. The mechanisms of interactions between the injected particles and the matrix materials during spray forming and their effects on the microstructures of the composites were discussed and clarified based on experimental and theoretical investigations. The current results show that the injected particles may penetrate into the metallic droplets or adhere to the surface of the droplets and, therefore, are incorporated into the deposits to form metal matrix composites. Substantial heat transfer from superheated metallic melts to the room temperature carbide particles takes place as they are incorporated into the matrix material. The matrix steel solidifies in the vicinity of the carbides due to their chilling effect, and thus, the carbides may be engulfed in the matrix or pushed to the grain boundaries by the solidification fronts. TiC particles essentially retain their shape and size in the steel composites, while VC particles dissolve at least partially in the matrix and reprecipitate or form new phases in the final solidification and cooling stage. The porosity in the deposits increases with the gas to melt ratio (GMR) and the powder to melt ratio (PMR) by increasing atomizing gas pressure and powder feeding rate. Carbide type also affects the porosity of the deposits, because different thermodynamic properties of carbides change the heat dissipation and local solidification behavior of the mixture of matrix material and dissolved carbides. Moreover, the microstructure of the matrix material X46Cr13 is refined considerably with increasing GMR and PMR.

  1. Aluminum-titanium hydride-boron carbide composite provides lightweight neutron shield material

    NASA Technical Reports Server (NTRS)

    Poindexter, A. M.

    1967-01-01

    Inexpensive lightweight neutron shield material has high strength and ductility and withstands high internal heat generation rates without excessive thermal stress. This composite material combines structural and thermal properties of aluminum, neutron moderating properties of titanium hydride, and neutron absorbing characteristics of boron carbide.

  2. Processing and microstructure of silicon carbide fiber-reinforced silicon carbide composite by hot-pressing

    NASA Astrophysics Data System (ADS)

    Yoshida, Katsumi; Budiyanto; Imai, Masamitsu; Yano, Toyohiko

    1998-10-01

    Continuous 2D woven fiber-reinforced SiC composites were fabricated by hot-pressing in Ar at 1750°C under a pressure of 40 MPa using Al-B-C or Al 2O 3-Y 2O 3-CaO system as sintering additives. In this study, fracture behavior and microstructure of the composites fabricated by this process were investigated. These composites achieved nearly full density in both cases. In the case of the composite with Al-B-C additives, the load-displacement behavior of the composite with non-coated Hi-Nicalon cloths showed completely brittle fracture, whereas that of the composite with BN-coated Hi-Nicalon cloths showed ductile fracture with a lot of fiber pull-out. On the contrary, in the case of the composite with Al 2O 3-Y 2O 3-CaO additives, the load-displacement behavior of the composite with non-coated Hi-Nicalon cloths showed slight ductile fracture with small tails, whereas that of the composite with BN-coated Hi-Nicalon cloths showed completely brittle fracture.

  3. Body composition in multiple sclerosis

    PubMed Central

    Dionyssiotis, Y

    2013-01-01

    Multiple sclerosis affects central nervous system leading to disability. Among other complications the deterioration of body composition is usually neglected and increases the risk for diseases such as coronary heart disease, non-insulin dependent diabetes mellitus, lipid abnormalities and bone loss leading to fractures in this population. Body mass index values, the effect of spasticity, the increased number of drugs used and the relationship between skeletal muscle and bone which interacts with impaired motor function leading to body composition alterations in multiple sclerosis are reviewed. PMID:23935336

  4. Microstructure and Wear Behavior of High-Cr WCI Matrix Surface Composite Reinforced with Cemented Carbide Rods

    NASA Astrophysics Data System (ADS)

    Hou, Shuzeng; Bao, Chonggao; Zhang, Zhiyun; Bai, Yaping

    2013-07-01

    The present article reports a new superior wear resistance surface composite prepared by a vacuum evaporative pattern casting-in process. This surface composite was constructed with reinforcing cemented carbide rod (CCR) array within high-Cr white cast iron (WCI) matrix. Three reaction zones that formed around the CCRs were characterized and established the good metallurgical bonding between CCRs and matrix. In addition, some compound carbide containing Fe, Cr, W, and Co elements were formed in the reaction zones, owing to the partial dissolution of the CCRs and the resulting interdiffusion of elements such as W, Co, C, Fe, and Cr. The wear behavior of the composite was evaluated and compared with unreinforced high-Cr WCI by means of a three-body abrasive wear tester. The results showed that the wear resistance of the composite was significantly higher than that of the unreinforced high-Cr WCI. The exciting wear resistance can be ascribed to protective effect introduced by the CCRs during wear process and the good metallurgical bonding between CCRs and matrix.

  5. Scalable and Tunable Carbide-Phosphide Composite Catalyst System for the Thermochemical Conversion of Biomass

    DOE PAGES

    Regmi, Yagya; Rogers, Bridget; Labbe, Nicole; ...

    2017-07-13

    We have prepared composite materials of hexagonal nickel phosphide and molybdenum carbide (Mo2C) utilizing a simple and scalable two-stage synthesis method comprised of carbothermic reduction followed by hydrothermal incubation. We observe the monophasic hexagonal phosphide Ni2P in the composite at low phosphide-to-carbide (P:C) ratios. Upon increasing the proportion of P:C, the carbide surface becomes saturated, and we detect the emergence of a second hexagonal nickel phosphide phase (Ni5P4) upon annealing. We demonstrate that vapor-phase upgrading (VPU) of whole biomass via catalytic fast pyrolysis is achievable using the composite material as a catalyst, and we monitor the resulting product slates usingmore » pyrolysis gas chromatography/mass spectrometry. Our analysis of the product vapors indicates that variation of the P:C molar ratio in the composite material affords product slates of varying complexity and composition, which is indicated by the number of products and their relative proportions in the product slate. Our results demonstrate that targeted vapor product composition can be obtained, which can potentially be utilized to tune the composition of the bio-oil downstream.« less

  6. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1991-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  7. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOEpatents

    Tiegs, T.N.; Lindemer, T.B.

    1991-02-19

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  8. Metallurgical and tensile property analysis of several silicon carbide/titanium composite systems

    NASA Technical Reports Server (NTRS)

    Brewer, W. D.; Unnam, J.

    1983-01-01

    Several silicon-carbide fiber reinforced titanium matrix composite systems were investigated to determine composite degradation mechanisms and to develop techniques to minimize loss of mechanical properties during fabrication and in service. Emphasis was on interface control by fiber or matrix coatings. Fibers and matrix materials were sputter coated with various metals to determine the effects of the coatings on basic fiber properties, fiber-matrix interactions, and on composite properties. The effects of limited variations in fabrication temperature on composite properties were determined for composites consolidated by standard press-diffusion-bonding techniques.

  9. Joining and Assembly of Silicon Carbide-based Advanced Ceramics and Composites for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Singh, M.

    2004-01-01

    Silicon carbide based advanced ceramics and fiber reinforced composites are under active consideration for use in wide variety of high temperature applications within the aeronautics, space transportation, energy, and nuclear industries. The engineering designs of ceramic and composite component require fabrication and manufacturing of large and complex shaped parts of various thicknesses. In many instances, it is more economical to build up complex shapes by joining simple geometrical shapes. In addition these components have to be joined or assembled with metallic sub-components. Thus, joining and attachment have been recognized as enabling technologies for successful utilization of ceramic components in various demanding applications. In this presentation, various challenges and opportunities in design, fabrication, and testing o high temperature joints in ceramic matrix composites will be presented. Silicon carbide based advanced ceramics (CVD and hot pressed), and C/SiC and SiC/SiC composites, in different shapes and sizes, have been joined using an affordable, robust ceramic joining technology (ARCJoinT). Microstructure and high temperature mechanical properties of joints in silicon carbide ceramics and CVI and melt infiltrated SiC matrix composites will,be reported. Various joint design philosophies and design issues in joining of ceramics and composites well be discussed.

  10. The utilization of composite carbon-silicon carbide sidewall blocks in cathodes

    SciTech Connect

    Curtis, E.L.; Mascieri, P.D.; Tabereaux, A.T.

    1996-10-01

    A new composite sidewall block SILCARB, consisting of a calcined anthracite carbon glued to a nitride-bonded silicon carbide, has performed well to date in the cathode sidewall lining of five 180 kA prebake reduction cells. The applications of the new sidewall composite material are to resist oxidation and/or erosion in the sidewalls caused by an active metal pad or the oxidation of materials during cell operations. In this instance, the composite material was used as a substitute for the conventional prebake anthracite sidewall block. The goals will be to increase the potlife of cells currently operating with conventional carbon sidewalls, or alternatively offer excellent cost savings while maintaining the desired operational results in cells using full size silicon carbide bricks. Sidewall shell temperature and frozen ledge profiles of cells with SILCARB sidewall blocks are compared with cells having conventional anthracite carbon block sidewall lining.

  11. Controlled release of indomethacin from alginate-poloxamer-silicon carbide composites decrease in-vitro inflammation.

    PubMed

    Díaz-Rodríguez, P; Landin, M

    2015-03-01

    Composites of biomorphic silicon carbides (bioSiCs) and hydrogels are proposed in order to obtain materials able to load and release poor soluble drugs with application in bone pathologies therapy. Hydrogels composed by alginate and poloxamer were loaded with indomethacin, incorporated into the ceramics and crosslinked. The indomethacin release profile is dependent on the microstructure of the bioSiC selected. The loaded oak and sapelli bioSiCs composites have adequate release profiles to promote the decreasing of the secretion of pro-inflammatory cytokines in LPS stimulated macrophages, showing stronger anti-inflammatory effects than pine bioSiC composites. The released indomethacin is able to modulate the degradation of chondrocytes extracellular matrix and promote the formation of new collagen by osteoarthritic chondrocytes. Particles derived from mechanical wear of biomorphic silicon carbides do not show high toxicity, being similar to the zirconia particles. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. High Temperature Joining and Characterization of Joint Properties in Silicon Carbide-Based Composite Materials

    NASA Technical Reports Server (NTRS)

    Halbig, Michael C.; Singh, Mrityunjay

    2015-01-01

    Advanced silicon carbide-based ceramics and composites are being developed for a wide variety of high temperature extreme environment applications. Robust high temperature joining and integration technologies are enabling for the fabrication and manufacturing of large and complex shaped components. The development of a new joining approach called SET (Single-step Elevated Temperature) joining will be described along with the overview of previously developed joining approaches including high temperature brazing, ARCJoinT (Affordable, Robust Ceramic Joining Technology), diffusion bonding, and REABOND (Refractory Eutectic Assisted Bonding). Unlike other approaches, SET joining does not have any lower temperature phases and will therefore have a use temperature above 1315C. Optimization of the composition for full conversion to silicon carbide will be discussed. The goal is to find a composition with no remaining carbon or free silicon. Green tape interlayers were developed for joining. Microstructural analysis and preliminary mechanical tests of the joints will be presented.

  13. Thermal expansion of laminated, woven, continuous ceramic fiber/chemical-vapor-infiltrated silicon carbide matrix composites

    NASA Technical Reports Server (NTRS)

    Eckel, Andrew J.; Bradt, Richard C.

    1990-01-01

    Thermal expansions of three two-dimensional laminate, continuous fiber/chemical-vapor-infiltrated silicon carbide matrix composites reinforced with either FP-Alumina (alumina), Nextel (mullite), or Nicalon (Si-C-O-N) fibers are reported. Experimental thermal expansion coefficients parallel to a primary fiber orientation were comparable to values calculated by the conventional rule-of-mixtures formula, except for the alumina fiber composite. Hysteresis effects were also observed during repeated thermal cycling of that composite. Those features were attributed to reoccurring fiber/matrix separation related to the micromechanical stresses generated during temperature changes and caused by the large thermal expansion mismatch between the alumina fibers and the silicon carbide matrix.

  14. Magnetic composites based on metallic nickel and molybdenum carbide: a potential material for pollutants removal.

    PubMed

    Mambrini, Raquel V; Fonseca, Thales L; Dias, Anderson; Oliveira, Luiz C A; Araujo, Maria Helena; Moura, Flávia C C

    2012-11-30

    New magnetic composites based on metallic nickel and molybdenum carbide, Ni/Mo(2)C, have been produced via catalytic chemical vapor deposition from ethanol. Scanning electron microscopy, thermal analysis, Raman spectroscopy and X-ray diffraction studies suggest that the CVD process occurs in a single step. This process involves the reduction of NiMo oxides at different temperatures (700, 800 and 900°C) with catalytic deposition of carbon from ethanol producing molybdenum carbide on Ni surface. In the absence of molybdenum the formation of Ni/C was observed. The magnetic molybdenum carbide was successfully used as pollutants removal by adsorption of sulfur and nitrogen compounds from liquid fuels and model dyes such as methylene blue and indigo carmine. The dibenzothiofene adsorption process over Ni/Mo(2)C reached approximately 20 mg g(-1), notably higher than other materials described in the literature and also removed almost all methylene blue dye. The great advantage of these carbide composites is that they may be easily recovered magnetically and reused.

  15. Current body composition measurement techniques.

    PubMed

    Lemos, Thaisa; Gallagher, Dympna

    2017-10-01

    The current article reviews the most innovative and precise, available methods for quantification of in-vivo human body composition. Body composition measurement methods are continuously being perfected. Ongoing efforts involve multisegmental and multifrequency bioelectrical impedance analysis, quantitative magnetic resonance for total body water, fat, and lean tissue measurements, imaging to further define ectopic fat depots. Available techniques allow for the measurement of fat, fat-free mass, bone mineral content, total body water, extracellular water, total adipose tissue and its subdepots (visceral, subcutaneous, and intermuscular), skeletal muscle, select organs, and ectopic fat depots. There is an ongoing need for methods that yield information on metabolic and biological functions. Based on the wide range of measurable properties, analytical methods and known body composition models, clinicians, and scientists can quantify a number of body components and with longitudinal assessment, can track changes in health and disease with implications for understanding efficacy of nutritional and clinical interventions, diagnosis, prevention, and treatment in clinical settings. With the greater need to understand precursors of health risk beginning prior to conception, a gap exists in appropriate in-vivo measurement methods with application beginning during gestation, that is, fetal development.

  16. Body Composition. A Round Table.

    ERIC Educational Resources Information Center

    Physician and Sportsmedicine, 1986

    1986-01-01

    Four experts discuss body composition, what it is, why it is assessed, how it is measured, and how to measure it in children and the aged. Standards of fatness, both overfat and underfat, and bone and muscle assessment are covered in the discussion. (MT)

  17. Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

    NASA Astrophysics Data System (ADS)

    Ambrosio, E. P.; Abdul Karim, M. R.; Pavese, M.; Biamino, S.; Badini, C.; Fino, P.

    2017-02-01

    Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

  18. Feasibility of Electrochemical Deposition of Nickel/Silicon Carbide Fibers Composites over Nickel Superalloys

    NASA Astrophysics Data System (ADS)

    Ambrosio, E. P.; Abdul Karim, M. R.; Pavese, M.; Biamino, S.; Badini, C.; Fino, P.

    2017-05-01

    Nickel superalloys are typical materials used for the hot parts of engines in aircraft and space vehicles. They are very important in this field as they offer high-temperature mechanical strength together with a good resistance to oxidation and corrosion. Due to high-temperature buckling phenomena, reinforcement of the nickel superalloy might be needed to increase stiffness. For this reason, it was thought to investigate the possibility of producing composite materials that might improve properties of the metal at high temperature. The composite material was produced by using electrochemical deposition method in which a composite with nickel matrix and long silicon carbide fibers was deposited over the nickel superalloy. The substrate was Inconel 718, and monofilament continuous silicon carbide fibers were chosen as reinforcement. Chemical compatibility was studied between Inconel 718 and the reinforcing fibers, with fibers both in an uncoated condition, and coated with carbon or carbon/titanium diboride. Both theoretical calculations and experiments were conducted, which suggested the use of a carbon coating over the fibers and a buffer layer of nickel to avoid unwanted reactions between the substrate and silicon carbide. Deposition was then performed, and this demonstrated the practical feasibility of the process. Yield strength was measured to detect the onset of interface debonding between the substrate and the composite layer.

  19. CVD of silicon carbide on structural fibers - Microstructure and composition

    NASA Technical Reports Server (NTRS)

    Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

    1992-01-01

    Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

  20. CVD of silicon carbide on structural fibers: Microstructure and composition

    NASA Technical Reports Server (NTRS)

    Veitch, Lisa C.; Terepka, Francis M.; Gokoglu, Suleyman A.

    1992-01-01

    Structural fibers are currently being considered as reinforcements for intermetallic and ceramic materials. Some of these fibers, however, are easily degraded in a high temperature oxidative environment. Therefore, coatings are needed to protect the fibers from environmental attack. Silicon carbide (SiC) was chemically vapor deposited (CVD) on Textron's SCS6 fibers. Fiber temperatures ranging from 1350 to 1500 C were studied. Silane (SiH4) and propane (C2H8) were used for the source gases and different concentrations of these source gases were studied. Deposition rates were determined for each group of fibers at different temperatures. Less variation in deposition rates were observed for the dilute source gas experiments than the concentrated source gas experiments. A careful analysis was performed on the stoichiometry of the CVD SiC coating using electron microprobe. Microstructures for the different conditions were compared. At 1350 C, the microstructures were similar; however, at higher temperatures, the microstructure for the more concentrated source gas group were porous and columnar in comparison to the cross sections taken from the same area for the dilute source gas group.

  1. Stress-Corrosion Cracking of Silicon Carbide Fiber/Silicon Carbide Composites

    SciTech Connect

    Jones, Russell H.; Henager, Charles H.; Lewinsohn, Charles A.; Windisch, Charles F.

    2000-08-01

    Ceramic matrix composites are being developed to operate at elevated temperatures and in oxidizing environments. Considerable improvements are being made in the creep resistance of SiC fibers and hence in the high-temperature properties of SiCf/SiC composites; however, more needs to be known about the stability of these materials in oxidizing environments before they will be widely accepted. Experimental weight change (1,2) and crack growth data (3,4) supports the conclusion that O2 enhanced crack growth of SiCf/SiC occurs by more than one mechanism depending on the experimental conditions. This data suggests an oxidation embrittlement mechanism (OEM) at temperatures below 1373?K and high O2 pressures and an interphase removal mechanism (IRM) at temperatures of about 700?K and above and low O2 pressures. The OEM, as proposed by Evans et al. (3), results from the reaction of O2 with SiC to form a glass layer on the fiber or within the fiber-matrix interphase region. The fracture stress of the fiber is reduced if this layer is thicker than a critical value (d>dc) and the temperature is below a critical value (TTg for d>dc. This paper summarizes the evidence for the existence of these two mechanisms and attempts to define the conditions for their operation.

  2. Evolution of Morphology and Composition of the Carbides in Cr-Mo-V Steel after Service Exposure

    NASA Astrophysics Data System (ADS)

    Dong, Jiling; Shin, Keesam; He, Yinsheng; Song, Geewook; Jung, Jinesung

    2011-06-01

    Low alloy Cr-Mo-V steels are usually used in steam power generation units. The evolution of the carbides often leads to embrittlement of the components during elongated service. Therefore, the determination of carbide evolution mechanism during long-time service is important to understand and prevent premature failures such as temper embrittlement. In this study, low alloy Cr-Mo-V steels used as main steam pipes in a thermal power plant were studied after various service times as well as in the as-fabricated condition. Electron microscopic analyses were carried out on extraction replicas to observe and analyze the morphology and composition of the carbides. Predominant plate-like vanadium-rich carbides were observed in the as-fabricated condition. When exposed to on-site service, the V-rich carbides transformed to Mo-rich carbides which have a typical H morphology. The change of morphology and composition of the carbide is mainly due to the gradual depletion of Mo from the solid solution. In addition, a non-destructive carbide extraction method was established for examination of the precipitates in the working turbine rotor.

  3. Synthesis and Characterization of In-situ Copper-Niobium Carbide Composite

    SciTech Connect

    Zuhailawati, H.; Othman, R.; Bui, D. L.; Umemoto, M

    2008-03-17

    In this work, synthesis of copper matrix composite powder reinforced by in situ niobium carbide particle was prepared by mechanical alloying of elemental powder and subsequent heat treatment. Elemental powders of Cu-Nb-C correspond to Cu-40wt%Nb-10%wtC composition was milled for 54 hours at room temperature in a planetary ball mill. The effect of heat treatment temperature on the formation of niobium carbide was analyzed. Characterization by X-ray diffraction was done on the milled powder and heat-treated powder in order to investigate NbC formation. Results indicate that NbC began to precipitate after mechanical alloying for about 54h with heat treatment temperature of 900 deg. C and 1000 deg. C.

  4. Synthesis and Characterization of In-situ Copper-Niobium Carbide Composite

    NASA Astrophysics Data System (ADS)

    Zuhailawati, H.; Othman, R.; Bui, D. L.; Umemoto, M.

    2008-03-01

    In this work, synthesis of copper matrix composite powder reinforced by in situ niobium carbide particle was prepared by mechanical alloying of elemental powder and subsequent heat treatment. Elemental powders of Cu-Nb-C correspond to Cu-40wt%Nb-10%wtC composition was milled for 54 hours at room temperature in a planetary ball mill. The effect of heat treatment temperature on the formation of niobium carbide was analyzed. Characterization by X-ray diffraction was done on the milled powder and heat-treated powder in order to investigate NbC formation. Results indicate that NbC began to precipitate after mechanical alloying for about 54h with heat treatment temperature of 900 °C and 1000 °C.

  5. Silicon carbide whisker composites. (Latest citations from Engineered Materials abstracts). Published Search

    SciTech Connect

    1996-02-01

    The bibliography contains citations concerning the manufacture and applications of silicon carbide whisker reinforced composites. Citations discuss the preparation of whiskers and the processing of composites containing the whiskers. Applications include aerospace engines, automotive components, engine components, and surgical implants. Physical properties such as bending strength, crack propagation, creep, fracture toughness, and stress strain curves are covered. Ceramic matrix, metal matrix, and carbon-carbon composites are examined. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  6. Factors Controlling Elevated Temperature Strength Degradation of Silicon Carbide Composites

    NASA Technical Reports Server (NTRS)

    2005-01-01

    For 5 years, the cooperative agreement NCC3-763 has focused on the development and understanding of Sic-based composites. Most of the work was performed in the area of SiC fiber-reinforced composites for UEET and NGLT and in collaboration with Goodrich Corporation under a partially reimbursable Space Act Agreement. A smaller amount of work was performed on C fiber-reinforced SiC matrix composites for NGLT. Major accomplishments during this agreement included: Improvements to the interphase used in melt-infiltrated (MI) SiC/SiC composites which increases the life under stressed-oxidation at intermediate temperatures referred to as "outside-debonding". This concept is currently in the patent process and received a Space Act Award. Mechanistic-based models of intermediate temperature degradation for MI SiC/SiC Quantification and relatively robust relationships for matrix crack evolution under stress in SiC/SiC composites which serve as the basis for stress-strain and elevated temperature life models The furthering of acoustic emission as a useful tool in composite damage evolution and the extension of the technique to other composite systems Development of hybrid C-SiC fiber-reinforced SiC matrix composites Numerous presentations at conferences, industry partners, and government centers and publications in recognized proceedings and journals. Other recognition of the author's accomplishments by NASA with a TGIR award (2004), NASA's Medal for Public Service (2004), and The American Ceramic Society s Richard M. Fulrath Award (2005). The following will briefly describe the work of the past five years in the three areas of interest: SiC/SiC composite development, mechanistic understanding and modeling of SiC/SiC composites, and environmental durability of C/SiC composites. More detail can be found in the publications cited at the end of this report.

  7. Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

    NASA Technical Reports Server (NTRS)

    Steibel, James D. (Inventor); Corman, Gregory S. (Inventor); Schikner, Robert C. (Inventor); Szweda, Andrew (Inventor)

    2001-01-01

    Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.

  8. Article and method for making complex shaped preform and silicon carbide composite by melt infiltration

    NASA Technical Reports Server (NTRS)

    Steibel, James D. (Inventor); Corman, Gregory S. (Inventor); Schikner, Robert C. (Inventor); Szweda, Andrew (Inventor)

    2000-01-01

    Small diameter silicon carbide-containing fibers are provided in a bundle such as a fiber tow that can be formed into a structure where the radii of curvature is not limited to 10-20 inches. An aspect of this invention is directed to impregnating the bundles of fibers with the slurry composition to substantially coat the outside surface of an individual fiber within the bundle and to form a complex shaped preform with a mass of continuous fibers.

  9. Development of a reaction-sintered silicon carbide matrix composite

    NASA Astrophysics Data System (ADS)

    Sayano, A.; Sutoh, C.; Suyama, S.; Itoh, Y.; Nakagawa, S.

    SiC matrix composites reinforced with continuous SiC-based fibres using reaction sintering (RS) for matrix processing were produced and their mechanical and physical properties were studied. Mechanical behaviour of SiCf/SiC (RS) composites in tension and in flexure exhibits improved toughness and a non-catastrophic failure due to fibre crack bridging and pullout from the matrix, and the composites exhibit high thermal conductivity, high Young's modulus and reduced porosity. Moreover, SiCf/SiC (RS) composites showed improved thermal shock resistance in comparison to monolithic RS-SiC. SiC matrix processing by RS leads to reduced production times and lower costs when compared with other methods such as polymer impregnation and pyrolysis (PIP) or chemical vapour infiltration (CVI). Composite prototypes were also produced for feasibility demonstration, and it was verified that the method could be applied to produce large parts and complex shapes.

  10. Microstructural and mechanical characterization of hybrid aluminum matrix composite containing boron carbide and Al-Cu-Fe quasicrystals

    NASA Astrophysics Data System (ADS)

    Khan, Mahmood; Zulfaqar, Muhammad; Ali, Fahad; Subhani, Tayyab

    2017-07-01

    Hybrid aluminum matrix composites containing particles of boron carbide and quasicrystals were manufactured to explore the combined effect of reinforcements on microstructural evolution and mechanical performance of the composites. The particles were incorporated at a loading of 6 wt% each making a total of 12 wt% reinforcement in pure aluminum. For comparison, two composites containing individually reinforced 12 wt% particles were also prepared along with a reference specimen of pure aluminum. Ball milling technique was employed to mix the composite constituents. The green bodies of composite powders were prepared by uniaxial pressing at room temperature followed by consolidation by pressureless sintering under inert atmosphere. The microstructural characterization was performed using scanning electron microscopy while phase identification was carried out by X-ray diffraction. The mechanical characterization was performed by Vickers hardness and compression tests. Hybrid composites showed increased compressive properties while the composites containing solely quasicrystals demonstrated improved hardness. The increase in mechanical performance was related to the microstructural evolution due to the presence and uniform dispersion of binary particles.

  11. Thermal cycling of silicon carbide whisker/aluminum alloy composite

    SciTech Connect

    Patterson, W.G.

    1988-01-01

    There are many aspects of the mechanical behavior of whisker reinforced alloys that are not well understood. The effects of thermal fatigue, for example, have been extensively studied for continuous-fiber composites but not for whisker composites. A model was developed here for thermal-fatigue damage in whisker-reinforced metal-matrix composites, taking into account both metallurgical transformations and thermal-stress damage. Also, thermal-cycling tests were performed on 2124-T6 aluminum alloy reinforced with a 15% volume fraction of SiC whiskers. The microstructure and mechanical properties of the composite were evaluate before and thermal cycling. Unlike metal-matrix composites with continuous fibers, the only thermal-stress damage sustained by SiC{sub w}/Al were changes in dimensions as large as 7.4%. There were no indications of matrix or fiber cracking, void formation, interfacial debonding, or concentrated plastic flow. Thermal-stress deformation appears to have been balanced by recovery and recrystallization. The effects of thermal cycling on composite strength were determined to be primarily due to overaging of matrix precipitates. The whiskers accelerated overaging, and may have increased the extent to which overaging could occur.

  12. Silicon carbide whisker reinforced composites and method for making same

    DOEpatents

    Wei, G.C.

    1984-02-09

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties, especially increased fracture toughness. In the formation of these ceramic composites, the single-crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al/sub 2/O/sub 3/, mullite, or B/sub 4/C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600 to 1950/sup 0/C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m/sup 1/2/ which represents as much as a two-fold increase over that of the matrix material.

  13. Dry Sliding Wear behaviour of Aluminium-Red mud- Tungsten Carbide Hybrid metal matrix composites

    NASA Astrophysics Data System (ADS)

    Devi Chinta, Neelima; Selvaraj, N.; Mahesh, V.

    2016-09-01

    Red mud is an industrial waste obtained during the processing of alumina by Bayer's process. An attempt has been made to utilize the solid waste by using it as the reinforcement material in metal matrix composites. Red mud received from NALCO has been subjected for sieve analysis and milled to 42 nanometers using high energy ball mill. Red mud is used as a reinforcement material in Pure Aluminium matrix composite at 2%, 4%, and 6% weight at 100 microns level as well as 42 nano meters along with 4%Tungsten carbide by weight. Micro and Nano structured red mud powders, Tungsten carbide powder and Aluminium is mixed in a V-Blender, compacted at a pressure of 40 bar and samples are prepared by conventional sintering with vacuum as medium. In this current work, dry sliding wear characteristics at normal and heat treatment conditions are investigated with optimal combination of Aluminium, Tungsten carbide and different weight fractions of micro and nano structured red mud powder.

  14. Modified Process For Formation Of Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Behrendt, Donald R.; Singh, Mrityunjay

    1996-01-01

    Modified version of process for making SiC-fiber/SiC-matrix composite material reduces damage to SiC (SCS-6) fibers and to carbon-rich coatings on fibers. Modification consists of addition of second polymer-infiltration-and-pyrolysis step to increase carbon content of porous matrix before infiltration with liquid silicon or silicon alloy.

  15. Isotopic Composition of Barium in Single Presolar Silicon Carbide Grains

    NASA Technical Reports Server (NTRS)

    Savina, M. R.; Tripa, C. E.; Pellin, M. J.; Davis, A. M.; Clayton, R. N.; Lewis, R. S.; Amari, S.

    2002-01-01

    We have measured Ba isotope distributions in individual presolar SiC grains. We find that the Ba isotopic composition in mainstream SiC grains is consistent with models of nucleosynthesis in low to intermediate mass asymptotic giant branch (AGB) stars. Additional information is contained in the original extended abstract.

  16. Modified Process For Formation Of Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Behrendt, Donald R.; Singh, Mrityunjay

    1996-01-01

    Modified version of process for making SiC-fiber/SiC-matrix composite material reduces damage to SiC (SCS-6) fibers and to carbon-rich coatings on fibers. Modification consists of addition of second polymer-infiltration-and-pyrolysis step to increase carbon content of porous matrix before infiltration with liquid silicon or silicon alloy.

  17. Isotopic Composition of Barium in Single Presolar Silicon Carbide Grains

    NASA Technical Reports Server (NTRS)

    Savina, M. R.; Tripa, C. E.; Pellin, M. J.; Davis, A. M.; Clayton, R. N.; Lewis, R. S.; Amari, S.

    2002-01-01

    We have measured Ba isotope distributions in individual presolar SiC grains. We find that the Ba isotopic composition in mainstream SiC grains is consistent with models of nucleosynthesis in low to intermediate mass asymptotic giant branch (AGB) stars. Additional information is contained in the original extended abstract.

  18. Microstructure and orientation effects on properties of discontinuous silicon carbide/aluminum composites

    NASA Technical Reports Server (NTRS)

    Mcdanels, D. L.; Hoffman, C. A.

    1984-01-01

    Composite panels containing up to 40 vol % discontinuous silicon carbide SiC whisker, nodule, or particulate reinforcement in several aluminum matrices are commercially fabricated and the mechanical properties and microstructual characteristics are evaluated. The yield and tensile strengths and the ductility are controlled primarily by the matrix alloy, the temper condition, and the reinforcement content. Particulate and nodule reinforcements are as effective as whisker reinforcement. Increased ductility is attributed to purer, more uniform starting materials and to more mechanical working during fabrication. Comparing mechanical properties with those of other aluminum alloys shows that these low cost, lightweight composites demonstrate very good potential for application to aerospace structures.

  19. Formation mechanism of a silicon carbide coating for a reinforced carbon-carbon composite

    NASA Technical Reports Server (NTRS)

    Rogers, D. C.; Shuford, D. M.; Mueller, J. I.

    1975-01-01

    Results are presented for a study to determine the mechanisms involved in a high-temperature pack cementation process which provides a silicon carbide coating on a carbon-carbon composite. The process and materials used are physically and chemically analyzed. Possible reactions are evaluated using the results of these analytical data. The coating is believed to develop in two stages. The first is a liquid controlled phase process in which silicon carbide is formed due to reactions between molten silicon metal and the carbon. The second stage is a vapor transport controlled reaction in which silicon vapors react with the carbon. There is very little volume change associated with the coating process. The original thickness changes by less than 0.7%. This indicates that the coating process is one of reactive penetration. The coating thickness can be increased or decreased by varying the furnace cycle process time and/or temperature to provide a wide range of coating thicknesses.

  20. Carbide/Fluoride/Silver Self-Lubricating Composite

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1987-01-01

    Bearing coatings survive at operating temperatures up to 870 degrees C. PS200 composite self-lubricating coating for bearing applications operating at temperatures above failure points of traditional solid lubricants. Excellent friction and wear performance in oxidizing atmospheres up to 1,600 degrees F and reducing atmospheres up to 1,400 degrees F. Performance needed for development of advanced heat engines as adiabatic diesel and Stirling engine.

  1. Carbide/Fluoride/Silver Self-Lubricating Composite

    NASA Technical Reports Server (NTRS)

    Sliney, Harold E.

    1987-01-01

    Bearing coatings survive at operating temperatures up to 870 degrees C. PS200 composite self-lubricating coating for bearing applications operating at temperatures above failure points of traditional solid lubricants. Excellent friction and wear performance in oxidizing atmospheres up to 1,600 degrees F and reducing atmospheres up to 1,400 degrees F. Performance needed for development of advanced heat engines as adiabatic diesel and Stirling engine.

  2. Carbide Coatings for Nickel Alloys, Graphite and Carbon/Carbon Composites to be used in Fluoride Salt Valves

    SciTech Connect

    Nagle, Denis; Zhang, Dajie

    2015-10-22

    The focus of this research was concerned with developing materials technology that supports the evolution of Generation IV Advanced High Temperature Reactor (AHTR) concepts. Specifically, we investigate refractory carbide coatings for 1) nickel alloys, and 2) commercial carbon-carbon composites (CCCs). Numerous compelling reasons have driven us to focus on carbon and carbide materials. First, unlike metals, the strength and modulus of CCCs increase with rising temperature. Secondly, graphite and carbon composites have been proven effective for resisting highly corrosive fluoride melts such as molten cryolite [Na₃AlF₆] at ~1000°C in aluminum reduction cells. Thirdly, graphite and carbide materials exhibit extraordinary radiation damage tolerance and stability up to 2000°C. Finally, carbides are thermodynamically more stable in liquid fluoride salt than the corresponding metals (i.e. Cr and Zr) found in nickel based alloys.

  3. Lightweight graphene nanoplatelet/boron carbide composite with high EMI shielding effectiveness

    SciTech Connect

    Tan, Yongqiang; Luo, Heng; Zhang, Haibin E-mail: pengshuming@caep.cn; Zhou, Xiaosong; Peng, Shuming E-mail: pengshuming@caep.cn

    2016-03-15

    Lightweight graphene nanoplatelet (GNP)/boron carbide (B{sub 4}C) composites were prepared and the effect of GNPs loading on the electromagnetic interference (EMI) shielding effectiveness (SE) has been evaluated in the X-band frequency range. Results have shown that the EMI SE of GNP/B{sub 4}C composite increases with increasing the GNPs loading. An EMI SE as high as 37 ∼ 39 dB has been achieved in composite with 5 vol% GNPs. The high EMI SE is mainly attributed to the high electrical conductivity, high dielectric loss as well as multiple reflections by aligned GNPs inside the composite. The GNP/B{sub 4}C composite is demonstrated to be promising candidate of high-temperature microwave EMI shielding material.

  4. Enhanced thermal conductivity of epoxy composites filled with silicon carbide nanowires.

    PubMed

    Shen, Dianyu; Zhan, Zhaolin; Liu, Zhiduo; Cao, Yong; Zhou, Li; Liu, Yuanli; Dai, Wen; Nishimura, Kazuhito; Li, Chaoyang; Lin, Cheng-Te; Jiang, Nan; Yu, Jinhong

    2017-06-01

    In this study, we report a facile approach to fabricate epoxy composite incorporated with silicon carbide nanowires (SiC NWs). The thermal conductivity of epoxy/SiC NWs composites was thoroughly investigated. The thermal conductivity of epoxy/SiC NWs composites with 3.0 wt% filler reached 0.449 Wm(-1) K(-1), approximately a 106% enhancement as compared to neat epoxy. In contrast, the same mass fraction of silicon carbide micron particles (SiC MPs) incorporated into epoxy matrix showed less improvement on thermal conduction properties. This is attributed to the formation of effective heat conduction pathways among SiC NWs as well as a strong interaction between the nanowires and epoxy matrix. In addition, the thermal properties of epoxy/SiC NWs composites were also improved. These results demonstrate that we developed a novel approach to enhance the thermal conductivity of the polymer composites which meet the requirement for the rapid development of the electronic devices.

  5. Silicon carbide composite for light water reactor fuel assembly applications

    NASA Astrophysics Data System (ADS)

    Yueh, Ken; Terrani, Kurt A.

    2014-05-01

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

  6. Superficial roughness on composite surface, composite enamel and composite dentin junctions after different finishing and polishing procedures. Part I: roughness after treatments with tungsten carbide vs diamond burs.

    PubMed

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The aim of this study is to investigate different instruments for finishing composite restorations, as well as examining different surfaces and interfaces of the same restoration. The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations finishing between tungsten carbide and diamond burs, furthermore the null hypothesis is that there are no significant differences on roughness between finishing on composite surfaces (C), compositeenamel (CE) and composite-dentin (CD) interfaces. The study was performed on 28 teeth, and class V cavities were prepared on the extracted teeth. Restorations were done in Filtek XTE nanofilled composite (3M Espe) in a standardized method, to then be finished. A comparison was made in the phase 1 between tungsten carbide burs (16 blades), diamond burs (46 μm), with a similar shape by the same manufacturer (Komet). Each surface received 5 bur applications. Consequently, an analysis with a profilometer was performed. Phase 2 involved further confrontation of ulterior finishing with ultrafine tungsten carbide burs (30 blades) and with extra and ultrafine diamond burs (25 and 8 μm) (the same shape as previously mentioned). A second analysis was then performed with a profilometer. All measurements were taken on C surfaces, CE and CD interfaces. Statistical analyses were carried out with c2 test (a = 0.05). The finishing procedures with fine grit or toothing burs gave a better smoothness with tungsten carbide burs compared to diamond burs. While with the ultrafine grit no significant differences were noted between tungsten carbide and diamond burs on the CE and CD interfaces, the diamond bur left less superficial roughness on the C surfaces. With regards to the superficial roughness of the different areas of restoration, it can be concluded that: minor roughness was detected on C surfaces, while the CD interface had the most superficial roughness, regardless of whether the

  7. Iron aluminide-titanium carbide composites by pressureless melt infiltration -- microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.; Alexander, K.B.; Plucknett, K.P.

    1996-09-01

    In this investigation, processing of fully dense TiC-based cermets with iron aluminide (Fe-40 at. % Al) as a binder by pressureless melt infiltration has been clearly demonstrated. The carbide contents in these composites varied from 70 to 85 vol. %. Specimens with 30 vol. % intermetallic exhibited bend strengths of 1034 MPa, fracture toughness of 18 MPa{center_dot}m{sup 1/2} and a Rockwell (R{sub A}) hardness of 83.5. Further improvements in bend strengths may be possible by controlling the grain size and by modifications of the Fe40Al/TiC interface strengths.

  8. Formation of boron nitride and boron carbide composite by nitrogen implantation at elevated temperature

    NASA Astrophysics Data System (ADS)

    Yu, N.; Romero-Borja, F.; Zhang, Z. H.; Cui, X. T.; Liu, J. R.; Wood, L. T.; Chu, W. K.; Marton, D.; Rabalais, J. W.; Forster, K. M.; Reeber, R. R.

    1993-09-01

    Boron carbide (B4C) is a wear resistant material with hardness slightly less than that of diamond. It has an excellent strength to weight ratio and relatively high toughness under controlled processing. These essential mechanical properties make B4C an ideal candidate for cutting tool and bearing applications. We will demonstrate that hexagonal boron nitride (h-BN), a good solid lubricant, can be formed on B4C surfaces through high temperature (850 °C) nitrogen ion implantation. The formation of composite B4C and h-BN on the B4C surface can potentially reduce surface friction coefficients, making the material more attractive for tribological applications.

  9. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    NASA Astrophysics Data System (ADS)

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-01

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900°C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W2C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  10. Phase evolution in carbide dispersion strengthened nanostructured copper composite by high energy ball milling

    SciTech Connect

    Hussain, Zuhailawati; Nur Hawadah, M. S.

    2012-09-06

    In this study, high-energy ball milling was applied to synthesis in situ nanostructured copper based composite reinforced with metal carbides. Cu, M (M=W or Ti) and graphite powder mixture were mechanically alloyed for various milling time in a planetary ball mill with composition of Cu-20vol%WC and Cu-20vol%TiC. Then the as-milled powder were compacted at 200 to 400 MPa and sintered in a vacuum furnace at 900 Degree-Sign C. The results of X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy analysis showed that formation of tungsten carbides (W{sub 2}C and WC phases) was observed after sintering of Cu-W-C mixture while TiC precipitated in as-milled powder of Cu-Ti-C composite after 5 h and become amorphous with longer milling. Mechanism of MA explained the cold welding and fracturing event during milling. Cu-W-C system shows fracturing event is more dominant at early stage of milling and W particle still existed after milling up to 60 h. While in Cu-Ti-C system, cold welding is more dominant and all Ti particles dissolved into Cu matrix.

  11. Development of high temperature materials for solid propellant rocket nozzle applications. [tantalum carbides-tungsten fiber composites

    NASA Technical Reports Server (NTRS)

    Manning, C. R., Jr.; Honeycutt, L., III

    1974-01-01

    Evaluation of tantalum carbide-tungsten fiber composites has been completed as far as weight percent carbon additions and weight percent additions of tungsten fiber. Extensive studies were undertaken concerning Young's Modulus and fracture strength of this material. Also, in-depth analysis of the embrittling effects of the extra carbon additions on the tungsten fibers has been completed. The complete fabrication procedure for the tantalum carbide-tungsten fiber composites with extra carbon additions is given. Microprobe and metallographic studies showed the effect of extra carbon on the tungsten fibers, and evaluation of the thermal shock parameter fracture strength/Young's Modulus is included.

  12. A Model for the Oxidation of Carbon Silicon Carbide Composite Structures

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.

    2004-01-01

    A mathematical theory and an accompanying numerical scheme have been developed for predicting the oxidation behavior of carbon silicon carbide (C/SiC) composite structures. The theory is derived from the mechanics of the flow of ideal gases through a porous solid. The result of the theoretical formulation is a set of two coupled nonlinear differential equations written in terms of the oxidant and oxide partial pressures. The differential equations are solved simultaneously to obtain the partial vapor pressures of the oxidant and oxides as a function of the spatial location and time. The local rate of carbon oxidation is determined using the map of the local oxidant partial vapor pressure along with the Arrhenius rate equation. The nonlinear differential equations are cast into matrix equations by applying the Bubnov-Galerkin weighted residual method, allowing for the solution of the differential equations numerically. The numerical method is demonstrated by utilizing the method to model the carbon oxidation and weight loss behavior of C/SiC specimens during thermogravimetric experiments. The numerical method is used to study the physics of carbon oxidation in carbon silicon carbide composites.

  13. Niobium Carbide-Reinforced Al Matrix Composites Produced by High-Energy Ball Milling

    NASA Astrophysics Data System (ADS)

    Travessa, Dilermando Nagle; Silva, Marina Judice; Cardoso, Kátia Regina

    2017-06-01

    Aluminum and its alloys are key materials for the transportation industry as they contribute to the development of lightweight structures. The dispersion of hard ceramic particles in the Al soft matrix can lead to a substantial strengthening effect, resulting in composite materials exhibiting interesting mechanical properties and inspiring their technological use in sectors like the automotive and aerospace industries. Powder metallurgy techniques are attractive to design metal matrix composites, achieving a homogeneous distribution of the reinforcement into the metal matrix. In this work, pure aluminum has been reinforced with particles of niobium carbide (NbC), an extremely hard and stable refractory ceramic. Its use as a reinforcing phase in metal matrix composites has not been deeply explored. Composite powders produced after different milling times, with 10 and 20 vol pct of NbC were produced by high-energy ball milling and characterized by scanning electron microscopy and by X-ray diffraction to establish a relationship between the milling time and size, morphology, and distribution of the particles in the composite powder. Subsequently, an Al/10 pct NbC composite powder was hot extruded into cylindrical bars. The strength of the obtained composite bars is comparable to the commercial high-strength, aeronautical-grade aluminum alloys.

  14. Gravitational effects on body composition in birds

    NASA Technical Reports Server (NTRS)

    Smith, A. H.; Sanchez P., O.; Burton, R. R.

    1975-01-01

    Gallinaceous birds, presenting a wide range of body size, were adapted physiologically to hyperdynamic environments, provided by chronic centrifugation. Chemical composition was measured directly on prepared carcasses, which were anatomically comparable, and more amenable to analysis than the intact body. Body mass and body fat decreased arithmetically with increasing field strength and also with increasing body mass. Water content of lean tissue increased in hyperdynamic environments, but irrespectively of body size.

  15. The effect of fiber microstructure on evolution of residual stresses in silicon carbide/titanium aluminide composites

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Freed, Alan D.

    1992-01-01

    This paper examines the effect of the morphology of the SCS6 silicon carbide fiber on the evolution of residual stresses in SiC/Ti composites. A micromechanics model based on the concentric cylinder concept is presented which is used to calculate residual stresses in a SiC/Ti composite during axisymmetric cooling by a spatially uniform temperature change. The silicon carbide fiber is modeled as a layered material with five distinct transversely isotropic and orthotropic, elastic layers, whereas the titanium matrix is taken to be isotropic, with temperature-dependent elastoplastic properties. The results arc compared with those obtained based on the assumption that the silicon carbide fiber is isotropic and homogeneous.

  16. The effect of fiber microstructure on evolution of residual stresses in silicon carbide/titanium aluminide composites

    NASA Technical Reports Server (NTRS)

    Pindera, Marek-Jerzy; Freed, Alan D.

    1992-01-01

    This paper examines the effect of the morphology of the SCS6 silicon carbide fiber on the evolution of residual stresses in SiC/Ti composites. A micromechanics model based on the concentric cylinder concept is presented which is used to calculate residual stresses in a SiC/Ti composite during axisymmetric cooling by a spatially uniform temperature change. The silicon carbide fiber is modeled as a layered material with five distinct transversely isotropic and orthotropic, elastic layers, whereas the titanium matrix is taken to be isotropic, with temperature-dependent elastoplastic properties. The results arc compared with those obtained based on the assumption that the silicon carbide fiber is isotropic and homogeneous.

  17. Shock response of boron carbide based composites infiltrated with magnesium alloys

    NASA Astrophysics Data System (ADS)

    Kafri, Mathan; Dariel, Moshe; Frage, Nahum; Zaretsky, Eugene

    2011-06-01

    The fully dense composites were obtained by vacuum infiltrating the boron carbide compacts (80% green density) with liquid AZ91 magnesium alloy (850 °C) and with the melt of 50/50 AZ91-silicon mixture (1050 °C). The densities, the elastic moduli and the Vickers hardness values of the obtained composites were, respectively, 2.44 g/cm3 and 2.54 g/cm3, 300 and 350 GPa, and 1200 and 1800 HV. The impact response of the composites was studied in a series of VISAR-instrumented planar impact experiments with velocities of W and Cu impactors ranged from 100 to 1000 m/s. It was found that velocity histories recorded for the composites produced by infiltration with Mg-Si alloy contain a distinct elastic precursor front followed by a plastic ramp. On the contrary, the velocity histories of the composites infiltrated with AZ91 do not display any step-like front; the amplitude of the elastic wave grows gradually from zero level and transforms smoothly into the plastic front. The influence of the composites microstructure on the compressive elastic-plastic behavior and on the dynamic tensile (spall) strength is discussed.

  18. Microstructure and thermal properties of copper–diamond composites with tungsten carbide coating on diamond particles

    SciTech Connect

    Kang, Qiping; He, Xinbo Ren, Shubin; Liu, Tingting; Liu, Qian; Wu, Mao; Qu, Xuanhui

    2015-07-15

    An effective method for preparing tungsten carbide coating on diamond surfaces was proposed to improve the interface bonding between diamond and copper. The WC coating was formed on the diamond surfaces with a reaction medium of WO{sub 3} in mixed molten NaCl–KCl salts and the copper–diamond composites were obtained by vacuum pressure infiltration of WC-coated diamond particles with pure copper. The microstructure of interface bonding between diamond and copper was discussed. Thermal conductivity and thermal expansion behavior of the obtained copper–diamond composites were investigated. Results indicated that the thermal conductivity of as-fabricated composite reached 658 W m{sup −} {sup 1} K{sup −} {sup 1}. Significant reduction in coefficient of thermal expansion of the composite compared with that of pure copper was obtained. - Highlights: • WC coating was successfully synthesized on diamond particles in molten salts. • WC coating obviously promoted the wettability of diamond and copper matrix. • WC coating greatly enhanced the thermal conductivity of Cu–diamond composite. • The composites are suitable candidates for heat sink applications.

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

    PubMed

    Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

    2016-08-24

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

  20. Silicon Carbide Shapes.

    DTIC Science & Technology

    Free-standing silicon carbide shapes are produced by passing a properly diluted stream of a reactant gas, for example methyltrichlorosilane, into a...reaction chamber housing a thin walled, hollow graphite body heated to 1300-1500C. After the graphite body is sufficiently coated with silicon carbide , the...graphite body is fired, converting the graphite to gaseous CO2 and CO and leaving a silicon carbide shaped article remaining.

  1. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  2. Nutritional assessment with body composition measurements

    SciTech Connect

    Shizgal, H.M.

    1987-09-01

    The measurement of body composition by multiple isotope dilution provides an accurate and precise measure of both the nutritional state and the response to nutritional support. A multiple isotope dilution technique has been developed that permits measurement of the three major components of body composition: body fat, extracellular mass (ECM), and body cell mass (BCM). Normal body composition was defined by data obtained in 25 healthy volunteers. Malnutrition is characterized by a loss of BCM and an expansion of the ECM, and as a result the lean body mass is not significantly different from normal. The loss of body weight with malnutrition therefore often reflects the loss of body fat. The utility of body composition measurements was demonstrated by determining the effect of total parenteral nutrition on body composition to determine the relationship between caloric intake and the change in the BCM. A statistically significant relationship was developed which demonstrated that a caloric intake in the range of 30-40 cal/kg/day is required for maintenance. To restore a depleted or malnourished BCM requires a caloric intake in excess of that required for maintenance. The measurement of body composition by multiple isotope dilution is complex and time consuming, and requires specialized laboratory facilities and specially trained personnel. As a result, these measurements are not suited for routine patient management, but should rather be reserved for research purposes.

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

    PubMed Central

    Zhang, Guangwu; Wang, Fuzhong; Huang, Zhixiong; Dai, Jing; Shi, Minxian

    2016-01-01

    Montmorillonite (MMT) was added to silicone rubber (SR) to improve the ablation resistance of the silicone. Following this, different quantities of silicon carbide whiskers (SiCw) were incorporated into the MMT/SR to yield a hybrid, ablative composite. The tensile strength and elongation at break of the composite increased after the addition of MMT. The ablation test results showed that MMT helped to form a covering layer by bonding with the silica and other components on the ablated surface. The linear and mass ablation rates exhibited decreases of 22.5% and 18.2%, respectively, in comparison to a control sample. After further incorporation of SiCw as the second filler, the resulting composites exhibited significantly higher tensile strength and ablation resistance, but not particularly lower elongation at break in comparison to the control sample. The SiCw/MMT fillers were beneficial in forming a dense and compact covering layer that delayed the heat and oxygen diffusion into the inner layers, which improved the ablation properties effectively. The remaining whiskers acted as a micro skeleton to maintain the composite’s char strength. Compared to the control sample, the linear and mass ablation rates of the composite after incorporating 6 phr SiCw and 10 phr MMT decreased by 59.2% and 43.6%, respectively. These experimental results showed that the fabricated composites exhibited outstanding mechanical properties and excellent ablation resistance. PMID:28773846

  4. Analysis of alumina-based titanium carbide composites by laser-induced breakdown spectroscopy

    NASA Astrophysics Data System (ADS)

    Ahmad, Kaleem; Tawfik, Walid; Farooq, Wazirzada A.; Singh, Jagdish P.

    2014-06-01

    In this work, alumina (Al2O3) containing different volume % of titanium carbide (TiC) ranging from 0 to 30 were consolidated by the novel spark plasma sintering. The spectroscopic analysis of the plasma generated by irradiation of laser Nd:YAG (λ = 1,064 nm) on different concentrations of the composites in air atmospheric pressure was performed. The qualitative examination of the composites confirms the presence of aluminum, titanium, and carbon as major elements, while magnesium and sodium have been found as minor trace elements. Plasma parameters were estimated by assuming the LTE conditions for optically thin plasma. The electron density and temperature were evaluated by using the Stark broadening and intensity of selected aluminum emission lines, respectively. The addition of TiC to Al2O3 shows a linear behavior with plasma temperature corroborated by the calibration curve of Ti in the composites. The results suggest that calibration curve between plasma temperature and the composites can be used to estimate different concentrations of TiC in Al2O3 without analyzing the whole elements in the composites and thus opens up new applications of LIBS in ceramic industry.

  5. Deposition of silicon carbide using the chemical vapor composites process: Process characterization and comparison with RASSPVDN model predictions

    SciTech Connect

    Allendorf, M.D.; Hurt, R.H.; Yang, N. ); Reagan, P.; Robbins, M. )

    1993-07-01

    In this work, we explore the use of the chemical vapor composites (CVC) process to increase the rates of silicon carbide (SiC) growth on graphite substrates. Large SiC seed particles are used that deposit by gravity-driven sedimentation. The results show that addition of large ([ital d][sub [ital p

  6. Elastic Moduli and Damping of Vibrational Modes of Aluminum/Silicon Carbide Composite Beams

    NASA Technical Reports Server (NTRS)

    Leidecker, Henning

    1996-01-01

    Elastic and shear moduli were determined for two aluminum matrix composites containing 20 and 40 volume percent discontinuous silicon carbide, respectively, using transverse, longitudinal, and torsional vibrational modes of specimens prepared as thin beams. These moduli are consistent with those determined from stress-strain measurements. The damping factors for these modes were also determined. Thermal properties are used to show that part of the damping of transverse modes is caused by the transverse thermal currents discussed by C. Zener (thermo-elastic damping); this damping is frequency-dependent with a maximum damping factor of approximately 0.002. The remaining damping is frequency-independent, and has roughly similar values in transverse, longitudinal, and torsional modes: approximately 0.0001.

  7. Additive Manufacturing of Silicon Carbide-Based Ceramic Matrix Composites: Technical Challenges and Opportunities

    NASA Technical Reports Server (NTRS)

    Singh, Mrityunjay; Halbig, Michael C.; Grady, Joseph E.

    2016-01-01

    Advanced SiC-based ceramic matrix composites offer significant contributions toward reducing fuel burn and emissions by enabling high overall pressure ratio (OPR) of gas turbine engines and reducing or eliminating cooling air in the hot-section components, such as shrouds, combustor liners, vanes, and blades. Additive manufacturing (AM), which allows high value, custom designed parts layer by layer, has been demonstrated for metals and polymer matrix composites. However, there has been limited activity on additive manufacturing of ceramic matrix composites (CMCs). In this presentation, laminated object manufacturing (LOM), binder jet process, and 3-D printing approaches for developing ceramic composite materials are presented. For the laminated object manufacturing (LOM), fiber prepreg laminates were cut into shape with a laser and stacked to form the desired part followed by high temperature heat treatments. For the binder jet, processing optimization was pursued through silicon carbide powder blending, infiltration with and without SiC nano powder loading, and integration of fibers into the powder bed. Scanning electron microscopy was conducted along with XRD, TGA, and mechanical testing. Various technical challenges and opportunities for additive manufacturing of ceramics and CMCs will be presented.

  8. Evaluation of Body Composition: Why and How?

    USDA-ARS?s Scientific Manuscript database

    Evaluation of human body composition in vivo remains a critical component in the assessment of nutritional status of an individual.Whereas traditional measurements of standing height and body weight provide information on body mass index and, hence, the risk of some chronic diseases, advanced techno...

  9. Characterization of boron carbide particulate reinforced in situ copper surface composites synthesized using friction stir processing

    SciTech Connect

    Sathiskumar, R.; Murugan, N.; Dinaharan, I.; Vijay, S.J.

    2013-10-15

    Friction stir processing has evolved as a novel solid state technique to fabricate surface composites. The objective of this work is to apply the friction stir processing technique to fabricate boron carbide particulate reinforced copper surface composites and investigate the effect of B{sub 4}C particles and its volume fraction on microstructure and sliding wear behavior of the same. A groove was prepared on 6 mm thick copper plates and packed with B{sub 4}C particles. The dimensions of the groove was varied to result in five different volume fractions of B{sub 4}C particles (0, 6, 12, 18 and 24 vol.%). A single pass friction stir processing was done using a tool rotational speed of 1000 rpm, travel speed of 40 mm/min and an axial force of 10 kN. Metallurgical characterization of the Cu/B{sub 4}C surface composites was carried out using optical microscope and scanning electron microscope. The sliding wear behavior was evaluated using a pin-on-disk apparatus. Results indicated that the B{sub 4}C particles significantly influenced the area, dispersion, grain size, microhardness and sliding wear behavior of the Cu/B{sub 4}C surface composites. When the volume fraction of B{sub 4}C was increased, the wear mode changed from microcutting to abrasive wear and wear debris was found to be finer. Highlights: • Fabrication of Cu/B{sub 4}C surface composite by friction stir processing • Analyzing the effect of B{sub 4}C particles on the properties of Cu/B4C surface composite • Increased volume fraction of B{sub 4}C particles reduced the area of surface composite. • Increased volume fraction of B{sub 4}C particles enhanced the microhardness and wear rate. • B{sub 4}C particles altered the wear mode from microcutting to abrasive.

  10. Abrasive wear of cemented carbides

    SciTech Connect

    Hawk, Jeffrey A.; Wilson, Rick D.

    2003-10-01

    Cemented carbides are used for a wide variety of applications where wear is a problem. Usually the wear of the cemented carbides is a combination of metal-to-metal and abrasion. Wear can occur at room or elevated temperatures. This research summarizes initial research to understand the abrasive wear of various cemented carbides (various grain sizes, carbide types, carbide grain sizes and binder compositions) in terms of absolute material removal rates and material removal mechanisms.

