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Sample records for addition cured silicone

  1. A comparison of dimensional accuracy between three different addition cured silicone impression materials.

    PubMed

    Forrester-Baker, L; Seymour, K G; Samarawickrama, D; Zou, L; Cherukara, G; Patel, M

    2005-06-01

    Ten impressions of a metal implant abutment were made with each of three addition-cured silicone impression materials. Using the technique of co-ordinate metrology, the shoulder region of the abutment and corresponding regions of both impressions and dies made from these impressions were scanned and measured. Comparison of these measurements indicated that the mean dimension measured from the shoulder region for each group of impression materials was significantly different from those taken from the original metal implant abutment. However, when these impressions were cast in a gypsum based die material, none of the measured dimensions taken from the casts were significantly different from those taken from the original metal implant abutment. Thus, any change in measured dimensions occurring during impression making, was compensated for in some way by the casting process. PMID:16011234

  2. New addition curing polyimides

    NASA Technical Reports Server (NTRS)

    Frimer, Aryeh A.; Cavano, Paul

    1991-01-01

    In an attempt to improve the thermal-oxidative stability (TOS) of PMR-type polymers, the use of 1,4-phenylenebis (phenylmaleic anhydride) PPMA, was evaluated. Two series of nadic end-capped addition curing polyimides were prepared by imidizing PPMA with either 4,4'-methylene dianiline or p-phenylenediamine. The first resulted in improved solubility and increased resin flow while the latter yielded a compression molded neat resin sample with a T(sub g) of 408 C, close to 70 C higher than PME-15. The performance of these materials in long term weight loss studies was below that of PMR-15, independent of post-cure conditions. These results can be rationalized in terms of the thermal lability of the pendant phenyl groups and the incomplete imidization of the sterically congested PPMA. The preparation of model compounds as well as future research directions are discussed.

  3. High Flow Addition Curing Polyimides

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Vannucci, Raymond D.; Ansari, Irfan; Cerny, Lawrence L.; Scheiman, Daniel A.

    1994-01-01

    A new series of high flow PMR-type addition curing polyimides was developed, which employed the substitution of 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl (BTDB) for p-phenylenediamine (p -PDA) in a PMR-IL formulation. These thermoset polyimides, designated as 12F resins, were prepared from BTDB and the dimethyl ester of 4,4'- (hexafluo- roisopropylidene) -diphthalic acid (HFDE) with either nadic ester (NE) or p-aminostyrene (PAS) as the endcaps for addition curing. The 12F prepolymers displayed lower melting temperatures in DSC analysis, and higher melt flow in rheological studies than the cor- responding PMR-11 polyimides. Long-term isothermal aging studies showed that BTDB- based 12F resins exhibited comparable thermo-oxidative stability to P-PDA based PMR-11 polyimides. The noncoplanar 2- and 2'-disubstituted biphenyldiamine (BTDB) not only lowered the melt viscosities of 12F prepolymers, but also retained reasonable thermal sta- bility of the cured resins. The 12F polyimide resin with p-aminostyrene endcaps showed the best promise for long-term, high-temperature application at 343 C (650 F).

  4. Influence of curing agent on fibrosis around silicone implants.

    PubMed

    Joseph, Josna; Mohanty, Mira

    2013-01-01

    Severe capsular contracture around silicone expander breast implants leading to pain and failure is a major clinical problem. Even though earlier studies have implicated the immunogenicity of silicone, the role of physical and chemical properties of the silicone material in excessive collagen deposition and fibrosis has been less addressed. The present study investigates whether there is any correlation between the type of curing systems i.e. addition and free radical curing and the fibrosis around silicone elastomer. The experiment carried out uses commercially available silicone ventriculo-peritoneal shunt material elastomer cured by platinum and the results are compared with results obtained in a similar study carried out by the authors using commercially available silicone tissue expander material cured by peroxide. Ultra-high molecular weight poly-ethylene (UHMWPE), the standard reference for biocompatibility evaluation, was used as the control material. The materials were implanted in rat skeletal muscle for 30 and 90 days. Inflammatory cells, myofibroblasts, cytokines, and collagen deposition at the material-tissue interface were identified by haematoxylin-eosin and Masson's Trichrome stains and semi-quantitated based on immunohistochemical studies. Results indicate that even though the cellular response in the initial phase of wound healing was similar in both platinum and peroxide-cured materials, the collagen deposition in the proliferative phase was more around peroxide-cured material in comparison to the platinum-cured silicone elastomer. There is a need to look into the molecular mechanisms of this interaction and the possibility of using curing systems other than free radical peroxide in the manufacture of silicone elastomer expanders for breast prosthesis. PMID:23683043

  5. Cure-rate data for silicone adhesive

    NASA Technical Reports Server (NTRS)

    Clatterbuck, C.; Fisher, A.

    1978-01-01

    Report describes work with concentrations down to 0.07 percent and is useful when applying adhesives in terrestrial and space applications. Cured Silicone retains low-outgassing properties as well as its snap, elongation, and resilience. Tests for hardness of silicone material also showed good results. No gross hysteresis observable on recovery from stretching nor was there any decrease in hardness.

  6. Improved Cure-in-Place Silicone Adhesives

    NASA Technical Reports Server (NTRS)

    Blevins, C. E.; Sweet, J.; Gonzalez, R.

    1982-01-01

    Two improved cure-in-place silicone-elastomer-based adhesives have low thermal expansion and low thermal conductivity. Adhesives are flexible at low temperature and withstand high temperatures without disintegrating. New ablative compounds were initially developed for in-flight repair of insulating tile on Space Shuttle orbiter. Could find use in other applications requiring high-performance adhesives, such as sealants for solar collectors.

  7. Improved cure method for single component silicone rubber

    NASA Technical Reports Server (NTRS)

    Lippitt, M. W.

    1969-01-01

    Water is incorporated in a carrier and then thoroughly mixed with the single component silicone rubber containing acetic anhydride as a curing agent. Because curing occurs with the water supplied internally, controlled curing is possible within a reasonable period of time, regardless of the thickness of the material.

  8. Silicone rubber curing by high intensity infrared radiation

    SciTech Connect

    Huang, T.; Tsai, J.; Cherng, C.; Chen, J.

    1994-08-10

    A high-intensity (12 kW) and compact (80 cm) infrared heating oven for fast curing (12 seconds) of tube-like silicone rubber curing studies is reported. Quality inspection by DSC and DMA and results from pilot-scale curing oven all suggest that infrared heating provides a better way of vulcanization regarding to curing time, quality, cost, and spacing over conventional hot air heating. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  9. Decreasing curing temperature of spin-on dielectrics by using additives

    NASA Astrophysics Data System (ADS)

    Bae, Jin Hee; Han, Kwen Woo; Park, Eun Su; Yoon, Hui Chan; Na, Yoong Hee; Seo, Jin Woo; Lim, Wan Hee; Kim, Bo Sun; Jang, Jun Young; Cho, Younjin

    2014-03-01

    Spin-on dielectric (SOD) is widely used in semiconductor industry, to form insulating layers including shallow trench isolation (STI) or inter-layer dielectrics (ILD). SOD has several advantages over high density plasma chemical vapor deposition (HDP-CVD) for manufacturing process, such as less defect and higher throughput. However, both SOD and HDP-CVD have a drawback, which is a high temperature curing process required to make pure silicon oxide layers. High temperature curing could cause high stress and thermal distortion. These disadvantages are becoming more problematic as the semiconductor device shrinks. To resolve the problem, we tested several additives to moderate the curing temperature. It was found out that amine compounds were effective to convert SOD polymer into silicon oxide, therefore the curing process could be performed at a lower temperature. We also observed that the SOD films containing amine additives have higher etch resistance during a wet etch process. These results, as well as the lower curing temperature, are beneficial for manufacturing insulating layers. Further investigation is ongoing to characterize other film properties of the SOD with additives, and to optimize the formulation conditions according to the requirements of manufacturing processes.

  10. Curing rate and flowing properties of silicone rubber at injection molding

    SciTech Connect

    Yoshino, M.; Nakamura, T. )

    1992-04-01

    Generally, silicone rubbers are mold-cured after mixing the rubber and peroxide curing agent with a two-roll mill or a kneader. Typically this is done at pressures of 5 MPa to 10 MPa and at temperatures between 120 to 200 C. Compression molding, transfer molding and injection molding are common molding ways for silicone rubbers. Recently, injection molding techniques are developing rapidly that have the advantages of molding automatically with high cycle mechanisms. To reduce the molding time and to make a precision part, both the flowing and curing properties of a particular rubber compound will be important. In this article, correlations between the curing and the flowing properties of silicone rubber are investigated by using the Rheovulkameter device.

  11. Toward 3D Printing of Medical Implants: Reduced Lateral Droplet Spreading of Silicone Rubber under Intense IR Curing.

    PubMed

    Stieghorst, Jan; Majaura, Daniel; Wevering, Hendrik; Doll, Theodor

    2016-03-01

    The direct fabrication of silicone-rubber-based individually shaped active neural implants requires high-speed-curing systems in order to prevent extensive spreading of the viscous silicone rubber materials during vulcanization. Therefore, an infrared-laser-based test setup was developed to cure the silicone rubber materials rapidly and to evaluate the resulting spreading in relation to its initial viscosity, the absorbed infrared radiation, and the surface tensions of the fabrication bed's material. Different low-adhesion materials (polyimide, Parylene-C, polytetrafluoroethylene, and fluorinated ethylenepropylene) were used as bed materials to reduce the spreading of the silicone rubber materials by means of their well-known weak surface tensions. Further, O2-plasma treatment was performed on the bed materials to reduce the surface tensions. To calculate the absorbed radiation, the emittance of the laser was measured, and the absorptances of the materials were investigated with Fourier transform infrared spectroscopy in attenuated total reflection mode. A minimum silicone rubber spreading of 3.24% was achieved after 2 s curing time, indicating the potential usability of the presented high-speed-curing process for the direct fabrication of thermal-curing silicone rubbers. PMID:26967063

  12. The effect of additional etching and curing mechanism of composite resin on the dentin bond strength

    PubMed Central

    Lee, In-Su; Son, Sung-Ae; Hur, Bock; Kwon, Yong-Hoon

    2013-01-01

    PURPOSE The aim of this study was to evaluate the effects of additional acid etching and curing mechanism (light-curing or self-curing) of a composite resin on the dentin bond strength and compatibility of one-step self-etching adhesives. MATERIALS AND METHODS Sixteen human permanent molars were randomly divided into eight groups according to the adhesives used (All-Bond Universal: ABU, Clearfil S3 Bond: CS3), additional acid etching (additional acid etching performed: EO, no additional acid etching performed: EX), and composite resins (Filtek Z-250: Z250, Clearfil FII New Bond: CFNB). Group 1: ABU-EO-Z250, Group 2: ABU-EO-CFNB, Group 3: ABU-EX-Z250, Group 4: ABU-EX-CFNB, Group 5: CS3-EO-Z250, Group 6: CS3-EO-CFNB, Group 7: CS3-EX-Z250, Group 8: CS3-EX-CFNB. After bonding procedures, composite resins were built up on dentin surfaces. After 24-hour water storage, the teeth were sectioned to make 10 specimens for each group. The microtensile bond strength test was performed using a microtensile testing machine. The failure mode of the fractured specimens was examined by means of an optical microscope at ×20 magnification. The data was analyzed using a one-way ANOVA and Scheffe's post-hoc test (α=.05). RESULTS Additional etching groups showed significantly higher values than the no additional etching group when using All-Bond Universal. The light-cured composite resin groups showed significantly higher values than the self-cured composite resin groups in the Clearfil S3 Bond. CONCLUSION The additional acid etching is beneficial for the dentin bond strength when using low acidic one-step self-etch adhesives, and low acidic one-step self-etch adhesives are compatible with self-cured composite resin. The acidity of the one-step self-etch adhesives is an influencing factor in terms of the dentin bonding strength and incompatibility with a self-cured composite resin. PMID:24353889

  13. High-Flow, High-Molecular-Weight, Addition-Curing Polyimides

    NASA Technical Reports Server (NTRS)

    Chuang, Kathy C.; Vannucci, Raymond D.

    1993-01-01

    In developed series of high-flow PMR-type polyimide resins, 2, 2'-bis(trifluoromethyl)-4, 4'-diaminobiphenyl (BTDB) substituted for 1, 4-pheylenediamine in PMR-II formulation. Polyimides designated either as PMR-12F when nadic ester (NE) end caps used, or as V-CAP-12F when p-aminostyrene end caps used. High-molecular-weight, addition-curing polyimides based on BTBD and HFDE highly processable high-temperature matrix resins used to make composite materials with excellent retention of properties during long-term exposure to air at 650 degrees F or higher temperature. Furthermore, 12F addition-curing polyimides useful for electronic applications; fluorinated rigid-rod polyimides known to exhibit low thermal expansion coefficients as well as low absorption of moisture.

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

    NASA Technical Reports Server (NTRS)

    Tanaka, Hidehiko

    1987-01-01

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

  15. Nanoscale semiconducting silicon as a nutritional food additive

    NASA Astrophysics Data System (ADS)

    Canham, L. T.

    2007-05-01

    Very high surface area silicon powders can be realized by high energy milling or electrochemical etching techniques. Such nanoscale silicon structures, whilst biodegradable in the human gastrointestinal tract, are shown to be remarkably stable in most foodstuffs and beverages. The potential for using silicon to improve the shelf life and bioavailability of specific nutrients in functional foods is highlighted. Published drug delivery data implies that the nanoentrapment of hydrophobic nutrients will significantly improve their dissolution kinetics, through a combined effect of nanostructuring and solid state modification. Nutrients loaded to date include vitamins, fish oils, lycopene and coenzyme Q10. In addition, there is growing published evidence that optimized release of orthosilicic acid, the biodegradation product of semiconducting silicon in the gut, offers beneficial effects with regard bone health. The utility of nanoscale silicon in the nutritional field shows early promise and is worthy of much further study.

  16. Consolidation of silicon nitride without additives

    NASA Technical Reports Server (NTRS)

    Sikora, P. F.; Yeh, H. C.

    1977-01-01

    The feasibility of producing a sound, dense Si3N4 body without additives was explored, using conventional gas hot isostatic pressing techniques and an uncommon hydraulic hot isostatic pressing technique. These two techniques produce much higher pressure 275-413 MN/m sq (40,000 - 60,000 psi) than hot-pressing techniques. Evaluation was based on density measurement, microscopic examination, both optical and electron, and X-ray diffraction analysis. The results are summarized as follows: (1) Si3N4 can be densified to high density, greater than 95% of theoretical, without additions. (2) The higher density Si3N4 specimens appear to be associated with a greater amount of alpha to beta transformation. (3) Under high pressure, the alpha to beta transformation can occur at a temperature as low as 1150 C. (4) Grain deformation and subsequent recrystallization and grain refinement result from hot isostatic pressing of Si3N4.

  17. Tin nanoparticles as an effective conductive additive in silicon anodes.

    PubMed

    Zhong, L; Beaudette, C; Guo, J; Bozhilov, K; Mangolini, L

    2016-01-01

    We have found that the addition of tin nanoparticles to a silicon-based anode provides dramatic improvements in performance in terms of both charge capacity and cycling stability. Using a simple procedure and off-the-shelf additives and precursors, we developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface. Even a minor addition of tin, as small as ∼2% by weight, results in a significant decrease in the anode resistance, as confirmed by electrochemical impedance spectroscopy. This leads to a decrease in charge transfer resistance, which prevents the formation of electrically inactive "dead spots" in the anode structure and enables the effective participation of silicon in the lithiation reaction. PMID:27484849

  18. Tin nanoparticles as an effective conductive additive in silicon anodes

    PubMed Central

    Zhong, L.; Beaudette, C.; Guo, J.; Bozhilov, K.; Mangolini, L.

    2016-01-01

    We have found that the addition of tin nanoparticles to a silicon-based anode provides dramatic improvements in performance in terms of both charge capacity and cycling stability. Using a simple procedure and off-the-shelf additives and precursors, we developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface. Even a minor addition of tin, as small as ∼2% by weight, results in a significant decrease in the anode resistance, as confirmed by electrochemical impedance spectroscopy. This leads to a decrease in charge transfer resistance, which prevents the formation of electrically inactive “dead spots” in the anode structure and enables the effective participation of silicon in the lithiation reaction. PMID:27484849

  19. Tin nanoparticles as an effective conductive additive in silicon anodes

    NASA Astrophysics Data System (ADS)

    Zhong, L.; Beaudette, C.; Guo, J.; Bozhilov, K.; Mangolini, L.

    2016-08-01

    We have found that the addition of tin nanoparticles to a silicon-based anode provides dramatic improvements in performance in terms of both charge capacity and cycling stability. Using a simple procedure and off-the-shelf additives and precursors, we developed a structure in which the tin nanoparticles are segregated at the interface between the silicon-containing active layer and the solid electrolyte interface. Even a minor addition of tin, as small as ∼2% by weight, results in a significant decrease in the anode resistance, as confirmed by electrochemical impedance spectroscopy. This leads to a decrease in charge transfer resistance, which prevents the formation of electrically inactive “dead spots” in the anode structure and enables the effective participation of silicon in the lithiation reaction.

  20. Effect of tiger nut fibre addition on the quality and safety of a dry-cured pork sausage ("Chorizo") during the dry-curing process.

    PubMed

    Sánchez-Zapata, E; Zunino, V; Pérez-Alvarez, J A; Fernández-López, J

    2013-11-01

    There is a growing interest in the revalorization of co-products from the food industry. Co-products from tiger nuts (Cyperus esculentus) milk production are a suitable fibre source. "Chorizo" is the most popular dry-cured meat product in Spain. The aim of this work was to study the effect of the tiger nut fibre addition (0, 5, and 7.5%) on the quality (composition, physicochemical, and sensorial properties) and safety (oxidation and microbial quality) of a Spanish dry-cured sausage, during the 28days of its dry-curing process. Tiger nut fibre (TNF) addition decreased fat and increased moisture content. The addition of TNF significantly increased (p<0.05) the total dietary fibre content of "Chorizo". Lightness (L*), yellowness (b*) and redness index (a*/b*) were significantly (p<0.05) affected by the fibre content. The addition of 5% and 7.5% TNF to chorizo provided rich fibre and a healthier product. Although there were slight changes in the physicochemical properties, its quality (traditional characteristics) and its safety remained. PMID:23793111

  1. Chemical Origins of Permanent Set in a Peroxide Cured Filled Silicone Elastomer - Tensile and 1H NMR Analysis

    SciTech Connect

    Chinn, S; Deteresa, S; Shields, A; Sawvel, A; Balazs, B; Maxwell, R S

    2004-10-29

    The aging of a commercial filled siloxane polymeric composite in states of high stress and Co-60 {gamma}-radiation exposure has been studied. DC-745 is a commercially available silicone elastomer consisting of dimethyl, methyl-phenyl, and vinyl-methyl siloxane monomers crosslinked with a peroxide vinyl specific curing agent. It is filled with {approx}30 wt.% mixture of high and low surface area silicas. This filled material is shown to be subject to permanent set if exposed to radiation while under tensile stress. Tensile modulus measurements show that the material gets marginally softer with combined radiation exposure and tensile strain as compared to material exposed to radiation without tensile strain. In addition, the segmental dynamics as measured by both uniaxial NMR relaxometry and Multiple Quantum NMR methods indicate that the material is undergoes radiatively-induced crosslinking in the absence of tensile strain and a combination of crosslinking and strain dependent increase in dynamic order parameter for the network chains. The MQ-NMR also suggests a small change in the number of polymer chains associated with the silica filler surface. Comparison of the prediction of the relative change in crosslink density from the NMR data as well as solvent swelling data and from that predicted from the Tobolsky model suggest that degradation leads to a deviation from Gaussian chain statistics and the formation of increased numbers of elastically ineffective network chains.

  2. Viscoelastic properties of addition-cured polyimides used in high temperature polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Roberts, Gary D; Malarik, Diane C.; Robaidek, Jerrold O.

    1991-01-01

    Viscoelastic properties of the addition cured polyimide, PMR-15, were studied using dynamic mechanical and stress relaxation tests. For temperatures below the glass transition temperature, T sub g, the dynamic mechanical properties measured using a temperature scan rate of 10 C/min were strongly affected by the presence of absorbed moisture in the resin. Dynamic mechanical properties measured as a function of time during an isothermal hold provided an indication of chemical changes occurring in the resin. For temperatures above (T sub g + 20 C), the storage modulus increased continuously as a function of time indicating that additional crosslinking is occurring in the resin. Because of these changes in chemical structures, the stress relaxation modulus could not be measured over any useful time interval for temperatures above T sub g. For temperatures below T sub g, dynamic mechanical properties appeared to be unaffected by chemical changes for times exceeding 1 hr. Since the duration of the stress relaxation tests was less than 1 hr, the stress relaxation modulus could be measured. As long as the moisture content of the resin was less than 2 pct, stress relaxation curves measured at different temperatures could be superimposed using horizontal shifts along the log(time) axis with only small shifts along the vertical axis.

  3. Effectiveness of antibacterial copper additives in silicone implants.

    PubMed

    Gosau, Martin; Bürgers, Ralf; Vollkommer, Tobias; Holzmann, Thomas; Prantl, Lukas

    2013-08-01

    Staphylococcus epidermidis plays a major role in capsular contractures of silicone breast implants. This in vitro study evaluates the antibacterial effect of copper on S. epidermidis in silicone implants. Specimens of a silicone material used for breast augmentation (Cu0) and specimens coated with different copper concentrations (Cu1, Cu2) were artificially aged. Surface roughness and surface free energy were assessed. The specimens were incubated in an S. epidermidis suspension. We assessed the quantification and the viability of adhering bacteria by live/dead cell labeling with fluorescence microscopy. Additionally, inhibition of bacterial growth was evaluated by agar diffusion, broth culture, and quantitative culture of surface bacteria. No significant differences in surface roughness and surface free energy were found between Cu0, Cu1 and Cu2. Aging did not change surface characteristics and the extent of bacterial adhesion. Fluorescence microscopy showed that the quantity of bacteria on Cu0 was significantly higher than that on Cu1 and Cu2. The ratio of dead to total adhering bacteria was significantly lower on Cu0 than on Cu1 and Cu2, and tended to be higher for Cu2 than for Cu1. Quantitative culture showed equal trends. Copper additives seem to have anti-adherence and bactericidal effects on S. epidermidis in vitro. PMID:22492200

  4. Volume stabilization of high MgO cement: Effect of curing conditions and fly ash addition

    SciTech Connect

    Ali, M.M.; Mullick, A.K.

    1998-11-01

    Hydration of high MgO cement paste under autoclave condition causes the rapid formation and crystallization of magnesium hydroxide and leads to the creation of larger pore sizes. This results in the loss of mechanical strength and higher expansion values. Under ambient water curing, precipitation and distribution of gelatinous calcium silicate hydrates into the finer network causes a homogeneous morphology and the development of smaller pores. The resultant higher mechanical strength associated with partial hydration of MgO yields reduced expansion. High MgO cement paste containing fly ash also showed considerable pore refinement and improved hydrate morphology favoring volume stability under both autoclave and ambient water curing.

  5. Addition polyimide adhesives containing ATBN and silicone elastomers

    NASA Technical Reports Server (NTRS)

    Saint Clair, A. K.; Saint Clair, T. L.

    1981-01-01

    A study was conducted to determine the effects of added elastomers on the thermal stability, adhesive strength, and fracture toughness of LARC-13, a high-temperature addition polyimide adhesive. Various butadiene/acrylonitrile and silicon elastomers were incorporated into the polyimide resin either as physical polyblends, or by chemically reacting the elastomers with the polyimide backbone. Adhesive single lap-shear and T-peel strengths were measured before and after ageing at elevated temperature. A tapered double-cantilever beam specimen was used to determine the fracture toughness of the elastomer-modified polyimide adhesives.

  6. Structure-to-property relationships in addition cured polymers. 4: Correlations between thermo-oxidative weight losses of norbornenyl cured polyimide resins and their composites

    NASA Technical Reports Server (NTRS)

    Alston, William B.

    1992-01-01

    Relationships are identified between the thermo-oxidative stability (TOS) at 316 C of a wide variety of PMR (polymerization of monomeric reactants) addition cured polyimide resins and their corresponding graphite fiber composites. Weight loss results at 316 C confirmed the expected relationship of increasing aliphatic endcap content with decreasing TOS. Moreover, the resin TOS study also showed an unexpected linear correlation of decreasing weight loss to increasing ratio of benzylic diamine to aliphatic endcap in the range of the stoichiometries studied. Only after long term 316 C aging does the dianhydride used with the benzylic diamines become an additional factor in influencing the amount of PMR resin and composite weight losses. Also, the benzylic systems consistently showed much lower resin and composite weight losses at 316 C than the corresponding nonbenzylic norbornenyl resins and composites, except when the nonbenzylic diamine monomer does not contain a connecting group. Instead, this diamine resulted in a 316 C resin and composite weight loss that was only competitive with benzylic type diamines. Results show excellent correlation between TOS of all graphite fiber PMR composites and resins.

  7. Properties of silicon-germanium thermoelectric alloys with additives

    NASA Technical Reports Server (NTRS)

    Mclane, George; Raag, Valvo; Danielson, Lee; Wood, Charles; Vandersande, Jan

    1986-01-01

    The paper reports the results of measurements (Seebeck and Hall coefficients, electrical resistivity, and thermal conductivity) on silicon-germanium (Si-20 at. pct Ge) alloy with boron phosphide, B(6.5)P) as an additive, prepared as described by McLane et al. (1986). The power factor (Seebeck coefficient squared divided by electrical resistivity) and the thermal conductivity of SeGe/B(6.5)P material were found to be lower than for the 'standard' SiGe (Si-22 at. pct Ge) material. However, no net improvement was achieved in the figure-of-merit of the sample tested. It is suggested that structural inhomogeneities, revealed by a SEM examination, might be responsible for this lack of improvement.

  8. Effect of pork fat addition on the volatile compounds of foal dry-cured sausage.

    PubMed

    Lorenzo, José M; Montes, Rosa; Purriños, Laura; Franco, Daniel

    2012-08-01

    The effect of fat content on volatile compounds from foal dry-cured sausage was studied. Three batches (10 units per batch) of dry fermented sausages with different pork back fat content (5%, 10% and 20%) were manufactured; low fat (LF), medium fat (MF) and high fat (HF), respectively. A total of 45 volatile compounds were extracted by purge-and-trap and identified by GC-MS in the headspace of the batches. The mixture comprised 11 terpenes, 15 esters, 14 hydrocarbons and 2 alcohols. Spices were responsible for the generation of 14 volatile compounds comprising terpenes and hydrocarbons. After 49 days of ripening volatile compounds from spices represented 52.9, 38.9 and 31.2% of the total area for samples from LF, MF and HF batches, respectively, while lipid autooxidation was responsible for the generation of 8 volatile compounds. The PCA offered a good separation of the mean samples according to their fat content. PMID:22498135

  9. Fatty acid profile, total cholesterol, vitamin content, and TBARS value of turkey breast muscle cured with the addition of lycopene.

    PubMed

    Skiepko, N; Chwastowska-Siwiecka, I; Kondratowicz, J; Mikulski, D

    2016-05-01

    The aim of this study was to determine the effect of lycopene addition for curing turkey meat on the profile of fatty acids, total cholesterol, vitamin content, and the TBARS of the final products. The analyzed material comprised 64 breast muscles, of which 16 (RBM) were immediately transported to a laboratory. Another 16 (UBM) were heat treated in a convection steam oven, and 32 muscles were cured for 3 days in two types of curing mixture: without (CBM) and with (CBM+Lyc) tomato peel extract standardized for 5% lycopene content. After completed curing, samples were steamed and grilled under the same conditions as raw samples. Statistical analysis demonstrated the highest (P≤0.01) mean content of vitamin A (0.07 μg/g) in chilled muscles. The content of vitamin E was lower (P≤0.01) in UBM samples than in CBM+Lyc and RBM. The TBARS value was the lowest (P≤0.01) in RBM muscles (0.35 mg MDA/kg of meat). Although there were no differences between products, but lower TBARS were found in CBM+Lyc samples. The content of cholesterol was higher (P≤0.01) in CBM+Lyc products than in the RBM and UBM. RBM samples contained (P≤0.01) the lowest amount of saturated, monounsaturated, and hypercholesterolemic fatty acids, and the highest of unsaturated, polyunsaturated, and hypocholesterolemic fatty acids. CBM+Lyc samples contained (P≤0.01) less hypercholesterolemic and more hypocholesterolemic fatty acids than CBM group. Higher (P≤0.01) unsaturated/saturated and hypocholesterolemic/hypercholesterolemic fatty acid ratios were also found in CBM+Lyc products. The study demonstrated that the used processing technology caused reduction (P≤0.01) of n-3 and n-6 PUFA content. Findings suggest that the addition of lycopene in the process of meat curing and heat treatment in meat industry do not change the content of vitamins and cholesterol or alter the TBARS value in turkey meat products. Nevertheless, lycopene can be used to increase the content of essential

  10. Effect of Addition of Natural Antioxidants on the Shelf-Life of "Chorizo", a Spanish Dry-Cured Sausage.

    PubMed

    Pateiro, Mirian; Bermúdez, Roberto; Lorenzo, José Manuel; Franco, Daniel

    2015-01-01

    The dose effect of the addition of natural antioxidants (tea, chestnut, grape seed and beer extracts) on physicochemical, microbiological changes and on oxidative stability of dry-cured "chorizo", as well as their effect during the storage under vacuum conditions was evaluated. Color parameters were significantly (p < 0.05) affected by the addition of antioxidants so that samples that contained antioxidants were more effective in maintaining color. The improving effects were dose-dependent with highest values with the dose of 50 mg/kg during ripening and depend on the extract during vacuum packaging. Addition of antioxidants decreased (p < 0.05) the oxidation, showing thiobarbituric acid reactive substances (TBARS) values below 0.4 mg MDA/kg. Natural antioxidants matched or even improved the results obtained for butylated hydroxytoluene (BHT). Regarding texture profile analysis (TPA) analysis, hardness values significantly (p < 0.001) decreased with the addition of antioxidants, obtaining the lower results with the dose of 200 mg/kg both during ripening and vacuum packaging. Antioxidants reduced the counts of total viable counts (TVC), lactic acid bacteria (LAB), mold and yeast. Free fatty acid content during ripening and under vacuum conditions showed a gradual and significant (p < 0.05) release as a result of lipolysis. At the end of ripening, the addition of GRA1000 protected chorizos from oxidative degradation. PMID:26785337

  11. Organic siliconate additive for alkaline zinc electrochemical cells

    SciTech Connect

    Dopp, R.B.

