Science.gov

Sample records for pack cementation diffusion

  1. Pack cementation diffusion coatings for iron-base alloys

    SciTech Connect

    Rapp, R.A.

    1995-02-01

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels. The Cr-Si ferrite layers have proven to be very resistant to high temperature cyclic oxidation and to pitting in aqueous solutions. The process has been patented, and is being transferred for industrial application, e.g. for water walls of utility boilers, etc. In the proposed extension of this project, the use of mixed pure metal powders in the pack will be extended to achieve similar ferrite Fe-Cr-Al coatings with excellent oxidation resistance, with the eventual transfer of the technology to industry. In other recent studies, Ni-base alloy rods were aluminized by the halide-activated pack cementation process to bring their average composition to that for the ORNL-developed Ni{sub 3}Al, for use as a welding rod. A similar effort to develop a welding rod for the ORNL Fe{sub 3}Al alloy did not yield reproducible coating compositions or growth kinetics. The continued effort to produce Duriron-type (Fe-18Si-5Cr) coatings on steels was not successful. Literature for the intrinsic diffusion coefficients suggests that this task cannot be achieved.

  2. Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

    SciTech Connect

    Rapp, R.A.

    1998-03-10

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

  3. Pack cementation coatings for alloys

    SciTech Connect

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A.

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  4. Effect of Al-Si Pack Cementation Diffusion Coating on High-Temperature Low-Cycle Fatigue Behavior of Inconel 713LC

    NASA Astrophysics Data System (ADS)

    Mansuri, Mohammadreza; Hadavi, Seyed Mohammad Mehdi; Zare, Esmail

    2016-01-01

    In this research, an Al-Si protective coating was applied on the surface of an IN713LC specimen using pack cementation method. Surface-treated and untreated specimens were exposed to low-cycle fatigue by tension-tension loading under total strain control at 1173 K (900 °C) in air. Based on the obtained results, the hardening/softening, cyclic stress-strain, and fatigue life curves were plotted and analyzed. The results showed that both the single-stage and two-stage coatings improved the fatigue life of the substrate. However, owing to more silicon content of single-stage coating compared to that of two-stage coating, the effect of single-stage coating was superior. The stress response of the treated material was lower compared with the untreated one. Observations of the specimen section and fracture surface examinations were used to analyze fatigue behavior of both coated and uncoated materials.

  5. Volatile species in halide-activated-diffusion coating packs

    NASA Technical Reports Server (NTRS)

    Bianco, Robert; Rapp, Robert A.; Jacobson, Nathan S.

    1992-01-01

    An atmospheric pressure sampling mass spectrometer was used to identify the vapor species generated in a halide-activated cementation pack. Pack powder mixtures containing a Cr-Al binary masteralloy powder, an NH4Cl activator salt, and either ZrO2 or Y2O3 (or neither) were analyzed at 1000 C. Both the equilibrium calculations for the pack and mass spectrometer results indicated that volatile AlCl(x) and CrCl(y) species were generated by the pack powder mixture; in packs containing the reactive element oxide, volatile ZrCl(z) and YCl(w) species were formed by the conversion of their oxide sources.

  6. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    SciTech Connect

    He, Y.R.; Zheng, M.H.; Rapp, R.A.

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  7. Analytical method to estimate resin cement diffusion into dentin

    NASA Astrophysics Data System (ADS)

    de Oliveira Ferraz, Larissa Cristina; Ubaldini, Adriana Lemos Mori; de Oliveira, Bruna Medeiros Bertol; Neto, Antonio Medina; Sato, Fracielle; Baesso, Mauro Luciano; Pascotto, Renata Corrêa

    2016-05-01

    This study analyzed the diffusion of two resin luting agents (resin cements) into dentin, with the aim of presenting an analytical method for estimating the thickness of the diffusion zone. Class V cavities were prepared in the buccal and lingual surfaces of molars (n=9). Indirect composite inlays were luted into the cavities with either a self-adhesive or a self-etch resin cement. The teeth were sectioned bucco-lingually and the cement-dentin interface was analyzed by using micro-Raman spectroscopy (MRS) and scanning electron microscopy. Evolution of peak intensities of the Raman bands, collected from the functional groups corresponding to the resin monomer (C–O–C, 1113 cm-1) present in the cements, and the mineral content (P–O, 961 cm-1) in dentin were sigmoid shaped functions. A Boltzmann function (BF) was then fitted to the peaks encountered at 1113 cm-1 to estimate the resin cement diffusion into dentin. The BF identified a resin cement-dentin diffusion zone of 1.8±0.4 μm for the self-adhesive cement and 2.5±0.3 μm for the self-etch cement. This analysis allowed the authors to estimate the diffusion of the resin cements into the dentin. Fitting the MRS data to the BF contributed to and is relevant for future studies of the adhesive interface.

  8. The influence of Cr and Al pack cementation on low carbon steel to improve oxidation resistance

    NASA Astrophysics Data System (ADS)

    Prasetya, Didik; Sugiarti, Eni; Destyorini, Fredina; Thosin, Kemas Ahmad Zaini

    2012-06-01

    Pack chromizing and aluminizing has been widely used for many years to improve hot temperature oxidation and corrosion resistance of metals. The coating process involves packing the steel in a powder mixture which contain aluminum and chromium source, and inert filler (usually alumina), and halide activator NH4Cl. Al and Cr were deposited onto carbon steel by pack cementation process using elemental Al and Cr powder as Al and Cr source, whereas NiCo alloys codeposited by electrodeposition. The position of Al and Cr could be under or over Ni-Co alloys deposited. Pack cementation was heated on dry inert gas at temperature 800 °C about 5 hours and 20 minute for Cr and Al respectively. Al and Cr was successfully deposited. Laying down effect of Al and Cr onto carbon steel whether up and down toward NiCo alloys coating have affected to oxidation resistance. The pack aluminizing as top layer given best resitance to restrain excessive oxide scale, in contrast pack chromizing reveal bad oxidation resistance, moreover occured spallation on layer.

  9. Silver-cemented frit formation for the stabilization of the packing structure in the microchannel of electrochromatographic microchips.

    PubMed

    Park, Jongman; Oh, Hyejin; Jeon, In-Sun

    2011-10-28

    A simple but effective frit formation technique was developed to stabilize the packing structure inside the microchannel of capillary electrochromatographic microchips, utilizing the electroless plating technique. A Ag(NH(3))(2)(+) solution was allowed to diffuse through the colloidal silica packing in the microchannel from the reservoir of the microchip for a limited amount of time, and then it was reduced by an excess amount of formaldehyde solution. A frit structure of ~70 μm in length was formed at the entrance of the microchannel without clogging when treated with 1mM Ag(NH(3))(2)(+) ion and formaldehyde for 30s and 150 s, respectively. The formation of the frit structure was confirmed by a scanning electron microscopy. The stability of the packing structure was tested rigorously and then confirmed by applying alternating electroosmotic flows back and forth with pulsed potential steps on both sides of the frit structure. The effect of the treatment on the electrochromatograms was evaluated after the microchips were repeatedly used and stored for a long period of time. The results indicated that the silver-cemented frit structure extended the lifetime of the fully packed CEC microchips distinctly. PMID:21945197

  10. Influence of slag blended cement concrete on chloride diffusion rate

    SciTech Connect

    Dehghanian, C.; Arjemandi, M.

    1997-06-01

    This research was conducted to investigate the effect of 0 to 30% partial replacement of cement by slag on chloride diffusion rate in concrete. Concretes with 0 to 30% slag were used and exposed to 2 to 5% NaCl solutions. The effect of different external salt concentration solutions and the influence of water-cement ratios ranging from 0.45 to 0.75 was also studied. In this research, different curing methods such as 9 to 18 days exposure to 100% humidity and 9 to 18 days submersion in distilled water were selected. The results indicated that after 90 days of exposure to salt solutions an/d 108 days of concrete age, chloride diffusivity for concretes containing slag almost remained the same. This effect was more pronounced for water-cement ratio of 0.45 and curing condition of 18 days submersion in water. An increase in water-cement ratio beyond 0.55 indicated a higher chloride diffusion rate. Curing condition for slag blended cement concrete also indicated a different behavior in chloride diffusivity. The best curing method obtained for this type of concrete was 18 days submersion in water.

  11. The effect of Al and Cr additions on pack cementation zinc coatings

    NASA Astrophysics Data System (ADS)

    Chaliampalias, D.; Papazoglou, M.; Tsipas, S.; Pavlidou, E.; Skolianos, S.; Stergioudis, G.; Vourlias, G.

    2010-03-01

    Zinc is widely used as a protective coating material due to its corrosion resistant properties. The structure and oxidation resistance of Al and Cr mixed zinc coatings, deposited by pack cementation process, is thoroughly examined in this work. The morphology and chemical composition of the as-deposited and oxidized samples was accomplished by electron microscopy while the phase identification was performed by XRD diffraction analysis. The experimental results showed that the addition of aluminum or chromium in the pack mixture forms only Al and Cr rich phases on the surface of the specimens without affecting significantly the phase composition of the rest zinc coatings. In the case of Zn-Al coatings, the overlying layer contains high concentrations of Al together with lower amounts of zinc and iron and in Zn-Cr coatings this layer contains Cr, Fe and Zn atoms and has much smaller thickness. The presence of these additional layers promotes significantly the oxidation resistance of the zinc pack coatings and they preserve most of their initial thickness and chemical content when exposed to an aggressive environment while their oxidation mass gain was measured at low levels during the oxidation tests.

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

    SciTech Connect

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

    2014-01-01

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

  13. Boundary conditions for diffusion in the pack-aluminizing of nickel.

    NASA Technical Reports Server (NTRS)

    Sivakumar, R.; Seigle, L. L.; Menon, N. B.

    1973-01-01

    The surface compositions of nickel specimens coated for various lengths of time in aluminizing packs at 2000 F were studied, in order to obtain information about the kinetics of the pack-cementation process in the formation of aluminide coatings. The results obtained indicate that the surface compositions of the coated nickel specimens are independent of time, at least for time between 0.5 and 20 hrs. Another important observation is that the specimens gained weight during the coating process.

  14. The bipolar plate of AISI 1045 steel with chromized coatings prepared by low-temperature pack cementation for proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Bai, Ching-Yuan; Wen, Tse-Min; Hou, Kung-Hsu; Ger, Ming-Der

    The low-temperature pack chromization, a reforming pack cementation process, is employed to modify AISI 1045 steel for the application of bipolar plates in PEMFC. The process is conducted to yield a coating, containing major Cr-carbides and minor Cr-nitrides, on the substrate in view of enhancing the steel's corrosion resistance and lowering interfacial contact resistance between the bipolar plate and gas diffusion layer. Electrical discharge machining and rolling approach are used as the pretreatment to produce an activated surface on the steel before pack chromization process to reduce operating temperatures and increase deposition rates. The rolled-chromized steel shows the lowest corrosion current density, 3 × 10 -8 A cm -2, and the smallest interfacial contact resistance, 5.9 mΩ cm 2, at 140 N cm -2 among all tested steels. This study clearly states the performance of 1045 carbon steel modified by activated and low-temperature pack chromization processes, which possess the potential to be bipolar plates in the application of PEMFC.

  15. Comparative examination of the microstructure and high temperature oxidation performance of NiCrBSi flame sprayed and pack cementation coatings

    NASA Astrophysics Data System (ADS)

    Chaliampalias, D.; Vourlias, G.; Pavlidou, E.; Skolianos, S.; Chrissafis, K.; Stergioudis, G.

    2009-01-01

    Coatings formed from NiCrBSi powder were deposited by thermal spray and pack cementation processes on low carbon steel. The microstructure and morphology of the coatings were studied by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Flame sprayed coatings exhibited high porosity and were mechanically bonded to the substrate while pack cementation coatings were more compact and chemically bonded to the substrate. The microhardness and the high temperature oxidation resistance of the coated samples were evaluated by a Vickers microhardness tester and by thermogravimetric measurements (TG), respectively. Pack cementation coatings showed higher hardness and were more protective to high temperature environments than the flame sprayed coatings.

  16. Pack Cementation Coatings for High-Temperature Oxidation Resistance of AISI 304 Stainless Steel

    NASA Astrophysics Data System (ADS)

    Zandrahimi, Morteza; Vatandoost, Javad; Ebrahimifar, Hadi

    2012-10-01

    Aluminum and titanium are deposited on the surface of steel by the pack cementation method to improve its hot-corrosion and high-temperature oxidation resistance. In this research, coatings of aluminum and titanium and a two-step coating of aluminum and titanium were applied on an AISI 304 stainless steel substrate. The coating layers were examined by carrying out scanning electron microscopy (SEM) and x-ray diffraction (XRD). The SEM results showed that the aluminized coating consisted of two layers with a thickness of 450 μm each, the titanized coating consisted of two layers with a thickness of 100 μm each, and the two-step coatings of Al and Ti consisted of three layers with a thickness of 200 μm each. The XRD investigation of the coatings showed that the aluminized coating consisted of Al2O3, AlCr2, FeAl, and Fe3Al phases; the titanized layers contained TiO2, Ni3Ti, FeNi, and Fe2TiO5 phases; and the two-step coating contained AlNi, Ti3Al, and FeAl phases. The uncoated and coated specimens were subjected to isothermal oxidation at 1050 °C for 100 h. The oxidation results revealed that the application of a coating layer increased the oxidation resistance of the coated AISI 304 samples as opposed to the uncoated ones.

  17. Cs diffusion in local Taiwan laterite with different solution concentration, pH and packing density.

    PubMed

    Wang, Tsing-Hai; Li, Ming-Hsu; Teng, Shi-Ping

    2008-09-01

    In this work we used an "in-diffusion" method to study the effects of pH, solution concentration and packing density on Cs diffusion by packing local Taiwan laterite (LTL) into modified capillary columns with 5mm diameter. These packed columns were first pre-equilibrated with synthetic groundwater (GW) for 3 weeks. The diffusion experiments were then carried out at ambient condition for 2 weeks. Our experimental results showed that the Cs diffusion profile fits Fick's second law very well in given experimental conditions, indicating the validity of modified capillary column method. Generally speaking, Cs diffusion in LTL decreases as the pH increases and as Cs concentration decreases. The apparent diffusion coefficient (D(a)) increases from 5.52 x 10(-12) (10(-7)M) to 2.18 x 10(-11) (10(-3)M)m(2)/s, while the effective diffusion coefficient (D(e)) shows slight variation as the Cs concentration changes. Both the derived D(a) and D(e) values decrease as the pH increases, implying that the diffusion mechanisms of Cs nuclide in alkaline and acid environment are different. In addition, our results show that Cs diffusion is unaffected by the given packing density, indicating the interlaminary space is not the major determinant of Cs adsorption and diffusion in LTL. PMID:18321721

  18. Oxidation-resistant coating for gamma titanium aluminides by pack cementation

    SciTech Connect

    Mabuchi, H.; Tsuda, H.; Kawakami, T.; Nakamatsu, S.; Matsui, T.; Morii, K.

    1999-08-06

    Gamma titanium aluminides ({gamma}-TiAl alloys), having an L1{sub 0}-type structure, are candidate materials for use in future gas turbine aero-engines and automotive engines because of their low density, high specific strength and high stiffness. In air, however, it is well known that titanium aluminide oxidizes at a more rapid rate at temperatures above 1,123 K; therefore, the oxidation resistance becomes a critical factor for TiAl alloys to be used at high temperatures (perhaps above 1,073 K). Coatings for the TiAl alloy are essential to high temperature oxidation resistance. The Al-Ti-Cr ternary phase diagram at 1,423 K indicates that the L1{sub 2} phase field is in equilibrium with the TiAl(L1{sub 0}) phase field. Furthermore, the L1{sub 0}- and L1{sub 2}-alloys in this ternary system resemble each other very closely in crystal structure and lattice parameter (TiAl(L1{sub 0}); a = 0.4005, c = 0.4070 nm (27), Ti-67Al-8Cr(L1{sub 2}); a = 0.3960nm (25)). Therefore, the L1{sub 2}-(Al,Cr){sub 3}Ti alloy can be considered applicable to L1{sub 0}-TiAl alloys as an optimum material for coatings. The purpose of this study is to apply L1{sub 2} alloy coatings to the TiAl alloys by pack cementation techniques, and to evaluate the oxidation resistance of the coated alloys.

  19. Chloride diffusivity in hardened cement paste from microscale analyses and accounting for binding effects

    NASA Astrophysics Data System (ADS)

    Carrara, P.; De Lorenzis, L.; Bentz, D. P.

    2016-08-01

    The diffusion of chloride ions in hardened cement paste (HCP) under steady-state conditions and accounting for the highly heterogeneous nature of the material is investigated. The three-dimensional HCP microstructures are obtained through segmentation of x-ray images of real samples as well as from simulations using the cement hydration model CEMHYD3D. Moreover, the physical and chemical interactions between chloride ions and HCP phases (binding), along with their effects on the diffusive process, are explicitly taken into account. The homogenized diffusivity of the HCP is then derived through a least square homogenization technique. Comparisons between numerical results and experimental data from the literature are presented.

  20. Open photoacoustic cell for thermal diffusivity measurements of a fast hardening cement used in dental restoring

    NASA Astrophysics Data System (ADS)

    Astrath, F. B. G.; Astrath, N. G. C.; Baesso, M. L.; Bento, A. C.; Moraes, J. C. S.; Santos, A. D.

    2012-01-01

    Thermal diffusivity and conductivity of dental cements have been studied using open photoacoustic cell (OPC). The samples consisted of fast hardening cement named CER, developed to be a root-end filling material. Thermal characterization was performed in samples with different gel/powder ratio and particle sizes and the results were compared to the ones from commercial cements. Complementary measurements of specific heat and mass density were also performed. The results showed that the thermal diffusivity of CER tends to increase smoothly with gel volume and rapidly against particle size. This behavior was linked to the pores size and their distribution in the samples. The OPC method was shown to be a valuable way in deriving thermal properties of porous material.

  1. Low-pressure, automated, sample packing unit for diffuse reflectance infrared spectrometry

    NASA Astrophysics Data System (ADS)

    Christy, Alfred A.; Tvedt, Jan Erik; Karstang, Terje V.; Velapoldi, Rance A.

    1988-03-01

    An automatic, low-pressure packing unit has been designed with control of packing time and pressure to prepare powder samples for diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). This unit also provides a polished packing surface that ensures constant measurement height of the sample in the spectrometer. Use of this unit coupled with sample rotation during measurement and control of particle size and size distribution, provides excellent precision in obtaining DRIFTS spectra. For example, repackings by a single person or by several untrained people gave coefficients of variation from 0.8% to 2.3% for each digital spectral value for a coal sample and from 1.3% to 3.7% for thymol blue, a sharp spectral featured organic, rather than the 15%-30% normally found for repackings of the same sample. Thus representative DRIFTS spectra can be obtained quickly and efficiently from a powder sample with a single spectrum using this low-pressure, mechanical packing device, control of particle parameters, and sample rotation as opposed to previous efforts requiring the repacking of several samples and averaging of the spectra.

  2. Diffusion and Filtration Properties of Self-assembled Close-packed Nanocrystal Membranes

    NASA Astrophysics Data System (ADS)

    He, Jinbo; Lin, Xiao-Min; Vukovic, Lela; Chan, Henry; Kral, Petr; Jaeger, Heinrich

    2011-03-01

    Small dyes are known to be able to penetrate through randomly packed nanoparticle monolayers, but a detailed understanding of the mechanisms for transport through the interstices between nanoparticles is still lacking. We report on systematic measurements of molecular transport across monolayers of close- packed, 5 nm diameter gold nanocrystals ligated with dodecanethiol. For water we find a filtration coefficient two orders of magnitude larger than for polymer-based nanofiltration membranes, while the self-diffusion coefficient is more than 100x smaller than in films of pure hydrocarbons. As we confirm by molecular dynamics simulations, larger molecules (tested molecular weight range: 200 - 43000) are unable to diffuse through the ligands. Instead, they most likely move through nm-sized regions of reduced ligand density, which are formed by slight variations in the local packing configuration and orientation of neighboring nanocrystals. In this intermediate size range we also find a pronounced dependence of the rejection rate on the molecules' charge. Molecules with cross-section above 2 nm are totally rejected.

  3. Structural disorder and anomalous water diffusion in random packing of spheres

    NASA Astrophysics Data System (ADS)

    Gabrielli, Andrea; Capuani, Silvia; Palombo, Marco; Servedio, Vito D. P.; Ruocco, Giancarlo

    2014-03-01

    Nowadays Nuclear Magnetic Resonance diffusion (dNMR) measurements of water molecules in heterogeneous systems have broad applications in material science, biophysics and medicine. Up to now, microstructural rearrangement in media has been experimentally investigated by studying the diffusion coefficient (D(t)) behavior in the tortuosity limit. However, this method is not able to describe structural disorder and transitions in complex systems. In this talk we show that, according to the continuous time random walk framework, the dNMR measurable parameter α, quantifying the anomalous regime of D(t) , provides a quantitative characterization of structural disorder and structural transition in heterogeneous systems. This is demonstrated by comparing α measurements obtained in random packed monodisperse micro-spheres with Molecular Dynamics simulations of disordered porous media and 3D Monte Carlo simulation of particles diffusion in these kind of systems. Experimental results agree well with simulations that correlate the most used parameters and functions characterizing the disorder in porous media.

  4. Experimental investigations and DICTRA simulations on formation of diffusion-controlled fcc-rich surface layers on cemented carbides

    NASA Astrophysics Data System (ADS)

    Garcia, José; Prat, Orlando

    2011-08-01

    Wear resistant fcc-rich surface layers were produced on cemented carbides by nitridation of W-Ti-Ta-Nb-Co-C compositions at 1400 °C in nitrogen atmosphere. A 15 ± 3 μm thick (Ti,Ta,Nb,W)(C,N) top-layer formed on the surface of the cemented carbides. The driving force for formation of the fcc-rich layers was the difference in nitrogen activity between the sintering atmosphere and the cemented carbide bulk, which promoted in-diffusion of nitrogen and out-diffusion of Ti, Ta and Nb. The diffusion-controlled process was modeled by DICTRA considering that all diffusion occurred in the liquid binder phase of a dispersed system model with a labyrinth factor of λ( f) = f. Good agreement between experimental and simulations regarding layer thickness, phase fraction distribution and element profiles was obtained for the presented model.

  5. Hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater using membrane diffusion packed-bed bioreactor.

    PubMed

    Li, Peng; Xing, Wei; Zuo, Jiane; Tang, Lei; Wang, Yajiao; Lin, Jia

    2013-09-01

    A lab-scale membrane diffusion packed-bed bioreactor was used to investigate hydrogenotrophic denitrification for tertiary nitrogen removal from municipal wastewater. After start-up, the bioreactor had been operated for 165 days by stepwise increasing influent loading rates at 30 and 15°C. The results indicated that this bioreactor could achieve relatively high nitrogen removal efficiencies. The denitrification rates reached 0.250 and 0.230 kg N/(m(3)d) at 30 and 15°C respectively. The total nitrogen concentration in effluent was entirely below 2.0 mg/L at the steady operation state. The average increase of total organic carbon in effluent was approximately 0.41 mg/L, suggesting the risk of organic residue can be completely controlled. Dissolved oxygen (DO) did not show obviously negative effects on hydrogenotrophic denitrification. There was only slight decrease of DO concentration in effluent, which demonstrated almost all of the hydrogen was used for nitrate reduction. PMID:23890978

  6. Water permeability and chloride ion diffusion in portland cement mortars: Relationship to sand content and critical pore diameter

    SciTech Connect

    Halamickova, P.; Detwiler, R.J.; Bentz, D.P.; Garboczi, E.J.

    1995-05-01

    The pore structure of hydrated cement in mortar and concrete is quite different from that of neat cement paste. The porous transition zones formed at the aggregate-paste interfaces affect the pore size distribution. The effect of the sand content on the development of pore structure, the permeability to water, and the diffusivity of chloride ions was studied on portland cement mortars. Mortars of two water-to-cement ratios and three sand volume fractions were cast together with pastes and tested at degrees of hydration ranging from 45 to 70%. An electrically-accelerated concentration cell test was used to determine the coefficient of chloride ion diffusion while a high pressure permeability cell was employed to assess liquid permeability. The coefficient of chloride ion diffusion varied linearly with the critical pore radius as determined by mercury intrusion porosimetry while permeability was found to follow a power-law relationship vs. this critical radius. The data set provides an opportunity to directly examine the application of the Katz-Thompson relationship to cement-based materials.

  7. Small-particle-size cement

    SciTech Connect

    Ewert, D.P.; Almond, S.W.; Blerhaus, W.M. II )

    1991-05-01

    Successful remedial cementing has historically been difficult in wells with large-interval, multizone, gravel-packed completions. The reason is the inability of conventional oilfield cements to penetrate gravel packs adequately. Small-particle-size cement (SPSC) was developed to penetrate gravel packs and to provide the zonal isolation required. This paper details the laboratory work, job design, and field implementation of this new cement.

  8. Long-term monitoring of microleakage of dental cements by radiochemical diffusion

    SciTech Connect

    Powis, D.R.; Prosser, H.J.; Wilson, A.D.