  11. Scatter in Carbon/Silicon Carbide (C/SiC) Composites Quantified

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. N.; Gyekenyesi, John P.; Mital, Subodh K.

    2004-01-01

    Carbon-fiber-reinforced silicon carbide matrix (C/SiC) composites processed by chemical vapor infiltration are candidate materials for aerospace thermal structures. Carbon fibers can retain properties at very high temperatures, but they are known to have poor oxidation resistance in adverse, high-temperature environments. Nevertheless, the combination of CVI-SiC matrix with higher stiffness and oxidation resistance, the interfacial coating, and additional surface-seal coating provides the necessary protection to the carbon fibers, and makes the material viable for high-temperature space applications operating under harsh environments. Furthermore, C/SiC composites, like other ceramic matrix composites (CMCs), exhibit graceful non-catastrophic failure because of various inherent energy dissipating mechanisms. The material exhibits nonlinearity in deformation even at very low stress levels. This is the result of the severe matrix microcracking present in the as processed composite because of large differences between the coefficients of thermal expansion of the fiber and the matrix. Utilization of these advanced composites in next generation space vehicles will require innovative structural configurations, updated materials, and refined analyses. Structural safety issues for these vehicles are in direct competition with performance and cost. One would have to quantify the uncertainties associated with the design using formal probabilistic methods. Specifically four fundamental aspects on which analyses are based-- (1) loading conditions, (2) material behavior, (3) geometrical configurations, and (4) structural connections between the composite components and baseline structure--are stochastic in nature. A direct way to formally account for uncertainties is to develop probabilistic structural analysis methods where all participating variables are described by appropriate probability density functions. The present work, however, focuses on analyzing the stochastic

  12. Solid Oxide Membrane (SOM) Process for Facile Electrosynthesis of Metal Carbides and Composites

    NASA Astrophysics Data System (ADS)

    Zou, Xingli; Chen, Chaoyi; Lu, Xionggang; Li, Shangshu; Xu, Qian; Zhou, Zhongfu; Ding, Weizhong

    2017-02-01

    Metal carbides (MCs) and composites including TiC, SiC, TaC, ZrC, NbC, Ti5Si3/TiC, and Nb/Nb5Si3 have been directly electrosynthesized from their stoichiometric metal oxides/carbon (MOs/C) mixture precursors by an innovative solid oxide membrane (SOM)-assisted electrochemical process. MOs/C mixture powders including TiO2/C, SiO2/C, Ta2O5/C, ZrO2/C, Nb2O5/C, TiO2/SiO2/C, Nb2O5/SiO2 were pressed to form porous pellets and then served as cathode precursors. A SOM-based anode, made from yttria-stabilized zirconia (YSZ)-based membrane, was used to control the electroreduction process. The SOM electrochemical process was performed at 1273 K (1000 °C) and 3.5 to 4.0 V in molten CaCl2. The oxygen component contained in the MOs/C precursors was gradually removed during electroreduction process, and thus, MOs/C can be directly converted into MCs and composites at the cathode. The reaction mechanism of the electroreduction process and the characteristics of the obtained MCs and composites products were systematically investigated. The results show that the electrosynthesis process typically involves compounding, electroreduction, dissolution-electrodeposition, and in situ carbonization processes. The products can be predesigned and controlled to form micro/nanostructured MCs and composites. Multicomponent multilayer composites (MMCs) have also been tried to electrosynthesize in this work. It is suggested that the SOM-assisted electroreduction process has great potential to be used for the facile and green synthesis of various MCs and composites.

  13. Electric Discharge Sintering and Joining of Tungsten Carbide--Cobalt Composite with High-Speed Steel Substrate

    SciTech Connect

    Grigoryev, Evgeny G.

    2011-01-17

    Simultaneous electro discharge sintering of high strength structure of tungsten carbide-cobalt composite and connection it with high-speed steel substrate is investigated and suitable operating parameters are defined. Tungsten carbide-cobalt and high-speed steel joining was produced by the method of high voltage electrical discharge together with application of mechanical pressure to powder compact. It was found that the density and hardness of composite material reach its maximum values at certain magnitudes of applied pressure and high voltage electrical discharge parameters. We show that there is an upper level for the discharge voltage beyond which the powder of composite material disintegrates like an exploding wire. Due to our results it is possible to determine optimal parameters for simultaneous electro discharge sintering of WC-Co and bonding it with high-speed steel substrate.

  14. Effect of Powder-Feeding Modes During Plasma Spray on the Properties of Tungsten Carbide Composite Coatings

    NASA Astrophysics Data System (ADS)

    Zhong, Yi-ming; Du, Xiao-dong; Wu, Gang

    2017-05-01

    A WC-reinforced composite coating was fabricated on the surface of 45 steel samples by plasma, cladding process with WC powder added to the molten pool synchronously or in the tail of the molten pool. The microstructure, phase composition, and element distribution in the coating were analyzed. The results show that the undissolved WC particles and crystallized carbide (WC, W2C) were distributed uniformly in the sub-eutectic matrix in both cases. Fewer of the WC particles are dissolved in the matrix when they are injected into the tail of the molten pool. There are fewer needle-like tungsten carbide formations seen in the composite coating fabricated by back-feeding process than in that formed by synchronous feeding. The former results in a finer microstructure and a higher concentration gradient of elements near the interface between the WC particles and the coating matrix.

  15. Some aspects of machining cast Al-SiCp composites with conventional high speed steel and tungsten carbide tools

    NASA Astrophysics Data System (ADS)

    Narahari, P.; Pai, B. C.; Pillai, R. M.

    1999-10-01

    An attempt was made to evaluate machining of eutectic Al-Si (LM6) and hypoeutectic Al-Si (LM25) alloys reinforced with 10, 15, and 20% SiCp of two particle sizes using conventional high-speed steel (HSS) and tungsten carbide (WC) tools by varying cutting speed, feed, depth of cut, and environment. Machining of metal matrix composites (MMCs) is a difficult task using HSS and WC tools. The tool life of both these conventional tools was observed to decrease with increasing percentage and coarseness of SiCp in the composites. Tungsten carbide tools had a longer tool life than HSS under all the different conditions studied. Contrary to the known phenomenon of enhanced tool life in machining monolithic alloys with the use of cutting fluid, the tool life of WC/HSS tool in machining composites with cutting fluid was only 10 to 20% of that without cutting fluid.

  16. Matrix cracking and creep behavior of monolithic zircon and zircon silicon carbide fiber composites

    NASA Astrophysics Data System (ADS)

    Anandakumar, Umashankar

    In this study, the first matrix cracking behavior and creep behavior of zircon matrix silicon carbide fiber composites were studied, together with the fracture and creep behavior of the monolithic zircon. These behaviors are of engineering and scientific importance, and the study was aimed at understanding the deformation mechanisms at elevated temperatures. The first matrix cracking behavior of zircon matrix uniaxially reinforced with silicon carbide fiber (SCS-6) composites and failure behavior of monolithic zircon were studied as a function of temperature (25°C, 500°C, and 1200°C) and crack length in three point bending mode. A modified vicker's indentation technique was used to vary the initial crack length in monolithic and composite samples. The interfacial shear strength was measured at these temperatures from matrix crack saturation spacing. The composites exhibited steady state and non steady state behaviors at the three different temperatures as predicted by theoretical models, while the failure stress of zircon decreased with increasing stress. The intrinsic properties of the composites were used to numerically determine the results predicted by three different matrix cracking models based on a fracture mechanics approach. The analysis showed that the model based on crack bridging analysis was valid at 25°C and 500°C, while a model based on statistical fiber failure was valid at 1200°C. Microstructural studies showed that fiber failure in the crack wake occurred at or below the matrix cracking stress at 1200°C, and no fiber failure occurred at the other two temperatures, which validated the results predicted by the theoretical models. Also, it was shown that the interfacial shear stress corresponding to debonding determined the matrix cracking stress, and not the frictional shear stress. This study showed for the first time, the steady state and non-steady state matrix cracking behavior at elevated temperatures, the difference in behavior between

  17. Method Developed for Improving the Thermomechanical Properties of Silicon Carbide Matrix Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.; DiCarlo, James A.

    2004-01-01

    Today, a major thrust for achieving engine components with improved thermal capability is the development of fiber-reinforced silicon-carbide (SiC) matrix composites. These materials are not only lighter and capable of higher use temperatures than state-of-the-art metallic alloys and oxide matrix composites (approx. 1100 C), but they can provide significantly better static and dynamic toughness than unreinforced silicon-based monolithic ceramics. However, for successful application in advanced engine systems, the SiC matrix composites should be able to withstand component service stresses and temperatures for the desired component lifetime. Since the high-temperature structural life of ceramic materials is typically controlled by creep-induced flaw growth, a key composite property requirement is the ability to display high creep resistance under these conditions. Also, because of the possibility of severe thermal gradients in the components, the composites should provide maximum thermal conductivity to minimize the development of thermal stresses. State-of-the-art SiC matrix composites are typically fabricated via a three-step process: (1) fabrication of a component-shaped architectural preform reinforced by high-performance fibers, (2) chemical vapor infiltration of a fiber coating material such as boron nitride (BN) into the preform, and (3) infiltration of a SiC matrix into the remaining porous areas in the preform. Generally, the highest performing composites have matrices fabricated by the CVI process, which produces a SiC matrix typically more thermally stable and denser than matrices formed by other approaches. As such, the CVI SiC matrix is able to provide better environmental protection to the coated fibers, plus provide the composite with better resistance to crack propagation. Also, the denser CVI SiC matrix should provide optimal creep resistance and thermal conductivity to the composite. However, for adequate preform infiltration, the CVI SiC matrix

  18. Recent advances and issues in development of silicon carbide composites for fusion applications

    SciTech Connect

    Nozawa, T.; Hinoki, Tetsuya; Hasegawa, Akira; Kohyama, Akira; Katoh, Yutai; Snead, Lance L.; Henager, Charles H.; Hegeman, Hans

    2009-04-30

    Radiation-resistant advanced silicon carbide composites (SiC/SiC) have been developed as a promising candidate of the high-temperature operating advanced fusion DEMO reactor. With the completion of the “proof-of-principle” phase in development of “nuclear-grade” SiC/SiC, the R&D on SiC/SiC is shifting toward the more pragmatic phase, i.e., industrialization of component manufactures and data-basing. In this paper, recent advances and issues in 1) development of component fabrication technology including joining and functional coating, e.g., a tungsten overcoat as a plasma facing barrier, 2) recent updates in characterization of non-irradiated properties, e.g., strength anisotropy and chemical compatibility with solid lithium-based ceramics and lead-lithium liquid metal breeders, and 3) irradiation effects were specifically reviewed. Importantly high-temperature neutron irradiation effects on microstructural evolution, thermal and electrical conductivities and mechanical properties including the fiber/matrix interfacial strength were specified under various irradiation conditions, indicating seemingly very minor influence on the composite performance in the design temperature range.

  19. Stress localization and size dependent toughening effects in silicon carbide composites

    NASA Astrophysics Data System (ADS)

    Beaber, Aaron Ross

    Coatings with high wear resistance have generated a great deal of interest due to a diverse range of applications, including cutting tools, turbine blades, and biomedical joint replacements. Ceramic nanocomposites offer a potential combination of high strength and toughness that is ideal for such environments. In the current dissertation research, silicon and silicon carbide based films and nanostructures were deposited using a hybrid of chemical vapor deposition and nanoparticle ballistic impaction known as hypersonic plasma particle deposition (HPPD). This included SiC/Ti-based multilayers and Si-SiC core-shell composite nanotowers. Using a combination of nanoindentation and confocal Raman microscopy, the role of plasticity and phase transformations was studied during fracture events at small length scales. In a parallel study, HPPD synthesized Si nanospheres and vapor-liquid-solid (VLS) Si nanotowers were compressed uniaxially inside the TEM. These experiments confirmed inverse length scale dependent relationships for strength and toughness in Si based on dislocation pile-up and crack tip shielding mechanisms, respectively. A transition was also identified in the deformation of Si under anisotropic loading below a critical size and used as the basis for a new toughening mechanism in Si-SiC composites. Overall, these results demonstrate the importance of nanoscale confinement and localized stress in the design of mechanically robust nanocomposites.

  20. Time-Dependent Stress Rupture Strength Degradation of Hi-Nicalon Fiber-Reinforced Silicon Carbide Composites at Intermediate Temperatures

    NASA Technical Reports Server (NTRS)

    Sullivan, Roy M.

    2016-01-01

    The stress rupture strength of silicon carbide fiber-reinforced silicon carbide composites with a boron nitride fiber coating decreases with time within the intermediate temperature range of 700 to 950 degree Celsius. Various theories have been proposed to explain the cause of the time-dependent stress rupture strength. The objective of this paper is to investigate the relative significance of the various theories for the time-dependent strength of silicon carbide fiber-reinforced silicon carbide composites. This is achieved through the development of a numerically based progressive failure analysis routine and through the application of the routine to simulate the composite stress rupture tests. The progressive failure routine is a time-marching routine with an iterative loop between a probability of fiber survival equation and a force equilibrium equation within each time step. Failure of the composite is assumed to initiate near a matrix crack and the progression of fiber failures occurs by global load sharing. The probability of survival equation is derived from consideration of the strength of ceramic fibers with randomly occurring and slow growing flaws as well as the mechanical interaction between the fibers and matrix near a matrix crack. The force equilibrium equation follows from the global load sharing presumption. The results of progressive failure analyses of the composite tests suggest that the relationship between time and stress-rupture strength is attributed almost entirely to the slow flaw growth within the fibers. Although other mechanisms may be present, they appear to have only a minor influence on the observed time-dependent behavior.

  1. Reaction sintering of two-dimensional silicon carbide fiber-reinforced silicon carbide composite by sheet stacking method

    NASA Astrophysics Data System (ADS)

    Yoshida, Katsumi; Mukai, Hideki; Imai, Masamitsu; Hashimoto, Kazuaki; Toda, Yoshitomo; Hyuga, Hideki; Kondo, Naoki; Kita, Hideki; Yano, Toyohiko

    2007-08-01

    Two-dimensionally plain woven SiC fiber-reinforced SiC composite has been developed by reaction sintering using a sheet stacking method in order to further increase mechanical and thermal properties of the composite and to obtain flexibility of manufacturing process of 2D woven SiC/SiC composites which can be applied to the fabrication of larger parts. In addition, sinterability and mechanical properties of the composite were investigated. In this study, relative density of the composites was about 90-93% and a dense composite could be obtained by reaction sintering using the sheet stacking method. The bulk density and maximum bending strength of SiC/SiC composite with a C/SiC weight ratio of 0.6 were higher than that of the composite with C/SiC ratios of 0.5 or 0.7. The values were 2.9 g/cm 3 and 200 MPa, respectively. However, the composites obtained in this study fractured in almost brittle manner due to the lower fiber volume fraction.

  2. Silicon carbide-aluminum nitride: new high-stability composition for MEMS

    NASA Astrophysics Data System (ADS)

    Luchinin, Victor V.; Korlyakov, Andrey V.; Vasil'ev, Alexander A.

    1999-03-01

    Consideration of candidate materials for MEMS points out silicon - silicon dioxide as a dominant structures at present. This paper deals with 'Silicon Carbide - Aluminum Nitride' (SiC-AlN): a novel alternative to Si-SiO2. The SiC-AlN composition applicability to MEMS can be substantiated by its capability to meet a number of very important MEMS-imposed requirements, such as a good compatibility and a high thermal, electric and mechanical strength of both materials. The two material: one being dielectric and the other - a wide band-gap semiconductor, when integrate in one structure, exhibit the high crystalochemical compatibility and perfectly compatible thermal expansion coefficient. Moreover, both materials have excellent heat conductances which are characteristics of their inherent perfect thermal resistance and low reactivity. In its mechanical strength, SiC yields among semiconductors to diamond only. In addition, the SiC-AlN composition combines strain gauge properties of SiC with piezoelectric properties of AlN. Besides, SiC and AlN both are optically-active up to the UV region of spectrum and may be employed both in light emitters and in photodetectors. Technologically, in application of a MEMS structure, aluminium nitride plays the role of a sacrificial layer to be selectively stripped away by an acid etchant in the epitaxial compositions SiC-AlN. The compatibility of such properties of SiC and AlN, especially in one structure, makes the SiC-AlN composition a promising candidate for MEMS-devices to be designed for the stable-performance operation under rather severe conditions.

  3. Effect of surface composition on the chemisorption of hydrogen on tungsten carbide

    SciTech Connect

    Boudart, M.; Lee, J.S.; Imura, K.; Yoshida, S.

    1987-01-01

    Polymeric carbon and oxygen were detected at the surface of tungsten carbide powders by Auger electron spectroscopy and electron spin resonance. Chemisorption of dihydrogen is suppressed by polymeric carbon but enhanced by surface oxygen as some of the latter reacts in the presence of water with hydrogen spilling over from the tungsten carbide parts of the surface. 21 references.

  4. Assessing body composition in infants and toddlers

    USDA-ARS?s Scientific Manuscript database

    The objective of this study was to compare different body composition techniques in infants and toddlers. Anthropometric measures including mid-upper arm circumference (MAC), triceps skinfold thickness (TSF), and weight-for-height or -length Z-scores (WHZ), and measures of body fat mass assessed wit...

  5. Measurement of Body Composition in Children.

    ERIC Educational Resources Information Center

    Lohman, T. G.

    1982-01-01

    Identification and treatment of obesity in children is believed to be an important factor in its control during the adult years. Laboratory and field methods for body composition measurement are described along with estimates of body fat content from anthropometric dimensions. (CJ)

  6. Effects of Fiber Coating Composition on Mechanical Behavior of Silicon Carbide Fiber-Reinforced Celsian Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P.; Elderidge, Jeffrey I.

    1998-01-01

    Celsian matrix composites reinforced with Hi-Nicalon fibers, precoated with a dual layer of BN/SiC by chemical vapor deposition in two separate batches, were fabricated. Mechanical properties of the composites were measured in three-point flexure. Despite supposedly identical processing, the composite panels fabricated with fibers coated in two batches exhibited substantially different mechanical behavior. The first matrix cracking stresses (sigma(sub mc)) of the composites reinforced with fibers coated in batch 1 and batch 2 were 436 and 122 MPa, respectively. This large difference in sigma(sub mc) was attributed to differences in fiber sliding stresses(tau(sub friction)), 121.2+/-48.7 and 10.4+/-3.1 MPa, respectively, for the two composites as determined by the fiber push-in method. Such a large difference in values of tau(sub friction) for the two composites was found to be due to the difference in the compositions of the interface coatings. Scanning Auger microprobe analysis revealed the presence of carbon layers between the fiber and BN, and also between the BN and SiC coatings in the composite showing lower tau(sub friction). This resulted in lower sigma(sub mc) in agreement with the ACK theory. The ultimate strengths of the two composites, 904 and 759 MPa, depended mainly on the fiber volume fraction and were not significantly effected by tau(sub friction) values, as expected. The poor reproducibility of the fiber coating composition between the two batches was judged to be the primary source of the large differences in performance of the two composites.

  7. Body composition analysis for healthy Italian vegetarians.

    PubMed

    Siani, V; Mohamed, E I; Maiolo, C; Di Daniele, N; Ratiu, A; Leonardi, A; De Lorenzo, A

    2003-10-01

    The elementary nutritional needs of vegetarians are totally, or in great part, supplied by vegetarian food; thus the body composition of vegetarians could differ from that of omnivorous persons. The objective of the present study was to compare healthy Italian vegetarians to healthy omnivorous individuals in terms of body composition, determined using dual X-ray absorptiometry. The study population consisted of 20 vegetarians [mean age (+/-SD), 34.78+/-15.07 years; mean BMI, 22.41+/-2.15 kg/m(2)] and 10 omnivorous persons matched for age and BMI. We found no significant differences between the two groups in terms of fat mass, lean body mass, soft tissue, bone mineral content, or bone mineral density. These findings suggest that the vegetarian diet does not induce negative alterations in body composition.

  8. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures.

    PubMed

    Hu, Liangfa; O'Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-10-18

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42-83 μm, 77-276 μm, and 167-545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

  9. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    PubMed Central

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-01-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed. PMID:27752106

  10. High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

    NASA Astrophysics Data System (ADS)

    Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

    2016-10-01

    The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed.

  11. Fractographic and three body abrasion behaviour of Al-Garnet-C hybrid chill cast composites

    NASA Astrophysics Data System (ADS)

    Bandekar, Nityanand; Prasad, M. G. Anantha

    2017-08-01

    Fractographic and tribological behaviour of hybrid composite of aluminum alloy LM13 matrix with garnet and carbon was investigated. Conventional stir casting technique was used to fabricate the composites with chill cast technique. Various chill materials like Copper, Steel, Iron and Silicon carbide were used to improve the directional solidification. The garnet being added ranges from 3 to 12 wt-% in steps of 3wt-% and constant 3wt-% of carbon. The experiment evaluates the mechanical, fractographic and three body abrasion behaviour of the hybrid composites for various parameters of load, garnet and chills. Microstructural characterization of the composite samples revealed a uniform distribution of reinforcements with minimum clustering. SEM was used for examine worn surfaces. The addition of garnet and carbon reinforcement decreases the wear rate of hybrid composites. Fracture behaviour showed the changes from ductile mode to brittle mode of failure. Further, directional chilling with copper chill improves the wear resistance of the composites.

  12. DEVELOPMENT OF ADVANCED DRILL COMPONENTS FOR BHA USING MICROWAVE TECHNOLOGY INCORPORATING CARBIDE, DIAMOND COMPOSITES AND FUNCTIONALLY GRADED MATERIALS

    SciTech Connect

    Dinesh Agrawal; Rustum Roy

    2003-01-01

    The microwave processing of materials is a new emerging technology with many attractive advantages over the conventional methods. The advantages of microwave technology for various ceramic systems has already been demonstrated and proven. The recent developments at Penn State have succeeded in applying the microwave technology for the commercialization of WC/Co and diamond based cutting and drilling tools, effectively sintering of metallic materials, and fabrication of transparent ceramics for advanced applications. In recent years, the Microwave Processing and Engineering Center at Penn State University in collaboration with our industrial partner, Dennis Tool Co. has succeeded in commercializing the developed microwave technology partially funded by DOE for WC/Co and diamond based cutting and drilling tools for gas and oil exploration operations. In this program we have further developed this technology to make diamond-carbide composites and metal-carbide-diamond functionally graded materials. Several actual product of diamond-carbide composites have been processed in microwave with better performance than the conventional product. The functionally graded composites with diamond as one of the components has been for the first time successfully developed. These are the highlights of the project.

  13. Steady State Sputtering Yields and Surface Compositions of Depleted Uranium and Uranium Carbide bombarded by 30 keV Gallium or 16 keV Cesium Ions.

    SciTech Connect

    Siekhaus, W. J.; Teslich, N. E.; Weber, P. K.

    2014-10-23

    Depleted uranium that included carbide inclusions was sputtered with 30-keV gallium ions or 16-kev cesium ions to depths much greater than the ions’ range, i.e. using steady-state sputtering. The recession of both the uranium’s and uranium carbide’s surfaces and the ion corresponding fluences were used to determine the steady-state target sputtering yields of both uranium and uranium carbide, i.e. 6.3 atoms of uranium and 2.4 units of uranium carbide eroded per gallium ion, and 9.9 uranium atoms and 3.65 units of uranium carbide eroded by cesium ions. The steady state surface composition resulting from the simultaneous gallium or cesium implantation and sputter-erosion of uranium and uranium carbide were calculated to be U₈₆Ga₁₄, (UC)₇₀Ga₃₀ and U₈₁Cs₉, (UC)₇₉Cs₂₁, respectively.

  14. Body Composition Changes Associated With Methadone Treatment

    PubMed Central

    Sadek, Gamal E.; Chiu, Simon; Cernovsky, Zack Z.

    2016-01-01

    Background: Methadone is associated with a statistically significant increase in BMI in the first 2 years of treatment. Objectives: To evaluate the changes of body composition (bone mass, % fat, % muscle mass, % water, and basal metabolic rate) related to this increase. Patients and Methods: Changes in body composition were monitored, via bioelectrical impedance, in 29 patients in methadone treatment for opiate dependency (age 18 to 44, mean = 29.3, SD = 7.0, 13 men, 16 women). Results: Within one year from admission to treatment, a statistically significant (t-tests, P < 0.05) increase was noted in their body mass index (BMI), % of body fat, average body mass, and average basal metabolic rate, and relative decrease in their % of muscle mass and % of bone mass. Neither absolute bone mass nor muscle mass changed significantly. Conclusions: Physicians involved in care of methadone patients should recommend dietary and lifestyle changes to improve their overall health. PMID:27162765

  15. Skeletal and body composition evaluation

    NASA Technical Reports Server (NTRS)

    Mazess, R. B.

    1983-01-01

    Research on radiation detectors for absorptiometry; analysis of errors affective single photon absorptiometry and development of instrumentation; analysis of errors affecting dual photon absorptiometry and development of instrumentation; comparison of skeletal measurements with other techniques; cooperation with NASA projects for skeletal evaluation in spaceflight (Experiment MO-78) and in laboratory studies with immobilized animals; studies of postmenopausal osteoporosis; organization of scientific meetings and workshops on absorptiometric measurement; and development of instrumentation for measurement of fluid shifts in the human body were performed. Instrumentation was developed that allows accurate and precise (2% error) measurements of mineral content in compact and trabecular bone and of the total skeleton. Instrumentation was also developed to measure fluid shifts in the extremities. Radiation exposure with those procedures is low (2-10 MREM). One hundred seventy three technical reports and one hundred and four published papers of studies from the University of Wisconsin Bone Mineral Lab are listed.

  16. Radiation-tolerant joining technologies for silicon carbide ceramics and composites

    SciTech Connect

    Katoh, Yutai; Snead, Lance L.; Cheng, Ting; Shih, Chunghao; Lewis, W. Daniel; Koyanagi, Takaaki; Hinoki, Tatsuya; Henager, Charles H.; Ferraris, Monica

    2014-05-01

    Silicon carbide (SiC) for nuclear structural applications, whether in the monolithic ceramic or composite form, will require a robust joining technology capable of withstanding the harsh nuclear environment. This paper presents significant progress made towards identifying and processing irradiation-tolerant joining methods for nuclear-grade SiC. In doing so, a standardized methodology for carrying out joint testing has been established consistent with the small volume samples mandated by neutron irradiation testing. Candidate joining technologies were limited to those that provide low induced radioactivity and included titanium diffusion bonding, Ti–Si–C MAX-phase joining, calcia–alumina glass–ceramic joining, and transient eutectic-phase SiC joining. Samples of these joints were irradiated in the Oak Ridge National Laboratory High Flux Isotope Reactor at 500 or 800 °C, and their microstructure and mechanical properties were compared to pre-irradiation conditions. Within the limitations of statistics, all joining methodologies presented retained their joint mechanical strength to ~3 dpa at 500 °C, thus indicating the first results obtained on irradiation-stable SiC joints. Finally, under the more aggressive irradiation conditions (800 °C, ~5 dpa), some joint materials exhibited significant irradiation-induced microstructural evolution; however, the effect of irradiation on joint strength appeared rather limited.

  17. Formation Mechanism of Titanium Silicon Carbide: The Effect of Different Composition of Starting Materials

    NASA Astrophysics Data System (ADS)

    Solihin; Mursito, Anggoro Tri; Sun, Zhengming

    2017-07-01

    Titanium silicon carbide (Ti3SiC2) is a kind of ceramic that has physical property value similar with metal. Ti3SiC2 has been synthesized through various methods based on solid state reaction. Although Ti3SiC2 has been synthesized through various methods by using various starting materials consisting titanium (Ti), silicon (Si), and carbon (C) the mechanism of Ti3SiC2 formation through sintering has not fully understood. The aim of this research is to reveal the mechanism happening during sintering. Two composition of starting material was used, 2Ti/2Si/3TiC and 5Ti/2Si/3C. The analysis through XRD and SEM-EDS shows that the formation of intermediate phases, TiC and Ti5Si3, takes place prior to the formation of Ti3SiC2. In other words, Ti3SiC2 can only be formed through solid state reaction between TiC and Ti5Si3. Since TiC has already available in the system 2Ti/2Si/3TiC, the phase purity of Ti3SiC2 in 2Ti/2Si/3TiC is always higher than that of 5Ti/2Si/3C.

  18. Suspension Plasma Spraying of Sub-micron Silicon Carbide Composite Coatings

    NASA Astrophysics Data System (ADS)

    Mubarok, F.; Espallargas, N.

    2015-06-01

    Thermal spraying of silicon carbide (SiC) material is a challenging task since SiC tends to decompose during atmospheric spraying process. The addition of metal or ceramic binders is necessary to facilitate the bonding of SiC particles, allowing SiC composite coating to be deposited. In the conventional procedures, the binders are added through mechanical mixing of powder constituents, making it difficult to achieve homogeneous distribution. In the new procedure proposed in this work, the binder is delivered as a nano-film of the surface of the individual SiC particles through co-precipitation treatment. Suspension plasma spray (SPS) coating technique has been used with the aim at avoiding the decomposition of SiC typically expected with atmospheric techniques, such as atmospheric plasma spray. The deposited SiC coatings by SPS showed identical SiC phase peak as identified in the suspension feedstock, indicating that the nano-film binder was able to protect SiC particles from decomposition. Further analysis by XPS revealed that SiC particles underwent some minor oxidation. Unfortunately, all the SiC coatings exhibited poor mechanical performance due to low cohesive strength, high porosity, and powdery structure making the coatings vulnerable to grain pull-out. This was due to the absence of sintering process during the spraying process contributing to the low performance of SiC SPS coatings.

  19. Re-determination of the reaction path parameters of silicon deposition for aerospace silicon carbide composites via chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Chandrasekaram, Sandeep D.

    Development of air travel technology is always increasing and fuel efficiency is one of the most important factors that's being looked into. For a 25% increase in fuel efficiency in the future aeroplanes, reduction in the weight of the engine is one of the factors that should be addressed while increasing the strength and power generated. For this purpose, General Electric Aviation has chosen Silicon Carbide as the material to build the turbine blades of its engines. Silicon carbide works best as it is strong, can withstand high temperature and lightweight. The downside of this material is that it reacts with water vapor at temperatures greater than 2700°F to form volatile Silicon hydroxide from Silicon dioxide, its protective layer; and furthermore it reduces to Silicon monoxide that vaporizes. To counter this problem, scientists at the National Aeronautics & Space Administration (NASA) have found that a rare earth silicate could be used as an environmental barrier coating (EBC) to prevent the exposure of Silicon Carbide to water vapor. The EBC can't be directly coated on the Silicon Carbide surface as it isn't chemically adhesive enough, therefore Silicon was chosen to act as the bond coat between the Silicon Carbide and EBC. The goal of this research is to design a reactor for the composites to be coated with Silicon using the reaction and diffusion kinetics determined at higher temperatures and different partial pressures compared to the standard electronics industry. Chemical Vapor Deposition is the technique that will be used in determining the necessary parameters. The findings from this research can be further used in optimizing the utilization of the reagents and optimizing the process economically.

  20. The material performance of HSS (high speed steel) tools and its relation with chemical composition and carbide distribution

    NASA Astrophysics Data System (ADS)

    Darmawan, B.; Kusman, M.; Hamdani, R. A.

    2016-04-01

    The study aims to compare the performance of two types of material HSS (High Speed Steel) are widely used. It also will be the chemical composition and distribution of carbide particles therein. Two types of HSS are available in the market: HSS from Germany (Bohler) and HSS from China. This research employed the pure experimental design. It consists of two stages. The first, aims to test/operate lathe machines to determine the lifetime and performance of tools based on specified wear criteria. The second, characterization of microstructure using SEM-EDS was conducted. Firstly, grinding of toolss was done so that the toolss could be used for cutting metal in the turning process. Grinding processes of the two types of toolss were done at the same geometry, that is side rake angle (12°-18°), angle of keenness (60°-68°), and side relief angle (10°-12°). Likewise, machining parameters were set in the same machining conditions. Based on the results of the tests, it is found that to reach 0.2 mm wear point, toolss made of HSS from Germany needed 24 minutes, while toolss made of HSS from China needed 8 minutes. Next, microstructure tests using SEM/EDS were done. The results of the SEM tests indicate that the carbide particles of HSS from Germany were more evenly distributed than the carbide particles of HSS from China. Carbide compounds identified in HSS from China were Cr23C6 and Fe4Mo2C. Oxide impurity of Al2O3 was also found in the material. On the other hand, in HSS from Germany, no impurity and other carbide compounds were identified, except Cr23C6 and Fe4Mo2C, also Fe4W2C, and VC or V4C3.

  1. Push-out tests on a new silicon carbide/reaction-bonded silicon carbide ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Curtin, William A.; Eldridge, Jeffrey I.; Srinivasan, Gajawalli V.

    1993-01-01

    Fiber push-out tests have been performed on a ceramic matrix composite consisting of carborundum-sintered SiC fibers, with a BN coating, embedded in a reaction-bonded SiC matrix. Analysis of the push-out data, utilizing the most complete theory presently available, shows that one of the fiber/coating/matrix interfaces has a low fracture energy (one-tenth that of the fiber) and a moderate sliding resistance of about 8 MPa. The debonded sliding interface shows some continuous but minor abrasion, which appears to increase the sliding resistance, but overall the system exhibits very clean smooth sliding. The tensile response of a full-scale composite is then modeled using data obtained here and known fiber strengths to demonstrate the good composite behavior predicted for this material.

  2. Body composition of female wheelchair athletes.

    PubMed

    Sutton, L; Wallace, J; Goosey-Tolfrey, V; Scott, M; Reilly, T

    2009-04-01

    Wheelchair users undergo changes in body composition as a result of disability. In this study the distribution of bone mineral, lean and fat mass was assessed in highly-trained female wheelchair athletes and a reference group by dual-energy X-ray absorptiometry (DXA). The transferability of anthropometric equations commonly used in female groups was examined in order to establish a suitable field method of body composition assessment. The DXA total-body results indicated no difference between groups, but segmental analyses uncovered regional differences. The wheelchair athletes had greater BMD (p=0.088), more lean mass (p<0.001) and a lower percent fat (p=0.050) in their arms. The reverse was true of the legs (p< or =0.001). The trunk as a whole did not differ between groups. In general, the anthropometric equations showed a lack of transferability to the wheelchair group and tended to underestimate total percent body fat. Anthropometric measures such as body mass index (BMI) and waist girth showed strong correlations with body fat in the wheelchair group (BMI: r=0.90, p=0.001; waist: r=0.83, p=0.001), but weaker results in the reference group. It is recommended that specific anthropometric equations be developed for use in the absence of a 'gold standard' measure of body composition such as DXA.

  3. Superficial roughness on composite surface, composite-enamel and composite-dentin junctions after different finishing and polishing procedures. Part II: roughness with diamond finishing and differences between enamel composite vs body composite.

    PubMed

    Ferraris, Federico; Conti, Alessandro

    2014-01-01

    The following study asks three principle questions relative to composite finishing and composite polishing: 1) Will the superficial roughness of different restoration surfaces have different values, utilizing the same polishing system (multistep), after finishing with the tungsten carbide or diamond bur? 2) Under the same conditions of finishing and polishing sequences, will the composite surfaces (C), the composite-enamel (CE) and composite-dentin (CD) interfaces show different roughness values? 3) Will the surface roughness of composites of different translucency in the various phases of finishing and polishing, and on different interfaces, have different results? The null hypothesis is represented by the fact that there are no significant differences on roughness of composite restorations when polishing, after finishing with tungsten carbide or diamond burs. Furthermore, the null hypothesis is that there are no significant differences on roughness between polishing on composite surface, composite-enamel and composite-dentin interfaces, and finally there are no differences on roughness after finishing and polishing of two composite with different translucency. For the study, 56 class V cavities were prepared on extracted teeth. Restorations were done in nanofilled composite Filtek XTE (3M Espe) in a standard fashion, and then finished and polished. The 28 buccal cavities were restored on the surface with composite enamel and the 28 palatals with composite body. Finishing was done with fine toothing burs in tungsten carbide (16 blades) or fine grit diamond burs (46 μm), and made by the same manufacturer (Komet). The second phase of finishing was done with burs (with the same form as already mentioned) ultrafine toothing tungsten carbide (30 blades) or with extra and ultrafine grit diamond (25 and 8 μm). The polishing phase for both of the earlier sequences was done with the application of three rubber tips with decreasing abrasiveness and an application with a

  4. Evaluation of body composition. Current issues.

    PubMed

    Heyward, V H

    1996-09-01

    In the selection of body composition field methods and prediction equations, exercise and health practitioners must consider their clients' demographics. Factors, such as age, gender, level of adiposity, physical activity and ethnicity influence the choice of method and equation. Also, it is important to evaluate the relative worth of prediction equations in terms of the criterion method used to derive reference measures of body composition for equation development. Given that hydrodensitometry, hydrometry and dual-energy x-ray absorptiometry are subject to measurement error and violation of basic assumptions underlying their use, none of these should be considered as a 'gold standard' method for in vivo body composition assessment. Reference methods, based on whole-body, 2-component body composition models, are limited, particularly for individuals whose fat-free body (FFB) density and hydration differ from values assumed for 2-component models. Use of field method prediction equations developed from 2-component model (Siri equation) reference measures of body composition will systematically underestimate relative body fatness of American Indian women, Black men and women, and Hispanic women because the average FFB density of these ethnic groups exceeds the assumed value (1.1 g/ml). Thus, some researchers have developed prediction equations based on multicomponent model estimates of body composition that take into account interindividual variability in the water, mineral, and protein content of the FFB. One multicomponent model approach adjusts body density (measured via hydrodensitometry) for total body water (measured by hydrometry) and/or total body mineral estimated from bone mineral (measured via dual-energy x-ray absorptiometry). Skinfold (SKF), bioelectrical impedance analysis (BIA), and near-infrared interactance (NIR) are 3 body composition methods used in clinical settings. Unfortunately, the overwhelming majority of field method prediction equations

  5. Reaction-Based SiC Materials for Joining Silicon Carbide Composites for Fusion Energy

    SciTech Connect

    Lewinsohn, Charles A.; Jones, Russell H.; Singh, M.; Serizawa, H.; Katoh, Y.; Kohyama, A.

    2000-09-01

    The fabrication of large or complex silicon carbide-fiber-reinforced silicon carbide (SiC/SiC) components for fusion energy systems requires a method to assemble smaller components that are limited in size by manufacturing constraints. Previous analysis indicates that silicon carbide should be considered as candidate joint materials. Two methods to obtain SiC joints rely on a reaction between silicon and carbon to produce silicon carbide. This report summarizes preliminary mechanical properties of joints formed by these two methods. The methods appear to provide similar mechanical properties. Both the test methods and materials are preliminary in design and require further optimization. In an effort to determine how the mechanical test data is influenced by the test methodology and specimen size, plans for detailed finite element modeling (FEM) are presented.

  6. Body Composition Methods: Comparisons and Interpretation

    PubMed Central

    Duren, Dana L.; Sherwood, Richard J.; Czerwinski, Stefan A.; Lee, Miryoung; Choh, Audrey C.; Siervogel, Roger M.; Cameron Chumlea, Wm.

    2008-01-01

    The incidence of obesity in the United States and other developed countries is epidemic. Because the prevalence of comorbidities to obesity, such as type 2 diabetes, has also increased, it is clear there is a great need to monitor and treat obesity and its comorbidities. Body composition assessments vary in precision and in the target tissue of interest. The most common assessments are anthropometric and include weight, stature, abdominal circumference, and skinfold measurements. More complex methods include bioelectrical impedance, dual-energy X-ray absorptiometry, body density, and total body water estimates. There is no single universally recommended method for body composition assessment in the obese, but each modality has benefits and drawbacks. We present here the most common methods and provide guidelines by way of examples to assist the clinician/researcher in choosing methods appropriate to their situation. PMID:19885303

  7. Corrosion resistant cemented carbide

    SciTech Connect

    Hong, J.

    1990-10-16

    This paper describes a corrosion resistant cemented carbide composite. It comprises: a granular tungsten carbide phase, a semi-continuous solid solution carbide phase extending closely adjacent at least a portion of the grains of tungsten carbide for enhancing corrosion resistance, and a substantially continuous metal binder phase. The cemented carbide composite consisting essentially of an effective amount of an anti-corrosion additive, from about 4 to about 16 percent by weight metal binder phase, and with the remaining portion being from about 84 to about 96 percent by weight metal carbide wherein the metal carbide consists essentially of from about 4 to about 30 percent by weight of a transition metal carbide or mixtures thereof selected from Group IVB and of the Periodic Table of Elements and from about 70 to about 96 percent tungsten carbide. The metal binder phase consists essentially of nickel and from about 10 to about 25 percent by weight chromium, the effective amount of an anti-corrosion additive being selected from the group consisting essentially of copper, silver, tine and combinations thereof.

  8. Childhood body composition in relation to body mass index.

    PubMed

    Maynard, L M; Wisemandle, W; Roche, A F; Chumlea, W C; Guo, S S; Siervogel, R M

    2001-02-01

    The aim is to describe body composition in relation to body mass index (BMI; body weight/stature(2)) to provide health care professionals insight into the meaning, significance, and limitations of BMI as an index of adiposity during childhood. Data from 387 healthy, white children 8 to 18 years of age from the Fels Longitudinal Study were analyzed. Measurements were scheduled annually and each child was examined 1 to 11 times, totaling 1748 observations. Total body fat (TBF) and fat-free mass (FFM) were determined from hydrodensitometry. Stature and weight were measured using standard methods and BMI and the components of BMI, TBF/stature(2), and FFM/stature(2) were calculated. Analyses included correlations between BMI and body composition variables; age-related patterns of BMI, TBF/stature(2), and FFM/stature(2); and annual changes in BMI, TBF/stature(2), and FFM/stature(2). Generally, correlations between BMI and body composition variables were strong and significantly different from zero. Means for BMI throughout childhood were similar for boys and girls, although significantly larger values were observed for girls at ages 12 to 13 years. Age-related patterns of TBF/stature(2) and FFM/stature(2) differed between sexes. In each sex, annual increases in BMI were driven primarily by increases in FFM/stature(2) until late adolescence, with increases in TBF/stature(2) contributing to a larger proportion of the BMI increases in girls than in boys. Unlike adults, annual increases in BMI during childhood are generally attributed to the lean rather than to the fat component of BMI. Because the properties of BMI vary during childhood, health care professionals must consider factors such as age and sex when interpreting BMI.

  9. Estimation of body composition of pigs

    SciTech Connect

    Ferrell, C.L.; Cornelius, S.G.

    1984-04-01

    A study was conducted to evaluate the use of deuterium oxide (D2O) for in vivo estimation of body composition of diverse types of pigs. Obese (Ob, 30) and contemporary Hampshire X Yorkshire (C, 30) types of pigs used in the study were managed and fed under typical management regimens. Indwelling catheters were placed in a jugular vein of 6 Ob and 6 C pigs at 4, 8, 12, 18 and 24 wk of age. The D2O was infused (.5 g/kg body weight) as a .9% NaCl solution into the jugular catheter. Blood samples were taken immediately before and at .25, 1, 4, 8, 12, 24 and 48 h after the D2O infusion and D2O concentration in blood water was determined. Pigs were subsequently killed by euthanasia injection. Contents of the gastrointestinal tract were removed and the empty body was then frozen and later ground and sampled for subsequent analyses. Ground body tissue samples were analyzed for water, fat, N, fat-free organic matter and ash. Pig type, age and the type X age interaction were significant sources of variation in live weight, D2O pool size and all empty body components, as well as all fat-free empty body components. Relationships between age and live weight or weight of empty body components, and between live weight, empty body weight, empty body water or D2O space and weight of empty components were highly significant but influenced, in most cases, by pig type. The results of this study suggested that, although relationships between D2O space and body component weights were highly significant, they were influenced by pig type and were little better than live weight for the estimation of body composition.

  10. Accurate body composition measures from whole-body silhouettes.

    PubMed

    Xie, Bowen; Avila, Jesus I; Ng, Bennett K; Fan, Bo; Loo, Victoria; Gilsanz, Vicente; Hangartner, Thomas; Kalkwarf, Heidi J; Lappe, Joan; Oberfield, Sharon; Winer, Karen; Zemel, Babette; Shepherd, John A

    2015-08-01

    Obesity and its consequences, such as diabetes, are global health issues that burden about 171 × 10(6) adult individuals worldwide. Fat mass index (FMI, kg/m(2)), fat-free mass index (FFMI, kg/m(2)), and percent fat mass may be useful to evaluate under- and overnutrition and muscle development in a clinical or research environment. This proof-of-concept study tested whether frontal whole-body silhouettes could be used to accurately measure body composition parameters using active shape modeling (ASM) techniques. Binary shape images (silhouettes) were generated from the skin outline of dual-energy x-ray absorptiometry (DXA) whole-body scans of 200 healthy children of ages from 6 to 16 yr. The silhouette shape variation from the average was described using an ASM, which computed principal components for unique modes of shape. Predictive models were derived from the modes for FMI, FFMI, and percent fat using stepwise linear regression. The models were compared to simple models using demographics alone [age, sex, height, weight, and body mass index z-scores (BMIZ)]. The authors found that 95% of the shape variation of the sampled population could be explained using 26 modes. In most cases, the body composition variables could be predicted similarly between demographics-only and shape-only models. However, the combination of shape with demographics improved all estimates of boys and girls compared to the demographics-only model. The best prediction models for FMI, FFMI, and percent fat agreed with the actual measures with R(2) adj. (the coefficient of determination adjusted for the number of parameters used in the model equation) values of 0.86, 0.95, and 0.75 for boys and 0.90, 0.89, and 0.69 for girls, respectively. Whole-body silhouettes in children may be useful to derive estimates of body composition including FMI, FFMI, and percent fat. These results support the feasibility of measuring body composition variables from simple cameras such as those found in cell

  11. Accurate body composition measures from whole-body silhouettes

    PubMed Central

    Xie, Bowen; Avila, Jesus I.; Ng, Bennett K.; Fan, Bo; Loo, Victoria; Gilsanz, Vicente; Hangartner, Thomas; Kalkwarf, Heidi J.; Lappe, Joan; Oberfield, Sharon; Winer, Karen; Zemel, Babette; Shepherd, John A.

    2015-01-01

    Purpose: Obesity and its consequences, such as diabetes, are global health issues that burden about 171 × 106 adult individuals worldwide. Fat mass index (FMI, kg/m2), fat-free mass index (FFMI, kg/m2), and percent fat mass may be useful to evaluate under- and overnutrition and muscle development in a clinical or research environment. This proof-of-concept study tested whether frontal whole-body silhouettes could be used to accurately measure body composition parameters using active shape modeling (ASM) techniques. Methods: Binary shape images (silhouettes) were generated from the skin outline of dual-energy x-ray absorptiometry (DXA) whole-body scans of 200 healthy children of ages from 6 to 16 yr. The silhouette shape variation from the average was described using an ASM, which computed principal components for unique modes of shape. Predictive models were derived from the modes for FMI, FFMI, and percent fat using stepwise linear regression. The models were compared to simple models using demographics alone [age, sex, height, weight, and body mass index z-scores (BMIZ)]. Results: The authors found that 95% of the shape variation of the sampled population could be explained using 26 modes. In most cases, the body composition variables could be predicted similarly between demographics-only and shape-only models. However, the combination of shape with demographics improved all estimates of boys and girls compared to the demographics-only model. The best prediction models for FMI, FFMI, and percent fat agreed with the actual measures with R2 adj. (the coefficient of determination adjusted for the number of parameters used in the model equation) values of 0.86, 0.95, and 0.75 for boys and 0.90, 0.89, and 0.69 for girls, respectively. Conclusions: Whole-body silhouettes in children may be useful to derive estimates of body composition including FMI, FFMI, and percent fat. These results support the feasibility of measuring body composition variables from simple

  12. Top 10 Research Questions Related to Body Composition

    ERIC Educational Resources Information Center

    Going, Scott; Lee, Vinson; Blew, Rob; Laddu, Deepika; Hetherington-Rauth, Megan

    2014-01-01

    An understanding of body composition is crucial to understanding human health, disease, and function. Research in body composition has focused on the development of assessment methods, description of normal changes in body composition with growth and development and aging, and the changes that occur in body composition in response to challenges…

  13. Top 10 Research Questions Related to Body Composition

    ERIC Educational Resources Information Center

    Going, Scott; Lee, Vinson; Blew, Rob; Laddu, Deepika; Hetherington-Rauth, Megan

    2014-01-01

    An understanding of body composition is crucial to understanding human health, disease, and function. Research in body composition has focused on the development of assessment methods, description of normal changes in body composition with growth and development and aging, and the changes that occur in body composition in response to challenges…

  14. Processing - microstructure relationships of chemically vapor deposited zirconia fiber coating for environmentally durable silicon carbide/silicon carbide composites

    NASA Astrophysics Data System (ADS)

    Lee, Jinil

    In SiC/SiC ceramic matrix composites, toughness is obtained by adding a fiber coating which provides a weak interface for crack deflection and debonding between the fiber and the matrix. However, the most commonly used fiber coatings, carbon and boron nitride, are unstable in oxidative environments. In the present study, the feasibility of using a chemically vapor deposited zirconia (CVD-ZrO 2) fiber coating as an oxidation-resistant interphase for SiC/SiC composites was investigated. The feasibility of the CVD-ZrO2 coating as a useful interphase for SiC/SiC composites was investigated with emphasis on developing critical processing-microstructure relationships. A study of morphological evolution in the CVD-ZrO2 coating suggested that a size-controlled displacive phase transformation from tetragonal ZrO2 (t-ZrO2) to monoclinic ZrO2 (m-ZrO2) was the key mechanism responsible for the weak interface behavior exhibited by the ZrO2 coating. The pre-delamination occurred as a result of (i) continuous formation of t-ZrO2 nuclei on the deposition surface; (ii) martensitic transformation of the tetragonal phase to a monoclinic phase upon reaching a critical grain size; and (iii) development of significant compressive hoop stresses due to the volume dilation associated with the transformation. We also discovered that low oxygen partial pressure in the CVD reactor was required for the nucleation of t-ZrO2 and was ultimately responsible for the delamination behavior. The effects of oxygen partial pressure on the nucleation behavior of the CVD-ZrO2 coating was systematically studied by intentionally adding the controlled amount of O2 into the CVD chamber. Characterization results suggested that the number density of t-ZrO2 nuclei apparently decreased with increasing the oxygen partial pressure from 0.004 to 1.6 Pa. Also, the coating layer became more columnar and contained larger m-ZrO2 grains. The observed relationships between the oxygen partial pressure and the morphological

  15. Body composition phenotypes and obesity paradox.

    PubMed

    Prado, Carla M; Gonzalez, M Cristina; Heymsfield, Steven B

    2015-11-01

    The obesity paradox is a highly controversial concept that may be attributed to methodological limitations related to its identification. One of the primary concerns is the use of BMI to define obesity. This index does not differentiate lean versus adipose tissue compartments (i.e. body composition) confounding health consequences for morbidity and mortality, especially in clinical populations. This review will describe the past year's evidence on the obesity paradox phenomenon, primarily focusing on the role of abnormal body composition phenotypes in explaining the controversies observed in the literature. In spite of the substantial number of articles investigating the obesity paradox phenomenon, less than 10% used a direct measure of body composition and when included, it was not fully explored (only adipose tissue compartment evaluated). When lean tissue or muscle mass is taken into account, the general finding is that a high BMI has no protective effect in the presence of low muscle mass and that it is the latter that associates with poor prognosis. In view of the body composition variability of patients with identical BMI, it is unreasonable to rely solely on this index to identify obesity. The consequences of a potential insubstantial obesity paradox are mixed messages related to patient-related prognostication.

  16. Writing Bodies: Somatic Mind in Composition Studies.

    ERIC Educational Resources Information Center

    Fleckenstein, Kristie S.

    1999-01-01

    Discusses the somatic mind, a permeable materiality in which mind and body resolve into a single entity which is (re)formed by the constantly shifting boundaries of discursive and corporeal intertextualities. Addresses its importance in composition studies. Critiques the poststructuralist disregard of corporeality. (CR)

  17. Comparison of Some Secondary Body Composition Algorithms

    ERIC Educational Resources Information Center

    Sutton, Robert A.; Miller, Carolyn

    2006-01-01

    Body composition measurements vary greatly in degree of measurement difficulty and accuracy. Hydrostatic weighing, chemical dilution or their equivalents were the accepted "gold" standards for assessing fat mass. Dual Energy X-ray Absorptiometry (DEXA) is fast replacing these techniques as the preferred standard. However, these direct measurement…

  18. Comparison of Some Secondary Body Composition Algorithms

    ERIC Educational Resources Information Center

    Sutton, Robert A.; Miller, Carolyn

    2006-01-01

    Body composition measurements vary greatly in degree of measurement difficulty and accuracy. Hydrostatic weighing, chemical dilution or their equivalents were the accepted "gold" standards for assessing fat mass. Dual Energy X-ray Absorptiometry (DEXA) is fast replacing these techniques as the preferred standard. However, these direct measurement…

  19. Microstructure-property relationships of chemically vapor deposited zirconia fiber coating for environmentally durable silicon carbide/silicon carbide composites

    NASA Astrophysics Data System (ADS)

    Li, Hao

    In SiC/SiC ceramic matrix composites, toughness is obtained by adding a fiber coating, which provides a weak interface for crack deflection and debonding between the fiber and the matrix. However, the most commonly used fiber coatings, carbon and boron nitride, are unstable in oxidative environments. In the present study, the feasibility of using a chemically vapor deposited zirconia (CVD-ZrO2) fiber coating as an oxidation-resistant interphase for SiC/SiC composites was investigated. A study of morphological evolution in the CVD-ZrO2 coating suggested that a size-controlled displacive phase transformation from tetragonal ZrO2 ( t-ZrO2) to monoclinic ZrO2 (m-ZrO 2) was the key mechanism responsible for the weak interface behavior exhibited by the ZrO2 coating. It appeared that a low oxygen partial pressure in the CVD reactor chamber was essential for the nucleation of t-ZrO2 and therefore was responsible for the delamination behavior. With this understanding of the weak interface mechanism, minicomposite specimens containing various ZrO2 fiber coating morphologies were fabricated and tested. A fractographic analysis showed that in-situ fiber strength and minicomposite failure loads were strongly dependent on the phase contents and microstructure of the ZrO2 coating. We determined that an optimum microstructure of the ZrO2 coating should contain a predelaminated interface surrounded by a dense outer layer. The outer layer was needed to protect the fiber from degradation during the subsequent SiC matrix infiltration procedure. A preliminary tensile stress-rupture study indicated that the ZrO2 coating exhibited promising performance in terms of providing the weak interface behavior and maintaining the thermal and oxidative stability at elevated temperatures.

  20. Assessment of Silicon Carbide Composites for Advanced Salt-Cooled Reactors

    SciTech Connect

    Katoh, Yutai; Wilson, Dane F; Forsberg, Charles W

    2007-09-01

    The Advanced High-Temperature Reactor (AHTR) is a new reactor concept that uses a liquid fluoride salt coolant and a solid high-temperature fuel. Several alternative fuel types are being considered for this reactor. One set of fuel options is the use of pin-type fuel assemblies with silicon carbide (SiC) cladding. This report provides (1) an initial viability assessment of using SiC as fuel cladding and other in-core components of the AHTR, (2) the current status of SiC technology, and (3) recommendations on the path forward. Based on the analysis of requirements, continuous SiC fiber-reinforced, chemically vapor-infiltrated SiC matrix (CVI SiC/SiC) composites are recommended as the primary option for further study on AHTR fuel cladding among various industrially available forms of SiC. Critical feasibility issues for the SiC-based AHTR fuel cladding are identified to be (1) corrosion of SiC in the candidate liquid salts, (2) high dose neutron radiation effects, (3) static fatigue failure of SiC/SiC, (4) long-term radiation effects including irradiation creep and radiation-enhanced static fatigue, and (5) fabrication technology of hermetic wall and sealing end caps. Considering the results of the issues analysis and the prospects of ongoing SiC research and development in other nuclear programs, recommendations on the path forward is provided in the order or priority as: (1) thermodynamic analysis and experimental examination of SiC corrosion in the candidate liquid salts, (2) assessment of long-term mechanical integrity issues using prototypical component sections, and (3) assessment of high dose radiation effects relevant to the anticipated operating condition.

  1. Assessment methods in human body composition.

    PubMed

    Lee, Seon Yeong; Gallagher, Dympna

    2008-09-01

    The present study reviews the most recently developed and commonly used methods for the determination of human body composition in vivo with relevance for nutritional assessment. Body composition measurement methods are continuously being perfected with the most commonly used methods being bioelectrical impedance analysis, dilution techniques, air displacement plethysmography, dual energy X-ray absorptiometry, and MRI or magnetic resonance spectroscopy. Recent developments include three-dimensional photonic scanning and quantitative magnetic resonance. Collectively, these techniques allow for the measurement of fat, fat-free mass, bone mineral content, total body water, extracellular water, total adipose tissue and its subdepots (visceral, subcutaneous, and intermuscular), skeletal muscle, select organs, and ectopic fat depots. There is an ongoing need to perfect methods that provide information beyond mass and structure (static measures) to kinetic measures that yield information on metabolic and biological functions. On the basis of the wide range of measurable properties, analytical methods and known body composition models, clinicians and scientists can quantify a number of body components and with longitudinal assessment, can track changes in health and disease with implications for understanding efficacy of nutritional and clinical interventions, diagnosis, prevention, and treatment in clinical settings. With the greater need to understand precursors of health risk beginning in childhood, a gap exists in appropriate in-vivo measurement methods beginning at birth.

