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Sample records for comparing thermal stability

  1. Comparative thermal stability characteristics and isothermal oxidation behavior of an aluminized and a Pt-aluminized Ni-base superalloy

    SciTech Connect

    Tawancy, H.M.; Sridhar, N.; Abbas, N.M.; Rickerby, D.

    1995-11-01

    It is the objective of this paper to compare the thermal stability characteristics and isothermal oxidation behavior of an aluminide coating and a Pt-aluminide coating of the same Al content on a Ni-base superalloy. Addition of Pt to an aluminide coating was found to improve its thermal stability as well as its capability for selective oxidation of Al resulting in a purer scale of slower growth rate. This was correlated with the greater diffusional stability of the Pt-aluminide coating restricting the transport of substrate elements into the outer coating layers.

  2. Jet Fuel Thermal Stability

    NASA Technical Reports Server (NTRS)

    Taylor, W. F. (Editor)

    1979-01-01

    Various aspects of the thermal stability problem associated with the use of broadened-specification and nonpetroleum-derived turbine fuels are addressed. The state of the art is reviewed and the status of the research being conducted at various laboratories is presented. Discussions among representatives from universities, refineries, engine and airframe manufacturers, airlines, the Government, and others are presented along with conclusions and both broad and specific recommendations for future stability research and development. It is concluded that significant additional effort is required to cope with the fuel stability problems which will be associated with the potentially poorer quality fuels of the future such as broadened specification petroleum fuels or fuels produced from synthetic sources.

  3. Steam generation in line-focus solar collectors: A comparative assessment of thermal performance, operating stability and cost issues

    NASA Astrophysics Data System (ADS)

    Murphy, L. M.; May, E. K.

    1982-04-01

    The engineering and system benefits of using direct steam (in situ) generation in line-focus collectors are assessed. The major emphasis of the analysis is a detailed thermal performance comparison of in situ systems (which utilize unfired boilers). The analysis model developed for this study is discussed in detail. An analysis of potential flow stability problems is also provided along with a cursory cost analysis and an assessment of freeze protection, safety, and control issues. Results indicated a significant thermal performance advantage over the more conventional oil and flash systems and the flow stability does not appear to be a significant problem. In particular, at steam temperatures of 220 C (430 F) under the chosen set of assumptions, annual delivered energy predictions indicate that the in situ system can deliver 15% more energy than an oil system and 12% more energy than flash system, with all of the systems using the same collector field. Further, the in situ system may result in a 10% capital cost reduction.

  4. Thermal stability of grafted fibers. [Gamma radiation

    SciTech Connect

    Sundardi, F.; Kadariah; Marlianti, I.

    1983-10-01

    Presented the experimental results on the study of thermal stability of grafted fibers, i.e., polypropylene-, polyester-, and rayon-grafted fibers. These fibers were obtained by radiation grafting processes using hydrophylic monomers such as 1-vinyl 2-pyrolidone, acrylic acid, N-methylol acrylamide, and acrylonitrile. The thermal stability of the fibers was studied using a Shimadzu Thermal Analyzer DT-30. The thermal stability of the fibers, which can be indicated by the value of the activation energy for thermal degradation, was not improved by radiation grafting. The degree of improvement depends on the thermal stability of the monomers used for grafting. The thermal stability of a polypropylene fiber, either a grafted or an ungrafted one, was found to be inferior compared to the polyester of a rayon fiber, which may be due to the lack of C=O and C=C bonds in the polypropylene molecules. The thermal stability of a fiber grafted with acrylonitrile monomer was found to be better than that of an ungrafted one. However, no improvement was detected in the fibers grafted with 1-vinyl 2-pyrrolidone monomer, which may be due to the lower thermal stability of poly(1-vinyl-2-pyrrolidone), compared to the polypropylene or polyester fibers. 17 figures, 3 tables.

  5. Comparative Study of Thermal Stability of NiFe and NiFeTa Thin Films Grown by Cosputtering Technique

    NASA Astrophysics Data System (ADS)

    Phuoc, Nguyen N.; Ong, C. K.

    2016-08-01

    A comparative study of the thermal behavior of dynamic permeability spectra for compositionally graded NiFeTa and uniform-composition NiFe thin films has been carried out. We found that the resonance frequency of the compositionally graded NiFeTa film increased with increasing temperature, while it decreased for the case of the uniform-composition NiFe thin film. This finding unambiguously suggests that the compositional gradient of the film is the only reason for the increase of the magnetic anisotropy with temperature due to its stress-induced origin, while the cosputtering technique does not play any role in this peculiar behavior. The temperature dependence of the frequency linewidth is also presented and discussed.

  6. Thermal Stability Of Formohydroxamic Acid

    SciTech Connect

    Fondeur, F. F.; Rudisill, T. S.

    2011-10-21

    The thermal stability of formohydroxamic acid (FHA) was evaluated to address the potential for exothermic decomposition during storage and its use in the uranium extraction process. Accelerating rate calorimetry showed rapid decomposition at a temperature above 65 {degree}C; although, the rate of pressure rise was greater than two orders of magnitude less than the lower bound for materials which have no explosive properties with respect to transportation. FHA solutions in water and nitric acid did not reach runaway conditions until 150 {degree}C. Analysis by differential scanning calorimetry showed that FHA melted at 67 {degree}C and thermally decomposed at 90 {degree}C with an enthalpy of -1924 J/g. The energics of the FHA thermal decomposition are comparable to those measured for aqueous solutions of hydroxylamine nitrate. Solid FHA should be stored in a location where the temperature does not exceed 20-25 {degree}C. As a best practice, the solid material should be stored in a climate-controlled environment such as a refrigerator or freezer. FHA solutions in water are not susceptible to degradation by acid hydrolysis and are the preferred way to handle FHA prior to use.

  7. Thermally stabilized heliostat

    DOEpatents

    Anderson, Alfred J.

    1983-01-01

    An improvement in a heliostat having a main support structure and pivoting and tilting motors and gears and a mirror module for reflecting solar energy onto a collector, the improvement being characterized by an internal support structure within each mirror module and front and back sheets attached to the internal support structure, the front and back sheets having the same coefficient of thermal expansion such that no curvature is induced by temperature change, and a layer of adhesive adhering the mirror to the front sheet. The adhesive is water repellent and has adequate set strength to support the mirror but has sufficient shear tolerance to permit the differential expansion of the mirror and the front sheet without inducing stresses or currature effect. The adhesive also serves to dampen fluttering of the mirror and to protect the mirror backside against the adverse effects of weather. Also disclosed are specific details of the preferred embodiment.

  8. Thermal stabilization of an endoglucanase by cyclization.

    PubMed

    van Lieshout, Johan F T; Pérez Gutiérrez, Odette N; Vroom, Wietse; Planas, Antoni; de Vos, Willem M; van der Oost, John; Koutsopoulos, Sotirios

    2012-08-01

    An intein-driven protein splicing approach allowed for the covalent linkage between the N- and C-termini of a polypeptide chain to create circular variants of the endo-β-1,3-1,4-glucanase, LicA, from Bacillus licheniformis. Two circular variants, LicA-C1 and LicA-C2, which have connecting loops of 20 and 14 amino acids, respectively, showed catalytic activities that are approximately two and three times higher, respectively, compared to that of the linear LicA (LicA-L1). The thermal stability of the circular variants was significantly increased compared to the linear form. Whereas the linear glucanase lost half of its activity after 3 min at 65 °C, the two circular variants have 6-fold (LicA-C1) and 16-fold (LicA-C2) increased half-life time of inactivation. In agreement with this, fluorescence spectroscopy and differential scanning calorimetry studies revealed that circular enzymes undergo structural changes at higher temperatures compared to that of the linear form. The effect of calcium on the conformational stability and function of the circular LicAs was also investigated, and we observed that the presence of calcium ions results in increased thermal stability. The impact of the length of the designed loops on thermal stability of the circular proteins is discussed, and it is suggested that cyclization may be an efficient strategy for the increased stability of proteins. PMID:22653681

  9. Thermal Stability of Dopamine Transporters.

    PubMed

    Kukk, Siim; Stepanov, Vladimir; Järv, Jaak

    2015-08-01

    The thermal stabilities of the rat and mouse dopamine transporter (DAT) proteins were studied within the temperature range of 0-37°C. The inactivation of the protein was followed by monitoring changes in radioligand-specific binding. We found that the process followed a rate equation with first-order kinetics and was characterized by having a single rate constant k inact. The activation energies (E a) that were calculated from the Arrhenius plots (ln k inact vs. 1/T) were 43 ± 5 and 45 ± 6 kJ/mol for the rat (rDAT) and mouse (mDAT) transporters, respectively, and 44 ± 7 kJ/mol for rDAT from PC-6.3 cell line. These E a values were similar to the E a values of thermal inactivation of the muscarinic receptor from rat brain cortex and to the thermal inactivation of other transmembrane proteins. However, all of these activation energy values were significantly lower than the E a values for soluble single-subunit proteins of similar size. These results therefore suggest that the thermal stability of transmembrane proteins may be governed to a significant extent by cell membrane properties and by interactions between the membrane components and the protein. In contrast, the stability of soluble proteins seems to be mostly governed by protein structure and size, which determine the sum of the stabilizing intramolecular interactions within the protein molecule. It is therefore not surprising that cell membrane properties and composition may have significant effects on the functional properties of transmembrane proteins. PMID:25812533

  10. Thermal and pH stability of "beta-benzyme".

    PubMed Central

    D'Souza, V T; Lu, X L; Ginger, R D; Bender, M L

    1987-01-01

    The thermal and pH stability of "beta-benzyme", an artificial chymotrypsin based on beta-cyclodextrin, has been studied and compared with the stability of real chymotrypsin. Artificial chymotrypsin is vastly superior to real chymotrypsin with regard to both temperature and pH stability. The reasons for this increased stability are discussed. PMID:3468505

  11. Thermal stability of sulfonated polymers

    SciTech Connect

    Audibert, A.; Argillier, J.F.

    1995-11-01

    Polyacrylamides which are used in oil applications i.e. polymer flooding and water based muds, are hydrolyzed versus time and temperature. This leads to a lack of tolerance towards electrolyte contamination and to a rapid degradation inducing a loss of their properties. Modifications of polyacrylamide structure have been proposed to postpone their thermal stability to higher temperatures. Monomers such as acrylamido methylpropane sulfonate (AMPS) or sulfonated styrene/maleic anhydride can be used to prevent acrylamide comonomer from hydrolysis. The aim of this work is to study under controlled conditions, i.e. anaerobic atmosphere, neutral pH, the stability of sulfonated polymers in order to distinguish between hydrolysis and radical degradation reactions. It has been observed that up to 100 C, the AMPS group is stable and protects the acrylamide function from hydrolysis up to 80%. At higher temperature, even the hydrolysis of the AMPS group occurs, giving acrylate and {beta},{beta} dimethyl taurine, with a kinetics that depends on temperature and time. Degradation in terms of molecular weight then occurs indicating that it follows a radical decarboxylation reaction. It can be limited either by the use of free radical scavenger or when the polymer is in the presence of a mineral phase such as bentonite. These results provide valuable data for the determination of the limits of use of sulfonated copolymers and guidelines for optimizing chemical structure of sulfonated polymers used in water based formulation, in particular to enhance their thermal stability.

  12. Multifunctional Composites for Improved Polyimide Thermal Stability

    NASA Technical Reports Server (NTRS)

    Miller, Sandi G.

    2007-01-01

    The layered morphology of silicate clay provides an effective barrier to oxidative degradation of the matrix resin. However, as resin thermal stability continues to reach higher limits, development of an organic modification with comparable temperature capabilities becomes a challenge. Typically, phyllosilicates used in polymer nanocomposites are modified with an alkyl ammonium ion. Such organic modifiers are not suited for incorporation into high temperature polymers as they commonly degrade below 200oC. Therefore, the development of nanoparticle specifically suited for high temperature applications is necessary. Several nanoparticles were investigated in this study, including pre-exfoliated synthetic clay, an organically modified clay, and carbon nanofiber. Dispersion of the layered silicate increases the onset temperature of matrix degradation as well as slows oxidative degradation. The thermally stable carbon nanofibers are also observed to significantly increase the resin thermal stability.

  13. The role of stabilization centers in protein thermal stability.

    PubMed

    Magyar, Csaba; Gromiha, M Michael; Sávoly, Zoltán; Simon, István

    2016-02-26

    The definition of stabilization centers was introduced almost two decades ago. They are centers of noncovalent long range interaction clusters, believed to have a role in maintaining the three-dimensional structure of proteins by preventing their decay due to their cooperative long range interactions. Here, this hypothesis is investigated from the viewpoint of thermal stability for the first time, using a large protein thermodynamics database. The positions of amino acids belonging to stabilization centers are correlated with available experimental thermodynamic data on protein thermal stability. Our analysis suggests that stabilization centers, especially solvent exposed ones, do contribute to the thermal stabilization of proteins. PMID:26845354

  14. Thermal stability of nanocrystalline microstructures

    NASA Astrophysics Data System (ADS)

    Darling, Kris Allen

    The objective of the proposed research is to develop the experimental data and scientific basis that can optimize the thermodynamic stabilization of a nanoscale microstructure during consolidation of Fe powder particles through select solute diffusion to grain boundaries. Fe based alloys were high energy ball milled to produce supersaturated solid solutions with a nominal grain size of ˜10nm. Solutes such as Y, W, Ta, Ni and Zr were selected based on their propensity to grain boundary segregated in Fe. Based on preliminary heat treatments Zr was selected as the solute of choice. Upon further heat treating experiments and microstructural analysis it was found that Zr solute additions of <4at% could stabilize a nanocrystalline microstructure of <100nm at temperatures in excess of 900°C. This is in stark comparison to pure nanocrystalline Fe which shows coarsening to the micron scale after annealing above 600°C. Reduction in grain boundary energy due to Zr segregation and solute drag are proposed as mechanism responsible for the observed thermal stability. In addition to the work presented on Fe based Zr alloys supplementary research is presented on the following systems: Fe based Ni alloys, Pd 20at%Zr, Cu3Ge and CuGeO3. The addition of Ni to Fe was selected as a control. Since Ni and Fe have similar atomic radii, the elastic enthalpy of segregation of Ni in Fe is low (+1kJ/mol) and at high temperatures Ni has complete solid solubility in Fe; it is suggested that Ni will have a negligible influence in the thermal stability of nanocrystalline Fe. It was shown that at 700°C the addition of 1at% Ni produce a bimodal microstructure consisting of ˜70% abnormally grown grains and ˜30% nanocrystalline grains of 100-200nm. While these results are interesting extensive work is still needed to understand the mechanisms governing the thermal stability in this system. A presentation of the collected data is given. Pd 20 at% Zr was high energy ball milled to produce an

  15. Thermally Stabilized Transmit/Receive Modules

    NASA Technical Reports Server (NTRS)

    Hoffman, James; DelCastillo, Linda; Miller, Jennifer; Birur, Gaj

    2011-01-01

    RF-hybrid technologies enable smaller packaging and mass reduction in radar instruments, especially for subsystems with dense electronics, such as electronically steered arrays. We are designing thermally stabilized RF-hybrid T/R modules using new materials for improved thermal performance of electronics. We are combining advanced substrate and housing materials with a thermal reservoir material, and develop new packaging techniques to significantly improve thermal-cycling reliability and performance stability over temperature.

  16. High stability buffered phase comparator

    NASA Technical Reports Server (NTRS)

    Adams, W. A.; Reinhardt, V. S. (Inventor)

    1984-01-01

    A low noise RF signal phase comparator comprised of two high stability driver buffer amplifiers driving a double balanced mixer which operate to generate a beat frequency between the two RF input signals coupled to the amplifiers from the RF sources is described. The beat frequency output from the mixer is applied to a low noise zero crossing detector which is the phase difference between the two RF inputs. Temperature stability is provided by mounting the amplifiers and mixer on a common circuit board with the active circuit elements located on one side of a circuit board and the passive circuit elements located on the opposite side. A common heat sink is located adjacent the circuit board. The active circuit elements are embedded into the bores of the heat sink which slows the effect of ambient temperature changes and reduces the temperature gradients between the active circuit elements, thus improving the cancellation of temperature effects. The two amplifiers include individual voltage regulators, which increases RF isolation.

  17. Thermal effects in borehole stability

    NASA Astrophysics Data System (ADS)

    Tran, Dung Trung

    ' uncertainties, the use of complex wellbore models might not necessarily reduce the uncertainty of the predictions, contrary to popular belief. The following studies explore the quantifications of rock parameters' uncertainties (ranges) that are used as input in a wellbore stability analysis. Firstly, three equivalent forms of Gassmann's equation are presented. These equations were applied to several sets of laboratory measurements (Berea sandstones and Bedford limestones) to determine the grain matrix bulk modulus and Biot-Willis coefficient based on measured compressive and shear velocities. A stochastic simulation was performed to examine the effect of uncertainty and/or measurement errors on calculated grain matrix bulk modulus and Biot-Willis coefficient. The results showed that the calculated grain matrix bulk modulus is relatively constant with applied differential pressure (up to 50 MPa) for sedimentary rocks, whereas Biot-Willis coefficient is a function of the confining pressure. Small errors in dry and saturated bulk modulus values (or of velocities), however, can significantly affect the calculated grain bulk modulus and Biot-Willis coefficient values. The uncertainties of rock failure parameters (Uniaxial Compressive Strength, cohesion, and internal friction angle) obtained from laboratory experiments are considered next. It is shown that different testing procedures and data analysis methods result in very different input rock failure parameter values. A new analytical solution to find the best-fit Mohr-Coulomb failure envelope from N Mohr's circles based on Least-Absolute Errors is presented, showing comparable results with those deduced from established least-square regression approaches. The problem is converted into N linear systems that can be solved readily using a common linear programming method. This method is found to be more useful than least-square regression when one has to deal with data sets of mixed qualities. Finally, a wellbore stability analysis

  18. Thermal Stability of Ni-Mn Electrodeposits

    SciTech Connect

    Talin, A. A.; Marquis, E. A.; Goods, S. H.; Kelly, J. J.; Miller, Michael K

    2006-01-01

    The effect of Mn additions on the structural stability of electrodeposited Ni is investigated by comparing the microstructure evolution of Ni and Ni-Mn specimens with similar crystallographic initial textures. As deposited, Ni-Mn electrodeposits have a smaller crystallite size and substantially higher yield strength than Ni deposits, in agreement with the Hall-Petch relationship. Moreover, dilute Ni-Mn electrodeposits exhibit a thermal stability that significantly exceeds that of pure Ni. Indeed, Ni-Mn retains its texture, fine-grain microstructure, and strength above 500 C (for 1 h anneal), and does not recrystallize up to 800 C. In contrast, pure Ni with larger average grain size and similar preferred orientation shows abnormal grain growth at 300 C and recrystallization at 600 C. This study suggests two distinct temperature regimes. Below 600 C, grain boundary segregation appears as a plausible mechanism for the thermal stability of Ni-Mn electrodeposits, whereas grain boundary pinning by precipitation contributes to the improved microstructural stability of Ni-Mn above 600 C.

  19. On the remarkable thermal stability of nanocrystalline cobalt via alloying

    PubMed Central

    Bachmaier, A.; Motz, C.

    2015-01-01

    Nanostructured Co materials are produced by severe plastic deformation via alloying with small amounts of C and larger amounts of Cu. The thermal stability of the different nanostructured Co materials is studied through isothermal annealing at different temperatures for various times and compared to the stability of severe plastically deformed high-purity nanocrystalline Co. The microstructural changes taking place during annealing are evaluated by scanning electron microscopy, transmission electron microscopy and microhardness measurements. In the present work it is shown that the least stable nanostructured material is the single-phase high purity Co. Alloying with C improves the thermal stability to a certain extent. A remarkable thermal stability is achieved by alloying Co with Cu resulting in stabilized nanostructures even after annealing for long times at high temperatures. The essential reason for the enhanced thermal stability is to be found in the immiscibility of both components of the alloy. PMID:25892849

  20. Protein thermal stabilization in aqueous solutions of osmolytes.

    PubMed

    Bruździak, Piotr; Panuszko, Aneta; Jourdan, Muriel; Stangret, Janusz

    2016-01-01

    Proteins' thermal stabilization is a significant problem in various biomedical, biotechnological, and technological applications. We investigated thermal stability of hen egg white lysozyme in aqueous solutions of the following stabilizing osmolytes: Glycine (GLY), N-methylglycine (NMG), N,N-dimethylglycine (DMG), N,N,N-trimethylglycine (TMG), and trimethyl-N-oxide (TMAO). Results of CD-UV spectroscopic investigation were compared with FTIR hydration studies' results. Selected osmolytes increased lysozyme's thermal stability in the following order: Gly>NMG>TMAO≈DMG>TMG. Theoretical calculations (DFT) showed clearly that osmolytes' amino group protons and water molecules interacting with them played a distinctive role in protein thermal stabilization. The results brought us a step closer to the exact mechanism of protein stabilization by osmolytes. PMID:26495438

  1. High Reynolds Number Thermal Stability Experiments

    NASA Technical Reports Server (NTRS)

    Emens, Jessica M.; Brown, Sarah P.; Frederick Robert A., Jr.; Wood, A. John

    2004-01-01

    This work represents preliminary thermal stability results for liquid hydrocarbon fuels. High Reynolds Number Thermal Stability experiments with Jet A and RP-1 resulted in a quantitative measurement of the thermal stability. Each fuel flowed through a heated capillary tube that held the outlet temperature at 290 C. An optical pyrometer measured the surface temperature of the tube at 12 locations as a function of time. The High Reynolds Number Thermal Stability number was then determined using standards published by the American Society for Testing and Materials. The results for Jet A showed lower thermal stability than similar tests conducted at another facility. The RP-1 results are the first reported using this technique. Because the temperature rise on the capillary tube during testing for the RP-1 fuels was not significant, a new standard for the testing conditions should be developed for these types of fuels.

  2. Thermal stability and degradation of chitosan modified by benzophenone

    NASA Astrophysics Data System (ADS)

    Diab, M. A.; El-Sonbati, A. Z.; Bader, D. M. D.

    2011-09-01

    N-(biphenylmethylidenyl) chitosan polymer was prepared, characterized and thermal stability was compared with chitosan. Thermal degradation products of the modified polymer were identified by GC-MS technique. It seems that the mechanism of degradation of the prepared polymer is characterized by formation of low molecular weight radicals, followed by random scission mechanism along the backbond chain.

  3. Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings

    SciTech Connect

    Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young

    2009-07-15

    In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

  4. Thermal stability of PLD grown silver nanoparticles

    NASA Astrophysics Data System (ADS)

    Shokeen, Poonam; Jain, Amit; Kapoor, Avinashi

    2016-05-01

    Present work discusses the stability of silver nanoparticles at different annealing temperatures. Air muffle furnace annealing is performed to study the thermal stability of pulsed laser deposited silver nanoparticles. Silver reacts with atmospheric oxygen to form silver oxide at annealing temperatures below 473K and thermal decomposition of silver oxide takes place at temperatures above 473K. Oxide formation results in core shrinkage of silver, which in turn affects the surface plasmon resonance of silver nanoparticles. With increase in annealing temperature, the surface plasmon effect of nanoparticles starts to fade. SEM, XRD and UV-vis spectroscopy have been performed to analysis various structural and optical properties.

  5. Thermal Stability of Rhodopsin and Progression of Retinitis Pigmentosa

    PubMed Central

    Liu, Monica Yun; Liu, Jian; Mehrotra, Devi; Liu, Yuting; Guo, Ying; Baldera-Aguayo, Pedro A.; Mooney, Victoria L.; Nour, Adel M.; Yan, Elsa C. Y.

    2013-01-01

    Over 100 point mutations in the rhodopsin gene have been associated with retinitis pigmentosa (RP), a family of inherited visual disorders. Among these, we focused on characterizing the S186W mutation. We compared the thermal properties of the S186W mutant with another RP-causing mutant, D190N, and with WT rhodopsin. To assess thermal stability, we measured the rate of two thermal reactions contributing to the thermal decay of rhodopsin as follows: thermal isomerization of 11-cis-retinal and hydrolysis of the protonated Schiff base linkage between the 11-cis-retinal chromophore and opsin protein. We used UV-visible spectroscopy and HPLC to examine the kinetics of these reactions at 37 and 55 °C for WT and mutant rhodopsin purified from HEK293 cells. Compared with WT rhodopsin and the D190N mutant, the S186W mutation dramatically increases the rates of both thermal isomerization and dark state hydrolysis of the Schiff base by 1–2 orders of magnitude. The results suggest that the S186W mutant thermally destabilizes rhodopsin by disrupting a hydrogen bond network at the receptor's active site. The decrease in the thermal stability of dark state rhodopsin is likely to be associated with higher levels of dark noise that undermine the sensitivity of rhodopsin, potentially accounting for night blindness in the early stages of RP. Further studies of the thermal stability of additional pathogenic rhodopsin mutations in conjunction with clinical studies are expected to provide insight into the molecular mechanism of RP and test the correlation between rhodopsin's thermal stability and RP progression in patients. PMID:23625926

  6. On the cause of low thermal stability of ethyl halodiazoacetates

    PubMed Central

    Mortén, Magnus; Hennum, Martin

    2016-01-01

    Summary Rates for the thermal decomposition of ethyl halodiazoacetates (halo = Cl, Br, I) have been obtained, and reported herein are their half-lives. The experimental results are supported by DFT calculations, and we provide a possible explanation for the reduced thermal stability of ethyl halodiazoacetates compared to ethyl diazoacetate and for the relative decomposition rates between the chloro, bromo and iodo analogs. We have also briefly studied the thermal, non-catalytic cyclopropanation of styrenes and compared the results to the analogous Rh(II)-catalyzed reactions. PMID:27559411

  7. On the cause of low thermal stability of ethyl halodiazoacetates.

    PubMed

    Mortén, Magnus; Hennum, Martin; Bonge-Hansen, Tore

    2016-01-01

    Rates for the thermal decomposition of ethyl halodiazoacetates (halo = Cl, Br, I) have been obtained, and reported herein are their half-lives. The experimental results are supported by DFT calculations, and we provide a possible explanation for the reduced thermal stability of ethyl halodiazoacetates compared to ethyl diazoacetate and for the relative decomposition rates between the chloro, bromo and iodo analogs. We have also briefly studied the thermal, non-catalytic cyclopropanation of styrenes and compared the results to the analogous Rh(II)-catalyzed reactions. PMID:27559411

  8. Temperature Stabilization Requirements for Unchopped Thermal Detectors

    NASA Technical Reports Server (NTRS)

    Foote, Marc C.

    2000-01-01

    The temperature stabilization requirements of unchopped thermistor bolometers and thermopile detectors are analyzed. The detector temperature, on which the bolometer output signal depends, is quite sensitive to changes in instrument temperature but relatively insensitive to changes in scene temperature. In contrast, the difference in temperature between detector and substrate (instrument), on which the thermopile signal depends, is equally sensitive to changes in instrument and scene temperature. Expressions for these dependencies are derived based on a simplified instrument model. It is shown that for a typical uncooled thermal imager, the temperature stabilization requirements for a bolometer are two orders of magnitude more stringent than those for a thermopile detector. Keywords: thermistor, bolometer, thermopile, detector, IR, thermal, temperature stabilization

  9. The Thermal Stability of Galaxy Cluster Plasmas

    NASA Astrophysics Data System (ADS)

    Quataert, Eliot

    2011-09-01

    The interplay between radiative cooling and heating at the centers of massive halos remains one of the major problems in galaxy formation. Absent heating, theoretical models overpredict cooling and star formation rates in these systems by several orders of magnitude. Some process must heat the gas to offset cooling, but it is not yet clear how global thermal stability can be achieved; moreover, the plasma is likely to remain prone to local thermal instability on small scales. We propose to explore physically-motivated heating models that stabilize groups and clusters against cooling catastrophes. Our proposed work will determine both why clusters have the multiphase structure they do, and what role the cold and hot gas play in the thermal evolution of the intracluster medium.

  10. CHEMICAL REACTIVITY TEST: Assessing Thermal Stability and Chemical Compatibility

    SciTech Connect

    Koerner, J; Tran, T; Gagliardi, F; Fontes, A

    2005-04-21

    The thermal stability of high explosive (HE) and its compatibility with other materials are of critical importance in storage and handling practices. These properties are measured at Lawrence Livermore National Laboratory using the chemical reactivity test (CRT). The CRT measures the total amount of gas evolved from a material or combination of materials after being heat treated for a designated period of time. When the test result is compared to a threshold value, the relative thermal stability of an HE or the compatibility of an HE with other materials is determined. We describe the CRT testing apparatus, the experimental procedure, and the comparison methodology and provide examples and discussion of results.

  11. Determination of the thermal stability of perfluoroalkylethers

    NASA Technical Reports Server (NTRS)

    Helmick, Larry S.; Jones, William R., Jr.

    1990-01-01

    The thermal decomposition temperatures of several commercial and custom synthesized perfluoroalkylether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for custom synthesized fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids is not affected by intrinsic factors such as carbon chain length, branching, or cumulated difluoroformal groups. Instead, correlation with extrinsic factors revealed that the stability may be limited by the presence of small quantities of thermally unstable material and/or chlorine-containing material arising from the use of chlorine-containing solvents during synthesis. Finally, correlation of decomposition temperatures with molecular weights for Demnum and Krytox fluids supports a chain cleavage reaction mechanism for Demnum fluids and an unzipping reaction mechanism for Krytox fluids.

  12. System Design Description PFP Thermal Stabilization

    SciTech Connect

    RISENMAY, H.R.

    2000-04-25

    The purpose of this document is to provide a system design description (SDD) and design basis for the Plutonium Finishing Plant (PFP) Thermal Stabilization project. The chief objective of the SDD is to document the Structures, Systems, and Components (SSCs) that establish and maintain the facility Safety Envelope necessary for normal safe operation of the facility; as identified in the FSAR, the OSRs, and Safety Assessment Documents (SADs). This safety equipment documentation should satisfy guidelines for the SDD given in WHC-SD-CP-TI-18 1, Criteria for Identification and Control of Equipment Necessary for Preservation of the Safety Envelope and Safe Operation of PFP. The basis for operational, alarm response, maintenance, and surveillance procedures are also identified and justified in this document. This document and its appendices address the following elements of the PFP Thermal Stabilization project: Functional and design requirements; Design description; Safety Envelope Analysis; Safety Equipment Class; and Operational, maintenance and surveillance procedures.

  13. Conditions for thermal stabilization of the superconductor's critical state

    NASA Astrophysics Data System (ADS)

    Romanovskii, V. R.

    2013-05-01

    Conditions for thermal stabilization of the electrodynamic states of a superconductor are studied. The macroscopic states are simulated in the nonisothermal approximation by numerically solving a set of the Fourier and Maxwell equations with the magnetic flux penetration boundary unknown. Stability criteria for the critical state described by the viscous flow model are formulated. The results are compared with those following from the isothermal theory. It is shown that errors inherent in the isothermal approximation are significant for a thermally insulated superconductor. Therefore, the well-known adiabatic criterion of stability formulated in the isothermal approximation limits the domain of stable states, since a correct determination of conditions for the superconducting-normal state transition must take into account the thermal history of the stable superconducting state formation. On the whole, the error of loss calculation in the isothermal approximation increases when the heat transfer coefficient decreases or an external magnetic field sweep and the size of the superconductor's cross section increases. On the other hand, nonisothermal stability conditions expand the variety of allowable states, since they include conditions that links the currently developed theory of thermomagnetic instability, the theory of losses, and the theory of a superconductor's thermal stabilization.

  14. Thermal Stability of Li-Ion Cells

    SciTech Connect

    ROTH,EMANUEL P.

    1999-09-17

    The thermal stability of Li-ion cells with intercalating carbon anodes and metal oxide cathodes was measured as a function of state of charge and temperature for two advanced cell chemistries. Cells of the 18650 design with Li{sub x}CoO{sub 2} cathodes (commercial SONY cells) and Li{sub x}Ni{sub 0.8}Co{sub 0.2}O{sub 2} cathodes were measured for thermal reactivity in the open circuit cell condition. Accelerating rate calorimetry (ARC) was used to measure cell thermal runaway as a function of state of charge (SOC). Microcalorimetry was used to measure the time dependence of heat generating side reactions also as a function of SOC. Components of cells were measured using differential scanning calorimetry (DSC) to study the thermal reactivity of the individual electrodes to determine the temperature regimes and conditions of the major thermal reactions. Thermal decomposition of the SEI layer at the anodes was identified as the initiating source for thermal runaway. The cells with Li{sub x}CoO{sub 2} cathodes showed greater sensitivity to SOC and higher accelerating heating rates than seen for the cells with Li{sub x}Ni{sub 0.8}Co{sub 0.2}O{sub 2}cathodes. Lower temperature reactions starting as low as 40 C were also observed that were SOC dependent but not accelerating. These reactions were also measured in the microcalorimeter and observed to decay over time with a power-law dependence and are believed to result in irreversible capacity loss in the cells.

  15. Plasma-Enhanced Chemical Vapor Deposition (PE-CVD) yields better Hydrolytical Stability of Biocompatible SiOx Thin Films on Implant Alumina Ceramics compared to Rapid Thermal Evaporation Physical Vapor Deposition (PVD).

    PubMed

    Böke, Frederik; Giner, Ignacio; Keller, Adrian; Grundmeier, Guido; Fischer, Horst

    2016-07-20

    Densely sintered aluminum oxide (α-Al2O3) is chemically and biologically inert. To improve the interaction with biomolecules and cells, its surface has to be modified prior to use in biomedical applications. In this study, we compared two deposition techniques for adhesion promoting SiOx films to facilitate the coupling of stable organosilane monolayers on monolithic α-alumina; physical vapor deposition (PVD) by thermal evaporation and plasma enhanced chemical vapor deposition (PE-CVD). We also investigated the influence of etching on the formation of silanol surface groups using hydrogen peroxide and sulfuric acid solutions. The film characteristics, that is, surface morphology and surface chemistry, as well as the film stability and its adhesion properties under accelerated aging conditions were characterized by means of X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), inductively coupled plasma-optical emission spectroscopy (ICP-OES), and tensile strength tests. Differences in surface functionalization were investigated via two model organosilanes as well as the cell-cytotoxicity and viability on murine fibroblasts and human mesenchymal stromal cells (hMSC). We found that both SiOx interfaces did not affect the cell viability of both cell types. No significant differences between both films with regard to their interfacial tensile strength were detected, although failure mode analyses revealed a higher interfacial stability of the PE-CVD films compared to the PVD films. Twenty-eight day exposure to simulated body fluid (SBF) at 37 °C revealed a partial delamination of the thermally deposited PVD films whereas the PE-CVD films stayed largely intact. SiOx layers deposited by both PVD and PE-CVD may thus serve as viable adhesion-promoters for subsequent organosilane coupling agent binding to α-alumina. However, PE-CVD appears to be favorable for long-term direct film exposure to aqueous

  16. Can green solvents be alternatives for thermal stabilization of collagen?

    PubMed

    Mehta, Ami; Rao, J Raghava; Fathima, Nishter Nishad

    2014-08-01

    "Go Green" campaign is gaining light for various industrial applications where water consumption needs to be reduced. To resolve this, industries have adopted usage of green, organic solvents, as an alternative to water. For leather making, tanning industry consumes gallons of water. Therefore, for adopting green solvents in leather making, it is necessary to evaluate its influence on type I collagen, the major protein present in the skin matrix. The thermal stability of collagen from rat tail tendon fiber (RTT) treated with seven green solvents namely, ethanol, ethyl lactate, ethyl acetate, propylene carbonate, propylene glycol, polyethylene glycol-200 and heptane was determined using differential scanning calorimetry (DSC). Crosslinking efficiency of basic chromium sulfate and wattle on RTT in green solvents was determined. DSC thermograms show increase in thermal stability of RTT collagen against heat with green solvents (>78°C) compared to water (63°C). In the presence of crosslinkers, RTT demonstrated thermal stability >100°C in some green solvents, resulting in increased intermolecular forces between collagen, solvent and crosslinkers. The significant improvement in thermal stability of collagen potentiates the capability of green solvents as an alternative for water. PMID:24942230

  17. Off-set stabilizer for comparator output

    DOEpatents

    Lunsford, James S.

    1991-01-01

    A stabilized off-set voltage is input as the reference voltage to a comparator. In application to a time-interval meter, the comparator output generates a timing interval which is independent of drift in the initial voltage across the timing capacitor. A precision resistor and operational amplifier charge a capacitor to a voltage which is precisely offset from the initial voltage. The capacitance of the reference capacitor is selected so that substantially no voltage drop is obtained in the reference voltage applied to the comparator during the interval to be measured.

  18. Ceramic membranes with enhanced thermal stability

    DOEpatents

    Anderson, Marc A.; Xu, Qunyin; Bischoff, Brian L.

    1993-01-01

    A method of creating a ceramic membrane with enhanced thermal stability is disclosed. The method involves combining quantities of a first metal alkoxide with a second metal, the quantities selected to give a preselected metal ratio in the resultant membrane. A limited amount of water and acid is added to the combination and stirred until a colloidal suspension is formed. The colloid is dried to a gel, and the gel is fired at a temperature greater than approximately 400.degree. C. The porosity and surface area of ceramic membranes formed by this method are not adversely affected by this high temperature firing.

  19. Thermal stabilized vegetable oil extended diesel fuels

    SciTech Connect

    Sweeney, W.M.; Lachowicz, D.R.

    1986-03-11

    A middle distillate fuel composition is described comprising: (a) a major portion of a middle distillate containing a hydrocarbon boiling in the middle distillate boiling range; (b) an extending portion of a vegetable oil; and (c) an effective thermal-stabilizing amount of a nitrogen-containing polymer prepared by reacting an ethylene/propylene copolymer with maleic anhydride, thereby forming a succinic anhydride, reacting the succinic anhydride, with an alcohol, thereby forming a succinate ester while leaving a portion of the succinic anhydride unreacted, and, reacting the succinate ester and the unreacted succinic anhydride with dimethylaminopropylamine, thereby forming a nitrogen-containing polymer.

  20. Thermal Stability of Chelated Indium Activable Tracers

    SciTech Connect

    Chrysikopoulos, Costas; Kruger, Paul

    1986-01-21

    The thermal stability of indium tracer chelated with organic ligands ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA) was measured for reservoir temperatures of 150, 200, and 240 C. Measurements of the soluble indium concentration was made as a function of time by neutron activation analysis. From the data, approximate thermal decomposition rates were estimated. At 150 C, both chelated tracers were stable over the experimental period of 20 days. At 200 C, the InEDTA concentration remained constant for 16 days, after which the thermal decomposition occurred at a measured rate constant of k = 0.09 d{sup -1}. The thermal decomposition of InNTA at 200 C showed a first order reaction with a measured rate constant of k = 0.16 d{sup -1}. At 240 C, both indium chelated tracers showed rapid decomposition with rate constants greater than 1.8 d{sup -1}. The data indicate that for geothermal reservoir with temperatures up to about 200 C, indium chelated tracers can be used effectively for transit times of at least 20 days. These experiments were run without reservoir rock media, and do not account for concomitant loss of indium tracer by adsorption processes.

  1. Enhanced thermal stability of phosphate capped magnetite nanoparticles

    NASA Astrophysics Data System (ADS)

    Muthukumaran, T.; Philip, John

    2014-06-01

    We have studied the effect of phosphate capping on the high temperature thermal stability and magnetic properties of magnetite (Fe3O4) nanoparticles synthesized through a single-step co-precipitation method. The prepared magnetic nanoparticles are characterized using various techniques. When annealed in air, the phosphate capped nanoparticle undergoes a magnetic to non-magnetic phase transition at a temperature of 689 °C as compared to 580 °C in the uncoated nanoparticle of similar size. The observed high temperature phase stability of phosphate capped nanoparticle is attributed to the formation of a phosphocarbonaceous shell over the nanoparticles, which acts as a covalently attached protective layer and improves the thermal stability of the core material by increasing the activation energy. The phosphocarbonaceous shell prevents the intrusion of heat, oxygen, volatiles, and mass into the magnetic core. At higher temperatures, the coalescence of nanoparticles occurs along with the restructuring of the phosphocarbonaceous shell into a vitreous semisolid layer on the nanoparticles, which is confirmed from the small angle X-ray scattering, Fourier transform infra red spectroscopy, and transmission electron microscopy measurements. The probable mechanism for the enhancement of thermal stability of phosphocarbonaceous capped nanoparticles is discussed.

  2. Enhanced thermal stability of phosphate capped magnetite nanoparticles

    SciTech Connect

    Muthukumaran, T.; Philip, John

    2014-06-14

    We have studied the effect of phosphate capping on the high temperature thermal stability and magnetic properties of magnetite (Fe{sub 3}O{sub 4}) nanoparticles synthesized through a single-step co-precipitation method. The prepared magnetic nanoparticles are characterized using various techniques. When annealed in air, the phosphate capped nanoparticle undergoes a magnetic to non-magnetic phase transition at a temperature of 689 °C as compared to 580 °C in the uncoated nanoparticle of similar size. The observed high temperature phase stability of phosphate capped nanoparticle is attributed to the formation of a phosphocarbonaceous shell over the nanoparticles, which acts as a covalently attached protective layer and improves the thermal stability of the core material by increasing the activation energy. The phosphocarbonaceous shell prevents the intrusion of heat, oxygen, volatiles, and mass into the magnetic core. At higher temperatures, the coalescence of nanoparticles occurs along with the restructuring of the phosphocarbonaceous shell into a vitreous semisolid layer on the nanoparticles, which is confirmed from the small angle X-ray scattering, Fourier transform infra red spectroscopy, and transmission electron microscopy measurements. The probable mechanism for the enhancement of thermal stability of phosphocarbonaceous capped nanoparticles is discussed.

  3. On the stability of subsonic thermal fronts

    SciTech Connect

    Ibanez S, Miguel H.; Shchekinov, Yuri; Bessega L, Maria C.

    2005-08-15

    The stability of subsonic thermal fronts against corrugation is analyzed and an exact dispersion relation is obtained taking into account the compressibility of the gas. For heat fronts, this dispersion equation has an unstable root ({omega}{sub ex}) corresponding to the Landau-Darrieus unstable mode ({omega}{sub 0}) modified by the compressional effects. In particular, the exact solution shows a conspicuous maximum very close to the value of the intake Mach number M{sub 1} at which a Chapman-Jouguet deflagration wave behind the heat front is formed. Cooling fronts are stable for corrugation-like disturbances. A maximum damping as well as a maximum in the frequency occur at a value of M{sub 1} depending on the value of the normalized cooling q.

  4. Thermal stability of sputtered iridium oxide films

    SciTech Connect

    Sanjines, R.; Aruchamy, A.; Levy, F. )

    1989-06-01

    Dry and partially hydrated films of IrO/sub 2/ were prepared by reactive sputtering. The authors discuss their thermal stability investigated by means of XPS, x-ray diffraction, and resistivity measurements. Dry films decomposed at about 400{sup 0}C iin air and at 200{sup 0}C in vacuum (10/sup -2/ Pa), whereas partially hydrated films decomposed at 350{sup 0} and 150{sup 0}C, respectively. After electrochemical treatments of the films mounted as electrochromic electrodes in an electrolytic cell, the decomposition occurred at different temperatures. In particular, the bleached state was found to have the relatively low decomposition temperature of about 100{sup 0}C in air.

  5. Thermal stability of simvastatin under different atmospheres.

    PubMed

    Simões, Ricardo G; Diogo, Hermínio P; Dias, Ana; Oliveira, Maria Conceição; Cordeiro, Carlos; Bernardes, Carlos E S; Minas Da Piedade, Manuel E

    2014-01-01

    Simvastatin (SV) is a widely used drug for the treatment of hypercholesterolemia in humans. Nevertheless, serious efforts are still being made to develop new SV formulations with, for example, improved tabletability or bioavailability properties. These efforts frequently involve heating the compound well above ambient temperature or even fusion. In this work, the thermal stability of solid SV under different atmospheres was investigated by using isothermal tests in glass ampules, differential scanning calorimetry, and Calvet-drop microcalorimetry experiments. These tests were combined with analytical data from diffuse reflectance infrared Fourier-transform spectroscopy and liquid chromatography coupled with tandem mass spectrometry or Fourier transform ion cyclotron resonance mass spectrometry (LC-FT-ICR-MS). No decomposition was observed when the sample was kept at a temperature ≤373 K under N2 or reduced pressure (13.3 Pa) atmospheres. Thermal degradation was, however, observed for temperatures ≥353 K in the presence of pure or atmospheric oxygen. The nature of the two main oxidative degradation products was determined through MS/MS experiments and accurate mass measurements of the precursor ions using FT-ICR-MS. The obtained results indicated that the decomposition process involves the oxidation of the hexahydronaphthalene fragment of SV. PMID:24272683

  6. Thermal stability of alpha-amylase in aqueous cosolvent systems.

    PubMed

    Yadav, Jay Kant; Prakash, V

    2009-09-01

    The activity and thermal stability of alpha-amylase were studied in the presence of different concentrations of trehalose, sorbitol, sucrose and glycerol. The optimum temperature of the enzyme was found to be 50 +/- 2 degrees C. Further increase in temperature resulted in irreversible thermal inactivation of the enzyme. In the presence of cosolvents, the rate of thermal inactivation was found to be significantly reduced. The apparent thermal denaturation temperature (Tm) app and activation energy (Ea) of alpha-amylase were found to be significantly increased in the presence of cosolvents in a concentration-dependent manner. In the presence of 40% trehalose, sorbitol, sucrose and glycerol, increments in the (Tm)app were 20 degrees C, 14 degrees C, 13 degrees C and 9 degrees C, respectively. The Ea of thermal denaturation of alpha-amylase in the presence of 20% (w/v) trehalose, sorbitol, sucrose and glycerol was found to be 126, 95, 90 and 43 kcal/mol compared with a control value of 40 kcal/mol. Intrinsic and 8-anilinonaphathalene-1-sulphonic acid (ANS) fluorescence studies indicated that thermal denaturation of the enzyme was accompanied by exposure of the hydrophobic cluster on the protein surface. Preferential interaction parameters indicated extensive hydration of the enzyme in the presence of cosolvents. PMID:19805899

  7. System Design Description PFP Thermal Stabilization

    SciTech Connect

    RISENMAY, H.R.

    2000-01-27

    DOE has authorized in their letter of August 2, 1999, the operation of these three furnaces, quote ''Operation of the three uncompleted muffle furnaces (No.3, No.4, and No.5) located in Room 235B is authorized, using the same feed charge limits as the two existing furnaces (No.1, and No.2) located in Room 230C,''. The above statement incorrectly refers to Room 230C whereas the correct location is Room 230A. The current effort is directed to initiate the operation and to complete the design activities DOE authorized the operation of the furnaces based on their Safety Evaluation Report (SER). Based on analogy and the principle of similarity, the risks and consequences of accidents both onsite and offsite due to operation of three furnaces are not significantly larger than those already evaluated with the two operating furnaces. Thermal stabilization operations and the material of feed for furnaces in Glovebox HA-21 I are essentially the same as those currently being stabilized in furnaces in Glovebox HC-21 C. Therefore the accident analysis has utilized identical accident scenarios in evaluation and no additional failure modes are introduced by HA-21 I muffle furnace operation that would enhance the consequences of accidents. Authorization Basis documents as referenced below (PFP FSAR and DOE Letter authorizing the operation) appear to contradict each other, i.e. one allows and authorizes the operation and the other imposes the restriction on the operation. The purpose of the PFP FSAR restrictions was to review thoroughly the design and installation of three furnaces and perform acceptance testing before approving the startup for operation. With the experience of operating the two furnaces in Glovebox HC-21C, and the knowledge of risks and hazards the facility operation, the plant is adequately prepared to operate these additional furnaces. ECN 653595 has been prepared to incorporate operation of the muffle furnaces in Glovebox HA-21 I into the PFP FSAR.

  8. Polarization-Mediated Thermal Stability of Metal/Oxide Heterointerface.

    PubMed

    Zhang, Qintong; You, Lu; Shen, Xi; Wan, Caihua; Yuan, Zhonghui; Zhang, Xuan; Huang, Li; Kong, Wenjie; Wu, Hao; Yu, Richeng; Wang, Junling; Han, Xiufeng

    2015-11-18

    A polarization-mediated heterointerface is designed to research the thermal stability of magnetic metal/oxide interfaces. Using polarization engineering, the thermal stability of the interface between BiFeO3 and CoFeB can be improved by about 100°C. This finding provides new insight into the chemistry of the metal/oxide heterointerface. PMID:26421975

  9. Thermal stabilization of uranium mill tailings

    SciTech Connect

    Dreesen, D.R.; Williams, J.M.; Cokal, E.J.

    1981-01-01

    The sintering of tailings at high temperatures (1200/sup 0/C) has shown promise as a conditioning approach that greatly reduces the /sup 222/Rn emanation of uranium mill tailings. The structure of thermally stabilized tailings has been appreciably altered producing a material that will have minimal management requirements and will be applicable to on-site processing and disposal. The mineralogy of untreated tailings is presented to define the structure of the original materials. Quartz predominates in most tailings samples; however, appreciable quantities of gypsum, clay, illite, or albites are found in some tailings. Samples from the Durango and Shiprock sites have plagioclase-type aluminosilicates and non-aluminum silicates as major components. The iron-rich vanadium tailings from the Salt Lake City site contain appreciable quantities of ..cap alpha..-hematite and chloroapatite. The reduction in radon emanation power and changes in mineralogy as a function of sintering temperature (500 to 1200(NiAsS) are considered possible species for consideraed. The calculated activity data of the various carbonate, sulfate and hydroxide species in the Li/sup +/Na/sup +/K/sup +//CO/sub 3/ = SO/sub 4/ = OH/sup -/ system have been combined f liquidus surfaces, and estimated error limits are given for each system. A comng payback period, but as the initial cost of the SAHPS is reduced and fuel prices increase, the payback period of a SAHPS will be shorter and could be competitive with other conventional heating/cooling systems.

  10. Improved Thermal Stability of RF Power BJT with Ballast Circuits

    NASA Astrophysics Data System (ADS)

    Guo, Benqing; Zhang, Qingzhong

    2013-12-01

    To improve thermal stability and relieve current convergence in rf power bjts, an embedded active CMOS ballast circuit is proposed. By detecting the inhomogeneous temperature through distributed temperature sensors, the adjacent ballast circuit is triggered to shunt the base convergence current of the power BJT cell, performing the ballast protection for the device. Simulations and measurements validate the effectiveness of the proposed ballast circuit. Compared to conventional ballast resistor methods, the improved device integrated with ballast circuits exhibits superior electrical performance. The single ballast circuit only consumes 6.5 mW with additional occupied area of 2530 um2.

  11. Enhanced Thermal Stability of Polylactide by Terminal Conjugation Groups

    NASA Astrophysics Data System (ADS)

    Tran, Hang Thi; Matsusaki, Michiya; Akashi, Mitsuru; Vu, Ngo Dinh

    2016-05-01

    Various acids such as aliphatic or carbocyclic fatty or aromatic acids were successfully conjugated into the ending hydroxyl group of poly( l-lactide) (PLLA). The chemical structures of various acid-PLLAs were confirmed by Fourier transform infrared and proton nuclear magnetic resonance analysis. The crystallinity and solubility of the original PLLA were maintained after the terminal conjugation of various acids. The thermal properties were significantly improved, especially the 10% weight-loss temperature that showed an increase of over 80°C for conjugation of aliphatic or aromatic acids as compared to that of the corresponding original PLLA. In addition, more than 60 wt.% of the aliphatic acid-PLLAs was pyrolyzed, and aromatic acid-PLLAs degraded only about 10 wt.% for 150 min, although the original PLLA was pyrolyzed completely at 250°C for 7 min. The thermal stability of PLLA was controlled by the conjugation of aliphatic or aromatic acids into a chain end. These acid-PLLAs may be useful as materials with high thermal stability for various application fields.

  12. The effects of thermally reversible agents on PVC stability properties

    NASA Astrophysics Data System (ADS)

    Wang, J.; Yao, J.; Xiong, X. H.; Jia, C. X.; Ren, R.; Chen, P.; Liu, X. M.

    2016-07-01

    One kind of thermally reversible cross-linking agents for improving PVC thermally stability was synthesized. The chemical structure and thermally reversible characteristics of cross-linking agents were investigated by FTIR and DSC analysis, respectively. FTIR results confirmed that the cyclopentadienyl barium mercaptides ((CPD-C2H4S)2Ba) were successfully synthesized. DSC results showed it has thermally reversible characteristics and the depolymerization temperature was between 170 °C and 205 °C. The effects of cross-linking reaction time on gel content of Poly(vinyl chloride) compounds was evaluated. The gel content value arrived at 42% after being cross-linked for 25 min at 180 C. The static thermally stability measurement proved that the thermally stability of PVC compounds was improved.

  13. RP-1 Thermal Stability and Copper Based Materials Compatibility Study

    NASA Technical Reports Server (NTRS)

    Stiegemeier, B. R.; Meyer, M. L.; Driscoll, E.

    2005-01-01

    A series of electrically heated tube tests was performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the effect that sulfur content, test duration, and tube material play in the overall thermal stability and materials compatibility characteristics of RP-1. Scanning-electron microscopic (SEM) analysis in conjunction with energy dispersive spectroscopy (EDS) were used to characterize the condition of the tube inner wall surface and any carbon deposition or corrosion formed during these runs. Results of the parametric study indicate that tests with standard RP-1 (total sulfur -23 ppm) and pure copper tubing are characterized by a depostion/deposit shedding process producing local wall temperature swings as high as 500 F. The effect of this shedding is to keep total carbon deposition levels relatively constant for run times from 20 minutes up to 5 hours, though increasing tube pressure drops were observed in all runs. Reduction in the total sulfur content of the fuel from 23 ppm to less than 0.1 ppm resulted in the elimination of deposit shedding, local wall temperature variation, and the tube pressure drop increases that were observed in standard sulfur level RP-1 tests. The copper alloy GRCop-84, a copper alloy developed specifically for high heat flux applications, was found to exhibit higher carbon deposition levels compared to identical tests performed in pure copper tubes. Results of the study are consistent with previously published heated tube data which indicates that small changes in fuel total sulfur content can lead to significant differences in the thermal stability of kerosene type fuels and their compatibility with copper based materials. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-1.

  14. Silphenylene elastomers have high thermal stability and tensile strength

    NASA Technical Reports Server (NTRS)

    1969-01-01

    Two polymeric silphenylene ethers, when cured by reactions with ethyl silicates and metal salts at room temperature, form elastomers having excellent thermal stability and tensile properties. The highest tensile strength obtained in a reinforced elastomer was 2800 psi.

  15. Stabilization of supercooled fluids by thermal hysteresis proteins.

    PubMed Central

    Wilson, P W; Leader, J P

    1995-01-01

    It has been reported that thermal hysteresis proteins found in many cold-hardy, freeze-avoiding arthropods stabilize their supercooled body fluids. We give evidence that fish antifreeze proteins, which also produce thermal hysteresis, bind to and reduce the efficiency of heterogenous nucleation sites, rather than binding to embryonic ice nuclei. We discuss both possible mechanisms for stabilization of supercooled body fluids and also describe a new method for measuring and defining the supercooling point of small volumes of liquid. PMID:7612853

  16. Thermal and electrochemical stability of tungsten carbide catalyst supports

    NASA Astrophysics Data System (ADS)

    Chhina, H.; Campbell, S.; Kesler, O.

    The thermal and electrochemical stability of tungsten carbide (WC), with and without a catalyst dispersed on it, have been investigated to evaluate the potential suitability of the material as an oxidation-resistant catalyst support. Standard techniques currently used to disperse Pt on carbon could not be used to disperse Pt on WC, so an alternative method was developed and used to disperse Pt on both commercially available WC and on carbon for comparison of stability. Electrochemical testing was performed by applying oxidation cycles between +0.6 V and +1.8 V to the support-catalyst material combinations and monitoring the activity of the supported catalyst over 100 oxidation cycles. Comparisons of activity change with cumulative oxidation cycles were made between C and WC supports with comparable loadings of catalyst by weight, solid volume, and powder volume. WC was found to be more thermally and electrochemically stable than currently used carbon support material Vulcan XC-72R. However, further optimization of the particle sizes and dispersion of Pt/WC catalyst/support materials and of comparison standards between new candidate materials and existing carbon-based supports are required.

  17. Soil thermal resistivity and thermal stability measuring instrument. Volume 1. Determination of soil thermal stability and other soil thermal properties. Final report

    SciTech Connect

    Boggs, S.A.; Radhakrishna, H.S.

    1981-11-01

    Numerous considerations influence the thermal design of an underground power cable, including the soil thermal resistivity, thermal diffusivity and thermal stability. Each of these properties is a function of soil moisture which is, in turn, a function of past weather, soil composition, and biological burden. The Neher-McGrath formalism has been widely used for thermal cable design. However, this formalism assumes knowledge of soil thermal properties (resistivity and diffusivity). For design purposes, these parameters should be treated statistically, since weather varies greatly from year-to-year. As well, soil thermal property surveys are normally required along the route to assess the thermal quality of the native soil. This project is intended to fill the gap between the need to carry out thermal design and the use of the Neher-McGrath formalism which is normally employed. This goal has been addressed through: (1) development of instrumentation and methods of measuring soil thermal properties in situ and in the laboratory; (2) recommendation of methods for conducting soil surveys along a proposed cable route and of assessing the thermal quality of soils; and (3) development of a computerized method to treat soil thermal design parameters on a statistical basis using computerized weather records as supplied by the US Environmental Data Service. This volume discussed methods for determining the thermal properties of soils. The use of the methods and instrumentation developed as a result of this contract should permit less conservative thermal design thereby improving the economics of underground transmission. As well, these techniques and instrumentation facilitate weather-dependent prediction of cable ampacity for installed cables, monitoring of backfill thermal stability, and many other new practices.

  18. Thermal Stability of Otto Fuel Prepolymer

    NASA Technical Reports Server (NTRS)

    Tompa, Albert S.; Sandagger, Karrie H.; Bryant, William F., Jr.; McConnell, William T.; Lacot, Fernando; Carr, Walter A.

    2000-01-01

    Otto Fuel II contains a nitrate ester, plasticizer, and 2-NPDA as a stabilizer. Otto Fuel with stabilizers from three vendors was investigated by dynamic and isothermal differential scanning calorimetry (DSC) using samples sealed in a glass ampoule and by Isothermal Microcalorimetry (IMC) using 10 gram samples aged at 75 C for 35 days. DSC kinetics did not show differences between the stabilizer; the samples had an activation energy of 36.7 +/- 0.6 kcal/mol. However, IMC analysis was sensitive enough to detect small differences between the stabilizer, namely energy of interaction values of 7 to 14 Joules. DSC controlled cooling and heating at 5 C/min from 30 to -60 to 40 C experiments were similar and showed a crystallization peak at -48 +/- 1 C during cooling, and upon heating there was a glass transition temperature step at approx. -54 +/- 0.5 C and a melting peak at -28 +/- 0.4 C.

  19. Thermal Stability of Otto Fuel Prepolymer

    NASA Technical Reports Server (NTRS)

    Tompa, Albert S.; Sandagger, Karrie H.; Bryant, William F., Jr.; McConnell, William T.; Lacot, Fernando; Carr, Walter A.

    2000-01-01

    Otto Fuel II contains a nitrate ester, plasticizer, and 2-NDPA as a stabilizer. Otto Fuel with stabilizers from three vendors was investigated by dynamic and isothermal DSC using samples sealed in a glass ampoule and by Isothermal Microcalorimetry (IMC) using 10 gram samples aged at 75 C for 35 days. DSC kinetics did not show differences between the stabilizer; the samples had an activation energy of 36.7 +/- 0.6 kcal/mol. However, IMC analysis was sensitive enough to detect small differences between the stabilizer, namely energy of interaction values of 7 to 14 Joules. DSC controlled cooling and heating at 5 C/min from 30 to -60 to 40 C experiments were similar and showed a crystallization peak at -48 +/- 1 C during cooling, and upon heating there was a glass transition temperature step at approx. -54 +/- 0.5 C and a melting peak at -28 +/- 0.4 C.

  20. Comparative stability of repackaged metoprolol tartrate tablets.

    PubMed

    Yang, Yongsheng; Gupta, Abhay; Carlin, Alan S; Faustino, Patrick J; Lyon, Robbe C; Ellison, Christopher D; Rothman, Barry; Khan, Mansoor A

    2010-01-29

    The stability of metoprolol tartrate tablets packaged in original high density polyethylene containers and repackaged in USP Class A unit-dose blister packs was investigated. Studies were conducted at 25 degrees C/60% relative humidity (RH) for 52 weeks and at 40 degrees C/75% RH for 13 weeks. The potency, dissolution, water content, loss on drying and hardness of the drug products were analyzed. Results indicated no differences in the stability between the tablets in both packages stored under 25 degrees C/60% RH. No difference in potency was found in both packages under either condition. However, a significant weight increase due to moisture uptake was observed for the repackaged tablets stored under 40 degrees C/75% RH. The weight increase was accompanied by a decrease in tablet hardness (6.5-0 kp) and a increase in dissolution rate (51-92%) in 5 min. Near-infrared (NIR) chemical imaging also monitored moisture uptake of the tablet non-invasively through the package. The observed changes in product stability may adversely affect the products bioavailability profile, even though the potency of the active drug remained within USP specification range of 90-110%. Study results suggest product quality can be negatively impacted even when using USP Class A repackaging materials. PMID:19879937

  1. Electroweak absolute, meta-, and thermal stability in neutrino mass models

    NASA Astrophysics Data System (ADS)

    Lindner, Manfred; Patel, Hiren H.; Radovčić, Branimir

    2016-04-01

    We analyze the stability of the electroweak vacuum in neutrino mass models containing right-handed neutrinos or fermionic isotriplets. In addition to considering absolute stability, we place limits on the Yukawa couplings of new fermions based on metastability and thermal stability in the early Universe. Our results reveal that the upper limits on the neutrino Yukawa couplings can change significantly when the top quark mass is allowed to vary within the experimental range of uncertainty in its determination.

  2. Effect of stabilizer on dynamic thermal transport property of ZnO nanofluid

    PubMed Central

    2013-01-01

    In this paper, we investigate the effect of adding a stabilizer on the dynamic thermal properties of ZnO nanofluid (containing 5 to 10 nm diameter of ZnO nanocrystals) measured using a 3ω method. Addition of the stabilizer leads to the stabilization of the nanofluid and also substantial reduction of the enhancement of thermal transport compared to that seen in the bare ZnO nanofluid. This also alters the frequency dependence of the thermal transport and the characteristic time scale associated with it. It is suggested that the addition of the stabilizer inhibits the thermodiffusion-assisted local aggregation thus leading to substantial reduction of the enhancement of thermal transport properties of the bare nanofluid as proposed in some recent models, and this also alters the characteristic time scales by altering the scale of aggregation. PMID:23497347

  3. Thermal Stability Comparison of Nanocrystalline Fe-Based Binary Alloy Pairs

    NASA Astrophysics Data System (ADS)

    Clark, B. G.; Hattar, K.; Marshall, M. T.; Chookajorn, T.; Boyce, B. L.; Schuh, C. A.

    2016-06-01

    The widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest; yet, they have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dominated systems. Although traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloys can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdoch et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10 at.% Mg) with a predicted non-NC stable alloy (Fe-10 at.% Cu) using the same processing and characterization methodologies. Results show improved thermal stability of the Fe-Mg alloy in comparison with the Fe-Cu, and thermally-evolved microstructures that are consistent with those predicted by Monte Carlo simulations.

  4. Thermal stability in exchange-spring chains of spins

    NASA Astrophysics Data System (ADS)

    Pellicelli, Raffaele; Solzi, Massimo

    2016-02-01

    Thermal stability and switching behaviour have been compared in pure-hard and soft-hard Heisenberg linear spin chains of the same total length and equal magnetic parameters (except for magnetic anisotropy) with the anisotropy axis and external magnetic field parallel to the chain direction. The zero-temperature energy barriers and finite-temperature transition rates between remanent equilibrium states have been calculated by utilizing the string method and the forward flux sampling (FFS) method, respectively. Depending on the assumed interfaces, the FFS method could in fact fail to correctly sample the characteristic transition paths at interfaces at which these paths have probabilities much lower than those associated with other non-characteristic transition paths. This can especially occur in the case of the asymmetric energy landscapes and multiple asymmetric minimum energy paths (MEPs) of soft-hard systems. Therefore, a proper interface definition is needed in order to deduce the correct transition rates. In particular, we show that the thermal switching of soft-hard chains starting in the soft or in the hard part turns out to occur with an equal rate provided that the interfaces of the FFS method are defined on the basis of the corresponding zero-temperature MEPs. The thermal stability of a soft-hard chain in the remanent equilibrium state could be to some extent lower with respect to that of a pure-hard chain, due to the shorter hard-part length crossed by the domain wall formed in the chain and also to the related slightly smaller energy barrier. However, its switching field at zero temperature is verified to be widely lower than that of the pure-hard chain. Analytical expressions of switching fields and energy barriers have been deduced in various cases.

  5. Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment

    NASA Astrophysics Data System (ADS)

    Park, Sejoon; Yoo, Seung Hwa; Kang, Ha Ri; Jo, Seong Mu; Joh, Han-Ik; Lee, Sungho

    2016-06-01

    An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100–130 °C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130–140 °C) of thermal stabilization. Finally, even at a low irradiation dose (200 kGy), followed by a short heat treatment (230 °C for 30 min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216 GPa, respectively, after carbonization.

  6. Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment

    PubMed Central

    Park, Sejoon; Yoo, Seung Hwa; Kang, Ha Ri; Jo, Seong Mu; Joh, Han-Ik; Lee, Sungho

    2016-01-01

    An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100–130 °C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130–140 °C) of thermal stabilization. Finally, even at a low irradiation dose (200 kGy), followed by a short heat treatment (230 °C for 30 min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216 GPa, respectively, after carbonization. PMID:27349719

  7. Comprehensive stabilization mechanism of electron-beam irradiated polyacrylonitrile fibers to shorten the conventional thermal treatment.

    PubMed

    Park, Sejoon; Yoo, Seung Hwa; Kang, Ha Ri; Jo, Seong Mu; Joh, Han-Ik; Lee, Sungho

    2016-01-01

    An electron beam was irradiated on polyacrylonitrile (PAN) fibers prior to thermal stabilization. The electron-beam irradiation effectively shortened the thermal stabilization process by one fourth compared with the conventional thermal stabilization process. A comprehensive mechanistic study was conducted regarding this shortening of the thermal stabilization by electron-beam irradiation. Various species of chain radicals were produced in PAN fibers by electron-beam irradiation and existed for a relatively long duration, as observed by electron spin resonance spectroscopy. Subsequently, these radicals were gradually oxidized to peroxy radicals in the presence of oxygen under storage or heating. We found that these peroxy radicals (CO) enabled such an effective shortcut of thermal stabilization by acting as intermolecular cross-linking and partial aromatization points in the low temperature range (100-130 °C) and as earlier initiation seeds of successive cyclization reactions in the next temperature range (>130-140 °C) of thermal stabilization. Finally, even at a low irradiation dose (200 kGy), followed by a short heat treatment (230 °C for 30 min), the PAN fibers were sufficiently stabilized to produce carbon fibers with tensile strength and modulus of 2.3 and 216 GPa, respectively, after carbonization. PMID:27349719

  8. Evaluation of the Lifetime and Thermal Conductivity of Dysprosia-Stabilized Thermal Barrier Coating Systems

    NASA Astrophysics Data System (ADS)

    Curry, Nicholas; Markocsan, Nicolaie; Östergren, Lars; Li, Xin-Hai; Dorfman, Mitch

    2013-08-01

    The aim of this study was the further development of dysprosia-stabilized zirconia coatings for gas turbine applications. The target for these coatings was a longer lifetime and higher insulating performance compared to today's industrial standard thermal barrier coating. Two morphologies of ceramic top coat were studied: one using a dual-layer system and the second using a polymer to generate porosity. Evaluations were carried out using a laser flash technique to measure thermal properties. Lifetime testing was conducted using thermo-cyclic fatigue testing. Microstructure was assessed with SEM and Image analysis was used to characterize porosity content. The results show that coatings with an engineered microstructure give performance twice that of the present reference coating.

  9. Thermal stability of two-dimensional gold nanocrystal superlattices.

    SciTech Connect

    Robel, I.; Lin, X.-M.; Sprung, M.; Wang, J.

    2009-07-01

    The thermal stability of highly ordered two-dimensional superlattices consisting of dodecanethiol-ligated Au nanoparticles has been investigated using in situ grazing incidence small-angle x-ray scattering in air and in vacuum. In the lower temperature region (<70 C), annealing in air results in a minimal change of superlattice structure, whereas annealing in vacuum leads to a considerable lattice contraction and a decrease in long-range order. At higher temperatures (>100 C), ligand desorption causes nanocrystals to sinter locally, destroying quasi-long-range order. The sintering process is significantly enhanced in vacuum compared to the case in air due to the increased desorption rate of thiol ligands under low pressure.

  10. Thermal barrier coating having high phase stability

    DOEpatents

    Subramanian, Ramesh

    2002-01-01

    A device (10) comprising a substrate (22) having a deposited ceramic thermal barrier coating characterized by a microstructure having gaps (28) where the thermal barrier coating comprises a first thermal barrier layer (40), and a second thermal barrier layer (30) with a pyrochlore crystal structure having a chemical formula of A.sup.n+.sub.2-x B.sup.m+.sub.2+x O.sub.7-y, where A is selected from the group of elements consisting of La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and mixtures thereof, where B is selected from the group of elements consisting of Zr, Hf, Ti and mixtures thereof, where n and m are the valence of A and B respectively, and for -0.5.ltoreq.x.ltoreq.0.5, ##EQU1## and excluding the following combinations for x=0, y=0: A=La and B=Zr; A=La and B=Hf; A=Gd and B=Hf; and A=Yb and B=Ti.

  11. A meningococcal vaccine antigen engineered to increase thermal stability and stabilize protective epitopes

    PubMed Central

    Konar, Monica; Pajon, Rolando; Beernink, Peter T.