    1988-06-01

    Radioactive /sup 14/C sucrose was found to be an ideal marker for microleakage because it did not penetrate tooth tissue, dental cement, or mounting resin. The main finding is that the adhesive cements--the glass-ionomer and polycarboxylate--are significantly more effective at preventing microleakage than are the traditional phosphate cements--silicate and zinc phosphate. The differences can be as high as two orders of magnitude. The adhesive cements provide almost perfect and reliable seals. By contrast, the nonadhesive cements are erratic sealants with most of the restorations leaking.

  9. Spatially resolved diffuse reflectance spectroscopy of two-layer turbid media by densely packed multi-pixel photodiode reflectance probe

    NASA Astrophysics Data System (ADS)

    Senlik, Ozlem; Greening, Gage; Muldoon, Timothy J.; Jokerst, Nan M.

    2016-03-01

    Spatially-resolved diffuse reflectance (SRDR) measurements provide photon path information, and enable layered tissue analysis. This paper presents experimental SRDR measurements on two-layer PDMS skin tissue-mimicking phantoms of varying top layer thicknesses, and bulk phantoms of varying optical properties using concentric multi-pixel photodiode array (CMPA) probes, and corresponding forward Monte Carlo simulations. The CMPA is the most densely packed semiconductor SRDR probe reported to date. Signal contrasts between the single layer phantom and bi-layer phantoms with varying top layer thicknesses are as high as 80%. The mean error between the Monte Carlo simulations and the experiment is less than 6.2 %.

  10. The evolution of health warning labels on cigarette packs: the role of precedents, and tobacco industry strategies to block diffusion

    PubMed Central

    Hiilamo, Heikki; Crosbie, Eric; Glantz, Stanton A

    2013-01-01

    Objective To analyse the evolution and diffusion of health warnings on cigarette packs around the world, including tobacco industry attempts to block this diffusion. Methods We analysed tobacco industry documents and public sources to construct a database on the global evolution and diffusion of health warning labels from 1966 to 2012, and also analysed industry strategies. Results Health warning labels, especially labels with graphic elements, threaten the tobacco industry because they are a low-cost, effective measure to reduce smoking. Multinational tobacco companies did not object to voluntary innocuous warnings with ambiguous health messages, in part because they saw them as offering protection from lawsuits and local packaging regulations. The companies worked systematically at the international level to block or weaken warnings once stronger more specific warnings began to appear in the 1970s. Since 1985 in Iceland, the tobacco industry has been aware of the effectiveness of graphic health warning labels (GWHL). The industry launched an all-out attack in the early 1990s to prevent GHWLs, and was successful in delaying GHWLs internationally for nearly 10 years. Conclusions Beginning in 2005, as a result of the World Health Organisation Framework Convention on Tobacco Control (FCTC), GHWLs began to spread. Effective implementation of FCTC labelling provisions has stimulated diffusion of strong health warning labels despite industry opposition. PMID:23092884

  11. Vapor aluminum diffused steels for high-temperature corrosion resistance

    SciTech Connect

    Bayer, G.T.

    1995-08-01

    Steel products and fabrications that are vapor aluminum diffused by the pack cementation process offer greatly enhanced corrosion resistance in high-temperature oxidizing, sulfidizing, carburizing, and hydrogen-containing environments. Pipes and tubing are most frequently diffused with aluminum for use as transfer lines, heat exchangers, reactors, or in process furnaces handling corrosive materials. Vapor aluminum diffusion by the pack cementation process is the only practical way of providing this form of high-temperature corrosion resistance on the inside of pipes and tubes.

  12. Determination of Diffusion Profiles in Altered Wellbore Cement Using X-ray Computed Tomography Methods

    SciTech Connect

    Mason, Harris E.; Walsh, Stuart D. C.; DuFrane, Wyatt L.; Carroll, Susan A.

    2014-06-17

    The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining “effective linear activity coefficients” (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO2-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment.

  13. Determination of diffusion profiles in altered wellbore cement using X-ray computed tomography methods.

    PubMed

    Mason, Harris E; Walsh, Stuart D C; DuFrane, Wyatt L; Carroll, Susan A

    2014-06-17

    The development of accurate, predictive models for use in determining wellbore integrity requires detailed information about the chemical and mechanical changes occurring in hardened Portland cements. X-ray computed tomography (XRCT) provides a method that can nondestructively probe these changes in three dimensions. Here, we describe a method for extracting subvoxel mineralogical and chemical information from synchrotron XRCT images by combining advanced image segmentation with geochemical models of cement alteration. The method relies on determining "effective linear activity coefficients" (ELAC) for the white light source to generate calibration curves that relate the image grayscales to material composition. The resulting data set supports the modeling of cement alteration by CO2-rich brine with discrete increases in calcium concentration at reaction boundaries. The results of these XRCT analyses can be used to further improve coupled geochemical and mechanical models of cement alteration in the wellbore environment. PMID:24869420

  14. [Pulmonary CO diffusion and radiological findings in subjects formerly exposed to asbestos cement].

    PubMed

    Zona, A; Bruno, C; Agabiti, N; Pizzutelli, G; Forastiere, F

    1998-01-01

    A cross-sectional study on 117 male former asbestos-cement workers was performed. The aims of the study were: evaluation of the prevalence of respiratory symptoms, measurement of pulmonary volumes, flows and DI(co) values, detection of asbestos-related diseases, and data collection for a medical follow-up of the participants. Medical examination included ECSC questionnaire, spirometry, DI(co) measurement and chest x-ray. Time since first exposure (latency) and duration of employment were used as exposure indices: participants were subdivided into three exposure groups, respectively for latency and duration of employment. For statistical analysis, multiple linear regression and logistic regression methods were applied; significance level was p < 0.05. In 28 participants abnormal DI(co) values (< 80% of predicted) were measured, 9 subjects (8%) had radiological asbestos-related abnormalities. Lower values of DI(co), after correcting for smoking, were observed in the third latency group of subjects; an increased risk of radiological asbestos-related abnormalities was observed in relation to the duration of employment and latency. This study confirmed DI(co) as an indicator of (asbestos-related) pulmonary interstitial disease. PMID:9608195

  15. Pre-packing of cost effective antibiotic cement beads for the treatment of traumatic osteomyelitis in the developing world - an in-vitro study based in Cambodia.

    PubMed

    Noor, S; Gilson, A; Kennedy, K; Swanson, A; Vanny, V; Mony, K; Chaudhry, T; Gollogly, J

    2016-04-01

    The developing world often lacks the resources to effectively treat the most serious injuries including osteomyelitis following open fractures or surgical fracture treatment. Antibiotic cement beads are a widely accepted method of delivering antibiotics locally to the infected area following trauma. This study is based in Cambodia, a low income country struggling to recover from a recent genocide. The study aims to test the effectiveness of locally made antibiotic beads and analyse their effectiveness after being gas sterilised, packaged and kept in storage Different antibiotic beads were manufactured locally using bone cement and tested against MRSA bacteria grown from a case of osteomyelitis. Each antibiotic was tested before and after a process of gas sterilisation as well as later being tested after storage in packaging up to 42 days. The gentamicin, vancomycin, amikacin and ceftriaxone beads all inhibited growth of the MRSA on the TSB and agar plates, both before and after gas sterilisation. All four antibiotics continued to show similar zones of inhibition after 42 days of storage. The results show significant promise to produce beads with locally obtainable ingredients in an austere environment and improve cost effectiveness by storing them in a sterilised condition. PMID:26899719

  16. Kinetics of pack aluminization of nickel

    NASA Technical Reports Server (NTRS)

    Seigle, L. L.; Gupta, B. K.; Shankar, R.; Sarkhel, A. K.

    1978-01-01

    The kinetics of pack aluminization of unalloyed nickel in packs of varying aluminum activity with various halide activators were studied. Surface compositions of the coatings as functions of time, temperature, and pack composition were obtained in order to establish the boundary conditions for diffusion in the system. The structure of the packs was also examined in order to clarify the mechanism of aluminum transport. The results indicate that the kinetics of pack aluminization are controlled jointly by gas diffusion in the pack and solid diffusion in the coating. Levine and Caves' model for gas diffusion was combined with calculations of rates of diffusion in the solid to formulate a more complete theory for the kinetics of pack aluminization.

  17. Migration and head penetration of Vitamin-E diffused cemented polyethylene cup compared to standard cemented cup in total hip arthroplasty: study protocol for a randomised, double-blind, controlled trial (E1 HIP)

    PubMed Central

    Sköldenberg, Olof; Rysinska, Agata; Chammout, Ghazi; Salemyr, Mats; Muren, Olle; Bodén, Henrik; Eisler, Thomas

    2016-01-01

    Introduction In vitro, Vitamin-E-diffused, highly cross-linked polyethylene (PE) has been shown to have superior wear resistance and improved mechanical properties when compared to those of standard highly cross-linked PE liners used in total hip arthroplasty (THA). The aim of the study is to evaluate the safety of a new cemented acetabular cup with Vitamin-E-doped PE regarding migration, head penetration and clinical results. Methods and analysis In this single-centre, double-blinded, randomised controlled trial, we will include 50 patients with primary hip osteoarthritis scheduled for THA and randomise them in a 1:1 ratio to a cemented cup with either argon gas-sterilised PE (control group) or Vitamin-E-diffused PE (vitamin-e group). All patients and the assessor of the primary outcome will be blinded and the same uncemented stem will be used for all participants. The primary end point will be proximal migration of the cup at 2 years after surgery measured with radiostereometry. Secondary end points include proximal migration at other follow-ups, total migration, femoral head penetration, clinical outcome scores and hip-related complications. Patients will be followed up at 3 months and at 1, 2, 5 and 10 years postoperatively. Results Results will be analysed using 95% CIs for the effect size. A regression model will also be used to adjust for stratification factors. Ethics and dissemination The ethical committee at Karolinska Institutet has approved the study. The first results from the study will be disseminated to the medical community via presentations and publications in relevant medical journals when the last patient included has been followed up for 2 years. Trial registration number NCT02254980. PMID:27388352

  18. Modeling packed bed sorbent systems with the Pore Surface Diffusion Model: Evidence of facilitated surface diffusion of arsenate in nano-metal (hydr)oxide hybrid ion exchange media.

    PubMed

    Dale, Sachie; Markovski, Jasmina; Hristovski, Kiril D

    2016-09-01

    This study explores the possibility of employing the Pore Surface Diffusion Model (PSDM) to predict the arsenic breakthrough curve of a packed bed system operated under continuous flow conditions with realistic groundwater, and consequently minimize the need to conduct pilot scale tests. To provide the nano-metal (hydr)oxide hybrid ion exchange media's performance in realistic water matrices without engaging in taxing pilot scale testing, the multi-point equilibrium batch sorption tests under pseudo-equilibrium conditions were performed; arsenate breakthrough curve of short bed column (SBC) was predicted by the PSDM in the continuous flow experiments; SBC tests were conducted under the same conditions to validate the model. The overlapping Freundlich isotherms suggested that the water matrix and competing ions did not have any denoting effect on sorption capacity of the media when the matrix was changed from arsenic-only model water to real groundwater. As expected, the PSDM provided a relatively good prediction of the breakthrough profile for arsenic-only model water limited by intraparticle mass transports. In contrast, the groundwater breakthrough curve demonstrated significantly faster intraparticle mass transport suggesting to a surface diffusion process, which occurs in parallel to the pore diffusion. A simple selection of DS=1/2 DP appears to be sufficient when describing the facilitated surface diffusion of arsenate inside metal (hydr)oxide nano-enabled hybrid ion-exchange media in presence of sulfate, however, quantification of the factors determining the surface diffusion coefficient's magnitude under different treatment scenarios remained unexplored. PMID:26672387

  19. Battery pack

    SciTech Connect

    Weaver, R.J.; Brittingham, D.C.; Basta, J.C.

    1993-07-06

    A battery pack is described, having a center of mass, for use with a medical instrument including a latch, an ejector, and an electrical connector, the battery pack comprising: energy storage means for storing electrical energy; latch engagement means, physically coupled to the energy storage means, for engaging the latch; ejector engagement means, physically coupled to the energy storage means, for engaging the ejector; and connector engagement means, physically coupled to the energy storage means, for engaging the connector, the latch engagement means, ejector engagement means, and connector engagement means being substantially aligned in a plane offset from the center of mass of the battery pack.

  20. Formation of Cr-modified silicide coatings on a Ti-Nb-Si based ultrahigh-temperature alloy by pack cementation process

    NASA Astrophysics Data System (ADS)

    Qiao, Yanqiang; Guo, Xiping

    2010-10-01

    Cr-modified silicide coatings were prepared on a Ti-Nb-Si based ultrahigh temperature alloy by Si-Cr co-deposition at 1250 °C, 1350 °C and 1400 °C for 5-20 h respectively. It was found that both coating structure and phase constituents changed significantly with increase in the co-deposition temperature and holding time. The outer layers in all coatings prepared at 1250 °C for 5-20 h consisted of (Ti,X) 5Si 3 (X represents Nb, Cr and Hf elements). (Ti,X) 5Si 4 was found as the only phase constituent in the intermediate layers in both coatings prepared at 1250 °C for 5 and 10 h, but the intermediate layers in the coatings prepared at 1250 °C for 15 and 20 h were mainly composed of (Ti,X) 5Si 3 phase that was derived from the decomposition of (Ti,X) 5Si 4 phase. In the coating prepared at 1350 °C for 5 h, single (Ti,X) 5Si 3 phase was found in its outmost layer, the same as that in the outer layers in the coatings prepared at 1250 °C; but in the coatings prepared at 1350 °C for 10-20 h, (Nb 1.95Cr 1.05)Cr 2Si 3 ternary phase was found in the outmost layers besides (Ti,X) 5Si 3 phase. In the coatings prepared at 1400 °C for 5-20 h, (Nb 1.95Cr 1.05)Cr 2Si 3 ternary phase was the single phase constituent in their outmost layers. The phase transformation (Ti,X) 5Si 4 → (Ti,X) 5Si 3 + Si occurred in the intermediate layers of the coatings prepared at 1350 and 1400 °C with prolonging co-deposition time, similar to the situation in the coatings prepared at 1250 °C for 15 and 20 h, but this transformation has been speeded up by increase in the co-deposition temperature. The transitional layers were mainly composed of (Ti,X) 5Si 3 phase in all coatings. The influence of co-deposition temperature on the diffusion ability of Cr atoms was greater than that of Si atoms in the Si-Cr co-deposition processes investigated. The growth of coatings obeyed inverse logarithmic laws at all three co-deposition temperatures. The Si-Cr co-deposition coating prepared at 1350

  1. Calculation of the geometrical three-point parameter constant appearing in the second order accurate effective medium theory expression for the B-term diffusion coefficient in fully porous and porous-shell random sphere packings.

    PubMed

    Deridder, Sander; Desmet, Gert

    2012-02-01

    Using computational fluid dynamics (CFD), the effective B-term diffusion constant γ(eff) has been calculated for four different random sphere packings with different particle size distributions and packing geometries. Both fully porous and porous-shell sphere packings are considered. The obtained γ(eff)-values have subsequently been used to determine the value of the three-point geometrical constant (ζ₂) appearing in the 2nd-order accurate effective medium theory expression for γ(eff). It was found that, whereas the 1st-order accurate effective medium theory expression is accurate to within 5% over most part of the retention factor range, the 2nd-order accurate expression is accurate to within 1% when calculated with the best-fit ζ₂-value. Depending on the exact microscopic geometry, the best-fit ζ₂-values typically lie in the range of 0.20-0.30, holding over the entire range of intra-particle diffusion coefficients typically encountered for small molecules (0.1 ≤ D(pz)/D(m) ≤ 0.5). These values are in agreement with the ζ₂-value proposed by Thovert et al. for the random packing they considered. PMID:22236565

  2. Determination of Diffusion Coefficients in Cement-Based Materials: An Inverse Problem for the Nernst-Planck and Poisson Models

    NASA Astrophysics Data System (ADS)

    Szyszkiewicz-Warzecha, Krzysztof; Jasielec, Jerzy J.; Fausek, Janusz; Filipek, Robert

    2016-06-01

    Transport properties of ions have significant impact on the possibility of rebars corrosion thus the knowledge of a diffusion coefficient is important for reinforced concrete durability. Numerous tests for the determination of diffusion coefficients have been proposed but analysis of some of these tests show that they are too simplistic or even not valid. Hence, more rigorous models to calculate the coefficients should be employed. Here we propose the Nernst-Planck and Poisson equations, which take into account the concentration and electric potential field. Based on this model a special inverse method is presented for determination of a chloride diffusion coefficient. It requires the measurement of concentration profiles or flux on the boundary and solution of the NPP model to define the goal function. Finding the global minimum is equivalent to the determination of diffusion coefficients. Typical examples of the application of the presented method are given.

  3. Pattern formations and optimal packing.

    PubMed

    Mityushev, Vladimir

    2016-04-01

    Patterns of different symmetries may arise after solution to reaction-diffusion equations. Hexagonal arrays, layers and their perturbations are observed in different models after numerical solution to the corresponding initial-boundary value problems. We demonstrate an intimate connection between pattern formations and optimal random packing on the plane. The main study is based on the following two points. First, the diffusive flux in reaction-diffusion systems is approximated by piecewise linear functions in the framework of structural approximations. This leads to a discrete network approximation of the considered continuous problem. Second, the discrete energy minimization yields optimal random packing of the domains (disks) in the representative cell. Therefore, the general problem of pattern formations based on the reaction-diffusion equations is reduced to the geometric problem of random packing. It is demonstrated that all random packings can be divided onto classes associated with classes of isomorphic graphs obtained from the Delaunay triangulation. The unique optimal solution is constructed in each class of the random packings. If the number of disks per representative cell is finite, the number of classes of isomorphic graphs, hence, the number of optimal packings is also finite. PMID:26852668

  4. Bone cement

    PubMed Central

    Vaishya, Raju; Chauhan, Mayank; Vaish, Abhishek

    2013-01-01

    The knowledge about the bone cement is of paramount importance to all Orthopaedic surgeons. Although the bone cement had been the gold standard in the field of joint replacement surgery, its use has somewhat decreased because of the advent of press-fit implants which encourages bone in growth. The shortcomings, side effects and toxicity of the bone cement are being addressed recently. More research is needed and continues in the field of nanoparticle additives, enhanced bone–cement interface etc. PMID:26403875

  5. Heterogeneity of packing: structural approach.

    PubMed Central

    Kurochkina, N.; Privalov, G.

    1998-01-01

    Analysis of the heterogeneity of packing in proteins showed that different groups of the protein preferentially contribute to low- or high-density regions. Statistical distribution reveals the two preferable values for packing density in the form of two peaks. One peak occurs in the range of densities 0.55-0.65, the other occurs in the range 0.75-0.8. The high-density peak is originated primarily by high packing inside the hydrogen bonded backbone and to some extent by side chains. Polar/charged and apolar side chains both contribute to the low-density peak. The average packing density values of individual atomic groups significantly vary for backbone atoms as well as for side chain atoms. The carbonyl oxygen atoms of protein backbone and the end groups of side chains show lower packing density than the rest of the protein. The side-chain atomic groups of a secondary structure element when packed against the neighboring secondary structure element form stronger contacts with the side chains of this element than with its backbone. Analysis of the low-density regions around each buried peptide group was done for the set of proteins with different types of packing, including alpha-alpha, alpha-beta, and beta-beta packing. It was shown that cavities are regularly situated in the groove of secondary structure element packed against neighboring elements for all types of packing. Low density in the regions surrounding the peptide groups and the end groups of side chains can be explained by their positioning next to a cavity formed upon the association of secondary structure elements. The model proposed can be applied to the analysis of protein internal motions, mechanisms of cellular signal transduction, diffusion through protein matrix, and other events. PMID:9568896

  6. Cement disease.

    PubMed

    Jones, L C; Hungerford, D S

    1987-12-01

    Does "cement disease" exist? The bony environment surrounding a loosened cemented prosthesis is an abnormal pathologic condition which, if left unattended, will progress to a total failure of the joint including an inhibition of function and immobilizing pain. That biomaterial properties of the cement used for fixation also contribute to the pathologic state separates this disease from other modes of loosening. This leads inevitably to the conclusion that "cement disease" does exist. Methyl methacrylate has revolutionized the treatment of severe joint dysfunction. There can be no doubt that improving surgical technique, cement handling, and the cement itself will continue to improve the results and reduce the incidence of failure due to loosening. Cement is undoubtedly satisfactory for elderly patients with low activity levels and relatively short life expectancies. However, because of the inherent biologic and biomechanical properties of methyl methacrylate, it is unlikely that it can be rendered satisfactory in the long run for the young, the active, or the overweight patient, for whom alternatives are currently being sought. In such cases, the elimination of "cement disease" can only occur with the elimination of cement. Alternatives include the search for other grouting materials and the development of prostheses with satisfactory surfaces for either press-fit or biologic ingrowth. PMID:3315375

  7. Does elevating silver content in zinc-based glass polyalkenoate cements increase their antibacterial efficacy against two common bacteria using the agar gel diffusion method?

    PubMed

    Coughlan, A; Breed, S M; Ashraf, C; Cardinale, J A; Hall, M M; Towler, M R

    2013-03-01

    The authors have previously shown that it is possible to incorporate silver into a soda-zinc-silicate glass and subsequently form a glass polyalkenoate cement from it. The objective of the research described herein is to determine if incremental increases in the silver content of these glass polyalkenoate cements will increase their antibacterial efficacy against gram-positive and gram-negative bacteria using the accepted spread plate method. Four glass polyalkenoate cements were formulated; three contained increasing amounts of silver incorporated into them (cements A, B, and C, containing 0.33 mol%, 0.66 mol%, and 0.99 mol% silver, respectively) and a fourth contained no silver, which acted as a control (control cement). The handling properties of the glass polyalkenoate cements were evaluated, where working times were around 2 min and setting times ranged from 1 h 17 min to 2 h 41 min. Inductively coupled plasma atomic emission spectroscopy was employed to determine silver ion release with cement maturation for up to 14 days. The majority of silver ions were released within the first 24 h, with up to 2 mg/L cumulative ion release recorded up to 14 days. The antibacterial properties of the coatings were evaluated against Staphylococcus aureus and Pseudomonas aeruginosa bacteria. The silver-glass polyalkenoate cements exhibited antibacterial effect against both bacterial strains. The maximum inhibition zones recorded against S. aureus was 14.8 mm (SD ± 1.11) and against P. aeruginosa was 20.6 mm (SD ± 0.81). Cement B had a greater antibacterial effect compared to cement A, however, cements B and C had comparable antibacterial effects after 14 days even though cement C contained 0.33 mol% more silver than B. This indicates that by increasing the silver content in these cements, the antibacterial efficacy increases to a point, but there is a threshold where further silver ion release does not increase the antibacterial effect

  8. Packed Bed Reactor Experiment

    NASA Video Gallery

    The purpose of the Packed Bed Reactor Experiment in low gravity is to determine how a mixture of gas and liquid flows through a packed bed in reduced gravity. A packed bed consists of a metal pipe ...

  9. Intrusion Characteristics of High Viscosity Bone Cements for the Tibial Component of a Total Knee Arthroplasty Using Negative Pressure Intrusion Cementing Technique

    PubMed Central

    Dinh, Nam L.; O’Chong, Alexander CM.; Walden, Justin K.; Adrian, Scott C.; Cusick, Robert P.

    2016-01-01

    Background With the advent of new bone cements with different viscosities, it is important to understand how they respond to different cementing techniques. The purpose of this study was to evaluate the high viscosity (HV) bone cement intrusion characteristics comparing negative pressure intrusion technique (NPI) and finger-packing technique in a cadaveric proximal tibial bone. Methods Soft tissues were removed from twenty- four fresh frozen cadaver proximal tibiae, and standard arthroplasty tibial cuts were performed. Palacos-R (Zimmer, Warsaw, IN) and Simplex-HV (Stryker Howmedica Osteonics, Mahwah, NJ) bone cement were used. Each tibia was randomly assigned to receive one of the two bone cements with finger-packing technique and NPI technique. Forty-five Newton weight was applied along the long axis of the tibia during cement-setting phase. Once the cement had cured, sagittal sections were prepared and analyzed for cement penetration depth using digital photography and stereoscopic micrographs. Area of interest (AOI) for each specimen was also used to quantitatively evaluate the area of cement penetration. Results When using Palacos-R, significant dif ferences were detected in cement penetration between the two cementing techniques. On the other hand, when using Simplex-HV, cement penetration was not significantly increased with finger-packing technique when compared to NPI technique. When comparing the two high-viscosity bone cements when using NPI cementing technique, significant differences were detected at Zone 4, where Simplex-HV penetrated deeper than the Palacos-R. When finger-packing technique was used with Simplex-HV, significant differences were detected in bone cement penetration at Zones 3-5. When looking at AOI, no significant differences were found between the Palacos-R and Simplex-HV bone cements in terms of penetration depths with NPI technique. Higher penetration depths were achieved with Simplex-HV bone cement compared to Palacos-R cement in

  10. Criteria for Remote Sensing Detection of Sulfate Cemented Soils on Mars

    NASA Technical Reports Server (NTRS)

    Cooper, Christopher D.; Mustard, John F.