  2. Assessment methods in human body composition

    PubMed Central

    Lee, Seon Yeong; Gallagher, Dympna

    2009-01-01

    Purpose of review The present study reviews the most recently developed and commonly used methods for the determination of human body composition in vivo with relevance for nutritional assessment. Recent findings Body composition measurement methods are continuously being perfected with the most commonly used methods being bioelectrical impedance analysis, dilution techniques, air displacement plethysmography, dual energy X-ray absorptiometry, and MRI or magnetic resonance spectroscopy. Recent developments include three-dimensional photonic scanning and quantitative magnetic resonance. Collectively, these techniques allow for the measurement of fat, fat-free mass, bone mineral content, total body water, extracellular water, total adipose tissue and its subdepots (visceral, subcutaneous, and intermuscular), skeletal muscle, select organs, and ectopic fat depots. Summary There is an ongoing need to perfect methods that provide information beyond mass and structure (static measures) to kinetic measures that yield information on metabolic and biological functions. On the basis of the wide range of measurable properties, analytical methods and known body composition models, clinicians and scientists can quantify a number of body components and with longitudinal assessment, can track changes in health and disease with implications for understanding efficacy of nutritional and clinical interventions, diagnosis, prevention, and treatment in clinical settings. With the greater need to understand precursors of health risk beginning in childhood, a gap exists in appropriate in-vivo measurement methods beginning at birth. PMID:18685451

  3. Carbide coated fibers in graphites-aluminum composites. [(fabrication of metal matrix composites)

    NASA Technical Reports Server (NTRS)

    Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

    1976-01-01

    Research activities are described for a NASA-supported program at the Los Alamos Scientific Laboratory to develop graphite fiber-aluminum matrix composites. A chemical vapor deposition apparatus was constructed for continuously coating graphite fibers with TiC. As much as 150 meters of continuously coated fibers were produced. Deposition temperatures were varied from 1365 K to about 1750 K, and deposition time from 6 to 150 seconds. The 6 sec deposition time corresponded to a fiber feed rate of 2.54 m/min through the coater. Thin, uniform, adherent TiC coats, with thicknesses up to approximately 0.1 micrometer were produced on the individual fibers of Thornel 50 graphite yarns without affecting fiber strength. Although coat properties were fairly uniform throughout a given batch, more work is needed to improve the batch-to-batch reproducibility. Samples of TiC-coated Thornel 50 fibers were infiltrated with an aluminum alloy and hot-pressed in vacuum to produce small composite bars for flexure testing. Strengths as high as 90% of the rule-of-mixtures strength were achieved. Results of the examination of the fracture surfaces indicate that the bonding between the aluminum and the TiC-coated fibers is better than that achieved in a similar, commercially infiltrated material made with fibers having no observable surface coats. Several samples of Al-infiltrated, TiC-coated Thornel 50 graphite yarns, together with samples of the commercially infiltrated, uncoated fibers, were heated for 100 hours at temperatures near the alloy solidus. The TiC-coated samples appear to undergo less reaction than do the uncoated samples. Photomicrographs are shown.

  4. Composites comprising silicon carbide fibers dispersed in magnesia-aluminate matrix and fabrication thereof and of other composites by sinter forging

    DOEpatents

    Panda, Prakash C.; Seydel, Edgar R.; Raj, Rishi

    1989-10-03

    A novel ceramic-ceramic composite of a uniform dispersion of silicon carbide fibers in a matrix of MgO.multidot.nAl.sub.2 O.sub.3 wherein n ranges from about 1 to about 4.5, said composite comprising by volume from 1 to 50% silicon carbide fibers and from 99 to 50% MgO.multidot.nAl.sub.2 O.sub.3. The composite is readily fabricated by forming a powder comprising a uniform dispersion of silicon carbide fibers in poorly crystalline phase comprising MgO and Al.sub.2 O.sub.3 in a mole ratio of n and either (a) hot pressing or preferably (b) cold pressing to form a preform and then forging utilizing a temperature in the range of 1100.degree. C. to 1900.degree. C. and a strain rate ranging from about 10.sup.-5 seconds .sup.-1 to about 1 seconds .sup.-1 so that surfaces cracks do not appear to obtain a shear deformation greater than 30%.

  5. Muscle fibre type composition and body composition in hammer throwers.

    PubMed

    Terzis, Gerasimos; Spengos, Konstantinos; Kavouras, Stavros; Manta, Panagiota; Georgiadis, Giorgos

    2010-01-01

    Aim of the present study was to describe the muscle fibre type composition and body composition of well-trained hammer throwers. Six experienced hammer throwers underwent the following measurements: one repetition maximum in squat, snatch, and clean, standing broad jump, backward overhead shot throw and the hammer throw. Dual x-ray absorptiometry was used for body composition analysis. Fibre type composition and cross sectional area was determined in muscle biopsy samples of the right vastus lateralis. Eight physical education students served as a control group. One repetition maximum in squat, snatch and clean for the hammer throwers was 245 ± 21, 132 ± 13 and 165 ± 12kg, respectively. Lean body mass was higher in hammer throwers (85.9 ± 3. 9kg vs. 62.7 ± 5.1kg (p < 0.01). The percentage area of type II muscle fibres was 66.1 ± 4% in hammer throwers and 51 ± 8% in the control group (p < 0.05). Hammer throwers had significantly larger type IIA fibres (7703 ± 1171 vs. 5676 ± 1270μm(2), p < 0.01). Hammer throwing performance correlated significantly with lean body mass (r = 0.81, p < 0.05). These data indicate that hammer throwers have larger lean body mass and larger muscular areas occupied by type II fibres, compared with relatively untrained subjects. Moreover, it seems that the enlarged muscle mass of the hammer throwers contributes significantly to the hammer throwing performance. Key pointsWell-trained hammer throwers had increased lean body mass, higher type IIA muscle fibres cross sectional areas, as well as higher bone mineral density, compared to controls.Increased lean body mass was closely related with hammer throwing performance.The relative high percentage of type IIX muscle fibres in vastus lateralis in hammer throwers warrants further investigation.

  6. Muscle Fibre Type Composition and Body Composition in Hammer Throwers

    PubMed Central

    Terzis, Gerasimos; Spengos, Konstantinos; Kavouras, Stavros; Manta, Panagiota; Georgiadis, Giorgos

    2010-01-01

    Aim of the present study was to describe the muscle fibre type composition and body composition of well-trained hammer throwers. Six experienced hammer throwers underwent the following measurements: one repetition maximum in squat, snatch, and clean, standing broad jump, backward overhead shot throw and the hammer throw. Dual x-ray absorptiometry was used for body composition analysis. Fibre type composition and cross sectional area was determined in muscle biopsy samples of the right vastus lateralis. Eight physical education students served as a control group. One repetition maximum in squat, snatch and clean for the hammer throwers was 245 ± 21, 132 ± 13 and 165 ± 12kg, respectively. Lean body mass was higher in hammer throwers (85.9 ± 3. 9kg vs. 62.7 ± 5.1kg (p < 0.01). The percentage area of type II muscle fibres was 66.1 ± 4% in hammer throwers and 51 ± 8% in the control group (p < 0.05). Hammer throwers had significantly larger type IIA fibres (7703 ± 1171 vs. 5676 ± 1270μm2, p < 0.01). Hammer throwing performance correlated significantly with lean body mass (r = 0.81, p < 0.05). These data indicate that hammer throwers have larger lean body mass and larger muscular areas occupied by type II fibres, compared with relatively untrained subjects. Moreover, it seems that the enlarged muscle mass of the hammer throwers contributes significantly to the hammer throwing performance. Key points Well-trained hammer throwers had increased lean body mass, higher type IIA muscle fibres cross sectional areas, as well as higher bone mineral density, compared to controls. Increased lean body mass was closely related with hammer throwing performance. The relative high percentage of type IIX muscle fibres in vastus lateralis in hammer throwers warrants further investigation. PMID:24149393

  7. Handbook of refractory carbides and nitrides: Properties, characteristics, processing and applications

    SciTech Connect

    Pierson, H.O.

    1997-12-31

    This reference work provides a complete review of the structure properties, processing and applications of refractory carbides and nitrides. The contents include: the refractory carbides; interstitial carbides, structure and composites; titanium, zirconium, and hafnium carbides; vanadium, niobium and tantalum carbides; chromium, molybdenum, and tungsten carbides; covalent carbides--structure and composition; characteristics and properties of silicon carbide and boron carbide; the refractory nitrides; interstitial nitrides--structure and composition; interstitial nitrides--properties and general characteristics; covalent nitrides--composition and structure; covalent nitrides--properties and general characteristics; processing of refractory carbides and nitrides and applications of refractory carbides and nitrides.

  8. Obesity, body composition, and prostate cancer.

    PubMed

    Fowke, Jay H; Motley, Saundra S; Concepcion, Raoul S; Penson, David F; Barocas, Daniel A

    2012-01-18

    Established risk factors for prostate cancer have not translated to effective prevention or adjuvant care strategies. Several epidemiologic studies suggest greater body adiposity may be a modifiable risk factor for high-grade (Gleason 7, Gleason 8-10) prostate cancer and prostate cancer mortality. However, BMI only approximates body adiposity, and may be confounded by centralized fat deposition or lean body mass in older men. Our objective was to use bioelectric impedance analysis (BIA) to measure body composition and determine the association between prostate cancer and total body fat mass (FM) fat-free mass (FFM), and percent body fat (%BF), and which body composition measure mediated the association between BMI or waist circumference (WC) with prostate cancer. The study used a multi-centered recruitment protocol targeting men scheduled for prostate biopsy. Men without prostate cancer at biopsy served as controls (n = 1057). Prostate cancer cases were classified as having Gleason 6 (n = 402), Gleason 7 (n = 272), or Gleason 8-10 (n = 135) cancer. BIA and body size measures were ascertained by trained staff prior to diagnosis, and clinical and comorbidity status were determined by chart review. Analyses utilized multivariable linear and logistic regression. Body size and composition measures were not significantly associated with low-grade (Gleason 6) prostate cancer. In contrast, BMI, WC, FM, and FFM were associated with an increased risk of Gleason 7 and Gleason 8-10 prostate cancer. Furthermore, BMI and WC were no longer associated with Gleason 8-10 (OR(BMI) = 1.039 (1.000, 1.081), OR(WC) = 1.016 (0.999, 1.033), continuous scales) with control for total body FFM (OR(BMI) = 0.998 (0.946, 1.052), OR(WC) = 0.995 (0.974, 1.017)). Furthermore, increasing FFM remained significantly associated with Gleason 7 (OR(FFM) = 1.030 (1.008, 1.052)) and Gleason 8-10 (OR(FFM) = 1.044 (1.014, 1.074)) after controlling for FM. Our results suggest that associations between BMI and

  9. Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

    DOEpatents

    Barton, T.J.; Ijadi-Maghsoodi, S.; Pang, Y.

    1994-05-17

    The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R[sup 1])(R[sup 2])Si--C[triple bond]C-(R[sup 3])(R[sup 4])Si--CH[double bond]CH--][sub n]--, wherein n[>=]2; and each R[sup 1], R[sup 2], R[sup 3], and R[sup 4] is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

  10. Diorganosilacetylene-alt-diorganosilvinylene polymers and a process densifying porous silicon-carbide bodies

    DOEpatents

    Barton, Thomas J.; Ijadi-Maghsoodi, Sina; Pang, Yi

    1994-05-17

    The present invention provides linear organosilicon polymers including acetylene and vinylene moieties, and a process for their preparation. These diorganosilacetylene-alt-diorganosilvinylene linear polymers can be represented by the formula: --[--(R.sup.1)(R.sup.2)Si--C.tbd.C--(R.sup.3)(R.sup.4)Si--CH=CH--].sub.n-- , wherein n.gtoreq.2; and each R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, aryl, and aralkyl radicals. The polymers are soluble in organic solvents, air stable, and can be pulled into fibers or cast into films. They can be thermally converted into silicon carbide ceramic materials.

  11. Method for production of ceramic oxide and carbide bodies by polymer inclusion and decomposition

    DOEpatents

    Quinby, T.C.

    1984-08-30

    A method for the preparation of thin, free-standing metal oxide films which are useful as nuclear accelerator target materials is described. Cations of any metal except those of Group IA and precious metals, such as, U, Zr, Nd, Ce, Th, Pr or Cr, are absorbed on a thin film of polymeric material, such as carboxymethylcellulose, viscose rayon or cellophane. The cation impregnated polymeric material is dried. Then the impregnated film is heated in an inert atmosphere to form a carbonized membrane. The carbonized membrane is oxidized to yield a thin, self-supporting, metal oxide membrane. Or, the membrane can be heated in an inert atmosphere to yield a thin, self-supporting, metal carbide-containing membrane.

  12. Method for production of ceramic oxide and carbide bodies by polymer inclusion and decomposition

    DOEpatents

    Quinby, Thomas C.

    1985-01-01

    A method for the preparation of thin, free-standing metal oxide films which are useful as nuclear accelerator target materials. Cations of any metal except those of Group IA and precious metals, such as, U, Zr, Nd, Ce, Th, pr or Cr, are absorbed on a thin film of polymeric material, such as, carboxymethylcellulose, viscose rayon or cellophane. The cation impregnated polymeric material is dried. Then the impregnated film is heated in an inert atmosphere to form a carbonized membrane. The carbonized membrane is oxidized to yield a thin, self-supporting, metal oxide membrane. Or, the membrane can be heated in an inert atmosphere to yield a thin, self-supporting, metal carbide-containing membrane.

  13. Method for production of ceramic oxide and carbide bodies by polymer inclusion and decomposition

    SciTech Connect

    Quinby, T. C.

    1985-08-27

    A method for the preparation of thin, free-standing metal oxide films which are useful as nuclear accelerator target materials. Cations of any metal except those of Group IA and precious metals, such as, U, Zr, Nd, Ce, Th, pr or Cr, are absorbed on a thin film of polymeric material, such as, carboxymethylcellulose, viscose rayon or cellophane. The cation impregnated polymeric material is dried. Then the impregnated film is heated in an inert atmosphere to form a carbonized membrane. The carbonized membrane is oxidized to yield a thin, self-supporting, metal oxide membrane. Or, the membrane can be heated in an inert atmosphere to yield a thin, self-supporting, metal carbide-containing membrane.

  14. Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1988-01-01

    The determination of the tribilogically optimum composition of chromium-carbide-based solid lubricant coatings using a foil gas bearing test apparatus is described. The coatings contain a wear resistant chromium carbide `base stock' with the lubricant additives silver and BaF2-CaF2 eutectic. The coating composition is optimized for air-lubricated foil gas bearings at temperatures ranging from 25 to 650 C. The various compositions were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized Ni-Cr alloy foils, and the test bearings were subjected to repeated start-stop cycles under a bearing unit of 14 kPa. Sliding contact between the coated journal and the smooth foil occurs during bearing start-up before lift-off or hydrodynamic lubrication by the air film and during bearing coast-down. The bearings were tested for 9000 start-stop cycles or until specimen reached a predetermined failure level.

  15. Tribological composition optimization of chromium-carbide-based solid lubricant coatings for foil gas bearings at temperatures to 650 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1988-01-01

    The determination of the tribilogically optimum composition of chromium-carbide-based solid lubricant coatings using a foil gas bearing test apparatus is described. The coatings contain a wear resistant chromium carbide `base stock' with the lubricant additives silver and BaF2-CaF2 eutectic. The coating composition is optimized for air-lubricated foil gas bearings at temperatures ranging from 25 to 650 C. The various compositions were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized Ni-Cr alloy foils, and the test bearings were subjected to repeated start-stop cycles under a bearing unit of 14 kPa. Sliding contact between the coated journal and the smooth foil occurs during bearing start-up before lift-off or hydrodynamic lubrication by the air film and during bearing coast-down. The bearings were tested for 9000 start-stop cycles or until specimen reached a predetermined failure level.

  16. A general approach towards carbon supported metal carbide composites for cobalt redox couple based dye-sensitized solar cells as counter electrodes

    NASA Astrophysics Data System (ADS)

    Guo, Hongyue; Han, Qianji; Gao, Chenjing; Zheng, Haihuo; Zhu, Yajing; Wu, Mingxing

    2016-11-01

    In this work, a feasible method is put forward to synthesize carbon supported transition metal carbide composites (Cr3C2-C, Mo2C-C, WC-C, VC-C, NbC-C, TaC-C, and TiC-C, et al.) by utilizing metal chlorides as metal sources, and phenolic resin as carbon source. As demonstrated by the cyclic voltammetry results, the carbon supported carbide composites present higher peak current densities as well as lower peak-to-peak separations. Moreover, the electrochemical impedance spectroscopy results indicate lower charge transfer resistance over the pristine carbides. Compared with the carbides, the carbon supported carbide composites show much higher catalytic activities towards the cobalt redox couple regeneration in dye-sensitized solar cells (DSCs) as counter electrode. In the DSCs system, the devices using the TiC-C, VC-C, and WC-C composite counter electrodes display power conversion efficiencies of 8.85%. 9.75% and 9.42%, respectively, which are much higher than those of the counterparts utilizing TiC, VC and WC counter electrodes.

  17. Durable and self-hydrating tungsten carbide-based composite polymer electrolyte membrane fuel cells.

    PubMed

    Zheng, Weiqing; Wang, Liang; Deng, Fei; Giles, Stephen A; Prasad, Ajay K; Advani, Suresh G; Yan, Yushan; Vlachos, Dionisios G

    2017-09-04

    Proton conductivity of the polymer electrolyte membranes in fuel cells dictates their performance and requires sufficient water management. Here, we report a simple, scalable method to produce well-dispersed transition metal carbide nanoparticles. We demonstrate that these, when added as an additive to the proton exchange Nafion membrane, provide significant enhancement in power density and durability over 100 hours, surpassing both the baseline Nafion and platinum-containing recast Nafion membranes. Focused ion beam/scanning electron microscope tomography reveals the key membrane degradation mechanism. Density functional theory exposes that OH• and H• radicals adsorb more strongly from solution and reactions producing OH• are significantly more endergonic on tungsten carbide than on platinum. Consequently, tungsten carbide may be a promising catalyst in self-hydrating crossover gases while retarding desorption of and capturing free radicals formed at the cathode, resulting in enhanced membrane durability.The proton conductivity of polymer electrolyte membranes in fuel cells dictates their performance, but requires sufficient water management. Here, the authors report a simple method to produce well-dispersed transition metal carbide nanoparticles as additives to enhance the performance of Nafion membranes in fuel cells.

  18. Methods for nurses to measure body composition.

    PubMed

    Moran, Jose Maria; Lavado-Garcia, Jesus Maria; Pedrera-Zamorano, Juan Diego

    2011-01-01

    Among the methods available for assessing body composition, traditional methods like hydrodensitometry and skin-fold measurements are well known. In this review, we focus on the impedance and interactance methods, which use systems that are usually inexpensive, easily transportable and simple to operate. We also discuss the usefulness of dual energy X-ray absorptiometry, particularly for the measurement of fat distribution. Nurses need to be skilled in the use of the equipment and familiar with the techniques.

  19. Thermal expansion properties of carbon nanotube/silicon carbide particle-reinforced magnesium composites fabricated by squeeze infiltration

    NASA Astrophysics Data System (ADS)

    Cho, Dae Hyun; Nam, Ji Hoon; Lee, Byoung Woo; Yim, Si On; Park, Ik Min

    2016-03-01

    In this study, hybrid composites of AZ91 Mg alloy reinforced with carbon nanotubes (CNTs) and silicon carbide particles (SiCps) were successfully fabricated by the squeeze infiltration method. For this fabrication, hybrid preforms of CNTs (5, 10, and 15 vol%) and SiCps (30 vol%) were produced by vacuum suction from slurry mix containing organic and inorganic binders. Hybrid CNT+SiCp/AZ91 Mg composites were fabricated by squeeze infiltration, and the melt infiltrated well between the reinforcements during squeeze infiltration to produce a hybrid MMC with virtually no pores. Their microstructural and thermal expansion properties were evaluated The resulting CNT+SiCp/AZ91 Mg hybrid composites were found to exhibit a significant decrease in their coefficients of thermal expansion with an increase in the CNT volume fraction, owing to the near-zero thermal expansion of the CNTs and the CTE mismatch between them and the AZ91 Mg matrix.

  20. Boron carbide: Consistency of components, lattice parameters, fine structure and chemical composition makes the complex structure reasonable

    NASA Astrophysics Data System (ADS)

    Werheit, Helmut

    2016-10-01

    The complex, highly distorted structure of boron carbide is composed of B12 and B11C icosahedra and CBC, CBB and B□B linear elements, whose concentration depends on the chemical composition each. These concentrations are shown to be consistent with lattice parameters, fine structure data and chemical composition. The respective impacts on lattice parameters are estimated and discussed. Considering the contributions of the different structural components to the energy of the overall structure makes the structure and its variation within the homogeneity range reasonable; in particular that of B4.3C representing the carbon-rich limit of the homogeneity range. Replacing in B4.3C virtually the B□B components by CBC yields the hypothetical moderately distorted B4.0C (structure formula (B11C)CBC). The reduction of lattice parameters related is compatible with recently reported uncommonly prepared single crystals, whose compositions deviate from B4.3C.

  1. Cryogenic optical measurements of 12-segment-bonded carbon-fiber-reinforced silicon carbide composite mirror with support mechanism

    NASA Astrophysics Data System (ADS)

    Kaneda, Hidehiro; Nakagawa, Takao; Onaka, Takashi; Enya, Keigo; Makiuti, Sin'itirou; Takaki, Junji; Haruna, Masaki; Kume, Masami; Ozaki, Tsuyoshi

    2008-03-01

    A 720 mm diameter 12-segment-bonded carbon-fiber-reinforced silicon carbide (C/SiC) composite mirror has been fabricated and tested at cryogenic temperatures. Interferometric measurements show significant cryogenic deformation of the C/SiC composite mirror, which is well reproduced by a model analysis with measured properties of the bonded segments. It is concluded that the deformation is due mostly to variation in coefficients of thermal expansion among segments. In parallel, a 4-degree-of-freedom ball-bearing support mechanism has been developed for cryogenic applications. The C/SiC composite mirror was mounted on an aluminum base plate with the support mechanism and tested again. Cryogenic deformation of the mirror attributed to thermal contraction of the aluminum base plate via the support mechanism is highly reduced by the support, confirming that the newly developed support mechanism is promising for its future application to large-aperture cooled space telescopes.

  2. COMPOSITION AND METHOD FOR COATING A CERAMIC BODY

    DOEpatents

    Blanchard, M.K.

    1958-11-01

    A method is presented for protecting a beryllium carbide-graphite body. The method consists in providing a ceramic coating which must contain at least one basic oxide component, such as CaO, at least one amphoteric oxide component, such as Al/sub 2/O/sub 3/, and at least one acidic oxide component, such as SiO/ sub 2/. Various specific formulations for this ceramic coating are given and the coating is applied by conventional ceramic techniques.

  3. Effect of precursor mass on product phase composition in plasma dynamic synthesis of tungsten carbide

    NASA Astrophysics Data System (ADS)

    Shatrova, K. N.; Sivkov, A. A.; Shanenkov, I. I.; Saigash, A. S.

    2017-05-01

    An interest in WC1-x cubic tungsten carbide results from its catalytic properties similar to those of platinum group metals and the synergistic effect between WC1-x and Pt in reactions of hydrogen evolution and hydrogen oxidation. However, according to the phase diagram of the W-C system, the cubic phase WC1-x only exists in a narrow range of temperature stability (about 2798-3058 K), which makes it difficult for being obtained. To date, there are different methods for synthesizing tungsten carbide powder with a low content of cubic phase that complicates the study of WC1-x properties. A direct plasma dynamic synthesis is known as one of the promising methods to produce WC1-x. The aim of this work is to find the optimal amount of tungsten precursor to obtain cubic tungsten carbide with a high purity by plasma dynamic method. The synthesized products were examined by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The XRD patterns showed that the main phase was cubic tungsten carbide with negligible content of hexagonal tungsten carbide W2C and pure tungsten W. According to a quantitative analysis of synthesized products, which were obtained using masses of initial tungsten equal to 1.0, 0.7, 0.6 and 0.5 gram, the yield of WC1-x phase was 84, 89, 95 and 92 wt%, respectively. The results of TEM displayed that the synthesized powders consist of crystallites, having the size less than 100 nm (WC1-x), and a carbon matrix. This carbon was not detected in XRD due to its presence as an amorphous phase.

  4. Women gaze behaviour in assessing female bodies: the effects of clothing, body size, own body composition and body satisfaction.

    PubMed

    Cundall, Amelia; Guo, Kun

    2017-01-01

    Often with minimally clothed figures depicting extreme body sizes, previous studies have shown women tend to gaze at evolutionary determinants of attractiveness when viewing female bodies, possibly for self-evaluation purposes, and their gaze distribution is modulated by own body dissatisfaction level. To explore to what extent women's body-viewing gaze behaviour is affected by clothing type, dress size, subjective measurements of regional body satisfaction and objective measurements of own body composition (e.g., chest size, body mass index, waist-to-hip ratio), in this self-paced body attractiveness and body size judgement experiment, we compared healthy, young women's gaze distributions when viewing female bodies in tight and loose clothing of different dress sizes. In contrast to tight clothing, loose clothing biased gaze away from the waist-hip to the leg region, and subsequently led to enhanced body attractiveness ratings and body size underestimation for larger female bodies, indicating the important role of clothing in mediating women's body perception. When viewing preferred female bodies, women's higher satisfaction of a specific body region was associated with an increased gaze towards neighbouring body areas, implying satisfaction might reduce the need for comparison of confident body parts; furthermore undesirable body composition measurements were correlated with a gaze avoidance process if the construct was less changeable (i.e. chest size) but a gaze comparison process if the region was more changeable (i.e. body mass index, dress size). Clearly, own body satisfaction and body composition measurements had an evident impact on women's body-viewing gaze allocation, possibly through different cognitive processes.

  5. Structural Evaluation and Mechanical Properties of Aluminum/Tungsten Carbide Composites Fabricated by Continual Annealing and Press Bonding (CAPB) Process

    NASA Astrophysics Data System (ADS)

    Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Drummen, G. P. C.

    2014-12-01

    In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of the fourteenth cycle, which was 1.6 times higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type.

  6. Composition optimization of chromium carbide based solid lubricant coatings for foil gas bearings at temperatures to 650 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1987-01-01

    A test program to determine the optimum composition of chromium carbide based solid lubricant coatings for compliant gas bearings is described. The friction and wear properties of the coatings are evaluated using a foil gas bearing test apparatus. The various coatings were prepared by powder blending, then plasma sprayed onto Inconel 718 test journals and diamond ground to the desired coating thickness and surface finish. The journals were operated against preoxidized nickel-chromium alloy foils. The test bearings were subjected to repeated start/stop cycles under a 14 kPa (2 psi) bearing unit load. The bearings were tested for 9000 start/stop cycles or until the specimen wear reached a predetermined failure level. In general, the addition of silver and eutectic to the chromium carbide base stock significantly reduced foil wear and increased journal coating wear. The optimum coating composition, PS212 (70 wt% metal bonded Cr3C2, 15 wt% Ag, 15% BaF2/CaF2 eutectic), reduced foil wear by a factor of two and displayed coating wear well within acceptable limits. The load capacity of the bearing using the plasma-sprayed coating prior to and after a run-in period was ascertained and compared to polished Inconel 718 specimens.

  7. DEXA body composition changes among 140 conscripts.

    PubMed

    Mattila, V M; Tallroth, K; Marttinen, M; Ohrankammen, O; Pihlajamaki, H

    2009-05-01

    The aim of the study was to determine changes in body composition and physical fitness during military service. A prospective cohort study of 140 healthy male conscripts was conducted. We examined subject characteristics, aerobic performance and muscle strength, and assessed body composition using dual-energy X-ray absorptiometry (DEXA) three times. Conscripts' mean baseline weight (79.5 kg) decreased by 2 kg during the first 3 months, but increased by 0.9 kg during the second 3-month period (p<0.001). Fat mass measured by DEXA decreased by 3.2 kg during the first but increased by 0.8 kg during the second 3-month period (p<0.001). Throughout the 6-month study, an increase was seen in distance of 12-min run test (from 2 380 m to 2 530 m; p<0.001), and muscle strength score (from 6.5 to 9.5 p<0.001). Finnish military training seems to have beneficial effects on physical fitness. However, considering the relatively modest changes in body fat and physical fitness seen in conscripts with average BMIs at baseline, design of diverse training programmes for the varying baseline BMI levels are warranted to improve the physical fitness results.

  8. Magnetically Induced Continuous CO2 Hydrogenation Using Composite Iron Carbide Nanoparticles of Exceptionally High Heating Power.

    PubMed

    Bordet, Alexis; Lacroix, Lise-Marie; Fazzini, Pier-Francesco; Carrey, Julian; Soulantica, Katerina; Chaudret, Bruno

    2016-12-19

    The use of magnetic nanoparticles to convert electromagnetic energy into heat is known to be a key strategy for numerous biomedical applications but is also an approach of growing interest in the field of catalysis. The heating efficiency of magnetic nanoparticles is limited by the poor magnetic properties of most of them. Here we show that the new generation of iron carbide nanoparticles of controlled size and with over 80 % crystalline Fe2.2 C leads to exceptional heating properties, which are much better than the heating properties of currently available nanoparticles. Associated to catalytic metals (Ni, Ru), iron carbide nanoparticles submitted to magnetic excitation very efficiently catalyze CO2 hydrogenation in a dedicated continuous-flow reactor. Hence, we demonstrate that the concept of magnetically induced heterogeneous catalysis can be successfully applied to methanation of CO2 and represents an approach of strategic interest in the context of intermittent energy storage and CO2 recovery.

  9. The Body and the Beautiful: Health, Attractiveness and Body Composition in Men's and Women's Bodies.

    PubMed

    Brierley, Mary-Ellen; Brooks, Kevin R; Mond, Jonathan; Stevenson, Richard J; Stephen, Ian D

    2016-01-01

    The dominant evolutionary theory of physical attraction posits that attractiveness reflects physiological health, and attraction is a mechanism for identifying a healthy mate. Previous studies have found that perceptions of the healthiest body mass index (weight scaled for height; BMI) for women are close to healthy BMI guidelines, while the most attractive BMI is significantly lower, possibly pointing to an influence of sociocultural factors in determining attractive BMI. However, less is known about ideal body size for men. Further, research has not addressed the role of body fat and muscle, which have distinct relationships with health and are conflated in BMI, in determining perceived health and attractiveness. Here, we hypothesised that, if attractiveness reflects physiological health, the most attractive and healthy appearing body composition should be in line with physiologically healthy body composition. Thirty female and 33 male observers were instructed to manipulate 15 female and 15 male body images in terms of their fat and muscle to optimise perceived health and, separately, attractiveness. Observers were unaware that they were manipulating the muscle and fat content of bodies. The most attractive apparent fat mass for female bodies was significantly lower than the healthiest appearing fat mass (and was lower than the physiologically healthy range), with no significant difference for muscle mass. The optimal fat and muscle mass for men's bodies was in line with the healthy range. Male observers preferred a significantly lower overall male body mass than did female observers. While the body fat and muscle associated with healthy and attractive appearance is broadly in line with physiologically healthy values, deviations from this pattern suggest that future research should examine a possible role for internalization of body ideals in influencing perceptions of attractive body composition, particularly in women.

  10. High Dose Neutron Irradiation of Hi-Nicalon Type S Silicon Carbide Composites, Part 2. Mechanical and Physical Properties

    SciTech Connect

    Katoh, Yutai; Nozawa, Takashi; Shih, Chunghao Phillip; Ozawa, Kazumi; Koyanagi, Takaaki; Porter, Wallace D; Snead, Lance Lewis

    2015-01-07

    Nuclear-grade silicon carbide (SiC) composite material was examined for mechanical and thermophysical properties following high-dose neutron irradiation in the High Flux Isotope Reactor at a temperature range of 573–1073 K. Likewise, the material was chemical vapor-infiltrated SiC-matrix composite with a two-dimensional satin weave Hi-Nicalon Type S SiC fiber reinforcement and a multilayered pyrocarbon/SiC interphase. Moderate (1073 K) to very severe (573 K) degradation in mechanical properties was found after irradiation to >70 dpa, whereas no evidence was found for progressive evolution in swelling and thermal conductivity. The swelling was found to recover upon annealing beyond the irradiation temperature, indicating the irradiation temperature, but only to a limited extent. Moreover, the observed strength degradation is attributed primarily to fiber damage for all irradiation temperatures, particularly a combination of severe fiber degradation and likely interphase damage at relatively low irradiation temperatures.

  11. Colloidal processing of silcon carbide whiskers/aluminum oxide ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Zhang, Mingli

    By manipulating the interparticle forces of ceramic colloidal systems, suspensions of different dispersing abilities were obtained. Changing the concentration of ionic species, pH, polyelectrolyte and the solution altered the net interparticle force. The zeta potentials of single component suspensions of varying concentration of ionic species, polyelectrolyte addition, pH and solution (electrolyte, ethanol, or a mixture of electrolyte and ethanol) were measured. The stability ratio, W, which measures the effectiveness of the potential barrier in preventing the particles from coagulation, and the interaction between the components were discussed. SiC whisker reinforced Al2O 3 suspensions were slip cast at different processing conditions (SiC whisker volume fraction, solids loading, ball milling, sintering aids, polyelectrolyte and pH). Green specimens were cold-isostatically pressed and pressureless sintered in a flowing nitrogen atmosphere. Homogeneous SiCw/Al2O3 green bodies with densities of 2.55 +/- 0.07 g/cm3 (~65% theoretical density) were obtained. Bulk densities of 3.80 +/- 0.06 g/cm3 (96% theoretical density), 3.79 +/- 0.06 g/cm3 (97% theoretical density), and 3.40 +/- 0.07 g/cm3 (89% theoretical density) were obtained at 1600°C for composite samples containing 5, 10 and 20 vol% SiC whiskers, respectively. Bulk densities of the 10 vol% SiCw/Al2O3 composites were 3.79 +/- 0.06 g/cm3 at PH 11 and 3.66 +/- 0.07 g/cm3 at pH 4, respectively. pH 11 was determined to be the optimum processing pH for SiCw/Al2O3 composites with sintering aids (2 wt% Y2O3 and 0.5 wt% MgO) and 2.5 vol% polyelectrolyte (Ammonia salt of a polymeric carboxylic acid). The final microstructure revealed homogeneous and near fully densified composites. Compositions of the composites were characterized using Energy Dispersive X-ray Spectrum (EDX). The effect of the aspect ratio of SiC whisker, the Y2O 3 content and the choice of polyelectrolyte were examined. The whisker aspect ratio

  12. DEVELOPMENT OF ADVANCED DRILL COMPONENTS FOR BHA USING MICROWAVE TECHNOLOGY INCORPORATING CARBIDE, DIAMOND COMPOSITES AND FUNCTIONALLY GRADED MATERIALS

    SciTech Connect

    Dinesh Agrawal; Rustum Roy

    2000-11-01

    The main objective of this program was to develop an efficient and economically viable microwave processing technique to process cobalt cemented tungsten carbide with improved properties for drill-bits for advanced drilling operations for oil, gas, geothermal and excavation industries. The program was completed in three years and successfully accomplished all the states goals in the original proposal. In three years of the program, we designed and built several laboratory scale microwave sintering systems for conducting experiments on Tungsten carbide (WC) based composites in controlled atmosphere. The processing conditions were optimized and various properties were measured. The design of the system was then modified to enable it to process large commercial parts of WC/Co and in large quantities. Two high power (3-6 kW) microwave systems of 2.45 GHz were built for multi samples runs in a batch process. Once the process was optimized for best results, the technology was successfully transferred to our industrial partner, Dennis Tool Co. We helped them to built couple of prototype microwave sintering systems for carbide tool manufacturing. It was found that the microwave processed WC/Co tools are not only cost effective but also exhibited much better overall performance than the standard tools. The results of the field tests performed by Dennis Tool Co. showed remarkable advantage and improvement in their overall performance. For example: wear test shows an increase of 20-30%, corrosion test showed much higher resistance to the acid attack, erosion test exhibited about 15% better resistance than standard sinter-HIP parts. This proves the success of microwave technology for WC/Co based drilling tools. While we have successfully transferred the technology to our industrial partner Dennis Tool Co., they have signed an agreement with Valenite, a world leading WC producer of cutting and drilling tools and wear parts, to push aggressively the new microwave technology in

  13. Effects of chronic acceleration on body composition

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.

    1982-01-01

    Studies of the centrifugation of adult rats showed an unexpected decrease in the mass of fat-free muscle and bone, in spite of the added load induced by centrifugation. It is suggested that the lower but constant fat-free body mass was probably regulated during centrifugation. Rats placed in weightless conditions for 18.5 days gave indirect but strong evidence that the muscle had increased in mass. Other changes in the rats placed in weightless conditions included a smaller fraction of skeletal mineral, a smaller fraction of water in the total fat-free body, and a net shift of fluid from skin to viscera. Adult rats centrifuged throughout the post-weaning growth period exhibited smaller masses of bone and central nervous system (probably attributable to slower growth of the total body), and a larger mass of skin than controls at 1 G. Efforts at simulating the effects of weightlessness or centrifugation on the body composition of rats by regimens at terrestrial gravity were inconclusive.

  14. Effects of chronic acceleration on body composition

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.

    1982-01-01

    Studies of the centrifugation of adult rats showed an unexpected decrease in the mass of fat-free muscle and bone, in spite of the added load induced by centrifugation. It is suggested that the lower but constant fat-free body mass was probably regulated during centrifugation. Rats placed in weightless conditions for 18.5 days gave indirect but strong evidence that the muscle had increased in mass. Other changes in the rats placed in weightless conditions included a smaller fraction of skeletal mineral, a smaller fraction of water in the total fat-free body, and a net shift of fluid from skin to viscera. Adult rats centrifuged throughout the post-weaning growth period exhibited smaller masses of bone and central nervous system (probably attributable to slower growth of the total body), and a larger mass of skin than controls at 1 G. Efforts at simulating the effects of weightlessness or centrifugation on the body composition of rats by regimens at terrestrial gravity were inconclusive.

  15. Body Composition and Inflammation in Hemodialysis Patients.

    PubMed

    Mandic, Ante; Cavar, Ivan; Skoro, Ivana; Tomic, Ivan; Ljubic, Kristina; Coric, Slavica; Mikulic, Ivanka; Azinovic, Igor; Pravdic, Danijel

    2017-09-22

    The volume state of dialysis patients is important in guiding the dialysis process. Volume overload in these patients is associated with inflammation. The objectives of the present study were to assess the body composition of patients on hemodialysis; to determine the concentrations of B-type natriuretic peptide (BNP) in plasma and evaluate the association of BNP concentrations with volume overload; to determine the concentrations of C-reactive protein (CRP), albumin and superoxide dismutase (SOD) activities as indicators of inflammatory or antioxidant processes. The study included 79 maintenance hemodialysis patients. Assessment of body compartments was carried out using a body composition monitor (BCM). After BCM measurements, blood samples were taken from the patients for laboratory tests. There were 40 (50.6%) volume-overloaded patients (relative overhydration >15%). These patients had a higher prevalence of arterial hypertension (P < 0.05), significantly higher concentrations of BNP (P = 0.01), lower body mass index (P < 0.05) and lower fat tissue index (P < 0.05). There was a positive correlation between plasma BNP and CRP concentrations (ρ = 0.231; P < 0.05), and a negative correlation between (log) BNP and albumin (r = -0.021; P < 0.05), as well as (log) CRP and albumin concentrations (r = -3; P < 0.01). SOD activity was positively correlated with albumin concentrations (r = 0.254; P < 0.05). The concentrations of BNP in this study were associated with volume overload and inflammatory markers. Patients with a higher albumin concentration had higher SOD activity. © 2017 International Society for Apheresis, Japanese Society for Apheresis, and Japanese Society for Dialysis Therapy.

  16. [Body composition and polycystic ovary syndrome].

    PubMed

    Zabuliene, Lina; Tutkuviene, Janina

    2010-01-01

    Polycystic ovary syndrome (PCOS) is one of the most common endocrine metabolic disorders of reproductive age women. The main signs of PCOS are as follows: androgen excess, menstrual dysfunction, infertility, obesity, and other numerous health problems. By different authors, the disorder affects 2-28% of reproductive age women. Polycystic ovary syndrome is characterized by presence of hyperandrogenism, anovulation, menstrual cycle disturbances, also by the other metabolic changes. The lack of well-defined and universally accepted diagnostic criteria makes identification of this syndrome confusing to many clinicians. There are only few studies concerning the correlations between phenotypic expression, body composition and PCOS, and relationship with the processes of growth and sexual maturation and various environmental factors (nutrition, physical activity, stress, and other factors). There is a lack of knowledge about further PCOS development and prognosis, considering the individual and environmental factors. Variation in human body composition and shape ranges considerably: many body size and shape indices (height, weight, body composition, and proportions) are the result of long evolution process and adaptation to environment. Obviously, the morphological body parameters, physiological and biochemical indices are complex and compound the interdependent system. By current literature, more than 50% of women are overweight or obese. If waist circumference and waist-to-hip ratio of women with PCOS increase, reproductive function and metabolic state of a woman is altered more than in cases when there are no changes in these parameters. The investigations of the strongest sexual dimorphism sign--the subcutaneous and visceral fat topography--showed that women with PCOS have greater adipose tissue mass in the areas of the abdomen, waist, and upper arms than control women. It is known that some indices of sexual dimorphism may be considered as the morphological signs of

  17. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Gephart, Sean

    The sintering behaviors of silicon carbide (SiC) and boron carbide (B4C) based materials were investigated using an emerging sintering technology known as field assisted sintering technology (FAST), also known as spark plasma sintering (SPS) and pulse electric current sintering (PECS). Sintering by FAST utilizes high density electric current, uniaxial pressure, and relatively high heating rate compared to conventional sintering techniques. This effort investigated issues of scaling from laboratory FAST system (25 ton capacity) to industrial FAST system (250 ton capacity), as well as exploring the difference in sintering behavior of single phase B4C and SiC using FAST and conventional sintering techniques including hot-pressing (HP) and pressure-less sintering (PL). Materials were analyzed for mechanical and bulk properties, including characterization of density, hardness, fracture toughness, fracture (bend) strength, elastic modulus and microstructure. A parallel investigation was conducted in the development of ceramic matrix composites (CMC) using SiC powder impregnation of fiber compacts followed by FAST sintering. The FAST technique was used to sinter several B4C and SiC materials to near theoretical density. Preliminary efforts established optimized sintering temperatures using the smaller 25 ton laboratory unit, targeting a sample size of 40 mm diameter and 8 mm thickness. Then the same B4C and SiC materials were sintered by the larger 250 ton industrial FAST system, a HP system, and PL sintering system with a targeted dense material geometry of 4 x 4 x 0.315 inches3 (101.6 x 101.6 x 8 mm3). The resulting samples were studied to determine if the sintering dynamics and/or the resulting material properties were influenced by the sintering technique employed. This study determined that FAST sintered ceramic materials resulted in consistently higher averaged values for mechanical properties as well as smaller grain size when compared to conventionally sintered

  18. Ultrasound: Which role in body composition?

    PubMed

    Bazzocchi, Alberto; Filonzi, Giacomo; Ponti, Federico; Albisinni, Ugo; Guglielmi, Giuseppe; Battista, Giuseppe

    2016-08-01

    Ultrasound is a non-invasive, fast, relatively inexpensive and available tool for estimating adiposity in clinical practice, and in several research settings. It does not expose patients to ionizing radiation risks, making the method ideal for the evaluation, and for follow-up studies. Several parameters and indexes based on adipose tissue thickness have been introduced and tested, and these have been correlated with clinical and laboratoristic parameters. Moreover, ultrasound can also be directed to the estimation of adipose tissue and intracellular fat indirectly, at cellular-molecular level: an opportunity for many radiologists who already and sometimes unconsciously perform "body composition" assessment when looking at the liver, at muscle as well as at other organs. However, standardized procedure and parameters are needing to improve accuracy and reproducibility. The purposes of this review are: 1) to provide a complete overview of the most used and shared measurements of adiposity; 2) to analyze technical conditions, accuracy, and clinical meaning of ultrasound in the study of body composition; 3) to provide some elements for the use of ultrasound in the evaluation of intra-cellular lipids accumulation, in two hot spots: liver and skeletal muscle.

  19. Enhanced thermal conductivity of uranium dioxide-silicon carbide composite fuel pellets prepared by Spark Plasma Sintering (SPS)

    NASA Astrophysics Data System (ADS)

    Yeo, S.; Mckenna, E.; Baney, R.; Subhash, G.; Tulenko, J.

    2013-02-01

    Uranium dioxide (UO2)-10 vol% silicon carbide (SiC) composite fuel pellets were produced by oxidative sintering and Spark Plasma Sintering (SPS) at a range of temperatures from 1400 to 1600 °C. Both SiC whiskers and SiC powder particles were utilized. Oxidative sintering was employed over 4 h and the SPS sintering was employed only for 5 min at the highest hold temperature. It was noted that composite pellets sintered by SPS process revealed smaller grain size, reduced formation of chemical products, higher density, and enhanced interfacial contact compared to the pellets made by oxidative sintering. For given volume of SiC, the pellets with powder particles yielded a smaller grain size than pellets with SiC whiskers. Finally thermal conductivity measurements at 100 °C, 500 °C, and 900 °C revealed that SPS sintered UO2-SiC composites exhibited an increase of up to 62% in thermal conductivity compared to UO2 pellets, while the oxidative sintered composite pellets revealed significantly inferior thermal conductivity values. The current study points to the improved processing capabilities of SPS compared to oxidative sintering of UO2-SiC composites.

  20. High dose neutron irradiations of Hi-Nicalon Type S silicon carbide composites, Part 1: Microstructural evaluations

    SciTech Connect

    Perez-Bergquist, Alex G.; Nozawa, Takashi; Shih, Chunghao Phillip; Leonard, Keith J.; Snead, Lance Lewis; Katoh, Yutai

    2014-07-01

    Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30-40 dpa at temperatures of 300-800 °C. However, more recent studies of these same fiber composites irradiated to damage levels of >70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 °C. Here, electron microscopy is used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 °C, substantial microstructural evolution is observed in those irradiated at 300° C. Furthermore, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.

  1. Characterization of anisotropic elastic constants of silicon-carbide particulate reinforced aluminum metal matrix composites; Part 1: Experiment

    SciTech Connect

    Jeong, H. ); Hsu, D.K. . Center for Nondestructive Evaluation); Shannon, R.E. . Materials Reliability Dept.); Liaw, P.K. . Dept. of Materials Science and Engineering)

    1994-04-01

    The anisotropic elastic properties of silicon-carbide particulate (SiC[sub p]) reinforced Al metal matrix composites were characterized using ultrasonic techniques and microstructural analysis. The composite materials, fabricated by a powder metallurgy extrusion process, included 2124, 6061, and 7091 Al alloys reinforced by 10 to 30 pct of [alpha]-SiC[sub p] by volume. Results were presented for the assumed orthotropic elastic constants obtained from ultrasonic velocities and for the microstructural data on particulate shape, aspect ratio, and orientation distribution. All of the composite samples exhibited a systematic anisotropy: the stiffness in the extrusion direction was the highest, and the stiffness in the out-of-plane direction was the lowest. Microstructural analysis suggested that the observed anisotropy could be attributed to the preferred orientation of SiC[sub p]. The ultrasonic velocity was found to be sensitive to internal defects such as porosity and intermetallic compounds. It has been observed that ultrasonics may be a useful, nondestructive technique for detecting small directional differences in the overall elastic constants of the composites since a good correlation has been noted between the velocity and microstructure and the mechanical test. By incorporating the observed microstructural characteristics, a theoretical model for predicting the anisotropic stiffnesses of the composites has been developed and is presented in a companion article (Part 2).

  2. Characterization of anisotropie elastic constants of silicon-carbide participate reinforced aluminum metal matrix composites: Part I. Experiment

    NASA Astrophysics Data System (ADS)

    Jeong, Hyunjo; Hsu, David K.; Shannon, Robert E.; Liaw, Peter K.

    1994-04-01

    The anisotropic elastic properties of silicon-carbide particulate (SiC p ) reinforced Al metal matrix composites were characterized using ultrasonic techniques and microstructural analysis. The composite materials, fabricated by a powder metallurgy extrusion process, included 2124, 6061, and 7091 Al alloys reinforced by 10 to 30 pct of α-SiC p by volume. Results were presented for the assumed orthotropic elastic constants obtained from ultrasonic velocities and for the microstructural data on particulate shape, aspect ratio, and orientation distribution. All of the composite samples exhibited a systematic anisotropy: the stiffness in the extrusion direction was the highest, and the stiffness in the out-of-plane direction was the lowest. Microstructural analysis suggested that the observed anisotropy could be attributed to the preferred orientation of SiC p . The ultrasonic velocity was found to be sensitive to internal defects such as porosity and intermetallic compounds. It has been observed that ultrasonics may be a useful, nondestructive technique for detecting small directional differences in the overall elastic constants of the composites since a good correlation has been noted between the velocity and microstructure and the mechanical test. By incorporating the observed microstructural characteristics, a theoretical model for predicting the anisotropic stiffnesses of the composites has been developed and is presented in a companion article (Part II).

  3. High dose neutron irradiations of Hi-Nicalon Type S silicon carbide composites, Part 1: Microstructural evaluations

    DOE PAGES

    Perez-Bergquist, Alex G.; Nozawa, Takashi; Shih, Chunghao Phillip; ...

    2014-07-01

    Over the past decade, significant progress has been made in the development of silicon carbide (SiC) composites, composed of near-stoichiometric SiC fibers embedded in a crystalline SiC matrix, to the point that such materials can now be considered nuclear grade. Recent neutron irradiation studies of Hi-Nicalon Type S SiC composites showed excellent radiation response at damage levels of 30-40 dpa at temperatures of 300-800 °C. However, more recent studies of these same fiber composites irradiated to damage levels of >70 dpa at similar temperatures showed a marked decrease in ultimate flexural strength, particularly at 300 °C. Here, electron microscopy ismore » used to analyze the microstructural evolution of these irradiated composites in order to investigate the cause of the degradation. While minimal changes were observed in Hi-Nicalon Type S SiC composites irradiated at 800 °C, substantial microstructural evolution is observed in those irradiated at 300° C. Furthermore, carbonaceous particles in the fibers grew by 25% compared to the virgin case, and severe cracking occurred at interphase layers.« less

  4. The preparation and performance of calcium carbide-derived carbon/polyaniline composite electrode material for supercapacitors

    NASA Astrophysics Data System (ADS)

    Zheng, Liping; Wang, Ying; Wang, Xianyou; Li, Na; An, Hongfang; Chen, Huajie; Guo, Jia

    Calcium carbide (CaC 2)-derived carbon (CCDC)/polyaniline (PANI) composite materials are prepared by in situ chemical oxidation polymerization of an aniline solution containing well-dispersed CCDC. The structure and morphology of CCDC/PANI composite are characterized by Fourier infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM) and N 2 sorption isotherms. It has been found that PANI was uniformly deposited on the surface and the inner pores of CCDC. The supercapacitive behaviors of the CCDC/PANI composite materials are investigated with cyclic voltammetry (CV), galvanostatic charge/discharge and cycle life measurements. The results show that the CCDC/PANI composite electrodes have higher specific capacitances than the as grown CCDC electrodes and higher stability than the conducting polymers. The capacitance of CCDC/PANI composite electrode is as high as 713.4 F g -1 measured by cyclic voltammetry at 1 mV s -1. Besides, the capacitance retention of coin supercapacitor remained 80.1% after 1000 cycles.

  5. Body composition in remission of childhood cancer

    NASA Astrophysics Data System (ADS)

    Tseytlin, G. Ja; Anisimova, A. V.; Godina, E. Z.; Khomyakova, I. A.; Konovalova, M. V.; Nikolaev, D. V.; Rudnev, S. G.; Starunova, O. A.; Vashura, A. Yu

    2012-12-01

    Here, we describe the results of a cross-sectional bioimpedance study of body composition in 552 Russian children and adolescents aged 7-17 years in remission of various types of cancer (remission time 0-15 years, median 4 years). A sample of 1500 apparently healthy individuals of the same age interval was used for comparison. Our data show high frequency of malnutrition in total cancer patients group depending on type of cancer. 52.7% of patients were malnourished according to phase angle and percentage fat mass z-score with the range between 42.2% in children with solid tumors located outside CNS and 76.8% in children with CNS tumors. The body mass index failed to identify the proportion of patients with malnutrition and showed diagnostic sensitivity 50.6% for obesity on the basis of high percentage body fat and even much less so for undernutrition - 13.4% as judged by low phase angle. Our results suggest an advantage of using phase angle as the most sensitive bioimpedance indicator for the assessment of metabolic alterations, associated risks, and the effectiveness of rehabilitation strategies in childhood cancer patients.

  6. A visible light-sensitive tungsten carbide/tungsten trioxde composite photocatalyst

    SciTech Connect

    Kim, Young-ho; Irie, Hiroshi; Hashimoto, Kazuhito

    2008-05-05

    A photocatalyst composed of tungsten carbide (WC) and tungsten oxide (WO{sub 3}) has been prepared by the mechanical mixing of each powder. Its photocatalytic activity was evaluated by the gaseous isopropyl alcohol decomposition process. The photocatalyst showed high visible light photocatalytic activity with a quantum efficiency of 3.2% for 400-530 nm light. The photocatalytic mechanism was explained by means of enhanced oxygen reduction reaction due to WC, which may serve as a multielectron reduction catalyst, as well as the photogeneration of holes in the valence band of WO{sub 3}.

  7. Validity of body composition methods across ethnic population groups.

    PubMed

    Deurenberg, P; Deurenberg-Yap, M

    2003-10-01

    Most in vivo body composition methods rely on assumptions that may vary among different population groups as well as within the same population group. The assumptions are based on in vitro body composition (carcass) analyses. The majority of body composition studies were performed on Caucasians and much of the information on validity methods and assumptions were available only for this ethnic group. It is assumed that these assumptions are also valid for other ethnic groups. However, if apparent differences across ethnic groups in body composition 'constants' and body composition 'rules' are not taken into account, biased information on body composition will be the result. This in turn may lead to misclassification of obesity or underweight at an individual as well as a population level. There is a need for more cross-ethnic population studies on body composition. Those studies should be carried out carefully, with adequate methodology and standardization for the obtained information to be valuable.

  8. Computational-Experimental Processing of Boride/Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C

    DTIC Science & Technology

    2015-09-16

    infiltration, reactions between the alloy melt and B4C will form an HfB2-HfC/Hf-Y-Ti composite, which will eventually develop an HfO2-Y2O3- TiO2 scale, as...of the pyrochlore phase (or Y2Ti2O7) within an HfO2-Y2O3- TiO2 scale may form as layers of Y2Ti2O7, HfTiO4, cubic-HfO2, or tetragonal-HfO2 as the...processing, a better understanding of the infusion of Figure 1 -- Oxide Scale developed from the ZrO2- Y2O3- TiO2 System to protect a boride/carbide

  9. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate.

    PubMed

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-10

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  10. Local anodic oxidation on hydrogen-intercalated graphene layers: oxide composition analysis and role of the silicon carbide substrate

    NASA Astrophysics Data System (ADS)

    Colangelo, Francesco; Piazza, Vincenzo; Coletti, Camilla; Roddaro, Stefano; Beltram, Fabio; Pingue, Pasqualantonio

    2017-03-01

    We investigate nanoscale local anodic oxidation (LAO) on hydrogen-intercalated graphene grown by controlled sublimation of silicon carbide (SiC). Scanning probe microscopy was used as a lithographic and characterization tool in order to investigate the local properties of the nanofabricated structures. The anomalous thickness observed after the graphene oxidation process is linked to the impact of LAO on the substrate. Micro-Raman (μ-Raman) spectroscopy was employed to demonstrate the presence of two oxidation regimes depending on the applied bias. We show that partial and total etching of monolayer graphene can be achieved by tuning the bias voltage during LAO. Finally, a complete compositional characterization was achieved by scanning electron microscopy and energy dispersive spectroscopy.

  11. Effect of body composition methodology on heritability estimation of body fatness

    USDA-ARS?s Scientific Manuscript database

    Heritability estimates of human body fatness vary widely and the contribution of body composition methodology to this variability is unknown. The effect of body composition methodology on estimations of genetic and environmental contributions to body fatness variation was examined in 78 adult male ...

  12. Heat and Mass Transfer in the Chemical Vapor Deposition of Silicon Carbide in a Porous Carbon-Carbon Composite Material for a Heat Shield

    NASA Astrophysics Data System (ADS)

    Reznik, S. V.; Mikhailovskii, K. V.; Prosuntsov, P. V.

    2017-03-01

    Physical and mathematical simulations of the chemical vapor deposition of silicon carbide in a porous carbon-carbon composite material in a chemical vapor deposition reactor for formation of a matrix of a carbon-ceramic composite material for a heat shield of an aerospace aircraft have been performed. Results of parametric calculations of the heat and mass transfer at the macro- and microlevels in representative elements of the microstructure of carbon-carbon composite materials different in residual porosity at different temperatures in the reaction zone of the reactor are presented. Features of compaction of the pore space of a carbon-carbon composite material by a silicon-carbide matrix depending on the technological parameters of the reaction medium were analyzed.

  13. [BODY COMPOSITION AND SOMATOTYPE IN UNIVERSITY TRIATHLETES].

    PubMed

    Guillén Rivas, Laura; Mielgo-Ayuso, Juan; Norte-Navarro, Aurora; Cejuela, Roberto; Cabañas, María Dolores; Martínez-Sanz, José Miguel

    2015-08-01

    the triathlon is an endurance sport and individual that consists of three different disciplines: swimming, cycling and running. The aim of the study was to describe and analyze the anthropometric characteristics, body composition and somatotype in male college triathletes. observational and descriptive study of anthropometric characteristics, body composition and somatotype of 39 male college athletes from 24 ± 4,5 years, participants in the championship of Spain university triathlon sprint mode (Alicante 2010), from different universities Spanish. According to anthropometric measurement techniques adopted by the International Society for the Advancement of Kinanthropometry (ISAK) and the Spanish Group Cineantropometría (GREC) by an accredited assessor ISAK Level II. we find athletes of stunting, where you destacanvalores below normal in the subscapularis, supraspinatus, triceps and biceps skinfold, percentage of muscle mass (45.27 ± 3.29%) and fat mass (10.22 ± 2.92%) and bone (16.65 ± 1.34%) and where mesomorphy somatotipo predominates. the triathletes and runners have lower size that cyclists and swimmers. Triathletes and cyclists show a similar weight, less than swimmers line, and more than 10km runners. Iliac crest skinfold, abdominal and thigh front cyclists are less than triathletes. The percentage of fat mass of runners triathletes and swimmers are similar, however the muscle mass of athletes usually less than cyclists but similar to other forms. Somatotype resembles triathlete cyclist (mesomorph). The corridor is ectomorph and mesomorph-swimmer can range from a ectomorph mesomorph. Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.

  14. Study of multi-carbide B4C-SiC/(Al, Si) reaction infiltrated composites by SEM with EBSD

    NASA Astrophysics Data System (ADS)

    Almeida, B. A.; Ferro, M. C.; Ravanan, A.; Grave, P. M. F.; Wu, H.-Y.; Gao, M.-X.; Pan, Y.; Oliveira, F. J.; Lopes, A. B.; Vieira, J. M.

    2014-03-01

    In the definition of conceptual developments and design of new materials with singular or unique properties, characterisation takes a key role in clarifying the relationships of composition, properties and processing that define the new material. B4C has a rare combination of properties that makes it suitable for a wide range of applications in engineering: high refractoriness, thermal stability, high hardness and abrasion resistance coupled to low density. However, the low self-diffusion coefficient of B4C limits full densification by sintering. A way to overturn this constraint is by using an alloy, for example Al-Si, forming composites with B4C. Multi-carbide B4C-SiC/(Al, Si) composites were produced by the reactive melt infiltration technique at 1200 - 1350 °C with up to 1 hour of isothermal temperature holds. Pressed preforms made from C-containing B4C were spontaneously infiltrated with Al-Si alloys of composition varying from 25 to 50 wt% Si. The present study involves the characterisation of the microstructure and crystalline phases in the alloys and in the composites by X-ray diffraction and SEM/EDS with EBSD. Electron backscatter diffraction is used in detail to look for segregation and spatial distribution of Si and Al containing phases during solidification of the metallic infiltrate inside the channels of the ceramic matrix when the composite cools down to the eutectic temperature (577 °C). It complements elemental maps of the SEM/EDS. The production of a flat surface by polishing is intrinsically difficult and the problems inherent to the preparation of EBSD qualified finishing in polished samples of such type of composites are further discussed.