    1986-10-14

    This patent describes an alkaline electrochemical comprising an air cathode sub-assembly, with a means for supplying air to the cathode sub-assembly, a zinc anode an organic siliconate in contact with the anode, an electrolyte in contact with the zinc anode and a non-metallic separator between the cathode and the anode.

  12. Effects of curing temperature and NaOH addition on hydration and strength development of clinker-free CKD-fly ash binders

    SciTech Connect

    Wang Kejin; Shah, Surendra P.; Mishulovich, Alexander

    2004-02-01

    Effects of curing temperature and NaOH addition on hydration and strength development of cement kiln dust (CKD)-fly ash (FA) binders were investigated. Pastes made with 50% CKD and 50% FA, having 0, 2, and 5% NaOH addition, and cured at temperatures of 24, 38, and 50 deg. C were evaluated. The hydration products of the binders were examined by thermogravimetric analysis (TGA) and X-ray diffraction (XRD) tests. The results indicate that the major crystalline hydration product of the CKD-FA binders is ettringite, and the ettringite is stable in the CKD-FA system at age over 100 days. Curing at elevated temperature is more effective for CKD-FA binder strength improvement than NaOH addition, the later often depressing ettringite formation in a CKD-FA system. At a proper curing temperature (38 deg. C), addition of a small amount of NaOH (2%) may increase CKD-FA binder strength; while at a high curing temperature (50 deg. C), addition of NaOH (2%) may reduce the binder strength.

  13. Balanced ternary addition using a gated silicon nanowire

    NASA Astrophysics Data System (ADS)

    Mol, J. A.; van der Heijden, J.; Verduijn, J.; Klein, M.; Remacle, F.; Rogge, S.

    2011-12-01

    Ternary logic has the lowest cost of complexity, here, we demonstrate a CMOS hardware implementation of a ternary adder using a silicon metal-on-insulator single electron transistor. Gate dependent rectifying behavior of a single electron transistor (SET) results in a robust three-valued output as a function of the potential of the single electron transistor island. Mapping logical, ternary inputs to the three gates controlling the potential of the single electron transistor island allows us to perform complex, inherently ternary operations, on a single transistor.

  14. Structure-to-property Relationships in Addition Cured Polymers 2: Resin Tg Composite Initial Mechanical Properties of Norbornenyl Cured Polyimide Resins

    NASA Technical Reports Server (NTRS)

    Alston, W. B.

    1986-01-01

    PRM (polymerization of monomeric reactants) methodology was used to prepare thirty different polyimide oligomeric resins. Monomeric composition as well as chain length between sites of crosslinks were varied to examine their effects on glass transition temperature (Tg) of the cured/postcured resins. An almost linear correlation of Tg versus molecular distance between the crosslinks was observed. An attempt was made to correlate Tg with initial mechanical properties (flexural strength and interlaminar shear strength) of unidirectional graphite fiber composites prepared with these resins. However, the scatter in mechanical strength data prevented obtaining as clear a correlation as was observed for the structural modification/crosslink distance versus Tg. Instead, only a range of composite mechanical properties was obtained at the test temperatures studied (room temperature, 288 and 316 C). Perhaps more importantly, what did become apparent during the attempted correlation study was: (1) that PMR methodology could be used to prepare composites from resins that contain a wide variety of monomer modifications, and (2) that these composites almost invariably provided satisfactory initial mechanical properties as long as the resins selected were melt processable.

  15. Developing a High Thermal Conductivity Fuel with Silicon Carbide Additives

    SciTech Connect

    baney, Ronald; Tulenko, James

    2012-11-20

    The objective of this research is to increase the thermal conductivity of uranium oxide (UO{sub 2}) without significantly impacting its neutronic properties. The concept is to incorporate another high thermal conductivity material, silicon carbide (SiC), in the form of whiskers or from nanoparticles of SiC and a SiC polymeric precursor into UO{sub 2}. This is expected to form a percolation pathway lattice for conductive heat transfer out of the fuel pellet. The thermal conductivity of SiC would control the overall fuel pellet thermal conductivity. The challenge is to show the effectiveness of a low temperature sintering process, because of a UO{sub 2}-SiC reaction at 1,377°C, a temperature far below the normal sintering temperature. Researchers will study three strategies to overcome the processing difficulties associated with pore clogging and the chemical reaction of SiC and UO{sub 2} at temperatures above 1,300°C:

  16. Effects of Silver Oxide Addition on the Electrical Resistivity and Microstructure of Low-Temperature-Curing Metallo-Organic Decomposition Silver Pastes

    NASA Astrophysics Data System (ADS)

    Lu, Chun-An; Lin, Pang; Lin, Hong-Ching; Wang, Sea-Fue

    2007-07-01

    The thermal decomposition of silver paste with the addition of a metallo-organic decomposition (MOD) compound generally requires a curing time of greater than 10 min and a curing temperature greater than 250 °C, which does not meet the requirement for high-speed production in flexible substrates. In this study, attempts to modify the curing conditions of MOD silver pastes through the substitutions of silver flakes with silver(I) oxide (Ag2O) and silver(II) oxide (AgO) were performed. Differential thermal analysis (DTA), derivative thermogravimetric analysis (DTG), and X-ray diffraction (XRD) results indicated that the presence of residual silver oxide, which effectively catalyzes the evaporation of α-terpineol and the decomposition of silver 2-ethylhexanoate, decreases the curing temperature and shortens the soaking time. The reduced silver and the remaining Ag2O enhance the connectivity and packing density of the silver flakes, and thus increase the electric conductivity of the films. For films prepared from pastes with 20 wt % Ag2O or AgO, resistivities of 14× 10-6 and 19× 10-6 μΩ\\cdotcm, respectively, were successfully achieved after being cured at 200 °C for 5 min.

  17. Oxidation and sulfidation resistant alloys with silicon additions

    SciTech Connect

    Dunning, John S.; Alman, David E.; Poston, J.A., Jr.; Siriwardane, R.

    2003-01-01

    The Albany Research Center (ARC) has considerable experience in developing lean chromium, austenitic stainless steels with improved high temperature oxidation resistance. Using basic alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo alloys with Si and Al addition at a maximum of 5 weight percent was selected for potential application at temperatures above 700ºC for supercritical and ultra-supercritical power plant application. The alloys were fully austenitic. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700ºC to 800ºC. Oxidation resistances of alloys with Si only additions were outstanding, particularly at 800ºC (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800ºC, showed a zero weight gain in subsequent testing for 1000 hours at 700ºC. Similar improvements were observed for Si only alloy after H2S exposure at 700ºC compared with type 304 stainless steel. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms at ARC. Depth profile analysis and element concentration profiles (argon ion etching/x-ray photoelectron spectroscopy) were conducted on oxidized specimens and base material at the National Energy Technology Laboratory.

  18. A New Attempt at Alkaline Texturization of Monocrystaline Silicon with Anionic Surfactant as the Additive

    NASA Astrophysics Data System (ADS)

    Li, Hailing; Wang, Wenjing; Zhao, Lei; Zhou, Chunlan; Diao, Hongwei

    2012-10-01

    Owing to the volatilization of isopropanol (IPA), instability in the alkaline texturization of monocrystalline silicon has been a big problem for a long time. Many additives were adapted to replace IPA, such as high boiling point alcohols. In this experiment, as a new attempt, sodium lauryl sulfate (SDS), a type of anionic surfactant, was used as the additive in NaOH solution. The etching properties of silicon in 2 wt % NaOH/15-30 mg/L SDS solution were analyzed. To improve the wettability of silicon, two types of metal salt, NaCl and Na2CO3 with concentration from 2 to 15 wt %, were applied to the 2 wt % NaOH/15 mg/L SDS solution. The results showed that the effect of NaCl was better than that of Na2CO3. Finally, the role of the additive was discussed.

  19. Sticky or Slippery Wetting: Network Formation Conditions Can Provide a One-Way Street for Water Flow on Platinum-cured Silicone.

    PubMed

    Wang, Chenyu; Nair, Sithara S; Veeravalli, Sharon; Moseh, Patricia; Wynne, Kenneth J

    2016-06-01

    In the course of studies on Sylgard 184 (S-PDMS), we discovered strong effects on receding contact angles (CAs), θrec, while cure conditions have little effect on advancing CAs. Network formation at high temperatures resulted in high θadv of 115-120° and high θrec ≥ 80°. After network formation at low temperatures (≤25 °C), θadv was still high but θrec was 30-50°. Uncertainty about compositional effects on wetting behavior resulted in similar experiments with a model D(V)D(H) silicone elastomer (Pt-PDMS) composed of a vinyl-terminated poly(dimethylsiloxane) (PDMS) base and a polymeric hydromethylsilane cross-linker. Again, network formation at high temperature (∼100 °C) resulted in high CAs, while low-temperature curing retained high advancing CAs but gave low receding CAs (θrec 30-50°). These changes in receding CAs translate to strong effects on water adhesion, wp, which is the actual work required to separate a liquid (water) from a surface: wp ∝ (1 + θrec). When the values θrec 84° for high-temperature and θrec 50° for low-temperature network formation are used, wp is ∼1.5 times higher for curing at low temperature. The origin of low receding contact angles was investigated by attenuated total reflectance IR spectroscopy. Absorptions for Si-OH hydrogen-bonded to water (3350 cm(-1)) were stronger for low- versus high-temperature curing. This result is attributed to faster hydrosilylation during curing at higher temperatures that consumes Si-H before autoxidation to Si-OH. Sharp bands at 3750 and 3690 cm(-1) due to isolated -Si-OH are more prominent for Pt-PDMS than those for S-PDMS, which may be due to an effect of functionalized nanofiller. To explore the impact of wp on water droplet flow, gradient coatings of S-PDMS and Pt-PDMS elastomers were prepared by coating a slide, maintaining opposite ends at high and low temperatures and thus forming a thermal gradient. When the slide was tilted, a droplet moved easily on the high

  20. Enhancing the effectiveness of silicone thermal grease by the addition of functionalized carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Hongyuan; Wei, Hanxing; Chen, Minghai; Meng, Fancheng; Li, Hongbo; Li, Qingwen

    2013-10-01

    Functionalized carbon nanotubes (CNTs) were introduced into silicone grease to accompany the subsistent metallic oxide particles (micron-sized Al2O3, submicron-sized ZnO) with the aim of enhancing the thermal contact conductance of the composite grease as thermal interface materials (TIMs). The well-dispersed CNTs located among the metallic oxide particles to construct a three dimensional network structure and cooperated with them to form a highly efficient thermal transferring path. The functionalization of CNTs played a key role in achieving a good dispersion of CNTs in silicone grease matrix. The carboxylated CNTs were observed to show better dispersion in silicone grease and weaker reaction with oxide particles than pristine CNTs and amino-functionalized CNTs. Thus the thermal impedance of the silicone grease could be further decreased by 35% (as low as 0.18 cm2 K/W) with the addition of 2 wt.% carboxylated CNTs. Finally, such CNT-modified silicone grease was used to enhance the performance of high-power light emitting diode and showed the prospective applications in TIMs.

  1. Novel Ceramic Additives for Screen-Printable Silicon Solar Cell Metallization

    NASA Astrophysics Data System (ADS)

    Shih, Yu-Chou; Shao, Yue; Shi, Frank G.

    2016-08-01

    The interfacial structure between front-side silver electrodes and n-type silicon emitters plays a very crucial role for the electrical and mechanical properties of silicon solar cells. Studies show that the residual glass layers at the Ag/Si interfaces will significantly increase the contact resistance, and this subsequently leads to a decrease in the overall efficiency of the silicon solar cells. In this work, silver-coated nano-sized non-glass frits using an electroless plating method were employed to improve the interfacial conductivity. Transfer length method was applied to evaluate the electrical performance of the samples made with different ceramic additives. For samples made with nano-sized silver-coated ceramic additives, the improvement of conductivity was found to be about 22% compared to additives with the same compositions with no surface treatment. The results indicate that the silver layer on the surface of ceramic additives provides a conducting channel within the residual insulating layer and therefore reduces overall electrical resistance.

  2. Novel Ceramic Additives for Screen-Printable Silicon Solar Cell Metallization

    NASA Astrophysics Data System (ADS)

    Shih, Yu-Chou; Shao, Yue; Shi, Frank G.

    2016-05-01

    The interfacial structure between front-side silver electrodes and n-type silicon emitters plays a very crucial role for the electrical and mechanical properties of silicon solar cells. Studies show that the residual glass layers at the Ag/Si interfaces will significantly increase the contact resistance, and this subsequently leads to a decrease in the overall efficiency of the silicon solar cells. In this work, silver-coated nano-sized non-glass frits using an electroless plating method were employed to improve the interfacial conductivity. Transfer length method was applied to evaluate the electrical performance of the samples made with different ceramic additives. For samples made with nano-sized silver-coated ceramic additives, the improvement of conductivity was found to be about 22% compared to additives with the same compositions with no surface treatment. The results indicate that the silver layer on the surface of ceramic additives provides a conducting channel within the residual insulating layer and therefore reduces overall electrical resistance.

  3. Modification of silicone sealant to improve gamma radiation resistance, by addition of protective agents

    NASA Astrophysics Data System (ADS)

    González-Pérez, Giovanni; Burillo, Guillermina

    2013-09-01

    Poly (dimethylsiloxane) (PDMS) sealant (SS) was modified with the addition of different protective compounds to conserve its physical-chemical properties during gamma irradiation. 2-Vinyl naphthalene (2-VN), bisphenol-A (BPA) and poly (vinyl carbazole) (PVK) were used to evaluate radiation protection through the crosslinking effect of radiation. The samples were irradiated with doses from 100 kGy to 500 kGy at room temperature in air, with a 60Co gamma source, and the changes in molecular weight, thermal behavior, elastic properties and infrared spectra (FTIR-ATR) absorbance analysis were determined. The molecular weight of unmodified silicone sealant increases with the absorbed dose because of crosslinking as predominant effect. However, the crosslinking effect was inhibited with the addition of protective agent due to the aromatic compounds present. Modified silicone sealant films present better radiation resistance than unmodified system.

  4. Effects of Fe2O3 addition on the nitridation of silicon powder

    NASA Technical Reports Server (NTRS)

    Hasegawa, Y.; Inomata, Y.; Kijima, K.; Matsuyama, T.

    1977-01-01

    The reaction of silicon powder and nitrogen was studied in the range of 1300-1400 C. When an addition of Fe2O3 was more than 0.8wt%, the reaction was linear and compared to samples with no Fe2O3, the reaction velocity increased 5 to 10 times. The reactions were mediated by the process of peeling and cracking in a thin layer of Si2N4 formed on the silicon particles or on the surface of the Fe-Si melts. As the addition of Fe2O3 increased, the reaction activation energy for highly pure samples decreased. Fe2O3 which exceeded the Si3N4 solubility limits was finally converted to d-Fe.

  5. Microbiological and physicochemical characterization of dry-cured Halal goat meat. Effect of salting time and addition of olive oil and paprika covering.

    PubMed

    Cherroud, Sanâa; Cachaldora, Aida; Fonseca, Sonia; Laglaoui, Amin; Carballo, Javier; Franco, Inmaculada

    2014-10-01

    The objective of this work was to define a simple technological process for dry-cured Halal goat meat elaboration. The aims of this study were to analyze physicochemical parameters and to enumerate the microbial population at the end of the different manufacturing processes (two salting times and the addition of olive oil and paprika covering) on 36 units of meat product. A total of 532 strains were isolated from several selective culture media and then identified using classical and molecular methods. In general, salt effect and the addition of olive oil and paprika were significant for all the studied microbial groups as well as on NaCl content and water activity. Molecular analysis proves that staphylococci, especially Staphylococcus xylosus and Staphylococcus equorum, were the most common naturally occurring microbiota. The best manufacturing process would be obtained with a longer salting time and the addition of the olive oil and paprika covering. PMID:24950081

  6. ENHANCED GROWTH RATE AND SILANE UTILIZATION IN AMORPHOUS SILICON AND NANOCRYSTALLINE-SILICON SOLAR CELL DEPOSITION VIA GAS PHASE ADDITIVES

    SciTech Connect

    Ridgeway, R G; Hegedus, S S; Podraza, N J

    2012-08-31

    Air Products set out to investigate the impact of additives on the deposition rate of both CSi and Si-H films. One criterion for additives was that they could be used in conventional PECVD processing, which would require sufficient vapor pressure to deliver material to the process chamber at the required flow rates. The flow rate required would depend on the size of the substrate onto which silicon films were being deposited, potentially ranging from 200 mm diameter wafers to the 5.7 m2 glass substrates used in GEN 8.5 flat-panel display tools. In choosing higher-order silanes, both disilane and trisilane had sufficient vapor pressure to withdraw gas at the required flow rates of up to 120 sccm. This report presents results obtained from testing at Air Products electronic technology laboratories, located in Allentown, PA, which focused on developing processes on a commercial IC reactor using silane and mixtures of silane plus additives. These processes were deployed to compare deposition rates and film properties with and without additives, with a goal of maximizing the deposition rate while maintaining or improving film properties.

  7. Silicon-organic hybrid slot waveguide based three-input multicasted optical hexadecimal addition/subtraction

    PubMed Central

    Gui, Chengcheng; Wang, Jian

    2014-01-01

    By exploiting multiple non-degenerate four-wave mixing in a silicon-organic hybrid slot waveguide and 16-ary phase-shift keying signals, we propose and simulate three-input (A, B, C) multicasted 40-Gbaud (160-Gbit/s) optical hexadecimal addition/subtraction (A + B − C, A + C − B, B + C − A, A + B + C, A − B − C, B − A − C). The error vector magnitude (EVM) and dynamic range of signal power are analyzed to evaluate the performance of optical hexadecimal addition/subtraction. PMID:25502618

  8. Densification of silicon carbide using oxy-nitride additives for space-based telescope mirror applications

    NASA Astrophysics Data System (ADS)

    Kumar, R. Suresh; Shukla, Anoop K.; Babu, Sankaranarayanan; Sivakumar, Dhenuvakonda; Gandhi, Ashutosh S.

    2011-07-01

    Densification behavior of alpha silicon carbide (SiC) during vacuum hot pressing was studied up to 1900ºC with sintering additives based on AlN and Y2O3 in different proportions. Near theoretical density was obtained with a total sintering additive content of < 4 vol.%. The microstructure of SiC sintered with AlN+Y2O3 revealed fine equiaxed grains against the additional elongated grains exhibited by SiC sintered with AlN alone. The SiC having high density exhibited very good strength, elastic modulus, high thermal conductivity, low coefficient of thermal expansion and excellent polishability for telescope mirror applications.

  9. Effect of Addition of Natural Antioxidants on the Shelf-Life of “Chorizo”, a Spanish Dry-Cured Sausage

    PubMed Central

    Pateiro, Mirian; Bermúdez, Roberto; Lorenzo, José Manuel; Franco, Daniel

    2015-01-01

    The dose effect of the addition of natural antioxidants (tea, chestnut, grape seed and beer extracts) on physicochemical, microbiological changes and on oxidative stability of dry-cured “chorizo”, as well as their effect during the storage under vacuum conditions was evaluated. Color parameters were significantly (p < 0.05) affected by the addition of antioxidants so that samples that contained antioxidants were more effective in maintaining color. The improving effects were dose-dependent with highest values with the dose of 50 mg/kg during ripening and depend on the extract during vacuum packaging. Addition of antioxidants decreased (p < 0.05) the oxidation, showing thiobarbituric acid reactive substances (TBARS) values below 0.4 mg MDA/kg. Natural antioxidants matched or even improved the results obtained for butylated hydroxytoluene (BHT). Regarding texture profile analysis (TPA) analysis, hardness values significantly (p < 0.001) decreased with the addition of antioxidants, obtaining the lower results with the dose of 200 mg/kg both during ripening and vacuum packaging. Antioxidants reduced the counts of total viable counts (TVC), lactic acid bacteria (LAB), mold and yeast. Free fatty acid content during ripening and under vacuum conditions showed a gradual and significant (p < 0.05) release as a result of lipolysis. At the end of ripening, the addition of GRA1000 protected chorizos from oxidative degradation. PMID:26785337

  10. Cure SMA

    MedlinePlus

    ... real progress toward a treatment and a cure. Latest News August 29, 2016 2016 SMA Researcher Meeting ... Fundraisers Connect with Us Sign up for the latest SMA information Let us help you connect to ...

  11. Effect of additives on the anisotropic etching of silicon by using a TMAH based solution

    NASA Astrophysics Data System (ADS)

    Jun, Ki-Hwa; Kim, Bum-Joon; Kim, Jung-Sik

    2015-09-01

    In this study, the anisotropic etching properties of single crystal silicon were examined using a tetramethyl ammonium hydroxide (TMAH). The variations in the Si etching rate and surface morphology at different etching temperatures and TMAH concentrations were evaluated. The effects of different additives were also examined. As the THAM concentration (10-25 wt. %) decreased, the etching rate increased from 10 μm/h to 70 μm/h at temperatures between 70°C and 90°C. On the other hand, the etched surface roughness became degraded as the hillock density and corner undercut ratio increased. To solve these problems, four additives, pyrazine, ammonium persulfate (AP), ammonium hydrogen sulfate (AHS), and isopropyl alcohol (IPA), were added to the TMAH solution. The experimental results showed that these additives play an important role in increasing the etching rate up to 10-20%. The etched surface was also improved significantly by the decreased hillock density on the surface. The addition of IPA to the TMAH solution showed excellent results in improving the etched surface flatness and the undercutting compensation. On the other hand, one of the characteristics of IPA is the decrease in etching rate with increasing amount of IPA. [Figure not available: see fulltext.

  12. Improved Irradiation Performance of Uranium-Molybdenum/Aluminum Dispersion Fuel by Silicon Addition in Aluminum

    SciTech Connect

    Yeon Soo Kim; G. L. Hofman; A. B. Robinson; D. M. Wachs

    2013-10-01

    Uranium-molybdenum fuel particle dispersion in aluminum is a form of fuel under development for conversion of high-power research and test reactors from highly enriched to low-enriched uranium in the U.S. Global Threat Reduction Initiative program (also known as the Reduced Enrichment for Research and Test Reactors program). Extensive irradiation tests have been conducted to find a solution for problems caused by interaction layer growth and pore formation between U-Mo and Al. Adding a small amount of Si (up to [approximately]5 wt%) in the Al matrix was one of the proposed remedies. The effect of silicon addition in the Al matrix was examined using irradiation test results by comparing side-by-side samples with different Si additions. Interaction layer growth was progressively reduced with increasing Si addition to the matrix Al, up to 4.8 wt%. The Si addition also appeared to delay pore formation and growth between the U-Mo and Al.

  13. Comparative study of dimensional accuracy of different impression techniques using addition silicone impression material.

    PubMed

    Penaflor, C F; Semacio, R C; De Las Alas, L T; Uy, H G

    1998-01-01

    This study compared dimensional accuracy of the single, double with spacer, double with cut-out and double mix impression technique using addition silicone impression material. A typhodont containing Ivorine teeth model with six (6) full-crown tooth preparations were used as the positive control. Two stone replication models for each impression technique were made as test materials. Accuracy of the techniques were assessed by measuring four dimensions on the stone dies poured from the impression of the Ivorine teeth model. Results indicated that most of the measurements for the height, width and diameter slightly decreased and a few increased compared with the Ivorine teeth model. The double with cut-out and double mix technique presents the least difference from the master model as compared to the two latter impression techniques. PMID:10202524

  14. The effect of dielectric properties of sintering additives on microwave sintered silicon nitride ceramics.

    PubMed

    Chockalingam, Sreekumar; George, Jacob; Earl, David; Amarakoon, Vasantha R W

    2008-01-01

    Silicon nitride requires the use of susceptive additives for microwave liquid phase sintering due to the material's low dielectric loss. In this article, we report the effect of complex dielectric properties of two compositions of sintering aids on 2.45 GHz microwave sintered Si3N4 with respect to power absorption, temperature distribution and densification behavior. The temperature dependent dielectric properties were measured from 25 degrees C to 1400 degrees C using a conventional cavity perturbation technique. Finite Difference Time Domain (FDTD) electromagnetic simulations coupled with a thermal solver was used to predict the microwave power absorption and the corresponding temperature evolution inside the samples. The additive with higher dielectric loss (4 wt% MgO, 6 wt% Y2O3 and 2.5 wt% ZrO2) produces a greater sintered density than the lower loss additive (4 wt% MgO and 6 wt% Y2O3) or pure Si3N4. Although microwave loss at temperatures below 600 degrees C is insignificant with or without the additives, the loss begins to increase at higher temperatures when the additives are present and has a strong upward trend above 1000 degrees C. Above 1200 degrees C the sample containing ZrO2 exhibited the greatest loss. Numerical simulations at the peak sintering temperature show greater microwave power absorption and higher temperature in the sample with the highest loss additive. The simulation results correlate to the difference in densification behavior observed. The simulation was also useful because the material temperature was not accurately provided by optical pyrometer measurements of the crucible sample holder. PMID:19227072

  15. The Influence of Silicon Additions on Friction and Wear of Nickel Alloys at Temperatures to 1000 Degrees Fahrenheit

    NASA Technical Reports Server (NTRS)

    Buckley, Donald H.; Johnson, Robert L.

    1960-01-01

    Small additions of silicon have considerable beneficial effect on performance on slider alloys. This effect has most frequently been attributed to increased hardness. The research reported was conducted to consider a hypothesis that the primary role of silicon in slider alloys is one of supporting the formation of protective surface films. Friction and wear data were obtained at temperatures from 75 to 1000 degrees Fahrenheit with a series of binary silicon-nickel alloys containing up to 10 percent silicon. Pertinent hot hardness, metallurgical and surface-film analysis data are included. Atmospheres used were air, mixtures of oxygen and argon, a mixture of hydrogen and nitrogen, and a halogenated methane gas lubricant. The results show the role of silicon as a film former to be of great importance in success of silicon-containing alloys as slider materials for extreme temperatures. The range of variables studied gave friction coefficients from 0.05 to greater than 10.00 depending on film formation tendencies. Alloys with 5 percent or more silicon having a duplex structure showed the best results. Film formation resulted from surface reactions or the smearing of the softer phase from the alloys having duplex structure.

  16. Hot-pressed silicon nitride with various lanthanide oxides as sintering additives

    NASA Technical Reports Server (NTRS)

    Ueno, K.; Toibana, Y.

    1984-01-01

    The effects of addition of various lanthanide oxides and their mixture with Y2O3 on the sintering of Si3N4 were investigated. The addition of simple and mixed lanthanide oxides promoted the densification of Si3N4 in hot-pressing at 1800 C under 300-400kg/ centimeters squared for 60 min. The crystallization of yttrium and lanthanide-silicon oxynitrides which was observed inn the sintered body containing yttrium-lanthanide mixed oxides as additives led to the formation of a highly refractory Si3N4 ceramic having a bending strength of 82 and 84 kg/millimeters squared at room temperature and 1300 C respectively. In a Y2O3+La2O3 system, a higher molar ratio of La2O3 to Y2O3 gave a higher hardness and strength at high temperatures. It was found that 90 min was an optimum sintering time for the highest strength.