    2015-01-01

    Factor H binding protein (FHbp) is part of two vaccines recently licensed for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp is classified in three phylogenic variant groups that have limited antigenic cross-reactivity, and FHbp variants in one of the groups have low thermal stability. In the present study, we replaced two amino acid residues, R130 and D133, in a stable FHbp variant with their counterparts (L and G) from a less stable variant. The single and double mutants decreased thermal stability of the amino- (N-) terminal domain compared with the wild-type protein as measured by scanning calorimetry. We introduced the converse substitutions, L130R and G133D, in a less stable wild-type FHbp variant, which increased the transition midpoint (Tm) for the N-terminal domain by 8 and 12 °C; together the substitutions increased the Tm by 21 °C. We determined the crystal structure of the double mutant FHbp to 1.6 Å resolution, which showed that R130 and D133 mediated multiple electrostatic interactions. Monoclonal antibodies specific for FHbp epitopes in the N-terminal domain had higher binding affinity for the recombinant double mutant by surface plasmon resonance and to the mutant expressed on meningococci by flow cytometry. The double mutant also had decreased binding of human complement Factor H, which in previous studies increased the protective antibody responses. The stabilized mutant FHbp thus has the potential to stabilize protective epitopes and increase the protective antibody responses to recombinant FHbp vaccines or native outer membrane vesicle vaccines with overexpressed FHbp. PMID:26627237

  12. A meningococcal vaccine antigen engineered to increase thermal stability and stabilize protective epitopes.

    PubMed

    Konar, Monica; Pajon, Rolando; Beernink, Peter T

    2015-12-01

    Factor H binding protein (FHbp) is part of two vaccines recently licensed for prevention of sepsis and meningitis caused by serogroup B meningococci. FHbp is classified in three phylogenic variant groups that have limited antigenic cross-reactivity, and FHbp variants in one of the groups have low thermal stability. In the present study, we replaced two amino acid residues, R130 and D133, in a stable FHbp variant with their counterparts (L and G) from a less stable variant. The single and double mutants decreased thermal stability of the amino- (N-) terminal domain compared with the wild-type protein as measured by scanning calorimetry. We introduced the converse substitutions, L130R and G133D, in a less stable wild-type FHbp variant, which increased the transition midpoint (Tm) for the N-terminal domain by 8 and 12 °C; together the substitutions increased the Tm by 21 °C. We determined the crystal structure of the double mutant FHbp to 1.6 Å resolution, which showed that R130 and D133 mediated multiple electrostatic interactions. Monoclonal antibodies specific for FHbp epitopes in the N-terminal domain had higher binding affinity for the recombinant double mutant by surface plasmon resonance and to the mutant expressed on meningococci by flow cytometry. The double mutant also had decreased binding of human complement Factor H, which in previous studies increased the protective antibody responses. The stabilized mutant FHbp thus has the potential to stabilize protective epitopes and increase the protective antibody responses to recombinant FHbp vaccines or native outer membrane vesicle vaccines with overexpressed FHbp. PMID:26627237

  13. Thermal stability of idealized folded carbyne loops.

    PubMed

    Cranford, Steven W

    2013-01-01

    Self-unfolding items provide a practical convenience, wherein ring-like frames are contorted into a state of equilibrium and subsequently  pop up' or deploy when perturbed from a folded structure. Can the same process be exploited at the molecular scale? At the limiting scale is a closed chain of single atoms, used here to investigate the limits of stability of such folded ring structures via full atomistic molecular dynamics. Carbyne is a one-dimensional carbon allotrope composed of sp-hybridized carbon atoms. Here, we explore the stability of idealized carbyne loops as a function of chain length, curvature, and temperature, and delineate an effective phase diagram between folded and unfolded states. We find that while overall curvature is reduced, in addition to torsional and self-adhesive energy barriers, a local increase in curvature results in the largest impedance to unfolding. PMID:24252156

  14. A Physics-Based Temperature Stabilization Criterion for Thermal Testing

    NASA Technical Reports Server (NTRS)

    Rickman, Steven L.; Ungar, Eugene K.

    2009-01-01

    Spacecraft testing specifications differ greatly in the criteria they specify for stability in thermal balance tests. Some specify a required temperature stabilization rate (the change in temperature per unit time, dT/dt), some specify that the final steady-state temperature be approached to within a specified difference, delta T , and some specify a combination of the two. The particular values for temperature stabilization rate and final temperature difference also vary greatly between specification documents. A one-size-fits-all temperature stabilization rate requirement does not yield consistent results for all test configurations because of differences in thermal mass and heat transfer to the environment. Applying a steady-state temperature difference requirement is problematic because the final test temperature is not accurately known a priori, especially for powered configurations. In the present work, a simplified, lumped-mass analysis has been used to explore the applicability of these criteria. A new, user-friendly, physics-based approach is developed that allows the thermal engineer to determine when an acceptable level of temperature stabilization has been achieved. The stabilization criterion can be predicted pre-test but must be refined during test to allow verification that the defined level of temperature stabilization has been achieved.

  15. Thermal and radiation resistance of stabilized LDPE

    NASA Astrophysics Data System (ADS)

    Zaharescu, T.; Jipa, S.; Henderson, D.; Kappel, W.; Mariş, D. A.; Mariş, M.

    2010-03-01

    The effect of capsaicin on the radiation stability of low density polyethylene was accomplished by applying the chemiluminescence procedure. The neat and modified polymer with 0.25% and 0.50% (w/w) capsaicin were exposed to γ-irradiation in air receiving 10, 20 and 30 kGy. The synergistic effect due to the presence of metallic selenium was demonstrated. The significant improvement in oxidation induction time was obtained demonstrating the efficient antioxidant activity of capsaicin in LDPE. The simultaneous protection action of metallic selenium in LDPE/capsaicin systems brought about a supplementary enhancement in the oxidation resistance of irradiated samples.

  16. Low Thermal Conductivity Yttria-Stabilized Zirconia Thermal Barrier Coatings Using the Solution Precursor Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Jordan, Eric H.; Jiang, Chen; Roth, Jeffrey; Gell, Maurice

    2014-06-01

    The primary function of thermal barrier coatings (TBCs) is to insulate the underlying metal from high temperature gases in gas turbine engines. As a consequence, low thermal conductivity and high durability are the primary properties of interest. In this work, the solution precursor plasma spray (SPPS) process was used to create layered porosity, called inter-pass boundaries, in yttria-stabilized zirconia (YSZ) TBCs. IPBs have been shown to be effective in reducing thermal conductivity. Optimization of the IPB microstructure by the SPPS process produced YSZ TBCs with a thermal conductivity of 0.6 W/mK, an approximately 50% reduction compared to standard air plasma sprayed (APS) coatings. In preliminary tests, SPPS YSZ with IPBs exhibited equal or greater furnace thermal cycles and erosion resistance compared to regular SPPS and commercially made APS YSZ TBCs.

  17. Thermal and mechanical stability of zeolitic imidazolate frameworks polymorphs

    SciTech Connect

    Bouëssel du Bourg, Lila; Ortiz, Aurélie U.; Coudert, François-Xavier; Boutin, Anne

    2014-12-01

    Theoretical studies on the experimental feasibility of hypothetical Zeolitic Imidazolate Frameworks (ZIFs) have focused so far on relative energy of various polymorphs by energy minimization at the quantum chemical level. We present here a systematic study of stability of 18 ZIFs as a function of temperature and pressure by molecular dynamics simulations. This approach allows us to better understand the limited stability of some experimental structures upon solvent or guest removal. We also find that many of the hypothetical ZIFs proposed in the literature are not stable at room temperature. Mechanical and thermal stability criteria thus need to be considered for the prediction of new MOF structures. Finally, we predict a variety of thermal expansion behavior for ZIFs as a function of framework topology, with some materials showing large negative volume thermal expansion.

  18. Chemical, thermal and mechanical stabilities of metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Howarth, Ashlee J.; Liu, Yangyang; Li, Peng; Li, Zhanyong; Wang, Timothy C.; Hupp, Joseph T.; Farha, Omar K.

    2016-03-01

    The construction of thousands of well-defined, porous, metal-organic framework (MOF) structures, spanning a broad range of topologies and an even broader range of pore sizes and chemical functionalities, has fuelled the exploration of many applications. Accompanying this applied focus has been a recognition of the need to engender MOFs with mechanical, thermal and/or chemical stability. Chemical stability in acidic, basic and neutral aqueous solutions is important. Advances over recent years have made it possible to design MOFs that possess different combinations of mechanical, thermal and chemical stability. Here, we review these advances and the associated design principles and synthesis strategies. We focus on how these advances may render MOFs effective as heterogeneous catalysts, both in chemically harsh condensed phases and in thermally challenging conditions relevant to gas-phase reactions. Finally, we briefly discuss future directions of study for the production of highly stable MOFs.

  19. Thermal Stability of Fluorinated Polydienes Synthesized by Addition of Difluorocarbene

    SciTech Connect

    Huang, Tianzi; Wang, Xiaojun; Malmgren, Thomas W; Hong, Kunlun; Mays, Jimmy

    2012-01-01

    Linear PCHD and polyisoprenes with different microstructures and molecular weights are synthesized and chemically modified to improve their thermal and chemical stability by forming a three-membered ring structure containing two C-F bonds. Pyrolysis of these fluorinated polydienes proceeds through a two-stage decomposition involving chain scission, crosslinking, dehydrogenation, and dehalogenation. The pyrolysis leads to graphite-like residues, whereas their polydiene precursors decompose completely under the same conditions. The fluorination of PCHD enhances its thermal stability. The stronger C-F bond along with high strain of the three-membered ring structure and formation of relatively stable free radicals play an important role in the thermal stability of fluorinated polydienes.

  20. Thermal barrier coating having high phase stability

    DOEpatents

    Subramanian, Ramesh

    2001-01-01

    A device (10) comprising a substrate (22) having a deposited ceramic thermal barrier coating layer (20) characterized by a microstructure having gaps (28) where the thermal barrier coating (20) consists essentially of a pyrochlore crystal structure having a chemical formula consisting essentially of A.sup.n+.sub.2-x B.sup.m+.sub.2+x O.sub.7-y, where A is selected from the group of elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and mixtures thereof; where B is selected from the group of elements selected from Zr, Hf, Ti and mixtures thereof; n and m are the valence of A and B respectively, and for -0.5.ltoreq.x.ltoreq.0.5, ##EQU1## and excluding the following combinations for x=0, y=0: A=La and B=Zr; A=La and B=Hf; A=Gd and B=Hf; and A=Yb and B=Ti.

  1. Problem of the lithium peroxide thermal stability

    NASA Astrophysics Data System (ADS)

    Nefedov, R. A.; Ferapontov, Yu A.; Kozlova, N. P.

    2016-01-01

    The behavior of lithium peroxide and lithium peroxide monohydrate samples under heating in atmospheric air was studied by the method of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). It was found that in the temperature range of 32°C to 82°C the interaction of lithium peroxides and steam with the formation of lithium peroxide monohydrate occurs, which was confirmed chemically and by X-ray Single-qualitative analysis. It was experimentally found that lithium peroxide starts to decompose into the lithium oxide and oxygen in the temperature range of 340 ÷ 348°C. It was established that the resulting thermal decomposition of lithium oxide, lithium peroxide at the temperature of 422°C melts with lithium carbonate eutecticly. The manifestation of polymorphism was not marked(seen or noticed) under the heating of studied samples of lithium peroxide and lithium peroxide monohydrate in the temperature range of 25°C ÷ 34°C.

  2. Thermal stability of the two-dimensional topological color code

    NASA Astrophysics Data System (ADS)

    Mohseninia, Razieh

    2016-08-01

    Thermal stability of the topological color code in the presence of a thermal bath is studied. We study the Lindblad evolution of the observables in the weak-coupling limit of the Born-Markov approximation. The autocorrelation functions of the observables are used as a figure of merit for the thermal stability. We show that all of the observables autocorrelation functions decay exponentially in time. By finding a lower bound of the decay rate, which is a constant independent of the system size, we show that the topological color code is unstable against thermal fluctuations from the bath at finite temperature, even though it is stable at T =0 against local quantum perturbations.

  3. Thermal stability comparison of nanocrystalline Fe-based binary alloy pairs

    DOE PAGESBeta

    Clark, Blythe G.; Hattar, Khalid Mikhiel; Marshall, Michael Thomas; Chookajorn, Tonghai; Boyce, Brad L.; Schuh, Christopher A.

    2016-02-01

    Here, the widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest, yet have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dense systems. While traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloy can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdock et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10at.% Mg) with a predicted non-NC stable alloy (Fe-10at.%more » Cu) using the same processing and characterization methodologies. Results indicate improved thermal stability of the Fe-Mg alloy in comparison to the Fe-Cu, and observed microstructures are consistent with those predicted by Monte Carlo simulations.« less

  4. Enhanced thermal stability of Ag nanorods through capping

    SciTech Connect

    Bachenheimer, Lou; Elliott, Paul; Stagon, Stephen; Huang, Hanchen

    2014-11-24

    Ag nanorods may serve as sensors in the detection of trace amounts of chemical agents, even single molecules, through surface enhanced Raman spectroscopy (SERS). However, thermal coarsening of Ag nanorods near room temperature limits their applications. This letter proposes the use of a thin oxide capping layer to enhance the thermal stability of Ag nanorods beyond 100 °C. Using electron microscopy characterization and SERS tests, the authors show that the proposed method is effective in stabilizing both morphology and sensitivity of Ag nanorods. The results of this work extend the applicability of Ag nanorods as chemical sensors to higher temperatures.

  5. Effects of sugars on the thermal stability of a protein

    NASA Astrophysics Data System (ADS)

    Oshima, Hiraku; Kinoshita, Masahiro

    2013-06-01

    It is experimentally known that the heat-denaturation temperature of a protein is raised (i.e., its thermal stability is enhanced) by sugar addition. In earlier works, we proposed a physical picture of thermal denaturation of proteins in which the measure of the thermal stability is defined as the solvent-entropy gain upon protein folding at 298 K normalized by the number of residues. A multipolar-model water was adopted as the solvent. The polyatomic structures of the folded and unfolded states of a protein were taken into account in the atomic detail. A larger value of the measure implies higher thermal stability. First, we show that the measure remains effective even when the model water is replaced by the hard-sphere solvent whose number density and molecular diameter are set at those of real water. The physical picture is then adapted to the elucidation of the effects of sugar addition on the thermal stability of a protein. The water-sugar solution is modeled as a binary mixture of hard spheres. The thermal stability is determined by a complex interplay of the diameter of sugar molecules dC and the total packing fraction of the solution η: dC is estimated from the volume per molecule in the sugar crystal and η is calculated using the experimental data of the solution density. We find that the protein is more stabilized as the sucrose or glucose concentration becomes higher and the stabilization effect is stronger for sucrose than for glucose. These results are in accord with the experimental observations. Using a radial-symmetric integral equation theory and the morphometric approach, we decompose the change in the measure upon sugar addition into two components originating from the protein-solvent pair and protein-solvent many-body correlations, respectively. Each component is further decomposed into the excluded-volume and solvent-accessible-surface terms. These decompositions give physical insights into the microscopic origin of the thermal-stability

  6. Effects of sugars on the thermal stability of a protein.

    PubMed

    Oshima, Hiraku; Kinoshita, Masahiro

    2013-06-28

    It is experimentally known that the heat-denaturation temperature of a protein is raised (i.e., its thermal stability is enhanced) by sugar addition. In earlier works, we proposed a physical picture of thermal denaturation of proteins in which the measure of the thermal stability is defined as the solvent-entropy gain upon protein folding at 298 K normalized by the number of residues. A multipolar-model water was adopted as the solvent. The polyatomic structures of the folded and unfolded states of a protein were taken into account in the atomic detail. A larger value of the measure implies higher thermal stability. First, we show that the measure remains effective even when the model water is replaced by the hard-sphere solvent whose number density and molecular diameter are set at those of real water. The physical picture is then adapted to the elucidation of the effects of sugar addition on the thermal stability of a protein. The water-sugar solution is modeled as a binary mixture of hard spheres. The thermal stability is determined by a complex interplay of the diameter of sugar molecules dC and the total packing fraction of the solution η: dC is estimated from the volume per molecule in the sugar crystal and η is calculated using the experimental data of the solution density. We find that the protein is more stabilized as the sucrose or glucose concentration becomes higher and the stabilization effect is stronger for sucrose than for glucose. These results are in accord with the experimental observations. Using a radial-symmetric integral equation theory and the morphometric approach, we decompose the change in the measure upon sugar addition into two components originating from the protein-solvent pair and protein-solvent many-body correlations, respectively. Each component is further decomposed into the excluded-volume and solvent-accessible-surface terms. These decompositions give physical insights into the microscopic origin of the thermal-stability

  7. Thermal Stability Analysis for a Heliocentric Gravitational Radiation Detection Mission

    NASA Technical Reports Server (NTRS)

    Folkner, W.; McElroy, P.; Miyake, R.; Bender, P.; Stebbins, R.; Supper, W.

    1994-01-01

    The Laser Interferometer Space Antenna (LISA) mission is designed for detailed studies of low-frequency gravitational radiation. The mission is currently a candidate for ESA's post-Horizon 2000 program. Thermal noise affects the measurement in at least two ways. Thermal variation of the length of the optical cavity to which the lasers are stabilized introduces phase variations in the interferometer signal, which have to be corrected for by using data from the two arms separately.

  8. Synthesis and thermal stability of carborane-containing phosphazenes

    NASA Technical Reports Server (NTRS)

    Fewell, L. L.; Parker, J. A.; Basi, R. J.

    1983-01-01

    Carborane-substituted polyphosphazenes were prepared by the thermal polymerization of phenyl-carboranyl pentachlorocylotriphosphazene. Successive isothermal vacuum pyrolyses were conducted on the polymer and examined for structural changes by infrared spectroscopy. The degradation products were ascertained by gas chromatography-mass spectrometric analysis. It was found that the presence of the carborane group improves the thermal stability of the polymer by retarding the ring-chain equilibrium processes of decomposition. Previously announced in STAR as A83-21034

  9. Synthesis and thermal stability of carborane containing phosphazenes

    NASA Technical Reports Server (NTRS)

    Fewell, L. L.; Basi, R. J.; Parker, J. A.

    1983-01-01

    Carborane substituted polyphosphazenes were prepared by the thermal polymerization of phenyl-carboranyl penta chlorocyclotriphosphazene. Successive isothermal vacuum pyrolyses were conducted on the polymer and examined for structural changes by infrared spectroscopy. The degradation products were ascertained by gas chromatography-mass spectrometric analysis. It was found that the presence of the carborane group improves the thermal stability of the polymer by retarding the ring chain equilibrium processes of decomposition.

  10. A numerical study of the thermal stability of solar loops

    NASA Technical Reports Server (NTRS)

    Klimchuk, J. A.; Antiochos, S. K.; Mariska, J. T.

    1987-01-01

    An important property of all loops is their thermal stability. If low lying hot loops were thermally unstable, for example, a great majority of the low loops on the Sun might be expected to be cool. How small perturbations evolve in low lying, linearly unstable hot loops was determined and how high lying, linearly stable hot loops respond to large amplitude disturbances such as might be expected on the Sun were examined. Only general descriptions and results are given.

  11. Boundary lubrication, thermal and oxidative stability of a fluorinated polyether and a perfluoropolyether triazine

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Snyder, C. E., Jr.

    1979-01-01

    Boundary lubricating characteristics, thermal stability and oxidation-corrosion stability were determined for a fluorinated polyether and a perfluoropolyether triazine. A ball-on-disk apparatus, a tensimeter and oxidation-corrosion apparatus were used. Results were compared to data for a polyphenyl ether and a C-ether. The polyether and triazine yielded better boundary lubricating characteristics than either the polyphenyl ether or C-ether. The polyphenyl ether had the greatest thermal stability (443 C) while the other fluids had stabilities in the range 389 to 397 C. Oxidation-corrosion results indicated the following order of stabilities: perfluoropolyether triazine greater than polyphenylether greater than C-ether greater than fluorinated polyether.

  12. Boundary lubrication, thermal and oxidative stability of a fluorinated polyether and a perfluoropolyether triazine

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Snyder, C. E., Jr.

    1979-01-01

    Boundary lubricating characteristics, thermal stability, and oxidation-corrosion stability were determined for a fluorinated polyether and a perfluoropolyether triazine. A ball-on-disk apparatus, a tensimeter, and oxidation-corrosion apparatus were used. Results were compared to data for a polyphenyl ether and a C-ether. The polyether and triazine yielded better boundary lubricating characteristics than either the polyphenyl ether or C-ether. The polyphenyl ether had the greatest thermal stability (443 C) while the other fluids had stabilities in the range 389 to 397 C. Oxidation-corrosion results indicated the following order of stabilities: perfluoropolyether trizine greater than polyphenyl ether greater than C-ether greater than fluorinated polyether.

  13. Thermal stability of liquid antioxidative extracts from pomegranate peel

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This research was carried out to assess the potential of using the natural antioxidants in pomegranate peel extracts as replacement for synthetic antioxidants. As a result the thermal stability of pomegranate peel extract products during sterilization and storage, and its effect on industrial, color...

  14. Substituted silane-diol polymers have improved thermal stability

    NASA Technical Reports Server (NTRS)

    Byrd, J. D.; Curry, J. E.

    1966-01-01

    Organosilicon polymers were synthesized to produce improved physical and chemical properties, including high thermal stability. Of the polymers produced, poly/4, 4 prime-bisoxybi- phenylene/diphenylsilane, formed from bis/anilino/diphenylsilane and p, p prime-biphenol, was found to have the most desirable properties.

  15. RP-1 and JP-8 Thermal Stability Experiments

    NASA Technical Reports Server (NTRS)

    Brown, Sarah P.; Emens, Jessica M.; Frederick, Robert A., Jr.

    2005-01-01

    This work experimentally investigates the effect of fuel composition changes on jet and rocket fuel thermal stability. A High Reynolds Number Thermal Stability test device evaluated JP-8 and RP-1 fuels. The experiment consisted of an electrically heated, stainless steel capillary tube with a controlled fuel outlet temperature. An optical pyrometer monitored the increasing external temperature profiles of the capillary tube as deposits build inside during each test. Multiple runs of each fuel composition provided results on measurement repeatability. Testing a t two different facilities provided data on measurement reproducibility. The technique is able to distinguish between thermally stable and unstable compositions of JP-8 and intermediate blends made by combining each composition. The technique is also able to distinguish among standard RP-1 rocket fuels and those having reduced sulfur levels. Carbon burn off analysis of residue in the capillary tubes on the RP-1 fuels correlates with the external temperature results.

  16. Prediction of the biochar carbon stability by thermal analysis

    NASA Astrophysics Data System (ADS)

    Méndez, Ana; Cely, Paola; Plaza, César; Paz-Ferreiro, Jorge; Gascó, Gabriel

    2015-04-01

    Thermal analysis (DTA, DSC, TG and dTG) has been used for decades to characterize carbonaceous materials used as fuels (oil, coal). Our research group has used these techniques for the characterisation of different biochars in order to assess proportions of labile and recalcitrant organic matter and to study the evolution of soil organic matter in soils amended with biochar. Thermal analysis could be used to determine the proximate analysis, i.e., the percentage of humidity, volatile matter and fixed carbon or to calculate the thermostability index, previously identified as a reliable parameter for evaluating the level of stability of organic matter in organic wastes and biochar. Relationship between the stability of biochar, the raw material and the pyrolysis conditions could be established by thermal analysis techniques.

  17. Thermal stability studies of polyimide-teflon blends

    SciTech Connect

    Davis, C.R.; Zimmerman, J.A.

    1993-12-31

    Polymers, such as poly(tetrafluoroethylene) (PTFE) that exhibit excellent thermal stability, in addition to other attractive physical properties, are an important component of high-performance devices. However, due to PTFE`s inertness and intractability, significant processing challenges exist and thus limit its successful widespread application in such industries an aerospace and electronics. One specific processing challenge example is the lack of available methods to uniformly and controllably form features in the neat fluoropolymer. Recently, it has been reported that excellent structuring of PTFE can be achieved by sensitizing the fluoropolymer to excimer laser of the sensitization agent, in addition to interacting strongly with the laser`s emitted energy, is suitable thermal stability. Using several analytical techniques, the thermal behavior of PTFE, polyimide sensitizer and resulting polyimide-fluoropolymer blend has been investigated and found to be excellent.

  18. Effect of some nitrogen compounds thermal stability of jet A

    NASA Technical Reports Server (NTRS)

    Antoine, A. C.

    1982-01-01

    The effect of known concentrations of some nitrogen containing compounds on the thermal stability of a conventional fuel, namely, Jet A was investigated. The concentration range from 0.01 to 0.1 wt% nitrogen was examined. Solutions were made containing, individually, pyrrole, indole, quinoline, pyridine, and 4 ethylpyridine at 0.01, 0.03, 0.06, and 0.1 wt% nitrogen concentrations in Jet A. The measurements were all made by using a standard ASTM test for evaluating fuel thermal oxidation behavior, namely, ASTM D3241, 'thermal oxidation stability of turbine fuels (JFTOT procedure).' Measurements were made at two temperature settings, and 'breakpoint temperatures' were determined. The results show that the pyrrole and indole solutions have breakpoint temperatures substantially lower than those of the Jet A used.

  19. Fuel thermal stability effects on spray characteristics

    NASA Technical Reports Server (NTRS)

    Lefebvre, A. H.; Nickolaus, D.

    1987-01-01

    The propensity of a heated hydrocarbon fuel toward solids deposition within a fuel injector is investigated experimentally. Fuel is arranged to flow through the injector at constant temperature, pressure, and flow rate and the pressure drop across the nozzle is monitored to provide an indication of the amount of deposition. After deposits have formed, the nozzle is removed from the test rig and its spray performance is compared with its performance before deposition. The spray characteristics measured include mean drop size, drop-size distribution, and radial and circumferential fuel distribution. It is found that small amounts of deposition can produce severe distortion of the fuel spray pattern. More extensive deposition restores spray uniformity, but the nozzle flow rate is seriously curtailed.

  20. Thermal stability of high temperature structural alloys

    SciTech Connect

    Jordan, C.E.; Rasefske, R.K.; Castagna, A.

    1999-03-01

    High temperature structural alloys were evaluated for suitability for long term operation at elevated temperatures. The effect of elevated temperature exposure on the microstructure and mechanical properties of a number of alloys was characterized. Fe-based alloys (330 stainless steel, 800H, and mechanically alloyed MA 956), and Ni-based alloys (Hastelloy X, Haynes 230, Alloy 718, and mechanically alloyed MA 758) were evaluated for room temperature tensile and impact toughness properties after exposure at 750 C for 10,000 hours. Of the Fe-based alloys evaluated, 330 stainless steel and 800H showed secondary carbide (M{sub 23}C{sub 6}) precipitation and a corresponding reduction in ductility and toughness as compared to the as-received condition. Within the group of Ni-based alloys tested, Alloy 718 showed the most dramatic structure change as it formed delta phase during 10,000 hours of exposure at 750 C with significant reductions in strength, ductility, and toughness. Haynes 230 and Hastelloy X showed significant M{sub 23}C{sub 6} carbide precipitation and a resulting reduction in ductility and toughness. Haynes 230 was also evaluated after 10,000 hours of exposure at 850, 950, and 1050 C. For the 750--950 C exposures the M{sub 23}C{sub 6} carbides in Haynes 230 coarsened. This resulted in large reductions in impact strength and ductility for the 750, 850 and 950 C specimens. The 1050 C exposure specimens showed the resolution of M{sub 23}C{sub 6} secondary carbides, and mechanical properties similar to the as-received solution annealed condition.

  1. X-ray Crystallographic Structure of Thermophilic Rhodopsin: IMPLICATIONS FOR HIGH THERMAL STABILITY AND OPTOGENETIC FUNCTION.

    PubMed

    Tsukamoto, Takashi; Mizutani, Kenji; Hasegawa, Taisuke; Takahashi, Megumi; Honda, Naoya; Hashimoto, Naoki; Shimono, Kazumi; Yamashita, Keitaro; Yamamoto, Masaki; Miyauchi, Seiji; Takagi, Shin; Hayashi, Shigehiko; Murata, Takeshi; Sudo, Yuki

    2016-06-01

    Thermophilic rhodopsin (TR) is a photoreceptor protein with an extremely high thermal stability and the first characterized light-driven electrogenic proton pump derived from the extreme thermophile Thermus thermophilus JL-18. In this study, we confirmed its high thermal stability compared with other microbial rhodopsins and also report the potential availability of TR for optogenetics as a light-induced neural silencer. The x-ray crystal structure of TR revealed that its overall structure is quite similar to that of xanthorhodopsin, including the presence of a putative binding site for a carotenoid antenna; but several distinct structural characteristics of TR, including a decreased surface charge and a larger number of hydrophobic residues and aromatic-aromatic interactions, were also clarified. Based on the crystal structure, the structural changes of TR upon thermal stimulation were investigated by molecular dynamics simulations. The simulations revealed the presence of a thermally induced structural substate in which an increase of hydrophobic interactions in the extracellular domain, the movement of extracellular domains, the formation of a hydrogen bond, and the tilting of transmembrane helices were observed. From the computational and mutational analysis, we propose that an extracellular LPGG motif between helices F and G plays an important role in the thermal stability, acting as a "thermal sensor." These findings will be valuable for understanding retinal proteins with regard to high protein stability and high optogenetic performance. PMID:27129243

  2. Organic underlayer materials with exceptionally high thermal stability

    NASA Astrophysics Data System (ADS)

    Cheon, Hwan-Sung; Yoon, Kyong-Ho; Kim, Min-Soo; Oh, Sung Bae; Song, Jee-Yun; Tokareva, Nataliya; Kim, Jong-Seob; Chang, Tuwon

    2009-03-01

    Multilayer hardmask (MLHM) schemes have been implemented as an indispensable process for ArF lithography which continues to demand thinner photoresist films. There are many variations of MLHM and semiconductor manufacturers choose to adopt their own designs, depending on their specific needs and technical advances. The quad-layer stack consisting of photoresist, organic ARC, CVD Si hardmask, and spin-on carbon underlayer is one of them. Despite the need for wafer transporting between the spin track and CVD equipment, this scheme is attractive because it can avoid laborious elaboration of sophisticated etching chemistries for spin-on Si-ARC and carbon underlayer. One of the issues arising from the mixed film forming process is the thermal stability of carbon underlayer at high temperatures during the CVD process of the Si hardmask. Organic underlayer which shows high thermal stability is crucial for this mixed hardmask process. These types of thermally stable organic film can also be used for other applications such as the spacer patterning technique for pitch size shrinkage. In this paper, we discuss the development of organic resins with high thermal stability, their physical properties, and their lithographic behaviors in the MLHM schemes.

  3. Thermal stability of nanocrystalline layers fabricated by surface nanocrystallization

    NASA Astrophysics Data System (ADS)

    Mai, Yong-jin; Jie, Xiao-hua; Liu, Li-li; Yu, Neng; Zheng, Xiang-xin

    2010-01-01

    A nanocrystalline layer with ultrafine grains (about 30-40 nm) on the surface of 7050 aluminum alloy was fabricated by a new technique called High Pressure Shot Peening (HPSP) which is the combination of common Shot Peening equipment with a pressurizing vessel. Relationship between hot flow and temperature was observed by Differential Scanning Calorimetry (DSC) and the activation energy, calculated by Kisssinger equation, of the as-treated sample increased 26.6 kJ/mol when it is compared with the as-reserved sample. The Bragg peaks of the as-prepared samples, respectively treated with various annealing treatments were characterized by XRD and the microhardness distribution along the depth from the treated surface were measured at the same time, which indicated that the broadening of Bragg peaks decreased with the increasing of anneal temperature; the grain size, calculated by Scherrer-Wilson equation, increased obviously during 180-220 °C, accordingly, the microhardness obviously decreased. According to the results of DSC, XRD and microhardness, it is reasonable to deduce that the temperature range of thermal stability for aluminum alloy nanocrystalline layer is lower than 200 °C.

  4. Thermal phase stability of some simulated Defense waste glasses

    SciTech Connect

    May, R.P.

    1981-04-01

    Three simulated defense waste glass compositions developed by Savannah River Laboratories were studied to determine viscosity and compositional effects on the comparative thermal phase stabilities of these glasses. The glass compositions are similar except that the 411 glasses are high in lithium and low in sodium compared to the 211 glass, and the T glasses are high in iron and low in aluminum compared to the C glass. Specimens of these glasses were heat treated using isothermal anneals as short as 10 min and up to 15 days over the temperature range of 450/sup 0/C to 1100/sup 0/C. Additionally, a specimen of each glass was cooled at a constant cooling rate of 7/sup 0/C/hour from an 1100/sup 0/C melt down to 500/sup 0/C where it was removed from the furnace. The following were observed. The slow cooling rate of 7/sup 0/C/hour is possible as a canister centerline cooling rate for large canisters. Accordingly, it is important to note that a short range diffusion mechanism like cooperative growth phenomena can result in extensive devitrification at lower temperatures and higher yields than a long-range diffusion mechanism can; and can do it without the growth of large crystals that can fracture the glass. Refractory oxides like CeO/sub 2/ and (Ni, Mn, Fe)/sub 2/O/sub 4/ form very rapidly at higher temperatures than silicates and significant yields can be obtained at sufficiently high temperatures that settling of these dense phases becomes a major microstructural feature during slow cooling of some glasses. These annealing studies further show that below 500/sup 0/C there is but little devitrification occurring implying that glass canisters stored at 300/sup 0/C may be kinetically stable despite not being thermodynamically so.

  5. Modifications to improve entrance slit thermal stability for grasshopper monochromators

    NASA Astrophysics Data System (ADS)

    Wallace, Daniel J.; Rogers, Gregory C.; Crossley, Sherry L.

    1994-08-01

    As new monochromators are designed for high-flux storage rings, computer modeling and thermal engineering can be done to process increased heat loads and achieve mechanical stability. Several older monochromators, such as the Mark 2 and Mark 5 Grasshopper monochromators, which were designed in 1974, have thermal instabilities in their entrance slit mechanisms. The Grasshoppers operating with narrow slits experience closure of the entrance slit from thermal expansion. In extreme cases, the thermal expansion of the precision components has caused permanent mechanical damage, leaving the slit uncalibrated and/or inoperable. For the Mark 2 and Mark 5 Grasshopper monochromators at the Synchrotron Radiation Center, the original 440 stainless steel entrance slit jaws were retrofitted with an Invar (low expansion Fe, Ni alloy) slit jaw. To transfer the heat from the critical components, two flexible heat straps of Cu were attached. These changes allow safe operation with a 10 μm entrance slit width where the previous limit was 30 μm. After an initial 2 min equilibration, the slit remains stable to 10%, with 100 mA of beam current. Additional improvements in slit thermal stability are planned for a third Grasshopper.

  6. Thermal stability testing of low-level waste forms

    SciTech Connect

    Piciulo, P.L.; Chan, S.F.

    1985-05-01

    The NRC Technical Position (TP) on Waste Form specifies that waste forms should be resistant to thermal degradation. The thermal cycle testing procedure outlined in the TP on Waste Form was carried out and is believed adequate for demonstrating the thermal stability of solidified waste forms. The inclusion of control samples and the monitoring of sample temperature are recommended additions to the test. An outline for reporting thermal cycling test results is given. To produce a data base on the applicability of the thermal cycling test, the following simulated laboratory-scale waste forms were prepared and tested: boric acid and sodium sulfate evaporator bottoms, mixed bed bead resins, and powdered resins each solidified in asphalt, cement and vinyl ester-styrene. Thermal cycling does not significantly affect the compressive strength of the solidified wastes, except powdered resins solidified in cement which disintegrated during the test and bead resins in cement which showed a loss of compressive strength. After temperature cycling, cement solidified bead resins showed areas of spalling and solidified sodium sulfate forms had surface deterioration. Asphalt solidified wastes, except powdered resins, deformed by slumping on temperature cycling. Free liquid was released from vinyl esterstyrene solidifed waste forms as a result of thermal cycling. Dewatered bead and powdered resins were also tested and no free liquid was released on temperature cycling. 11 refs., 12 figs., 4 tabs.

  7. Thermal stability of lanthanum scandate dielectrics on Si(100)

    SciTech Connect

    Sivasubramani, P.; Lee, T. H.; Kim, M. J.; Kim, J.; Gnade, B. E.; Wallace, R. M.; Edge, L. F.; Schlom, D. G.; Stevie, F. A.; Garcia, R.; Zhu, Z.; Griffis, D. P.

    2006-12-11

    The authors have examined the thermal stability of amorphous, molecular beam deposited lanthanum scandate dielectric thin films on top of Si (100) after a 1000 deg. C, 10 s rapid thermal anneal. After the anneal, crystallization of LaScO{sub 3} is observed. Excellent suppression of lanthanum and scandium diffusion into the substrate silicon is indicated by the back-side secondary ion mass spectrometry (SIMS) analyses. In contrast, front-side SIMS and high-resolution electron energy loss analyses of the amorphous Si/LaScO{sub 3}/Si (100) stack indicated the outdiffusion of lanthanum and scandium into the silicon capping layer during the anneal.

  8. The thermal stability of coronal loops by nonlinear diffusion asymptotics

    NASA Technical Reports Server (NTRS)

    Pakkert, J. W.; Verhulst, F.; Martens, P. C. H.

    1987-01-01

    A nonlinear reaction-diffusion equation and some additional constraints are derived which describe the time-dependent behavior of the temperature structure of the plasma in coronal loops. The equation is analyzed using nonlinear diffusion asymptotics, in particular singular perturbation techniques, and the results are interpreted in the context of the physical problem of the thermal stability and temporal behavior of the plasma. The results are consistent with the possibility of cyclic thermal behavior of the plasma, as suggested by Kuin and Martens (1982).

  9. Thermal stability studies of Li-ion cells and components

    SciTech Connect

    Maleki, H.; Deng, G.; Anani, A.; Howard, J.

    1999-09-01

    A Li-ion cell consists of a carbon-based negative electrode (NE); a porous polymer membrane separator (high density polypropylene and/or polyethylene); and positive electrode (PE) containing lithium transition metal oxides (LiMo{sub 2}, M = Co, Ni, or Mn); and a mixture of lithium salt and organic solvents provides an electrolytic medium for Li-ions to shuttle between the PE and NE. Electrodes are produced by coating slurries of active PE or NE material, polymer binder, most commonly polyvinylidene difluoride (PVDF), and small amounts of high surface area carbon onto a metallic current collectors. Thermal stability of fully charged 550 mAh prismatic Li-ion cells (Sn-doped LiCoO{sub 2}/graphitic carbon) and their components are investigated. Accelerating rate calorimetry (ARC) is used to determine the onset temperature of exothermic chemical reactions that force the cell into thermal runaway. Differential scanning calorimetry (DSC) and thermogravimetry analysis are used to determine the thermal stability of the cell's positive electrode (PE) and negative electrode (NE) materials from 35 to 400 C. The cell self-heating exothermic reactions start at 123 C, and thermal runaway occurs near 167 C. The total exothermic heat generation of the NE and PE materials are 697 and 407 J/g, respectively. Heat generations of the NE and PE materials, washed in diethyl carbonate (DEC) and dried at {approx}65 C under vacuum, are significantly lower than unwashed samples. Lithium plating increases the heat generation of the NE material at temperatures near the lithium melting point. Comparison of the heat generation profiles from DSC and ARC tests indicates that thermal runaway of this cell is close to the decomposition temperature range of the unwashed PE material. The authors conclude that the heat generation from the decomposition of PE material and reaction of that with electrolyte initiates thermal runaway in a Li-ion cell, under thermally or abusive conditions.

  10. Determination of the thermal stability of perfluoropolyalkyl ethers by tensimetry

    NASA Technical Reports Server (NTRS)

    Helmick, Larry A.; Jones, William R., Jr.

    1992-01-01

    The thermal decomposition temperatures of several perfluoropolyalkyl ether fluids were determined with a computerized tensimeter. In general, the decomposition temperatures of the commercial fluids were all similar and significantly higher than those for noncommercial fluids. Correlation of the decomposition temperatures with the molecular structures of the primary components of the commercial fluids revealed that the stability of the fluids was not affected by carbon chain length, branching, or adjacent difluoroformal groups. Instead, stability was limited by the presence of small quantities of thermally unstable material and/or chlorine-containing material arising from the use of chlorine containing solvents during synthesis. Finally, correlation of decomposition temperatures with molecular weights for two fluids supports a chain cleavage reaction mechanism for one and an unzipping reaction mechanism for the other.

  11. Thermal stability of poly(3-hydroxybutyrate)/vegetable fiber composites

    NASA Astrophysics Data System (ADS)

    Cipriano, Pâmela Bento; de Sá, Mayelli Dantas; Andrade, André L. Simões; de Carvalho, Laura Hecker; Canedo, Eduardo Luis

    2015-05-01

    The present work deals with the thermal stability during and after processing of composites of poly(3-hydroxybutyrate) (PHB) - a fully biodegradable semi-crystalline thermoplastic obtained from renewable resources through low-impact biotechnological process, biocompatible and non-toxic - and vegetable fiber from the fruit (coconut) of babassu palm tree. PHB/babassu composites with 0, 5, 10 and 20% w/w load were prepared in a laboratory internal mixer. Two fractions of the mesocarp of babassu with different particle sizes were compounded with PHB and test specimens molded by compression. The effect of loading level and processing conditions on torque, temperature and mechanical energy dissipation were studied using a new engineering model. It was found that PHB degrades during processing at temperatures slightly above the melting point. To minimize thermal degradation stabilizer and chain extender additives were incorporated, with mixed results. These findings were confirmed by the dependence of the melt flow rate on the processing temperature.

  12. On the thermal stability of coronal loop plasma

    NASA Technical Reports Server (NTRS)

    Antiochos, S. K.; Emslie, A. G.; Shoub, E. C.; An, C. H.

    1982-01-01

    The stability to thermal perturbation of static models of coronal loops is considered including the effects of cool, radiatively stable material at the loop base. The linear stability turns out to be sensitive only to the boundary conditions assumed on the velocity at the loop base. The question of the appropriate boundary conditions is discussed, and it is concluded that the free surface condition (the pressure perturbation vanishes), rather than the rigid wall (the velocity vanishes), is relevant to the solar case. The static models are found to be thermally unstable, with a growth time of the order of the coronal cooking time. The physical implications of these results for the solar corona and transition region are examined.

  13. Exceptional chemical and thermal stability of zeolitic imidazolate frameworks

    PubMed Central

    Park, Kyo Sung; Ni, Zheng; Côté, Adrien P.; Choi, Jae Yong; Huang, Rudan; Uribe-Romo, Fernando J.; Chae, Hee K.; O’Keeffe, Michael; Yaghi, Omar M.

    2006-01-01

    Twelve zeolitic imidazolate frameworks (ZIFs; termed ZIF-1 to -12) have been synthesized as crystals by copolymerization of either Zn(II) (ZIF-1 to -4, -6 to -8, and -10 to -11) or Co(II) (ZIF-9 and -12) with imidazolate-type links. The ZIF crystal structures are based on the nets of seven distinct aluminosilicate zeolites: tetrahedral Si(Al) and the bridging O are replaced with transition metal ion and imidazolate link, respectively. In addition, one example of mixed-coordination imidazolate of Zn(II) and In(III) (ZIF-5) based on the garnet net is reported. Study of the gas adsorption and thermal and chemical stability of two prototypical members, ZIF-8 and -11, demonstrated their permanent porosity (Langmuir surface area = 1,810 m2/g), high thermal stability (up to 550°C), and remarkable chemical resistance to boiling alkaline water and organic solvents. PMID:16798880

  14. Unusual Thermal Stability of Nano-structured Ferritic alloys

    SciTech Connect

    Wang, Xun-Li; Liu, Chain T; Stoica, A. D.; Keiderling, Dr. Uwe; Yang, Ling; Miller, Michael K; Fu, Chong Long; Ma, Dong; An, Ke

    2012-01-01

    A scientific question vitally important to the materials community is whether there exist self-assembled nanoclusters that are thermodynamically stable at elevated temperatures. Using in-situ neutron scattering, we characterized the structure and thermal stability of a nano-structured ferritic (NSF) alloy. Nanometer sized clusters were found to persist up to ~1400 C, providing direct evidence of a thermodynamically stable alloying state for the nanoclusters. Cluster formation requires the coexistence of Y, Ti, and O without the precipitation of oxide phases. The presence of thermally stable nanoclusters at grain boundaries limits the diffusion of Fe atoms, thereby stabilizing the microstructure of the ferritic matrix at high temperatures. Our experimental results provide physical insights of the dramatically improved high-temperature mechanical properties in NSF alloy and point to a new direction in alloy design.

  15. Scandia-and-Yttria-Stabilized Zirconia for Thermal Barriers

    NASA Technical Reports Server (NTRS)

    Mess, Derek

    2003-01-01

    yttria in suitable proportions has shown promise of being a superior thermal- barrier coating (TBC) material, relative to zirconia stabilized with yttria only. More specifically, a range of compositions in the zirconia/scandia/yttria material system has been found to afford increased resistance to deleterious phase transformations at temperatures high enough to cause deterioration of yttria-stabilized zirconia. Yttria-stabilized zirconia TBCs have been applied to metallic substrates in gas turbine and jet engines to protect the substrates against high operating temperatures. These coatings have porous and microcracked structures, which can accommodate strains induced by thermal-expansion mismatch and thermal shock. The longevity of such a coating depends upon yttria as a stabilizing additive that helps to maintain the zirconia in an yttria-rich, socalled non-transformable tetragonal crystallographic phase, thus preventing transformation to the monoclinic phase with an associated deleterious volume change. However, at a temperature greater than about 1,200 C, there is sufficient atomic mobility that the equilibrium, transformable zirconia phase is formed. Upon subsequent cooling, this phase transforms to the monoclinic phase, with an associated volume change that adversely affects the integrity of the coating. Recently, scandia was identified as a stabilizer that could be used instead of, or in addition to, yttria. Of particular interest are scandia-and-yttria-stabilized zirconia (SYSZ) compositions of about 6 mole percent scandia and 1 mole percent yttria, which have been found to exhibit remarkable phase stability at a temperature of 1,400 C in simple aging tests. Unfortunately, scandia is expensive, so that the problem becomes one of determining whether there are compositions with smaller proportions of scandia that afford the required high-temperature stability. In an attempt to solve this problem, experiments were performed on specimens made with reduced

  16. Flexible all-carbon photovoltaics with improved thermal stability

    SciTech Connect

    Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C.

    2015-04-15

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C{sub 60}s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C{sub 60}s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that “lock up” the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C{sub 60}s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C{sub 60}s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current–voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C{sub 60}:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests. - Graphical abstract: The incorporation of solvent resistant, mechanically flexible and electrically addressable 2-D soft graphene nanoribbons facilitates the assembly of photoconductive carbon nano-p/n junctions for thermally stable and flexible photovoltaic cells.

  17. Thermal stability of ion-implanted ZnO

    SciTech Connect

    Coleman, V; Tan, H; Jagadish, C; Kucheyev, S; Zou, J

    2005-06-16

    Zinc oxide single crystals implanted at room temperature with high-dose (1.4 x 10{sup 17} cm{sup -2}) 300 keV As{sup +} ions are annealed at 1000-1200 C. Damage recovery is studied by a combination of Rutherford backscattering/ channeling spectrometry (RBS/C), cross-sectional transmission electron microscopy (XTEM), and atomic force microscopy (AFM). Results show that such a thermal treatment leads to the decomposition and evaporation of the heavily-damaged layer instead of apparent defect recovery and recrystallization that could be inferred from RBS/C and XTEM data alone. Such a relatively poor thermal stability of heavily-damaged ZnO has significant implications for understanding results on thermal annealing of ion-implanted ZnO.

  18. Thermal stability of hexagonal OsB{sub 2}

    SciTech Connect

    Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A.; Andrew Payzant, E.

    2014-11-15

    parameters and no phase changes detected during cooling. - Graphical abstract: The in situ high temperature XRD contour plot (A) and XRD patterns (B) of h-OsB{sub 2} upon heating and cooling under an argon atmosphere. - Highlights: • Different boron sources were compared for the synthesis of h-OsB{sub 2}. • The phase stability and thermal behavior of h-OsB{sub 2} were studied by in situ XRD. • Shrinkage of the a lattice parameter was observed from 276 °C to 426 °C upon heating. • Oxidation of OsB{sub 2} produced B vacancies led to the shrinkage of a lattice parameter.

  19. Thermal conductivity and stability of commercial MgB2 conductors

    NASA Astrophysics Data System (ADS)

    Bonura, Marco; Senatore, Carmine

    2015-11-01

    This paper presents a study of the thermal transport properties of MgB2 tapes differing in architecture, stabilization and constituent materials. The temperature and field dependence of thermal conductivity, κ (T,B), was investigated both along the conductor and in the direction perpendicular to the tape. These data provide fundamental input parameters to describe the 3D heat diffusion process in a winding. Thermal transport properties—even in field—are typically deduced using semi-empirical formulas based on the residual resistivity ratio of the stabilizer measured in absence of magnetic field. The accuracy of these procedures was evaluated comparing the calculated κ values with the measured ones. Based on the experimental thermal conduction properties κ (T,B) and critical current surface {J}{{C}}(T,B) we determined the dependence of minimum quench energy and normal zone propagation velocity on the operating parameters of the conductor. The correlation between thermal properties and tape layout allowed us to provide information on how to optimize the thermal stability of MgB2 conductors.

  20. Graphene oxide immobilized enzymes show high thermal and solvent stability

    NASA Astrophysics Data System (ADS)

    Hermanová, Soňa; Zarevúcká, Marie; Bouša, Daniel; Pumera, Martin; Sofer, Zdeněk

    2015-03-01

    The thermal and solvent tolerance of enzymes is highly important for their industrial use. We show here that the enzyme lipase from Rhizopus oryzae exhibits exceptionally high thermal stability and high solvent tolerance and even increased activity in acetone when immobilized onto a graphene oxide (GO) nanosupport prepared by Staudenmaier and Brodie methods. We studied various forms of immobilization of the enzyme: by physical adsorption, covalent attachment, and additional crosslinking. The activity recovery was shown to be dependent on the support type, enzyme loading and immobilization procedure. Covalently immobilized lipase showed significantly better resistance to heat inactivation (the activity recovery was 65% at 70 °C) in comparison with the soluble counterpart (the activity recovery was 65% at 40 °C). Physically adsorbed lipase achieved over 100% of the initial activity in a series of organic solvents. These findings, showing enhanced thermal stability and solvent tolerance of graphene oxide immobilized enzyme, will have a profound impact on practical industrial scale uses of enzymes for the conversion of lipids into fuels.The thermal and solvent tolerance of enzymes is highly important for their industrial use. We show here that the enzyme lipase from Rhizopus oryzae exhibits exceptionally high thermal stability and high solvent tolerance and even increased activity in acetone when immobilized onto a graphene oxide (GO) nanosupport prepared by Staudenmaier and Brodie methods. We studied various forms of immobilization of the enzyme: by physical adsorption, covalent attachment, and additional crosslinking. The activity recovery was shown to be dependent on the support type, enzyme loading and immobilization procedure. Covalently immobilized lipase showed significantly better resistance to heat inactivation (the activity recovery was 65% at 70 °C) in comparison with the soluble counterpart (the activity recovery was 65% at 40 °C). Physically adsorbed

  1. Structural stability vs. thermal performance: old dilemma, new solutions

    SciTech Connect

    Kosny, J.; Christian, J.E.

    1996-10-01

    In many building envelopes, actual thermal performance falls quite a bit short of nominal design parameters given in standards. Very often only windows, doors, and a small part of the wall area meet standards requirements. In the other parts of the building envelope, unaccounted thermal bridges reduce the effective thermal resistance of the insulation material. Such unaccounted heat losses compromise the thermal performance of the whole building envelope. For the proper analysis of the thermal performance of most wall and roof details, measurements and three-dimensional thermal modeling are necessary. For wall thermal analysis the whole-wall R-value calculation method can be very useful. In ties method thermal properties of all wall details are incorporated as an area weighted average. For most wall systems, the part of the wall that is traditionally analyzed, is the clear wall, that is, the flat part of the wall that is uninterrupted by details. It comprises only 50 to 80% of the total area of the opaque wall. The remaining 20 to 50% of the wall area is not analyzed nor are its effects incorporated in the thermal performance calculations. For most of the wall technologies, traditionally estimated R-values are 20 to 30% higher than whole-wall R-values. Such considerable overestimation of wall thermal resistance leads to significant errors in building heating and cooling load estimations. In this paper several examples are presented of the use of the whole-wall R-value procedure for building envelope components. The advantages of the use of the whole wall R-value calculation procedure are also discussed. For several building envelope components, traditional clear-wall R-values are compared with the results of whole-wall thermal analysis to highlight significant limits on the use of the traditional methods and the advantages of advanced computer modeling.

  2. Thermal Stability of RP-2 for Hydrocarbon Boost Regenerative Cooling

    NASA Technical Reports Server (NTRS)

    Kleinhenz, Julie E.; Deans, Matthew C.; Stiegemeier, Benjamin R.; Psaras, Peter M.

    2013-01-01

    A series of tests were performed in the NASA Glenn Research Centers Heated Tube Facility to study the heat transfer and thermal stability behavior of RP-2 under conditions similar to those found in rocket engine cooling channels. It has long been known that hydrocarbon fuels, such as RP-2, can decompose at high temperature to form deposits (coke) which can adversely impact rocket engine cooling channel performance. The heated tube facility provides a simple means to study these effects. Using resistively heated copper tubes in a vacuum chamber, flowing RP-2 was heated to explore thermal effects at a range of test conditions. Wall temperature (850-1050F) and bulk fluid temperature (300-500F) were varied to define thermal decomposition and stability at each condition. Flow velocity and pressure were fixed at 75 fts and 1000 psia, respectively. Additionally, five different batches of RP-2 were tested at identical conditions to examine any thermal stability differences resulting from batch to batch compositional variation. Among these tests was one with a potential coke reducing additive known as 1,2,3,4-Tetrahydroquinoline (THQ). While copper tubes were used for the majority of tests, two exploratory tests were performed with a copper alloy known as GRCop-42. Each tube was instrumented with 15 thermocouples to examine the temperature profile, and carbon deposition at each thermocouple location was determined post-test in an oxidation furnace. In many tests, intermittent local temperature increases were observed visually and in the thermocouple data. These hot spots did not appear to correspond with a higher carbon deposition.

  3. Synthesis, characterization and application of enrofloxacin complexes as thermal stabilizers for rigid poly(vinyl chloride).

    PubMed

    el-Gamel, Nadia E A; Mohamed, Riham R; Zayed, M A

    2012-02-14

    Synthesis and characterization of both binary Co(II)- (1), Ni(II)- (2) complexes with enrofloxacin drug (HL(1)) and ternary Co(II)- (3), Ni(II)- (4) complexes in presence of DL-alanine (H(2)L(2)) are reported using physico-chemical techniques. The antimicrobial activity of these complexes has been screened against two gram-positive and two gram-negative bacteria. Antifungal activity against two different fungi has been evaluated and compared with reference drug. All the binary and ternary complexes showed remarkable potential antimicrobial activity higher than the recommended standard agents. Ni(II)-complexes exhibited higher potency as compared to the parent drug against bacterial and fungal strain. In addition, it was of interest to investigate the reported complexes as thermal stabilizers and co-stabilizers for rigid PVC in air at 180 °C. Their high stabilizing efficiency is detected by their high induction period values (T(s)) compared with some of the common reference stabilizers used industrially, such as dibasic lead carbonate (DBLC) and calcium-zinc soap. Blending these complexes with some of the reference stabilizers in different ratios had a synergistic effect on both induction period as it gave better thermal stability and lower extent of discoloration. The stabilizing efficiency is attributed at least partially to the ability of the metal complex stabilizer to be incorporated in the polymeric chains, thus disrupting the chain degradation and replace the labile chlorine atoms on PVC chains by a relatively more s moiety of the inorganic stabilizer. Their amenability to use as a biomedical additives for PVC, has afforded them great potential for various medical applications. PMID:22159190

  4. A self-adaptive thermal switch array for rapid temperature stabilization under various thermal power inputs

    NASA Astrophysics Data System (ADS)

    Geng, Xiaobao; Patel, Pragnesh; Narain, Amitabh; Desheng Meng, Dennis

    2011-08-01

    A self-adaptive thermal switch array (TSA) based on actuation by low-melting-point alloy droplets is reported to stabilize the temperature of a heat-generating microelectromechanical system (MEMS) device at a predetermined range (i.e. the optimal working temperature of the device) with neither a control circuit nor electrical power consumption. When the temperature is below this range, the TSA stays off and works as a thermal insulator. Therefore, the MEMS device can quickly heat itself up to its optimal working temperature during startup. Once this temperature is reached, TSA is automatically turned on to increase the thermal conductance, working as an effective thermal spreader. As a result, the MEMS device tends to stay at its optimal working temperature without complex thermal management components and the associated parasitic power loss. A prototype TSA was fabricated and characterized to prove the concept. The stabilization temperatures under various power inputs have been studied both experimentally and theoretically. Under the increment of power input from 3.8 to 5.8 W, the temperature of the device increased only by 2.5 °C due to the stabilization effect of TSA.

  5. Magnetic thermal stability of permalloy microstructures with shape-induced bi-axial anisotropy

    NASA Astrophysics Data System (ADS)

    Telepinsky, Yevgeniy; Sinwani, Omer; Mor, Vladislav; Schultz, Moty; Klein, Lior

    2016-02-01

    We study the thermal stability of the magnetization states in permalloy microstructures in the form of two crossing elongated ellipses, a shape which yields effective bi-axial magnetic anisotropy in the overlap area. We prepare the structure with the magnetization along one of the easy axes of magnetization and measure the waiting time for switching when a magnetic field favoring the other easy axis is applied. The waiting time for switching is measured as a function of the applied magnetic field and temperature. We determine the energy barrier for switching and estimate the thermal stability of the structures. The experimental results are compared with numerical simulations. The results indicate exceptional stability which makes such structures appealing for a variety of applications including magnetic random access memory based on the planar Hall effect.

  6. Thermal Stability Analysis for Superconducting Coupling Coil in MICE

    SciTech Connect

    Wu, Hong; Wang, Li; Pan, Heng; Guo, XingLong; Green, M.A.

    2010-06-28

    The superconducting coupling coil to be used in the Muon Ionization Cooling Experiment (MICE) with inner radius of 750 mm, length of 285 mm and thickness of 110.4 mm will be cooled by a pair of 1.5 W at 4.2 K cryo-coolers. When the coupling coil is powered to 210 A, it will produce about 7.3 T peak magnetic field at the conductor and it will have a stored energy of 13 MJ. A key issue for safe operation of the coupling coil is the thermal stability of the coil during a charge and discharge. The magnet and its cooling system are designed for a rapid discharge where the magnet is to be discharged in 5400 seconds. The numerical simulation for the thermal stability of the MICE coupling coil has been done using ANSYS. The analysis results show that the superconducting coupling coil has a good stability and can be charged and discharged safely.

  7. Enhancement of Aviation Fuel Thermal Stability Characterization Through Application of Ellipsometry

    NASA Technical Reports Server (NTRS)

    Browne, Samuel Tucker; Wong, Hubert; Hinderer, Cameron Branch; Klettlinger, Jennifer

    2012-01-01

    ASTM D3241/Jet Fuel Thermal Oxidation Tester (JFTOT) procedure, the standard method for testing thermal stability of conventional aviation turbine fuels is inherently limited due to the subjectivity in the color standard for tube deposit rating. Quantitative assessment of the physical characteristics of oxidative fuel deposits provides a more powerful method for comparing the thermal oxidation stability characteristics of fuels, especially in a research setting. We propose employing a Spectroscopic Ellipsometer to determine the film thickness and profile of oxidative fuel deposits on JFTOT heater tubes. Using JP-8 aviation fuel and following a modified ASTM D3241 testing procedure, the capabilities of the Ellipsometer will be demonstrated by measuring oxidative fuel deposit profiles for a range of different deposit characteristics. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project

  8. Thermal stability of spent coffee ground polysaccharides: galactomannans and arabinogalactans.

    PubMed

    Simões, Joana; Maricato, Elia; Nunes, Fernando M; Domingues, M Rosário; Coimbra, Manuel A

    2014-01-30

    In order to better understand the thermal stability of spent coffee grounds (SCG) galactomannans and arabinogalactans and the reactions that can occur upon roasting, long term isothermal exposures, up to 3h, were performed at 160, 180, 200, 220, and 240 °C. The resultant products were analysed according to the sugars and linkage composition and also by electrospray mass spectrometry. Galactomannans did not loss mass at T ≤ 200 °C during exposures up to 3h whereas the arabinogalactans showed that thermal stability only for T ≤ 180 °C. This was in accordance with the estimated activation energies of their thermal decomposition of 138 kJ/mol and 94 kJ/mol, respectively. The roasting of galactomannans promoted the formation of new glycosidic linkages, with occurrence of 2-, 6-, 2,3-, 2,6-, 3,6-, 2,3,6-, 3,4,6-linked mannose residues, 3,4,6-linked galactose residues, and terminally-linked glucose residues, observed by methylation analysis. Depolymerisation and formation of anhydrohexose residues at the reducing end and mannose-glucose isomerisation were also observed. The roasting of galactomannans at 200 °C promoted their solubility in water upon alkali extraction and neutralisation. PMID:24299772

  9. Flexible all-carbon photovoltaics with improved thermal stability

    NASA Astrophysics Data System (ADS)

    Tang, Chun; Ishihara, Hidetaka; Sodhi, Jaskiranjeet; Chen, Yen-Chang; Siordia, Andrew; Martini, Ashlie; Tung, Vincent C.

    2015-04-01

    The structurally robust nature of nanocarbon allotropes, e.g., semiconducting single-walled carbon nanotubes (SWCNTs) and C60s, makes them tantalizing candidates for thermally stable and mechanically flexible photovoltaic applications. However, C60s rapidly dissociate away from the basal of SWCNTs under thermal stimuli as a result of weak intermolecular forces that "lock up" the binary assemblies. Here, we explore use of graphene nanoribbons (GNRs) as geometrically tailored protecting layers to suppress the unwanted dissociation of C60s. The underlying mechanisms are explained using a combination of molecular dynamics simulations and transition state theory, revealing the temperature dependent disassociation of C60s from the SWCNT basal plane. Our strategy provides fundamental guidelines for integrating all-carbon based nano-p/n junctions with optimized structural and thermal stability. External quantum efficiency and output current-voltage characteristics are used to experimentally quantify the effectiveness of GNR membranes under high temperature annealing. Further, the resulting C60:SWCNT:GNR ternary composites display excellent mechanical stability, even after iterative bending tests.

  10. Thermal stability, optical property, and morphology of flexible organoclay films.

    PubMed

    Shin, Jieun; Chang, Jin-Hae

    2011-07-01

    Novel organo-saponite (organo-SPT) films with excellent thermal stability and optical property were synthesized by solution casting. Na ion-exchanged saponite (pristine SPT), hexadecylammonium ion-exchanged SPT (C16-SPT), hexadecyltriphenyl phosphonium ion-exchanged SPT (C16PPh3-SPT), and tetraphenyl phosphonium ion-exchanged SPT (PPh4-SPT) were used to prepare clay films. We examined the relationship between the structures and properties of the various SPT films. SPT films were examined by means of wide-angle X-ray diffraction (XRD), electronic microscopy (FE-SEM), thermogravimetric analysis (TGA), ultraviolet-visible (UV-vis.) spectrometer. On the basis of these analyses, we sought to improve both the thermal stability and the optical properties. Clay films composed of C16PPh3-SPT and PPh4-SPT were found to be more thermally stable than those composed of pristine SPT or C16-SPT. On the other hand, the transmittance was not significantly affected by variations in the organo-SPT material. PMID:22121657

  11. Layered and intercalated hydrotalcite-like materials as thermal stabilizers in PVC resin

    NASA Astrophysics Data System (ADS)

    Lin, Yanjun; Wang, Jianrong; Evans, David G.; Li, Dianqing

    2006-05-01

    In the light of the accepted mechanism of thermal stabilization of PVC by layered double hydroxides (LDHs), the layer cations and interlayer counterions in LDHs were tailored to give MgZnAl-CO3-LDH and MgZnAl-maleate-LDH. These materials were characterized by XRD, FT-IR, and TG DTA. The thermal stability of PVC composites containing different LDH additives was tested in sheets having a thickness of about 1 mm. The results showed that compared with MgAl-CO3-LDH, MgZnAl-CO3-LDH enhances the thermal stability of PVC in terms of both long-term stability and early coloring. After intercalation of maleate in the LDH by reaction of maleic acid with the MgZnAl-CO3-LDH precursor, the interlayer distance increases from 0.75 to 1.11 nm. Since Cl- promotes the autocatalytic dehydrochlorination of PVC, which is responsible for its degradation, an increased interlayer distance should facilitate entry of Cl- into the interlayer galleries and inhibit the decomposition of PVC. In addition, maleic acid has a conjugated C=C double bond which can react with double bond formed in the dehydrochlorination of PVC and thus further inhibit the autocatalytic degradation reaction. The results show that the early coloring of PVC is markedly improved and the long-term stability slightly reduced by addition of the MgZnAl-maleate-LDH.

  12. The work function engineering and thermal stability of novel metal gate electrodes for advanced CMOS devices

    NASA Astrophysics Data System (ADS)

    Zhao, Penghui

    depleted silicon on insulator (FDSOI) NMOS or PMOS with thermal stability up to 1000°C. Compared to MoXSi YNZ (X=46% Y=12%, Z=42%) gates on HfO2, the gates on FlfSiO provides better thermal stability up to 1000°C with no degradation of work function (˜4.4 eV), EOT, fixed charge density, or gate leakage current. These results suggest that MoSiN films with optimized compositions could be promising metal gate candidates for advanced CMOS devices. The thermal stability of FUSI NiSi metal gate electrodes on both SiON and Hf-based high-kappadielectrics after typical back-end of line (BEOL) thermal annealing has been also investigated. It has been found that the thermal stability of FUSI NiSi metal gates is strongly dependent on the dopants and annealing ambient. The dependence of nickel diffusion on the dielectric thickness and dopants into the silicon channel is discussed in detail. It was found that 5 nm gate dielectric layers are sufficient to inhibit any detectable nickel diffusion from the FUSI NiSi metal gates into the silicon channel.

  13. High-thermal-stability white light-emitting-diodes employing broadband glass phosphor

    NASA Astrophysics Data System (ADS)

    Cheng, Wood-Hi; Chen, Li-Yin; Cheng, Wei-Chih

    2014-09-01

    We report the high-thermal-stability white light-emitting-diodes (WLEDs) employing broadband glass phosphors. The broadband glass phosphors were fabricated by sintering the mixture of multiple phosphors and SiO2-based glass (SiO2-Na2O-Al2O3-CaO) at 680°. Y3Al5O12:Ce 3+ (YAG), Lu3Al5O12:Ce3+ (LuAG), and CaAlSiN3: Eu2+ (Nitride) phosphor crystals were chosen as the yellow, green, and red emitters of the glass phosphors, respectively. The results showed that the broadband phosphors exhibited high quantum-yield of 54% and color-rendering index (CRI) of 90. The lumen degradation, chromaticity shift, and transmittance loss in the broadband glass-based WLEDs under thermal aging temperature at 150, 250, 350 and 450° were also presented and compared with those of silicone-based WLEDs under thermal aging temperature at 150 and 250°. The results demonstrated that the broadband glass-based WLEDs exhibited better thermal stability in lumen degradation, chromaticity shift, and transmittance loss than the silicone-based WLEDs. The excellent thermal stability of the broadband glass-based WLEDs with high CRI is essentially beneficial to the applications for next-generation solid-state indoor lighting, especially in the area where high power and absolute reliability are required.

  14. Optical stabilization of Rb vapor density above thermal equilibrium

    NASA Astrophysics Data System (ADS)

    Burchianti, A.; Bogi, A.; Marinelli, C.; Mariotti, E.; Moi, L.

    2010-08-01

    We stabilize the Rb vapor density above its thermal equilibrium value in sealed glass cells, which are generally used in atomic physics experiments. The method relies on light-induced desorption of Rb atoms from dielectric surfaces. The process does not demand high light intensities so that LEDs or laser diodes can be used as desorbing sources. The experiments are carried out in Pyrex cells either coated with a polydimethylsiloxane film or containing a porous glass sample. Under illumination both the organic coating and the porous sample release a large amount of Rb atoms into the cell volume. We show that the Rb vapor density can be maintained to a preset value, using a desorbing light intensity controlled by a feedback signal given by the Rb absorption or fluorescence level. Moreover, we find that the stabilization technique does not depend on the microscopic mechanisms underlying photodesorption.

  15. Thermal Rossby waves in a rotating annulus. Their stability.

    PubMed

    Pino, D; Net, M; Sánchez, J; Mercader, I

    2001-05-01

    Nonlinear thermal convection in a fast rotating annulus about its axis, with slightly inclined ends, radial gravity and heating, is studied numerically for a fluid of Prandtl number sigma=0.7 and different values of the radius ratio and rotation rate. The properties of the rotating waves that appear after the Hopf bifurcation of the conductive state are analyzed. Near the critical Rayleigh number, different types of solutions with the same wave number coexist, and they are classified as a function of their connection with the two types of modes identified in the linear analysis for this Prandtl number. For different rotation rates, the stability of the primary solutions as a function of the radius ratio is also studied. The shape of the stability regions and the type of dominant disturbances that limit these regions are very sensitive to the proximity to the value of the radius ratio for which the type of dominant mode changes. PMID:11415011

  16. Study of thermal stability of Cu2Se thermoelectric material

    NASA Astrophysics Data System (ADS)

    Bohra, Anil; Bhatt, Ranu; Bhattacharya, Shovit; Basu, Ranita; Ahmad, Sajid; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    Sustainability of thermoelectric parameter in operating temperature range is a key consideration factor for fabricating thermoelectric generator or cooler. In present work, we have studied the stability of thermoelectric parameter of Cu2Se within the temperature range of 50-800°C. Temperature dependent Seebeck coefficients and electrical resistivity measurement are performed under three continuous thermal cycles. X-ray diffraction pattern shows the presence of mixed cubic-monoclinic Cu2Se phase in bare pellet which transforms to pure α-Cu2Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed in EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu2Se phase.