  15. Compositional effects on mechanical properties of hafnium-carbide-strengthened molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Witzke, W. R.

    1975-01-01

    The mechanical properties of swaged rod thermomechanically processed from arc melted Mo-2Re-Hf-C alloys containing as much as 0.9-mol% HfC were evaluated. The low-temperature ductilities of these alloys were not influenced by the amount of HfC present but by the amount of Hf in excess of stoichiometry. Maximum ductility occurred at 0.2- to 0.3-at.% excess Hf. At 0.3- to 0.5-mol% HfC, alloy strength varied directly with the Mo content of extracted carbide particles, both decreasing as the amount of excess Hf increased. Additions of 2-at.% Re had little effect on strength or ductility. Tensile and creep strengths of Mo-2Re-0.7Hf-0.5C alloy equaled or exceeded those of other high strength Mo alloys.

  16. Hertzian indentation of colloidally processed titanium carbide-nickel aluminide composites

    NASA Astrophysics Data System (ADS)

    Collier, R. Bradley

    Advanced cermets based on titanium carbide (TiC), with a ductile nickel aluminide (Ni3Al) binder, have shown significant promise for use in a variety of demanding wear environments, due to a combination of high strength and good corrosion behaviour. A unique feature of TiC-Ni3Al cermets is that they show increasing strength from room temperature up to ˜1,000°C, while current materials such as tungsten carbide/cobalt (WC/Co) show significant strength degradation above ˜500°C. In this thesis, aqueous colloidal forming methods have been applied to process TiC preforms. The mechanisms and effectiveness of suspension stabilization were examined using methods such as zeta potential analysis, rheological measurements, and sedimentation trials for two common dispersants; an ammonium salt of polymethacrylate (PMA-NH 4) and two molecular weights (l,800 and 10,000) of polyethylenimine (PEI). TiC preforms were prepared by slip casting suspensions of up to 50 vol. % solids content. After drying, the TiC-based cermets were processed by melt infiltration with the Ni3Al alloy (IC-50) at 1475°C.Ni 3Al content was varied between 20 and 50 vol. % using this approach, resulting in final densities that exceeded 98% of theoretical. These samples were subjected to Hertzian indentation testing with loads ranging from 250 -- 2000 N, using WC-Co spheres with sizes ranging from 1.191 to 2.38 mm. Indentation stress-strain curves were produced from the indentation data and compared to the calculated elastic Hertzian response. The bonded interface method was used to examine the subsurface deformation of the material under load. Significant deformation of the binder and the eventual fracture of the TiC grains were observed. The nature of the quasi-plasticity of TiC-Ni 3Al and the effects of binder content on surface and subsurface deformation is examined.

  17. Methods for Producing High-Performance Silicon Carbide Fibers, Architectural Preforms, and High-Temperature Composite Structures

    NASA Technical Reports Server (NTRS)

    DiCarlo, James A. (Inventor); Yun, Hee-Mann (Inventor)

    2014-01-01

    Methods are disclosed for producing architectural preforms and high-temperature composite structures containing high-strength ceramic fibers with reduced preforming stresses within each fiber, with an in-situ grown coating on each fiber surface, with reduced boron within the bulk of each fiber, and with improved tensile creep and rupture resistance properties tier each fiber. The methods include the steps of preparing an original sample of a preform formed from a pre-selected high-strength silicon carbide ceramic fiber type, placing the original sample in a processing furnace under a pre-selected preforming stress state and thermally treating the sample in the processing furnace at a pre-selected processing temperature and hold time in a processing gas having a pre-selected composition, pressure, and flow rate. For the high-temperature composite structures, the method includes additional steps of depositing a thin interphase coating on the surface of each fiber and forming a ceramic or carbon-based matrix within the sample.

  18. Body image, body mass index, and body composition in young adults.

    PubMed

    Streeter, Veronica M; Milhausen, Robin R; Buchholz, Andrea C

    2012-01-01

    Associations were examined between body image and body mass index (BMI) in comparison with body composition in healthy weight, overweight, and obese young adults. Weight and height were determined, and the percentage of fat mass (%FM) and percentage of fat-free mass (%FFM) were measured by dual energy X-ray absorptiometry in 75 male and 87 female young adults (21.1 ± 1.9 years; 25.2 ± 4.4 kg/m² [mean ± standard deviation]). Body image was measured using the three subscales Weight Esteem, Appearance Esteem, and External Attribution of the Body-Esteem Scale for Adolescents and Adults (BESAA). Body mass index and %FM were highly correlated (r for males = 0.74, r for females = 0.82; both p<0.001), and were inversely associated with body image, particularly Weight Esteem. After adjustment for physical activity, BMI and %FM (and %FFM, although in the opposite direction) were associated with each BESAA subscale: %FM, %FFM, and BMI explained 12% to 14% of the variance in Appearance Esteem for both sexes, 33% to 41% in Weight Esteem in women and 16% to 18% in men, and 8% to 10% in External Attribution in women (all p<0.05) and <5% for men (NS). Clinicians should be aware that as their clients' BMI and %FM increase, body image decreases, particularly in women.

  19. Tungsten carbide/porous carbon composite as superior support for platinum catalyst toward methanol electro-oxidation

    SciTech Connect

    Jiang, Liming; Fu, Honggang; Wang, Lei; Mu, Guang; Jiang, Baojiang; Zhou, Wei; Wang, Ruihong

    2014-01-01

    Graphical abstract: The WC nanoparticles are well dispersed in the carbon matrix. The size of WC nanoparticles is about 30 nm. It can be concluded that tungsten carbide and carbon composite was successfully prepared by the present synthesis conditions. - Highlights: • The WC/PC composite with high specific surface area was prepared by a simple way. • The Pt/WC/PC catalyst has superior performance toward methanol electro-oxidation. • The current density for methanol electro-oxidation is as high as 595.93 A g{sup −1} Pt. • The Pt/WC/PC catalyst shows better durability and stronger CO electro-oxidation. • The performance of Pt/WC/PC is superior to the commercial Pt/C (JM) catalyst. - Abstract: Tungsten carbide/porous carbon (WC/PC) composites have been successfully synthesized through a surfactant assisted evaporation-induced-assembly method, followed by a thermal treatment process. In particular, WC/PC-35-1000 composite with tungsten content of 35% synthesized at the carbonized temperature of 1000 °C, exhibited a specific surface area (S{sub BET}) of 457.92 m{sup 2} g{sup −1}. After loading Pt nanoparticles (NPs), the obtained Pt/WC/PC-35-1000 catalyst exhibits the highest unit mass electroactivity (595.93 A g{sup −1} Pt) toward methanol electro-oxidation, which is about 2.6 times as that of the commercial Pt/C (JM) catalyst. Furthermore, the Pt/WC/PC-35-1000 catalyst displays much stronger resistance to CO poisoning and better durability toward methanol electrooxidation compared with the commercial Pt/C (JM) catalyst. The high electrocatalytic activity, strong poison-resistivity and good stability of Pt/WC/PC-35-1000 catalyst are attributed to the porous structures and high specific surface area of WC/PC support could facilitate the rapid mass transportation. Moreover, synergistic effect between WC and Pt NPs is favorable to the higher catalytic performance.

  20. Effects of Whole Body Vibration Training on Body Composition in Adolescents with Down Syndrome

    ERIC Educational Resources Information Center

    Gonzalez-Aguero, Alejandro; Matute-Llorente, Angel; Gomez-Cabello, Alba; Casajus, Jose A.; Vicente-Rodriguez, German

    2013-01-01

    The present study aimed to determine the effect of 20 weeks of whole body vibration (WBV) on the body composition of adolescents with Down syndrome (DS). Thirty adolescent with DS were divided into two groups: control and WBV. Whole body, upper and lower limbs body fat and lean body mass were measured with dual energy X-ray absorptiometry (DXA)…

  1. Effects of Whole Body Vibration Training on Body Composition in Adolescents with Down Syndrome

    ERIC Educational Resources Information Center

    Gonzalez-Aguero, Alejandro; Matute-Llorente, Angel; Gomez-Cabello, Alba; Casajus, Jose A.; Vicente-Rodriguez, German

    2013-01-01

    The present study aimed to determine the effect of 20 weeks of whole body vibration (WBV) on the body composition of adolescents with Down syndrome (DS). Thirty adolescent with DS were divided into two groups: control and WBV. Whole body, upper and lower limbs body fat and lean body mass were measured with dual energy X-ray absorptiometry (DXA)…

  2. Effect of alloying elements on the composition of carbide phases and mechanical properties of the matrix of high-carbon chromium-vanadium steel

    NASA Astrophysics Data System (ADS)

    Titov, V. I.; Tarasenko, L. V.; Utkina, A. N.

    2017-01-01

    Based on the results of phase physicochemical analysis of high-carbon chromium-vanadium steel, the predominant type of carbide that provides high wear resistance has been established, and its amount and amount of carbon in martensite have been determined. Data on the composition and the amount of carbide phase and on the chemical composition of the martensite of high-carbon steel have been obtained, which allows determination of the alloying-element concentration limits. The mechanical testing of heats of a chosen chemical composition has been carried out after quenching and low-temperature tempering. The tests have demonstrated benefits of new steel in wear resistance and bending strength with the fatigue strength being retained, compared to steels subjected to cementation. The mechanism of secondary strengthening of the steel upon high-temperature tempering has been revealed. High-temperature tempering can be applied to articles that are required to possess both high wear resistance and heat resistance.

  3. Comparison of different body composition models in acromegaly.

    PubMed

    Brummer, R J; Lönn, L; Bengtsson, B A; Kvist, H; Bosaeus, I; Sjöström, L

    1996-12-01

    The aberrant body composition of 10 patients with active acromegaly was used to evaluate the validity and limitations of several models and methods to assess body composition. Body composition was determined using either a two-compartment model, dividing the body in a body fat (BF) compartment and a fat-free mass (FFM) compartment, or a four-compartment model in which the FFM compartment comprises the three following components: body cell mass, extracellular water and the fat-free extracellular solids. The measurement techniques consisted of anthropometry, bioelectrical impedance analysis (BIA)-applying various established regression equations-tritiated water dilution, whole body 40K-counting, and whole body computed tomography (CT). This latter method was used as the reference technique. Assessment of total body water using BIA - applying the RJL or Kushner equation-correlated significantly with the assessment using tritiated water dilution (P < 0.01). Body fat assessment using the two-compartment model based on either tritiated water dilution or BIA-applying the RJL or Lukaski equation-as well as body fat assessment using the four-compartment model based on tritiated water dilution and whole body 40K-counting were significantly correlated with body fat assessment using CT (P < 0.01) and resulted in good agreement with each other with respect to the absolute values of the body fat determination. BIA using other regression equations overestimated body fat by 7.2-13.7 kg. Whole body 40K-counting was significantly correlated with CT-determined muscle plus skin volume (P < 0.001). CT-calibrated anthropometric predictions significantly overestimated body fat. It is concluded that in patients with active acromegaly, the determination of body composition using either certain two-compartment models based on measurement of total body water or bioelectrical impedance, or a four-compartment model based on total body water and total body potassium measurements show good

  4. Body Composition and Somatotype of Male and Female Nordic Skiers

    ERIC Educational Resources Information Center

    Sinning, Wayne E.; And Others

    1977-01-01

    Anthropometric measurements (body composition and somatotype characteristics) for male and female Nordic skiers showed small values for measures of variance, suggesting that the subjects represented a select body type for the sport. (Author/MJB)

  5. The computation of body composition data using a programmable calculator.

    PubMed

    Withers, R T

    1986-01-01

    A body composition programme has been developed for the Texas Instruments TI 59 programmable calculator and printer. The methodology involves the determination of body density by underwater weighing with the ventilated residual volume being measured by helium dilution. Some of the labelled output variables included on the printout are: body density, percent body fat, fat mass and fat free mass.

  6. Human body composition: advances in models and methods.

    PubMed

    Heymsfield, S B; Wang, Z; Baumgartner, R N; Ross, R

    1997-01-01

    The field of human body composition research is reaching a mature stage in its development: The three interconnected areas that define body composition research--models and their rules, methodology, and biological effects--are well-defined and are actively investigated by scientists in diverse disciplines from many different nations; and methods are available for measuring all major atomic, molecular, cellular, and tissue-system level body composition components in research, clinical, and epidemiological settings. This review summarizes main body composition research concepts, examines new component-measurement methodologies, and identifies potential areas of future research.

  7. Rat body size, composition and growth at hypo- and hypergravity

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.

    1983-01-01

    The effects of hypergravity (centrifugation) on body composition were investigated. Hypogravitational and hypergravitational aspects were reflected in the research effort. A list of publications is provided.

  8. Body composition in MesoAmerica.

    PubMed

    Solomons, N W; Mazariegos, M

    1995-03-01

    The fundamental paradigm for the region is short stature. Adult height is on the order of 160 cm for men and 140 cm for women. The timing of this delayed growth has been fixed to the first two years of life, when as much as 2 Z-scores of stature may be loss to the median of the NCHS reference. In the elderly of the region, we have the issue of being initially short and then suffering further loss of stature with age. The height/armspan ratio has proven instructive for exploring that change in height with age. It appears to be less than in Europeans. Demands of a rigorous agricultural lifestyle, the energy content and density of the diet, and the ravages of recurrent infection and parasitism comprise the environmental determinants of body composition in poor MesoAmerican population. They are conducive to a low storage of fat, with lean body mass being subject to response to infections. Because of the basic short stature but muscular maturity of children and adults, one questions whether the assumptions of proportionality of weight for height from the NCHS reference data apply, or whether MesoAmericans should be normally greater in weight for height than a comparably short North American. For some at the lower end of the stature scale, no international reference standards actually exist for adults. All than can be measured with microtoise, calliper, flexible tape and balance has long been recorded in MesoAmerican populations. Certain high-cost and facility- dependent technologies, such as nuclear magnetic resonance imaging and whole-body neutron activation analysis, are beyond the scientific economies of any part of the region. Dual energy x-ray absorbitometry instruments are available for clinical diagnosis in Mexico, Guatemala and Costa Rica, and could be turned to research ends. Underwater weighing has been practiced variously in MesoAmerica. Researchers in Guatemala have pioneered in the investigative use of bioelectrical impedance analysis to all ages from low

  9. Validity of body impedance analysis for evaluating body composition in patients undergoing long-term hemodialysis.

    PubMed

    Noguchi, Masahiro; Yamaguchi, Shinichi; Koshino, Yoshitaka; Kimura, Akira; Miyagi, Shigeji

    2015-06-01

    [Purpose] This study assessed changes in body composition before and after dialysis in chronic hemodialysis patients and determined the relationships between various body composition parameters and blood lipid levels in these patients. [Subjects] The cross-sectional study included 19 dialysis outpatients (17 men and 2 women, aged 35-82 years). [Methods] Body mass index, body weight, percent body fat, and percent skeletal muscle were measured before and after dialysis by using body impedance analysis. Blood lipid levels were obtained from patients' clinical records. The body composition parameters before and after dialysis were compared using paired t-tests. Spearman's rank correlation coefficients were calculated to determine relationships between the body composition parameters, before and after dialysis, and the blood lipid levels. [Results] All body composition parameters differed significantly before and after dialysis. High-density lipoprotein cholesterol level significantly correlated with all the body composition parameters, whereas total cholesterol, low-density lipoprotein cholesterol, and triglyceride levels significantly correlated with some of these parameters. The correlation coefficients revealed no major differences in the relationships between blood lipid parameters and body compositions before and after dialysis. [Conclusion] Our findings suggest that body composition parameters, whether measured before or after dialysis, can be used to evaluate obesity in longitudinal studies.

  10. REVIEW: Development of methods for body composition studies

    NASA Astrophysics Data System (ADS)

    Mattsson, Sören; Thomas, Brian J.

    2006-07-01

    This review is focused on experimental methods for determination of the composition of the human body, its organs and tissues. It summarizes the development and current status of fat determinations from body density, total body water determinations through the dilution technique, whole and partial body potassium measurements for body cell mass estimates, in vivo neutron activation analysis for body protein measurements, dual-energy absorptiometry (DEXA), computed tomography (CT) and magnetic resonance imaging (MRI, fMRI) and spectroscopy (MRS) for body composition studies on tissue and organ levels, as well as single- and multiple-frequency bioimpedance (BIA) and anthropometry as simple easily available methods. Methods for trace element analysis in vivo are also described. Using this wide range of measurement methods, together with gradually improved body composition models, it is now possible to quantify a number of body components and follow their changes in health and disease.

  11. Wear resistance and electrical property of infrared processed copper/tungsten carbide composites

    NASA Astrophysics Data System (ADS)

    Deshpande, Pranav K.

    Copper matrix composites with 53 vol% of WC particle reinforcements have been prepared with an infrared infiltration technique. The process produced fully dense composite owing to excellent wetting between copper and WC. The microhardness values of completely infiltrated Cu/WC composites were in the range of 360-370 HV which is significantly higher than the microhardness of pure copper, 65 HV. The electric conductivity of these composites, as determined by a four-point-probe method, is similar to commercially available Cu/W composites containing 52 vol% of tungsten. The wear behavior of Cu/WC composites has been determined with a pin-on-disk technique against a sintered SiC abrasive disk. The wear rate as a function of a normal wear stress and composite porosity was investigated. Results have shown that up to a normal load of around 9 N (or 0.55 MPa pressure), the wear rate of fully dense Cu/WC composites increases linearly with the applied pressure. Results also show that porosity in the Cu/WC composite increases wear. A model of wear, taking into account various wear mechanisms, was developed. This model successfully predicts the wear behavior of dense Cu/WC composites. Owing to its significantly better wear resistance, as compared to Cu/W composites, the composition of Cu/53 vol% WC composite was varied by an innovative technique to improve the electrical conductivity of these composites without much compensation on its wear resistance. The technique of composition variation also helped in overcoming the shortcomings of pressure-less infiltration technique.

  12. Processing and response of aluminum-lithium alloy composites reinforced with copper-coated silicon carbide particulates

    NASA Astrophysics Data System (ADS)

    Khor, K. A.; Cao, Y.; Boey, F. Y. C.; Hanada, K.; Murakoshi, Y.; Sudarshan, T. S.; Srivatsan, T. S.

    1998-02-01

    Lithium-containing aluminum alloys have shown promise for demanding aerospace applications because of their light weight, high strength, and good damage tolerance characteristics. Additions of ceramic reinforcements to an aluminum-lithium alloy can significantly enhance specific strength, and specific modulus while concurrently offering acceptable performance at elevated temperatures. The processing and fabrication of aluminum-lithium alloy-based composites are hampered by particulate agglomeration or clustering and the existence of poor interfacial relationships between the reinforcing phase and the matrix. The problem of distribution of the reinforcing phase in the metal matrix can be alleviated by mechanical alloying. This article presents the results of a study aimed at addressing and improving the interfacial relationship between the host matrix and the reinforcing phase. Copper-coated silicon carbide particulates are introduced as the particulate reinforcing phase, and the resultant composite mixture is processed by conventional milling followed by hot pressing and hot extrusion. The influence of extrusion ratio and extrusion temperature on microstructure and mechanical properties was established. Post extrusion processing by hot isostatic pressing was also examined. Results reveal the increase in elastic modulus of the aluminum-lithium alloy matrix reinforced with copper-coated SiC to be significantly more than the mechanically alloyed Al-Li/SiC counterpart. This suggests the possible contributions of interfacial strengthening on mechanical response in direct comparison with a uniform distribution of the reinforcing ceramic particulates.

  13. Titania Composites with 2 D Transition Metal Carbides as Photocatalysts for Hydrogen Production under Visible-Light Irradiation

    DOE PAGES

    Wang, Hui; Peng, Rui; Hood, Zachary D.; ...

    2016-05-24

    In the MXenes family of two-dimensional transition-metal carbides there were successful demonstrations of co-catalysts with rutile TiO2 for visible-light-induced solar hydrogen production from water splitting. The physicochemical properties of Ti3C2Tx MXene coupled with TiO2 were investigated by a variety of characterization techniques. The effect of the Ti3C2Tx loading on the photocatalytic performance of the TiO2/Ti3C2Tx composites was elucidated. Moreover, with an optimized Ti3C2Tx content of 5 wt %, the TiO2/Ti3C2Tx composite shows a 400 % enhancement in the photocatalytic hydrogen evolution reaction compared with that of pure rutile TiO2. We also expanded our exploration to other MXenes (Nb2CTx and Ti2CTx)more » as co-catalysts coupled with TiO2, and these materials also exhibited enhanced hydrogen production. These results manifest the generality of MXenes as effective co-catalysts for solar hydrogen production.« less

  14. Capacitance of two-dimensional titanium carbide (MXene) and MXene/carbon nanotube composites in organic electrolytes

    NASA Astrophysics Data System (ADS)

    Dall'Agnese, Yohan; Rozier, Patrick; Taberna, Pierre-Louis; Gogotsi, Yury; Simon, Patrice

    2016-02-01

    Pseudocapacitive materials that store charges by fast redox reactions are promising candidates for designing high energy density electrochemical capacitors. MXenes - recently discovered two-dimensional carbides, have shown excellent capacitance in aqueous electrolytes, but in a narrow potential window, which limits both the energy and power density. Here, we investigated the electrochemical behavior of Ti3C2 MXene in 1M solution of 1-ethly-3-methylimidazolium bis- (trifluoromethylsulfonyl)-imide (EMITFSI) in acetonitrile and two other common organic electrolytes. This paper describes the use of clay, delaminated and composite Ti3C2 electrodes with carbon nanotubes in order to understand the effect of the electrode architecture and composition on the electrochemical performance. Capacitance values of 85 F g-1 and 245 F cm-3 were obtained at 2 mV s-1, with a high rate capability and good cyclability. In situ X-ray diffraction study reveals the intercalation of large EMI+ cations into MXene, which leads to increased capacitance, but may also be the rate limiting factor that determines the device performance.

  15. Composite uranium carbide targets at TRIUMF: Development and characterization with SEM, XRD, XRF and L-edge densitometry

    NASA Astrophysics Data System (ADS)

    Kunz, Peter; Bricault, Pierre; Dombsky, Marik; Erdmann, Nicole; Hanemaayer, Vicky; Wong, John; Lützenkirchen, Klaus

    2013-09-01

    The production of radioactive ion beams (RIB) from spallation targets by irradiation with a continuous 500 MeV proton beam, has been routine at TRIUMF for several years. Based on the experience with composite refractory carbide targets a procedure for the fabrication of UC2/C targets was developed. It includes the preparation of UC2 by carbothermal reduction of UO2, the slip-casting of fine-grained UC2/C slurry on graphite foil under inert gas atmosphere and the cutting of composite target discs which are stacked up to a lamellar structure. The thermal properties of such an arrangement are adequate to withstand the high power deposition of an intense, continuous proton beam and also beneficial for the fast release of short-lived radioactive isotopes. Molecular structure, particle size and the impact of sintering of the target discs were investigated via XRD and SEM. Thickness and mass distribution were measured with position-sensitive LIII-edge densitometry. The results confirm that the properties of the UC2/C target material are well suited for RIB production at TRIUMF while there is still room for improvement with regard to uniformity of mass distribution in target disc thickness.

  16. Titania Composites with 2 D Transition Metal Carbides as Photocatalysts for Hydrogen Production under Visible-Light Irradiation.

    PubMed

    Wang, Hui; Peng, Rui; Hood, Zachary D; Naguib, Michael; Adhikari, Shiba P; Wu, Zili

    2016-06-22

    MXenes, a family of two-dimensional transition-metal carbides, were successfully demonstrated as co-catalysts with rutile TiO2 for visible-light-induced solar hydrogen production from water splitting. The physicochemical properties of Ti3 C2 Tx MXene coupled with TiO2 were investigated by a variety of characterization techniques. The effect of the Ti3 C2 Tx loading on the photocatalytic performance of the TiO2 /Ti3 C2 Tx composites was elucidated. With an optimized Ti3 C2 Tx content of 5 wt %, the TiO2 /Ti3 C2 Tx composite shows a 400 % enhancement in the photocatalytic hydrogen evolution reaction compared with that of pure rutile TiO2 . We also expanded our exploration to other MXenes (Nb2 CTx and Ti2 CTx ) as co-catalysts coupled with TiO2 , and these materials also exhibited enhanced hydrogen production. These results manifest the generality of MXenes as effective co-catalysts for solar hydrogen production. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. High Dose Neutron Irradiation of Hi-Nicalon Type S Silicon Carbide Composites, Part 2. Mechanical and Physical Properties

    DOE PAGES

    Katoh, Yutai; Nozawa, Takashi; Shih, Chunghao Phillip; ...

    2015-01-07

    Nuclear-grade silicon carbide (SiC) composite material was examined for mechanical and thermophysical properties following high-dose neutron irradiation in the High Flux Isotope Reactor at a temperature range of 573–1073 K. Likewise, the material was chemical vapor-infiltrated SiC-matrix composite with a two-dimensional satin weave Hi-Nicalon Type S SiC fiber reinforcement and a multilayered pyrocarbon/SiC interphase. Moderate (1073 K) to very severe (573 K) degradation in mechanical properties was found after irradiation to >70 dpa, whereas no evidence was found for progressive evolution in swelling and thermal conductivity. The swelling was found to recover upon annealing beyond the irradiation temperature, indicating themore » irradiation temperature, but only to a limited extent. Moreover, the observed strength degradation is attributed primarily to fiber damage for all irradiation temperatures, particularly a combination of severe fiber degradation and likely interphase damage at relatively low irradiation temperatures.« less

  18. Effect of temper on seawater corrosion of an aluminum-silicon carbide composite alloy

    SciTech Connect

    Ahmad, Z.; Abdul Aleem, B.J.

    1996-11-01

    The corrosion behavior of annealed (O), as-fabricated (F), and naturally age-hardened (T4) aluminum alloy Al 6013 with 20 vol% silicon carbide in particulate form was investigated in 3.5 wt% sodium chloride and in Arabian Gulf water. Of the three tempers, T4 showed the lowest corrosion rate (0.04 mpy and 2.61 mpy) in deaerated and aerated NaCl, respectively. The corrosion rate in seawater was slightly higher. Predominant forms of corrosion were pitting and intergranular corrosion. Formation of corrosion chimneys was observed. X-ray diffraction Fourier transform infrared spectroscopy and energy dispersive spectroscopy showed intermetallic formation and the presence of a gelatinous film of aluminum hydroxide of bayrite type. The higher corrosion resistance of the T4 temper resulted from finer and more homogeneously distributed precipitates compared to tempers F and O. In view of the alloy`s good corrosion resistance and outstanding ultimate tensile strength, yield strength and specific modulus, it can be considered a strong competitor to Al 2024, Al 2014, and Al 6061, which are used mainly for structural applications.

  19. Thermodynamic modelling of phase equilibrium in system Ti-B-Si-C, synthesis and phases composition of borides and carbides layers on titanic alloyVT-1 at electron beam treatment in vacuum

    NASA Astrophysics Data System (ADS)

    Smirnyagina, N. N.; Khaltanova, V. M.; Lapina, A. E.; Dasheev, D. E.

    2017-01-01

    Composite layers on the basis of carbides and borides the titan and silicon on titanic alloy VT-1 are generated at diffused saturation in vacuum. Formation in a composite of MAX phase Ti3SiC2 is shown. Thermodynamic research of phase equilibrium in systems Ti-Si-C and Ti-B-C in the conditions of high vacuum is executed. The thermodynamics, formation mechanisms of superfirm layers borides and carbides of the titan and silicon are investigated.

  20. Peer Victimisation and Its Relationships with Perceptions of Body Composition

    ERIC Educational Resources Information Center

    Frisen, Ann; Lunde, Carolina; Hwang, Philip

    2009-01-01

    The present study examined the links between children's exposure to peer victimisation, in terms of type and frequency, their body composition and subjective perceptions of body composition. A total of 960 Swedish 10-year-olds (515 girls and 445 boys) completed questionnaires about their peer victimisation experiences, weight and height, and…

  1. The Body Composition of a College Football Team.

    ERIC Educational Resources Information Center

    Wickkiser, John D.; Kelly, John M.

    This study focuses on the body composition and anthropometric measurements of 65 college football players. Body composition was determined by underwater weighing with an accurate assessment of residual volume. The anthropometric measurements included height, weight, seven skinfolds, waist circumference, and wrist diameter. A step-wise multiple…

  2. Peer Victimisation and Its Relationships with Perceptions of Body Composition

    ERIC Educational Resources Information Center

    Frisen, Ann; Lunde, Carolina; Hwang, Philip

    2009-01-01

    The present study examined the links between children's exposure to peer victimisation, in terms of type and frequency, their body composition and subjective perceptions of body composition. A total of 960 Swedish 10-year-olds (515 girls and 445 boys) completed questionnaires about their peer victimisation experiences, weight and height, and…

  3. Micromechanical analysis of a hybrid composite—effect of boron carbide particles on the elastic properties of basalt fiber reinforced polymer composite

    NASA Astrophysics Data System (ADS)

    Krishna Golla, Sai; Prasanthi, P.

    2016-11-01

    A fiber reinforced polymer (FRP) composite is an important material for structural application. The diversified application of FRP composites has become the center of attention for interdisciplinary research. However, improvements in the mechanical properties of this class of materials are still under research for different applications. The reinforcement of inorganic particles in a composite improves its structural properties due to their high stiffness. The present research work is focused on the prediction of the mechanical properties of the hybrid composites where continuous fibers are reinforced in a micro boron carbide particle mixed polypropylene matrix. The effectiveness of the addition of 30 wt. % of boron carbide (B4C) particle contributions regarding the longitudinal and transverse properties of the basalt fiber reinforced polymer composite at various fiber volume fractions is examined by finite element analysis (FEA). The experimental approach is the best way to determine the properties of the composite but it is expensive and time-consuming. Therefore, the finite element method (FEM) and analytical methods are the viable methods for the determination of the composite properties. The FEM results were obtained by adopting a micromechanics approach with the support of FEM. Assuming a uniform distribution of reinforcement and considering one unit-cell of the whole array, the properties of the composite materials are determined. The predicted elastic properties from FEA are compared with the analytical results. The results suggest that B4C particles are a good reinforcement for the enhancement of the transverse properties of basalt fiber reinforced polypropylene.

  4. Stress rupture behavior of silicon carbide coated, low modulus carbon/carbon composites

    SciTech Connect

    Rozak, G.A.; Wallace, J.F.

    1988-01-01

    The disadvantages of carbon-carbon composites, in addition to the oxidation problem, are low thermal expansion, expensive fabrication procedures, and poor off axis properties. The background of carbon-carbon composites, their fabrication, oxidation, oxidation protection and mechanical testing in flexure are discussed.

  5. Assessing body composition: the skinfold method.

    PubMed

    Talbot, L A; Lister, Z

    1995-12-01

    1. Excess body fat contributes to many chronic diseases. Using a case scenario, an initial screening assessment is performed on two clients. The occupational health nurse provides feedback on current lifestyle behaviors and educates the clients about relevant lifestyle changes. 2. Tables illustrate the step by step procedures for measuring body fat using the skinfold thickness method. Photographs show the multiple body sites used in the skinfold analysis. 3. Commonly asked client questions related to body fat are discussed in detail, and the use of body fat assessment as a screening method for the health promotion professional is described.

  6. Body composition and dietary intake in neoplasic disease

    SciTech Connect

    Cohn, S.H.; Gartenhaus, W.; Vartsky, D.; Sawitsky, A.; Zanzi, I.; Vaswani, A. Yasummure, S.; Rai, K.; Cartes, E.; Ellis, K.J.

    1981-10-01

    Changes in body composition in 37 cancer patients were studied over a period of 6 months. Initially, the patients were divided into two groups: those who lost body weight (over 10%) and those who maintained or gained body weight before the study. Analysis of body composition indicated that patients who lost body weight has caloric and protein intakes markedly below ''normal'' levels at the beginning of the study. There also appears to be a direct relationship between the protein intake and the total body potassium/total body water ratio in the cancer patients. At the end of the 6-month study, the patients were again placed into two groups on the basis of weight loss or gain (and maintenance). Changes in body composition over the period were analyzed in terms of lean body mass, its protein constituent, water, and fat. Weight loss was found to reflect primarily the loss of fat, water, lean body mass (potassium), and only to a minor extent the protein component of lean body mass (nitrogen). Further, on the basis of the values of the ratios of total body nitrogen/total body potassium/total body water, it was possible to ascertain the relative normalcy of the body tissue gained or lost in the 6-month period. The results of the study suggest that the ratio total body nitrogen/total body potassium may serve as the best indicator of recent or ongoing catabolism or anabolism of the neoplastic process. By means of the application of the techniques used for the determination of body composition, it should be possible to assess regimes of hyperalimentation of cancer patients who lose body weight. (JMT)

  7. Materials characterization of silicon carbide reinforced titanium (Ti/SCS-6) metal matrix composites: Part I. Tensile and fatigue behavior

    NASA Astrophysics Data System (ADS)

    Liaw, P. K.; Diaz, E. S.; Chiang, K. T.; Loh, D. H.

    1995-12-01

    Flexural fatigue behavior was investigated on titanium (Ti-15V-3Cr) metal matrix composites reinforced with cross-ply, continuous silicon carbide (SiC) fibers. The titanium composites had an eightply (0, 90, +45, -45 deg) symmetric layup. Fatigue life was found to be sensitive to fiber layup sequence. Increasing the test temperature from 24 °C to 427 °C decreased fatigue life. Interface debonding and matrix and fiber fracture were characteristic of tensile behavior regardless of test temperature. In the tensile fracture process, interface debonding between SiC and the graphite coating and between the graphite coating and the carbon core could occur. A greater amount of coating degradation at 427 °C than at 24 °C reduced the Ti/SiC interface bonding integrity, which resulted in lower tensile properties at 427 °C. During tensile testing, a crack could initiate from the debonded Ti/SiC interface and extend to the debonded interface of the neighboring fiber. The crack tended to propagate through the matrix and the interface. Dimpled fracture was the prime mode of matrix fracture. During fatigue testing, four stages of flexural deflection behavior were observed. The deflection at stage I increased slightly with fatigue cycling, while that at stage II increased significantly with cycling. Interestingly, the deflection at stage III increased negligibly with fatigue cycling. Stage IV was associated with final failure, and the deflection increased abruptly. Interface debonding, matrix cracking, and fiber bridging were identified as the prime modes of fatigue mechanisms. To a lesser extent, fiber fracture was observed during fatigue. However, fiber fracture was believed to occur near the final stage of fatigue failure. In fatigued specimens, facet-type fracture appearance was characteristic of matrix fracture morphology. Theoretical modeling of the fatigue behavior of Ti/SCS-6 composites is presented in Part II of this series of articles.

  8. Creep deformation in an alumina-silicon carbide composite produced via a directed metal oxidation process

    SciTech Connect

    Lin, H.T.; Breder, K.

    1996-08-01

    Flexural creep studies were conducted in a commercially available alumina matrix composite reinforced with SiC particulates (SiC{sub p}) and aluminum metal at temperatures from 1,200 to 1,300 C under selected stress levels in air. The alumina composite (5 to 10 {micro}m alumina grain size) containing 48 vol% SiC particulates and 13 vol% aluminum alloy was fabricated via a directed metal oxidation process (DIMOX{trademark}) and had an external 15 {micro}m oxide coating. Creep results indicated that the DIMOX Al{sub 2}O{sub 3}-SiC{sub p} composite exhibited creep rates that were comparable to alumina composites reinforced with 10 vol% (8 {micro}m grain size) and 50 vol% (1.5 {micro}m grain size) SiC whiskers under the employed test conditions. The DIMOX Al{sub 2}O{sub 3}-SiC{sub p} composite exhibited a stress exponent of 2 at 1,200 C and a higher exponent value (2.6) at {ge}1,260 C, which is associated with the enhanced creep cavitation. The creep mechanism in the DIMOX alumina composite was attributed to grain boundary sliding accommodated by diffusional processes. Creep damage observed in the DIMOX Al{sub 2}O{sub 3}-SiC{sub p} composite resulted from the cavitation at alumina two-grain facets and multiple-grain junctions where aluminum alloy was present.

  9. Body Composition Measurements of 161-km Ultramarathon Participants

    USDA-ARS?s Scientific Manuscript database

    This study compares body composition characteristics with performance among participants in a 161-km trail ultramarathon. Height, mass, and percent body fat from bioimpedence spectroscopy were measured on 72 starters. Correlation analyses were used to compare body characteristics with finish time, ...

  10. Changes in body composition of neonatal piglets during growth

    USDA-ARS?s Scientific Manuscript database

    During studies of neonatal piglet growth it is important to be able to accurately assess changes in body composition. Previous studies have demonstrated that quantitative magnetic resonance (QMR) provides precise and accurate measurements of total body fat mass, lean mass and total body water in non...

  11. Body composition of piglets exhibiting different growth rates

    USDA-ARS?s Scientific Manuscript database

    The growth and composition of the neonatal pig is of interest because of potential impact on subsequent growth and finally, composition at market weight. The purpose of this study was to compare at weaning the growth and body composition of the largest and smallest pigs (excluding runts) from each o...

  12. New composite composed of boron carbide and carbon fiber with high thermal conductivity for first wall

    NASA Astrophysics Data System (ADS)

    Jimbou, R.; Saidoh, M.; Nakamura, K.; Akiba, M.; Suzuki, S.; Gotoh, Y.; Suzuki, Y.; Chiba, A.; Yamaki, T.; Nakagawa, M.; Morita, K.; Tsuchiya, B.

    1996-10-01

    A new composite was created from B 4C powder and carbon fiber by hot-pressing at 1700°C or more. The composite sintered at 1700°C with 20-35 vol% B 4C shows a thermal conductivity of 250 W/m·K at 25°C which is slightly lower than the felt type C/C, but its value becomes higher than the C/C at temperatures above 400°C. The composite with 40 at% B shows more controllable recycling properties than B 4C. The erosion yield for the composite is about half the yield for graphite at 800 K. After electron beam irradiation in order to test heat resistance no cracks were detected up to 22-23 MW/m 2 leading to a surface temperature of 2500°C.

  13. Investigation of Thermo-Mechanical Effects in Silicon Carbide Whisker/Al Alloy Composites

    DTIC Science & Technology

    1990-06-01

    reinforced aluminum composite material. This material is composed of typically 15-20 volume percent whiskers in various aluminum alloy matrices and has...dominate failure in the present composite systems of interest (i.e. SiC/ 2124 and 2 SiC/6061). These particles, identified through X-ray analysis as AI2...pure aluminum matrix, at least up to a tempera- ture of 400 0C. At temperatures higher than this it appears as if precipitation strengthening offers

  14. Hard coating of ultrananocrystalline diamond/nonhydrogenated amorphous carbon composite films on cemented tungsten carbide by coaxial arc plasma deposition

    NASA Astrophysics Data System (ADS)

    Naragino, Hiroshi; Egiza, Mohamed; Tominaga, Aki; Murasawa, Koki; Gonda, Hidenobu; Sakurai, Masatoshi; Yoshitake, Tsuyoshi

    2016-08-01

    Ultrananocrystalline diamond (UNCD)/nonhydrogenated amorphous carbon (a-C) composite (UNCD/a-C) films were deposited on cemented carbide containing Co by coaxial arc plasma deposition. With decreasing substrate temperature, the hardness was enhanced accompanied by an enhancement in the sp3/(sp2 + sp3). Energy-dispersive X-ray and secondary ion mass spectrometry spectroscopic measurements exhibited that the diffusion of Co atoms from the substrates into the films hardly occurs. The film deposited at room temperature exhibited the maximum hardness of 51.3 GPa and Young's modulus of 520.2 GPa, which evidently indicates that graphitization induced by Co in the WC substrates, and thermal deformation from sp3 to sp2 bonding are suppressed. The hard UNCD/a-C films can be deposited at a thickness of approximately 3 μm, which is an order larger than that of comparably hard a-C films. The internal compressive stress of the 51.3-GPa film is 4.5 GPa, which is evidently smaller than that of comparably hard a-C films. This is a reason for the thick deposition. The presence of a large number of grain boundaries in the film, which is a structural specific to UNCD/a-C films, might play a role in releasing the internal stress of the films.

  15. A Revival of Waste: Atmospheric Pressure Nitrogen Plasma Jet Enhanced Jumbo Silicon/Silicon Carbide Composite in Lithium Ion Batteries.

    PubMed

    Chen, Bing-Hong; Chuang, Shang-I; Liu, Wei-Ren; Duh, Jenq-Gong

    2015-12-30

    In this study, a jumbo silicon/silicon carbide (Si/SiC) composite (JSC), a novel anode material source, was extracted from solar power industry cutting waste and used as a material for lithium-ion batteries (LIBs), instead of manufacturing the nanolized-Si. Unlike previous methods used for preventing volume expansion and solid electrolyte interphase (SEI), the approach proposed here simply entails applying surface modification to JSC-based electrodes by using nitrogen-atmospheric pressure plasma jet (N-APPJ) treatment process. Surface organic bonds were rearranged and N-doped compounds were formed on the electrodes through applying different plasma treatment durations, and the qualitative examinations of before/after plasma treatment were identified by X-ray photoelectron spectroscopy (XPS) and electron probe microanalyzer (EPMA). The surface modification resulted in the enhancement of electrochemical performance with stable capacity retention and high Coulombic efficiency. In addition, depth profile and scanning electron microscope (SEM) images were executed to determine the existence of Li-N matrix and how the nitrogen compounds change the surface conditions of the electrodes. The N-APPJ-induced rapid surface modification is a major breakthrough for processing recycled waste that can serve as anode materials for next-generation high-performance LIBs.

  16. Effect of physical activity on body composition

    SciTech Connect

    Zanzi, I; Ellis, K J; Aloia, J; Cohn, S H

    1980-01-01

    It has been noted that the deleterious effects on bone calcium of prolonged periods of inactivity, such as bed rest, are halted following resumption of activity. It would seem possible in light of the observations that have been made, that exercise may stimulate bone formation and perhaps counter, to some extent, bone loss as observed in the osteoporosis of aging. The present study was designed to determine the relation between total body calcium, total body potassium and bone mineral content of the radius to the degree of physical activity in a population of normal subjects. Measurement of the calcium was made by in-vivo total body neutron activation analysis. Bone mineral content of the radius and total body potassium, (an index of lean body mass) were measured by photon absorptiometry and the whole body counter, respectively.

  17. Laser cladding of Inconel 625-based composite coatings reinforced by porous chromium carbide particles

    NASA Astrophysics Data System (ADS)

    Janicki, Damian

    2017-09-01

    Inconel 625/Cr3C2 composite coatings were produced via a laser cladding process using Cr3C2 reinforcing particles presenting an open porosity of about 60%. A laser cladding system used consisted of a direct diode laser with a rectangular beam spot and the top-hat beam profile, and an off-axis powder injection nozzle. The microstructural characteristics of the coatings was investigated with the use of scanning electron microscopy and X-ray diffraction. A complete infiltration of the porous structure of Cr3C2 reinforcing particles and low degree of their dissolution have been achieved in a very narrow range of processing parameters. Crack-free composite coatings having a uniform distribution of the Cr3C2 particles and their fraction up to 36 vol% were produced. Comparative erosion tests between the Inconel 625/Cr3C2 composite coatings and the metallic Inconel 625 coatings were performed following the ASTM G 76 standard test method. It was found that the composite coatings have a significantly higher erosion resistance to that of metallic coatings for both 30° and 90° impingement angles. Additionally, the erosion performances of composite coatings were similar for both the normal and oblique impact conditions. The erosive wear behaviour of composite coatings is discussed and related to the unique microstructure of these coatings.

  18. Oxidation behavior of zirconium diboride-silicon carbide composites at high temperatures

    NASA Astrophysics Data System (ADS)

    Karlsdottir, Sigrun N.

    The ZrB2-SiC composite is a prominent member of Ultra-High Temperature Ceramics (UHTCs). Here the oxidation behavior of ZrB 2-SiC composites at temperatures between 1500-1900°C is studied. The structure and composition of complex oxide scales, formed at these temperatures, are characterized using microstructural and elemental analysis. A novel method, called the Ribbon Method, was developed for testing UHTCs at high temperatures, rapidly at low cost. Self-supported UHTC ribbon specimens are resistively heated with a table-top apparatus to achieve temperatures from 900-2000°C. The Ribbon Method is a novel method for rapid oxidation characterization of UHTC at high temperatures and a valuable alternative to the current high temperature facilities for UHTCs. Oxidation studies with the Ribbon Method showed that a SiO2 rich borosilicate surface layer forms during the oxidation of the ZrB2-SiC composite and acts as a protective barrier at lower temperatures by hindering oxygen diffusion through the surface layer. The SiO2-rich surface layer starts to volatilize extensively at temperatures above 1700°C resulting in a decreases in the oxidation resistance of the composite. A novel mechanism is proposed for the high temperature oxidation of ZrB 2-SiC based composites. This mechanism is based on liquid transport of oxide liquid solution formed during oxidation at temperatures around 1550°C. Patterns in borosilicate surface layer of oxidized ZrB2-SiC composites were discovered, showing evidence of liquid flow in the oxide film. These patterns, called here convection cells, are formed when a fluid B2O 3-rich borosilicate liquid containing dissolved ZrO2 is transported to the surface where the B2O3 is lost by evaporation, depositing ZrO2 in a viscous SiO2-rich liquid. The driving force for the liquid transport is proposed to be the large volume increase upon oxidation. Liquid transport of the oxide liquid solution is claimed to play a significant role in the formation of

  19. Effects of interfaces and preferred orientation on the electrical response of composites of alumina and silicon carbide whiskers

    NASA Astrophysics Data System (ADS)

    Bertram, Brian D.

    Ceramic-matrix composites of alumina and silicon carbide whiskers have recently found novel commercial application as electromagnetic absorbers. However, a detailed understanding of how materials issues influence the composite electrical response which underpins this application has been absent until now. In this project, such composites were electrically measured over a wide range of conditions and modeled in terms of various aspects of the microstructure in order to understand how they work. For this purpose, three types of composites were made by different methods from the same set of ceramic powder blends loaded with different volume fractions of whiskers. In doing so, the interfaces between whiskers, the preferred orientations of whiskers, and the structure of electrically-connected whisker clusters were varied. In Chapter 3, it shown that Schottky energy barriers form at the junctions of the wide-bandgap semiconductor whiskers when metal electrodes are applied for measurements. These barriers were characterized on the microscopic and macroscopic level, and the gap between these different scales was bridged. Also, a modeling approach was developed for the loading dependence of the composite non-linear response which results from the barriers. In Chapter 4, the effects of significantly different types of preferred orientation are elucidated and a strong structure-property correlation is established. The effects of other structural issues on the electrical response are uncovered as well, such as those pertaining to porosity in the ceramic and the interfaces between electrically-connected SiCw. In Chapter 5, the non-linear response model of Chapter 3 is adapted in the development of a new model for electrically-percolated clusters. This model demonstrates how loading and interfacial issues influence the cluster topology and may result in the cluster having a non-linear electrical response. In Chapter 6, the effects of various factors on the broadband frequency

  20. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1993-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  1. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1985-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  2. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MP.am.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  3. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1993-11-16

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  4. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, G.C.

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al{sub 2}O{sub 3}, mullite, or B{sub 4}C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1,600 to 1,950 C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness which represents as much as a two-fold increase over that of the matrix material.

  5. Properties of silicon carbide fiber-reinforced silicon nitride matrix composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishna T.

    1988-01-01

    The mechanical properties of NASA Lewis developed SiC/RBSN composites and their thermal and environmental stability havd been studied. The composites consist of nearly 30 vol pct of aligned 142 micron diameter chemically vapor-deposited SiC fibers in a relatively porous silicon nitride matrix. In the as-fabricated condition, the unidirectional and 2-D composites exhibited metal-like stress-strain behavior, graceful failure, and showed improved properties when compared with unreinforced matrix of comparable density. Furthermore, the measured room temperature tensile properties were relativley independent of tested volume and were unaffected by artifical notches normal to the loading direction or by thermal shocking from temperatures up to 800 C. The four-point bend strength data measured as a function of temperature to 1400 C in air showed that as-fabricated strength was maintained to 1200 C. At 1400 C, however, nearly 15 pct loss in strength was observed. Measurement of room temperature tensile strength after 100 hr exposure at temperatures to 1400 C in a nitrogen environment indicated no loss from the as-fabricated composite strength. On the other hand, after 100 hr exposure in flowing oxygen at 1200 and 1400 C, the composites showed approximately 40 pct loss from their as-fabricated ultimate tensile strength. Those exposed between 400 to 1200 C showed nearly 60 pct strength loss. Oxidation of the fiber/matrix interface as well as internal oxidation of the porous Si3N4 matrix are likely mechanisms for strength degradation. The excellent strength reproducibility, notch insensitivity, and high temperature strength of the composite makes it an ideal candidate for advanced heat engine applications provided coating or densification methods are developed to avoid internal oxidation attack.

  6. Titania Composites with 2 D Transition Metal Carbides as Photocatalysts for Hydrogen Production under Visible-Light Irradiation

    SciTech Connect

    Wang, Hui; Peng, Rui; Hood, Zachary D.; Naguib, Michael; Adhikari, Shiba P.; Wu, Zili

    2016-05-24

    In the MXenes family of two-dimensional transition-metal carbides there were successful demonstrations of co-catalysts with rutile TiO2 for visible-light-induced solar hydrogen production from water splitting. The physicochemical properties of Ti3C2Tx MXene coupled with TiO2 were investigated by a variety of characterization techniques. The effect of the Ti3C2Tx loading on the photocatalytic performance of the TiO2/Ti3C2Tx composites was elucidated. Moreover, with an optimized Ti3C2Tx content of 5 wt %, the TiO2/Ti3C2Tx composite shows a 400 % enhancement in the photocatalytic hydrogen evolution reaction compared with that of pure rutile TiO2. We also expanded our exploration to other MXenes (Nb2CTx and Ti2CTx) as co-catalysts coupled with TiO2, and these materials also exhibited enhanced hydrogen production. These results manifest the generality of MXenes as effective co-catalysts for solar hydrogen production.

  7. Titania Composites with 2 D Transition Metal Carbides as Photocatalysts for Hydrogen Production under Visible-Light Irradiation

    SciTech Connect

    Wang, Hui; Peng, Rui; Hood, Zachary D.; Naguib, Michael; Adhikari, Shiba P.; Wu, Zili

    2016-05-24

    In the MXenes family of two-dimensional transition-metal carbides there were successful demonstrations of co-catalysts with rutile TiO2 for visible-light-induced solar hydrogen production from water splitting. The physicochemical properties of Ti3C2Tx MXene coupled with TiO2 were investigated by a variety of characterization techniques. The effect of the Ti3C2Tx loading on the photocatalytic performance of the TiO2/Ti3C2Tx composites was elucidated. Moreover, with an optimized Ti3C2Tx content of 5 wt %, the TiO2/Ti3C2Tx composite shows a 400 % enhancement in the photocatalytic hydrogen evolution reaction compared with that of pure rutile TiO2. We also expanded our exploration to other MXenes (Nb2CTx and Ti2CTx) as co-catalysts coupled with TiO2, and these materials also exhibited enhanced hydrogen production. These results manifest the generality of MXenes as effective co-catalysts for solar hydrogen production.

  8. Body composition changes in pregnancy: measurement, predictors and outcomes

    PubMed Central

    Widen, EM; Gallagher, D

    2014-01-01

    Prevalence of overweight and obesity has risen in the United States over the past few decades. Concurrent with this rise in obesity has been an increase in pregravid body mass index and gestational weight gain affecting maternal body composition changes in pregnancy. During pregnancy, many of the assumptions inherent in body composition estimation are violated, particularly the hydration of fat-free mass, and available methods are unable to disentangle maternal composition from fetus and supporting tissues; therefore, estimates of maternal body composition during pregnancy are prone to error. Here we review commonly used and available methods for assessing body composition changes in pregnancy, including: (1) anthropometry, (2) total body water, (3) densitometry, (4) imaging, (5) dual-energy X-ray absorptiometry, (6) bioelectrical impedance and (7) ultrasound. Several of these methods can measure regional changes in adipose tissue; however, most of these methods provide only whole-body estimates of fat and fat-free mass. Consideration is given to factors that may influence changes in maternal body composition, as well as long-term maternal and offspring outcomes. Finally, we provide recommendations for future research in this area. PMID:24667754

  9. Tensile and creep behavior of a silicon carbide fiber-reinforced aluminosilicate composite

    SciTech Connect

    Khobaib, M.; Zawada, L.

    1991-08-01

    Tensile and tensile creep tests were conducted with a Nicalon/aluminosilicate (Si-C-O/1723) glass composite. Tensile tests were conducted at room temperature, and the creep tests were conducted at 600, 700, and 750 C. Room temperature tensile test failure features exhibited a tortuous crack path and extensive fiber pull-out. The failure features in creep were characterized by flat fracture and little fiber pull-out. The environment appeared to play a significant role in creep failure of this composite system. 6 refs.

  10. Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam (Inventor)

    1992-01-01

    A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  11. Method of producing a silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam P. (Inventor)

    1995-01-01

    A SrO-Al2O3-2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed.

  12. Non-invasive techniques for determining musculoskeleton body composition

    SciTech Connect

    Cohn, S.H.

    1984-01-01

    In vivo neutron activation analysis, combined with gamma spectrometry, has ushered in a new era of clinical diagnosis and evaluation of therapies, as well as investigation into and modelling of body composition in both normal individuals and patients suffering from various diseases and dysfunctions. Body composition studies have provided baseline data on such vital constituents as nitrogen, potassium and calcium. The non-invasive measurement techniques are particularly suitable for study of the musculo-skeletal changes in body composition. Of particular relevance here is the measurement of calcium loss in astronauts during prolonged space flights.

  13. Damage evolution in uniaxial silicon carbide fiber-reinforced titanium matrix composites

    NASA Astrophysics Data System (ADS)

    Hanan, Jay Clarke

    Fiber fractures initiate damage zones ultimately determining the strength and lifetime of metal matrix composites (MMCs). The evolution of damage in a MMC comprising a row of unidirectional SiC fibers (32 vol.%) surrounded by a Ti matrix was examined using X-ray microdiffraction (gym beam size) and macrodiffraction (mm beam size). A comparison of high-energy X-ray diffraction (XRD) techniques including a powerful two-dimensional XRD method capable of obtaining powder averaged strains from a small number of grains is presented (HEmuXRD2). Using macrodiffraction, the bulk residual strain in the composite was determined against a true strain-free reference. In addition, the bulk in situ response of both the fiber reinforcement and the matrix to tensile stress was observed and compared to a three-dimensional finite element model. Using microdiffraction, multiple strain maps including both phases were collected in situ before, during, and after the application of tensile stress, providing an unprecedented detailed picture of the micromechanical behavior in the laminate metal matrix composite. Finally, the elastic axial strains were compared to predictions from a modified shear lag model, which unlike other shear lag models, considers the elastic response of both constituents. The strains showed excellent correlation with the model. The results confirmed, for the first time, both the need and validity of this new model specifically developed for large scale multifracture and damage evolution simulations of metal matrix composites. The results also provided unprecedented insight for the model, revealing the necessity of incorporating such factors as plasticity of the matrix, residual stress in the composite, and selection of the load sharing parameter. The irradiation of a small number of grains provided strain measurements comparable to a continuum mechanical state in the material. Along the fiber axes, thermal residual stresses of 740 MPa (fibers) and +350 MPa (matrix

  14. Infant BMI trajectories are associated with young adult body composition

    PubMed Central

    Slining, M. M.; Herring, A. H.; Popkin, B. M.; Mayer-Davis, E. J.; Adair, L. S.

    2013-01-01

    The dynamic aspect of early life growth is not fully captured by typical analyses, which focus on one specific time period. To better understand how infant and young child growth relate to the development of adult body composition, the authors characterized body mass index (BMI) trajectories using latent class growth analysis (LCGA) and evaluated their association with adult body composition. Data are from the Cebu Longitudinal Health and Nutrition Survey, which followed a birth cohort to age 22 years (n=1749). In both males and females, LCGA identified seven subgroups of respondents with similar BMI trajectories from 0 to 24 months (assessed with bimonthly anthropometrics). Trajectory groups were compared with conventional approaches: (1) accelerated growth between two time points (0–4 months), (2) continuous BMI gain between two points (0–4 months and 0–24 months) and (3) BMI measured at one time point (24 months) as predictors of young adult body composition measures. The seven trajectory groups were distinguished by age-specific differences in tempo and timing of BMI gain in infancy. Infant BMI trajectories were better than accelerated BMI gain between 0 and 4 months at predicting young adult body composition. After controlling for BMI at age 2 years, infant BMI trajectories still explained variation in adult body composition. Using unique longitudinal data and methods, we find that distinct infant BMI trajectories have long-term implications for the development of body composition. PMID:24040489

  15. Mechanical behaviour of an alumina fibre reinforced silicon carbide matrix composite at high temperature

    SciTech Connect

    Steen, M.; Valles, J.L.; Lamouroux, F. |

    1995-12-01

    In this study, the high temperature mechanical response of a 2D Al{sub 2}O{sub 3}(f)/SiC composite is investigated by uniaxial tensile, creep and fatigue tests under vacuum. During the tests, unloading-reloading cycles are introduced in order to study the evolution of damage with accumulated strain. The results show that creep damage is governed by interfacial debonding, whereas in the cyclic tests either fatigue damage only, or combined creep-fatigue damage occurs.