    2000-01-01

    Spectral measurements of loose and cemented mixtures of palagonitic soil and sulfates were made to determine whether cemented soils could be identified on Mars. Cemented MgSO4 mixtures exhibit an enhanced 9 micron sulfate fundamental compared to gypsum mixtures due to more diffuse and pervasive cementing.

  11. Thermodynamics and kinetics of pack aluminide coating formation on IN-100

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Caves, R. M.

    1973-01-01

    An investigation of the effects of pack variables on the formation of aluminide coatings on nickel-base superalloy IN-100 was conducted. Also, the thermodynamics and kinetics of coating formation were analyzed. Observed coating weights were in good agreement with predictions made from the analysis. Pack temperature rather than pack aluminum activity controls the principal coating phase formed. In 1 weight percent aluminum packs, aluminum weight gains were related to the halide pack activator. Solid-state nickel diffusion controlled coating formation from sodium fluoride and chloride and ammonium fluoride activated packs. In other ammonium and sodium halide activated 1 weight percent aluminum packs, gaseous diffusion controlled coating formation.

  12. The impact of cemented layers and hardpans on oxygen diffusivity in mining waste heaps: a field study of the Halsbrücke lead-zinc mine tailings (Germany).

    PubMed

    Kohfahl, Claus; Graupner, Torsten; Fetzer, Christian; Pekdeger, Asaf

    2010-11-01

    This article reports fibre-optic oxygen measurements on a reactive mine waste heap located in the polymetallic sulphide mine district of Freiberg in south-eastern Germany. The heaped material consists of sulphide-bearing tailings from a processing plant of a lead-zinc mine. Mine waste material was deposited in the water phase after separation of mining ores in a flotation process. The tailing impoundment is partly covered with coarse sand and topsoil. Oxygen profiles were monitored during one year at eleven locations showing different physical and mineralogical compositions. At each location a borehole was drilled where the optic sensors were installed at 2-5 different depths. After installation the oxygen profiles were monitored seven times during one year from 2006-2007 and three to five oxygen profiles at each location were obtained. Oxygen measurements were accompanied by physical, chemical and mineralogical data of the tailing material. Additionally, a detailed mineralogical profile was analysed at a location representative for the central part of the heap, where the cemented layers show lateral continuity. Results showed that cemented layers have a significant influence on natural attenuation of the toxic As and Pb species owing to their capacity of water retention. The measured oxygen profiles are controlled by the zone of active pyrite weathering as well as by the higher water content in the cemented layers which reduces gaseous atmospheric oxygen supply. In contrast, gypsum bearing hardpans detected at three other locations have no detectable influence on oxygen profiles. Furthermore, the grain size distribution was proved to have a major effect on oxygen diffusivity due to its control on the water saturation. Temporal changes of the oxygen profiles were only observed at locations with coarse sediment material indicating also an important advective part of gas flux. PMID:20850166

  13. Lunar cement

    NASA Technical Reports Server (NTRS)

    Agosto, William N.

    1992-01-01

    With the exception of water, the major oxide constituents of terrestrial cements are present at all nine lunar sites from which samples have been returned. However, with the exception of relatively rare cristobalite, the lunar oxides are not present as individual phases but are combined in silicates and in mixed oxides. Lime (CaO) is most abundant on the Moon in the plagioclase (CaAl2Si2O8) of highland anorthosites. It may be possible to enrich the lime content of anorthite to levels like those of Portland cement by pyrolyzing it with lunar-derived phosphate. The phosphate consumed in such a reaction can be regenerated by reacting the phosphorus product with lunar augite pyroxenes at elevated temperatures. Other possible sources of lunar phosphate and other oxides are discussed.

  14. Sculpting with Cement.

    ERIC Educational Resources Information Center

    Olson, Lynn

    1983-01-01

    Cement offers many creative possibilities for school art programs. Instructions are given for sculpting with fiber-cement and sand-cement, as well as for finishing processes and the addition of color. Safety is stressed. (IS)

  15. On the kinetics of the pack - Aluminization process

    NASA Technical Reports Server (NTRS)

    Sivakumar, R.; Seigle, L. L.

    1976-01-01

    An investigation has been made of the aluminization of unalloyed Ni in fluoride-activated packs of varying Al activity. In packs of low Al activity, in which the ratio of Al to Ni was less than 50 at. pct, the specimen surface quickly came to equilibrium with the pack and remained close to equilibrium for the duration of normal coating runs. In these packs the kinetics of aluminization was controlled by diffusion in the solid. In packs of higher Al activity the surface of the specimen did not come to equilibrium with the pack and the kinetics of the process was governed by a combination of solid and gas diffusion rates. Under most conditions however, the surface composition was time-invariant and a steady-state appeared to exist at the pack-coating interface. By combining Levine and Caves' model for gaseous diffusion in pure-Al packs with calculations of solid diffusion rates some success has been achieved in explaining the results.

  16. Flat Pack Toy Design

    ERIC Educational Resources Information Center

    Hutcheson, Brian

    2007-01-01

    In this article, the author introduces the concept of flat pack toys. Flat pack toys are designed using a template on a single sheet of letter-sized card stock paper. Before being cut out and built into a three-dimensional toy, they are scanned into the computer and uploaded to a website. With the template accessible from the website, anyone with…

  17. TLC Pack Unpacked

    ERIC Educational Resources Information Center

    Oberhofer, Margret; Colpaert, Jozef

    2015-01-01

    TLC Pack stands for Teaching Languages to Caregivers and is a course designed to support migrants working or hoping to work in the caregiving sector. The TLC Pack resources range from A2 to B2 level of the Common European Framework of Reference for Languages (CEFR), and will be made available online in the six project languages: Dutch, English,…

  18. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-07-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that was performed to analyze the alkali-silica reactivity of ULHS in cement slurries.

  19. Barrier properties of k-mer packings

    NASA Astrophysics Data System (ADS)

    Lebovka, N.; Khrapatiy, S.; Vygornitskyi; Pivovarova, N.

    2014-08-01

    This work discusses numerical studies of the barrier properties of k-mer packings by the Monte Carlo method. The studied variants of regular and non-regular arrangements on a square lattice included models of random sequential adsorption (RSA) and random deposition (RD). The discrete problem of diffusion through the bonds of a square lattice was considered. The k-mers were perfectly oriented perpendicular to the diffusion direction and blocked certain fraction of bonds fb against diffusion. The barrier efficiency was estimated by calculation of the ratio D/Do where D is diffusion coefficient in direction perpendicular to the orientation of k-mers and Do is the same value for diffusion on the square lattice without blocked bonds, i.e., at fb=0. The value of k varied from 1 to 512 and different lattice sizes up to L=8192 lattice units were used. For dense packings (p=1), the obtained D/Do versus fb dependences deviated from the theoretical prediction of effective medium (EM) theory and deviation was the most obvious for the regular non-staggered arrangement. For loose RSA and RD packings, the percolation like-behavior of D/Do with threshold at fb=p∞ was observed and the data evidenced that their barrier properties at large values of k may be more effective than those of some dense packings. Such anomalous behavior can reflect the details of k-mer spatial organization (aggregation) and structure of pores in RD and RSA packings. The contradictions between simulation data and predictions of EM theory were also discussed.

  20. Development of fluidized bed cement sintering technology

    SciTech Connect

    Mukai, Katsuji

    1994-12-31

    In the new system presented in this paper, the cement clinker is sintered, not in a rotary kiln, but in two different furnaces: a spouted bed kiln and a fluidized bed kiln. The heat generated in the process of cooling the cement clinker is recovered by a fluidized bed cooler and a packed bed cooler, which are more efficient than the conventional coolers. Compared with the rotary kiln system, the new technology significantly reduces NO{sub x} emissions, appreciably cuts energy consumption, and reduces CO{sub 2} emissions as well. Thus, the new system is an efficient cement sintering system that is friendly to the global environment. In this paper, we describe this new technology as one of the applied technologies at an industrial level that is being developed in the Clean Coal Technology Project, and we present the results from test operations at our pilot plant.

  1. Gelatin manipulation of latent macropores formation in brushite cement.

    PubMed

    Yin, Yuji; Ye, Fen; Cai, Shu; Yao, Kangde; Cui, Junfeng; Song, Xuefeng

    2003-03-01

    Macroporous brushite cement was prepared from a mixture of beta-tricalcium phosphate (beta-TCP) and monocalcium phosphate monohydrate (MCPM) using gelatin powder as a latent templates. In a setting reaction coexisting with gelatin, closed packed, open-pore structure with 100-200 microm macropores are obtained after immersion of the set cement into PBS buffer (pH 7.4) at 37 degrees C for 1-4 weeks. The macroporous brushite cement has compressive strength of 15 MPa originally, which reducing to 5.5 MPa with macropore formation gradually in comparison to that of cancellous bone (5-10 MPa). PMID:15348472

  2. Graphitic packing removal tool

    SciTech Connect

    Meyers, K.E.; Kolsun, G.J.

    1996-12-31

    Graphitic packing removal tools are described for removal of the seal rings in one piece from valves and pumps. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  3. Graphitic packing removal tool

    DOEpatents

    Meyers, K.E.; Kolsun, G.J.

    1997-11-11

    Graphitic packing removal tools for removal of the seal rings in one piece are disclosed. The packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal. 5 figs.

  4. Graphitic packing removal tool

    DOEpatents

    Meyers, Kurt Edward; Kolsun, George J.

    1997-01-01

    Graphitic packing removal tools for removal of the seal rings in one piece. he packing removal tool has a cylindrical base ring the same size as the packing ring with a surface finish, perforations, knurling or threads for adhesion to the seal ring. Elongated leg shanks are mounted axially along the circumferential center. A slit or slits permit insertion around shafts. A removal tool follower stabilizes the upper portion of the legs to allow a spanner wrench to be used for insertion and removal.

  5. Packed bed carburization of tantalum and tantalum alloy

    DOEpatents

    Lopez, Peter C.; Rodriguez, Patrick J.; Pereyra, Ramiro A.

    1999-01-01

    Packed bed carburization of a tantalum or tantalum alloy object. A method for producing corrosion-resistant tantalum or tantalum alloy objects is described. The method includes the steps of placing the object in contact with a carburizing pack, heating the packed object in vacuum furnace to a temperature whereby carbon from the pack diffuses into the object forming grains with tantalum carbide along the grain boundaries, and etching the surface of the carburized object. This latter step removes tantalum carbides from the surface of the carburized tantalum object while leaving the tantalum carbide along the grain boundaries.

  6. Packed bed carburization of tantalum and tantalum alloy

    DOEpatents

    Lopez, P.C.; Rodriguez, P.J.; Pereyra, R.A.

    1999-06-29

    Packed bed carburization of a tantalum or tantalum alloy object is disclosed. A method for producing corrosion-resistant tantalum or tantalum alloy objects is described. The method includes the steps of placing the object in contact with a carburizing pack, heating the packed object in vacuum furnace to a temperature whereby carbon from the pack diffuses into the object forming grains with tantalum carbide along the grain boundaries, and etching the surface of the carburized object. This latter step removes tantalum carbides from the surface of the carburized tantalum object while leaving the tantalum carbide along the grain boundaries. 4 figs.

  7. Nasal packing and stenting

    PubMed Central

    Weber, Rainer K.

    2011-01-01

    Nasal packs are indispensable in ENT practice. This study reviews current indications, effectiveness and risks of nasal packs and stents. In endoscopic surgery, nasal packs should always have smooth surfaces to minimize mucosal damage, improve wound healing and increase patient comfort. Functional endoscopic endonasal sinus surgery allows the use of modern nasal packs, since pressure is no longer required. So called hemostatic/resorbable materials are a first step in this direction. However, they may lead to adhesions and foreign body reactions in mucosal membranes. Simple occlusion is an effective method for creating a moist milieu for improved wound healing and avoiding dryness. Stenting of the frontal sinus is recommended if surgery fails to produce a wide, physiologically shaped drainage path that is sufficiently covered by intact tissue. PMID:22073095

  8. Tiber winding pack design

    SciTech Connect

    Miller, J.R.

    1985-08-19

    A preliminary winding pack design was performed with the goal of showing feasibility of producing 10-T maximum field with a pack current density of 40 A.mm/sup -2/ while accepting 2.7 kW per coil nuclear heating. A cable-in-conduit conductor design (CIC), reported at the 6th Topical Meeting on the Technology of Fusion Energy, was based on several key issues.

  9. Thermodynamics and kinetics of pack aluminide coating formation on IN-100

    NASA Technical Reports Server (NTRS)

    Levine, S. R.; Caves, R. M.

    1973-01-01

    An investigation of the effects of pack variables on the formation of aluminide coatings on nickel-base superalloy IN-100 was conducted. Also, the thermodynamics and kinetics of coating formation were analyzed. Observed coating weights were in good agreement with predictions made from the analysis. Pack temperature rather than pack aluminum activity controls the principal coating phase formed. Solid-state nickel diffusion controlled coating formation from sodium fluoride and chloride and ammonium fluoride activated packs. In other ammonium and sodium halide activated 1 weight percent aluminum packs, gaseous diffusion controlled coating formation.

  10. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-10-31

    The objective of this project is to develop an improved ultra- lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries.

  11. In vitro antibacterial activity of glass-ionomer cements.

    PubMed

    Herrera, M; Carrión, P; Baca, P; Liébana, J; Castillo, A

    2001-01-01

    The in vitro antibacterial activity of the glass-ionomer restorative cements Ketac-Cem, Ketac-Bond, Ketac-Silver and Vitrebond was studied in conjunction with 32 strains of five bacteria involved in the development of caries: Streptococcus spp., Lactobacillus spp., Actinomyces spp., Porphyromonas spp. and Clostridium spp. The agar plate diffusion method was used for the cultures, which included a chlorhexidine positive control. All the glass-ionomer cements tested inhibited bacterial growth, but with considerable differences in the scope of their action. Of the four cements, Vitrebond, a resin-modified glass-ionomer cement, was determined to be the most effective bacterial inhibitor. PMID:11327108

  12. The packing of particles

    SciTech Connect

    Cumberland, D.J.; Crawford, R.J.

    1987-01-01

    The wide range of information currently available on the packing of particles is brought together in this monograph. The authors' interest in the subject was initially aroused by the question of whether there is an optimum particle size distribution which would maximise the packing density of particles - a question which has attracted the interest of scientists and engineers for centuries. The densification of a powder mass is of relevance in a great many industries, among them the pharmaceutical, ceramic, powder metallurgy and civil engineering industries. In addition, the packing of regular - or irregular - shaped particles is also of relevance to a surprisingly large number of other industries and subject areas, i.e. the foundry industry, nuclear engineering, chemical engineering, crystallography, geology, biology, telecommunications, and so on. Accordingly, this book is written for a wide audience.

  13. Pessimal shapes for packing

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav

    2014-03-01

    The question of which convex shapes leave the most empty space in their densest packing is the subject of Reinhardt's conjecture in two dimensions and Ulam's conjecture in three dimensions. Such conjectures about pessimal packing shapes have proven notoriously difficult to make progress on. I show that the regular heptagon is a local pessimum among all convex shapes, and that the 3D ball is a local pessimum among origin-symmetric shapes. Any shape sufficiently close in the space of shapes to these local pessima can be packed at a greater efficiency than they. In two dimensions and in dimensions above three, the ball is not a local pessimum, so the situation in 3D is unusual and intriguing. I will discuss what conditions conspire to make the 3D ball a local pessimum and whether we can prove that it is also a global pessimum.

  14. Dynamics of random packings in granular flow

    NASA Astrophysics Data System (ADS)

    Rycroft, Chris H.; Bazant, Martin Z.; Grest, Gary S.; Landry, James W.

    2006-05-01

    We present a multiscale simulation algorithm for amorphous materials, which we illustrate and validate in a canonical case of dense granular flow. Our algorithm is based on the recently proposed spot model, where particles in a dense random packing undergo chainlike collective displacements in response to diffusing “spots” of influence, carrying a slight excess of interstitial free volume. We reconstruct the microscopic dynamics of particles from the “coarse grained” dynamics of spots by introducing a localized particle relaxation step after each spot-induced block displacement, simply to enforce packing constraints with a (fairly arbitrary) soft-core repulsion. To test the model, we study to what extent it can describe the dynamics of up to 135 000 frictional, viscoelastic spheres in granular drainage simulated by the discrete-element method (DEM). With only five fitting parameters (the radius, volume, diffusivity, drift velocity, and injection rate of spots), we find that the spot simulations are able to largely reproduce not only the mean flow and diffusion, but also some subtle statistics of the flowing packings, such as spatial velocity correlations and many-body structural correlations. The spot simulations run over 100 times faster than the DEM and demonstrate the possibility of multiscale modeling for amorphous materials, whenever a suitable model can be devised for the coarse-grained spot dynamics.

  15. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-04-15

    The objective of this project is to develop an improved ultra-lightweight cement using ultralight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Problems and Task 3: Test Ultra-Lightweight Cements. Results reported this quarter include a review and summary of Halliburton Energy Services (HES) and BJ Services historical performance data for lightweight cement applications. These data are analyzed and compared to ULHS cement and foamed cement performances. Similar data is expected from Schlumberger, and an analysis of this data will be completed in the following phases of the project. Quality control testing of materials used to formulate ULHS cements in the laboratory was completed to establish baseline material performance standards. A testing protocol was developed employing standard procedures as well as procedures tailored to evaluate ULHS and foamed cement. This protocol is presented and discussed. Results of further testing of ULHS cements are presented along with an analysis to establish cement performance design criteria to be used during the remainder of the project. Finally, a list of relevant literature on lightweight cement performance is compiled for review during the next quarter.

  16. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-07-18

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses Task 1: Assess Ultra-Lightweight Cementing Issues, Task 2: Review Russian Ultra-Lightweight Cement Literature, Task 3: Test Ultra-Lightweight Cements, and Task 8: Develop Field ULHS Cement Blending and Mixing Techniques. Results reported this quarter include: preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; summary of pertinent information from Russian ultra-lightweight cement literature review; laboratory tests comparing ULHS slurries to foamed slurries and sodium silicate slurries for two different applications; and initial laboratory studies with ULHS in preparation for a field job.

  17. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-04-29

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, and shear bond. Testing to determine the effect of temperature cycling on the shear bond properties of the cement systems was also conducted. In addition, the stress-strain behavior of the cement types was studied. This report discusses a software program that is being developed to help design ULHS cements and foamed cements.

  18. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-10-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems, including foamed and sodium silicate slurries. During this project quarter, a comparison study of the three cement systems examined the effect that cement drillout has on the three cement systems. Testing to determine the effect of pressure cycling on the shear bond properties of the cement systems was also conducted. This report discusses testing that will be performed for analyzing the alkali-silica reactivity of ULHS in cement slurries, as well as the results of Field Tests 1 and 2.

  19. Economics Action Pack.

    ERIC Educational Resources Information Center

    McDonald's Corp., Oak Brook, IL.

    One of five McDonald's Action Packs, this learning package introduces intermediate grade students to basic economic concepts. The fourteen activities include the topics of consumption (4 activities), production (5), the market system (3), a pretest, and a posttest. Specific titles under consumption include The Wonderful Treasure Tree (introduction…

  20. AUTOmatic Message PACKing Facility

    Energy Science and Technology Software Center (ESTSC)

    2004-07-01

    AUTOPACK is a library that provides several useful features for programs using the Message Passing Interface (MPI). Features included are: 1. automatic message packing facility 2. management of send and receive requests. 3. management of message buffer memory. 4. determination of the number of anticipated messages from a set of arbitrary sends, and 5. deterministic message delivery for testing purposes.

  1. Packing Them In.

    ERIC Educational Resources Information Center

    Carter, Claudia

    1997-01-01

    This activity involves students investigating the mathematics of packaging and exploring various concepts in geometry, including area and the Pythagorean theorem. Mathematics comes out of the discussion of packaging cans into six-packs and focuses on the cost-effectiveness of the horizontal storage area used. Students learn how knowledge of…

  2. Sun Packs Double Punch

    NASA Video Gallery

    On August 3, the sun packed a double punch, emitting a M6.0-class flare at 9:43 am EDT. This video is of the second, slightly stronger M9.3-class flare at 11:41 pm EDT. Both flares had significant ...

  3. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

    Describes a very successful attempt to teach fractions to year 5 pupils based on pupils making their own fraction pack. Children decided for themselves how to make the fractional slices used in the activity using colored cardboard sheets and templates of a paper circle consisting of 24 equal slices. (Author/NB)

  4. Nutrition Action Pack.

    ERIC Educational Resources Information Center

    Sockut, Joanne; Stumpe, Stephanie

    One of five McDonald's Action Packs, these instructional materials integrate elementary school-level nutrition education into other disciplines--biology, sociology, physiology, mathematics, and art. Contents include four units consisting of twelve activities. Unit 1, Why You Need Food, is a self-examination of what is needed for growth, health,…

  5. Pack aluminization of nickel anode for molten carbonate fuel cells

    NASA Astrophysics Data System (ADS)

    Chun, H. S.; Park, G. P.; Lim, J. H.; Kim, K.; Lee, J. K.; Moon, K. H.; Youn, J. H.

    1994-04-01

    The aluminum pack cementation (pack aluminization) process on a porous nickel anode for molten carbonate fuel cells has been studied to improve anode creep resistance. The porous nickel substrates used in this study were fabricated by doctor blade equipment followed by sintering (850 C). Packs surrounding the Ni anode were made by mixing Al2O3 powder, Al powder, and NaCl as activator. The pack aluminization was performed at 700 to 850 C for 0.5-5.0 h. After pack aluminization, the principal Ni-Al intermetallic compounds detected were Ni3Al at 700 C, NiAl at 750 C and Ni3Al2 at 800 C. The aluminum content in the aluminized Ni anode was proportional to the square root of pack aluminizing time. With increasing the Al content in the anode, the creep of the anode decreased. It was nearly constant (2.0%) when the Al content was above 5.0%. Although the exchange current density (24 mA/sq cm) for the aluminized (2.5 wt.%) Ni anode was somewhat lower than that of the pure Ni anode (40 mA/sq cm), the performance of a single cell using an aluminized Ni anode was similar to that of the one with pure Ni anode.

  6. [Release amount of heavy metals in cement product from co-processing waste in cement kiln].

    PubMed

    Yang, Yu-Fei; Huang, Qi-Fei; Zhang, Xia; Yang, Yu; Wang, Qi

    2009-05-15

    Clinker was produced by Simulating cement calcination test, and concrete samples were also prepared according to national standard GB/T 17671-1999. Long-term cumulative release amount of heavy metals in cement product from co-processing waste in cement kiln was researched through leaching test which refers to EA NEN 7371 and EA NEN 7375, and one-dimensional diffusion model which is on the base of Fick diffusion law. The results show that availabilities of heavy metals are lower than the total amounts in concrete. The diffusion coefficients of heavy metals are different (Cr > As > Ni > Cd). During 30 years service, the cumulative release amounts of Cr, As, Ni and Cd are 4.43 mg/kg, 0.46 mg/kg, 1.50 mg/kg and 0.02 mg/kg, respectively, and the ratios of release which is the division of cumulative release amount and availability are 27.0%, 18.0%, 3.0% and 0.2%, respectively. The most important influence factor of cumulative release amount of heavy metal is the diffusion coefficient, and it is correlative to cumulative release amount. The diffusion coefficient of Cr and As should be controlled exactly in the processing of input the cement-kiln. PMID:19558131

  7. Effect of packing method on the randomness of disc packings

    NASA Astrophysics Data System (ADS)

    Zhang, Z. P.; Yu, A. B.; Oakeshott, R. B. S.

    1996-06-01

    The randomness of disc packings, generated by random sequential adsorption (RSA), random packing under gravity (RPG) and Mason packing (MP) which gives a packing density close to that of the RSA packing, has been analysed, based on the Delaunay tessellation, and is evaluated at two levels, i.e. the randomness at individual subunit level which relates to the construction of a triangle from a given edge length distribution and the randomness at network level which relates to the connection between triangles from a given triangle frequency distribution. The Delaunay tessellation itself is also analysed and its almost perfect randomness at the two levels is demonstrated, which verifies the proposed approach and provides a random reference system for the present analysis. It is found that (i) the construction of a triangle subunit is not random for the RSA, MP and RPG packings, with the degree of randomness decreasing from the RSA to MP and then to RPG packing; (ii) the connection of triangular subunits in the network is almost perfectly random for the RSA packing, acceptable for the MP packing and not good for the RPG packing. Packing method is an important factor governing the randomness of disc packings.

  8. Chloride ingress in cement paste and mortar

    SciTech Connect

    Jensen, O.M.; Hansen, P.F.; Coats, A.M.; Glasser, F.P.

    1999-09-01

    In this paper chloride ingress in cement paste and mortar is followed by electron probe microanalysis. The influence of several paste and exposure parameters on chloride ingress are examined (e.g., water-cement ratio, silica fume addition, exposure time, and temperature). The measurements are modelled on Fick's law modified by a term for chloride binding. Inclusion of chloride binding significantly improves the profile shape of the modelled ingress profiles. The presence of fine aggregate and formation of interfacial transition zones at paste-aggregate boundaries does not significantly affect diffusion rates.