  17. Thermal Stability of Distillate Hydrocarbon Fuels. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Reddy, Kishenkumar Tadisina; Cernansky, Nicholas P.

    1987-01-01

    Thermal stability of fuels is expected to become a severe problem in the future due to the anticipated use of broadened specification and alternative fuels. Future fuels will have higher contents of heteroatomic species which are reactive constituents and are known to influence fuel degradation. To study the degradation chemistry of selected model fuels, n-dodecane and n-dodecane plus heteroatoms were aerated by bubbling air through the fuels amd stressed on a modified Jet Fuel Thermal Oxidation Tester facility operating at heater tube temperatures between 200 to 400 C. The resulting samples were fractionated to concentrate the soluble products and then analyzed using gas chromatographic and mass spectrometric techniques to quantify and identify the stable reaction intermediate and product specifically. Heteroatom addition showed that the major soluble products were always the same, with and without heteroatoms, but their distributions varied considerably.

  18. On the thermal stability of radiation-dominated accretion disks

    SciTech Connect

    Jiang, Yan-Fei; Stone, James M.; Davis, Shane W.

    2013-11-20

    We study the long-term thermal stability of radiation-dominated disks in which the vertical structure is determined self-consistently by the balance of heating due to the dissipation of MHD turbulence driven by magneto-rotational instability (MRI) and cooling due to radiation emitted at the photosphere. The calculations adopt the local shearing box approximation and utilize the recently developed radiation transfer module in the Athena MHD code based on a variable Eddington tensor rather than an assumed local closure. After saturation of the MRI, in many cases the disk maintains a steady vertical structure for many thermal times. However, in every case in which the box size in the horizontal directions are at least one pressure scale height, fluctuations associated with MRI turbulence and dynamo action in the disk eventually trigger a thermal runaway that causes the disk to either expand or contract until the calculation must be terminated. During runaway, the dependence of the heating and cooling rates on total pressure satisfy the simplest criterion for classical thermal instability. We identify several physical reasons why the thermal runaway observed in our simulations differ from the standard α disk model; for example, the advection of radiation contributes a non-negligible fraction to the vertical energy flux at the largest radiation pressure, most of the dissipation does not happen in the disk mid-plane, and the change of dissipation scale height with mid-plane pressure is slower than the change of density scale height. We discuss how and why our results differ from those published previously. Such thermal runaway behavior might have important implications for interpreting temporal variability in observed systems, but fully global simulations are required to study the saturated state before detailed predictions can be made.

  19. Ionoluminscence of partially-stabilized zirconia for thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Rebollo, N. R.; Ruvalcaba-Sil, J. L.; Miranda, J.

    2007-08-01

    Ionoluminescence is explored as an alternative technique to study the high temperature phase stability of zirconia-based oxides. The evolution of an initially metastable single tetragonal phase towards de-stabilization is investigated for three single-doped zirconia compositions with Y, Yb and Gd. The differences in de-stabilization paths are identified using X-ray diffraction and ionoluminescence; elemental analysis is also performed using particle-induced X-ray emission. X-ray diffraction studies reveal a different scenario for each of the compositions selected; the differences are strongly influenced by the thermodynamic driving forces associated to the fluorite-to-tetragonal displacive transformation. Ionoluminescence studies indicate a significant increment on the signal intensity for de-stabilized samples, relative to previous annealing stages. There are also more subtle differences in the luminescent response from the samples at intermediate annealing stages also related to phase changes. This study provides a basis to characterize phase evolution in single-doped zirconia compositions for thermal insulation applications using luminescence.

  20. Thermal Stabilization in a High Vacuum Cryogenic Optical System

    NASA Astrophysics Data System (ADS)

    Wallace, Rosa; Cripe, Jonathan; Corbitt, Thomas

    2016-03-01

    The existing technology for gravitational wave detection is limited in part by quantum noise. In our tabletop experiments, we are attempting to lower the noise floor to the quantum limit through the use of a seismically isolated cryogenic high vacuum environment, with the intention of exploring different methods to reduce quantum noise. In the development phase of this environment, we have implemented a customized strategy of ultraviolet irradiation combined with cryogenically cooled radiation shielding to reduce the impact of water vapor and blackbody radiation on the thermal stability of the cryogenic micro-components. Supported by National Science Foundation REU Site #1262890 and CAREER Award #1150531.

  1. Substituted Cyclohexene Endcaps for Polymers with Thermal-Oxidative Stability

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This invention relates to polyimides having improved thermal-oxidative stability, to the process of preparing said polyimides, and the use of polyimide prepolymers in the preparation of prepregs and composites. The polyimides are particularly usefull in the preparation of fiber-reinforced, high-temperature composites for use in various engine parts including inlets, fan ducts, exit flaps and other parts of high speed aircraft. The polyimides are derived from the polymerization of effective amounts of at least one tetracarboxylic dianhydride, at least one polyamine and a novel dicarboxylic endcap having the formula presented.

  2. Chemically Locked Bicelles with High Thermal and Kinetic Stability.

    PubMed

    Matsui, Ryoichi; Ohtani, Masataka; Yamada, Kuniyo; Hikima, Takaaki; Takata, Masaki; Nakamura, Takashi; Koshino, Hiroyuki; Ishida, Yasuhiro; Aida, Takuzo

    2015-11-01

    In situ polymerization of a bicellar mixture composed of a phospholipid and polymerizable surfactants afforded unprecedented stable bicelles. The polymerized composite showed an aligned phase over a wide thermal range (25 to >90 °C) with excellent (2)H quadrupole splitting of the solvent signal, thus implying versatility as an alignment medium for NMR studies. Crosslinking of the surfactants also brought favorable effects on the kinetic stability and alignment morphology of the bicelles. This system could thus offer a new class of scaffolds for biomembrane models. PMID:26373898

  3. Si-substituted hydroxyapatite nanopowders: Synthesis, thermal stability and sinterability

    SciTech Connect

    Bianco, Alessandra Cacciotti, Ilaria; Lombardi, Mariangela Montanaro, Laura

    2009-02-04

    Synthetic hydroxyapatites incorporating small amounts of Si have shown improved biological performances in terms of enhanced bone apposition, bone in-growth and cell-mediated degradation. This paper reports a systematic investigation on Si-substituted hydroxyapatite (Si 1.40 wt%) nanopowders produced following two different conventional wet methodologies: (a) precipitation of Ca(NO{sub 3}){sub 2}.4H{sub 2}O and (b) titration of Ca(OH){sub 2}. The influence of the synthesis process on composition, thermal behaviour and sinterability of the resulting nanopowders is studied. Samples were characterised by electron microscopy, induced coupled plasma atomic emission spectroscopy, thermal analysis, infrared spectroscopy, N{sub 2} adsorption measurements, X-ray diffraction and dilatometry. Semicrystalline Si-substituted hydroxyapatite powders made up of needle-like nanoparticles were obtained, the specific surface area ranged between 84 and 110 m{sup 2}/g. Pure and Si-substituted hydroxyapatite nanopowders derived from Ca(NO{sub 3}){sub 2}.4H{sub 2}O decomposed around 1000 deg. C. Si-substituted hydroxyapatite nanopowders obtained from Ca(OH){sub 2} were thermally stable up to 1200 deg. C and showed a distinct decreased thermal stability with respect to the homologous pure sample. Si-substituted hydroxyapatites exhibited higher sintering temperature and increased total shrinkage with respect to pure powders. Nanostructured dense ceramics were obtained by sintering at 1100 deg. C Si-substituted hydroxyapatites derived from Ca(OH){sub 2}.

  4. Organic transistors with high thermal stability for medical applications

    NASA Astrophysics Data System (ADS)

    Kuribara, Kazunori; Wang, He; Uchiyama, Naoya; Fukuda, Kenjiro; Yokota, Tomoyuki; Zschieschang, Ute; Jaye, Cherno; Fischer, Daniel; Klauk, Hagen; Yamamoto, Tatsuya; Takimiya, Kazuo; Ikeda, Masaaki; Kuwabara, Hirokazu; Sekitani, Tsuyoshi; Loo, Yueh-Lin; Someya, Takao

    2012-03-01

    The excellent mechanical flexibility of organic electronic devices is expected to open up a range of new application opportunities in electronics, such as flexible displays, robotic sensors, and biological and medical electronic applications. However, one of the major remaining issues for organic devices is their instability, especially their thermal instability, because low melting temperatures and large thermal expansion coefficients of organic materials cause thermal degradation. Here we demonstrate the fabrication of flexible thin-film transistors with excellent thermal stability and their viability for biomedical sterilization processes. The organic thin-film transistors comprise a high-mobility organic semiconductor, dinaphtho[2,3-b:2‧,3‧-f]thieno[3,2-b]thiophene, and thin gate dielectrics comprising a 2-nm-thick self-assembled monolayer and a 4-nm-thick aluminium oxide layer. The transistors exhibit a mobility of 1.2 cm2 V-1s-1 within a 2 V operation and are stable even after exposure to conditions typically used for medical sterilization.

  5. Radiation and Thermal Stability of Murataite Ceramics Nuclear Waste Forms

    NASA Astrophysics Data System (ADS)

    Lian, J.; Yudintsev, S. V.; Stefanovsky, S. V.

    2006-05-01

    The wide range of complex nuclear wastes requires a variety of robust hosts for long-term storage during disposal. Wastes with high actinide and iron concentrations have generated intense interest in murataite ceramics as a candidate waste form due to its four distinct cation sites as well as cation vacancies. Critical to this application is the radiation stability of the waste host. We have determined both the radiation and thermal stabilities of murataite ceramics using in situ observations in a transmission electron microscope during ion bombardment at the Electron Microscopy Center at Argonne National Laboratory. A central issue for structural stability is radiation damage-induced crystalline-to-amorphous transformation that may result in macroscopic swelling, cracking and phase decomposition. Such a response would lead to a significant change in chemical durability and release of incorporated radionuclides. We found that, murataite ceramics are susceptible to ion beam induce ordered-disordered transition and amorphization. The ion dose required for amorphization was determined as a function of temperature and the degree of initial structural disorder. The upper temperature limit for amorphization of murataites was determined to be in the range of 860 K to 1060 K for 1 MeV Kr2+ ion irradiation. Decrease of the susceptibility to irradiation induced amorphization for disordered murataite, suggests that the amorphization susceptibility depends, in part, on the initial degree of intrinsic disorder prior to irradiation. The thermal stability of murataite polytypes was studied by in-situ TEM observation. Phase decomposition with the precipitation of Fe-rich nanocrystals was induced in the murataite structure. The phase decomposition and nanocrystal formation have no significant effects on the radiation resistance of murataite ceramics used as potential host phases for the immobilization of actinides.

  6. Ultrafast thermal plasma physical vapor deposition of yttria-stabilized zirconia for novel thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Huang, Heji; Eguchi, Keisuke; Kambara, Makoto; Yoshida, Toyonobu

    2006-03-01

    This research aims to develop advanced thermal plasma spraying technology for the next-generation thermal barrier coatings (TBCs) with a high power hybrid plasma spraying system. By using thermal plasma physical vapor deposition (TP-PVD), various functional structured yttria-stabilized zirconia (YSZ) coatings were deposited. Parameters, such as powder feeding rate, hydrogen gas concentration, and total mass flow rate of the plasma gas, were optimized, and their influences on the evaporation of YSZ powder were investigated. Ultrafast deposition of a thick coating was achieved at a rate of over 150 μm/min. The deposited porous coating has a low thermal conductivity of 0.7W/mK and the dense coating with interlaced t' domains possesses a high nanohardness of 27.85 GPa and a high reflectance. These characteristics show that the TP-PVD technique is a very valuable process for manufacturing novel TBCs.

  7. Antioxidant-Based Phase-Change Thermal Interface Materials with High Thermal Stability

    NASA Astrophysics Data System (ADS)

    Aoyagi, Yasuhiro; Chung, D. D. L.

    2008-04-01

    This work provides phase-change thermal interface materials (TIMs) with high thermal stability and high heat of fusion. They are based on antioxidants mainly in the form of hydrocarbons with linear segments. The thermal stability is superior to paraffin wax and four commercial phase-change materials (PCMs). The use of 98.0 wt.% thiopropionate antioxidant (SUMILIZER TP-D) with 2.0 wt.% sterically half-hindered phenolic antioxidant (GA80) as the matrix and the use of 16 vol.% boron nitride particles as the solid component give a PCM with a 100°C lifetime indicator of 5.3 years, in contrast to 0.95 year or less for the commercial PCMs. The heat of fusion is much higher than those of commercial PCMs; the values for antioxidants with nonbranched molecular structures exceed that of wax; the value for one with a branched structure is slightly below that of wax. The phase-change properties are degraded by heating at 150°C much less than those of the commercial PCMs. The stability of the heat of fusion upon phase-change cycling is also superior. The viscosity is essentially unaffected by heating at 150°C. Commercial PCMs give slightly lower values of the thermal contact conductance for the case of rough (12 μm) mating surfaces, in spite of the lower values of the bond-line thickness.

  8. Thermal stability of magnetron and ion beam sputtered top and bottom spin-valve films

    SciTech Connect

    Mao, Ming; Cerjan, Charlie; Hung, Stephanie; Miloslavsky, Lena; Chien, Chester; Sant, Sudhi

    2001-06-01

    The thermal stability of top and bottom IrMn exchange-biased spin-valve films prepared by ion beam deposition (IBD) and magnetron sputtering physical vapor deposition (PVD) is compared. These films exhibit identical temperature dependence for the exchange bias field H{sub ex}, with a blocking temperature of T{sub B}=250{degree}C, that is independent of preparation technique. Isothermal annealing at temperatures below T{sub B} led to a ln(t) dependent degradation in H{sub ex}, suggesting a thermal activation process. The high crystallographic quality of the IBD films leads to a superior stability compared to PVD films. Top spin-valve films are also found to be more stable than bottom spin-valve films. {copyright} 2001 American Institute of Physics.

  9. Thermal stability of magnetron and ion beam sputtered top and bottom spin-valve films

    NASA Astrophysics Data System (ADS)

    Mao, Ming; Cerjan, Charlie; Hung, Stephanie; Miloslavsky, Lena; Chien, Chester; Sant, Sudhi

    2001-06-01

    The thermal stability of top and bottom IrMn exchange-biased spin-valve films prepared by ion beam deposition (IBD) and magnetron sputtering physical vapor deposition (PVD) is compared. These films exhibit identical temperature dependence for the exchange bias field Hex, with a blocking temperature of TB=250 °C, that is independent of preparation technique. Isothermal annealing at temperatures below TB led to a ln(t) dependent degradation in Hex, suggesting a thermal activation process. The high crystallographic quality of the IBD films leads to a superior stability compared to PVD films. Top spin-valve films are also found to be more stable than bottom spin-valve films.

  10. Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet and magnesium oxide.

  11. Thermal-Mechanical Stability of Single Crystal Oxide Refractive Concentrators for High-Temperature Solar Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Single crystal oxides such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO) and sapphire (Al2O3) are candidate refractive secondary concentrator materials for high temperature solar propulsion applications. However, thermo-mechanical reliability of these components in severe thermal environments during the space mission sun/shade transition is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions, and thus provide vital information for the component design. In this paper, a controlled heat flux thermal shock test approach is established for the single crystal oxide materials using a 3.0 kW continuous wave CO2 laser, with a wavelength 10.6 micron. Thermal fracture behavior and failure mechanisms of these oxide materials are investigated and critical temperature gradients are determined under various temperature and heating conditions. The test results show that single crystal sapphire is able to sustain the highest temperature gradient and heating-cooling rate, and thus exhibit the best thermal shock resistance, as compared to the yttria-stabilized zirconia, yttrium aluminum garnet, and magnesium oxide.

  12. On the thermal stability of a radiating plasma subject to nonlocal thermal conduction. I - Linear analysis

    NASA Technical Reports Server (NTRS)

    Chun, E.; Rosner, R.

    1993-01-01

    We study the linear stability of an optically thin uniform radiating plasma subject to nonlocal heat transport. We derive the dispersion relation appropriate to this problem, and the marginal wavenumbers for instability. Our analysis indicates that nonlocal heat transport acts to reduce the stabilizing influence of thermal conduction, and that there are critical values for the electron mean free path such that the plasma is always unstable. Our results may be applied to a number of astrophysical plasmas, one such example being the halos of clusters of galaxies.

  13. Mathematical model of thermal shields for long-term stability optical resonators.

    PubMed

    Sanjuan, Josep; Gürlebeck, Norman; Braxmaier, Claus

    2015-07-13

    Modern experiments aiming at tests of fundamental physics, like measuring gravitational waves or testing Lorentz Invariance with unprecedented accuracy, require thermal environments that are highly stable over long times. To achieve such a stability, the experiment including typically an optical resonator is nested in a thermal enclosure, which passively attenuates external temperature fluctuations to acceptable levels. These thermal shields are usually designed using tedious numerical simulations or with simple analytical models. In this paper, we propose an accurate analytical method to estimate the performance of passive thermal shields in the frequency domain, which allows for fast evaluation and optimization. The model analysis has also unveiled interesting properties of the shields, such as dips in the transfer function for some frequencies under certain combinations of materials and geometries. We validate the results by comparing them to numerical simulations performed with commercial software based on finite element methods. PMID:26191850

  14. Factors affecting the microstructural stability and durability of thermal barrier coatings fabricated by air plasma spraying

    SciTech Connect

    Helminiak, M A; Yanar, N M; Pettit, F S; Taylor, T A; Meier, G H

    2012-10-01

    The high-temperature behavior of high-purity, low-density (HP-LD) air plasma sprayed (APS) thermal barrier coatings (TBCs) with NiCoCrAlY bond coats deposited by argon-shrouded plasma spraying is described. The high purity yttria-stabilized zirconia resulted in top coats which are highly resistant to sintering and transformation from the metastable tetragonal phase to the equilibrium mixture of monoclinic and cubic phases. The thermal conductivity of the as-processed TBC is low but increases during high temperature exposure even before densification occurs. The porous topcoat microstructure also resulted in good spallation resistance during thermal cycling. The actual failure mechanisms of the APS coatings were found to depend on topcoat thickness, topcoat density, and the thermal cycle frequency. The failure mechanisms are described and the durability of the HP-LD coatings is compared with that of state-of-the-art electron beam physical vapor deposition TBCs.

  15. Thermal and mechanical stability of nanograined FCC metals

    NASA Astrophysics Data System (ADS)

    Hattar, Khalid Mikhiel

    The mechanisms governing and factors controlling the thermal and mechanical stability of nanograined free-standing face-centered cubic thin films were investigated through in situ transmission electron microscopy annealing and straining experiments. A variety of sample preparation techniques were developed to investigate the active mechanisms. The results obtained from the select face-centered cubic metals studied were used to develop a general understanding of face-centered cubic metals with microstructure limited to the nanometer scale. The films were analyzed, both prior to and following the in situ transmission electron microscopy experiments, via a range of analytical techniques in order to characterize chemical and microstructural details. The mechanisms observed were compared to the pertinent theories and models. In situ transmission electron microscopy heating and annealing experiments were performed on free-standing pulsed-laser deposited Au, Cu, and Ni thin films. The grain growth of pulsed-laser deposited Ni films was studied and the growth rate was found to be a function of time, temperature, film thickness, and surface abnormalities. The grain growth was classified as abnormal in nature resulting in a bimodal grain size distribution. Abnormal grain growth was found to increase with an increase in film thickness. This increase was attributed to the presence of a higher density of preferred nanograins for abnormal grain growth in thicker films, although the mechanisms that induce the rapid growth were not determined. A higher percentage of abnormal large grains were found along ridges templated from the substrate, and in regions with extensive electron beam exposure. Post-annealing analysis of pulsed-laser deposited Ni films revealed an unexpected myriad of microstructural defects including dislocations, twins, stacking faults, dislocation loops, and stacking-fault tetrahedra, as well as a metastable hexagonal closed-packed phase. The production of these

  16. Pressure effects on the thermal stability of silicon carbide fibers

    NASA Technical Reports Server (NTRS)

    Jaskowiak, Martha H.; Dicarlo, James A.

    1989-01-01

    Commercially available polymer derived SiC fibers were treated at temperatures from 1000 to 2200 C in vacuum and argon gas pressure of 1 and 1360 atm. Effects of gas pressure on the thermal stability of the fibers were determined through property comparison between the pressure treated fibers and vacuum treated fibers. Investigation of the thermal stability included studies of the fiber microstructure, weight loss, grain growth, and tensile strength. The 1360 atm argon gas treatment was found to shift the onset of fiber weight loss from 1200 to above 1500 C. Grain growth and tensile strength degradation were correlated with weight loss and were thus also inhibited by high pressure treatments. Additional heat treatment in 1 atm argon of the fibers initially treated at 1360 atm argon caused further weight loss and tensile strength degradation, thus indicating that high pressure inert gas conditions would be effective only in delaying fiber strength degradation. However, if the high gas pressure could be maintained throughout composite fabrication, then the composites could be processed at higher temperatures.

  17. Speciation of copper in the thermally stabilized slag

    NASA Astrophysics Data System (ADS)

    Tuan, Y.-J.; Paul Wang, H.; Chang, J.-E.; Chao, C.-C.; Tsai, C.-K.

    2010-07-01

    The Taiwan universities laboratory hazardous wastes have been treated by incineration at the temperature range of 1173-1273 K. By X-ray absorption near edge structure (XANES) spectroscopy, mainly CuO and CuSO 4 are found in the incineration bottom and fly ashes. The incineration fly ash can be stabilized thermally at 1773 K in the plasma melting reaction chamber (integrated with the incinerator), and converted to slag. The concentration of leachable copper in the slag is reduced significantly mainly due to the fact that copper is encapsulated in the SiO 2 matrix. In addition, the refined extended X-ray adsorption fine structure (EXAFS) spectra of copper also indicate formation of the Cu-O-Si species in the slag as the bond distances of 1.95 Å for Cu-O and 2.67 Å for O-Si are observed. This work exemplifies utilization of the synchrotron X-ray absorption spectroscopy to facilitate the thermal stabilization treatments of the fly ash hazardous waste using the plasma melting method.

  18. The stability of bFGF against thermal denaturation.

    PubMed

    Vemuri, S; Beylin, I; Sluzky, V; Stratton, P; Eberlein, G; Wang, Y J

    1994-06-01

    The influence of sulphated ligand and pH on thermal denaturation of basic fibroblast growth factor (bFGF) was investigated by differential scanning calorimetry (DSC), and verified by fluorescence spectrophotometry. Purity of bFGF before and after heat denaturation was assessed by SDS-PAGE analysis. In DSC studies the samples were heated to 95 degrees C. The midpoint of the temperature change in the thermogram was designated as Tm. Sulphated ligand experiments were undertaken in potassium phosphate (pH 6.5) and sodium acetate buffers. Control thermograms (with no ligand) showed a Tm at 59 degrees C in potassium phosphate buffer. Higher Tm values were noted as sulphated ligand concentration was increased. Similarly when heparin was added, the Tm moved to a higher temperature. A ratio as low as 0.3:1 of heparin to bFGF, increased the Tm to 90 degrees C, which is a 31 degrees C shift in Tm. The effect of pH on thermal denaturation of bFGF was studied in a citrate-phosphate-borate buffer system. A shift in Tm from 46 to 65 degrees C was observed as the pH is changed from 4 to 8. Changes in protein conformation as a function of pH were monitored by fluorescence spectroscopy. It was found that a pH range from 5 to 9 is optimal for the stability of bFGF formulations. In a stability study it was noted that heparin protected bFGF from thermal denaturation only at high temperature. PMID:7932043

  19. Thermal stability of sputtered intermetallic Al-Au coatings

    SciTech Connect

    Moser, M.; Mayrhofer, P. H.; Ross, I. M.; Rainforth, W. M.

    2007-09-15

    Recently, the authors have shown that single-phase Al{sub 2}Au coatings, prepared by unbalanced magnetron sputtering, exhibit a dense columnar structure and highest hardness and indentation moduli of 8 and 144 GPa, respectively, within the Al-Au films investigated. This study focuses on the thermal stability of Al{sub 2}Au with respect to films containing more Al and Au having Al/Au at. % ratios of 4.32 and 1.85, respectively. Single-phase Al{sub 2}Au has the highest onset temperature for recovery of 475 deg. C and recrystallization of 575 deg. C. Upon annealing Au- and Al-rich films, their stresses deviate from the linear thermoelastic behavior at temperatures (T) above 200 and 450 deg. C, respectively, due to pores and metallic phases present. Metastable Au within the as-deposited Au-rich film is consumed by the growing intermetallic AlAu and AlAu{sub 2} phases at T{>=}450 deg. C, which themselves melt at {approx}625 deg. C. Due to nanometer scale segregations of Al, encapsulated by Al{sub 2}Au in Al-rich coatings, their melting point is reduced by {approx}85 deg. C to 575 deg. C. Dynamic thermal analyses up to 1100 deg. C in synthetic air reveal the single-phase Al{sub 2}Au films with a superior thermal stability and only negligible oxidation. At 750 deg. C, the mass gain is {approx}1.5 mg/cm{sup 2} after 50 h isothermal exposure. Based on the investigations, the authors can conclude that single-phase intermetallic Al{sub 2}Au films have a high potential for oxidation protection of sensitive materials.

  20. Thermal stability of matrix protein from Newcastle disease virus.

    PubMed

    Morán, Irene Sánchez; Cuadrado-Castano, Sara; Barroso, Isabel Muñoz; Kostetsky, Eduard Ya; Zhadan, Galina; Gómez, Javier; Shnyrov, Valery L; Villar, Enrique

    2013-10-01

    The thermal stability of the matrix protein (M protein) of Newcastle disease virus (NDV) has been investigated using high-sensitivity differential scanning calorimetry (DSC) at pH 7.4. The thermal folding/unfolding of M protein at this pH value is a reversible process involving a highly cooperative transition between folded and unfolded monomers with a transition temperature (Tm) of 63 °C, an unfolding enthalpy, ΔH(Tm), of 340 kcal mol(-1), and the difference in heat capacity between the native and denatured states of the protein, ΔCp, of 5.1 kcal K(-1) mol(-1). The heat capacity of the native state of the protein is in good agreement with the values calculated using a structure-based parameterization, whereas the calculated values for the hypothetical fully-unfolded state of the protein is higher than those determined experimentally. This difference between the heat capacity of denatured M protein and the heat capacity expected for an unstructured polypeptide of the same sequence, together with the data derived from the heat-induced changes in the steady-state fluorescence of the protein, indicates that the polypeptide chain maintains a significant amount of residual structure after thermal denaturation. PMID:23916643

  1. Transient thermal conductivity and colloidal stability measurements of nanofluids by using the 3omega method.

    PubMed

    Oh, Dong-Wook; Kwon, Ohmyoung; Lee, Joon Sik

    2008-10-01

    Nanofluid is a mixture of nanoscale particles of metal, metal oxide or carbon nanotube and heat transfer fluids such as water and ethylene glycol. This work presents the application of the 3-omega (3omega) method for measuring the colloidal stability and the transient thermal conductivity of multi-wall carbon nanotube (MWCNT), Al2O3 and TiO2 nanoparticles suspended in water or ethylene glycol. The microfabricated 3omega device is verified by comparing the measured thermal conductivities of pure fluids with the table values. After the validation, the transient thermal responses of the nanofluids are measured to evaluate the colloidal stability. All of Al2O3 nanofluid samples show a clear sign of sedimentation while the acid-treated MWCNT (tMWCNT) nanofluid and a couple of TiO2 nanofluids with pH control or surfactant addition are found to have excellent colloidal stability. The thermal conductivities of tMWCNT nanofluids in the de-ionized water and ethylene glycol are measured, which are found to be in good agreement with previous data. PMID:19198364

  2. Evaluation of Thermal Stability of Organic Electro-Optic Device by Using Thermally Stimulated Current.

    PubMed

    Ikemoto, Ryoma; Taguchi, Dai; Manaka, Takaaki; Iwamoto, Mitsumasa; Yamada, Toshiki; Otomo, Akira

    2016-04-01

    Thermally stimulated current (TSC) measurement was employed to study the thermal stability of electro-optic (EO) polymers, i.e., guest/host polymer DR1/PMMA and side-chain polymer PMMA-co-DR1. Here the isothermal relaxation test showed that the relaxation time τ (85 °C) of side-chain polymer PMMA-co-DR1 is longer than that of guest/host polymer DR1/PMMA. TSC peaks appeared symmetrically in proportion to the poling electric field Ep, indicating that DR1 molecules make a dominant contribution to dipolar depolarization. Thermal sampling (TS) method showed that the activation energy of the DR1/PMMA is around 1 eV, while that of the PMMA-co-DR1 is distributed >1 eV. Results suggested that side-chain polymer is preferable to the guest/host polymer in the thermal stability. TSC measurement is helpful as a conventional method for studying the life time of EO polymers in terms of dipolar motion. PMID:27451636

  3. Formation and thermal stability of amorphous Cu-Zr thin films deposited by coevaporation

    SciTech Connect

    Minemura, T.; van den Broek, J.J.; Daams, J.L.C.

    1988-05-01

    The formation and thermal stability of amorphous thin films have been characterized by comparing them with those of melt-spun ribbons. The various Cu/sub 1-//sub x/Zr/sub x/ thin films were deposited by coevaporation. The amorphous formation range and the crystallization behavior in the films were investigated with x-ray diffraction and differential scanning calorimetry. The amorphous thin films are formed in the composition range x = 0.20--0.75, which is wider than that found for the melt-spun ribbons. The crystallization temperature and the activation energy for crystallization are lower than those of the melt-spun ribbons, although the composition dependencies show tendencies similar to those of the ribbons. These differences in thermal stability between amorphous films and ribbons might be due to a lower degree of the short-range ordering in the films.

  4. Fabrication and thermal stability of Ni-P coated diamond powder using electroless plating

    NASA Astrophysics Data System (ADS)

    Dong, Ying-Hu; He, Xin-Bo; Ud-Din, Rafi; Guo, Cai-Yu; Xu, Liang; Huang, Yu-Ting; Qu, Xuan-Hui

    2011-08-01

    Ni-P coated diamond powder was fabricated successfully by using electroless plating. Effects of active solutions, plating time, reaction temperature, and the components of the plating bath on the Ni-P coating were investigated systematically. Moreover, a study on the thermal stability of Ni-P coated diamond under various atmospheres was performed. The results indicate that Pd atoms absorbed on the diamond surface as active sites can consequently enhance the deposition rate of Ni effectively. The optimized plating bath and reaction conditions improve both the plating speed and the coverage rate of Ni-P electroless plating on the diamond surface. Compared to the diamond substrate, the diamond coated with Ni-P films exhibits very high thermal stability and can be processed up to 900°C in air and 1300°C in protective atmosphere such as H2.

  5. Thermal unfolding of Apo and Holo Desulfovibrio desulfuricans flavodoxin: cofactor stabilizes folded and intermediate states.

    PubMed

    Muralidhara, B K; Wittung-Stafshede, Pernilla

    2004-10-12

    We here compare thermal unfolding of the apo and holo forms of Desulfovibrio desulfuricans flavodoxin, which noncovalently binds a flavin mononucleotide (FMN) cofactor. In the case of the apo form, fluorescence and far-UV circular dichroism (CD) detected transitions are reversible but do not overlap (T(m) of 50 and 60 degrees C, respectively, pH 7). The thermal transitions for the holo form follow the same pattern but occur at higher temperatures (T(m) of 60 and 67 degrees C for fluorescence and CD transitions, respectively, pH 7). The holoprotein transitions are also reversible and exhibit no protein concentration dependence (above 10 microM), indicating that the FMN remains bound to the polypeptide throughout. Global analysis shows that the thermal reactions for both apo and holo forms proceed via an equilibrium intermediate that has approximately 90% nativelike secondary structure and significant enthalpic stabilization relative to the unfolded states. Incubation of unfolded holoflavodoxin at high temperatures results in FMN dissociation. Rebinding of FMN at these conditions is nominal, and therefore, cooling of holoprotein heated to 95 degrees C follows the refolding pathway of the apo form. However, FMN readily rebinds to the apoprotein at lower temperatures. We conclude that (1) a three-state thermal unfolding behavior appears to be conserved among long- and short-chain, as well as apo and holo forms of, flavodoxins and (2) flavodoxin's thermal stability (in both native and intermediate states) is augmented by the presence of the FMN cofactor. PMID:15461458

  6. Comparative Study of the Thermal Conductivity of Solid Biomass Fuels

    PubMed Central

    2016-01-01

    The thermal conductivity of solid biomass fuels is useful information in the investigation of biomass combustion behavior and the development of modeling especially in the context of large scale power generation. There are little published data on the thermal conductivity of certain types of biomass such as wheat straw, miscanthus, and torrefied woods. Much published data on wood is in the context of bulk materials. A method for determining the thermal conductivities of small particles of biomass fuels has been developed using a custom built test apparatus. Fourteen different samples of various solid biomass fuel were processed to form a homogenized pellet for analysis. The thermal conductivities of the pelletized materials were determined and compared against each other and to existing data. PMID:27041819

  7. Thermal stability of CVD-SiC lightweight optics

    NASA Astrophysics Data System (ADS)

    Goela, Jitendra S.; Desai, Hemant D.; Taylor, Raymond L.; Olson, Steven E.

    1995-10-01

    The lightweight SiC mirrors that are fabricated by the CVD process at Morton Advanced Materials contain graphite core enclosed in the SiC backstructure. A finite element analysis of a lightweight SiC model mirror was performed to assess the effect of the graphite core on the thermal stability of the SiC mirror in the temperature range of 77 - 1623 K. The results indicate that for both no-slip (SiC deposit adhered to graphite core) and slip cases, the maximum stresses in the SiC mirror structure are significantly less than the flexural strength of SiC. Further, the maximum stress in graphite core is close to the tensile strength of graphite indicating that graphite core will probably fracture. Finally, the SiC faceplate figure distortion due to the presence of the graphite core is quite small, on the order of a few tens of nanometers.

  8. Stability of mixed time integration schemes for transient thermal analysis

    NASA Technical Reports Server (NTRS)

    Liu, W. K.; Lin, J. I.

    1982-01-01

    A current research topic in coupled-field problems is the development of effective transient algorithms that permit different time integration methods with different time steps to be used simultaneously in various regions of the problems. The implicit-explicit approach seems to be very successful in structural, fluid, and fluid-structure problems. This paper summarizes this research direction. A family of mixed time integration schemes, with the capabilities mentioned above, is also introduced for transient thermal analysis. A stability analysis and the computer implementation of this technique are also presented. In particular, it is shown that the mixed time implicit-explicit methods provide a natural framework for the further development of efficient, clean, modularized computer codes.

  9. Joule-Thomson cryogenic cooler with extremely high thermal stability

    NASA Technical Reports Server (NTRS)

    Bard, Steven; Wu, J. J.; Trimble, Curt

    1991-01-01

    An 80-K Joule-Thomson (J-T) cooling system designed for the Probe Infrared Laser Spectrometer (PIRLS) proposed for the Huygens Titan Probe of the Cassini Saturn orbiter mission is presented. The cryogenic cooling requirements of the PIRLS instrument are listed, and the cooler system design including details of a J-T cryostat, cold head, and dewar design is described along with the results of a thermal modeling effort and lab cooler performance testing. It is shown that by using active feedback temperature control of the cold head in combination with the self-regulating action of the J-T cryostat, a temperature stability of less than 0.1 mK/min is achieved by the cooler weighting 1.8 kg.

  10. Thermal stability of the polyheme cytochrome c3 superfamily.

    PubMed

    Florens, L; Bianco, P; Haladjian, J; Bruschi, M; Protasevich, I; Makarov, A

    1995-10-16

    The cytochrome c3 superfamily includes Desulfovibrio polyheme cytochromes c. We report the characteristic thermal stability parameters of the Desulfovibrio desulfuricans Norway (D.d.N.) cytochromes c3 (M(r) 13,000 and M(r) 26,000) and the Desulfovibrio vulgaris Hildenborough (D.v.H.) cytochrome c3 (M(r) 13,000) and high molecular mass cytochrome c (Hmc), as obtained with the help of electronic spectroscopy, voltammetric techniques and differential scanning calorimetry. The polyheme cytochromes are denatured over a wide range of temperatures: the D.v.H. cytochrome c3 is highly thermostable (Td = 121 degrees C) contrary to the D.d.N. protein (Td = 73 degrees C). The thermostability of the polyheme cytochromes is redox state dependent. The results are discussed in the light of the structural and functional relationships within the cytochrome c3 superfamily. PMID:7589483

  11. Thermal stability study of nitrogen functionalities in a graphene network

    NASA Astrophysics Data System (ADS)

    Kumar, Ajay; Ganguly, Abhijit; Papakonstantinou, Pagona

    2012-06-01

    Catalyst-free vertically aligned graphene nanoflakes possessing a large amount of high density edge planes were functionalized using nitrogen species in a low energy N+ ion bombardment process to achieve pyridinic, cyanide and nitrogen substitution in hexagonal graphitic coordinated units. The evolution of the electronic structure of the functionalized graphene nanoflakes over the temperature range 20-800 °C was investigated in situ, using high resolution x-ray photoemission spectroscopy. We demonstrate that low energy irradiation is a useful tool for achieving nitrogen doping levels up to 9.6 at.%. Pyridinic configurations are found to be predominant at room temperature, while at 800 °C graphitic nitrogen configurations become the dominant ones. The findings have helped to provide an understanding of the thermal stability of nitrogen functionalities in graphene, and offer prospects for controllable tuning of nitrogen doping in device applications.

  12. Synthesis and characterization of processable polyimides with enhanced thermal stability

    NASA Technical Reports Server (NTRS)

    Harris, Frank W.

    1987-01-01

    Many of the emerging applications of polymers on space vehicles require materials with outstanding thermal stability. These polymers must also be readily processable in order to facilitate their use. The syntheses and polymerization of a cardo dianhydride were investigated. This monomer was prepared via the reaction of N-methyl 4-nitrophthalimide with a cardo diol. Polyimides containing oxyalkylene linkages were studied. The effects of two additional structural modifications on the polymers' properties were investigated. The effects of carrying out the preparation of poly(amic acid)s under non-equilibrium conditions were examined. Approaches that were investigated included the in-situ neutralization of the generated amic acid and its in-situ esterification.

  13. Frequency stabilization of laser diodes in an aggressive thermal environment

    NASA Astrophysics Data System (ADS)

    Minch, J. R.; Walther, F. G.; Savage, S.; Plante, A.; Scalesse, V.

    2015-03-01

    Mobile free-space laser communication systems must reconcile the requirements of low size, weight, and power with the ability to both survive and operate in harsh thermal and mechanical environments. In order to minimize the aperture size and amplifier power requirements of such systems, communication links must exhibit performance near theoretical limits. Such performance requires laser transmitters and receiver filters and interferometers to maintain frequency accuracy to within a couple hundred MHz of the design frequency. We demonstrate an approach to achieving high frequency stability over wide temperature ranges by using conventional DFB lasers, tuned with TEC and current settings, referenced to an HCN molecular frequency standard. A HCN cell absorption line is scanned across the TEC set-point to adjust the DFB laser frequency. Once the center of the line is determined, the TEC set-point is offset as required to obtain frequency agility. To obtain large frequency offsets from an HCN absorption line, as well as continuous laser source operation, a second laser is offset from the reference laser and the resulting beat tone is detected in a photoreceiver and set to the desired offset using a digital frequency-locked loop. Using this arrangement we have demonstrated frequency accuracy and stability of better than 8 MHz RMS over an operational temperature range of 0ºC to 50º C, with operation within minutes following 8 hour soaks at -40º C and 70º C.

  14. Thermal stability of Mo/Au bilayers for TES applications

    NASA Astrophysics Data System (ADS)

    Parra-Borderías, María; Fernández-Martínez, Iván; Fàbrega, Lourdes; Camón, Agustín; Gil, Oscar; González-Arrabal, Raquel; Sesé, Javier; Costa-Krämer, José Luis; Warot-Fonrose, Bénédicte; Serin, Virginie; Briones, Fernando

    2012-09-01

    Mo/Au bilayers are among the most suitable materials to be used as transition-edge sensors (TES) in cryogenic microcalorimeters and bolometers, developed, among other fields, for space missions. For this purpose the thermal stability of TES at temperatures below 150 °C is a critical issue. We report on the dependence of functional properties (superconducting critical temperature, residual resistance and α) as well as on microstructure, chemical composition and interface quality for optimized high quality Mo/Au bilayers on annealing temperature and time. Data show that the functional properties of the bilayers remain stable at T < 150 °C, but changes in microstructure, interface quality and functional properties were observed for layers heated at T ≥ 200 °C. Microstructural and chemical composition data suggest that the measured changes in residual resistance ratio (RRR) and TC at T ≥ 200 °C are mainly due to an increase in the average Au grain size and to Au migration along the Mo grain boundaries at the Au/Mo interface. A way to stabilize the functional properties of the Mo/Au bilayers against temperature enhancements is proposed.

  15. Thermal stability of laser-produced iron nitrides

    NASA Astrophysics Data System (ADS)

    Han, M.; Carpene, E.; Landry, F.; Lieb, K.-P.; Schaaf, P.

    2001-04-01

    Laser nitriding is a very efficient method to improve the mechanical properties, surface hardness, corrosion, and wear resistance of iron and steel, with the advantages of a high nitrogen concentration, fast treatment, and accurate position control, and without any undesired heating effect on the substrate. However, the stability of laser-produced iron nitrides is still under investigation. This article reports investigations of the thermal stability of these iron nitrides upon annealing treatments, which were conducted both in vacuum and air. The phase and elemental composition of the nitride layers were deduced from conversion electron Mössbauer spectroscopy, resonant nuclear reaction analysis, and grazing incidence x-ray diffraction. The surface hardness was measured by the nanoindentation method. In laser-nitrided iron, two critical temperatures are found: at 523 K the predominant iron-nitride phase changes from the γ/ɛ to the γ' phase. When the temperature exceeds 773 K, all of the nitrogen has escaped from the surface layer. For annealing in air the nitrogen escapes completely already at 673 K, where a thick oxide layer has formed. Stainless steel proved to be more stable than iron, and even up to 973 K no new phases or oxides were produced, here, also, only at 973 K the nitrogen content decreased significantly. Therefore, laser-nitrided stainless steel is well suited for applications.

  16. Experimental study of thermal stability of thin nanowires.

    PubMed

    Gordon, Eugene B; Karabulin, Alexander V; Matyushenko, Vladimir I; Khodos, Igor I

    2015-03-19

    Thin (D < 10 nm) nanowires are in principle promising for their application as catalysts and as elements of nanocomputers and quantum devices. To perform these tasks, their structure and properties must be stable at least at standard conditions. Using our technique based on the capture of small particles to the core of quantized vortices in superfluid helium, we synthesized nanowires made of various metals and alloys and investigated their thermal stability. The indium nanowires (D = 8 nm) were shown to be stable when heated to 100 °C, i.e., almost to the melting point, whereas the silver nanowires (D = 5 nm) disintegrated into traces of individual nanoclusters at 300 K. The gold and platinum nanowires also decomposed at temperatures more than twice as low as the melting point. A model is proposed to explain the premature decay of thin nanowires by unfreezing of the surface-atom mobility in combination with the anomalous dependence of the surface tension on the nanowire radius. Methods for improving the stability limits of thin nanowires by saturation of their surface with immobilized atoms as well as by surface oxidation have been proposed and experimentally tested. PMID:25375969

  17. MODIS thermal emissive band calibration stability derived from surface targets

    NASA Astrophysics Data System (ADS)

    Wenny, B. N.; Xiong, X.; Dodd, J.

    2009-09-01

    The 16 MODIS Thermal Emissive Bands (TEB), with wavelengths covering from 3.7μm to 14.4μm, are calibrated using scan-by-scan observations of an on-orbit blackbody (BB). Select Earth surface targets can be used to track the long-term consistency, stability and relative bias between the two MODIS instruments currently in orbit. Measurements at Dome C, Antarctica have shown a relative bias of less than 0.01K over a 5 year period between Terra and Aqua MODIS Band 31 (11μm). Dome C surface temperatures are typically outside the MODIS BB calibration range. Sea surface temperature (SST) measurements from data buoys provide a useful reference at higher scene temperatures. This paper extends the techniques previously applied only to Band 31 to the remaining TEB using both Dome C and SST sites. The long-term calibration stability and relative bias between Terra and Aqua MODIS is discussed.

  18. Thermal stability and kinetic of decomposition of nitrated HTPB.

    PubMed

    Wang, Qingfa; Wang, Li; Zhang, Xiangwen; Mi, Zhentao

    2009-12-30

    Nitrated HTPB (NHTPB) is a potential energetic binder to replace the conventional inert binder, HTPB, for the composite solid propellants and plastic bonded explosives (PBXs). The thermal stability of the NHTPB sample with 10% double bonds converted to dinitrate ester group (10% NHTPB) was evaluated by high-pressure differential scanning calorimeter (PDSC) measurement. The influences of pressure (0.1, 2.5 and 5.0 MPa) and the heating rate (4, 6, 8 and 10 degrees C min(-1)) on the DSC behavior of the 10% NHTPB sample were investigated. The decomposition temperature of this compound decreased with the increase of pressure, meanwhile, increased as the heating rate increasing. The thermal decomposition at 150-250 degrees C followed a first-order law. The kinetic parameters and thermodynamic parameters for the 10% NHTPB sample at 150-250 degrees C under ambient pressure were obtained from the DSC data by non-isothermal methods proposed by ASTM E698 and Flynn-Wall-Ozawa. The critical temperature for this compound was estimated at about 154 degrees C. PMID:19740607

  19. Thermal stability of a thin disk with magnetically driven winds

    SciTech Connect

    Li, Shuang-Liang; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2014-05-01

    The absence of thermal instability in the high/soft state of black hole X-ray binaries, in disagreement with the standard thin disk theory, has been a long-standing riddle for theoretical astronomers. We have tried to resolve this question by studying the thermal stability of a thin disk with magnetically driven winds in the M-dot −Σ plane. It is found that disk winds can greatly decrease the disk temperature and thus help the disk become more stable at a given accretion rate. The critical accretion rate, M-dot {sub crit}, corresponding to the thermal instability threshold, is significantly increased in the presence of disk winds. For α = 0.01 and B {sub φ} = 10B {sub p}, the disk is quite stable even for a very weak initial poloidal magnetic field [β{sub p,0}∼2000,β{sub p}=(P{sub gas}+P{sub rad})/(B{sub p}{sup 2}/8π)]. However, when B {sub φ} = B {sub p} or B {sub φ} = 0.1B {sub p}, a somewhat stronger (but still weak) field (β{sub p,} {sub 0} ∼ 200 or β{sub p,} {sub 0} ∼ 20) is required to make the disk stable. Nevertheless, despite the great increase of M-dot {sub crit}, the luminosity threshold, corresponding to instability, remains almost constant or decreases slowly with increasing M-dot {sub crit} due to decreased gas temperature. The advection and diffusion timescales of the large-scale magnetic field threading the disk are also investigated in this work. We find that the advection timescale can be smaller than the diffusion timescale in a disk with winds, because the disk winds take away most of the gravitational energy released in the disk, resulting in the decrease of the magnetic diffusivity η and the increase of the diffusion timescale.

  20. Thermal Stability of Jet Fuels: Kinetics of Forming Deposit Precursors

    NASA Technical Reports Server (NTRS)

    Naegeli, David W.

    1997-01-01

    The focus of this study was on the autoxidation kinetics of deposit precursor formation in jet fuels. The objectives were: (1) to demonstrate that laser-induced fluorescence is a viable kinetic tool for measuring rates of deposit precursor formation in jet fuels; (2) to determine global rate expressions for the formation of thermal deposit precursors in jet fuels; and (3) to better understand the chemical mechanism of thermal stability. The fuels were isothermally stressed in small glass ampules in the 120 to 180 C range. Concentrations of deposit precursor, hydroperoxide and oxygen consumption were measured over time in the thermally stressed fuels. Deposit precursors were measured using laser-induced fluorescence (LIF), hydroperoxides using a spectrophotometric technique, and oxygen consumption by the pressure loss in the ampule. The expressions, I.P. = 1.278 x 10(exp -11)exp(28,517.9/RT) and R(sub dp) = 2.382 x 10(exp 17)exp(-34,369.2/RT) for the induction period, I.P. and rate of deposit precursor formation R(sub dp), were determined for Jet A fuel. The results of the study support a new theory of deposit formation in jet fuels, which suggest that acid catalyzed ionic reactions compete with free radical reactions to form deposit precursors. The results indicate that deposit precursors form only when aromatics are present in the fuel. Traces of sulfur reduce the rate of autoxidation but increase the yield of deposit precursor. Free radical chemistry is responsible for hydroperoxide formation and the oxidation of sulfur compounds to sulfonic acids. Phenols are then formed by the acid catalyzed decomposition of benzylic hydroperoxides, and deposit precursors are produced by the reaction of phenols with aldehydes, which forms a polymer similar to Bakelite. Deposit precursors appear to have a phenolic resin-like structure because the LIF spectra of the deposit precursors were similar to that of phenolic resin dissolved in TAM.

  1. Comparison of stabilization by Vitamin E and 2,6-di-tert-butylphenols during polyethylene radio-thermal-oxidation

    NASA Astrophysics Data System (ADS)

    Richaud, Emmanuel

    2014-10-01

    This paper reports a compilation of data for PE+Vitamin E and 2,6-di-tert-butylphenols oxidation in radio-thermal ageing. Data unambiguously show that Vitamin E reacts with Prad and POOrad whereas 2,6-di-tert-butyl phenols only react with POOrad . Kinetic parameters of the stabilization reactions for both kinds of antioxidants were tentatively extracted from phenol depletion curves, and discussed regarding the structure of the stabilizer. They were also used for completing an existing kinetic model used for predicting the stabilization by antioxidants. This one permits to compare the efficiency of stabilizer with dose rate or sample thickness.

  2. Thermal-stability studies of electrode materials for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Jiang, Junwei

    2005-07-01

    The thermal stability of lithium-ion batteries has recently attracted attention for two major reasons. (1) Attempts to make large-size cells used in power tools, E-bikes and EVs. Large cells have lower surface area to volume ratios and hence heat dissipation is more problematic than 18650-size cells. Safety problems, therefore, for large cells are more serious. (2) Next generation high-capacity electrodes will increase the energy density of lithium-ion cells meaning even an 18650-size cell may face safety concerns. This thesis presents studies of the thermal stability of electrode materials in electrolytes to understand their reactivity. A search for new positive electrode materials with high thermal stability was made. The thermal stability of two common electrode materials (Li0.81 C6 and Li0.5CoO2) in lithium-ion cells was studied by Accelerating Rate Calorimeter (ARC). Li0.81C 6 has much lower reactivity with lithium bis(oxalato)borate (LiBOB) electrolyte compared to LiPF6 electrolyte. It is not the case, however, for Li0.5CoO2. Oven tests of full LiCoO 2/C 18650-size cells with LiBOB or LiPF6 electrolytes, confirmed the ARC results. ARC was then used to study the reactivity of existing electrode materials. The thermal stability of a negative electrode material was found to increase with the binding energy of Li atoms hosted in the material. Li0.5VO 2 (B) has a higher lithium binding energy (2.45 eV vs. Li) than Li 0.81C6 (0.1 eV vs. Li) and Li7Ti5O 12 (1.55 eV) and it shows the highest thermal stability in EC/DEC among the three materials. The reactivity of two existing positive electrode materials, LiMn2O4 and LiFePO4, was studied. Cell systems expected to be highly tolerant to thermal abuse were suggested: LiFePO 4/C or Li4Ti5O12 in LiBOB electrolytes. The system, x Li[Ni1/2Mn1/2]O2 • y LiCoO2 • z Li[Li1/3Mn2/3]O2 (x + y + z = 1), was explored for new positive electrode materials with large capacity and high thermal stability. Li[(Ni0.5Mn0.5) xCo1-x]O2 (0

  3. An experimental study on thermal stability of biodiesel fuel

    NASA Astrophysics Data System (ADS)

    Zhu, Yiying

    Biodiesel fuel, as renewable energy, has been used in conventional diesel engines in pure form or as biodiesel/diesel blends for many years. However, thermal stability of biodiesel and biodiesel/diesel blends has been minimally explored. Aimed to shorten this gap, thermal stability of biodiesel is investigated at high temperatures. In this study, batch thermal stressing experiments of biodiesel fuel were performed in stainless steel coils at specific temperature and residence time range from 250 to 425 °C and 3 to 63 minutes, respectively. Evidence of different pathways of biodiesel fuel degradation is demonstrated chromatographically. It was found that biodiesel was stable at 275 °C for a residence time of 8 minutes or below, but the cis-trans isomerization reaction was observed at 28 minutes. Along with isomerization, polymerization also took place at 300 °C at 63 minutes. Small molecular weight products were detected at 350 °C at 33 minutes resulting from pyrolysis reactions and at 360 °C for 33 minutes or above, gaseous products were produced. The formed isomers and dimers were not stable, further decomposition of these compounds was observed at high temperatures. These three main reactions and the temperature ranges in which they occurred are: isomerization, 275--400 °C; polymerization (Diels-Alder reaction), 300--425 °C; pyrolysis reaction, ≥350 °C. The longer residence time and higher temperature resulted in greater decomposition. As the temperature increased to 425 °C, the colorless biodiesel became brownish. After 8 minutes, almost 84% of the original fatty acid methyl esters (FAMEs) disappeared, indicating significant fuel decomposition. A kinetic study was also carried out subsequently to gain better insight into the biodiesel thermal decomposition. A three-lump model was proposed to describe the decomposition mechanism. Based on this mechanism, a reversible first-order reaction kinetic model for the global biodiesel decomposition was shown to

  4. Thermal stability evaluation of microstructures and mechanical properties of tungsten vanadium alloys

    NASA Astrophysics Data System (ADS)

    Arshad, Kameel; Zhao, Ming-Yue; Yuan, Yue; Zhang, Ying; Zhou, Zhang-Jian; Lu, Guang-Hong

    2014-10-01

    The thermal stability is important for tungsten based alloys as plasma facing materials to survive against high heat flux in fusion reactors. In this work, the thermal stability of W-5%V alloy fabricated following a powder metallurgy route by spark plasma sintering technique has been studied. To investigate the impact of temperature on the mechanical properties and microstructures, the alloy was subjected to heat treatment for 2 h over the temperature range 900-1500°C in a pure argon furnace. The micro-hardness values of the heat treated alloys were highly stable as compared to pure tungsten. A slight decrease flexural strength was observed with increasing annealing temperature. The maximum change flexural strength at the highest treated temperature was noted about 14% lower. The morphology analyses of the crack surfaces by scanning electron microscopy did not identify a drastic change in tungsten grain size, after heat treatment. The results indicate that the addition of vanadium in tungsten improves the overall thermal stability of microstructures and mechanical properties.

  5. Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method.

    PubMed

    Segerström, Lova; Gustavsson, Jenny; Nylander, Ingrid

    2016-04-01

    Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg(6) (LARG), and Met-enkephalin-Arg(6)-Phe(7) (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid

  6. Minimizing Postsampling Degradation of Peptides by a Thermal Benchtop Tissue Stabilization Method

    PubMed Central

    Segerström, Lova; Gustavsson, Jenny

    2016-01-01

    Enzymatic degradation is a major concern in peptide analysis. Postmortem metabolism in biological samples entails considerable risk for measurements misrepresentative of true in vivo concentrations. It is therefore vital to find reliable, reproducible, and easy-to-use procedures to inhibit enzymatic activity in fresh tissues before subjecting them to qualitative and quantitative analyses. The aim of this study was to test a benchtop thermal stabilization method to optimize measurement of endogenous opioids in brain tissue. Endogenous opioid peptides are generated from precursor proteins through multiple enzymatic steps that include conversion of one bioactive peptide to another, often with a different function. Ex vivo metabolism may, therefore, lead to erroneous functional interpretations. The efficacy of heat stabilization was systematically evaluated in a number of postmortem handling procedures. Dynorphin B (DYNB), Leu-enkephalin-Arg6 (LARG), and Met-enkephalin-Arg6-Phe7 (MEAP) were measured by radioimmunoassay in rat hypothalamus, striatum (STR), and cingulate cortex (CCX). Also, simplified extraction protocols for stabilized tissue were tested. Stabilization affected all peptide levels to varying degrees compared to those prepared by standard dissection and tissue handling procedures. Stabilization increased DYNB in hypothalamus, but not STR or CCX, whereas LARG generally decreased. MEAP increased in hypothalamus after all stabilization procedures, whereas for STR and CCX, the effect was dependent on the time point for stabilization. The efficacy of stabilization allowed samples to be left for 2 hours in room temperature (20°C) without changes in peptide levels. This study shows that conductive heat transfer is an easy-to-use and efficient procedure for the preservation of the molecular composition in biological samples. Region- and peptide-specific critical steps were identified and stabilization enabled the optimization of tissue handling and opioid

  7. Comparative Thermal Degradation Patterns of Natural Yellow Colorants Used in Foods.

    PubMed

    Giménez, Pedro J; Fernández-López, José A; Angosto, José M; Obón, José M

    2015-12-01

    There is a great interest in natural yellow colorants due to warnings issued about certain yellow food colorings of synthetic origin. However, no comparative studies have been reported of their thermal stability. For this reason, the thermal stabilities of six natural yellow colorants used in foods--lutein, riboflavin, curcumin, ß-carotene, gardenia yellow and Opuntia betaxanthins--were studied in simple solutions over a temperature range 30-90 °C. Spectral properties and visual color were investigated during 6 h of heat treatment. Visual color was monitored from the CIEL*a*b* parameters. The remaining absorbance at maximum wavelength and the total color difference were used to quantify color degradation. The rate of color degradation increased as the temperature rose. The results showed that the thermal degradation of the colorants followed a first-order reaction kinetics. The reaction rate constants and half-life periods were determined as being central to understanding the color degradation kinetics. The temperature-dependent degradation was adequately modeled on the Arrhenius equation. Activation energies ranged from 3.2 kJmol(-1) (lutein) to 43.7 kJmol(-1) (Opuntia betaxanthins). ß-carotene and lutein exhibited high thermal stability, while betaxanthins and riboflavin degraded rapidly as temperature increased. Gardenia yellow and curcumin were in an intermediate position. PMID:26141372

  8. Contrasting tropical estuarine ecosystem functioning and stability: A comparative study

    NASA Astrophysics Data System (ADS)

    Villanueva, Maria Ching

    2015-03-01

    A comparative study of the Sine-saloum (Senegal) and Gambia (The Gambia) estuaries was performed based on trophic model outputs that describe the system structure and functioning. These trophic models were constructed such as to differentiate main energetic flows in the systems and express how climate change may have impacted ecosystem resilience to change. Estuarine fish assemblages are highly resilient despite exposure to vast hydrodynamic variations and stress. Coupled with strong anthropogenic-driven stresses such as fisheries and climate change, ecosystems may undergo severe regime shifts that may weaken their resilience and stability. Taxonomically related and morphologically similar species do not necessarily play similar ecological roles in these two ecosystems. Biomass and production in the Sine-saloum are concentrated at trophic levels (TLs) 2 and 3, while for the Gambia, both are concentrated at TL3. Higher TL biomasses in Gambia compared to Sine-Saloum may be explained by the latter ecosystem being characterized by inverse hypersalinity. Higher TL of production in Sine-Saloum is due to higher exploitations compared to Gambia where fishing activities are still less developed. High production and consumption rates of some groups in both ecosystems indicate high system productivity. Elevated productivity may be due to higher abundance of juvenile fishes in most groups that utilize the latter as refuge and/or nursery zones. Both ecosystems are phytoplankton-driven. Differences in group trophic and ecological roles are mainly due to adaptive responses of these species to seasonal and long-term climate and anthropogenic stressors. System indicators suggest different levels of ecosystem resilience and stability as a function of biodiversity. Relevance of other observations on ecosystem functioning and indicators in relation to perturbation is discussed.

  9. Guanidine hydrochloride and urea effects upon thermal stability of Glossoscolex paulistus hemoglobin (HbGp).

    PubMed

    Carvalho, Francisco A O; Alves, Fernanda R; Carvalho, José W P; Tabak, Marcel

    2015-03-01

    Glossoscolex paulistus hemoglobin (HbGp) has a molecular mass of 3600kDa. It belongs to the hexagonal bilayer hemoglobin class, which consists of highly cooperative respiratory macromolecules found in mollusks and annelids. The present work focusses on oxy-HbGp thermal stability, in the presence of urea and guanidine hydrochloride (GuHCl), monitored by several techniques. Initially, dynamic light scattering data show that the presence of GuHCl induces the protein oligomeric dissociation, followed by a significant 11-fold increase in the hydrodynamic diameter (DH) values, due to the formation of protein aggregates in solution. In contrast, urea promotes the HbGp oligomeric dissociation, followed by unfolding process at high temperatures, without aggregation. Circular dichroism data show that unfolding critical temperature (Tc) of oxy-HbGp decreases from 57°C, at 0.0 mol/L of the denaturant, to 45°C, in the presence of 3.5 mol/L of urea, suggesting the reduction of HbGp oligomeric stability. Moreover, differential scanning calorimetry results show that at lower GuHCl concentrations, some thermal stabilization of the hemoglobin is observed, whereas at higher concentrations, the reduction of stability takes place. Besides, HbGp is more stable in the presence of urea when compared with the guanidine effect, as deduced from the differences in the concentration range of denaturants. PMID:25433131

  10. High-temperature stability and selective thermal emission of polycrystalline tantalum photonic crystals.

    PubMed

    Rinnerbauer, Veronika; Yeng, Yi Xiang; Chan, Walker R; Senkevich, Jay J; Joannopoulos, John D; Soljačić, Marin; Celanovic, Ivan

    2013-05-01

    We present the results of extensive characterization of selective emitters at high temperatures, including thermal emission measurements and thermal stability testing at 1000 °C for 1h and 900 °C for up to 144 h. The selective emitters were fabricated as 2D photonic crystals (PhCs) on polycrystalline tantalum (Ta), targeting large-area applications in solid-state heat-to-electricity conversion. We characterized spectral emission as a function of temperature, observing very good selectivity of the emission as compared to flat Ta, with the emission of the PhC approaching the blackbody limit below the target cut-off wavelength of 2 μm, and a steep cut-off to low emission at longer wavelengths. In addition, we study the use of a thin, conformal layer (20 nm) of HfO(2) deposited by atomic layer deposition (ALD) as a surface protective coating, and confirm experimentally that it acts as a diffusion inhibitor and thermal barrier coating, and prevents the formation of Ta carbide on the surface. Furthermore, we tested the thermal stability of the nanostructured emitters and their optical properties before and after annealing, observing no degradation even after 144 h (6 days) at 900 °C, which demonstrates the suitability of these selective emitters for high-temperature applications. PMID:23670005

  11. Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

    NASA Technical Reports Server (NTRS)

    Cofield, Richard E.; Kasl, Eldon P.

    2011-01-01

    The Scanning Microwave Limb Sounder (SMLS) is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission in [180,680] GHz. SMLS, planned for the NRC Decadal Survey's Global Atmospheric Composition Mission, uses a novel toric Cassegrain antenna to perform both elevation and azimuth scanning. This provides better horizontal and temporal resolution and coverage than were possible with elevation-only scanning in the two previous MLS satellite instruments. SMLS is diffraction-limited in the vertical plane but highly astigmatic in the horizontal (beam aspect ratio approx. 1:20). Nadir symmetry ensures that beam shape is nearly invariant over plus or minus 65 deg azimuth. A low-noise receiver FOV is swept over the reflector system by a small azimuth-scanning mirror. We describe the fabrication and thermal-stability test of a composite demonstration primary reflector, having full 4m height and 1/3 the width planned for flight. Using finite-element models of reflectors and structure, we evaluate thermal deformations and optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during soak tests in a chamber. The test temperature range exceeds predicted orbital ranges by large factors, implying in-orbit thermal stability of 0.21 micron rms (root mean square)/C, which meets SMLS requirements.

  12. Improving the thermal dimensional stability of flexible polymer composite backing materials for ultrasound transducers.

    PubMed

    State, Mihai; Brands, Peter J; van de Vosse, Frans N

    2010-04-01

    Novel ultrasound backing materials based on polymer composites with improved dimensional stability and low coefficient of thermal expansion are being developed and analyzed. For this purpose a filled epoxy resin (Stycast(1265)), a commonly used backing material, was considered reference material and polyurethane composites (PU(2305), PU(2350)) were proposed as better alternatives. When compared to the reference, the PU(2350) filled with a mixture of Al(2)O(3) and tungsten exhibited an approximately 15 times lower glassy transition temperature and a 2.5 time lower longitudinal thermal expansion at 20 degrees C. This ensures that within the entire operational temperature range the backing material is flexible, minimizing the thermal stresses induced onto transducer elements soldered joints and piezoceramic core. For the same material, the attenuation at 5MHz was similar to the reference material while at 7 and 8.5MHz it was 33% and 54% higher respectively. From these analyses it is concluded that the newly developed polyurethane composites outperform the reference backing with respect to the thermal dimensional stability as well as to the damping properties. An integrated rigorous mechano-acoustical approach is being proposed as an appropriate passive material design path. It can be easily extended to any other passive materials used for ultrasound transducer conception. PMID:19897218

  13. On the physics of thermal-stability changes upon mutations of a protein

    NASA Astrophysics Data System (ADS)

    Murakami, Shota; Oshima, Hiraku; Hayashi, Tomohiko; Kinoshita, Masahiro

    2015-09-01

    It is of great interest from both scientific and practical viewpoints to theoretically predict the thermal-stability changes upon mutations of a protein. However, such a prediction is an intricate task. Up to now, significantly many approaches for the prediction have been reported in the literature. They always include parameters which are adjusted so that the prediction results can be best fitted to the experimental data for a sufficiently large set of proteins and mutations. The inclusion is necessitated to achieve satisfactorily high prediction performance. A problem is that the resulting values of the parameters are often physically meaningless, and the physicochemical factors governing the thermal-stability changes upon mutations are rather ambiguous. Here, we develop a new measure of the thermal stability. Protein folding is accompanied by a large gain of water entropy (the entropic excluded-volume (EV) effect), loss of protein conformational entropy, and increase in enthalpy. The enthalpy increase originates primarily from the following: The energy increase due to the break of protein-water hydrogen bonds (HBs) upon folding cannot completely be cancelled out by the energy decrease brought by the formation of protein intramolecular HBs. We develop the measure on the basis of only these three factors and apply it to the prediction of the thermal-stability changes upon mutations. As a consequence, an approach toward the prediction is obtained. It is distinguished from the previously reported approaches in the following respects: The parameters adjusted in the manner mentioned above are not employed at all, and the entropic EV effect, which is ascribed to the translational displacement of water molecules coexisting with the protein in the system, is fully taken into account using a molecular model for water. Our approach is compared with one of the most popular approaches, FOLD-X, in terms of the prediction performance not only for single mutations but also for

  14. Thermal stability of ladderane lipids as determined by hydrous pyrolysis

    USGS Publications Warehouse

    Jaeschke, A.; Lewan, M.D.; Hopmans, E.C.; Schouten, S.; Sinninghe, Damste J.S.

    2008-01-01

    Anaerobic ammonium oxidation (anammox) has been recognized as a major process resulting in loss of fixed inorganic nitrogen in the marine environment. Ladderane lipids, membrane lipids unique to anammox bacteria, have been used as markers for the detection of anammox in marine settings. However, the fate of ladderane lipids after sediment burial and maturation is unknown. In this study, anammox bacterial cell material was artificially matured by hydrous pyrolysis at constant temperatures ranging from 120 to 365 ??C for 72 h to study the stability of ladderane lipids during progressive dia- and catagenesis. HPLC-MS/MS analysis revealed that structural alterations of ladderane lipids already occurred at 120 ??C. At temperatures >140 ??C, ladderane lipids were absent and only more thermally stable products could be detected, i.e., ladderane derivatives in which some of the cyclobutane rings were opened. These diagenetic products of ladderane lipids were still detectable up to temperatures of 260 ??C using GC-MS. Thus, ladderane lipids are unlikely to occur in ancient sediments and sedimentary rocks, but specific diagenetic products of ladderane lipids will likely be present in sediments and sedimentary rocks of relatively low maturity (i.e., C31 hopane 22S/(22S + 22R) ratio 0.5). ?? 2008 Elsevier Ltd.

  15. Determination of thermal stability of oils by pyrolytic gas chromatography

    SciTech Connect

    Kudryavtseva, N.A.; Mikhailov, I.A.; Nikonorov, E.M.; Rakova, L.A.

    1984-03-01

    This article demonstrates how pyrolytic gas chromatography (PGC) offers a means for unambiguous differentiation of the decomposition products from the accompanying products of oil vaporization. The proposed method based on PGC uses a furnace-type pyrolyzer connected to an LKhM-7A chromatograph. The common peak of propane with propylene was selected as a characteristic peak to indicate the oil decomposition temperature. Propane and propylene, along with lighter hydrocarbons, are always present in the decomposition products. A volume graph method is used to determine the temperature of vaporization or decomposition of the substance, based on plotting a curve for the relationship between the heating temperature and the relative volume (or pressure) of the test sample. The decomposition temperatures determined by the PGC method agree with the values report by foreign manufacturers (deviation no greater than 2/sup 0/C). The accuracy of calculation of the thermal stability of the hydrocarbon oils by the PGC method was 5-10/sup 0/C as a result of deficiencies in the heating device in the pyrolytic unit. Includes a table.