  16. Versatile Boron Carbide-Based Visual Obscurant Compositions for Smoke Munitions

    DTIC Science & Technology

    2015-04-17

    fuel, KNO3 as a pyrotechnic oxidizer , and KCl as a combustion temperature moderator. Small amounts of calcium stearate and polymeric binders may be added...Similarly, pyrotechnic compositions based on hexachloroethane, a known toxin and suspected carcinogen,5 produce a thick hygroscopic zinc chloride aerosol...B4C) as a pyrotechnic fuel, KNO3 as a pyrotechnic oxidizer , and KCl as a combustion temperature moderator. Small amounts of calcium stearate and

  17. Influence of Interfacial Carbide Layer Characteristics on Thermal Properties of Copper-Diamond Composites (Postprint)

    DTIC Science & Technology

    2014-04-01

    Cr3C2 diamond composites, a mixture of pre-alloyed Cu Cr powder and diamond particles was hot pressed for sufficient time at a high enough temperature ...done by AM2T, LLC (formerly Ceracon, Inc., Sacramento, CA) at a pressure of 345 MPa and a temperature of 850 C (the forging time was *10 s). The...suggests that deformation during temperature excursions involves shear. 15. SUBJECT TERMS thermal management, copper-diamond substrates, low

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

    PubMed

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

    2009-05-20

    Age-related changes in body composition are well-documented with a decrease in lean body mass and a redistribution of body fat generally observed. Resistance training alone has been shown to have positive effects on body composition, however, these benefits may be enhanced by the addition of a vibration stimulus. The purpose of this study was to determine the effects of 8 months of resistance training with and without whole-body vibration (WBV) on body composition in sedentary postmenopausal women. Fifty-five women were assigned to resistance only (RG, n=22), vibration plus resistance (VR, n=21) or non-exercising control (CG, n=12) groups. Resistance training (3 sets 10 repetitions 80% strength) was performed using isotonic weight training equipment and whole-body vibration was done with the use of the power plate (Northbrooke, IL) vibration platform for three times per week for 8 months. Total and regional body composition was assessed from the total body DXA scans at baseline (pre) and after 8 months (post) of training. In the VR group, total % body fat decreased from pre- to post-time points (p<0.05), whereas, the CG group had a significant increase in total % body fat (p<0.05). Both training groups exhibited significant increases in bone free lean tissue mass for the total body, arm and trunk regions from pre to post (p<0.05). CG did not show any changes in lean tissue. In older women, resistance training alone and with whole-body vibration resulted in positive body composition changes by increasing lean tissue. However, only the combination of resistance training and whole-body vibration was effective for decreasing percent body fat.

  19. Comparison of the effectiveness of body mass index and body fat percentage in defining body composition.

    PubMed

    Goonasegaran, Arvin Raj; Nabila, Fatin Nabila; Shuhada, Nurul Shuhada

    2012-06-01

    Body mass index (BMI) has limited diagnostic performance due to its inability to discriminate between fat and lean mass. This study was conducted to compare the effectiveness of body fat percentage (BFP) against BMI in defining body composition. A cross-sectional study was conducted on students aged 17-30 years in Melaka, Malaysia. Basic anthropometric measurements were acquired using a manual weighing scale, measuring tape and a fixed stadiometer. BFP was calculated using the United States Navy formula. Data was tabulated and analysed using Epi Info and Statistical Package for the Social Sciences software. Pearson's correlation coefficient and Kappa values were used. A p-value < 0.05 was considered statistically significant. Out of the 490 subjects recruited, 43% of males and 24.6% of females were found to be overweight, while 14.3% of males and 7.8% of females were obese, when calculated using BMI. However, 8.9% of males and 22.8% of females were considered obese based on the BFP. BFP plays a more important role in distinguishing between healthy and obese individuals, as it has a greater ability to differentiate between lean mass and fat mass compared to BMI.

  20. Association between Human Body Composition and Periodontal Disease.

    PubMed

    Salekzamani, Yagoub; Shirmohammadi, Adileh; Rahbar, Mohammad; Shakouri, Seyed-Kazem; Nayebi, Farough

    2011-01-01

    Obesity in humans might increase the risk of periodontitis. The aim of the present study was to examine the relationship between body composition of males and their periodontal status. AS total of 150 males (aged 30-60) were selected: 31 were periodontally healthy, 45 had gingivitis, 39 had initial periodontitis, and 35 suffered from established periodontitis. BMI (body mass index), WC (waist circumference), and body composition parameters (consisting of body water, body fat, and skeletal muscle and bone mass) were measured. After adjusting for age, history of diabetes, smoking, physical activity status, and socioeconomic status, statistically significant correlations were found between periodontitis and BMI, WC, and body composition. There was only a statistically significant difference between the periodontal health and established periodontitis; that is, periodontal disease in mild forms (gingivitis) and initial periodontitis do not influence these variables (BMI, WC, and body composition parameters) and only the severe form of the disease influences the variables. These data suggest that there is a considerable association between severe forms of periodontal disease in males and their body composition, but this preliminary finding needs to be confirmed in more extensive studies.

  1. A study of silicon carbide synthesis from waste serpentine.

    PubMed

    Cheng, T W; Hsu, C W

    2006-06-01

    There are 60000 tons of serpentine wastes produced in year 2004 in Taiwan. This is due to the well-developed joints in the serpentine ore body as well as the stringent requirements of the particle size and chemical composition of serpentine by iron making company. The waste also creates considerable environmental problems. The purpose of this study is reutilization of waste serpentine to produce a high value silica powder after acid leaching. These siliceous microstructure products obtained from serpentine would be responsible for high reactivity and characteristic molecular sieving effect. In this study, the amorphous silica powder was then synthesized to silicon carbide with the C/SiO(2) molar ratio of 3. The experiment results show that silicon carbide can be synthesized in 1550 degrees C. The formed silicon carbide was whisker beta type SiC which can be used as raw materials for industry.

  2. The preparation and economics of silicon carbide matrix composites by chemical vapor infiltration

    SciTech Connect

    Roman, Y.G.; Stinton, D.P.

    1995-10-01

    This paper describes a number of processing techniques that are currently in use for the development and production of continuous fiber reinforced ceramic composite materials. The limited number of available processing routes are compared with respect to the resulting material properties. As it appears the Chemical Vapor Infiltration technique is one of the most extensively developed methods. During the last decade, at least five different modifications of the isobaric isothermal CVI principle have been developed; each route having its own benefits. CVI techniques have now been developed to the extent that industrial commercialization is being realized. Projected cost aspects of the various CVI manufacturing techniques have been examined and compared.

  3. Mechanical Behaviour of Alumina Silicon Carbide Reinforced Particulate Reinforced Metal Matrix Composite

    NASA Astrophysics Data System (ADS)

    Raghu Ram, K. S.; Sweanney Bandi, Sharon Rose; Sivarama Krishna, Ch.

    2017-08-01

    The present study was aimed at evaluating the effect of hardness and impact strength of Aluminum Al2O3SiC particulate reinforced Composites. These AMCs with multiple reinforcement (hybrid MMCs) are finding increased applications in aerospace, automobile, space, underwater and transportation applications. An effort is made to enhance the Hardness, flexural strength and Impact properties of AMCs by reinforcing Aluminum matrix with Varying Proportion of small particles of Al2O3SiC by stir casting method. Aluminum alloy matrix varying proportions of Al2O3SiC particulates were fabricated. The microstructure, hardness and impact strength properties of the fabricated AMCs were analyzed. The optical microstructure study revealed the homogeneous dispersion of Al2O3SiC particles in the matrix. Based on the results obtained from the Hardness and Impact of the metal matrix composites it is observed that, the hardness and impact strength increases with increase in the amount of reinforcement content.

  4. Bioelectrical Impedance and Body Composition Assessment

    ERIC Educational Resources Information Center

    Martino, Mike

    2006-01-01

    This article discusses field tests that can be used in physical education programs. The most common field tests are anthropometric measurements, which include body mass index (BMI), girth measurements, and skinfold testing. Another field test that is gaining popularity is bioelectrical impedance analysis (BIA). Each method has particular strengths…

  5. Bioelectrical Impedance and Body Composition Assessment

    ERIC Educational Resources Information Center

    Martino, Mike

    2006-01-01

    This article discusses field tests that can be used in physical education programs. The most common field tests are anthropometric measurements, which include body mass index (BMI), girth measurements, and skinfold testing. Another field test that is gaining popularity is bioelectrical impedance analysis (BIA). Each method has particular strengths…

  6. Chromium and Iron Isotopic Composition of Presolar Silicon Carbide Stardust Grains

    NASA Astrophysics Data System (ADS)

    Savina, M.; Levine, J.; Dauphas, N.; Pellin, M.; Willingham, D.; Stephan, T.; Trappitsch, R.; Davis, A. M.

    2011-12-01

    Most presolar SiC stardust grains derive from Asymptotic Giant Branch (AGB) stars, which are the main source of s-process nuclides in the galaxy. s-Process nucleosynthesis is not a major contributor to iron peak nuclides. The most interesting of these isotopes from an AGB nucleosynthetic standpoint are the trace isotopes 54Cr and 58Fe, which are predicted to have deviations from average Solar System ratios of ~100% and >200%, respectively. The other isotopes of Cr and Fe are essentially unchanged by AGB stars, and are representative of the isotopic composition of the protostellar cloud from which the SiC grains formed. They are thus tracers of Galactic Chemical Evolution, and provide a benchmark for the isotopic composition of the galaxy some five to seven billion years ago. SiC grains were isolated from the Murchison meteorite using high purity reagents and techniques specifically designed to prevent contamination with terrestrial Cr and Fe. Grains from the 2-4 μm size fraction were pressed into a high purity gold foil. Chromium and iron isotopic compositions were measured by Resonance Ionization Mass Spectrometry (RIMS) using new techniques specifically developed for high precision isotopic analysis of iron-peak elements. The Cr isotopic compositions of 19 grains form a distinct group. Several grains had resolvable (>2σ) 50Cr and 53Cr deficits ranging as low as -178%. The 54Cr/ 52Cr δ-values were all within 2σ of the Solar System value, though most were slightly higher. The average δ-values for the grains were -45±31% for 50Cr, -37±21% for 53Cr, and +25±26% for 54Cr. Iron results are pending. Given that AGB stars change most Fe and Cr isotope ratios very little, and that these grains' progenitor stars formed from a few hundred million to about three billion years before the Solar System formed (assuming their initial masses were 1.5 - 3 solar masses), and that grain interstellar residence times are likely less than ~100 - 200 million years, the Fe and Cr

  7. Impact of Body Weight and Body Composition on Ovarian Cancer Prognosis.

    PubMed

    Purcell, Sarah A; Elliott, Sarah A; Kroenke, Candyce H; Sawyer, Michael B; Prado, Carla M

    2016-02-01

    Measures of body weight and anthropometrics such as body mass index (BMI) are commonly used to assess nutritional status in clinical conditions including cancer. Extensive research has evaluated associations between body weight and prognosis in ovarian cancer patients, yet little is known about the potential impact of body composition (fat mass (FM) and fat-free mass (FFM)) in these patients. Thus, the purpose of this publication was to review the literature (using PubMed and EMBASE) evaluating the impact of body weight and particularly body composition on surgical complications, morbidity, chemotherapy dosing and toxicity (as predictors of prognosis), and survival in ovarian cancer patients. Body weight is rarely associated with intra-operative complications, but obesity predicts higher rates of venous thromboembolism and wound complications post-operatively in ovarian cancer patients. Low levels of FM and FFM are superior predictors of length of hospital stay compared to measures of body weight alone, but the role of body composition on other surgical morbidities is unknown. Obesity complicates chemotherapy dosing due to altered pharmacokinetics, imprecise dosing strategies, and wide variability in FM and FFM. Measurement of body composition has the potential to reduce toxicity if the results are incorporated into chemotherapy dosing calculations. Some findings suggest that excess body weight adversely affects survival, while others find no such association. Limited studies indicate that FM is a better predictor of survival than body weight in ovarian cancer patients, but the direction of this relationship has not been determined. In conclusion, body composition as an indicator of nutritional status is a better prognostic tool than body weight or BMI alone in ovarian cancer patients.

  8. Fatigue behavior of silicon carbide whisker/aluminum composite. Final report

    SciTech Connect

    Lee, E.E.

    1988-10-01

    Specimens of an extruded 19.8 vol % SiCw/2124 aluminum alloy composite were subjected to constant amplitude loading of stress ratio 0.1 at room temperature in a laboratory atmosphere. The fatigue crack growth path is tortuous and much of it is nearly parallel to the extrusion direction of the specimen. This is attributable to the SiCw aligned in the extrusion direction. The logarithm of fatigue-fracture life, NF, increases linearly with decreasing stress range, within the limits of the applied stress range. The observed fractographic features are facets and steps in the initial stage, striations in the subsequent stage, and dimples in the final stage of fatigue.

  9. CORRELATED STRONTIUM AND BARIUM ISOTOPIC COMPOSITIONS OF ACID-CLEANED SINGLE MAINSTREAM SILICON CARBIDES FROM MURCHISON

    SciTech Connect

    Liu, Nan; Savina, Michael R.; Gallino, Roberto; Davis, Andrew M.; Bisterzo, Sara; Gyngard, Frank; Käppeler, Franz; Cristallo, Sergio; Dauphas, Nicolas; Pellin, Michael J.; Dillmann, Iris

    2015-04-08

    We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated Sr-88/Sr-86 and Ba-138/Ba-136 ratios in mainstream SiC grains, we are able to resolve the effect of C-13 concentration from that of C-13-pocket mass on s-process nucleosynthesis, which points toward the existence of large C-13 pockets with low C-13 concentrations in asymptotic giant branch stars. The presence of such large C-13 pockets with a variety of relatively low C-13 concentrations seems to require multiple mixing processes in parent asymptotic giant branch stars of mainstream SiC grains.

  10. CORRELATED STRONTIUM AND BARIUM ISOTOPIC COMPOSITIONS OF ACID-CLEANED SINGLE MAINSTREAM SILICON CARBIDES FROM MURCHISON

    SciTech Connect

    Liu, Nan; Davis, Andrew M.; Dauphas, Nicolas; Pellin, Michael J.; Savina, Michael R.; Gallino, Roberto; Bisterzo, Sara; Gyngard, Frank; Käppeler, Franz; Cristallo, Sergio; Dillmann, Iris

    2015-04-10

    We present strontium, barium, carbon, and silicon isotopic compositions of 61 acid-cleaned presolar SiC grains from Murchison. Comparison with previous data shows that acid washing is highly effective in removing both strontium and barium contamination. For the first time, by using correlated {sup 88}Sr/{sup 86}Sr and {sup 138}Ba/{sup 136}Ba ratios in mainstream SiC grains, we are able to resolve the effect of {sup 13}C concentration from that of {sup 13}C-pocket mass on s-process nucleosynthesis, which points toward the existence of large {sup 13}C pockets with low {sup 13}C concentrations in asymptotic giant branch stars. The presence of such large {sup 13}C pockets with a variety of relatively low {sup 13}C concentrations seems to require multiple mixing processes in parent asymptotic giant branch stars of mainstream SiC grains.

  11. Body Composition Assessment--Some Practical Answers to Teachers' Questions.

    ERIC Educational Resources Information Center

    Thomas, David Q.; Whitehead, James R.

    1993-01-01

    Presents information about body composition assessment, including how useful the measurement is, how to conduct assessment, accurate skinfold measurement, body mass index versus skinfold results, interpreting results, standards for score interpretation, other types of measurement, how to approach skinfold assessment, and handling sensitivity and…

  12. Enamel Surface Evaluation after Removal of Orthodontic Composite Remnants by Intraoral Sandblasting Technique and Carbide Bur Technique: A Three-Dimensional Surface Profilometry and Scanning Electron Microscopic Study

    PubMed Central

    Mhatre, Amol C; Tandur, Arundhati P; Reddy, Sumitra S; Karunakara, B C; Baswaraj, H

    2015-01-01

    Background: The purpose of this thesis is to present a practical and efficient clinical method of returning enamel to as near its original condition as possible following removal of bonded orthodontic attachments. The main objective of this study is to evaluate and compare the iatrogenic enamel damage caused by use of two different remnant removal techniques – sandblasting technique and carbide bur technique. Materials and Methods: 40 extracted premolar teeth were selected as sample. Premolar brackets were bonded on these teeth with two different types of light cure adhesive composite resin. The remnants present on these samples after debonding the brackets were removed with two different types of remnant removal techniques namely – Carbide bur technique and sandblasting technique. Then these treated surfaces were studied under Scanning electron microscope and three-dimensional profilometer for the damage caused to the enamel. Statistical analysis used Student’s t-tests. Results: The enamel surface structure after remnant removal with intraoral sandblasting is better than that after removal with a low-speed handpiece using tungsten carbide bur. Conclusion: Sandblasting can be an acceptable alternative to rotatory handpieces to restore the enamel surface to its near-original state and prevent permanent damage to the tooth. PMID:26668478

  13. In vivo measurement of human body composition

    NASA Technical Reports Server (NTRS)

    Pace, N.; Grunbaum, B. W.; Kodama, A. M.; Price, D. C.

    1974-01-01

    The female bed rest study has shown that, the response of women to prolonged recumbency of 2 to 3 weeks duration is very similar to that displayed by men. Some of the key findings in the women after 17 days of continuous recumbency are: (1) a decrease in plasma volume of 12-13 per cent; (2) a small decrease in total body water; (3) a decrease in total body potassium of 3 to 4 per cent; (4) a decrease in plasma potassium concentration of 4 to 5 per cent; (5) a decrease in total circulating plasma protein of 11 to 12 per cent; (6) a decrease in urinary norepinephrine excretion rate of 27 to 28 per cent; (7) a possible increase in urinary magnesium, calcium, and phosphate excretion rates; and (8) a possible increase in urinary citrate excretion rate.

  14. Impact of Incident Heart Failure on Body Composition Over Time in the Health, Aging, and Body Composition Study Population.

    PubMed

    Forman, Daniel E; Santanasto, Adam J; Boudreau, Robert; Harris, Tamara; Kanaya, Alka M; Satterfield, Suzanne; Simonsick, Eleanor M; Butler, Javed; Kizer, Jorge R; Newman, Anne B

    2017-09-01

    Prevalence of heart failure (HF) increases significantly with age, coinciding with age-related changes in body composition that are common and consequential. Still, body composition is rarely factored in routine HF care. The Health, Aging, and Body Composition study is a prospective cohort study of nondisabled adults. Using yearly dual-energy x-ray absorptiometry, body composition was assessed in the Health, Aging, and Body Composition study over 6 years, comparing those who developed incident HF versus those who did not. Among 2815 Health, Aging, and Body Composition participants (48.5% men; 59.6% whites; mean age, 73.6±2.9 years), 111 developed incident HF over the 6-year study period. At entry into the Health, Aging, and Body Composition study, men and women who later developed HF had higher total body mass when compared with those versus those who did not develop HF (men, 80.9±10 versus 78.6±12.9 kg, P=0.05; women, 72.7±15.0 versus 68.2±14.2 kg, P=0.01, respectively). However, after developing HF, loss of total lean body mass was disproportionate; men with HF lost 654.6 versus 391.4 g/y in non-HF participants, P=0.02. Loss of appendicular lean mass was also greater with HF (-419.9 versus -318.2 g/y; P=0.02), even after accounting for total weight change. Among women with HF, loss of total and appendicular lean mass were also greater than in non-HF participants but not to the extent seen among men. Incident HF in older adults was associated with disproportionate loss of lean mass, particularly among men. Prognostic implications are significant, with key sex-specific inferences on physical function, frailty, disability, and pharmacodynamics that all merit further investigation. © 2017 American Heart Association, Inc.

  15. Application of standards and models in body composition analysis.

    PubMed

    Müller, Manfred J; Braun, Wiebke; Pourhassan, Maryam; Geisler, Corinna; Bosy-Westphal, Anja

    2016-05-01

    The aim of this review is to extend present concepts of body composition and to integrate it into physiology. In vivo body composition analysis (BCA) has a sound theoretical and methodological basis. Present methods used for BCA are reliable and valid. Individual data on body components, organs and tissues are included into different models, e.g. a 2-, 3-, 4- or multi-component model. Today the so-called 4-compartment model as well as whole body MRI (or computed tomography) scans are considered as gold standards of BCA. In practice the use of the appropriate method depends on the question of interest and the accuracy needed to address it. Body composition data are descriptive and used for normative analyses (e.g. generating normal values, centiles and cut offs). Advanced models of BCA go beyond description and normative approaches. The concept of functional body composition (FBC) takes into account the relationships between individual body components, organs and tissues and related metabolic and physical functions. FBC can be further extended to the model of healthy body composition (HBC) based on horizontal (i.e. structural) and vertical (e.g. metabolism and its neuroendocrine control) relationships between individual components as well as between component and body functions using mathematical modelling with a hierarchical multi-level multi-scale approach at the software level. HBC integrates into whole body systems of cardiovascular, respiratory, hepatic and renal functions. To conclude BCA is a prerequisite for detailed phenotyping of individuals providing a sound basis for in depth biomedical research and clinical decision making.

  16. Body composition assessment in horses using bioimpedance spectroscopy.

    PubMed

    Ward, L C; White, K J; van der Aa Kuhle, K; Cawdell-Smith, J; Bryden, W L

    2016-02-01

    Assessment of equine body composition using objective measurements is difficult owing to the large size of the animals and the costs involved. Bioelectrical impedance spectroscopy (BIS), a technique widely used for the assessment of body composition in humans, was investigated for practicality of use in horses. BIS uses algorithms that require values for the apparent resistivities of body fluids and body proportion factors (Kb), currently not available for horses. Aims of the present study were to derive resistivity coefficients and body proportion factors and to validate their use for prediction of body composition horses. Validation of coefficients and predictive power using a split-sample agreement study design using correlation and limits of agreement analysis. Whole body impedance measurements were performed on 35 standardbred horses, yearlings to 14 yr, concurrently with determination of total body water volume (TBW) by deuterium dilution and extracellular water volume (ECW) by bromide dilution. Kb was determined in an independent group of 38 mixed-breed, age, and sex horses. Mean apparent resistivity coefficients were 511.4 and 1415.9 ohm.cm for intracellular water and TBW, respectively. Mean Kb was 1.52 ± 0.1. Using these coefficients, TBW and fat-free mass could be predicted with limits of agreement (2SD) of ± 11.6%; mean fat-free mass and fat mass were under- and overestimated by 3.1% and 14.1%, respectively, compared to measured reference values although these differences were not statistically significant. BIS is a practical technique for the assessment of body composition in equids, but the relatively wide limits of agreement, particularly for fat mass, may limit its usefulness for predicting body composition in individual horses.

  17. Effect of intense military training on body composition.

    PubMed

    Malavolti, Marcella; Battistini, Nino C; Dugoni, Manfredo; Bagni, Bruno; Bagni, Ilaria; Pietrobelli, Angelo

    2008-03-01

    Individuals in a structural physical training program can show beneficial changes in body composition, such as body fat reduction and muscle mass increase. This study measured body composition changes by using 3 different techniques-skinfold thickness (SF) measurements, air displacement plethysmography (BOD-POD), and dual-energy x-ray absorptiometry (DXA)-during 9 months of intense training in healthy young men engaged in military training. Twenty-seven young men were recruited from a special faction of the Italian Navy. The program previewed three phases: ground combat, sea combat, and amphibious combat. Body composition was estimated at the beginning, in the middle, and at the end of the training. After the subjects performed the ground combat phase, body composition variables significantly decreased: body weight (P < 0.05), fat-free mass (FFM) (P < 0.001), and fat mass (FM) (P < 0.03). During the amphibious combat phase, body weight increased significantly (P < 0.01), mainly because of an increase in FFM (P < 0.001) and a smaller mean decrease in FM. There was a significant difference (P < 0.05) in circumferences and SF at various sites after starting the training course. Bland-Altman analysis did not show any systematic difference between FM and FFM measured with the 3 different techniques on any occasion. On any visit, FFM and FM correlation measured by BOD-POD (P = 0.90) and DXA was significantly greater than measured by SF. A significant difference was found in body mass index (BMI) measured during the study. BOD-POD and SF, compared with DXA, provide valid and reliable measurement of changes in body composition in healthy young men engaged in military training. In conclusion, the findings suggest that for young men of normal weight, changes in body weight alone and in BMI are not a good measure to assess the effectiveness of intense physical training programs, because lean mass gain can masquerade fat weight loss.

  18. Two- and three-body wear of composite resins.

    PubMed

    Koottathape, Natthavoot; Takahashi, Hidekazu; Iwasaki, Naohiko; Kanehira, Masafumi; Finger, Werner J

    2012-12-01

    The aim of the present study was to investigate two- and three-body wear of microfilled, micro-hybrid and nano-hybrid composite resins using a ball-on-disc sliding device. One microfilled (Durafill VS), one micro-hybrid (Filtek Z250), one hybrid (Clearfil AP-X), one nanofilled (Filtek Supreme XT), and two nano-hybrid (MI Flow, Venus Diamond) composite resins were examined. The composites were filled in a cylindrical cavity, and light polymerized. After storage in 37°C distilled water for 7days, all specimens were tested with a custom-made ball-on-disc sliding device with a zirconia ball as antagonist (50N loads, 1.2Hz, 10,000 cycles) immersed in water, poppy seed slurry and polymethyl methacrylate slurry, respectively. Maximum wear depth and volume loss of worn surfaces were quantified by a digital CCD microscope and analyzed with two-way analysis of variance. The interactions between composite resin and condition of their maximum wear depth and volume loss were significant (p<0.01). The abrasive wear produced at three-body loading with poppy seed slurry was very large for the microfilled composite, and small for all other composites tested. In contrast, two-body wear of the microfilled composite, and one nano-hybrid composite was very low. The ball-on-disc sliding device used is considered suitable to simulate sliding of an antagonist cusp on an opposing occlusal composite restoration, either in the two- or the three-body wear mode. All tested materials except for the microfilled composite showed low surface wear when exposed to poppy seed as the third-body medium. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  19. The influence of body composition on youth throwing kinetics.

    PubMed

    Garner, John C; MacDonald, Chris; Wade, Chip; Johnson, Andrea; Ford, M Allison

    2011-08-01

    The primary objective of this study was to investigate the influence of segmental mass and body composition on the upper extremity biomechanics of overweight youth participating in baseball activities. The study used a regression framework to investigate the relationship between whole body, throwing arm segmental mass and body composition measures to kinetic variables about the shoulder and elbow. The multivariate regression results indicated a strong positive significant relationship between each of the mass variables to that of the moment variables about the shoulder and elbow. Participants who had a greater percentage of fat mass produced greater injury correlated moments about the shoulder and elbow.

  20. Influence of oxidation on the composition and structure of the surface layer of hot-pressed boron carbide

    SciTech Connect

    Lavrenko, V.A.; Gogotsi, Yu.G.

    1988-04-01

    The oxidation of hot-pressed boron carbide under isothermal conditions and under conditions of programmed heating up to 1500/degrees/C was investigated. Oxidized samples were studied by secondary-ion mass spectrometry, X-ray photoelectron spectroscopy, scanning electron microscopy, energy-dispersive X-ray microanalysis, X-ray diffraction, and other methods. It has been demonstrated that oxidation starts above 600/degrees/C and results in the formation of a thin transparent B/sub 2/O/sub 3/ film that is cracked after cooling. Up to 1200/degrees/C, the oxidation process is limited by the diffusion of reagents through the oxide layer; at higher temperatures, it is determined by the rate of chemical reaction of carbide with oxygen in the air. During boron carbide oxidation the etching of grain boundaries occurs, it results in strength degradation at higher temperatures.

  1. Isotopic compositions of s-process elements in acid-cleaned mainstream presolar silicon carbide

    NASA Astrophysics Data System (ADS)

    Liu, Nan

    Pristine meteorites contain ancient stellar relicts that survived destructions in the early solar system. Isotopic studies of these presolar grains have proven to be a unique method to understand various known and unknown nucleosynthetic processes occurred in their parent stars. Previous studies of isotopic compositions of heavy elements in mainstream SiC grains from low-mass asymptotic giant branch (AGB) stars reported contamination from solar system materials with normal isotopic compositions on grain surfaces and prevented the authors from obtaining the pure nucleosynthetic isotopic signature from stars. In addition, in these previous studies uncertainties in the major neutron source 13C within the 13C-pocket were underestimated because only the 13C mass fraction was considered as a parameter with the 13C-pocket mass and the 13C profile fixed in model calculations. The oversimplified treatment of the 13C-pocket mainly resulted from the fact that it was unclear if there exists any tracer to distinguish different effects of the 13C concentration, the 13C-pocket mass, and the 13C profile within the 13C-pocket. To address these issues, we acid-cleaned all the presolar SiC grains used in this study after their separation from the bulk Murchison meteorite. In addition, we chose to measure strontium and barium isotopic compositions in these acid-cleaned SiC grains, because both elements sit at the first and second s-process peaks along the s-process path, and are sensitive to varying parameters for the s-process in model calculations. By comparing our new acid-cleaned grain data with single grain data from previous studies for barium isotopes, we conclude that the acid-cleaning procedure is quite effective in removing surface barium contamination. For the first time, we find that model predictions for 138Ba/ 136Ba are sensitive to all three variables of the 13C-pocket adopted in AGB model calculations. In order to match the low 138Ba/ 136Ba values in a minor group of

  2. Relationships Between Body Image, Body Composition, Sexual Functioning, and Sexual Satisfaction Among Heterosexual Young Adults.

    PubMed

    Milhausen, Robin R; Buchholz, Andrea C; Opperman, Emily A; Benson, Lindsay E

    2015-08-01

    This study investigated the association between body image and body-image self-consciousness on sexual satisfaction, accounting for relationships between body fat and body image, and between sexual functioning and sexual satisfaction, while controlling for relationship satisfaction. Participants were 143, 18-25 year-old Caucasian men and women in heterosexual monogamous relationships, recruited from the University of Guelph and surrounding community in Ontario, Canada. Various domains of body image, body-image self-consciousness, sexual satisfaction and functioning, and relationship satisfaction data were collected by questionnaires. Body fat was measured using dual energy X-ray absorptiometry. Among men, body image was positively associated with sexual satisfaction, after controlling for relationship satisfaction. Men with greater body fat were more likely to have poorer behavioral and affective body image. Only body image specific to the sexual encounter influenced sexual functioning. Among women, no domain of body image was associated with sexual satisfaction, after controlling for relationship satisfaction. Women with greater body fat were more likely to have poorer affective and sexual-encounter-specific body image. As percent total fat increased, sexual functioning decreased. Our results suggest a complex pattern of relationships exists among body image and body composition constructs and sexual and relationship variable; and that these relationships are not the same for men and women.

  3. Influence of increased body mass and body composition on cycling anaerobic power.

    PubMed

    Maciejczyk, Marcin; Wiecek, Magdalena; Szymura, Jadwiga; Szygula, Zbigniew; Brown, Lee E

    2015-01-01

    Recent evidence suggests that not only body fat (BF) but high lean body mass (HLBM) adversely affects aerobic performance and may reduce aerobic endurance performance as well. However, the influence of body composition on anaerobic performance remains controversial. This study aimed to examine the effects of increased body mass (BM) and body composition on cycling anaerobic power. Peak power (PP) and mean power (MP) measurements were conducted in 2 groups of men with similar total BM but different body compositions resulting from (a) high level of BF [HBF group] or (b) high level of lean body mass [HLBM group] and in a control group. Peak power and MP were calculated in absolute values, relative to BM and lean body mass (LBM), and using allometric scaling. Absolute PP and MP were significantly higher in the HLBM group compared with the control and HBF groups. However, PP and MP relative to BM and using allometric scaling were similar in the HLBM and control groups, yet significantly higher than in the HBF group. There were no significant differences between groups in PP and MP when presented relative to LBM. Therefore, it seems that it is not BM but rather body composition that affects PP. Increased BM, resulting from increased LBM, does not adversely affect cycling anaerobic power, but a BM increase resulting from an increase in BF may adversely affect PP. Therefore, coaches and athletes should avoid excess BF to maximize cycling anaerobic power.

  4. Skeletal and body composition evaluation. Final report

    SciTech Connect

    Mazess, R.B.

    1983-03-01

    Research on radiation detectors for absorptiometry analysis of errors affecting single photon absorptiometry and development of instrumentation, analysis of errors affecting dual photon absorptiometry and development of instrumentation, comparison of skeletal measurements with other techniques, cooperation with NASA projects for skeletal evaluation in spaceflight (Experiment MO-78) and in laboratory studies with immobilized animals, studies of postmenopausal osteoporosis, organization of scientific meetings and workshops on absorptiometric measurement, and development of instrumentation for measurement of fluid shifts in the human body were performed. Instrumentation was developed that allows accurate and precise (2% error) measurements of mineral content in compact and trabecular bone and of the total skeleton. Instrumentation was also developed to measure fluid shifts in the extremities. Radiation exposure with those procedures is low (2-10 MREM). One hundred seventy three technical reports and one hundred and four published papers of studies from the University of Wisconsin Bone Mineral Lab are listed.

  5. Optimum Anthropometric Criteria for Ideal Body Composition Related Fitness

    PubMed Central

    Kilani, Hashem; Abu-Eisheh, Asem

    2010-01-01

    Objectives The three aims of this study were to establish equations for ideal body composition related fitness to be used by adults willing to gain optimum body composition related fitness; to predict the possible symmetrical major muscle circumference, and to compute the ideal body fat percentage (BFP) with ideal body weight (IBW) based on the body mass index (BMI). Methods Twenty-four athletes were intentionally selected, with heights of 166–190 cm and aged 20–42 years, according to a judging committee that used modified International Fitness Federation criteria for the Mr. Fitness competition “super body category”. Common anthropometric and body composition measurements were taken for the following independent variables: body height, upper limb length, lower limb length, thigh length, arm length, shoulder width, forearm length, shank length, and wrist girth; and for the following dependent variables: circumferences of shoulder, thigh, waist, hip, chest, biceps, forearm, shank, and neck. Skin fold thickness was measured at three sites by a Harpenden caliper to calculate BFP. Results The findings indicate that there was a predictive correlation between major independent variables and body circumferences. The mean range used to find out the ideal BFP percentage which was 5.6–6.7 %. The BMI equation used to find the IBW was H2 × 23.77 ± 2 SE. Stepwise multiple regressions were also used to derive predictive equations. The most predictive independent variables were wrist girth and height. Conclusion It is suggested that the above equations, the ideal BFP percentage and the IBW be used as criteria in training sessions to achieve ideal body composition related fitness. PMID:21509084

  6. Body composition estimations by BIA versus anthropometric equations in body builders and other power athletes.

    PubMed

    Huygens, W; Claessens, A L; Thomis, M; Loos, R; Van Langendonck, L; Peeters, M; Philippaerts, R; Meynaerts, E; Vlietinck, R; Beunen, G

    2002-03-01

    Two main questions are stated: 1) are BIA and anthropometric equations accurate in estimating body composition in male power athletes and more specifically in body builders and 2) is there a difference in body composition when body builders are compared to weight and power lifters? this is a descriptive, comparative study on a selected sample of power athletes. 49 Belgian elite and sub-top male power athletes (34 body builders and 15 weight and power lifters) were included in this sample. More than 70% was in preparation of competition at time of data collection. an extended set of anthropometric measures was taken. Body composition was estimated by BIA (Bioelectrical Impedance Analysis) and by regression equations of skinfolds. Somatotype and muscle+bone areas were calculated. Factor analysis on all anthropometric measures was carried out to determine the body structure of the athletes. Compared to external visual criteria, the equations of Durnin and Womersley and Lohman (skinfolds) and the Guo-equation (BIA) were the only equations that could accurately estimate the body composition for this specific group of athletes. However, the sum of skinfolds attains the most accurate estimate of subcutaneous fatness. Body builders have significantly (p<0.01) larger arm and thigh circumferences and are more mesomorfic than the other power athletes (5.9 vs 3.8). This study shows that to estimate body composition in extreme power athletes BIA is not as accurate as compared to anthropometric equations. Moreover, the sum of a larger set of skinfolds is preferred to anthropometric prediction equations. In addition, body builders are more muscular and leaner than other power athletes.

  7. Top 10 research questions related to body composition.

    PubMed

    Going, Scott; Lee, Vinson; Blew, Rob; Laddu, Deepika; Hetherington-Rauth, Megan

    2014-03-01

    An understanding of body composition is crucial to understanding human health, disease, and function. Research in body composition has focused on the development of assessment methods, description of normal changes in body composition with growth and development and aging, and the changes that occur in body composition in response to challenges ranging from illness to planned interventions. Each focus is significant, and in a sense, they are interdependent, because technological advances allow more sophisticated questions to be addressed, which in turn drives the development of better methods. Significant advances have been made in each area, although perhaps surprisingly basic questions remain. For example, growth trajectories are often estimated from cross-sectional data, given the resources needed for long-term observational studies, and thus, longitudinal descriptive data are still needed. Along with advances in laboratory methods, development of field methods remains relevant for screening and clinical practice. Despite recognition of wide interindividual differences in intervention response, average outcomes continue to be emphasized. With technological advances, it is now possible to examine genetic along with nongenetic factors that underlie changes in body composition, and these techniques need to be applied in long-term, well-controlled trials. In this article, we review 10 key questions in related areas in which research is needed to continue to advance the field.

  8. Construction of reduced graphene oxide supported molybdenum carbides composite electrode as high-performance anode materials for lithium ion batteries

    SciTech Connect

    Chen, Minghua; Zhang, Jiawei; Chen, Qingguo; Qi, Meili; Xia, Xinhui

    2016-01-15

    Highlights: • Reduced graphene oxide supported molybdenum carbides are prepared by two-step strategy. • A unique sheet-on-sheet integrated nanostructure is favorable for fast ion/electron transfer. • The integrated electrode shows excellent Li ion storage performance. - Abstract: Metal carbides are emerging as promising anodes for advanced lithium ion batteries (LIBs). Herein we report reduced graphene oxide (RGO) supported molybdenum carbides (Mo{sub 2}C) integrated electrode by the combination of solution and carbothermal methods. In the designed integrated electrode, Mo{sub 2}C nanoparticles are uniformly dispersed among graphene nanosheets, forming a unique sheet-on-sheet integrated nanostructure. As anode of LIBs, the as-prepared Mo{sub 2}C-RGO integrated electrode exhibits noticeable electrochemical performances with a high reversible capacity of 850 mAh g{sup −1} at 100 mA g{sup −1}, and 456 mAh g{sup −1} at 1000 mA g{sup −1}, respectively. Moreover, the Mo{sub 2}C-RGO integrated electrode shows excellent cycling life with a capacity of ∼98.6 % at 1000 mA g{sup −1} after 400 cycles. Our research may pave the way for construction of high-performance metal carbides anodes of LIBs.

  9. Boron carbides formed by coevaporation of B and C atoms: Vapor reactivity, B{sub x}C{sub 1-x} composition, and bonding structure

    SciTech Connect

    Caretti, I.; Albella, J. M.; Jimenez, I.

    2008-05-01

    Boron carbides (B{sub x}C{sub 1-x}) in thin film form have been synthesized in a high vacuum by coevaporation of B and C atoms from independent sources, allowing a study of the whole composition range from pure B films to pure C films. The relationship between the impinging B/C atomic fluxes and the film composition has been studied, providing information on the chemical reactivity between the B and C vapors. The composition was determined with x-ray emission energy dispersion spectroscopy and x-ray absorption near edge spectroscopy (XANES). Finally, the bonding structure of the films has been determined by XANES, showing a change from structures based on B{sub 12}-icosahedral units for the B-rich samples to hexagonal-like structures for the C-rich samples. The study shows that the structural transition takes place for x{approx}0.5.

  10. Somatotype and Body Composition of Normal and Dysphonic Adult Speakers.

    PubMed

    Franco, Débora; Fragoso, Isabel; Andrea, Mário; Teles, Júlia; Martins, Fernando

    2017-01-01

    Voice quality provides information about the anatomical characteristics of the speaker. The patterns of somatotype and body composition can provide essential knowledge to characterize the individuality of voice quality. The aim of this study was to verify if there were significant differences in somatotype and body composition between normal and dysphonic speakers. Cross-sectional study. Anthropometric measurements were taken of a sample of 72 adult participants (40 normal speakers and 32 dysphonic speakers) according to International Society for the Advancement of Kinanthropometry standards, which allowed the calculation of endomorphism, mesomorphism, ectomorphism components, body density, body mass index, fat mass, percentage fat, and fat-free mass. Perception and acoustic evaluations as well as nasoendoscopy were used to assign speakers into normal or dysphonic groups. There were no significant differences between normal and dysphonic speakers in the mean somatotype attitudinal distance and somatotype dispersion distance (in spite of marginally significant differences [P < 0.10] in somatotype attitudinal distance and somatotype dispersion distance between groups) and in the mean vector of the somatotype components. Furthermore, no significant differences were found between groups concerning the mean of percentage fat, fat mass, fat-free mass, body density, and body mass index after controlling by sex. The findings suggested no significant differences in the somatotype and body composition variables, between normal and dysphonic speakers. Copyright © 2017 The Voice Foundation. Published by Elsevier Inc. All rights reserved.

  11. Somatic maturation and body composition in female healthy adolescents with or without adjustment for body fat

    PubMed Central

    Miranda, Valter Paulo N.; de Faria, Franciane Rocha; de Faria, Eliane Rodrigues; Priore, Silvia Eloiza

    2014-01-01

    Objective: To evaluate the relationship between the stages of somatic maturation and body composition in eutrophic female adolescents with or without excessive body fat. Methods: Cross-sectional study of 118 female adolescents, from 14 to 19 years-old, in Viçosa, Minas Gerais, Southeast Brazil. The adolescents were divided in two groups: Group 1 (G1), eutrophic with adequate body fat percentage, and Group 2 (G2), eutrophic with high body fat percentage. The somatic maturation was assessed by the formula for estimating the Peak Height Velocity (PHV). Results: The PHV had higher average score in G1 adolescents compared to G2 (0.26 versus 0.05; p=0.032). There was an association between G1, G2 and the somatic maturation (p=0.049). The female adolescents before and during PHV presented higher values of fat body BMI (p=0.034) and percentage of central fat (p=0.039) compared to the adolescents after PHV. There was a correspondence between before PHV stage and the excess of body fat (α=0.751). Conclusions: There was an association between somatic maturation and body composition in eutrophic female adolescents. Length, BMI and fat percentage were different among the somatic maturation stages. It is relevant to evaluate the somatic maturation and the changes occurring in the body composition during adolescence in order to better evaluate and manage the nutritional status and the body fat excess. PMID:24676194

  12. REGULATION OF BODY COMPOSITION AND BIOENERGETICS BY ESTROGENS

    PubMed Central

    Van Pelt, Rachael E.; Gavin, Kathleen M.; Kohrt, Wendy M.

    2015-01-01

    SYNOPSIS Evidence from basic, preclinical, and clinical research points to an important role of estradiol (E2) in the regulation of body composition and bioenergetics. There is consistent evidence from basic and preclinical research that the disruption of E2 signaling, through either genetic manipulation (e.g., estrogen receptor deletion) or surgical intervention (e.g., ovariectomy), accelerates fat accumulation, with a disproportionate increase in abdominal fat. Clinical evidence for the regulation of body composition and bioenergetics by E2 is less consistent. Evidence exists both for and against menopause as the mediator of changes in body composition. This is likely related to the prolonged nature of the menopause transition in women and the associated complexities of distinguishing effects of the loss of gonadal function from other phenomena of aging. However, a need remains to better understand the metabolic actions of estrogens in women because of the potential impact on health after the menopause. PMID:26316249

  13. The Body and the Beautiful: Health, Attractiveness and Body Composition in Men’s and Women’s Bodies

    PubMed Central

    Brierley, Mary-Ellen; Brooks, Kevin R.; Mond, Jonathan; Stevenson, Richard J.

    2016-01-01

    The dominant evolutionary theory of physical attraction posits that attractiveness reflects physiological health, and attraction is a mechanism for identifying a healthy mate. Previous studies have found that perceptions of the healthiest body mass index (weight scaled for height; BMI) for women are close to healthy BMI guidelines, while the most attractive BMI is significantly lower, possibly pointing to an influence of sociocultural factors in determining attractive BMI. However, less is known about ideal body size for men. Further, research has not addressed the role of body fat and muscle, which have distinct relationships with health and are conflated in BMI, in determining perceived health and attractiveness. Here, we hypothesised that, if attractiveness reflects physiological health, the most attractive and healthy appearing body composition should be in line with physiologically healthy body composition. Thirty female and 33 male observers were instructed to manipulate 15 female and 15 male body images in terms of their fat and muscle to optimise perceived health and, separately, attractiveness. Observers were unaware that they were manipulating the muscle and fat content of bodies. The most attractive apparent fat mass for female bodies was significantly lower than the healthiest appearing fat mass (and was lower than the physiologically healthy range), with no significant difference for muscle mass. The optimal fat and muscle mass for men’s bodies was in line with the healthy range. Male observers preferred a significantly lower overall male body mass than did female observers. While the body fat and muscle associated with healthy and attractive appearance is broadly in line with physiologically healthy values, deviations from this pattern suggest that future research should examine a possible role for internalization of body ideals in influencing perceptions of attractive body composition, particularly in women. PMID:27257677

  14. Validation and calibration of DEXA body composition in mice.

    PubMed

    Brommage, Robert

    2003-09-01

    Validated methods of determining murine body composition are required for studies of obesity in mice. Dual-energy X-ray absorptiometry (DEXA) provides a noninvasive approach to assess body fat and lean tissue contents. Similar to DEXA analyses in other species, body fat measurements in mice show acceptable precision but suffer from poor accuracy. Because fat and lean tissues each contain various components, these inaccuracies likely result from selection of inappropriate calibration standards. Analysis of solvents showed that the PIXImus2 DEXA gave results consistent with theoretical calculations. Male mice weighing 26-60 g and having body fat percentages ranging from 3 to 49% were analyzed by both PIXImus2 DEXA and chemical carcass analysis. DEXA overestimated mouse fat content by an average of 3.3 g, and algorithms were generated to calculate body fat from both measured body fat values and the measured ratio of high- to low-energy X-ray attenuations. With calibration to mouse body fat content measured by carcass analysis, the PIXImus2 DEXA gives accurate body composition values in mice.

  15. In vivo animal models of body composition in aging

    SciTech Connect

    Yasumura, S. |; Jones, K.; Spanne, P.; Schidlovsky, G.; Wielopolski, L.; Ren, X.; Glaros, D.; Xatzikonstantinou, Y. |

    1992-12-31

    We developed several techniques that provide data on body elemental composition from in vivo measurements in rats. These methods include total body potassium by whole-body counting of endogenous {sup 40}K; total body calcium (TBCa), sodium and chloride by in vivo neutron activation analysis and total body phosphorus (TBP) and nitrogen (TBN) by photon activation analysis. These elements provide information on total body fat, total body protein and skeletal mass. Measurements were made in 6-, 12- and 24-month-old rats. TBN Increased slightly between 6 and 12 months but was significantly lower by 24 months, indicating a substantial loss in total body protein. Working at the National Synchrotron light Source, we studied rat femurs by computed microtomography (CMT), and the elemental profile of the femur cortex by synchrotron-radiation induced X-ray emission (SRIXE). Although there were no significant changes in TBCA and TBP, indices of skeletal mass, CMT revealed a marked increase in the size and number of cavities in the endosteal region of the femur cortex with increasing age. The SRIXE analysis of this cortical bone revealed a parallel decrease in the endosteal Ca/P ratio. Thus, there are major alterations in bone morphology and regional elemental composition despite only modest changes in total skeletal mass.

  16. Asymmetry in body composition in female hockey players.

    PubMed

    Krzykała, M; Leszczyński, P

    2015-08-01

    The aim of the study was to determine if a sport in which one side of the body is dominant, like field hockey, influences regional body composition and bone mineral density (BMD) distribution in particular body segments, and whether the sporting level is a determining factor. Dual energy X-ray absorptiometry (DXA) method (Lunar Prodigy Advance; General Electric, Madison, USA) with the whole body scan was used to measure bone mineral density, fat mass and lean mass in 31 female field hockey players divided according to their sporting level. The morphological asymmetry level was assessed between two body sides and body segments in athletes from the National Team (n=17) and from the Youth Team (n=14) separately and between groups. Bone mineral density in the lower extremity and of the trunk was significantly asymmetric in favor of the left side in the National Team. In the case of the Youth Team, only the trunk BMD indicated clear left-right difference with left side dominance. Both the lean mass and fat mass values were relatively higher on the left side of all body segments and it related to both analyzed groups of athletes. The present study shows that playing field hockey contributes to laterality in body composition and BMD and that the sporting level is a determining factor. In most cases the left side dominated. A greater asymmetry level was observed in more experienced female field hockey players.

  17. [Analysis of the body composition of Spanish women with fibromyalgia].

    PubMed

    Aparicio, Virginia A; Ortega, Francisco B; Heredia, José M; Carbonell-Baeza, Ana; Delgado-Fernández, Manuel

    2011-01-01

    To describe the anthropometric profile and body composition of women from Southern Spain diagnosed with fibromyalgia (FM) and to compare the observed values with values from other studies conducted on FM patients and with national reference values. The body composition of 104 women diagnosed with FM was assessed using an eight-electrode impedance meter. The reliability of the body composition measurement was tested in a randomly selected sub-sample (n=28). The reliability study showed a test-retest systematic error close to zero in most of the parameters studied. The women with FM who were studied had a mean weight of 71.3±13.4 kg, height of 158±6 cm, body mass index of 28.6±5.1 kg/m(2), body fat mass of 38.6±7.6%, total body water of 31.6±3.8 l and muscle mass of 23.4±3.0 kg. In general, there were no substantial differences in weight and body mass index between women with FM and those analyzed in other Spanish and European studies involving FM patients, nor when they were compared with regional or national reference values. However, the prevalence of obesity in the women with FM under study was 33.7%, a higher figure than that from the national reference data for obesity in similarly aged women (i.e. 26,4%). The results suggest that obesity is a common condition in women diagnosed with FM, its prevalence in this population being higher than the national reference values. This study provides detailed information about the body composition characteristics of women with FM. Copyright © 2010 Elsevier España, S.L. All rights reserved.

  18. Determination of carcass and body fat compositions of grazing crossbred bulls using body measurements.

    PubMed

    Fernandes, H J; Tedeschi, L O; Paulino, M F; Paiva, L M

    2010-04-01

    The objectives of this study were to analyze body measurements of 40 crossbred bulls grazing low quality forage with different supplementation strategies, to estimate interrelationships among those measurements and carcass and body compositions, and to develop systems of equations to predict body fat using body and carcass measurements. Eight animals were slaughtered at the beginning of the experiment, and the remaining animals were slaughtered at 90 or 220 d. The biometric measures (BM) were obtained the day before the slaughter and included hook width, pin width, pelvic girdle length, rump depth, rump height, abdomen width, body length, height at withers, rib depth, girth, and body diagonal length. Other measurements included full, shrunk, and empty BW; internal physical and chemical fats; body volume; body area; carcass weight; 9th- to 11th-rib section weight and composition; fat thickness; subcutaneous fat; intermuscular fat; carcass chemical fat; and empty body physical and chemical fats. The relationships between BM and body components were evaluated, and equations to predict body area, body volume, subcutaneous fat, and carcass and body physical and chemical fat were developed. Biological interpretations of the parameter estimates of equations were similar to those found in the literature such as a ratio of 1 kg of subcutaneous fat to 1.6 kg of intermuscular fat and a deposit of 72 to 76% of body fat in the carcass. The first system used to predict carcass and empty body physical and chemical fat was devised using in vivo information, whereas the second system used BW and the 9th- to 11th-rib fat weight. Our results indicated the combination of BW, carcass traits, and BM was precise and accurate in estimating carcass and body fat composition of backgrounding bulls. The second system had better adequacy statistics [r(2) > 0.92, concordance correlation coefficient (CCC) > 0.957, and root mean square error (RMSE) < 14.4% of the average observed value] compared

  19. Body composition and risk for metabolic alterations in female adolescents

    PubMed Central

    de Faria, Eliane Rodrigues; Gontijo, Cristiana Araújo; Franceschini, Sylvia do Carmo C.; Peluzio, Maria do Carmo G.; Priore, Silvia Eloiza

    2014-01-01

    OBJECTIVE: To study anthropometrical and body composition variables as predictors of risk for metabolic alterations and metabolic syndrome in female adolescents. METHODS: Biochemical, clinical and corporal composition data of 100 adolescents from 14 to 17 years old, who attended public schools in Viçosa, Southeastern Brazil, were collected. RESULTS: Regarding nutritional status, 83, 11 and 6% showed eutrophia, overweight/obesity and low weight, respectively, and 61% presented high body fat percent. Total cholesterol presented the highest percentage of inadequacy (57%), followed by high-density lipoprotein (HDL - 50%), low-density lipoprotein (LDL - 47%) and triacylglycerol (22%). Inadequacy was observed in 11, 9, 3 and 4% in relation to insulin resistance, fasting insulin, blood pressure and glycemia, respectively. The highest values of the fasting insulin and the Homeostasis Model Assessment-Insulin Resistance (HOMA-IR) were verified at the highest quartiles of body mass index (BMI), waist perimeter, waist-to-height ratio and body fat percent. Body mass index, waist perimeter, and waist-to-height ratio were the better predictors for high levels of HOMA-IR, blood glucose and fasting insulin. Waist-to-hip ratio was associated to arterial hypertension diagnosis. All body composition variables were effective in metabolic syndrome diagnosis. CONCLUSIONS: Waist perimeter, BMI and waist-to-height ratio showed to be good predictors for metabolic alterations in female adolescents and then should be used together for the nutritional assessment in this age range. PMID:25119752

  20. Determination of body composition from skinfold thickness: a validation study.

    PubMed Central

    Reilly, J J; Wilson, J; Durnin, J V

    1995-01-01

    Measurement of body composition is proving increasingly important in clinical nutrition and research. Skinfold thickness is a simple means of estimating body composition which is widely used in children, but there is little information on its validity. There has been a proliferation of equations for estimation of body composition from skinfolds, but some doubt as to their general applicability. The aim of the present study was to validate five currently used equations for this purpose in a sample of 98 healthy prepubertal children (64 boys, 34 girls), mean (SD) age 9.1 (1.7) years by comparison of estimates from each equation with measurements of fatness derived from hydrodensitometry. Differences between methods were determined by calculation of biases and limits of agreement. Limits of agreement between predicted and measured fatness were wide, particularly in the girls, and some distinct biases were apparent. Choice of prediction equation therefore has a substantial influence on the estimate of fatness obtained when using skinfolds in children. The existing published equations are associated with large random errors or significant systematic errors. For the time being skinfolds might best be regarded as indices (rather than measures) of body fatness in individuals, or means of estimating body fatness of groups. Estimating the total body fatness of individual prepubertal children using skinfolds, on the basis of this evidence, is not advisable at present. PMID:7492193

  1. Body composition assessment in Taiwanese individuals with poliomyelitis.

    PubMed

    Chang, Kwang-Hwa; Lai, Chien-Hung; Chen, Shih-Ching; Hsiao, Wen-Tien; Liou, Tsan-Hon; Lee, Chi-Ming

    2011-07-01

    To measure the changes in the total and regional body fat mass, and assess the clinical usefulness of the body mass index (BMI) in detecting overweight subjects with sequelae of poliomyelitis. Prospective, cross-sectional study. General community. Subjects with poliomyelitis (n=17; age range, 42-57y; mean, 47y; 12 men, 5 women) and able-bodied people (n=17) matched by sex, age, body weight, and body height participated in the study. Not applicable. Total and regional body composition was measured with dual-energy x-ray absorptiometry. Clinical characteristics such as blood pressure, serum biochemical studies, and habitual behaviors (daily cigarette smoking, alcohol consumption, and exercise regimen) of all participants were evaluated. Compared with able-bodied controls, subjects with poliomyelitis had a 50% greater total body fat mass, significant increases in the regional fat mass in every part of the body, and had the greatest increase of fat mass in the thorax. Nearly all the subjects (94%) with poliomyelitis were obese according to standards of body composition. However, one third of them had a BMI value of less than 25.0kg/m(2). People with poliomyelitis have a higher prevalence of obesity and a significant increase in total and regional fat mass. Current BMI underestimates the total body fat mass percentage compared with the control; therefore, a population-specific BMI should be used to address the prevalence of obesity in postpolio survivors. Copyright © 2011 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

  2. Structural characterization of hard materials by transmission electron microscopy (TEM): Diamond-Silicon Carbide composites and Yttria-stabilized Zirconia

    NASA Astrophysics Data System (ADS)

    Park, Joon Seok

    2008-10-01

    Diamond-Silicon Carbide (SiC) composites are excellent heat spreaders for high performance microprocessors, owing to the unparalleled thermal conductivity of the former component. Such a combination is obtained by the infiltration of liquid silicon in a synthetic diamond compact, where a rigid SiC matrix forms by the reaction between the raw materials. As well as the outstanding thermal properties, this engineered compound also retains the extreme hardness of the artificial gem. This makes it difficult to perform structural analysis by transmission electron microscopy (TEM), for it is not possible to produce thin foils out of this solid by conventional polishing methods. For the first time, a dual-beam focused ion beam (FIB) instrument successfully allowed site-specific preparation of electron-transparent specimens by the lift-out technique. Subsequent TEM studies revealed that the highest concentration of structural defects occurs in the vicinity of the diamond-SiC interfaces, which are believed to act as the major barriers to the transport of thermal energy. Diffraction contrast analyses showed that the majority of the defects in diamond are isolated perfect screw or 60° dislocations. On the other hand, SiC grains contain partial dislocations and a variety of imperfections such as microtwins, stacking faults and planar defects that are conjectured to consist of antiphase (or inversion) boundaries. Clusters of nanocrystalline SiC were also observed at the diamond-SiC boundaries, and a specific heteroepitaxial orientation relationship was discovered for all cubic SiC that grows on diamond {111} facets. Yttria-stabilized Zirconia (YSZ) is the most common electrolyte material for solid oxide fuel cell (SOFC) applications. It is an ionic conductor in which charge transfer is achieved by the transport of oxygen ions (O 2-). Like the diamond composite above, it is hard and brittle, and difficult to make into electron transparent TEM samples. Provided an effective

  3. Spark Plasma Sintering of Aluminum-Magnesium-Matrix Composites with Boron Carbide and Tungsten Nano-powder Inclusions: Modeling and Experimentation

    NASA Astrophysics Data System (ADS)

    Dvilis, E. S.; Khasanov, O. L.; Gulbin, V. N.; Petyukevich, M. S.; Khasanov, A. O.; Olevsky, E. A.

    2016-03-01

    Spark-plasma sintering (SPS) is used to fabricate fully-dense metal-matrix (Al/Mg) composites containing hard ceramic (boron carbide) and refractory metal (tungsten) inclusions. The study objectives include the modeling (and its experimental verification) of the process of the consolidation of the composites consisted of aluminum-magnesium alloy AMg6 (65 wt.%), B4C powder (15 wt.%), and W nano-powder (20 wt.%), as well as the optimization of the composite content and of the SPS conditions to achieve higher density. Discrete element modeling of the composite particles packing based on the particle size distribution functions of real powders is utilized for the determination of the powder compositions rendering maximum mixture packing densities. Two models: a power-law creep model of the high temperature deformation of powder materials, and an empirical logarithmic pressure-temperature-relative density relationship are successfully applied for the description of the densification of the aluminum-magnesium metal matrix powder composite subjected to spark-plasma sintering. The elastoplastic properties of the sintered composite samples are assessed by nanoindentation.