  9. Recycling of ladle slag in cement composites: Environmental impacts.

    PubMed

    Serjun, Vesna Zalar; Mladenovič, Ana; Mirtič, Breda; Meden, Anton; Ščančar, Janez; Milačič, Radmila

    2015-09-01

    In the present work compact and ground cement composites in which 30% of cement by mass was replaced by ladle slag were investigated for their chemical and physico-mechanical properties. To evaluate long-term environmental impacts, leachability test based on diffusion, which combined both, diffusion and dissolution of contaminants, was performed in water and saline water. Total element concentrations and Cr(VI) were determined in leachates over a time period of 180days. At the end of the experiment, the mineralogical composition and the physico-mechanical stability of cement composites was also assessed. The results revealed that Cr(III) and Cr(VI) were immobilized by the hydration products formed in the cement composites with the addition of ladle slag. Cr(VI) content originating from the cement was also appreciably reduced by Fe(II) from minerals present in the added ladle slag, which thus had significant positive environmental effects. Among metals, only Mo and Ba were leached in elevated concentrations, but solely in ground cement composites with the addition of ladle slag. Lower V concentrations were observed in leachates of ground than compact composite. It was demonstrated that the presence of ladle slag in cement composites can even contribute to improved mortar resistance. The investigated ladle slag can be successfully implemented in cement composites as supplementary cementitious material. PMID:26008145

  10. Abyssal seep site cementation

    SciTech Connect

    Neumann, A.C.; Paull, C.K.; Commeau, R.; Commeau, J.

    1988-01-01

    The deepest submarine cements known so far occur along the 3,300-m deep base of the Florida escarpment and are associated with methane-bearing brine seeps, which emanate there. These deep Holocene carbonates, which occur as surficial and buried crusts, burrow fillings, and friable horizons, were sampled via ALVIN. The carbonates form irregular halos extending up to 20 m from seeps colonized by chemosynthetic fauna. Mussels, gastropods, and clams, the carbonate components of the community, produce a shell hash that is locally cemented by coarsely crystalline low-Mg calcite. Halos of palisade calcite are reminiscent of ancient examples of marine cements. Also present are carbonate hemipelagics cemented by micrite into crusts and burrow fillings. The degree of cementation varies from pervasive to light. Slabs of cemented crust up to 30 cm thick contrast with typical shallow crusts and exhibit irregular tops and smooth bottoms indicating different chemical gradients and pathways.

  11. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-01-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. DOE joined the Materials Management Service (MMS)-sponsored joint industry project ''Long-Term Integrity of Deepwater Cement under Stress/Compaction Conditions.'' Results of the project contained in two progress reports are also presented in this report.

  12. Cements from nanocrystalline hydroxyapatite.

    PubMed

    Barralet, J E; Lilley, K J; Grover, L M; Farrar, D F; Ansell, C; Gbureck, U

    2004-04-01

    Calcium phosphate cements are used as bone substitute materials because they may be moulded to fill a void or defect in bone and are osteoconductive. Although apatite cements are stronger than brushite cements, they are potentially less resorbable in vivo. Brushite cements are three-component systems whereby phosphate ions and water react with a soluble calcium phosphate to form brushite (CaHPO4 x 2H2O). Previously reported brushite cement formulations set following the mixture of a calcium phosphate, such as beta-tricalcium phosphate (beta-TCP), with an acidic component such as H3PO4 or monocalcium phosphate monohydrate (MCPM). Due to its low solubility, hydroxyapatite (HA) is yet to be reported as a reactive component in calcium phosphate cement systems. Here we report a new cement system setting to form a matrix consisting predominantly of brushite following the mixture of phosphoric acid with nanocrystalline HA. As a result of the relative ease with which ionic substitutions may be made in apatite this route may offer a novel way to control cement composition or setting characteristics. Since kinetic solubility is dependent on particle size and precipitation temperature is known to affect precipitated HA crystal size, the phase composition and mechanical properties of cements made from HA precipitated at temperatures between 4 and 60 degrees C were investigated. PMID:15332608

  13. Leaching of metals from cement under simulated environmental conditions.

    PubMed

    Lu, Huixia; Wei, Fang; Tang, Jingchun; Giesy, John P

    2016-03-15

    Leaching of metals from cement under various environmental conditions was measured to evaluate their environmental safety. A cement product containing clinker, which was produced from cement kiln co-processing of hazardous wastes, was solidified and leaching of metals was characterized using the 8-period test. Concentrations and speciation of metals in cements were determined. Effects of ambient environment and particle size on leachability of metals and mineralogical phases of cement mortars were evaluated by use of XRD and SEM. Results indicated that metals in cements were leachable in various media in descending order of: sea water, groundwater and acid rain. Cr, Ni, As, Co and V were leached by simulated sea water, while Cu, Cd, Pb, Zn, Mn, Sb and Tl were not leached in simulated sea water, groundwater or acid rain. When exposed to simulated acid rain or groundwater, amounts of Cr, Ni, As and V leached was inversely proportional to particle size of cement mortar. According to the one-dimensional diffusion equation, Cr was most leachable and the cumulative leached mass was predicted to be 9.6 mg kg(-1) after 20 years. Results of this study are useful in predicting releases of metals from cement products containing ash and clinkers cement kiln co-processing of hazardous wastes, so that they can be safely applied in the environment. PMID:26802528

  14. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2004-01-30

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries.

  15. Pulmonary Artery Cement Embolism after a Vertebroplasty

    PubMed Central

    Nooh, Anas; Abduljabbar, Fahad H.; Abduljabbar, Ahmed H.; Jarzem, Peter

    2015-01-01

    Background Context. Vertebroplasty is a minimally invasive procedure most commonly used for the treatment of vertebral compression fractures. Although it is relatively safe, complications have been reported over time. Among those complications, massive cement pulmonary embolism is considered a rare complication. Here we report a case of massive diffuse cement pulmonary embolism following percutaneous vertebroplasty for a vertebral compression fracture. Study Design. Case report. Methods. This is a 70-year-old female who underwent vertebroplasty for T11 and T12 vertebral compression fracture. Results. CT-scan revealed an incidental finding of cement embolism in the pulmonary trunk and both pulmonary arteries. Since the patient was asymptomatic, she was monitored closely and she did not need any intervention. Conclusion. Vertebroplasty is a minimally invasive procedure used for treatment of vertebral compression fracture. Despite the low rate of complications, a pulmonary cement embolism can occur. The consequences of cement embolism range widely from being asymptomatic to embolism that can cause paralysis, radiculopathy, or a fatal pulmonary embolism. PMID:26221556

  16. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2002-01-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report includes results from laboratory testing of ULHS systems along with other lightweight cement systems: foamed and sodium silicate slurries. Comparison studies of the three cement systems examined several properties: tensile strength, Young's modulus, water permeability, and shear bond. Testing was also done to determine the effect that temperature cycling has on the shear bond properties of the cement systems. In addition, analysis was carried out to examine alkali silica reactivity of slurries containing ULHS. Data is also presented from a study investigating the effects of mixing and pump circulation on breakage of ULHS. Information is also presented about the field application of ULHS in cementing a 7-in. intermediate casing in south Texas.

  17. Acoustic probing of elastic behavior and damage in weakly cemented granular media

    NASA Astrophysics Data System (ADS)

    Langlois, V.; Jia, X.

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ϕ = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981), 10.1115/1.3157738] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994), 10.1016/0167-6636(94)90044-2]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (<1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces.

  18. Acoustic probing of elastic behavior and damage in weakly cemented granular media.

    PubMed

    Langlois, V; Jia, X

    2014-02-01

    We investigate the elastic behavior and damage of weakly cemented granular media under external load with ultrasound. The cementation controlled experiments are performed by freezing the capillary liquid at the bead contact in a dense glass or polymeric [poly(methyl methacrylate)] bead pack wet by tetradecane of volume fraction ϕ = 0.1%-4%. When the pendular rings are solidified, an abrupt increase by a factor of 2 in the compressional wave velocity is observed. We interpret the data in terms of effective medium models in which the contact stiffnesses are derived by either a bonded contact model [P. J. Digby, J. Appl. Mech. 48, 803 (1981)] or a cemented contact model [J. Dvorkin, A. Nur, and H. Yin, Mech. Mater. 18, 351 (1994)]. The former fails to quantitatively account for the results with a soft cement relative to the grain, whereas the latter considering the mechanical properties of the cement does apply. Moreover, we monitor the irreversible behavior of the cemented granular packs under moderate uniaxial loading (1.3 MPa) with the correlation method of ultrasound scattering. The damage of the cemented materials is accompanied by a compressional wave velocity decrease up to 60%, likely due to the fractures induced at the grain-cement interfaces. PMID:25353594

  19. Computational studies of two-phase cement-CO2-brine interaction in wellbore environments

    SciTech Connect

    Carey, James William; Lichtner, Peter C

    2009-01-01

    Wellbore integrity is essential to ensuring long-term isolation of buoyant supercritical CO{sub 2} during geologic sequestration of CO{sub 2}. In this report, we summarize recent progress in numerical simulations of cement-brine-CO{sub 2} interactions with respect to migration of CO{sub 2} outside of casing. Using typical values for the hydrologic properties of cement, caprock (shale) and reservoir materials, we show that the capillary properties of good quality cement will prevent flow of CO{sub 2} into and through cement. Rather, CO{sub 2}, if present, is likely to be confined to the casing-cement or cement-formation interfaces. CO{sub 2} does react with the cement by diffusion from the interface into the cement, in which case it produces distinct carbonation fronts within the cement. This is consistent with observations of cement performance at the CO{sub 2}-enhanced oil recovery SACROC Unit in West Texas (Carey et al. 2007). For poor quality cement, flow through cement may occur and would produce a pattern of uniform carbonation without reaction fronts. We also consider an alternative explanation for cement carbonation reactions as due to CO{sub 2} derived from caprock. We show that carbonation reactions in cement are limited to surficial reactions when CO{sub 2} pressure is low (< 10 bars) as might be expected in many caprock environments. For the case of caprock overlying natural CO{sub 2} reservoirs for millions of years, we consider Scherer and Huet's (2009) hypothesis of diffusive steady-state between CO{sub 2} in the reservoir and in the caprock. We find that in this case, the aqueous CO{sub 2} concentration would differ little from the reservoir and would be expected to produce carbonation reaction fronts in cements that are relatively uniform as a function of depth.

  20. An Experimental Study to Determine the Role of Inferior Vena Cava Filter in Preventing Bone Cement Implantation Syndrome

    PubMed Central

    Guo, Wangang; Zheng, Qiangsun; Li, Bingling; Shi, Xiaoqin; Xiang, Dingcheng; Wang, Chen

    2015-01-01

    Background: Inferior vena cava filters (IVCF) are frequently used for preventing pulmonary embolism (PE) following deep venous thromboembolism. Objectives: The present study was designed to investigate whether IVCF could prevent or impede the occurrence of bone cement implantation syndrome (BCIS), since PE is considered as the central mechanism of BCIS. Materials and Methods: Fifteen sheep were divided into three groups: bone cement free (BCF) group, cement implantation (CI) group and IVCF group. In all the groups, an osteotomy proximal to the greater trochanter of left femur was carried out. In BCF group, the femoral canal was not reamed out or packed with any bone cement. In CI and IVCF groups, the left femoral canals were packed with bone cement, to simulate the cementing procedures carried out in hip replacement. An OptEase® filter was placed and released in inferior vena cava, prior to packing cement in the femoral canal in IVCF group, while the IVCF was not released in the CI group. The BCF group was considered as control. Results: Systolic blood pressure (SBP), saturation of oxygen (SaO2) and partial pressure of carbon dioxide (PaCO2) declined significantly 10 min after the bone cement packing, in CI group, compared to those in BCF group. This was accompanied by a rise in the arterial pH. However, IVCF prevented those changes in the CI group. On ultrasonography, there were dotted echoes in right atrium in the CI group, after bone cement packing, while such echoes were hardly seen in the IVCF group. Conclusion: This study demonstrates that IVCF could prevent BCIS effectively, and, as a corollary, suggests that PE represents the leading cause of the constellation of BCIS symptoms. PMID:26557267

  1. Cement-cement interface strength: influence of time to apposition.

    PubMed

    Park, S H; Silva, M; Park, J S; Ebramzadeh, E; Schmalzried, T P

    2001-01-01

    Cement-cement interfaces were created under simulated operating-room conditions. In order to analyze the effect of time to apposition on interface strength, two cement surfaces were brought together 1, 2, 4, and 6 min after 1 min of mixing and 45 s of waiting. Cement-cement interface strength was evaluated with the use of a three-point bending to failure test. Scanning electron microscopy (SEM) images of the failed interface were obtained. The mean interface strength decreased when the cement-cement interface was time delayed. Compared to bulk cement, interface strength in time-delayed groups decreased 8% after 1-min delay (p=.037), 18% after 2-min delay (p=.0004), 20% after 4-min delay (p=.0005), and 42% after 6-min delay (p<.0001). No statistically significant differences in interface strength were found between the 2- and 4-min delayed groups (p=.73). SEM images revealed that after 6-min delay, up to 50% of the cement surface can remain unbonded, explaining the decrease in strength of the cement-cement interface as a function of time to apposition. This laboratory study indicates that time to apposition plays a critical role in cement-cement interface strength. If any cementing technique involves the joining of two cement surfaces, it is recommended that the two cement surfaces be mated together within 5 min and 45 s after the start of mixing (1 min mixing; 45 s waiting; 4 min delay), in order to obtain a strong cement-cement interface bond. Delay beyond this can result in substantial reduction in the strength of the cement-cement interface bond. PMID:11745529

  2. Timing of syntaxial cement

    SciTech Connect

    Perkins, R.D.

    1985-02-01

    Echinodermal fragments are commonly overgrown in ancient limestones, with large single crystals growing in optical continuity over their skeletal hosts (i.e., syntaxial overgrowths). Such syntaxial cements are usually considered to have precipitated from meteoric pore waters associated with a later stage of subaerial exposure. Although several examples have been reported from ancient carbonates where petrographic relationships may indicate an early submarine formation of syntaxial cement, no occurrences have been noted in Holocene submarine-cemented rocks. Syntaxial cements of submarine origin have been found in Bermuda beachrock where isopachous high-magnesian calcite cements merge with large optically continuous crystals growing on echinodermal debris. Examination of other Holocene sediments cemented by magnesian calcite indicates that echinodermal fragments are not always overgrown syntaxially, but may be rimmed by microcrystalline calcite. The reason for this difference is not clear, although it may be a function of the spacing of nucleation sites and rates of crystal growth. A review of syntaxial cements from several localities in ancient carbonate sequences reveals that many are best interpreted as having formed in the submarine setting, whereas it is more clear that others formed from meteoric precipitation. These occurrences suggest that care should be exercised in inferring meteoric diagenesis from syntaxial overgrowths and that the possibility of submarine formation should be considered.

  3. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2003-07-31

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). This report discusses testing that was performed for analyzing the alkali-silica reactivity of ULHS in cement slurries. Laboratory testing during the eleventh quarter focused on evaluation of the alkali-silica reaction of eight different cement compositions, four of which contain ULHS. This report provides a progress summary of ASR testing. The original laboratory procedure for measuring set cement expansion resulted in unacceptable erosion of the test specimens. In subsequent tests, a different expansion procedure was implemented and an alternate curing method for cements formulated with TXI Lightweight cement was employed to prevent sample failure caused by thermal shock. The results obtained with the modified procedure showed improvement over data obtained with the original procedure, but data for some compositions were still questionable. Additional modification of test procedures for compositions containing TXI Lightweight cement were implemented and testing is ongoing.

  4. Packing fraction of continuous distributions

    NASA Astrophysics Data System (ADS)

    Brouwers, Jos

    2014-03-01

    This study addresses the packing and void fraction of polydisperse particles with geometric and lognormal size distribution. It is demonstrated that a bimodal discrete particle distribution can be transformed into said continuous particle-size distributions. Furthermore, original and exact expressions are presented that predict the packing fraction of these particle assemblies. For a number of particle shapes and their packing modes (close, loose) the applicable parameters are given. The closed-form analytical expression governing the packing fractions are thoroughly compared with empirical and computational data reported in the literature, and good agreement is found.

  5. Granular packings and fault zones

    PubMed

    Astrom; Herrmann; Timonen

    2000-01-24

    The failure of a two-dimensional packing of elastic grains is analyzed using a numerical model. The packing fails through formation of shear bands or faults. During failure there is a separation of the system into two grain-packing states. In a shear band, local "rotating bearings" are spontaneously formed. The bearing state is favored in a shear band because it has a low stiffness against shearing. The "seismic activity" distribution in the packing has the same characteristics as that of the earthquake distribution in tectonic faults. The directions of the principal stresses in a bearing are reminiscent of those found at the San Andreas Fault. PMID:11017335

  6. Method for dense packing discovery

    NASA Astrophysics Data System (ADS)

    Kallus, Yoav; Elser, Veit; Gravel, Simon

    2010-11-01

    The problem of packing a system of particles as densely as possible is foundational in the field of discrete geometry and is a powerful model in the material and biological sciences. As packing problems retreat from the reach of solution by analytic constructions, the importance of an efficient numerical method for conducting de novo (from-scratch) searches for dense packings becomes crucial. In this paper, we use the divide and concur framework to develop a general search method for the solution of periodic constraint problems, and we apply it to the discovery of dense periodic packings. An important feature of the method is the integration of the unit-cell parameters with the other packing variables in the definition of the configuration space. The method we present led to previously reported improvements in the densest-known tetrahedron packing. Here, we use the method to reproduce the densest-known lattice sphere packings and the best-known lattice kissing arrangements in up to 14 and 11 dimensions, respectively, providing numerical evidence for their optimality. For nonspherical particles, we report a dense packing of regular four-dimensional simplices with density ϕ=128/219≈0.5845 and with a similar structure to the densest-known tetrahedron packing.

  7. Random very loose packings.

    PubMed

    Ciamarra, Massimo Pica; Coniglio, Antonio

    2008-09-19

    We measure the number Omega(phi) of mechanically stable states of volume fraction phi of a granular assembly under gravity. The granular entropy S(phi)=logOmega(phi) vanishes both at high density, at phi approximately equal to phi_rcp, and a low density, at phi approximately equal to phi_rvlp, where phi_rvlp is a new lower bound we call random very loose pack. phi_rlp is the volume fraction where the entropy is maximal. These findings allow for a clear explanation of compaction experiments and provide the first first-principle definition of the random loose volume fraction. In the context of the statistical mechanics approach to static granular materials, states with phi

  8. Packings of soft disks

    NASA Astrophysics Data System (ADS)

    Ziherl, Primoz; Vidmar, Marija

    2011-03-01

    We explore the stability of 2D ordered structures formed by soft disks treated as isotropic solid bodies. Using a variational model, we compute the equilibrium shapes and the elastic energy of disks in regular columnar, honeycomb, square, and hexagonal lattice. The results reproduce the Hertzian interaction in the regime of small deformations. The phase diagram of elastic disks is characterized by broad regions of phase coexistence; its main feature is that the coordination number of the stable phases decreases with density. These results may provide an insight into structure of the non-close-packed lattices observed in certain nanocolloidal systems. This work was supported by Slovenian Research Agency (grant No. P1-0055) and by EU through ITN COMPLOIDS (grant FP7-People-ITN-2008 No. 234810).

  9. Polarizable protein packing.

    PubMed

    Ng, Albert H; Snow, Christopher D

    2011-05-01

    To incorporate protein polarization effects within a protein combinatorial optimization framework, we decompose the polarizable force field AMOEBA into low order terms. Including terms up to the third-order provides a fair approximation to the full energy while maintaining tractability. We represent the polarizable packing problem for protein G as a hypergraph and solve for optimal rotamers with the FASTER combinatorial optimization algorithm. These approximate energy models can be improved to high accuracy [root mean square deviation (rmsd) < 1 kJ mol(-1)] via ridge regression. The resulting trained approximations are used to efficiently identify new, low-energy solutions. The approach is general and should allow combinatorial optimization of other many-body problems. PMID:21264879

  10. Liquid antibiotics in bone cement

    PubMed Central

    Chang, Y. H.; Tai, C. L.; Hsu, H. Y.; Hsieh, P. H.; Lee, M. S.; Ueng, S. W. N.

    2014-01-01

    Objectives The objective of this study was to compare the elution characteristics, antimicrobial activity and mechanical properties of antibiotic-loaded bone cement (ALBC) loaded with powdered antibiotic, powdered antibiotic with inert filler (xylitol), or liquid antibiotic, particularly focusing on vancomycin and amphotericin B. Methods Cement specimens loaded with 2 g of vancomycin or amphotericin B powder (powder group), 2 g of antibiotic powder and 2 g of xylitol (xylitol group) or 12 ml of antibiotic solution containing 2 g of antibiotic (liquid group) were tested. Results Vancomycin elution was enhanced by 234% in the liquid group and by 12% in the xylitol group compared with the powder group. Amphotericin B elution was enhanced by 265% in the liquid group and by 65% in the xylitol group compared with the powder group. Based on the disk-diffusion assay, the eluate samples of vancomycin-loaded ALBC of the liquid group exhibited a significantly larger inhibitory zone than samples of the powder or the xylitol group. Regarding the ALBCs loaded with amphotericin B, only the eluate samples of the liquid group exhibited a clear inhibitory zone, which was not observed in either the xylitol or the powder groups. The ultimate compressive strength was significantly reduced in specimens containing liquid antibiotics. Conclusions Adding vancomycin or amphotericin B antibiotic powder in distilled water before mixing with bone cement can significantly improve the efficiency of antibiotic release than can loading ALBC with the same dose of antibiotic powder. This simple and effective method for preparation of ALBCs can significantly improve the efficiency of antibiotic release in ALBCs. Cite this article: Bone Joint Res 2014;3:246–51. PMID:25104836

  11. Stage cementing apparatus

    SciTech Connect

    Blamford, D.M.; Easter, J.H.

    1988-06-21

    A stage cementing apparatus for selectively passing cement from the interior passage of a casing to the annulus between the exterior of the casing and borehole, the casing having an upper portion and a lower portion, is described comprising: a barrel secured to the upper portion of the casing; a mandrel secured to the lower portion of the casing, and a stage cementing tool having a generally cylindrical configuration adapted for attachment to the lower end of the barrel about a portion of the mandrel.

  12. Cement and concrete

    NASA Technical Reports Server (NTRS)

    Corley, Gene; Haskin, Larry A.

    1992-01-01

    To produce lunar cement, high-temperature processing will be required. It may be possible to make calcium-rich silicate and aluminate for cement by solar heating of lunar pyroxene and feldspar, or chemical treatment may be required to enrich the calcium and aluminum in lunar soil. The effects of magnesium and ferrous iron present in the starting materials and products would need to be evaluated. So would the problems of grinding to produce cement, mixing, forming in vacuo and low gravity, and minimizing water loss.

  13. Thermodynamics and cement science

    SciTech Connect

    Damidot, D.; Lothenbach, B.; Herfort, D.; Glasser, F.P.

    2011-07-15

    Thermodynamics applied to cement science has proved to be very valuable. One of the most striking findings has been the extent to which the hydrate phases, with one conspicuous exception, achieve equilibrium. The important exception is the persistence of amorphous C-S-H which is metastable with respect to crystalline calcium silicate hydrates. Nevertheless C-S-H can be included in the scope of calculations. As a consequence, from comparison of calculation and experiment, it appears that kinetics is not necessarily an insuperable barrier to engineering the phase composition of a hydrated Portland cement. Also the sensitivity of the mineralogy of the AFm and AFt phase compositions to the presence of calcite and to temperature has been reported. This knowledge gives a powerful incentive to develop links between the mineralogy and engineering properties of hydrated cement paste and, of course, anticipates improvements in its performance leading to decreasing the environmental impacts of cement production.

  14. [Allergy towards bone cement].

    PubMed

    Thomas, P; Schuh, A; Summer, B; Mazoochian, F; Thomsen, M

    2006-09-01

    Bone cements based on polymethylmethacrylate are typically used for fixation of artificial joints. Intolerance reactions to endoprostheses not explained by infection or mechanical failure may lead to allergological diagnostics, which mostly focuses on metal allergy. However, also bone cement components may provoke hypersensitivity reactions leading to eczema, implant loosening, or fistula formation. Elicitors of such reactions encompass acrylates and additives such as benzoyl peroxide, N,N-dimethyl-p-toluidine, hydroquinone, or antibiotics (particularly gentamicin). Upon repeated contact with bone cement components, e.g., acrylate monomers, also in medical personnel occasionally hand eczema or even asthma may develop. Therefore, in the case of suspected hypersensitivity reactions to arthroplasty, the allergological diagnostics should include bone cement components. PMID:16865384

  15. Environmentally compatible spray cement

    SciTech Connect

    Loeschnig, P.