  16. Controlled synthesis and thermal stability of hydroxyapatite hierarchical microstructures

    SciTech Connect

    Sun, Ruixue; Chen, Kezheng; Liao, Zhongmiao; Meng, Nan

    2013-03-15

    Highlights: ► Hydroxyapatite hierarchical microstructures have been synthesized by a facile method. ► The morphology and size of the building units of 3D structures can be controlled. ► The hydroxyapatite with 3D structure is morphologically and structurally stable up to 800 °C. - Abstract: Hydroxyapatite (HAp) hierarchical microstructures with novel 3D morphology were prepared through a template- and surfactant-free hydrothermal homogeneous precipitation method. Field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction (XRD) were used to characterize the morphology and composition of the synthesized products. Interestingly, the obtained HAp with 3D structure is composed of one-dimensional (1D) nanorods or two-dimensional (2D) nanoribbons, and the length and morphology of these building blocks can be controlled through controlling the pH of the reaction. The building blocks are single crystalline and have different preferential orientation growth under different pH conditions. At low pH values, octacalcium phosphate (OCP) phase formed first and then transformed into HAp phase due to the increased pH value caused by the decomposition of urea. The investigation on the thermal stability reveals that the prepared HAp hierarchical microstructures are morphologically and structurally stable up to 800 °C.

  17. Thermal stability of DNA adducts induced by cyanomorpholinoadriamycin in vitro.

    PubMed Central

    Cullinane, C; Phillips, D R

    1993-01-01

    The Adriamycin derivative, cyanomorpholinoadriamycin (CMA) was reacted with DNA in vitro to form apparent interstrand crosslinks. The extent of interstrand crosslink formation was monitored by a gel electrophoresis assay and maximal crosslinking of DNA was observed within 1 hr with 5 microM of drug. The interstrand crosslinks were heat labile, with a midpoint melting temperature of 70 degrees C (10 min exposure to heat) in 45% formamide. When CMA-induced adducts were detected as blockages of lambda-exonuclease, 12 blockage sites were observed with 8 being prior to 5'-GG sequences, one prior to 5'-CC, one prior to 5'-GC and 2 at unresolved combinations of these sequences. These exonuclease-detected blockages reveal the same sites of CMA-induced crosslinking as detected by in vitro transcription footprinting and primer-extension blockages on single strand DNA, where the blockages at 5'-GG and 5'-CC were identified as sites of intrastrand crosslinking and the 5'-GC blockage as a probable site of interstrand crosslinking. The thermal stability of both types of crosslink (10 min exposure to heat) ranged from 63-70 degrees C at individual sites. High levels of adduct were detected with poly (dG-dC) but not with poly (dI-dC). These results suggest adduct formation involving an aminal linkage between the 3 position of the morpholino moiety and N2 of guanine. Images PMID:8493102

  18. The thermal stability of radiation-induced defects in illite

    NASA Astrophysics Data System (ADS)

    Riegler, T.; Allard, T.; Beaufort, D.; Cantin, J.-L.; von Bardeleben, H. J.

    2016-01-01

    High-purity illite specimens from the Mesoproterozoic unconformity-related uranium deposits of Kiggavik, Thelon basin, Nunavut (Canada), and Shea Creek (Athabasca basin, Saskatchewan, Canada) have been studied using electron paramagnetic resonance spectroscopy to determine the thermal stability of the main radiation-induced defects and question the potential of using illite as a natural dosimeter. The observed spectra are complex as they can show in the same region several contributions: (1) an unstable native defect, (2) the main stable defect named Ai by reference to a previous study (Morichon et al. in Phys Chem Minerals 35:339-346, 2008), (3) a signal at g = 2.063 assigned to a new defect, not yet fully characterized, named Ai2 center and (4) impurities such as vanadyl complex or divalent manganese. Isochronal heating shows that the new signal corresponds to a stable species. Isothermal heating experiments at 400 and 450 °C provide values of half-life extrapolated at room temperature and activation energy of 1.9-29,109 years and 1.3-1.4 eV, respectively, corresponding to the Ai center. These parameters allow the use of stable radiation-induced defects as a record of radioactivity down to the Paleoproterozoic period.

  19. Experimental study of the thermal stability of hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Marteney, P. J.; Colket, M. B.; Vranos, A.

    1982-01-01

    The thermal stability of two hydrocarbon fuels (premium diesel and regular diesel) was determined in a flow reactor under conditions representing operation of an aircraft gas turbine engine. Temperature was varied from 300 to 750 F (422 to 672 K) for fuel flows of 2.84 to 56.8 liters/hr (corresponding to 6.84 x 0.00010 to 1.63 x 0.010 kg/sec for regular diesel fuel and 6.55 x 0.00010 to 1.37 x 0.010 kg/sec for premium diesel fuel); test times varied between 1 and 8 hr. The rate of deposition was obtained through measurement of weight gained by metal discs fixed along the channel wall. The rate of deposit formation is best correlated by an Arrhenius expression. The sample discs in the flow reactor were varied among stainless steel, aluminum and brass; fuels were doped with quinoline, indole, and benzoyl perioxide to yield nitrogen or oxygen concentrations of approximately 1000 ppm. The most substantial change in rate was an increase in deposits for brass discs; other disc materials or the additives caused only small perturbations. Tests were also conducted in a static reactor at temperatures of 300 to 800 F for times of 30 min to 2 1/2 hr. Much smaller deposition was found, indicating the importance of fluid transport in the mechanism.

  20. Synthesis, thermal stability, and photocatalytic activity of nanocrystalline titanium carbide

    SciTech Connect

    Chen, Youjian; Zhang, Hong; Ma, DeKun; Ma, Jianhua; Ye, Hongnan; Qian, Gaojin; Ye, Yi

    2011-11-15

    Highlights: {yields} The synthesized temperature is lower than some conventional methods. {yields} These raw materials are safe; all manipulations are rather safe and convenient. {yields} The product exhibits photocatalytic activity in degradation of Rhodamine-B. -- Abstract: Titanium carbide (TiC) was prepared via one simple route by the reaction of metallic magnesium powders with titanium dioxide (TiO{sub 2}) and potassium acetate (CH{sub 3}COOK) in an autoclave at 600 {sup o}C and 8 h. Phase structure and morphology were characterized by X-ray powder diffraction (XRD) and Scanning electron microscopy (SEM). The results indicated that the product was cubic TiC, which consisted of particles with an average size of about 100 nm in diameter. The product was also studied by the thermogravimetric analysis (TGA) and its photocatalysis. It had good thermal stability and oxidation resistance below 350 {sup o}C in air. In addition, we discovered that the cubic TiC powders exhibited photocatalytic activity in degradation of Rhodamine-B (RhB) under 500 W mercury lamp light irradiation.

  1. Thermal Stability of MnBi Magnetic Materials

    SciTech Connect

    Cui, Jun; Choi, Jung-Pyung; Li, Guosheng; Polikarpov, Evgueni; Darsell, Jens T.; Overman, Nicole R.; Olszta, Matthew J.; Schreiber, Daniel K.; Bowden, Mark E.; Droubay, Timothy C.; Kramer, Matthew J.; Zarkevich, Nikolai; Wang, L. L.; Johnson, Duane D.; Marinescu, Melania; Takeuchi, Ichiro; Huang, Qingzhen; Wu, Hui; Reeve, Hayden; Vuong, Nguyen V.; Liu, J.Ping

    2014-01-01

    MnBi attracts great attention in recent years for its great potential as permanent magnet materials. It is unique because its coercivity increases with increasing temperature, which makes it a good hard phase for exchange coupling nanocomposite magnet. MnBi phase is difficult to obtain, partly because the reaction between Mn and Bi is peritectic, and partly because Mn is easy to react with oxygen. MnO formation is irreversible and causes degradation to the magnetic properties. In this paper, we report our effort on developing MnBi permanent magnet. High purity MnBi (>90%) can be routinely produced in large quantity. The obtained powder exhibit 74 emu/g saturation magnetization at room temperature with 9 T applied field. After alignment, the powder exhibits 11.6 MGOe, and the sintered bulk magnet exhibit 7.8 MGOe at room temperature. Thermal stability study shows that the MnBi is stable up to 473 K in air.

  2. Thermal stability of MnBi magnetic materials

    SciTech Connect

    Cui, Jinfang; Choi, J. P.; Li, G.; Polikarpov, E.; Darsell, J.; Overman, N.; Olszta, M.; Schreiber, D.; Bowden, M.; Droubay, T.; Kramer, Matthew J.; Zarkevich, Nikolay A.; Wang, L L.; Johnson, Duane D.; Marinescu, M.; Takeuchi, I.; Huang, Q. Z.; Wu, H.; Reeve, H.; Vuong, N. V.; Liu, J P.

    2014-01-27

    MnBi has attracted much attention in recent years due to its potential as a rare-earth-free permanent magnet material. It is unique because its coercivity increases with increasing temperature, which makes it a good hard phase material for exchange coupling nanocomposite magnets. MnBi phase is difficult to obtain, partly because the reaction between Mn and Bi is peritectic, and partly because Mn reacts readily with oxygen. MnO formation is irreversible and harmful to magnet performance. In this paper, we report our efforts toward developing MnBi permanent magnets. To date, high purity MnBi (>90%) can be routinely produced in large quantities. The produced powder exhibits 74:6 emu g1 saturation magnetization at room temperature with 9 T applied field. After proper alignment, the maximum energy product (BH) max of the powder reached 11.9 MGOe, and that of the sintered bulk magnet reached 7.8 MGOe at room temperature. A comprehensive study of thermal stability shows that MnBi powder is stable up to 473 K in air.

  3. Zirconia coating for enhanced thermal stability of gold nanoparticles

    NASA Astrophysics Data System (ADS)

    Pastre, A.; Cristini-Robbe, O.; Bois, L.; Chassagneux, F.; Branzea, D.; Boé, A.; Kinowski, C.; Raulin, K.; Rolland, N.; Bernard, R.

    2016-01-01

    This paper describes a rapid, simple and one-step method for the preparation of 2-4 nm diameter zirconia-coated gold nanoparticles at room temperature. These nanoparticles were synthesized by two simultaneous processes: the chemical reduction of tetrachloroauric acid with sodium borohydride and the formation of zirconia sol-gel matrices. All the gold nanoparticle sols were characterized by UV-visible absorption and transmission electron microscopy to determine the nanoparticle size and shape. The synthesis method is a combination of a polymeric structure of the amorphous zirconia and the use of a strong reducing agent, and it yields to very small quasi-spherical gold nanoparticles at room temperature. The thermal stability up to 1200 °C of the coated nanoparticles was studied by x-ray diffraction. The metastable tetragonal phase of the zirconia coating was obtained at 400 °C, and a progressive transformation from tetragonal to monoclinic phases of the zirconia coating was observed up to 1100 °C. After the heat treatment at 400 °C, the crystallite size of the gold nanoparticles was about 29 nm, and it remained unchanged from 400 °C to 1200 °C. These results are promising for the development of such materials as doping elements for optical fiber applications.

  4. Synthesis and characterization of rodlike liquid crystalline polyester/multi-walled carbon nanotubes and study of their thermal stability

    NASA Astrophysics Data System (ADS)

    Hu, Wu-Quan; Cui, Zhen-Kai; Jin, Jun; Dong, Zheng-Ping; Li, Shu-Wen; Wang, Peng; Ding, Wen; Li, Rong

    2011-10-01

    Rodlike thermotropic liquid crystalline polyester (TLCP) was synthesized from 4,4'-oxydibenzoyl chloride and resorcinol containing modified multi-walled carbon nanotubes (MWCNTs) by in situ high-temperature solution polymerization. The liquid crystalline properties and thermal stability of the resulted TLCP nanocomposites were characterized by XRD, DSC, TGA, SEM, POM, and optical analysis. The addition of small amount of MWCNTs into TLCP matrix could significantly improve the thermal stability. The mesophase temperature range of nanocomposites were widened and shifted to higher temperatures. This nanocomposite melting phase transition ( Tm) value increases maximally to 38.4 °C compared with pure copolymer. Using the Horowits-Metzger kinetic method, the PE/M-0.5 gave the best performance in terms of the thermal stability. This result can be explained that the incorporation of MWCNTs into TLCP caused an interaction between TLCP and MWCNTs through π-π* conjugation.

  5. Effect of salt and organic solvents on DNA thermal stability and structure

    NASA Astrophysics Data System (ADS)

    Sorokin, V. A.; Gladchenko, G. O.; Valeev, V. A.; Sysa, I. V.; Petrova, L. G.; Blagoi, Yu. P.

    1997-06-01

    At low ionic strength the thermal stability of DNA was observed to be strongly enhanced by the presence of glycerol. The stabilizing effect went down as the Na + concentration was increased. With high concentrations of the ions or glycerol a further increase in the glycerol concentration suppressed the thermal stability of DNA. The effects observed may be attributed to enhanced Coulombic Na +-DNA interaction as the dielectric constant of the solution decreases.

  6. Thermal and Chemical Stabilization of Silver Nanoplates for Plasmonic Sensor Application.

    PubMed

    Takahashi, Yukina; Suga, Koichi; Ishida, Takuya; Yamada, Sunao

    2016-01-01

    Thermal and chemical stabilities of silver nanoplates (AgPLs), which are triangle plate-shaped silver nanoparticles, were improved by coating with titanium oxide. The titanium oxide layer prepared by a dip-coating method was certainly advantageous for the improvement of thermal stability. Furthermore, the overlayering of titanium oxide by a spray pyrolysis method was quite useful for improving the chemical stability against I(-) exposure. Such a coating exhibited satisfactory refractive index sensitivities. PMID:26960605

  7. SiC-dopped MCM-41 materials with enhanced thermal and hydrothermal stabilities

    SciTech Connect

    Wang, Yingyong; Jin, Guoqiang; Tong, Xili; Guo, Xiangyun

    2011-11-15

    Graphical abstract: Novel SiC-dopped MCM-41 materials were synthesized by adding silicon carbide suspension in the molecular sieve precursor solvent followed by in situ hydrothermal synthesis. The dopped materials have a wormhole-like mesoporous structure and exhibit enhanced thermal and hydrothermal stabilities. Highlights: {yields} SiC-dopped MCM-41 was synthesized by in situ hydrothermal synthesis of molecular sieve precursor combined with SiC. {yields} The dopped MCM-41 materials show a wormhole-like mesoporous structure. {yields} The thermal stability of the dopped materials have an increment of almost 100 {sup o}C compared with the pure MCM-41. {yields} The hydrothermal stability of the dopped materials is also better than that of the pure MCM-41. -- Abstract: SiC-dopped MCM-41 mesoporous materials were synthesized by the in situ hydrothermal synthesis, in which a small amount of SiC was added in the precursor solvent of molecular sieve before the hydrothermal treatment. The materials were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, N{sub 2} physical adsorption and thermogravimetric analysis, respectively. The results show that the thermal and hydrothermal stabilities of MCM-41 materials can be improved obviously by incorporating a small amount of SiC. The structure collapse temperature of SiC-dopped MCM-41 materials is 100 {sup o}C higher than that of pure MCM-41 according to the differential scanning calorimetry analysis. Hydrothermal treatment experiments also show that the pure MCM-41 will losses it's ordered mesoporous structure in boiling water for 24 h while the SiC-dopped MCM-41 materials still keep partial porous structure.

  8. Thermal stability of hexagonal OsB2

    SciTech Connect

    Xie, Zhilin; Blair, Richard G.; Orlovskaya, Nina; Cullen, David A; Payzant, E Andrew

    2014-01-01

    The synthesis of novel hexagonal ReB2-type OsB2 ceramic powder was performed by high energy ball milling of elemental Os and B powders. Two different sources of B powder have been used for this mechanochemical synthesis. One B powder consisted of a mixture of amorphous and crystalline phases and a mixture of 10B and 11B isotopes with a fine particle size, while another B powder was a purely crystalline (rhombohedral) material consisting of enriched 11B isotope with coarse particle size. The same Os powder was used for the synthesis in both cases. It was established that, in the first case, the hexagonal OsB2 phase was the main product of synthesis with a small quantity of Os2B3 phase present after synthesis as an intermediate product. In the second case, where coarse crystalline 11B powder was used as a raw material, only Os2B3 boride was synthesized mechanochemically. The thermal stability of hexagonal OsB2 powder was studied by heating under argon up to 876 C and cooling in vacuo down to 225 C. During the heating, the sacrificial reaction 2OsB2+3O2 2Os+2B2O3 took place due to presence of O2/water vapor molecules in the heating chamber, resulting in the oxidation of B atoms and formation of B2O3 and precipitation of Os metal out of the OsB2 lattice. As a result of such phase changes during heating, the lattice parameters of hexagonal OsB2 changed significantly. The shrinkage of the a lattice parameter was recorded in 276 426 C temperature range upon heating, which was attributed to the removal of B atoms from the OsB2 lattice due to oxidation followed by the precipitation of Os atoms and formation of Os metal. While significant structural changes occurred upon heating due to presence of O2, the hexagonal OsB2 ceramic demonstrated good phase stability upon cooling in vacuo with linear shrinkage of the lattice parameters and no phase changes detected during cooling.

  9. Thermal Stability of Ice on Ceres with Rough Topography

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.; Aharonson, Oded

    2015-11-01

    The dwarf planet Ceres may have an ice-rich crust, and subsurface ice exposed by impacts or endogenic activity would be subject to sublimation. The “bright spots” recently discovered by the Dawn mission on the illuminated surface of Ceres have prompted speculation regarding their possible icy composition and the youthful age this might imply. Furthermore, sublimation of ice at the surface or in the interior of Ceres could explain water vapor observed on more than one occasion in the exosphere. We investigated the possible distribution and lifetimes of water ice and other volatiles on Ceres using detailed thermal models, including realistic thermophysical properties and surface roughness.Topographic shadowing creates polar cold traps where a small, but non-negligible fraction (~0.4%) of Ceres' surface is perennially below the ~110 K criterion for 1 Gyr of H2O ice stability. These areas are found above 60° latitude. Other molecules (CH3OH, NH3, SO2, CO2) may be cold-trapped in smaller abundances. A model for the transport, gravitational escape and photoionization of H2O molecules suggests net accumulation in the cold traps. At latitudes 0° - 30°, ice is stable under solar illumination only briefly (~10-100 yr), unless it has high albedo and thermal inertia, in which case lifetimes of > 104 yr are possible.Buried ice is stable within a meter for > 1 Gyr at latitudes higher than ~50°. An illuminated polar cap of water ice would be stable within a few degrees of the poles only if it maintained a high albedo (> 0.5) at present obliquity. If the obliquity exceeded 5° in the geologically recent past, then a putative polar cap would have been erased. Finally, a small hemispheric asymmetry exists due to the timing of Ceres' perihelion passage, which would lead to a detectable enhancement of ice in the northern hemisphere if the orbital elements vary slowly relative to the ice accumulation rate. Our model results are potentially testable during the Dawn science

  10. Comparative performance of solar thermal power generation concepts

    NASA Technical Reports Server (NTRS)

    Wen, L.; Wu, Y. C.

    1976-01-01

    A performance comparison is made between the central receiver system (power tower) and a distributed system using either dishes or troughs and lines to transport fluids to the power station. These systems were analyzed at a rated capacity of 30 MW of thermal energy delivered in the form of superheated steam at 538 C (1000 F) and 68 atm (1000 psia), using consistent weather data, collector surface waviness, pointing error, and electric conversion efficiency. The comparisons include technical considerations for component requirements, land utilization, and annual thermal energy collection rates. The relative merits of different representative systems are dependent upon the overall conversion as expressed in the form of performance factors in this paper. These factors are essentially indices of the relative performance effectiveness for different concepts based upon unit collector area. These performance factors enable further economic tradeoff studies of systems to be made by comparing them with projected production costs for these systems.

  11. Conjugation of D-glucosamine to bovine trypsin increases thermal stability and alters functional properties.

    PubMed

    Gizurarson, Jóhann Grétar Kröyer; Filippusson, Hörður

    2015-01-01

    D-Glucosamine was conjugated to bovine trypsin by carbodiimide chemistry, involving a water-soluble carbodiimide and a succinimide ester, with the latter being to increase the yield of the conjugation. Mass spectrometric data suggested that several glycoforms were formed, with around 12 D-glucosamine moieties coupled to each trypsin molecule on average. The moieties were probably coupled to eight carboxyl groups (of glutamyl and aspartyl residues) and to four tyrosyl residues on the surface of the enzyme. The glycated trypsin possessed increased thermal stability. When compared with its unmodified counterpart, T50% was increased by 7 °C, thermal inactivation of the first step was increased 34%, and long-term stability assay revealed 71-times higher residual activity at 25 °C (without stabilizing Ca(2+) ions in aqueous buffer) after 67 days. Furthermore, resistance against autolysis was increased almost two-fold. Altered functional properties of the glycated trypsin were also observed. The glycated trypsin was found to become increasingly basophilic, and was found to be slightly structurally altered. This was indicated by 1.2 times higher catalytic efficiency (k(cat)/K(m)) than unmodified trypsin against the substrate N-α-benzoyl-L-arginine-p-nitroanilide. Circular dichroism spectropolarimetry suggested a minor change in spatial arrangement of α-helix/helices, resulting in an increased affinity of the glycated trypsin for this small synthetic substrate. PMID:26047909

  12. Influence of attachment strategy on the thermal stability of hybridized DNA on gold surfaces.

    PubMed

    Petty, Tyler J; Wagner, Caleb E; Opdahl, Aric

    2014-12-23

    The thermal stabilities of double-stranded DNA hybrids immobilized on gold surfaces are shown to be significantly affected by the conformation of the hybrid. To analyze this behavior, DNA probes were immobilized using attachment strategies where the nucleotides within the strand had varying levels of interactions with the gold substrate. The abilities of these probes to form double-stranded hybrids with solution DNA targets were evaluated by surface plasmon resonance (SPR) over a temperature range 25-60 °C. The measurements were used to construct thermal stability profiles for hybrids in each conformation. We observe that DNA hybrids formed with probe strands that interact extensively with the gold surface have stability profiles that are shifted lower by 5-10 °C compared to hybrids formed with end-tethered probes that have fewer interactions with the surface. The results provide an understanding of the experimental conditions in which these weaker DNA hybrids can form and show the additional complexity of evaluating denaturation profiles generated from DNA on surfaces. PMID:25457775

  13. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties.

    PubMed

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-06-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ∼4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (∼60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications. PMID:27227818

  14. Phosphorus-Assisted Biomass Thermal Conversion: Reducing Carbon Loss and Improving Biochar Stability

    PubMed Central

    Zhao, Ling; Cao, Xinde; Zheng, Wei; Kan, Yue

    2014-01-01

    There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT), and triple superphosphate (TSP), were used as additives to wheat straw with a ratio of 1: 0.4–0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar) to 46.9%–56.9% (modified biochars). Carbon loss during pyrolysis was reduced from 51.7% to 35.5%–47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity. PMID:25531111

  15. Phosphorus-assisted biomass thermal conversion: reducing carbon loss and improving biochar stability.

    PubMed

    Zhao, Ling; Cao, Xinde; Zheng, Wei; Kan, Yue

    2014-01-01

    There is often over 50% carbon loss during the thermal conversion of biomass into biochar, leading to it controversy for the biochar formation as a carbon sequestration strategy. Sometimes the biochar also seems not to be stable enough due to physical, chemical, and biological reactions in soils. In this study, three phosphorus-bearing materials, H3PO4, phosphate rock tailing (PRT), and triple superphosphate (TSP), were used as additives to wheat straw with a ratio of 1: 0.4-0.8 for biochar production at 500°C, aiming to alleviate carbon loss during pyrolysis and to increase biochar-C stabilization. All these additives remarkably increased the biochar yield from 31.7% (unmodified biochar) to 46.9%-56.9% (modified biochars). Carbon loss during pyrolysis was reduced from 51.7% to 35.5%-47.7%. Thermogravimetric analysis curves showed that the additives had no effect on thermal stability of biochar but did enhance its oxidative stability. Microbial mineralization was obviously reduced in the modified biochar, especially in the TSP-BC, in which the total CO2 emission during 60-d incubation was reduced by 67.8%, compared to the unmodified biochar. Enhancement of carbon retention and biochar stability was probably due to the formation of meta-phosphate or C-O-PO3, which could either form a physical layer to hinder the contact of C with O2 and bacteria, or occupy the active sites of the C band. Our results indicate that pre-treating biomass with phosphors-bearing materials is effective for reducing carbon loss during pyrolysis and for increasing biochar stabilization, which provides a novel method by which biochar can be designed to improve the carbon sequestration capacity. PMID:25531111

  16. Comparative evaluation of different thermally modified wood samples finishing with UV-curable and waterborne coatings

    NASA Astrophysics Data System (ADS)

    Herrera, René; Muszyńska, Monika; Krystofiak, Tomasz; Labidi, Jalel

    2015-12-01

    Thermally modified wood has been developed as an industrial method to improve durability and dimensional stability of wood and thus extends the range of uses and service life of wood-based products. Despite the improvements gained by treatment, surface finishing using coatings prevents esthetical changes such as color degradation or occasional growth of mold adding protection in outdoor use and extending the service life of products. The wood finishing process was carried out with commercially available waterborne and UV-curable coatings on industrially modified at 192, 200, 212 °C and unmodified European ash (Fraxinus excelsior L.) wood, using an industrial rollers system and a laboratory brushing system. Changes caused by thermal treatment which could affect the surface finish were measured and compared with control samples, such as water uptake, wettability and acidity. Following the wood finishing, surface properties and esthetic changes were evaluated; as well as the coatings performance. Thermally modified wood presented improved adherence compared with unmodified wood with a significant improvement in samples modified at 212 °C, which also present the highest hardness when UV-cured. Finishes with UV-curing maintain the hydrophobic effect of thermally modified wood, whereas waterborne finishes increase the surface wettability. Thermal modification did not negatively influence on the elastic properties of the coated substrate and thus allows this material to be finished with different coating systems in the same conditions as unmodified wood.

  17. Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

    NASA Technical Reports Server (NTRS)

    Cofield, Richard; Kasl, Eldon P.

    2010-01-01

    We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

  18. Thermal and trophic stability of deeper Maine lakes in granite waterhsheds implacted by acid deposition

    SciTech Connect

    Stauffer, R.E.; Wittchen, B.D. )

    1990-09-01

    Acid deposition can lead to lake and watershed acidification, increases in lake transparency, and reduction in thermal stability and hypolimnetic oxygen deficits. On the basis of lake surveys during August-September 1985, we determined to what extent the deeper (maximum depth z{sub m}{gt}17 m) Maine lakes in acid-sensitive granitic watersheds have registered changes in temperature and oxygen stratification, as compared to 1938-1942, when G.P. Cooper performed the earliest scientific surveys of the state's lakes. After correcting for small but geographically consistent interannual differences in summer hypolimnetic temperatures related to spring turnover, and weather-dependent differences in mixed layer depth, there has been no significant change in thermal stratification in these Maine lakes over approximately 43 years. On the basis of specific historical contrasts in the late summer metalimnetic, hypolimnetic, and bathylimnetic oxygen concentrations there has been no significant change in lake trophic state or transparency.

  19. Improvements in UV stability for FEP/Ag based thermal control materials

    NASA Astrophysics Data System (ADS)

    Grieser, James; Maas, Gerald

    2003-09-01

    Darkening of FEP/Ag based Thermal Control (TC) materials after UV exposure has been documented for several years. This End of Life (EOL) Solar Absorptance (α) increase and the corresponding performance degradation must be taken into account in the preliminary design of spacecraft. Astral Technology Unlimited, Inc. (ATU) has developed new processes and coatings to improve the UV stability of FEP/Ag based TC materials. Test results of this development effort are presented. Data for several new coating combinations along with data on the current "Industry Standard" material are compared for up to 27,000 Equivalent Sun Hours (ESH) of UV exposure. The resulting solar absorptance improvements are very dramatic and should allow future satellite designs with the EOL solar alpha to be nearly identical to the Beginning of Life (BOL) values. Satellites using these new TC materials can have optimum thermal-optical performance for the life of the spacecraft.

  20. Study of phase transformation and microstructure of alcohol washed titania nanoparticles for thermal stability

    SciTech Connect

    Kaur, Manpreet Singh, Gaganjot; Bimbraw, Keshav; Uniyal, Poonam

    2015-08-28

    Nanostructured titania have been successfully synthesized by hydrolysis of alkoxide at calcination temperatures 500 °C, 600 °C and 700 °C. As the calcination temperature increases, alcohol washed samples show lesser rutile content as compared to water washed samples. Morphology and Particle sizes was determined by field emission scanning electron microscopy (FESEM), while thermogravimetric-differential scanning calorimetry (TG-DSC) was used to determine thermal stability. Alcohol washed samples undergo 30% weight loss whereas 16% in water washed samples was observed. The mean particle sizes were found to be increase from 37 nm to 100.9 nm and 35.3 nm to 55.2 nm for water and alcohol washed samples respectively. Hydrolysis of alkoxide was shown to be an effective means to prepare thermally stable titania by using alcohol washed samples as a precursor.

  1. Thermal Stability of Nanocrystalline Alloys by Solute Additions and A Thermodynamic Modeling

    NASA Astrophysics Data System (ADS)

    Saber, Mostafa

    an example, model predictions are compared to experimental results for Fe-Cr-Zr and Fe-Ni-Zr alloy systems. Consistency between the experimental results and the present model predictions provide a more rigorous criterion for investigating thermal stabilization. However, other possible contributions for grain growth stabilization should still be considered.

  2. Towards a better understanding of rock wall thermal regime and stability in Norway

    NASA Astrophysics Data System (ADS)

    Sæterdal Myhra, Kristin; Etzelmüller, Bernd

    2013-04-01

    Hazardous rock fall events caused by slope failure have drawn attention towards the physical processes that affect slope stability of rock walls. The stability of a slope is determined by the interplay between driving and resisting forces acting on the site. A typical scenario is a gravity driving force that is counteracted by friction and cohesion forces. The nature of these forces is dependent on a complex interaction between a range of factors, amongst them topography, rock mass quality and hydrology. Steep topography increases the gravitational driving force, while factors such as water pressure and discontinuities in the rock mass decrease the resisting forces. Hence, slope instabilities evolve in time and space and is dependent upon a range of factors influencing each other through feedback processes. During the past century, the number of slope failures in the European Alps have increased, leading to an increasing focus on degrading permafrost as a possible factor for slope failure. Degrading permafrost might influence both the driving shear stresses and the resisting shear forces in frozen rock faces, causing changes in the force balance of the bedrock. Though degrading permafrost is considered to have an impact on the stability of rock slopes, the physical processes behind the causality are not fully understood. For the Scandinavian mountains, a possible relationship between permafrost and rock slope stability is poorly investigated and understood. Many unstable rock faces have been mapped and some are surveyed, and in several locations temperature loggers monitor the ground thermal regime in steep slopes. It is evident that many unstable rock faces are situated in or close to the zone of mountain permafrost. This project tries to contribute to the understanding of rock wall stability with respect to the influence of ground thermal regime and changing climatic conditions. A first goal of this study is to gain a better understanding of the sensitivity of

  3. Acacia gum as modifier of thermal stability, solubility and emulsifying properties of α-lactalbumin.

    PubMed

    de Oliveira, Fabíola Cristina; Dos Reis Coimbra, Jane Sélia; de Oliveira, Eduardo Basílio; Rodrigues, Marina Quadrio Raposo Branco; Sabioni, Rachel Campos; de Souza, Bartolomeu Warlene Silva; Santos, Igor José Boggione

    2015-03-30

    Protein-polysaccharide conjugates often display improved techno-functional properties when compared to their individual involved biomolecules. α-Lactalbumin:acacia gum (α-la:AG) conjugates were prepared via Maillard reaction by the dry-heating method. Conjugate formation was confirmed using results of absorbance, o-phthalaldehyde test, sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) and size exclusion chromatography. Techno-functional properties (emulsifying characteristics, solubility, and thermal stability) were evaluated for α-la, α-la/AG mixtures and α-la:AG conjugates. Conjugate thermal stability was improved compared to pure α-la treated at the same conditions of conjugate formation. Response surface methodology was used to establish models to predict solubility and emulsifying activity as functions of the salt concentration, pH and reaction time. α-la:AG conjugate solubility is affected in a complex manner by the three factors analyzed. Emulsifying activity index (EAI) of α-la is significantly affected by pH, while the α-la:AG EAI is affected by the three analyzed factors. Both solubility and EAI are maximized with pH 8.0, NaCl concentration of 0.3 mol L(-1) and two days of Maillard reaction. PMID:25563962

  4. Improving thermal stability of thermophilic L-threonine aldolase from Thermotoga maritima.

    PubMed

    Wieteska, Lukasz; Ionov, Maksim; Szemraj, Janusz; Feller, Claudia; Kolinski, Andrzej; Gront, Dominik

    2015-04-10

    Threonine aldolase (TA) catalyzes a reversible reaction, in which threonine is decomposed into glycine and acetaldehyde. The same enzyme can be used to catalyze aldol reaction between glycine and a variety of aromatic and aliphatic aldehydes, thus creating various alpha-amino-alcohols. Therefore, TA is a very promising enzyme that could be used to prepare biologically active compounds or building blocks for pharmaceutical industry. Rational design was applied to thermophilic TA from Thermotoga maritima to improve thermal stability by the incorporation of salt and disulfide bridges between subunits in the functional tetramer. An activity assay together with CD analysis and Western-blot detection was used to evaluate mutants. Except one, each of the designed mutants preserved activity toward the natural substrate. One of the 10 proposed single point mutants, P56C, displayed significantly enhanced stability compared to the wild type (WT). Its initial activity was not affected and persisted longer than WT, proportionally to increased stability. Additionally one of the mutants, W86E, displayed enhanced activity, with stability similar to WT. Higher activity may be explained by a subtle change in active site availability. Salt bridge formation between glutamic acid at position 86 and arginine at position 120 in the neighboring chain may be responsible for the slight shift of the chain fragment, thus creating wider access to the active site both for the substrate and PLP. PMID:25701680

  5. Thermal gravity analysis for the study of stability of graphene oxide-glycine nanocomposites

    NASA Astrophysics Data System (ADS)

    Najafi, F.; Rajabi, M.

    2015-05-01

    In this work, we synthesized graphene oxide-glycine (GO-G) nanocomposite. To produce this nanocomposite with GO surface, glycine with known concentration was added to GO suspension in ethanol solvent. Nanocomposites provided were characterized by scanning electron microscope (SEM) and Fourier transform infrared (FT-IR) spectroscopy, respectively. Thermogravimetric analysis (TGA) was employed to investigate the thermal stability of these nanocomposites. Results of characterization by SEM and FT-IR showed that nanocomposite was created by the reaction between GO and G. Study of thermal stability by TGA showed that thermal stability of GO was more than that of the GO-G nanocomposite.

  6. Experimentation and Modeling of Jet A Thermal Stability in a Heated Tube

    NASA Technical Reports Server (NTRS)

    Khodabandeh, Julia W.

    2005-01-01

    High performance aircraft typically use hydrocarbon fuel to regeneratively cool the airframe and engine components. As the coolant temperatures increase, the fuel may react with dissolved oxygen forming deposits that limit the regenerative cooling system performance. This study investigates the deposition of Jet A using a thermal stability experiment and computational fluid dynamics (CFD) modeling. The experimental portion of this study is performed with a high Reynolds number thermal stability (HiRets) tester in which fuel passes though an electrically heated tube and the fuel outlet temperature is held constant. If the thermal stability temperature of the fuel is exceeded, deposits form and adhere to the inside of the tube creating an insulating layer between the tube and the fuel. The HiRets tester measures the tube outer wall temperatures near the fuel outlet to report the effect of deposition occurring inside the tube. Final deposits are also estimated with a carbon burn off analysis. The CFD model was developed and used to simulate the fluid dynamics, heat transfer, chemistry, and transport of the deposit precursors. The model is calibrated to the experiment temperature results and carbon burn-off deposition results. The model results show that the dominant factor in deposition is the heated wall temperature and that most of the deposits are formed in the laminar sublayer. The models predicted a 7.0E-6 kilograms per square meter-sec deposition rate, which compared well to the carbon burn-off analysis deposition rate of 1.0E-6 kilograms per square meter-sec.

  7. Development and evaluation of suspension plasma sprayed yttria stabilized zirconia coatings as thermal barriers

    NASA Astrophysics Data System (ADS)

    van Every, Kent J.

    The insulating effects from thermal barrier coatings (TBCs) in gas turbine engines allow for increased operational efficiencies and longer service lifetimes. Consequently, improving TBCs can lead to enhanced gas turbine engine performance. This study was conducted to investigate if yttria-stabilized zirconia (YSZ) coatings, the standard industrial choice for TBCs, produced from nano-sized powder could provide better thermal insulation than current commericial YSZ coatings generated using micron-sized powders. The coatings for this research were made via the recently developed suspension plasma spraying (SPS) process. With SPS, powders are suspended in a solvent containing dispersing agents; the suspension is then injected directly into a plasma flow that evaporates the solvent and melts the powder while transporting it to the substrate. Although related to the industrial TBC production method of air plasma spraying (APS), SPS has two important differences---the ability to spray sub-micron diameter ceramic particles, and the ability to alloy the particles with chemicals dissolved in the solvent. These aspects of SPS were employed to generate a series of coatings from suspensions containing ˜100 nm diameter YSZ powder particles, some of which were alloyed with neodymium and ytterbium ions from the solvent. The SPS coatings contained columnar structures not observed in APS TBCs; thus, a theory was developed to explain the formation of these features. The thermal conductivity of the coatings was tested to evaluate the effects of these unique microstructures and the effects of the alloying process. The results for samples in the as-sprayed and heat-treated conditions were compared to conventional YSZ TBCs. This comparison showed that, relative to APS YSZ coatings, the unalloyed SPS samples typically exhibited higher as-sprayed and lower heat-treated thermal conductivities. All thermal conductivity values for the alloyed samples were lower than conventional YSZ TBCs

  8. Production and thermal stability of pure and Cr3+ -doped hydroxyapatite

    NASA Astrophysics Data System (ADS)

    de Araujo, T. S.; de Souza, S. O.; de Sousa, E. M. B.; Araújo, M. S.

    2010-11-01

    Hydroxyapatite (HAP) have been used as starting material for biomedical applications. The pure and Cr3+ -doped hydroxyapatite were prepared by chemical precipitation reactions at 100, 500 e 800 °C in order to investigate the thermal stability of these materials. The characterization of the thermal behavior of this phosphate, especially on the structural changes with heating, is very important for production of sunscreens The powders were characterized using chemical analysis: X-ray diffraction (XRD) and thermal analysis. The present study was successful in the preparation of pure hydroxyapatite and chromium substituted hydroxyapatites with good thermal stability and nanoparticles formation.

  9. A bio-imprinted urease biosensor: Improved thermal and operational stabilities.

    PubMed

    Teke, Mustafa; Sezgintürk, Mustafa Kemal; Dinçkaya, Erhan; Telefoncu, Azmi

    2008-01-15

    Despite the increasing number of applications of biosensors in many fields, the construction of a steady biosensor remains still challenging. The high stability of molecularly bio-imprinted enzymes for its substrate can make them ideal alternatives as recognition elements for sensors. Urease (urea aminohydrolase, EC 3.5.1.5), which catalysis the hydrolysis of urea to ammonia and carbon dioxide, has been used in immobilized form in artificial kidney for blood detoxification. According to one report approximately half a million patients worldwide are being supported by haemodialysis. In this study, the enzyme of urease was first complexed by using a substrate analogue, thiourea, in aqueous medium and then this enzyme was immobilized on gelatin by crosslinking with glutaraldehyde on a glass electrode surface. Similarly, urease noncomplexed with thiourea was also immobilized on a glass electrode in the same conditions. The aim of the study was to compare the two biosensors in terms of their repeatability, pH stability and thermal stability, and also, linear ranges of two biosensors were compared with each other. PMID:18371690

  10. Impact of active material surface area on thermal stability of LiCoO2 cathode

    NASA Astrophysics Data System (ADS)

    Geder, Jan; Hoster, Harry E.; Jossen, Andreas; Garche, Jürgen; Yu, Denis Y. W.

    2014-07-01

    Thermal stability of charged LiCoO2 cathodes with various surface areas of active material is investigated in order to quantify the effect of LiCoO2 surface area on thermal stability of cathode. Thermogravimetric analyses and calorimetry have been conducted on charged cathodes with different active material surface areas. Besides reduced thermal stability, high surface area also changes the active material decomposition reaction and induces side reactions with additives. Thermal analyses of LiCoO2 delithiated chemically without any additives or with a single additive have been conducted to elaborate the effect of particle size on side reactions. Stability of cathode-electrolyte system has been investigated by accelerating rate calorimetry (ARC). Arrhenius activation energy of cathode decomposition has been calculated as function of conversion at different surface area of active material.

  11. Flammability, odor, offgassing, thermal vacuum stability, and compatibility with aerospace fluids of wire insulations

    NASA Technical Reports Server (NTRS)

    Hirsch, David; Johnson, Harry

    1994-01-01

    The NASA Lewis Research Center requested NASA Johnson Space Center White Sands Test Facility to conduct flammability, odor, offgassing, thermal vacuum stability, and compatibility tests with aerospace fluids of several wire insulations.

  12. Thermal-oxidation stability of diesel fuels. Interim report, October 1983-January 1986

    SciTech Connect

    Stavinoha, L.L.; Barbee, J.G.; Yost, D.M.

    1986-02-01

    Injector fouling bench tests(IFBT) and modified Jet Fuel Thermal Oxidation Test(JFTOT, ASTMD 3241) were used to develop methodology for evaluating the thermal stability of diesel fuels. A new method for measuring the thickness of lacquer-type fuel deposits formed on test surfaces at elevated temperatures was developed and applied to a variety of fuels, both with and without MIL-S-53021(additive stabilizer package). The utility of this technique greatly expands the capability for exploring and defining diesel-fuel thermal stability with respect to both material and kinetic studies. Correlation of IFBT and JFTOT type tests including definitions of temperature, flow, test-surface metallurgy and fuel additive effects can now be performed to better understand diesel thermal stability and provide test methodology/test limit information for fuel-specification consideration.

  13. Thermal destruction of erythrocyte spectrin: Rheology, deformability, and stability with respect to detergents

    NASA Astrophysics Data System (ADS)

    Yamaikina, M. V.; Mansurov, V. A.; Ivashkevich, É. V.

    1996-05-01

    By means of blood heating in the region of the thermal denaturation transition of spectrin (50°C) the relationship between the stability of erythrocytes with respect to detergents and their deformability and rheological parameters of blood was studied.

  14. Correlation between iron self-diffusion and thermal stability in doped iron nitride thin films

    SciTech Connect

    Tayal, Akhil; Gupta, Mukul E-mail: dr.mukul.gupta@gmail.com; Kumar, D.; Reddy, V. R.; Gupta, Ajay; Amir, S. M.; Korelis, Panagiotis; Stahn, Jochen

    2014-12-14

    Nanocrystalline Fe-X-N thin films (with doping X = 0, 3.1 at. % Al, 1.6 at. % Zr), were deposited using reactive ion beam sputtering. Magnetization study reveals that the deposited films exhibit a perpendicular magnetic anisotropy. Thermal stability of the films was investigated systematically and it was observed that the structural and the magnetic stability gets significantly enhanced with Al doping, whereas Zr doping has only a marginal effect. Fe self-diffusion, obtained using polarized neutron reflectivity, shows a suppression with both additives. A correlation between the thermal stability and the diffusion process gives a direct evidence that the enhancement in the thermal stability is primarily diffusion controlled. A combined picture of diffusion, structural, and magnetic stability has been drawn to understand the obtained results.

  15. Engineering Interface Structures and Thermal Stabilities via SPD Processing in Bulk Nanostructured Metals

    DOE PAGESBeta

    Zheng, Shijian; Carpenter, John S.; McCabe, Rodney J.; Beyerlein, Irene J.; Mara, Nathan A.

    2014-02-27

    Nanostructured metals achieve extraordinary strength but suffer from low thermal stability, both a consequence of a high fraction of interfaces. Overcoming this tradeoff relies on making the interfaces themselves thermally stable. In this paper, we show that the atomic structures of bi-metal interfaces in macroscale nanomaterials suitable for engineering structures can be significantly altered via changing the severe plastic deformation (SPD) processing pathway. Two types of interfaces are formed, both exhibiting a regular atomic structure and providing for excellent thermal stability, up to more than half the melting temperature of one of the constituents. Most importantly, the thermal stability ofmore » one is found to be significantly better than the other, indicating the exciting potential to control and optimize macroscale robustness via atomic-scale bimetal interface tuning. As a result, we demonstrate an innovative way to engineer pristine bimetal interfaces for a new class of simultaneously strong and thermally stable materials.« less

  16. Engineering Interface Structures and Thermal Stabilities via SPD Processing in Bulk Nanostructured Metals

    SciTech Connect

    Zheng, Shijian; Carpenter, John S.; McCabe, Rodney J.; Beyerlein, Irene J.; Mara, Nathan A.

    2014-02-27

    Nanostructured metals achieve extraordinary strength but suffer from low thermal stability, both a consequence of a high fraction of interfaces. Overcoming this tradeoff relies on making the interfaces themselves thermally stable. In this paper, we show that the atomic structures of bi-metal interfaces in macroscale nanomaterials suitable for engineering structures can be significantly altered via changing the severe plastic deformation (SPD) processing pathway. Two types of interfaces are formed, both exhibiting a regular atomic structure and providing for excellent thermal stability, up to more than half the melting temperature of one of the constituents. Most importantly, the thermal stability of one is found to be significantly better than the other, indicating the exciting potential to control and optimize macroscale robustness via atomic-scale bimetal interface tuning. As a result, we demonstrate an innovative way to engineer pristine bimetal interfaces for a new class of simultaneously strong and thermally stable materials.

  17. Remarkable thermal stability of gold nanoparticles functionalised with ruthenium phthalocyanine complexes

    NASA Astrophysics Data System (ADS)

    King, Shirin R.; Shimmon, Susan; Gentle, Angus R.; Westerhausen, Mika T.; Dowd, Annette; McDonagh, Andrew M.

    2016-05-01

    A gold nanoparticle (AuNP) ruthenium phthalocyanine (RuPc) nanocomposite has been synthesised that exhibits high thermal stability. Electrical resistance measurements revealed that the nanocomposite is stable up to ∼320 °C. Examination of the nanocomposite and the RuPc stabiliser complex using thermogravimetric analysis and differential scanning calorimetry show that the remarkable thermal stability is due to the RuPc molecules, which provide an effective barrier to sintering of the AuNPs.

  18. Remarkable thermal stability of gold nanoparticles functionalised with ruthenium phthalocyanine complexes.

    PubMed

    King, Shirin R; Shimmon, Susan; Gentle, Angus R; Westerhausen, Mika T; Dowd, Annette; McDonagh, Andrew M

    2016-05-27

    A gold nanoparticle (AuNP) ruthenium phthalocyanine (RuPc) nanocomposite has been synthesised that exhibits high thermal stability. Electrical resistance measurements revealed that the nanocomposite is stable up to ∼320 °C. Examination of the nanocomposite and the RuPc stabiliser complex using thermogravimetric analysis and differential scanning calorimetry show that the remarkable thermal stability is due to the RuPc molecules, which provide an effective barrier to sintering of the AuNPs. PMID:27087638

  19. Thermal stability and strength of deformation microstructures in pure copper

    SciTech Connect

    Saldana, C.; King, Alex H.; Chandrasekar, S.

    2012-05-18

    The plastic flow field produced by machining is utilized to access a range of deformation parameters in pure copper: strains of 1–7, strain rates of 1–1000 s−1 and temperatures as low as 77 K. The strength and stability of the severe plastic deformation microstructures including cellular, elongated, equiaxed and twinned types are characterized. Unique combinations of strengthening and stability are identified in the case of heavily twinned microstructures. These observations offer insights for improving the stability of both single-phase and multicomponent ultrafine-grained alloys.

  20. Thermal stabilization of chromium(VI) in kaolin.

    PubMed

    Wei, Yu-Ling; Chiu, Shu-Yuan; Tsai, Hsien-Neng; Yang, Yaw-Wen; Lee, Jyh-Fu

    2002-11-01

    Reduction of Cr(VI) by heating may be a useful detoxification mechanism for thermal immobilization. Using X-ray absorption spectroscopy, the change of speciation of chromium in 105 degrees C dried 3.7% Cr(VI)-sorbed kaolin further heated at 500, 900, or 1100 degrees C was studied. The 105 degrees C dried 3.7% Cr(VI)-sorbed kaolin sample was prepared by mixing 1.5 L of 0.257 M CrO3 solution (pH 0.71) with 0.5 kg of kaolin powder for 48 h, and then the slurry was heated (dried) at 105 degrees C until a constant weight was reached. The toxicity characteristic leaching procedure method was used to determine the percentage of leached chromium from all heated samples. In all 500-900 degrees C heated Cr(VI)-sorbed kaolin samples, Cr2O3 transformed from the hydrated Cr(VI) by a 4-h heat application was identified by the X-ray absorption near edge structure and extended X-ray absorption fine structure (EXAFS) spectroscopy as the key species that is leaching-resistant due to its low solubility. For the 1100 degrees C heated Cr(VI)-sorbed kaolin sample, the Fourier transform of its EXAFS spectrum indicates that the intensity of the peaks at 2.45 (Cr-Cr shell of Cr2O3) and 5.00 A (Cr-Cr and Cr-O shells of Cr2O3) without phase shift correction is either relatively smaller or disappearing, compared with that of the 500-900 degrees C heated Cr(VI)-sorbed kaolin samples. It is suggested that chromium octahedra were bridged to silica tetrahedra and incorporated in minerals formed at 1100 degrees C, such as mullite or sillimanite, since these phases were detected by XRD. Cr of this form is not easily leached. PMID:12433175

  1. Thermal Stabilization and Mechanical Properties of Nanocrystalline Iron-Nickel-Zirconium Alloys

    NASA Astrophysics Data System (ADS)

    Kotan, Hasan

    Ultrafine grained and nanostructured materials are promising for structural applications because of the high strength compared to coarse grained counterparts. However, their widespread application is limited by an inherently high driving force for thermally induced grain growth, even at low temperatures. Accordingly, the understanding of and control over grain growth in nanoscale materials is of great technological and scientific importance as many physical properties (i.e. mechanical properties) are functions of the average grain size and the grain size distribution within the microstructure. Here, we investigate the microstructural evolution and grain growth in Fe-Ni alloys with Zr addition and differentiate the stabilization mechanisms acting on grain boundaries. Fe-Ni alloys are chosen for stability investigations since they are important for understanding the behavior of many steels and other ferrous alloys. Zirconium is proven to be an effective grain size stabilizer in pure Fe and Fe-base systems. In this study, nanocrystalline alloys were prepared by high energy ball milling. In situ and ex situ experiments were utilized to directly follow grain growth and microstructural evolution as a function of temperature and composition. The information obtained from these experiments enables the real time observation of microstructural evolution and phase transformation and provides a unique view of dynamic reactions as they occur. The knowledge of the thermal stability will exploit the potential high temperature applications and the consolidation conditions (i.e. temperature and pressure) to obtain high dense materials for advanced mechanical tests. Our investigations reveal that the grain growth of Fe-Ni alloys is not affected by Ni content but strongly inhibited by the addition of 1 at% Zr up to about 700 °C. The microstructural stability is lost due to the bcc-to-fcc transformation (occurring at 700°C) by the sudden appearance of abnormally grown fcc grains

  2. Thermal stability of bimetallic Au/Fe nanoparticles in silica matrix

    SciTech Connect

    Pannu, Compesh Singh, Udai B. Hooda, Sonu Kabiraj, D. Avasthi, D. K.

    2014-04-24

    Thin silica film containing Au and Fe bimetallic nanoparticles were prepared by atom beam cosputtering. The samples were annealed at different temperatures from 400 to 800° C to study the thermal stability of bimetallic nanoparticles using X ray diffraction. It is observed that at 800° C strong structural rearrangement took place leading to thermal decomposition of bimetallic nanoparticles.

  3. Coaxial carbon@boron nitride nanotube arrays with enhanced thermal stability and compressive mechanical properties

    NASA Astrophysics Data System (ADS)

    Jing, Lin; Tay, Roland Yingjie; Li, Hongling; Tsang, Siu Hon; Huang, Jingfeng; Tan, Dunlin; Zhang, Bowei; Teo, Edwin Hang Tong; Tok, Alfred Iing Yoong

    2016-05-01

    Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability. CNT arrays are grown using a commercially available thermal chemical vapor deposition (TCVD) technique and an outer BNNT with a wall thickness up to 1.37 nm is introduced by a post-growth TCVD treatment. Importantly, compared to the as-grown CNT arrays which deform almost plastically upon compression, the coaxial C@BNNT arrays exhibit an impressive ~4-fold increase in compressive strength with nearly full recovery after the first compression cycle at a 50% strain (76% recovery maintained after 10 cycles), as well as a significantly high and persistent energy dissipation ratio (~60% at a 50% strain after 100 cycles), attributed to the synergistic effect between the CNT and outer BNNT. Additionally, the as-prepared C@BNNT arrays show an improved structural stability in air at elevated temperatures, attributing to the outstanding thermal stability of the outer BNNT. This work provides new insights into tailoring the mechanical and thermal behaviours of arbitrary CNT arrays which enables a broader range of applications.Vertically aligned carbon nanotube (CNT) arrays have aroused considerable interest because of their remarkable mechanical properties. However, the mechanical behaviour of as-synthesized CNT arrays could vary drastically at a macro-scale depending on their morphologies, dimensions and array density, which are determined by the synthesis method. Here, we demonstrate a coaxial carbon@boron nitride nanotube (C@BNNT) array with enhanced compressive strength and shape recoverability

  4. Effect of Si additions on thermal stability and the phase transition sequence of sputtered amorphous alumina thin films

    SciTech Connect

    Bolvardi, H.; Baben, M. to; Nahif, F.; Music, D. Schnabel, V.; Shaha, K. P.; Mráz, S.; Schneider, J. M.; Bednarcik, J.; Michalikova, J.

    2015-01-14

    Si-alloyed amorphous alumina coatings having a silicon concentration of 0 to 2.7 at. % were deposited by combinatorial reactive pulsed DC magnetron sputtering of Al and Al-Si (90-10 at. %) split segments in Ar/O{sub 2} atmosphere. The effect of Si alloying on thermal stability of the as-deposited amorphous alumina thin films and the phase formation sequence was evaluated by using differential scanning calorimetry and X-ray diffraction. The thermal stability window of the amorphous phase containing 2.7 at. % of Si was increased by more than 100 °C compared to that of the unalloyed phase. A similar retarding effect of Si alloying was also observed for the α-Al{sub 2}O{sub 3} formation temperature, which increased by more than 120 °C. While for the latter retardation, the evidence for the presence of SiO{sub 2} at the grain boundaries was presented previously, this obviously cannot explain the stability enhancement reported here for the amorphous phase. Based on density functional theory molecular dynamics simulations and synchrotron X-ray diffraction experiments for amorphous Al{sub 2}O{sub 3} with and without Si incorporation, we suggest that the experimentally identified enhanced thermal stability of amorphous alumina with addition of Si is due to the formation of shorter and stronger Si–O bonds as compared to Al–O bonds.

  5. High thermal stability and sluggish crystallization kinetics of high-entropy bulk metallic glasses

    NASA Astrophysics Data System (ADS)

    Yang, M.; Liu, X. J.; Ruan, H. H.; Wu, Y.; Wang, H.; Lu, Z. P.

    2016-06-01

    Metallic glasses are metastable and their thermal stability is critical for practical applications, particularly at elevated temperatures. The conventional bulk metallic glasses (BMGs), though exhibiting high glass-forming ability (GFA), crystallize quickly when being heated to a temperature higher than their glass transition temperature. This problem may potentially be alleviated due to the recent developments of high-entropy (or multi-principle-element) bulk metallic glasses (HE-BMGs). In this work, we demonstrate that typical HE-BMGs, i.e., ZrTiHfCuNiBe and ZrTiCuNiBe, have higher kinetic stability, as compared with the benchmark glass Vitreoy1 (Zr41.2Ti13.8Cu12.5Ni10Be22.5) with a similar chemical composition. The measured activation energy for glass transition and crystallization of the HE-BMGs is nearly twice that of Vitreloy 1. Moreover, the sluggish crystallization region ΔTpl-pf, defined as the temperature span between the last exothermic crystallization peak temperature Tpl and the first crystallization exothermic peak temperature Tpf, of all the HE-BMGs is much wider than that of Vitreloy 1. In addition, high-resolution transmission electron microscopy characterization of the crystallized products at different temperatures and the continuous heating transformation diagram which is proposed to estimate the lifetime at any temperature below the melting point further confirm high thermal stability of the HE-BMGs. Surprisingly, all the HE-BMGs show a small fragility value, which contradicts with their low GFA, suggesting that the underlying diffusion mechanism in the liquid and the solid of HE-BMGs is different.

  6. Thermal stability of alpha-amylase from malted jowar (Sorghum bicolor).

    PubMed

    Kumar, R Siva Sai; Singh, Sridevi Annapurna; Rao, A G Appu

    2005-08-24

    Malted cereals are rich sources of alpha-amylase, which catalyzes the random hydrolysis of internal alpha-(1-4)-glycosidic bonds of starch, leading to liquefaction. Amylases play a role in the predigestion of starch, leading to a reduction in the water absorption capacity of the cereal. Among the three cereal amylases (barley, ragi, and jowar), jowar amylase is found to be the most thermostable. The major amylase from malted jowar, a 47 kDa alpha-amylase, purified to homogeneity, is rich in beta structure ( approximately 60%) like other cereal amylases. T(m), the midpoint of thermal inactivation, is found to be 69.6 +/- 0.3 degrees C. Thermal inactivation is found to follow first-order kinetics at pH 4.8, the pH optimum of the enzyme. Activation energy, E(a), is found to be 45.3 +/- 0.2 kcal mol(-)(1). The activation enthalpy (DeltaH), entropy (DeltaS*), and free energy change (DeltaG) are calculated to be 44.6 +/- 0.2 kcal mol(-)(1), 57.1 +/- 0.3 cal mol(-)(1) K(-)(1), and 25.2 +/- 0.2 kcal mol(-)(1), respectively. The thermal stability of the enzyme in the presence of the commonly used food additives NaCl and sucrose has been studied. T(m) is found to decrease to 66.3 +/- 0.3, 58.1 +/- 0.2, and 48.1 +/- 0.5 degrees C, corresponding to the presence of 0.1, 0.5, and 1 M NaCl, respectively. Sucrose acts as a stabilizer; the T(m) value is found to be 77.3 +/- 0.3 degrees C compared to 69.6 +/- 0.3 degrees C in the control. PMID:16104815

  7. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-09-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  8. Thermal Shock Resistance of Stabilized Zirconia/Metal Coat on Polymer Matrix Composites by Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Zhu, Ling; Huang, Wenzhi; Cheng, Haifeng; Cao, Xueqiang

    2014-12-01

    Stabilized zirconia/metal coating systems were deposited on the polymer matrix composites by a combined thermal spray process. Effects of the thicknesses of metal layers and ceramic layer on thermal shock resistance of the coating systems were investigated. According to the results of thermal shock lifetime, the coating system consisting of 20 μm Zn and 125 μm 8YSZ exhibited the best thermal shock resistance. Based on microstructure evolution, failure modes and failure mechanism of the coating systems were proposed. The main failure modes were the formation of vertical cracks and delamination in the outlayer of substrate, and the appearance of coating spallation. The residual stress, thermal stress and oxidation of substrate near the substrate/metal layer interface were responsible for coating failure, while the oxidation of substrate near the substrate/coating interface was the dominant one.

  9. Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices

    NASA Astrophysics Data System (ADS)

    Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T.; Durrant, James R.

    2015-10-01

    Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PEDOT:PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced “burn-in” effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions.

  10. Toward Improved Lifetimes of Organic Solar Cells under Thermal Stress: Substrate-Dependent Morphological Stability of PCDTBT:PCBM Films and Devices

    PubMed Central

    Li, Zhe; Ho Chiu, Kar; Shahid Ashraf, Raja; Fearn, Sarah; Dattani, Rajeev; Cheng Wong, Him; Tan, Ching-Hong; Wu, Jiaying; Cabral, João T.; Durrant, James R.

    2015-01-01

    Morphological stability is a key requirement for outdoor operation of organic solar cells. We demonstrate that morphological stability and lifetime of polymer/fullerene based solar cells under thermal stress depend strongly on the substrate interface on which the active layer is deposited. In particular, we find that the stability of benchmark PCDTBT/PCBM solar cells under modest thermal stress is substantially increased in inverted solar cells employing a ZnO substrate compared to conventional devices employing a PEDOT:PSS substrate. This improved stability is observed to correlate with PCBM nucleation at the 50 nm scale, which is shown to be strongly influenced by different substrate interfaces. Employing this approach, we demonstrate remarkable thermal stability for inverted PCDTBT:PC70BM devices on ZnO substrates, with negligible (<2%) loss of power conversion efficiency over 160 h under 85 °C thermal stress and minimal thermally induced “burn-in” effect. We thus conclude that inverted organic solar cells, in addition to showing improved environmental stability against ambient humidity exposure as widely reported previously, can also demonstrate enhanced morphological stability. As such we show that the choice of suitable substrate interfaces may be a key factor in achieving prolonged lifetimes for organic solar cells under thermal stress conditions. PMID:26468676

  11. Dimensional stability of fused silica, Invar, and several ultralow thermal expansion materials

    NASA Technical Reports Server (NTRS)

    Berthold, J. W., III; Jacobs, S. F.; Norton, M. A.

    1976-01-01

    A method is developed for testing the long-term dimensional stability of an iodine-stabilized He-Ne laser, using a technique whereby thermal expansion coefficients are measured by forming a Fabry-Perot etalon from the sample and monitoring the optical resonant frequencies with tunable sidebands impressed on a laser beam from a frequency-stabilized He-Ne laser. A change of 1 ppm over a 3-yr period on the part of fused silica dimensions and the differential thermal expansion of Invar LR-35 and Super Invar materials are noted. The method is of interest for the metrology of extremely stable structures such as telescopes and optical resonators.

  12. Infiltrated Phlogopite Micas with Superior Thermal Cycle Stability as Compressive Seals for Solid Oxide Fuel Cells

    SciTech Connect

    Chou, Y S.; Stevenson, Jeffry W.

    2005-03-01

    Thermal cycle stability is one of the most stringent requirements for sealants in solid oxide fuel cell stacks. The sealants have to survive several hundreds to thousands of thermal cycles during lifetime operation in stationary and transportation applications. Recently, researchers at the Pacific Northwest National Laboratory have developed a novel method to infiltrate the mica flakes with a wetting or liquid forming material such that the leak path will be reduced from 3-D to 2-D and achieve good thermal cycle stability with low leak rates.

  13. Investigating the Thermal and Phase Stability of Nanocrystalline Ni-W Produced by Electrodeposition, Sputtering, and Mechanical Alloying

    NASA Astrophysics Data System (ADS)

    Marvel, Christopher Jonathan

    The development of nanocrystalline materials has been increasingly pursued over the last few decades. They have been shown to exhibit superior properties compared to their coarse-grain counterparts, and thus present a tremendous opportunity to revolutionize the performance of nanoscale devices or bulk structural materials. However, nanocrystalline materials are highly prone to grain growth, and if the nanocrystalline grains coarsen, the beneficial properties are lost. There is a strong effort to determine the most effective thermal stability mechanisms to avoid grain growth, but the physical nature of nanocrystalline grain growth is still unclear due to a lack of detailed understanding of nanocrystalline microstructures. Furthermore, the influence of contamination has scarcely been explored with advanced transmission electron microscopy techniques, nor has there been a direct comparison of alloys fabricated with different bulk processes. Therefore, this research has applied aberration-corrected scanning transmission electron microscopy to characterize nanocrystalline Ni-W on the atomic scale and elucidate the physical grain growth behavior. Three primary objectives were pursued: (1) explore the thermal stability mechanisms of nanocrystalline Ni-W, (2) evaluate the phase stability of Ni-W and link any findings to grain growth behavior, and (3) compare the influences of bulk fabrication processing, including electrodeposition, DC magnetron sputtering, and mechanical alloying, on the thermal stability and phase stability of Ni-W. Several thermal stability mechanisms were identified throughout the course of this research. First and foremost, W-segregation was scarcely observed to grain boundaries, and it is unclear if W-segregation improves thermal stability contrary to most reports in the 2 literature. Long-range Ni4W chemical ordering was observed in alloys with more than 20 at.% W, and it is likely Ni4W domains reduce grain boundary mobility. In addition, lattice

  14. A thermally baffled device for highly stabilized convective PCR.

    PubMed

    Chang, Hsiao-Fen Grace; Tsai, Yun-Long; Tsai, Chuan-Fu; Lin, Ching-Ko; Lee, Pei-Yu; Teng, Ping-Hua; Su, Chen; Jeng, Chien-Chung

    2012-05-01

    Rayleigh-Bénard convective PCR is a simple and effective design for amplification of DNA. Convective PCR is, however, extremely sensitive to environmental temperature fluctuations, especially when using small- diameter test tubes. Therefore, this method is inherently unstable with limited applications. Here, we present a convective PCR device that has been modified by adding thermal baffles. With this thermally baffled device the influence from fluctuations in environmental temperature were significantly reduced, even in a wind tunnel (1 m/s). The thermally baffled PCR instrument described here has the potential to be used as a low-cost, point-of-care device for PCR-based molecular diagnostics in the field. PMID:22241586

  15. Thermal and electrochemical stability of organosilicon electrolytes for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Chen, Xin; Usrey, Monica; Peña-Hueso, Adrian; West, Robert; Hamers, Robert J.

    2013-11-01

    Organosilicon (OS) electrolytes that integrate an ethylene glycol oligomer with a trimethylsilane head group are promising substitutes for commercial carbonate-based electrolytes because of their low flammability and their high electrochemical and thermal stability. To explore the factors that control thermal and electrochemical stability of these compounds, we developed a real-time headspace analysis apparatus with a mass spectrometer to detect the evolution of decomposition products during thermal cycling and during electrochemical measurements. Here we present mass spectroscopy, XPS, and SEM results exploring the thermal stability of [2-[2-(2-Methoxyethoxy)ethoxy]ethoxy]trimethylsilane (1NM3) with LiPF6, and its electrochemical stability against graphite anodes and LiCoO2 cathodes. Our results show that 1NM3 + LiPF6 shows no significant decomposition below 100 °C and at potentials below 4.5 V. At higher temperatures and/or potentials, decomposition of LiPF6 induces hydrolysis of 1NM3. Our results show that LiPF6 decomposition is the limiting factor controlling stability of 1NM3 + LiPF6 electrolytes and also provide fundamental insights into the molecular bonds of 1NM3 that are attacked by PF5 and its decomposition products. Full-cell measurements of 1NM3 + LiPF6 + vinyl carbonate show Coulombic efficiencies of >99.6%. These results point the way to new molecular structures that may have even further enhanced electrochemical and thermal stability.

  16. The effect of an anisotropic pressure of thermal particles on resistive wall mode stability

    SciTech Connect

    Berkery, J. W. Sabbagh, S. A.; Betti, R.; Guazzotto, L.; Manickam, J.

    2014-11-15

    The effect of an anisotropic pressure of thermal particles on resistive wall mode stability in tokamak fusion plasmas is derived through kinetic theory and assessed through calculation with the MISK code [B. Hu et al., Phys. Plasmas 12, 0 57301 (2005)]. The fluid anisotropy is treated as a small perturbation on the plasma equilibrium and modeled with a bi-Maxwellian distribution function. A complete stability treatment without an assumption of high frequency mode rotation leads to anisotropic kinetic terms in the dispersion relation in addition to anisotropy corrections to the fluid terms. With the density and the average pressure kept constant, when thermal particles have a higher temperature perpendicular to the magnetic field than parallel, the fluid pressure-driven ballooning destabilization term is reduced. Additionally, the stabilizing kinetic effects of the trapped thermal ions can be enhanced. Together these two effects can lead to a modest increase in resistive wall mode stability.

  17. Thermal stability of alpha-amylase from Aspergillus oryzae entrapped in polyacrylamide gel.

    PubMed

    Raviyan, Patcharin; Tang, Juming; Rasco, Barbara A

    2003-08-27

    To determine the suitability as a time-temperature indicator for dielectric pasteurization processes, the thermal stability (50-75 degrees C) of Aspergillus oryzae alpha-amylase immobilized in polyacrylamide gel in phosphate buffer, mashed potatoes, and minced shrimp was examined. Changing the cross-linking agent concentration from 3.3 to 5.3% and adding 2% salt did not markedly affect the thermal stability of the immobilized alpha-amylase. Thermal inactivation was first order, and immobilization generally improved the thermal stability of alpha-amylase. z values of the immobilized system in test food systems were 10.2 degrees C (phosphate buffer), 8.45 degrees C (minced shrimp), and 7.78 degrees C (mashed potatoes). PMID:12926898

  18. Effect of alcohols and neutral salt on the thermal stability of soluble and precipitated acid-soluble collagen

    PubMed Central

    Russell, Allan E.