  4. Anthropometry and body composition of south Indian babies at birth.

    PubMed

    Muthayya, S; Dwarkanath, P; Thomas, T; Vaz, M; Mhaskar, A; Mhaskar, R; Thomas, A; Bhat, S; Kurpad, Av

    2006-10-01

    To assess the consequences on body composition of increasing birth weight in Indian babies in relation to reported values in Western babies, and to assess the relationship between maternal and neonatal anthropometry and body composition. Prospective observational study. Bangalore City, India. A total of 712 women were recruited at 12.5+/-3.1 weeks of gestation (mean+/-standard deviation, SD) and followed up until delivery; 14.5% were lost to follow-up. Maternal body weight, height, mid upper-arm circumference and skinfold thicknesses were measured at recruitment. Weight and body composition of the baby (skinfold thicknesses, mid upper-arm circumference, derived arm fat index and arm muscle index; AFI and AMI, respectively) were measured at birth in hospital. The mean+/-SD birth weight of all newborns was 2.80+/-0.44 kg. Birth weight was significantly related to the triceps and subscapular skinfold thickness of the baby. In a small number of babies with large birth weight for gestational age, there was a relatively higher normalised AFI relative to AMI than for babies with lower or appropriate birth weight for gestational age. Maternal height and fat-free mass were significantly associated with the baby's length at birth. Skinfold thicknesses in Indian babies were similar to those reported in a Western population with comparable birth weights, and the relationship of AFI to birth weight appeared to be steeper in Indian babies. Thus, measures to increase birth weight in Indian babies should take into account possible adverse consequences on body composition. There were no significant relationships between maternal anthropometry and body composition at birth on multivariate analysis, except for sum of the baby's skinfold thicknesses and maternal fat-free mass (P<0.02).

  5. Eicosapentaenoic acid in cancer improves body composition and modulates metabolism.

    PubMed

    Pappalardo, Giulia; Almeida, Ana; Ravasco, Paula

    2015-04-01

    The objective of this review article is to present the most recent intervention studies with EPA on nutritional outcomes in cancer patients, e.g. nutritional status, weight & lean body mass. For this purpose a PubMed(®) and MedLine(®) search of the published literature up to and including January 2014 that contained the keywords: cancer, sarcopenia, EPA, ω-3 fatty acids, weight, intervention trial, muscle mass was conducted. The collected data was summarized and written in text format and in tables that contained: study design, patient' population, sample size, statistical significance and results of the intervention. The paper will cover malignancy, body composition, intervention with EPA, physiological mechanisms of action of EPA, effect of EPA on weight and body composition, future research. In cancer patients deterioration of muscle mass can be present regardless of body weight or Body Mass Index (BMI). Thus, sarcopenia in cancer patients with excessive fat mass (FM), entitled sarcopenic obesity, has gained greater relevance in clinical practice; it can negatively influence patients' functional status, tolerance to treatments & disease prognosis. The search for an effective nutritional intervention that improves body composition (preservation of muscle mass and muscle quality) is of utmost importance for clinicians and patients. The improvement of muscle quality is an even more recent area of interest because it has probable implications in patients' prognosis. Eicosapentaenoic acid (EPA) has been identified as a promising nutrient with the wide clinical benefits. Several mechanisms have been proposed to explain EPA potential benefits on body composition: inhibition of catabolic stimuli by modulating pro-inflammatory cytokines production and enhancing insulin sensitivity that induces protein synthesis; also, EPA may attenuate deterioration of nutritional status resulting from antineoplastic therapies by improving calorie and protein intake as well. Indeed

  6. Reference Values for Body Composition and Anthropometric Measurements in Athletes

    PubMed Central

    Santos, Diana A.; Dawson, John A.; Matias, Catarina N.; Rocha, Paulo M.; Minderico, Cláudia S.; Allison, David B.; Sardinha, Luís B.; Silva, Analiza M.

    2014-01-01

    Background Despite the importance of body composition in athletes, reference sex- and sport-specific body composition data are lacking. We aim to develop reference values for body composition and anthropometric measurements in athletes. Methods Body weight and height were measured in 898 athletes (264 female, 634 male), anthropometric variables were assessed in 798 athletes (240 female and 558 male), and in 481 athletes (142 female and 339 male) with dual-energy X-ray absorptiometry (DXA). A total of 21 different sports were represented. Reference percentiles (5th, 25th, 50th, 75th, and 95th) were calculated for each measured value, stratified by sex and sport. Because sample sizes within a sport were often very low for some outcomes, the percentiles were estimated using a parametric, empirical Bayesian framework that allowed sharing information across sports. Results We derived sex- and sport-specific reference percentiles for the following DXA outcomes: total (whole body scan) and regional (subtotal, trunk, and appendicular) bone mineral content, bone mineral density, absolute and percentage fat mass, fat-free mass, and lean soft tissue. Additionally, we derived reference percentiles for height-normalized indexes by dividing fat mass, fat-free mass, and appendicular lean soft tissue by height squared. We also derived sex- and sport-specific reference percentiles for the following anthropometry outcomes: weight, height, body mass index, sum of skinfold thicknesses (7 skinfolds, appendicular skinfolds, trunk skinfolds, arm skinfolds, and leg skinfolds), circumferences (hip, arm, midthigh, calf, and abdominal circumferences), and muscle circumferences (arm, thigh, and calf muscle circumferences). Conclusions These reference percentiles will be a helpful tool for sports professionals, in both clinical and field settings, for body composition assessment in athletes. PMID:24830292

  7. Body composition and nutrient intake of Buddhist vegetarians.

    PubMed

    Lee, Yujin; Krawinkel, Michael

    2009-01-01

    We described the body composition and nutrient intake of Buddhist vegetarians and compared the data with that of omnivores in South Korea. Vegetarian subjects were 54 Buddhist nuns, who adhered to a vegetarian diet in accordance with Buddhist teachings. We compared these finding with a group of 31 omnivore Catholic nuns who shared a similar lifestyle but different dietary pattern than those of the Buddhist nuns. All subjects completed the estimated three-day dietary record. Body composition was determined by a segmental multi-frequency-bioelectrical impedance analysis method. No height difference between the dietary groups existed but the vegetarians had a significantly higher body weight, fat free mass, body fat and body mass index (BMI, kg/m2) than the omnivores. The median BMI of both vegetarians and omnivores fell in the normal range (22.6 vs. 20.7 kg/m2). In vegetarians, body fat was inversely correlated with the duration of vegetarianism (p for trend=0.043). The long duration group of the vegetarians had lower body fat than the short duration group (12.l vs. 15.0 kg, p=0.032). The status of the nutrient intake of Korean Buddhist vegetarians was comparable to that of omnivores, and the intake of some nutrients in vegetarians was more favorable than in the omnivores.

  8. Body composition: A predictive factor of cycle fecundity

    PubMed Central

    Kayatas, Semra; Api, Murat; Kurt, Didar; Eroglu, Mustafa; Arınkan, Sevcan Arzu

    2014-01-01

    Objective To study the effect of body composition on reproduction in women with unexplained infertility treated with a controlled ovarian hyperstimulation and intrauterine insemination programme. Methods This prospective observational study was conducted on 308 unexplained infertile women who were scheduled for a controlled ovarian hyperstimulation and intrauterine insemination programme and were grouped as pregnant and non-pregnant. Anthropometric measurements were performed using TANITA-420MA before the treatment cycle. Body composition was determined using a bioelectrical impedance analysis system. Results Body fat mass was significantly lower in pregnant women than in non-pregnant women (15.61±3.65 vs.18.78±5.97, respectively) (p=0.01). In a multiple regression analysis, body fat mass proved to have a stronger association with fecundity than the percentage of body fat, body mass index, or the waist/hip ratio (standardized regression coefficient≥0.277, t-value≥2.537; p<0.05). The cut-off value of fat mass, which was evaluated using the receiver operating characteristics curve, was 16.65 with a sensitivity of 61.8% and a specificity of 70.2%. Below this cut-off value, the odds of the pregnancy occurrence was found to be 2.5 times more likely. Conclusion Body fat mass can be predictive for pregnancy in patients with unexplained infertility scheduled for a controlled ovarian hyperstimulation and intrauterine insemination programme. PMID:25045631

  9. What is the impact of Silicon Carbide nanoparticles to the mineral composition of rat lungs? A PIXE-μPIXE comparative study

    NASA Astrophysics Data System (ADS)

    Lozano, O.; Colaux, J. L.; Laloy, J.; Dogné, J. M.; Lucas, S.

    2015-05-01

    The exposure to nanomaterials can yield changes in the mineral composition of tissues which may have long term health repercussions. In this study, the changes in mineral composition of rat lungs, exposed to a nanoaerosol of silicon carbide (SiC), has been studied by means of global and local ion beam probes with the Particle-Induced X-ray Emission (PIXE) technique, measuring the whole lung contents and selected areas where SiC was found, respectively. It was found that from a global perspective there is a small decrease in the mineral contents (phosphorous, sulphur, chlorine and potassium) of the lung except for Ca, while locally these mineral contents tend fluctuate.

  10. Effect of Body Composition Methodology on Heritability Estimation of Body Fatness

    PubMed Central

    Elder, Sonya J.; Roberts, Susan B.; McCrory, Megan A.; Das, Sai Krupa; Fuss, Paul J.; Pittas, Anastassios G.; Greenberg, Andrew S.; Heymsfield, Steven B.; Dawson-Hughes, Bess; Bouchard, Thomas J.; Saltzman, Edward; Neale, Michael C.

    2014-01-01

    Heritability estimates of human body fatness vary widely and the contribution of body composition methodology to this variability is unknown. The effect of body composition methodology on estimations of genetic and environmental contributions to body fatness variation was examined in 78 adult male and female monozygotic twin pairs reared apart or together. Body composition was assessed by six methods – body mass index (BMI), dual energy x-ray absorptiometry (DXA), underwater weighing (UWW), total body water (TBW), bioelectric impedance (BIA), and skinfold thickness. Body fatness was expressed as percent body fat, fat mass, and fat mass/height2 to assess the effect of body fatness expression on heritability estimates. Model-fitting multivariate analyses were used to assess the genetic and environmental components of variance. Mean BMI was 24.5 kg/m2 (range of 17.8–43.4 kg/m2). There was a significant effect of body composition methodology (p<0.001) on heritability estimates, with UWW giving the highest estimate (69%) and BIA giving the lowest estimate (47%) for fat mass/height2. Expression of body fatness as percent body fat resulted in significantly higher heritability estimates (on average 10.3% higher) compared to expression as fat mass/height2 (p=0.015). DXA and TBW methods expressing body fatness as fat mass/height2 gave the least biased heritability assessments, based on the small contribution of specific genetic factors to their genetic variance. A model combining DXA and TBW methods resulted in a relatively low FM/ht2 heritability estimate of 60%, and significant contributions of common and unique environmental factors (22% and 18%, respectively). The body fatness heritability estimate of 60% indicates a smaller contribution of genetic variance to total variance than many previous studies using less powerful research designs have indicated. The results also highlight the importance of environmental factors and possibly genotype by environmental

  11. Body composition of women and men with complete motor paraplegia.

    PubMed

    Beck, Lisa A; Lamb, Jeffry L; Atkinson, Elizabeth J; Wuermser, Lisa-Ann; Amin, Shreyasee

    2014-07-01

    To examine body composition, including the relationship between body mass index (BMI) and total body fat, in women and men with complete motor paraplegia and to make comparisons with able-bodied controls. In 13 subjects with traumatic, complete motor paraplegia (six women, seven men) and 39 sex-, age-, and BMI-matched controls from the community (18 women, 21 men), we measured total and regional (upper extremities, trunk, and lower extremities) lean and fat mass using total body dual-energy X-ray absorptiometry. Both women and men with paraplegia had significantly lower lean mass in their lower extremities, as would be expected, and in their total body when compared with controls. However, they had significantly greater lean mass in their upper extremities than controls (4.4 kg vs. 3.6 kg, P = 0.004 and 8.6 kg vs. 6.7 kg, P < 0.001 in women and men, respectively); all subjects with paraplegia studied used manual wheelchairs. Although total body fat mass was significantly greater in women (P = 0.010) and men (P = <0.001) with paraplegia compared with controls, for the equivalent total body fat mass, BMI was actually lower in women and men with paraplegia than controls (e.g. 20.2 kg/m² vs. 25.0 kg/m², respectively). We report on body composition in persons with complete motor paraplegia, including women on whom limited information is currently available. Our results support the need to define better assessments of obesity in both women and men following spinal cord injury, particularly of central body fat distribution, as BMI underestimates adiposity in this population.

  12. Body Composition After Bone Marrow Transplantation in Childhood

    PubMed Central

    Ruble, Kathy; Hayat, Matthew; Stewart, Kerry J.; Chen, Allen

    2014-01-01

    Purpose/Objectives To describe the body composition and fat distribution of childhood bone marrow transplantation (BMT) survivors at least one year post-transplantation and examine the ability of the Centers for Disease Control and Prevention criteria to identify survivors with elevated body fat percentage. Design Cross-sectional, descriptive. Setting Pediatric oncology program at a National Cancer Institute–designated comprehensive cancer center. Sample 48 childhood BMT survivors (27 males and 21 females). Methods Measurements included dual-energy x-ray absorptiometry scan, height, weight, and physical activity. Descriptive statistics were reported and mixed-model linear regression models were used to describe findings and associations. Main Research Variables Total body fat percentage and central obesity (defined as a ratio of central to peripheral fat of 1 or greater). Findings Fifty-four percent of survivors had body fat percentages that exceeded recommendations for healthy body composition and 31% qualified as having central obesity. Previous treatment with total body irradiation was associated with higher body fat percentage and central obesity, and graft-versus-host disease was associated with lower body fat percentage. The body mass index (BMI) criteria did not correctly identify the BMT survivors who had elevated body fat percentage. Conclusions Survivors of childhood BMT are at risk for obesity and central obesity that is not readily identified with standard BMI criteria. Implications for Nursing Nurses caring for BMT survivors should include evaluation of general and central obesity in their assessments. Patient education materials and resources for healthy weight and muscle building should be made available to survivors. Research is needed to develop appropriate interventions. PMID:22374492

  13. Body composition of women and men with complete motor paraplegia

    PubMed Central

    Beck, Lisa A.; Lamb, Jeffry L.; Atkinson, Elizabeth J.; Wuermser, Lisa-Ann; Amin, Shreyasee

    2014-01-01

    Objectives To examine body composition, including the relationship between body mass index (BMI) and total body fat, in women and men with complete motor paraplegia and to make comparisons with able-bodied controls. Methods In 13 subjects with traumatic, complete motor paraplegia (six women, seven men) and 39 sex-, age-, and BMI-matched controls from the community (18 women, 21 men), we measured total and regional (upper extremities, trunk, and lower extremities) lean and fat mass using total body dual-energy X-ray absorptiometry. Results Both women and men with paraplegia had significantly lower lean mass in their lower extremities, as would be expected, and in their total body when compared with controls. However, they had significantly greater lean mass in their upper extremities than controls (4.4 kg vs. 3.6 kg, P = 0.004 and 8.6 kg vs. 6.7 kg, P < 0.001 in women and men, respectively); all subjects with paraplegia studied used manual wheelchairs. Although total body fat mass was significantly greater in women (P = 0.010) and men (P = <0.001) with paraplegia compared with controls, for the equivalent total body fat mass, BMI was actually lower in women and men with paraplegia than controls (e.g. 20.2 kg/m2 vs. 25.0 kg/m2, respectively). Conclusion We report on body composition in persons with complete motor paraplegia, including women on whom limited information is currently available. Our results support the need to define better assessments of obesity in both women and men following spinal cord injury, particularly of central body fat distribution, as BMI underestimates adiposity in this population. PMID:24090208

  14. Body size and composition of National Football League players.

    PubMed

    Kraemer, William J; Torine, Jon C; Silvestre, Ricardo; French, Duncan N; Ratamess, Nicholas A; Spiering, Barry A; Hatfield, Disa L; Vingren, Jakob L; Volek, Jeff S

    2005-08-01

    The purpose of this study was to present a profile of body size and composition of National Football League (NFL) players prior to the start of the regular season. Fifty-three members of the Indianapolis Colts professional football team were measured for height, body mass, and percentage body fat using the BOD POD air-displacement plethysmography system during summer camp of the 2003 football season. These data were categorized by position for comparison with previous studies of NFL football players. The relationships observed were as follows (= represents nonsignificant; > represents p < or = 0.05): Height: Offensive Line = Defensive Line = Quarterbacks/Kickers/Punters = Tight Ends > Linebackers > Running Backs = Wide Receivers = Defensive Backs. Body Mass: Offensive Line = Defensive Line > Tight Ends = Linebackers > Running Backs = Quarterbacks/ Kickers/Punters > Wide Receivers = Defensive Backs. Percentage Body Fat: Offensive Line > Defensive Line > Quarterbacks/ Kickers/Punters = Linebackers = Tight Ends > Running Backs = Wide Receivers = Defensive Backs. Comparisons to teams in the 1970s indicate that body mass has increased only for offensive and defensive linemen; however, height and body fat among player positions have not dramatically changed. Furthermore, the body mass index is not an accurate measure or representation of body fat or obesity in NFL players. These data provide a basic template for size profiles and differences among various positions and allow comparisons with other studies for changes in the NFL over the past 3 decades.

  15. Design for manufacturability evaluation: Composite NIF Pockel Cell body

    SciTech Connect

    Jensen, W.A.; Spellman, G.P.

    1994-04-01

    A survey of composite materials and processes for the NIF Optical Switch Body is described. Mechanical and physical criterion set upon the part are used as guidelines for the selection of materials and processes for manufacturing. Benefits, costs, and risks associated with selected processes, as well as a recommendation for prototype fabrication is presented.

  16. Assessment and Interpretation of Body Composition in Physical Education

    ERIC Educational Resources Information Center

    Vehrs, Pat; Hager, Ron

    2006-01-01

    The physical educator's role is evolving into that of a teacher who is well educated in the areas of teaching, skill acquisition and development, motor learning, exercise physiology, physical conditioning, weight management, health, and lifestyle management. In an era when childhood obesity is at an all-time high, body composition can be one…

  17. Second quantization techniques in the scattering of nonidentical composite bodies

    NASA Technical Reports Server (NTRS)

    Norbury, J. W.; Townsend, L. W.; Deutchman, P. A.

    1986-01-01

    Second quantization techniques for describing elastic and inelastic interactions between nonidentical composite bodies are presented and are applied to nucleus-nucleus collisions involving ground-state and one-particle-one-hole excitations. Evaluations of the resultant collision matrix elements are made through use of Wick's theorem.

  18. Student Body Composition and School Performance: Evidence from Norway.

    ERIC Educational Resources Information Center

    Bonesronning, Hans

    1996-01-01

    Investigates the relationship between student achievement gains and student body composition in Norwegian uppersecondary schools, using a multilevel model considering assignment of students to departments. Estimates a reference frontier to identify best school practices and efficient and inefficient departments. Student achievement varies…

  19. [Body composition investigation of 2321 Shenzhen government and enterprise staffs].

    PubMed

    Liu, Xiaoli; Zhou, Jichang; Sun, Shiqiang; Xu, Jiazhang; Zhou, Xiaoying; Huang, Changhua; He, Shan; Liu, Can; Xu, Jian; Gong, Chunmei

    2016-01-01

    To understand the laws of human body composition change and the status of the overweight and obesity of government and enterprise staffs. In July 2013 - January 2014, 2321 adults more than 20-year-old healthy check-up crowd with complete human body composition and height as well as weight data in a medical center in Shenzhen were collected by convenience sampling method. The overweight rates of male and female were 46.41% and 18.94% respectively (standardized overweight rates were 44.02% and 14.51%, respectively), and the difference between them was statisically significant (Χ2 = 201.01, P = 0. 000). The obesity rates of male and female were 12.13% and 3.57%, respectively (standardized overweight rates were 11.11% (see symbol) 2.63%, respectively), and the difference between them was statisically significant (X2 = 48.45, P = 0.000). The parameters of bone mineral quality, visceral fat area, body fat, body fat percentage, abdominal obesity, body moisture and free fat weight increased with body weight, and there were statistical significance among normal weight, overweight and obesity groups (P = 0.000). Bone mineral quality was highest at the age of 30 to 40 for men and women, and there was the statistical significance. There was statistical significance in visceral fat area between different ages in the same gender. Body fat percentage (34.24 + 5.39)% of all ages 50 to 59 years old and body moisture (28.53 + 3.77)% of age 40 - 49 group were highest in women. Male body fat percentage (27.08 + 5.01)% at the age of 60-age group was the highest. Male and female visceral fat area increasesd with age, but there was no statistical difference between men and women at the same age. The human body composition had not a statistically significant difference among normal weight and overweight groups, but a significant difference between normal weight and obesity groups (P = 0.000). Overweight and obesity rates in Shenzhen government and enterprise staffs increase with age

  20. Effect of chronic centrifugation on body composition in the rat.

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.; Bull, L. S.; Oyama, J.

    1972-01-01

    Two groups of adult female rats were chronically centrifuged for 60 days (2.76 G, 4.15 G, controls at 1.00 G). Live weights of centrifugal rats decreased about 20 g (6%) per Delta 1 G above control. This weight loss comprised reductions in both body fat and fat-free body weight (FFBW) as determined by body-composition studies on eight rats per group killed at the end of centrifugation. Of nine components constituting the FFBW, only skeletal muscle, liver, and heart changed significantly in weight. Chemical composition showed reductions (compared with controls) in the fat fraction of most components and increases in the water fraction of liver and gut. Identical measurements were made on the remaining eight rats per group killed 43 days after return to 1 G. Neither centrifuged group had reached the control body-weight level at this time. No statistically significant effect of previous G level was found in any of the body-composition parameters. The possible involvment of physiological regulation was considered.

  1. Body composition and nutritional parameters in HIV and AIDS patients.

    PubMed

    Salomon, Jérôme; de Truchis, Pierre; Melchior, Jean-Claude

    2002-12-01

    Undernutrition is a frequent complication of evolutive and chronic HIV (human immunodeficiency virus) infection characterized by bodyweight loss and changes in body composition. The Centers for Disease Control and Prevention define AIDS wasting as involuntary loss of more than 10% of body weight, plus more than 30 days of either diarrhea, or weakness and fever. Wasting syndrome has been considered as a case definition of the AIDS disease since 1987. Wasting syndrome is clearly linked to disease progression and death. Despite the progress under the era of highly active antiretroviral therapy (HAART), wasting is still a problem for people with AIDS. A small part of the weight lost is fat. More important is the loss of "lean body mass", which is mostly muscle. Body composition changes during HIV infection are different from those observed in food deprivation. Under the era of HAART, a HIV-associated adipose redistribution syndrome (HARS) was described that associates subcutaneous lipoatrophy and abdominal obesity linked to various metabolic disorders. Several factors contribute to wasting syndrome. Not only low food intake and poor nutrient absorption, but mainly altered metabolism (increased resting energy expenditure) and specific disturbances in protein turnover, which is also increased. Nutritional evaluation of HIV-infected patients should include the measurement of body composition and analysis of nutritional parameters, including albumin, transthyretin and C-reactive protein. Transthyretin seems to be particularly useful to follow the recovery period of malnutrition.

  2. Effect of chronic centrifugation on body composition in the rat.

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.; Bull, L. S.; Oyama, J.

    1972-01-01

    Two groups of adult female rats were chronically centrifuged for 60 days (2.76 G, 4.15 G, controls at 1.00 G). Live weights of centrifugal rats decreased about 20 g (6%) per Delta 1 G above control. This weight loss comprised reductions in both body fat and fat-free body weight (FFBW) as determined by body-composition studies on eight rats per group killed at the end of centrifugation. Of nine components constituting the FFBW, only skeletal muscle, liver, and heart changed significantly in weight. Chemical composition showed reductions (compared with controls) in the fat fraction of most components and increases in the water fraction of liver and gut. Identical measurements were made on the remaining eight rats per group killed 43 days after return to 1 G. Neither centrifuged group had reached the control body-weight level at this time. No statistically significant effect of previous G level was found in any of the body-composition parameters. The possible involvment of physiological regulation was considered.

  3. The oxidation resistance optimization of titanium carbide/hastelloy (Ni-based alloy) composites applied for intermediate-temperature solid oxide fuel cell interconnects

    NASA Astrophysics Data System (ADS)

    Qi, Qian; Liu, Yan; Wang, Lujie; Huang, Jian; Xin, Xianshuang; Gai, Linlin; Huang, Zhengren

    2017-08-01

    Titanium carbide/hastelloy (TiC/hastelloy) composites are potential candidates for intermediate-temperature solid oxide fuel cell interconnects. In this work, TiC/hastelloy composites with suitable coefficient of thermal expansion are fabricated by in-situ reactive infiltration method, and their properties are optimized by adjusting TiC particle size (dTiC). The oxidation process of TiC/hastelloy composites is comprehensive performance of TiC and Ni-Cr alloy and determined by outward diffusion of Ti and Ni atoms and internal diffusion of O2. The oxidation resistance of composites could be improved by the decrease of dTiC through accelerating the formation of continuous and dense TiO2/Cr2O3 oxide scale. Moreover, the electrical conductivity of composites at 800 °C for 100 h is 5600-7500 S cm-1 and changes little with the prolongation of oxidation time. The decrease of dTiC is favorable for the properties optimization, and composites with 2.16 μm TiC exhibits good integrated properties.

  4. Nano-molybdenum carbide/carbon nanotubes composite as bifunctional anode catalyst for high-performance Escherichia coli-based microbial fuel cell.

    PubMed

    Wang, Yaqiong; Li, Bin; Cui, Dan; Xiang, Xingde; Li, Weishan

    2014-01-15

    A novel electrode, carbon felt-supported nano-molybdenum carbide (Mo2C)/carbon nanotubes (CNTs) composite, was developed as platinum-free anode of high performance microbial fuel cell (MFC). The Mo2C/CNTs composite was synthesized by using the microwave-assisted method with Mo(CO)6 as a single source precursor and characterized by using X-ray diffraction and transmission electron microscopy. The activity of the composite as anode electrocatalyst of MFC based on Escherichia coli (E. coli) was investigated with cyclic voltammetry, chronoamperometry, and cell discharge test. It is found that the carbon felt electrode with 16.7 wt% Mo Mo2C/CNTs composite exhibits a comparable electrocatalytic activity to that with 20 wt% platinum as anode electrocatalyst. The superior performance of the developed platinum-free electrode can be ascribed to the bifunctional electrocatalysis of Mo2C/CNTs for the conversion of organic substrates into electricity through bacteria. The composite facilitates the formation of biofilm, which is necessary for the electron transfer via c-type cytochrome and nanowires. On the other hand, the composite exhibits the electrocatalytic activity towards the oxidation of hydrogen, which is the common metabolite of E. coli.

  5. Sex-specific genetic effects influence variation in body composition.

    PubMed

    Zillikens, M C; Yazdanpanah, M; Pardo, L M; Rivadeneira, F; Aulchenko, Y S; Oostra, B A; Uitterlinden, A G; Pols, H A P; van Duijn, C M

    2008-12-01

    Despite well-known sex differences in body composition it is not known whether sex-specific genetic or environmental effects contribute to these differences. We assessed body composition in 2,506 individuals, from a young Dutch genetic isolate participating in the Erasmus Rucphen Family study, by dual-energy X-ray absorptiometry and anthropometry. We used variance decomposition procedures to partition variation of body composition into genetic and environmental components common to both sexes and to men and women separately and calculated the correlation between genetic components in men and women. After accounting for age, sex and inbreeding, heritability ranged from 0.39 for fat mass index to 0.84 for height. We found sex-specific genetic effects for fat percentage (fat%), lean mass, lean mass index (LMI) and fat distribution, but not for BMI and height. Genetic correlations between sexes were significantly different from 1 for fat%, lean mass, LMI, android fat, android:gynoid fat ratio and WHR, indicating that there are sex-specific genes contributing to variation of these traits. Genetic variance was significantly higher in women for the waist, hip and thigh circumference and WHR, implying that genes account for more variance of fat distribution in women than in men. Environmental variance was significantly higher in men for the android:gynoid fat ratio. Sex-specific genetic effects underlie sexual dimorphism in several body composition traits. The findings are relevant for studies on the relationship of body composition with common diseases like cardiovascular disease and type 2 diabetes and for genetic association studies.

  6. Effects of caloric restriction on body composition and total body nitrogen as measured by neutron activation.

    PubMed

    Vaswani, A N; Vartsky, D; Ellis, K J; Yasumura, S; Cohn, S H

    1983-02-01

    The purpose of this study was to compare the effects of two isocaloric diets (800 Kcals) on the changes in body composition during weight reduction. While the protein content of both diets was 70 g, the carbohydrate content of diet A was 10 g and that of diet B was 70 g. The various parameters of body composition were determined as follows: Total body potassium (TBK) by 40K counting, total body water (TBW) by the tritiated water technique, total body nitrogen (TBN) by prompt gamma neutron activation analysis (PGNAA) and total body fat was estimated by measuring the skinfold thickness. Routine serum chemistries were performed every 2 wk and serum insulin and triiodothyronine by radioimmunoassay were done at 4-wk intervals. Seventeen obese women who were at least 30% above ideal body weight volunteered for the outpatient study, (group A--10 subjects, group B--7 subjects). At the end of the 12 wk study, the percent changes in the above parameters of body composition were not significantly different for the two groups. The biochemical changes were consistent with the degree of caloric restriction. We conclude that: (1) the technique of prompt gamma neutron activation analysis can be used effectively to determine long term changes in total body nitrogen during weight reduction, (2) loss of lean tissue (water, potassium and nitrogen) as well as fat tissue occurred during weight reduction. The loss of TBN in absolute quantities was less for diet A compared to diet B; however, there was no significant difference between the two diets when the data was expressed as a percent change from the baseline values, and (3) TBK determination probably provides the best estimate of total body fat.

  7. Do Lower-Body Dimensions and Body Composition Explain Vertical Jump Ability?

    PubMed

    Caia, Johnpaul; Weiss, Lawrence W; Chiu, Loren Z F; Schilling, Brian K; Paquette, Max R; Relyea, George E

    2016-11-01

    Caia, J, Weiss, LW, Chiu, LZF, Schilling, BK, Paquette, MR, and Relyea, GE. Do lower-body dimensions and body composition explain vertical jump ability? J Strength Cond Res 30(11): 3073-3083, 2016-Vertical jump (VJ) capability is integral to the level of success attained by individuals participating in numerous sport and physical activities. Knowledge of factors related to jump performance may help with talent identification and/or optimizing training prescription. Although myriad variables are likely related to VJ, this study focused on determining if various lower-body dimensions and/or body composition would explain some of the variability in performance. Selected anthropometric dimensions were obtained from 50 university students (25 men and 25 women) on 2 occasions separated by 48 or 72 hours. Estimated body fat percentage (BF%), height, body weight, hip width, pelvic width, bilateral quadriceps angle (Q-angle), and bilateral longitudinal dimensions of the feet, leg, thigh, and lower limb were obtained. Additionally, participants completed countermovement VJs. Analysis showed BF% to have the highest correlation with countermovement VJ displacement (r = -0.76, p < 0.001). When examining lower-body dimensions, right-side Q-angle displayed the strongest association with countermovement VJ displacement (r = -0.58, p < 0.001). Regression analysis revealed that 2 different pairs of variables accounted for the greatest variation (66%) in VJ: (a) BF% and sex and (b) BF% and body weight. Regression models involving BF% and lower-body dimensions explained up to 61% of the variance observed in VJ. Although the variance explained by BF% may be increased by using several lower-body dimensions, either sex identification or body weight explains comparatively more. Therefore, these data suggest that the lower-body dimensions measured herein have limited utility in explaining VJ performance.

  8. Changes in body composition in triathletes during an Ironman race.

    PubMed

    Mueller, Sandro Manuel; Anliker, Elmar; Knechtle, Patrizia; Knechtle, Beat; Toigo, Marco

    2013-09-01

    Triathletes lose body mass during an Ironman triathlon. However, the associated body composition changes remain enigmatic. Thus, the purpose of this study was to investigate Ironman-induced changes in segmental body composition, using for the first time dual-energy X-ray absorptiometry (DXA) and peripheral quantitative computed tomography (pQCT). Before and after an Ironman triathlon, segmental body composition and lower leg tissue mass, areas and densities were assessed using DXA and pQCT, respectively, in eight non-professional male triathletes. In addition, blood and urine samples were collected for the determination of hydration status. Body mass decreased by 1.9 ± 0.8 kg. This loss was due to 0.4 ± 0.3 and 1.4 ± 0.8 kg decrease in fat and lean mass, respectively (P < 0.01). Calf muscle density was reduced by 1.93 ± 1.04 % (P < 0.01). Hemoglobin, hematocrit, and plasma [K(+)] remained unchanged, while plasma [Na(+)] (P < 0.05), urine specific gravity and plasma and urine osmolality increased (P < 0.01). The loss in lean mass was explained by a decrease in muscle density, as an indicator of glycogen loss, and increases in several indicators for dehydration. The measurement of body composition with DXA and pQCT before and after an Ironman triathlon provided exact values for the loss in fat and lean mass. Consequently, these results yielded more detailed insights into tissue catabolism during ultra-endurance exercise.

  9. Relationship Between Diet and Body Composition After Biliopancreatic Diversion.

    PubMed

    Calleja-Fernández, Alicia; Pintor-de-la-Maza, Begoña; Diez-Rodríguez, Rubén; Vidal-Casariego, Alfonso; Urioste-Fondo, Ana; Cano-Rodríguez, Isidoro; Ballesteros-Pomar, María D

    2015-11-01

    Biliopancreatic diversion (BPD) has been shown to be one of the most effective techniques for losing weight, although the relationship between body composition and diet after the procedure is not well known. Our aim was to assess dietary changes and their effects on body composition. This longitudinal study included all patients eligible for BPD who had undergone body composition analysis. Two assessments were performed: 6 weeks before and 1 year after surgery. Nutritional education was given after surgery by a registered dietitian, and dual energy X-ray absorptiometry was performed and a 3-day food record was collected for further analysis at both of the visits. Forty-six patients were included. The percentage of excess of weight loss was 61.03 % (SD 14.01 %), which was statistically different by gender (p = 0.045). The percentage of subjects reporting a low daily protein consumption of less than 60 g and 1.2 g/kg of ideal body weight (IBW)/day was 15.2 % before surgery and 19.6 % at 12 months (p = 0.006). The weight loss was mainly of fat mass (FM). There were differences of body composition by gender before and after surgery. A simple correlation analysis showed a significant association between daily energy intake and FM (g) only before surgery (p = 0.030), and also between daily protein intake (expressed as total g) and lean body mass (LBM) 12 months after surgery (p = 0.018), but no association was found with achieved protein goal. BPD enhanced by nutritional education seems to improve its results by achieving an adequate weight loss, preserving LBM, decreasing FM, and guaranteeing an appropriate protein intake.

  10. LIQUID PHASE SINTERING OF METALLIC CARBIDES

    DOEpatents

    Hammond, J.; Sease, J.D.

    1964-01-21

    An improved method is given for fabricating uranium carbide composites, The method comprises forming a homogeneous mixture of powdered uranium carbide, a uranium intermetallic compound which wets and forms a eutectic with said carbide and has a non-uranium component which has a relatively high vapor pressure at a temperature in the range 1200 to 1500 deg C, and an organic binder, pressing said mixture to a composite of desired green strength, and then vacuum sintering said composite at the eutectic forming temperature for a period sufficient to remove at least a portion of the non-uranium containing component of said eutectic. (AEC)

  11. Body composition comparison in two elite female wheelchair athletes.

    PubMed

    Lussier, L; Knight, J; Bell, G; Lohman, T; Morris, A F

    1983-02-01

    It was the purpose of this study to determine body composition by two methods in two excellent female athletes. One sportswoman (SRH) was national wheelchair marathon champion in 1977 in 3 hours, 40 minutes on the Boston course. She still competes internationally and has won three gold medals and set three world records in the last Olympiad for the handicapped in 1980. The second woman athlete (LSJ) competes in wheelchair basketball and track on a national level. Body density was determined by the standard underwater weighing procedure and residual volume determination. A second method to calculate cellular body mass was the measure of potassium 40 (40K) activity by whole body scintillation counter. The characteristics of these athletes are listed as follows: (formula; see text) The results show that both methods of determining adiposity produce results differing by only one percentage point. It is important to determine body composition in these wheelchair athletes since their cellular body mass is decreased because of their disability.

  12. Diffusion barriers for silicon carbide particle reinforcements by ion-beam assisted deposition: Effects on interphase stability in silicon carbide(p/beta)-nickel aluminide and silicon carbide(p/gamma)-nickel aluminide composites

    NASA Astrophysics Data System (ADS)

    Cai, Zhiwei

    In this study, aluminum nitride and aluminum oxide films were used as diffusion barriers for SiC particles that were consolidated with beta-NiAl and gamma-Ni3Al matrices at temperatures of 1673 K and 1373 K, respectively. The focus of this study was to understand factors influencing the effectiveness of the diffusion barriers during the consolidation processes of the two composite systems. The barrier films were deposited on SiC particles by ion-beam assisted vacuum evaporation during which the SiC particles were radiantly heated and acoustically levitated. The nitride film formed reactively on SiC particles, and consisted of 95% aluminum nitride (balanced with aluminum nitrate and oxide). The oxygen content in the nitride film was a result of the impingement of residual oxygen and water molecules in the deposition environment. A voided globular structure of fine-grained clusters was found in a nitride film deposited on SiC particles at 593 K, which was attributed to the levitation of the particles and the deposition temperature. Nitride films deposited at a higher temperature of 793 K consisted of a fine-grained dense structure with few voids. The oxide film deposited at room temperature had a fine-grained dense structure with some globular features. This study found that film material affected film's ability of retaining integrity during compositing process, which was important for the success of the barrier films. Annealed at 1673 K, grains in a nitride film (deposited at 793 K) coalesced to an average size of 0.5 mum that was comparable to the film thickness. Grain boundaries in the film were widened by the pore agglomeration, resulting in micro-cracks. The oxide film exhibited a similar phenomenon of uninhibited grain growth and micro-crack formation at a lower temperature of 1273 K. Both films failed to be an effective barrier in SiC/beta-NiAl composite during the compositing process at 1673 K. This study showed the influence of film structure on grain growth

  13. Effects of weightlessness on body composition in the rat

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.; Ushakov, A. S.; Pace, N.; Smith, A. H.; Rahlmann, D. F.; Smirnova, T. A.

    1983-01-01

    The effects of weightlessness on the body composition of rats were investigated using 5 male rats exposed to 18.5 days of weightlessness on the COSMOS 1129 biosatellite and killed after reentry. The animals were immediately dissected and the three major body divisions (musculoskeletal system, skin, and pooled viscera) were analyzed for fat, water, solids, and six elements. These results were determined as percentages of the fat-free body or its components and then compared with two groups of terrestrial controls, one of which was subjected to a flight simulation in a spacecraft mock-up while the other was under standard vivarium conditions. Compared with the control groups, the flight group was found to exhibit a reduced fraction of total body water, a net shift of body water from skin to viscera, a marked diminution in the fraction of extracellular water in the fat-free body, a marked reduction in the fraction of bone mineral, no change in the quantity of stored fat or adrenal masses, and a net increase in total muscle mass as indicated by total body creatine, protein, and body cell mass.

  14. Effects of weightlessness on body composition in the rat

    NASA Technical Reports Server (NTRS)

    Pitts, G. C.; Ushakov, A. S.; Pace, N.; Smith, A. H.; Rahlmann, D. F.; Smirnova, T. A.

    1983-01-01

    The effects of weightlessness on the body composition of rats were investigated using 5 male rats exposed to 18.5 days of weightlessness on the COSMOS 1129 biosatellite and killed after reentry. The animals were immediately dissected and the three major body divisions (musculoskeletal system, skin, and pooled viscera) were analyzed for fat, water, solids, and six elements. These results were determined as percentages of the fat-free body or its components and then compared with two groups of terrestrial controls, one of which was subjected to a flight simulation in a spacecraft mock-up while the other was under standard vivarium conditions. Compared with the control groups, the flight group was found to exhibit a reduced fraction of total body water, a net shift of body water from skin to viscera, a marked diminution in the fraction of extracellular water in the fat-free body, a marked reduction in the fraction of bone mineral, no change in the quantity of stored fat or adrenal masses, and a net increase in total muscle mass as indicated by total body creatine, protein, and body cell mass.

  15. Latino Mothers' Cumulative Food Insecurity Exposure and Child Body Composition.

    PubMed

    Hernandez, Daphne C

    2016-01-01

    To document whether an intergenerational transmission of food insecurity is occurring by assessing low-income foreign-born Latino mothers' experiences with food insecurity as none, once (either childhood or adulthood) or twice (during both childhood and adulthood). Also the association between maternal cumulative food insecurity and children's body composition was examined. Maternal self-reported surveys on retrospective measures of food insecurity during childhood, current measures of food insecurity, and demographics were collected from Houston-area community centers (N = 96). Children's body mass index (BMI) and waist circumference (WC) were directly assessed. Covariate-adjusted logistic regression models analyzed the association between cumulative food insecurity experiences and children's body composition. Fifty-eight percent of mothers experienced food insecurity both as a child and as an adult and 31% of the mothers experienced food insecurity either as a child or adult. Maternal cumulative exposure to food insecurity was unrelated to BMI but was negatively related to elevated WC. Although an intergenerational transmission of food insecurity does exist, maternal cumulative exposure to food insecurity does not impact children's body composition negatively in the short term. Studying the long-term effects of cumulative food insecurity exposure can provide information for the development and timing of obesity interventions.

  16. ["In vivo" body composition assessment; part I: a historic overview].

    PubMed

    Carnero, Elvis A; Alvero-Cruz, José Ramón; Giráldez García, Manuel Avelino; Sardinha, Luis B

    2015-05-01

    The study of body composition (BC) has gained in relevance over the last decades, mainly because of its important health- and disease- related applications within both the clinical and the sports setting. It is not a new area, and its especial relevance as an area of biology dates from the second half of the nineteenth century. In this paper, we have reviewed the three historic periods of BC, with special reference to the most important advances in in vivo assessment. Even though the earliest findings about human BC date from antiquity, the first (or 'early') stage of discovery began in 1850. Said early stage was mainly characterized by data obtained from the dissection of cadavers and by the application of biochemical methods in vivo. Longitudinal changes in body composition were also a concern. The second (so called 'recent') stage, in the second half of the twentieth century, was marked by milestones such as the formulation of the first mathematical models for the estimation of body components, and technological advances. Within the third ('contemporary' or 'current') stage of research, several groups have focused on validating the classical BC models in specific populations, on analysis of the genetic determinants (i.e. phenotypes and, more recently genotypes) of body composition, and on re-instigating the study of dynamic BC.

  17. Effect of the silicon-carbide micro- and nanoparticle size on the thermo-elastic and time-dependent creep response of a rotating Al-SiC composite cylinder

    NASA Astrophysics Data System (ADS)

    Loghman, A.; Hammami, M.; Loghman, E.

    2017-05-01

    The history of stresses and creep strains of a rotating composite cylinder made of an aluminum matrix reinforced by silicon carbide particles is investigated. The effect of uniformly distributed SiC micro- and nanoparticles on the initial thermo-elastic and time-dependent creep deformation is studied. The material creep behavior is described by Sherby's constitutive model where the creep parameters are functions of temperature and the particle sizes vary from 50 nm to 45.9 μm. Loading is composed of a temperature field due to outward steady-state heat conduction and an inertia body force due to cylinder rotation. Based on the equilibrium equation and also stress-strain and strain-displacement relations, a constitutive second-order differential equation for displacements with variable and time-dependent coefficients is obtained. By solving this differential equation together with the Prandtl-Reuss relation and the material creep constitutive model, the history of stresses and creep strains is obtained. It is found that the minimum effective stresses are reached in a material reinforced by uniformly distributed SiC particles with the volume fraction of 20% and particle size of 50 nm. It is also found that the effective and tangential stresses increase with time at the inner surface of the composite cylinder; however, their variation at the outer surface is insignificant.

  18. Effect of particle size and percentages of Boron carbide on the thermal neutron radiation shielding properties of HDPE/B4C composite: Experimental and simulation studies

    NASA Astrophysics Data System (ADS)

    Soltani, Zahra; Beigzadeh, Amirmohammad; Ziaie, Farhood; Asadi, Eskandar

    2016-10-01

    In this paper the effects of particle size and weight percentage of the reinforcement phase on the absorption ability of thermal neutron by HDPE/B4C composites were investigated by means of Monte-Carlo simulation method using MCNP code and experimental studies. The composite samples were prepared using the HDPE filled with different weight percentages of Boron carbide powder in the form of micro and nano particles. Micro and nano composite were prepared under the similar mixing and moulding processes. The samples were subjected to thermal neutron radiation. Neutron shielding efficiency in terms of the neutron transmission fractions of the composite samples were investigated and compared with simulation results. According to the simulation results, the particle size of the radiation shielding material has an important role on the shielding efficiency. By decreasing the particle size of shielding material in each weight percentages of the reinforcement phase, better radiation shielding properties were obtained. It seems that, decreasing the particle size and homogeneous distribution of nano forms of B4C particles, cause to increase the collision probability between the incident thermal neutron and the shielding material which consequently improve the radiation shielding properties. So, this result, propose the feasibility of nano composite as shielding material to have a high performance shielding characteristic, low weight and low thick shielding along with economical benefit.

  19. Risk of Mortality According to Body Mass Index and Body Composition Among Postmenopausal Women

    PubMed Central

    Bea, Jennifer W.; Thomson, Cynthia A.; Wertheim, Betsy C.; Nicholas, J. Skye; Ernst, Kacey C.; Hu, Chengcheng; Jackson, Rebecca D.; Cauley, Jane A.; Lewis, Cora E.; Caan, Bette; Roe, Denise J.; Chen, Zhao

    2015-01-01

    Obesity, often defined as a body mass index (BMI; weight (kg)/height (m)2) of 30 or higher, has been associated with mortality, but age-related body composition changes can be masked by stable BMI. A subset of Women's Health Initiative participants (postmenopausal women aged 50–79 years) enrolled between 1993 and 1998 who had received dual-energy x-ray absorptiometry scans for estimation of total body fat (TBF) and lean body mass (LBM) (n = 10,525) were followed for 13.6 (standard deviation, 4.6) years to test associations between BMI, body composition, and incident mortality. Overall, BMI ≥35 was associated with increased mortality (adjusted hazard ratio (HR) = 1.45, 95% confidence interval (CI): 1.16, 1.82), while TBF and LBM were not. However, an interaction between age and body composition (P < 0.001) necessitated age stratification. Among women aged 50–59 years, higher %TBF increased risk of death (HR = 2.44, 95% CI: 1.38, 4.34) and higher %LBM decreased risk of death (HR = 0.41, 95% CI: 0.23, 0.74), despite broad-ranging BMIs (16.4–69.1). However, the relationships were reversed among women aged 70–79 years (P < 0.05). BMI did not adequately capture mortality risk in this sample of postmenopausal women. Our data suggest the clinical utility of evaluating body composition by age group to more robustly assess mortality risk among postmenopausal women. PMID:26350478

  20. Analysis of Relationship between the Body Mass Composition and Physical Activity with Body Posture in Children.

    PubMed

    Wyszyńska, Justyna; Podgórska-Bednarz, Justyna; Drzał-Grabiec, Justyna; Rachwał, Maciej; Baran, Joanna; Czenczek-Lewandowska, Ewelina; Leszczak, Justyna; Mazur, Artur

    2016-01-01

    Introduction. Excessive body mass in turn may contribute to the development of many health disorders including disorders of musculoskeletal system, which still develops intensively at that time. Aim. The aim of this study was to assess the relationship between children's body mass composition and body posture. The relationship between physical activity level of children and the parameters characterizing their posture was also evaluated. Material and Methods. 120 school age children between 11 and 13 years were enrolled in the study, including 61 girls and 59 boys. Each study participant had the posture evaluated with the photogrammetric method using the projection moiré phenomenon. Moreover, body mass composition and the level of physical activity were evaluated. Results. Children with the lowest content of muscle tissue showed the highest difference in the height of the inferior angles of the scapulas in the coronal plane. Children with excessive body fat had less slope of the thoracic-lumbar spine, greater difference in the depth of the inferior angles of the scapula, and greater angle of the shoulder line. The individuals with higher level of physical activity have a smaller angle of body inclination. Conclusion. The content of muscle tissue, adipose tissue, and physical activity level determines the variability of the parameter characterizing the body posture.

  1. Analysis of Relationship between the Body Mass Composition and Physical Activity with Body Posture in Children

    PubMed Central

    Baran, Joanna; Czenczek-Lewandowska, Ewelina; Leszczak, Justyna; Mazur, Artur

    2016-01-01

    Introduction. Excessive body mass in turn may contribute to the development of many health disorders including disorders of musculoskeletal system, which still develops intensively at that time. Aim. The aim of this study was to assess the relationship between children's body mass composition and body posture. The relationship between physical activity level of children and the parameters characterizing their posture was also evaluated. Material and Methods. 120 school age children between 11 and 13 years were enrolled in the study, including 61 girls and 59 boys. Each study participant had the posture evaluated with the photogrammetric method using the projection moiré phenomenon. Moreover, body mass composition and the level of physical activity were evaluated. Results. Children with the lowest content of muscle tissue showed the highest difference in the height of the inferior angles of the scapulas in the coronal plane. Children with excessive body fat had less slope of the thoracic-lumbar spine, greater difference in the depth of the inferior angles of the scapula, and greater angle of the shoulder line. The individuals with higher level of physical activity have a smaller angle of body inclination. Conclusion. The content of muscle tissue, adipose tissue, and physical activity level determines the variability of the parameter characterizing the body posture. PMID:27761467

  2. Body surface temperature distribution in relation to body composition in obese women.

    PubMed

    Chudecka, Monika; Lubkowska, Anna; Kempińska-Podhorodecka, Agnieszka

    2014-07-01

    Adipose tissue levels and human obesity are known to be associated with increased heat production. At the same time, subcutaneous adipose tissue provides an insulating layer that impedes heat loss. The energy implications of obesity and body thermoregulatory mechanisms remain relatively poorly understood. This study attempted to examine the potential relationship between body composition (subcutaneous and visceral fat) determined by bioimpedance as well as BMI (body mass index), and skin surface temperature distribution recorded at rest. One specific aim of this study was to draw a thermal map of body areas in obese women and compare this with women of normal body mass, and thus to identify body regions within which heat transfer is particularly impeded. As high fat content is a good insulator, it could reduce the body's ability to respond effectively to changes in environmental temperature, which would be problematic for thermal homeostasis. Our results showed that core temperature did not differ between obese and normal body mass participants, while skin temperature of most body surfaces was lower in obese subjects. The results of regression analysis showed that the mean body surface temperature (Tmean) decreased with increasing percentage of body fat (PBF) of the abdominal area. The opposite relationship was observed for the front area of the hand (simultaneous increase in Tmean and PBF). We also found a negative correlation between BMI and Tmean of the thigh areas, both the front and the back. From this it could be concluded that the mean body surface temperature is dependent on body fat. Copyright © 2014 Elsevier Ltd. All rights reserved.

  3. Effects of catechin enriched green tea on body composition.

    PubMed

    Wang, Hongqiang; Wen, Yibo; Du, Yaping; Yan, Xiuyuan; Guo, Hongwei; Rycroft, Jane A; Boon, Niels; Kovacs, Eva M R; Mela, David J

    2010-04-01

    Obesity is a major health problem in the developed and developing world. Many "functional" foods and ingredients are advocated for their effects on body composition but few have consistent scientific support for their efficacy. However, an increasing amount of mechanistic and clinical evidence is building for green tea (GT). This experiment was therefore undertaken to study the effects of a high-catechin GT on body composition in a moderately overweight Chinese population. In a randomized placebo-controlled trial, 182 moderately overweight Chinese subjects, consumed either two servings of a control drink (C; 30 mg catechins, 10 mg caffeine/day), one serving of the control drink and one serving of an extra high-catechin GT1 (458 mg catechins, 104 mg caffeine/day), two servings of a high-catechin GT2 (468 mg catechins, 126 mg caffeine/day) or two servings of the extra high-catechin GT3 (886 mg catechins, 198 mg caffeine/day) for 90 days. Data were collected at 0, 30, 60, and 90 days. We observed a decrease in estimated intra-abdominal fat (IAF) area of 5.6 cm(2) in the GT3 group. In addition, we found decreases of 1.9 cm in waist circumference and 1.2 kg body weight in the GT3 group vs. C (P < 0.05). We also observed reductions in total body fat (GT2, 0.7 kg, P < 0.05) and body fat % (GT1, 0.6%, P < 0.05). We conclude that consumption of two servings of an extra high-catechin GT leads to improvements in body composition and reduces abdominal fatness in moderately overweight Chinese subjects.

  4. Gender Differences in Insulin Resistance, Body Composition, and Energy Balance

    PubMed Central

    Geer, Eliza B.; Shen, Wei

    2010-01-01

    Background Men and women differ substantially in regard to degrees of insulin resistance, body composition, and energy balance. Adipose tissue distribution, in particular the presence of elevated visceral and hepatic adiposity, plays a central role in the development of insulin resistance and obesity-related complications. Objective This review summarizes published data on gender differences in insulin resistance, body composition, and energy balance, to provide insight into novel gender-specific avenues of research as well as gender-tailored treatments of insulin resistance, visceral adiposity, and obesity. Methods English-language articles were identified from searches of the PubMed database through November 2008, and by reviewing the references cited in these reports. Searches included combinations of the following terms: gender, sex, insulin resistance, body composition, energy balance, and hepatic adipose tissue. Results For a given body mass index, men were reported to have more lean mass, women to have higher adiposity. Men were also found to have more visceral and hepatic adipose tissue, whereas women had more peripheral or subcutaneous adipose tissue. These differences, as well as differences in sex hormones and adipokines, may contribute to a more insulin-sensitive environment in women than in men. When normalized to kilograms of lean body mass, men and women had similar resting energy expenditure, but physical energy expenditure was more closely related to percent body fat in men than in women. Conclusion Greater amounts of visceral and hepatic adipose tissue, in conjunction with the lack of a possible protective effect of estrogen, may be related to higher insulin resistance in men compared with women. PMID:19318219

  5. Handgrip strength as a predictor for post bariatric body composition.

    PubMed

    Otto, Mirko; Kautt, Sandra; Kremer, Melanie; Kienle, Peter; Post, Stefan; Hasenberg, Till

    2014-12-01

    After bariatric surgery, the postoperative quality of weight loss is variable. The aim of weight loss treatment is to reduce fat mass while keeping fat free mass, in particular body cell mass (BCM), constant. Detection of low BCM is an important aspect of surgical follow up. Handgrip dynamometry is a rapid and inexpensive test to measure static muscle strength, which is an independent outcome indicator of various medical conditions. The objective of this study is to examine the change in handgrip strength after bariatric surgery and its predictive value for postoperative body composition. Furthermore, this study was carried out at the University Hospital, Germany. Twenty-five patients who underwent a bariatric procedure (laparoskopic Roux-Y gastric bypass n=16 or sleeve resection n=9) were included in this study. Bioelectrical impedance analysis and hand-grip strength were measured preoperatively and repeated every 6 weeks for 4 months. An analysis of variance was performed to observe the changes in these individual parameters. Postoperatively, all patients showed a significant decrease in the body mass index and body fat. The extracellular mass, BCM, and the lean mass of the patients remained constant. Handgrip strength showed no significant changes during the postoperative course. Nevertheless, the preoperative hand-grip strength showed a strong positive correlation with the postoperative body composition. This study showed no changes in the static muscle force after bariatric surgery. The preoperative handgrip strength was strongly correlated with postoperative body composition and may be used to identify patients who need more attention before surgery and in the early postoperative phase.

  6. Body composition in ambulatory women with multiple sclerosis.

    PubMed

    Lambert, Charles P; Lee Archer, R; Evans, William J

    2002-11-01

    To compare whole-body fat mass and fat-free mass (FFM) in ambulatory patients with multiple sclerosis (MS) and control subjects without MS. Nonrandomized controlled trial or cross-sectional study. An exercise physiology laboratory at a medical school. Seventeen ambulatory patients with MS and 12 control subjects (all subjects were women). The median Expanded Disability Status Scale (EDSS) score was 4.0 for the individuals with MS. Not applicable. Whole-body percentage of fat-free mass (%FFM), percentage of body fat (%BF), FFM, and fat mass. A significant difference in age was observed between the groups; thus, age was used as a covariate in the body composition analyses. No significant differences were observed between the groups in %BF: 32.5+/-13.9 and 27.8+/-5.6 (P=.54) for MS and controls, respectively, or %FFM, 67.1+/-14.9 and 71.3+/-12.4 (P=.42) for MS and controls, respectively. For individuals with MS, no significant relation was observed between EDSS score and %BF (P=.24) or between EDSS score and %FFM (P=.24). No significant differences were observed in body composition between ambulatory MS patients and controls. Furthermore, the EDSS score was not a significant predictor of %BF or %FFM for people with MS. Copyright 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation

  7. Association between actigraphic sleep metrics and body composition

    PubMed Central

    Wirth, Michael D.; Hébert, James R.; Hand, Gregory A.; Youngstedt, Shawn D.; Hurley, Thomas G.; Shook, Robin P.; Paluch, Amanda E.; Sui, Xuemei; James, Shelli L.; Blair, Steven N.

    2015-01-01

    Purpose Determine if individuals with poor sleep characteristics (i.e., late sleep onset or wake times, short sleep duration, long sleep latency, low sleep efficiency, high wake-after-sleep-onset [WASO]) have greater body mass index (BMI=kg/m2) or body fat. Methods Data for these cross-sectional analyses were from the Energy Balance Study (University of South Carolina). Participants were between 21 and 35 years of age and had a BMI of 20–35 kg/m2. Body fat percent was measured by dual X-ray absorptiometry. Sleep and physical activity were measured by actigraphy (BodyMedia’s SenseWear® physical activity armband). General linear models were used to estimate mean BMI and body fat percent by sleep metric categories. Results Greater BMI and body fat percent were associated with low sleep efficiency (BMI=25.5 vs. 24.8kg/m2, p<0.01; body fat=27.7 vs. 26.5%, p=0.04) and high WASO (BMI=25.6 vs. 25.0 kg/m2, p=0.02; body fat=28.0 vs. 26.7%, p=0.03). Elevated BMI or body fat percent also were observed for later wake times, shorter sleep duration, and longer sleep latency. Sex modified the association between wake times and body composition. Conclusions Understanding the complex relationships between sleep and health outcomes could help reduce chronic disease burden by incorporating sleep components, measured through novel non-invasive techniques (SenseWear® armband), into weight loss interventions. PMID:26071309

  8. Body composition in patients with classical homocystinuria: body mass relates to homocysteine and choline metabolism.

    PubMed

    Poloni, Soraia; Leistner-Segal, Sandra; Bandeira, Isabel Cristina; D'Almeida, Vânia; de Souza, Carolina Fischinger Moura; Spritzer, Poli Mara; Castro, Kamila; Tonon, Tássia; Nalin, Tatiéle; Imbard, Apolline; Blom, Henk J; Schwartz, Ida V D

    2014-08-10

    Classical homocystinuria is a rare genetic disease caused by cystathionine β-synthase deficiency, resulting in homocysteine accumulation. Growing evidence suggests that reduced fat mass in patients with classical homocystinuria may be associated with alterations in choline and homocysteine pathways. This study aimed to evaluate the body composition of patients with classical homocystinuria, identifying changes in body fat percentage and correlating findings with biochemical markers of homocysteine and choline pathways, lipoprotein levels and bone mineral density (BMD) T-scores. Nine patients with classical homocystinuria were included in the study. Levels of homocysteine, methionine, cysteine, choline, betaine, dimethylglycine and ethanolamine were determined. Body composition was assessed by bioelectrical impedance analysis (BIA) in patients and in 18 controls. Data on the last BMD measurement and lipoprotein profile were obtained from medical records. Of 9 patients, 4 (44%) had a low body fat percentage, but no statistically significant differences were found between patients and controls. Homocysteine and methionine levels were negatively correlated with body mass index (BMI), while cysteine showed a positive correlation with BMI (p<0.05). There was a trend between total choline levels and body fat percentage (r=0.439, p=0.07). HDL cholesterol correlated with choline and ethanolamine levels (r=0.757, p=0.049; r=0.847, p=0.016, respectively), and total cholesterol also correlated with choline levels (r=0.775, p=0.041). There was no association between BMD T-scores and body composition. These results suggest that reduced fat mass is common in patients with classical homocystinuria, and that alterations in homocysteine and choline pathways affect body mass and lipid metabolism. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Scaling of adult regional body mass and body composition as a whole to height: Relevance to body shape and body mass index.