    1995-12-31

    Within the framework of a European research project, Heidelberger Zement developed a quickly setting and hardening binder for shotcrete, called Chronolith S, which avoids the application of setting accelerators. Density and strength of the shotcrete produced with this spray cement correspond to those of an unaccelerated shotcrete. An increased hazard for the heading team and for the environment, which may occur when applying setting accelerators, can be excluded here. Owing to the special setting properties of a spray cement, the process engineering for its manufacturing is of great importance. The treatment of a spray cement as a dry concrete with kiln-dried aggregates is possible without any problems. The use of a naturally damp pre-batched mixture is possible with Chronolith S but requires special process engineering; spray cement and damp aggregate are mixed with one another immediately before entering the spraying machinery.

  16. Packing Products: Polystyrene vs. Cornstarch

    ERIC Educational Resources Information Center

    Starr, Suzanne

    2009-01-01

    Packing materials such as polystyrene take thousands of years to decompose, whereas packing peanuts made from cornstarch, which some companies are now using, can serve the same purpose, but dissolve in water. The author illustrates this point to her class one rainy day using the sculptures students made from polystyrene and with the cornstarch…

  17. Influence of the radiopacifier in an acrylic bone cement on its mechanical, thermal, and physical properties: barium sulfate-containing cement versus iodine-containing cement.

    PubMed

    Lewis, Gladius; van Hooy-Corstjens, Catharina S J; Bhattaram, Anuradha; Koole, Leo H

    2005-04-01

    In all acrylic bone cement formulations in clinical use today, radiopacity is provided by micron-sized particles (typical mean diameter of between about 1 and 2 microm) of either BaSO(4) or ZrO(2). However, a number of research reports have highlighted the fact that these particles have deleterious effects on various properties of the cured cement. Thus, there is interest in alternative radiopacifiers. The present study focuses on one such alternative. Specifically, a cement that contains covalently bound iodine in the powder (herein designated the I-cement) was compared with a commercially available cement of comparable composition (C-ment3), in which radiopacity is provided by BaSO(4) particles (this cement is herein designated the B-cement), on the basis of the strength (sigma(b)), modulus (E(b)), and work-to-fracture (U(b)), under four-point bending, plane-strain fracture toughness (K(IC)), Weibull mean fatigue life, N(WM) (fatigue conditions: +/-15 MPa; 2 Hz), activation energy (Q), and frequency factor (ln Z) for the cement polymerization process (both determined by using differential scanning calorimetry at heating rates of 5, 10, 15, and 20 K min(-1)), and the diffusion coefficient for the absorption of phosphate-buffered saline at 37 degrees C (D). For the B-cement, the values of sigma(b), E(b), U(b), K(IC), N(WM), Q, ln Z, and D were 53 +/- 3 MPa, 3000 +/- 120 MPa, 108 +/- 15 kJ m(-3), 1.67 +/- 0.02 MPa check mark m, 7197 cycles, 243 +/- 17 kJ mol(-1), 87 +/- 6, and (3.15 +/- 0.94) x 10(-12) m(2) s(-1), respectively. For the I-cement, the corresponding values were 58 +/- 5 MPa, 2790 +/- 140 MPa, 118 +/- 45 kJ m(-3), 1.73 +/- 0.11 MPa check mark m, 5520 cycles, 267 +/- 19 kJ mol(-1), 95 +/- 9, and (3.83 +/- 0.25) x 10(-12) m(2) s(-1). For each of the properties of the fully cured cement, except for the rate constant of the polymerization reaction, at 37 degrees C (k'), as estimated from the Q and ln Z results, there is no statistically significant

  18. Atomic packing and diffusion in Fe{sub 85}Si{sub 2}B{sub 9}P{sub 4} amorphous alloy analyzed by ab initio molecular dynamics simulation

    SciTech Connect

    Wang, Yaocen; Takeuchi, Akira; Makino, Akihiro; Liang, Yunye; Kawazoe, Yoshiyuki

    2015-05-07

    In the work reported in this paper, ab initio molecular dynamics simulation was performed on Fe{sub 85}Si{sub 2}B{sub 9}P{sub 4} amorphous alloy. Preferred atomic environment of the elements was analyzed with Voronoi polyhedrons. It showed that B and P atoms prefer less neighbors compared with Fe and Si, making them structurally incompatible with Fe rich structure and repulsive to the formation of α-Fe. However, due to the low bonding energy of B and P caused by low coordination number, the diffusion rates of them were considerably large, resulting in the requirement of fast annealing for achieving optimum nano-crystallization for its soft magnetic property. The simulation work also indicates that diffusion rate in amorphous alloy is largely determined by bonding energy rather than atomic size.

  19. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  20. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  1. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged according to approved and... that apples are of the proper size for molds or cell compartments in which they are packed, and...

  2. Cement-based materials' characterization using ultrasonic attenuation

    NASA Astrophysics Data System (ADS)

    Punurai, Wonsiri

    The quantitative nondestructive evaluation (NDE) of cement-based materials is a critical area of research that is leading to advances in the health monitoring and condition assessment of the civil infrastructure. Ultrasonic NDE has been implemented with varying levels of success to characterize cement-based materials with complex microstructure and damage. A major issue with the application of ultrasonic techniques to characterize cement-based materials is their inherent inhomogeneity at multiple length scales. Ultrasonic waves propagating in these materials exhibit a high degree of attenuation losses, making quantitative interpretations difficult. Physically, these attenuation losses are a combination of internal friction in a viscoelastic material (ultrasonic absorption), and the scattering losses due to the material heterogeneity. The objective of this research is to use ultrasonic attenuation to characterize the microstructure of heterogeneous cement-based materials. The study considers a real, but simplified cement-based material, cement paste---a common bonding matrix of all cement-based composites. Cement paste consists of Portland cement and water but does not include aggregates. First, this research presents the findings of a theoretical study that uses a set of existing acoustics models to quantify the scattered ultrasonic wavefield from a known distribution of entrained air voids. These attenuation results are then coupled with experimental measurements to develop an inversion procedure that directly predicts the size and volume fraction of entrained air voids in a cement paste specimen. Optical studies verify the accuracy of the proposed inversion scheme. These results demonstrate the effectiveness of using attenuation to measure the average size, volume fraction of entrained air voids and the existence of additional larger entrapped air voids in hardened cement paste. Finally, coherent and diffuse ultrasonic waves are used to develop a direct

  3. Dense periodic packings of tori

    NASA Astrophysics Data System (ADS)

    Gabbrielli, Ruggero; Jiao, Yang; Torquato, Salvatore

    2014-02-01

    Dense packings of nonoverlapping bodies in three-dimensional Euclidean space R3 are useful models of the structure of a variety of many-particle systems that arise in the physical and biological sciences. Here we investigate the packing behavior of congruent ring tori in R3, which are multiply connected nonconvex bodies of genus 1, as well as horn and spindle tori. Specifically, we analytically construct a family of dense periodic packings of unlinked tori guided by the organizing principles originally devised for simply connected solid bodies [22 Torquato and Jiao, Phys. Rev. E 86, 011102 (2012), 10.1103/PhysRevE.86.011102]. We find that the horn tori as well as certain spindle and ring tori can achieve a packing density not only higher than that of spheres (i.e., π /√18 =0.7404...) but also higher than the densest known ellipsoid packings (i.e., 0.7707...). In addition, we study dense packings of clusters of pair-linked ring tori (i.e., Hopf links), which can possess much higher densities than corresponding packings consisting of unlinked tori.

  4. Valve stem and packing assembly

    DOEpatents

    Wordin, John J.

    1991-01-01

    A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents overtightening of the retaining nut and the resulting excessive friction between stem and stem packing.

  5. Valve stem and packing assembly

    DOEpatents

    Wordin, J.J.

    1991-09-03

    A valve stem and packing assembly is provided in which a rotatable valve stem includes a first tractrix surface for sliding contact with a stem packing and also includes a second tractrix surface for sliding contact with a bonnet. Force is applied by means of a spring, gland flange, and gland on the stem packing so the stem packing seals to the valve stem and bonnet. This configuration serves to create and maintain a reliable seal between the stem packing and the valve stem. The bonnet includes a second complementary tractrix surface for contacting the second sliding tractrix surface, the combination serving as a journal bearing for the entire valve stem and packing assembly. The journal bearing so configured is known as a Schiele's pivot. The Schiele's pivot also serves to maintain proper alignment of the valve stem with respect to the bonnet. Vertical wear between the surfaces of the Schiele's pivot is uniform at all points of contact between the second sliding tractrix surface and the second complementary tractrix surface of a bonnet. The valve stem is connected to a valve plug by means of a slip joint. The valve is opened and closed by rotating the valve stem. The slip joint compensates for wear on the Schiele's pivot and on the valve plug. A ledge is provided on the valve bonnet for the retaining nut to bear against. The ledge prevents over tightening of the retaining nut and the resulting excessive friction between stem and stem packing. 2 figures.

  6. Large-scale simulation of flow and transport in reconstructed HPLC-microchip packings.

    PubMed

    Khirevich, Siarhei; Höltzel, Alexandra; Ehlert, Steffen; Seidel-Morgenstern, Andreas; Tallarek, Ulrich

    2009-06-15

    Flow and transport in a particle-packed microchip separation channel were investigated with quantitative numerical analysis methods, comprising the generation of confined, polydisperse sphere packings by a modified Jodrey-Tory algorithm, 3D velocity field calculations by the lattice-Boltzmann method, and modeling of convective-diffusive mass transport with a random-walk particle-tracking approach. For the simulations, the exact conduit cross section, the particle-size distribution of the packing material, and the respective average interparticle porosity (packing density) of the HPLC-microchip packings was reconstructed. Large-scale simulation of flow and transport at Peclet numbers of up to Pe = 140 in the reconstructed microchip packings (containing more than 3 x 10(5) spheres) was facilitated by the efficient use of supercomputer power. Porosity distributions and fluid flow velocity profiles for the reconstructed microchip packings are presented and analyzed. Aberrations from regular geometrical conduit shape are shown to influence packing structure and, thus, porosity and velocity distributions. Simulated axial dispersion coefficients are discussed with respect to their dependence on flow velocity and bed porosity. It is shown by comparison to experimental separation efficiencies that the simulated data genuinely reflect the general dispersion behavior of the real-life HPLC-microchip packings. Differences between experiment and simulation are explained by differing morphologies of real and simulated packings (intraparticle porosity, packing structure in the corner regions). PMID:19459621

  7. Method for packing chromatographic beds

    DOEpatents

    Freeman, David H.; Angeles, Rosalie M.; Keller, Suzanne

    1991-01-01

    Column chromatography beds are packed through the application of static force. A slurry of the chromatography bed material and a non-viscous liquid is filled into the column plugged at one end, and allowed to settle. The column is transferred to a centrifuge, and centrifuged for a brief period of time to achieve a predetermined packing level, at a range generally of 100-5,000 gravities. Thereafter, the plug is removed, other fixtures may be secured, and the liquid is allowed to flow out through the bed. This results in an evenly packed bed, with no channeling or preferential flow characteristics.

  8. Spectroscopy of Loose and Cemented Sulfate-Bearing Soils: Implications for Duricrust on Mars

    NASA Astrophysics Data System (ADS)

    Cooper, Christopher D.; Mustard, John F.

    2002-07-01

    The goal of this work is to determine the spectroscopic properties of sulfate in martian soil analogs over the wavelength range 0.3 to 25 μm (which is relevant to existing and planned remotely sensed data sets for Mars). Sulfate is an abundant component of martian soil (up to 9% SO 3 by weight) and apparently exists as a particulate in the soil but also as a cement. Although previous studies have addressed the spectroscopic identity of sulfates on Mars, none have used laboratory mixtures of materials with sulfates at the abundances measured by landed spacecraft, nor have any works considered the effect of salt-cementation on spectral properties of soil materials. For this work we created mixtures of a palagonitic soil (JSC Mars-1) and sulfates (MgSO 4 and CaSO 4·2H 2O). The effects of cementation were determined and separated from the effects of packing and hydration by measuring the samples as loose powders, packed powders, cemented materials, and disaggregated materials. The results show that the presence of particulate sulfate is best observed in the 4-5 μm region. Soils cemented with sulfate exhibit a pronounced restrahlen band between 8 and 9 μm as well as well-defined absorptions in the 4-5 μm region. Cementation effects are distinct from packing effects and disaggregation of cemented samples rapidly diminishes the strength of the restrahlen bands. The results of this study show that sulfate in loose materials is more detectable in the near infrared (4-5 μm) than in the thermal infrared (8-9 μm). However, cemented materials are easily distinguished from loose mixtures in the thermal infrared because of the high values of their absorption coefficient in this region. Together these results suggest that both wavelength regions are important for determining the spatial extent and physical form of sulfates on the surface of Mars.

  9. ULTRA-LIGHTWEIGHT CEMENT

    SciTech Connect

    Fred Sabins

    2001-10-23

    The objective of this project is to develop an improved ultra-lightweight cement using ultra-lightweight hollow glass spheres (ULHS). Work reported herein addresses tasks performed in the fourth quarter as well as the other three quarters of the past year. The subjects that were covered in previous reports and that are also discussed in this report include: Analysis of field laboratory data of active cement applications from three oil-well service companies; Preliminary findings from a literature review focusing on problems associated with ultra-lightweight cements; Summary of pertinent information from Russian ultra-lightweight cement literature review; and Comparison of compressive strengths of ULHS systems using ultrasonic and crush methods Results reported from the fourth quarter include laboratory testing of ULHS systems along with other lightweight cement systems--foamed and sodium silicate slurries. These comparison studies were completed for two different densities (10.0 and 11.5 lb/gal) and three different field application scenarios. Additional testing included the mechanical properties of ULHS systems and other lightweight systems. Studies were also performed to examine the effect that circulation by centrifugal pump during mixing has on breakage of ULHS.

  10. Ready-to-use injectable calcium phosphate bone cement paste as drug carrier.

    PubMed

    Vorndran, E; Geffers, M; Ewald, A; Lemm, M; Nies, B; Gbureck, U

    2013-12-01

    Current developments in calcium phosphate cement (CPC) technology concern the use of ready-to-use injectable cement pastes by dispersing the cement powder in a water-miscible solvent, such that, after injection into the physiological environment, setting of cements occurs by diffusion of water into the cement paste. It has also been demonstrated recently that the combination of a water-immiscible carrier liquid combined with suitable surfactants facilitates a discontinuous liquid exchange in CPC, enabling the cement setting reaction to take place. This paper reports on the use of these novel cement paste formulations as a controlled release system of antibiotics (gentamicin, vancomycin). Cement pastes were applied either as a one-component material, in which the solid drugs were physically dispersed, or as a two-component system, where the drugs were dissolved in an aqueous phase that was homogeneously mixed with the cement paste using a static mixing device during injection. Drug release profiles of both antibiotics from pre-mixed one- and two-component cements were characterized by an initial burst release of ∼7-28%, followed by a typical square root of time release kinetic for vancomycin. Gentamicin release rates also decreased during the first days of the release study, but after ∼1 week, the release rates were more or less constant over a period of several weeks. This anomalous release kinetic was attributed to participation of the sulfate counter ion in the cement setting reaction altering the drug solubility. The drug-loaded cement pastes showed high antimicrobial potency against Staphylococcus aureus in an agar diffusion test regime, while other cement properties such as mechanical performance or phase composition after setting were only marginally affected. PMID:23954526

  11. System for radioactive waste cementation

    SciTech Connect

    Dmitriev, S.A.; Barinov, A.S.; Varlakov, A.P.; Volkov, A.S.; Karlin, S.V.

    1995-12-31

    NPP, research reactors and radiochemical enterprises produce a great amount of liquid radioactive waste (LRW). One of the methods of LRW solidification is cementation. The recent investigations demonstrated possible inclusion of sufficient amount of waste in the cement matrix (up to 20--30 mass% on dry residue). In this case the cementation process becomes competitive with bituminization process, where the matrix can include 40--50 mass% and the solidified product volume is equal to the volume, obtained by cementation. Additionally, the cement matrix in contrast with the bituminous one is unburnable. Many countries are investigating the cementation process. The main idea governing technological process is the waste and cement mixing method and type of mixer. In world practice some principal types of cementation systems are used. The paper describes the SIA Radon industrial plant in Moscow.

  12. Recycled rubber in cement composites

    SciTech Connect

    Raghavan, D.; Tratt, K.; Wool, R.P.

    1994-12-31

    Disposal of 200 million waste tires in the US each year has become a major problem. An environmentally sound innovative technology of recycling rubber in cement matrix was examined. Using silane coupling agent the rubber was bonded to the hydrating cement making a lighter composite, which absorbed more energy than ordinary Portland cement. The bonding information was obtained by peel strength analysis. SEM was used to understand the mode of fracture in pure cement paste, cement bonded rubber composite and rubber filled cement paste. It was found that cracks propagate through the rubber particle in rubber bonded cement composite while in unbonded rubber cement mix, the cracks propagate around the interface. The density and shrinkage measurements are also discussed.

  13. Heating Luggage Sends Bedbugs Packing

    MedlinePlus

    ... gov/news/fullstory_160234.html Heating Luggage Sends Bedbugs Packing Just 6 minutes at about 160 degrees ... 3, 2016 WEDNESDAY, Aug. 3, 2016 (HealthDay News) -- Bedbugs, those creepy crawly insects that feed on your ...

  14. Impact of Wellbore Cement Degradation on CO2 Storage Integrity

    NASA Astrophysics Data System (ADS)

    Kutchko, B.; Strazisar, B.; Lowry, G.; Dzombak, D.; Thaulow, N.

    2007-12-01

    zone. Over the one-year time period of the experiments, this condition led to a smaller amount of total degradation than in the aqueous phase. However, in this case, there was no deceleration of the reaction observed. It is unlikely that the diffusion controlled degradation process observed in these experiments would lead to well failure in well completions that are well cemented with neat Portland cement (without additives). Further investigation is required to evaluate the effect of cement additives, fractures or channels in the cement, and geomechanical stress.

  15. Are proteins well-packed?

    PubMed

    Liang, J; Dill, K A

    2001-08-01

    The average packing density inside proteins is as high as in crystalline solids. Does this mean proteins are well-packed? We go beyond average densities, and look at the full distribution functions of free volumes inside proteins. Using a new and rigorous Delaunay triangulation method for parsing space into empty and filled regions, we introduce formal definitions of interior and surface packing densities. Although proteins look like organic crystals by the criterion of average density, they look more like liquids and glasses by the criterion of their free volume distributions. The distributions are broad, and the scalings of volume-to-surface, volume-to-cluster-radius, and numbers of void versus volume show that the interiors of proteins are more like randomly packed spheres near their percolation threshold than like jigsaw puzzles. We find that larger proteins are packed more loosely than smaller proteins. And we find that the enthalpies of folding (per amino acid) are independent of the packing density of a protein, indicating that van der Waals interactions are not a dominant component of the folding forces. PMID:11463623

  16. Reducing cement's CO2 footprint

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2011-01-01

    The manufacturing process for Portland cement causes high levels of greenhouse gas emissions. However, environmental impacts can be reduced by using more energy-efficient kilns and replacing fossil energy with alternative fuels. Although carbon capture and new cements with less CO2 emission are still in the experimental phase, all these innovations can help develop a cleaner cement industry.

  17. Cement Mason's Curriculum. Instructional Units.

    ERIC Educational Resources Information Center

    Hendirx, Laborn J.; Patton, Bob

    To assist cement mason instructors in providing comprehensive instruction to their students, this curriculum guide treats both the skills and information necessary for cement masons in commercial and industrial construction. Ten sections are included, as follow: related information, covering orientation, safety, the history of cement, and applying…

  18. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi.

    1989-10-03

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed. 3 figs.

  19. High temperature lightweight foamed cements

    DOEpatents

    Sugama, Toshifumi

    1989-01-01

    Cement slurries are disclosed which are suitable for use in geothermal wells since they can withstand high temperatures and high pressures. The formulation consists of cement, silica flour, water, a retarder, a foaming agent, a foam stabilizer, and a reinforcing agent. A process for producing these cements is also disclosed.

  20. Vanadium diffusion coating on HT-9 cladding for mitigating the fuel cladding chemical interactions

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Yang, Yong

    2014-08-01

    Fuel cladding chemical interaction (FCCI) has been identified as one of the crucial issues for developing Ferritic/Martensitic (F/M) stainless steel claddings for metallic fuels in a fast reactor. The anticipated elevated temperature and high neutron flux can significantly aggravate the FCCI, in terms of formation of inter-diffusion and lower melting point eutectic phases. To mitigate the FCCI, vanadium carbide coating as a diffusion barrier was deposited on the HT-9 substrate using a pack cementation diffusion coating (PCDC) method, and the processing temperature was optimized down to 730 °C. A solid metallurgical bonding between the coating layer and substrate was achieved, and the coating is free from through depth cracks. The microstructural characterizations using SEM and TEM show a nanostructured grain structure. EDS/WDS and XRD analysis confirm the phase of coating layer as V2C. Diffusion couple tests at 660 °C for 100 h demonstrate that V2C layer with a thickness of less than 5 μm can effectively eliminate the inter-diffusion between the lanthanide cerium and HT-9 steel.

  1. Cementing a wellbore using cementing material encapsulated in a shell

    DOEpatents

    Aines, Roger D.; Bourcier, William L.; Duoss, Eric B.; Spadaccini, Christopher M.; Cowan, Kenneth Michael

    2016-08-16

    A system for cementing a wellbore penetrating an earth formation into which a pipe extends. A cement material is positioned in the space between the wellbore and the pipe by circulated capsules containing the cement material through the pipe into the space between the wellbore and the pipe. The capsules contain the cementing material encapsulated in a shell. The capsules are added to a fluid and the fluid with capsules is circulated through the pipe into the space between the wellbore and the pipe. The shell is breached once the capsules contain the cementing material are in position in the space between the wellbore and the pipe.

  2. Intrusion Characteristics of Three Bone Cements for Tibial Component of Total Knee Arthroplasty in a Cadaveric Bone Model.

    PubMed

    Walden, Justin K; Chong, Alexander C M; Dinh, Nam L; Adrian, Scott; Cusick, Robert; Wooley, Paul H

    2016-01-01

    The purpose of this study was to evaluate and compare the intrusion characteristics of Simplex-HV to Simplex-P and Palacos-R in cadaveric proximal tibial bone. Eighteen fresh-frozen cadaver proximal tibiae were examined with standard arthroplasty tibial cuts. Each tibia was randomly assigned to receive one of the three bone cements for use with finger packing technique. Sagittal sections were prepared and analyzed using digital photography and stereoscopic micrographs to evaluate cement intrusion characteristics. The cement penetration depth was measured from the tibial bone cut surface, which did not include the cement thickness under the tibial base plate. Significant differences were detected in the bone cement penetration between the three cements. Penetration was increased using the Simplex-HV (average, 2.7 mm; range, 2.0-3.0 mm) compared with Simplex-P (average, 2.2 mm) and Palacos-R (average, 1.8 mm). These depths approximate to 3.7, 3.2, and 2.8 mm of total cement penetration, respectively. The data suggest that high-viscosity bone cement may provide good fixation of the tibial component of a total knee arthroplasty when using the finger packing technique. PMID:27518289

  3. Retention of posts cemented with various dentinal bonding cements.

    PubMed

    Mendoza, D B; Eakle, W S

    1994-12-01

    This investigation evaluated the retention of preformed posts with four different cements: C & B Metabond, Panavia, All-Bond 2, and Ketac-Cem. Sixty intact maxillary canines were selected for the study. The clinical crowns were removed and endodontic therapy done on each root, which was then prepared to receive prefabricated posts. The 60 samples were divided into four groups of 15, and the posts in each group were cemented with one of the four cements. The roots were mounted in acrylic resin blocks and the posts were separated from the canals with an Instron testing machine. Analysis of the forces needed to dislodge the posts with analysis of variance and Student-Newman-Keuls test disclosed that C & B Metabond cement was the most retentive (p < 0.05). No difference in retention was recorded between Ketac-Cem and Panavia cements. All-Bond 2 cement was the least retentive of cements. PMID:7853255

  4. Physico-chemical studies of hardened cement paste structure with micro-reinforcing fibers

    NASA Astrophysics Data System (ADS)

    Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya

    2016-01-01

    The results of physico-chemical studies of modified hardened cement paste with micro-reinforcing fibers are given in this article. The goal was to study the reasons of the increase of strength properties of modified hardened cement paste by the method of X-ray diffraction and electron microscopy. It is shown that the use of mineral fibers in the production of cement based material has positive effect on its properties. The study found out that the increase in the strength of the hardened cement paste with micro-reinforcing fibers is due to the increase of the rate of hydration of cement without a significant change in the phase composition in comparison with hardened cement paste without additive. The results of microstructure investigation (of control samples and samples of the reinforced hardened cement paste) have shown that introduction of mineral fibers in the amount of 0.1-2 % by weight of cement provides the structure of the homogeneous microporous material with uniform distribution of the crystalline phase provided by densely packed hydrates.

  5. Cement compositions for cementing wells allowing pressure gas channeling in the cemented annulus to be controlled

    SciTech Connect

    Porcevaux, P. A.; Piot, B. M.; Vercaemer, C. J.