    1973-01-01

    The effects of mono- and poly-hydric alcohols in the presence of KCl on the intrinsic stability of collagen molecules in dilute acid solution were compared with corresponding solvent and salt effects on the increased stability of the aggregated molecules in salt-precipitated fibrils. Salt addition decreased solubility and increased the thermal stability of fibrils, but progressively decreased the stability of collagen molecules in solution. In contrast, the alcohols enhanced solubility and decreased fibril stability, the effects increasing with solvent hydrocarbon chain length and with decreasing hydroxyl/methylene-group ratio. Molar destabilization of dissolved collagen by alcohols was lower than for fibrils, and at low salt concentration, both ethylene glycol and glycerol were structural stabilizers. Electron-micrograph studies indicated that salt-precipitated fibrils tended to adopt the native aggregation mode, and qualitatively similar solvent effects were observed in insoluble collagens. Implications of the experimental findings are discussed in terms of a model in which electrostatic and apolar interactions mainly govern the excess of stability in collagen fibrils whereas intrinsic stability of single molecules is a function of polar interactions and polypeptide-chain rigidity. PMID:4737319

  19. Heat Transfer and Thermal Stability Research for Advanced Hydrocarbon Fuel Technologies

    NASA Technical Reports Server (NTRS)

    DeWitt, Kenneth; Stiegemeier, Benjamin

    2005-01-01

    In recent years there has been increased interest in the development of a new generation of high performance boost rocket engines. These efforts, which will represent a substantial advancement in boost engine technology over that developed for the Space Shuttle Main Engines in the early 1970s, are being pursued both at NASA and the United States Air Force. NASA, under its Space Launch Initiative s Next Generation Launch Technology Program, is investigating the feasibility of developing a highly reliable, long-life, liquid oxygen/kerosene (RP-1) rocket engine for launch vehicles. One of the top technical risks to any engine program employing hydrocarbon fuels is the potential for fuel thermal stability and material compatibility problems to occur under the high-pressure, high-temperature conditions required for regenerative fuel cooling of the engine combustion chamber and nozzle. Decreased heat transfer due to carbon deposits forming on wetted fuel components, corrosion of materials common in engine construction (copper based alloys), and corrosion induced pressure drop increases have all been observed in laboratory tests simulating rocket engine cooling channels. To mitigate these risks, the knowledge of how these fuels behave in high temperature environments must be obtained. Currently, due to the complexity of the physical and chemical process occurring, the only way to accomplish this is empirically. Heated tube testing is a well-established method of experimentally determining the thermal stability and heat transfer characteristics of hydrocarbon fuels. The popularity of this method stems from the low cost incurred in testing when compared to hot fire engine tests, the ability to have greater control over experimental conditions, and the accessibility of the test section, facilitating easy instrumentation. These benefits make heated tube testing the best alternative to hot fire engine testing for thermal stability and heat transfer research. This investigation

  20. Comparative experimental biomechanical study of different types of stabilization methods of the lower cervical spine.

    PubMed

    Kalff, R; Ulrich, C; Claes, L; Wilke, H J; Grote, W

    1992-01-01

    In a comparative experimental biodynamic study using thirty-two human cervical spines of cadavers the primary stabilization effect of different types of spondylodesis was examined. Whereas in flexion stress all methods showed a sufficient stability, the rotation tests proved, that in case of a dorsal instability of the lower cervical spine, posterior interlaminar wiring or anterior plate stabilization showed no reliable stabilization effect. However, the compression clamps by ROOSEN and TRAUSCHEL as well as the hook-plates by MAGERL are suitable dorsal stabilization methods with excellent rotation stability. In case of dorsal instability of the lower cervical spine a posterior spondylodesis is necessary and sufficient. PMID:1480272

  1. Improved thermal oxidation stability of solution-processable silver nanowire transparent electrode by reduced graphene oxide.

    PubMed

    Ahn, Yumi; Jeong, Youngjun; Lee, Youngu

    2012-12-01

    Solution-processable silver nanowire-reduced graphene oxide (AgNW-rGO) hybrid transparent electrode was prepared in order to replace conventional ITO transparent electrode. AgNW-rGO hybrid transparent electrode exhibited high optical transmittance and low sheet resistance, which is comparable to ITO transparent electrode. In addition, it was found that AgNW-rGO hybrid transparent electrode exhibited highly enhanced thermal oxidation and chemical stabilities due to excellent gas-barrier property of rGO passivation layer onto AgNW film. Furthermore, the organic solar cells with AgNW-rGO hybrid transparent electrode showed good photovoltaic behavior as much as solar cells with AgNW transparent electrode. It is expected that AgNW-rGO hybrid transparent electrode can be used as a key component in various optoelectronic application such as display panels, touch screen panels, and solar cells. PMID:23206541

  2. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

    NASA Astrophysics Data System (ADS)

    Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R. D. K.

    2015-12-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50-80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss.

  3. Laser-assisted plasma coating at atmospheric pressure: production of yttria-stabilized zirconia thermal barriers

    NASA Astrophysics Data System (ADS)

    Ouyang, Zihao; Meng, Liang; Raman, Priya; Cho, Tae S.; Ruzic, D. N.

    2011-07-01

    A laser-assisted plasma-coating technique at atmospheric pressure (LAPCAP) has been investigated. The electron temperature, electron density and gas temperature of the atmospheric-pressure plasma have been measured using optical emission spectroscopy (OES). LAPCAP utilizes laser ablation of 3 mol% yttria-stabilized zirconia into an atmospheric helium/nitrogen plasma to deposit thermal barrier coatings on a nickel-based substrate. The deposited film shows columnar structures similar to films prepared by high-vacuum deposition methods, such as physical vapour deposition and conventional pulsed-laser deposition. However, the LAPCAP films have smaller columns and higher porosity, compared with the films deposited by other techniques. The morphology and characteristics of the films have been analysed by scanning electron microscope, focused ion beam and x-ray diffraction.

  4. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel

    PubMed Central

    Hu, J.; Du, L.-X.; Sun, G.-S.; Xie, H.; Misra, R.D.K.

    2015-01-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50–80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss. PMID:26687012

  5. Low temperature superplasticity and thermal stability of a nanostructured low-carbon microalloyed steel.

    PubMed

    Hu, J; Du, L-X; Sun, G-S; Xie, H; Misra, R D K

    2015-01-01

    We describe here for the first time the low temperature superplasticity of nanostructured low carbon steel (microalloyed with V, N, Mn, Al, Si, and Ni). Low carbon nanograined/ultrafine-grained (NG/UFG) bulk steel was processed using a combination of cold-rolling and annealing of martensite. The complex microstructure of NG/UFG ferrite and 50-80 nm cementite exhibited high thermal stability at 500 °C with low temperature elongation exceeding 100% (at less than 0.5 of the absolute melting point) as compared to the conventional fine-grained (FG) counterpart. The low temperature superplasticity is adequate to form complex components. Moreover, the low strength during hot processing is favorable for decreasing the spring back and minimize die loss. PMID:26687012

  6. The antioxidant activity and thermal stability of lemon verbena (Aloysia triphylla) infusion.

    PubMed

    Abderrahim, Fatima; Estrella, Seyer; Susín, Cristina; Arribas, Silvia M; González, M Carmen; Condezo-Hoyos, Luis

    2011-05-01

    Because of its good sensorial attributes, lemon verbena is used as a primary ingredient in infusions and nonalcoholic drinks. The present study was designed to assess the antioxidant activity (AA) of lemon verbena infusion (LVI) as well as the thermal stability of its AA and the content of polyphenolic compounds. The values reflecting the AA of LVI, including AA index, fast scavenging rate against 2,2-diphenyl-1-picrylhydrazyl, Trolox equivalent antioxidant capacity, and hydroxyl radical scavenging, are higher than those of many herbal infusions and antioxidant drinks estimated from reported data. In addition, the slope lag time and specific oxyradical antioxidant capacity values of LVI are comparable to those of a commercial antioxidant drink based on green tea. Hence, LVI is a source of bifunctional antioxidants, and thus in vivo studies of the antioxidant capacity of LVI would be useful to evaluate its potential as an ingredient in antioxidant drinks. PMID:21434775

  7. Stabilized thermally beneficiated low rank coal and method of manufacture

    SciTech Connect

    Viall, A.J.; Richards, J.M.

    2000-07-18

    A process is described for reducing the spontaneous combustion tendencies of thermally beneficiated low rank coals employing heat, air or an oxygen containing gas followed by an optional moisture addition. Specific reaction conditions are supplied along with knowledge of equipment types that may be employed on a commercial scale to complete the process.

  8. Stabilized thermally beneficiated low rank coal and method of manufacture

    DOEpatents

    Viall, Arthur J.; Richards, Jeff M.

    2000-01-01

    A process for reducing the spontaneous combustion tendencies of thermally beneficiated low rank coals employing heat, air or an oxygen containing gas followed by an optional moisture addition. Specific reaction conditions are supplied along with knowledge of equipment types that may be employed on a commercial scale to complete the process.

  9. Stabilized thermally beneficiated low rank coal and method of manufacture

    DOEpatents

    Viall, A.J.; Richards, J.M.

    1999-01-26

    A process is described for reducing the spontaneous combustion tendencies of thermally beneficiated low rank coals employing heat, air or an oxygen containing gas followed by an optional moisture addition. Specific reaction conditions are supplied along with knowledge of equipment types that may be employed on a commercial scale to complete the process. 3 figs.

  10. Stabilized thermally beneficiated low rank coal and method of manufacture

    DOEpatents

    Viall, Arthur J.; Richards, Jeff M.

    1999-01-01

    A process for reducing the spontaneous combustion tendencies of thermally beneficiated low rank coals employing heat, air or an oxygen containing gas followed by an optional moisture addition. Specific reaction conditions are supplied along with knowledge of equipment types that may be employed on a commercial scale to complete the process.

  11. Al-Ti Particulate Composite: Processing and Studies on Particle Twinning, Microstructure, and Thermal Stability

    NASA Astrophysics Data System (ADS)

    Yadav, Devinder; Bauri, Ranjit; Kauffmann, Alexander; Freudenberger, Jens

    2016-08-01

    The present investigation shows that alternate to the ceramic particles, hard metallic particles can be used as reinforcement in an aluminum matrix to achieve a good strength-ductility combination in a composite. Titanium particles were incorporated into aluminum by friction stir processing (FSP) to process an Al-Ti particulate composite. FSP led to uniform distribution of the particles in the stir zone without any particle-matrix reaction, thereby retaining the particles in their elemental state. Fracture and twinning of the Ti particles with different frequency of occurrence on the advancing and retreating sides of the stir zone was observed. Twinning of the particles was studied by focused ion beam-assisted transmission electron microscopy. The processed Al-Ti composite exhibited a significant improvement in strength and also retained appreciable amount of ductility. The thermal stability of the fine-grained structure against abnormal grain growth (AGG) was improved by the Ti particles. The AGG in the Al-Ti composite occurred at 713 K (440 °C) compared to 673 K (400 °C) in the unreinforced aluminum processed under the same conditions. On the other hand, the particle-matrix reaction occurred only at 823 K (550 °C), and hence the Ti particles were thermally more stable compared to the matrix grain structure.

  12. Al-Ti Particulate Composite: Processing and Studies on Particle Twinning, Microstructure, and Thermal Stability

    NASA Astrophysics Data System (ADS)

    Yadav, Devinder; Bauri, Ranjit; Kauffmann, Alexander; Freudenberger, Jens

    2016-06-01

    The present investigation shows that alternate to the ceramic particles, hard metallic particles can be used as reinforcement in an aluminum matrix to achieve a good strength-ductility combination in a composite. Titanium particles were incorporated into aluminum by friction stir processing (FSP) to process an Al-Ti particulate composite. FSP led to uniform distribution of the particles in the stir zone without any particle-matrix reaction, thereby retaining the particles in their elemental state. Fracture and twinning of the Ti particles with different frequency of occurrence on the advancing and retreating sides of the stir zone was observed. Twinning of the particles was studied by focused ion beam-assisted transmission electron microscopy. The processed Al-Ti composite exhibited a significant improvement in strength and also retained appreciable amount of ductility. The thermal stability of the fine-grained structure against abnormal grain growth (AGG) was improved by the Ti particles. The AGG in the Al-Ti composite occurred at 713 K (440 °C) compared to 673 K (400 °C) in the unreinforced aluminum processed under the same conditions. On the other hand, the particle-matrix reaction occurred only at 823 K (550 °C), and hence the Ti particles were thermally more stable compared to the matrix grain structure.

  13. Thermal stability of electrodes in Lithium-ion cells

    SciTech Connect

    ROTH,EMANUEL P.; NAGASUBRAMANIAN,GANESAN

    2000-02-07

    Differential scanning calorimetry (DSC) analysis was used to identify thermal reactions in Sony-type lithium-ion cells and to correlate these reactions with interactions of cell constituents and reaction products. An electrochemical half-cell was used to cycle the anode and cathode materials and to set the state-of-charge (SOC). Three temperature regions of interaction were identified and associated with the SOC (degree of Li intercalation) of the cell. Anodes were shown to undergo exothermic reactions as low as 80 C involving decomposition of the solid electrolyte interphase (SEI) layer. The LiPF{sub 6} salt in the electrolyte (EC:PC:DEC/1M LiPF{sub 6}) was seen to play an essential role in this reaction. DSC analysis of the anodes from disassembled Sony cells showed similar behavior to the half-cell anodes with a strong exotherm beginning in the 80 C--90 C range. Exothermic reactions were also observed in the 200 C--300 C region between the intercalated lithium anodes, the LiPF{sub 6} salt, and the PVDF binder. These reactions were followed by a high-temperature reaction region, 300 C--400 C, also involving the PVDF binder and the intercalated lithium anodes. Cathode exothermic reactions with the PVDF binder were observed above 200 C and increased with the SOC (decreasing Li content in the cathode). No thermal reactions were seen at lower temperatures suggesting that thermal runaway reactions in this type of cell are initiated at the anode. An Accelerating Rate Calorimeter (ARC) was used to perform measurements of thermal runaway on commercial Sony Li-ion cells as a function of SOC. The cells showed sustained thermal output as low as 80 C in agreement with the DSC observations of anode materials but the heating rate was strongly dependent on the SOC.

  14. FDSOI bottom MOSFETs stability versus top transistor thermal budget featuring 3D monolithic integration

    NASA Astrophysics Data System (ADS)

    Fenouillet-Beranger, C.; Previtali, B.; Batude, P.; Nemouchi, F.; Cassé, M.; Garros, X.; Tosti, L.; Rambal, N.; Lafond, D.; Dansas, H.; Pasini, L.; Brunet, L.; Deprat, F.; Grégoire, M.; Mellier, M.; Vinet, M.

    2015-11-01

    To set up specification for 3D monolithic integration, for the first time, the thermal stability of state-of-the-art FDSOI (Fully Depleted SOI) transistors electrical performance is quantified. Post fabrication annealings are performed on FDSOI transistors to mimic the thermal budget associated to top layer processing. Degradation of the silicide for thermal treatments beyond 400 °C is identified as the main responsible for performance degradation for PMOS devices. For the NMOS transistors, arsenic (As) and phosphorus (P) dopants deactivation adds up to this effect. By optimizing both the n-type extension implantations and the bottom silicide process, thermal stability of FDSOI can be extended to allow relaxing upwards the thermal budget authorized for top transistors processing.

  15. Comparative stability calculations of the Pleistocene landslide in France

    NASA Astrophysics Data System (ADS)

    Fabre, R.; Martins Campina, B.; Riss, J.; Bertran, P.

    2003-04-01

    Remnants of the Petit-Bost landslide that occurred during the Pleistocene have been observed during field investigations in Quaternary alluvial formations, southwestern France. The work presented demonstrates how field observations can be used to calculate slope stability. A sliding surface and other related features due to soil deformation have been discovered within a clay layer that overlays the gravel. Abundant periglacial features such as ice-wedge casts have also been found in the colluvium and testify to a former permafrost, suggesting that sliding may be closely linked with Pleistocene periglacial conditions. The surface of rupture is located in a 0.5 m thick, very plastic mottled clay at the top of an alluvial gravel. The initial topography at the time of sliding is not known, but the gradient was thought to be close to that of the present soil surface. This ranges between 3 and 4°; a value of 3° has been used in the following stability calculations. The landslide corresponds to a 2-m-thick colluvium formations with 1.5-m thick permafrost that has been subjected to gravity-induced instability in saturated soil in a periglacial environment. The stability calculations for the Petit-Bost landslide have been performed using an infinite plane sliding and according to two complementary methods. The first one has been usually used for plane sliding, the Carter method. The second one used also for plane sliding with the FLAC computer method (Fast Lagrangian Analysis of Continua method). Following the first one Carter method, calculations were made for an impermeable upper layer, that leads to the development of high pore water pressure in the clay layer. These first results show that instability in the clay only occurs for very low angle of internal friction and cohesion values. Under such conditions, artesian water pressures may have triggered sliding. This could have occurred if the thawed clay layer was trapped between a permafrost table and an overlying

  16. Pump power stability range of single-mode solid-state lasers with rod thermal lensing

    SciTech Connect

    De Silvestri, S.; La Porta, P.; Magni, V.

    1987-11-01

    The pump power stability range of solid-state laser resonators operating in the TEM/sub 00/ mode has been thoroughly investigated. It has been shown that, for a very general resonator containing intracavity optical systems, rod thermal lensing engenders a pump power stability range which is a characteristic parameter of laser material and pump cavity, but is independent of resonator configuration. Stability ranges have been calculated and critically discussed for Nd:YAG, Nd:Glasses, Nd:Cr:GSGG, and alexandrite. The independence of the pump power stability range from the resonator configuration has been experimentally demonstrated for a CW Nd:YAG laser.

  17. Stability of absorption phenomena in laser-thermal propulsion

    NASA Technical Reports Server (NTRS)

    Merkle, C. L.; Tsai, Y.-L. P.

    1984-01-01

    The mean flow and stability characteristics of laser absorption phenomena in a choked converging-diverging nozzle are considered. Calculations are presented for a given nozzle geometry and a series of laser intensities. Gas absorptivities corresponding to a hydrogen-cesium mixture are used with different initial temperatures being selected to investigate the effects of changes in the shape of the k-T curve. Both stability and mean flow calculations are limited to the one-dimensional case. The mean flow results show a decrease in mass flow as laser power is increased, along with increasingly steep temperature profiles. Calculations span regions of partial and complete absorption. One region is found where multiple solutions exist. Local stability results indicate the u-c characteristic is the only unstable mode in the unheated case. Laser heat addition makes this mode more unstable and also destabilizes the u-characteristic. Numerical calculations of disturbance propagation show that the instability of the u-c disturbances is counteracted by their reflection to u + c disturbances at the upstream end. The growth of the u-disturbances is localized in regions where the temperature profile is steep and they are damped in other regions. The increasing destabilization that is observed with increased laser power is probably the reason for difficulty in obtaining converged mean flow solutions at high laser intensities.

  18. Thermal stability relationships between PMR-15 resin and its composites

    SciTech Connect

    Bowles, K.J.; Jayne, D.; Leonhardt, T.A.; Bors, D.

    1993-10-01

    A study was conducted to investigate the relationship between the thermo-oxidative stability of PMR-15 matrix resin and the stability of graphite-fiber-reinforced composites that contain this resin as the matrix material. Three areas were investigated. The first was the effect of fiber/matrix interfacial bond strength on the isothermal aging weight loss of composites. By using type-A graphite fibers produced by Hercules, it was possible to study composites reinforced with fibers that were processed to receive different surface treatments. One of the fibers was untreated, a second fiber was treated by oxidation to enhance fiber/matrix bonding, and the third type of fiber was coated with an epoxy sizing. These treatments produced three significantly different interfacial bond strengths. The epoxy sizing on the third fiber was quickly oxidized from the bare fiber surfaces at 288, 316, and 343 C. The weight loss due to the removal of the sizing was constant at 1.5 percent. This initial weight loss was not observed in thermo-oxidative stability studies of composites. The PMR-15 matrix satisfactorily protected the reinforcemnt at all three temperatures.

  19. Thermal stability relationships between PMR-15 resin and its composites

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.; Jayne, Douglas; Leonhardt, Todd A.; Bors, Dennis

    1993-01-01

    A study was conducted to investigate the relationship between the thermo-oxidative stability of PMR-15 matrix resin and the stability of graphite-fiber-reinforced composites that contain this resin as the matrix material. Three areas were investigated. The first was the effect of fiber/matrix interfacial bond strength on the isothermal aging weight loss of composites. By using type-A graphite fibers produced by Hercules, it was possible to study composites reinforced with fibers that were processed to receive different surface treatments. One of the fibers was untreated, a second fiber was treated by oxidation to enhance fiber/matrix bonding, and the third type of fiber was coated with an epoxy sizing. These treatments produced three significantly different interfacial bond strengths. The epoxy sizing on the third fiber was quickly oxidized from the bare fiber surfaces at 288, 316, and 343 C. The weight loss due to the removal of the sizing was constant at 1.5 percent. This initial weight loss was not observed in thermo-oxidative stability studies of composites. The PMR-15 matrix satisfactorily protected the reinforcemnt at all three temperatures.

  20. Investigation on the near-infrared-emitting thermal stability of Bi activated alkaline-earth aluminoborosilicate glasses

    NASA Astrophysics Data System (ADS)

    Wan, Ronghua; Song, Zhiguo; Li, Yongjin; Zhou, Yuting; Liu, Qun; Qiu, Jianbei; Yang, Zhengwen; Yin, Zhaoyi

    2015-02-01

    Stability of near-infrared (NIR) emission form Bi doped 42.5SiO2-12.5B2O3-25Al2O3-20RO (SBAR, R = Ca, Sr, Ba) glasses under treatment between annealing and softening temperature were studied. Results show that the thermal stability of Bi-NIR-emitting centers in SBAR glasses generally decreases with the increase of the radius of modifier cations but is greatly higher that in similar alkali glasses. Comparative experiments indicate these phenomena can be understood by the tendency that the smaller and higher charged alkaline earth ions as higher field strength modifier cations will increase the concentration of negative charge on non-bridging oxygens and also help to stabilize the non-bridging oxygens, which can restrain the thermally activated diffusion and valence change of Bi-activated centers, respectively. The results can provide an improved understanding for the NIR-emitting thermal stability of Bi doped glasses and a scientific reference for composition design of Bi-doped optical fiber.

  1. Thermal stability of zeolitic tuff from Yucca Mountain, Nevada

    SciTech Connect

    Bish, D.L.

    1990-04-01

    Thermal models of the proposed repository at Yucca Mountain, Nevada, suggest that rocks near the proposed host rock will experience elevated temperatures for at least 1000 yrs. In order to assess the effects of elevated temperatures on zeolites clinoptilolite and mordenite were investigated using a combination of high-temperature X-ray powder diffraction, thermogravimetric and differential scanning calorimetric analysis, and long-term heating experiments. 13 refs., 7 figs.

  2. Effects of a carbon implant on thermal stability of Ni0.95(Pt0.05)Si

    NASA Astrophysics Data System (ADS)

    Shuai, Feng; Lichuan, Zhao; Qingzhu, Zhang; Pengpeng, Yang; Zhaoyun, Tang; Jiang, Yan; Cinan, Wu

    2015-06-01

    The effects of a carbon implant on thermal stability of Ni0.95(Pt0.05)Si films are investigated by implanting carbon of different doses into Si substrates before silicidation with two steps of rapid thermal annealing. Compared with the Ni0.95(Pt0.05)Si films without carbon implanting, the thermal stability of Ni0.95(Pt0.05)Si films with two carbon implant doses are improved 100 °C (1 × 1015 cm-2) and 150 °C (3 × 1015 cm-2), respectively. Through sheet resistance measurement, X-ray diffraction and scanning electron microscopy, we conclude that carbon atoms precipitated at Ni(Pt0.05)Si grain boundaries and Ni0.95(Pt0.05)Si/Si interface account for the improved thermal stability of Ni0.95(Pt0.05)Si films. Furthermore, the presence of C in Ni0.95(Pt0.05)Si films changes the preferred orientation of polycrystalline NiSi which will benefit the practical application of this material.

  3. Comprehensive transient-state study for CARMENES NIR high-thermal stability

    NASA Astrophysics Data System (ADS)

    Becerril, Santiago; Sánchez, Miguel A.; Cárdenas, M. C.; Rabaza, Ovidio; Ramón, Alejandro; Abril, Miguel; Costillo, Luis P.; Morales, Rafael; Rodríguez, Alicia; Amado, Pedro J.

    2010-07-01

    CARMENES has been proposed as a next-generation instrument for the 3.5m Calar Alto Telescope. Its objective is finding habitable exoplanets around M dwarfs through radial velocity measurements (m/s level) in the near-infrared. Consequently, the NIR spectrograph is highly constraint regarding thermal/mechanical requirements. Indeed, the requirements used for the present study limit the thermal stability to +/-0.01K (within year period) over a working temperature of 243K in order to minimise radial velocity drifts. This can be achieved by implementing a solution based on several temperature-controlled rooms (TCR), whose smallest room encloses the vacuum vessel which houses the spectrograph's optomechanics. Nevertheless, several options have been taken into account to minimise the complexity of the thermal design: 1) Large thermal inertia of the system, where, given a thermal instability of the environment (typically, +/-0.1K), the optomechanical system remains stable within +/-0.01K in the long run; 2) Environment thermal control, where thermal stability is ensured by controlling the temperature of the environment surrounding the vacuum vessel. The present article also includes the comprehensive transient-state thermal analyses which have been implemented in order to make the best choice, as well as to give important inputs for the thermal layout of the instrument.

  4. Invaded grassland communities have altered stability-maintenance mechanisms but equal stability compared to native communities

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Theory predicts that stability should increase with diversity via several mechanisms. We tested predictions in a five-year experiment with exotic and native plant mixtures under two irrigation treatments. Diversity declined faster after planting in exotic than native mixtures. Variation in biomas...

  5. Enhancement of thermal stability and water resistance in yttrium-doped GeO{sub 2}/Ge gate stack

    SciTech Connect

    Lu, Cimang Hyun Lee, Choong; Zhang, Wenfeng; Nishimura, Tomonori; Nagashio, Kosuke; Toriumi, Akira

    2014-03-03

    We have systematically investigated the material and electrical properties of yttrium-doped GeO{sub 2} (Y-GeO{sub 2}) on Germanium (Ge). A significant improvement of both thermal stability and water resistance were demonstrated by Y-GeO{sub 2}/Ge stack, compared to that of pure GeO{sub 2}/Ge stack. The excellent electrical properties of Y-GeO{sub 2}/Ge stacks with low D{sub it} were presented as well as enhancement of dielectric constant in Y-GeO{sub 2} layer, which is beneficial for further equivalent oxide thickness scaling of Ge gate stack. The improvement of thermal stability and water resistance are discussed both in terms of the Gibbs free energy lowering and network modification of Y-GeO{sub 2}.

  6. Microparticles containing lemongrass volatile oil: preparation, characterization and thermal stability.

    PubMed

    Weisheimer, V; Miron, D; Silva, C B; Guterres, S S; Schapoval, E E S

    2010-12-01

    Lemongrass volatile oil (LVO) is an important ingredient in cosmetics, presenting antimicrobial properties, in particular antifungal activity, and it is a promising raw material for the development of pharmaceutical products. However, its volatility and susceptibility to degradation are the major drawbacks for the use of Cymbopogon citratus oil in pharmaceutical compounding. Thus, the aim of this work was to develop and to characterize microparticles containing this oil viewing the stabilization of LVO. Two techniques of preparation were evaluated; spray drying and precipitation, and two encapsulation materials, beta-cyclodextrin (beta-CD) and hydroxypropyl-beta-cyclodextrin (HP-beta-CD) were tested. The microparticles were characterized in terms of content of water, yield, percentage of inclusion, infrared spectroscopy. Morphology was evaluated by scanning electronic microscopy. Studies of stability were also conducted. The content of citral (neral and geranial), major component of the oil, present in microparticles was assayed by a validated HPLC method. The percentage of inclusion of LVO into the microparticles was 56-60% and 26-29% using beta-CD and HP-beta-CD, respectively. The results showed that the use of the beta-CD as encapsulant material was more efficient. Additionally, an increased inclusion of lemongrass oil was observed with the precipitation technique. PMID:21284257

  7. Thermal Transfer Compared To The Fourteen Other Imaging Technologies

    NASA Astrophysics Data System (ADS)

    O'Leary, John W.

    1989-07-01

    A quiet revolution in the world of imaging has been underway for the past few years. The older technologies of dot matrix, daisy wheel, thermal paper and pen plotters have been increasingly displaced by laser, ink jet and thermal transfer. The net result of this revolution is improved technologies that afford superior imaging, quiet operation, plain paper usage, instant operation, and solid state components. Thermal transfer is one of the processes that incorporates these benefits. Among the imaging application for thermal transfer are: 1. Bar code labeling and scanning. 2. New systems for airline ticketing, boarding passes, reservations, etc. 3. Color computer graphics and imaging. 4. Copying machines that copy in color. 5. Fast growing communications media such as facsimile. 6. Low cost word processors and computer printers. 7. New devices that print pictures from video cameras or television sets. 8. Cameras utilizing computer chips in place of film.

  8. Thermal stability of a free nanotube from single-layer black phosphorus

    NASA Astrophysics Data System (ADS)

    Cai, Kun; Wan, Jing; Wei, Ning; Cai, Haifang; Qin, Qing-Hua

    2016-06-01

    Similar to a carbon nanotube fabricated from a graphene sheet, a black phosphorus nanotube (BPNT) can also be theoretically produced by curling rectangular single-layer black phosphorus (SLBP). In the present study, the effect of the thermal vibration of atoms on the failure of a BPNT is investigated using molecular dynamics simulations. Two types of double-shell BPNTs obtained by curling the SLBP along its armchair/pucker and zigzag directions respectively are involved in simulation. At finite temperature, a bond on the outer shell of the tube is under tension due to both the curvature of the tube and the serious thermal vibration of the atoms. As the length of a bond with such elongation approaches its critical value, i.e. 0.279 nm, or the smallest distance between two nonbonding phosphorus atoms is over 0.389 nm caused by a great variation of the bond angle, the tube fails quickly. The critical stable states of either an armchair or a zigzag BPNT at finite temperature are calculated and compared. To achieve a stable BPNT with high robustness, the tube should have a higher radius or should work at a lower temperature. Only when the BPNT has structural stability does it have the potential application as a nanowire in a future nano electro-mechanical system.

  9. Thermal stability of a free nanotube from single-layer black phosphorus.

    PubMed

    Cai, Kun; Wan, Jing; Wei, Ning; Cai, Haifang; Qin, Qing-Hua

    2016-06-10

    Similar to a carbon nanotube fabricated from a graphene sheet, a black phosphorus nanotube (BPNT) can also be theoretically produced by curling rectangular single-layer black phosphorus (SLBP). In the present study, the effect of the thermal vibration of atoms on the failure of a BPNT is investigated using molecular dynamics simulations. Two types of double-shell BPNTs obtained by curling the SLBP along its armchair/pucker and zigzag directions respectively are involved in simulation. At finite temperature, a bond on the outer shell of the tube is under tension due to both the curvature of the tube and the serious thermal vibration of the atoms. As the length of a bond with such elongation approaches its critical value, i.e. 0.279 nm, or the smallest distance between two nonbonding phosphorus atoms is over 0.389 nm caused by a great variation of the bond angle, the tube fails quickly. The critical stable states of either an armchair or a zigzag BPNT at finite temperature are calculated and compared. To achieve a stable BPNT with high robustness, the tube should have a higher radius or should work at a lower temperature. Only when the BPNT has structural stability does it have the potential application as a nanowire in a future nano electro-mechanical system. PMID:27125722

  10. The effects of polyols on the thermal stability of calf thymus DNA.

    PubMed

    Del Vecchio, P; Esposito, D; Ricchi, L; Barone, G

    1999-05-01

    The effects on thermal denaturation of calf thymus DNA (ct-DNA) and its conformational changes induced by the presence in solution of different polyols, namely glycerol, i-erytritol, L( -- ) and D( + ) arabitol, D-mannitol, D-sorbitol and myo-inositol, have been investigated by means of differential scanning calorimetry (DSC) and circular dichroism (CD). By increasing the concentration of these additives a decrease in both the denaturation enthalpy (deltadH) and temperature of the maximum of the denaturation peak (Tmax) of DNA is observed. The values of these thermodynamic parameters depend on both the nature and concentration of the solute. The overall destabilization of DNA molecule has been related to the different capability of polyhydric alcohols to interact with the polynucleotide solvation sites replacing water and to the modification of the electrostatic interactions between the polynucleotide and its surrounding atmosphere of counterions. The particular behaviour of L( -- ) arabitol, which showed a much greater destabilizing ability compared to the other polyols, was further investigated and attributed to a direct more effective interaction with the double helix of DNA. CD spectra showed only a slight alteration of DNA-B structure in the presence of all the molecules here studied, except for L( -- ) arabitol where the DNA molecule seems to undergo a meaningful conformational change. The salt concentration dependence of DNA thermal stability in the presence of L( -- ) arabitol indicates a conformational change of polynucleotide towards a more extended conformation. PMID:10408643

  11. Pickering emulsions with α-cyclodextrin inclusions: Structure and thermal stability.

    PubMed

    Diaz-Salmeron, Raul; Chaab, Ismail; Carn, Florent; Djabourov, Madeleine; Bouchemal, Kawthar

    2016-11-15

    This paper explores structural, interfacial and thermal properties of two types of Pickering emulsions containing α-cyclodextrin inclusion complexes: on one hand, emulsions were obtained between aqueous solutions of α-cyclodextrin and different oils (fatty acids, olive oil, silicone oil) and on the other hand, emulsions were obtained between these oils, water and micro or nano-platelet suspensions with inclusion complexes of hydrophobically-modified polysaccharides. The emulsions exhibit versatile properties according to the molecular architecture of the oils. Experiments were performed by microcalorimetry, X-ray diffraction and confocal microscopy. The aptitude of oil molecules to be threaded in α-cyclodextrin cavity is a determining parameter in emulsification and thermal stability. The heat flow traces and images showed dissolution, cooperative melting and de-threading of inclusion complexes which take place progressively, ending at high temperatures, close or above 100°C. Another important feature observed in the emulsions with micro-platelets is the partial substitution of the guest molecules occurring at room temperature at the oil/water interfaces without dissolution, possibly by a diffusion mechanism of the oil. Accordingly, the dissolution and the cooperative melting temperatures of the inclusion crystals changed, showing marked differences upon the type of guest molecules. The enthalpies of dissolution of crystals were measured and compared with soluble inclusions. PMID:27491001

  12. Kinetic properties and thermal stabilities of mutant forms of mitochondrial aspartate aminotransferase.

    PubMed

    Azzariti, A; Vacca, R A; Giannattasio, S; Merafina, R S; Marra, E; Doonan, S

    1998-07-28

    Kinetic properties and thermal stabilities of the precursor form of mitochondrial aspartate aminotransferase, the mature form lacking 9 amino acids from the N-terminus, and forms of the mature protein in which cysteine-166 had been mutated to serine or alanine were compared with those of the mature enzyme. The precursor and the cysteine mutants showed moderately impaired catalytic properties consistent with decreased ability to undergo transition from the open to the closed conformation which is an integral part of the mechanism of action of the enzyme. The deletion mutant had a kcat only 2% of that of the mature enzyme but also much reduced Km values for both substrates. In addition it showed enhanced reactivity of cysteine-166 with 5,5'-dithiobis(2-nitrobenzoate), which is characteristic of the closed form of the enzyme, with no enhancement of reactivity in the presence of substrates. This is taken to show that the deletion mutant adopts a conformation that is significantly different from that of the mature enzyme particularly in respect of the small domain. The deletion mutant was found to be more resistant to thermal inactivation over a range of temperatures than were the other forms of the enzyme consistent with its having a more tightly packed small domain. PMID:9675237

  13. Infrared Radiative Properties of Yttria-Stabilized Zirconia Thermal Barrier Coatings

    NASA Technical Reports Server (NTRS)

    Eldridge, Jeff I.; Spuckler, Charles M.; Street, Ken W.; Markham, Jim R.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    The infrared (IR) transmittance and reflectance of translucent thermal barrier coatings (TBCs) have important implications for both the performance of these coatings as radiation barriers and emitters as well as affecting measurements of TBC thermal conductivity, especially as TBCs are being pushed to higher temperatures. In this paper, the infrared spectral directional-hemispherical transmittance and reflectance of plasma-sprayed 8wt% yttria-stabilized zirconia (8YSZ) TBCs are reported. These measurements are compared to those for single crystal YSZ specimens to show the effects of the plasma-sprayed coating microstructure. It is shown that the coatings exhibit negligible absorption at wavelengths up to about 5 micrometers, and that internal scattering rather than surface reflections dominates the hemispherical reflectance. The translucent nature of the 8YSZ TBCs results in the absorptance/emittance and reflectance of TBC-coated substrates depending on the TBC thickness, microstructure, as well as the radiative properties of the underlying substrate. The effects of these properties on TBC measurements and performance are discussed.

  14. Thermal stability of soils and detectability of intrinsic soil features

    NASA Astrophysics Data System (ADS)

    Siewert, Christian; Kucerik, Jiri

    2014-05-01

    Soils are products of long term pedogenesis in ecosystems. They are characterized by a complex network of interactions between organic and inorganic constituents, which influence soil properties and functions. However, the interrelations cannot easily be determined. Our search for unifying principles of soil formation focuses on water binding. This approach was derived from water-dependent soil formation. It considers the importance of water binding in theories about the origin of genes, in the structural arrangement and functionality of proteins, and in the co-evolution of organism species and the biosphere during the history of earth. We used thermogravimetry as a primary experimental technique. It allows a simple determi-nation of bound water together with organic and inorganic components in whole soil samples without a special preparation. The primary goal was to search for fingerprinting patterns using dynamics of thermal mass losses (TML) caused by water vaporization from natural soils, as a reference base for soil changes under land use. 301 soil samples were collected in biosphere reserves, national parks and other areas as-sumingly untouched by human activity in Siberia, North and South America, Antarctica, and in several long term agricultural experiments. The results did not support the traditional data evaluation procedures used in classical differ-ential thermogravimetry. For example, peak positions and amplitudes did not provide useful information. In contrast, using thermal mass losses (TML) in prefixed smaller, e.g. 10 °C temperature intervals allowed the determination of the content of carbon, clay, nitrogen and carbonates with high accuracy. However, this approach was applicable for soils and neither for soil-like carbon containing mineral substrates without pedogenetic origin, nor for plant residues or soils containing ashes, cinder, or charcoal. Therefore, intrinsic soil regulation processes are discussed as a possible factor causing

  15. The Universal Thermal Climate Index UTCI compared to ergonomics standards for assessing the thermal environment.

    PubMed

    Bröde, Peter; Błazejczyk, Krzysztof; Fiala, Dusan; Havenith, George; Holmér, Ingvar; Jendritzky, Gerd; Kuklane, Kalev; Kampmann, Bernhard

    2013-01-01

    The growing need for valid assessment procedures of the outdoor thermal environment in the fields of public weather services, public health systems, urban planning, tourism & recreation and climate impact research raised the idea to develop the Universal Thermal Climate Index UTCI based on the most recent scientific progress both in thermo-physiology and in heat exchange theory. Following extensive validation of accessible models of human thermoregulation, the advanced multi-node 'Fiala' model was selected to form the basis of UTCI. This model was coupled with an adaptive clothing model which considers clothing habits by the general urban population and behavioral changes in clothing insulation related to actual environmental temperature. UTCI was developed conceptually as an equivalent temperature. Thus, for any combination of air temperature, wind, radiation, and humidity, UTCI is defined as the air temperature in the reference condition which would elicit the same dynamic response of the physiological model. This review analyses the sensitivity of UTCI to humidity and radiation in the heat and to wind in the cold and compares the results with observational studies and internationally standardized assessment procedures. The capabilities, restrictions and potential future extensions of UTCI are discussed. PMID:23411753

  16. Thermal stability of hydrocarbons in nature - Limits, evidence, characteristics, and possible controls

    NASA Astrophysics Data System (ADS)

    Price, Leigh C.

    1993-07-01

    Accepted petroleum-geochemical paradigms place rigid limits on hydrocarbon (HC) thermal stability: C(15+) HCs begin thermal cracking at R(0) values of 0.9 and are completely thermally destroyed by R(0) = 1.35 percent; C2-C4 HC gases are thermally destroyed by R(0) = 2.0 percent; and methane is thermally destroyed by R(0) = 4.0 percent. The fact that observed data is so far removed from predicted behavior may be due to: a lack of recognition of some important possible controlling parameters of organic matter metamorphism and too much imporance given to other assumed controlling parameters; and assigning HC distribution patterns in petroleum basins to HC thermal cracking when such patterns may be due to other causes.

  17. Investigation of thermal stability and fingerprint spectra of energetic 1,2,3-triazole using pulsed photoacoustic pyrolysis technique

    NASA Astrophysics Data System (ADS)

    Rao, K. S.; Chaudhary, A. K.; Yehya, F.

    2015-12-01

    This paper reports on a comparative study of UV and visible radiation-based pulsed photoacoustic (PA) pyrolysis technique examining thermal stability and acoustic fingerprint spectra of a newly synthesized high-energy molecule named 1-(2,4-dinitrobenzyl)-4-nitro-1H-1,2,3-triazole ( S 6). The thermal PA spectra of S 6 were recorded in temperatures ranging between 30 and 350 °C using second and fourth harmonic wavelengths (i.e., 532 and 266 nm), obtained from Q-switched Nd:YAG laser pulses of duration 7 ns at 10 Hz repetition rate. The PA results are further compared with TG-DTA data to understand the release mechanism of NO2 along with other gaseous by-products. The difference in thermal PA spectra of S 6 which follows two different mechanisms, such as vibronic transition V-V and V-T relaxation in NO2 functional group, while electronic π* ← n transition in the entire molecule, is due to selection of visible and UV wavelengths. In addition, the effect of data acquisition time and incident laser energy has been examined in order to understand the behavior of acoustic modes of a PA cavity at the desired vapor temperature. The stability of the compound is also evaluated on the basis of thermal quality factor ( Q), of PA cavity.

  18. Tuneable enhancement of the salt and thermal stability of polymeric micelles by cyclized amphiphiles

    PubMed Central

    Honda, Satoshi; Yamamoto, Takuya; Tezuka, Yasuyuki

    2013-01-01

    Cyclic molecules provide better stability for their aggregates. Typically in nature, the unique cyclic cell membrane lipids allow thermophilic archaea to inhabit extreme conditions. By mimicking the biological design, the robustness of self-assembled synthetic nanostructures is expected to be improved. Here we report topology effects by cyclized polymeric amphiphiles against their linear counterparts, demonstrating a drastic enhancement in the thermal, as well as salt stability of self-assembled micelles. Furthermore, through coassembly of the linear and cyclic amphiphiles, the stability was successfully tuned for a wide range of temperatures and salt concentrations. The enhanced thermal/salt stability was exploited in a halogen exchange reaction to stimulate the catalytic activity. The mechanism for the enhancement was also investigated. These topology effects by the cyclic amphiphiles offer unprecedented opportunities in polymer materials design unattainable by traditional means. PMID:23481382

  19. Time and Temperature Test Results for PFP Thermal Stabilization Furnaces

    SciTech Connect

    COMPTON, J.A.

    2000-08-09

    The national standard for plutonium storage acceptability (standard DOE-STD-3013-99, generally known as ''the 3013 standard'') has been revised to clarify the requirement for processes that will produce acceptable storage materials. The 3013 standard (Reference 1) now states that ''Oxides shall be stabilized by heating the material in an oxidizing atmosphere to a Material Temperature of at least 950 C (1742 F) for not less than 2 hours.'' The process currently in use for producing stable oxides for storage at the Plutonium Finishing Plant (PFP) heats a furnace atmosphere to 1000 C and holds it there for 2 hours. The temperature of the material being stabilized is not measured directly during this process. The Plutonium Process Support Laboratories (PPSL) were requested to demonstrate that the process currently in use at PFP is an acceptable method of producing stable plutonium dioxide consistently. A spare furnace identical to the production furnaces was set up and tested under varying conditions with non-radioactive surrogate materials. Reference 2 was issued to guide the testing program. The process currently in use at the PFP for stabilizing plutonium-bearing powders was shown to heat all the material in the furnace to at least 950 C for at least 2 hours. The current process will work for (1) relatively pure plutonium dioxide, (2) dioxide powders mixed with up to 20 weight percent magnesium oxide, and (3) dioxide powders with up to 11 weight percent magnesium oxide and 20 weight percent magnesium nitrate hexahydrate. Time and temperature data were also consistent with a successful demonstration for a mixture containing 10 weight percent each of sodium and potassium chloride; however, the molten chloride salts destroyed the thermocouples in the powder and temperature data were unavailable for part of that run. These results assume that the current operating limits of no more than 2500 grams per furnace charge and a powder height of no more than 1.5 inches remain

  20. Thermal stabilization of thymidylate synthase by engineering two disulfide bridges across the dimer interface.

    PubMed

    Gokhale, R S; Agarwalla, S; Francis, V S; Santi, D V; Balaram, P

    1994-01-01

    Thermal inactivation of oligomeric enzymes is most often irreversible and is frequently accompanied by precipitation. We have engineered two symmetry related disulfide bridges (155-188' and 188-155') across the subunit interface of Lactobacillus casei thymidylate synthase, at sites chosen on the basis of an algorithm for the introduction of stereochemically unstrained bridges into proteins. In this communication, we demonstrate a remarkable enhancement in the thermal stability of the covalently cross-linked double disulfide containing dimeric enzyme. The mutant enzyme remains soluble and retains secondary structure even at 90 degrees C, in contrast to the wild-type enzyme which precipitates at 52 degrees C. Furthermore, the mutant enzyme has a temperature optimum of 55 degrees C and possesses appreciable enzymatic activity at 65 degrees C. Cooling restores complete activity, in the mutant protein, demonstrating reversible thermal unfolding. The results suggest that inter-subunit crosslinks can impart appreciable thermal stability in multimeric enzymes. PMID:7904654

  1. Enzyme inhibitors in tuber crops and their thermal stability.

    PubMed

    Prathibha, S; Nambisan, B; Leelamma, S

    1995-10-01

    Tubers of Cassava (Manihot esculenta), yams (Dioscorea esculenta), aroids (Amorphophallus campanulatus, Colocasia esculenta, Xanthosoma sagittfolium) and Coleus (Solenostemon rotundifolius) were screened for inhibitory activities against amylase, trypsin and chymotrypsin. Coleus tuber possessed the highest anti-amylase activity, whereas Colocasia tuber was the most potent source of anti-tryptic and anti-chymotryptic activity. Xanthosoma tubers exhibited amylase inhibitory activity and Amorphophallus tubers antiprotease activity. Dioscorea esculenta had low levels of amylase and chymotrypsin inhibitors, while Cassava tubers were totally free of inhibitors. When tubers were processed by pressure cooking, there was significant reduction/complete elimination in inhibitory activity. Partial retention of inhibition was observed in the case of amylase inhibitor in Dioscorea, chymotrypsin inhibitor in Colocasia and trypsin inhibitor in Colocasia, Coleus and Amorphophallus. In vitro experiments on heat stability of the different inhibitors revealed almost similar pattern of inactivation. PMID:8833431

  2. Thermal Stability of Magnesium Silicide/Nickel Contacts

    NASA Astrophysics Data System (ADS)

    de Boor, J.; Droste, D.; Schneider, C.; Janek, J.; Mueller, E.

    2016-06-01

    Magnesium silicide-based materials are a very promising class of thermoelectric materials with excellent potential for thermoelectric waste heat recovery. For the successful application of magnesium silicide-based thermoelectric generators, the development of long-term stable contacts with low contact resistance is as important as material optimization. We have therefore studied the suitability of Ni as a contact material for magnesium silicide. Co-sintering of magnesium silicide and Ni leads to the formation of a stable reaction layer with low electrical resistance. In this paper we show that the contacts retain their low electrical contact resistance after annealing at temperatures up to 823 K for up to 168 h. By employing scanning electron microscope analysis and time-of-flight (ToF)-secondary ion mass spectrometry, we can further show that elemental diffusion is occurring to a very limited extent. This indicates long-term stability under practical operation conditions for magnesium silicide/nickel contacts.

  3. Developing Multilayer Thin Film Strain Sensors With High Thermal Stability

    NASA Technical Reports Server (NTRS)

    Wrbanek, John D.; Fralick, Gustave C.; Gonzalez, Jose M., III

    2006-01-01

    A multilayer thin film strain sensor for large temperature range use is under development using a reactively-sputtered process. The sensor is capable of being fabricated in fine line widths utilizing the sacrificial-layer lift-off process that is used for micro-fabricated noble-metal sensors. Tantalum nitride films were optimized using reactive sputtering with an unbalanced magnetron source. A first approximation model of multilayer resistance and temperature coefficient of resistance was used to set the film thicknesses in the multilayer film sensor. Two multifunctional sensors were fabricated using multilayered films of tantalum nitride and palladium chromium, and tested for low temperature resistivity, TCR and strain response. The low temperature coefficient of resistance of the films will result in improved stability in thin film sensors for low to high temperature use.

  4. Effects of thermal lensing on stability and astigmatic compensation of a Z-fold laser cavity

    SciTech Connect

    Huang, X.G.; Lee, W.K.; Wong, S.P.; Zhou, J.Y.; Yu, Z.X.

    1996-12-01

    The {ital ABCD} transfer matrix method is used to study the stability of a Z-fold cavity with two concave and two flat mirrors and a Brewster-cut crystal. Analytical solutions of stable regions of the cavity without thermal lensing have been obtained. The influences of thermal lensing on stability, beam waists, and astigmatic compensation are discussed. By use of a Ti:sapphire laser with a Z-fold cavity, lasing action was achieved in the predicted stable subregions that are accessible. {copyright} {ital 1996 Optical Society of America.}

  5. Effects of curvature and compressibility on the stability of thermal fronts

    SciTech Connect

    Ibanez S, Miguel H.; Bessega L, Maria C.; Shchekinov, Yuri

    2006-06-15

    The stability of subsonic thermal fronts against corrugation is analyzed and an exact dispersion relation is obtained taking into account the effects of the curvature of the distorted front as well as the compressibility of the gas. At a certain value of the Mach number ahead of the thermal front, unstable rates show a maximum; these rates drop to zero when a Chapman-Jouguet regime is established behind heat fronts. It is shown that curvature effects tend to stabilize conductive heat fronts propagating in a compressible gas.

  6. Surge discharge capability and thermal stability of a metal oxide surge arrester

    SciTech Connect

    Kan, M.; Kojima, S.; Nishiwaki, S.; Sato, T.; Yanabu, S.

    1983-02-01

    The surge discharge capability and the thermal stability of a metal oxide surge arrester were examined experimentally. It was found that the breakdown energy is nearly the same against the switching surge and the temporary overvoltage of various peak values and time durations. Heat dissipation capability of an 84kV porcelain-type model arrester was examined and found to be less than that of a small model unit, while this relation of the value had been considered opposite in a previously published paper. From these experimental data, the limit at high operation stress was found to be determined by the thermal stability rather than by the discharge capability

  7. PMR-15/Layered Silicate Nanocomposites For Improved Thermal Stability And Mechanical Properties

    NASA Technical Reports Server (NTRS)

    Campbell, Sandi; Scheiman, Daniel; Faile, Michael; Papadopoulos, Demetrios; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    Montmorillonite clay was organically modified by co-exchange of an aromatic diamine and a primary alkyl amine. The clay was dispersed into a PMR (Polymerization of Monomer Reactants)-15 matrix and the glass transition temperature and thermal oxidative stability of the resulting nanocomposites were evaluated. PMR-15/ silicate nanocomposites were also investigated as a matrix material for carbon fabric reinforced composites. Dispersion of the organically modified silicate into the PMR-15 matrix enhanced the thermal oxidative stability, the flexural strength, flexural modulus, and interlaminar shear strength of the polymer matrix composite.

  8. Thermal Mechanical Stability of Single-Crystal-Oxide Refractive Concentrators Evaluated for High-Temperature Solar-Thermal Propulsion

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Jacobson, Nathan S.; Miller, Robert A.

    1999-01-01

    Recently, refractive secondary solar concentrator systems were developed for solar thermal power and propulsion (ref. 1). Single-crystal oxides-such as yttria-stabilized zirconia (Y2O3-ZrO2), yttrium aluminum garnet (Y3Al5O12, or YAG), magnesium oxide (MgO), and sapphire (Al2O3)-are candidate refractive secondary concentrator materials. However, the refractive concentrator system will experience high-temperature thermal cycling in the solar thermal engine during the sun/shade transition of a space mission. The thermal mechanical reliability of these components in severe thermal environments is of great concern. Simulated mission tests are important for evaluating these candidate oxide materials under a variety of transient and steady-state heat flux conditions. In this research at the NASA Lewis Research Center, a controlled heat flux test approach was developed for investigating the thermal mechanical stability of the candidate oxide. This approach used a 3.0-kW continuous-wave (wavelength, 10.6 mm) carbon dioxide (CO2) laser (ref. 2). The CO2 laser is especially well-suited for single-crystal thermal shock tests because it can directly deliver well-characterized heat energy to the oxide surfaces. Since the oxides are opaque at the 10.6-mm wavelength of the laser beam, the light energy is absorbed at the surfaces rather than transmitting into the crystals, and thus generates the required temperature gradients within the specimens. The following figure is a schematic diagram of the test rig.

  9. Examining the stability of thermally fissile Th and U isotopes

    NASA Astrophysics Data System (ADS)

    Kumar, Bharat; Biswal, S. K.; Singh, S. K.; Patra, S. K.

    2015-11-01

    The properties of recently predicted thermally fissile Th and U isotopes are studied within the framework of the relativistic mean-field approach using the axially deformed basis. We calculate the ground, first intrinsic excited state for highly neutron-rich thorium and uranium isotopes. The possible modes of decay such as α decay and β decay are analyzed. We found that neutron-rich isotopes are stable against α decay, however, they are very unstable against β decay. The lifetime of these nuclei is predicted to be tens of seconds against β decay. If these nuclei are utilized before their decay time, a lot of energy can be produced with the help of multifragmentation fission. Also, these nuclei have great implications from the astrophysical point of view. In some cases, we found that the isomeric states with energy range from 2 to 3 MeV and three maxima in the potential energy surface of Th-230228 and U-234228 isotopes.

  10. Improved thermal stability of oxide-supported naked gold nanoparticles by ligand-assisted pinning

    SciTech Connect

    Moreno, C; Divins, N. J.; Gazquez, Jaume; Varela, Maria; Angurell, I; Llorca, J

    2012-01-01

    We report a method to improve the thermal stability, up to 900 C, of bare-metal (naked) gold nanoparticles supported on top of SiO{sub 2} and SrTiO{sub 3} substrates via ligand-assisted pinning. This approach leads to monodisperse naked gold nanoparticles without significant sintering after thermal annealing in air at 900 C. The ligand-assisted pinning mechanism is described.

  11. Thermal equation of state and stability of (Mg0.06Fe0.94)O

    NASA Astrophysics Data System (ADS)

    Wicks, June K.; Jackson, Jennifer M.; Sturhahn, Wolfgang; Zhuravlev, Kirill K.; Tkachev, Sergey N.; Prakapenka, Vitali B.

    2015-12-01

    We present the pressure-volume-temperature (P-V-T) equation of state of polycrystalline (Mg0.06Fe0.94)O (Mw94) determined from laser-heated X-ray diffraction experiments up to 122 GPa and 2100 K, conditions approaching those of the deep mantle. We conducted two sets of experiments, one with an in situ Fe metal oxygen fugacity buffer and one without such a buffer. The internal pressure markers used in these experiments were B 2 -NaCl and hcp-Fe in the buffered experiment and B 2 -NaCl in the unbuffered experiment. In the sampled P-T range of the high temperature part of this study, only the B 1 structure of Mw94 was observed, indicating that the addition of Mg to FeO stabilizes the B 1 phase with respect to the B 8 phase at these conditions. Both datasets were fit to a Birch-Murnaghan and Mie-Grüneisen-Debye thermal equation of state using a new open-source fitting routine, also presented here. Analysis of these data sets using the same internal pressure marker shows that the P-V-T data of Mw94 obtained in the unbuffered experiment are well explained by the equation of state parameters determined from the buffered data set. We have also compared the thermal equation of state of Mw94 to that of wüstite and conclude that Mw94 has measurably distinct thermoelastic properties compared with those of wüstite. We use the results obtained in the buffered experiment to determine the density and bulk sound velocity of Mw94 at the base of the mantle and compare these values to geophysical observations of ultralow-velocity zones.

  12. Research on the stability of heavy metals (Cu, Zn) in excess sludge with the pretreatment of thermal hydrolysis.

    PubMed

    Wu, Huimin; Li, Meng; Zhang, Lei; Sheng, Chao

    2016-01-01

    Thermal hydrolysis (TH) has been used to improve anaerobic digestion performance as well as the stability of heavy metals in sludge. Because the toxicity of heavy metals is closely related to both the concentration and the chemical speciation, more exhaustive studies on speciation distribution are urgently needed. This research aimed to investigate the effects of TH treatment (especially the time and temperature) on the concentration and stability of heavy metals in sludge, and to define the optimal TH conditions. The TH experiment indicated that the content of the stable form of Cu and Zn reached 83% and 47.4%, respectively, with TH at 210°C and 30 min. Compared with the raw sludge, the proportion of Cu and Zn increased by 11.88% and 7.3%, respectively. Results indicated that the heavy metals were combined with sludge in a more stable form with the pretreatment of TH, which improved the stability of heavy metals. PMID:26901733

  13. Enhanced thermal stability of lysosomal beta-D-galactosidase in parenchymal cells of tumour bearing mice.

    PubMed Central

    Lenti, L.; Lipari, M.; Lombardi, D.; Zicari, A.; Dotta, A.; Pontieri, G. M.

    1986-01-01

    The thermal stability of the enzyme beta-D-galactosidase varies among different organs in normal C57Bl/6 mice, and increases in the same organs in mice with Lewis Lung carcinoma. Thermal stability of this enzyme is also increased by treatment of the mice with cell-free extracts of tumour cells or with inflammatory compounds such as carrageenan or orosomucoid. After desialylation, orosomucoid more effectively increases the heat stability of the enzyme. By contrast talc, which has no galactosyl groups, is without effect on the stability of the enzyme in vivo. Macrophages of tumour bearing mice release into the culture medium a more heat resistant enzyme than macrophages from control mice. In both cases the heat resistance of the secreted enzyme is higher when fetal calf serum is present in the culture medium. Bovine serum does not modify the thermal stability of beta-D-galactosidase in this system. Incubation of lysosomal fractions of various organs with the synthetic beta-D-galactosidase substrate, p-nitrophenyl-galactopyranoside, also strongly increases the heat resistance of the enzyme. The results suggest that one factor influencing the heat resistance of this enzyme may be complex formation between the enzyme and its substrates, an example of substrate protection of the enzyme. This may not be the only factor involved in enzyme stabilization in vivo. PMID:3099822

  14. Thermal stability of meso-substituted metal corroles in inert and oxidative media

    NASA Astrophysics Data System (ADS)

    Thao, Vu Thi; Karimov, D. R.; Guseinov, S. S.; Balantseva, E. V.; Berezin, D. B.

    2016-03-01

    The thermal stability of 5,10,15-triphenylcorrole as the simplest representative of meso-substituted corroles and its complexes with d-metals (Cu3+, Mn3+, Mn4+, Co3+, Co4+, and Zn2+) is studied for the first time via thermogravimetry in oxidizing and inert atmospheres. It is shown that corroles, both as free ligands and in the form of metal complexes, are less thermally stable than porphyrins with a similar structure. It is found that if the free ligands of porphyrins are thermally more stable with respect to thermal oxidation than d-metal complexes, the thermal stability of metal corroles can be both lower and higher than those of free ligands. It is concluded that the order of thermal stability of compounds MnCor < CoCor < H3Cor < ZnCorH < CuCor is reversed upon moving from an oxidizing to an inert medium. It is shown that corroles complexes with many d-metals (Co, Mn, and others) readily participate in extracoordination reactions with electron-donating solvents, e.g., DMF, as is indicated by spectrophotometry and thermogravimetry.

  15. SiC fiber and yttria-stabilized zirconia composite thick thermal barrier coatings fabricated by plasma spray

    NASA Astrophysics Data System (ADS)

    Ma, Rongbin; Cheng, Xudong; Ye, Weiping

    2015-12-01

    Approximately 4 mm-thick SiC fiber/yttria-stabilized zirconia (YSZ) composite thermal barrier coatings (TBCs) were prepared by atmospheric plasma spray (APS). The composite coatings have a 'reinforced concrete frame structure', which can protect the coating from failure caused by increasing thickness of coating. The SiC fiber plays an important role in reducing the residual stress level of the composite coatings. The thermal conductivity (TC) value of the composite coatings is 0.632 W/m K, which is about 50% reduction compared to that of typical APS YSZ TBCs. And the composite coatings have higher fracture toughness and better thermal shock resistance than the YSZ TBCs.

  16. Thermal/chemical stability of ceramic cross flow filter materials

    SciTech Connect

    Alvin, M.A.; Bahovchin, D.M.; Lippert, T.E.; Tressler, R.E.; McNerney, K.B.

    1992-01-01

    Westinghouse has undertaken a two phase program to determine possible long-term, high temperature influence that advanced coal-based power system environments may have on the stability of the ceramic cross flow filter elements. During the past year, we have principally focused our efforts on developing an understanding of the stability of the alumina/mullite filter material at high temperature (i.e., 870, 980, and 1100[degrees]C) under oxidizing conditions which contain gas phase alkali species. The alumina/mullite cross flow liter material that has consistently been used throughout the flow-through gas phase alkali testing segment of this program, consists of mullite rods or needles that are embedded within an amorphous phase which contains corundum (Al[sub 2]O[sub 3]) and anorthite (CaAl[sub 2]Si[sub 2]O[sub 8]). Due to the rapid cooling rate that was used to produce the alumina/mullite filter disc material from high fire, the matrix consists of 59.6 wt% mullite, 30.5 wt% amorphous, 5.1 wt% anorthite, and 4.8 wt% alumina. The relatively low, as-fabricated, hot strength of this material (841[plus minus]259 psi at 870[degrees]C) is a direct result of the high amorphous content which softens at temperatures of 870[degrees]C. Load versus deflection curves as a function of temperature indicate that this material is relatively brittle up to temperatures of 600[degrees]C. Both a loss of strength, as well as plastic deformation of the matrix occurs at [approximately]700[degrees]C. If cross flow filters are manufactured from an alumina/mullite matrix that contains an [approximately]30.5 wt% amorphous content, we suspect that the plastic nature of the glass phase could potentially serve as a substrate for fines collection during initial filter operation at 700[degrees]C. Similarly the plastic nature could potentially cause deformation of the liter under load.

  17. Thermal/chemical stability of ceramic cross flow filter materials

    SciTech Connect

    Alvin, M.A.; Bahovchin, D.M.; Lippert, T.E.; Tressler, R.E.; McNerney, K.B.

    1992-11-01

    Westinghouse has undertaken a two phase program to determine possible long-term, high temperature influence that advanced coal-based power system environments may have on the stability of the ceramic cross flow filter elements. During the past year, we have principally focused our efforts on developing an understanding of the stability of the alumina/mullite filter material at high temperature (i.e., 870, 980, and 1100{degrees}C) under oxidizing conditions which contain gas phase alkali species. The alumina/mullite cross flow liter material that has consistently been used throughout the flow-through gas phase alkali testing segment of this program, consists of mullite rods or needles that are embedded within an amorphous phase which contains corundum (Al{sub 2}O{sub 3}) and anorthite (CaAl{sub 2}Si{sub 2}O{sub 8}). Due to the rapid cooling rate that was used to produce the alumina/mullite filter disc material from high fire, the matrix consists of 59.6 wt% mullite, 30.5 wt% amorphous, 5.1 wt% anorthite, and 4.8 wt% alumina. The relatively low, as-fabricated, hot strength of this material (841{plus_minus}259 psi at 870{degrees}C) is a direct result of the high amorphous content which softens at temperatures of 870{degrees}C. Load versus deflection curves as a function of temperature indicate that this material is relatively brittle up to temperatures of 600{degrees}C. Both a loss of strength, as well as plastic deformation of the matrix occurs at {approximately}700{degrees}C. If cross flow filters are manufactured from an alumina/mullite matrix that contains an {approximately}30.5 wt% amorphous content, we suspect that the plastic nature of the glass phase could potentially serve as a substrate for fines collection during initial filter operation at 700{degrees}C. Similarly the plastic nature could potentially cause deformation of the liter under load.

  18. Diffusion and the Thermal Stability of Amorphous Copper-Zirconium

    NASA Astrophysics Data System (ADS)

    Stelter, Eric Carl

    Measurements have been made of diffusion and thermal relaxation in amorphous Cu(,50)Zr(,50). Samples were prepared by melt-spinning under vacuum. Diffusion measurements were made over the temperature range from 317 to 385 C, using Ag and Au as substitutional impurities, by means of Auger electron spectrometry (AES) and Rutherford backscattering spectrometry (RBS). Thermal measurements were made by differential scanning calorimetry (DSC) up to 550 C. The diffusion coefficients of Ag and Au in amorphous Cu(,50)Zr(,50) are found to be somewhat higher than, but very close in magnitude to the coefficient of self-diffusion in crystalline Cu at the same temperatures. The activation energies for diffusion in the amorphous alloy are 0.72 to 1.55 eV/atom, much closer to the activation energy for self-diffusion in liquid Cu, 0.42 eV/atom, than that for the crystalline solid, 2.19 eV/atom. The mechanism for diffusion in the amorphous metal is presumably quite different from the monovacancy mechanism dominant in the crystalline solid. The pre-exponential terms are found to be extremely small, on the order of 10('-10) to 10('-11) cm('2)/sec for Ag diffusion. This indicates that diffusion in amorphous Cu(,50)Zr(,50) may involve an extended defect of 10 or more atoms. Analysis of the data in terms of the free -volume model also lends strength to this conclusion and indicates that the glass is composed of liquid-like clusters of 15 to 20 atoms. The initial stage of relaxation in amorphous CuZr occurs with a spectrum of activation energies. The lowest activation energy involved, 0.78 eV/atom, is almost identical to the average activation energy of Ag diffusion in the glass, 0.77 eV/atom, indicating that relaxation occurs primarily through diffusion. The activation energy of crystallization, determined by Kissinger's method, is 3.10 eV/atom. The large difference, on the order of 2.3 eV/atom, between the activation energies of crystallization and diffusion is attributed to the energy

  19. Thermal stability and thermal expansion studies of cubic fluorite-type MgF{sub 2} up to 135 GPa

    SciTech Connect

    Sun, X.W.; Song, T.; Wei, X.P.; Quan, W.L.; Liu, X.B.; Su, W.F.

    2014-04-01

    Highlights: • The thermal expansion of MgF{sub 2} with a fluorite-type structure has been investigated. • The quasi-harmonic Debye model is applied to take into account the thermal effect. • Particular attention is paid to the prediction of thermal expansion for the first time. - Abstract: The thermal expansion of MgF{sub 2} with a fluorite structure has been investigated at high pressures using plane-wave pseudopotential scheme within the local density approximation correction in the frame of density functional theory based on the analysis of thermal stability using classical molecular dynamics simulations up to 6500 K. To investigate the thermodynamic properties like as the P–V–T equation of state and volumetric thermal expansion coefficient α{sub V} of cubic fluorite-type MgF{sub 2} at extended pressure and temperature ranges, we apply the quasi-harmonic Debye model in which the phononic effects are considered. The P–V relationship and α{sub V} dependence of the pressure up to 135 GPa at different temperatures, and the V–T relationship and α{sub V} dependence of the temperature up to the melting temperature 1500 K at different pressures have been obtained.

  20. Stability of thermal convection in a rotating cylindrical container

    NASA Astrophysics Data System (ADS)

    Herrada, Miguel; Shtern, Vladimir

    2016-08-01

    The rotation and an axial gradient of temperature drive the meridional circulation of a fluid filling a sealed cylindrical container. This numerical study explains why the flow remains stable up to the Grashof number Gr around 1011; Gr characterizes the circulation strength. The shear-layer instability, occurring in a rotating pipe for small values of the Prandtl number Pr [M. A. Herrada and V. N. Shtern, "Stability of centrifugal convection in a rotating pipe," Phys. Fluids 27, 064106 (2015)], is suppressed here even for the cylinder length-to-radius ratio being ten. The cold end disk enhances the fluid circulation near the sidewall and diminishes it near the axis. The inflection point in the radial profile of axial velocity shifts to the sidewall vicinity where the stable centrifugal stratification and the no-slip condition prevent the disturbance growth. The cases Pr = 0, 0.015 (mercury), 0.7 (air), and 5.8 (water) are particularly analyzed. At Pr > 0, the stable density stratification develops and helps to suppress the disturbances. The obtained results are of fundamental interest and might be important for the development of efficient heat exchangers.

  1. Thermal stabilization of collagen in skin and decalcified bone

    NASA Astrophysics Data System (ADS)

    Miles, Christopher A.; Avery, Nicholas C.

    2011-04-01

    The state of collagen molecules in the fibres of tail tendon, skin and demineralized bone has been investigated in situ using differential scanning calorimetry (DSC). Hydroxyproline analysis and tissue digestion with bacterial collagenase and trypsin were used to confirm that the common cause of all the DSC endotherms was collagen denaturation. This occurred within a narrow temperature range in tendons, but over a wide temperature range in demineralized bone and old skin and demonstrated that in tendon and demineralized bone at least the same type I collagen molecule exists in different thermal states. Hypothesizing that this might be caused by different degrees of confinement within the fibre lattice, experiments were performed to measure the effect of changing the lattice dimensions by extracting the collagen into dilute solution with pepsin, swelling the lattice in acetic acid, and contracting the lattice by dehydration. A theoretical analysis was undertaken to predict the effect of dehydration. Results were consistent with the hypothesis, demonstrating that collagen molecules within the natural fibres of bone and old skin are located at different intermolecular spacings, revealing differences between molecules in the magnitude of either the attractive or repulsive forces controlling their separation. One potential cause of such variation is known differences in covalent cross-linking.