    PubMed

    Schuna, John M; Peterson, Courtney M; Thomas, Diana M; Heo, Moonseong; Hong, Sangmo; Choi, Woong; Heymsfield, Steven B

    2015-01-01

    Adult body mass (MB) empirically scales as height (Ht) squared (MB ∝ Ht(2) ), but does regional body mass and body composition as a whole also scale as Ht(2) ? This question is relevant to a wide range of biological topics, including interpretation of body mass index (BMI). Dual-energy X-ray absorptiometry (DXA) was used to quantify regional body mass [head (MH), trunk, arms, and legs] and whole-body composition [fat, lean soft tissue (LST), and bone mineral content (BMC)] in non-Hispanic (NH) white, NH black, Mexican American, and Korean adults participating in the National Health and Nutrition Examination Survey (NHANES; n = 17,126) and Korean NHANES (n = 8,942). Regression models were developed to establish Ht scaling powers for each measured component with adjustments for age and adiposity. Exploratory analyses revealed a consistent scaling pattern across men and women of the four population groups: regional mass powers, head (∼0.8-1) < arms and trunk (∼1.8-2.3) < legs (∼2.3-2.6); and body composition, LST (∼2.0-2.3) < BMC (∼2.1-2.4). Small sex and population differences in scaling powers were also observed. As body mass scaled uniformly across the eight sex and population groups as Ht(∼2) , tall and short subjects differed in body shape (e.g., MH/MB ∝ Ht(-∼1) ) and composition. Adult human body shape and relative composition are a function of body size as represented by stature, a finding that reveals a previously unrecognized phenotypic heterogeneity as defined by BMI. These observations provide new pathways for exploring mechanisms governing the interrelations between adult stature, body morphology, biomechanics, and metabolism. © 2014 Wiley Periodicals, Inc.

  10. Nutrition, endocrinology, and body composition during space flight

    NASA Technical Reports Server (NTRS)

    Lane, H. W.; Gretebeck, R. J.; Smith, S. M.

    1998-01-01

    Space flight induces endocrine changes that perturb metabolism. This altered metabolism affects both the astronauts' body composition and the nutritional requirements necessary to maintain their health. During the last 25 years, a combination of studies conducted on Skylab (the first U.S. space laboratory), U.S. Shuttle flights, and Soviet and Russian flights provides a range of data from which general conclusions about energy and protein requirements can be drawn. We have reviewed the endocrine data from those studies and related it to changes in body composition. From these data it appears that protein and energy intake of astronauts are similar to those on Earth. However, a combination of measures, including exercise, appropriate diet, and, potentially, drugs, is required to provide the muscle health needed for long duration space flight.

  11. Sarcopenia and the Analysis of Body Composition12

    PubMed Central

    Ribeiro, Sandra M. L.; Kehayias, Joseph J.

    2014-01-01

    Reduction of lean mass is a primary body composition change associated with aging. Because many factors contribute to lean mass reduction, the problem has been given various names depending on the proposed cause, such as “age-related sarcopenia,” “dynapenia,” “myopenia,” “sarcopenic obesity,” or simply “sarcopenia.” There is currently no consensus on how to best diagnose the reduction of lean mass and its consequences on health. We propose that simple body composition methods can be used to indirectly evaluate sarcopenia, provided that those techniques are validated against the “quality of lean” criterion that associates muscle mass and metabolic function with the components of fat-free mass. Promising field methods include the use of stable isotopes for the evaluation of water compartments and new approaches to bioelectrical impedance analysis, which is also associated with the monitoring of water homeostasis. PMID:24829472

  12. Composition and function of P bodies in Arabidopsis thaliana

    PubMed Central

    Maldonado-Bonilla, Luis D.

    2014-01-01

    mRNA accumulation is tightly regulated by diverse molecular pathways. The identification and characterization of enzymes and regulatory proteins involved in controlling the fate of mRNA offers the possibility to broaden our understanding of posttranscriptional gene regulation. Processing bodies (P bodies, PB) are cytoplasmic protein complexes involved in degradation and translational arrest of mRNA. Composition and dynamics of these subcellular structures have been studied in animal systems, yeasts and in the model plant Arabidopsis. Their assembly implies the aggregation of specific factors related to decapping, deadenylation, and exoribonucleases that operate synchronously to regulate certain mRNA targets during development and adaptation to stress. Although the general function of PB along with the flow of genetic information is understood, several questions still remain open. This review summarizes data on the composition, potential molecular roles, and biological significance of PB and potentially related proteins in Arabidopsis. PMID:24860588

  13. Nutrition, endocrinology, and body composition during space flight

    NASA Technical Reports Server (NTRS)

    Lane, H. W.; Gretebeck, R. J.; Smith, S. M.

    1998-01-01

    Space flight induces endocrine changes that perturb metabolism. This altered metabolism affects both the astronauts' body composition and the nutritional requirements necessary to maintain their health. During the last 25 years, a combination of studies conducted on Skylab (the first U.S. space laboratory), U.S. Shuttle flights, and Soviet and Russian flights provides a range of data from which general conclusions about energy and protein requirements can be drawn. We have reviewed the endocrine data from those studies and related it to changes in body composition. From these data it appears that protein and energy intake of astronauts are similar to those on Earth. However, a combination of measures, including exercise, appropriate diet, and, potentially, drugs, is required to provide the muscle health needed for long duration space flight.

  14. Tungsten carbide nanorods with titanium dioxide composite counter electrode: Effect of NMP to enhanced efficiency in dye sensitized solar cell (DSSC)

    NASA Astrophysics Data System (ADS)

    Vijayakumar, P.; Pandian, M. Senthil; Ramasamy, P.

    2017-05-01

    Tungsten carbide Nanorods / Titanium dioxide (WC NRs/TiO2) composite material was successfully prepared and used as a counter electrode (CE) in DSSC. The N-Methyl pyrrolidone (NMP) played a crucial role in determining the efficiency of a resultant counter eelctrode material. The structural and morphological analysis were confirmed by XRD and FESEM with EDS. The photovoltaic performance was evaluated under the simulated conditions AM 1.5 light intensity (100 mW/cm2). DSSC fabricated using WC NRs/TiO2 with NMP showed an efficiency (η) of 4.7%, which is compared with WC NRs/TiO2 with 2-propanol based DSSC (η =2.9%). The results concluded NMP is the suitable organic binder for counter electrode preparation.

  15. Temperature Dependence on the Strength and Stress Rupture Behavior of a Carbon-Fiber Reinforced Silicon Carbide (C/SiC) Composite

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Calomino, Anthony

    2002-01-01

    Tensile strengths and stress rupture lives of carbon-fiber reinforced silicon carbide (C/SiC) specimens were measured at 800 C and are compared to previously reported 1200 C data. All tests were conducted in an environmental chamber containing 1000 ppm of oxygen in argon. The average 800 C tensile strength of 610 MPa is 10% greater than at 1200 C. Average stress rupture lives at 800 C were 2.5 times longer than those obtained at 1200 C. The difference in the 800 and 1200 C lives is related to the oxidation rate of the reinforcing carbon fibers, which is the primary damage mode of C/SiC composites in oxygen-containing environments.

  16. Effects of neutron irradiation on mechanical properties of silicon carbide composites fabricated by nano-infiltration and transient eutectic-phase process

    NASA Astrophysics Data System (ADS)

    Koyanagi, Takaaki; Ozawa, Kazumi; Hinoki, Tatsuya; Shimoda, Kazuya; Katoh, Yutai

    2014-05-01

    Unidirectional silicon carbide (SiC)-fiber-reinforced SiC matrix (SiC/SiC) composites fabricated by a nano-infiltration and transient eutectic-phase (NITE) process were irradiated with neutrons at 600 °C to 0.52 dpa, at 830 °C to 5.9 dpa, and at 1270 °C to 5.8 dpa. The in-plane and trans-thickness tensile and the inter-laminar shear properties were evaluated at ambient temperature. The mechanical characteristics, including the quasi-ductile behavior, the proportional limit stress, and the ultimate tensile strength, were retained subsequent to irradiation. Analysis of the stress-strain hysteresis loop indicated the increased fiber/matrix interface friction and the decreased residual stresses. The inter-laminar shear strength exhibited a significant decrease following irradiation.

  17. Composition of intraocular foreign bodies: experimental study of ultrasonographic presentation.

    PubMed

    Costa, Márcio Augusto Nogueira; Garcia, Patrícia Novita; Barroso, Letícia Fernandes; Ferreira, Marco Antonio; Okuda, Érika Araki; Allemann, Norma

    2013-01-01

    To investigate the reliability of ultrasound in determining the size and identify the sonographic features and artifacts generated by intraocular foreign bodies of different materials. Experimental study using 36 enucleated porcine eyes. Fragments of nine different compositions (wood, glass, plastic, cardboard, iron, aluminum, lead, powder and concrete) and similar dimensions (4 mm) were implanted via scleral incision into the vitreous cavity of 36 porcine eyes, four eyes were used for each material. Ultrasound examination was performed in all eyes using the contact technique, conductive gel and 10-MHz transducer (EZScan, Sonomed). Considering the material fragments of gunpowder, lead, concrete, aluminum, wood and glass, the size determined by ultrasound was considered statistically similar to the actual size. The material iron presented ultrasound-determined dimension statistically smaller than its actual size. Cardboard and plastic materials showed ultrasound-determined measurements far greater than the actual. All fragments of intraocular foreign bodies demonstrated hyper-reflective interfaces, irrespective of their composition. Whereas the artifacts generated by different materials, it was found that the materials iron, aluminum and lead showed reverberation of great extent. The material wood showed no reverberation. The length of the reverberation artifact for the materials iron, glass, aluminum and cardboard was lower when compared to other materials. All materials presented posterior shadowing artifact, with the exception of aluminum. Ultrasonography was considered a reliable technique to determine the size of intraocular foreign bodies in pigs, with little influence caused by its composition. Ultrasound artifacts generated were considered material-dependent and can assist the examiner to identify the nature of a foreign body of unknown etiology. Ultrasonography aided the surgeon to identify, locate and measure the intraocular foreign body, directing

  18. Effect of Environment on Stress-Rupture Behavior of a Carbon Fiber-Reinforced Silicon Carbide (C/SiC) Ceramic Matrix Composite

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Opila, Elizabeth J.; Calomino, Anthony; Kiser, J. Douglas

    2002-01-01

    Stress-rupture tests were conducted in air, vacuum, and steam-containing environments to identify the failure modes and degradation mechanisms of a carbon fiber-reinforced silicon carbide (C/SiC) composite at two temperatures, 600 and 1200 C. Stress-rupture lives in air and steam containing environments (50 - 80% steam with argon) are similar for a composite stress of 69 MPa at 1200 C. Lives of specimens tested in a 20% steam/argon environment were about twice as long. For tests conducted at 600 C, composite life in 20% steam/argon was 20 times longer than life in air. Thermogravimetric analysis of the carbon fibers was conducted under similar conditions to the stress-rupture tests. The oxidation rate of the fibers in the various environments correlated with the composite stress-rupture lives. Examination of the failed specimens indicated that oxidation of the carbon fibers was the primary damage mode for specimens tested in air and steam environments at both temperatures.

  19. Effect of Environment on Stress-Rupture Behavior of a Carbon Fiber-Reinforced Silicon Carbide (C/SiC) Ceramic Matrix Composite

    NASA Technical Reports Server (NTRS)

    Verrilli, Michael J.; Opila, Elizabeth J.; Calomino, Anthony; Kiser, J. Douglas

    2002-01-01

    Stress-rupture tests were conducted in air, vacuum, and steam-containing environments to identify the failure modes and degradation mechanisms of a carbon fiber-reinforced silicon carbide (C/SiC) composite at two temperatures, 600 and 1200 C. Stress-rupture lives in air and steam containing environments (50 - 80% steam with argon) are similar for a composite stress of 69 MPa at 1200 C. Lives of specimens tested in a 20% steam/argon environment were about twice as long. For tests conducted at 600 C, composite life in 20% steam/argon was 20 times longer than life in air. Thermogravimetric analysis of the carbon fibers was conducted under similar conditions to the stress-rupture tests. The oxidation rate of the fibers in the various environments correlated with the composite stress-rupture lives. Examination of the failed specimens indicated that oxidation of the carbon fibers was the primary damage mode for specimens tested in air and steam environments at both temperatures.

  20. Scaling of Adult Regional Body Mass and Body Composition as a Whole to Height: Relevance to Body Shape and Body Mass Index

    PubMed Central

    Schuna, John M.; Peterson, Courtney M.; Thomas, Diana M.; Heo, Moonseong; Hong, Sangmo; Choi, Woong; Heymsfield, Steven B.

    2015-01-01

    Objectives Adult body mass (MB) empirically scales as height (Ht) squared (MB ∝ Ht2), but does regional body mass and body composition as a whole also scale as Ht2? This question is relevant to a wide range of biological topics, including interpretation of body mass index. Methods Dual-energy x-ray absorptiometry (DXA) was used to quantify regional body mass (head [MH], trunk, arms, legs) and whole-body composition (fat, lean soft tissue [LST], and bone mineral content [BMC]) in non-Hispanic (NH) white, NH black, Mexican American, and Korean adults participating in the National Health and Nutrition Examination Survey (NHANES; n=17,126) and Korean NHANES (n=8,942). Regression models were developed to establish Ht scaling powers for each measured component with adjustments for age and adiposity. Results Exploratory analyses revealed a consistent scaling pattern across men and women of the four race/ethnic groups: regional mass powers, head (~0.8-1) < arms and trunk (~1.8-2.3) < legs (~2.3-2.6); and body composition, LST (~2.0-2.3) < BMC (~2.1-2.4). Small sex and race/ethnic differences in scaling powers were also observed. As body mass scaled uniformly across the eight sex and race/ethnic groups as Ht~2, tall and short subjects differed in body shape (e.g., Mh/Mb ∝ Ht−~1) and composition. Conclusions Adult human body shape and relative composition are a function of body size as defined by stature, a finding that has important implications in multiple areas of biological research. PMID:25381999

  1. Silicon carbide sewing thread

    NASA Technical Reports Server (NTRS)

    Sawko, Paul M. (Inventor)

    1995-01-01

    Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

  2. [Dermatoglyphics and body composition in obstructive sleep apnea].

    PubMed

    Mercanti, Luiz Bittencourt; Bezerra, Marcio L de S; Fernandes Filho, José; Struchiner, Claudio José

    2004-09-01

    Obesity is the main risk factor for obstructive sleep apnea syndrome (OSAS) and genetic patterns can modulate the pathogenesis of the disease. The aim of this study is to describe the anthropometrics and dermatoglyphics features among OSAS carriers. We collected information on Body Mass Index (BMI), Conicity Index (CI), Body Fat Mass (BFM), somatotype and fingerprints. Thirty-one cases of OSAS were compared to an equal number of controls. Membership to the obese category is based on observed BMI and BFM. The CI distribution among cases shows a strong central obesity component. The endomorph-mesomorph somatotype category predominates among cases showing high adiposity and relative muscle-skeletic development, such as relative linearity of great mass per unit of height. Increased morbidity, as given by more serious indices of apnea, correlates positively with higher mesomorphic predominance in the body composition. Analysis of dermatoglyphic data does not show significant statistical differences between OSAS--patients and controls.

  3. Protein composition of oil bodies from mature Brassica napus seeds.

    PubMed

    Jolivet, Pascale; Boulard, Céline; Bellamy, Annick; Larré, Colette; Barre, Marion; Rogniaux, Hélène; d'Andréa, Sabine; Chardot, Thierry; Nesi, Nathalie

    2009-06-01

    Seed oil bodies (OBs) are intracellular particles storing lipids as food or biofuel reserves in oleaginous plants. Since Brassica napus OBs could be easily contaminated with protein bodies and/or myrosin cells, they must be purified step by step using floatation technique in order to remove non-specifically trapped proteins. An exhaustive description of the protein composition of rapeseed OBs from two double-zero varieties was achieved by a combination of proteomic and genomic tools. Genomic analysis led to the identification of sequences coding for major seed oil body proteins, including 19 oleosins, 5 steroleosins and 9 caleosins. Most of these proteins were also identified through proteomic analysis and displayed a high level of sequence conservation with their Arabidopsis thaliana counterparts. Two rapeseed oleosin orthologs appeared acetylated on their N-terminal alanine residue and both caleosins and steroleosins displayed a low level of phosphorylation.

  4. Body composition and calcium metabolism in adult treated coeliac disease.

    PubMed Central

    Bodé, S; Hassager, C; Gudmand-Høyer, E; Christiansen, C

    1991-01-01

    Twenty two treated adult patients with coeliac disease (aged 20-70 years) were examined. Body composition was assessed from anthropometry and directly measured by dual photon absorptiometry. Bone mineral content was measured in the spine (dual photon absorptiometry) and at two forearm sites (single photon absorptiometry). Compared with age matched healthy subjects, treated coeliac patients had lower body mass index (-5%, p less than 0.05) and lower directly measured total body fat mass (-30%, p less than 0.001). They also had decreased bone mineral content (-9 to -13%, p less than 0.01) in the spine and in the forearms. The serum concentrations of albumin, D vitamin binding protein, and iron were reduced (-6 to -22%, p less than 0.01), but otherwise blood and urine analyses were normal. We conclude that this group of treated adult coeliac patients had a reduced fat mass and bone mineral content compared with the general population. PMID:1752465

  5. Body composition and somatotype of experienced mountain climbers.

    PubMed

    Barbieri, Davide; Zaccagni, Luciana; Cogo, Annalisa; Gualdi-Russo, Emanuela

    2012-03-01

    In order to evaluate body composition and somatotype, 10 Italian experienced mountain climbers were assessed from an anthropometric point of view, before a high altitude ascent. Body mass, height, girths, skinfolds, and bone breadths were gathered and used to calculate body composition and somatotype of each subject. Means and standard deviations of the subjects' anthropometric characteristics were calculated. Mesomorphism (5.28±1.10) is the dominant somatotype component in all but one the participants, endomorphism (1.55±0.49) is low, and body fat percentage (11.76%±2.93) is low. Comparisons with athletes involved in other climbing subdisciplines highlight the specificity of elite mountain climbers anthropometry. The elite mountain climbers in our sample were predominantly mesomorphic with somatotype attitudinal mean values lower than reported for male athletes participating in free-climbing, volleyball, gymnastics, and soccer. Anthropometric characteristics may therefore play a role in mountain climbing, even though the trainable components may be more relevant than the nontrainable ones.

  6. Bioimpedance measurements of human body composition: critical analysis and outlook.

    PubMed

    Matthie, James R

    2008-03-01

    Bioimpedance spectroscopy represents one of the largest emerging medical device technologies. The method is generally known as impedance spectroscopy and is an inexpensive, yet extremely powerful, analytical technique for studying the electrical properties of materials. Much of what we know about biological cells and tissues comes from use of this technique in vitro. Due to the high impedance of the cell membrane, current flow through the cell is frequency dependent and this allows the fluid volume inside versus outside the body's cells to be determined. The fluid outside the cells is primarily related to fluid volume status while the intracellular fluid also relates to the body's cellular mass. Technical advances have removed much of the method's basic complexities. The first commercial bioimpedance spectroscopy device for in vivo human body composition studies was introduced in 1990. Major strides have been made and the method is now poised to enter mainstream clinical medicine but the field is only in its infancy. This paper attempts to fully describe the current use of impedance in the body composition field.

  7. Heterogeneous composite bodies with isolated lenticular shaped cermet regions

    SciTech Connect

    Sherman, Andrew J.

    2009-12-22

    A heterogeneous body having ceramic rich cermet regions in a more ductile metal matrix. The heterogeneous bodies are formed by thermal spray operations on metal substrates. The thermal spray operations apply heat to a cermet powder and project it onto a solid substrate. The cermet powder is composed of complex composite particles in which a complex ceramic-metallic core particle is coated with a matrix precursor. The cermet regions are generally comprised of complex ceramic-metallic composites that correspond approximately to the core particles. The cermet regions are approximately lenticular shaped with an average width that is at least approximately twice the average thickness. The cermet regions are imbedded within the matrix phase and generally isolated from one another. They have obverse and reverse surfaces. The matrix phase is formed from the matrix precursor coating on the core particles. The amount of heat applied during the formation of the heterogeneous body is controlled so that the core particles soften but do not become so fluid that they disperse throughout the matrix phase. The force of the impact on the surface of the substrate tends to flatten them. The flattened cermet regions tend to be approximately aligned with one another in the body.

  8. Total body composition by dual-photon (153Gd) absorptiometry

    SciTech Connect

    Mazess, R.B.; Peppler, W.W.; Gibbons, M.

    1984-10-01

    The lean-fat composition (%FATR) of soft tissue and the mineral mass of the skeleton were determined in vivo using dual-photon (153Gd) absorptiometry (dose under 2 mrem). A rectilinear raster scan was made over the entire body in 18 subjects (14 female, 4 male). Single-photon absorptiometry (125I) measured bone mineral content on the radius. Percentage fat (%FATD) was determined in the same subjects using body density (from underwater weighing with correction for residual lung volume). Lean body mass (LBM) was determined using both %FATR and %FATD. Percentage fat from absorptiometry and from underwater density were correlated (r . 0.87). The deviation of %FATD from %FATR was due to the amount of skeletal mineral as a percentage of the LBM (r . 0.90). Therefore, skeletal variability, even in normal subjects, where mineral ranges only from 4 to 8% of the LBM, essentially precludes use of body density as a composition indicator unless skeletal mass is measured. Anthropometry (fatfolds and weight) predicted %FATR and LBM at least as well as did underwater density. The predictive error of %FATR from fatfolds was 5% while the predictive error in predicting LBM from anthropometry was 2 to 3 kg (3%).

  9. Anthropometry and body composition analysis in children with cerebral palsy.

    PubMed

    Tomoum, Hoda Y; Badawy, Nagia B; Hassan, Nayera E; Alian, Khadija M

    2010-08-01

    This study was undertaken to describe anthropometry, body composition parameters and assess serum levels of leptin and other biochemical markers of the nutritional status in a sample of Egyptian children with cerebral palsy(CP). Anthropometric measurements (body weight, knee height, head, mid-upper arm, waist and hip circumferences, triceps and subscapular skin-fold thickness) were taken. Using the bioelectrical impedance technique, total body water(TBW), fat-free mass, fat mass, fat percentage and basal metabolic rate(BMR) were calculated. Serum levels of total proteins, albumin, ferritin and leptin were measured. Results were compared to that of healthy controls. Patients had significantly lower anthropometric measurements than controls, except for mid-upper arm and hip circumferences, and subscapular skin-fold thickness which were not different in both groups. Fat mass, fat free mass, fat percentage, TBW and BMR were lower in the patients. Serum protein and leptin levels were not different in patients and controls, though other biochemical markers were reduced in the patients. Patients with more severe motor handicap had lower skin-fold thickness, fat percentage and serum ferritin than those with milder affection. Parameters of growth, body composition analysis and nutritional status are significantly altered in CP patients especially those with severe motor handicap and oromotor dysfunction. Copyright 2009 Elsevier Ltd and European Society for Clinical Nutrition and Metabolism. All rights reserved.

  10. Alterations of body mass index and body composition in atomic bomb survivors.

    PubMed

    Tatsukawa, Y; Misumi, M; Yamada, M; Masunari, N; Oyama, H; Nakanishi, S; Fukunaga, M; Fujiwara, S

    2013-08-01

    Obesity, underweight, sarcopenia and excess accumulation of abdominal fat are associated with a risk of death and adverse health outcomes. Our aim was to determine whether body mass index (BMI) and body composition, assessed with dual-energy X-ray absorptiometry (DXA), are associated with radiation exposure among atomic bomb (A-bomb) survivors. This was a cross-sectional study conducted in the Adult Health Study of the Radiation Effects Research Foundation. We examined 2686 subjects (834 men and 1852 women), aged 48-89 years (0-40 years at A-bomb exposure), for BMI analysis. Among them, 550 men and 1179 women underwent DXA in 1994-1996 and were eligible for a body composition study. After being adjusted for age and other potential confounding factors, A-bomb radiation dose was associated significantly and negatively with BMI in both sexes (P=0.01 in men, P=0.03 in women) and appendicular lean mass (P<0.001 in men, P=0.05 in women). It was positively associated with trunk-to-limb fat ratio in women who were less than 15 years old at the time of exposure (P=0.03). This is the first study to report a significant dose response for BMI and body composition 50 years after A-bomb radiation exposure. We will need to conduct further studies to evaluate whether these alterations affect health status.

  11. Silicon carbide

    SciTech Connect

    Ault, N.N.; Crowe, J.T. )

    1991-05-01

    This paper reports that, since silicon carbide (SiC) does not occur in nature, it must be synthesized by a high-temperature chemical reaction. The first commercial production began at the end of the 19th century when Acheson developed a process of reacting sand and coke in a resistance furnace. This process is still the basic SiC manufacturing process used today. High-quality silica sand (99.5% SiO{sub 2}), low-sulfur petroleum coke, and electricity (23.8 MJ/kg) are the major ingredients in the production of SiC. The reaction takes place in a trough-like furnace with a removable refractory side (or some similar configuration) and with permanent refractory ends holding carbon electrodes. When the furnace is started, the carbon electrodes are joined by the graphite core laid the length of the furnace near the center of the mixture which fills the furnace.

  12. Gravity, Body Mass and Composition, and Metabolic Rate

    NASA Technical Reports Server (NTRS)

    Pace, N.; Smith, A. H.

    1985-01-01

    Metabolic rate and body composition as a function of sex and age were defined in 5 species of common laboratory mammals, the mouse, hamster, rat, guinea pig and rabbit. Oxygen consumption and carbon dioxide production rates were measured individually in 6 male and 6 female animals for each of 8 age cohorts ranging from 1 month to 2 years, and for each of the species. From the results it is evident that among these small mammals there is no indication of scaling of muscularity to body size, despite the 100-fold difference in body mass represented by the skeletal musculature seems to reach a pronounced peak value at age 2 to 3 months and then declines, the fraction of the fat-free body represented by other body components in older animals must increase complementarily. Under normal gravity conditions muscularity in small laboratory mammals displays large, systematic variation as a function both of species and age. This variation must be considered when such animals are subjects of experiments to study the effects of altered gravitational loading on the skeletal musculature of the mammal.

  13. Gravity, Body Mass and Composition, and Metabolic Rate

    NASA Technical Reports Server (NTRS)

    Pace, N.; Smith, A. H.

    1985-01-01

    Metabolic rate and body composition as a function of sex and age were defined in 5 species of common laboratory mammals, the mouse, hamster, rat, guinea pig and rabbit. Oxygen consumption and carbon dioxide production rates were measured individually in 6 male and 6 female animals for each of 8 age cohorts ranging from 1 month to 2 years, and for each of the species. From the results it is evident that among these small mammals there is no indication of scaling of muscularity to body size, despite the 100-fold difference in body mass represented by the skeletal musculature seems to reach a pronounced peak value at age 2 to 3 months and then declines, the fraction of the fat-free body represented by other body components in older animals must increase complementarily. Under normal gravity conditions muscularity in small laboratory mammals displays large, systematic variation as a function both of species and age. This variation must be considered when such animals are subjects of experiments to study the effects of altered gravitational loading on the skeletal musculature of the mammal.

  14. The independent association between diet quality and body composition.

    PubMed

    Drenowatz, Clemens; Shook, Robin P; Hand, Gregory A; Hébert, James R; Blair, Steven N

    2014-05-12

    Excess body weight is associated with an imbalance between energy expenditure and dietary intake but evidence on the association between diet quality and body composition remains equivocal. Rather than relying on differences in diet quality between overweight/obese and normal weight adults, this study examined the association between the Healthy Eating Index 2010 (HEI-2010) and body fatness on a continuous scale, independent of physical activity (PA). Further the association between components of the HEI-2010 and risk for overweight/obesity was explored. 407 adults (27.6 ± 3.7 years) provided at least two 24-hour diet recalls over a period of 14 days, which were used to calculate the HEI-2010. Percent body fat (BF) was assessed via dual X-ray absorptiometry and PA was determined via a multi-sensor device, worn over a period of 10 days. PA was a stronger contributor to the variability in BF than the HEI-2010 and the association between HEI-2010 and BF was significant only in men. Particularly a high consumption of protein, sodium and empty calories increased the risk for overweight/obesity. Adherence to dietary guidelines positively affects body fatness in men, independent of PA. In contrast to current dietary recommendations, the risk for overweight/obesity was increased with a higher protein intake.

  15. Effect of surfactant concentration in the electrolyte on the tribological properties of nickel-tungsten carbide composite coatings produced by pulse electro co-deposition

    NASA Astrophysics Data System (ADS)

    Kartal, Muhammet; Uysal, Mehmet; Gul, Harun; Alp, Ahmet; Akbulut, Hatem

    2015-11-01

    A nickel plating bath containing WC particles was used to obtain hard and wear-resistant particle reinforced Ni/WC MMCs on steel surfaces for anti-wear applications. Copper substrates were used for electro co-deposition of Ni matrix/WC with the particle size of <1 μm tungsten carbide reinforcements. The influence of surfactant (sodium dodecyl sulfate, SDS) concentration on particle distribution, microhardness and wear resistance of composite coatings has been studied. The nickel films were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of the surfactant on the zeta potential, co-deposition and distribution of WC particles in the nickel matrix, as well as the tribological properties of composite coatings were also investigated. The tribological behaviors of the electrodeposited WC composite coatings sliding against M50 steel ball (Ø 10 mm) were examined on a CSM Instrument. All friction and wear tests were performed without lubrication at room temperature and in the ambient air (relative humidity 55-65%).

  16. Childhood thyroid function, body composition and cardiovascular function.

    PubMed

    Barjaktarovic, Mirjana; Korevaar, Tim I M; Gaillard, Romy; de Rijke, Yolanda B; Visser, Theo J; Jaddoe, Vincent W V; Peeters, Robin P

    2017-10-01

    The cardiovascular system is a known target for thyroid hormone. Early-life cardiovascular alterations may lead to a higher risk of cardiovascular disease in adulthood. Little is known about the effects of thyroid hormone on cardiovascular function during childhood, including the role of body composition in this association. Population-based prospective cohort of children (n = 4251, median age 6 years, 95% range: 5.7-8.0 years). Thyroid-stimulating hormone (TSH) and free thyroxine (FT4) concentrations were measured to assess thyroid function. Left ventricular (LV) mass was assessed with echocardiography. Arterial stiffness was assessed with carotid-femoral pulse wave velocity (CFPWV). Systolic and diastolic blood pressure (BP) was measured. Body composition was assessed by dual-energy X-ray absorptiometry scan. FT4 was inversely associated with LV mass (P = 0.002), and with lean body mass (P < 0.0001). The association of FT4 with LV mass was partially mediated through variability in lean body mass (55% mediated effect). TSH was inversely associated with LV mass (P = 0.010), predominantly in boys. TSH was positively associated with systolic and diastolic BP (both P < 0.001). FT4 was positively associated with CFPWV and diastolic BP (P < 0.0001, P = 0.008, respectively), and the latter association attenuated after adjustment for CFPWV. At the age of 6 years, higher FT4 is associated with lower LV mass (partially through effects on lean body mass) and with higher arterial stiffness, which may lead to higher BP. Our data also suggest different mechanisms via which TSH and FT4 are associated with cardiovascular function during early childhood. © 2017 European Society of Endocrinology.

  17. Computer technology to evaluate body composition, nutrition, and exercise.

    PubMed

    Katch, F I; Katch, V L

    1983-09-01

    The use of computer technology has made it possible to make accurate determinations of body composition, nutrition, and exercise. With the FITCOMP computer assessment system, detailed measurements of physique status have been made on a variety of world-class athletes, including professional football and baseball players, as well as on diverse groups of young and older men and women throughout the United States. The FITCOMP measurement system allows the user a choice of measurement techniques: fatfolds, girths, bone diameters, and hydrostatic weighing. Combined with body composition assessment is a nutrition and exercise plan. The nutrition plan is based on guidelines formulated by the American Dietetic Association. This application of computer technology is unique, because individuals can select the foods they will eat from a list of preferred choices from the basic food groups. Individual menu plans for breakfast, lunch, and dinner are generated to provide an optimal blend of nutrients aimed at achieving ideal body mass and fat percentage. This is coupled with an aerobic exercise program that is selected by the individual from nine different forms, including walking, jogging, running, swimming, cycling, and various sport activities. The caloric output is designed to reduce total body fat through reductions in body weight of 1.4 to 2.5 pounds per week, depending on the exercise selected and total weight loss necessary to achieve a weight goal (and ideal fat percentage). The aerobic exercise plan is based on the method of overload, where intensity and duration are periodically increased dependent on individual capabilities. The use of fitness-oriented computer technology makes it possible to prepare detailed reports about current status and progress as well as to systematize record keeping.

  18. Efficiency of energy utilization: effects of diet composition on body composition and mammary neoplasia

    SciTech Connect

    Boissonneault, G.A.; Elson, C.E.; Pariza, M.W.

    1986-03-05

    Multiple interactions between the efficiency of utilization of dietary fat and carbohydrate energy, energy intake changes in body composition and 7,12-dimethylbenz(a)anthracene (DMBA) DMBA-induced mammary tumorigenesis were examined using female F-344 rats. The rats were fed ad libitum a semipurified diet containing 5% corn oil (LF) from weaning to 50 d of age at which each was given, by gavage, 65 mg DMBA/kg body weight. The rats were randomly assigned to diets containing 5% 17.5% (MF) and 30% (HF) corn oil. All diets were balanced with respect per unit of energy in terms of protein, vitamins, minerals and fiber. For 28 d post-DMBA, the rats were fed 40 or 42 kcal daily and thereafter, diet was provided ad libitium. Daily energy intakes were recorded throughout the study. The mean energy intakes during the first 35 wk were: LF, 240 +/- 12.3 kcal/wk; MF, 237 +/- 11.7 kcal/wk; and HF, 237 +/- 11.1 kcal/wk. Body weight at 35 wk were: LF, 196 +/- 9.5 g; MF, 206 +/- 13.9 g; and HF, 210 +/- 20.6 g. No differences in tumor incidence (LF, 55%; MF, 46%; HF, 51%), tumors/group (LF, 24; MF, 28; HF, 25) and tumors/tumor-bearing rat (LF, 1.3 +/- 0.7; MF 1.6 +/- 1.0;p HF, 1.2 +/- 0.4) were noted. Within dietary groups tumor incidence was positively correlated with energy intake. However, there were no differences among the various parameters between dietary groups at any energy intake level. Body compositions were monitored during this study. The body fat mass and % carcass weight increased in parallel with the % dietary fat. Concomitantly, % lean body and, to a lesser extent lean body mass decreased. Both body size and body composition, influenced by energy intake and retention, affected the response to DMBA.

  19. Measurement and Predition Errors in Body Composition Assessment and the Search for the Perfect Prediction Equation.

    ERIC Educational Resources Information Center

    Katch, Frank I.; Katch, Victor L.

    1980-01-01

    Sources of error in body composition assessment by laboratory and field methods can be found in hydrostatic weighing, residual air volume, skinfolds, and circumferences. Statistical analysis can and should be used in the measurement of body composition. (CJ)

  20. Nutritional Markers and Body Composition in Hemodialysis Patients

    PubMed Central

    Valtuille, Rodolfo; Casos, Maria Elisa; Fernandez, Elmer Andres; Guinsburg, Adrian; Marelli, Cristina

    2015-01-01

    The aims of this study were to analyse body composition, to detect the presence of undernutrition, and to establish a relationship between undernutrition and the biological markers routinely used as indicators of nutritional status in hemodialysis (HD) patients (pts). We used a body composition monitor (BCM) that expresses body weight in terms of lean tissue mass (LTM) and fat tissue mass (FTM) independent of hydration status. From nine HD units, 934 pts were included. Undernutrition was defined as having a lean tissue index (LTI = LTM/height2) below the 10th percentile of a reference population. Biochemical markers and parameters delivered by BCM were used to compare low LTI and normal LTI groups. Undernutrition prevalence was 58.8% of the population studied. Low LTI pts were older, were significantly more frequently overhydrated, and had been on HD for a longer period of time than the normal LTI group. FTI (FTI = FTM/ height2) was significantly higher in low LTI pts and increased according to BMI. LTI was not influenced by different BMI levels. Albumin and C-reactive protein correlated inversely (r = −0.28). However neither of them was statistically different when considering undernourished and normal LTI pts. Our BCM study was able to show a high prevalence of undernutrition, as expressed by low LTI. In our study, BMI and other common markers, such as albumin, failed to predict malnutrition as determined by BCM. PMID:27347538

  1. New reusable elastomer electrodes for assessing body composition

    NASA Astrophysics Data System (ADS)

    Moreno, M.-V.; Chaset, L.; Bittner, P. A.; Barthod, C.; Passard, M.

    2013-04-01

    The development of telemedicine requires finding solutions of reusable electrodes for use in patients' homes. The objective of this study is to evaluate the relevance of reusable elastomer electrodes for measuring body composition. We measured a population of healthy Caucasian (n = 17). A measurement was made with a reference device, the Xitron®, associated with AgCl Gel electrodes (Gel) and another measurement with a multifrequency impedancemeter Z-Metrix® associated with reusable elastomer electrodes (Elast). We obtained a low variability with an average error of repeatability of 0.39% for Re and 0.32% for Rinf. There is a non significantly difference (P T-test > 0.1) about 200 ml between extracellular water Ve measured with Gel and Elast in supine and in standing position. For total body water Vt, we note a non significantly difference (P T-test > 0.1) about 100 ml and 2.2 1 respectively in supine and standing position. The results give low dispersion, with R2 superior to 0.90, with a 1.5% maximal error between Gel and Elast on Ve in standing position. It looks possible, taking a few precautions, using elastomer electrodes for assessing body composition.

  2. Nutritional Markers and Body Composition in Hemodialysis Patients.

    PubMed

    Valtuille, Rodolfo; Casos, Maria Elisa; Fernandez, Elmer Andres; Guinsburg, Adrian; Marelli, Cristina

    2015-01-01

    The aims of this study were to analyse body composition, to detect the presence of undernutrition, and to establish a relationship between undernutrition and the biological markers routinely used as indicators of nutritional status in hemodialysis (HD) patients (pts). We used a body composition monitor (BCM) that expresses body weight in terms of lean tissue mass (LTM) and fat tissue mass (FTM) independent of hydration status. From nine HD units, 934 pts were included. Undernutrition was defined as having a lean tissue index (LTI = LTM/height(2)) below the 10th percentile of a reference population. Biochemical markers and parameters delivered by BCM were used to compare low LTI and normal LTI groups. Undernutrition prevalence was 58.8% of the population studied. Low LTI pts were older, were significantly more frequently overhydrated, and had been on HD for a longer period of time than the normal LTI group. FTI (FTI = FTM/ height(2)) was significantly higher in low LTI pts and increased according to BMI. LTI was not influenced by different BMI levels. Albumin and C-reactive protein correlated inversely (r = -0.28). However neither of them was statistically different when considering undernourished and normal LTI pts. Our BCM study was able to show a high prevalence of undernutrition, as expressed by low LTI. In our study, BMI and other common markers, such as albumin, failed to predict malnutrition as determined by BCM.

  3. Effects of betaine on body composition, performance, and homocysteine thiolactone

    PubMed Central

    2013-01-01

    Background This study investigated the effects of long term betaine supplementation on body composition, performance, and homocysteine thiolactone (HCTL) in experienced strength trained men. Methods Twenty-three subjects were matched for training experience (4.8 ± 2.3 years) and body fat percentage (BF%: 16.9 ± 8.0%), randomly assigned to either a placebo (PL; n = 12) or betaine group (BET; n = 11; 2.5 g/day), and completed a 6 week periodized training program consisting of 3 two-week micro-cycles. Bench press and back squat training volumes were recorded and changes in training volume were assessed at each micro-cycle. Fasting urine was collected at baseline (BL), weeks 2, 4 and 6, and assayed for HCTL. Subjects were tested prior to and following 6 weeks of treatment. Arm and thigh cross sectional area (CSA) was estimated via girth and skin fold measurements. Body density was estimated via skin fold calipers and used to estimate BF%, fat mass (FM), and lean body mass (LBM). Performance was assessed via vertical jump (VJ), bench press 1 RM (BP), and back squat 1 RM (BS). Results Arm CSA increased significantly (p < .05) in BET but not PL. No differences existed between group and time for changes in thigh CSA. Back squat training volume increased significantly (p < .05) for both groups throughout training. Bench press training volume was significantly (p < .05) improved for BET compared to PL at microcycles one and three. Body composition (BF%, FM, LBM) improved significantly (p < .05) in BET but not PL. No differences were found in performance variables (BP, BS, VJ) between groups, except there was a trend (p = .07) for increased VJ power in BET versus PL. A significant interaction (p < .05) existed for HCTL, with increases from BL to week 2 in PL, but not BET. Additionally, HCTL remained elevated at week 4 in PL, but not BET. Conclusion Six-weeks of betaine supplementation improved body composition, arm size, bench press

  4. Body composition is associated with multisite lower body musculoskeletal pain in a community-based study.

    PubMed

    Brady, Sharmayne R E; Mamuaya, Bambino B; Cicuttini, Flavia; Wluka, Anita E; Wang, Yuanyuan; Hussain, Sultana Monira; Urquhart, Donna M

    2015-08-01

    Population-based studies suggest that pain in the lower body is common and that pain at multiple sites is more prevalent than single-site pain. Obesity is a risk factor for multisite musculoskeletal pain, but there are limited data on the role of body composition. Therefore, we sought to determine whether body composition is associated with multisite musculoskeletal pain involving the low back, knee, and foot. A total of 133 participants were recruited for a study examining the relationship between obesity and musculoskeletal disease. Participants completed validated questionnaires that examined levels of pain at the low back, knee, and foot. Body composition was assessed using dual-energy x-ray absorptiometry. Multisite pain was common, with 26.3% of participants reporting pain at 2 sites and 31.6% at 3 sites, and only 20% were pain free. The low back was the most common site of pain (63%). Greater fat mass and fat mass index, but not fat-free mass, were associated with pain at a greater number of sites, independent of age, gender, and fat-free mass (P < .01). Longitudinal studies exploring the mechanism of action by which increased fat mass is associated with pain may provide important insights into therapeutic strategies for the prevention of multisite pain. Greater fat mass and fat mass index were associated with a greater number of lower body pain sites, with no association observed for fat-free mass. Understanding the mechanism by which increased fat mass is associated with pain may provide important insights into therapeutic strategies for the prevention of pain. Copyright © 2015 American Pain Society. Published by Elsevier Inc. All rights reserved.

  5. Body size, body composition, and metabolic profile explain higher energy expenditure in overweight children.

    PubMed

    Butte, Nancy F; Puyau, Maurice R; Vohra, Firoz A; Adolph, Anne L; Mehta, Nitesh R; Zakeri, Issa

    2007-12-01

    Lower relative rates of energy expenditure (EE), increased energetic efficiency, and altered fuel utilization purportedly associated with obesity have not been demonstrated indisputably in overweight children. We hypothesized that differences in energy metabolism between nonoverweight and overweight children are attributable to differences in body size and composition, circulating thyroid hormones, sympathetic nervous system, and adrenomedullary activity. A total of 836 Hispanic children, 5-19 y old, participated in 24-h calorimetry, anthropometric, and dual-energy X-ray absorptiometry measurements. Biochemistries were determined by standard techniques. Absolute total EE (TEE) and its components (sleep EE, basal EE, sedentary EE, cycling EE, walking EE, activity EE, nonexercising activity thermogenesis) were higher in overweight children (P = 0.001). Net mechanical energetic efficiency of cycling was lower in overweight children (P = 0.001). Adjusting for body size and composition accounted for differences in TEE, its components, and energetic efficiency. Net carbohydrate and fat utilization did not differ between groups. TEE was independently influenced by sex, Tanner stage, fat free mass, fat mass (FM), fasting serum nonesterified fatty acids (NEFA), leptin, free thyroxine, triiodothyronine, and 24-h urinary norepinephrine and epinephrine. Fat utilization was independently associated with age2, sex, FM, fasting serum NEFA, triacylglycerol, adiponectin, leptin, total thyroxine, and free triiodothyronine. Higher EE in overweight children was largely explained by differences in body size and composition, with minor contributions of thyroid and sympathoadrenal systems. Alterations in EE, energetic efficiency, and substrate utilization were not evident in the overweight children.

  6. Body mass index and body composition among rescue firefighters personnel in Selangor, Malaysia

    NASA Astrophysics Data System (ADS)

    Rahimi, Nor Atiqah; Sedek, Razalee; Teh, Arnida Hani

    2016-11-01

    Obesity is a major public health problem in general population and there is no exception for firefighters. This disorder is definitely a burden for firefighters as they needed to be physically fit in order to work in dangerous situation and extinguishing fires. The purposes of this study were to determine physical characteristics and body composition among Malaysian Firefighters (MF) and to explore their association. This cross-sectional study involved 330 rescue firefighters aged between 20-50 years old from nine different districts in Selangor conducted between August and November 2015. Anthropometric measurements included height, weight and waist circumference (WC). Body composition was measured using bioelectrical impedance. The mean height, weight, body mass index (BMI), WC and body fat percentage were 169.4±5.3 cm, 74.5±12.2 kg, 25.9±3.82 kg/m2, 90.7±48.3 cm and 25.8±6.2 % respectively. The results also showed that 0.6% of them were underweight, 41.5% were normal, 44.8% were overweight and 13% were obese. The percentage of 34.8% firefighters with WC values of more than 90 cm means that they were at greater risk to have cardiovascular and diabetes disease. Body composition analysis showed that 75.5% of the subjects have high body fat level, 19.7% subjects were in healthy range but only 4.8% were considered as lean subjects. BMI was highly correlated with weight (r=0.917, p<0.01), WC (r=0.858, p<0.01) and body fat percentage (r=0.757, <0.01). Body fat percentage also showed to have a high correlation with BMI (r=0.757, p<0.01) and WC (r=0.693, p<0.01). Furthermore, overweight and obesity were found to be more prevalent among firefighters personnel of older age, married, less educated and have longer duration of services. It can be concluded that more than half of the firefighter personnel were either overweight or obese and 35% of them were at greater risk of having non-communicable diseases. This study provides useful information and serves as a source of

  7. Effects of Rapid or Slow Body Mass Reduction on Body Composition in Adult Rats

    PubMed Central

    Tai, Shinji; Tsurumi, Yasukimi; Yokota, Yukari; Masuhara, Mitsuhiko; Okamura, Koji

    2009-01-01

    Whether the speed of body mass (BM) reduction influences the body composition is uncertain. To investigate the effects of rapid vs slow body mass reduction on body composition, rats were divided into three groups; fed ad libitum for 16-day (Control, C); received restricted food intake during 16-day to decrease BM slowly (Slow, S); or fed ad libitum for 13-days and fasted for the last 3 days to rapidly reach a BM comparable to that of S (Rapid, R). Drinking water was restricted for R on day 16 to rapidly decrease their BM. All rats trained during the study. Final BM and adipose tissues mass were similar for R and S, and both were lesser than C. The skeletal muscle mass did not decrease in R and S. The liver mass was lower in R and S than C, and the decrease tended to be greater in R than S. Both the stomach and small intestine masses were significantly lower in R than C, but did not differ between S and C. In conclusion, differences of the speed of BM reduction affect the splanchnic tissues, and the decrease in splanchnic tissue mass was greater with rapid than slow BM reduction. PMID:19794927

  8. Longitudinal body composition of children born to normal weight, overweight and obese mothers

    USDA-ARS?s Scientific Manuscript database

    Objective: The longitudinal trajectories of body composition of children born to normal weight, overweight and obese mothers have not been evaluated using precise body composition methods. This study investigated the relationship between maternal pre-pregnancy BMI and offspring body composition traj...

  9. Seasonal variations in the body composition of lightweight rowers.

    PubMed Central

    Morris, F L; Payne, W R

    1996-01-01

    OBJECTIVE: To monitor the seasonal body composition alterations in 18 lightweight rowers (six females, 12 males) across a rowing season incorporating preseason, early competition, competition, and postseason. METHODS: Subject age was 23.1 (SD 4.5) years, height 170.8 (5.6) cm (female, 23.5 (3.5) years, 180.5 (2.7) cm (male). Body weight, fat mass, and fat-free mass (FFM) were assessed using dual energy x ray absorptiometry (DXA-L Lunar) and skinfold techniques. Weight control techniques were documented before major regattas by a questionnaire. RESULTS: Female body weight was reduced from 61.3 (2.9) to 57.0 (1.1) kg (5.9%), while male body weight was reduced from 75.6 (3.1) to 69.8 (1.6) kg (7.8%) preseason to competition season respectively. These body weight reductions were mirrored by a significant reduction in fat mass as indicated by the sum of skinfolds [female seven sites: 80.9 (8.1) to 68.2 (11.8) mm; male eight sites: 54.2 (8.7) to 41.8 (4.8) mm], percentage body fat [female 22.1 (1.0) to 19.7 (2.4)%; male 10.0 (0.9) to 7.8 (0.8)%], and total fat [female 12.5 (5.2) to 10.9 (1.4) kg; male 7.3 (1.9) to 5.6 (1.8) kg] (DXA). In contrast, no changes were observed in FFM despite a season of intensive rowing training. Seasonal body weight control was achieved through reduced total energy and dietary fat intakes. Acute body weight reductions were achieved by exercise in 73.3% of participants, food restriction in 71.4%, and fluid restrictions in 62.9%. CONCLUSIONS: Seasonal body weight alterations in lightweight rowers are in response to a significant reduction in fat mass. However, the weight restrictions appear to be limiting an increase in FFM which could be beneficial to rowing performance. Images Figure 2 Figure 3 PMID:9015590

  10. Body Composition in Adult Patients with Thalassemia Major

    PubMed Central

    Alexiou, Evangelos; Thriskos, Paschalis; Fezoulidis, Ioannis; Vassiou, Katerina

    2016-01-01

    Objective. To assess body composition in adult male and female patients with thalassemia major by dual-energy X-ray absorptiometry (DXA) and to compare the findings with a group of healthy age-matched controls. Methods. Our study group included sixty-two patients (27 males, mean age 36 years, and 35 females, mean age 36.4 years) and fifteen age-matched healthy controls. All patients had an established diagnosis of thalassemia major and followed a regular blood transfusion scheme since childhood and chelation treatment. Fat, lean, and bone mineral density (BMD) were assessed with dual-energy X-ray absorptiometry. Ferritin levels and body mass index of all patients and controls were also recorded. Student t-test and Wilcoxon test were performed and statistical significance was set at p < 0.05. Results. BMD and whole body lean mass are lower in both male and female adult patients compared with controls (p < 0.01 in both groups), whereas whole body fat mass was found to have no statistically significant difference compared to controls. Regional trunk fat around the abdomen was found to be lower in male patients compared to controls (p = 0.02). Conclusion. Severe bone loss and diminished lean mass are expected in adult male and female patients with thalassemia major. Fat changes seem to affect mainly male patients. PMID:27956899

  11. Iron status and body composition of competitive female ice skaters

    SciTech Connect

    Ziegler, P.J.; Caldwell, M.J.; Gerber, L.E.; Rand, A.G.

    1986-03-01

    The effects of training and competition on iron status and body composition of ice skaters were evaluated pre-season (PS), during competitive season (CS), and out of season (OS). Eighteen females, aged 14 to 16, with mean heights and weights of 158.2 +/- 4.1cm, and 50.9 +/- 5.2 kg, respectively, participated. During each season, fasted, cenous blood samples were analyzed for hematocrit (Hct), hemoglobin (Mg), serum iron (SI), total iron-binding capacity (TIBC), and serum ferritin (F). Percent body fat was estimated from skinfolds (SF) and from underwater weighting (UW). Mean percent PS body fat was 20% by both UW and SF. UW values did not change significantly with seasons. In contrast, percent SF body fat were significantly higher OS than PS and CS. Heights and weights did not differ significantly during the year. Mean Hcts were normal throughout the seasons, however mean Hbs were significantly lower during CS than OS (14.5 vs. 15.5gm/dl, respectively). Mean F did not vary significantly PS and OS. Mean SI and TIBC were in normal ranges although OS means were significantly higher than PS and CS. The results indicate that the iron status of the ice skaters in the study varied with the training seasons and was lower during CS.

  12. Body weight and composition dynamics of fall migrating canvasbacks

    USGS Publications Warehouse

    Serie, J.R.; Sharp, D.E.

    1989-01-01

    We studied body weights and composition of canvasbacks (Aythya valisineria) during fall migration 1975-77 on stopover sites along the upper Mississippi River near La Crosse, Wisconsin (Navigational Pools 7 and 8) and Keokuk, Iowa (Navigational Pool 19). Body weights varied (P < 0.001) by age and sex without interaction. Weights varied by year (P < 0.001) on Pools 7 and 8. Mean weights increased (P < 0.01) within age and sex classes by date and averaged 3.6 and 2.7 g daily on Pools 7 and 8 and Pool 19, respectively. Percent fat was highly correlated (P < 0.001) with carcass weight for each age and sex. Live weight was a good predictor of total body fat. Mean estimated total body fat ranged from 200 to 300 g and comprised 15-20% of live weights among age and sex classes. Temporal weight patterns were less variable for adults than immatures, but generally increased during migration. Length of stopover varied inversely with fat reserves among color-marked adult males. Variation in fat condition of canvasbacks during fall may explain the mechanism regulating population ingress and egress on stopover sites. Fat reserves attained by canvasbacks during fall stopover may have adaptive significance in improving survival by conditioning for winter.

  13. Body Composition in Adult Patients with Thalassemia Major.

    PubMed

    Vlychou, Marianna; Alexiou, Evangelos; Thriskos, Paschalis; Fezoulidis, Ioannis; Vassiou, Katerina

    2016-01-01

    Objective. To assess body composition in adult male and female patients with thalassemia major by dual-energy X-ray absorptiometry (DXA) and to compare the findings with a group of healthy age-matched controls. Methods. Our study group included sixty-two patients (27 males, mean age 36 years, and 35 females, mean age 36.4 years) and fifteen age-matched healthy controls. All patients had an established diagnosis of thalassemia major and followed a regular blood transfusion scheme since childhood and chelation treatment. Fat, lean, and bone mineral density (BMD) were assessed with dual-energy X-ray absorptiometry. Ferritin levels and body mass index of all patients and controls were also recorded. Student t-test and Wilcoxon test were performed and statistical significance was set at p < 0.05. Results. BMD and whole body lean mass are lower in both male and female adult patients compared with controls (p < 0.01 in both groups), whereas whole body fat mass was found to have no statistically significant difference compared to controls. Regional trunk fat around the abdomen was found to be lower in male patients compared to controls (p = 0.02). Conclusion. Severe bone loss and diminished lean mass are expected in adult male and female patients with thalassemia major. Fat changes seem to affect mainly male patients.

  14. [An instrument for estimating human body composition using impedance measurement].

    PubMed

    Yin, J; Peng, C

    1997-03-01

    According to the impedance feature of biological tissue, the instrument was designed at 1, 5, 10, 50, 100kHz to measure human impedance, and then to calculate human FAT, FFM, FAT%, TBW, ECW, ICW and so on. A 8031 singlechip microprocessor contacuting used as a control center in the instrument. The part of electric circuit contacuting human body in the instrument was unreally earthing. The instrument was safty, effective, repeatable, and easily manpulative. Prelimintary clinical experiment showed the results measured with the instrument could effectively reflect practical, status of human composition.

  15. The effects of different exercise programmes on female body composition.

    PubMed

    de Mendonça, Rosa Maria Soares Costa; de Araújo Júnior, Adenilson Targino; de Sousa, Maria do Socorro Cirilo; Fernandes, Helder Miguel

    2014-09-29

    The purpose of this study was to verify the effects of 16 weeks of practicing different exercise programmes on body composition. This is an exploratory and descriptive study of 89 women aged 25 to 55 years (41.42 ± 9.23 years). The subjects were randomly divided into three experimental groups (EG): practitioners of strength training (SG), dance (DG), hydrogymnastics (HG), and a control group (CG) with sedentary women. Measurements of body mass and height, circumferences of the chest, waist, abdomen, hips, thighs, calves, and skinfolds of the triceps, suprailiac and thigh were registered in three different moments: prior to the commencement of the training program, again after 8 weeks of training, and finally after 16 weeks of training. Body density was estimated by using the trifold protocol by Jackson, Pollock and Ward. The ANOVA and deltas of change (Δ%) were used for data analysis. The level of significance was set at p<0.05. The effects of greater statistical significance on body composition related the variables "time", "group" and the interaction between the two (time × group) were observed for the percentage of fat - F% (F (1.79, 152.52) = 24.59, p <0.001, η (2) = 0.22), fat mass - FM (F (1.75, 149.01) = 12.65, p <0.001, η (2) = 0.13) and lean mass - LM (F (1.77, 150.66) = 47.38, p <0.001, η (2) = 0.36). The HG and SG were more beneficial in reducing F%. It was observed that the EG indicated healthier anthropometric aspects compared to the CG, regardless of the type of exercise programmes practiced. The time factor was more representative over the effects of exercise on anthropometric dimensions.