    1985-08-27

    The invention relates to cement compositions for cementing wells, which allow pressure gas-channeling to be effectively controlled up to more than about 485 F. The cement composition contains a styrene-butadiene latex and a stabilizer. The film of latex interrupts gas-channeling after an extremely brief path.

  6. Rubber cement poisoning

    MedlinePlus

    ... common household glue. It is often used for arts and crafts projects. Breathing in large amounts of rubber cement fumes or swallowing any amount can be extremely dangerous, especially for a small child. This article is for information only. Do NOT ...

  7. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  8. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S....

  9. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  10. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S....

  11. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged.... 3 2 “Fairly tight” means that apples are of the proper size for molds or cell compartments in...

  12. 7 CFR 51.310 - Packing requirements.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... (INSPECTION, CERTIFICATION, AND STANDARDS) United States Standards for Grades of Apples Packing Requirements § 51.310 Packing requirements. (a) Apples tray packed or cell packed in cartons shall be arranged.... 3 2 “Fairly tight” means that apples are of the proper size for molds or cell compartments in...

  13. 7 CFR 51.1217 - Standard pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Peaches Standard Pack § 51.1217 Standard pack. (a) Each package shall be packed so that the peaches in the shown face shall be reasonably representative in size, color and quality of the contents of the package. (b) Peaches packed in U.S. Standard bushel baskets, or half-bushel baskets,...

  14. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and size of those in the remainder of the package. (3) “Well filled” means that the plums or prunes packed...

  15. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and size of those in the remainder of the package. (3) “Well filled” means that the plums or prunes packed...

  16. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Standards for Grades of Fresh Plums and Prunes Standard Pack § 51.1527 Standard pack. (a) Packing. (1) All... plums or prunes in the top layer of any package shall be reasonably representative in quality and size of those in the remainder of the package. (3) “Well filled” means that the plums or prunes packed...

  17. Volatile Components from Packing Matrials, Rev. 2

    SciTech Connect

    Smith, R. A.

    2006-03-01

    An outgassing study was conducted on five packing materials, comprising two experiments. These materials comprised 277-4 borated concrete, Borobond4 concrete, polyethylene bags, silica-filled silicone rubber seals, and silicone foam padding. The purpose was measure the volume of gases which diffuse from packaging materials when sealed in containers. Two heating profiles were used to study the offgassing quantities in a set of accelerated aging tests. It was determined that the concretes contain a large quantity of water. The plastic materials hold much less moisture, with the silicone materials even consuming water, possibly due to the presence of silica filler. Polyethylene tends to degrade as the temperature is elevated and the foam stiffens.

  18. Hard sphere packings within cylinders.

    PubMed

    Fu, Lin; Steinhardt, William; Zhao, Hao; Socolar, Joshua E S; Charbonneau, Patrick

    2016-02-23

    Arrangements of identical hard spheres confined to a cylinder with hard walls have been used to model experimental systems, such as fullerenes in nanotubes and colloidal wire assembly. Finding the densest configurations, called close packings, of hard spheres of diameter σ in a cylinder of diameter D is a purely geometric problem that grows increasingly complex as D/σ increases, and little is thus known about the regime for D > 2.873σ. In this work, we extend the identification of close packings up to D = 4.00σ by adapting Torquato-Jiao's adaptive-shrinking-cell formulation and sequential-linear-programming (SLP) technique. We identify 17 new structures, almost all of them chiral. Beyond D ≈ 2.85σ, most of the structures consist of an outer shell and an inner core that compete for being close packed. In some cases, the shell adopts its own maximum density configuration, and the stacking of core spheres within it is quasiperiodic. In other cases, an interplay between the two components is observed, which may result in simple periodic structures. In yet other cases, the very distinction between the core and shell vanishes, resulting in more exotic packing geometries, including some that are three-dimensional extensions of structures obtained from packing hard disks in a circle. PMID:26843132

  19. Valve packings conquer fugitive emissions

    SciTech Connect

    1995-11-01

    In the early 1990s, when the US Environmental Protection Agency (EPA; Washington, D.C.) declared its intent to regulate fugitive emissions from valve-stem leakage, much of the chemical process industries (CPI) responded with fear and uncertainty. The biggest fear was that valve packing would not meet the required limits on leak rates and that expensive bellows seals may be required on many applications. The uncertainly was about how much it would cost. Today, for the most part, these concerns have been mitigated. It is estimated that about 80--90% of valves satisfy the emission requirements. The rest need some improvement in their packing systems to meet the regulations. Generally, these valves can be brought within compliance if the packing designers follow a few basic principles: Employ less-pliable outer rings and more-pliable inner rings; and don`t use excessive packing. While interest in valve packing remains high, mechanical seals continue to become more user-friendly. Many of those covered below are designed to run dry, and some can even tolerate high shaft-wobble without damage. Also look for improved flange gaskets and a host of seals to protect bearings. Twenty-one summaries are presented on new products and services.

  20. Sleeping distance in wild wolf packs

    USGS Publications Warehouse

    Knick, S.T.; Mech, L.D.

    1980-01-01

    Sleeping distances were observed among members of 13 wild wolf (Canis lupus) packs and 11 pairs in northeastern Minnesota to determine if the distances correlated with pack size and composition. The study utilized aerial radio-tracking and observation during winter. Pack size and number of adults per pack were inversely related to pack average sleeping distance and variability. No correlation between sleeping distance and microclimate was observed. Possible relationships between social bonding and our results are discussed.

  1. Cylinder valve packing nut studies

    SciTech Connect

    Blue, S.C.

    1991-12-31

    The design, manufacture, and use of cylinder valve packing nuts have been studied to improve their resistance to failure from stress corrosion cracking. Stress frozen photoelastic models have been analyzed to measure the stress concentrations at observed points of failure. The load effects induced by assembly torque and thermal expansion of stem packing were observed by strain gaging nuts. The effects of finishing operations and heat treatment were studied by the strain gage hole boring and X-ray methods. Modifications of manufacturing and operation practices are reducing the frequency of stress corrosion failures.

  2. Mineral resource of the month: hydraulic cement

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2012-01-01

    Hydraulic cements are the binders in concrete and most mortars and stuccos. Concrete, particularly the reinforced variety, is the most versatile of all construction materials, and most of the hydraulic cement produced worldwide is portland cement or similar cements that have portland cement as a basis, such as blended cements and masonry cements. Cement typically makes up less than 15 percent of the concrete mix; most of the rest is aggregates. Not counting the weight of reinforcing media, 1 ton of cement will typically yield about 8 tons of concrete.

  3. US cement industry

    SciTech Connect

    Nisbet, M.A.

    1997-12-31

    This paper describes the cement and concrete industry, and provides data on energy use and carbon dioxide emissions. The potential impact of an energy tax on the industry is briefly assessed. Opportunities identified for reducing carbon dioxide emissions include improved energy efficiency, alternative fuels, and alternative materials. The key factor in determining CO{sub 2} emissions is the level of domestic production. The projected improvement in energy efficiency and the relatively slow growth in domestic shipments indicate that CO{sub 2} emissions in 2000 should be about 5% above the 1990 target. However, due to the cyclical nature of cement demand, emissions will probably be above target levels during peak demand and below target levels during demand troughs. 7 figs., 2 tabs.

  4. Ecology and Energy Action Pack.

    ERIC Educational Resources Information Center

    McDonald's Corp., Oak Brook, IL.

    One of five McDonald's Action Packs, these elementary school-level instructional materials are for use as an introduction to existing units of study, supplements to a textbook, or a source of special projects for environmental education. Contents include these six units: Make Your Own Ecology Mini-spinner, Let's Look at a Food Chain, Drip the…

  5. Microfabricated packed gas chromatographic column

    DOEpatents

    Kottenstette, Richard; Matzke, Carolyn M.; Frye-Mason, Gregory C.

    2003-12-16

    A new class of miniaturized gas chromatographic columns has been invented. These chromatographic columns are formed using conventional micromachining techniques, and allow packed columns having lengths on the order of a meter to be fabricated with a footprint on the order of a square centimeter.

  6. Set covering, partition and packing

    SciTech Connect

    Hulme, B.L.; Baca, L.S.

    1984-03-01

    Set covering problems are known to be solvable by Boolean algebraic methods. This report shows that set partition and set packing problems can be solved by the same algebraic methods because these problems can be converted into covering problems. Many applications are possible including security patrol assignment which is used as an example.

  7. Computer simulations of particle packing

    SciTech Connect

    Cesarano, J. III; McEuen, M.J.; Swiler, T.

    1996-09-01

    Computer code has been developed to rapidly simulate the random packing of disks and spheres in two and three dimensions. Any size distribution may be packed. The code simulates varying degrees of inter particle conditions ranging from sticky to free flowing. The code will also calculate the overall packing density, density distributions, and void size distributions (in two dimensions). An important aspect of the code is that it is written in C++ and incorporates a user-friendly graphical interface for standard Macintosh and Power PC platforms. Investigations as to how well the code simulates the realistic random packing have begun. The code has been developed in consideration of the problem of filling a container (or die) with spray-dried granules of ceramic powder (represented by spheres). Although not presented here, the futuristic goal of this work is to give users the ability to predict homogeneity of filled dies prior to dry pressing. Additionally, this software has educational utility for studying relationships between particle size distributions and macrostructures.

  8. Well cementing in permafrost

    SciTech Connect

    Wilson, W.N.

    1980-01-01

    A process for cementing a string of pipe in the permafrost region of a borehole of a well wherein aqueous drilling fluid actually used in drilling the wellbore in the permafrost region of a wellbore is employed. The drilling fluid contains or is adjusted to contain from about 2 to about 16 volume percent solids. Mixing with the drilling fluid (1) an additive selected from the group consisting of ligno-sulfonate, lignite, tannin, and mixtures thereof, (2) sufficient base to raise the pH of the drilling fluid into the range of from about 9 to about 12, and (3) cementitious material which will harden in from about 30 to about 40 hours at 40/sup 0/F. The resulting mixture is pumped into the permafrost region of a wellbore to be cemented and allowed to harden in the wellbore. There is also provided a process for treating an aqueous drilling fluid after it has been used in drilling the wellbore in permafrost, and a cementitious composition for cementing in a permafrost region of a wellbore.

  9. Tympanoplasty with ionomeric cement.

    PubMed

    Kjeldsen, A D; Grøntved, A M

    2000-01-01

    Patients with isolated erosion of the long incus process suffer from severe hearing loss caused by lack of continuity of the ossicular chain. This study is a retrospective evaluation of the hearing results using two different surgical procedures. Since January 1993, 12 consecutive patients with isolated erosion of the long incus process have been treated with a new surgical technique in which the ossicular chain was rebuilt with ionomeric cement. The results in hearing performance (mean pure-tone average (PTA) 0.5, 1 and 2 kHz) were evaluated pre- and post-surgery, and compared to those in a group of 20 historical controls who underwent surgery in 1991 and 1992 using incus autograft interposition. Among the 12 index patients, 7 (58%) achieved improvement in PTA of > 10 dB, in 3 there was no difference and in 2 a slight decline. Among the 20 controls, 14 (70%) achieved improvement in PTA of > 10 dB, in 4 there was a slight improvement and in 2 a decline. The difference was not statistically significant. Hearing improvement using ionomeric cement in type II tympanoplasty was satisfactory. Reconstruction of the ossicular chain with ionomeric cement is recommended, as the procedure is easy to perform, presents less risk of damage to the stapes and cochlea, requires less extensive surgery and does not exclude other surgical methods in cases of reoperation. PMID:10909000

  10. Innovations in acrylic bone cement and application equipment.

    PubMed

    Kindt-Larsen, T; Smith, D B; Jensen, J S

    1995-01-01

    A new bone cement was developed with the purpose of reducing the adverse biological effects during cementation of implants. This bone cement is characterized by lower exotherm, low release of monomer, low residual content of monomer, and retained physical properties. The essential innovation was substitution of half of the methylmethacrylate (MMA) in the monomer with long chain, high molecular weight, less volatile, and less soluble methacrylates (n-decylmethacrylate, isobornyl-methacrylate), as well as alteration of the accelerator system to a mix of dihydroxypropyl-p-toluidine and N,N-dimethyl-p-toluidine. The powder contains butylmethacrylate-MMA copolymers. These measures lower the glass-transition temperature, and permit more complete mixing in an integrated package, mixing, and delivery system consisting of a vacuum packed, double chamber pouch. The porosity was reduced to about 2% and the largest voids measured 0.1 mm. The polymerization exotherm was reduced to 58 degrees C. The compressive strength was 82 MPa, the four-point bending strength 55 MPa, the flexural modulus 2.24 GPa, the tensile strength 32 MPa, and the shear strength 36 MPa. The fracture toughness was 0.89 MPa square root of cm. These mechanical properties together with the fatigue life were on level with manually mixed, conventional PMMA bone cements. PMID:7703541

  11. Gelation of calcium-silicate-hydrate in cement

    NASA Astrophysics Data System (ADS)

    Ioannidou, Katerina; Kanduc, Matej; Li, Lunna; Frenkel, Daan; Dobnikar, Jure; Pellenq, Roland; Del Gado, Emanuela

    The calcium-silicate-hydrate (C-S-H) gel forms and densifies via precipitation and aggregation of nano-scale hydrates within a couple of hours during cement hydration and it is the main responsible for cement strength. We have investigated equilibrium and arrested states representative of the effective interactions between the nano-scale C-S-H at different stages of the hydration. The inter-hydrate interactions are due to ion correlation forces arising from strong surface charge heterogeneities and change from repulsive to strongly attractive during the early stages of cement hydration, according to the ionic concentration. We analyze the cluster size distributions, the morphology, the local packing and the free energy of aggregates and crystalline phases, using molecular dynamics and Monte Carlo simulations. We compare the results of equilibrium calculations with non-equilibrium simulations that capture the main features of the hydration kinetics. The emerging picture is that the evolving effective interactions provide a thermodynamic driving for the growth of the gel and for its continuous densification that is crucial to cement strength.

  12. Cementing oil and gas wells

    SciTech Connect

    Bloys, J.B.; Wilson, W.N.; Bradshaw, R.D.

    1991-08-13

    This patent describes a method for cementing a wellbore penetrating an earth formation to which a conduit extends, the wellbore having a space occupied by a fluid composition to be converted to cement for cementing the space to form a seal between spaced apart points in the formation. It comprises providing means for adding cementitious material and a dispersant to the fluid, circulating the fluid and adding the cementitious material and the dispersant to a quantity of the fluid in predetermined proportions to form a settable cement composition comprising a major portion of the drilling fluid in the well as it was drilled; and water; a lesser proportion of dry cementitious material; a minor amount of a dispersant that does not effect a satisfactory set cement within an acceptable time interval; and a compatible accelerator selected from the class consisting of acetic acid; the first four carbon esters thereof; and acedamide and filling the wellbore with the cement composition.

  13. Alkali burns from wet cement.

    PubMed Central

    Peters, W. J.

    1984-01-01

    When water is added to the dry materials of Portland cement calcium hydroxide is formed; the wet cement is caustic (with a pH as high as 12.9) and can produce third-degree alkali burns after 2 hours of contact. Unlike professional cement workers, amateurs are usually not aware of any danger and may stand or kneel in the cement for long periods. As illustrated in a case report, general physicians may recognize neither the seriousness of the injury in its early stages nor the significance of a history of prolonged contact with wet cement. All people working with cement should be warned about its dangers and advised to immediately wash and dry the skin if contact does occur. Images Fig. 1 PMID:6561052

  14. Micro- and nano-scale characterization to study the thermal degradation of cement-based materials

    SciTech Connect

    Lim, Seungmin Mondal, Paramita

    2014-06-01

    The degradation of hydration products of cement is known to cause changes in the micro- and nano-structure, which ultimately drive thermo-mechanical degradation of cement-based composite materials at elevated temperatures. However, a detailed characterization of these changes is still incomplete. This paper presents results of an extensive experimental study carried out to investigate micro- and nano-structural changes that occur due to exposure of cement paste to high temperatures. Following heat treatment of cement paste up to 1000 °C, damage states were studied by compressive strength test, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) atomic force microscopy (AFM) and AFM image analysis. Using experimental results and research from existing literature, new degradation processes that drive the loss of mechanical properties of cement paste are proposed. The development of micro-cracks at the interface between unhydrated cement particles and paste matrix, a change in C–S–H nano-structure and shrinkage of C–S–H, are considered as important factors that cause the thermal degradation of cement paste. - Highlights: • The thermal degradation of hydration products of cement is characterized at micro- and nano-scale using scanning electron microscopy (SEM) and atomic force microscopy (AFM). • The interface between unhydrated cement particles and the paste matrix is considered the origin of micro-cracks. • When cement paste is exposed to temperatures above 300 ºC, the nano-structure of C-S-H becomes a more loosely packed globular structure, which could be indicative of C-S-H shrinkage.

  15. Mineral of the month: cement

    USGS Publications Warehouse

    van Oss, Hendrik G.

    2006-01-01

    Hydraulic cement is a virtually ubiquitous construction material that, when mixed with water, serves as the binder in concrete and most mortars. Only about 13 percent of concrete by weight is cement (the rest being water and aggregates), but the cement contributes all of the concrete’s compressional strength. The term “hydraulic” refers to the cement’s ability to set and harden underwater through the hydration of the cement’s components.

  16. Cement penetration after patella venting.

    PubMed

    Jones, Christopher W; Lam, Li-On; Butler, Adam; Wood, David J; Walsh, William R

    2009-01-01

    There is a high rate of patellofemoral complications following total knee arthroplasty. Optimization of the cement-bone interface by venting and suction of the tibial plateau has been shown to improve cement penetration. Our study was designed to investigate if venting the patella prior to cementing improved cement penetration. Ten paired cadaver patellae were allocated prior to resurfacing to be vented or non-vented. Bone mineral density (BMD) was measured by DEXA scanning. In vented specimens, a 1.6 mm Kirschner wire was used to breach the anterior cortex at the center. Specimens were resurfaced with standard Profix instrumentation and Versabond bone cement (Smith and Nephew PLC, UK). Cement penetration was assessed from Faxitron and sectioned images by a digital image software package (ImageJ V1.38, NIH, USA). Wilcoxon rank sum test was used to assess the difference in cement penetration between groups. The relationship between BMD and cement penetration was analyzed by Pearson correlation coefficient. There was a strong negative correlation between peak BMD and cement penetration when analyzed independent of experimental grouping (r(2)=-0.812, p=0.004). Wilcoxon rank sum testing demonstrated no significant difference (rank sum statistic W=27, p=0.579) in cement penetration between vented (10.53%+/-4.66; mean+/-std dev) and non-vented patellae (11.51%+/-6.23; mean+/-std dev). Venting the patella using a Kirschner wire does not have a significant effect on the amount of cement penetration achieved in vitro using Profix instrumentation and Versabond cement. PMID:19010682

  17. [Haemotoxicity of dental luting cements].

    PubMed

    Anders, A; Welker, D

    1989-06-01

    A glass ionomer luting cement (AquaCem) shows a relatively low haemolytic activity in comparison with two zinc phosphate cements. Especially the initial irritation by this cement is smaller. Although it is possible that AquaCem particularly, in unfavourable cases, may damage the pulpa dentin system; this is due to the slowly decrease of the haemolytic activity with increasing of the probes. We found that Adhesor showed in dependence of the batches a varying quality. PMID:2626769

  18. Cross-shift study of acute respiratory effects in cement production workers.

    PubMed

    Aminian, Omid; Aslani, Maryam; Sadeghniiat Haghighi, Khosro

    2014-01-01

    Cement dust exposure is associated with increased respiratory impairment. As the major occupational hazard in the cement production industry is cement particles, our aim was to more thoroughly examine the acute effects of occupational exposure to cement dust on the respiratory system. A cross-shift study was conducted in a cement factory in Iran. 100 high exposed workers from production and packing sections and 100 low exposed from office workers were included. Environmental total dust was measured in each section. Assessment of lung function was done by pre and post shift spirometry. At the end of the day shift, acute respiratory symptoms were recorded. The means of total dust among high and low exposed workers were 16.55 mg/m3 and 0.9 mg/m3, respectively. The most common acute respiratory symptoms in high exposed workers were stuffy nose (52%) and shortness of breath (49%). A statistically significant post shift reduction in PEF, FEV1, FEF 25-75, FVC and FEV1/ FVC was demonstrated in high exposed group. Multivariate linear regression showed a significant relationship between the percentage of the cross-shift decrease in spirometric indices and exposure to cement dust. We detected significant relationship between exposure to cement dust and acute respiratory symptoms and pulmonary function indices. Effective dust-control measures and preparing a suitable strategy for respiratory protection are highly recommended. PMID:24659073

  19. Caustic reaction caused by cement.

    PubMed

    Rados, Jaka; Lipozencić, Jasna; Milavec-Puretić, Visnja

    2005-01-01

    A case is reported of a patient who developed full thickness chemical burns of the skin after a prolonged contact while working with wet cement. The history, course of disease, and therapy are described. Cement is an alkaline substance (pH >12) leading to colliquative necrosis. Tissue damage is due to the exothermic reaction of calcium oxide and water forming calcium hydroxide. Patch test was performed to test sensitization to chromium, chromate and cobalt, the usual cement ingredients. In our opinion, such lesions may not be rare because cement is widely used in construction, but are rarely described or under-recognized. PMID:16324425

  20. [Allergy to bone cement components].

    PubMed

    Thomas, P; Schuh, A; Eben, R; Thomsen, M

    2008-02-01

    Intolerance reactions to endoprostheses may lead to allergological diagnostics, which focus mainly on metal allergy. However, bone cement may also contain potential allergens, e.g. acrylates and additives such as benzoyl peroxide (BPO), N,N-dimethyl-p-toluidine, hydroquinone, and antibiotics (particularly gentamicin). In the Munich implant allergy clinic, we found that 28 of 113 patients (24.8%) with cemented prostheses had contact allergies to bone cement components, mostly to gentamicin (16.8%) and BPO (8.0%). The clinical significance of test results cannot always be shown, but we still recommend including bone cement components in the allergological diagnostics of suspected hypersensitivity reactions to arthroplasty. PMID:18227996

  1. Speciality cements with advanced properties

    SciTech Connect

    Scheetz, B.E. ); Landers, A.G. ); Odler, I. ); Jennings, H. )

    1991-01-01

    The subject matter, specialty cements with advanced properties, highlight some of the recent progress in the non-standard cementitious systems. The topic was intended to be broad enough to include MDF and DSP cement, as well as phosphate-based and other binders. The response to this broad request resulted in a wide variational sampling of potential binder systems, which included calcium phosphates, magnesium phosphates, silica systems derived from sodium fluosilicates, stratlingite glasses, alkali-activated blended cements, and aluminophosphates. Presentations also addressed in depth, the underlying processing and fundamental insight into macro defect cements and DSP.

  2. A case of hypercalcemia and gastric necrosis from hot pack ingestion.

    PubMed

    Padmanabhan, Pradeep; Spiller, Henry A; Bosse, George M

    2010-06-01

    Hot packs (instant hot compresses) are frequently used to relieve pain. We report a patient who had significant complications from ingestion of a hot pack containing calcium salts. A 35-year-old male swallowed three hot packs, and developed hematemesis, severe abdominal pain, and hypercalcemia (21.1 mg/dl). He developed diffuse gastric necrosis requiring gastrectomy and colonic interposition. Hypercalcemia was treated with intravenous fluids, pamidronate, and calcitonin. A Medline search revealed no prior report on hot pack ingestion though ingestion of calcium salts has been reported. Hot packs can potentially cause significant injury both from an exothermic reaction and hypercalcemia. Ingestions of calcium salts can result in necrosis of the stomach. Management includes aggressive treatment of hypercalcemia, supportive care and upper gastrointestinal endoscopy. PMID:20376594

  3. Cemented total hip prosthesis: Radiographic and scintigraphic evaluation

    SciTech Connect

    Aliabadi, P.; Tumeh, S.S.; Weissman, B.N.; McNeil, B.J. )

    1989-10-01

    Conventional radiographs, technetium-99m bone scans, and gallium-67 scans were reviewed in 44 patients who had undergone cemented total hip joint replacement and were imaged because of suspicion of prosthesis loosening or infection. A complete radiolucent line of 2 mm or wider along the bone-cement interface or metal-cement lucency on conventional radiographs was used as the criterion for prosthetic loosening with or without infection and proved to be 54% sensitive and 96% specific. Scintigraphic criteria for prosthetic loosening were increased focal uptake of the radiopharmaceutical for the femoral component and increased focal or diffuse uptake for the acetabular component. For bone scintigraphy, sensitivity was 73% and specificity was 96%. Combining the results of conventional radiographs and bone scans increased sensitivity to 84% and decreased specificity to 92% for the diagnosis of loosening, infection, or both. The study also showed that Ga-67 scintigraphy has a low sensitivity for the detection of infection.