  17. Relaxed Poisson cure rate models.

    PubMed

    Rodrigues, Josemar; Cordeiro, Gauss M; Cancho, Vicente G; Balakrishnan, N

    2016-03-01

    The purpose of this article is to make the standard promotion cure rate model (Yakovlev and Tsodikov, ) more flexible by assuming that the number of lesions or altered cells after a treatment follows a fractional Poisson distribution (Laskin, ). It is proved that the well-known Mittag-Leffler relaxation function (Berberan-Santos, ) is a simple way to obtain a new cure rate model that is a compromise between the promotion and geometric cure rate models allowing for superdispersion. So, the relaxed cure rate model developed here can be considered as a natural and less restrictive extension of the popular Poisson cure rate model at the cost of an additional parameter, but a competitor to negative-binomial cure rate models (Rodrigues et al., ). Some mathematical properties of a proper relaxed Poisson density are explored. A simulation study and an illustration of the proposed cure rate model from the Bayesian point of view are finally presented. PMID:26686485

  18. Defining cure.

    PubMed

    Hilton, Paul; Robinson, Dudley

    2011-06-01

    This paper is a summary of the presentations made as Proposal 2-"Defining cure" to the 2nd Annual meeting of the ICI-Research Society, in Bristol, 16th June 2010. It reviews definitions of 'cure' and 'outcome', and considers the impact that varying definition may have on prevalence studies and cure rates. The difference between subjective and objective outcomes is considered, and the significance that these different outcomes may have for different stakeholders (e.g. clinicians, patients, carers, industry etc.) is discussed. The development of patient reported outcome measures and patient defined goals is reviewed, and consideration given to the use of composite end-points. A series of proposals are made by authors and discussants as to how currently validated outcomes should be applied, and where our future research activity in this area might be directed. PMID:21661023

  19. The Effect of Fluoroethylene Carbonate as an Additive on the Solid Electrolyte Interphase on Silicon Lithium-Ion Electrodes

    DOE PAGESBeta

    Schroder, Kjell; Li, Juchuan; Dudney, Nancy J.; Meng, Ying Shirley; Stevenson, Keith J.; Alvarado, Judith

    2015-08-03

    Fluoroethylene carbonate (FEC) has become a standard electrolyte additive for use with silicon negative electrodes, but how FEC affects solid electrolyte interphase (SEI) formation on the silicon anode’s surface is still not well understood. Herein, SEI formed from LiPF6-based carbonate electrolytes, with and without FEC, were investigated on 50 nm thick amorphous silicon thin film electrodes to understand the role of FEC on silicon electrode surface reactions. In contrast to previous work, anhydrous and anoxic techniques were used to prevent air and moisture contamination of prepared SEI films. This allowed for accurate characterization of the SEI structure and composition bymore » X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling. These results show that FEC reduction leads to fluoride ion and LiF formation, consistent with previous computational and experimental results. Surprisingly, we also find that these species decrease lithium-ion solubility and increase the reactivity of the silicon surface. We conclude that the effectiveness of FEC at improving the Coulombic efficiency and capacity retention is due to fluoride ion formation from reduction of the electrolyte, which leads to the chemical attack of any silicon-oxide surface passivation layers and the formation of a kinetically stable SEI comprising predominately lithium fluoride and lithium oxide.« less

  20. The Effect of Fluoroethylene Carbonate as an Additive on the Solid Electrolyte Interphase on Silicon Lithium-Ion Electrodes

    SciTech Connect

    Schroder, Kjell; Li, Juchuan; Dudney, Nancy J.; Meng, Ying Shirley; Stevenson, Keith J.; Alvarado, Judith

    2015-08-03

    Fluoroethylene carbonate (FEC) has become a standard electrolyte additive for use with silicon negative electrodes, but how FEC affects solid electrolyte interphase (SEI) formation on the silicon anode’s surface is still not well understood. Herein, SEI formed from LiPF6-based carbonate electrolytes, with and without FEC, were investigated on 50 nm thick amorphous silicon thin film electrodes to understand the role of FEC on silicon electrode surface reactions. In contrast to previous work, anhydrous and anoxic techniques were used to prevent air and moisture contamination of prepared SEI films. This allowed for accurate characterization of the SEI structure and composition by X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry depth profiling. These results show that FEC reduction leads to fluoride ion and LiF formation, consistent with previous computational and experimental results. Surprisingly, we also find that these species decrease lithium-ion solubility and increase the reactivity of the silicon surface. We conclude that the effectiveness of FEC at improving the Coulombic efficiency and capacity retention is due to fluoride ion formation from reduction of the electrolyte, which leads to the chemical attack of any silicon-oxide surface passivation layers and the formation of a kinetically stable SEI comprising predominately lithium fluoride and lithium oxide.

  1. Crystallization of grain boundary phases in silicon nitride with low additive contents by microwave annealing

    SciTech Connect

    Tiegs, T.N.; Ploetz, K.L.; Kiggans, J.O.; Yeckley, R.L.

    1993-06-01

    Microwave annealing of dense Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials showed improvements over conventional heating. Increases in fracture toughness were observed for annealing between 1200--1650C. The high temperature strength was related to the residual {alpha}-Si{sub 3}N{sub 4} content which is indicative of a finer average grain size in the specimens. The high temperature dynamic fatigue showed increased stress to failure for specimens microwave annealed between 1400--1550C for periods >5 h. Silicon nitrides with different sintering additives would require different conditions for optimum crystallization. While there were some observed property improvements, they were not so dramatic to justify abandoning conventional over microwave heating. The Si{sub 3}N{sub 4}-4% Y{sub 2}O{sub 3} materials used in the study were developed for elevated temperature use and already posses excellent good high temperature strength, fatigue resistance and creep properties. This is due to the very refractory nature of the grain boundary phases and the small quantity of secondary phase present. However, microwave annealing of these materials may be necessary in applications where the maximum in fracture toughness and fatigue resistance are required and thus justifies its use.

  2. Use of additives to improve microstructures and fracture resistance of silicon nitride ceramics

    DOEpatents

    Becher, Paul F.; Lin, Hua-Tay

    2011-06-28

    A high-strength, fracture-resistant silicon nitride ceramic material that includes about 5 to about 75 wt-% of elongated reinforcing grains of beta-silicon nitride, about 20 to about 95 wt-% of fine grains of beta-silicon nitride, wherein the fine grains have a major axis of less than about 1 micron; and about 1 to about 15 wt-% of an amorphous intergranular phase comprising Si, N, O, a rare earth element and a secondary densification element. The elongated reinforcing grains have an aspect ratio of 2:1 or greater and a major axis measuring about 1 micron or greater. The elongated reinforcing grains are essentially isotropically oriented within the ceramic microstructure. The silicon nitride ceramic exhibits a room temperature flexure strength of 1,000 MPa or greater and a fracture toughness of 9 MPa-m.sup.(1/2) or greater. The silicon nitride ceramic exhibits a peak strength of 800 MPa or greater at 1200 degrees C. Also included are methods of making silicon nitride ceramic materials which exhibit the described high flexure strength and fracture-resistant values.

  3. Dielectric cure monitoring: Preliminary studies

    NASA Technical Reports Server (NTRS)

    Goldberg, B. E.; Semmel, M. L.

    1984-01-01

    Preliminary studies have been conducted on two types of dielectric cure monitoring systems employing both epoxy resins and phenolic composites. An Audrey System was used for 23 cure monitoring runs with very limited success. Nine complete cure monitoring runs have been investigated using a Micromet System. Two additional measurements were performed to investigate the Micromet's sensitivity to water absorption in a post-cure carbon-phenolic material. While further work is needed to determine data significance, the Micromet system appears to show promise as a feedback control device during processing.

  4. The properties of polycrystalline silicon solar cells with controlled titanium additions

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.; Hopkins, R. H.; Davis, J. R., Jr.

    1981-01-01

    By coupling the results of electrical measurements, such as spectral response, lighted and dark I-V determinations, and deep-level-transient spectroscopy with optical and laser scan photomicroscopy, the effects of grain boundaries and impurities on silicon solar cells were evaluated. Titanium, which produces two deep levels in silicon, degrades cell performance by reducing bulk lifetime and thus cell short-circuit current. Electrically active grain boundaries induce carrier recombination in the bulk and depletion regions of the solar cell. Experimental data imply a small but measurable segregation of titanium into some grain boundaries of the polycrystalline silicon containing high Ti concentration. However, for the titanium-contaminated polycrystalline material used in this study, solar cell performance is dominated by the electrically active titanium concentration in the grains. Microstructural impacts on the devices are of secondary importance

  5. Additive-free hot-pressed silicon carbide ceramics-A material with exceptional mechanical properties

    SciTech Connect

    Sajgalik, P.; Sedlacek, J.; Lences, Z.; Dusza, J.; Lin, H. -T.

    2015-12-30

    Densification of silicon carbide without any sintering aids by hot-pressing and rapid hot pressing was investigated. Full density (>99% t.d.) has been reached at 1850 °C, a temperature of at least 150-200 °C lower compared to the up to now known solid state sintered silicon carbide powders. Silicon carbide was freeze granulated and heat treated prior the densification. Furthermore, evolution of microstructure, mechanical properties and creep behavior were evaluated and compared to reference ceramics from as received silicon carbide powder as well as those of commercial one. Novel method results in dense ceramics with Vickers hardness and indentation fracture toughness of 29.0 GPa and 5.25 MPam1/2, respectively. Moreover, the creep rate of 3.8 x 10–9 s–1 at 1450 °C and the load of 100 MPa is comparable to the commercial α-SiC solid state sintered at 2150 °C.

  6. Additive-free hot-pressed silicon carbide ceramics-A material with exceptional mechanical properties

    DOE PAGESBeta

    Sajgalik, P.; Sedlacek, J.; Lences, Z.; Dusza, J.; Lin, H. -T.

    2015-12-30

    Densification of silicon carbide without any sintering aids by hot-pressing and rapid hot pressing was investigated. Full density (>99% t.d.) has been reached at 1850 °C, a temperature of at least 150-200 °C lower compared to the up to now known solid state sintered silicon carbide powders. Silicon carbide was freeze granulated and heat treated prior the densification. Furthermore, evolution of microstructure, mechanical properties and creep behavior were evaluated and compared to reference ceramics from as received silicon carbide powder as well as those of commercial one. Novel method results in dense ceramics with Vickers hardness and indentation fracture toughnessmore » of 29.0 GPa and 5.25 MPam1/2, respectively. Moreover, the creep rate of 3.8 x 10–9 s–1 at 1450 °C and the load of 100 MPa is comparable to the commercial α-SiC solid state sintered at 2150 °C.« less

  7. Alleviation of Copper Toxicity in Arabidopsis Thaliana and Zinnia Elegans by Silicon Addition

    Technology Transfer Automated Retrieval System (TEKTRAN)

    While the role of silicon in plants has been studied for over 150 years, and this element can mitigate the effects of certain heavy metals, its role in Cu metabolism is unclear. Therefore, the role of Si in plant response to Cu stress was investigated in Arabidopsis thaliana L. (Heyn) and Zinnia el...

  8. Additives

    NASA Technical Reports Server (NTRS)

    Smalheer, C. V.

    1973-01-01

    The chemistry of lubricant additives is discussed to show what the additives are chemically and what functions they perform in the lubrication of various kinds of equipment. Current theories regarding the mode of action of lubricant additives are presented. The additive groups discussed include the following: (1) detergents and dispersants, (2) corrosion inhibitors, (3) antioxidants, (4) viscosity index improvers, (5) pour point depressants, and (6) antifouling agents.

  9. Influences of nitrogen, phosphorus and silicon addition on plant productivity and species richness in an alpine meadow

    PubMed Central

    Xu, Danghui; Fang, Xiangwen; Zhang, Renyi; Gao, Tianpeng; Bu, Haiyan; Du, Guozhen

    2015-01-01

    Fertilization, especially with nitrogen (N), increases aboveground primary productivity (APP), but reduces plant species richness at some level. Silicon (Si) fertilization alone, or with addition of N or phosphorus (P), has multiple direct and indirect beneficial effects on plant growth and development, both for individuals and the whole community. This study aimed to examine the effects of Si, N, P, NSi and PSi combinations on APP and species richness of the community and of four functional groups in an alpine meadow. The results showed that plots fertilized with Si in combination with either N or P had higher APP than when fertilized with N or P alone. Addition of N or P increased APP, and the higher APP occurred when the highest level of N was added, indicating co-limitation of N and P, with N being most limiting. Silicon fertilization alone or with addition of N increased the APP of grasses and forbs. Nitrogen addition decreased the community species richness; Si with addition of N alleviated the loss of species richness of the whole community and the forbs group. For the four functional groups, N or P addition increased the species richness of grasses and decreased that of forbs. Our findings highlight the importance of Si in improving APP and alleviating N fertilization-induced biodiversity loss in grasslands, and will help improve our ability to predict community composition and biomass dynamics in alpine meadow ecosystems subject to changing nutrient availability. PMID:26574603

  10. Influences of nitrogen, phosphorus and silicon addition on plant productivity and species richness in an alpine meadow.

    PubMed

    Xu, Danghui; Fang, Xiangwen; Zhang, Renyi; Gao, Tianpeng; Bu, Haiyan; Du, Guozhen

    2015-01-01

    Fertilization, especially with nitrogen (N), increases aboveground primary productivity (APP), but reduces plant species richness at some level. Silicon (Si) fertilization alone, or with addition of N or phosphorus (P), has multiple direct and indirect beneficial effects on plant growth and development, both for individuals and the whole community. This study aimed to examine the effects of Si, N, P, NSi and PSi combinations on APP and species richness of the community and of four functional groups in an alpine meadow. The results showed that plots fertilized with Si in combination with either N or P had higher APP than when fertilized with N or P alone. Addition of N or P increased APP, and the higher APP occurred when the highest level of N was added, indicating co-limitation of N and P, with N being most limiting. Silicon fertilization alone or with addition of N increased the APP of grasses and forbs. Nitrogen addition decreased the community species richness; Si with addition of N alleviated the loss of species richness of the whole community and the forbs group. For the four functional groups, N or P addition increased the species richness of grasses and decreased that of forbs. Our findings highlight the importance of Si in improving APP and alleviating N fertilization-induced biodiversity loss in grasslands, and will help improve our ability to predict community composition and biomass dynamics in alpine meadow ecosystems subject to changing nutrient availability. PMID:26574603

  11. SEMICONDUCTOR TECHNOLOGY Texturization of mono-crystalline silicon solar cells in TMAH without the addition of surfactant

    NASA Astrophysics Data System (ADS)

    Weiying, Ou; Yao, Zhang; Hailing, Li; Lei, Zhao; Chunlan, Zhou; Hongwei, Diao; Min, Liu; Weiming, Lu; Jun, Zhang; Wenjing, Wang

    2010-10-01

    Etching was performed on (100) silicon wafers using silicon-dissolved tetramethylammonium hydroxide (TMAH) solutions without the addition of surfactant. Experiments were carried out in different TMAH concentrations at different temperatures for different etching times. The surface phenomena, etching rates, surface morphology and surface reflectance were analyzed. Experimental results show that the resulting surface covered with uniform pyramids can be realized with a small change in etching rates during the etching process. The etching mechanism is explained based on the experimental results and the theoretical considerations. It is suggested that all the components in the TMAH solutions play important roles in the etching process. Moreover, TMA+ ions may increase the wettability of the textured surface. A good textured surface can be obtained in conditions where the absorption of OH-/H2O is in equilibrium with that of TMA+/SiO2 (OH)22-.

  12. A clinical comparative study of Cadiax Compact II and intraoral records using wax and addition silicone.

    PubMed

    Torabi, Kianoosh; Pour, Sasan Rasaei; Ahangari, Ahmad Hassan; Ghodsi, Safoura

    2014-01-01

    Evaluation of mandibular movements is necessary to form the occlusal anatomical contour, analyze the temporomandibular joint status, and evaluate the patient's occlusion. This clinical study was conducted to compare the mandibular recording device Cadiax Compact II with routine intraoral records for measuring condylar inclinations. The results showed that the differences between Cadiax and intraoral records were statistically significant for all measurements. Cadiax measurements had a stronger correlation with silicone records. The quantities of recorded Bennett angles were lower and the values of sagittal condylar inclination were higher with Cadiax than with routine intraoral records. PMID:25390868

  13. Additive analysis of nano silicon under the influence of neutron irradiation

    NASA Astrophysics Data System (ADS)

    Garibli, Aydan; Huseynov, Elchin; Garibov, Adil; Mehdiyeva, Ravan

    2016-04-01

    Nano silicon with 80m2g‑1 specific surface area, 100 nm size and 0.08 g/cm3 density has been irradiated continuously with neutrons (2 × 1013n ṡcm‑2s‑1) up to 20 h at various periods in TRIGA Mark II type research reactor. After the neutron irradiation, cooling time of the samples is taken approximately 360 h. It is found that the initial radioactivity of the irradiated samples changes within 0.1 kBq-3.1 GBq range. Definition of elements’ concentration is determined based on the activities formed in the relevant energy range. After the irradiation, the result of activity analysis carried out the element content of 1% mixture existing in nano Si which has been defined with radionuclides of the relevant element. Moreover, from activities of mixed radioisotopes, their amounts in percentage has been determined.

  14. The addition of silicon carbide to surrogate nuclear fuel kernels made by the internal gelation process

    NASA Astrophysics Data System (ADS)

    Hunt, R. D.; Hunn, J. D.; Birdwell, J. F.; Lindemer, T. B.; Collins, J. L.

    2010-06-01

    The US Department of Energy plans to use the internal gelation process to make tristructural isotropic (TRISO)-coated transuranic (TRU) fuel particles. The focus of this work is to develop TRU fuel kernels with high crush strengths, good ellipticity, and adequately dispersed silicon carbide (SiC). The submicron SiC particles in the TRU kernels are to serve as getters for excess oxygen and to potentially sequester palladium, rhodium, and ruthenium, which could damage the coatings during irradiation. Zirconium oxide microspheres stabilized with yttrium were used as surrogates because zirconium and TRU microspheres from the internal gelation process are amorphous and encounter similar processing problems. The hardness of SiC required modifications to the experimental system that was used to make uranium carbide kernels. Suitable processing conditions and equipment changes were identified so that the SiC could be homogeneously dispersed in gel spheres for subsequent calcination into strong spherical kernels.

  15. Sintered-reaction Bonded Silicon Nitride Densified by a Gas Pressure Sintering Process Effects of Rare Earth Oxide Sintering Additives

    SciTech Connect

    Lee, S. H.; Ko, J. W.; Park, Y. J.; Kim, H. D.; Lin, Hua-Tay; Becher, Paul F

    2012-01-01

    Reaction-bonded silicon nitrides containing rare-earth oxide sintering additives were densified by gas pressure sintering. The sintering behavior, microstructure and mechanical properties of the resultant specimens were analyzed. For that purpose, Lu2O3-SiO2 (US), La2O3-MgO (AM) and Y2O3-Al2O3 (YA) additive systems were selected. Among the tested compositions, densification of silicon nitride occurred at the lowest temperature when using the La2O3-MgO system. Since the Lu2O3-SiO2 system has the highest melting temperature, full densification could not be achieved after sintering at 1950oC. However, the system had a reasonably high bending strength of 527 MPa at 1200oC in air and a high fracture toughness of 9.2 MPa m1/2. The Y2O3-Al2O3 system had the highest room temperature bending strength of 1.2 GPa

  16. Bis(tri-n-hexylsilyl oxide) silicon phthalocyanine: a unique additive in ternary bulk heterojunction organic photovoltaic devices.

    PubMed

    Lessard, Benoît H; Dang, Jeremy D; Grant, Trevor M; Gao, Dong; Seferos, Dwight S; Bender, Timothy P

    2014-09-10

    Previous studies have shown that the use of bis(tri-n-hexylsilyl oxide) silicon phthalocyanine ((3HS)2-SiPc) as an additive in a P3HT:PC61BM cascade ternary bulk heterojunction organic photovoltaic (BHJ OPV) device results in an increase in the short circuit current (J(SC)) and efficiency (η(eff)) of up to 25% and 20%, respectively. The previous studies have attributed the increase in performance to the presence of (3HS)2-SiPc at the BHJ interface. In this study, we explored the molecular characteristics of (3HS)2-SiPc which makes it so effective in increasing the OPV device J(SC) and η(eff. Initially, we synthesized phthalocyanine-based additives using different core elements such as germanium and boron instead of silicon, each having similar frontier orbital energies compared to (3HS)2-SiPc and tested their effect on BHJ OPV device performance. We observed that addition of bis(tri-n-hexylsilyl oxide) germanium phthalocyanine ((3HS)2-GePc) or tri-n-hexylsilyl oxide boron subphthalocyanine (3HS-BsubPc) resulted in a nonstatistically significant increase in JSC and η(eff). Secondly, we kept the silicon phthalocyanine core and substituted the tri-n-hexylsilyl solubilizing groups with pentadecyl phenoxy groups and tested the resulting dye in a BHJ OPV. While an increase in JSC and η(eff) was observed at low (PDP)2-SiPc loadings, the increase was not as significant as (3HS)2-SiPc; therefore, (3HS)2-SiPc is a unique additive. During our study, we observed that (3HS)2-SiPc had an extraordinary tendency to crystallize compared to the other compounds in this study and our general experience. On the basis of this observation, we have offered a hypothesis that when (3HS)2-SiPc migrates to the P3HT:PC61BM interface the reason for its unique performance is not solely due to its frontier orbital energies but also might be due to a high driving force for crystallization. PMID:25105425

  17. Advances in light curing adhesives

    NASA Astrophysics Data System (ADS)

    Bachmann, Andy

    2001-11-01

    This paper describes the development of a new family of light curing adhesives containing a new reactive additive previously not used in optical grade light curing adhesives are obtained with the addition of functionalized cellulositics. Outgassing as low as 10-6 grams/gram has been observed based on headspace sampling. Other additives have lowered the shrinkage rates of positioning adhesives from near 1 percent to less than 0.1 percent with fractional, percentage movements over thermal range of -40 degrees C to +200 degrees C.

  18. The Effect of Calcium Oxide Addition on the Removal of Metal Impurities from Metallurgical-Grade Silicon by Acid Leaching

    NASA Astrophysics Data System (ADS)

    He, Falin; Zheng, Songsheng; Chen, Chao

    2012-10-01

    The removal of metal impurities from metallurgical grade silicon (MG-Si) by acid leaching has been investigated with the addition of CaO. Prior to adding CaO, Fe is the main impurity in the MG-Si sample, and the 2nd-phase precipitates in silicon are Si-Fe-based alloys, such as Si-Fe, Si-Fe-Ti, Si-Fe-Al, Si-Fe-Mn, and Si-Fe-Ni. The phases of Si-Fe and Si-Fe-Ti are not appreciably soluble in HCl. After the introduction of CaO, Ca becomes the dominant impurity, and the 2nd-phase precipitates become Si-Fe-based alloys, such as Si-Ca, Si-Ca-(Fe, Ti, Ni, Al), and Si-Ca-Fe-Al. These are effectively leached with HCl. Therefore, the HCl leaching effect on the removal of metal impurities has been improved. The optimum content of Ca in the MG-Si samples after adding CaO is in the range of 1 pct to 4 pct, the contents of Fe, Al, Ti, and Ni have been decreased to a minimum of less than 5 ppmw (ppm by weight) each, and the acid leaching results do not show a dependence on Ca content at this range.

  19. Effects of oxide additions and temperature on sinterability of milled silicon nitride

    NASA Technical Reports Server (NTRS)

    Arias, A.

    1980-01-01

    Specimens of milled alpha-Si3N4 with 0 to 5.07 equivalent percent of oxide additions were pressureless sintered at 1650 to 1820 C for 4 hours in nitrogen while covered with powdered Si3N4 + SiO2. Densities of less than or equal to 97.5 percent resulted with approximately 2.5 equivalent percent of MgO, CeO2, Y2O3, and three mixtures involving these oxides. Densities of greater than or equal to 94 percent were obtained with approximately 0.62 equivalent percent of the same additives. At most temperatures, best sinterability (density maxima) was obtained with 1.2 to 2.5 equivalent percent additive.

  20. Pressureless sintering of plasma-reacted nanosemicrystalline silicon nitride ceramics with doped sintering additives

    NASA Astrophysics Data System (ADS)

    Ryu, Kevin Hojun

    For the past few years, synthesis and consolidation of ceramics using nanoparticles have been a focus of much research. The obvious advantage is their low process temperatures (<200°C). In addition, the process results in super-plastic deformation, and drastically enhances the mechanical properties of the ceramics. Recently, a plasma-assisted chemical reaction was adopted to produce nanosize Si3N4 powders that have the characteristics of sintering additive elements on individual particles. Homogeneous size distribution of the additives can eliminate inhomogeneous shrinkage of the sintered body during the mixing process. In this work, the behavior of plasma-reacted nano-size Si3N 4 powders intrinsically doped with sintering additives was explored. These particles were doped with Y2O3 and Al2O 3, and processed under a low process temperature in the absence of pressurizing equipment. Several experiments were performed to address the effects of the powders on the phase transformation rate from a to b phase, and on the mechanical properties due to the microstructure evolution under different sintering conditions. The existence of sintering additive elements in each individual powder was verified by electron microscope and energy dispersive spectroscopy. The doped powders were 60% crystalline and had a specific surface area of ˜24 m2/g. The powders showed excellent sinterability at low temperature, compared to the other powders used in commercial processes. In spite of the low process temperature, the a→ b phase transformation occurred rapidly. The homogeneous distribution of Si3N4 powders was speculated as the reason for fast phase transformation. In addition, evolution of the microstructures in different sintering conditions produced materials with vastly different mechanical properties. Thus, one may obtain ceramics with desired mechanical properties by carefully controlling the sintering additives. Finally, a mathematical model, based on the previous work done by

  1. Consolidation of silicon nitride without additives. [for gas turbine engine efficiency increase

    NASA Technical Reports Server (NTRS)

    Sikora, P. F.; Yeh, H. C.

    1976-01-01

    The use of ceramics for gas turbine engine construction might make it possible to increase engine efficiency by raising operational temperatures to values beyond those which can be tolerated by metallic alloys. The most promising ceramics being investigated in this connection are Si3N4 and SiC. A description is presented of a study which had the objective to produce dense Si3N4. The two most common methods of consolidating Si3N4 currently being used include hot pressing and reaction sintering. The feasibility was explored of producing a sound, dense Si3N4 body without additives by means of conventional gas hot isostatic pressing techniques and an uncommon hydraulic hot isostatic pressing technique. It was found that Si3N4 can be densified without additions to a density which exceeds 95% of the theoretical value

  2. Hot isostatic pressing of silicon nitride with boron nitride, boron carbide, and carbon additions

    NASA Technical Reports Server (NTRS)

    Mieskowski, Diane M.; Sanders, William A.

    1989-01-01

    Si3N4 test bars containing additions of BN, B4C, and C, were hot isostatically pressed in Ta cladding at 1900 and 2050 C to 98.9 percent to 99.5 percent theoretical density. Room-temperature strength data on specimens containing 2 wt pct BN and 0.5 wt pct C were comparable to data obtained for Si3N4 sintered with Y2O3, Y2O3 and Al2O3, or ZrO2. The 1370 C strengths were less than those obtained for additions of Y2O3 or ZrO2 but greater than those obtained from a combination of Y2O3 and Al2O3. SEM fractography indicated that, as with other types of Si3N4, room-temperature strength was controlled by processing flaws. The decrease in strength at 1370 C was typical of Si3N4 having an amorphous grain-boundary phase. The primary advantage of nonoxide additions appears to be in facilitating specimen removal from the Ta cladding.

  3. Densification of Reaction Bonded Silicon Nitride with the Addition of Fine Si Powder Effects on the Sinterability and Mechanical Properties

    SciTech Connect

    Lee, Sea-Hoon; Cho, Chun-Rae; Park, Young-Jo; Ko, Jae-Woong; Kim, Hai-Doo; Lin, Hua-Tay; Becher, Paul F

    2013-01-01

    The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain Lu2O3-SiO2 additives were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering (GPS) at 1850oC through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at 1950oC. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped the compaction of green bodies and induced the formation of fine Si3N4 particles after nitridation and sintering at and above 1600oC. The amount of residual SiO2 within the specimens was not strongly affected by adding fine Si powder because most of the SiO2 layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of the specimens were 991 MPa and 8.0 MPa m1/2, respectively.

  4. Suppression of the vapor-liquid-solid growth of silicon nanowires by antimony addition.

    PubMed

    Nimmatoori, Pramod; Zhang, Qi; Dickey, Elizabeth C; Redwing, Joan M

    2009-01-14

    The effect of Sb addition on the growth rate and structural properties of Si nanowires synthesized by vapor-liquid-solid growth was investigated. The nanowire growth rate was reduced by an order of magnitude following the addition of a low concentration pulse of trimethylantimony (TMSb) to the gas phase during growth. Transmission electron microscopy analysis revealed that the wires had a thick amorphous coating ( approximately 8 nm) around the catalyst particle and a distorted catalyst shape. Energy-dispersive x-ray spectroscopy showed the presence of trace amounts of Sb in the amorphous coating around the catalyst and at the catalyst-wire interface. Antimony was also found to be incorporated in the Si nanowires with a peak in the Sb concentration measured at the initial point where the TMSb pulse was added to the gas stream. The significant reduction in wire growth rate was attributed to Sb segregation at the vapor-liquid and liquid-solid interfaces which results in a change in interfacial energies and a reduction in the rate of Si incorporation at these interfaces. PMID:19417276

  5. Effects of silicon, carbon and molybdenum additions on IASCC of neutron irradiated austenitic stainless steels

    NASA Astrophysics Data System (ADS)

    Nakano, J.; Miwa, Y.; Kohya, T.; Tsukada, T.