  2. Optical and Thermal Stability of Oligofluorene/Rubber Luminescent Blend.

    PubMed

    Barbosa, Camila G; Faez, Roselena; Péres, Laura O

    2016-09-01

    This paper proposes to obtain homogeneous and stable blends of oligo(9,9-dioctylfluorene)-co-phenylene (OF), a conjugated oligomer with strong tendency of formation of excimers in the solid state, and nitrile rubber (NBR). This rubber protection reduces the formation of polymer excimers in the films. The fluorene oligomer was synthesized via Suzuki reaction and incorporated in the nitrile rubber. The films were formed by spin coating and casting techniques on the proportions of 1, 5, 10, 20 and 50 % (w/w) of OF in the nitrile rubber (NBR). The structural, optical and thermal properties of the films were evaluated with infrared, UV-Vis, fluorescence and thermogravimetry, respectively. The nitrile rubber proved to be essential for the preparation of homogeneous and stable films, since it was not possible to obtain films with only fluorene using the above-mentioned techniques. Furthermore, luminescent properties of OF are unchanged and the excimers formation in the solid state decrease suggesting the efficiency of nitrile rubber as the matrix for making films. PMID:27351668

  3. Rigidity versus flexibility: the dilemma of understanding protein thermal stability.

    PubMed

    Karshikoff, Andrey; Nilsson, Lennart; Ladenstein, Rudolf

    2015-10-01

    The role of fluctuations in protein thermostability has recently received considerable attention. In the current literature a dualistic picture can be found: thermostability seems to be associated with enhanced rigidity of the protein scaffold in parallel with the reduction of flexible parts of the structure. In contradiction to such arguments it has been shown by experimental studies and computer simulation that thermal tolerance of a protein is not necessarily correlated with the suppression of internal fluctuations and mobility. Both concepts, rigidity and flexibility, are derived from mechanical engineering and represent temporally insensitive features describing static properties, neglecting that relative motion at certain time scales is possible in structurally stable regions of a protein. This suggests that a strict separation of rigid and flexible parts of a protein molecule does not describe the reality correctly. In this work the concepts of mobility/flexibility versus rigidity will be critically reconsidered by taking into account molecular dynamics calculations of heat capacity and conformational entropy, salt bridge networks, electrostatic interactions in folded and unfolded states, and the emerging picture of protein thermostability in view of recently developed network theories. Last, but not least, the influence of high temperature on the active site and activity of enzymes will be considered. PMID:26074325

  4. Thermal-noise limit in the frequency stabilization of lasers with rigid cavities.

    PubMed

    Numata, Kenji; Kemery, Amy; Camp, Jordan

    2004-12-17

    We evaluate thermal noise (Brownian motion) in a rigid reference cavity used for frequency stabilization of lasers, based on the mechanical loss of cavity materials and the numerical analysis of the mirror-spacer mechanics with the direct application of the fluctuation dissipation theorem. This noise sets a fundamental limit for the frequency stability achieved with a rigid frequency-reference cavity of order 1 Hz/ square root Hz (0.01 Hz/ square root Hz) at 10 mHz (100 Hz) at room temperature. This level coincides with the world-highest level stabilization results. PMID:15697887

  5. Thermal Response and Stability Characteristics of Bistable Composite Laminates by Considering Temperature Dependent Material Properties and Resin Layers

    NASA Astrophysics Data System (ADS)

    Moore, M.; Ziaei-Rad, S.; Salehi, H.

    2013-02-01

    In this study, the stability characteristics and thermal response of a bistable composite plate with different asymmetric composition were considered. The non-linear finite element method (FEM) was utilized to determine the response of the laminate. Attention was focused on the temperature dependency of laminate mechanical properties, especially on the thermal expansion coefficients of the composite graphite-epoxy plate. Also the effect of including the resin layers on the stability characteristics of the laminate was investigated. The effect of the temperature on the laminate cured configurations in the range of 25°C to 180°C and -60°C to 40°C was examined. The results indicate that the coefficient of thermal expansions has a major effect on the cured shapes. Next, optical microscopy was used to characterize the laminate composition and for the first time the effect of including the resin layers on the actuation loads that causes snapping behavior between two stable shapes was studied. The results obtained from the finite element simulations were compared with experimental results and a good correlation was obtained. Finally, the stability characteristics of a tapered composite panel were investigated for using in a sample winglet as a candidate application of bistable structures.

  6. Effects of terbium sulfide addition on magnetic properties, microstructure and thermal stability of sintered Nd–Fe–B magnets

    NASA Astrophysics Data System (ADS)

    Xiang-Bin, Li; Shuo, Liu; Xue-Jing, Cao; Bei-Bei, Zhou; Ling, Chen; A-Ru, Yan; Gao-Lin, Yan

    2016-07-01

    To increase coercivity and thermal stability of sintered Nd–Fe–B magnets for high-temperature applications, a novel terbium sulfide powder is added into (Pr0.25Nd0.75)30.6Cu0.15FebalB1 (wt.%) basic magnets. The effects of the addition of terbium sulfide on magnetic properties, microstructure, and thermal stability of sintered Nd–Fe–B magnets are investigated. The experimental results show that by adding 3 wt.% Tb2S3, the coercivity of the magnet is remarkably increased by about 54% without a considerable reduction in remanence and maximum energy product. By means of the electron probe microanalyzer (EPMA) technology, it is observed that Tb is mainly present in the outer region of 2:14:1 matrix grains and forms a well-developed Tb-shell phase, resulting in enhancement of H A, which accounts for the coercivity enhancement. Moreover, compared with Tb2S3-free magnets, the reversible temperature coefficients of remanence (α) and coercivity (β) and the irreversible flux loss of magnetic flow (h irr) values of Tb2S3-added magnets are improved, indicating that the thermal stability of the magnets is also effectively improved. Project supported by the Science Funds from the Ministry of Science and Technology, China (Grant Nos. 2014DFB50130 and 2011CB612304) and the National Natural Science Foundation of China (Grant Nos. 51172168 and 51072139).

  7. Solution-processed silver nanowire/indium-tin-oxide nanoparticle hybrid transparent conductors with high thermal stability.

    PubMed

    Hong, Sung-Jei; Kim, Jong-Woong; Kim, Yong-Hoon

    2014-12-01

    In this study, solution-processed hybrid structure transparent conductors consisting of silver nanowires (AgNWs) and indium-tin-oxide nanoparticle (ITO-NP) layers are investigated. Fabricated transparent conductors had stacked structures of ITO-NP/AgNW and ITO-NP/AgNW/ITO-NP, and a successful integration was possible on glass substrates. Compared to a single-layered ITO-NP film which has a sheet resistance value of 1.31 k Ω/⟂, a remarkable enhancement in sheet resistance was achieved from the hybrid structures, showing sheet resistance values of 44.74 Ω/⟂ and 28.07 Ω/⟂ for ITO-NP/AgNW and ITO-NP/AgNW/ITO-NP structures, respectively. In addition, the ITO-NP/AgNW/ITO-NP triple-layered transparent conductor showed greatly enhanced thermal stability in terms of sheet resistance and transmittance against a high-temperature environment up to 300 degrees C. Based on these results, it can be suggested that the hybrid structure has advantages of enhancing both electrical properties of ITO-NP layer and thermal stability of AgNW layer, and we believe the hybrid structure transparent conductors can be a suitable option for applications which require high electrical conductivity, transmittance, and thermal stability. PMID:25971091

  8. Solute-Derived Thermal Stabilization of Nano-sized Grains in Melt-Spun Aluminum

    NASA Astrophysics Data System (ADS)

    Baker, A. H.; Sanders, P. G.; Lass, E. A.; Kapoor, Deepak; Kampe, S. L.

    2016-08-01

    Thermal stabilization of nanograined metallic microstructures (or nanostructures) can be difficult due to the large driving force for growth that arises from the inherently significant boundary area. Kinetic approaches for stabilization of the nanostructure effective at low homologous temperatures often fail at higher homologous temperatures. Alternatively, thermodynamic approaches for thermal stabilization may offer higher temperature stability. In this research, modest alloying of aluminum with solute (1 pct by mole Sc, Yb, or Sr) was examined as a means to thermodynamically stabilize a bulk nanostructure at elevated temperatures. Following 1-hour annealing treatments at 673 K (400 °C) (0.72 Tm), 773 K (500 °C) (0.83 Tm), and 873 K (600 °C) (0.94 Tm), the alloys remain nanocrystalline (<100 nm) as measured by Warren-Averbach Fourier analysis of X-ray diffraction peaks and direct observation of TEM dark-field micrographs, with the efficacy of stabilization: Sr ≈ Yb > Sc. The disappearance of intermetallic phases in the Sr- and Yb-containing alloys in the X-ray diffraction spectra is observed to occur coincident with the stabilization after annealing, suggesting that precipitates dissolve and the boundaries are enriched with solute.

  9. Solute-Derived Thermal Stabilization of Nano-sized Grains in Melt-Spun Aluminum

    NASA Astrophysics Data System (ADS)

    Baker, A. H.; Sanders, P. G.; Lass, E. A.; Kapoor, Deepak; Kampe, S. L.

    2016-06-01

    Thermal stabilization of nanograined metallic microstructures (or nanostructures) can be difficult due to the large driving force for growth that arises from the inherently significant boundary area. Kinetic approaches for stabilization of the nanostructure effective at low homologous temperatures often fail at higher homologous temperatures. Alternatively, thermodynamic approaches for thermal stabilization may offer higher temperature stability. In this research, modest alloying of aluminum with solute (1 pct by mole Sc, Yb, or Sr) was examined as a means to thermodynamically stabilize a bulk nanostructure at elevated temperatures. Following 1-hour annealing treatments at 673 K (400 °C) (0.72 Tm), 773 K (500 °C) (0.83 Tm), and 873 K (600 °C) (0.94 Tm), the alloys remain nanocrystalline (<100 nm) as measured by Warren-Averbach Fourier analysis of X-ray diffraction peaks and direct observation of TEM dark-field micrographs, with the efficacy of stabilization: Sr ≈ Yb > Sc. The disappearance of intermetallic phases in the Sr- and Yb-containing alloys in the X-ray diffraction spectra is observed to occur coincident with the stabilization after annealing, suggesting that precipitates dissolve and the boundaries are enriched with solute.

  10. Stability of lysozyme in aqueous extremolyte solutions during heat shock and accelerated thermal conditions.

    PubMed

    Avanti, Christina; Saluja, Vinay; van Streun, Erwin L P; Frijlink, Henderik W; Hinrichs, Wouter L J

    2014-01-01

    The purpose of this study was to investigate the stability of lysozyme in aqueous solutions in the presence of various extremolytes (betaine, hydroxyectoine, trehalose, ectoine, and firoin) under different stress conditions. The stability of lysozyme was determined by Nile red Fluorescence Spectroscopy and a bioactivity assay. During heat shock (10 min at 70°C), betaine, trehalose, ectoin and firoin protected lysozyme against inactivation while hydroxyectoine, did not have a significant effect. During accelerated thermal conditions (4 weeks at 55°C), firoin also acted as a stabilizer. In contrast, betaine, hydroxyectoine, trehalose and ectoine destabilized lysozyme under this condition. These findings surprisingly indicate that some extremolytes can stabilize a protein under certain stress conditions but destabilize the same protein under other stress conditions. Therefore it is suggested that for the screening extremolytes to be used for protein stabilization, an appropriate storage conditions should also be taken into account. PMID:24465983

  11. Double-Layer Gadolinium Zirconate/Yttria-Stabilized Zirconia Thermal Barrier Coatings Deposited by the Solution Precursor Plasma Spray Process

    NASA Astrophysics Data System (ADS)

    Jiang, Chen; Jordan, Eric H.; Harris, Alan B.; Gell, Maurice; Roth, Jeffrey

    2015-08-01

    Advanced thermal barrier coatings (TBCs) with lower thermal conductivity, increased resistance to calcium-magnesium-aluminosilicate (CMAS), and improved high-temperature capability, compared to traditional yttria-stabilized zirconia (YSZ) TBCs, are essential to higher efficiency in next generation gas turbine engines. Double-layer rare-earth zirconate/YSZ TBCs are a promising solution. From a processing perspective, solution precursor plasma spray (SPPS) process with its unique and beneficial microstructural features can be an effective approach to obtaining the double-layer microstructure. Previously durable low-thermal-conductivity YSZ TBCs with optimized layered porosity, called the inter-pass boundaries (IPBs) were produced using the SPPS process. In this study, an SPPS gadolinium zirconate (GZO) protective surface layer was successfully added. These SPPS double-layer TBCs not only retained good cyclic durability and low thermal conductivity, but also demonstrated favorable phase stability and increased surface temperature capabilities. The CMAS resistance was evaluated with both accumulative and single applications of simulated CMAS in isothermal furnaces. The double-layer YSZ/GZO exhibited dramatic improvement in the single application, but not in the continuous one. In addition, to explore their potential application in integrated gasification combined cycle environments, double-layer TBCs were tested under high-temperature humidity and encouraging performance was recorded.

  12. Edge/basal/defect ratios in graphite and their influence on the thermal stability of lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Foss, Carl Erik Lie; Svensson, Ann Mari; Sunde, Svein; Vullum-Bruer, Fride

    2016-06-01

    Raw graphite can be processed industrially in large quanta but for the graphite to be useful in lithium ion batteries (LIB's) certain parameters needs to be optimized. Some key parameters are graphite morphology, active surface area, and particle size. These parameters can to some extent be manipulated by surface coatings, milling processes and heat treatment in various atmospheres. Industrial graphite materials have been investigated for use as anode material in LIB's and compared with commercial graphite. These materials have been exposed to two different milling processes, and some of these materials were further heat treated in nitrogen atmosphere above 2650 °C. Brunauer-Emmett-Teller (BET) theory combined with density functional theory (DFT) has been employed to study the ratio of basal to non-basal plane and to determine the relative amount of defects. Thermal properties have been investigated with differential scanning calorimetry (DSC). High ethylene carbonate (EC) content improved the thermal stability for graphite with high amount of edge/defect surface area, but showed no improvement of graphite with lower amount of edge/defects. High irreversible capacity loss (ICL) combined with low surface area improved the thermal properties. DFT combined with ICL could potentially be used as a tool to predict thermal stability.

  13. The effect of phytosterol concentration on oxidative stability and thermal polymerization of heated oils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study determined the effect of adding mixed phytosterols, at various concentrations, on the thermal polymerization and oxidative stability index (OSI) of soybean and high-oleic sunflower oils. The indigenous tocopherols and phytosterols were removed from the oils by molecular distillation. Pu...

  14. Solidification/stabilization of contaminated soil and concrete debris with thermal-treated BTM

    SciTech Connect

    Hsieh, Hsin-Neng; Yu, Qing-Rui; Chang, J.

    1994-12-31

    Contaminated black tarry materials was treated thermally and converted to a material with properties similar to petroleum-based asphalt. This property-improved material was then used as a binder to enclose contaminated concrete debris and soil in the solidification/stabilization process. The final product can be used for medium traffic pavement. 9 refs., 5 tabs.

  15. Fullerene-Free Polymer Solar Cells with over 11% Efficiency and Excellent Thermal Stability.

    PubMed

    Zhao, Wenchao; Qian, Deping; Zhang, Shaoqing; Li, Sunsun; Inganäs, Olle; Gao, Feng; Hou, Jianhui

    2016-06-01

    A nonfullerene-based polymer solar cell (PSC) that significantly outperforms fullerene-based PSCs with respect to the power-conversion efficiency is demonstrated for the first time. An efficiency of >11%, which is among the top values in the PSC field, and excellent thermal stability is obtained using PBDB-T and ITIC as donor and acceptor, respectively. PMID:27061511

  16. New class of thermosetting plastics has improved strength, thermal and chemical stability

    NASA Technical Reports Server (NTRS)

    Burns, E. A.; Dubrow, B.; Lubowitz, H. R.

    1967-01-01

    New class of thermosetting plastics has high hydrocarbon content, high stiffness, thermal stability, humidity resistance, and workability in the precured state. It is designated cyclized polydiene urethane, and is applicable as matrices to prepare chemically stable ablative materials for rocket nose cones of nozzles.

  17. Engineering deamidation-susceptible asparagines leads to improved stability to thermal cycling in a lipase

    PubMed Central

    Bhanuramanand, K; Ahmad, Shoeb; Rao, N M

    2014-01-01

    At high temperatures, protein stability is influenced by chemical alterations; most important among them is deamidation of asparagines. Deamidation kinetics of asparagines depends on the local sequence, solvent, pH, temperature, and the tertiary structure. Suitable replacement of deamidated asparagines could be a viable strategy to improve deamidation-mediated loss in protein properties, specifically protein thermostability. In this study, we have used nano RP-HPLC coupled ESI MS/MS approach to identify residues susceptible to deamidation in a lipase (6B) on heat treatment. Out of 15 asparagines and six glutamines in 6B, only five asparagines were susceptible to deamidation at temperatures higher than 75°C. These five positions were subjected to site saturation mutagenesis followed by activity screen to identify the most suitable substitutions. Only three of the five asparagines were found to be tolerant to substitutions. Best substitutions at these positions were combined into a mutant. The resultant lipase (mutC) has near identical secondary structure and improved thermal tolerance as compared to its parent. The triple mutant has shown almost two-fold higher residual activity compared to 6B after four cycles at 90°C. MutC has retained more than 50% activity even after incubation at 100°C. Engineering asparagines susceptible to deamidation would be a potential strategy to improve proteins to withstand very high temperatures. PMID:25043738

  18. The Effect of Homogenization Heat Treatment on Thermal Expansion Coefficient and Dimensional Stability of Low Thermal Expansion Cast Irons

    NASA Astrophysics Data System (ADS)

    Chen, Li-Hao; Liu, Zong-Pei; Pan, Yung-Ning

    2016-08-01

    In this paper, the effect of homogenization heat treatment on α value [coefficient of thermal expansion (10-6 K-1)] of low thermal expansion cast irons was studied. In addition, constrained thermal cyclic tests were conducted to evaluate the dimensional stability of the low thermal expansion cast irons with various heat treatment conditions. The results indicate that when the alloys were homogenized at a relatively low temperature, e.g., 1023 K (750 °C), the elimination of Ni segregation was not very effective, but the C concentration in the matrix was moderately reduced. On the other hand, if the alloys were homogenized at a relatively high temperature, e.g., 1473 K (1200 °C), opposite results were obtained. Consequently, not much improvement (reduction) in α value was achieved in both cases. Therefore, a compound homogenization heat treatment procedure was designed, namely 1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ, in which a relatively high homogenization temperature of 1473 K (1200 °C) can effectively eliminate the Ni segregation, and a subsequent holding stage at 1023.15 K (750 °C) can reduce the C content in the matrix. As a result, very low α values of around (1 to 2) × 10-6 K-1 were obtained. Regarding the constrained thermal cyclic testing in 303 K to 473 K (30 °C to 200 °C), the results indicate that regardless of heat treatment condition, low thermal expansion cast irons exhibit exceedingly higher dimensional stability than either the regular ductile cast iron or the 304 stainless steel. Furthermore, positive correlation exists between the α 303.15 K to 473.15 K value and the amount of shape change after the thermal cyclic testing. Among the alloys investigated, Heat I-T3B (1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ) exhibits the lowest α 303 K to 473 K value (1.72 × 10-6 K-1), and hence has the least shape change (7.41 μm) or the best dimensional stability.

  19. The Effect of Homogenization Heat Treatment on Thermal Expansion Coefficient and Dimensional Stability of Low Thermal Expansion Cast Irons

    NASA Astrophysics Data System (ADS)

    Chen, Li-Hao; Liu, Zong-Pei; Pan, Yung-Ning

    2016-05-01

    In this paper, the effect of homogenization heat treatment on α value [coefficient of thermal expansion (10-6 K-1)] of low thermal expansion cast irons was studied. In addition, constrained thermal cyclic tests were conducted to evaluate the dimensional stability of the low thermal expansion cast irons with various heat treatment conditions. The results indicate that when the alloys were homogenized at a relatively low temperature, e.g., 1023 K (750 °C), the elimination of Ni segregation was not very effective, but the C concentration in the matrix was moderately reduced. On the other hand, if the alloys were homogenized at a relatively high temperature, e.g., 1473 K (1200 °C), opposite results were obtained. Consequently, not much improvement (reduction) in α value was achieved in both cases. Therefore, a compound homogenization heat treatment procedure was designed, namely 1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ, in which a relatively high homogenization temperature of 1473 K (1200 °C) can effectively eliminate the Ni segregation, and a subsequent holding stage at 1023.15 K (750 °C) can reduce the C content in the matrix. As a result, very low α values of around (1 to 2) × 10-6 K-1 were obtained. Regarding the constrained thermal cyclic testing in 303 K to 473 K (30 °C to 200 °C), the results indicate that regardless of heat treatment condition, low thermal expansion cast irons exhibit exceedingly higher dimensional stability than either the regular ductile cast iron or the 304 stainless steel. Furthermore, positive correlation exists between the α 303.15 K to 473.15 K value and the amount of shape change after the thermal cyclic testing. Among the alloys investigated, Heat I-T3B (1473 K (1200 °C)/4 hours/FC/1023 K (750 °C)/2 hours/WQ) exhibits the lowest α 303 K to 473 K value (1.72 × 10-6 K-1), and hence has the least shape change (7.41 μm) or the best dimensional stability.

  20. Comparative environmental analysis of waste brominated plastic thermal treatments.

    PubMed

    Bientinesi, M; Petarca, L

    2009-03-01

    The aim of this research activity is to investigate the environmental impact of different thermal treatments of waste electric and electronic equipment (WEEE), applying a life cycle assessment methodology. Two scenarios were assessed, which both allow the recovery of bromine: (A) the co-combustion of WEEE and green waste in a municipal solid waste combustion plant, and (B) the staged-gasification of WEEE and combustion of produced syngas in gas turbines. Mass and energy balances on the two scenarios were set and the analysis of the life cycle inventory and the life cycle impact assessment were conducted. Two impact assessment methods (Ecoindicator 99 and Impact 2002+) were slightly modified and then used with both scenarios. The results showed that scenario B (staged-gasification) had a potentially smaller environmental impact than scenario A (co-combustion). In particular, the thermal treatment of staged-gasification was more energy efficient than co-combustion, and therefore scenario B performed better than scenario A, mainly in the impact categories of "fossil fuels" and "climate change". Moreover, the results showed that scenario B allows a higher recovery of bromine than scenario A; however, Br recovery leads to environmental benefits for both the scenarios. Finally the study demonstrates that WEEE thermal treatment for energy and matter recovery is an eco-efficient way to dispose of this kind of waste. PMID:18829288

  1. Comparative environmental analysis of waste brominated plastic thermal treatments

    SciTech Connect

    Bientinesi, M. Petarca, L.

    2009-03-15

    The aim of this research activity is to investigate the environmental impact of different thermal treatments of waste electric and electronic equipment (WEEE), applying a life cycle assessment methodology. Two scenarios were assessed, which both allow the recovery of bromine: (A) the co-combustion of WEEE and green waste in a municipal solid waste combustion plant, and (B) the staged-gasification of WEEE and combustion of produced syngas in gas turbines. Mass and energy balances on the two scenarios were set and the analysis of the life cycle inventory and the life cycle impact assessment were conducted. Two impact assessment methods (Ecoindicator 99 and Impact 2002+) were slightly modified and then used with both scenarios. The results showed that scenario B (staged-gasification) had a potentially smaller environmental impact than scenario A (co-combustion). In particular, the thermal treatment of staged-gasification was more energy efficient than co-combustion, and therefore scenario B performed better than scenario A, mainly in the impact categories of 'fossil fuels' and 'climate change'. Moreover, the results showed that scenario B allows a higher recovery of bromine than scenario A; however, Br recovery leads to environmental benefits for both the scenarios. Finally the study demonstrates that WEEE thermal treatment for energy and matter recovery is an eco-efficient way to dispose of this kind of waste.

  2. Observations on the effect of time dependent gravitational fields on the thermal convective stability of a fluid layer heated from above

    NASA Astrophysics Data System (ADS)

    Shukla, P. K.; Narayanan, R.

    The effect of a time dependent gravity vector on the thermal stability of a fluid layer heated from above is explained physically and by way of a calculation. An analytical result for the stability is obtained and this is compared favorably with a full numerical calculation using Floquet coefficients. Two cases are studied. These are the single and double frequency cases. Contrary to our initial expectations the fluid layer can become more unstable as it is heated from above.

  3. Increased Thermal Stability of Chromatin Containing 5-Bromodeoxyuridine-Substituted DNA

    PubMed Central

    David, John; Gordon, Joel S.; Rutter, William J.

    1974-01-01

    The replacement of thymidine by 5-bromodeoxyuridine in DNA leads to a greatly enhanced stability of chromatin from hepatoma tissue culture or embryonic rat pancreas, as measured by thermal chromatography on hydroxylapatite. The increased stability is directly correlated with the degree of bromodeoxyuridine substitution. On the other hand, the incorporation of bromodeoxyuridine into DNA results in a modest stabilization of purified DNA. Substitution of nucleotide also alters slightly the hyperchromicity profile generated during the thermal denaturation of purified DNA and chromatin. The observed changes can best be explained by an altered interaction between the bromodeoxyuridine-DNA and other chromatin components, presumably proteins. These results suggests that the selective effects of bromodeoxyuridine on cytodifferentiation may be due to an increased affinity of regulatory proteins for bromodeoxyuridine-DNA. PMID:4368811

  4. High-throughput thermal scanning for protein stability: making a good technique more robust.

    PubMed

    Seabrook, Shane A; Newman, Janet

    2013-08-12

    We present a high-throughput approach to help define experimental formulations that enhance protein stability, which is based on differential scanning fluorimetry (DSF). The method involves defining the thermal stability of a protein against a screen of 13 buffer systems, systematically sampling pH from 5.0 to 9.0 at high and low salt concentrations, using both redundancy and extensive controls to make the method robust. The screen allows rapid determination of a suitable base formulation for protein samples, and is particularly useful for difficult samples: those that are rapidly degraded or cannot be sufficiently concentrated for downstream analyses. Data obtained from three samples in this assay illustrate the vastly different values for thermal stability that can be obtained from different formulations. This approach is simple to interpret and reliable enough that it has been implemented as a service through the Collaborative Crystallisation Centre (C3). PMID:23710551

  5. Morphologies, mechanical properties and thermal stability of poly(lactic acid) toughened by precipitated barium sulfate

    NASA Astrophysics Data System (ADS)

    Yang, Jinian; Wang, Chuang; Shao, Kaiyun; Ding, Guoxin; Tao, Yulun; Zhu, Jinbo

    2015-11-01

    Poly(lactic acid) (PLA)-based composites were prepared by blending PLA with precipitated barium sulfate (BaSO4) modified with stearic acid. The morphologies, mechanical properties and thermal stability of samples with increased mass fraction of BaSO4 were investigated. Results showed that PLA was toughened and reinforced simultaneously by incorporation of precipitated BaSO4 particles. The highest impact toughness and elongation at break were both achieved at 15% BaSO4, while the elastic modulus increased monotonically with increasing BaSO4 loading. Little effect of BaSO4 on the thermal behavior of PLA was observed in the present case. However, the thermal stability of PLA/BaSO4 composites at high temperature was enhanced.

  6. Radial effects in heating and thermal stability of a sub-ignited tokamak

    SciTech Connect

    Fuchs, V.; Shoucri, M.M.; Thibaudeau, G.; Harten, L.; Bers, A.

    1982-02-01

    The existence of thermally stable sub-ignited equilibria of a tokamak reactor, sustained in operation by a feedback-controlled supplementary heating source, is demonstrated. The establishment of stability depends on a number of radially non-uniform, nonlinear processes whose effect is analyzed. One-dimensional (radial) stability analyses of model transport equations, together with numerical results from a 1-D transport code, are used in studying the heating of DT-plasmas in the thermonuclear regime. Plasma core supplementary heating is found to be a thermally more stable process than bulk heating. In the presence of impurity line radiation, however, core-heated temperature profiles may collapse, contracting inward from the limiter, the result of an instability caused by the increasing nature of the radiative cooling rate, with decreasing temperature. Conditions are established for the realization of a sub-ignited high-Q, toroidal reactor plasma with appreciable output power (approx. = 2000 MW thermal).

  7. Effect of supramolecular organization of a cartilaginous tissue on thermal stability of collagen II

    NASA Astrophysics Data System (ADS)

    Ignat'eva, N. Yu.; Averkiev, S. V.; Lunin, V. V.; Grokhovskaya, T. E.; Obrezkova, M. V.

    2006-08-01

    The thermal stability of collagen II in various cartilaginous tissues was studied. It was found that heating a tissue of nucleus pulposus results in collagen II melting within a temperature range of 60-70°C; an intact tissue of hyaline cartilage (of nasal septum and cartilage endplates) is a thermally stable system, where collagen II is not denatured completely up to 100°C. It was found that partial destruction of glycosaminoglycans in hyaline cartilage leads to an increase in the degree of denaturation of collagen II upon heating, although a significant fraction remains unchanged. It was shown that electrostatic interactions of proteoglycans and collagen only slightly affect the thermal stability of collagen II in the tissues. Evidently, proteoglycan aggregates play a key role: they create topological hindrances for moving polypeptide chains, thereby reducing the configurational entropy of collagen macromolecules in the state of a random coil.

  8. Thermal stability and energy harvesting characteristics of Au nanorods: harsh environment chemical sensing

    NASA Astrophysics Data System (ADS)

    Karker, Nicholas; Dharmalingam, Gnanaprakash; Carpenter, Michael A.

    2015-05-01

    Monitoring the levels of polluting gases such as CO and NOx from high temperature (500°C and higher) combustion environments requires materials with high thermal stability and resilience that can withstand harsh oxidizing and reducing environments. Au nanorods (AuNRs) have shown potential in plasmonic gas sensing due to their catalytic activity, high oxidation stability, and absorbance sensitivity to changes in the surrounding environment. By using electron beam lithography, AuNR geometries can be patterned with tight control of the rod dimensions and spacings, allowing tunability of their optical properties. Methods such as NR encapsulation within an yttria-stabilized zirconia overcoat layer with subsequent annealing procedures will be shown to improve temperature stability within a simulated harsh environment. Since light sources and spectrometers are typically required to obtain optical measurements, integration is a major barrier for harsh environment sensing. Plasmonic sensing results will be presented where thermal energy is harvested by the AuNRs, which replaces the need for an external incident light source. Results from gas sensing experiments that utilize thermal energy harvesting are in good agreement with experiments which use an external incident light source. Principal component analysis results demonstrate that by selecting the most "active" wavelengths in a plasmonic band, the wavelength space can be reduced from hundreds of monitored wavelengths to just four, without loss of information about selectivity of the AuNRs. By combining thermal stability, the thermal energy harvesting capability, and the selectivity in gas detection (achieved through multivariate analysis), integration of plasmonic sensors into combustion environments can be greatly simplified.

  9. Carbohydrates and thermal analysis reflects changes in soil organic matter stability after forest expansion on abandoned grassland

    NASA Astrophysics Data System (ADS)

    Guidi, Claudia; Vesterdal, Lars; Cannella, David; Leifeld, Jens; Gianelle, Damiano; Rodeghiero, Mirco

    2014-05-01

    Grassland abandonment, followed by progressive forest expansion, is the dominant land-use change in the Southern Alps, Europe. Land-use change can affect not only the amount of organic matter (OM) in soil but also its composition and stability. Our objective was to investigate changes in organic matter properties after forest expansion on abandoned grasslands, combining analysis of carbohydrates, indicative of labile OM compounds with prevalent plant or microbial origin, with thermal analysis. Thermal analysis was used as a rapid assessment method for the characterization of SOM stability. A land-use gradient was investigated in four land-use types in the subalpine area of Trentino region, Italy: i) managed grassland, mown and fertilized for the past 100 years; ii) grassland abandoned since 10 years, with sparse shrubs and Picea abies saplings; iii) early-stage forest, dominated by P. abies and established on a grassland abandoned around 1970; iv) old forest, dominated by Fagus sylvatica and P. abies. Mineral soil was sampled at three subplots in each land use type with eight soil cores, which were subsequently pooled by depth (0-5 cm, 5-10 cm, 10-20 cm). Sugars were extracted from bulk soil samples through acid hydrolysis with H2SO4 (0.5 M). The analytical composition of sugar monomers was performed with HPAEC technology (Dionex ICS5000), equipped with PAD-detection. Thermal stability was assessed with a differential scanning calorimeter DSC100, heating soil samples up to 600°C at a heating rate of 10°C min-1 in synthetic air. Peak height (W g OC-1) of 1st DSC exotherm, dominated by burning of labile OM compounds, was used as thermal stability index. In the abandoned grassland, carbohydrates compounds accounted for a greater proportion of soil OC than in other land use types. Microbially derived sugars, as rhamnose and galactose, were more abundant in managed and abandoned grasslands compared with early-stage and old forest. The amount of thermally labile sugars

  10. Impact of revised thermal stability on pollutant transport time in a deep reservoir

    NASA Astrophysics Data System (ADS)

    Wu, Binbin; Wang, Guoqiang; Jiang, Hong; Wang, Jingfu; Liu, Changming

    2016-04-01

    Thermal stability (Schmidt stability) and water age, which are significantly related to water quality and algae bloom in deep reservoirs, are two crucial indicators of stratification strength and pollutant transport time, respectively. Here, the original Schmidt stability, which was derived from a one-dimensional assumption, was theoretically extended to a three-dimensional water body. In addition, a three-dimensional model was verified for the case study of Hongfeng Reservoir in China based on data from 2009 and 2010. Although the revised stability was similar to the original stability of Hongfeng Reservoir, which occurred at a relatively low level, the greater stratification in other deep water bodies would enhance their difference. Air temperature and water depth were the most important factors of the temporal variation in stability and the spatial variation in stability, respectively. The pollutant transport processes in the Hongfeng Reservoir was very complex with alternate appearances of overflow, interflow and underflow, depending on the season. The spatial water age was primarily determined by the morphometry and the inflow/outflow (with the highest water age in North Lake), whereas the vertical difference in the water age among the layers was primarily controlled by thermal stratification. Negative linear relationships between the average stability and the water ages of the bottom layers in three representative sites during summer were observed. Positive linear relationships between the average stability and the water ages of the surface layers were also observed. These findings enable a better understanding of the hydrodynamic and pollutant transport processes in a deep reservoir.

  11. Thermal Stabilization of Dihydrofolate Reductase Using Monte Carlo Unfolding Simulations and Its Functional Consequences

    PubMed Central

    Whitney, Anna; Shakhnovich, Eugene I.

    2015-01-01

    Design of proteins with desired thermal properties is important for scientific and biotechnological applications. Here we developed a theoretical approach to predict the effect of mutations on protein stability from non-equilibrium unfolding simulations. We establish a relative measure based on apparent simulated melting temperatures that is independent of simulation length and, under certain assumptions, proportional to equilibrium stability, and we justify this theoretical development with extensive simulations and experimental data. Using our new method based on all-atom Monte-Carlo unfolding simulations, we carried out a saturating mutagenesis of Dihydrofolate Reductase (DHFR), a key target of antibiotics and chemotherapeutic drugs. The method predicted more than 500 stabilizing mutations, several of which were selected for detailed computational and experimental analysis. We find a highly significant correlation of r = 0.65–0.68 between predicted and experimentally determined melting temperatures and unfolding denaturant concentrations for WT DHFR and 42 mutants. The correlation between energy of the native state and experimental denaturation temperature was much weaker, indicating the important role of entropy in protein stability. The most stabilizing point mutation was D27F, which is located in the active site of the protein, rendering it inactive. However for the rest of mutations outside of the active site we observed a weak yet statistically significant positive correlation between thermal stability and catalytic activity indicating the lack of a stability-activity tradeoff for DHFR. By combining stabilizing mutations predicted by our method, we created a highly stable catalytically active E. coli DHFR mutant with measured denaturation temperature 7.2°C higher than WT. Prediction results for DHFR and several other proteins indicate that computational approaches based on unfolding simulations are useful as a general technique to discover stabilizing

  12. Examination of lignocellulosic fibers for chemical, thermal, and separations properties: Addressing thermo-chemical stability issues

    NASA Astrophysics Data System (ADS)

    Johnson, Carter David

    Natural fiber-plastic composites incorporate thermoplastic resins with fibrous plant-based materials, sometimes referred to as biomass. Pine wood mill waste has been the traditional source of natural fibrous feedstock. In anticipation of a waste wood shortage other fibrous biomass materials are being investigated as potential supplements or replacements. Perennial grasses, agricultural wastes, and woody biomass are among the potential source materials. As these feedstocks share the basic chemical building blocks; cellulose, hemicellulose, and lignin, they are collectively called lignocellulosics. Initial investigation of a number of lignocellulosic materials, applied to fiber-plastic composite processing and material testing, resulted in varied results, particularly response to processing conditions. Less thermally stable lignocellulosic filler materials were physically changed in observable ways: darkened color and odor. The effect of biomass materials' chemical composition on thermal stability was investigated an experiment involving determination of the chemical composition of seven lignocellulosics: corn hull, corn stover, fescue, pine, soy hull, soy stover, and switchgrass. These materials were also evaluated for thermal stability by thermogravimetric analysis. The results of these determinations indicated that both chemical composition and pretreatment of lignocellulosic materials can have an effect on their thermal stability. A second study was performed to investigate what effect different pretreatment systems have on hybrid poplar, pine, and switchgrass. These materials were treated with hot water, ethanol, and a 2:1 benzene/ethanol mixture for extraction times of: 1, 3, 6, 12, and 24 hours. This factorial experiment demonstrated that both extraction time and medium have an effect on the weight percent of extractives removed from all three material types. The extracted materials generated in the above study were then subjected to an evaluation of thermal

  13. Thermal stability of collagen fibers in ethylene glycol.

    PubMed

    Miles, C A; Burjanadze, T V

    2001-03-01

    The mechanism that renders collagen molecules more stable when precipitated as fibers than the same molecules in solution is controversial. According to the polymer-melting mechanism the presence of a solvent depresses the melting point of the polymer due to a thermodynamic mechanism resembling the depression of the freezing point of a solvent due to the presence of a solute. On the other hand, according to the polymer-in-a-box mechanism, the change in configurational entropy of the collagen molecule on denaturation is reduced by its confinement by surrounding molecules in the fiber. Both mechanisms predict an approximately linear increase in the reciprocal of the denaturation temperature with the volume fraction (epsilon) of solvent, but the polymer-melting mechanism predicts that the slope is inversely proportional to the molecular mass of the solvent (M), whereas the polymer-in-a-box mechanism predicts a slope that is independent of M. Differential scanning calorimetry was used to measure the denaturation temperature of collagen in different concentrations of ethylene glycol (M = 62) and the slope found to be (7.29 +/- 0.37) x 10(-4) K(-1), compared with (7.31 +/- 0.42) x 10(-4) K(-1) for water (M = 18). This behavior was consistent with the polymer-in-a-box mechanism but conflicts with the polymer-melting mechanism. Calorimetry showed that the enthalpy of denaturation of collagen fibers in ethylene glycol was high, varied only slowly within the glycol volume fraction range 0.2 to 1, and fell rapidly at low epsilon. That this was caused by the disruption of a network of hydrogen-bonded glycol molecules surrounding the collagen is the most likely explanation. PMID:11222308

  14. Protein comparability assessments and potential applicability of high throughput biophysical methods and data visualization tools to compare physical stability profiles

    PubMed Central

    Alsenaidy, Mohammad A.; Jain, Nishant K.; Kim, Jae H.; Middaugh, C. Russell; Volkin, David B.

    2014-01-01

    In this review, some of the challenges and opportunities encountered during protein comparability assessments are summarized with an emphasis on developing new analytical approaches to better monitor higher-order protein structures. Several case studies are presented using high throughput biophysical methods to collect protein physical stability data as function of temperature, agitation, ionic strength and/or solution pH. These large data sets were then used to construct empirical phase diagrams (EPDs), radar charts, and comparative signature diagrams (CSDs) for data visualization and structural comparisons between the different proteins. Protein samples with different sizes, post-translational modifications, and inherent stability are presented: acidic fibroblast growth factor (FGF-1) mutants, different glycoforms of an IgG1 mAb prepared by deglycosylation, as well as comparisons of different formulations of an IgG1 mAb and granulocyte colony stimulating factor (GCSF). Using this approach, differences in structural integrity and conformational stability profiles were detected under stress conditions that could not be resolved by using the same techniques under ambient conditions (i.e., no stress). Thus, an evaluation of conformational stability differences may serve as an effective surrogate to monitor differences in higher-order structure between protein samples. These case studies are discussed in the context of potential utility in protein comparability studies. PMID:24659968

  15. ALD Functionalized Nanoporous Gold: Thermal Stability, Mechanical Properties, and Catalytic Activity

    SciTech Connect

    Biener, M M; Biener, J; Wichmann, A; Wittstock, A; Baumann, T F; Baeumer, M; Hamza, A V

    2011-03-24

    Nanoporous metals have many technologically promising applications but their tendency to coarsen limits their long-term stability and excludes high temperature applications. Here, we demonstrate that atomic layer deposition (ALD) can be used to stabilize and functionalize nanoporous metals. Specifically, we studied the effect of nanometer-thick alumina and titania ALD films on thermal stability, mechanical properties, and catalytic activity of nanoporous gold (np-Au). Our results demonstrate that even only one-nm-thick oxide films can stabilize the nanoscale morphology of np-Au up to 1000 C, while simultaneously making the material stronger and stiffer. The catalytic activity of np-Au can be drastically increased by TiO{sub 2} ALD coatings. Our results open the door to high temperature sensor, actuator, and catalysis applications and functionalized electrodes for energy storage and harvesting applications.

  16. Measurement of the thermal conductivity of dielectric thin solid films with a thermal comparator

    SciTech Connect

    Amsden, C.A.; Gilman, S.E.; Jacobs, S.D.; Torok, J.S.

    1988-04-01

    Low thermal conductivity has important implications for electric and optical applications, where heat deposited in a thin layer must be dissipated to prevent damage. Models which account for thermal transport in thin film structures may have no predictive value if they employ bulk conductivity data. Most techniques utilized to measure the thermal conductivity of thin solid films are difficult and time consuming. The method we have developed is relatively rapid, nondestructive, and is capable of evaluating the samples in a conventional film on substrate geometry. Our thermal conductivity apparatus consists of a control and readout module, signal processing equipment, and an environmentally isolated sample chamber enclosing a sample stage. The commercial unit was converted into a high precision device by temperature controlling both the samples and the sample stage, and by performing averaging of the output signal. The thermal conductivity values obtained are below those of bulk solids. In addition, the conductivities seem to increase with increasing film thickness. Titania seems to have a higher thermal conductivity when deposited by ion-beam sputtering rather than electron-beam evaporation. Some of the electron-beam films were crazed, indicating high levels of stress. The effect of stress and crazing on thermal conductivity is not readily apparent. 11 refs., 1 fig., 1 tab.

  17. Expanded polytetrafluoroethylene reinforced polyvinylidenefluoride-hexafluoropropylene separator with high thermal stability for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Xiong, Ming; Tang, Haolin; Wang, Yadong; Lin, Yu; Sun, Meiling; Yin, Zhuangfei; Pan, Mu

    2013-11-01

    PVDF-HFP/ePTFE composite separator with high thermal stability and low thermal shrinkage characteristic has been developed. The PVDF-HFP acts to absorb the electrolyte and shutdown at elevated temperature. The thermally stable ePTFE matrix is adopted to improve the mechanical strength and sustain the insulation after the shutdown. This novel separator presents good ion conductivity (up to 1.29 mS cm-1) and has a low thermal shrinkage of 8.8% at 162 °C. The composite separator shutdown at 162 °C and keep its integrity before 329 °C. Cells based on the composite separator show excellent capacities at high rate discharge and stable cycling performance.

  18. Thermal stability and flame resistance of cotton fabrics treated with whey proteins.

    PubMed

    Bosco, Francesca; Carletto, Riccardo Andrea; Alongi, Jenny; Marmo, Luca; Di Blasio, Alessandro; Malucelli, Giulio

    2013-04-15

    It is well described in the literature that whey proteins are able to form coatings, which exhibit high mechanical and oxygen barrier properties, notwithstanding a great water vapour adsorption. These peculiarities have been exploited for applying a novel protein-based finishing treatment to cotton and for assessing the protein effect on the thermal and thermo-oxidative stability and on the flame retardant properties of the cellulosic fabric. Indeed, the deposited whey protein coatings have turned out to significantly affect the thermal degradation of cotton in inert and oxidative atmosphere, and to somehow modify its combustion when a flame has been applied. Furthermore, the influence of the secondary and tertiary structure of these proteins on the morphology of the deposited coating, and thus on the thermal and flame retardant properties of the treated fabrics, has been evaluated by performing a denaturation thermal treatment before the protein application. PMID:23544551

  19. Evaluation of Thermal Stability of Nomex® Brand Paper in Main Transformer of Shinkansen Train Series 100

    NASA Astrophysics Data System (ADS)

    Tanaka, Hirokazu; Kondo, Chihiro; Naruse, Shinji; Ishii, Yoshitada

    Nomex® brand paper has been used as wire wrapping insulation material of main transformers of Shinkansen Train Series 100 with silicone oil. After approximately 12-13 years service, 8 transformers of Series 100 were sampled to evaluate degradation of Nomex® brand paper in terms of tensile strength and intrinsic viscosity. All data were compared with initial data. The result of less degradation shows Nomex® has good thermal stability in silicone oil in the main transformer of Shinkansen Train which were used in very severe condition.

  20. Stability of adaptive control of a light beam in the presence of nonstationary thermal blooming in a moving medium

    SciTech Connect

    Egorov, K.D.

    1988-06-01

    The adaptive control problem for a nonlinearly propagating light beam in a moving atmosphere presupposes continuous optimization of the beam parameters while the characteristics of the medium are varying. If the time scales of such variations are comparable to the characteristic times for the establishment of a thermal lens along the ray path, the beam can be controlled under highly nonstationary propagation conditions. We investigate the mechanism of stability loss during adaptive focusing of a light beam subject to wind refraction. In the aberrationless approximation, we examine the dynamics of beam parameters controlled by adaptive systems capable of operating at different speeds.

  1. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  2. Thermal stability enhancement of modified carboxymethyl cellulose films using SnO2 nanoparticles.

    PubMed

    Baniasad, Arezou; Ghorbani, Mohsen

    2016-05-01

    In this study, in-situ and ex-situ hydrothermal synthesis procedures were applied to synthesize novel CMC/porous SnO2 nanocomposites from rice husk extracted carboxymethyl cellulose (CMC) biopolymer. In addition, the effects of SnO2 nanoparticles on thermal stability of the prepared nanocomposite were specifically studied. Products were investigated in terms of morphology, particle size, chemical structure, crystallinity and thermal stability by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and thermogravimetric analysis (TGA), respectively. Presence of characteristic bands in the FTIR spectra of samples confirmed the successful formation of CMC and CMC/SnO2 nanocomposites. In addition, FESEM images revealed four different morphologies of porous SnO2 nanoparticles including nanospheres, microcubes, nanoflowers and olive-like nanoparticles with hollow cores which were formed on CMC. These nanoparticles possessed d-spacing values of 3.35Å. Thermal stability measurements revealed that introduction of SnO2 nanoparticles in the structure of CMC enhanced stability of CMC to 85%. PMID:26893046

  3. Thermal stability of vapor-deposited stable glasses of an organic semiconductor

    SciTech Connect

    Walters, Diane M.; Ediger, M. D.; Richert, Ranko

    2015-04-07

    Vapor-deposited organic glasses can show enhanced kinetic stability relative to liquid-cooled glasses. When such stable glasses of model glassformers are annealed above the glass transition temperature T{sub g}, they lose their thermal stability and transform into the supercooled liquid via constant velocity propagating fronts. In this work, we show that vapor-deposited glasses of an organic semiconductor, N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD), also transform via propagating fronts. Using spectroscopic ellipsometry and a new high-throughput annealing protocol, we measure transformation front velocities for TPD glasses prepared with substrate temperatures (T{sub Substrate}) from 0.63 to 0.96 T{sub g}, at many different annealing temperatures. We observe that the front velocity varies by over an order of magnitude with T{sub Substrate}, while the activation energy remains constant. Using dielectric spectroscopy, we measure the structural relaxation time of supercooled TPD. We find that the mobility of the liquid and the structure of the glass are independent factors in controlling the thermal stability of TPD films. In comparison to model glassformers, the transformation fronts of TPD have similar velocities and a similar dependence on T{sub Substrate}, suggesting universal behavior. These results may aid in designing active layers in organic electronic devices with improved thermal stability.

  4. Thermal stability of vapor-deposited stable glasses of an organic semiconductor

    NASA Astrophysics Data System (ADS)

    Walters, Diane M.; Richert, Ranko; Ediger, M. D.

    2015-04-01

    Vapor-deposited organic glasses can show enhanced kinetic stability relative to liquid-cooled glasses. When such stable glasses of model glassformers are annealed above the glass transition temperature Tg, they lose their thermal stability and transform into the supercooled liquid via constant velocity propagating fronts. In this work, we show that vapor-deposited glasses of an organic semiconductor, N,N'-bis(3-methylphenyl)-N,N'-diphenylbenzidine (TPD), also transform via propagating fronts. Using spectroscopic ellipsometry and a new high-throughput annealing protocol, we measure transformation front velocities for TPD glasses prepared with substrate temperatures (TSubstrate) from 0.63 to 0.96 Tg, at many different annealing temperatures. We observe that the front velocity varies by over an order of magnitude with TSubstrate, while the activation energy remains constant. Using dielectric spectroscopy, we measure the structural relaxation time of supercooled TPD. We find that the mobility of the liquid and the structure of the glass are independent factors in controlling the thermal stability of TPD films. In comparison to model glassformers, the transformation fronts of TPD have similar velocities and a similar dependence on TSubstrate, suggesting universal behavior. These results may aid in designing active layers in organic electronic devices with improved thermal stability.

  5. Critical cooling rate and thermal stability of Zr--Ti--Cu--Ni--Be alloys

    SciTech Connect

    Waniuk, Theodore A.; Schroers, Jan; Johnson, William L.

    2001-02-26

    The critical cooling rate as well as the thermal stability are measured for a series of alloys in the Zr--Ti--Cu--Ni--Be system. Upon cooling from the molten state with different rates, alloys with compositions ranging along a tie line from (Zr{sub 70}Ti{sub 30}){sub 55}(Ni{sub 39}Cu{sub 61}){sub 25}Be{sub 20} to (Zr{sub 85}Ti{sub 15}){sub 55}(Ni{sub 57}Cu{sub 43}){sub 22.5}Be{sub 27.5} show a continuous increase in the critical cooling rate to suppress crystallization. In contrast, thermal analysis of the same alloys shows that the undercooled liquid region, the temperature difference between the glass transition temperature and the crystallization temperature, is largest for some compositions midway between the two endpoints, revealing that glass forming ability does not correlate with thermal stability. The relationship between the composition-dependent glass forming ability and thermal stability is discussed with reference to a chemical decomposition process.

  6. Thermal Stability Results of a Fischer-Tropsch Fuel With Various Blends of Aromatic Solution

    NASA Technical Reports Server (NTRS)

    Lindsey, Jennifer; Klettlinger, Suder

    2013-01-01

    Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. F-T fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal paraffins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of F-T fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonic Fixed Wing Project. Two different aromatic content fuels from Rentech, as well as these fuels with added aromatic blend were analyzed for thermal stability using the JFTOT method. Preliminary results indicate a reduction in thermal stability occurs upon increasing the aromatic content to 10% by adding an aromatic blend to the neat fuel. These results do not specify a failure based on pressure drop, but only on tube color. It is unclear whether tube color correlates to more deposition on the tube surface or not. Further research is necessary in order to determine if these failures are true failures based on tube color. Research using ellipsometry to determine tube deposit thickness rather than color will be continued in follow-up of this study.

  7. Thermal stabilization of chromium slag by sewage sludge: effects of sludge quantity and temperature.

    PubMed

    Wu, Changlin; Zhang, Hua; He, Pinjing; Shao, Liming

    2010-01-01

    To investigate the feasibility of detoxifying chromium slag by sewage sludge, synthetic chromium slag containing 3% of Cr(VI) was mixed with sewage sludge followed by thermal treatment in nitrogen gas for stabilizing chromium. The effects of slag to sludge ratio (0.5, 1 and 2) and temperature (200, 300, 500, 700 and 900 degrees C) on treatment efficiency were investigated. During the mixing process before thermal treatment, 59.8%-99.7% of Cr(VI) was reduced, but Cr could be easily leached from the reduction product. Increasing heating temperature and decreasing slag to sludge ratio strengthened the reduction and stabilization of Cr(VI). When the slag to sludge ratio was 0.5 and thermal treatment temperature was 300 degrees C, the total leached Cr and Cr(VI) declined to 0.55 mg/L and 0.17 mg/L respectively, and 45.5% of Cr in the thermally treated residue existed as residual fraction. A two-stage mechanism was proposed for the reduction and stabilization of Cr. PMID:21175004

  8. Comparative Study of Vibration Stability at Operating Light Source Facilities and Lessons Learned in Achieving NSLS II Stability Goals

    SciTech Connect

    Simos,N.; Fallier, M.; Amick, H.

    2008-06-23

    In an effort to ensure that the stability goals of the NSLS II will be met once the accelerator structure is set on the selected BNL site a comprehensive evaluation of the ground vibration observed at existing light source facilities has been undertaken. The study has relied on measurement data collected and reported by the operating facilities as well as on new data collected in the course of this study. The primary goal of this comprehensive effort is to compare the green-field conditions that exist in the various sites both in terms of amplitude as well as frequency content and quantify the effect of the interaction of these accelerator facilities with the green-field vibration. The latter represents the ultimate goal of this effort where the anticipated motion of the NSLS II ring is estimated prior to its construction and compared with the required stability criteria.

  9. Air, aqueous and thermal stabilities of Ce3+ ions in cerium oxide nanoparticle layers with substrates.

    PubMed

    Naganuma, Tamaki; Traversa, Enrico

    2014-06-21

    Abundant oxygen vacancies coexisting with Ce(3+) ions in fluorite cerium oxide nanoparticles (CNPs) have the potential to enhance catalytic ability, but the ratio of unstable Ce(3+) ions in CNPs is typically low. Our recent work, however, demonstrated that the abundant Ce(3+) ions created in cerium oxide nanoparticle layers (CNPLs) by Ar ion irradiation were stable in air at room temperature. Ce valence states in CNPs correlate with the catalytic ability that involves redox reactions between Ce(3+) and Ce(4+) ions in given application environments (e.g. high temperature in carbon monoxide gas conversion and immersion conditions in biomedical applications). To better understand the mechanism by which Ce(3+) ions achieve stability in CNPLs, we examined (i) extra-long air-stability, (ii) thermal stability up to 500 °C, and (iii) aqueous stability of Ce(3+) ions in water, buffer solution and cell culture medium. It is noteworthy that air-stability of Ce(3+) ions in CNPLs persisted for more than 1 year. Thermal stability results showed that oxidation of Ce(3+) to Ce(4+) occurred at 350 °C in air. Highly concentrated Ce(3+) ions in ultra-thin CNPLs slowly oxidized in water within 1 day, but stability was improved in the cell culture medium. Ce(3+) stability of CNPLs immersed in the medium was associated with phosphorus adsorption on the Ce(3+) sites. This study also illuminates the potential interaction mechanisms of stable Ce(3+) ions in CNPLs. These findings could be utilized to understand catalytic mechanisms of CNPs with abundant oxygen vacancies in their application environments. PMID:24812662

  10. Quantitation of protein-protein interactions by thermal stability shift analysis.

    PubMed

    Layton, Curtis J; Hellinga, Homme W

    2011-08-01

    Thermal stability shift analysis is a powerful method for examining binding interactions in proteins. We demonstrate that under certain circumstances, protein-protein interactions can be quantitated by monitoring shifts in thermal stability using thermodynamic models and data analysis methods presented in this work. This method relies on the determination of protein stabilities from thermal unfolding experiments using fluorescent dyes such as SYPRO Orange that report on protein denaturation. Data collection is rapid and straightforward using readily available real-time polymerase chain reaction instrumentation. We present an approach for the analysis of the unfolding transitions corresponding to each partner to extract the affinity of the interaction between the proteins. This method does not require the construction of a titration series that brackets the dissociation constant. In thermal shift experiments, protein stability data are obtained at different temperatures according to the affinity- and concentration-dependent shifts in unfolding transition midpoints. Treatment of the temperature dependence of affinity is, therefore, intrinsic to this method and is developed in this study. We used the interaction between maltose-binding protein (MBP) and a thermostable synthetic ankyrin repeat protein (Off7) as an experimental test case because their unfolding transitions overlap minimally. We found that MBP is significantly stabilized by Off7. High experimental throughput is enabled by sample parallelization, and the ability to extract quantitative binding information at a single partner concentration. In a single experiment, we were able to quantify the affinities of a series of alanine mutants, covering a wide range of affinities (∼ 100 nM to ∼ 100 μM). PMID:21674662

  11. Effect of phosphorylation on the thermal and light stability of the thylakoid membranes.

    PubMed

    Várkonyi, Zsuzsanna; Nagy, Gergely; Lambrev, Petar; Kiss, Anett Z; Székely, Noémi; Rosta, László; Garab, Gyözö

    2009-03-01

    Higher plant thylakoid membranes contain a protein kinase that phosphorylates certain threonine residues of light-harvesting complex II (LHCII), the main light-harvesting antenna complexes of photosystem II (PSII) and some other phosphoproteins (Allen, Biochim Biophys Acta 1098:275, 1992). While it has been established that phosphorylation induces a conformational change of LHCII and also brings about changes in the lateral organization of the thylakoid membrane, it is not clear how phosphorylation affects the dynamic architecture of the thylakoid membranes. In order to contribute to the elucidation of this complex question, we have investigated the effect of duroquinol-induced phosphorylation on the membrane ultrastructure and the thermal and light stability of the chiral macrodomains and of the trimeric organization of LHCII. As shown by small angle neutron scattering on thylakoid membranes, duroquinol treatment induced a moderate (~10%) increase in the repeat distance of stroma membranes, and phosphorylation caused an additional loss of the scattering intensity, which is probably associated with the partial unstacking of the granum membranes. Circular dichroism (CD) measurements also revealed only minor changes in the chiral macro-organization of the complexes and in the oligomerization state of LHCII. However, temperature dependences of characteristic CD bands showed that phosphorylation significantly decreased the thermal stability of the chiral macrodomains in phosphorylated compared to the non-phosphorylated samples (in leaves and isolated thylakoid membranes, from 48.3 degrees C to 42.6 degrees C and from 47.5 degrees C to 44.3 degrees C, respectively). As shown by non-denaturing PAGE of thylakoid membranes and CD spectroscopy on EDTA washed membranes, phosphorylation decreased by about 5 degrees C, the trimer-to-monomer transition temperature of LHCII. It also enhanced the light-induced disassembly of the chiral macrodomains and the monomerization of the

  12. Chitosan nanocomposite films: enhanced electrical conductivity, thermal stability, and mechanical properties.

    PubMed

    Marroquin, Jason B; Rhee, K Y; Park, S J

    2013-02-15

    A novel, high-performance Fe(3)O(4)/MWNT/Chitosan nanocomposite has been prepared by a simple solution evaporation method. A significant synergistic effect of Fe(3)O(4) and MWNT provided enhanced electrical conductivity, mechanical properties, and thermal stability on the nanocomposites. A 5% (wt) loading of Fe(3)O(4)/MWNT in the nanocomposite increased conductivity from 5.34×10(-5) S/m to 1.49×10(-2) S/m compared to 5% (wt) MWNT loadings. The Fe(3)O(4)/MWNT/Chitosan films also exhibited increases in tensile strength and modulus of 70% and 155%, respectively. The integral procedure decomposition temperature (IPDT) was enhanced from 501 °C to 568 °C. These effects resulted from a number of factors: generation of a greater number of conductive channels through interactions between MWNT and Fe(3)O(4) surfaces, a higher relative crystallinity, the antiplasticizing effects of Fe(3)O(4), a restricted mobility and hindrance of depolymerization of the Chitosan chain segments, as well as uniform distribution, improved dispersion, and strong interfacial adhesion between the MWNT and Chitosan matrix. PMID:23399220

  13. Polyetherimide/bucky gels nanocomposites with superior conductivity and thermal stability.

    PubMed

    Chen, Ye; Tao, Jing; Deng, Lin; Li, Liang; Li, Jun; Yang, Yang; Khashab, Niveen M

    2013-08-14

    Polyetherimide (PEI) nanocomposites comprising bucky gels of industrial-grade multiwalled carbon nanotubes (MWCNTs) and ionic liquid (IL, 1-butyl-3-methyl imidazolium hexafluorophosphate ([BMIM][PF6])) were prepared. The processing framework for this nanocomposite is simple, reproducible, and easily scalable. The strong interaction between IL and MWCNTs caused the latter to uniformly disperse in the PEI matrix while IL flowed into the gaps between the nanotubes' walls. The nanocomposite exhibited an enhanced conductivity of 2.01 × 10(4) Ω·cm volume resistivity at room temperature; the value decreased dramatically by 12 orders of magnitude, compared to pristine PEI. The IL free ions and MWCNTs networks provided excellent channels for electron transfer. PEI/bucky gels nanocomposites also showed improved thermal stability and high tensile strength. Other than having antiwear properties, this material can have numerous applications in the aerospace and electronics industries. Moreover, our work presents a "green" method toward modified nanocomposites industrial production as IL is environmentally safe and is easily recyclable. PMID:23865563

  14. Ultroviolet (UV)- and thermal-stability of absorbing coatings for space instrumentation

    NASA Astrophysics Data System (ADS)

    Weissbrodt, P.; Raupach, L.; Hacker, Erich; Wagner, S.; Kappel, H.

    1994-09-01

    Absorbing coatings for space-borne optical instruments must accept - besides optical requirements - unusual challenges regarding their chemical stability and their emission of gaseous and condensable materials under space conditions. Consideration of mass balances according to ANSI/ASTM E 595 do not provide enough information for proper choice of the coatings in the vicinity of sensitive optical elements. By in-situ mass spectrometric and XPS measurements we have investigated chemical changes of different black paints and inorganic coatings, their outgassing and the contamination of the surfaces near the coatings. In general, organic black paints are threatened by UV- irradiation and by thermal loads. Changes of their chemical composition under energetic UV-irradiation and the intense emission of contaminating materials were proved. The inorganic coatings investigated do not change their chemical composition and cause only comparatively small contamination on surfaces in their vicinity. For reducing the problem of contamination in optical systems it is still necessary to make available appropriate inorganic coatings with improved absorbing characteristics. However, if lower absorption can be tolerated, the use of inorganic coatings in sensible optical equipment should be considered already now.

  15. Electrical Conductivity, Thermal Stability, and Lattice Defect Evolution During Cyclic Channel Die Compression of OFHC Copper

    NASA Astrophysics Data System (ADS)

    Satheesh Kumar, S. S.; Raghu, T.

    2015-02-01

    Oxygen-free high-conductivity (OFHC) copper samples are severe plastically deformed by cyclic channel die compression (CCDC) technique at room temperature up to an effective plastic strain of 7.2. Effect of straining on variation in electrical conductivity, evolution of deformation stored energy, and recrystallization onset temperatures are studied. Deformation-induced lattice defects are quantified using three different methodologies including x-ray diffraction profile analysis employing Williamson-Hall technique, stored energy based method, and electrical resistivity-based techniques. Compared to other severe plastic deformation techniques, electrical conductivity degrades marginally from 100.6% to 96.6% IACS after three cycles of CCDC. Decrease in recrystallization onset and peak temperatures is noticed, whereas stored energy increases and saturates at around 0.95-1.1J/g after three cycles of CCDC. Although drop in recrystallization activation energy is observed with the increasing strain, superior thermal stability is revealed, which is attributed to CCDC process mechanics. Low activation energy observed in CCDC-processed OFHC copper is corroborated to synergistic influence of grain boundary characteristics and lattice defects distribution. Estimated defects concentration indicated continuous increase in dislocation density and vacancy with strain. Deformation-induced vacancy concentration is found to be significantly higher than equilibrium vacancy concentration ascribed to hydrostatic stress states experienced during CCDC.

  16. International Space Station Internal Thermal Control System Cold Plate/Fluid-Stability Test: Two Year Update

    NASA Technical Reports Server (NTRS)

    Wieland, Paul; Holt, Mike; Roman, Monsi; Cole, Harold; Daugherty, Steve

    2003-01-01

    Operation of the Internal Thermal Control System (ITCS) Cold Plate/Fluid-Stability Test Facility commenced on September 5, 2000. The facility was intended to provide advance indication of potential problems on board the International Space Station (ISS) and was designed: 1) To be materially similar to the flight ITCS. 2) To allow for monitoring during operation. 3) To run continuously for three years. During the first two years of operation the conditions of the coolant and components were remarkably stable. During this same period of time, the conditions of the ISS ITCS significantly diverged from the desired state. Due to this divergence, the test facility has not been providing information useful for predicting the flight ITCS condition. Results of the first two years are compared with flight conditions over the same time period, showing the similarities and divergences. To address the divergences, the test facility was modified incrementally to more closely match the flight conditions, and to gain insight into the reasons for the divergence. Results of these incremental changes are discussed and provide insight into the development of the conditions on orbit.

  17. Multifunctional cyclotriphosphazene/hexagonal boron nitride hybrids and their flame retarding bismaleimide resins with high thermal conductivity and thermal stability.

    PubMed

    Jin, Wenqin; Yuan, Li; Liang, Guozheng; Gu, Aijuan

    2014-09-10

    A novel hybridized multifunctional filler (CPBN), cyclotriphosphazene/hexagonal boron nitride (hBN) hybrid, was synthesized by chemically coating hBN with hexachlorocyclotriphosphazene and p-phenylenediamine, its structure was systemically characterized. Besides, CPBN was used to develop new flame retarding bismaleimide/o,o'-diallylbisphenol A (BD) resins with simultaneously high thermal conductivity and thermal stability. The nature of CPBN has a strong influence on the flame behavior of the composites. With the addition of only 5 wt % CPBN to BD resin, the thermal conductivity increases 2 times; meanwhile the flame retardancy of BD resin is remarkably increased, reflected by the increased limited oxygen index, much longer time to ignition, significantly reduced heat release rate. The thermogravimetric kinetics, structures of chars and pyrolysis gases, and cone calorimeter tests were investigated to reveal the unique flame retarding mechanism of CPBN/BD composites. CPBN provides multieffects on improving the flame retardancy, especially in forming a protective char layer, which means a more thermally stable and condensed barrier for heat and mass transfer, and thus protecting the resin from further combustion. PMID:25140735

  18. Can template-based protein models guide the design of sequence fitness for enhanced thermal stability of single domain antibodies?

    PubMed

    Olson, Mark A; Zabetakis, Dan; Legler, Patricia M; Turner, Kendrick B; Anderson, George P; Goldman, Ellen R

    2015-10-01

    We investigate the practical use of comparative (template-based) protein models in replica-exchange simulations of single-domain antibody (sdAb) chains to evaluate if the models can correctly predict in rank order the thermal susceptibility to unfold relative to experimental melting temperatures. The baseline model system is the recently determined crystallographic structure of a llama sdAb (denoted as A3), which exhibits an unusually high thermal stability. An evaluation of the simulation results for the A3 comparative model and crystal structure shows that, despite the overall low Cα root-mean-square deviation between the two structures, the model contains misfolded regions that yields a thermal profile of unraveling at a lower temperature. Yet comparison of the simulations of four different comparative models for sdAb A3, C8, A3C8 and E9, where A3C8 is a design of swapping the sequence of the complementarity determining regions of C8 onto the A3 framework, discriminated among the sequences to detect the highest and lowest experimental melting transition temperatures. Further structural analysis of A3 for selected alanine substitutions by a combined computational and experimental study found unexpectedly that the comparative model performed admirably in recognizing substitution 'hot spots' when using a support-vector machine algorithm. PMID:26374895

  19. A comparative analysis of loop heat pipe based thermal architectures for spacecraft thermal control

    NASA Technical Reports Server (NTRS)

    Pauken, Mike; Birur, Gaj

    2004-01-01

    Loop Heat Pipes (LHP) have gained acceptance as a viable means of heat transport in many spacecraft in recent years. However, applications using LHP technology tend to only remove waste heat from a single component to an external radiator. Removing heat from multiple components has been done by using multiple LHPs. This paper discusses the development and implementation of a Loop Heat Pipe based thermal architecture for spacecraft. In this architecture, a Loop Heat Pipe with multiple evaporators and condensers is described in which heat load sharing and thermal control of multiple components can be achieved. A key element in using a LHP thermal architecture is defining the need for such an architecture early in the spacecraft design process. This paper describes an example in which a LHP based thermal architecture can be used and how such a system can have advantages in weight, cost and reliability over other kinds of distributed thermal control systems. The example used in this paper focuses on a Mars Rover Thermal Architecture. However, the principles described here are applicable to Earth orbiting spacecraft as well.

  20. Thermal Stability of Frozen Volatiles in the North Polar Region of Mercury

    NASA Technical Reports Server (NTRS)

    Paige, David A.; Siegler, Matthew A.; Harmon, John K.; Smith, David E.; Zuber, Maria T.; Neumann, Gregory A.; Solomon, Sean C.

    2012-01-01

    Earth-based radar observations have revealed the presence on Mercury of anomalously bright, depolarizing features that appear to be localized in the permanently shadowed regions of high-latitude impact craters [1]. Observations of similar radar signatures over a range of radar wavelengths implies that they correspond to deposits that are highly transparent at radar wavelengths and extend to depths of several meters below the surface [1]. Thermal models using idealized crater topographic profiles have predicted the thermal stability of surface and subsurface water ice at these same latitudes [2]. One of the major goals of the MESSENGER mission is to characterize the nature of radar-bright craters and presumed associated frozen volatile deposits at the poles of Mercury through complementary orbital observations by a suite of instruments [3]. Here we report on an examination of the thermal stability of water ice and other frozen volatiles in the north polar region of Mercury using topographic profiles obtained by the Mercury Laser Altimeter (MLA) instrument [4] in conjunction with a three-dimensional ray-tracing thermal model previously used to study the thermal environment of polar craters on the Moon [5].

  1. Synergistic thermal stabilization of ceramic/co-polyimide coated polypropylene separators for lithium-ion batteries

    NASA Astrophysics Data System (ADS)

    Lee, Yunju; Lee, Hoogil; Lee, Taejoo; Ryou, Myung-Hyun; Lee, Yong Min

    2015-10-01

    To improve the safety of lithium-ion batteries (LIBs), co-polyimide (PI) P84 was introduced as a polymeric binder for Al2O3/polymer composite surface coatings on polypropylene (PP) separators. By monitoring the dimensional shrinkage of the PP separators at high temperatures, we verified a synergistic thermal stabilization effect between the Al2O3 ceramic and the PI polymeric binder. Although PI was thermally stable up to 300 °C, a coating consisting solely of PI did not impede the PP separator dimensional changes (-22% at 150 °C). On the other hand, the Al2O3/PI-coated PP separators efficiently impeded the thermal shrinkage (-10% at 150 °C). In contrast, an Al2O3/poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) combination lowered the thermal stability of the PP separators (-33% at 150 °C). As a result, the Al2O3/PI-coated PP separators remarkably suppressed the internal short-circuit of the unit half-cells associated with separator thermal shrinkage (100 min at 160 °C), whereas the PVdF-HFP retained only 40 min under identical conditions. The Al2O3/PI-coated PP separators achieved rate capabilities and cell performances similar to those of the bare PP separators.