  4. The use of EAF dust in cement composites: assessment of environmental impact.

    PubMed

    Sturm, Tina; Milacic, Radmila; Murko, Simona; Vahcic, Mitja; Mladenovic, Ana; Suput, Jerneja Strupi; Scancar, Janez

    2009-07-15

    Electric arc filter dust (EAF dust) is a waste by-product which occurs in the production of steel. Instead of being disposed of, it can be used in cement composites for civil engineering, and for balances in washing machines. To estimate the environmental impact of the use of EAF dust in cement composites leachability tests based on diffusion were performed using water and salt water as leaching agents. Compact and ground cement composites, and cement composites with addition of 1.5% of EAF dust by mass were studied. The concentrations of total Cr and Cr(VI) were determined in leachates over a time period of 175 days. At the end of the experiment the concentrations of some other metals were also determined in leachates. The results indicated that Cr in leachates was present almost solely in its hexavalent form. No leaching of Cr(VI) was observed in aqueous leachates from compact cement composites and compact cement composites to which different quantities of EAF dust have been added. In ground cement composites and in ground cement composites with addition of EAF dust, Cr(VI) was leached with water in very low concentrations up to 5 microg L(-1). Cr(VI) concentrations were higher in salt water leachates. In compact and ground cement composites with addition of EAF dust Cr(VI) concentrations were 40 and 100 microg L(-1), respectively. It was experimentally found that addition of EAF dust had almost no influence on leaching of Cr(VI) from cement composites. Leaching of Cr(VI) originated primarily from cement. Leaching of other metals from composites investigated did not represent an environmental burden. From the physico-mechanical and environmental aspects EAF dust can be used as a component in cement mixtures. PMID:19097693

  5. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  6. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  7. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  8. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  9. 7 CFR 984.15 - Pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE WALNUTS GROWN IN CALIFORNIA Order Regulating Handling Definitions § 984.15 Pack. Pack means to bleach, clean, grade, shell or otherwise prepare walnuts for market as inshell or shelled walnuts....

  10. Thermal Shock-resistant Cement

    SciTech Connect

    Sugama T.; Pyatina, T.; Gill, S.

    2012-02-01

    We studied the effectiveness of sodium silicate-activated Class F fly ash in improving the thermal shock resistance and in extending the onset of hydration of Secar #80 refractory cement. When the dry mix cement, consisting of Secar #80, Class F fly ash, and sodium silicate, came in contact with water, NaOH derived from the dissolution of sodium silicate preferentially reacted with Class F fly ash, rather than the #80, to dissociate silicate anions from Class F fly ash. Then, these dissociated silicate ions delayed significantly the hydration of #80 possessing a rapid setting behavior. We undertook a multiple heating -water cooling quenching-cycle test to evaluate the cement’s resistance to thermal shock. In one cycle, we heated the 200 and #61616;C-autoclaved cement at 500 and #61616;C for 24 hours, and then the heated cement was rapidly immersed in water at 25 and #61616;C. This cycle was repeated five times. The phase composition of the autoclaved #80/Class F fly ash blend cements comprised four crystalline hydration products, boehmite, katoite, hydrogrossular, and hydroxysodalite, responsible for strengthening cement. After a test of 5-cycle heat-water quenching, we observed three crystalline phase-transformations in this autoclaved cement: boehmite and #61614; and #61543;-Al2O3, katoite and #61614; calcite, and hydroxysodalite and #61614; carbonated sodalite. Among those, the hydroxysodalite and #61614; carbonated sodalite transformation not only played a pivotal role in densifying the cementitious structure and in sustaining the original compressive strength developed after autoclaving, but also offered an improved resistance of the #80 cement to thermal shock. In contrast, autoclaved Class G well cement with and without Class F fly ash and quartz flour failed this cycle test, generating multiple cracks in the cement. The major reason for such impairment was the hydration of lime derived from the dehydroxylation of portlandite formed in the autoclaved

  11. Corrosion behavior of coated 2 1/4 Cr-1 Mo and carbon steels in a simulated high p/sub S/sub 2// waste heat recovery system environment of a coal gasifier. [Al and/or Cr coatings applied by pack-diffusion process

    SciTech Connect

    Baxter, D.J.

    1986-03-01

    Corrosion tests have been conducted on coated 2-1/4Cr-1Mo and A106 carbon steels in a gaseous environment typical of that expected in a downstream waste-heat recovery system of a coal gasifier. The environment contained controlled oxygen and sulfur partial pressures, and the tests were run in a rig designed to expose specimens under simulated heat-exchanger conditions. Uncoated steel substrates exhibited breakaway corrosion behavior. Incoloy 800 also exhibited breakaway corrosion behavior. Coatings containing the stable oxide-forming elements Al and/or Cr were applied by pack-diffusion processes by several commercial vendors. Coatings containing Al contained numerous internal oxide particles and cracks while chromizing occasionally resulted in coatings containing voids. Results indicate that a minimum Cr concentration of approximately 20 to 22 wt % is required to suppress rapid corrosive degradation in the most aggressive environment used in the investigation. A minimum Al concentration could not be as closely defined, but would appear to lie in the range of 14 to 20 wt %. A minimum total concentration of combined additions of Al and Cr could not be defined. The presence of cracks in the aluminized materials promotes internal oxidation. Two Ni-base weld metals were used to simulate joining or repair operations of prior aluminized steel substrates. Both Inconel 625 and Inconel 72 exhibited breakaway corrosion behavior, the former at an unacceptable rate and the latter at a rate on the borderline of acceptability. The corrosion behavior of all coated and coated/welded materials is described and the results used to formulate a provisional specification for the procurement of coatings for eventual commercial application. 11 refs., 15 figs., 5 tabs.

  12. Corrosion behavior of coated 2 1/4 Cr-1Mo and mild steel substrates in a simulated waste heat recovery system environment of a coal gasifier. [FeCrAl or CoCrAl alloys and pack-diffusion aluminizing or chromizing

    SciTech Connect

    Baxter, D.J.

    1985-07-01

    Cossosion tests have been conducted on coated 2 1/4Cr-1Mo and A106 mild steel in a gaseous environment typical of that expected in a downstream waste-heat recovery system of a coal gasifier. The environment contained controlled oxygen and sulfur levels, and the tests were run in a rig designed to expose specimens under simulated heat-exchanger conditions. Uncoated steel substrates exhibited breakaway corrosion behavior. Furnace-fused coatings of FeCrAl or CoCrAl alloys contained numerous defects, such as voids and cracks, and subsequently underwent substantial degradation during exposure. Coatings containing the stable oxide-forming elements Al and Cr were also applied by pack diffusion processes. Sequential chromizing of the A106 mild steel could not be achieved due to massive Cr carbide formation in the initial chromizing stage. Sequential chromizing/aluminizing of the 2 1/4Cr-1Mo steel was successful, but the coating contained numerous defects, which permitted considerable attack of the coated substrate. Simultaneous aluminizing/chromizing produced mixed results, depending upon the particular process used in applying the coating. Coatings exhibited behavior ranging from protective to complete breakdown. A solid FeCrAlY alloy exhibited protective oxidation behavior. With respect to joining or repair methods for coated steels, four different weld metals were used to simulate joining or repair operations of prior aluminized steel substrates. The Ni-base Inconel 625 weld showed good corrosion resistance with Inconel 72 sustaining minor internal attack. The Co-base L605 and Fe-base 309 SS weld metals exhibited breakaway corrosion characterized by the formation of thick scales and deep internal attack. 19 refs., 21 figs., 3 tabs.

  13. 7 CFR 966.11 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE TOMATOES GROWN IN FLORIDA Order Regulating Handling Definitions § 966.11 Pack. Pack means any of the packs of tomatoes as defined and set forth in the United States Standards for Fresh Tomatoes issued by the United States Department of Agriculture (§§...

  14. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Fresh Plums and Prunes Standard Pack § 51... the approved and recognized methods. (2) The plums or prunes in the top layer of any package shall be...” means that the plums or prunes packed in loose or volume filled containers are packed within 1 inch...

  15. 7 CFR 51.1527 - Standard pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ..., CERTIFICATION, AND STANDARDS) United States Standards for Grades of Fresh Plums and Prunes Standard Pack § 51... the approved and recognized methods. (2) The plums or prunes in the top layer of any package shall be...” means that the plums or prunes packed in loose or volume filled containers are packed within 1 inch...

  16. Performance of Diffusion Aluminide Coatings Applied on Alloy CF8C-Plus at 800oC

    SciTech Connect

    Kumar, Deepak; Dryepondt, Sebastien N; Zhang, Ying; Haynes, James A; Pint, Bruce A; Armstrong, Beth L; Shyam, Amit; Lara-Curzio, Edgar

    2012-01-01

    High performance cast stainless steel, CF8C-Plus, is a low cost alloy with prospective applications ranging from covers and casings of small and medium size gas turbines to turbocharger housing and manifolds in internal combustion engines. Diffusion aluminide coatings were applied on this alloy as a potential strategy for improved oxidation resistance, particularly in wet air and steam. In this paper the performance of the aluminide coatings evaluated by cyclic oxidation experiments in air containing 10 vol.% H2O at 800 C and conventional tension-compression low-cycle-fatigue tests in air at 800 C with a strain range of 0.5% is presented. The results show that specimens coated by a chemical vapor deposition process provide better oxidation resistance than those coated by an Al-slurry coating process. The application of a coating by pack cementation reduced the fatigue life by 15%.

  17. Advanced cement solidification system

    SciTech Connect

    Nakashima, T.; Kuribayashi, H.; Todo, F.

    1993-12-31

    In order to easily and economically store and transport radioactive waste generated at nuclear power stations, it is essential to reduce the waste volume to the maximum extent. It is also necessary to transform the waste into a stable form for final disposal which will maintain its chemical and physical stability over a long period of time. For this purpose, the Advanced Cement Solidification Process (AC-process) was developed. The AC-process, which utilizes portland cement, can be applied to several kinds of waste such as boric acid waste, laboratory drain waste, incineration ash and spent ion exchange resin. In this paper, the key point of the AC-process, the pretreatment concept for each waste, is described. The AC-process has been adopted for two Japanese PWR stations: the Genkai Nuclear Power Station (Kyushu Electric Power Co.) and the Ikata Nuclear Power Station (Shikoku Electric Power Co.). Construction work has almost finished and commissioning tests are under way at both power stations.

  18. Dense Regular Packings of Irregular Nonconvex Particles

    NASA Astrophysics Data System (ADS)

    de Graaf, Joost; van Roij, René; Dijkstra, Marjolein

    2011-10-01

    We present a new numerical scheme to study systems of nonconvex, irregular, and punctured particles in an efficient manner. We employ this method to analyze regular packings of odd-shaped bodies, both from a nanoparticle and from a computational geometry perspective. Besides determining close-packed structures for 17 irregular shapes, we confirm several conjectures for the packings of a large set of 142 convex polyhedra and extend upon these. We also prove that we have obtained the densest packing for both rhombicuboctahedra and rhombic enneacontrahedra and we have improved upon the packing of enneagons and truncated tetrahedra.

  19. The effect of unsaturated fatty acid and triglyceride oil addition on the mechanical and antibacterial properties of acrylic bone cements.

    PubMed

    Persson, Cecilia; Robert, Elise; Carlsson, Elin; Robo, Céline; López, Alejandro; Godoy-Gallardo, Maria; Ginebra, Maria-Pau; Engqvist, Håkan

    2015-09-01

    Acrylic bone cements have an elastic modulus several times higher than the surrounding trabecular bone. This has been hypothesized to contribute to certain clinical complications. There are indications that the addition of specific fatty acids and triglyceride oils may reduce the elastic modulus of these types of cements. Some of these additives also appear to have inherent antibiotic properties, although this has never been evaluated in bone cements. In this study, several types of fatty acids and triglyceride oils were evaluated for use in acrylic bone cements. Their mechanical properties were evaluated under uniaxial compression testing and selected cements were then further characterized in terms of microstructure, handling and antibacterial properties using scanning electron microscopy, polymerization temperature measurements, agar diffusion tests and bactericidal activity assays of cement extracts. It was found that any of the evaluated fatty acids or triglyceride oils could be used to tailor the stiffness of acrylic bone cements, although at varying concentrations, which also depended on the type of commercial base cement used. In particular, the addition of very small amounts of linoleic acid (<2.0 wt%) resulted in Young's moduli and compressive strengths in the range of human trabecular bone, while maintaining a similar setting time. Further, the addition of 12.6 wt% ricinoleic acid to Osteopal V cement was found to have a significant antibacterial effect, inhibiting growth of Staphylococcus aureus in an agar diffusion test as well as demonstrating 100% bactericidal activity against the same strain. PMID:25876889

  20. Percolation behavior of tritiated water into a soil packed bed

    SciTech Connect

    Honda, T.; Katayama, K.; Uehara, K.; Fukada, S.; Takeishi, T.

    2015-03-15

    A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)

  1. Radon resistant potential of concrete manufactured using Ordinary Portland Cement blended with rice husk ash

    NASA Astrophysics Data System (ADS)

    Chauhan, R. P.; Kumar, Amit

    2013-12-01

    The emission of radon from building materials and soil depends upon the radium content, porosity, moisture content and radon diffusion length of materials. Several techniques have been used to reduce the radon emission from the soil using different flooring materials. But the effectiveness of radon shielding depends upon the diffusion of radon through these materials. The present study proposes a method for producing a radon resistant material for decreasing radon diffusion through it. The method involves rice husk ash (RHA) in addition to cement for the preparation of concrete used for flooring and walls. The radon diffusion, exhalation and mechanical property of concrete prepared by rice husk ash blended cement were studied. The addition of RHA caused the reduction in radon diffusion coefficient, exhalation rates, porosity and enhanced the compressive strength of concrete. The bulk radon diffusion coefficient of cementitious concrete was reduced upto 69% by addition of rice husk ash as compare to that of control concrete.

  2. Electrolyte diffusion in compacted montmorillonite engineered barriers

    SciTech Connect

    Jahnke, F.M.; Radke, C.J.

    1985-09-01

    The bentonite-based engineered barrier or packing is a proposed component of several designs conceived to dispose of high-level nuclear waste in geologic repositories. Once radionuclides escape the waste package, they must first diffuse through the highly impermeable clay-rich barrier before they reach the host repository. To determine the effectiveness of the packing as a sorption barrier in the transient release period and as a mass-transfer barrier in the steady release period over the geologic time scales involved in nuclear waste disposal, a fundamental understanding of the diffusion of electrolytes in compacted clays is required. We present, and compare with laboratory data, a model quantifying the diffusion rates of cationic cesium and uncharged tritium in compacted montmorillonite clay. Neutral tritium characterizes the geometry (i.e., tortuosity) of the particulate gel. After accounting for cation exchange, we find that surface diffusion is the dominant mechanism of cation transport, with an approximate surface diffusion coefficient of 2 x 10 W cmS/s for cesium. This value increases slightly with increasing background ionic strength. The implications of this work for the packing as a migration barrier are twofold. During the transient release period, K/sub d/ values are of little importance in retarding ion migration. This is because sorption also gives rise to a surface diffusion path, and it is surface diffusion which controls the diffusion rate of highly sorbing cations in compacted montmorillonite. During the steady release period, the presence of surface diffusion leads to a flux through the packing which is greatly enhanced. In either case, if surface diffusion is neglected, the appropriate diffusion coefficient of ions in compacted packing will be in considerable error relative to current design recommendations. 11 refs., 4 figs., 1 tab.

  3. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  4. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  5. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  6. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  7. 21 CFR 888.4200 - Cement dispenser.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cement dispenser. 888.4200 Section 888.4200 Food... DEVICES ORTHOPEDIC DEVICES Surgical Devices § 888.4200 Cement dispenser. (a) Identification. A cement dispenser is a nonpowered syringe-like device intended for use in placing bone cement (§ 888.3027)...

  8. Strontium-loaded mineral bone cements as sustained release systems: Compositions, release properties, and effects on human osteoprogenitor cells.

    PubMed

    Tadier, Solène; Bareille, Reine; Siadous, Robin; Marsan, Olivier; Charvillat, Cédric; Cazalbou, Sophie; Amédée, Joelle; Rey, Christian; Combes, Christèle

    2012-02-01

    This study aims to evaluate in vitro the release properties and biological behavior of original compositions of strontium (Sr)-loaded bone mineral cements. Strontium was introduced into vaterite CaCO3 -dicalcium phosphate dihydrate cement via two routes: as SrCO3 in the solid phase (SrS cements), and as SrCl2 dissolved in the liquid phase (SrL cements), leading to different cement compositions after setting. Complementary analytical techniques implemented to thoroughly investigate the release/dissolution mechanism of Sr-loaded cements at pH 7.4 and 37°C during 3 weeks revealed a sustained release of Sr and a centripetal dissolution of the more soluble phase (vaterite) limited by a diffusion process. In all cases, the initial burst of the Ca and Sr release (highest for the SrL cements) that occurred over 48 h did not have a significant effect on the expression of bone markers (alkaline phosphatase, osteocalcin), the levels of which remained overexpressed after 15 days of culture with human osteoprogenitor (HOP) cells. At the same time, proliferation of HOP cells was significantly higher on SrS cements. Interestingly, this study shows that we can optimize the sustained release of Sr(2+) , the cement biodegradation and biological activity by controlling the route of introduction of strontium in the cement paste. PMID:22102621

  9. Characterizing Reactive Flow Paths in Fractured Cement

    NASA Astrophysics Data System (ADS)

    Wenning, Q. C.; Huerta, N. J.; Hesse, M. A.; Bryant, S. L.

    2011-12-01

    Geologic carbon sequestration can be a viable method for reducing anthropogenic CO2 flux into the atmosphere. However, the technology must be economically feasible and pose acceptable risk to stakeholders. One key risk is CO2 leakage out of the storage reservoir. Potential driving forces for leakage are the overpressure due to CO2 injection and the buoyancy of free phase CO2. Potential hazards of leakage are contamination of Underground Sources of Drinking Water or the atmosphere and would be deemed an unacceptable risk. Wells potentially provide a fast path for leakage from the reservoir. While the well's cement casing is reactive with CO2 and CO2-saturated brine, the low cement matrix permeability and slow diffusion rate make it unlikely that CO2 will escape through a properly constructed wellbore. However, highly permeable fractures with micrometer scale apertures can occur in cement casings. Reactions that occur in the flow in these fractures can either be self-limiting or self-enhancing. Therefore, understanding the reactive flow is critical to understanding of leakage evolution through these fractures. The goal of our work is to characterize the modification of the flow paths in the fracture due to reaction with acidic brine. With this aim we have characterized both the initial flow path of un-reactive flow and the final flow path after introduction of low-pH acid along the same fracture. Class H cement cores 3-6 cm in length and 2.5 cm diameter are created and a single natural and unique fracture is produced in each core using the Brazilian method. Our experimental fluid is injected at a constant rate into the cement core housed in a Hassler Cell under confining pressure. A solution of red dye and deionized water is pumped through the fracture to stain the un-reactive flow paths. Deionized water is then pumped through the core to limit diffusion of the dye into non-flowing portions of the fracture. After staining the initial flow path, low pH water due to

  10. Formation and Oxidation Performance of Low-Temperature Pack Aluminide Coatings on Ferritic-Martensitic Steels

    SciTech Connect

    Bates, Brian; Wang, Y. Q.; Zhang, Ying; Pint, Bruce A

    2009-01-01

    A pack cementation process was developed to coat commercial 9% Cr ferritic-martensitic steel T91 at temperatures below its normal tempering temperature to avoid any potential detrimental effect on the mechanical properties of the coated alloy. In order to prevent the formation of Fe{sub 2}Al{sub 5} coatings, the Al activity in the pack cementation process was reduced by substituting the pure Al masteralloy with binary Cr-Al masteralloys containing either 15 or 25 wt.% Al. When the Cr-25Al masteralloy was used, a duplex coating was formed at 700 C, consisting of a thin Fe{sub 2}Al{sub 5} outer layer and an inner layer of FeAl. With the Cr-15Al masteralloy, an FeAl coating of {approx} 12 {micro}m thick was achieved at 700 C. The pack aluminide coatings fabricated at 700 C are being evaluated in air + 10 vol.% H{sub 2}O at 650 C and 700 C to determine their long-term oxidation performance.

  11. Reinforcement of cement-based matrices with graphite nanomaterials

    NASA Astrophysics Data System (ADS)

    Sadiq, Muhammad Maqbool

    micro-scale fibers were used for comparison purposes at different volume fractions. Replicated mixes and tests were considered to provide the basis for statistically reliable inferences. Theoretical studies were conducted in order to develop insight into the reinforcement mechanisms of properly functionalized graphite nanomaterials. The results suggested that modified graphite nanomaterials improve the mechanical performance of cement-based matrices primarily through control of microcrack size and propagation, relying on their close spacing within matrix and dissipation of substantial energy by debonding and frictional pullout over their enormous surface areas. The gains in barrier qualities of cement-based materials with introduction of modified graphite nanomaterials could be attributed to the increased tortuosity of diffusion paths in the presence of closely spaced nanomaterials. Experimental investigations were designed and implemented towards identification of the optimum (nano- and micro-scale) reinforcement systems for high-performance concrete through RSA (Response Surface Analysis). A comprehensive experimental data base was developed on the mechanical, physical and durability characteristics as well as the structure and composition of high-performance cementitious nanocomposites reinforced with modified graphite nanomaterials and/ or different micro-fibers.

  12. Rupture in cemented granular media: application to wheat endosperm

    NASA Astrophysics Data System (ADS)

    Topin, V.; Delenne, J.-Y.; Radjai, F.

    2009-06-01

    The mechanical origin of the wheat hardness used to classify wheat flours is an open issue. Wheat endosperm can be considered as a cemented granular material, consisting of densely packed solid particles (the starch granules) and a pore-filling solid matrix (the protein) sticking to the particles. We use the lattice element method to investigate cemented granular materials with a texture close to that of wheat endosperm and with variable matrix volume fraction and particle-matrix adherence. From the shape of the probability density of vertical stresses we distinguish weak, intermediate and strong stresses. The large stresses occur mostly at the contact zones as in noncohesive granular media with a decreasing exponential distribution. The weak forces reflect the arching effect. The intermediate stresses belong mostly to the bulk of the particles and their distribution is well fit to a Gaussian distribution. We also observe that the stress chains are essentially guided by the cementing matrix in tension and by the particulate backbone in compression. Crack formation is analyzed in terms of particle damage as a function of matrix volume fraction and particle-matrix adherence. Our data provide evidence for three regimes of crack propagation depending on the crack path through the material. We find that particle damage scales well with the relative toughness of the particle-matrix interface. The interface toughness appears therefore to be strongly correlated with particle damage and determines transition from soft to hard behavior in wheat endosperm.

  13. Cementing porcelain-fused-to-metal crowns.

    PubMed

    Vadachkoria, D

    2009-12-01

    The clinical success of fixed prosthodontic restorations can be complex and involve multifaceted procedures. Preparation design, oral hygiene/micro flora, mechanical forces, and restorative materials are only a few of the factors which contribute to overall success. One key factor to success is choosing the proper cement. Popular use of cements for PFM crowns has shifted from zinc phosphate and glass ionomer cements to resin-reinforced glass ionomer, or RRGI, cements. This change has been rapid and profound. Dental cements have always been less than ideal materials, but this is shift to the relatively new RRGI category justified. Resin-reinforced glass ionomer (RRGI) cements appear to be better than zinc phosphate and glass ionomer cements when placing porcelain-to-metal crowns. RRGI cements, such as RelyX Luting, Fuji Plus and Vitremer Luting Cement, satisfy more of the ideal characteristics of PFM cementation than any other previous cement. Expansion of all three cements has not caused any apparent problems with the cements when used with PFM or metal crowns, but these cements, however, should be avoided when cementing all-ceramic crowns. PMID:20090144

  14. The dermal toxicity of cement.

    PubMed

    Winder, Chris; Carmody, Martin

    2002-08-01

    Cement and concrete are products used widely in the construction sector, with a traditional perception that any hazards that they have are limited to dermatitis in a small number of workers. In some cases, employers and builders do not think that concrete is a chemical. However, contact dermatitis is one of the most frequently reported health problems among construction workers. A review of the available literature suggests that cement has constituents that produce both irritant contact dermatitis and corrosive effects (from alkaline ingredients such as lime) and sensitization, leading to allergic contact dermatitis (from ingredients such as chromium). These findings indicate that cement and concrete should be treated as hazardous materials, and that workers handling such products should reduce exposure wherever possible. Initiatives to reduce the chromium content of cement have been shown to be successful in reducing the incidence of allergic dermatitis, although the irritant form remains. PMID:15068132

  15. Process for cementing geothermal wells

    SciTech Connect

    Eilers, L. H.

    1985-12-03

    A pumpable slurry of coal-filled furfuryl alcohol, furfural, and/or a low molecular weight monoor copolymer thereof containing, preferably, a catalytic amount of a soluble acid catalyst is used to cement a casing in a geothermal well.