    2004-08-01

    To study the effects of minor elements on irradiation assisted stress corrosion cracking (IASCC), high purity type 304 and 316 stainless steels (SSs) were fabricated and minor elements, Si or C were added. After neutron irradiation to 3.5 × 10 25 n/m 2 ( E>1 MeV), slow strain rate tests (SSRTs) of irradiated specimens were conducted in oxygenated high purity water at 561 K. Specimen fractured surfaces were examined using a scanning electron microscope (SEM) after the SSRTs. The fraction of intergranular stress corrosion cracking (IGSCC) on the fractured surface after the SSRTs increased with neutron fluence. In high purity SS with added C, the fraction of IGSCC was the smallest in the all SSs, although irradiation hardening level was the largest of all the SSs. Addition of C suppressed the susceptibility to IGSCC.

  6. Microstructure development in hot-pressed silicon carbide: Effects of aluminum, boron, and carbon additives

    SciTech Connect

    Zhang, Xiao Feng; Yang, Qing; De Jonghe, Lutgard C.

    2002-12-18

    SiC was hot-pressed with aluminum, boron, and carbon additives. The Al content was modified either to obtain SiC samples containing a continuous Al gradient, or to vary the average Al content. In both cases, dramatic changes in microstructure, phase composition, and grain boundary structure were observed as a result of the Al variation. Similar processing and characterization were done with modified boron and carbon average contents. The systematic experiments allowed identification of the roles of Al, B, and C in developing grain morphology and phase composition. The experiments also clarified the mechanical property responses to microstructural modification. Tailoring of the SiC microstructure to suit different applications would be possible.

  7. Effect of silicon addition on soybean (Glycine max) and cucumber (Cucumis sativus) plants grown under iron deficiency.

    PubMed

    Gonzalo, María José; Lucena, Juan J; Hernández-Apaolaza, Lourdes

    2013-09-01

    Silicon is considered an essential element in several crops enhancing growth and alleviating different biotic and abiotic stresses. In this work, the role of Si in the alleviation of iron deficiency symptoms and in the Fe distribution in iron deficient plants has been studied. Thus, soybean and cucumber plants grown in hydroponic culture under iron limiting conditions were treated with different Si doses (0.0, 0.5 and 1.0 mM). The use of a strong chelating agent such as HBED avoided Fe co-precipitation in the nutrient solution and allowed for the first time the analysis of Si effect in iron nutrition without the interference of the iron rhizospheric precipitation. SPAD index, plant growth parameters and mineral content in plant organs were determined. For soybean, the addition of 0.5 mM of Si to the nutrient solution without iron, initially or continuously during the experiment, prevented the chlorophyll degradation, slowed down the growth decrease due to the iron deficiency and maintained the Fe content in leaves. In cucumber, Si addition delayed the decrease of stem dry weight, stem length, node number and iron content in stems and roots independently of the dose, but no-effect was observed in chlorosis symptoms alleviation in leaves. The observed response to Si addition in iron deficiency was plant-specific, probably related with the different Fe efficiency strategies developed by these two species. PMID:23845824

  8. Curing agent for polyepoxides and epoxy resins and composites cured therewith. [preventing carbon fiber release

    NASA Technical Reports Server (NTRS)

    Serafini, T. T.; Delvigs, P.; Vannucci, R. D. (Inventor)

    1981-01-01

    A curing for a polyepoxide is described which contains a divalent aryl radical such as phenylene a tetravalent aryl radical such as a tetravalent benzene radical. An epoxide is cured by admixture with the curing agent. The cured epoxy product retains the usual properties of cured epoxides and, in addition, has a higher char residue after burning, on the order of 45% by weight. The higher char residue is of value in preventing release to the atmosphere of carbon fibers from carbon fiber-epoxy resin composites in the event of burning of the composite.

  9. Radiation curing: Science and technology

    SciTech Connect

    Pappas, S.P.

    1992-01-01

    The science and technology of radiation curing have progressed substantially within the last 20 years. Nevertheless, radiation-curable compositions typically command relatively small shares in many of their competitive markets. This situation signifies that potential advantages of radiation curing are not generally perceived to overcome their limitations. An important objective of this book is to address this issue, within the scope of the subjects offered, by providing the present state of knowledge and by identifying the directions and challenges for future studies. The first chapter introduces radiation curing. Chapter 2 offers the first systematic presentation of inorganic and organometallic photoinitiators. Chapters 3 and 4 present the analytical techniques of photocalorimetry and real-time infrared spectroscopy, respectively. Recent advances in resin technology are offered in Chapters 5 and 6, which constitute the first comprehensive accounts of (meth)acrylated silicones and vinyl ethers, respectively. Radiation-curable coatings, printing inks, and adhesives are discussed in Chapters 7-9, respectively. Chapter 10 offers a discussion on photopolymer imaging systems.

  10. New pressure-sensitive silicone adhesive

    NASA Technical Reports Server (NTRS)

    Leiffer, J. L.; Stoops, W. E., Jr.; St. Clair, T. L.; Watkins, V. E., Jr.; Kelly, T. P.

    1981-01-01

    Adhesive for high or low temperatures does not stretch severely under load. It is produced by combining intermediate-molecular-weight pressure sensitive adhesive which does not cure with silicone resin that cures with catalyst to rubbery tack-free state. Blend of silicone tackifier and cured rubbery silicone requires no solvents in either atmospheric or vacuum environments. Ratio of ingredients varies for different degrees of tack, creep resistance, and tensile strength.

  11. Radiation curing of epoxies

    NASA Astrophysics Data System (ADS)

    Dickson, Lawrence W.; Singh, Ajit

    The literature on radiation polymerization of epoxy compounds has been reviewed to assess the potential use of radiation for curing these industrially important monomers. Chemical curing of epoxies may proceed by either cationic or anionic mechanisms depending on the nature of the curing agent, but most epoxies polymerize by cationic mechanisms under the influence of high-energy radiation. Radiation-induced cationic polymerization of epoxy compounds is inhibited by trace quantities of water because of proton transfer from the chain-propagating epoxy cation to water. Several different methods with potential for obtaining high molecular weight polymers by curing epoxies with high-energy radiation have been studied. Polymeric products with epoxy-like properties have been produced by radiation curing of epoxy oligomers with terminal acrylate groups and mixtures of epoxies with vinyl monomers. Both of these types of resin have good potential for industrial-scale curing by radiation treatment.

  12. Quantitation of buried contamination by use of solvents. [degradation of silicone polymers by amine solvents

    NASA Technical Reports Server (NTRS)

    Pappas, S. P.; Hsiao, Y. C.; Hill, L. W.

    1973-01-01

    Spore recovery form cured silicone potting compounds using amine solvents to degrade the cured polymers was investigated. A complete list of solvents and a description of the effect of each on two different silicone polymers is provided.

  13. Curing of Furfuryl Alcohol-Impregnated Parts

    NASA Technical Reports Server (NTRS)

    Lawton, J. W.; Brayden, T. H.

    1983-01-01

    Delamination problem in reinforced carbon/carbon parts impregnated with oxalic acid-catalyzed furfuryl alcohol overcome by instituting two additional quality-control tests on alcohol and by changing curing conditions.

  14. Biodegradable Epoxy Networks Cured with Polypeptides

    NASA Astrophysics Data System (ADS)

    Nakamura, Shigeo; Kramer, Edward J.

    2006-03-01

    Epoxy resins are used widely for adhesives as well as coatings. However, once cured they are usually highly cross-linked and are not biodegradable. To obtain potentially biodegradable polypeptides that can cure with epoxy resins and achieve as good properties as the conventional phenol novolac hardeners, poly(succinimide-co-tyrosine) was synthesized by thermal polycondensation of L-aspartic acid and L-tyrosine with phosphoric acid under reduced pressure. The tyrosine/succinimide ratio in the polypeptide was always lower than the tyrosine/(aspartic acid) feed ratio and was influenced by the synthesis conditions. Poly(succinimide-tyrosine- phenylalanine) was also synthesized from L-aspartic acid, L- tyrosine and L-phenylalanine. The thermal and mechanical properties of epoxy resins cured with these polypeptides are comparable to those of similar resins cured with conventional hardeners. In addition, enzymatic degradability tests showed that Chymotrypsin or Subtilisin A could cleave cured films in an alkaline borate buffer.

  15. Reaction cured glass and glass coatings

    NASA Technical Reports Server (NTRS)

    Goldstein, H. E.; Leiser, D. B.; Katvala, V. W. (Inventor)

    1978-01-01

    The invention relates to reaction cured glass and glass coatings prepared by reacting a compound selected from the group consisting of silicon tetraboride, silicon hexaboride, other boron silicides, boron and mixtures with a reactive glass frit composed of a porous high silica borosilicate glass and boron oxide. The glassy composites of the present invention are useful as coatings on low density fibrous porous silica insulations used as heat shields and for articles such as reaction vessels that are subjected to high temperatures with rapid heating and cooling and that require resistance to temperature and repeated thermal shock at temperatures up to about 1482C (2700PF).

  16. Effects of fibre type and structure of longissimus lumborum (Ll), biceps femoris (Bf) and semimembranosus (Sm) deer muscles salting with different Nacl addition on proteolysis index and texture of dry-cured meats.

    PubMed

    Żochowska-Kujawska, J

    2016-11-01

    The aim of the present study was to describe the effect of fibre type and structure as well as NaCl level on the proteolysis index and texture parameters observed in dry-cured meats produced from individual deer muscles. The biceps femoris, semimembranosus and longissimus lumborum muscles were cut from deer main elements, shaped into blocks by trimming off the edges, cured by adding 4, 6 and 8% of salt (w/w) and dried in a ripening chamber for 29days. The results indicated that deer dry-cured muscles with higher percentage of red fibres (type I) showed higher texture parameters, proteolysis index as well as lower moisture losses than muscles with higher amount of white fibres (type IIB). Dry-cured deer muscles with lower NaCl content showed higher values of proteolysis index and lower hardness, cohesiveness, springiness, and chewiness, as well as lower changes in structure elements. PMID:27442183

  17. The influence of silicon and phosphorus additions on neutron induced microstructural evolution of Fe sbnd Cr sbnd Ni ternary alloys at 646-703 K

    NASA Astrophysics Data System (ADS)

    Watanabe, H.; Garner, F. A.; Muroga, T.; Yoshida, N.

    1995-08-01

    The influence of silicon and phosphorus additions on void swelling in austenitic stainless steels under fast neutron irradiation has been investigated. A series of silicon containing alloys (Fe sbnd 15Cr sbnd 20Ni sbnd Si) and two series of phosphorus containing alloys (Fe sbnd 15Cr sbnd 25Ni sbnd P and Fe sbnd 16Cr sbnd 17Ni sbnd P) were irradiated in the temperature range of 646-703 K and 2 to 36 dpa. Fast neutron irradiation was performed in both FFTF and JOYO. Non-monotonic swelling in response to the solute level was observed in alloys with higher nickel content and at the solute levels where precipitation was not prominent. The enhanced void swelling observed at relatively low solute levels was mirrored by an enhanced void density. The results suggest that the enhancement of swelling by solute addition occurs when void nucleation was initially difficult.

  18. A cure for dyslexia?

    PubMed

    2007-02-01

    A company is promoting behavioral exercises as a cure for dyslexia. Scientists worry that evaluation of the program is compromised by design flaws and conflicts of interest and that responses to critics restrict academic freedom. PMID:17259957

  19. Silicone encapsulant development for fireset applications

    SciTech Connect

    Sayre, J.A.; Curro, J.G.; Paulsen, L.L.

    1983-05-01

    Purpose of this program is to formulate an encapsulant which is acceptable from a nuclear-safety standpoint, and can be used for encapsulation of firesets. Systems based on silicone resins have the lowest conductivity at elevated temperatures of any encapsulant studied. Unfortunately, silicone resins also have relatively low tear strengths and high-thermal-expansion coefficients. Despite these limitations, we previously formulated a Sylgard 184/glass microballoon encapsulant with acceptable mechanical and thermal properties. The Sylgard 184 resin system, which is a vinyl-addition silicone manufactured by Dow Corning has the undesirable property (for fireset applications) of outgassing substantial amounts of hydrogen. In order to eliminate this undersirable feature, we have recently formulated a new material based on a vinyl-addition silicone system which is cured with a peroxide and does not outgas hydrogen. Preliminary measurements on this new system look encouraging. An acceptable cure can be achieved at 40/sup 0/C; the viscosity, modulus and thermal expansion coefficient are virtually identical to the commercial Sylgard system. The tear strength, however, is about half the value of the Sylgard formulation (3.4 versus 6.4 Kj/m/sup 2/).

  20. Solubilization and spore recovery from silicone polymers. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Hsiao, Y. C.

    1974-01-01

    A non-sporicidal technique for solvent degradation of cured silicone polymers was developed which involves chemical degradation of cured silicone polymers by amine solvents at room temperature. Substantial improvements were obtained in the recovery of seeded spores from room temperature cured polymers as compared to the standard recovery procedures, which indicates that the curing process is not sufficiently exothermic to reduce spore viability. The dissolution reaction of cured silicone polymers whith amine solvents is proposed to occur by bimolecular nucleophilic displacement. The chemical structure of silicone polymers was determined by spectroscopic methods. The phenyl to methyl ratio, R/Si ratio, molecular weight, and hydroxyl content of the silicone resins were determined.

  1. Fast Curing of Composite Wood Products

    SciTech Connect

    Dr. Arthur J. Ragauskas

    2006-04-26

    The overall objective of this program is to develop low temperature curing technologies for UF and PF resins. This will be accomplished by: • Identifying the rate limiting UF and PF curing reactions for current market resins; • Developing new catalysts to accelerate curing reactions at reduced press temperatures and times. In summary, these new curing technologies will improve the strength properties of the composite wood products and minimize the detrimental effects of wood extractives on the final product while significantly reducing energy costs for wood composites. This study is related to the accelerated curing of resins for wood composites such as medium density fiberboard (MDF), particle board (PB) and oriented strandboard (OSB). The latter is frequently manufactured with a phenol-formaldehyde resin whereas ureaformaldehyde (UF) resins are usually used in for the former two grades of composite wood products. One of the reasons that hinder wider use of these resins in the manufacturing of wood composites is the slow curing speed as well as inferior bondability of UF resin. The fast curing of UP and PF resins has been identified as an attractive process development that would allow wood to be bonded at higher moisture contents and at lower press temperatures that currently employed. Several differing additives have been developed to enhance cure rates of PF resins including the use of organic esters, lactones and organic carbonates. A model compound study by Conner, Lorenz and Hirth (2002) employed 2- and 4-hydroxymethylphenol with organic esters to examine the chemical basis for the reported enhanced reactivity. Their studies suggested that the enhance curing in the presence of esters could be due to enhanced quinone methide formation or enhanced intermolecular SN2 reactions. In either case the esters do not function as true catalysts as they are consumed in the reaction and were not found to be incorporated in the polymerized resin product. An

  2. Additional fluorine passivation to pyrolytic-N2O passivated ultrathin silicon oxide/Si(100) films

    NASA Astrophysics Data System (ADS)

    Yamada, Hiroshi

    2006-08-01

    To enhance the reliability of ultrathin silicon oxide/Si(100) films and clarify the effect of fluorine on it, in situ pyrolytic-gas passivation (PGP) using NF3 was simultaneously performed with the previously proposed PGP using N2O. As a result, the following synergistic effects of F and N passivation for the films were confirmed: The electrical characteristics, such as the time-dependent dielectric breakdown lifetime, potential barrier height energy of the oxide, and interface state density, were significantly improved. Quantitative analyses of F and N indicated that this is probably caused by microscopic structural changes in the oxide near the oxide-Si(100) substrate interface. It is, therefore, believed that F passivation effectively contributes to compensate the inconsistent-state bonding sites near the interface that remain with N passivation.

  3. Modeling the mechanical and aging properties of silicone rubber and foam - stockpile-historical & additively manufactured materials

    SciTech Connect

    Maiti, A.; Weisgraber, T. H.; Gee, R. H.

    2014-09-30

    M97* and M9763 belong to the M97xx series of cellular silicone materials that have been deployed as stress cushions in some of the LLNL systems. Their purpose of these support foams is to distribute the stress between adjacent components, maintain relative positioning of various components, and mitigate the effects of component size variation due to manufacturing and temperature changes. In service these materials are subjected to a continuous compressive strain over long periods of time. In order to ensure their effectiveness, it is important to understand how their mechanical properties change over time. The properties we are primarily concerned about are: compression set, load retention, and stress-strain response (modulus).

  4. Curing Metastatic Breast Cancer.

    PubMed

    Sledge, George W

    2016-01-01

    Metastatic breast cancer is generally considered incurable, and this colors doctor-patient interactions for patients with metastatic disease. Although true for most patients, there appear to be important exceptions, instances where long-term disease-free survival occurs. Although these instances are few in number, they suggest the possibility of cure. How will we move toward cure for a much larger population of patients with metastatic disease? This article outlines a potential research agenda that might move us toward that distant goal. PMID:26759458

  5. Vinyl ether silicones

    SciTech Connect

    Herzig, C.; Dauth, J.; Deubzer, B.; Weis, J.

    1995-12-01

    Siloxanes with vinyl ether groups are prepared by hydrosilylation reaction of dihydrosiloxanes with divinyl ethers in excess. Different stoichiometry, produces linear copolymers of different viscosities and double bond concentrations always with an active vinyl ether group at each chain end. Polymerisations triggered by UV light were done with mixtures of these compounds and a series of onium salts. Very fast cure is observed even with low doses at 290 nm. V.E. silicones are found to cure essentially quantitative. The comparison with other highly reactive cationic monomers revealed that compounds are among the fastest curing prepolymers in cationic chemistry.

  6. New advanced shotcrete admixtures: Internal curing

    SciTech Connect

    Melbye, T.A.

    1995-12-31

    Tunnels and other underground construction projects have one of the worst curing conditions due to the ventilation that blows continuously dry (cold or hot) air into the tunnel. It can be compared with concrete exposed to a windy area. One would think that tunnels have ideal curing conditions with high humidity (water leakage), no wind and no sun exposure. However, this is not the case. MBT has developed a new system for more efficient and secure curing of wet shotcrete, repair mortars as well as concrete. Internal curing means that a special admixture is added to the concrete/mortar during batching as a normal admixture. This admixture produces an internal barrier in the shotcrete/concrete which secures safer hydration and better chemical resistance than the application of conventional curing agents. The benefits resulting from the new technology are impressive: The time consuming application and, in the case of various shotcrete layers, removal of curing agents are no longer necessary; curing is guaranteed from the very beginning of hydration; and there is no negative influence on bonding between layers. As a consequence of th is optimum curing effect, all other shotcrete characteristics are improved: density, final strengths, freeze/thaw and chemical resistances, watertightness, less cracking and shrinkage. In addition, MEYCO TCC 735 also improves pumpability and workability of shotcrete, even with low-grade aggregates. It particularly improves the pumpability of steel fiber reinforced shotcrete mixes. In combination with the MEYCO TCC system it contrives to even increase the beneficial effects of the slump killing system by further improving fiber orientation, reducing fiber rebound and thus raising toughness values.

  7. Curing Children's Cancer

    MedlinePlus

    ... ALL is a cancer of the white blood cells, which fight infection. It is the most common cancer in children, representing 23 percent of all cancers among those 15 or younger. Forty years ago, ALL was incurable. Today, in the United States, its cure rate is a major success story—as many ...

  8. Cure shrinkage effects in epoxy and polycyanate matrix composites

    SciTech Connect

    Spellman, G.P.

    1995-12-22

    A relatively new advanced composite matrix, polycyanate ester, was evaluated for cure shrinkage. The chemical cure shrinkage of composites is difficult to model but a number of clever experimental techniques are available to the investigator. In this work the method of curing a prepreg layup on top of a previously cured laminate of identical ply composition is utilized. The polymeric matrices used in advanced composites have been primarily epoxies and therefore a common system of this type, Fiberite 3501-6, was used as a base case material. Three polycyanate matrix systems were selected for the study. These are: Fiberite 954-2A, YLA RS-3, and Bryte Technology BTCy-1. The first three of these systems were unidirectional prepreg with carbon fiber reinforcement. The Bryte Technology material was reinforced with E-glass fabric. The technique used to evaluate cure shrinkage results in distortion of the flatness of an otherwise symmetric laminate. The first laminate is cured in a conventional fashion. An identical layup is cured on this first laminate. During the second cure all constituents are exposed to the same thermal cycles. However, only the new portion of the laminate will experience volumetric changes associate with matrix cure. The additional strain of cure shrinkage results in an unsymmetric distribution of residual stresses and an associated warpage of the laminate. The baseline material, Fiberite 3501-6, exhibited cure shrinkage that was in accordance with expectations. Cure strains were {minus}4.5E-04. The YLA RS-3 material had cure strains somewhat lower at {minus}3.2E-04. The Fiberite 954-2A cure strain was {minus}1.5E-04 that is 70% lower than the baseline material. The glass fabric material with the Bryte BTCy-1 matrix did not result in meaningful results because the processing methods were not fully compatible with the material.

  9. The effect of curing modes on polymerization contraction stress of a dual cured composite.

    PubMed

    Feng, L; Suh, B I

    2006-01-01

    Although a lower curing rate is often cited as the reason why a chemical cured (CC) dental composite produces lower polymerization contraction stress (PCS) than a light cured (LC) composite, the exact mechanism is still unclear. In addition, the comparison is often made by using different brands of composites. The comparison's fairness is questionable because the two composites have different compositions and preparation procedures. The goal of the present work was to determine if the curing mode alone can produce different PCS. We formulated a dual cured composite and prepared it the same way for both CC and LC modes. We measured PCS by a strain gauge method, shrinkage by a video-imagining technique, degree of conversion (DC) by infrared spectroscopy, and flexural modulus by the three-point bending test. The CC specimens showed lower PCS and lower flexural modulus than the LC specimens, although both possessed an identical chemical composition and physical texture before cure. This finding indicates that the curing mode alone can affect PCS. Because the CC and LC specimens produced a similar shrinkage and DC, the lower modulus is considered to be one of the reasons for the lower stress. Using a structural inhomogeneity model, we explained how a resin composite with an identical DC can have different physical properties such as the modulus. PMID:16047326

  10. Effect of silicon alloying additions on growth temperature and primary spacing of Al{sub 3}Fe in Al-8wt%Fe alloy

    SciTech Connect

    Liang, D.; Jones, H.; Gilgien, P.

    1995-05-15

    Alloys of Al-8.4Fe-1.7Si, Al-8.5Fe-3.4Si and Al-8.5Fe-5.6Si (wt%) designated A, B and C, respectively, were prepared from high purity (99.99%) aluminum, Japanese electrolytic iron (99.9%) and superpure silicon (99.99%). Melting was carried out in a recrystallized alumina crucible by using a Radyne induction furnace and was followed by chill casting under flowing argon into steel molds of cavity dimension 15 mm thick, 50 mm wide and 150 mm high. Rods 3 mm in diameter were fabricated directly from the ingots. Lengths of the rods, which were contained in 3 mm bore tubular alumina crucibles, were melted in a Bridgman growth facility. After maintaining the melt at 100K above the liquidus temperatures liquidus: 1,118, 1,108 and 1,092 K for 1.7, 3.4 and 5.6 wt%Si, respectively, for about 10 minutes, crucibles containing the melt were withdrawn at a speed of 0.34 mm/s into a water bath. The following conclusions can be drawn from analysis of the specimens. Addition of silicon to Al-8wt%Fe alloy results in an increase in growth undercooling and primary spacing of Al{sub 3}Fe dendrites Bridgman grown at 0.34 mm/s and 10K/mm. This increase in growth undercooling, relative to predicted local liquidus temperatures which have been corrected for observed macrosegregation of Fe, is in good accord with the predictions of the Kurz-Giovanola-Trivedi model for needle-like dendrite growth. The silicon content of the Al{sub 3}Fe dendrites obtained is consistent with previously reported measurements for a range of cast Al-Fe-Si alloys.

  11. Electron beam curing of EPDM

    SciTech Connect

    Vroomen, G.L.M.; Visser, G.W.; Gehring, J.

    1991-11-01

    Normally EPDM rubbers are vulcanized by systems based on sulphur, resin or peroxide. The common feature of these systems is that they all require activator energy in the form of heat. The (extremely) high temperatures (approximately 180C) have the disadvantage that the final properties of the finished product may be affected in one way or another by a variety of uncontrolled side reactions which may occur. Radiation curing, on the other hand, is a process which differs from those mentioned above in that the final curing is carried out at about 20C under closely controlled conditions (such as radiation dose, penetration depth, etc.), and this form of curing ultimately results in a more well-defined end product. In the rubber industry, this technique is used by large rubber processors (for example, in roof sheeting and cable production). Its widespread use is, however, impeded by the high investment costs. One way of avoiding these high costs is to arrange for the products to be irradiated by contractors. The optimum radiation dose for EPDM is determined by the required pattern of properties. From this study it may be concluded that the network is primarily built up at a radiation dose of up to approximately 100 kGy. The degree to which it is built up depends partly on the coactivator used and the EPDM type used. In choosing the coactivator, allowance has to be made for its solubility in EPDM. The type of oil chosen and any stabilizer additions will affect the crosslinking efficiency. Contrary to studies published earlier, in this study it was found that when EDMA is used as a coactivator, no difference can be detected between a DCPD type (4%) and an ENB type (4%), provided both have an identical molecular weight distribution. Increasing the ENB content has less effect on the final crosslink density than using a type having a broader molecular weight distribution.

  12. Process for curing bismaleimide resins

    NASA Technical Reports Server (NTRS)

    Parker, John A. (Inventor); OTHY S.imides alone. (Inventor)

    1986-01-01

    This invention relates to vinyl pyridine group containing compounds and oligomers, their advantageous copolymerization with bismaleimide resins, and the formation of reinforced composites based on these copolymers. When vinyl pyridines including vinyl stilbazole materials and vinyl styrylpyridine oligomer materials are admixed with bismaleimides and cured to form copolymers the cure temperatures of the copolymers are substantially below the cure temperatures of the bismaleimides alone.

  13. Applications of mass spectrometry techniques to autoclave curing of materials

    NASA Technical Reports Server (NTRS)

    Smith, A. C.

    1983-01-01

    Mass spectrometer analysis of gases evolved from polymer materials during a cure cycle can provide a wealth of information useful for studying cure properties and procedures. In this paper data is presented for two materials to support the feasibility of using mass spectrometer gas analysis techniques to enhance the knowledge of autoclave curing of composite materials and provide additional information for process control evaluation. It is expected that this technique will also be useful in working out the details involved in determining the proper cure cycle for new or experimental materials.

  14. Effects of silicon additions on oxidation and mechanical behavior of the nickel-base superalloy B-1900

    NASA Technical Reports Server (NTRS)

    Miner, R. V., Jr.; Lowell, C. E.

    1975-01-01

    Test specimens with nominal additions of Si were tested in oxidation, thermal fatigue, sulfidation, tension, and stress rupture, and were also extensively studied metallographically. Alloy B-1900 modified with 0.6- or 1.2-wt% Si exhibited oxidation resistance equivalent to that of aluminide-coated B-1900 during cyclic, high-gas-velocity oxidation tests. Resistances to thermal fatigue and sulfidation were improved by the Si additions, but were not superior to aluminide-coated B-1900. Stress-rupture tests at 1000 C of specimens given the standard heat treatment to simulate an aluminide coating cycle showed Si to be detrimental. However, application of another heat treatment increased the rupture life of the alloy with 0.6-wt% Si to that of the unmodified B-1900 given the standard heat treatment.

  15. FTIR Monitoring Of Curing Of Composites

    NASA Technical Reports Server (NTRS)

    Druy, Mark A.; Stevenson, William A.; Young, Philip R.

    1990-01-01

    Infrared-sensing optical fiber system developed to monitor principal infrared absorption bands resulting from vibrations of atoms and molecules as chemical bonds form when resin cured. System monitors resin chemistry more directly. Used to obtain Fourier transform infrared (FTIR) spectrum from graphite fiber/polyimide matrix resin prepreg. Embedded fiber optic FTIR sensor used to indicate state of cure of thermosetting composite material. Developed primarily to improve quality of advanced composites, many additional potential applications exist because principal of operation applicable to all organic materials and most inorganic gases. Includes monitoring integrities of composite materials in service, remote sensing of hazardous materials, and examination of processes in industrial reactors and furnaces.