  2. Thermal Cycling of Yttria-Stabilized Zirconia-Coated Hot Work Tool Steel

    NASA Astrophysics Data System (ADS)

    Birol, Yucel

    2011-09-01

    Thermal fatigue performance of yttria-stabilized zirconia-coated hot work tool steel was investigated under conditions encountered by thixoforming dies in semi-solid processing of steels. The thermal barrier effect of the YSZ coating was evident from the relatively smaller and more uniform temperature gradients set up across the section of the sample, which in turn, had a direct impact on the magnitude of thermal stresses generated at the surface of the tool steel. In spite of some thermal expansion mismatch with the substrate tool steel and occasional discontinuous thermally grown oxides along the splat boundaries and between the BC and TC, the YSZ coating survived thermal cycling under steel thixoforming conditions for over 12,000 cycles with no evidence of debonding and spallation. This is a nearly ten-fold increase in thermal fatigue life with respect to the uncoated counterpart. An increasingly dense YSZ layer and the toughening linked with the tetragonal to monoclinic ZrO2 phase transformation are credited for the remarkable performance of the YSZ-coating. It is fair to conclude that the YSZ coating offers adequate protection for the underlying tool steel, which without YSZ coating, suffers severe oxidation after only several hundred cycles and extensive cracking after 1000 cycles.

  3. Radiation and Thermal Stability of Solid Radwaste After Immobilization in Polymer Matrix - 13504

    SciTech Connect

    Pokhitonov, Yu.; Babain, V.; Strelkov, S.; Kuznetsov, D.; Kelley, Dennis

    2013-07-01

    The paper will illustrate results of the various experiments on radiation and thermal stability of polymer matrixes after solutions solidification including aqueous and organic solutions and mixed waste. It was shown that- after irradiation the specimen and after solidification the mixture with oil and TBP hydrogen has been observed (less 1%) and some others gases have been detected. Results of the performed experiments and the radiation stability data of the polymer compositions allow the conclusion that the technological process of immobilizing the above mentioned aqueous solutions and solutions with organic products into polymers at room temperature is the explosion- and flameproof as well as the storage thereof. (authors)

  4. Thermal and structural stability of medium energy target carrier assembly for NOvA at Fermilab

    SciTech Connect

    McGee, M.W.; Ader, C.; Anderson, K.; Hylen, J.; Martens, M.; /Fermilab

    2010-05-01

    The NOvA project will upgrade the existing Neutrino at Main Injector (NuMI) project beamline at Fermilab to accommodate beam power of 700 kW. The Medium Energy (ME) graphite target assembly is provided through an accord with the State Research Center of Russia Institute for High Energy Physics (IHEP) at Protvino, Russia. The effects of proton beam energy deposition within beamline components are considered as thermal stability of the target carrier assembly and alignment budget are critical operational issues. Results of finite element thermal and structural analysis involving the target carrier assembly is provided with detail regarding the target's beryllium windows.

  5. Study of thermal stability and degradation of fire resistant candidate polymers for aircraft interiors

    NASA Technical Reports Server (NTRS)

    Hsu, M. T. S.

    1976-01-01

    The thermochemistry of bismaleimide resins and phenolphthalein polycarbonate was studied. Both materials are fire-resistant polymers and may be suitable for aircraft interiors. The chemical composition of the polymers has been determined by nuclear magnetic resonance and infrared spectroscopy and by elemental analysis. Thermal properties of these polymers have been characterized by thermogravimetric analyses. Qualitative evaluation of the volatile products formed in pyrolysis under oxidative and non-oxidative conditions has been made using infrared spectrometry. The residues after pyrolysis were analyzed by elemental analysis. The thermal stability of composite panel and thermoplastic materials for aircraft interiors was studied by thermogravimetric analyses.

  6. Thermal stability of higher plant biomarkers evaluated through pyrolysis; geologic implications in thermally-mature sediment

    NASA Astrophysics Data System (ADS)

    Longbottom, T. L.; Hockaday, W. C.; Von Bargen, J.

    2013-12-01

    The organic molecules known as n-alkanes, n-alkanoic acids, and sterols are widely used biomarkers in paleoecological and organic matter source-apportionment studies, and are complementary to traditional bulk organic matter proxies (organic carbon stable isotopes and C/N ratios). These organic matter parameters are hindered by early and late diagenesis, through a combination of biotic and abiotic factors, which can lead to uncertainty in sediments on geologic timescales. This study seeks to use modern central Texas plants and soils as tools for our understanding and interpretation of biomarker patterns deep time, specifically in thermally mature sediment and paleosols. Bulk leaf and soil samples were heat treated to a range of temperatures in a muffle furnace in the absence of oxygen in order to clarify the role of abiotic degradation (thermal cracking) on bulk SOM and biomarker distributions. Preliminary results for unaltered n-alkane distributions of Southern Cattail (Typha domingensis) biomass shows a strong odd-over-even predominance, where the most abundant n-alkanes are nC23, nC25, nC27, and nC29. The biomass exposed to slow pyrolysis temperature of 300°C had n-alkanes ranging from nC11-nC29, with no odd-over-even predominance. The high abundance of lower molecular weight n-alkanes (thermal cracking of high molecular weight alkanes into smaller fragments. It is evident that the n-alkane distributions of modern plant material is severely disrupted by modest heating, an observation that must be taken into account when interpreting these biomarkers in deeply-buried geological samples.

  7. Stability Behaviour of the Atlantic Thermohaline Circulation Under Different Climate Conditions: The Thermal Component

    NASA Astrophysics Data System (ADS)

    Knorr, G.; Eichinger, R.; Lohmann, G.; Prange, M.; Barker, S.

    2010-05-01

    During the Last Glacial Maximum the Atlantic Thermohaline Circulation (THC) was characterized by a southward shift of the North Atlantic deep water (NADW) formation sites and a relatively shallow NADW- overturning cell, compared to the present mode of operation. Furthermore, abrupt climate events during the last glacial are associated with rapid changes in the THC and accompanying changes of the inter-hemispheric northward oceanic heat transport. Using an interhemispheric box model of the Atlantic THC, coupled to a moist energy balance model of the atmosphere we present a new approach, which is based on the assumption that a completely sea ice covered North Atlantic would inhibit the generation of deep water. Therefore we introduce a dependence of the overturning strength from the sea ice extent in the North Atlantic. This approach can be viewed as a loss of efficiency of the inter-hemispheric density gradient in driving the overturning with cooler climate conditions. The transition from the present day climate to a colder climate forces the Atlantic THC to collapse in an intermediate climate state. This change in the stability behaviour is a consequence of the model response to gradual changes in the outgoing infra-red radiation at the top of the atmosphere. At cooler climate states the increasing atmosphere-ocean temperature contrast and associated ocean heat loss dominates the insulating effect of sea ice on North Atlantic temperature and promotes a sea ice growth. This effect is amplified by a weaker overturning circulation and decreased northward oceanic heat transport, which leads to a positive feedback loop and the existence of multiple equilibria in an intermediate climate state. Based on the reduction of the system to key variables governing the stability, we will also discuss the internal and structural stability of the system with the aid of numerical and analytical solutions to gain a deeper understanding of the underlying dynamics. A comparison with

  8. The effect of polymeric filler on poling behavior and thermal stability of 1-3 piezoelectric composites

    NASA Astrophysics Data System (ADS)

    Wang, Chunying; Zhang, Rui; Jing, Yujia; Cao, Wenwu

    2016-01-01

    In this paper, the influence of polymeric filler with different glass transition temperature (T g) on the poling behavior and thermal stability of 1-3 piezoelectric composites were investigated, with emphasis on the relationship between T g and temperature dependent properties. The results revealed that high poling temperature improves the piezoelectric coefficient by nearly 12% for composites filled with epoxy (Epotek301, T g above room temperature). On the contrary, high temperature gives a negative impact on the poling of composites filled with rubber (Ke45W, T g below room temperature). In addition, it was found that rubber-filled composites possess better temperature stability between room temperature to140 °C, including dielectric and electromechanical properties, compared with epoxy-filled composites.

  9. Exceptional thermal stability of Pd@CeO2 core-shell catalyst nanostructures grafted onto an oxide surface.

    PubMed

    Adijanto, Lawrence; Bennett, David A; Chen, Chen; Yu, Anthony S; Cargnello, Matteo; Fornasiero, Paolo; Gorte, Raymond J; Vohs, John M

    2013-05-01

    Monolayer films of highly catalytically active Pd@CeO2 core-shell nanocomposites were grafted onto a planar YSZ(100) (yttria-stabilized zirconia, YSZ) single crystal support that was functionalized with a CVD-deposited layer of triethoxy(octyl)silane (TEOOS). The resulting monolayer films were found to exhibit exceptionally high thermal stability compared to bare Pd nanoparticles with the Pd@CeO2 nanostructures remaining intact and highly dispersed upon calcining in air at temperatures in excess of 1000 K. The CeO2 shells were also shown to be more easily reduced than bulk CeO2, which may partially explain their unique activity as oxidation catalysts. The use of both TEOOS and tetradecylphosphonic acid (TDPA) as coupling agents for dispersing Pd@CeO2 core-shell nanocomposites onto a high surface area γ-Al2O3 support is also demonstrated. PMID:23557343

  10. Comparative structure analysis of non-polar organic ferrofluids stabilized by saturated mono-carboxylic acids.

    PubMed

    Avdeev, M V; Bica, D; Vékás, L; Aksenov, V L; Feoktystov, A V; Marinica, O; Rosta, L; Garamus, V M; Willumeit, R

    2009-06-01

    The structure of ferrofluids (magnetite in decahydronaphtalene) stabilized with saturated mono-carboxylic acids of different chain lengths (lauric, myristic, palmitic and stearic acids) is studied by means of magnetization analysis and small-angle neutron scattering. It is shown that in case of saturated acid surfactants, magnetite nanoparticles are dispersed in the carrier approximately with the same size distribution whose mean value and width are significantly less as compared to the classical stabilization with non-saturated oleic acid. The found thickness of the surfactant shell around magnetite is analyzed with respect to stabilizing properties of mono-carboxylic acids. PMID:19376524

  11. Stability diagram of the collective atomic recoil laser with thermal atoms

    NASA Astrophysics Data System (ADS)

    Tomczyk, H.; Schmidt, D.; Georges, C.; Slama, S.; Zimmermann, C.

    2015-06-01

    We experimentally investigate cold thermal atoms in a single sidedly pumped optical ring resonator for temperatures between 0.4 and 9 μ K . The threshold for collective atomic recoil lasing (CARL) is recorded for various pump-cavity detunings. The resulting stability diagram is interpreted by simulating the classical CARL equations. We find that the stability diagram for thermal atoms shows the same asymmetry as observed for Bose-Einstein condensates in previous experiments. Whereas for condensates the asymmetry is well explained by a Dicke-type quantum model we here discuss a simplified classical model. It complements the quantum model and provides an intuitive explanation based on the change in the long-range atomic interaction with pump-cavity detuning.

  12. Applications of high pressure differential scanning calorimetry to aviation fuel thermal stability research

    NASA Technical Reports Server (NTRS)

    Neveu, M. C.; Stocker, D. P.

    1985-01-01

    High pressure differential scanning calorimetry (DSC) was studied as an alternate method for performing high temperature fuel thermal stability research. The DSC was used to measure the heat of reaction versus temperature of a fuel sample heated at a programmed rate in an oxygen pressurized cell. Pure hydrocarbons and model fuels were studied using typical DSC operating conditions of 600 psig of oxygen and a temperature range from ambient to 500 C. The DSC oxidation onset temperature was determined and was used to rate the fuels on thermal stability. Kinetic rate constants were determined for the global initial oxidation reaction. Fuel deposit formation is measured, and the high temperature volatility of some tetralin deposits is studied by thermogravimetric analysis. Gas chromatography and mass spectrometry are used to study the chemical composition of some DSC stressed fuels.

  13. Thermal stability of sputter deposited nanomosaic rutile TiO{sub 2}

    SciTech Connect

    Aita, Carolyn Rubin

    2009-07-15

    A domain structure based on the rutile lattice with a large density of (1/2)<011>{l_brace}011{r_brace}-type stacking faults is found in sputter deposited TiO{sub 2} films [J. Vac. Sci. Technol. A 24, 2054 (2006)]. The thermal stability of nanomosaic rutile at moderate temperature is reported here. Films are annealed at 973 K for 0.25-15 h, characterized by x-ray diffraction. A Johnson-Mehl-Avrami-Kolmogorov analysis indicates impeded crystallite growth. A dislocation-locking mechanism is proposed for this behavior. Partial dislocations with (1/2)<011> Burgers vectors that bound the stacking faults glide on intersecting {l_brace}011{r_brace} slip planes and react to produce sessile stair rod dislocations. Without the high temperature required for dislocation climb, (1/2)<011>{l_brace}011{r_brace}-type faults inherent to nanomosaic rutile provide thermal stability against massive crystallite growth.

  14. Thermal stability of ferroelectric domain gratings in Rb-doped KTP

    NASA Astrophysics Data System (ADS)

    Lindgren, Gustav; Peña, Alexandra; Zukauskas, Andrius; Liljestrand, Charlotte; Ménaert, Bertrand; Boulanger, Benoît.; Canalias, Carlota

    2015-08-01

    We study the thermal stability of domain walls in periodically poled Rb-doped KTP crystals. Domain-wall motion is observed after annealing the crystals above 550 °C. This motion is highly anisotropic along the a- and b- crystallographic axes. Along the b-axis domain wall motion is in the order of tens of micrometers. In the a-direction, it results in either three orders of magnitude smaller domain wall displacement or in domain merging, depending on the initial domain configuration. We show that the thermal stability of the domain gratings depends on their periodicity, resulting in complete backswitching for sub-micrometer domains annealed at 730 °C.

  15. Investigation on the thermal stability of PVC filled with hydrotalcite by the UV-vis spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Qiang; Li, Hancheng

    2008-01-01

    The thermal stability of the polyvinyl chloride (PVC) filled with hydrotalcite was studied in this paper. It was found that the stability of the PVC resin mixed with organic Sn and hydrotalcite was better than that of the PVC resin mixed with organic Sn alone. The UV-vis spectra showed that under certain heat treatment conditions, the sample without hydrotalcite embodied relatively high content of the conjugated double bonds with the chain length of about 3-5, however, the content of the conjugated double bond with the chain length of about 7 was greatly increased when the hydrotalcite was filled into the PVC resin. The hydrotalcite could inhibit the thermal degradation process of PVC resin in ionic mechanism.

  16. Synthesis and thermal stability of selenium-doped hydroxyapatite with different substitutions

    NASA Astrophysics Data System (ADS)

    Liu, Yonghui; Ma, Jun; Zhang, Shengmin

    2015-12-01

    Selenium (Se) plays a specific role in human health, especially for its antitumor effect. Incorporation of selenium into biocompatible hydroxyapatite (HAP) may endow the materials with novel characteristics. In the current work, a series of seleniumdoped hydroxyapatite (Se-HAP) nanoparticles with different Se/P ratios were synthesized by a modified chemical precipitation. It was revealed that the powders with/without heattreatment were nano-sized needle-like HAP while the heat-treated samples have high crystallinity. The addition of selenium decreases the crystallinity of the synthesized apatite, and also takes a negative effect on the thermal stability of the as-prepared powders. The Se-HAP nanoparticles with Se/P molar ratio not more than 5% sintered at 900°C can achieve good crystallinity and thermal stability.

  17. Thermal Stability of Photosensitive Bragg Gratings in Sputter-Deposited Germanosilicate Glass

    SciTech Connect

    POTTER JR.,BARRETT G.; POTTER,KELLY SIMMONS; DUNBAR,TIMOTHY D.

    2000-07-24

    The thermal stability of photo-imprinted Bragg gratings formed in reactive-atmosphere, RF-magnetron sputtered germanosilicate thin films was evaluated in terms of point defect modifications observed during isochronal annealing. Optical and magnetic spectroscopes were utilized to evaluate structural relaxation in these sputtered glasses on both a local and medium-range size scale. Depending upon the substrate temperature used during deposition, significant structural rearrangement was found to occur with increasing post-deposition anneal temperature to 600 C. This resulted in changes in the photobleaching response of the material itself as the identity of optically active structural defects evolved. Based on a color center model for photosensitivity in these materials and measured changes in optical absorption with annealing, the thermal stability of a photo-imprinted Bragg grating was modeled. Good qualitative agreement with experiment was observed.

  18. Investigation of the microstructure, mechanical properties and thermal stability of nanocomposite coatings based on amorphous carbon

    NASA Astrophysics Data System (ADS)

    Andreev, A. V.; Litovchenko, I. Y.; Korotaev, A. D.; Borisov, D. P.

    2015-10-01

    The Ti-C-Ni-Cr and Ti-C-Ni-Cr-Al-Si nanocomposite coatings based on amorphous carbon and the nanosized particles were synthesized by magnetron method. The results of the microstructure features and mechanical properties investigations of these coatings are presented. The thermal stability of microstructure and properties of these coatings at tempering up to 900°C were investigated. These coatings have a high (11-18 GPa) hardness, low (μ < 0.2) the coefficient of friction and high thermal stability of the microstructure and properties up to 700°C. The features of elastically stressed state of nanosized particles in these coatings were founded. A high local internal stresses in the TiC nanoscale particles do not observed.

  19. Thermal stability of piezoelectric properties and infrared sensor performance of spin-coated polyurea thin films

    NASA Astrophysics Data System (ADS)

    Morimoto, Masahiro; Koshiba, Yasuko; Misaki, Masahiro; Ishida, Kenji

    2015-10-01

    We have investigated the temperature dependence of the piezoelectric coefficients and infrared sensor performance of spin-coated thin films of polyundecylurea (PUA11). The piezoelectric coefficients of the PUA11 films remained constant at temperatures above 180 °C and these films demonstrated thermal resistance superior to those of poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)] films. The infrared sensor performance of the PUA11 films was measured after annealing at 125 °C for 500 h and was found to have retained 84% of its preannealing level. The thermal stability of the PUA11 films was higher than that of the P(VDF/TrFE) films; moreover, PUA11 is also expected to have superior electrothermal stability.

  20. Cancellation of drift kinetic effects between thermal and energetic particles on the resistive wall mode stabilization

    NASA Astrophysics Data System (ADS)

    Guo, S. C.; Liu, Y. Q.; Xu, X. Y.; Wang, Z. R.

    2016-07-01

    Drift kinetic stabilization of the resistive wall mode (RWM) is computationally investigated using MHD-kinetic hybrid code MARS-K following the non-perturbative approach (Liu et al 2008 Phys. Plasmas 15 112503), for both reversed field pinch (RFP) and tokamak plasmas. Toroidal precessional drift resonance effects from trapped energetic ions (EIs) and various kinetic resonances between the mode and the guiding center drift motions of thermal particles are included into the self-consistent toroidal computations. The results show cancellation effects of the drift kinetic damping on the RWM between the thermal particles and EIs contributions, in both RFP and tokamak plasmas, even though each species alone can provide damping and stabilize RWM instability by respective kinetic resonances. The degree of cancellation generally depends on the EIs equilibrium distribution, the particle birth energy, as well as the toroidal flow speed of the plasma.

  1. Thermal stability of fission gas bubble superlattice in irradiated U–10Mo fuel

    SciTech Connect

    Gan, J.; Keiser, D. D.; Miller, B. D.; Robinson, A. B.; Wachs, D. M.; Meyer, M. K.

    2015-09-01

    To investigate the thermal stability of the fission gas bubble superlattice, a key microstructural feature in both irradiated U-7Mo dispersion and U-10Mo monolithic fuel plates, a FIB-TEM sample of the irradiated U-10Mo fuel with a local fission density of 3.5×1021 fissions/cm3 was used for an in-situ heating TEM experiment. The temperature of the heating holder was raised at a ramp rate of approximately 10 ºC/min up to ~700 ºC, kept at that temperature for about 34 min, continued to 850 ºC with a reduced rate of 5 ºC/min. The result shows a high thermal stability of the fission gas bubble superlattice. The implication of this observation on the fuel microstructural evolution and performance under irradiation is discussed.

  2. Novel triplet host materials with high energy gap and thermal stability for organic electrophosphorescent devices

    NASA Astrophysics Data System (ADS)

    Qiao, Juan; Wang, Li D.; Qiu, Yong

    2006-04-01

    Organic electrophosphorescent materials and devices are the prime focus of organic light-emitting diodes research due to their high external quantum efficiency and power efficiency. The host materials with both high triplet energy level and high thermal stability are especially formidable for blue phosphorescent emitters. Herewith we report a novel triplet host material based on fluorene, 9,9-bis(4'-carbazol-phenyl)fluorene (CPF), in which two phenyl-carbazole moieties are connected to C9 carbon of the fluorene. This compound possesses not only desirably high triplet (2.9 eV) energies, but also extremely high glass transition temperature (Tg = 165 °C) and thermal stability. By using CPF as the host material, blue-emitting phosphorescent devices exhibited much higher efficiency and longer lifetime than those with CBP host.

  3. Thermal stability and decomposition mechanism of YBa 2Cu 4O 8

    NASA Astrophysics Data System (ADS)

    Isobe, M.; Suzuki, M.; Ami, T.; Tanaka, M.

    1991-12-01

    The thermal stability and decomposition mechanism of YBa 2Cu 4O 8 were studied by using TG, DTA and X-ray diffractometry. The results clearly show the correspondence between oxygen deficiency and phase stability. The decomposition activation energy at Po 2=1 atm was estimated as 2.18∗10 6J/mol by a kinetic analysis of the thermal gravity. This value indicates that the decomposition is very slow. The time dependence of mass loss could be also estimated at 900°C. We conclude that the Y 2Ba 4Cu 7O 15 phase appears only as an intermediate phase in the YBa 2Cu 4O 8 decomposition process, and that the Y 2Ba 4Cu 7O 15 phase is metastable at Po 2=1 atm.

  4. Design considerations of a thermally stabilized continuous flow electrophoresis chamber 2

    NASA Technical Reports Server (NTRS)

    Jandebeur, T. S.

    1982-01-01

    The basic adjustable parameters of a Beckman Continouous Particle Electrophoresis (CPE) Apparatus are investigated to determine the optimum conditions for ground based operation for comparison with space experiments. The possible application of electrically insulated copper/aluminum chamber walls is evaluated as a means to thermally stabilize or equilibrate lateral temperature gradients which exist on the walls of conventional plastic chambers and which distort the rectilinear base flow of buffer through the chamber, significantly affecting sample resolution.

  5. Thermal stability of kudzu root (Pueraria Radix) isoflavones as additives to beef patties.

    PubMed

    Kumari, S; Raines, J M; Martin, J M; Rodriguez, J M

    2015-03-01

    Kudzu root, Pueraria radix, extracts are a rich source of isoflavones. This study investigates the thermal stability of Pueraria radix extracts as a natural nutraceutical supplement in beef patties. The extract contained puerarin, diadzin, genistin, ononin, daidzein, glycitein, calycosin, genistein, formononetin and biochanin A; however, puerarin, daidzein and glycitein were the main components. The isoflavones concentrations in the spiked beef patties with kudzu root extracts were unaffected by cooking. PMID:25745227

  6. Ordered domain lateral location, symmetry, and thermal stability in Ge:Si islands

    SciTech Connect

    Richard, M.-I.; Schülli, T. U.; Zhong, Z.; Metzger, T. H.; Renaud, G.

    2015-01-05

    Compositional atomic ordering is a crucial issue in the epitaxial growth of nanoparticles and thin films. Here, we report on a method based on x-ray diffuse scattering close to basis forbidden Bragg reflections to infer the lateral location, the symmetry, and the thermal stability of ordered domains in GeSi dome-shaped islands on Si(001) after growth and during annealing. We observe that atomic ordering does not disappear after annealing, demonstrating that it is a resilient metastable phenomenon.

  7. Resumption of thermal stabilization of plutonium oxide in Building 707, Rocky Flats Plant, Golden, Colorado. Environmental Assessment

    SciTech Connect

    Not Available

    1994-02-01

    The Department of Energy is proposing thermal stabilization to enhance the safe storage of plutonium at Rocky Flats Plant until decisions are made on long-term storage and disposition of the material. The proposed action is to resume thermal stabilization of pyrophoric plutonium in Building 707 at Rocky Flats Plant. Thermal stabilization would heat the pyrophoric plutonium under controlled conditions in a glovebox furnace to promote full oxidation and convert the material into stable plutonium oxide in the form of PuO{sub 2}. Other activities associated with thermal stabilization would include post-stabilization characterization of non-pyrophoric plutonium and on-site movement of pyrophoric and non-pyrophoric plutonium. This report covers; purpose and need; proposed action; alternatives to the proposed action; affected environment; environmental effects of proposed action and no action alternative; agencies and person consulted; and public participation.

  8. A Materials Compatibility and Thermal Stability Analysis of Common Hydrocarbon Fuels

    NASA Technical Reports Server (NTRS)

    Meyer, M. L.; Stiegemeier, B. R.

    2005-01-01

    A materials compatibility and thermal stability investigation was conducted using five common liquid hydrocarbon fuels and two structural materials. The tests were performed at the NASA Glenn Research Center Heated Tube Facility under environmental conditions similar to those encountered in regeneratively cooled rocket engines. Scanning-electron microscopic analysis in conjunction with energy dispersive spectroscopy (EDS) was utilized to characterize the condition of the tube inner wall surface and any carbon deposition or corrosion that was formed during selected runs. Results show that the carbon deposition process in stainless steel tubes was relatively insensitive to fuel type or test condition. The deposition rates were comparable for all fuels and none of the stainless steel test pieces showed any signs of corrosion. For tests conducted with copper tubing, the sulfur content of the fuel had a significant impact on both the condition of the tube wall and carbon deposition rates. Carbon deposition rates for the lowest sulfur fuels (2 ppm) were slightly higher than those recorded in the stainless steel tubes with no corrosion observed on the inner wall surface. For slightly higher sulfur content (25 ppm) fuels, nodules that intruded into the flow area were observed to form on the inner wall surface. These nodules induced moderate tube pressure drop increases. The highest sulfur content fuels (400 ppm) produced extensive wall pitting and dendritic copper sulfide growth that was continuous along the entire tube wall surface. The result of this tube degradation was the inability to maintain flow rate due to rapidly increasing test section pressure drops. Accompanying this corrosion were carbon deposition rates an order of magnitude greater than those observed in comparable stainless steel tests. The results of this investigation indicate that trace impurities in fuels (i.e. sulfur) can significantly impact the carbon deposition process and produce unacceptable

  9. Linking measurements of biodegradability, thermal stability and chemical composition to evaluate the effects of management on soil organic matter

    NASA Astrophysics Data System (ADS)

    Gregorich, Ed; Gillespie, Adam; Beare, Mike; Curtin, Denis; Sanei, Hamed; Yanni, Sandra

    2015-04-01

    The stability of soil organic matter (SOM) as it relates to resistance to microbial degradation has important implications for nutrient cycling, emission of greenhouse gases, and C sequestration. Hence, there is interest in developing new ways to accurately quantify and characterise the labile and stable forms of soil organic C. Our objectives in this study were to evaluate and describe relationships among the biodegradability, thermal stability and chemistry of SOM in soil under widely contrasting management regimes. Samples from the same soil under permanent pasture, an arable cropping rotation, and chemical fallow were fractionated (sand: 2000-50 μm; silt: 50-5 μm, and clay: < 5 μm). Biodegradability of the SOM in size fractions and whole soils was assessed in a laboratory mineralization study. The chemical composition of SOM was characterized by X-ray absorption near-edge structure (XANES) spectroscopy at the K-edge and its thermal stability was determined by analytical pyrolysis using a Rock-Eval pyrolyser. The mineralization bioassay showed that whole soils and soil fractions under fallow were less susceptible to biodegradation than other managements and that sand-associated organic matter was significantly more susceptible than that in the silt or clay fractions. Analysis by XANES showed accumulation of carboxylates and strong depletion of amides (protein) and aromatics in the fallow whole soil. Moreover, protein depletion was most significant in the sand fraction of the fallow soil. Sand fractions in fallow and cropped soils were, however, enriched in plant-derived phenols, aromatics and carboxylates compared to the sand fraction of pasture soils. In contrast, ketones, which have been identified as products of microbially-processed organic matter, were slightly enriched in the silt fraction of the pasture soil. These data suggest reduced inputs and cropping restrict the decomposition of plant residues and, without supplemental N additions, protein-N in

  10. Thermal Stability of Co-Sputtered Ru Ti Alloy Electrodes for Dynamic Random Access Memory Applications

    NASA Astrophysics Data System (ADS)

    Horng, Ray-Hua; Wuu, Dong-Sing; Wu, Luh-Huei; Lee, Ming-Kwei; Chan, Shih-Hsiung; Leu, Ching-Chich; Huang, Tiao-Yuan; Sze, Simon

    1998-10-01

    Ru Ti alloy films were studied for use as a bottom electrode of ferroelectric/paraelectric thin film capacitors. These thin films with different Ru/Ti compositions were first prepared by co-sputtering. The Ru/Ti ratio in the alloy was found to strongly affect the resistivity, structure formation and thermal stability. The resistivity of the as-deposited films decreases and closes to that of pure Ru metal films as the amount of Ru atoms increasing. From X-ray diffraction measurement, it was found that the RuTi phase has formed for the as-deposited sample. There also exist Ru and Ti phases for Ru-enriched and Ti-enriched samples, respectively. As-deposited alloy films were also annealed by rapid thermal processing (RTP, 600 750°C, 1 min) in oxygen ambient to simulate the processing of ferroelectric/paraelectric thin film capacitors. It was found that the composition of the thin film has a large effect on the thermal stability. The resistivity of alloy thin films is thermally stable as the Ru composition varies from 0.68 to 0.81. It may be due to the RuTiO2 formation at the surface and play an important role in preventing further oxidation of the Ru-enriched layer. This oxide also presents conductive behavior. On the other hand, the interface between Ru-enriched alloys and Si substrate was still sharp for the RTP-treated sample at 600°C for 1 min. The alloy film with high Ru composition shows excellent thermal stability and barriers against interdiffusion of Si and oxygen. These results suggest that the Ru-enriched alloy films are suitable for the bottom electrode application in ferroelectric/paraelectric thin film capacitors.

  11. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    NASA Astrophysics Data System (ADS)

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH)max of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  12. Stability of Pin1 as revealed by thermal and spectroscopic studies

    NASA Astrophysics Data System (ADS)

    Wang, Jing-Zhang; Lin, Tao; Zhu, Guo-Fei; Du, Lin-Fang

    2010-06-01

    Pin1 is a two-domain enzyme which has peptidyl-prolyl cis/trans isomerase activity. Pin1 recognizes phospho-Ser/Thr-Pro motifs in cell-signaling proteins, and is both a cancer and an Alzheimer's disease target. The thermal stability of Pin1 was studied intensively by SDS-PAGE, enzymatic activity assay, intrinsic fluorescence spectroscopy and circular dichroism spectroscopy. The activity of Pin1 gradually decreased above 40 °C, and the Tm was 57.6 ± 1.0 °C. Fluorescence experiments indicated that heat treatment induced changes in the substructures in Pin1, resulting in that the polarity in the microenvironments of the tryptophan residues increased. It is assumed that the thermal denaturation of Pin1 involved a three-state transition. The intermediate state of Pin1 at about 60 °C was confirmed by fluorescence emission spectra, the synchronous fluorescence spectra and CD measurements. Decreases in α-helix and β-sheet appeared above 40 °C, which was balanced by an enhancement in unordered coil. The Tm values calculated from α-helix transition and β-sheet transition were 54.6 ± 0.6 °C and 70.7 ± 3.3 °C, respectively. Our results illustrated that Pin1 had a relatively high thermal stability and the WW domain had a higher stability than the PPIase domain.

  13. Influence of Nitrogen Content on Thermal Stability and Grain Growth Kinetics of Cryomilled Al Nanocomposites

    NASA Astrophysics Data System (ADS)

    Hashemi-Sadraei, L.; Mousavi, S. E.; Vogt, R.; Li, Y.; Zhang, Z.; Lavernia, E. J.; Schoenung, J. M.

    2012-02-01

    Nanocomposite powders of Al 5083/B4C were produced via cryogenic milling (cryomilling) of boron carbide (B4C) particles in Al 5083 matrix. The effect of milling time (up to 24 hours), and consequential nitrogen content, on grain growth in the nanocrystalline Al 5083 matrix was investigated. Thermal stability was studied at temperatures as high as ~0.96 T m and annealing times of up to 24 hours. Average grain sizes increased with time and temperature and tended to stabilize after longer annealing times, regardless of nitrogen content. Higher thermal stability was observed in samples with higher nitrogen content, with the average grain size remaining in the range of 30 nm, even after exposure to the most extreme annealing conditions. This behavior was attributed to the retarding effect that nitrides have on grain growth, as a result of pinning grain boundaries. Kinetic studies based on the Burke equation showed two thermally activated grain growth regimes—a low-temperature regime with an activation energy of 15 kJ/mol and a high-temperature regime with an activation energy of 58 kJ/mol.

  14. Improvement of thermal stability of amorphous CoFeSiB thin films

    SciTech Connect

    Jimbo, M. Shimizu, T.; Fujiwara, Y.

    2015-05-07

    The excellent soft magnetic properties of amorphous (a-) CoFeSiB films make it suited for use in the yoke of granular-in-gap sensors, but only if their thermal stability can be improved. To this end, this study investigated the effects of adding small amounts of other metals on the magnetic and structural properties of a-CoFeSiB films. It was found that adding metals with relatively large atomic radii is an effective way to increase thermal stability, with both Ta and Hf showing good thermal stability after annealing at temperatures of 473 to 573 K. Indeed, a -(CoFeSiB){sub 96.2}Hf{sub 3.8} film was found to maintain its initial coercivity of 0.2 Oe without very little decrease in magnetization after annealing at 623 K. Furthermore, even after annealing at 673 K a -(CoFeSiB){sub 93.0}Hf{sub 7.0} film still had a relatively low coercivity of approximately 0.5 Oe.

  15. Magnetic properties and thermal stability of MnBi/NdFeB hybrid bonded magnets

    SciTech Connect

    Cao, S.; Yue, M.; Yang, Y. X.; Zhang, D. T.; Liu, W. Q.; Zhang, J. X.; Guo, Z. H.; Li, W.

    2011-04-01

    Magnetic properties and thermal stability were investigated for the MnBi/NdFeB (MnBi = 0, 20, 40, 60, 80, and 100 wt.%) bonded hybrid magnets prepared by spark plasma sintering (SPS) technique. Effect of MnBi content on the magnetic properties of the hybrid magnets was studied. With increasing MnBi content, the coercivity of the MnBi/NdFeB hybrid magnets increases rapidly, while the remanence and maximum energy product drops simultaneously. Thermal stability measurement on MnBi magnet, NdFeB magnet, and the hybrid magnet with 20 wt.% MnBi indicates that both the NdFeB magnet and the MnBi/NdFeB hybrid magnet have a negative temperature coefficient of coercivity, while the MnBi magnet has a positive one. The (BH){sub max} of the MnBi/NdFeB magnet (MnBi = 20 wt.%) is 5.71 MGOe at 423 K, which is much higher than 3.67 MGOe of the NdFeB magnet, indicating a remarkable improvement of thermal stability.

  16. Shelf stability of nanofluids and its effect on thermal conductivity and viscosity

    NASA Astrophysics Data System (ADS)

    Haghighi, E. B.; Nikkam, N.; Saleemi, M.; Behi, M.; Mirmohammadi, S. A.; Poth, H.; Khodabandeh, R.; Toprak, M. S.; Muhammed, M.; Palm, B.

    2013-10-01

    This study proposes a method and apparatus to estimate shelf stability of nanofluids. Nanofluids are fabricated by dispersion of solid nanoparticles in base fluids, and shelf stability is a key issue for many practical applications of these fluids. In this study, shelf stability is evaluated by measuring the weight of settled solid particles on a suspended tray in a colloid versus time and correlated with the performance change of some nanofluid systems. The effects of solid particle concentration and bath sonication time were investigated for selected nanofluids. The results show the applicability of this simple method and the apparatus to evaluate nanofluid shelf stability. Furthermore, it shows that Stokes’ law is not valid for determining the settling time of the tested nanoparticles probably due to their complicated shape and presence of surface modifiers. The effect of shelf stability on thermal conductivity and viscosity was illustrated for some nanofluids. Experimental results show that water-based Al2O3 nanofluids have quite good shelf stability and can be good candidates for industrial applications.

  17. Thermal Conductivity and Water Vapor Stability of Ceramic HfO2-Based Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dong-Ming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2-15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermal/environmental barrier coating applications will also be discussed.

  18. Thermal stability and long-chain fatty acid positional distribution on glycerol of argan oil.

    PubMed

    Khallouki, Farid; Mannina, Luisa; Viel, Stéphane; Owen, Robert W

    2008-09-01

    The primary aim of this study was to determine the oxidative stability of argan oils by using peroxides and conjugated diene hydroperoxides measurements as analytical indicators. Both food and cosmetic argan oils were investigated. Their oxidative stability was also determined by monitoring the relative changes of their fatty acid profiles by (1)H NMR. In addition, valuable information regarding minor components as well as the acyl positional distribution, were obtained for both grades by high field (1)H and (13)C NMR, respectively. Given that the cosmetic and food grades have a similar profile and content of phenolic antioxidants, vitamers, and squalene, it appears that the ratio of fatty acid aliphatic to bisallylic CH2 groups, much higher in argan oils than in other vegetable oils, is responsible for their higher thermal stability. PMID:26050165

  19. Prediction of salt effects on protein phase behavior by HIC retention and thermal stability.

    PubMed

    Baumgartner, Kai; Großhans, Steffen; Schütz, Juliane; Suhm, Susanna; Hubbuch, Jürgen

    2016-09-01

    In the biopharmaceutical industry it is mandatory to know and ensure the correct protein phase state as a critical quality attribute in every process step. Unwanted protein precipitation or crystallization can lead to column, pipe or filter blocking. In formulation, the formation of aggregates can even be lethal when injected into the patient. The typical methodology to illustrate protein phase states is the generation of protein phase diagrams. Commonly, protein phase behavior is shown in dependence of protein and precipitant concentration. Despite using high-throughput methods for the generation of phase diagrams, the time necessary to reach equilibrium is the bottleneck. Faster methods to predict protein phase behavior are desirable. In this study, hydrophobic interaction chromatography retention times were correlated to crystal size and form. High-throughput thermal stability measurements (melting and aggregation temperatures), using an Optim(®)2 system, were successfully correlated to glucose isomerase stability. By using hydrophobic interaction chromatography and thermal stability determinations, glucose isomerase conformational and colloidal stability were successfully predicted for different salts in a specific pH range. PMID:27268946

  20. Buffer influence on magnetic dead layer, critical current, and thermal stability in magnetic tunnel junctions with perpendicular magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Frankowski, Marek; Żywczak, Antoni; Czapkiewicz, Maciej; Zietek, Sławomir; Kanak, Jarosław; Banasik, Monika; Powroźnik, Wiesław; Skowroński, Witold; Checiński, Jakub; Wrona, Jerzy; Głowiński, Hubert; Dubowik, Janusz; Ansermet, Jean-Philippe; Stobiecki, Tomasz

    2015-06-01

    We present a detailed study of Ta/Ru-based buffers and their influence on features crucial from the point of view of applications of Magnetic Tunnel Junctions (MTJs) such as critical switching current and thermal stability. We study buffer/FeCoB/MgO/Ta/Ru and buffer/MgO/FeCoB/Ta/Ru layers, investigating the crystallographic texture, the roughness of the buffers, the magnetic domain pattern, the magnetic dead layer thickness, and the perpendicular magnetic anisotropy fields for each sample. Additionally, we examine the effect of the current induced magnetization switching for complete nanopillar MTJs with lateral dimensions of 270 × 180 nm. Buffer Ta 5/Ru 10/Ta 3 (thicknesses in nm), which has the thickest dead layer, exhibits a much larger thermal stability factor (63 compared to 32.5) while featuring a slightly lower critical current density value (1.25 MA/cm2 compared to 1.5 MA/cm2) than the buffer with the thinnest dead layer Ta 5/Ru 20/Ta 5. We can account for these results by considering the difference in damping which compensates for the difference in the switching barrier heights.

  1. Thermal-conductivity measurements of tungsten-fiber-reinforced superalloy composites using a thermal-conductivity comparator

    NASA Technical Reports Server (NTRS)

    Westfall, L. J.; Winsa, E. A.

    1979-01-01

    The thermal conductivity (TC) of tungsten-fiber-reinforced superalloys was determined for two composite systems by using a thermal conductivity standard from the National Bureau of Standards and a comparator and technique developed for that purpose. The results were compared with TC data for the nickel-base alloy MAR-M200. The technique lends itself to applications involving thin specimens, such as thin-walled turbine blades. The TC's of the composite systems were considerably higher in both the longitudinal and transverse directions than that of the monolithic superalloys used as the matrices.

  2. Thermal stability of antiparasitic macrocyclic lactones milk residues during industrial processing.

    PubMed

    Imperiale, F A; Farias, C; Pis, A; Sallovitz, J M; Lifschitz, A; Lanusse, C

    2009-01-01

    The chemical stability of residues of different antiparasitic macrocyclic lactone compounds in milk subjected to thermal treatment was assessed. Concentrations of ivermectin (IVM), moxidectin (MXD) and eprinomectin (EPM) in sheep milk, equivalent to those measured in vivo in milk excretion studies, were subjected to 65 degrees C over 30 min or to 75 degrees C for 15 s. Residue concentrations of IVM, MXD and EPM in milk were measured by high-performance liquid chromatography (HPLC) (fluorescence detection) before and after heat treatment of the drug-fortified milk samples. No evidence of chemical loss was obtained in either of the thermal treatments under evaluation. The stability of the parent compounds in milk was evidenced by the lack of bioconversion products (metabolites) after both thermal treatments. Only very minor changes on drug concentrations were observed at the end of the treatments, which fell within the limits of the variation of the validated analytical method. In conclusion, residue concentrations of macrocyclic lactones are unaffected by industrial-simulated milk thermal procedures. Based on the reported findings, it can be postulated that residue concentrations of IVM, MXD and EPM measured in raw sheep milk may be used to estimate consumer exposure and dietary intake for these veterinary drugs. PMID:19680871

  3. Thermally Driven Stability of Octadecylphosphonic Acid Thin Films Grown on SS316L

    PubMed Central

    Lim, Min Soo; Smiley, Katelyn J.; Gawalt, Ellen S.

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF and water flushes while untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a three hour period while the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface. PMID:20648546

  4. Activity and stability of the oxygen evolution reaction on electrodeposited Ru and its thermal oxides

    NASA Astrophysics Data System (ADS)

    Kim, Jin Yeong; Choi, Jihui; Kim, Ho Young; Hwang, Eunkyoung; Kim, Hyoung-Juhn; Ahn, Sang Hyun; Kim, Soo-Kil

    2015-12-01

    The activity and stability of Ru metal and its thermal oxide films for the oxygen evolution reaction (OER) were investigated. The metallic Ru films were prepared by electrodeposition on a Ti substrate and then thermally oxidized at various temperatures under atmospheric conditions. During long-term operation of the OER with cyclic voltammetry (CV) in H2SO4 electrolyte, changes in the properties of the Ru and its thermal oxides were monitored in terms of their morphology, crystal structure, and electronic structure. In the initial stages of the OER, all of the Ru thermal oxide films underwent an activation process that was related to the continuous removal of low-activity Ru oxides from the surface. With further cycling, the OER activity decreased. The rate of decrease was different for each Ru film and was related to the annealing temperatures. Monitoring of material properties indicates that the amount of stable anhydrous RuO2 is important for OER stability because it prevents both the severe dissolution of metallic Ru beneath the oxide surface and the formation of a less active hydrous RuO2 at the surface.

  5. Thermally driven stability of octadecylphosphonic acid thin films grown on SS316L.

    PubMed

    Lim, Min Soo; Smiley, Katelyn J; Gawalt, Ellen S

    2010-01-01

    Stainless steel 316L is widely used as a biomedical implant material; however, there is concern about the corrosion of metallic implants in the physiological environment. The corrosion process can cause mechanical failure due to resulting cracks and cavities in the implant. Alkyl phosphonic acid forms a thin film by self-assembly on the stainless steel surface and this report conclusively shows that thermal treatment of the octadecylphosphonic acid (ODPA) film greatly enhances the stability of the ODPA molecules on the substrate surface. AFM images taken from the modified substrates revealed that thermally treated films remain intact after methanol, THF, and water flushes, whereas untreated films suffer substantial loss. Water contact angles also show that the hydrophobicity of thermally treated films does not diminish after being incubated in a dynamic flow of water for a 3-hour period, whereas the untreated film becomes increasingly hydrophilic due to loss of ODPA. IR spectra taken of both treated and untreated films after water and THF flushes show that the remaining film retains its initial crystallinity. A model is suggested to explain the stability of ODPA film enhanced by thermal treatment. An ODPA molecule is physisorbed to the surface weakly by hydrogen bonding. Heating drives away water molecules leading to the formation of strong monodentate or mixed mono/bi-dentate bonds of ODPA molecule to the surface. PMID:20648546

  6. Thermal properties of the optically transparent pore-free nanostructured yttria-stabilized zirconia

    SciTech Connect

    Ghosh, S.; Teweldebrhan, D.; Morales, J. R.; Garay, J. E.; Balandin, A. A.

    2009-12-01

    The authors report results of investigation of thermal conductivity of nanocrystalline yttria-stabilized zirconia. The optically transparent pore-free bulk samples were prepared via the spark plasma sintering process to ensure homogeneity. Thermal conductivity K was measured by two different techniques. It was found that the pore-free nanostructured bulk zirconia is an excellent thermal insulator with the room-temperature Kapprox1.7-2.0 W/m K. It was also shown that the 'phonon-hopping' model can accurately describe specifics of K dependence on temperature and the grain size. The obtained results are important for optimization of zirconia properties for specific applications in advanced electronics and coatings.

  7. Application of a Physics-Based Stabilization Criterion to Flight System Thermal Testing

    NASA Technical Reports Server (NTRS)

    Baker, Charles; Garrison, Matthew; Cottingham, Christine; Peabody, Sharon

    2010-01-01

    The theory shown here can provide thermal stability criteria based on physics and a goal steady state error rather than on an arbitrary "X% Q/mC(sub P)" method. The ability to accurately predict steady-state temperatures well before thermal balance is reached could be very useful during testing. This holds true for systems where components are changing temperature at different rates, although it works better for the components closest to the sink. However, the application to these test cases shows some significant limitations: This theory quickly falls apart if the thermal control system in question is tightly coupled to a large mass not accounted for in the calculations, so it is more useful in subsystem-level testing than full orbiter tests. Tight couplings to a fluctuating sink causes noise in the steady state temperature predictions.

  8. Friction, wear, and thermal stability studies of some organotin and organosilicon compounds

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1973-01-01

    Thermal decomposition temperatures were determined for a number of organotin and organosilicon compounds. A ball-on-disk sliding friction apparatus was used to determine the friction and wear characteristics of two representative compounds, (1) 3-tri-n-butylstannyl (diphenyl) and (2) 3-tri-n-butylsilyl (diphenyl). Friction and wear test conditions included a 1-kg load, 25 to 225 C disk temperatures, and a dry air atmosphere. The tin and silicon compounds yielded friction and wear results either lower than or similar to those obtained with a polyphenyl ether and a C-ether. The maximum thermal decomposition temperatures obtained in the silicon and tin series were 358 and 297 C, respectively. Increasing the steric hindrance around the silicon or tin atoms increased the thermal stability. Future work with these compounds will emphasize their use as antiwear additives rather than base fluids.

  9. V-groove-based compact FBG package for thermal tuning and mechanical stability

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Fang, Wei; Wang, Di; Chen, Di-Jun; Cai, Hai-Wen; Qu, Rong-Hui

    2016-04-01

    We demonstrated a V-groove-based fiber Bragg grating (FBG) package that has been glue-filled and cured to make it a bulky component with much improved mechanical stability. The V-groove can be executed with many types of materials including plastics, ceramics, semiconductors, and metals, providing an easy method for redesigning the thermal tuning performance of FBGs by selecting among a wide variety of materials and processes. We achieved more than 10-nm thermal wavelength tuning and thermal sensitivity ranging from 15 to 160 pm/K. The original FBG spectrum can be maintained without any degradation because the fiber is buried in the V-groove. The compact package does not increase the original grating length and turns the FBG into a planar waveguide grating, improving FBG applications in telecommunications, external cavity lasers, and sensing areas.

  10. Flame retardancy and thermal stability of polyurethane foam composites containing carbon additives

    NASA Astrophysics Data System (ADS)

    Lee, Pyoung-Chan; Kim, Bo-Ram; Jeoung, Sun Kyoung; Lee, Geesoo; Han, San Wook; Kim, Hyunchul; Lee, Ki-Dong; Han, Joo-Kwon

    2016-03-01

    Polyurethane (PU) is an important class of polymers that have wide application in a number of different industrial sectors. The goal of this work was the synthesis of flame-retarded PU foam with expandable graphite (EG) or commercial graphene. The flame retardancy and thermal stability of the foams has been studied through cone calorimeter analysis, the limited oxygen index and thermal conductivity. The presence of expandable graphite brings an improvement in fire behavior. In particular, the limited oxygen index increases in a linear way and the highest limited oxygen index values are obtained for EG-PU foams. The results from the cone calorimeter are in agreement with those of oxygen index; EG filled foams show a considerable decrease of maximum-heat release rate (M-HRR) with respect to unfilled foams. The results of thermal conductivity show that an increase in expandable graphite amount in PU foams lead to an increased conductivity.

  11. The comparative study of thermal fatigue behavior of laser deep penetration spot cladding coating and brush plating Ni W Co coating

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Li, Zhengyang; Zhu, Wenhui; Liu, Zili; Liu, Wenjin

    2006-12-01

    For improving the thermal fatigue behavior of hot work die steel in engineering application, the present work compare the influence of thermal fatigue resistance by the two different surface modified processes, the laser deep penetration spot cladding (LDPSC) and brush plating on the Cr12MoNi hot rolling tool steel. The thermal fatigue tests were fulfilled by heating and quenching in water at a cycle period of 2 min. Before and after thermal fatigue testing, the microhardness distribution profile and microstructure of LDPSC have been investigated. The results show that the LDPSC can be divided to three zones: cladding zone, alloying zone and heat affected zone. The major phases in cladding zone consist of Fe 3C, Cr 7C 3, Cr 23C 6 and martensite. The oxidation resistance and thermal stability of brush plating Ni-W-Co coating and reference materials has been determined. The results of thermal fatigue testing show that LDPSC and brush plating Ni-W-Co coating can improve thermal fatigue resistance as compared to the reference material. The brush plating Ni-W-Co coating is more effective than the former owing to its higher thermal stability, oxidation resistance, superfine grain, high-density dislocation in microstructure and combination of strength and ductility.

  12. Soil thermal resistivity and thermal stability measuring instrument. Volume 2. Manual for operation and use of the thermal property analyzer and statistical weather analysis program to determine thermal design parameters. Final report

    SciTech Connect

    Boggs, S.A.; Radhakrishna, H.S.

    1981-11-01

    Numerous considerations influence the thermal design of an underground power cable, including the soil thermal resistivity, thermal diffusivity and thermal stability. Each of these properties is a function of soil moisture which is, in turn, a function of past weather, soil composition, and biological burden. The Neher-McGrath formalism has been widely used for thermal cable design. However, this formalism assumes knowledge of soil thermal properties (resistivity and diffusivity). For design purposes, these parameters should be treated statistically, since weather varies greatly from year-to-year. As well, soil thermal property surveys are normally required along the route to assess the thermal quality of the native soil. This project is intended to fill the gap between the need to carry out thermal design and the use of the Neher-McGrath formalism which is normally employed. This goal has been addressed through: development of instrumentation and methods of measuring soil thermal properties in situ and in the laboratory; recommendation of methods for conducting soil surveys along a proposed cable route and of assessing the thermal quality of soils; and development of a computerized method to treat soil thermal design parameters on a statistical basis using computerized weather records as supplied by the US Environmental Data Service. The use of the methods and instrumentation developed as a result of this contract should permit less conservative thermal design thereby improving the economics of underground transmission. As well, these techniques and instrumentation facilitate weather-dependent prediction of cable ampacity for installed cables, monitoring of backfill thermal stability, and many other new practices.

  13. Thermal Stability of Nanocrystalline Copper for Potential Use in Printed Wiring Board Applications

    NASA Astrophysics Data System (ADS)

    Woo, Patrick Kai Fai

    Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultra-fine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25-230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40?C to 400?C. During isothermal annealing experiments samples were annealed at 23?C, 100?C and 300?C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of

  14. High thermal stability of La2O3 and CeO2-stabilized tetragonal ZrO2

    DOE PAGESBeta

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R.; Li, Tao; Winans, Randall E.; Cui, Yanran; Ribeiro, Fabio H.; Canlas, Christian P.; Elam, Jeffrey W.; et al

    2016-02-15

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From In Situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with thermal stability up to 1000 °C in air. These supports had an average size of ~10 nm and a surface area of 59-97 m2/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3-12.4 wt %.more » Mono-dispersed Pt nanoparticles of ~3 nm were obtained for these catalysts. As a result, the incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas-shift (WGS) reaction.« less

  15. High Thermal Stability of La2O3- and CeO2-Stabilized Tetragonal ZrO2.

    PubMed

    Wang, Shichao; Xie, Hong; Lin, Yuyuan; Poeppelmeier, Kenneth R; Li, Tao; Winans, Randall E; Cui, Yanran; Ribeiro, Fabio H; Canlas, Christian P; Elam, Jeffrey W; Zhang, Hongbo; Marshall, Christopher L

    2016-03-01

    Catalyst support materials of tetragonal ZrO2, stabilized by either La2O3 (La2O3-ZrO2) or CeO2 (CeO2-ZrO2), were synthesized under hydrothermal conditions at 200 °C with NH4OH or tetramethylammonium hydroxide as the mineralizer. From in situ synchrotron powder X-ray diffraction and small-angle X-ray scattering measurements, the calcined La2O3-ZrO2 and CeO2-ZrO2 supports were nonporous nanocrystallites that exhibited rectangular shapes with a thermal stability of up to 1000 °C in air. These supports had an average size of ∼10 nm and a surface area of 59-97 m(2)/g. The catalysts Pt/La2O3-ZrO2 and Pt/CeO2-ZrO2 were prepared by using atomic layer deposition with varying Pt loadings from 6.3 to 12.4 wt %. Monodispersed Pt nanoparticles of ∼3 nm were obtained for these catalysts. The incorporation of La2O3 and CeO2 into the t-ZrO2 structure did not affect the nature of the active sites for the Pt/ZrO2 catalysts for the water-gas shift reaction. PMID:26878202

  16. Deciphering the Dynamics of Non-Covalent Interactions Affecting Thermal Stability of a Protein: Molecular Dynamics Study on Point Mutant of Thermus thermophilus Isopropylmalate Dehydrogenase

    PubMed Central

    Sharma, Reetu; Sastry, G. Narahari

    2015-01-01

    Thermus thermophilius isopropylmalate dehydrogenase catalyzes oxidative decarboxylation and dehydrogenation of isopropylmalate. Substitution of leucine to alanine at position 172 enhances the thermal stability among the known point mutants. Exploring the dynamic properties of non-covalent interactions such as saltbridges, hydrogen bonds and hydrophobic interactions to explain thermal stability of a protein is interesting in its own right. In this study dynamic changes in the non-covalent interactions are studied to decipher the deterministic features of thermal stability of a protein considering a case study of a point mutant in Thermus thermophilus isopropylmalate dehydrogenase. A total of four molecular dynamic simulations of 0.2 μs were carried out on wild type and mutant’s functional dimers at 300 K and 337 K. Higher thermal stability of the mutant as compared to wild type is revealed by root mean square deviation, root mean square fluctuations and Cα-Cα distance with an increase in temperature from 300 K to 337 K. Most of the regions of wild type fluctuate higher than the corresponding regions of mutant with an increase in temperature. Cα-Cα distance analysis suggests that long distance networks are significantly affected in wild type as compared to the mutant. Short lived contacts are higher in wild type, while long lived contacts are lost at 337 K. The mutant forms less hydrogen bonds with water as compared to wild type at 337 K. In contrast to wild type, the mutant shows significant increase in unique saltbridges, hydrogen bonds and hydrophobic contacts at 337 K. The current study indicates that there is a strong inter-dependence of thermal stability on the way in which non-covalent interactions reorganize, and it is rewarding to explore this connection in single mutant studies. PMID:26657745

  17. Deciphering the Dynamics of Non-Covalent Interactions Affecting Thermal Stability of a Protein: Molecular Dynamics Study on Point Mutant of Thermus thermophilus Isopropylmalate Dehydrogenase.

    PubMed

    Sharma, Reetu; Sastry, G Narahari

    2015-01-01

    Thermus thermophilius isopropylmalate dehydrogenase catalyzes oxidative decarboxylation and dehydrogenation of isopropylmalate. Substitution of leucine to alanine at position 172 enhances the thermal stability among the known point mutants. Exploring the dynamic properties of non-covalent interactions such as saltbridges, hydrogen bonds and hydrophobic interactions to explain thermal stability of a protein is interesting in its own right. In this study dynamic changes in the non-covalent interactions are studied to decipher the deterministic features of thermal stability of a protein considering a case study of a point mutant in Thermus thermophilus isopropylmalate dehydrogenase. A total of four molecular dynamic simulations of 0.2 μs were carried out on wild type and mutant's functional dimers at 300 K and 337 K. Higher thermal stability of the mutant as compared to wild type is revealed by root mean square deviation, root mean square fluctuations and Cα-Cα distance with an increase in temperature from 300 K to 337 K. Most of the regions of wild type fluctuate higher than the corresponding regions of mutant with an increase in temperature. Cα-Cα distance analysis suggests that long distance networks are significantly affected in wild type as compared to the mutant. Short lived contacts are higher in wild type, while long lived contacts are lost at 337 K. The mutant forms less hydrogen bonds with water as compared to wild type at 337 K. In contrast to wild type, the mutant shows significant increase in unique saltbridges, hydrogen bonds and hydrophobic contacts at 337 K. The current study indicates that there is a strong inter-dependence of thermal stability on the way in which non-covalent interactions reorganize, and it is rewarding to explore this connection in single mutant studies. PMID:26657745

  18. Stabilization of simulated lead sludge with iron sludge via formation of PbFe₁₂O₁₉ by thermal treatment.

    PubMed

    Mao, Linqiang; Cui, Hao; An, Hao; Wang, Bing; Zhai, Jianping; Zhao, Yongbin; Li, Qin

    2014-12-01

    This study investigated the feasibility of stabilizing lead sludge by reaction with iron sludge via the formation of PbFe12O19 through a thermal treatment process. Lead hydroxide was used to simulate lead-laden sludge and the sintering procedure was performed by firing a mixture of this simulated sludge together with iron sludge at a Fe/Pb molar ratio of 12 over the temperature range from 650 to 1400 °C. The accompanying phase transformations as well as the surface characteristic of sintered samples were observed by XRD and SEM, while the leaching behavior of the stabilized sludge in an acidic environment was evaluated by a modified Toxicity Characteristic Leaching Procedure (TCLP) test. The results confirmed that PbFe12O19 acts as a stabilization phase for lead, and showed that the formation of a PbFe12O19 phase began at 750 °C with the lead completely incorporated into the PbFe12O19 phase at 1050 °C. Above 1100 °C, the PbFe12O19 phase began to decompose, accompanied by the reappearance of Fe2O3. The volumes of compressed sludge samples were reduced significantly after thermal treatment, with accompanying volume reductions of 40% at 1050 °C. This study compared the leaching of lead from PbO and sintered sludge samples using a prolonged TCLP test, and the data showed that the PbFe12O19 phase was superior to the PbO and that the sintered sludge sample exhibited very high stability under acidic environments. These results suggest a promising and reliable method of reducing lead sludge mobility and toxicity has been identified. PMID:25461943

  19. Stability of the lac repressor headpiece against thermal denaturation and tryptic hydrolysis.

    PubMed

    Schnarr, M; Maurizot, J C

    1982-04-01

    The stability of the conformation of the lac repressor headpiece against thermal denaturation and tryptic hydrolysis has been studied by circular dichroism measurements. In both cases the stability depends strongly on the concentration of NaCl. This effect is larger than generally observed for proteins. The midpoint of the thermal denaturation curve (Tm) is shifted from about 37 degrees C in the absence of NaCl to about 68 degrees C in 1 M NaCl. After a first non-linear increase of the Tm with the NaCl concentration (up to about 0.2 M NaCl) the Tm varies linearly with the salt concentration. Assuming a two-state mechanism for the thermal denaturation, enthalpies of 30-36 kcal/mol have been determined. The decrease of the circular dichroism signal due to the tryptic cleavage follows pseudo first-order kinetics for all salt concentrations studied. The half-life time of hydrolysis increased by about 40-times from 2 mM to the highest NaCl concentration we have used (655 mM). Assuming that only the unfolded state of the headpiece is a good substrate for trypsin, the observed stabilization against proteolytic degradation may be explained by a shift of the unfolding equilibrium of the headpiece due to the salt, and a subsequent decrease of the concentration of the unfolded state. The unusual stabilization of the headpiece is discussed with respect to its positive charge and to its function to bind to DNA. PMID:7044423

  20. Thermal stability of purified and reconstituted CFTR in a locked open channel conformation.

    PubMed

    Aleksandrov, Luba A; Jensen, Timothy J; Cui, Liying; Kousouros, Joseph N; He, Lihua; Aleksandrov, Andrei A; Riordan, John R

    2015-12-01

    CFTR is unique among ABC transporters as the only one functioning as an ion channel and from a human health perspective because mutations in its gene cause cystic fibrosis. Although considerable advances have been made towards understanding CFTR's mechanism of action and the impact of mutations, the lack of a high-resolution 3D structure has hindered progress. The large multi-domain membrane glycoprotein is normally present at low copy number and when over expressed at high levels it aggregates strongly, limiting the production of stable mono-disperse preparations. While the reasons for the strong self-association are not fully understood, its relatively low thermal stability seems likely to be one. The major CF causing mutation, ΔF508, renders the protein very thermally unstable and therefore a great deal of attention has been paid to this property of CFTR. Multiple second site mutations of CFTR in NBD1 where F508 normally resides and small molecule binders of the domain increase the thermal stability of the mutant. These manipulations also stabilize the wild-type protein. Here we have applied ΔF508-stabilizing changes and other modifications to generate wild-type constructs that express at much higher levels in scaled-up suspension cultures of mammalian cells. After purification and reconstitution into liposomes these proteins are active in a locked-open conformation at temperatures as high as 50 °C and remain monodisperse at 4 °C in detergent or lipid for at least a week. The availability of adequate amounts of these and related stable active preparations of homogeneous CFTR will enable stalled structural and ligand binding studies to proceed. PMID:26384709

  1. Comparing the Temporal Stability of Self-Report and Interview Assessed Personality Disorder

    PubMed Central

    Samuel, Douglas B.; Hopwood, Christopher J.; Ansell, Emily B.; Morey, Leslie C.; Sanislow, Charles A.; Markowitz, John C.; Yen, Shirley; Shea, M. Tracie; Skodol, Andrew E.; Grilo, Carlos M.

    2015-01-01

    Findings from several large-scale, longitudinal studies over the last decade have challenged the long held assumption that personality disorders (PDs) are stable and enduring. However, the findings, including those from the Collaborative Longitudinal Personality Disorders Study (CLPS; Gunderson et al., 2000), rely primarily upon results from semistructured interviews. As a result, less is known about the stability of PD scores from self-report questionnaires, which differ from interviews in important ways (e.g., source of the ratings, item development, and instrument length) that might increase temporal stability. The current study directly compared the stability of the DSM-IV PD constructs assessed via the Schedule for Nonadaptive and Adaptive Personality (SNAP – 2; Clark, Simms, Wu, & Casillas, in press) with those from the Diagnostic Interview for DSM-IV Personality Disorders (DIPD-IV; Zanarini, Frankenburg, Sickel & Yong, 1996) over two years in a sample of 529 CLPS participants. Specifically, we compared dimensional and categorical representations from both measures in terms of rank-order and mean-level stability. Results indicated that the dimensional scores from the self-report questionnaire had significantly greater rank order (mean r = .69 versus .59) and mean-level (mean d = .21 versus .30) stability. In contrast, categorical diagnoses from the two measures evinced comparable rank-order (mean kappa = .38 versus .37) and mean-level stability (median prevalence rate decrease of 3.5% versus 5.6%). These findings suggest the stability of PD constructs depends at least partially on the method of assessment and are discussed in the context of previous research and future conceptualizations of personality pathology. PMID:21443287

  2. Stabilization of Enzymes against Thermal Stress and Freeze-Drying by Mannosylglycerate

    PubMed Central

    Ramos, A.; Raven, N.; Sharp, R. J.; Bartolucci, S.; Rossi, M.; Cannio, R.; Lebbink, J.; Van Der Oost, J.; De Vos, W. M.; Santos, H.

    1997-01-01

    2-O-(beta)-Mannosylglycerate, a solute that accumulates in some (hyper)thermophilic organisms, was purified from Pyrococcus furiosus cells, and its effect on enzyme stabilization in vitro was assessed. Enzymes from hyperthermophilic, thermophilic, and mesophilic sources were examined. The thermostabilities of alcohol dehydrogenases from P. furiosus and Bacillus stearothermophilus and of glutamate dehydrogenases from Thermotoga maritima and Clostridium difficile were improved to a significant extent when enzyme solutions were incubated at supraoptimal temperatures in the presence of 2-O-(beta)-mannosylglycerate, but no effect on the thermostability of glutamate dehydrogenase from P. furiosus was detected. On the other hand, there was a remarkable effect on the thermal stabilities of rabbit muscle lactate dehydrogenase, baker's yeast alcohol dehydrogenase, and bovine liver glutamate dehydrogenase, which were used as model systems to evaluate stabilization of enzymes of mesophilic origin. For all of the enzymes examined and at the highest temperatures tested, 2-O-(beta)-mannosylglycerate was a better thermoprotectant than trehalose. The stabilizing effect exerted by 2-O-(beta)-mannosylglycerate on enzymes suggests a role for this compound as a protein thermostabilizer under physiological conditions. 2-O-(beta)-Mannosylglycerate was also effective in the protection of enzymes against stress imposed by freeze-drying, with its protecting effect being similar to or better than that exerted by trehalose. The data show 2-O-(beta)-mannosylglycerate to be a potential enzyme stabilizer in biotechnological applications. PMID:16535713

  3. High-throughput screening of formulations to optimize the thermal stability of a therapeutic monoclonal antibody.

    PubMed

    Niedziela-Majka, Anita; Kan, Elaine; Weissburg, Perry; Mehra, Upasana; Sellers, Scott; Sakowicz, Roman

    2015-04-01

    Monoclonal antibodies (mAbs) are an important class of biotherapeutics. Successful development of a mAb depends not only on its biological activity but also on its physicochemical properties, such as homogeneity and stability. mAb stability is affected by its formulation. Among the many techniques used to study the stability of mAbs, differential scanning fluorimetry (DSF) offers both excellent throughput and minimal material consumption. DSF measures the temperature of the protein unfolding transition (Tm) based on the change in fluorescence intensity of the environmentally sensitive dye SYPRO Orange. With DSF adapted to a 96-well plate format, we have shown that low-pH or high-salt concentrations decrease the thermal stability of mAb1, whereas some excipients, such as sucrose, polysorbate 80, and sodium phosphate, increase its stability. The basal fluorescence of SYPRO Orange was enhanced by the presence of detergents, limiting the use of this approach to diluted detergent solutions. Throughput of DSF can be increased further with the use of a 384-well plate. DSF thermograms are in good agreement with the melting profiles obtained by differential scanning calorimetry (DSC). The Tms determined by DSF and DSC were well correlated, with the former being on average lower by 3 °C. PMID:25385011

  4. Studies on chalcone derivatives: Complex formation, thermal behavior, stability constant and antioxidant activity

    NASA Astrophysics Data System (ADS)

    El-Sayed, Yusif S.; Gaber, M.

    2015-02-01

    The chalcone 3-[4‧-dimethylaminophenyl]-1-(2-pyridyl) prop-2-en-1-one (DMAPP) and 3-(4‧-diethylaminophenyl)-1-(2-pyridinyl) prop-2-en-1-one abbreviated as DEAPP have been synthesized and characterized with IR, 1H NMR, 13C NMR spectroscopic techniques as described previously (El-Daly et al., 2008; Gaber et al., 2009; El-Sayed, 2013). By using UV visible spectroscopy method the mole fraction ratio for copper with DMAPP and DEAPP complexes were determined and it was found to be 1:1. The stability constants of this complex have been determined by Job's method. The stability constant (Kf) of copper with DMAPP and DEAPP complexes in universal buffer pH = 3.2 was determined to be 9.9 × 104 and 5.2 × 104 respectively. The effect of Cu(II) ion on the emission spectrum of the free chalcone is also assigned. Adherence to Beer's law and Ringbom optimum concentration ranges are determined. The thermal decomposition of the metal complexes is studied by TGA technique. The kinetic parameters like activation energy, pre-exponential factor and entropy of activation are estimated. The structure of complexes was energetically optimized through molecular mechanics applying MM+ force field coupled with molecular dynamics simulation. The bond lengths and bond angles have been calculated to confirm the geometry of the ligands and their Cu(II) complexes. The mode of interaction of the chalcone to copper nanoparticles was studied. The apparent association constants of the colloidal copper nanoparticles:chalcone complexes in solution were evaluated using the spectral method and compared with the formation constant of the Cu(II) chalcone complexes. Antioxidant activity of these chalcones was evaluated by using 1,1‧-diphenyl-2-picrylhydrazyl (DPPHrad) radicals scavenging method, which showed that the antioxidant activity of DMAPP has higher value than the DEAPP. Semi-empirical study results showed that DMAPP have higher dipole moment than DEAPP [1].