  16. Magnesium substitution in brushite cements.

    PubMed

    Alkhraisat, Mohammad Hamdan; Cabrejos-Azama, Jatsue; Rodríguez, Carmen Rueda; Jerez, Luis Blanco; Cabarcos, Enrique López

    2013-01-01

    The use of magnesium-doped ceramics has been described to modify brushite cements and improve their biological behavior. However, few studies have analyzed the efficiency of this approach to induce magnesium substitution in brushite crystals. Mg-doped ceramics composed of Mg-substituted β-TCP, stanfieldite and/or farringtonite were reacted with primary monocalcium phosphate (MCP) in the presence of water. The cement setting reaction has resulted in the formation of brushite and newberyite within the cement matrix. Interestingly, the combination of SAED and EDX analyses of single crystal has indicated the occurrence of magnesium substitution within brushite crystals. Moreover, the effect of magnesium ions on the structure, and mechanical and setting properties of the new cements was characterized as well as the release of Ca(2+) and Mg(2+) ions. Further research would enhance the efficiency of the system to incorporate larger amounts of magnesium ions within brushite crystals. PMID:25428098

  17. Graphite-reinforced bone cement

    NASA Technical Reports Server (NTRS)

    Knoell, A. C.

    1976-01-01

    Chopped graphite fibers added to surgical bone cement form bonding agent with mechanical properties closely matched to those of bone. Curing reaction produces less heat, resulting in reduced traumatization of body tissues. Stiffness is increased without affecting flexural strength.

  18. The Packing of Granular Polymer Chains

    SciTech Connect

    Zou, Ling-Nan; Cheng, Xiang; Rivers, Mark L.; Jaeger, Heinrich M.; Nagel, Sidney R.; UC

    2009-12-01

    Rigid particles pack into structures, such as sand dunes on the beach, whose overall stability is determined by the average number of contacts between particles. However, when packing spatially extended objects with flexible shapes, additional concepts must be invoked to understand the stability of the resulting structure. Here, we examine the disordered packing of chains constructed out of flexibly connected hard spheres. Using x-ray tomography, we find that long chains pack into a low-density structure whose mechanical rigidity is mainly provided by the backbone. On compaction, randomly oriented, semi-rigid loops form along the chain, and the packing of chains can be understood as the jamming of these elements. Finally, we uncover close similarities between the packing of chains and the glass transition in polymers.

  19. Mapping the depth to ice-cemented ground in the high elevation Dry Valleys, Antarctica

    NASA Astrophysics Data System (ADS)

    Marinova, M.; McKay, C. P.; Heldmann, J. L.; Davila, A. F.; Andersen, D. T.; Jackson, A.; Lacelle, D.; Paulsen, G.; Pollard, W. H.; Zacny, K.

    2011-12-01

    The high elevation Dry Valleys of Antarctica provide a unique location for the study of permafrost distribution and stability. In particular, the extremely arid and cold conditions preclude the presence of liquid water, and the exchange of water between the ice-cemented ground and the atmosphere is through vapour transport (diffusion). In addition, the low atmospheric humidity results in the desiccation of the subsurface, forming a dry permafrost layer (i.e., cryotic soils which are dry and not ice-cemented). Weather data suggests that subsurface ice is unstable under current climatic conditions. Yet we do find ice-cemented ground in these valleys. This contradiction provides insight into energy balance modeling, vapour transport, and additional climate effects which stabilize subsurface ice. To study the driving factors in the stability and distribution of ice-cemented ground, we have extensively mapped the depth to ice-cemented ground in University Valley (1730 m; 77°S 51.8', 160°E 43'), and three neighbouring valleys in the Beacon Valley area. We measured the depth to ice-cemented ground at 15-40 locations per valley by digging soil pits and drilling until ice was reached; for each location 3-5 measurements within a ~1 m2 area were averaged (see figure). This high-resolution mapping of the depth to ice-cemented ground provides new insight on the distribution and stability of subsurface ice, and shows significant variability in the depth to ground ice within each valley. We are combining data from mapping the depth to ice-cemented ground with year-round, in situ measurements of the atmospheric and subsurface conditions, such as temperature, humidity, wind, and light, to model the local stability of ice-cemented ground. We are using this dataset to examine the effects of slopes, shading, and soil properties, as well as the suggested importance of snow recurrence, to better understand diffusion-controlled subsurface ice stability.

  20. Solubility of cobalt in cement.

    PubMed

    Fregert, S; Gruvberger, B

    1978-02-01

    Unlike chromate, cobalt occurring as cobalt oxides in cement is not water-soluble in a detectable amount. Cobalt oxides are to some extent soluble in the presence of amino acids with which cobalt forms complexes. Such complexes can elicit patch test reactions. It is postulated that cobalt is more readily dissolved by forming complexes in eczematous skin than in normal skin. This may explain why cobalt sensitization in cement eczemas is secondary to chromate sensitivity. PMID:657784

  1. Random packing of spheres in Menger sponge

    NASA Astrophysics Data System (ADS)

    Cieśla, Michał; Barbasz, Jakub

    2013-06-01

    Random packing of spheres inside fractal collectors of dimension 2 < d < 3 is studied numerically using Random Sequential Adsorption (RSA) algorithm. The paper focuses mainly on the measurement of random packing saturation limit. Additionally, scaling properties of density autocorrelations in the obtained packing are analyzed. The RSA kinetics coefficients are also measured. Obtained results allow to test phenomenological relation between random packing saturation density and collector dimension. Additionally, performed simulations together with previously obtained results confirm that, in general, the known dimensional relations are obeyed by systems having non-integer dimension, at least for d < 3.

  2. Random packing of spheres in Menger sponge.

    PubMed

    Cieśla, Michał; Barbasz, Jakub

    2013-06-01

    Random packing of spheres inside fractal collectors of dimension 2 < d < 3 is studied numerically using Random Sequential Adsorption (RSA) algorithm. The paper focuses mainly on the measurement of random packing saturation limit. Additionally, scaling properties of density autocorrelations in the obtained packing are analyzed. The RSA kinetics coefficients are also measured. Obtained results allow to test phenomenological relation between random packing saturation density and collector dimension. Additionally, performed simulations together with previously obtained results confirm that, in general, the known dimensional relations are obeyed by systems having non-integer dimension, at least for d < 3. PMID:23758392

  3. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  4. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  5. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  6. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  7. 7 CFR 982.11 - Pack.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... ORDERS; FRUITS, VEGETABLES, NUTS), DEPARTMENT OF AGRICULTURE HAZELNUTS GROWN IN OREGON AND WASHINGTON... according to size, internal quality, and external appearance and condition of hazelnuts packed in...

  8. Minimally packed phases in holography

    NASA Astrophysics Data System (ADS)

    Donos, Aristomenis; Gauntlett, Jerome P.

    2016-03-01

    We numerically construct asymptotically AdS black brane solutions of D = 4 Einstein-Maxwell theory coupled to a pseudoscalar. The solutions are holographically dual to d = 3 CFTs at finite chemical potential and in a constant magnetic field, which spontaneously break translation invariance leading to the spontaneous formation of abelian and momentum magnetisation currents flowing around the plaquettes of a periodic Bravais lattice. We analyse the three-dimensional moduli space of lattice solutions, which are generically oblique, and show, for a specific value of the magnetic field, that the free energy is minimised by the triangular lattice, associated with minimal packing of circles in the plane. We show that the average stress tensor for the thermodynamically preferred phase is that of a perfect fluid and that this result applies more generally to spontaneously generated periodic phases. The triangular structure persists at low temperatures indicating the existence of novel crystalline ground states.

  9. Cemented femoral fixation: the North Atlantic divide.

    PubMed

    Murray, David W

    2011-09-01

    In the United Kingdom, more cemented than cementless stems are implanted, whereas in North America, few cemented stems are implanted. This is primarily because cemented stems have not performed well in North America, whereas they have in the United Kingdom, as different designs have been used. The majority of cemented stems used in the United Kingdom are polished, collarless, and tapered. These are forgiving, as they subside within the cement mantle and compress the cement and stabilize the interface. They perform well in both young and active patients and elderly patients. They also do well in osteoporotic bone, with deformity, or with suboptimal cementing techniques. As the position of the stem can be varied, it is simple to achieve appropriate leg length, offset, and version. Cement can be used to deliver antibiotics locally. If revision is necessary, it is relatively straightforward. Cement has numerous advantages that outweigh the main disadvantage of an extended operating time. PMID:21902131

  10. Manufacture and properties of fluoride cement

    NASA Astrophysics Data System (ADS)

    Malata-Chirwa, Charles David

    This research work aimed at characterising composition, hydration and physical properties of fluoride cement, by studying samples of the cement obtained from Malawi, and comparing them to ordinary Portland cement. By confirming the suitable characteristics of fluoride cement through this work, the results of the research work provide a good basis for the wider adoption of fluoride cement as an alternative to ordinary Portland cement, especially in developing economies. Numerous accounts have been cited regarding the production and use of fluoride cement. Since there have not been conclusive agreement as to its properties, this study was limited to the theories of successful incorporation of fluoride compounds in the manufacture of fluoride cement. Hence, the properties and characteristics reported in this study relate to the cement currently manufactured in Malawi, and, on a comparative basis only, to that manufactured in other parts of the world. Samples of the fluoride cement used in the study were obtained by synthetic manufacture of the cement using common raw materials for the manufacture of fluoride cement that is limestone, silica sand, and fluorspar. These samples were subjected to several comparative tests used to characterise cements including examination under x-ray diffractometer, scanning electron microscopy and tests for setting time and compressive strength. Under similar laboratory conditions, it was possible to prove that fluoride cement hardens more rapidly than ordinary Portland cement. Also observed during the experimental work is that fluoride cement develops higher compressive strengths than ordinary Portland cement. The hardening and setting times are significantly different between the two cements. Also the nature of the hydration products, that is the microstructural development is significantly different in the two cements. The differences brought about between the two cements are because of the presence of fluorine during the clinkering

  11. Confined disordered strictly jammed binary sphere packings

    NASA Astrophysics Data System (ADS)

    Chen, D.; Torquato, S.

    2015-12-01

    Disordered jammed packings under confinement have received considerably less attention than their bulk counterparts and yet arise in a variety of practical situations. In this work, we study binary sphere packings that are confined between two parallel hard planes and generalize the Torquato-Jiao (TJ) sequential linear programming algorithm [Phys. Rev. E 82, 061302 (2010), 10.1103/PhysRevE.82.061302] to obtain putative maximally random jammed (MRJ) packings that are exactly isostatic with high fidelity over a large range of plane separation distances H , small to large sphere radius ratio α , and small sphere relative concentration x . We find that packing characteristics can be substantially different from their bulk analogs, which is due to what we term "confinement frustration." Rattlers in confined packings are generally more prevalent than those in their bulk counterparts. We observe that packing fraction, rattler fraction, and degree of disorder of MRJ packings generally increase with H , though exceptions exist. Discontinuities in the packing characteristics as H varies in the vicinity of certain values of H are due to associated discontinuous transitions between different jammed states. When the plane separation distance is on the order of two large-sphere diameters or less, the packings exhibit salient two-dimensional features; when the plane separation distance exceeds about 30 large-sphere diameters, the packings approach three-dimensional bulk packings. As the size contrast increases (as α decreases), the rattler fraction dramatically increases due to what we call "size-disparity" frustration. We find that at intermediate α and when x is about 0.5 (50-50 mixture), the disorder of packings is maximized, as measured by an order metric ψ that is based on the number density fluctuations in the direction perpendicular to the hard walls. We also apply the local volume-fraction variance στ2(R ) to characterize confined packings and find that these

  12. The effect of cement creep and cement fatigue damage on the micromechanics of the cement-bone interface.

    PubMed

    Waanders, Daan; Janssen, Dennis; Mann, Kenneth A; Verdonschot, Nico

    2010-11-16

    The cement-bone interface provides fixation for the cement mantle within the bone. The cement-bone interface is affected by fatigue loading in terms of fatigue damage or microcracks and creep, both mostly in the cement. This study investigates how fatigue damage and cement creep separately affect the mechanical response of the cement-bone interface at various load levels in terms of plastic displacement and crack formation. Two FEA models were created, which were based on micro-computed tomography data of two physical cement-bone interface specimens. These models were subjected to tensile fatigue loads with four different magnitudes. Three deformation modes of the cement were considered: 'only creep', 'only damage' or 'creep and damage'. The interfacial plastic deformation, the crack reduction as a result of creep and the interfacial stresses in the bone were monitored. The results demonstrate that, although some models failed early, the majority of plastic displacement was caused by fatigue damage, rather than cement creep. However, cement creep does decrease the crack formation in the cement up to 20%. Finally, while cement creep hardly influences the stress levels in the bone, fatigue damage of the cement considerably increases the stress levels in the bone. We conclude that at low load levels the plastic displacement is mainly caused by creep. At moderate to high load levels, however, the plastic displacement is dominated by fatigue damage and is hardly affected by creep, although creep reduced the number of cracks in moderate to high load region. PMID:20692663

  13. Continuous monitoring of the zinc-phosphate acid-base cement setting reaction by proton nuclear magnetic relaxation

    NASA Astrophysics Data System (ADS)

    Apih, T.; Lebar, A.; Pawlig, O.; Trettin, R.

    2001-06-01

    Proton nuclear magnetic relaxation is a well-established technique for continuous and non destructive monitoring of hydration of conventional Portland building cements. Here, we demonstrate the feasibility of nuclear magnetic resonance (NMR) monitoring of the setting reaction of zinc-phosphate acid-base dental cements, which harden in minutes as compared to days, as in the case of Portland cements. We compare the setting of cement powder (mainly, zinc oxide) prepared with clinically used aluminum-modified orthophosphoric acid solution with the setting of a model system where cement powder is mixed with pure orthophosphoric acid solution. In contrast to previously published NMR studies of setting Portland cements, where a decrease of spin-lattice relaxation time is attributed to enhanced relaxation at the growing internal surface, spin-lattice relaxation time T1 increases during the set of clinically used zinc-phosphate cement. Comparison of these results with a detailed study of diffusion, viscosity, and magnetic-field dispersion of T1 in pure and aluminum-modified orthophosphoric acid demonstrates that the increase of T1 in the setting cement is connected with the increase of molecular mobility in the residual phosphoric acid solution. Although not taken into account so far, such effects may also significantly influence the relaxation times in setting Portland cements, particularly when admixtures with an effect on water viscosity are used.

  14. Kid's PACK: Population Awareness Campaign Kit.

    ERIC Educational Resources Information Center

    Zero Population Growth, Inc., Washington, DC.

    This fun and educational kit is designed specifically for elementary students. The "Kid's PACK" (Population Awareness Campaign Kit) entertains and informs children on the environment and human population growth through stories, games, and concrete ideas for making a difference. In three booklets, the "Kid's PACK" offers elementary students…

  15. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  16. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  17. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  18. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  19. Record high Wolf, Canis lupus, pack density

    USGS Publications Warehouse

    Mech, L.D.; Tracy, S.

    2004-01-01

    This report documents a year-around Wolf (Canis lupus) density of 18.2/100 km2 and a summer density of 30.8/100 km2, in a northeastern Minnesota Wolf pack. The previous record was a summer density of 14.1/100 km2, for a Wolf pack on Vancouver Island, British Columbia, Canada.

  20. Record high wolf, Canis lupus, pack density

    USGS Publications Warehouse

    Mech, L.D.; Tracy, S.

    2004-01-01

    This report documents a year-around wolf (Canis lupus) density of 18.2/100 m2 and summer density of 30.8/100 km2, in a northeastern Minnesota wolf pack. The previous record was a summer density of 14.1/100 km2, for a wolf pack on Vancouver Island, BC, Canada.

  1. Development of an effective valve packing program

    SciTech Connect

    Hart, K.A.

    1996-12-01

    Current data now shows that graphite valve packing installed within the guidance of a controlled program produces not only reliable stem sealing but predictable running loads. By utilizing recent technological developments in valve performance monitoring for both MOV`s and AOV`s, valve packing performance can be enhanced while reducing maintenance costs. Once known, values are established for acceptable valve packing loads, the measurement of actual valve running loads via the current MOV/AOV diagnostic techniques can provide indication of future valve stem sealing problems, improper valve packing installation or identify the opportunity for valve packing program improvements. At times the full benefit of these advances in material and predictive technology remain under utilized due to simple past misconceptions associated with valve packing. This paper will explore the basis for these misconceptions, provide general insight into the current understanding of valve packing and demonstrate how with this new understanding and current valve diagnostic equipment the key aspects required to develop an effective, quality valve packing program fit together. The cost and operational benefits provided by this approach can be significant impact by the: elimination of periodic valve repacking, reduction of maintenance costs, benefits of leak-free valve operation, justification for reduced Post Maintenance Test Requirements, reduced radiation exposure, improved plant appearance.

  2. 21 CFR 890.5700 - Cold pack.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Cold pack. 890.5700 Section 890.5700 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5700 Cold pack. (a) Identification....

  3. Pack rats (Neotoma spp.): Keystone ecological engineers?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential role of two species of pack rats (Neotoma albigula and Neotoma micropus) as keystone ecological engineers was examined by estimating the species diversity of invertebrates living in the nest middens, and nitrogen mineralization rates in soils associated with the middens. Although pack-...

  4. Probe with integrated heater and thermocouple pack

    SciTech Connect

    McCulloch, R.W.; Dial, R.E.; Finnell, W.F.R.

    1988-02-16

    This patent describes a gamma thermometer probe for detecting heat produced within the thermometer probe. It comprises: an outer elongate thermometer sheath; an elongate rod; annular recesses; a longitudinal bore; and an integrated thermocouple pack. The thermocouple pack comprises: a first type wire, and second type wires. The second type wires comprises: an outer section; and an inner segment.

  5. New value packing technology extends service life

    SciTech Connect

    Miller, M.; Jackson, R. )

    1993-10-01

    New packing techniques can extend packing life and retain low stem leakage. The HPI can use these designs to avoid mandatory monitoring and repair schedules for valves that exceed the 500-ppm emission threshold. New EPA leakage limits will enforce monitoring and maintenance programs if more than 2% of the facility's valves exceed this limit. Because valves are dynamic, their control actions are prone to leakage. Also, the best fire-resistant packing material, graphite, has inherent deficiencies such as high compression stress and a high-friction coefficient that shortens its service life. Four basic principles overcome graphite packing's shortcomings for control valve applications. Examples show how these criteria improve sliding stem and rotary valve performance. Incorporating these principles into valve-packing designs can ensure long, low-maintenance service life, and the added benefit of low leakage. Graphite is a very important packing material for the HPI. Unlike fluoropolymer (e.g., PTFE) packing, graphite can tolerate high process temperature without decomposing or losing its sealing properties. More importantly, graphite packing is fire safe. It can survive a fire without a catastrophic failure that could add more flammable materials.

  6. Pack Density Limitations of Hybrid Parachutes

    NASA Technical Reports Server (NTRS)

    Zwicker, Matthew L.; Sinclair, Robert J.

    2013-01-01

    The development and testing of the Orion crew capsule parachute system has provided a unique opportunity to study dense parachute packing techniques and limits, in order to establish a new baseline for future programs. The density of parachute packs has a significant influence on vibration loads, retention system stresses, and parachute mortar performance. Material compositions and pack densities of existing designs for space capsule recovery were compared, using the pack density of the Apollo main parachutes as the current baseline. The composition of parachutes has changed since Apollo, incorporating new materials such as Kevlar , Vectran , Teflon and Spectra . These materials have different specific densities than Nylon, so the densities of hybrid parachute packs cannot be directly compared to Nylon parachutes for determination of feasibility or volume allocation. Six parachute packs were evaluated in terms of weighted average solid density in order to achieve a non-dimensional comparison of packing density. Means of mitigating damage due to packing pressure and mortar firing were examined in light of the Capsule Parachute Assembly System (CPAS) and Apollo experience. Parachute design improvements including incorporation of modern materials and manufacturing processes serves to make CPAS the new knowledge base on which future spacecraft parachute systems will be built.

  7. Method of gravel packing a well

    SciTech Connect

    Almond, S. W.; Himes, R. E.

    1985-11-12

    The present invention relates to a thermally stable crosslinked gel gravel packing fluid for use in the treatment of highly deviated well bores penetrating a subterranean formation. The gravel packing fluid comprises an aqueous liquid, a gelling agent comprising a selected modified cellulose ether, a crosslinking agent, a breaker, a particulate agent and any additional additives that may be present.

  8. Loading and release of doxycycline hyclate from strontium-substituted calcium phosphate cement.

    PubMed

    Alkhraisat, M Hamdan; Rueda, C; Cabrejos-Azama, J; Lucas-Aparicio, J; Mariño, F Tamimi; Torres García-Denche, J; Jerez, L Blanco; Gbureck, U; Cabarcos, E Lopez

    2010-04-01

    Novel Sr-substituted calcium phosphate cement (CPC) loaded with doxycycline hyclate (DOXY-h) was employed to elucidate the effect of strontium substitution on antibiotic delivery. The cement was prepared using as reactants Sr-substituted beta-tricalcium phosphate (Sr-beta-TCP) and acidic monocalcium phosphate monohydrate. Two different methods were used to load DOXY-h: (i) the adsorption on CPC by incubating the set cement in drug-containing solutions; and (ii) the use of antibiotic solution as the cement liquid phase. The results revealed that the Sr-substituted cement efficiently adsorbs the antibiotic, which is attributed to an enhanced accessibility to the drug-binding sites within this CPC. DOXY-h desorption is influenced by the initial adsorbed amount and the cement matrix type. Furthermore, the fraction of drug released from CPCs set with DOXY-h solution was higher, and the release rate was faster for the CPC prepared with 26.7% Sr-beta-TCP. The analysis of releasing profiles points to Fickian diffusion as the mechanism responsible for antibiotic delivery. We can conclude that Sr substitution in secondary calcium phosphate cements improves their efficiency for DOXY-h adsorption and release. The antibiotic loading method provides a way to switch from rapid and complete to slower and prolonged drug release. PMID:19879982

  9. Comparative Evaluation of the Antimicrobial Properties of Glass Ionomer Cements with and without Chlorhexidine Gluconate

    PubMed Central

    Jampanapalli, Sharada Reddy; Konda, Suhasini; Inguva, Hema Chandrika; Chimata, Vamsi Krishna

    2016-01-01

    ABSTRACT Background: Chlorhexidine gluconate is a widely used antimicrobial agent. Adding chlorhexidine and quaternary ammonium compounds to filling materials, such as composite resins, acrylic resins, and glass ionomer cements increases the antibacterial property of restorative materials. This study includes antibacterial property of glass ionomer restorative cements with chlorhexidine gluconate. Aim: The primary objective of our study was to compare the antimicrobial properties of two commercially available glass ionomer cements with and without chlorhexidine gluconate on strains of mutans streptococci. Materials and methods: Two glass ionomers (Fuji II Conventional and Fuji IX) were used. Chlorhexidine gluconate was mixed with glass ionomer cements, and antimicrobial properties against mutans streptococci were assessed by agar diffusion. The tested bacterial strain was inhibited and the antimicrobial properties decreased with time. Results: The highest amount of antimicrobial activity with mean inhibitory zone was found in Fuji II with chlorhexidine gluconate followed by Fuji IX with chlorhexidine gluconate, Fuji II without chlorhexidine gluconate, and Fuji IX without chlorhexidine gluconate. Conclusion: The results of the study confirmed that the addition of 5% chlorhexidine gluconate to Fuji II and Fuji IX glass ionomer cements resulted in a restorative material that had increased antimicrobial properties over the conventional glass ionomer cements alone for Streptococcus mutans. How to cite this article: Yadiki JV, Jampanapalli SR , Konda S, Inguva HC, Chimata VK. Comparative Evaluation of the Antimicrobial Properties of Glass Ionomer Cements with and without Chlorhexidine Gluconate. Int J Clin Pediatr Dent 2016;9(2):99-103. PMID:27365927

  10. Evaluation of antibacterial and antifungal activity of new calcium-based cement (Biodentine) compared to MTA and glass ionomer cement

    PubMed Central

    Bhavana, Vankayala; Chaitanya, Krishna Popuri; Gandi, Padma; Patil, Jayaprakash; Dola, Binoy; Reddy, Rahul B.

    2015-01-01

    Objective: To evaluate the antibacterial and antifungal properties of calcium-based cement, Biodentine (Ca3SiO2), compared to commercial glass ionomer cements (GICs) and mineral trioxide aggregate (MTA). Materials and Methods: Pellets of GICs, ProRoot MTA, and Biodentine were prepared to test the influence of these cements on the growth of four oral microbial strains: Streptococcus mutans, Enterococcus faecalis, Escherichia coli, and Candida albicans; using agar diffusion method. Wells were formed by removing the agar and the manipulated materials were immediately placed in the wells. The pellets were lodged in seeded plates and the growth inhibition diameter around the material was measured after 24-72 h incubation at 37°C. The data were analyzed using analysis of variance (ANOVA) test to compare the differences among the three cements at different concentrations. Results: Test indicates that the antimicrobial activity of Biodentine, on all the microorganisms tested, was very strong, showing a mean inhibition zone of 3.2 mm, which extends over time towards all the strains. For Biodentine, GIC, and MTA, the diameters of the inhibition zones for S. mutans were significantly larger than for E. faecalis, Candida, and E. coli (P < 0.05). Conclusion: All materials showed antimicrobial activity against the tested strains except for GIC on Candida. Largest inhibition zone was observed for Streptococcus group. Biodentine created larger inhibition zones than MTA and GIC. PMID:25657526