  16. Addition polymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and Bis-dienes. 2: Evidence for thermal dehydration occurring in the cure process

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Olshavsky, Michael A.; Meador, Michael A.; Ahn, Myong-Ku

    1988-01-01

    Diels-Alder cycloaddition copolymers from 1,4,5,8-tetrahydro-1,4;5,8-diepoxyanthracene and anthracene end-capped polyimide oligomers appear, by thermogravimetric analysis (TGA), to undergo dehydration at elevated temperatures. This would produce thermally stable pentiptycene units along the polymer backbone, and render the polymers incapable of unzipping through a retro-Diels-Alder pathway. High resolution solid 13C nuclear magnetic resonance (NMR) of one formulation of the polymer system before and after heating at elevated temperatures, shows this to indeed be the case. NMR spectra of solid samples of the polymer before and after heating correlated well with those of the parent pentiptycene model compound before and after acid-catalyzed dehydration. Isothermal gravimetric analyses and viscosities of the polymer before and after heat treatment support dehydration as a mechanism for the cure reaction.

  17. Effect of tungsten, molybdenum and silicon additions on the creep resistance of a gamma titanium aluminide alloy

    SciTech Connect

    Seo, D.Y.; Bieler, T.R.; An, S.U.; Larsen, D.E.; Bhowal, P.; Merrick, H.

    1995-12-31

    Alloy development programs involving gamma titanium aluminide alloys have mainly focused on increasing room temperature ductility, but this has been achieved at the expense of creep properties. Since recent engine tests have been successful with materials having a ductility of about 1.5%, this study focuses on the effects of W, Mo and Si additions. The creep rate is reduced by a factor of 30 at 760 C (1,400 F). Microstructure studies described below show that 0.2--2 {micro}m precipitates form during primary creep deformation and these precipitates interfere with dislocation mobility. These precipitates contain higher concentrations of W and Mo than found in the matrix, but they have a crystal structure that correlates with the Ti{sub 5}Si{sub 3} crystal structure. In addition, a substantial fraction of initial creep strain is accommodated by formation of mechanical twins parallel to lamellar planes that refine the lamellar spacing, and these also initiate mechanical twinning in the equiaxed grains.

  18. Isothiourea-Mediated Organocatalytic Michael Addition-Lactonization on a Surface: Modification of SAMs on Silicon Oxide Substrates.

    PubMed

    Chisholm, Ross; Parkin, John D; Smith, Andrew D; Hähner, Georg

    2016-04-01

    Tailoring the functionality of self-assembled monolayers (SAMs) can be achieved either by depositing prefunctionalized molecules with the appropriate terminal groups or by chemical modification of an existing SAM in situ. The latter approach is particularly advantageous to allow for diversity of surface functionalization from a single SAM and if the incorporation of bulky groups is desired. In the present study an organocatalytic isothiourea-mediated Michael addition-lactonization process analogous to a previously reported study in solution is presented. An achiral isothiourea, 3,4-dihydro-2H-pyrimido[2,1-b]benzothiazole (DHPB), promotes the intermolecular Michael addition-lactonization of a trifluoromethylenone terminated SAM and a variety of arylacetic acids affording C(6)-trifluoromethyldihydropyranones tethered to the surface. X-ray photoelectron spectroscopy, atomic force microscopy, contact angle, and ellipsometry analysis were conducted to confirm the presence of the substituted dihydropyranone. A model study of this approach was also performed in solution to probe the reaction diastereoselectivity as it cannot be measured directly on the surface. PMID:27015037

  19. Quenching and partitioning response of carbon-manganese-silicon sheet steels containing nickel, molybdenum, aluminum and copper additions

    NASA Astrophysics Data System (ADS)

    Kahkonen, Joonas

    . Retained austenite fractions up to 28 pct and UTS levels exceeding 1500, 1600, and 1700 MPa with TE levels of 20, 17 and 12 pct respectively were measured for the 0.3C-5Mn-1.6Si alloy. Molybdenum and aluminum additions to a 0.3C-3Mn-1.5Si alloy were not observed to significantly affect the resulting tensile properties at a partitioning temperature of 400 °C. Partitioning at 450 °C increased the TE levels of the 0.3C-3Mn-1.5Si-0.25Mo-0.85Al alloy and decreased the TE levels of the 0.3C-3Mn-1.5Si-0.25Mo alloy while similar UTS levels were measured in both alloys. The aluminum addition potentially increased strain hardening. RA fractions were observed to be close to predicted levels in both alloys. Copper and nickel additions were not observed to increase the resulting maximum UTS˙TE levels. Copper and nickel additions increased RA levels and the measured RA levels were observed to be close to the predicted values.

  20. The Lourdes Medical Cures Revisited†

    PubMed Central

    François, Bernard; Sternberg, Esther M.; Fee, Elizabeth

    2014-01-01

    This article examines the cures recorded in Lourdes, France, between 1858, the year of the Visions, and 1976, the date of the last certified cure of the twentieth century. Initially, the records of cures were crude or nonexistent, and allegations of cures were accepted without question. A Medical Bureau was established in 1883 to examine and certify the cures, and the medical methodology improved steadily in the subsequent years. We discuss the clinical criteria of the cures and the reliability of medical records. Some 1,200 cures were said to have been observed between 1858 and 1889, and about one hundred more each year during the “Golden Age” of Lourdes, 1890–1914. We studied 411 patients cured in 1909–14 and thoroughly reviewed the twenty-five cures acknowledged between 1947 and 1976. No cure has been certified from 1976 through 2006. The Lourdes phenomenon, extraordinary in many respects, still awaits scientific explanation. Lourdes concerns science as well as religion. PMID:22843835

  1. Silicone based artificial skin for humanoid facial expressions

    NASA Astrophysics Data System (ADS)

    Tadesse, Yonas; Moore, David; Thayer, Nick; Priya, Shashank

    2009-03-01

    Artificial skin materials were synthesized using platinum-cured silicone elastomeric material (Reynolds Advanced Materials Inc.) as the base consisting of mainly polyorganosiloxanes, amorphous silica and platinum-siloxane complex compounds. Systematic incorporation of porosity in this material was found to lower the force required to deform the skin in axial direction. In this study, we utilized foaming agents comprising of sodium bicarbonate and dilute form of acetic acid for modifying the polymeric chain and introducing the porosity. Experimental determination of functional relationship between the concentration of foaming agent, slacker and non-reactive silicone fluid and that of force - deformation behavior was conducted. Tensile testing of material showed a local parabolic relationship between the concentrations of foaming agents used (per milliliter of siloxane compound) and strain. This data can be used to optimize the amount of additives in platinum cured silicone to obtain desired force - displacement characteristics. Addition of "silicone thinner" and "slacker" showed a monotonically increasing strain behavior. A mathematical model was developed to arrive at the performance metrics of artificial skin.

  2. Effect of Curing Profile on Kaolin-based Geopolymers

    NASA Astrophysics Data System (ADS)

    Heah, C. Y.; Kamarudin, H.; Bakri, A. M. Mustafa Al; Binhussain, M.; Luqman, M.; Nizar, I. Khairul; Ruzaidi, C. M.; Liew, Y. M.

    Depending on the processing conditions, geopolymers can exhibit a wide variety of properties and characteristics. Curing profile serves as a crucial parameter in synthesis of geopolymers. In this paper, the influence of curing temperature and curing time on the properties of kaolin-based geopolymer was studied. The samples were separated into several curing conditions; including curing at ambient temperature, 40 °C, 60 °C, 80 °C and 100 °C for 1 day, and up to 3 days. The compressive strength and SEM analysis of geopolymer products were evaluated. Results showed that curing condition has a significant effect on the mechanical properties of kaolin-based geopolymer. Generally, curing at ambient temperature was not feasible, while increase in temperature favored the strength development. In addition, prolonged curing time improved the geopolymerization process, and led to higher strength gain. However, curing at high temperature for a long period of time caused failure of the sample at a later age.

  3. Comparative static curing versus dynamic curing on tablet coating structures.

    PubMed

    Gendre, Claire; Genty, Muriel; Fayard, Barbara; Tfayli, Ali; Boiret, Mathieu; Lecoq, Olivier; Baron, Michel; Chaminade, Pierre; Péan, Jean Manuel

    2013-09-10

    Curing is generally required to stabilize film coating from aqueous polymer dispersion. This post-coating drying step is traditionally carried out in static conditions, requiring the transfer of solid dosage forms to an oven. But, curing operation performed directly inside the coating equipment stands for an attractive industrial application. Recently, the use of various advanced physico-chemical characterization techniques i.e., X-ray micro-computed tomography, vibrational spectroscopies (near infrared and Raman) and X-ray microdiffraction, allowed new insights into the film-coating structures of dynamically cured tablets. Dynamic curing end-point was efficiently determined after 4h. The aim of the present work was to elucidate the influence of curing conditions on film-coating structures. Results demonstrated that 24h of static curing and 4h of dynamic curing, both performed at 60°C and ambient relative humidity, led to similar coating layers in terms of drug release properties, porosity, water content, structural rearrangement of polymer chains and crystalline distribution. Furthermore, X-ray microdiffraction measurements pointed out different crystalline coating compositions depending on sample storage time. An aging mechanism might have occur during storage, resulting in the crystallization and the upward migration of cetyl alcohol, coupled to the downward migration of crystalline sodium lauryl sulfate within the coating layer. Interestingly, this new study clearly provided further knowledge into film-coating structures after a curing step and confirmed that curing operation could be performed in dynamic conditions. PMID:23792043

  4. Modeling HIV Cure

    NASA Astrophysics Data System (ADS)

    Perelson, Alan; Conway, Jessica; Cao, Youfang

    A large effort is being made to find a means to cure HIV infection. I will present a dynamical model of post-treatment control (PTC) or ``functional cure'' of HIV-infection. Some patients treated with suppressive antiviral therapy have been taken off of therapy and then spontaneously control HIV infection such that the amount of virus in the circulation is maintained undetectable by clinical assays for years. The model explains PTC occurring in some patients by having a parameter regime in which the model exhibits bistability, with both a low and high steady state viral load being stable. The model makes a number of predictions about how to attain the low PTC steady state. Bistability in this model depends upon the immune response becoming exhausted when over stimulated. I will also present a generalization of the model in which immunotherapy can be used to reverse immune exhaustion and compare model predictions with experiments in SIV infected macaques given immunotherapy and then taken off of antiretroviral therapy. Lastly, if time permits, I will discuss one of the hurdles to true HIV eradication, latently infected cells, and present clinical trial data and a new model addressing pharmacological means of flushing out the latent reservoir. Supported by NIH Grants AI028433 and OD011095.

  5. Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

    NASA Astrophysics Data System (ADS)

    Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

    2016-06-01

    In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients ( L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient ( β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

  6. Thermodynamics and Kinetics of Boron Removal from Metallurgical Grade Silicon by Addition of High Basic Potassium Carbonate to Calcium Silicate Slag

    NASA Astrophysics Data System (ADS)

    Wu, Jijun; Wang, Fanmao; Ma, Wenhui; Lei, Yun; Yang, Bin

    2016-02-01

    In this study, we investigated the thermodynamics and kinetics of boron removal from metallurgical grade silicon (MG-Si) using a calcium silicate slag containing a high basic potassium carbonate. The distribution of boron between slag and silicon was theoretically derived and the distribution coefficients (L B) of boron with different compositions of CaO, SiO2, and K2CO3 in slag reagents were determined. The maximal value of L B reached 2.08 with a high basicity slag of 40 pctCaO-40 pctSiO2-20 pctK2CO3 (Λ = 0.73). The boron removal rates from MG-Si using CaO-SiO2 and CaO-SiO2-K2CO3 slags at 1823 K (1550 °C) were investigated in an electromagnetic induction furnace. The results showed that the boron concentration in MG-Si can be reduced from 22 to 1.8 ppmw at 1823 K (1550 °C) with 20 pct K2CO3 addition to calcium silicate slag, where the removal efficiency of boron reached 91.8 pct. The mass transfer coefficient (β S) of boron in binary 50 pctCaO-50 pctSiO2 slag was 3.16 × 10-6 m s-1 at 1823 K (1550 °C) and was 2.43 × 10-5 m s-1 in ternary 40 pctCaO-40 pctSiO2-20 pctK2CO3 slag.

  7. Direct Imprinting of Liquid Silicon.

    PubMed

    Masuda, Takashi; Takagishi, Hideyuki; Yamazaki, Ken; Shimoda, Tatsuya

    2016-04-20

    A polymeric precursor solution for semiconducting silicon called "liquid silicon" was synthesized and directly imprinted to form well-defined and fine amorphous silicon patterns. The spin-coated film was cured and imprinted followed by annealing at 380 °C to complete the polymer-to-silicon conversion. A pattern with dimensions of several hundreds of nanometers or less was obtained on a substrate. We demonstrated that the curing step before imprinting is particularly important in the imprinting process. A curing temperature of 140-180 °C was found to be optimal in terms of the film's deformability and molding properties. Fourier transform infrared spectroscopy and thermal analysis clarified that the cross-linking of the polymer due to the 1,2-hydrogen shift reaction was induced exponentially with the release of a large amount of SiH4/H2 gases at temperatures between 140 and 220 °C, leading to the solidification of the film. Consequently, the film completely lost its deformability at higher temperatures. Despite a volume shrinkage as large as 53-56% during the polymer-to-silicon conversion, well-defined angular patterns were preserved. Fine silicon patterns were formed via the direct imprinting of liquid silicon with high resolution and high throughput, demonstrating the usefulness of this technique for the future manufacturing of silicon electronics. PMID:27028558

  8. Effects of Interface Coating and Nitride Enhancing Additive on Properties of Hi-Nicalon SiC Fiber Reinforced Reaction-Bonded Silicon Nitride Composites

    NASA Technical Reports Server (NTRS)

    Bhatt, Ramakrishana T.; Hull, David R.; Eldridge, Jeffrey I.; Babuder, Raymond

    2000-01-01

    Strong and tough Hi-Nicalon SiC fiber reinforced reaction-bonded silicon nitride matrix composites (SiC/ RBSN) have been fabricated by the fiber lay-up approach. Commercially available uncoated and PBN, PBN/Si-rich PBN, and BN/SiC coated SiC Hi-Nicalon fiber tows were used as reinforcement. The composites contained approximately 24 vol % of aligned 14 micron diameter SiC fibers in a porous RBSN matrix. Both one- and two-dimensional composites were characterized. The effects of interface coating composition, and the nitridation enhancing additive, NiO, on the room temperature physical, tensile, and interfacial shear strength properties of SiC/RBSN matrix composites were evaluated. Results indicate that for all three coated fibers, the thickness of the coatings decreased from the outer periphery to the interior of the tows, and that from 10 to 30 percent of the fibers were not covered with the interface coating. In the uncoated regions, chemical reaction between the NiO additive and the SiC fiber occurs causing degradation of tensile properties of the composites. Among the three interface coating combinations investigated, the BN/SiC coated Hi-Nicalon SiC fiber reinforced RBSN matrix composite showed the least amount of uncoated regions and reasonably uniform interface coating thickness. The matrix cracking stress in SiC/RBSN composites was predicted using a fracture mechanics based crack bridging model.

  9. Delayed cure bismaleimide resins

    DOEpatents

    Adams, Johnnie E.; Jamieson, Donald R.

    1984-08-07

    Polybismaleimides prepared by delayed curing of bis-imides having the formula ##STR1## wherein R.sub.1 and R.sub.2 each independently is H, C.sub.1-4 -alkyl, C.sub.1-4 -alkoxy, Cl or Br, or R.sub.1 and R.sub.2 together form a fused 6-membered hydrocarbon aromatic ring, with the proviso that R.sub.1 and R.sub.2 are not t-butyl or t-butoxy; X is O, S or Se; n is 1-3; and the --(CH.sub.2).sub.n -- group, optionally, is substituted by 1-3 methyl groups or by fluorine.

  10. Nonpost mold cure compound

    NASA Astrophysics Data System (ADS)

    Hirata, Akihiro

    1997-08-01

    The recent low price trend of electronic products has made IC manufacturing efficiency a top priority in the semiconductor industry. Post mold cure (PMC) process, which generally involves heating the packages in the oven at 175 C for 4 to 8 hours, takes up much longer time than most other assembly processes. If this PMC process can be reduced or eliminated, semiconductor makers will be rewarded with a much higher cost merit. We define the purpose of Non-PMC as 'to get high reliability with suitable physical and electrical properties without PMC'. We compared carious properties of molding compound before and after PMC. We found that curing reaction has almost complete through DSC and C-NMR measurement, but several properties have not stabilized yet, and that not all properties after PMC were better than before PMC. We developed new grade of molding compound considering these facts. And we found that main factors to accomplish non-PMC compound are curability and flowability, and more, increasing of fundamental properties. To accomplish non-PMC, at first, molding compound need to have very high curability. Generally speaking, too high curability causes low flowability, and causes incomplete filing, wire sweep, pad shift, and weak adhesion to inner parts of IC packages. To prevent these failures, various compound properties were studied, and we achieved in adding good flowability to very high curable molding compound. Finally, anti-popcorn property was improved by adding low moisture, high adhesion, high Tg, and high flexural strengths at high temperature. Through this study, we developed new compound grade for various package, especially large QFP using standard ECN resin.

  11. Purified silicon production system

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2004-03-30

    Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

  12. Is the soft-start polymerisation concept still relevant for modern curing units?

    PubMed

    Ilie, Nicoleta; Jelen, Esther; Hickel, Reinhard

    2011-02-01

    Shrinkage stress, degree of cure and mechanical properties are contradicting properties, forcing to a compromise between an adequate curing and low stress at the interface tooth-restoration. The purpose of this study was to quantify this relations for a micro-hybrid composite, by analysing in real time the development of degree of cure at depths of 2 and 6 mm, shrinkage stress and curing time until gelation, as well as the variation of micro-mechanical properties with depth, after curing with 13 regimes of one halogen and two light-emitting diode (LED) curing units. A nano-dynamic mechanical test was additionally performed on selected regimes (Ramp, Pulse and Fast Cure) of the same curing unit. The present study showed that the soft-start polymerization concept is still valid for less deep cavities (2 mm), even by curing with high-power LED curing units, since a soft-cure polymerization resulted in a delayed gel point and a lower shrinkage stress, keeping simultaneously the degree of cure and mechanical properties constant. At 6 mm depth, curing with soft-start regimes resulted in a significant decrease in degree of cure, although this decrease was less than 10%, while the mechanical properties were maintained. PMID:19937074

  13. Curing chemistry of phenylethynyl-terminated imide oligomers: Model compounds, carbon-13 labeling and cure analysis

    NASA Astrophysics Data System (ADS)

    Roberts, Christopher Chad

    1998-11-01

    determining the structure of the cured resin. In addition, several relationships between the fina

  14. Effects of Rare Earth (RE) Intergranular Adsorption on the Phase Transformation and Microstructure Evolution in Silicon Nitride with RE2O3 + MgO Additives: Fracture Behavior

    SciTech Connect

    Becher, Paul F; Painter, Gayle S; Shibata, Naoya; Waters, Shirley B; Lin, Hua-Tay

    2008-07-01

    Silicon nitride powders consist primarily of the alpha phase, which transforms to the beta phase during the densification and microstructural evolution of Si3N4 ceramics. The temperature at which the transformation initiates in the presence of a combination of MgO and RE2O3 densification additives is found to decrease with increasing atomic number of the rare earth (RE). This trend coincides with the predicted and observed decrease in the affinity of the rare earth to segregate to and absorb on the prism planes of hexagonal prism shaped beta grains with increase in the atomic number of the RE. When RE adsorption is diminished, Si (and N) attachment on the smooth prism planes is enhanced, which increases diametrical growth rates, normally reaction-rate limited by an attachment mechanism. Combined with the typically fast [0001] growth, it is this augmented grain growth that contributes towards the initiation of the alpha-beta transformation at lower temperatures. With the enhanced transformation, observations reveal an increase in the number of beta grains growing in the early stages of densification. On the other hand, increased RE adsorption leads to greater growth anisotropy resulting in the formation of higher aspect ratio grains. Thus, Lu2O3 generates larger diameter, yet elongated, reinforcing grains, while La2O3 results in reinforcing grains of higher aspect ratio. The Gd2O3 additive transformation and microstructual characteristics lie intermediate to those of the lanthanide end member elements. Despite these differences, a substantial fraction of large reinforcing grains were found for each additive composition. As a result, the mechanical properties of the resultant ceramics are similar with flexure strengths in excess of 1 GPa, fracture toughness values greater than 10 MPa m1/2 at room temperature and excellent strength retention (>800 MPa) at 1200 C.

  15. Fiber-optic epoxy composite cure sensor. II. Performance characteristics

    NASA Astrophysics Data System (ADS)

    Lam, Kai-Yuen; Afromowitz, Martin A.

    1995-09-01

    The performance of a fiber-optic epoxy composite cure sensor, as previously proposed, depends on the optical properties and the reaction kinetics of the epoxy. The reaction kinetics of a typical epoxy system are presented. It is a third-order autocatalytic reaction with a peak observed in each isothermal reaction-rate curve. A model is derived to describe the performance characteristics of the epoxy cure sensor. If a composite coupon is cured at an isothermal temperature, the sensor signal can be used to predict the time when the gel point occurs and to monitor the cure process. The sensor is also shown to perform well in nonstoichiometric epoxy matrices. In addition the sensor can detect the end of the cure without calibration.

  16. Ambient curing fire resistant foams

    NASA Technical Reports Server (NTRS)

    Hamermesh, C. L.; Hogenson, P. A.; Tung, C. Y.; Sawko, P. M.; Riccitiello, S. R.

    1979-01-01

    The feasibility of development of an ambient curing foam is described. The thermal stability and flame spread index of the foams were found to be comparable to those of the high-temperature cured polyimide foams by Monsanto two-foot tunnel test and NASA T-3 Fire test. Adaptation of the material to spray in place applications is described

  17. Recent developments in radiation curing in the USA

    NASA Astrophysics Data System (ADS)

    Nablo, Sam V.

    Radiation curing activities in the USA continue to focus strongly on the use of both UV and EB for the polymerization of silicone release coatings on paper and film. The high speeds of cure (200 m/minute) achievable at "room temperature" continue to make this the process of choice for the siliconization of both film and paper. Some of the process difficulties peculiar to this chemistry will be discussed. The success of the multi-color lithographic printing of web using single station electron curing has resulted in a major market for electron processors. The aesthetic and physical properties of the overprint varnishes used in this application are important and will be discussed. The relatively high costs of both the inks and varnishes will probably limit this application to folding carton use for foodstuffs and high quality products, with UV continuing to dominate in lower speed, less demanding applications. The application of electron initiated graft modification of polymer materials, particularly for biological/medical device application, is showing a good rate of development as is the use of selective treatment of materials for functional modification of packaging films, particularly for gas permeability control. Some examples of these applications will be reviewed. Continued work with "deep" curing or vulcanization of composite structures, particularly in the elastomers field, will be discussed with a brief review of the continuing growth of electron processing in this industry, particularly for tires and roofing products.

  18. Vacuum deposition and curing of liquid monomers

    DOEpatents

    Affinito, J.D.

    1995-03-07

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of ``standard`` polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal or oxide may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface.

  19. Vacuum deposition and curing of liquid monomers

    DOEpatents

    Affinito, John D.

    1993-01-01

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of "standard" polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface.

  20. Vacuum deposition and curing of liquid monomers

    DOEpatents

    Affinito, John D.

    1995-01-01

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of "standard" polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal or oxide may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface.

  1. Vacuum deposition and curing of liquid monomers

    DOEpatents

    Affinito, J.D.

    1993-11-09

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of standard polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface.

  2. Antibiotics Cure Anthrax in Animal Models▿

    PubMed Central

    Weiss, Shay; Kobiler, David; Levy, Haim; Pass, Avi; Ophir, Yakir; Rothschild, Nili; Tal, Arnon; Schlomovitz, Josef; Altboum, Zeev

    2011-01-01

    Respiratory anthrax, in the absence of early antibiotic treatment, is a fatal disease. This study aimed to test the efficiency of antibiotic therapy in curing infected animals and those sick with anthrax. Postexposure prophylaxis (24 h postinfection [p.i.]) of guinea pigs infected intranasally with Bacillus anthracis Vollum spores with doxycycline, ofloxacin, imipenem, and gentamicin conferred protection. However, upon termination of treatment, the animals died from respiratory anthrax. Combined treatment with antibiotics and active vaccination with a protective antigen-based vaccine leads to full protection even after cessation of treatment. Delaying the initiation of antibiotic administration to over 24 h p.i. resulted in treatment of animals with anthrax exhibiting various degrees of bacteremia and toxemia. Treatment with doxycycline or ciprofloxacin cured sick guinea pigs and rabbits exhibiting bacteremia levels up to 105 CFU/ml. Addition of anti-protective antigen (PA) antibodies augmented the efficiency of protection, allowing the cure of guinea pigs and rabbits with 10- to 20-fold-higher bacteremia levels, up to 7 × 105 CFU/ml and 2 × 106 CFU/ml, respectively. Treatment with ciprofloxacin and a monoclonal anti-PA antibody rescued rabbits with bacteremia levels up to 4 × 106 CFU/ml. During antibiotic administration, all surviving animals developed a protective immune response against development of a fatal disease and subcutaneous challenge with Vollum spores. In conclusion, these results demonstrate that antibiotic treatment can prevent the development of fatal disease in respiratory-anthrax-infected animals and can cure animals after disease establishment. A therapeutic time window of 40 h to 48 h from infection to initiation of efficient antibiotic-mediated cure was observed. PMID:21263056

  3. Towards a 'cure' for IBD.

    PubMed

    Fiocchi, Claudio

    2012-01-01

    To discuss a cure for IBD, one should first define the concept 'a cure'. If it is intended as the general restoration of health, this is already possible, as many current therapies do a good job in inducing long periods of remission in Crohn's disease, and colectomy can technically cure ulcerative colitis. If it is more strictly defined as the complete and permanent elimination of the cause, predisposing and permissive factors, reinstatement of normal microbial ecology and restoration of mucosal immune homeostasis, then a cure for IBD is out of reach, at least for now. Regardless of the definition, major strides have been made in attempting to cure IBD by addressing the key components of its pathogenesis: the environment (exposome), the genetic makeup (genome), the gut microbiota (microbiome) and the immune system (immunome). However, the isolated modulation of each component is insufficient to provide a cure, and different requirements may be needed depending on the stage of the disease and each patient subset. To achieve a cure, one key approach is currently missing: the integration of knowledge from all the pathogenic components. We continue to learn more and more about each component using traditional 'canonical' systems, which allow the accumulation of data without taking into consideration the other components. We are still not studying the 'omes' of IBD, we should be using 'omics' technologies that can generate a more global vision of IBD pathogenesis on which to base novel, multiple pathway-integrated therapies. PMID:22796811

  4. Effect of small additions of silicon, iron, and aluminum on the room-temperature tensile properties of high-purity uranium

    SciTech Connect

    Ludwig, R.L.

    1983-11-14

    Eleven binary and ternary alloys of uranium and very low concentrations of iron, silicon, and aluminum were prepared and tested for room-temperature tensile properties after various heat treatments. A yield strength approximately double that of high-purity derby uranium was obtained from a U-400 ppM Si-200 ppM Fe alloy after beta solution treatment and alpha aging. Higher silicon plus iron alloy contents resulted in increased yield strength, but showed an unacceptable loss of ductility.

  5. Accelerated Cure Project for Multiple Sclerosis

    MedlinePlus

    ... tweets Tweets by @AcceleratedCure Front The Accelerated Cure Project for MS is a non-profit, 501(c)( ... determines its causes and mechanisms. © 2016 Accelerated Cure Project. All rights reserved. Site Map Contact Us Privacy ...

  6. Slide Rule For Calculating Curing Schedules

    NASA Technical Reports Server (NTRS)

    Heater, Don

    1995-01-01

    Special-purpose slide rule devised for calculating schedules for storing and curing adhesives, sealants, and other materials characterized by known curing times and shelf lives. Prevents mistakes commonly made in determining storage and curing schedules.

  7. Curing HIV: Moving Forward Faster.

    PubMed

    Flores, Marcella; Johnston, Rowena

    2016-02-01

    There is enormous enthusiasm in the scientific community for finding a cure for HIV. Although much remains to be discovered regarding the mechanisms of viral persistence and how it may be disrupted, some assumptions regarding the goals of a cure, applicability to target populations, and what is required of the assays we employ, may lead to missed opportunities and discoveries and hamper the discovery of a product that will safely cure tens of millions of HIV-infected people around the world. The field will benefit from an awareness and critical interrogation of assumptions that may be implicit in their scientific pursuits. PMID:26862662

  8. Additive manufacturing of polymer-derived ceramics.

    PubMed

    Eckel, Zak C; Zhou, Chaoyin; Martin, John H; Jacobsen, Alan J; Carter, William B; Schaedler, Tobias A

    2016-01-01

    The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging. PMID:26721993

  9. Additive manufacturing of polymer-derived ceramics

    NASA Astrophysics Data System (ADS)

    Eckel, Zak C.; Zhou, Chaoyin; Martin, John H.; Jacobsen, Alan J.; Carter, William B.; Schaedler, Tobias A.