  5. Thermal stabilization of multimeric proteins: a case study with alpha-globulin.

    PubMed

    Radha, C; Muralidhara, B K; Kumar, P R; Tasneem, R; Prakash, V

    1998-04-01

    Preferential interaction parameters of multisubunit protein, alpha-globulin and monomeric protein human serum albumin (HSA) were determined in different cosolvents using precision densitymetry. The apparent partial specific volumes were determined under both isomolal and isopotential conditions for alpha-globulin in 0.02 M glycine-NaOH buffer at pH 10 and the values were 0.692+/-0.002 and 0.688+/-0.001, ml/g, respectively, at 20.00+/-0.01 degrees C. From the partial specific volume data with cosolvents the preferential interaction parameter (xi3) and other thermodynamic parameters were calculated at different solvent concentrations. The (xi3) values increased with an increase in the solvent concentration up to 30% and reached a maximum with the values of-0.111+/-0.018 g/g and -0.076+/-0.012 g/g in sucrose and sorbitol, respectively. In glycerol the (xi3) values decreased with an increase in solvent concentration. The above data is further supported by thermal denaturation profiles in which the apparent thermal denaturation temperature (apparent Tm) of alpha-globulin shows an increase from 63 degrees C to higher temperatures in the order of sucrose, sorbitol and glycerol. Alpha-globulin showed coagulation due to protein interaction at temperatures above 50 degree C. The apparent Tm of 63 degrees C for control protein was increased significantly up to 75 degrees C in 40% sorbitol with two fold increase in the delta(S) values showing the increased structural stability of alpha-globulin. At high solvent concentration the protein gets dissociated and the resultant monomers are hydrated which was evident by fluorescence data and the difference spectral results with a 6nm red shift in the emission maximum and 2 nm blue shift in UV-absorption maximum arising out of perturbation of aromatic chromophores. The studies were performed both at native pH of 7.9 where the protein is in its oligomeric form and at pH of 10 where it is dissociated form and the results compared. The

  6. Hot corrosion and high-temperature deformation of yttria-stabilized zirconia thermal barrier coatings

    NASA Astrophysics Data System (ADS)

    Chen, Zun

    The effect of V2O5 melt infiltration on the phase stability, thermal and mechanical properties of plasma-sprayed 7 wt% Y 2O3-ZrO2 (YSZ) was assessed by infiltration experiments at temperatures of 750°-1200°. Based on SEM and TEM observations combined with EDS, reactions between molten V2O'5 and YSZ were found to occur concomitantly with the infiltration process at all temperatures investigated. Near the surface, the reaction front proceeds in a planar fashion presumably via dissolution and precipitation, while the V2O5 melt infiltrates along the interconnected pores and reacts with the YSZ deep inside the coating. Typically, two different morphologies could be distinguished in the cross-section of the infiltrated coating that corresponds to the planar reacted zone (PRZ) and the melt infiltrated reaction zone (MIRZ). PRZ is a fine-grained surface reacted region where the vanadium concentration is higher or comparable to the yttrium concentration and MIRZ is a dense infiltrated region which displays abrupt vanadium concentration changes along the thickness direction. Temperature as well as morphological parameters, such as pore size and connectivity, was found to influence the dissolution/infiltration kinetics. In-situ XRD was employed to clarify the reaction mechanism between V 2O5 melt and YSZ. Concurrent formation of zirconium vanadate and yttrium vanadate were observed at 700°C and 750°C, suggesting a similar reactivity of yttrium and zirconia with vanadium oxide. The zirconium vanadate phase decomposed subsequently after 150 and 60 minutes at 700° and 750°C, respectively. The t'-ZrO2 phase transformed to a monoclinic phase through the formation of ZrV2O7, without gradually losing yttrium in t'-ZrO2 or partitioning into a cubic zirconia phase as previously thought. Therefore, zirconia-based ceramics have very limited resistance to vanadium oxide because of the zirconia. The Johnson-Mehl-Avrami (JMA) analysis based on the in-situ X-ray results at

  7. Metabolic rate, latitude and thermal stability of roosts, but not phylogeny, affect rewarming rates of bats.

    PubMed

    Menzies, Allyson K; Webber, Quinn M R; Baloun, Dylan E; McGuire, Liam P; Muise, Kristina A; Coté, Damien; Tinkler, Samantha; Willis, Craig K R

    2016-10-01

    Torpor is an adaptation that allows many endotherms to save energy by abandoning the energetic cost of maintaining elevated body temperatures. Although torpor reduces energy consumption, the metabolic heat production required to arouse from torpor is energetically expensive and can impact the overall cost of torpor. The rate at which rewarming occurs can impact the cost of arousal, therefore, factors influencing rewarming rates of heterothermic endotherms could have influenced the evolution of rewarming rates and overall energetic costs of arousal from torpor. Bats are a useful taxon for studies of ecological and behavioral correlates of rewarming rate because of the widespread expression of heterothermy and ecological diversity across the >1200 known species. We used a comparative analysis of 45 bat species to test the hypothesis that ecological, behavioral, and physiological factors affect rewarming rates. We used basal metabolic rate (BMR) as an index of thermogenic capacity, and local climate (i.e., latitude of geographic range), roost stability and maximum colony size as ecological and behavioral predictors of rewarming rate. After controlling for phylogeny, high BMR was associated with rapid rewarming while species that live at higher absolute latitudes and in less thermally stable roosts also rewarmed most rapidly. These patterns suggests that some bat species rely on passive rewarming and social thermoregulation to reduce costs of rewarming, while others might rely on thermogenic capacity to maintain rapid rewarming rates in order to reduce energetic costs of arousal. Our results highlight species-specific traits associated with maintaining positive energy balance in a wide range of climates, while also providing insight into possible mechanisms underlying the evolution of heterothermy in endotherms. PMID:27317837

  8. Earthworms facilitate carbon sequestration through unequal amplification of carbon stabilization compared with mineralization

    NASA Astrophysics Data System (ADS)

    Zhang, Weixin; Hendrix, Paul F.; Dame, Lauren E.; Burke, Roger A.; Wu, Jianping; Neher, Deborah A.; Li, Jianxiong; Shao, Yuanhu; Fu, Shenglei

    2013-10-01

    A recent review concluded that earthworm presence increases CO2 emissions by 33% but does not affect soil organic carbon stocks. However, the findings are controversial and raise new questions. Here we hypothesize that neither an increase in CO2 emission nor in stabilized carbon would entirely reflect the earthworms’ contribution to net carbon sequestration. We show how two widespread earthworm invaders affect net carbon sequestration through impacts on the balance of carbon mineralization and carbon stabilization. Earthworms accelerate carbon activation and induce unequal amplification of carbon stabilization compared with carbon mineralization, which generates an earthworm-mediated ‘carbon trap’. We introduce the new concept of sequestration quotient to quantify the unequal processes. The patterns of CO2 emission and net carbon sequestration are predictable by comparing sequestration quotient values between treatments with and without earthworms. This study clarifies an ecological mechanism by which earthworms may regulate the terrestrial carbon sink.

  9. Surface thermal stability of free-standing GaN substrates

    NASA Astrophysics Data System (ADS)

    Okada, Shunsuke; Miyake, Hideto; Hiramatsu, Kazumasa; Miyagawa, Reina; Eryu, Osamu; Hashizume, Tamotsu

    2016-01-01

    The thermal stability of GaN surfaces was investigated with respect to homo-epitaxy on free-standing GaN substrates. Morphologies and etching rates of the GaN surfaces for free-standing polar (0001), nonpolar (10\\bar{1}0), and semipolar (20\\bar{2}1) and (20\\bar{2}\\bar{1}) planes were studied before and after thermal cleaning. In the case of the polar (0001) plane, polishing scratches disappeared after thermal cleaning at temperatures above 1000 °C. The surface morphology depended on not only the cleaning temperature, but also the substrate off-angle. The surface after thermal cleaning became rough for the substrate with off-angle less than 0.05°. In the case of nonpolar and semipolar planes after thermal cleaning, surface morphologies and etching rates were strongly dependent on the planes. A flat surface was maintained at cleaning temperatures up to 1100 °C for the (10\\bar{1}0) plane, but the surface of the (20\\bar{2}1) plane became rough with increasing cleaning temperature.

  10. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    DOE PAGESBeta

    Patel, Mogon; Pitts, Simon; Beavis, Peter; Robinson, Mathew; Morrell, Paul; Khan, Niaz; Khan, Imran; Pockett, Nicola; Letant, Sonia; Von White, Gregory; et al

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageingmore » induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.« less

  11. Thermal stability of poly(ethylene-co-vinyl acetate) based materials

    SciTech Connect

    Patel, Mogon; Pitts, Simon; Beavis, Peter; Robinson, Mathew; Morrell, Paul; Khan, Niaz; Khan, Imran; Pockett, Nicola; Letant, Sonia; Von White, Gregory; Labouriau, Andrea

    2013-03-26

    The thermal stability properties of poly (ethylene-co-vinyl acetate) composites have been studied in support of our core programmes in materials qualification and life assessment. The material is used as a binder phase for boron particles in highly filled (70 wt %) composites. Our studies show that the uncured resin readily accumulates acetic acid through hydrolysis of the pendent acetate groups which alters the acidity (pH) of the material. Thermal desorption studies in combination with gas-chromatography-mass spectrometry show that the resin readily evolves acetic acid when thermally aged to temperatures up to 75°C. Gel Permeation Chromatography (GPC) suggests that thermal ageing induces a gradual reduction in resin molecular weight and confirms the susceptibility of the material to chain scission. Heating at elevated temperatures in excess of 300oC is required to induce significant changes in the carbon skeleton through deacetylation and dehydration processes and the production of unsaturated main chain double bonds. Overall, the mechanical response of these filled composites are found to be relatively complex with the extent of polymer-filler interactions possibly playing an important role in determining key engineering properties. Mechanical property studies confirm a small but significant decrease in modulus presumably linked to thermally induced chain scission of the EVA binder.

  12. Thermal Conductivity and Water Vapor Stability of HfO2-based Ceramic Coating Materials

    NASA Technical Reports Server (NTRS)

    Zhu, Dongming; Fox, Dennis S.; Bansal, Narottam P.; Miller, Robert A.

    2004-01-01

    HfO2-Y2O3 and La2Zr2O7 are candidate thermal/environmental barrier coating materials for gas turbine ceramic matrix composite (CMC) combustor liner applications because of their relatively low thermal conductivity and high temperature capability. In this paper, thermal conductivity and high temperature phase stability of plasma-sprayed coatings and/or hot-pressed HfO2-5mol%Y2O3, HfO2- 15mol%Y2O3 and La2Zr2O7 were evaluated at temperatures up to 1700 C using a steady-state laser heat-flux technique. Sintering behavior of the plasma-sprayed coatings was determined by monitoring the thermal conductivity increases during a 20-hour test period at various temperatures. Durability and failure mechanisms of the HfO2-Y2O3 and La2Zr2O7 coatings on mullite/SiC Hexoloy or CMC substrates were investigated at 1650 C under thermal gradient cyclic conditions. Coating design and testing issues for the 1650 C thermaVenvironmenta1 barrier coating applications will also be discussed.

  13. International Comparative Evaluation of Knee Replacement with Fixed or Mobile Non-Posterior-Stabilized Implants

    PubMed Central

    Namba, Robert; Graves, Stephen; Robertsson, Otto; Furnes, Ove; Stea, Susanna; Puig-Verdié, Lluis; Hoeffel, Daniel; Cafri, Guy; Paxton, Elizabeth; Sedrakyan, Art

    2014-01-01

    Background: Mobile-bearing total knee prostheses were designed to reduce wear and improve implant survivorship following total knee arthroplasty. However, the benefit of mobile-bearing total knee arthroplasty remains unproven. Both mobile-bearing and fixed-bearing total knee arthroplasty implants are available in posterior-stabilized and non-posterior-stabilized designs. With the latter, the implant does not recreate the function of the posterior cruciate ligament (PCL) with a posterior-stabilizing cam mechanism. The purpose of the present study was to compare mobile-bearing, non-posterior-stabilized devices with fixed-bearing, non-posterior-stabilized devices used in total knee arthroplasty through a novel multinational study design. Methods: Through the use of a distributed health data network, primary total knee arthroplasties performed for osteoarthritis from 2001 to 2010 were identified from six national and regional total joint arthroplasty registries. Multivariate meta-analysis was performed with use of linear mixed models, with the primary outcome of interest being revision for any reason. Survival probabilities and their standard errors were extracted from each registry for each unique combination of the covariates. Results: A total of 319,616 patients (60% female) underwent non-posterior-stabilized total knee arthroplasty. A fixed-bearing, non-posterior-stabilized design was used in 258,190 (81%) of the knees and a mobile-bearing, non-posterior-stabilized design in 61,426 (19%) of the knees. Sixty-nine percent of the patients who received a fixed-bearing implant were over sixty-five years of age, compared with 63% of those who received a mobile-bearing implant. Mobile-bearing designs had a higher risk of revision, with a hazard ratio of 1.43 (95% confidence interval, 1.36 to 1.51; p < 0.001). Conclusions: Previous comparisons of mobile-bearing and fixed-bearing total knee arthroplasty outcomes have been inconclusive. The current study utilized an advanced

  14. Effects of thermal manipulations during embryogenesis of broiler chickens on developmental stability, hatchability and chick quality.

    PubMed

    Narinç, D; Erdoğan, S; Tahtabiçen, E; Aksoy, T

    2016-08-01

    Stress based on high temperature and humidity reduces the production performance of fast-growing broilers and causes high mortality. Temperatures higher than optimum have been applied to broilers in the embryonic period in order to overcome thermal stress. This study was conducted to investigate the effects of exposure to two long-term high-thermal environments on the developmental stability of embryonic growth, hatchability and chick quality. For this purpose, 600 broiler eggs were incubated. Treatments consisted of eggs incubated at 37.8°C at 55% relative humidity throughout (control), heated to 39.6°C at 60% relative humidity for 6 h daily from 0 to 8th day, and heated to 39.6°C at 60% relative humidity for 6 h daily from the 10 to 18th day. Embryo weights and lengths of face, wing, femur, tibia and metatarsus were measured daily between the 10th and 21st day of the experiment. Daily relative asymmetry values of bilateral traits were estimated. The hatchability, the weight of the 1-day-old chicks and chick quality were determined. In conclusion, no negative effects of the treatments of the long-term high-thermal environment in the early and late stages of incubation for epigenetic adaptation were determined on the embryo morphology, development stability and weight of the chick. Moreover, regressed hatchability of embryos that were exposed to a long-term high-thermal environment was detected. Especially between the 10 and 18th day, the thermal manipulation considerably reduced the quality of the chicks. Acclimation treatments of high temperature on the eggs from cross-breeding flocks should not be made long term; instead, short-term treatments should be made by determining the stage that generates epigenetic adaptation. PMID:26932726

  15. Synthesis, thermal stability and reactivity towards 9-aminoellipticine of double-stranded oligonucleotides containing a true abasic site.

    PubMed Central

    Bertrand, J R; Vasseur, J J; Rayner, B; Imbach, J L; Paoletti, J; Paoletti, C; Malvy, C

    1989-01-01

    A 13 mers abasic oligonucleotide was synthetized. It was therefore possible to compare thermal stability and reactivity of duplex oligonucleotides either with an apurinic/apyrimidinic site or without any lesion. An important decrease in the melting temperature appeared for duplexes with an abasic site. The chemical reaction of these modified oligonucleotides with the intercalating agent 9-aminoellipticine was studied by gel electrophoresis and by fluorescence. The formation of a Schiff base between 9-aminoellipticine and abasic sites was rapid and complete with duplexes at 11 degrees C. Schiff base related fluorescence and beta-elimination cleavage were more important with the apyrimidinic sites than with the apurinic ones. When compared to previous results obtained with the model d(TprpT) some unexpected behaviours appeared with longer and duplex oligonucleotides. For instance only partial beta-elimination cleavage was observed. It is likely that stacking parameters in the double helix play a great role in the studied reaction. Images PMID:2602153

  16. The stability analysis of magnetohydrodynamic equilibria - Comparing the thermodynamic approach with the energy principle

    NASA Technical Reports Server (NTRS)

    Brinkmann, R. P.

    1989-01-01

    This paper is a contribution to the stability analysis of current-carrying plasmas, i.e., plasma systems that are forced by external mchanisms to carry a nonrelaxing electrical current. Under restriction to translationally invariant configurations, the thermodynamic stability criterion for a multicomponent plasma is rederived within the framework of nonideal MHD. The chosen dynamics neglects scalar resistivity, but allows for other types of dissipation effects both in Ohm's law and in the equation of motion. In the second section of the paper, the thermodynamic stability criterion is compared with the ideal MHD based energy principle of Bernstein et al. With the help of Schwarz's inequality, it is shown that the former criterion is always more 'pessimistic' than the latter, i.e., that thermodynamic stability implies stability according to the MHD principle, but not vice versa. This reuslt confirms the physical plausible idea that dissipational effects tend to weaken the stability properties of current-carrying plasma equilibria by breaking the constraints of ideal MHD and allowing for possibly destabilizing effects such as magnetic field line reconfiguration.

  17. Novel LLM series high density energy materials: Synthesis, characterization, and thermal stability

    NASA Astrophysics Data System (ADS)

    Pagoria, Philip; Zhang, Maoxi; Tsyshevskiy, Roman; Kuklja, Maija

    Novel high density energy materials must satisfy specific requirements, such as an increased performance, reliably high stability to external stimuli, cost-efficiency and ease of synthesis, be environmentally benign, and be safe for handling and transportation. During the last decade, the attention of researchers has drifted from widely used nitroester-, nitramine-, and nitroaromatic-based explosives to nitrogen-rich heterocyclic compounds. Good thermal stability, the low melting point, high density, and moderate sensitivity make heterocycle materials attractive candidates for use as oxidizers in rocket propellants and fuels, secondary explosives, and possibly as melt-castable ingredients of high explosive formulations. In this report, the synthesis, characterization, and results of quantum-chemical DFT study of thermal stability of LLM-191, LLM-192 and LLM-200 high density energy materials are presented. Work performed under the auspices of the DOE by the LLNL (Contract DE-AC52-07NA27344). This research is supported in part by ONR (Grant N00014-12-1-0529) and NSF. We used NSF XSEDE (Grant DMR-130077) and DOE NERSC (Contract DE-AC02-05CH11231) resources.

  18. Effect of Hofmeister ions on protein thermal stability: roles of ion hydration and peptide groups?

    PubMed

    Sedlák, Erik; Stagg, Loren; Wittung-Stafshede, Pernilla

    2008-11-01

    We have systematically explored the Hofmeister effects of cations and anions (0.3-1.75 M range) for acidic Desulfovibrio desulfuricans apoflavodoxin (net charge -19, pH 7) and basic horse heart cytochrome c (net charge +17, pH 4.5). The Hofmeister effect of the ions on protein thermal stability was assessed by the parameter dT trs/d[ion] (T trs; thermal midpoint). We show that dT trs/d[ion] correlates with ion partition coefficients between surface and bulk water and ion surface tension effects: this suggests direct interactions between ions and proteins. Surprisingly, the stability effects of the different ions on the two model proteins are similar, implying a major role of the peptide backbone, instead of charged groups, in mediation of the interactions. Upon assessing chemical/physical properties of the ions responsible for the Hofmeister effects on protein stability, ion charge density was identified as most important. Taken together, our study suggests key roles for ion hydration and the peptide group in facilitating interactions between Hofmeister ions and proteins. PMID:18782555

  19. A linear stability analysis for nonlinear, grey, thermal radiative transfer problems

    SciTech Connect

    Wollaber, Allan B.; Larsen, Edward W.

    2011-02-20

    We present a new linear stability analysis of three time discretizations and Monte Carlo interpretations of the nonlinear, grey thermal radiative transfer (TRT) equations: the widely used 'Implicit Monte Carlo' (IMC) equations, the Carter Forest (CF) equations, and the Ahrens-Larsen or 'Semi-Analog Monte Carlo' (SMC) equations. Using a spatial Fourier analysis of the 1-D Implicit Monte Carlo (IMC) equations that are linearized about an equilibrium solution, we show that the IMC equations are unconditionally stable (undamped perturbations do not exist) if {alpha}, the IMC time-discretization parameter, satisfies 0.5 < {alpha} {<=} 1. This is consistent with conventional wisdom. However, we also show that for sufficiently large time steps, unphysical damped oscillations can exist that correspond to the lowest-frequency Fourier modes. After numerically confirming this result, we develop a method to assess the stability of any time discretization of the 0-D, nonlinear, grey, thermal radiative transfer problem. Subsequent analyses of the CF and SMC methods then demonstrate that the CF method is unconditionally stable and monotonic, but the SMC method is conditionally stable and permits unphysical oscillatory solutions that can prevent it from reaching equilibrium. This stability theory provides new conditions on the time step to guarantee monotonicity of the IMC solution, although they are likely too conservative to be used in practice. Theoretical predictions are tested and confirmed with numerical experiments.

  20. Thermal stability and binding energetics of thymidylate synthase ThyX.

    PubMed

    Krumova, Sashka; Todinova, Svetla; Tileva, Milena; Bouzhir-Sima, Latifa; Vos, Marten H; Liebl, Ursula; Taneva, Stefka G

    2016-10-01

    The bacterial thymidylate synthase ThyX is a multisubstrate flavoenzyme that takes part in the de novo synthesis of thymidylate in a variety of microorganisms. Herein we study the effect of FAD and dUMP binding on the thermal stability of wild type (WT) ThyX from the mesophilic Paramecium bursaria chlorella virus-1 (PBCV-1) and from the thermophilic bacterium Thermotoga maritima (TmThyX), and from two variants of TmThyX, Y91F and S88W, using differential scanning calorimetry. The energetics underlying these processes was characterized by isothermal titration calorimetry. The PBCV-1 protein is significantly less stable against the thermal challenge than the TmThyX WT. FAD exerted stabilizing effect greater for PBCV-1 than for TmThyX and for both mutants, whereas binding of dUMP to FAD-loaded proteins stabilized further only TmThyX. Different thermodynamic signatures describe the FAD binding to the WT ThyX proteins. While TmThyX binds FAD with a low μM binding affinity in a process characterized by a favorable entropy change, the assembly of PBCV-1 with FAD is governed by a large enthalpy change opposed by an unfavorable entropy change resulting in a relatively strong nM binding. An enthalpy-driven formation of a high affinity ternary ThyX/FAD/dUMP complex was observed only for TmThyX. PMID:27268384

  1. Mg-based multilayers and their thermal stabilities for EUV range

    NASA Astrophysics Data System (ADS)

    Zhu, Jingtao; Zhou, Sika; Li, Haochuan; Huang, Qiushi; Jiang, Li; Wang, Fengli; Zhang, Zhong; Wang, Zhanshan; Zhou, Hongjun; Huo, Tonglin

    2011-09-01

    We have investigated the optical properties and thermal stabilities of a serial of Mg-based multilayers including Mg/SiC, Mg/Co and Mg/Zr in extreme ultraviolet (EUV) range. Mg/X multilayer mirrors were deposited by magnetron sputtering technique onto polished silicon wafers. In order to study their stabilities under heat resistance, annealing experiments were carried out in vacuum environment keeping 1hour at different temperatures from 200°C to 550°C. Their EUV reflectivities were measured by using synchrotron radiation. Grazing incident X-ray and EUV reflection measurements were used to estimate the thermal stability of these multilayer systems. Mg/SiC and Mg/Co are stable up to 200°C and the reflectivity decreases drastically with the increase of temperature, while the reflectivity of Mg/Zr keeps constant during annealing at 300°C and falls slowly as the temperature increases. Up to 550°C, Bragg peaks of Mg/Zr multilayer are still sharp in X-ray reflectivity curve, and EUV reflectivity is 25% at 26.2nm at 30 degree incidence. These measurement results indicate that Mg/Co and Mg/SiC should be used in application requiring no heating above 200°C, while the new material combination Mg/Zr is a promising multilayer for practical application requiring stronger heat resistance in EUV range.

  2. Diffusion mechanism and the thermal stability of fluorine ions in GaN after ion implantation

    SciTech Connect

    Wang, M. J.; Yuan, L.; Chen, K. J.; Xu, F. J.; Shen, B.

    2009-04-15

    The diffusion mechanisms of fluorine ions in GaN are investigated by means of time-of-flight secondary ion mass spectrometry. Instead of incorporating fluorine ions close to the sample surface by fluorine plasma treatment, fluorine ion implantation with an energy of 180 keV is utilized to implant fluorine ions deep into the GaN bulk, preventing the surface effects from affecting the data analysis. It is found that the diffusion of fluorine ions in GaN is a dynamic process featuring an initial out-diffusion followed by in- diffusion and the final stabilization. A vacancy-assisted diffusion model is proposed to account for the experimental observations, which is also consistent with results on molecular dynamic simulation. Fluorine ions tend to occupy Ga vacancies induced by ion implantation and diffuse to vacancy rich regions. The number of continuous vacancy chains can be significantly reduced by a dynamic thermal annealing process. As a result, strong local confinement and stabilization of fluorine ions can be obtained in GaN crystal, suggesting excellent thermal stability of fluorine ions for device applications.

  3. A highly efficient silole-containing dithienylethene with excellent thermal stability and fatigue resistance: a promising candidate for optical memory storage materials.

    PubMed

    Chan, Jacky Chi-Hung; Lam, Wai Han; Yam, Vivian Wing-Wah

    2014-12-10

    Diarylethene compounds are potential candidates for applications in optical memory storage systems and photoswitchable molecular devices; however, they usually show low photocycloreversion quantum yields, which result in ineffective erasure processes. Here, we present the first highly efficient photochromic silole-containing dithienylethene with excellent thermal stability and fatigue resistance. The photochemical quantum yields for photocyclization and photocycloreversion of the compound are found to be high and comparable to each other; the latter of which is rarely found in diarylethene compounds. These would give rise to highly efficient photoswitchable material with effective writing and erasure processes. Incorporation of the silole moiety as a photochromic dithienylethene backbone also was demonstrated to enhance the thermal stability of the closed form, in which the thermal backward reaction to the open form was found to be negligible even at 100 °C, which leads to a promising candidate for use as photoswitchable materials and optical memory storage. PMID:25427229

  4. Increased functional properties and thermal stability of flexible cellulose nanocrystal/ZnO films.

    PubMed

    Lizundia, E; Urruchi, A; Vilas, J L; León, L M

    2016-01-20

    In this work we attempt to improve the functional properties and thermal stability of cellulose nanocrystal (CNC) films by means of eco-friendly materials and processes. Mechanically flexible films of closely packed CNCs with concentrations up to 5 wt.% of zinc oxide (ZnO) nanoparticles have been prepared by a simple, standard and environmentally friendly method using solely water. Results reveal that ultraviolet light is blocked by 98.5% at 1 wt.% ZnO while good transparency is maintained. A sharp hydrophobicity increase is observed with the addition of ZnO which would enhance the durability of films by decreasing the water diffusion through the material. The thermal degradation activation energy (E) presents an increase of 141%, denoting a high thermal stability of films, which would result beneficial for their potential application in the field of flexible electronics. Mechanical results demonstrate a high structural integrity of CNC/ZnO as a result of the occurring strong cellulosic inter- and intramolecular interactions within the closely packed CNC network. In overall, this work highlights the potential for environmentally friendly processing of sustainable nanostructured functional materials based on cellulose. PMID:26572353

  5. RP-2 Thermal Stability and Heat Transfer Investigation for Hydrocarbon Boost Engines

    NASA Technical Reports Server (NTRS)

    VanNoord, J. L.; Stiegemeier, B. R.

    2010-01-01

    A series of electrically heated tube tests were performed at the NASA Glenn Research Center s Heated Tube Facility to investigate the use of RP-2 as a fuel for next generation regeneratively cooled hydrocarbon boost engines. The effect that test duration, operating condition and test piece material have on the overall thermal stability and materials compatibility characteristics of RP-2 were evaluated using copper and 304 stainless steel test sections. The copper tests were run at 1000 psia, heat flux up to 6.0 Btu/in.2-sec, and wall temperatures up to 1180 F. Preliminary results, using measured wall temperature as an indirect indicator of the carbon deposition process, show that in copper test pieces above approximately 850 F, RP-2 begins to undergo thermal decomposition resulting in local carbon deposits. Wall temperature traces show significant local temperature increases followed by near instantaneous drops which have been attributed to the carbon deposition/shedding process in previous investigations. Data reduction is currently underway for the stainless steel test sections and carbon deposition measurements will be performed in the future for all test sections used in this investigation. In conjunction with the existing thermal stability database, these findings give insight into the feasibility of cooling a long life, high performance, high-pressure liquid rocket combustor and nozzle with RP-2.

  6. Innovative hybrid optics: combining the thermal stability of glass with low manufacturing cost of polymers

    NASA Astrophysics Data System (ADS)

    Doushkina, Valentina

    2010-08-01

    Innovative hybrid glass-polymer optical solutions on a component, module, or system level offer thermal stability of glass with low manufacturing cost of polymers reducing component weight, enhancing the safety and appeal of the products. Narrow choice of polymer materials is compensated by utilizing sophisticated optical surfaces such as refractive, reflective, and diffractive substrates with spherical, aspherical, cylindrical, and freeform prescriptions. Current advancements in polymer technology and injection molding capabilities placed polymer optics in the heart of many high tech devices and applications including Automotive Industry, Defense & Aerospace; Medical/Bio Science; Projection Displays, Sensors, Information Technology, Commercial and Industrial. This paper is about integration of polymer and glass optics for enhanced optical performance with reduced number of components, thermal stability, and low manufacturing cost. The listed advantages are not achievable when polymers or glass optics are used as stand-alone. The author demonstrates that integration of polymer and glass on component or optical system level on one hand offers high resolution and diffraction limited image quality, similar to the glass optics with stable refractive index and stable thermal performance when design is athermalized within the temperature range. On the other hand, the integrated hybrid solution significantly reduces cost, weight, and complexity, just like the polymer optics. The author will describe the design and analyzes process of combining glass and polymer optics for variety of challenging applications such as fast optics with low F/#, wide field of view lenses or systems, free form optics, etc.

  7. Thermal Design to Meet Stringent Temperature Gradient/Stability Requirements of SWIFT BAT Detectors

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2000-01-01

    The Burst Alert Telescope (BAT) is an instrument on the National Aeronautics and Space Administration (NASA) SWIFT spacecraft. It is designed to detect gamma ray burst over a broad region of the sky and quickly align the telescopes on the spacecraft to the gamma ray source. The thermal requirements for the BAT detector arrays are very stringent. The maximum allowable temperature gradient of the 256 cadmium zinc telluride (CZT) detectors is PC. Also, the maximum allowable rate of temperature change of the ASICs of the 256 Detector Modules (DMs) is PC on any time scale. The total power dissipation of the DMs and Block Command & Data Handling (BCDH) is 180 W. This paper presents a thermal design that uses constant conductance heat pipes (CCHPs) to minimize the temperature gradient of the DMs, and loop heat pipes (LHPs) to transport the waste heat to the radiator. The LHPs vary the effective thermal conductance from the DMs to the radiator to minimize heater power to meet the heater power budget, and to improve the temperature stability. The DMs are cold biased, and active heater control is used to meet the temperature gradient and stability requirements.

  8. Thermal stability of SF6 associated with metallic conductors incorporated in gas insulated switchgear power substations

    NASA Astrophysics Data System (ADS)

    Dervos, C. T.; Vassiliou, P.; Mergos, J. A.

    2007-11-01

    SF6 is generally treated as thermally stable and inert for applications below 500 °C. This work investigates the thermal stability of pure SF6 gas under 1.2 atm pressure between 200 and 450 °C in the presence of construction metals (Cu, Al), without any applied electric field. The obtained experimental results indicate that SF6 may react with metallic surfaces forming solid and gaseous by-products, either in the gas matrix or diffused in the metallic surfaces. The phenomenon is enhanced in the presence of adsorbed moisture. For copper surfaces, sulfide layers are formed. By-products are not formed for pure Al surfaces. However, when Al is covered by a few micrometres thick Al2O3 film, hot SF6 molecules have a structure change effect, i.e. reduce porosity in the oxide and in the substrate, provide smooth transition layers Al/Al2O3 and increase the Al2O3 layer width. In the presence of moisture this phenomenon is significantly intensified and a diffused overlayer of AlF3 also forms. The by-products in the gas matrix are mainly sulfur oxides for hot spot temperatures below 300 °C, while at higher temperatures oxyfluorides SO2Fx and HF are mainly formed. These by-products are either toxic or corrosive. Thus, the thermal stability issue of SF6 may have to be reconsidered.

  9. Silicate formation and thermal stability of ternary rare earth oxides as high-k dielectrics

    SciTech Connect

    Elshocht, S. van; Adelmann, C.; Conard, T.; Delabie, A.; Franquet, A.; Nyns, L.; Richard, O.; Lehnen, P.; Swerts, J.; Gendt, S. de

    2008-07-15

    Hf-based dielectrics are currently being introduced into complementary metal oxide semiconductor transistors as replacement for SiON to limit gate leakage current densities. Alternative materials such as rare earth based dielectrics are of interest to obtain proper threshold voltages as well as to engineer a material with a high thermal stability. The authors have studied rare earth based dielectrics such as Dy{sub 2}O{sub 3}, DyHfO{sub x}, DyScO{sub x}, La{sub 2}O{sub 3}, HfLaO{sub x}, and LaAlO{sub x} by means of ellipsometry, time of flight secondary ion mass spectroscopy x-ray diffraction, and x-ray photoelectron spectroscopy. The authors show that ellipsometry is an easy and powerful tool to study silicate formation. For ternary rare earth oxides, this behavior is heavily dependent on the composition of the deposited layer and demonstrates a nonlinear dependence. The system evolves to a stable composition that is controlled by the thermal budget and the rare earth content of the layer. It is shown that silicate formation can lead to a severe overestimation of the thermal stability of ternary rare earth oxides.

  10. Co-solvent mediated thermal stabilization of chondroitinase ABC I form Proteus vulgaris.

    PubMed

    Nazari-Robati, Mahdieh; Khajeh, Khosro; Aminian, Mahdi; Fathi-Roudsari, Mehrnoosh; Golestani, Abolfazl

    2012-04-01

    Chondroitinase ABC I (cABC I) from Proteus vulgaris cleaves glycosaminoglycan chains which are responsible for most of the inhibition of axon regrowth in spinal cord injury. The clinical utilization of this enzyme is mainly limited by its thermal instability. This study has been undertaken to determine the effects of glycerol, sorbitol and trehalose on cABC I activity and thermal stability. The results indicated that the enzyme catalytic activity and intrinsic fluorescence intensity increased in the presence of these cosolvents whereas no considerable conformational changes observed in far-UV CD spectra. Thermal CD experiment revealed an increase in T(m) of cABC I in the presence of cosolvents which was significant for trehalose. Our results support the idea that cABC I has stabilized in the presence of glycerol, sorbitol and trehalose. Therefore, the use of these cosolvents seems to be promising for improvement in shelf-life and clinical applications of this drug enzyme. PMID:22274395

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  12. Viscosity and thermal conductivity of nanofluids containing multi-walled carbon nanotubes stabilized by chitosan

    SciTech Connect

    Phuoc, Tran X.; Massoudi, Mehrdad; Chen, Ruey-Hung

    2011-01-01

    Thermal conductivity, viscosity, and stability of nanofluids containing multi-walled carbon nanotubes (MWCNTs) stabilized by cationic chitosan were studied. Chitosan with weight fraction of 0.1%, 0.2 wt%, and 0.5 wt% was used to disperse stably MWCNTs in water. The measured thermal conductivity showed an enhancement from 2.3% to 13% for nanofluids that contained from 0.5 wt% to 3 wt% MWCNTs (0.24 to 1.43 vol %). These values are significantly higher than those predicted using the Maxwell's theory. We also observed that the enhancements were independent of the base fluid viscosity. Thus, use of microconvection effect to explain the anomalous thermal conductivity enhancement should be reconsidered. MWCNTs can be used either to enhance or reduce the fluid base viscosity depending on the weight fractions. In the viscosity-reduction case, a reduction up to 20% was measured by this work. In the viscosity-enhancement case, the fluid behaved as a non-Newtonian shear-thinning fluid. By assuming that MWCNT nanofluids behave as a generalized second grade fluid where the viscosity coefficient depends upon the rate of deformation, a theoretical model has been developed. The model was found to describe the fluid behavior very well.

  13. Enhanced thermal- and photo-stability of acid yellow 17 by incorporation into layered double hydroxides

    SciTech Connect

    Wang Qian; Feng Yongjun; Feng Junting; Li Dianqing

    2011-06-15

    2,5-dichloro-4-(5-hydroxy-3-methyl-4-(sulphophenylazo) pyrazol-1-yl) benzenesulphonate (DHSB) anions, namely acid yellow 17 anions, have been successfully intercalated into Zn-Al layered double hydroxides (LDH) to produce a novel organic-inorganic pigment by a simple method involving separate nucleation and aging steps (SNAS), and the dye-intercalated LDH was analyzed by various techniques, e.g., XRD, SEM, FT-IR, TG-DTA and ICP. The d-spacing of the prepared LDH is 2.09 nm. Furthermore, the incorporation of the DHSB aims to enhance the thermal- and photo-stability of the guest dye molecule, for example, the less color change after accelerated thermal- and photo-aging test. - Graphical abstract: Acid yellow anions were successfully assembled into ZnAl layered double hydroxides (LDH) to produce a novel organic-inorganic composite pigment by a simple method involving separate nucleation and aging steps (SNAS). Highlights: > Acid yellow 17 was directly intercalated into ZnAl-LDH to form a novel pigment. > The pigment was prepared by a method involving separate nucleation and aging steps. > The intercalation of dye anions enhances its thermal- and photo-stability.

  14. Comparable Stability of Hoogsteen and Watson–Crick Base Pairs in Ionic Liquid Choline Dihydrogen Phosphate

    PubMed Central

    Tateishi-Karimata, Hisae; Nakano, Miki; Sugimoto, Naoki

    2014-01-01

    The instability of Hoogsteen base pairs relative to Watson–Crick base pairs has limited biological applications of triplex-forming oligonucleotides. Hydrated ionic liquids (ILs) provide favourable environments for a wide range of chemical reactions and are known to impact the stabilities of Watson–Crick base pairs. We found that DNA triplex formation was significantly stabilized in hydrated choline dihydrogen phosphate as compared with an aqueous buffer at neutral pH. Interestingly, the stability of Hoogsteen base pairs was found to be comparable with that of Watson–Crick base pairs in the hydrated IL. Molecular dynamics simulations of a DNA triplex in the presence of choline ions revealed that the DNA triplex was stabilized because of the binding of choline ion around the third strand in the grooves. Our finding will facilitate the development of new DNA materials. Our data also indicate that triplex formation may be stabilized inside cells where choline ions and their derivatives are abundant in vivo. PMID:24399194

  15. Comparable stability of Hoogsteen and Watson-Crick base pairs in ionic liquid choline dihydrogen phosphate.

    PubMed

    Tateishi-Karimata, Hisae; Nakano, Miki; Sugimoto, Naoki

    2014-01-01

    The instability of Hoogsteen base pairs relative to Watson-Crick base pairs has limited biological applications of triplex-forming oligonucleotides. Hydrated ionic liquids (ILs) provide favourable environments for a wide range of chemical reactions and are known to impact the stabilities of Watson-Crick base pairs. We found that DNA triplex formation was significantly stabilized in hydrated choline dihydrogen phosphate as compared with an aqueous buffer at neutral pH. Interestingly, the stability of Hoogsteen base pairs was found to be comparable with that of Watson-Crick base pairs in the hydrated IL. Molecular dynamics simulations of a DNA triplex in the presence of choline ions revealed that the DNA triplex was stabilized because of the binding of choline ion around the third strand in the grooves. Our finding will facilitate the development of new DNA materials. Our data also indicate that triplex formation may be stabilized inside cells where choline ions and their derivatives are abundant in vivo. PMID:24399194

  16. Tribological and thermal stability study of nanoporous amorphous boron carbide films prepared by pulsed plasma chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liza, Shahira; Ohtake, Naoto; Akasaka, Hiroki; Munoz-Guijosa, Juan M.

    2015-06-01

    In this work, the thermal stability and the oxidation and tribological behavior of nanoporous a-BC:H films are studied and compared with those in conventional diamond-like carbon (DLC) films. a-BC:H films were deposited by pulsed plasma chemical vapor deposition using B(CH3)3 gas as the boron source. A DLC interlayer was used to prevent the a-BC:H film delamination produced by oxidation. Thermal stability of a-BC:H films, with no delamination signs after annealing at 500 °C for 1 h, is better than that of the DLC films, which completely disappeared under the same conditions. Tribological test results indicate that the a-BC:H films, even with lower nanoindentation hardness than the DLC films, show an excellent boundary oil lubricated behavior, with lower friction coefficient and reduce the wear rate of counter materials than those on the DLC film. The good materials properties such as low modulus of elasticity and the formation of micropores from the original nanopores during boundary regimes explain this better performance. Results show that porous a-BC:H films may be an alternative for segmented DLC films in applications where severe tribological conditions and complex shapes exist, so surface patterning is unfeasible.

  17. Enhancement of thermal stability of chondroitinase ABC I by site-directed mutagenesis: an insight from Ramachandran plot.

    PubMed

    Nazari-Robati, Mahdieh; Khajeh, Khosro; Aminian, Mahdi; Mollania, Nasrin; Golestani, Abolfazl

    2013-02-01

    The application of chondroitinase ABC I (cABC I) in damaged nervous tissue is believed to prune glycosaminoglycan chains of proteoglycans, thereby facilitates axon regeneration. However, the utilization of cABC I as therapeutics is notably restricted due to its thermal instability. In the present study, we have explored the possibility of thermostabilization of cABC I through release of its conformational strain using Ramachandran plot information. In this regard, Gln140 with non-optimal φ and ψ values were replaced with Gly, Ala and Asn. The results indicated that Q140G and Q140A mutants were able to improve both activity and thermal stability of the enzyme while Q140N variant reduced the enzyme activity and destabilized it. Moreover, the two former variants displayed a remarkable resistance to trypsin degradation. Structural analysis of all mutants showed an increase in intrinsic fluorescence intensity and secondary structure content of Q140G and Q140A compared to the wild type which indicated more compact structure upon mutation. This investigation demonstrated that relief of conformational tension can be considered as a possible approach to increase the stability of the protein. PMID:23159774

  18. Titanate nanotube thin films with enhanced thermal stability and high-transparency prepared from additive-free sols

    NASA Astrophysics Data System (ADS)

    Kőrösi, László; Papp, Szilvia; Hornok, Viktória; Oszkó, Albert; Petrik, Péter; Patko, Daniel; Horvath, Robert; Dékány, Imre

    2012-08-01

    Titanate nanotubes were synthesized from TiO2 in alkaline medium by a conventional hydrothermal method (150 °C, 4.7 bar). To obtain hydrogen titanates, the as-prepared sodium titanates were treated with either HCl or H3PO4 aqueous solutions. A simple synthesis procedure was devised for stable titanate nanotube sols without using any additives. These highly stable ethanolic sols can readily be used to prepare transparent titanate nanotube thin films of high quality. The resulting samples were studied by X-ray diffraction, N2-sorption measurements, Raman spectroscopy, transmission and scanning electron microscopy, X-ray photoelectron spectroscopy and spectroscopic ellipsometry. The comparative results of using two kinds of acids shed light on the superior thermal stability of the H3PO4-treated titanate nanotubes (P-TNTs). X-ray photoelectron spectroscopy revealed that P-TNTs contains P in the near-surface region and the thermal stability was enhanced even at a low (˜0.5 at%) concentration of P. After calcination at 500 °C, the specific surface areas of the HCl- and H3PO4-treated samples were 153 and 244 m2 g-1, respectively. The effects of H3PO4 treatment on the structure, morphology and porosity of titanate nanotubes are discussed.

  19. Enhanced thermal stability of carbon nanotubes by plasma surface modification in Al{sub 2}O{sub 3} composites

    SciTech Connect

    Cho, Hoonsung; Guo Yan; Shi Donglu; Ren Zhifeng; Poudel, Bed; Song Yi; Abot, Jandro L.; Singh, Dileep; Routbort, Jules; Wang Lumin; Ewing, Rodney C.

    2008-10-01

    A plasma polymerization method was employed to deposit an ultrathin pyrrole film of 3 nm onto the surfaces of single wall carbon nanotubes (SWCNTs) and Al{sub 2}O{sub 3} nanoparticles for developing high-strength nanocomposites. The surfaces of plasma coated SWCNTs and Al{sub 2}O{sub 3} nanoparticles were studied by high resolution transmission electron microscopy (TEM) and time-of-flight secondary ion mass spectroscopy. After sintering the SWCNTs-Al{sub 2}O{sub 3} composites at different temperatures (maximum of 1200 deg. C), the thermal stability of plasma-coated SWCNTs was significantly increased, compared to their uncoated counterparts. After hot-press sintering, the SWCNTs without plasma coating were essentially decomposed into amorphous clusters in the composites, leading to degraded mechanical properties. However, under the same sintering conditions, the plasma surface modified SWCNTs were well preserved and distributed in the composite matrices. The effects of plasma surface coating on the thermal stability of SWCNTs and mechanical behavior of the nanocomposites are discussed.

  20. The Matrix Gene Segment Destabilizes the Acid and Thermal Stability of the Hemagglutinin of Pandemic Live Attenuated Influenza Virus Vaccines

    PubMed Central

    O'Donnell, Christopher D.; Vogel, Leatrice; Matsuoka, Yumiko; Jin, Hong

    2014-01-01

    ABSTRACT The threat of future influenza pandemics and their potential for rapid spread, morbidity, and mortality has led to the development of pandemic vaccines. We generated seven reassortant pandemic live attenuated influenza vaccines (pLAIVs) with the hemagglutinin (HA) and neuraminidase (NA) genes derived from animal influenza viruses on the backbone of the six internal protein gene segments of the temperature sensitive, cold-adapted (ca) A/Ann Arbor/60 (H2N2) virus (AA/60 ca) of the licensed seasonal LAIV. The pLAIV viruses were moderately to highly restricted in replication in seronegative adults; we sought to determine the biological basis for this restriction. Avian influenza viruses generally replicate at higher temperatures than human influenza viruses and, although they shared the same backbone, the pLAIV viruses had a lower shutoff temperature than seasonal LAIV viruses, suggesting that the HA and NA influence the degree of temperature sensitivity. The pH of HA activation of highly pathogenic avian influenza viruses was greater than human and low-pathogenicity avian influenza viruses, as reported by others. However, pLAIV viruses had a consistently higher pH of HA activation and reduced HA thermostability compared to the corresponding wild-type parental viruses. From studies with single-gene reassortant viruses bearing one gene segment from the AA/60 ca virus in recombinant H5N1 or pH1N1 viruses, we found that the lower HA thermal stability and increased pH of HA activation were associated with the AA/60 M gene. Together, the impaired HA acid and thermal stability and temperature sensitivity likely contributed to the restricted replication of the pLAIV viruses we observed in seronegative adults. IMPORTANCE There is increasing evidence that the HA stability of influenza viruses depends on the virus strain and host species and that HA stability can influence replication, virulence, and transmission of influenza A viruses in different species. We

  1. pH dependence of the stability of barstar to chemical and thermal denaturation.

    PubMed Central

    Khurana, R.; Hate, A. T.; Nath, U.; Udgaonkar, J. B.

    1995-01-01

    Equilibrium unfolding of barstar with guanidine hydrochloride (GdnHCl) and urea as denaturants as well as thermal unfolding have been carried out as a function of pH using fluorescence, far-UV and near-UV CD, and absorbance as probes. Both GdnHCl-induced and urea-induced denaturation studies at pH 7 show that barstar unfolds through a two-state F<->U mechanism and yields identical values for delta GU, the free energy difference between the fully folded (F) and unfolded (U) forms, of 5.0 +/- 0.5 kcal.mol-1 at 25 degrees C. Thermal denaturation of barstar also follows a two-state F<->U unfolding transition at pH 7, and the value of delta GU at 25 degrees C is similar to that obtained from chemical denaturation. The pH dependence of denaturation by GdnHCl is complex. The Cm value (midpoint of the unfolding transition) has been used as an index for stability in the pH range 2-10, because barstar does not unfold through a two-state transition on denaturation by GdnHCl at all pH values studied. Stability is maximum at pH 2-3, where barstar exists in a molten globule-like form that forms a large soluble oligomer. The stability decreases with an increase in pH to 5, the isoelectric pH of the protein. Above pH 5, the stability increases as the pH is raised to 7. Above pH 8, it again decreases as the pH is raised to 10. The decrease in stability from pH 7 to 5 in wild-type (wt) barstar, which is shown to be characterized by an apparent pKa of 6.2 +/- 0.2, is not observed in H17Q, a His 17-->Gln 17 mutant form of barstar. This decrease in stability has therefore been correlated with the protonation of His 17 in barstar. The decrease in stability beyond pH 8 in wt barstar, which is characterized by an apparent pKa of 9.2 +/- 0.2, is not detected in BSCCAA, the Cys 40 Cys 82-->Ala 40 Ala 82 double mutant form of barstar. Thus, this decrease in stability has been correlated with the deprotonation of at least one of the two cysteines present in wt barstar. The increase in

  2. Effects of overdischarge on performance and thermal stability of a Li-ion cell

    NASA Astrophysics Data System (ADS)

    Maleki, Hossein; Howard, Jason N.

    Overdischarge effects on cycle-life and thermal stability of a commercially available Li-ion cell (rated at 780 mA h) were investigated. Cells were overdischarged and kept at 2.0, 1.5, 1.0, 0.5 or 0.0 V for 72 h (3 days) and then cycled five times (discharge to 3.0 V at 0.4 A and charged to 4.2 V at 0.8 A). This process was repeated five times. The cells overdischarged between 2.0 and 0.5 V experienced irreversible capacity losses of 2-16%. The same cells lost between 8 and 26% more capacity after they were cycled 100 times between 4.2 and 3.0 V at 0.8 A. Behavior of the cells overdischarged to 0.0 V was unpredictable. Some cells lost nearly 65% of their initial capacities after 15 days of being kept at 0.0 V, and others failed in different stages of overdischarging to 0.0 V. Overdischarging to 0.5 V had minimal effects on thermal stability, overcharge performance and a.c. impedance, but led to considerable swelling of the cells. Overdischarge to 0.0 V caused cell thickness and a.c. impedance to increase by ∼70 and 250% of their initial values, respectively. This article addresses concerns that overdischarging of Li-ion cells below 1.5 V may cause capacity losses and/or thermal stability changes which could impact tolerance to abuse conditions.

  3. Phase Stability of t;#8242;-Zirconia-Based Thermal Barrier Coatings: Mechanistic Insights

    SciTech Connect

    Krogstad, Jessica A.; Krämer, Stephan; Lipkin, Don M.; Johnson, Curtis A.; Mitchell, David R.G.; Cairney, Julie M.; Levi, Carlos G.

    2011-11-07

    The temperature capability of yttria-stabilized zirconia thermal barrier coatings (TBCs) is ultimately tied to the rate of evolution of the 'nontransformable' t' phase into a depleted tetragonal form predisposed to the monoclinic transformation on cooling. The t' phase, however, has been shown to decompose in a small fraction of the time necessary to form the monoclinic phase. Instead, a modulated microstructure consisting of a coherent array of Y-rich and Y-lean lamellar phases develops early in the process, with mechanistic features suggestive of spinodal decomposition. Coarsening of this microstructure leads to loss of coherency and ultimately transformation into the monoclinic form, making the kinetics of this process, and not the initial decomposition, the critical factor in determining the phase stability of TBCs. Transmission electron microscopy is shown to be essential not only for characterizing the microstructure but also for proper interpretation of X-ray diffraction analysis.

  4. A compact optical pickup head in blue wavelength with high horizontal stability for laser thermal lithography.

    PubMed

    Lee, Yuan-Chin; Chao, Shiuh; Huang, Chun-Chieh; Cheng, Kuen-Chiuan

    2013-10-01

    A compact optical pickup head in blue wavelength with a single-axial actuator i.e. focusing, for laser thermal lithography was designed, fabricated, and tested. The numerical aperture of the objective lens was 0.85. The linear range of the focus error signal was 3 μm. A planar spring structure for improving the horizontal stability was designed and incorporated into the actuator. We applied a modified push-pull method together with a static Blu-ray re-writable disc to test the horizontal stability of the pickup head. We found that the in-plane jitter of the pickup head in two orthogonal directions were 0.34 nm and 1.59 nm, respectively. We demonstrated an example of applying the pickup head to write an inorganic photo-resist GeSbSnO film, and well-defined pattern was obtained with ~220 nm spot size. PMID:24104268

  5. Dielectric Coating Thermal Stabilization During GaAs-Based Laser Fabrication for Improved Device Yield

    NASA Astrophysics Data System (ADS)

    Connors, Michael K.; Millsapp, Jamal E.; Turner, George W.

    2016-06-01

    The quality and yield of GaAs-based ridge waveguide devices fabricated at MIT Lincoln Laboratory were negatively impacted by the random lot-to-lot appearance of blisters in the front-side contact metal. The blisters signaled compromised adhesion between the front-side contact metal, underlying SiO2 dielectric coating, and semiconductor surface. A thermal-anneal procedure developed for the fabrication of GaAs slab coupled optical waveguide (SCOW) ridge waveguide devices stabilizes the SiO2 dielectric coating by means of outgassing and stress reduction. This process eliminates a primary source of adhesion loss, as well as blister generation, and thereby significantly improves device yield. Stoney's equation was used to analyze stress-induced bow in device wafers fabricated using this stabilization procedure. This analysis suggests that changes in wafer bow contribute to the incidence of metal blisters in SCOW devices.

  6. Dielectric Coating Thermal Stabilization During GaAs-Based Laser Fabrication for Improved Device Yield

    NASA Astrophysics Data System (ADS)

    Connors, Michael K.; Millsapp, Jamal E.; Turner, George W.

    2016-03-01

    The quality and yield of GaAs-based ridge waveguide devices fabricated at MIT Lincoln Laboratory were negatively impacted by the random lot-to-lot appearance of blisters in the front-side contact metal. The blisters signaled compromised adhesion between the front-side contact metal, underlying SiO2 dielectric coating, and semiconductor surface. A thermal-anneal procedure developed for the fabrication of GaAs slab coupled optical waveguide (SCOW) ridge waveguide devices stabilizes the SiO2 dielectric coating by means of outgassing and stress reduction. This process eliminates a primary source of adhesion loss, as well as blister generation, and thereby significantly improves device yield. Stoney's equation was used to analyze stress-induced bow in device wafers fabricated using this stabilization procedure. This analysis suggests that changes in wafer bow contribute to the incidence of metal blisters in SCOW devices.

  7. DIAGNOSIS, ANALYSIS, AND RESOLUTION OF THERMAL STABILITY ISSUES WITH HOM COUPLERS ON PROTOTYPE CEBAF SRF CAVITIES

    SciTech Connect

    Charles Reece; Edward Daly; G. Davis; William Hicks; Timothy Rothgeb; H. Phillips; Joseph Preble; Haipeng Wang; Genfa Wu

    2008-02-12

    During initial testing of the prototype cavities incorporated into the developmental cryomodule Renascence severe thermal stability issues were encountered during CW operation. Additional diagnostic instrumentation was added. This enabled identification of an unanticipated thermal impedance between the HOM coupler probe feedthrough assembly and the cavity beamtube. Subsequent detailed FE analysis successfully modeled the situation and indicated the need for alternate cooling path for the couplers on those cavities. HOM damping was measured to be adequate employing only two of the four HOM couplers. The two pickup probes on the couplers at the input power coupler side of each cavity were removed, the remaining HOM probe feedthroughs were heat stationed to two-phase helium supply piping, and a novel heat sink was added to station both the inner and outer conductors of the remaining HOM rf cables. The characterization measurements, analysis, modifications, and resulting performance are presented.

  8. Dramatic thermal stability of virus-polymer conjugates in hydrophobic solvents.

    PubMed

    Holder, Patrick G; Finley, Daniel T; Stephanopoulos, Nicholas; Walton, Ross; Clark, Douglas S; Francis, Matthew B

    2010-11-16

    We have developed a method for integrating the self-assembling tobacco mosaic virus capsid into hydrophobic solvents and hydrophobic polymers. The capsid was modified at tyrosine residues to display an array of linear poly(ethylene glycol) chains, allowing it to be transferred into chloroform. In a subsequent step, the capsids could be transferred to a variety of hydrophobic solvents, including benzyl alcohol, o-dichlorobenzene, and diglyme. The thermal stability of the material against denaturation increased from 70 °C in water to at least 160 °C in hydrophobic solvents. With a view toward material fabrication, the polymer-coated TMV rods were also incorporated into solid polystyrene and thermally cast at 110 °C. Overall, this process significantly expands the range of processing conditions for TMV-based materials, with the goal of incorporating these templated nanoscale systems into conductive polymer matrices. PMID:20964388

  9. Effect of Aromatic Concentration of a Fischer-Tropsch Fuel on Thermal Stability

    NASA Technical Reports Server (NTRS)

    Klettlinger, Jennifer Lindsey Suder

    2012-01-01

    Fischer-Tropsch (F-T) jet fuel composition differs from petroleum-based, conventional commercial jet fuel because of differences in feedstock and production methodology. Fischer­ Tropsch fuel typically has a lower aromatic and sulfur content and consists primarily of iso and normal parafins. The ASTM D3241 specification for Jet Fuel Thermal Oxidation Test (JFTOT) break point testing method was used to test the breakpoint of a baseline commercial grade F-T jet fuel, and various blends of this F-T fuel with an aromatic solution. The goal of this research is to determine the effect of aromatic content on the thermal stability of Fischer-Tropsch fuel. The testing completed in this report was supported by the NASA Fundamental Aeronautics Subsonics Fixed Wing Project.

  10. Low pH modulates the macroorganization and thermal stability of PSII supercomplexes in grana membranes.

    PubMed

    Stoichev, Svetozar; Krumova, Sashka B; Andreeva, Tonya; Busto, Jon V; Todinova, Svetla; Balashev, Konstantin; Busheva, Mira; Goñi, Félix M; Taneva, Stefka G

    2015-02-17

    Protonation of the lumen-exposed residues of some photosynthetic complexes in the grana membranes occurs under conditions of high light intensity and triggers a major photoprotection mechanism known as energy dependent nonphotochemical quenching. We have studied the role of protonation in the structural reorganization and thermal stability of isolated grana membranes. The macroorganization of granal membrane fragments in protonated and partly deprotonated state has been mapped by means of atomic force microscopy. The protonation of the photosynthetic complexes has been found to induce large-scale structural remodeling of grana membranes-formation of extensive domains of the major light-harvesting complex of photosystem II and clustering of trimmed photosystem II supercomplexes, thinning of the membrane, and reduction of its size. These events are accompanied by pronounced thermal destabilization of the photosynthetic complexes, as evidenced by circular dichroism spectroscopy and differential scanning calorimetry. Our data reveal a detailed nanoscopic picture of the initial steps of nonphotochemical quenching. PMID:25692589

  11. Dynamics and thermal stability of surface-confined metal-organic chains

    NASA Astrophysics Data System (ADS)

    Ecija, D.; Marschall, M.; Reichert, J.; Kasperski, A.; Nieckarz, D.; Szabelski, P.; Auwärter, W.; Barth, J. V.

    2016-01-01

    Understanding the dynamics and thermal stability of metallosupramolecular chains on surfaces is of relevance for the development of molecular connectors in nanoelectronics or other fields. Here we present a combined study using temperature-controlled STM and Monte Carlo simulations to explore the behavior of metal-organic porphyrin chains on Cu(111) based on two-fold pyridyl-Cu-pyridyl coordination motifs. We monitor their behavior in the 180-360 K range, revealing three thermal regimes: i) flexibility up to 240 K, ii) diffusion of chain fragments and partial dissociation into a fluid phase for T > 240 K, and iii) full dissolution with temperatures exceeding ~ 320 K. The experimentally estimated reaction enthalpy of the metal-organic bonding is ~ 0.6 eV. Monte Carlo simulations reproduce qualitatively our STM observations and reveal the preference for linear and extended supramolecular chains with reduced substrate temperatures.

  12. Simulation of Electromagnetic and Thermal Processes in Fastcycling Magnets for Calculation Parameters of Stability

    NASA Astrophysics Data System (ADS)

    Zubko, V.; Kozub, S.; Tkachenko, L.

    SIS300 fast-cycling superconducting quadrupole magnet is developed at IHEP. Temperature margin and minimum quench energy are main parameters of stability of superconducting magnets. These parameters are important for the design and safe operation of superconducting magnets. But additional understanding for fast-cycling superconducting magnets is needed. To calculate the temperature margin one needs coupled numerical transient simulation of electromagnetic and thermal processes in the coil because critical temperature, operating temperature and AC losses are nonuniform over turns and their magnitudes vary in time during accelerator cycles. For calculation of the minimum quench energy the combination of the network model with thermal analysis is necessary, which allows one to model quench dynamics, including the effects of a current redistribution between strands of cable and spatial inhomogeneity of cable. Results for the temperature margin and the minimum quench energy for the magnet are presented and theirs dependence on various parameters is discussed.

  13. Thermal stability and decompositions kinetics under non-isothermal conditions of imatinib mesylate α form.

    PubMed

    Mucha, Igor; Baranowski, Przemysław; Owczarek, Artur; Gajda, Maciej; Pluta, Janusz; Górniak, Agata; Niklewicz, Paweł; Karolewicz, Bożena

    2016-09-10

    The thermal decomposition and kinetic parameters of synthetized imatinib mesylate α form α form were determined by thermogravimetry (TGA/DTG) under non-isothermal conditions. The experiments were performed at a 25-940°C temperature range at five different heating rates: 2.5Kmin(-1), 5Kmin(-1), 10Kmin(-1), 15Kmin(-1) and 20Kmin(-1) per minute in a nitrogen atmosphere. Imatinib mesylate α form presents one-step mass loss during the degradation process. The thermal stability of the examined material, the melting temperature (Tonset=220.6°C) and ΔH fusion=-95.74Jg(-1) at a heating rate of 10°Cmin(-1) was established. The values of activation energies have been estimated using Kissinger, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) methods. PMID:27392171

  14. Investigation of jet fuel thermal stability using photon correlation spectroscopy and a quartz crystal microbalance

    SciTech Connect

    Trott, W.M.

    1995-12-31

    The thermal stability of aviation fuels is an important concern in designs for enhanced aircraft performance. In addition to its primary use as a propellant, jet fuel serves as a coolant for the environmental control system, engine lubrication, avionics, etc. in present military applications. Thermal loads on the fuel are anticipated to increase concurrently with the demands of advanced aircraft. Unfortunately, elevated temperatures in hydrocarbon-based fuels lead to oxidative degradation, producing insoluble products in the bulk liquid as well as deposits on contacting. These processes reduce heat exchanger efficiencies and can result in obstructions of critical components, including valves, filters, and injection nozzles. real-time diagnostics for monmitoring incipient particle formation as well as mass deposition on surfaces is needed. This report describes an experimental assembly designed for simultaneous application of photon correlation spectroscopy and a quartz crystal microbalance. Results from measurements are discussed.

  15. EXPANDED IRON UTA SPECTRA-PROBING THE THERMAL STABILITY LIMITS IN AGN CLOUDS

    SciTech Connect

    Ferland, G. J.; Lykins, M. L.; Kisielius, R.; Jonauskas, V.; Keenan, F. P.; Van Hoof, P. A. M.; Porter, R. L.; Williams, R. J. R.

    2013-04-20

    The Fe unresolved transition arrays (UTAs) produce prominent features in the {approx}15-17 A wavelength range in the spectra of active galactic nuclei (AGNs). Here, we present new calculations of the energies and oscillator strengths of inner-shell lines from Fe XIV, Fe XV, and Fe XVI. These are crucial ions since they are dominant at inflection points in the gas thermal stability curve, and UTA excitation followed by autoionization is an important ionization mechanism for these species. We incorporate these, and data reported in previous papers, into the plasma simulation code Cloudy. This updated physics is subsequently employed to reconsider the thermally stable phases in absorbing media in AGNs. We show how the absorption profile of the Fe XIV UTA depends on density, due to the changing populations of levels within the ground configuration.

  16. Machine-able Yttria Stabilized Zirconia Composites for Thermal Insulation in Nuclear Reactors

    NASA Astrophysics Data System (ADS)

    Lo, J.; Zhang, R.; Santos, R.

    2016-02-01

    Ceramics are a promising insulating material for high temperature environment. To qualify for in-core use in nuclear reactors, there are many other materials requirements to be met, such as neutron irradiation resistance, corrosion resistance, low thermal conductivity, high coefficient of thermal expansion, high strength, high fracture toughness, ease of fabricability, etc. And among the promising ceramics meeting most of the requirements, with the exception of fabricability, is yttria-stabilized zirconia (YSZ). Like all ceramics, YSZ is hard, brittle and difficult to machine. At CanmetMATERIALS, YSZ-based composites for in-core insulation that are machine-able and capable of being formed into complex shapes have been developed. In this paper, the focus is geared towards the fabrication and property evaluation of such composites. In addition, the machinability aspect of the YSZ composites was addressed with a demonstration of a machined component.

  17. Thermal stability and adhesion of low-emissivity electroplated Au coatings.

    SciTech Connect

    Jorenby, Jeff W.; Hachman, John T., Jr.; Yang, Nancy Y. C.; Chames, Jeffrey M.; Clift, W. Miles

    2010-12-01

    We are developing a low-emissivity thermal management coating system to minimize radiative heat losses under a high-vacuum environment. Good adhesion, low outgassing, and good thermal stability of the coating material are essential elements for a long-life, reliable thermal management device. The system of electroplated Au coating on the adhesion-enhancing Wood's Ni strike and 304L substrate was selected due to its low emissivity and low surface chemical reactivity. The physical and chemical properties, interface bonding, thermal aging, and compatibility of the above Au/Ni/304L system were examined extensively. The study shows that the as-plated electroplated Au and Ni samples contain submicron columnar grains, stringers of nanopores, and/or H{sub 2} gas bubbles, as expected. The grain structure of Au and Ni are thermally stable up to 250 C for 63 days. The interface bonding is strong, which can be attributed to good mechanical locking among the Au, the 304L, and the porous Ni strike. However, thermal instability of the nanopore structure (i.e., pore coalescence and coarsening due to vacancy and/or entrapped gaseous phase diffusion) and Ni diffusion were observed. In addition, the study also found that prebaking 304L in the furnace at {ge} 1 x 10{sup -4} Torr promotes surface Cr-oxides on the 304L surface, which reduces the effectiveness of the intended H-removal. The extent of the pore coalescence and coarsening and their effect on the long-term system integrity and outgassing are yet to be understood. Mitigating system outgassing and improving Au adhesion require a further understanding of the process-structure-system performance relationships within the electroplated Au/Ni/304L system.

  18. Thermal and shape stability of high-index-faceted rhodium nanoparticles: a molecular dynamics investigation.

    PubMed

    Zeng, Xiang-Ming; Huang, Rao; Wen, Yu-Hua; Sun, Shi-Gang

    2015-02-28

    Nanosized noble metallic particles enclosed by high-index facets exhibit superior catalytic activity because of their high density of low-coordinated step atoms at the surface, and thus have attracted growing interest over the past decade. In this article, we employed molecular dynamics simulations to investigate the thermodynamic evolution of tetrahexahedral Rh nanoparticles respectively covered by {210}, {310}, and {830} facets during the heating process. Our results reveal that the {210} faceted nanoparticle exhibits better thermal and shape stability than the {310} and {830} faceted ones. Meanwhile, because the {830} facet consists of {210} and {310} subfacets, the stability of the {830} faceted Rh nanoparticle is dominated by the {310} subfacet, which possesses a relatively poor stability. Furthermore, the shape transformation of these nanoparticles occurs much earlier than their melting. Further analyses indicate that surface atoms with higher coordination numbers display lower surface diffusivity, and are thus more helpful for stabilizing the particle shape. This study offers an atomistic understanding of the thermodynamic behaviors of high-index-faceted Rh nanoparticles. PMID:25628229

  19. Increasing Thermal Stability of Gelatin by UV-Induced Cross-Linking with Glucose

    PubMed Central

    Masutani, Evan M.; Kinoshita, Christopher K.; Tanaka, Travis T.; Ellison, Andrew K. D.; Yoza, Brandon A.

    2014-01-01

    The effects of ultraviolet (254 nm) radiation on a hydrated gelatin-glucose matrix were investigated for the development of a physiologically thermostable substrate for potential use in cell scaffold production. Experiments conducted with a differential scanning calorimeter indicate that ultraviolet irradiation of gelatin-glucose hydrogels dramatically increases thermal stability such that no melting is observed at temperatures of at least 90°C. The addition of glucose significantly increases the yield of cross-linked product, suggesting that glucose has a role in cross-link formation. Comparisons of lyophilized samples using scanning electron microscopy show that irradiated materials have visibly different densities. PMID:24963297

  20. Nature of astoichiometry and thermal stability in InVo/sub 4/

    SciTech Connect

    Kozhevnikov, V.L.; Leonidov, L.A.; Fotiev, A.A.

    1988-02-01

    The aim of our work was to investigate the processes of disordering in InVo/sub 4/ and to study its thermal stability in relation to the temperature and partial pressure of oxygen PO/sub 2/. The temperature dependence of the electrical conductivity at PO/sub 2/ = 21 kPa is shown. The activation energy of the total ionic (%) and electron (sigma) conductivities in the interval 920-1170/sup 0/K is (87 +/- 2) kJ. The isothermal dependence of the total electrical conductivity on PO/sub 2/ is also shown.