  16. Muscle strength and body composition in severe obesity.

    PubMed

    Gadducci, Alexandre Vieira; de Cleva, Roberto; de Faria Santarém, Gabriela Correia; Silva, Paulo Roberto Santos; Greve, Julia Maria D'Andréa; Santo, Marco Aurélio

    2017-05-01

    The aim of our study was to evaluate associations between maximum voluntary contraction torques of the lower limbs and body composition for subjects with severe obesity. Body composition was evaluated by bioelectrical impedance analysis, and maximum voluntary contraction torques of the lower limbs were measured using an isokinetic dynamometer. One hundred thirty-two patients were enrolled (100 females and 32 males). Eighty-seven patients had a body mass index between 40 and 49.9 kg/m2 (the A group), and 45 patients had a body mass index between 50 and 59.9 kg/m2 (the B group). Absolute extension and flexion torques had weak associations with fat-free mass but a moderate association with absolute extension torque and fat-free mass of the lower limbs. There were no significant differences between the A and B groups with respect to absolute extension and flexion torques. For the A group, absolute extension and flexion torques were moderately associated with fat-free mass and with fat-free mass of the lower limbs. For the B group, there were only moderate associations between absolute extension and flexion torques with fat-free mass of the lower limbs. Our findings demonstrate that both groups exhibited similar absolute torque values. There were weak to moderate associations between absolute extension and flexion torques and fat-free mass but a moderate association with fat-free mass of the lower limbs. Individuals with severe obesity should strive for greater absolute torques, fat-free mass and especially fat-free mass of the lower limbs to prevent functional limitations and physical incapacity.

  17. Dietary intake and body composition of prepubescent female aesthetic athletes.

    PubMed

    Soric, Maroje; Misigoj-Durakovic, Marjeta; Pedisic, Zeljko

    2008-06-01

    The purpose of this study was to assess dietary intake and body composition of prepubescent girls competing in 3 aesthetic sports (artistic and rhythmic gymnastics and ballet). Because physiological demands of ballet training are similar to those in other aesthetic sports, ballet dancers were, for the purpose of this study, regarded as athletes. The sample consisted of 39 athletes (median age, 11 years, range 9-13) and 15 controls (median age, 11 years, range 10-12). Dietary intake was assessed using a quantitative food frequency questionnaire, and body composition, by means of anthropometry. There was no significant difference in total energy intake between groups, but there was a significant difference in energy substrate distribution. Artistic gymnasts reported significantly higher carbohydrate and lower fat contribution to total energy (57% +/- 6% and 29% +/- 5%, respectively) than rhythmic gymnasts (48% +/- 6% and 36% +/- 5%), ballet dancers (51% +/- 4% and 34% +/- 3%), or controls (51% +/- 5% and 34% +/- 4%). Relative to body weight, artistic gymnasts reported higher intake of carbohydrates (9.1 +/- 4.2 g/kg) than rhythmic gymnasts (5.6 +/- 3.1 g/kg), ballet dancers (6.6 +/- 2.5 g/kg), or controls (5.4 +/- 1.9 g/kg). Artistic gymnasts also had the lowest body-fat percentage among the groups. In all the groups mean reported daily intakes of most nutrients were higher than the current daily recommended intakes. The exceptions were dietary fiber and calcium. The proportion of athletes with an inadequate reported intake was highest for phosphorus (33%), followed by vitamin A and niacin (18%) and zinc (13%).

  18. Boron-carbide-aluminum and boron-carbide-reactive metal cermets

    DOEpatents

    Halverson, Danny C.; Pyzik, Aleksander J.; Aksay, Ilhan A.

    1986-01-01

    Hard, tough, lightweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidation step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modulus of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi.sqroot.in. These composites and methods can be used to form a variety of structural elements.

  19. Association between body composition and body mass index in young Japanese women.

    PubMed

    Yamagishi, Hiroyuki; Kitano, Takao; Kuchiki, Tsutomu; Okazaki, Hideki; Shibata, Shigeo

    2002-06-01

    The National Nutrition Survey of Japan indicated a trend toward a decreasing body mass index (BMI; kg/m2) among young Japanese women. Current studies suggest that not-high BMI often does not correlate with not-high body fat percentage. Recently, the classification of BMI in adult Asians was proposed by the International Obesity Task Force. The addition of an "at risk of overweight" category, BMI as 23.0-24.9, was intended to prevent chronic diseases. We investigated the association between body fat percentage (BF%) and BMI to evaluate the screening performance of BMI focused on individual preventive medicine. The subjects consisted of 605 female college students. The subjects' ages (y), heights (cm), body weights (kg), BMIs, and BF percents with underwater weighing expressed as the means +/- SD were 19.6 +/- 0.5, 158.7 +/- 5.6, 53.8 +/- 7.2, 21.3 +/- 2.4, and 24.9 +/- 4.9, respectively. We defined high BF% as +/- 85th percentile of BF% (29.8%). High-BF% individuals are often not classified into BMI > or = 23.0 because their BMI readings are very broad (18.4-31.7). In comparison to the screening performances (specificity and sensitivity), BMI > or = 23.0 (85.3% and 52.1%, respectively), rather than BMI > or = 25.0 (96.7% and 29.8%, respectively), is recommended for the mass evaluation of fatness. For this reason, the BMI "at risk of overweight" category is characterized as the threshold of increasing the appearance ratio of high-BF% individuals. In conclusion, the BMI > or = 25.0 kg/m2 category is determined as high BF%, regardless of body composition measurement for mass evaluation as a result of quite high specificity. Even so, body composition measurement is necessitated by the individual evaluation of fatness focused on preventive medicine because BMI performed a poor representation of body composition, especially BMI < 25.0 kg/m2 individuals.

  20. Elasticity and inelasticity of biomorphic carbon, silicon carbide, and SiC/Si composite produced on the basis of medium density fiberboard

    NASA Astrophysics Data System (ADS)

    Kardashev, B. K.; Orlova, T. S.; Smirnov, B. I.; de Arellano-Lopez, A. R.; Martinez-Fernandez, J.

    2010-10-01

    The amplitude and temperature dependences of the Young’s modulus and the internal friction (ultrasonic absorption) of biomorphic carbon, silicon carbide, and SiC/Si composite produced from medium density fiberboard (MDF) by pyrolysis (carbonization), followed by infiltration of molten silicon into the prepared carbon preform have been studied in the temperature range 100-293 K in air and under vacuum. The measurements have been performed by the acoustic resonance method with the use of a composite vibrator for longitudinal vibrations at frequencies of approximately 100 kHz. The data obtained by acoustic measurements of the amplitude dependences of the elastic modulus have been used for evaluating the microplastic properties of samples under study. It has been shown that the Young’s modulus, the decrement of elastic vibrations, and the conventional microyield strength of the MDF samples differ from the corresponding data for previously studied similar materials produced from natural eucalyptus, beech, sapele, and pine woods. In particular, the desorption of environmental molecules at small amplitudes of vibrations, which is typical of biomorphic materials based on natural wood, is almost absent for the MDF samples. The results obtained have been explained by different structures and the influence of pores and other defects, which, to a large extent, determine the mechanical characteristics of the biomaterials under investigation.

  1. Technical note: Estimating body weight and body composition of beef cattle trough digital image analysis.

    PubMed

    Gomes, R A; Monteiro, G R; Assis, G J F; Busato, K C; Ladeira, M M; Chizzotti, M L

    2016-12-01

    The use of digital images could be a faster and cheaper alternative technique to assess BW, HCW, and body composition of beef cattle. The objective of this study was to develop equations to predict body and carcass weight and body fat content of young bulls using digital images obtained through a Microsoft Kinect device. Thirty-five bulls with an initial BW of 383 (±5.38) kg (20 Black Angus, 390 [±7.48] kg initial BW, and 15 Nellore, 377 [±8.66] kg initial BW) were used. The Kinect sensor, installed on the top of a cattle chute, was used to take infrared light-based depth videos, recorded before the slaughter. For each animal, a quality control was made, running and pausing the video at the moment that the animal was standing with its body and head in line. One frame from recorded videos was selected and used to analyze the following body measurements: chest width, thorax width, abdomen width, body length, dorsal height, and dorsal area. From these body measurements, 23 indexes were generated and tested as potential predictors. The BW and HCW were assessed with a digital scale, whereas empty body fat (EBF) was estimated through ground samples of all tissues. To better understand the relationship among the measurements, the correlations between final BW (488 [±10.4] kg), HCW (287 [±12.5] kg), EBF (14 [±0.610] % empty BW) content, body measurements (taken through digital images), and developed indexes were evaluated. The REG procedure was used to develop the regressions, and the important independent variables were identified using the options STEPWISE and Mallow's Cp in the SELECTION statement. Chest width was the trait most related to weights and the correlations between this measurement and BW and HCW were above 0.85. The analysis of linear regressions between observed and predicted values showed that all models pass through the origin and have a slope of unity (null hypothesis [H]: = 0 and = 1; ≥ 0.993). The models to estimate BW and HCW of Angus and

  2. Determination of body composition in growing rats by total body electrical conductivity.

    PubMed

    Morbach, C A; Brans, Y W

    1992-04-01

    Total body electrical conductivity (TOBEC), measured with an Em-Scan SA-1 analyzer, was evaluated as a means of estimating fat-free mass and total body water content noninvasively in small laboratory animals. Ninety-four rats whose weight ranged from 5.53 to 170.84 g at 0-50 days of age were studied. The animals were killed by intraperitoneal injection of a pentobarbital overdose. After weight, crown-rump length (CRL) and TOBEC were measured, and the animals were minced with scissors and desiccated to constant weight in a convection oven. Fat was extracted by multiple bathings in petroleum ether followed by Soxhlet extraction. Fifty-four rats were used to determine the relation between fat-free mass (FFM), total body water (TBW), and TOBEC# (E) by regression analysis. The best correlations were observed between FFM and (E x CRL)1/2 (r = 0.995, p less than 0.0001). Forty rats were used to determine the predictive value of TOBEC estimates. With this instrument, TOBEC tended to underestimate FFM by an average of 3.9% and TBW by 5.3%. Accuracy was questionable for animals smaller than 13 g and TOBEC did not provide useful estimates of total body fat. Subject to these limitations, TOBEC instruments should prove to be useful for sequential in vivo estimations of body composition during growth and development of small animals.

  3. Biological characteristics of the MG-63 human osteosarcoma cells on composite tantalum carbide/amorphous carbon films.

    PubMed

    Chang, Yin-Yu; Huang, Heng-Li; Chen, Ya-Chi; Hsu, Jui-Ting; Shieh, Tzong-Ming; Tsai, Ming-Tzu

    2014-01-01

    Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics.

  4. Effect of added silicon carbide nanowires and carbon nanotubes on mechanical properties of 0-3 natural rubber composites

    NASA Astrophysics Data System (ADS)

    Janyakunmongkol, Khantichai; Nhuapeng, Wim; Thamjaree, Wandee

    2016-01-01

    In this work, the mechanical properties of 0-3 nanocomposite materials containing silicon carbide nanowires (SiCNWs), carbon nanotubes (CNTs), and natural rubber were studied. The SiCNWs and CNTs were used as reinforcement fiber whereas natural rubber was used as the matrix phase. The chemical vapor depositions (CVD) was used for synthesizing the nanowire and nanotube phases. The volume fraction of reinforcement was varied from 0 to 10%. The nanophases were mixed in the natural rubber matrix and molded by the hand lay-up technique. The mechanical properties of the samples were examined and compared with those of neat natural rubber. From the results, it was found that the hardness and density of the samples increased with the quantities of nanophases. The nanocomposites with a volume fraction of 10% exhibited maximum hardness (50.5 SHORE A). The maximum tensile strength and extent of elongation at break of the samples were obtained from the 4% volume fraction sample, which were 16.13 MPa and 1,540%, respectively.

  5. Biological Characteristics of the MG-63 Human Osteosarcoma Cells on Composite Tantalum Carbide/Amorphous Carbon Films

    PubMed Central

    Chang, Yin-Yu; Huang, Heng-Li; Chen, Ya-Chi; Hsu, Jui-Ting; Shieh, Tzong-Ming; Tsai, Ming-Tzu

    2014-01-01

    Tantalum (Ta) is a promising metal for biomedical implants or implant coating for orthopedic and dental applications because of its excellent corrosion resistance, fracture toughness, and biocompatibility. This study synthesizes biocompatible tantalum carbide (TaC) and TaC/amorphous carbon (a-C) coatings with different carbon contents by using a twin-gun magnetron sputtering system to improve their biological properties and explore potential surgical implant or device applications. The carbon content in the deposited coatings was regulated by controlling the magnetron power ratio of the pure graphite and Ta cathodes. The deposited TaC and TaC/a-C coatings exhibited better cell viability of human osteosarcoma cell line MG-63 than the uncoated Ti and Ta-coated samples. Inverted optical and confocal imaging was used to demonstrate the cell adhesion, distribution, and proliferation of each sample at different time points during the whole culture period. The results show that the TaC/a-C coating, which contained two metastable phases (TaC and a-C), was more biocompatible with MG-63 cells compared to the pure Ta coating. This suggests that the TaC/a-C coatings exhibit a better biocompatible performance for MG-63 cells, and they may improve implant osseointegration in clinics. PMID:24760085

  6. Gender differences in body composition, physical activity, eating behavior and body image among normal weight adolescents--an evolutionary approach.

    PubMed

    Kirchengast, Sylvia; Marosi, Andrea

    2008-12-01

    Body composition but also physical activity patterns underlie gender typical differences throughout human life. In the present study the body composition of 354 girls and 280 boys ageing between 11 and 18 years originating from Eastern Austria were analyzed using bioelectrical impedance method. Normal weight according to body mass index categories was a strict inclusion criterion. Information regarding physical activity during school and leisure time, daily nutritional habits, subjective body satisfaction and weight control practices were collected by means of a structured and standardized questionnaire. Results of the analyses reveal that--as to be expected--adolescent boys and girls differed significantly in body composition, but also in physical activity patterns. Even normal weight girls exhibited a significantly higher amount of absolute and relative fat mass, whereas normal weight boys showed a significantly higher amount of fat free body mass. Furthermore male adolescents were significantly more physically active than their female counterparts. According to the results of multiple regression analyses physical activity patterns had beside sex an independent influence on body composition parameters during adolescence. In contrast, girls and boys showed only minor differences in nutritional habits and weight control practices. Nutritional habits, body satisfaction and weight control practices were not significantly related to body composition parameters. The observed gender differences in body composition as well as in physical activity patterns are interpreted in an evolutionary sense.

  7. Validation of Body Condition Indices and Quantitative Magnetic Resonance in Estimating Body Composition in a Small Lizard

    PubMed Central

    WARNER, DANIEL A.; JOHNSON, MARIA S.; NAGY, TIM R.

    2017-01-01

    Measurements of body condition are typically used to assess an individual’s quality, health, or energetic state. Most indices of body condition are based on linear relationships between body length and mass. Although these indices are simple to obtain, nonlethal, and useful indications of energetic state, their accuracy at predicting constituents of body condition (e.g., fat and lean mass) are often unknown. The objectives of this research were to (1) validate the accuracy of another simple and noninvasive method, quantitative magnetic resonance (QMR), at estimating body composition in a small-bodied lizard, Anolis sagrei, and (2) evaluate the accuracy of two indices of body condition (based on length–mass relationships) at predicting body fat, lean, and water mass. Comparisons of results from QMR scans to those from chemical carcass analysis reveal that QMR measures body fat, lean, and water mass with excellent accuracy in male and female lizards. With minor calibration from regression equations, QMR will be a reliable method of estimating body composition of A. sagrei. Body condition indices were positively related to absolute estimates of each constituent of body composition, but these relationships showed considerable variation around regression lines. In addition, condition indices did not predict fat, lean, or water mass when adjusted for body mass. Thus, our results emphasize the need for caution when interpreting body condition based upon linear measurements of animals. Overall, QMR provides an alternative noninvasive method for accurately measuring fat, lean, and water mass in these small-bodied animals. PMID:28035770

  8. New techniques in nutritional assessment: body composition methods.

    PubMed

    Elia, M; Ward, L C

    1999-02-01

    New techniques in air-displacement plethysmography seem to have overcome many of the previous problems of poor reproducibility and validity. These have made body-density measurements available to a larger range of individuals, including children, elderly and sick patients who often have difficulties in being submerged underwater in hydrodensitometry systems. The BOD POD air-displacement system (BOD POD body composition system; Life Measurement Instruments, Concord, CA, USA) is more precise than hydrodensitometry, is simple and rapid to operate (approximately 1 min measurements) and the results agree closely with those of hydrodensitometry (e.g. +/- 3.4% for estimation of body fat). Body line scanners employing the principles of three-dimensional photography are potentially able to measure the surface area and volume of the body and its segments even more rapidly (approximately 10 s), but the validity of the measurements needs to be established. Advances in i.r. spectroscopy and mathematical modelling for calculating the area under the curve have improved precision for measuring enrichment of 2H2O in studies of water dilution (CV 0.1-0.9% within the range of 400-1000 microliters/l) in saliva, plasma and urine. The technique is rapid and compares closely with mass spectrometry (bias 1 (SD 2) %). Advances in bedside bioelectrical-impedance techniques are making possible potential measurements of skinfold thicknesses and limb muscle mass electronically. Preliminary results suggest that the electronic method is more reproducible (intra- and inter-individual reproducibility for measuring skinfold thicknesses) and associated with less bias (+12%), than anthropometry (+40%). In addition to these selected examples, the 'mobility' or transfer of reference methods between centres has made the distinction between reference and bedside or field techniques less distinct than in the past.

  9. Risk identification in haemodialysis patients by appropriate body composition assessment.

    PubMed

    Castellano, Sandra; Palomares, Inés; Moissl, Ulrich; Chamney, Paul; Carretero, Diana; Crespo, Antonio; Morente, Camilo; Ribera, Laura; Wabel, Peter; Ramos, Rosa; Merello, José Ignacio

    2016-01-01

    Circumstances such as gender, age, diabetes mellitus (DM) and renal failure impact on the body composition of patients. However, we use nutritional parameters such as lean and fat tissue with reference values from healthy subjects to assess the nutritional status of haemodialysis (HD) patients. To analyse body composition by bioimpedance spectroscopy (BIS) of 6395 HD patients in order to obtain reference values of lean tissue index (LTI) and fat tissue index (FTI) from HD patients; and to confirm its validity by showing that those patients with LTI below the 10th percentile calculated for their group have greatest risk of death. We used the BIS to determine the LTI and FTI in our cohort of HD patients in Spain. We calculated the 10th percentile and 90th percentile of LTI and FTI in each age decile for patients grouped by gender and presence of DM. We collected clinical, laboratory and demographic parameters. The LTI/FTI 10 and 90 percentile values varied by group (age, gender and presence of DM) and, after adjusting for other risk factors such as fluid overload, those patients with LTI lower than percentile 10 had a higher relative risk of death (OR 1.57) than those patients with higher values. Monitoring the LTI and FTI of patients on HD using suitable reference values may help to identify risk in this patient population. Copyright © 2016 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

  10. Body composition in healthy older persons: role of the ratio of extracellular/total body water.

    PubMed

    Malczyk, E; Dzięgielewska-Gęsiak, S; Fatyga, E; Ziółko, E; Kokot, T; Muc-Wierzgon, M

    2016-01-01

    The aim of this study was to identify the best prognostic parameters for quickly assessing fluid volume status in the context of nutritional status and water balance in older persons and to facilitate decision-making of the general practitioner (GP). This pilot study was conducted with 142 volunteers aged 60 years or older who were Polish students of the University of the Third Age. Inclusion and exclusion criteria for the study were defined. Assessment tools included: the Mini Nutritional Assessment questionnaire (MNA®) and the anthropometric measurements. Weight and body composition analysis were determined by Bioelectrical Impedance Analysis (BIA) using the Tanita MC-780 multi frequency segmental Body Composition Analyzer. According to the MNA scale, 89.2% of the sample was wellnourished and 10.8% were at risk of malnutrition. A total of 47.1% participants had normal body mass index, 20.6% were overweight, and 32.3% were obese. The BIA showed that females had more fat mass (FM) compared to males (35.84% vs 23.90%), while men had more free fat mass (FFM) and total body water (TBW; 61.16% vs 45.22% and 53.31% vs 45.22%respectively). There were no statistically significant differences in FM, FFM, and TBW by age. The ratio of Extracellular to Total Body Water (ECW/TBW) was higher in women than in men (46.76% vs 43.66%). Of all measures, only ECW/TBW increased significantly with age and sex, especially after 65 years. We propose that ECW/TBW may be used as the first, simple, and fast indicator of water volume status in the context of nutritional status and water balance in older subjects. Systematic control of the ECW/TBW by GP or nurse may increase senior independence, resulting in longer self-maintenance at home and reduced hospital admissions.

  11. Body composition and somatotype of the elite of Polish fencers.

    PubMed

    Sterkowicz-Przybycień, Katarzyna

    2009-09-01

    The purpose of this study was to determine body composition and somatotype of the male fencers who were grouped by different fencing weapons. Analysis of body composition, with untrained men as background, will update the data necessary for the somatic profiles of fencers. Thirty contestants were examined during the Polish Fencing Championships in 2004. They took part in epée (n = 10), foil (n = 10) and sabre (n = 10). They were aged 23.3 +/- 2.9; their length of training was 12.6 +/- 2.5 years, with the frequency of training 15.9 +/- 3.1 hours per week. In each weapon style there were champions and vice-champions of Poland from the year 2004. Twelve of them were classified among the first fifty contestants according to the D'Escrime International Federation (FIE) ranking. An experienced evaluator performed 10 measurements necessary to designate somatotypes by means of Heath-Carter method and to estimate the percentage of body fat and composition. Sabre fencers (weight = 84.4 kg, somatotype = 3.4-5.4-1.8) were heavier than both epée fencers (77.9 kg, 3.6-4.9-2.5) and foil fencers (74.9 kg, 2.9-4.2-2.8). Sabre specialists had higher mesomorphy than foil fencers (ANOVA and Bonferroni's multi comparison test). Sabre fencers were characterized by higher fat free mass and a higher BMI and fat free mass index than fencers of the other two weapons. Discriminant analysis result was significant (p < 0.01) with a relative percentage with a 72.4 and a canonical correlation coefficient 0.692, and Wilks' lambda = 0.385. Amongst the 30 observations used to fit the model, 22 (73.3%) were correctly classified. Against the background of non-training men, fencers were distinguished by a higher body weight (79.0 vs. 72.1 kg, t = 3.97, p < 0.001) and a higher height-weight ratio (43.21 vs. 42.46, t = 2.24, p < 0.05). Fencers' somatotypes differed from the somatotypes of the untrained (3.3-4.8-2.3 vs. 3.7-4.3-3.1). They were characterized by their higher mesomorphy (t = 2.10, p < 0

  12. Longitudinal Physical Activity, Body Composition, and Physical Fitness in Preschoolers.

    PubMed

    Leppänen, Marja H; Henriksson, Pontus; Delisle Nyström, Christine; Henriksson, Hanna; Ortega, Francisco B; Pomeroy, Jeremy; Ruiz, Jonatan R; Cadenas-Sanchez, Cristina; Löf, Marie

    2017-10-01

    This study aimed to investigate longitudinal associations of objectively measured physical activity (PA) and sedentary behavior (SB) with body composition and physical fitness at a 12-month follow-up in healthy Swedish 4-yr-old children. The data from the population-based MINISTOP trial were collected between 2014 and 2016, and this study included the 138 children who were in the control group. PA and SB were assessed using the wrist-worn ActiGraph (wGT3x-BT) accelerometer during seven 24-h periods and, subsequently, defined as SB, light-intensity PA, moderate-intensity PA, vigorous-intensity PA (VPA), and moderate-to-vigorous PA (MVPA). Body composition was measured using air-displacement plethysmography and physical fitness (cardiorespiratory fitness, lower and upper muscular strength as well as motor fitness) by the PREFIT fitness battery. Linear regression and isotemporal substitution models were applied. Greater VPA and MVPA at the age of 4.5 yr were associated with higher fat-free mass index (FFMI) at 5.5 yr (P < 0.001 and P = 0.044, respectively). Furthermore, greater VPA and MVPA at the age of 4.5 yr were associated with higher scores for cardiorespiratory fitness, lower body muscular strength, and motor fitness at 12-month follow-up (P = 0.001 to P = 0.031). Substituting 5 min·d of SB, light-intensity PA, or moderate-intensity PA for VPA at the age of 4.5 yr were associated with higher FFMI, and with greater upper and lower muscular strength at 12-month follow-up (P < 0.001 to P = 0.046). Higher VPA and MVPA at the age of 4.5 yr were significantly associated with higher FFMI and better physical fitness at 12-month follow-up. Our results indicate that promoting high-intensity PA at young ages may have long-term beneficial effects on childhood body composition and physical fitness, in particular muscular strength.

  13. [Body composition at menarche. Estimation of total body weight, total body water, lean and fat body weight].

    PubMed

    Zurlo de Mirotti, S M; Lesa, A M; Barrón de Carbonetti, M; Roitter, H; Villagra de Lacuara, S

    1995-01-01

    Our aim was to confirm in our environment what has been observed and described by other writers about the importance of achieving a "critical body weight'' and an adequate "fat percentage'' -on the basis of the calculation of total body water- for the initiation and development of pubertal events. This study included 92 girls, healthy, well nourished, belonging to upper middle class from a high school of The National University of Cordoba. The longitudinal method of control was used every 6 months and at the precise moment of menarche. Out of 20 antropometrical variables observed height, weight and height, TBW as percentage of body weight, lean body and fat weight, fat percentage and skin folds ppercentiles for each girl at menarche. A regression between fat percentage and skin folds was done. Percentiles 5 to 95 of fat percentage in relation to body water percentage were estimated. At menarche the average for the different variables are: Heigth 155.6 cm +/- 0.469; Weight 45.8 Kg +/- 0,5; TBW 25.216 lit. +/- 0.318; lean body weigth 35.02 Kg (S.D.2.98); fat weigth 10.86 Kg (S. D. 3.17). The addition of skin folds was correlated fat percentage, thus, an equation was obtained for the average calculation of such percentage %F= 12.16 + (0.313 x fold addition). The minium percentage for the onset of menstrual cycles is 17.3% and corresponds to percentile 10. However, there is a 5% of girls who start to menstruate with a 15.5% of fat and none of them is below that value. The reasons mentioned above suggest that is necessary to obtain a "critical body weigth'' as well as a "fat percentage'' minimum for the onset and maintenance of menstrual cycles, among our girls, similar o what has been obtained by doctor Frisch.

  14. Familial resemblance for body composition measures: the HERITAGE Family Study.

    PubMed

    Rice, T; Daw, E W; Gagnon, J; Bouchard, C; Leon, A S; Skinner, J S; Wilmore, J H; Rao, D C

    1997-11-01

    A sex-specific familial correlation model was used to assess the heritable contributions to several measures of body composition in 86 sedentary white families participating in the HERITAGE Family Study. For this study, sedentary families were recruited, tested for a battery of measures, endurance exercise trained for 20 weeks, and remeasured. This sample is unique in that activity level was controlled for in these families at baseline measurement. In this report, three body composition variables measured at baseline were analyzed, two indexing adiposity (total subcutaneous fat based on eight skinfold measurements [SF8] and percent body fat measured by underwater weighing techniques [%BF]) and one assessing fat free mass ([FFM] derived from underwater weighing). The maximal heritabilities for SF8 (34%) and %BF (62%) were consistent with those reported in previous studies. There were no sex nor generation differences in the familial correlations, and the spouse correlation was significant, consistent with the hypothesis that the familial aggregation reflects genetic and familial environmental factors. However, the results for FFM were very different. The most parsimonious pattern of familial resemblance was consistent with mitochondrial inheritance (i.e., mother-offspring and sibling correlations were equal and were larger than those for spouse and father-offspring pairs). Under the mitochondrial hypothesis, 39% of the variance was accounted for by familial/genetic effects. However, under a nonmitochondrial hypothesis, which could not be ruled out, 65% of the FFM phenotypic variance was accounted for by familial/genetic factors. This high heritability level, as compared with results from previous studies, is consistent with the hypothesis that activity may constitute an important environmental determinant of FFM. These alternative hypotheses for FFM warrant further investigation using complex multilocus-multitrait segregation models, which allow for major genetic

  15. Body composition predictors of skeletal integrity in obesity.

    PubMed

    Schorr, Melanie; Dichtel, Laura E; Gerweck, Anu V; Torriani, Martin; Miller, Karen K; Bredella, Miriam A

    2016-06-01

    To determine body composition predictors of skeletal integrity in overweight/obese subjects using dual energy X-ray absorptiometry (DXA). We hypothesized that visceral adiposity would be negatively, and lean mass positively, associated with DXA measures of skeletal integrity in obesity. Our study was institutional review board (IRB)-approved and Health Insurance Portability and Accountability Act (HIPAA)-compliant and written informed consent was obtained. We studied 82 overweight or obese, but otherwise healthy premenopausal women and men of similar age who were part of a clinical trial (mean age: 37 ± 10 years, mean BMI: 34 ± 7 kg/m(2)). All subjects underwent DXA of the spine and hip for assessment of bone mineral density (BMD), trabecular bone score (TBS), and hip structural analysis (HSA), and of the whole body for the assessment of body composition, including estimated visceral adipose tissue (VAT). Sixty-three subjects (77 %) had normal BMD and 19 subjects (23 %) had osteopenia. There were strong age-, sex-, and BMD-independent positive associations between lean mass and HSA parameters (r = 0.50 to r = 0.81, p < 0.0001), whereas there was no association with TBS. There were strong age-, sex- and BMD-independent inverse associations between total fat and VAT mass and TBS (r = -0.60 and r = -0.72, p < 0.0001 for both correlations), whereas there were no associations with HSA parameters. Lean mass is a positive predictor of hip geometry, whereas fat and VAT mass are negative predictors of trabecular microarchitecture in overweight/obese subjects.

  16. Obesity paradox in cancer: new insights provided by body composition.

    PubMed

    Gonzalez, Maria Cristina; Pastore, Carla A; Orlandi, Silvana P; Heymsfield, Steven B

    2014-05-01

    Obesity, defined by body mass index (BMI), appears to have a paradoxical protective effect in several chronic diseases. We investigated the obesity paradox in cancer patients by using body composition. The study was an observational study of 175 cancer patients assessed before chemotherapy. Obesity was defined as BMI (in kg/m(2)) ≥30 or fat mass index (FMI; fat mass divided by the square of height) ≥5.2 (men) and ≥8.2 (women) measured by using a bioelectrical impedance analysis. Low muscle mass (sarcopenia) was defined as fat-free mass index (fat-free mass divided by the square of height) <17.5 (men) and <15.1 (women). Most patients were women (65.7%) and had a mean (±SD) age of 56.9 ± 12.8 y. According to BMI criteria, 60% of patients were overweight or obese. The median survival time for overweight (2.64 y; range: 0.23-3.16 y) and obese (2.61 y; range: 0.26-3.20 y) patients was significantly higher than for patients with a normal (2.04 y; range: 0.06-3.05 y) or low (0.52 y; range: 0.19-0.98 y) BMI (P < 0.001). Sarcopenic patients had shorter survival, regardless of their FMI. Obesity predicted higher survival rates only when sarcopenia was absent. In a multivariate Cox regression model, sarcopenia was an independent predictor of higher mortality (HR: 5.19; 95% CI: 2.58, 10.43) after we controlled for BMI, age, and tumor stage. The obesity paradox is present in cancer patients only when obesity is defined by BMI. Patients with sarcopenic obesity had the poorest prognosis. Cancer patients with high mortality risk can be identified by a body-composition assessment.

  17. Carbide Transformations in Tempering of Complexly Alloyed White Cast Iron

    NASA Astrophysics Data System (ADS)

    Vdovin, K. N.; Gorlenko, D. A.; Zavalishchin, A. N.

    2015-07-01

    Variation of the chemical composition of all phases and structural components (metallic matrix, eutectic and secondary carbides) in complexly alloyed cast iron is studied after crystallization and different variants of tempering. It is shown that several groups of secondary carbides may be distinguished according to their morphology and chemical composition.

  18. Impact of body-composition methodology on the composition of weight loss and weight gain.

    PubMed

    Pourhassan, M; Schautz, B; Braun, W; Gluer, C-C; Bosy-Westphal, A; Müller, M J

    2013-05-01

    We intended to (i) to compare the composition of weight loss and weight gain using densitometry, deuterium dilution (D₂O), dual-energy X-ray absorptiometry (DXA), magnetic resonance imaging (MRI) and the four-compartment (4C) model and (ii) to compare regional changes in fat mass (FM), fat-free mass (FFM) and skeletal muscle as assessed by DXA and MRI. Eighty-three study participants aged between 21 and 58 years with a body mass index range of 20.2-46.8 kg/m(2) had been assessed at two different occasions with a mean follow-up between 23.5 and 43.5 months. Body-weight changes within < 3% were considered as weight stable, a gain or a loss of >3% of initial weight was considered as a significant weight change. There was a considerable bias between the body-composition data obtained by the individual methods. When compared with the 4C model, mean bias of D₂O and densitometry was explained by the erroneous assumption of a constant hydration of FFM, thus, changes in FM were underestimated by D₂O but overestimated by densitometry. Because hydration does not normalize after weight loss, all two-component models have a systematic error in weight-reduced subjects. The bias between 4C model and DXA was mainly explained by FM% at baseline, whereas FFM hydration contributed to additional 5%. As to the regional changes in body composition, DXA data had a considerable bias and, thus, cannot replace MRI. To assess changes in body composition associated with weight changes, only the 4C model and MRI can be used with confidence.

  19. [Endocrine obesity: bioelectric profiles (biotypes) detected in the body composition].

    PubMed

    Miggiano, G A D; Petitti, T

    2004-09-01

    136 patients were selected (16 men and 120 women with non-specific menstrual disturbances) with a BMI (Body Mass Index) between 25 and 45 kg/m2, which were diagnosed with "disendocrinia" (GH deficit, hyperadrenocorticism, hypothyroidsm, hyperandrogenism, menstrual cycle disorders). The proposed approach, based on the visualization of the value distribution of the electric measures in different graphics, is able to immediately explain the bioelectric state of the individual's lean-mass. Subjects with hypothyroidism present, along with their overweight, less bio-conducting mass, with an altered fluid intra/extra-cellular distribution. Patients with hyperadrenocorticism show instead an hyperhydratation of the body mass, especially in the extracellular level. Patients with menstrual disorders (amenorrea, polycystic ovary syndrome, anovulatory cycle etc...) present a lean mass reduction (elevated Rs) and an increase of the intra-cellular compartment (elevated-Xc). Patients with hyper-androgenism (and hirsutism) show a characteristic bioelectric "pattern", with low Rs levels and high Xc levels. Subjects with GH deficit (men and women), has a trend of documenting bioelectric measures with lower lean mass and higher fat-mass. Different electric biotypes seem to characterize the body composition in the several endocrine disorders.

  20. Growth and body composition in Brazilian female rhythmic gymnastics athletes.

    PubMed

    Camargo, Cristiane Teixeira Amaral; Gomez-Campos, Rossana Anelice; Cossio-Bolaños, Marco Antonio; Barbeta, Vinicius Justino De Oliveira; Arruda, Miguel; Guerra-Junior, Gil

    2014-01-01

    The aim was to analyse the physical growth and body composition of rhythmic gymnastics athletes relative to their level of somatic maturation. This was a cross-sectional study of 136 athletes on 23 teams from Brazil. Mass, standing height and sitting height were measured. Fat-free and fat masses, body fat percentages and ages of the predicted peak height velocity (PHV) were calculated. The z scores for mass were negative during all ages according to both WHO and Brazilian references, and that for standing height were also negative for all ages according to WHO reference but only until 12 years old according to Brazilian reference. The mean age of the predicted PHV was 12.1 years. The mean mass, standing and sitting heights, body fat percentage, fat-free mass and fat mass increased significantly until 4 to 5 years after the age of the PHV. Menarche was reached in only 26% of these athletes and mean age was 13.2 years. The mass was below the national reference standards, and the standing height was below only for the international reference, but they also had late recovery of mass and standing height during puberty. In conclusion, these athletes had a potential to gain mass and standing height several years after PHV, indicating late maturation.

  1. Gravity, body mass and composition, and metabolic rate

    NASA Technical Reports Server (NTRS)

    Pace, N.; Smith, A. H.

    1984-01-01

    The scale effects of increased gravitational loading by chronic centrifugation on metabolic rate and body composition in metabolically mature mammals were investigated. Individual oxygen consumption rates in groups of 12 each, 8-month-old, hamster, rats, guinea pigs, and rabbits were measured at weekly intervals at 1.0 g, then 2.0 g for 6 weeks. Metabolic rate was increased significantly in all species, and stabilized after 2 weeks at 2.0 g. Statistical analysis of the data revealed that the larger the animal the greater was the increase in mass-specific metabolic rate, or metabolic intensity, over the 1.0 g value for the same animal, with the result that the interspecies allometric scaling relationship between metabolic rate and total body mass is different at 2.0 g compared 10 1.0 g. Analysis of covariance shows that the postioning constant at 2.0 g is increased by 17% at 2.0 g at the P .001 level, and the exponent is increased by 8% at the P = 0.008 level. Thus, the hypothesis that augmented gravitational loading should shift the allometric relationship between metabolic rate and body size by an increase in both parameters is supported.

  2. Gravity, body mass and composition, and metabolic rate

    NASA Technical Reports Server (NTRS)

    Pace, N.; Smith, A. H.

    1984-01-01

    The scale effects of increased gravitational loading by chronic centrifugation on metabolic rate and body composition in metabolically mature mammals were investigated. Individual oxygen consumption rates in groups of 12 each, 8-month-old, hamster, rats, guinea pigs, and rabbits were measured at weekly intervals at 1.0 g, then 2.0 g for 6 weeks. Metabolic rate was increased significantly in all species, and stabilized after 2 weeks at 2.0 g. Statistical analysis of the data revealed that the larger the animal the greater was the increase in mass-specific metabolic rate, or metabolic intensity, over the 1.0 g value for the same animal, with the result that the interspecies allometric scaling relationship between metabolic rate and total body mass is different at 2.0 g compared 10 1.0 g. Analysis of covariance shows that the postioning constant at 2.0 g is increased by 17% at 2.0 g at the P .001 level, and the exponent is increased by 8% at the P = 0.008 level. Thus, the hypothesis that augmented gravitational loading should shift the allometric relationship between metabolic rate and body size by an increase in both parameters is supported.

  3. Bipolaron Hopping Conduction in Boron Carbides

    SciTech Connect

    ASELAGE, TERRENCE L.; EMIN, D.; MCCREADY, STEVEN S.

    1999-09-20

    The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small (bi)polarons. The activation energies of the nobilities are low, {approx} 0.16 eV, and are nearly independent of the composition. At lower temperatures, conductivities have non-Arrhenius temperature dependencies and strong sensitivity to carbon concentration. Percolative aspects of low-temperature hopping are evident in this sensitivity to composition. Boron carbides' Seebeck coefficients are anomalous in that (1) they are much larger than expected from boron carbides' large carrier densities and (2) they depend only weakly on the carrier density. Carrier-induced softening of local vibrations gives contributions to the Seebeck coefficient that mirror the magnitudes and temperature dependencies found in boron carbides.

  4. Microstructure Analysis of Tungsten Carbide Hardfacing on Carbon Steel Blade

    NASA Astrophysics Data System (ADS)

    Nagentrau, M.; Tobi, A. L. Mohd; Kamdi, Z.; Ismail, M. I.; Sambu, M.

    2017-05-01

    Tungsten carbide (WC) hardfacing coating is commonly used to enhance carbon steel blade performance which works in acidic and abrasive condition during production process. This paper deals with tungsten carbide (WC) hardfacing microstructure analysis on a carbon steel blade. Mixing of ilmenite ore with sulphuric acid is performed by the carbon steel blade as part of a production process. Tungsten carbide hardfacing is deposited on the carbon steel blade to enhance its wear resistance. The carbide distribution along with elemental composition analysis of the hardfaced carbon steel blade specimens is examined using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-Ray Diffraction (XRD) respectively. Microstructure analysis revealed that different sizes of carbides with non-uniform distribution are found around the coating region. The carbide region is contains high percentage of tungsten (W) meanwhile, non-carbide region rich in tungsten (W) and iron (Fe).

  5. Quantitative evaluation of carbides in nickel-base superalloy MAR-M247

    NASA Astrophysics Data System (ADS)

    Szczotok, A.

    2011-05-01

    It has been established that carbides in superalloys serve three functions. Fine carbides precipitated in the matrix give strengthening results. Carbides also can tie up certain elements that would otherwise promote phase instability during service. Grain boundary carbides prevent or retard grain-boundary sliding and strengthen the grain boundary, which depends significantly on carbide shape, size and distribution. Various types of carbides are possible, depending on superalloy composition and processing. In the paper optical and scanning electron microscopy investigations of carbides occurring in specimens of the polycrystalline nickel-base superalloy MAR-M247 were carried out. Conditions of carbides revealing and microstructure images acquisition have been described. Taking into consideration distribution and morphology of the carbides in matrix a method of quantitative description of Chinese script-like and blocky primary carbides on the basis of image analysis was proposed.

  6. How Effective Is Sun Salutation in Improving Muscle Strength, General Body Endurance and Body Composition?

    PubMed Central

    Bhutkar, Milind V.; Bhutkar, Pratima M.; Taware, Govind B.; Surdi, Anil D.

    2011-01-01

    Purpose The purpose of the present study was to evaluate effects of regular practice of sun salutation on muscle strength, general body endurance and body composition. Methods Subjects (49 male and 30 female) performed 24 cycles of sun salutation, 6 days a week for 24 weeks. Upper body muscle strength was determined by 1 repetition maximum (1RM) for bench press and shoulder press technique. Back and leg dynamometry was used to assess strength of back and leg muscles. General body endurance was evaluated by push-up and sit-up tests. Body composition was assessed by noting% body fat by using bioelectric impedance analysis. Perceived intensity of exercise by subjects was noted by Borg scale. Results Muscle strength by bench press showed significant increase in male (29.49±9.70 to 36.12±9.09 Kg, P<0.001) and female (10.5±4.42 to 13.16±4.44 Kg, P<0.001) subjects. Strength by shoulder press also increased (males; 22.96±9.57 Kg to 26.53±11.05 Kg, P<0.001, females; 6.83±2.78 to 8.83±3.87, P<0.001). Endurance by push-ups & sit-ups showed similar findings in male (19.0±9.58 to 21.98±8.98, P<0.001 and 24.92±10.41 to 29.84±12.64, P<0.001 respectively) and female (14.66±6.80 to 18.56±6.97 and 13.16±7.75 to 19.23±8.25, P<0.001 respectively) subjects. A significant decrease in body fat percent was observed only in female (27.68±5.46 to 25.76±4.72, P<0.001) but not in male subjects. BMI significantly decreased in both the groups (z=4.37, P<001 and t=5.41, P<0.001 respectively). Conclusion From our observations we conclude that sun salutation can be an ideal exercise to keep oneself in optimum level of fitness. PMID:22375247

  7. Morphology of powders of tungsten carbide used in wear-resistant coatings and deposition on the PDC drill bits

    NASA Astrophysics Data System (ADS)

    Zakharova, E. S.; Markova, I. Yu; Maslov, A. L.; Polushin, N. I.; Laptev, A. I.

    2017-05-01

    Modern drill bits have high abrasive wear in the area of contact with the rock and removed sludge. Currently, these bits have a protective layer on the bit body, which consists of a metal matrix with inclusions of carbide particles. The research matrix of this coating and the wear-resistant particles is a prerequisite in the design and production of drill bits. In this work, complex investigation was made for various carbide powders of the grades Relit (tungsten carbide produced by Ltd “ROSNAMIS”) which are used as wear-resistant particles in the coating of the drill bit body. The morphology and phase composition of the chosen powders as well as the influence of a particle shape on prospects of their application in wear-resistance coating presented in this work.

  8. Stress Rupture Behavior of Silicon Carbide Coated, Low Modulus Carbon/Carbon Composites. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Rozak, Gary A.; Wallace, John F.

    1988-01-01

    The disadvantages of carbon-carbon composites, in addition to the oxidation problem, are low thermal expansion, expensive fabrication procedures, and poor off axis properties. The background of carbon-carbon composites, their fabrication, oxidation, oxidation protection and mechanical testing in flexure are discussed.

  9. New way of body composition analysis using total body electrical conductivity method

    NASA Astrophysics Data System (ADS)

    Piasecki, Wojciech; Koteja, Pawel; Weiner, January; Froncisz, Wojciech

    1995-04-01

    Traditional methods of measuring total body water and fat content of animals that require sacrificing specimens are generally unacceptable when endangered species, or large animal sizes, or humans are involved. These methods are also unsuitable for following changes of fat and water content in individuals. An alternative method, based on the nonresonant absorption of a rf electromagnetic field has been used for constructing a new body composition analyzer. As the electrical conductivity of lipids is approximately 20 times lower than that of lean tissues, the rf power absorbed by the animal provides information which enables one to calculate the lean body mass and total body water. The new instrument measures rf power absorbed by an animal by measuring the quality factor (Q) of the resonant circuit with an animal placed inside the coil. Numerical calculations of the rf power absorbed by a cylindrical object containing 0.9% NaCl aqueous solution have also been performed. Experimental values confirmed the calculated dependence of the absorbed power on the cylinder radius. The device built has been calibrated on 9 males and 11 females of laboratory mice. The amount of lipids was then measured by ether extraction. The relation between instrument reading, which is proportional to the power absorption, and lean body mass (LBM) or water mass (WM) was linear and highly significant: the simple regression coefficients of determination were 0.983 for LBM, and 0.990 for WM (p<0.001). It has been found that for an individual animal with a body mass ranging from 15.9 to 40.7 g, the accuracy of measurement was ±1.6 g for LBM and ±1 g for WM.

  10. Microstructural, phase evolution and corrosion properties of silicon carbide reinforced pulse electrodeposited nickel-tungsten composite coatings

    NASA Astrophysics Data System (ADS)

    Singh, Swarnima; Sribalaji, M.; Wasekar, Nitin P.; Joshi, Srikant; Sundararajan, G.; Singh, Raghuvir; Keshri, Anup Kumar

    2016-02-01

    Silicon carbide (SiC) reinforced nickel-tungsten (Ni-W) coatings were successfully fabricated on steel substrate by pulse electrodeposition method (PED) and the amount of SiC was varied as 0 g/l, 2 g/l, and 5 g/l in Ni-W coating. Effect of subsequent addition of SiC on microstructures, phases and on corrosion property of the coating was investigated. Field emission scanning electron microscopy (FE-SEM) image of the surface morphology of the coating showed the transformation from the dome like structure to turtle shell like structure. X-ray diffraction (XRD) of Ni-W-5 g/l SiC showed the disappearance of (220) plane of Ni(W), peak splitting in major peak of Ni(W) and formation of distinct peak of W(Ni) solid solution. Absence of (220) plane, peak splitting and presence of W(Ni) solid solution was explained by the high resolution transmission electron microscopy (HR-TEM) images. Tafel polarization plot was used to study the corrosion property of the coatings in 0.5 M NaCl solution. Ni-W-5 g/l SiC coating was showed higher corrosion resistance (i.e. ∼21% increase in corrosion potential, Ecorr) compared to Ni-W coating. Two simultaneous phenomena have been identified for the enhanced corrosion resistance of Ni-W-5 g/l SiC coating. (a) Presence of crystallographic texture (b) formation of continuous double barrier layer of NiWO4 and SiO2.

  11. Body Composition and Pulmonary Function in Cystic Fibrosis

    PubMed Central

    Sheikh, Saba; Zemel, Babette S.; Stallings, Virginia A.; Rubenstein, Ronald C.; Kelly, Andrea

    2014-01-01

    Background: Lower body mass index (BMI) is associated with worse pulmonary function in cystic fibrosis (CF). Hypothesis: lean body mass (LBM) is more strongly associated with pulmonary function than BMI is. Methods: Anthropometrics, body composition by dual x-ray absorptiometry, and pulmonary function were determined in pancreatic insufficient CF (PI-CF) youth. Sex and age-adjusted Z-scores (BMI-Z, LBMI-Z, FMI-Z) were generated for CF and controls. (1) Associations of BMI-Z with LBMI-Z and FMI-Z and (2) age-adjusted associations of BMI-Z, LBMI-Z, and FMI-Z with FEV1%-predicted were tested. Results: Two hundred eight PI-CF subjects had lower BMI-Z, LBMI-Z, and FMI-Z compared to 390 controls. BMI-Z was associated with lower LBMI-Z (p < 0.0001) in PI-CF. In females, LBMI-Z and BMI-Z were positively associated with FEV1%-predicted; this relationship did not persist for FMI-Z after adjustment for LBMI-Z. In males, only LBMI-Z and BMI-Z were associated with FEV1%-predicted. Conclusion: In PI-CF youth, deficits in LBM were apparent. At lower BMI percentiles, BMI may not accurately depict LBM in PI-CF. In under-nourished PI-CF youth, this preservation of FM in preference to LBM is relevant since LBMI-Z, but not FMI-Z, is positively associated with FEV1%-predicted. Lean body mass index is more strongly associated with lung function compared to BMI, especially in the under-nourished child and adolescent with PI-CF. PMID:24783186

  12. Fabrication of thorium bearing carbide fuels

    DOEpatents

    Gutierrez, R.L.; Herbst, R.J.; Johnson, K.W.R.

    Thorium-uranium carbide and thorium-plutonium carbide fuel pellets have been fabricated by the carbothermic reduction process. Temperatures of 1750/sup 0/C and 2000/sup 0/C were used during the reduction cycle. Sintering temperatures of 1800/sup 0/C and 2000/sup 0/C were used to prepare fuel pellet densities of 87% and > 94% of theoretical, respectively. The process allows the fabrication of kilogram quantities of fuel with good reproductibility of chemical and phase composition.

  13. Scaling of human body composition to stature: new insights into body mass index.

    PubMed

    Heymsfield, Steven B; Gallagher, Dympna; Mayer, Laurel; Beetsch, Joel; Pietrobelli, Angelo

    2007-07-01

    Although Quetelet first reported in 1835 that adult weight scales to the square of stature, limited or no information is available on how anatomical body compartments, including adipose tissue (AT), scale to height. We examined the critical underlying assumptions of adiposity-body mass index (BMI) relations and extended these analyses to major anatomical compartments: skeletal muscle (SM), bone, residual mass, weight (AT+SM+bone), AT-free mass, and organs (liver, brain). This was a cross-sectional analysis of 2 body-composition databases: one including magnetic resonance imaging and dual-energy X-ray absorptiometry (DXA) estimates of evaluated components in adults (total n=411; organs=76) and the other a larger DXA database (n=1346) that included related estimates of fat, fat-free mass, and bone mineral mass. Weight, primary lean components (SM, residual mass, AT-free mass, and fat-free mass), and liver scaled to height with powers of approximately 2 (all P<0.001); bone and bone mineral mass scaled to height with powers >2 (2.31-2.48), and the fraction of weight as bone mineral mass was significantly (P<0.001) correlated with height in women. AT scaled weakly to height with powers of approximately 2, and adiposity was independent of height. Brain mass scaled to height with a power of 0.83 (P=0.04) in men and nonsignificantly in women; the fraction of weight as brain was inversely related to height in women (P=0.002). These observations suggest that short and tall subjects with equivalent BMIs have similar but not identical body composition, provide new insights into earlier BMI-related observations and thus establish a foundation for height-normalized indexes, and create an analytic framework for future studies.

  14. (10)B/(11)B isotopic ratio and atomic composition of boron carbide: Determination by proton induced γ-ray emission and proton elastic backscattering spectrometry.

    PubMed

    Sunitha, Y; Kumar, Sanjiv

    2017-10-01

    The (10)B/(11)B isotopic ratio and the atomic composition of boron carbide, an important non-metallic ceramic, have been determined non-destructively by the particle induced γ-ray emission (PIGE) and elastic backscattering spectrometry (EBS) techniques with proton beams. The analysis has been performed on powder as well as sintered ceramics containing boron in natural or (10)B enriched composition. The PIGE technique, performed at a 4.0-4.2MeV proton energy, utilizes the (10)B(p,αγ)(7)Be, (10)B(p,p'γ)(10)B and (11)B(p, p'γ)(11)B nuclear reactions for (a) the isotopic analysis of boron and (b) the determination of total boron, and the (13)C(p,p'γ)(13)C nuclear reaction for the determination of carbon. The irradiation conditions were optimized by determining the thick targets yields of prompt γ-rays, characteristic of these reactions, in the 3.0-4.2MeV proton energy range. The quantitative analysis was performed by comparison with standards taking into account the attenuation of γ-rays in the specimens. The uncertainty in the determination of the (10)B/(11)B isotopic ratio and the B/C atomic ratio is about 2% and about 5% respectively. The analysis by EBS, on the other hand, involves the (10)B(p,p)(10)B, (11)B(p,p)(11)B and (12)C(p,p)(12)C elastic scatterings at the 2.0MeV proton energy. This method too yields satisfactory results. Between the two, PIGE is the method of choice for bulk analysis while EBS is useful in discerning compositional variations in surface regions. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides.

    PubMed

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-14

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  16. Reinforcement of tungsten carbide grains by nanoprecipitates in cemented carbides

    NASA Astrophysics Data System (ADS)

    Liu, Xingwei; Song, Xiaoyan; Wang, Haibin; Hou, Chao; Liu, Xuemei; Wang, Xilong

    2016-10-01

    In contrast to the conventional method that obtains a high fracture strength of tungsten carbide-cobalt (WC-Co) cemented carbides by reducing WC grain size to near-nano or nanoscale, a new approach has been developed to achieve ultrahigh fracture strength by strengthening the WC grains through precipitate reinforcement. The cemented carbides were prepared by liquid-state sintering the in situ synthesized WC-Co composite powders with a little excess carbon and pre-milled Cr3C2 particles having different size scales. It was found that the nanoscale dispersed particles precipitate in the WC grains, which mainly have a coherent or semi-coherent interface with the matrix. The pinning effect of the nanoparticles on the motion of dislocations within the WC grains was observed. The mechanisms for the precipitation of nanoparticles in the WC grains were discussed, based on which a new method to enhance the resistance against the transgranular fracture of cemented carbides was proposed.

  17. Aqueous Alteration and Hydrogen Generation on Parent Bodies of Unequilibrated Ordinary Chondrites: Thermodynamic Modeling for the Semarkona Composition

    NASA Technical Reports Server (NTRS)

    Zolotov, M. Y.; Mironenko, M. V.; Shock, E. L.

    2005-01-01

    Ordinary chondrites are the most abundant class of meteorites that could represent rocky parts of solar system bodies. However, even the most primitive unequilibrated ordinary chondrites (UOC) reveal signs of mild alteration that affected the matrix and peripheral zones of chondrules. Major chemical changes include oxidation of kamacite, alteration of glass, removal of alkalis, Al, and Si from chondrules, and formation of phases enriched in halogens, alkalis, and hydrogen. Secondary mineralogical changes include formation of magnetite, ferrous olivine, fayalite, pentlandite, awaruite, smectites, phosphates, carbonates, and carbides. Aqueous alteration is consistent with the oxygen isotope data for magnetite. The presence of secondary magnetite, Ni-rich metal alloys, and ferrous silicates in UOC implies that H2O was the oxidizing agent. However, oxidation by H2O means that H2 is produced in each oxidative pathway. In turn, production of H2, and its redistribution and possible escape should have affected total pressure, as well as the oxidation state of gas, aqueous and mineral phases in the parent body. Here we use equilibrium thermodynamic modeling to explore water-rock reactions in UOC. The chemical composition of gas, aqueous, and mineral phases is considered.

  18. Measurement of Body Composition: is there a Gold Standard?

    PubMed Central

    Branski, Ludwik K; Norbury, William B; Herndon, David N; Chinkes, David L; Cochran, Amalia; Suman, Oscar; Benjamin, Deb; Jeschke, Marc G

    2015-01-01

    Background Maintaining lean body mass (LBM) after a severe burn is an essential goal of modern burn treatment. An accurate determination of LBM is necessary for short- and longterm therapeutic decisions. The aim of this study was to compare 2 measurement methods for body composition, wholebody potassium counting (K count) and dual x-ray absorptiometry (DEXA), in a large prospective clinical trial in severely burned pediatric patients. Methods Two-hundred seventy-nine patients admitted with burns covering 40% of total body surface area (TBSA) were enrolled in the study. Patients enrolled were controls or received long-term treatment with recombinant human growth hormone (rhGH). Near-simultaneous measurements of LBM with DEXA and fat-free mass (FFM) with K count were performed at hospital discharge and at 6, 9, 12, 18, and 24 months post injury. Results were correlated using Pearson’s regression analysis. Agreement between the 2 methods was analyzed with the Bland-Altman method. Results Age, gender distribution, weight, burn size, and admission time from injury were not significantly different between control and treatment groups. rhGH and control patients at all time points postburn showed a good correlation between LBM and FFM measurements (R2 between 0.9 and 0.95). Bland-Altman revealed that the mean bias and 95% limits of agreement depended only on patient weight and not on treatment or time postburn. The 95% limits ranged from 0.1 ± 2.9 kg for LBM or FFM in 7- to 18-kg patients to 16.3 ± 17.8 kg for LBM or FFM in patients >60 kg. Conclusions DEXA can provide a sufficiently accurate determination of LBM and changes in body composition, but a correction factor must be included for older children and adolescents with more LBM. DEXA scans are easier, cheaper, and less stressful for the patient, and this method should be used rather than the K count. PMID:19884353

  19. Relationship of sarcopenia and body composition with osteoporosis.

    PubMed

    He, H; Liu, Y; Tian, Q; Papasian, C J; Hu, T; Deng, H-W

    2016-02-01

    The purpose of the study is to investigate the relationship between sarcopenia and body composition and osteoporosis in cohorts of three different races with a total of 17,891 subjects. Lean mass and grip strength were positively associated with bone mineral densities (BMDs). Subjects with sarcopenia were two times more likely to have osteoporosis compared with normal subjects. The relationship between sarcopenia and osteoporosis is not totally clear. First, the present study assessed this relationship by using two different definitions for sarcopenia. Second, we examined the associations of body composition (including muscle mass as a major and important component) and muscle strength on regional and whole-body BMDs. In total, 17,891 subjects of African American, Caucasian, and Chinese ethnicities were analyzed. Sarcopenia was defined by relative appendicular skeletal muscle mass (RASM) cut points and also by the definition of the European Working Group on Sarcopenia in Older People (low RASM plus low muscle function). Multiple regression analyses were conducted to examine the association of fat mass, lean mass (including muscle mass), and grip strength with regional and whole-body BMDs. Multivariate logistic regression analysis was performed to explore the association between sarcopenia and osteopenia/osteoporosis. BMDs were positively associated with lean mass and negatively associated with fat mass, after controlling for potential confounders. Grip strength was significantly associated with higher BMDs. Each standard deviation (SD) increase in RASM resulted in a ~37 % reduction in risk of osteopenia/osteoporosis (odds ratio (OR) = 0.63; 95 % confidence interval (CI) = 0.59, 0.66). Subjects with sarcopenia defined by RASM were two times more likely to have osteopenia/osteoporosis compared with the normal subjects (OR = 2.04; 95 % CI = 1.61, 2.60). Similarly, subjects with sarcopenia (low muscle mass and low grip strength) were ~1.8 times more

  20. Temperature control of thermal radiation from composite bodies

    NASA Astrophysics Data System (ADS)

    Jin, Weiliang; Polimeridis, Athanasios G.; Rodriguez, Alejandro W.

    2016-03-01