    2016-01-01

    The extremely high melting point of many ceramics adds challenges to additive manufacturing as compared with metals and polymers. Because ceramics cannot be cast or machined easily, three-dimensional (3D) printing enables a big leap in geometrical flexibility. We report preceramic monomers that are cured with ultraviolet light in a stereolithography 3D printer or through a patterned mask, forming 3D polymer structures that can have complex shape and cellular architecture. These polymer structures can be pyrolyzed to a ceramic with uniform shrinkage and virtually no porosity. Silicon oxycarbide microlattice and honeycomb cellular materials fabricated with this approach exhibit higher strength than ceramic foams of similar density. Additive manufacturing of such materials is of interest for propulsion components, thermal protection systems, porous burners, microelectromechanical systems, and electronic device packaging.

  10. Silicone-Rubber Stitching Seal

    NASA Technical Reports Server (NTRS)

    Wang, D. S.

    1985-01-01

    Fabric products protected from raveling by coating threads and filling stitching holes with silicone rubber. Uncored silicone rubber applied to stitching lines with air-pressurized sealant gun. Next, plastic release film placed on coated side, and blanket flipped over so release film lies underneath. Blanket then bagged and adhesive cured under partial vacuum of about 3.5 psi or under pressure. Applications include balloons, parachutes, ultralight aircraft, sails, rescue harnesses, tents, or other fabric products highly stressed in use.

  11. Curing Behaviors of UV-Curable Temporary Adhesives for a 3D Multichip Package Process

    NASA Astrophysics Data System (ADS)

    Lee, Seung-Woo; Lee, Tae-Hyung; Park, Ji-Won; Park, Cho-Hee; Kim, Hyun-Joong; Song, Jun-Yeob; Lee, Jae-Hak

    2014-11-01

    Temporary bonding adhesives for a three-dimensional (3D) multichip package process have been synthesized. To enhance the thermal stability, the adhesives used a fluorinated silicon urethane acrylic binder and ultraviolet (UV) curing for crosslinked network structures. Focusing on different photoinitiator contents and UV doses, the UV-curing behaviors and thermal stability were studied using Fourier-transform infrared spectroscopy attenuated total reflectance, gel fraction, swelling ratio, shrinkage, and thermogravimetric analyses.

  12. Diamine curing agents for polyurethanes

    NASA Technical Reports Server (NTRS)

    Bell, V. L.; St. Clair, T. L.

    1975-01-01

    Three aromatic diamines have properties that make them promising candidates as curing agents for converting isocyanates to polyurethanes with higher adhesive strengths, higher softening temperatures, better toughness, and improved abrasion resistance.

  13. Curing Behavior and Viscoelasticity of Dual-Curable Adhesives Based on High-Reactivity Azo Initiator

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Gyu; Shim, Gyu-Seong; Park, Ji-Won; Kim, Hyun-Joong; Moon, Sang-Eun; Kim, Young-Kwan; No, Dong-Hun; Kim, Jong-Hwan; Han, Kwan-Young

    2016-04-01

    We have investigated the curing behavior of dual-curable acrylic resin to solve problems associated with curing of adhesives in shaded areas during display manufacture. A low-temperature curing-type thermal initiator, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), with a 30°C half-life decomposition temperature was used in the investigation. Dual-curable adhesives were prepared according to the thermal initiator content and ultraviolet (UV) radiation dose. The effects of thermal initiator and UV irradiation on the curing behavior and viscoelasticity were investigated. Using Fourier-transform infrared spectroscopy and gel-fraction analysis, an evaluation was carried out to determine the degree of curing after dual UV/thermal curing. In addition, the real-time curing behavior was evaluated using thermogravimetric analysis, differential scanning calorimetry, and a UV/advanced rheometric expansion system. A lift-off test was carried out to verify the effects of dual curing on adhesion performance. Application of UV irradiation before thermal curing suppressed the thermal curing efficiency. Also, the network structure formed after dual curing with low UV dose showed higher crosslinking density. Therefore, the thermal initiator radical effectively influenced uncured areas with low curing temperature and initiator content without causing problems in UV-curable zones.

  14. Curing Behavior and Viscoelasticity of Dual-Curable Adhesives Based on High-Reactivity Azo Initiator

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Gyu; Shim, Gyu-Seong; Park, Ji-Won; Kim, Hyun-Joong; Moon, Sang-Eun; Kim, Young-Kwan; No, Dong-Hun; Kim, Jong-Hwan; Han, Kwan-Young

    2016-07-01

    We have investigated the curing behavior of dual-curable acrylic resin to solve problems associated with curing of adhesives in shaded areas during display manufacture. A low-temperature curing-type thermal initiator, 2,2'-azobis (4-methoxy-2,4-dimethylvaleronitrile), with a 30°C half-life decomposition temperature was used in the investigation. Dual-curable adhesives were prepared according to the thermal initiator content and ultraviolet (UV) radiation dose. The effects of thermal initiator and UV irradiation on the curing behavior and viscoelasticity were investigated. Using Fourier-transform infrared spectroscopy and gel-fraction analysis, an evaluation was carried out to determine the degree of curing after dual UV/thermal curing. In addition, the real-time curing behavior was evaluated using thermogravimetric analysis, differential scanning calorimetry, and a UV/advanced rheometric expansion system. A lift-off test was carried out to verify the effects of dual curing on adhesion performance. Application of UV irradiation before thermal curing suppressed the thermal curing efficiency. Also, the network structure formed after dual curing with low UV dose showed higher crosslinking density. Therefore, the thermal initiator radical effectively influenced uncured areas with low curing temperature and initiator content without causing problems in UV-curable zones.

  15. Comprehensive study of dynamic curing effect on tablet coating structure.

    PubMed

    Gendre, Claire; Genty, Muriel; da Silva, Julio César; Tfayli, Ali; Boiret, Mathieu; Lecoq, Olivier; Baron, Michel; Chaminade, Pierre; Péan, Jean Manuel

    2012-08-01

    The dissolution method is still widely used to determine curing end-points to ensure long-term stability of film coatings. Nevertheless, the process of curing has not yet been fully investigated. For the first time, joint techniques were used to elucidate the mechanisms of dynamic curing over time from ethylcellulose (Aquacoat)-based coated tablets. X-ray micro-computed tomography (XμCT), Near Infrared (NIR), and Raman spectroscopies as well as X-ray microdiffraction were employed as non-destructive techniques to perform direct measurements on tablets. All techniques indicated that after a dynamic curing period of 4h, reproducible drug release can be achieved and no changes in the microstructure of the coating were any longer detected. XμCT analysis highlighted the reduced internal porosity, while both NIR and Raman measurements showed that spectral information remained unaltered after further curing. X-ray microdiffraction revealed densification of the coating layer with a decrease in the overall coating thickness of about 10 μm as a result of curing. In addition, coating heterogeneity attributed to cetyl alcohol was observed from microscopic images and Raman analysis. This observation was confirmed by X-ray microdiffraction that showed that crystalline cetyl alcohol melted and spread over the coating surface with curing. Prior to curing, X-ray microdiffraction also revealed the existence of two coating zones differing in crystalline cetyl alcohol and sodium lauryl sulfate concentrations which could be explained by migration of these constituents within the coating layer. Therefore, the use of non-destructive techniques allowed new insights into tablet coating structures and provided precise determination of the curing end-point compared to traditional dissolution testing. This thorough study may open up new possibilities for process and formulation control. PMID:22561957

  16. Urethane/Silicone Adhesives for Bonding Flexing Metal Parts

    NASA Technical Reports Server (NTRS)

    Edwards, Paul D.

    2004-01-01

    Adhesives that are blends of commercially available urethane and silicone adhesives have been found to be useful for bonding metal parts that flex somewhat during use. These urethane/silicone adhesives are formulated for the specific metal parts to be bonded. The bonds formed by these adhesives have peel and shear strengths greater than those of bonds formed by double-sided tapes and by other adhesives, including epoxies and neat silicones. In addition, unlike the bonds formed by epoxies, the bonds formed by these adhesives retain flexibility. In the initial application for which the urethane/silicone adhesives were devised, there was a need to bond spring rings, which provide longitudinal rigidity for inflatable satellite booms, with the blades that provide the booms axial strength. The problem was to make the bonds withstand the stresses, associated with differences in curvature between the bonded parts, that arose when the booms were deflated and the springs were compressed. In experiments using single adhesives (that is, not the urethane/ silicone blends), the bonds were broken and, in each experiment, it was found that the adhesive bonded well with either the ring or with the blade, but not both. After numerous experiments, the adhesive that bonded best with the rings and the adhesive that bonded best with the blades were identified. These adhesives were then blended and, as expected, the blend bonded well with both the rings and the blades. The two adhesives are Kalex (or equivalent) high-shear-strength urethane and Dow Corning 732 (or equivalent) silicone. The nominal mixture ratio is 5 volume parts of the urethane per 1 volume part of the silicone. Increasing the proportion of silicone makes the bond weaker but more flexible, and decreasing the proportion of silicone makes the bond stronger but more brittle. The urethane/silicone blend must be prepared and used quickly because of the limited working time of the urethane: The precursor of the urethane

  17. Evaluation of new UV-cured adhesives and effects of post-cure UV exposure

    NASA Astrophysics Data System (ADS)

    Daly, John G.

    2002-09-01

    Recent developments in adhesives have yielded products well suited for optical applications. Ultraviolet light-cured adhesives can be cured in seconds and are an attractive candidate. Selection of the adhesive properties can be made to achieve optimum performance. For improved alignment stability and reduced stress, low shrinkage adhesives have been needed. New UV-cured adhesives are evaluated with shrinkage values of less than 0.2%. In addition to controlled bonding for alignment stability, the effects of post-cure UV laser exposure (266 nm) are evaluated. Adhesives needed for systems employing UV lasers must consider off-axis exposure that can cause photo-reactive degradation. Relatively low power laser exposure is used as a simulated source for off-axis or scattered irradiation. None of these candidate adhesives are intended for in-the-light path use at 266 nm, but rather as structural adhesives. Evaluation of these candidates included a outgassing screening test that may be employed to select materials.

  18. A New Kind of Curing

    NASA Technical Reports Server (NTRS)

    2001-01-01

    A new curing method using automated tape placement (ATP) with electron beam (EB), or e-beam, produces a combination known as in situ e-beam curing. Through a Small Business Innovation Research (SBIR) contract from NASA's Marshall Space Flight Center, Science Research Laboratory, Inc., created the in situ e-beam curing technique, which uses a low-energy electron beam gun to cure various composite materials. One important benefit is the technique's utilization of room temperature curing, which lessens the chance of mismatching the thermal expansion coefficients of different materials. For instance, metals and composites will expand at different rates when heated, but the low-energy e-beam gun reduces the expansion differential. Using a low-energy gun also results in less x-ray shielding, significantly reduced capital costs, reduced facility space, and increased processing capabilities for larger parts. However, using a low-energy gun also means that each tape layer is treated individually because the gun can penetrate only one layer at a time. The e-beam gun emits lower energy x-rays, which are more easily shielded than those emitted by previous guns. The low-energy system is relatively portable due to its light weight and small size. The gun weighs about 70 pounds and can be easily mounted on a robotic arm or an ATP head.

  19. A cure shrinkage model for analyzing the stresses and strains in encapsulated assemblies

    NASA Astrophysics Data System (ADS)

    Chambers, R. S.; Lagasse, R. R.; Guess, T. R.; Plazek, D. J.; Bero, C.

    Electrical component assemblies are encapsulated to provide delicate parts with voltage isolation and protection against damage caused by shock, vibration, and harsh atmospheric environments. During cure, thermosetting resins shrink and harden simultaneously. If the natural deformation of the resin is constrained by adhesion to the mold or to relatively stiff embedded components, cure shrinkage stresses are generated in the encapsulant. Subsequent cooling or thermal cycling produces additional stresses that are caused by the mismatches in thermal strains among the materials in the encapsulated assembly. Although cure shrinkage stresses frequently are neglected because they are considerably smaller than thermal stresses, cure shrinkage stresses can cause delamination or fractures in the encapsulant, since the partially cured resin is not as tough as the fully cured material. Cracks generated during cure can compromise performance (e.g., permit dielectric breakdown), degrade a component's protection, and grow under subsequent thermal cycling producing residual stresses that differ from those found in uncracked assemblies.

  20. Heteroscedastic transformation cure regression models.

    PubMed

    Chen, Chyong-Mei; Chen, Chen-Hsin

    2016-06-30

    Cure models have been applied to analyze clinical trials with cures and age-at-onset studies with nonsusceptibility. Lu and Ying (On semiparametric transformation cure model. Biometrika 2004; 91:331?-343. DOI: 10.1093/biomet/91.2.331) developed a general class of semiparametric transformation cure models, which assumes that the failure times of uncured subjects, after an unknown monotone transformation, follow a regression model with homoscedastic residuals. However, it cannot deal with frequently encountered heteroscedasticity, which may result from dispersed ranges of failure time span among uncured subjects' strata. To tackle the phenomenon, this article presents semiparametric heteroscedastic transformation cure models. The cure status and the failure time of an uncured subject are fitted by a logistic regression model and a heteroscedastic transformation model, respectively. Unlike the approach of Lu and Ying, we derive score equations from the full likelihood for estimating the regression parameters in the proposed model. The similar martingale difference function to their proposal is used to estimate the infinite-dimensional transformation function. Our proposed estimating approach is intuitively applicable and can be conveniently extended to other complicated models when the maximization of the likelihood may be too tedious to be implemented. We conduct simulation studies to validate large-sample properties of the proposed estimators and to compare with the approach of Lu and Ying via the relative efficiency. The estimating method and the two relevant goodness-of-fit graphical procedures are illustrated by using breast cancer data and melanoma data. Copyright © 2016 John Wiley & Sons, Ltd. PMID:26887342

  1. The viscoelasticity of curing thermosets

    SciTech Connect

    Adolf, D.; Martin, J.E.

    1990-01-01

    As a crosslinking polymer cures, dramatic changes in molecular architecture occur. These structural changes in turn affect the viscoelastic behavior of the material. At a critical extent of reaction (the gel point), the polymer undergoes a transition from a viscous liquid to an elastic solid. We have monitored the evolution of structure and viscoelasticity in an epoxy encapsulant used at Sandia, the diglycidyl ether of Bisphenol A (BADGE) cured with diethanolamine (DEA). The structure evolves according to percolation theory, and the viscoelasticity evolves according to out dynamic scaling theory for branched polymers. 7 refs., 4 figs.

  2. Challenging Roadblocks to Cancer Cure.

    PubMed

    Loda, Massimo

    2016-09-01

    The Pezcoller Symposium in Trento, Italy, June 2015, focused entirely on the question of why advanced cancer cure is so uncommon despite the extraordinarily rapid growth of invaluable therapeutic information. Participants were asked to define and to critically evaluate real and potential obstacles to permanent disease eradication. High-level concepts on potential road blocks to cures as well as opportunities for intervention in diverse areas of investigation ranging from genomic alterations to metabolism, microenvironment, immunity, and mechanotransduction were discussed. Provocative concepts and novel therapeutic avenues were proposed. What follows is a critical analysis of the highlights of this meeting. Cancer Res; 76(17); 4924-30. ©2016 AACR. PMID:27520451

  3. Dynamically cured thermoplastic olefin polymers

    SciTech Connect

    Hazelton, D.R.; Puydak, R.C.; Booth, D.A.

    1986-08-19

    A thermoplastic composition is described comprising a polyolefin resin, a first rubber component selected from the group consisting of polyisobutylene, and ethylene propylene copolymer (EPM) and EPDM and a second rubber component selected from the group consisting of halogenated butyl rubber and polychoroprene, the second rubber component being cured utilizing a curative other than a peroxide, which is a vulcanizing agent for the second rubber but not for the first rubber, the second rubber being cured to a fully vulcanized state by dynamic vulcanization in the presence of the polyolefin resin and first rubber compound.

  4. Eco-friendly step-and-flash imprint lithography using ultraviolet-curing liquid material with lactulose derivative derived from medicinal drugs for biomicrochips

    NASA Astrophysics Data System (ADS)

    Takei, Satoshi

    2014-02-01

    Eco-friendly step-and-flash imprint lithography was investigated for the future high-volume manufacture of biomicrochips. A nanoimprinted ultraviolet-curing liquid material with a lactulose derivative derived from medicinal drugs was found to have excellent UV curing properties, film shrinkage during a UV curing reaction, and good etch selectivity with a silicon-based middle layer in CF4 plasma treatment. 80 nm half-pitch lines of the nanoimprinted ultraviolet-curing liquid material with a lactulose derivative were resolved using the process conditions for a trilayer including a silicon-based middle layer with a high silicon concentration of 21.5 wt % and a novolac-based bottom layer on a 100 mm silicon wafer in step-and-flash imprint lithography.

  5. Curing chemistry of phenylethynyl-terminated imide oligomers: Model compounds, carbon-13 labeling and cure analysis

    NASA Astrophysics Data System (ADS)

    Roberts, Christopher Chad

    1998-11-01

    determining the structure of the cured resin. In addition, several relationships between the final structure of the cured resin and properties were noted.

  6. D0 Silicon Upgrade: Ladder Assembly Sequences

    SciTech Connect

    Ratzmann, Paul; /Fermilab

    1994-08-17

    This is an abridged version of the assembly sequence described by the DO assembly subgroup of Cooper, Hrycyk, Kowalski, Rapidis, and Ratzmann. This primarily is used to indicate major steps during the sequence and to list fixturing requirements. Assembly - (1) Place support rails in (1) 3 Chip Ladder Construction fixture. The two rails get held under vacuum. (2) Apply adhesive to the region where contact will be made with the beryllium substrates. (3) Place underside beryllium pieces (active and dummy ends) into the (1) 3 Chip Ladder Construction fixture. These pieces get placed in the fixture against the appropriate pins to mimic final positioning in the bulkhead. Apply vacuum to the beryllium pieces. Allow to cure? (4) Align silicon in (1) 3 Chip Ladder Construction fixture. Reference features on the fixture will be parameterized. Holes in the fixture near the silicon center line will be targeted to set the silicon axis relative to the beryllium slot edge. Z positioning of the detectors will be achieved by shimming between the detectors and butting up the end of the silicon against the fixture. (5) Remove silicon detectors and apply adhesive to the rails and upper surfaces of the beryllium. (6) Replace silicon and check final position of the detectors. (7) Release vacuum on the rails so they cure in a stress-free state. Allow adhesive to cure. (8) Apply adhesive and align HDI to the silicon using (2) 3 Chip HDI Gluing fixture. The HDI will have tabs which are held by the fixture for location relative to the detectors. Allow adhesive to cure. (9) Move ladder to (3) 3 Chip Wirebonding Fixture. Transfer fixture to the wirebonder and bond chip-silicon and silicon-silicon.

  7. Curing the noise epidemic

    NASA Astrophysics Data System (ADS)

    Mazer, Susan

    2005-09-01

    The argument is made that design does not stop when the fixed architectural and acoustical components are in place. Spaces live and breathe with the people who reside in them. Research and examples are presented that show that noise, auditory clutter, thrives on itself in hospitals. Application of the Lombard reflex studies fit into the hospital setting, but do not offer solutions as to how one might reduce the impact. In addition, the basis for looking at the noise component as a physical as well cultural dynamic will be addressed. Whether the result of the wrong conversation in the wrong place or the right conversation in an unfortunate place, talk mixed with sounds of technology is shown to cause its own symptoms. From heightened anxiety and stress to medical errors, staff burnout, or HIPAA violations, the case is made that noise is pandemic in hospitals and demands financial and operational investment. An explanation of how to reduce noise by design of the dynamic environment - equipment, technology, staff protocols is also provided.

  8. 3D silicone rubber interfaces for individually tailored implants.

    PubMed

    Stieghorst, Jan; Bondarenkova, Alexandra; Burblies, Niklas; Behrens, Peter; Doll, Theodor

    2015-01-01

    For the fabrication of customized silicone rubber based implants, e.g. cochlear implants or electrocortical grid arrays, it is required to develop high speed curing systems, which vulcanize the silicone rubber before it runs due to a heating related viscosity drop. Therefore, we present an infrared radiation based cross-linking approach for the 3D-printing of silicone rubber bulk and carbon nanotube based silicone rubber electrode materials. Composite materials were cured in less than 120 s and material interfaces were evaluated with scanning electron microscopy. Furthermore, curing related changes in the mechanical and cell-biological behaviour were investigated with tensile and WST-1 cell biocompatibility tests. The infrared absorption properties of the silicone rubber materials were analysed with fourier transform infrared spectroscopy in transmission and attenuated total reflection mode. The heat flux was calculated by using the FTIR data, emissivity data from the infrared source manufacturer and the geometrical view factor of the system. PMID:25975600

  9. 7 CFR 30.10 - Cure.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Cure. 30.10 Section 30.10 Agriculture Regulations of... AND STANDARDS Classification of Leaf Tobacco Covering Classes, Types and Groups of Grades § 30.10 Cure. To dry the sap from newly harvested tobacco by either natural or artificial process. Proper curing...

  10. 7 CFR 51.1412 - Well cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Well cured. 51.1412 Section 51.1412 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Pecans in the Shell 1 Definitions § 51.1412 Well cured. Well cured means that...

  11. 7 CFR 51.1412 - Well cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Well cured. 51.1412 Section 51.1412 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... Standards for Grades of Pecans in the Shell 1 Definitions § 51.1412 Well cured. Well cured means that...

  12. HBV cure: why, how, when?

    PubMed

    Levrero, Massimo; Testoni, Barbara; Zoulim, Fabien

    2016-06-01

    Current HBV treatments control replication and liver disease progression in the vast majority of treated patients. However, HBV patients often require lifelong therapies due to the persistence of transcriptionally active viral cccDNA mini-chromosome in the nucleus, which is not directly targeted by current antiviral therapies. A true complete cure of HBV would require clearance of intranuclear cccDNA from all infected hepatocytes. An intermediate but still relevant step forward that would allow treatment cessation would be reaching a functional cure, equivalent to resolved acute infection, with a durable HBsAg loss±anti-HBs seroconversion, undetectable serum DNA and persistence of cccDNA in a transcriptionally inactive status. Recent advances in technologies and pharmaceutical sciences, including the cloning of the mayor HBV receptor (i.e. the NTCP transporter) and the development in vitro HBV infection models, have heralded a new horizon of innovative antiviral and immune-therapeutic approaches. PMID:27447092

  13. Chromothriptic cure of WHIM syndrome.

    PubMed

    McDermott, David H; Gao, Ji-Liang; Liu, Qian; Siwicki, Marie; Martens, Craig; Jacobs, Paejonette; Velez, Daniel; Yim, Erin; Bryke, Christine R; Hsu, Nancy; Dai, Zunyan; Marquesen, Martha M; Stregevsky, Elina; Kwatemaa, Nana; Theobald, Narda; Long Priel, Debra A; Pittaluga, Stefania; Raffeld, Mark A; Calvo, Katherine R; Maric, Irina; Desmond, Ronan; Holmes, Kevin L; Kuhns, Douglas B; Balabanian, Karl; Bachelerie, Françoise; Porcella, Stephen F; Malech, Harry L; Murphy, Philip M

    2015-02-12

    Chromothripsis is a catastrophic cellular event recently described in cancer in which chromosomes undergo massive deletion and rearrangement. Here, we report a case in which chromothripsis spontaneously cured a patient with WHIM syndrome, an autosomal dominant combined immunodeficiency disease caused by gain-of-function mutation of the chemokine receptor CXCR4. In this patient, deletion of the disease allele, CXCR4(R334X), as well as 163 other genes from one copy of chromosome 2 occurred in a hematopoietic stem cell (HSC) that repopulated the myeloid but not the lymphoid lineage. In competitive mouse bone marrow (BM) transplantation experiments, Cxcr4 haploinsufficiency was sufficient to confer a strong long-term engraftment advantage of donor BM over BM from either wild-type or WHIM syndrome model mice, suggesting a potential mechanism for the patient's cure. Our findings suggest that partial inactivation of CXCR4 may have general utility as a strategy to promote HSC engraftment in transplantation. PMID:25662009

  14. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2006-12-05

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  15. Silicone metalization

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter; Hamilton, Julie

    2008-12-09

    A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.

  16. Cure shrinkage of thermoset composites

    SciTech Connect

    Russell, J.D. )

    1993-01-01

    The shrinkage of thermoset composites during cure was studied using a volumetric dilatometer. The material systems studied were AS4 carbon fiber/Hercules' 3501-6 epoxy, IM7 carbon fiber/Hercules 8551-7A toughened epoxy and IM7 carbon fiber/BASF's 5250-4 bismaleimide. Shrinkage of the samples due to both polymerization and thermal expansion effects was seen. The volume changes of the materials during cure were then compared to results from dynamic mechanical analysis (DMA) and dielectric cure monitoring. Maximums in volume corresponded to minimums in storage and loss modulus from DMA and maximums in the dielectric loss factor. Resin shrinkage during the 177 deg C (350 F) hold corresponded to the onset of polymerization seen by the rapid increase in the storage modulus and the decrease in the dielectric loss factor response due to reduced ion mobility. These results show that volumetric dilatometry can be an effective tool in the development of materials processing strategies and can be useful in studying residual stresses in composites. 9 refs.

  17. Freud's psychoanalysis: a moral cure.

    PubMed

    Eriksson, Johan

    2014-08-01

    That psychoanalytical treatment in its classical Freudian sense is primarily a moral or ethical cure is not a very controversial claim. However, it is far from obvious how we are to understand precisely the moral character of psychoanalysis. It has frequently been proposed that this designation is valid because psychoanalysis strives neither to cure psychological symptoms pharmaceutically, nor to superficially modify the behaviour of the analysand, but to lead the analysand through an interpretive process during which he gradually gains knowledge of the unconscious motives that determine his behaviour, a process that might ideally liberate him to obtain, in relation to his inner desires, the status of a moral agent. There resides something appealing in these claims. But it is the author's belief that there is an even deeper moral dimension applying to psychoanalytical theory and praxis. Freudian psychoanalysis is a moral cure due to its way of thematizing psychological suffering as moral suffering. And this means that the moral subject - the being that can experience moral suffering - is not primarily something that the psychoanalytical treatment strives to realize, but rather the presupposition for the way in which psychoanalysis theorizes psychological problems as such. PMID:24720632

  18. The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Santoro, G. J.

    1972-01-01

    The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  1. Measurement of the degree of cure in epoxies with ultrasonic velocity

    NASA Technical Reports Server (NTRS)

    Winfree, W. P.; Parker, F. R.

    1986-01-01

    The use of ultrasonic longitudinal velocity values to measure the degree of cure (defined for an epoxide system as the concentration of epoxide/amine bonds divided by the initial epoxide concentration) in epoxy resins is investigated. The experimental setup used to measure the changes in longitudinal velocity with time is described, together with the technique used to calculate the degree of cure from the acoustic data, using the principle of additive module. Measurements were done with diglycidyl ether of bisphenol A epoxy resin cured with an amine adduct agent. Good qualitative agreement was shown between the time dependence of the acoustically measured degree of cure and the predicted rate of reaction.

  2. Characterization-curing-property studies of HBRF 55A resin formulations

    NASA Technical Reports Server (NTRS)

    Pearce, E. M.; Mijovic, J.

    1985-01-01

    Characterization curing property investigations on HBRF 55A resin formulations are reported. The initial studies on as received cured samples cut from a full-size FWC are reviewed. Inadequacies of as-received and aged samples are pointed out and additional electron microscopic evidence is offered. Characterization of as-received ingredients of HBRF 55A formulation is described. Specifically, Epon 826, Epon 828, EpiRez 5022, RD-2 and various amines, including Tonox and Tonox 60.40, were characterized. Cure kinetics of various formulations are investigated. Changes in physical/thermal properties (viscosity, specific heat, thermal conductivity and density) during cure are described.

  3. Radical-cured block copolymer-modified thermosets

    SciTech Connect

    Redline, Erica M.; Francis, Lorraine F.; Bates, Frank S.

    2013-01-10

    Poly(ethylene-alt-propylene)-b-poly(ethylene oxide) (PEP-PEO) diblock copolymers were synthesized and added at 4 wt % to 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane (BisGMA), a monomer that cures using free radical chemistry. In separate experiments, poly(ethylene glycol) dimethacrylate (PEGDMA) was combined as a secondary monomer with BisGMA and the monomers were loaded with 4 wt % PEP-PEO. The diblock copolymers self-assembled into well-dispersed spherical micelles with PEP cores and PEO coronas. No appreciable change in the final extent of cure of the thermosets was caused by the addition of diblock copolymer, except in the case of BisGMA, where the addition of the block copolymer increased extent of cure by 12%. Furthermore, the extent of cure was increased by 29% and 37% with the addition of 25 and 50 wt % PEGDMA, respectively. Elastic modulus and fracture resistance were also determined, and the values indicate that the addition of block copolymers does not significantly toughen the thermoset materials. This finding is surprising when compared with the large increase in fracture resistance seen in block copolymer-modified epoxies, and an explanation is proposed.

  4. Photo-Curing: UV Radiation curing of polymers

    NASA Technical Reports Server (NTRS)

    Inman, Christina A.

    2004-01-01

    The Polymers Branch of the Materials Division is dedicated to the development of high-performance for a variety of applications. Areas of significant interest include high- temperature polymers, low density, and high strength insulating materials, conductive polymers, and high density polymer electrolytes. This summer our group is working diligently on a photo-curing project. There is interest in the medical community feel the need for a new and improved balloon that will be used for angioplasty (a form of heart surgery). This product should maintain flexibility but add many other properties. Like possibly further processability and resistance to infection. Our group intends on coming up with this product by using photo-enolization (or simply, photo-curing) by Diels-Alder trapping. The main objective was to synthesize a series of new polymers by Diels-Alder cycloaddition of photoenols with more elastomeric properties. Our group was responsible for performing the proper photo-curing techniques of the polymers with diacrylates and bismaleimides, synthesizing novel monomers, and evaluating experimental results. We attempted to use a diacrylate to synthesize the polymer because of previous research done within the Polymers Branch here at NASA. Most acrylates are commercially available, have more elastometric properties than a typical rigid aromatic structure has and they contain ethylene oxides in the middle of their structure that create extensive flexibility. The problem we encountered with the acrylates is that they photo chemically and thermally self polymerize and create diradicals at low temperatures; these constraints caused a lot of unnecessary side reactions. We want to promote solely, diketone polymerization because this type of polymerization has the ability to cause very elastic polymers. We chose to direct our attention towards the usage of maleimides because they are known for eliminating these unnecessary side reactions.

  5. Latency reversal and viral clearance to cure HIV-1.

    PubMed

    Margolis, David M; Garcia, J Victor; Hazuda, Daria J; Haynes, Barton F

    2016-07-22

    Research toward a cure for human immunodeficiency virus type 1 (HIV-1) infection has joined prevention and treatment efforts in the global public health agenda. A major approach to HIV eradication envisions antiretroviral suppression, paired with targeted therapies to enforce the expression of viral antigen from quiescent HIV-1 genomes, and immunotherapies to clear latent infection. These strategies are targeted to lead to viral eradication--a cure for AIDS. Paired testing of latency reversal and clearance strategies has begun, but additional obstacles to HIV eradication may emerge. Nevertheless, there is reason for optimism that advances in long-acting antiretroviral therapy and HIV prevention strategies will contribute to efforts in HIV cure research and that the implementation of these efforts will synergize to markedly blunt the effect of the HIV pandemic on society. PMID:27463679

  6. Multifarious immunotherapeutic approaches to cure HIV-1 infection

    PubMed Central

    Imami, Nesrina; Herasimtschuk, Anna A

    2015-01-01

    Immunotherapy in the context of treated HIV-1 infection aims to improve immune responses to achieve better control of the virus. To date, multifaceted immunotherapeutic approaches have been shown to reduce immune activation and increase CD4 T-lymphocyte counts, further to the effects of antiretroviral therapy alone, in addition to improving HIV-1-specific T-cell responses. While sterilizing cure of HIV-1 would involve elimination of all replication-competent virus, a functional cure in which the host has long-lasting control of viral replication may be more feasible. In this commentary, we discuss novel strategies aimed at targeting the latent viral reservoir with cure of HIV-1 infection being the ultimate goal, an achievement that would have considerable impact on worldwide HIV-1 infection. PMID:26048144

  7. Silicon on insulator with active buried regions

    DOEpatents

    McCarthy, Anthony M.

    1998-06-02

    A method for forming patterned buried components, such as collectors, sources and drains, in silicon-on-insulator (SOI) devices. The method is carried out by epitaxially growing a suitable sequence of single or multiple etch stop layers ending with a thin silicon layer on a silicon substrate, masking the silicon such that the desired pattern is exposed, introducing dopant and activating in the thin silicon layer to form doped regions. Then, bonding the silicon layer to an insulator substrate, and removing the silicon substrate. The method additionally involves forming electrical contact regions in the thin silicon layer for the buried collectors.

  8. Silicon on insulator with active buried regions

    DOEpatents

    McCarthy, Anthony M.

    1996-01-01

    A method for forming patterned buried components, such as collectors, sources and drains, in silicon-on-insulator (SOI) devices. The method is carried out by epitaxially growing a suitable sequence of single or multiple etch stop layers ending with a thin silicon layer on a silicon substrate, masking the silicon such that the desired pattern is exposed, introducing dopant and activating in the thin silicon layer to form doped regions. Then, bonding the silicon layer to an insulator substrate, and removing the silicon substrate. The method additionally involves forming electrical contact regions in the thin silicon layer for the buried collectors.

  9. Silicon on insulator with active buried regions

    DOEpatents

    McCarthy, A.M.

    1998-06-02

    A method is disclosed for forming patterned buried components, such as collectors, sources and drains, in silicon-on-insulator (SOI) devices. The method is carried out by epitaxially growing a suitable sequence of single or multiple etch stop layers ending with a thin silicon layer on a silicon substrate, masking the silicon such that the desired pattern is exposed, introducing dopant and activating in the thin silicon layer to form doped regions. Then, bonding the silicon layer to an insulator substrate, and removing the silicon substrate. The method additionally involves forming electrical contact regions in the thin silicon layer for the buried collectors. 10 figs.

  10. Silicon on insulator with active buried regions

    DOEpatents

    McCarthy, A.M.

    1996-01-30

    A method is disclosed for forming patterned buried components, such as collectors, sources and drains, in silicon-on-insulator (SOI) devices. The method is carried out by epitaxially growing a suitable sequence of single or multiple etch stop layers ending with a thin silicon layer on a silicon substrate, masking the silicon such that the desired pattern is exposed, introducing dopant and activating in the thin silicon layer to form doped regions. Then, bonding the silicon layer to an insulator substrate, and removing the silicon substrate. The method additionally involves forming electrical contact regions in the thin silicon layer for the buried collectors. 10 figs.

  11. Phenylethynyl Containing Reactive Additives

    NASA Technical Reports Server (NTRS)

    Connell, John W. (Inventor); Smith, Joseph G., Jr. (Inventor); Hergenrother, Paul M. (Inventor)

    2002-01-01

    Phenylethynyl containing reactive additives were prepared from aromatic diamine, containing phenylethvnvl groups and various ratios of phthalic anhydride and 4-phenylethynviphthalic anhydride in glacial acetic acid to form the imide in one step or in N-methyl-2-pvrrolidinone to form the amide acid intermediate. The reactive additives were mixed in various amounts (10% to 90%) with oligomers containing either terminal or pendent phenylethynyl groups (or both) to reduce the melt viscosity and thereby enhance processability. Upon thermal cure, the additives react and become chemically incorporated into the matrix and effect an increase in crosslink density relative to that of the host resin. This resultant increase in crosslink density has advantageous consequences on the cured resin properties such as higher glass transition temperature and higher modulus as compared to that of the host resin.

  12. Compounding with Silicones.

    PubMed

    Allen, Loyd V

    2015-01-01

    Since the 1940s, methylchlorosilanes have been used to treat glassware to prevent blood from clotting. The use of silicones in pharmaceutical and medical applications has grown to where today they are used in many life-saving devices (pacemakers, hydrocephalic shunts) and pharmaceutical applications from tubing, to excipients in topical formulations, to adhesives to affix transdermal drug delivery systems, and are also being used in products as active pharmaceutical ingredients, such as antiflatulents. About 60% of today's skin-care products now contain some type of silicone where they are considered safe and are known to provide a pleasant "silky-touch," non-greasy, and non-staining feel. Silicones exhibit many useful characteristics, and the safety of these agents supports their numerous applications; their biocompatibility is partially due to their low-chemical reactivity displayed by silicones, low-surface energy, and their hydrophobicity. Silicones are used both as active ingredients and as excipients. In addition is their use for "siliconization," or surface treatment, of many parenteral packaging components. Dimethicone and silicone oil are used as lubricants on stoppers to aid machineability, in syringes to aid piston movement, or on syringe needles to reduce pain upon injection. Silicones are also useful in pharmaceutical compounding as is discussed in this artiele included with this article are in developing formulations with silicones. PMID:26714363

  13. Performance of concrete under different curing conditions

    SciTech Connect

    Tan, K.; Gjorv, O.E.

    1996-03-01

    The effect of curing conditions on strength and permeability of concrete was studied. Test results showed that after 3 and 7 days moist curing only the concretes with w/c ratios equal to or less than 0.4 were accepted, while after 28 days of moist curing however, even the concrete with w/c of 0.6 could be accepted. Silica fume has a significant effect on the resistance to water penetration. For the concretes both with and without silica fume and with w/c + s of 0.5, the 28-day compressive strengths of 3 and 7 days moist curing were higher than those of 28 days moist curing, and the silica fume concrete seemed to be less sensitive to early drying. The curing temperatures did not affect the water penetration of concrete, but affected the chloride penetration and compressive strength of concrete significantly.

  14. ASRM test report: Autoclave cure process development

    NASA Technical Reports Server (NTRS)

    Nachbar, D. L.; Mitchell, Suzanne

    1992-01-01

    ASRM insulated segments will be autoclave cured following insulation pre-form installation and strip wind operations. Following competitive bidding, Aerojet ASRM Division (AAD) Purchase Order 100142 was awarded to American Fuel Cell and Coated Fabrics Company, Inc. (Amfuel), Magnolia, AR, for subcontracted insulation autoclave cure process development. Autoclave cure process development test requirements were included in Task 3 of TM05514, Manufacturing Process Development Specification for Integrated Insulation Characterization and Stripwind Process Development. The test objective was to establish autoclave cure process parameters for ASRM insulated segments. Six tasks were completed to: (1) evaluate cure parameters that control acceptable vulcanization of ASRM Kevlar-filled EPDM insulation material; (2) identify first and second order impact parameters on the autoclave cure process; and (3) evaluate insulation material flow-out characteristics to support pre-form configuration design.

  15. Investigation of Film Curing by Dielectric Analysis.

    NASA Astrophysics Data System (ADS)

    Guma, Noemi Candelaria

    1995-01-01

    Dielectric analysis (DEA) relies on the response of molecules to a changing electric field. Permittivity (epsilon^') is a parameter obtained from DEA, which is proportional to the amount of molecular alignment (or motion). A DEA methodology was developed to evaluate and classify the degree of cure of films, and to demonstrate the mechanism of the curing phenomenon at a molecular level. The model material employed in the study was Eudragit^circler RS30D, an aqueous-based film forming polymeric material, containing 20% acetyl tributyl citrate as plasticizer. The data showed changes in the dielectric behavior of the polymer molecules in films that were subjected to accelerated stability or improper curing conditions. These dielectric changes were also manifested as changes in the permeability characteristics of the film, which ultimately influenced the final performance of the dosage form. By monitoring the dielectric behavior of the coating material during a curing cycle, a classification of three stages of curing was developed, namely undercured, optimally cured, and overcured. The changes in dielectric properties of the film reflected the changes in molecular structure, which correlated with changes in permeability and surface morphology. Based on the data, a mechanism of improper cure was proposed, which contends that the curing phenomenon is driven by two major forces, namely: the heterogenous loss and/or redistribution of plasticizer molecules during the curing process and the development of strain in the film structure during the coating process. A mathematical equation was derived to predict the epsilon^' of film-coated beads based on the epsilon^ ' data of free films cured under the same conditions. The model is based on the premise that "equal epsilon^' denotes equal mobility" for the same material, whether as free film or applied onto a substrate. The DEA technique developed and the proposed rationale of the curing phenomenon may be useful in optimizing the

  16. Interfacial Properties of Electron Beam Cured Composites

    SciTech Connect

    Eberle, C.C.

    1999-12-30

    The objectives of the CRADA are to: Confirm that fiber-resin adhesion is responsible for the observed poor shear properties; Determine the mechanism(s) responsible for poor adhesion between carbon fibers and epoxy resins after e-beam curing; Develop and evaluate resin systems and fiber treatments to improve the properties of e-beam cured, carbon-fiber-reinforced composites; and Develop refined methods for processing e-beam cured, carbon-fiber-reinforced composites.

  17. Bond Sensitivity to Silicone Contamination

    NASA Technical Reports Server (NTRS)

    Caldwell, G. A.; Hudson, W. D.; Hudson, W. D.; Cash, Stephen F. (Technical Monitor)

    2003-01-01

    Currently during fabrication of the Space Shuttle booster rocket motors, the use of silicone and silicone-containing products is prohibited in most applications. Many shop aids and other materials containing silicone have the potential, if they make contact with a bond surface, to transfer some of the silicone to the substrates being bonded. Such transfer could result in a reduction of the bond strength or even failure of the subsequent bonds. This concern is driving the need to understand the effect of silicones and the concentration needed to affect a given bond-line strength. Additionally, as silicone detection methods used for materials acceptance improve what may have gone unnoticed earlier is now being detected. Thus, realistic silicone limits for process materials (below which bond performance is satisfactory) are needed rather than having an absolute no silicone permitted policy.

  18. Effects of Temperature and Humidity on Wilethane 44 Cure

    SciTech Connect

    John C. Weigle

    2006-10-01

    Wilethane 44 is a polyurethane adhesive developed by the Materials Team within ESA-MEE at Los Alamos National Laboratory as a replacement for Hexcel Corporation Urethane 7200. Urethane 7200 is used in numerous weapon systems, but it was withdrawn from the market in 1989. The weapons complex requires a replacement material for use in the W76-1 LEP and the W88, as well as for assembly of JTAs for other warheads. All polyurethane systems are susceptible to moisture reacting with unreacted isocyanate groups. This side reaction competes with the curing reaction and results in CO{sub 2} formation. Therefore, a polyurethane adhesive can exhibit foaming if appropriate environmental controls are not in place while it cures. A designed experiment has been conducted at TA-16-304 to determine the effects of ambient conditions on the properties of cured Wilethane 44. Temperature was varied from 15 C to 30 C and relative humidity from 15% to 40%. The density, hardness at 24 hours, and butt tensile strength on aluminum substrates were measured and fitted to quadratic equations over the experimental space. Additionally, the loss and storage moduli during cure were monitored as a function of cure temperature. These experiments provide a stronger basis for establishing appropriate environmental conditions and cure times when using Wilethane 44. The current guidelines are a working time of 90 minutes, a cure time of 18 hours, and a relative humidity of less than 25%, regardless of ambient temperature. Viscosity measurements revealed that the working time is a strong function of temperature and can be as long as 130 minutes at 15 C or as short as 90 minutes at 30 C. The experiments also showed that the gel time is much longer than originally thought, as long as 13 hours at 15 C. Consequently, it may be necessary to extend the required cure time at temperatures below 20 C. Allowable humidity varies as a function of temperature from 34% at 15 C to 15% at 30 C.

  19. [Nonnius and the Spa cure].

    PubMed

    Lecomte, J; Lemli, J; Marganne, M H; Melard, M

    1996-01-01

    The 12th of July 1635, Jan van Beverwyck wrote a letter from Dordrecht to his esteemed friend Luis Nunez, in Antwerp. He asked him for indications about the cure of kidney stones of which he was suffering. He had just passed two calculi very painfully. Nunez answered on July 31. His letter summarized his own experience with this disease. In such cases, temperate diuretics and emollients are well indicated: ingestion of light decoctions of Malva and Viola, Caerefolium and Parieteria as well as Marshmallow syrup. No purge and no 'chemicals'. However, the best remedy was drinking Spa water. Usually the best way to absorb it is to come to the springs, in the Ardennes, part of the independent Principality of Liège. However, considering the horrors of the war (the Thirty Years War) endangering the country, van Beverwyck would be wise to drink imported water during 40 or 50 days, while staying home quietly, in Dordrecht. The letter points out the importance of provoked diuresis in the treatment of kidney stones. On the other hand the letter is an illustration of the continuing contacts between the United Provinces and the Spanish territories and of the commercial traffic between Antwerp, Dordrecht and Spa. The exported water was bottled from many 'pouhons'. It was acid, ferruginous, sulfurous and saturated with carbon dioxide; no pathogen germs, at least at the spring. Nunez quoted the large number of his patients cured with Spa water in Antwerp. This is an illustration of its commercial expansion even during this critical period. PMID:8848877

  20. Hepatitis C, stigma and cure

    PubMed Central

    Marinho, Rui Tato; Barreira, David Pires

    2013-01-01

    The infection with hepatitis C virus (HCV) is one of the most important global chronic viral infections worldwide. It is estimated to affect around 3% of the world population, about 170-200 million people. Great part of the infections are asymptomatic, the patient can be a chronic carrier for decades without knowing it. The most severe consequences of the chronic infection are liver cirrhosis and hepatocellular carcinoma, which appears in 20%-40% of the patients, leading to hepatic failure and death. The HCV was discovered 25 years ago in 1989, is a RNA virus and classified by the World Health Organization as an oncogenic one. Hepatocellular carcinoma is one of the most important cancers, the fifth worldwide in terms of mortality. It has been increasing in the Ocidental world, mainly due to chronic hepatitis C. Hepatitis C is not only a liver disease and a cause of cirrhosis, but also a mental, psychological, familiar, and social disease. The stigma that the infected person sometimes carries is tremendous having multiple consequences. The main cause is lack of adequate information, even in the health professionals setting. But, besides the “drama” of being infected, health professionals, family, society and the infected patients, must be aware of the chance of real cure and total and definitive elimination of the virus. The treatment for hepatitis C has begun in the last 80´s with a percentage of cure of 6%. Step by step the efficacy of the therapy for hepatitis C is rapidly increasing and nowadays with the very new medications, the so called Direct Antiviral Agents-DAAs of new generation, is around 80%-90%. PMID:24187444

  1. Grain-boundary phases in hot-pressed silicon nitride containing Y2O3 and CeO2 additives

    NASA Technical Reports Server (NTRS)

    Guha, J. P.; Hench, L. L.

    1983-01-01

    Auger electron spectroscopy in conjunction with X-ray powder diffraction and scanning electron microscopy is used to analyze the grain-boundary phases of Y2O3- and CeO2-doped Si3N4 hot-pressed materials in order to demonstrate that the additives concentrate predominantly in the grain boundaries of Si3N4 in the form of various oxynitride phases. A high oxygen content observed in sample fracture surfaces was found to be consistent with the existence of an oxygen-enriched phase in the grain boundaries. The presence of yttrium and cerium in the fracture surfaces and an overall increase in the O/N ratio imply that the additive oxides are predominantly concentrated in the intergranular phases.

  2. A new hypothesis on HIV cure

    PubMed Central

    Hladik, Florian

    2015-01-01

    In this opinion article, I provide the rationale for my hypothesis that nucleoside reverse transcriptase inhibitors (NRTIs) may prevent human immunodeficiency virus (HIV) cure by promoting the survival of cells with integrated provirus. If correct, we may be closer to a cure than we realize. PMID:26380071

  3. Ultrasonic mixing of epoxy curing agents

    NASA Technical Reports Server (NTRS)

    Hodges, W. T.; St.clair, T. L.

    1983-01-01

    A new technique for mixing solid curing agents into liquid epoxy resins using ultrasonic energy was developed. This procedure allows standard curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents such as 4,4 prime-diaminodiphenyl sulfone (4,4 prime-DDS) and its 3,3 prime-isomer, (3,3 prime-DDS) to be mixed without prior melting of the curing agent. It also allows curing agents with very high melt temperatures such as 4,4 prime-diaminobenzophenone (4,4 prime-DABP) (242 C) to be mixed without premature curing. Four aromatic diamines were ultrasonically blended into MY-720 epoxy resin. These were 4,4 prime-DDS; 3,3 prime-DDA; 4,4 prime-DABP and 3,3 prime-DABP. Unfilled moldings were cast and cured for each system and their physical and mechanical properties compared.

  4. Animal Models for HIV Cure Research

    PubMed Central

    Policicchio, Benjamin B.; Pandrea, Ivona; Apetrei, Cristian

    2016-01-01

    The HIV-1/AIDS pandemic continues to spread unabated worldwide, and no vaccine exists within our grasp. Effective antiretroviral therapy (ART) has been developed, but ART cannot clear the virus from the infected patient. A cure for HIV-1 is badly needed to stop both the spread of the virus in human populations and disease progression in infected individuals. A safe and effective cure strategy for human immunodeficiency virus (HIV) infection will require multiple tools, and appropriate animal models are tools that are central to cure research. An ideal animal model should recapitulate the essential aspects of HIV pathogenesis and associated immune responses, while permitting invasive studies, thus allowing a thorough evaluation of strategies aimed at reducing the size of the reservoir (functional cure) or eliminating the reservoir altogether (sterilizing cure). Since there is no perfect animal model for cure research, multiple models have been tailored and tested to address specific quintessential questions of virus persistence and eradication. The development of new non-human primate and mouse models, along with a certain interest in the feline model, has the potential to fuel cure research. In this review, we highlight the major animal models currently utilized for cure research and the contributions of each model to this goal. PMID:26858716

  5. Framing expectations in early HIV cure research.

    PubMed

    Dubé, Karine; Henderson, Gail E; Margolis, David M

    2014-10-01

    Language used to describe clinical research represents a powerful opportunity to educate volunteers. In the case of HIV cure research there is an emerging need to manage expectations by using the term 'experiment'. Cure experiments are proof-of-concept studies designed to evaluate novel paradigms to reduce persistent HIV-1 reservoirs, without any expectation of medical benefit. PMID:25280965

  6. Animal Models for HIV Cure Research.

    PubMed

    Policicchio, Benjamin B; Pandrea, Ivona; Apetrei, Cristian

    2016-01-01

    The HIV-1/AIDS pandemic continues to spread unabated worldwide, and no vaccine exists within our grasp. Effective antiretroviral therapy (ART) has been developed, but ART cannot clear the virus from the infected patient. A cure for HIV-1 is badly needed to stop both the spread of the virus in human populations and disease progression in infected individuals. A safe and effective cure strategy for human immunodeficiency virus (HIV) infection will require multiple tools, and appropriate animal models are tools that are central to cure research. An ideal animal model should recapitulate the essential aspects of HIV pathogenesis and associated immune responses, while permitting invasive studies, thus allowing a thorough evaluation of strategies aimed at reducing the size of the reservoir (functional cure) or eliminating the reservoir altogether (sterilizing cure). Since there is no perfect animal model for cure research, multiple models have been tailored and tested to address specific quintessential questions of virus persistence and eradication. The development of new non-human primate and mouse models, along with a certain interest in the feline model, has the potential to fuel cure research. In this review, we highlight the major animal models currently utilized for cure research and the contributions of each model to this goal. PMID:26858716

  7. Sodium nitrite: the "cure" for nitric oxide insufficiency.

    PubMed

    Parthasarathy, Deepa K; Bryan, Nathan S

    2012-11-01

    This process of "curing" food is a long practice that dates back thousands of years long before refrigeration or food safety regulations. Today food safety and mass manufacturing are dependent upon safe and effective means to cure and preserve foods including meats. Nitrite remains the most effective curing agent to prevent food spoilage and bacterial contamination. Despite decades of rigorous research on its safety and efficacy as a curing agent, it is still regarded by many as a toxic undesirable food additive. However, research within the biomedical science community has revealed enormous therapeutic benefits of nitrite that is currently being developed as novel therapies for conditions associated with nitric oxide (NO) insufficiency. Much of the same biochemistry that has been understood for decades in the meat industry has been rediscovered in human physiology. This review will highlight the fundamental biochemistry of nitrite in human physiology and highlight the risk benefit evaluation surrounding nitrite in food and meat products. Foods or diets enriched with nitrite can have profound positive health benefits. PMID:22464105

  8. Cure Chemistry of Phenylethynyl Terminated Oligomers

    NASA Technical Reports Server (NTRS)

    Wood, Karen H.; Orwoll, Robert A.; Young, Philip R.; Jensen, Brian J.; McNair, Harold M.

    1997-01-01

    The ability to process high performance polymers into quality, void-free composites has been significantly advanced using oligomers terminated with reactive groups which cure or crosslink at elevated temperature without the evolution of volatile byproducts. Several matrix resin systems of considerable interest to the aerospace community utilize phenylethynyl-terminated imide (PETI) technology to achieve this advantage. The present paper addresses the cure chemistry of PETI oligomers. The thermal cure of a low molecular weight model compound was studied using a variety of analytical techniques including differential scanning calorimetry, Fourier transform infrared spectroscopy, and liquid chromatography-mass spectroscopy. The studies indicate an extremely complex cure process. Many stable products were isolated and this paper reports current work on identification of those products. The intent of this research is to provide fundamental insight into the molecular structure of the cured PETI engineering materials so that performance and durability can be more fully assessed.

  9. 7 CFR 29.2519 - Fire-cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2519 Fire-cured. Tobacco cured under... 7 Agriculture 2 2010-01-01 2010-01-01 false Fire-cured. 29.2519 Section 29.2519...

  10. 7 CFR 29.2519 - Fire-cured.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2519 Fire-cured. Tobacco cured under... 7 Agriculture 2 2012-01-01 2012-01-01 false Fire-cured. 29.2519 Section 29.2519...

  11. 7 CFR 29.2519 - Fire-cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2519 Fire-cured. Tobacco cured under... 7 Agriculture 2 2011-01-01 2011-01-01 false Fire-cured. 29.2519 Section 29.2519...

  12. 7 CFR 29.2519 - Fire-cured.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2519 Fire-cured. Tobacco cured under... 7 Agriculture 2 2013-01-01 2013-01-01 false Fire-cured. 29.2519 Section 29.2519...

  13. 7 CFR 29.2519 - Fire-cured.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... INSPECTION Standards Official Standard Grades for Kentucky and Tennessee Fire-Cured and Foreign-Grown Fire-Cured Tobacco (u.s. Types 22, 23, and Foreign Type 96) § 29.2519 Fire-cured. Tobacco cured under... 7 Agriculture 2 2014-01-01 2014-01-01 false Fire-cured. 29.2519 Section 29.2519...

  14. 9 CFR 319.103 - Cured beef tongue.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 9 Animals and Animal Products 2 2010-01-01 2010-01-01 false Cured beef tongue. 319.103 Section 319... Cured beef tongue. In preparing “Cured Beef Tongue,” the application of curing solution to the fresh beef tongue shall not result in an increase in the weight of the cured beef tongue of more than...

  15. 9 CFR 319.103 - Cured beef tongue.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 9 Animals and Animal Products 2 2011-01-01 2011-01-01 false Cured beef tongue. 319.103 Section 319... Cured beef tongue. In preparing “Cured Beef Tongue,” the application of curing solution to the fresh beef tongue shall not result in an increase in the weight of the cured beef tongue of more than...

  16. Knowledge based control for microwave curing of polymer composite materials

    SciTech Connect

    Hawkins, R.; Sticklen, J.; Hawley, M.C.

    1996-12-31

    Traditionally, the majority of thermoset composite materials have been autoclave cured. Some alternatives to curing in an autoclave include E-Beam and microwave curing. In the Microwave Research Group at MSU, microwave curing technology is being pursued for the purpose of achieving higher throughput, lower cost and higher energy efficiency, relative to autoclave curing.

  17. Observations on the Influence of Secondary Me Oxides Additives (Me=Si,Al, Mg) on the Microstructural Evolution and Mechanical Behavior of Silicon Nitride Ceramics Containing RE2O3 (RE=La, Gd, Lu)

    SciTech Connect

    Becher, Paul F; Averill, Frank; Lin, Hua-Tay; Waters, Shirley B; Shibata, Naoya; Painter, Gayle S; van Benthem, Klaus

    2010-01-01

    The evolution of β Si3N4 microstructures is influenced by the adsorption of rare earth elements at grain surfaces and by the viscosity of the intergranular phases. Theoretical and STEM studies show that the RE atoms exhibit different tendencies to segregate from the liquid phase to grain surfaces and different binding strengths at these surfaces. When combined with MgO (or Al2O3) secondary additions, the rare earth additives are combined in low viscosity intergranular phases during densification and the α to β phase transformation and microstructural evolution are dominated by the RE adsorption behavior. On the other hand, a much higher viscosity intergranular phase forms when the RE2O3 are combined with SiO2. While the rare earth adsorption behavior remains the same, the phase transformation and microstructure are now dominated by Si3N4 solubility and transport in the high liquid phase. By understanding these additive effects, one can develop reinforced microstructures leading silicon nitride ceramics with greatly improved mechanical behavior.

  18. Vacuum deposition and curing of liquid monomers apparatus

    DOEpatents

    Affinito, John D.

    1996-01-01

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of "standard" polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal or oxide may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface.

  19. Vacuum deposition and curing of liquid monomers apparatus

    DOEpatents

    Affinito, J.D.

    1996-08-20

    The present invention is the formation of solid polymer layers under vacuum. More specifically, the present invention is the use of ``standard`` polymer layer-making equipment that is generally used in an atmospheric environment in a vacuum, and degassing the monomer material prior to injection into the vacuum. Additional layers of polymer or metal or oxide may be vacuum deposited onto solid polymer layers. Formation of polymer layers under a vacuum improves material and surface characteristics, and subsequent quality of bonding to additional layers. Further advantages include use of less to no photoinitiator for curing, faster curing, fewer impurities in the polymer electrolyte, as well as improvement in material properties including no trapped gas resulting in greater density, and reduced monomer wetting angle that facilitates spreading of the monomer and provides a smoother finished surface. 3 figs.

  20. Effects of Silicon and Boron Additions on the Susceptibility to Quench Embrittlement and the Bending Fatigue Performance of Vacuum Carburized Modified 4320 Steel

    SciTech Connect

    Meyer III, Harry M; Spice, Jason J; Greer, John G.; Krauss, George; Matlock, D. K.

    2007-01-01

    The potential to reduce the susceptibility to quench embrittlement, a fracture mechanism that promotes intergranular fracture in high carbon steels, and to improve the bending fatigue performance of vacuum carburized modified SAE 4320 steels was evaluated. Data were obtained on an industrially produced SAE 4320 steel and four laboratory produced steels based on the 4320 composition but with additions of Si (1.0 or 2.0 wt pct) and B (0 or 17 ppm). All five alloys were vacuum carburized together and gas quenched with three different cooling rates as controlled by the gas quench conditions: 10 bar nitrogen, and 15 and 20 bar helium. Modified Brugger fatigue samples of each alloy and quench condition were tested in cantilever bending and failed samples were analyzed with scanning electron and Auger spectroscopy. Standard S-N curves and endurance limits were obtained and the fracture surfaces were evaluated using both light and electron microscopy techniques to determine fracture initiation sites and fracture growth mechanisms, both in the stable fatigue crack growth zone and in the overload zone. The percentage of transgranular fracture in the carburized case was quantified and used as a measure of the susceptibility to quench embrittlement. The susceptibility to quench embrittlement was observed to be independent of quench rate and boron additions, but depended on Si content. With an increase in Si content, the extent of intergranular fracture decreased, indicating a decrease in the susceptibility to quench embrittlement. However, with an increase in Si content to 2 wt pct, significant grain growth occurred producing prior austenite grain sizes 2 to 3 times those observed in the base or 1 pct Si alloys. The grain growth experienced by the high Si alloys was interpreted to result from the effects the retardation of cementite nucleation and growth at austenite grain boundaries. The fatigue properties were shown to be essentially independent of cooling rate and

  1. Influence of Thermo-Light Curing with Dental Light-Curing Units on the Microhardness of Glass-Ionomer Cements.

    PubMed

    Gavic, Lidia; Gorseta, Kristina; Borzabadi-Farahani, Ali; Tadin, Antonija; Glavina, Domagoj; van Duinen, Raymond N; Lynch, Edward

    2016-01-01

    The purpose of this study was to verify for various glass-ionomer cement (GIC) products whether the application of thermo-light curing on the initial curing material produces an increase in microhardness, and to determine whether this hardness varies depending on the depths of the GIC samples. The efficacy of various polymerization units on this additional hardening was also examined. The GIC samples were thermo-light cured for 60 seconds with three polymerization units. The Vickers microhardness was measured at three different depths: 2 mm, 3 mm, and 4 mm. Analysis of variance and Newman-Keuls test showed statistically significant differences among tested samples for all three GIC groups (P < .001). The results of linear regression analysis showed a statistically significant relationship between the hardness of the material and the temperature for samples with depths of 2 mm (R = 0.78; P = .0028) and 3 mm (R = 0.59; P = .045). The findings of this study indicate that thermo-light curing of GIC with different polymerization units for 60 seconds during setting reaction increases the microhardness of the GICs at all depths tested and may increase resistance to mastication forces, which can be validated in future clinical studies. PMID:27100813

  2. [Little histories of magnetic cures].

    PubMed

    Pinet, Patrice

    2009-02-01

    Men were very early fascinated by magnetism because of its manifest and particular working at distance, which looked different of gravity. It was tryed to be explained by mecanism, for exemple Descartes and Boyle. Paracelse valued the therapeutics with magnets and conceived medicines as working by a magnetic virtue. Gilbert limited the medicinal properties of magnet but helded it to be animated. Many authors praised remedies that work at distance of the evil as Bacon, Van Helmont, Croll, Porta, Goclenius, Digby. Such a belief related to magic ideas of this time. In the Bacon's way Boyle collected facts of magnetic cures, and his actual testing of the divisibility of bodies led him to conceive imponderable corpuscles. Newton supposed a subtil and universel fluid going through every solid body. Mesmer misappropriated this idea by founding the animal magnetism of which physical working was only proceeding from the inside of the patient by an effect of suggestion (psychosomatic). Homeopathy took again the notion of remedies having an infinite or a magnetic virtue, which partly issued from Paracelse's and Mesmer's doctrines, which were extolled in Germany at the time of Hahnemann. The latter decided in favour of a spiritualist and not corpuscular interpretation of the working of his homeopathic medicines. PMID:19579649

  3. Phosphazene-based ionic liquids: synthesis, temperature-dependent viscosity, and effect as additives in water lubrication of silicon nitride ceramics.

    PubMed

    Omotowa, Bamidele A; Phillips, Benjamin S; Zabinski, Jeffery S; Shreeve, Jean'ne M

    2004-08-23

    Phosphazene rings with (dimethylamino)ethoxy (1, 2), pyridylmethoxy (3), or (dimethylamino)propoxy (4) chains were synthesized and quaternized at the substitutent nitrogen by treatment with methyl iodide at 35 degrees C over 3-6 h to give polyiodo salts, 5-8. Subsequent metathesis with LiN(SO(2)CF(3))(2) or NaBF(4) gave the respective ionic salts, 9-13. The amide salts, 9-12, were viscous liquids with pour points at 55-100 degrees C, and the tetrafluoroborate salt, 13, was a solid, mp 168 degrees C. The compositions of 2 and 5-13 were confirmed by elemental analysis and spectroscopic methods. Compounds 1, 2, and 4 were viscous liquids (d(25) = 1.67 g cm(-3); eta(25) = 0.76-1.56 mPa s(-1) ) with pour points at approximately 15 degrees C. The solid polyquaternary salts, 5-8, melted at 130-194 degrees C. The ionic liquids, 9-12, had an average density of approximately 1.73 g cm(-3) at 25 degrees C, and viscosities (25 degrees C) ranged between 68.3 and 139.2 mPa s(-1). A plot of the viscosities of 9-12 vs temperature revealed an almost linear correlation between 55 and 120 degrees C. Friction and wear properties of water with 0.25 wt % of 9-12 as boundary lubricant additives were evaluated on Si(3)N(4)/Si(3)N(4) ceramic interfaces. The most significant observation is that they caused a decrease in the running-in period. PMID:15310229

  4. 21 CFR 172.480 - Silicon dioxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and... PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food in accordance with the following...

  5. Addition of Small Electrophiles to N-Heterocyclic-Carbene-Stabilized Disilicon(0): A Revisit of the Isolobal Concept in Low-Valent Silicon Chemistry.

    PubMed

    Arz, Marius I; Straßmann, Martin; Geiß, Daniel; Schnakenburg, Gregor; Filippou, Alexander C

    2016-04-01

    Protonation and alkylation of (Idipp)Si═Si(Idipp) (1) afforded the mixed-valent disilicon(I)-borates [(Idipp)(R)Si(II)═Si(0)(Idipp)][B(Ar(F))4] (1R[B(Ar(F))4]; R = H, Me, Et; Ar(F) = C6H3-3,5-(CF3)2; Idipp = C[N(C6H3-2,6-iPr2)CH]2) as red to orange colored, highly air-sensitive solids, which were characterized by single-crystal X-ray diffraction, IR spectroscopy and multinuclear NMR spectroscopy. Dynamic NMR studies in solution revealed a degenerate isomerization (topomerization) of the "σ-bonded" tautomers of 1H[B(Ar(F))4], which proceeds according to quantum chemical calculations via a NHC-stabilized (NHC = N-heterocyclic carbene) disilahydronium ion ("π-bonded" isomer) and is reminiscent of the degenerate rearrangement of carbenium ions formed upon protonation of olefins. The topomerization of 1H[B(Ar(F))4] provides the first example of a reversible 1,2-H migration along a Si═Si bond observed in a molecular system. In contrast, 1Me[B(Ar(F))4] adopts a "rigid" structure in solution due to the higher energy required for the interconversion of the "σ-bonded" isomer into a putative NHC-stabilized disilamethonium ion. Addition of alkali metal borates to 1 afforded the alkali metal disilicon(0) borates 1M[BAr4] (M = Li, Ar = C6F5; M = Na, Ar = Ar(F)) as brown, air-sensitive solids. Single-crystal X-ray diffraction analyses and NMR spectroscopic studies of 1M[BAr4] suggest in concert with quantum chemical calculations that encapsulation of the alkali metal cations in the cavity of 1 predominantly occurs via electrostatic cation-π interactions with the Si═Si π-bond and the peripheral NHC aryl rings. Displacement of the [Si(NHC)] fragments by the isolobal fragments [PR] and [SiR](-) interrelates the cations [(NHC)(R)Si═Si(NHC)](+) to a series of familiar, multiply bonded Si and P compounds as verified by analyses of their electronic structures. PMID:26978031

  6. [Is it possible to cure HIV infection?].

    PubMed

    Gutiérrez, Carolina; Madrid, Nadia P; Moreno, Santiago

    2015-09-01

    Antiretroviral therapy has significantly improved the life expectancy in HIV-infected people, but it cannot cure the disease by itself. Several barriers have been identified for the cure of HIV infection, including a reservoir of latently infected cells, persistent viral replication in tissues, and anatomical sanctuaries. The main strategy proposed for the cure of HIV consists on the administration of drugs that, through the reactivation of latent HIV, would eliminate the cell reservoir. Ongoing clinical trials have shown the proof of concept, but the efficacy of these drugs in decreasing the reservoir size has not been proved so far. PMID:26365737

  7. Light emission from porous silicon

    NASA Astrophysics Data System (ADS)

    Penczek, John

    The continuous evolution of silicon microelectronics has produced significant gains in electronic information processing. However, greater improvements in performance are expected by utilizing optoelectronic techniques. But these techniques have been severely limited in silicon- based optoelectronics due to the lack of an efficient silicon light emitter. The recent observation of efficient light emission from porous silicon offer a promising opportunity to develop a suitable silicon light source that is compatible with silicon microelectronics. This dissertation examined the porous silicon emission mechanism via photoluminescence, and by a novel device structure for porous silicon emitters. The investigation first examined the correlation between porous silicon formation conditions (and subsequent morphology) with the resulting photoluminescence properties. The quantum confinement theory for porous silicon light emission contends that the morphology changes induced by the different formation conditions determine the optical properties of porous silicon. The photoluminescence spectral shifts measured in this study, in conjunction with TEM analysis and published morphological data, lend support to this theory. However, the photoluminescence spectral broadening was attributed to electronic wavefunction coupling between adjacent silicon nanocrystals. An novel device structure was also investigated in an effort to improve current injection into the porous silicon layer. The selective etching properties of porous silicon were used to create a p-i-n structure with crystalline silicon contacts to the porous silicon layer. The resulting device was found to have unique characteristics, with a negative differential resistance region and current-induced emission that spanned from 400 nm to 5500 nm. The negative differential resistance was correlated to resistive heating effects in the device. A numerical analysis of thermal emission spectra from silicon films, in addition to

  8. Toughening reinforced epoxy composites with brominated polymeric additives

    NASA Technical Reports Server (NTRS)

    Nir, Z. (Inventor); Gilwee, W. J., Jr. (Inventor)

    1985-01-01

    Cured polyfunctional epoxy resins including tris(hydroxyphenyl)methane triglycidyl ether are toughened by addition of polybrominated polymeric additives having an EE below 1500 to the pre-cure composition. Carboxy-terminated butadiene-acrylonitrile rubber is optionally present in the pre-cure mixture as such or as a pre-formed copolymer with other reactants. Reinforced composites, particularly carbon-reinforced composites, of these resins are disclosed and shown to have improved toughness.

  9. Optimal cure cycle design for autoclave processing of thick composites laminates: A feasibility study

    NASA Technical Reports Server (NTRS)

    Hou, Jean W.

    1985-01-01

    The thermal analysis and the calculation of thermal sensitivity of a cure cycle in autoclave processing of thick composite laminates were studied. A finite element program for the thermal analysis and design derivatives calculation for temperature distribution and the degree of cure was developed and verified. It was found that the direct differentiation was the best approach for the thermal design sensitivity analysis. In addition, the approach of the direct differentiation provided time histories of design derivatives which are of great value to the cure cycle designers. The approach of direct differentiation is to be used for further study, i.e., the optimal cycle design.

  10. [Mineral water as a cure].

    PubMed

    Nocco, Priska Binz

    2008-01-01

    The treatment of diseases with mineral spring water belongs to the oldest medical therapies. The "remedy" mineral water is therefore of importance also within the pharmacy. The present pharmacy historical work examines the impact of the use of mineral waters, as well as of their dried components, as therapeutic agents in the 19th and early 20th centuries, i.e. from approx. 1810 to 1930, as well as the contributions given by pharmacists in the development and analysis of mineral water springs. Beside these aspects, the aim here is also to describe the role played by pharmacists in the production of artificial mineral water as well as in the sale and wholesale of natural and artificial mineral water. In the first part of this work the situation in Switzerland and its surrounding countries, such as Germany, France, Italy and Austria, is discussed. The second part contains a case-study of the particular situation in the Canton Tessin. It is known from the scientific literature published at that time that information on mineral water was frequently reported. Starting from the beginning of the 19th century the number of such publications increased tremendously. The major part of them were publications in scientific journals or contributions to medical and pharmaceutical manuals and reference books. In particular the spa-related literature, such as spa-guides, was of growing interest to a broad public. The inclusion of monographs into the Swiss, the Cantonal as well the foreign pharmacopoeias granted a legal frame for the mineral waters and their dried components. These works are of major importance from a pharmacy historical standpoint and represent a unique proof of historical evidence of the old medicinal drug heritage. The most frequently used therapies based on mineral waters were drinking and bath cures. Several diseases, particularly those of a chronic character, were treated with mineral waters. The positive influence of these cures on the recovery of the patients

  11. Use of silicon in liquid sintered silicon nitrides and sialons

    DOEpatents

    Raj, R.; Baik, S.

    1984-12-11

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

  12. Use of silicon in liquid sintered silicon nitrides and sialons

    DOEpatents

    Raj, Rishi; Baik, Sunggi

    1984-12-11

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

  13. Application of silicon piezoresistive stress test chips in electronic packages

    NASA Astrophysics Data System (ADS)

    Zou, Yida

    In this work, both special (100) and (111) silicon test chips containing an array of optimized piezoresistive stress sensor rosettes have been successfully applied within several electronic packaging configurations. Unlike (100) silicon test chips, (111) silicon test chips are able to measure the complete stress state on the die surface. After calibration and characterization of the test chips, they were packaged into various assemblies. The post packaging resistances of the sensors were then recorded at room temperature, as a function of temperature excursion, and during long term packaging reliability qualification tests (thermal cycling and thermal aging). The stresses on the die surface were calculated using the measured resistance changes and the appropriate theoretical equations. For comparison purposes, three-dimensional nonlinear finite element simulations of the packaging processes were also performed, and the stress predictions were correlated with the experimental test chip data. AAA2 (100) silicon test chips containing optimized four element dual polarity rosettes have been applied within 44 pin Plastic Leaded Chip Carrier (PLCC) packages and 240 pin Quad Flat Packs (QFP's). In these plastic package experiments, comparison of the stress levels induced by various molding compounds was emphasized. Advanced (111) silicon test chips (BMW-1 or BMW-2) comprising an array of optimized eight-element dual polarity piezoresistive sensor rosettes were encapsulated in 240 pin QFP's, 160 pin QFP's, Chip on Board (COB) packages, and 281 pin ceramic Pin Grid Array (PGA) packages. In addition to molding compound evaluations, BMW-1 test chips encapsulated in 240 pin QFP's were used to detect the presence of delaminations between the die surface and the encapsulant. In the wire bonded COB package studies, die surface stress evaluations were conducted after die attachment, and throughout the cure cycle of the liquid encapsulant. The stresses were also studied as a

  14. Financing cures in the United States.

    PubMed

    Basu, Anirban

    2015-02-01

    True cures in health care are rare but likely not for long. The high price tag that accompanies a cure along with its rapid uptake create challenges in the financing of cures by public and private payers. In the US, the disaggregated nature of health insurance system adds to this challenge as patients frequently churn across multiple health plans. This creates a 'free-rider' problem, where no one health plan has the incentive to invest in cure since the returns will be scattered over many health plans. Here, a new health currency is proposed as a generalized version of a social impact bond that has the potential to solve this free-rider problem, as it can be traded not only between public and private payers but also within the private sector. An ensuing debate as to whether and how to develop such a currency can serve the US health care system well. PMID:25482146

  15. Thread-Pull Test Of Curing Adhesive

    NASA Technical Reports Server (NTRS)

    Johnson, James A.

    1992-01-01

    Hardness (and degree of cure) of adhesive layer measured by pulling previously inserted thread out of layer. Strength of bond measured directly on assembly rather than on samples, which can be misleading.

  16. Inelastic micromechanics of curing stresses in composites

    NASA Technical Reports Server (NTRS)

    Foye, R. L.

    1975-01-01

    The combined finite element/laminate analysis method is used to study the thermal curing stresses in composite materials with a nonlinearly elastic matrix subject to creep. The application of this analysis to boron/epoxy composites shows that curing stress levels in the laminate are of sufficient magnitude to cause widespread yielding in the matrix. The stress levels, based on the creep analysis of a typical laminate cure cycle, indicate that the residual stresses can vary from 80 to 100% of the residual stress estimates based on linear thermoelastic analysis. It is shown that there is virtually no change in the static longitudinal or shear response of unidirectional and cross-ply boron/epoxy laminates as a result of curing stresses. Results of a series of constant-stress, high temperature creep tests are presented.

  17. Susan G. Komen for the Cure

    MedlinePlus

    ... Washington West Virginia Wisconsin Wyoming -INTERNATIONAL- Bahamas Belgium Bosnia and Herzegovina Georgia Germany Greece Italy Tanzania Uzbekistan ... TX Saturday, October 1, 2016 Susan G. Komen Bosnia and Herzegovina Race for the Cure Sarajevo, N/ ...

  18. Energy curable compositions having improved cure speeds

    DOEpatents

    Halm, L.W.

    1993-05-18

    The composition and method provide improved physical properties and cure speed of polyurethane precursors, with or without free radical polymerizable monomers or oligomers present, by use of a two component catalyst system. The resin blend can be activated with a latent organometallic catalyst combined with an organic peroxide which can be a hydroperoxide or an acyl peroxide to decrease the cure time while increasing the break energy and tangent modulus of the system.

  19. Energy curable compositions having improved cure speeds

    DOEpatents

    Halm, Leo W.

    1993-01-01

    A composition and method provide improved physical properties and cure speed of polyurethane precursors, with or without free radical polymerizable monomers or oligomers present, by use of a two component catalyst system. The resin blend can be activated with a latent organometallic catalyst combined with an organic peroxide which can be a hydroperoxide or an acyl peroxide to decrease the cure time while increasing the break energy and tangent modulus of the system.

  20. Tracking Polymer Cure Via Embedded Optical Fibers

    NASA Technical Reports Server (NTRS)

    Dean, David L.; Davidson, T. Fred

    1993-01-01

    Fourier-transform infrared spectroscopy applied in interior of specimen of material by bringing infrared light through specimen in optical fiber. Light interacts with material via evanescent-wave effect. Spectra obtained in this way at various times during curing process also combined with data from ultrasonic, thermographic, and dielectric-impedance monitoring, and other measurement techniques to obtain more complete characterization of progress of curing process.

  1. The stability of new transparent polymeric materials: The epoxy trimethoxyboroxine system. Part 1: The preparation, characterization and curing of epoxy resins and their copolymers

    NASA Technical Reports Server (NTRS)

    Pearce, E.; Lin, S. C.

    1981-01-01

    The effects of resin composition, curing conditions fillers, and flame retardant additives on the flammability of diglycidyl ether of bisphenol-A (DGEBA) as measured by the oxygen index is examined. The oxygen index of DGEBA cured with various curing agents was between 0.198 to 0.238. Fillers and flame retardant additives can increase the oxygen index dependent on the material and the amount used. Changes in the basic cured resin properties can be anticipated with the addition of noncompatible additives. High flame resistant epoxy resins with good stability and mechanical properties are investigated.

  2. High Power UV LED Industrial Curing Systems

    SciTech Connect

    Karlicek, Robert, F., Jr; Sargent, Robert

    2012-05-14

    UV curing is a green technology that is largely underutilized because UV radiation sources like Hg Lamps are unreliable and difficult to use. High Power UV LEDs are now efficient enough to replace Hg Lamps, and offer significantly improved performance relative to Hg Lamps. In this study, a modular, scalable high power UV LED curing system was designed and tested, performing well in industrial coating evaluations. In order to achieve mechanical form factors similar to commercial Hg Lamp systems, a new patent pending design was employed enabling high irradiance at long working distances. While high power UV LEDs are currently only available at longer UVA wavelengths, rapid progress on UVC LEDs and the development of new formulations designed specifically for use with UV LED sources will converge to drive more rapid adoption of UV curing technology. An assessment of the environmental impact of replacing Hg Lamp systems with UV LED systems was performed. Since UV curing is used in only a small portion of the industrial printing, painting and coating markets, the ease of use of UV LED systems should increase the use of UV curing technology. Even a small penetration of the significant number of industrial applications still using oven curing and drying will lead to significant reductions in energy consumption and reductions in the emission of green house gases and solvent emissions.

  3. A new resin technology: a glaze/composite sealant that cures without forming an oxygen-inhibited layer.

    PubMed

    Suh, Byoung I

    2003-08-01

    Until now, intraoral composite resin sealants cured with an oxygen-inhibited layer. In addition, resin glazes used for temporaries and processed appliances could not be used intraorally. This article describes the strategies behind the development of a new resin product that can be used intra- and extraorally as a sealant/glaze without forming an oxygen-inhibited layer after curing. PMID:14692216

  4. Silicon production process evaluations

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Engineering design of the third distillation column in the process was accomplished. The initial design is based on a 94.35% recovery of dichlorosilane in the distillate and a 99.9% recovery of trichlorosilane in the bottoms. The specified separation is achieved at a reflux ratio of 15 with 20 trays (equilibrium stages). Additional specifications and results are reported including equipment size, temperatures and pressure. Specific raw material requirements necessary to produce the silicon in the process are presented. The primary raw materials include metallurgical grade silicon, silicon tetrachloride, hydrogen, copper (catalyst) and lime (waste treatment). Hydrogen chloride is produced as by product in the silicon deposition. Cost analysis of the process was initiated during this reporting period.

  5. Materials for single-etch double patterning process: surface curing agent and thermal cure resist

    NASA Astrophysics Data System (ADS)

    Bae, Young C.; Liu, Yi; Cardolaccia, Thomas; McDermott, John C.; Trefonas, Peter; Spizuoco, Ken; Reilly, Michael; Pikon, Amandine; Joesten, Lori; Zhang, Gary G.; Barclay, George G.; Simon, Julia; Gaurigan, Stéphanie

    2009-03-01

    Two different pattern curing techniques were developed to stabilize first lithographic images for the single-etch double patterning process. The first method uses a surface curing agent (SCA) that is coated on top of the patterned surface to form a protective coating layer during the curing bake process. It was found that the surface curing process with SCA offers minimum CD changes before and after the double patterning process. Virtually no CD change was observed with the first lithographic images at various curing bake temperatures ranging from 120 ~160°C indicating the curing reaction is limited on the patterned surface. The second method uses a thermal cure resist (TCR) that is a special 193nm photoresist with a crosslinkable functional group to form an insoluble network upon heating at higher temperature. A single-step curing process of the first lithographic images was achieved using TCR by baking the patterned images at 180°C for 60sec. A cross-line contact hole double patterning method was used to evaluate these two different curing techniques and both SCA and TCR successfully demonstrated their capability to print 45nm contact holes with excellent CD uniformity in immersion lithography (1.35NA) with a 45nm half pitch mask. It was also confirmed that both SCA and TCR can be extended to the top-coat free immersion double patterning process using an embedded barrier layer technique.

  6. Effect of network structure on thermal and mechanical properties of cured epoxy resin containing mesogenic group

    SciTech Connect

    Ochi, M.; Shimizu, Y.; Tsuyuno, N.

    1996-10-01

    Epoxy resin containing biphenol group as a mesogenic group was cured with phenol (PN) and catechol (CN) novolacs. In the CN-cured biphenol type epoxy resin, the glass-rubber transition, almost disappeared and thus the very high elastic modulus was obtained in the high temperature region. It is clear that the micro-Brownian motion of the network chains is highly suppressed in this cured system. On the other hand, the PN-cured resin showed the well-defined glass-rubber transition and thus the low rubbery modulus. In addition, in the former system, the characteristic pattern like a schlieren texture was clearly observed in the polarized optical microphotographs. This shows that the mesogenic group contained in the epoxy molecule is oriented in the system cued with catechol novolac, which has neighboring active hydrogens. The computer simulation based on the molecular mechanics also showed that the orientation of the network chains should occur in the CN-cured biphenol epoxy system. Thus, we conclude that the suppression of the micro-Brownian motion in the CN-cured system is due to the orientation of network chains containing a mesogenic group. Moreover, it has been shown that die mechanical and bonding strength at high temperature is considerably improved by the suppression of the network chain in the CN-cured biphenol resin system.

  7. Injectable Polymerized High Internal Phase Emulsions with Rapid in Situ Curing

    PubMed Central

    2015-01-01

    Polymerized high internal phase emulsions (polyHIPEs) have been utilized in the creation of injectable scaffolds that cure in situ to fill irregular bone defects and potentially improve tissue healing. Previously, thermally initiated scaffolds required hours to cure, which diminished the potential for clinical translation. Here, a double-barrel syringe system for fabricating redox-initiated polyHIPEs with dramatically shortened cure times upon injection was demonstrated with three methacrylated macromers. The polyHIPE cure time, compressive properties, and pore architecture were investigated with respect to redox initiator chemistry and concentration. Increased concentrations of redox initiators reduced cure times from hours to minutes and increased the compressive modulus and strength without compromising the pore architecture. Additionally, storage of the uncured emulsion at reduced temperatures for 6 months was shown to have minimal effects on the resulting graft properties. These studies indicate that the uncured emulsions can be stored in the clinic until they are needed and then rapidly cured after injection to rigid, high-porosity scaffolds. In summary, we have improved upon current methods of generating injectable polyHIPE grafts to meet translational design goals of long storage times and rapid curing (<15 min) without sacrificing porosity or mechanical properties. PMID:25006990

  8. Color Developing Capacity of Plasma-treated Water as a Source of Nitrite for Meat Curing

    PubMed Central

    Jung, Samooel; Kim, Hyun Joo; Park, Sanghoo; Choe, Jun Ho; Jeon, Hee-Joon; Choe, Wonho

    2015-01-01

    The interaction of plasma with liquid generates nitrogen species including nitrite (NO−2). Therefore, the color developing capacity of plasma-treated water (PTW) as a nitrite source for meat curing was investigated in this study. PTW, which is generated by surface dielectric barrier discharge in air, and the increase of plasma treatment time resulted in increase of nitrite concentration in PTW. The PTW used in this study contains 46 ppm nitrite after plasma treatment for 30 min. To evaluate the effect of PTW on the cured meat color, meat batters were prepared under three different conditions (control, non-cured meat batter; PTW, meat batter cured with PTW; Sodium nitrite, meat batter cured with sodium nitrite). The meat batters were vacuum-packaged and cooked in a water-bath at 80℃ for 30 min. The typical color of cured meat developed in cooked meat batter treated with sodium nitrite or PTW. The lightness (L*) and yellowness (b*) values were similar in all conditions, whereas, the redness (a*) values of cooked meat batter with PTW and sodium nitrite (p<0.05) were significantly higher than the control. These data indicate that PTW can be used as a nitrite source in the curing process of meat without addition of other nitrite sources. PMID:26761900

  9. Modifying a silicone potting compound for space flight applications

    NASA Technical Reports Server (NTRS)

    Park, J. J.; Clatterbuck, C. H.

    1982-01-01

    RTV-615 has been devolatilized by subjecting the uncatalyzed resin to a temperature of between 125 and 150 C for 24 hours in a vacuum of about 10 to the -6th torr. The resultant resin can be catalyzed and after a room temperature cure the outgassing of the resin is sufficiently low when tested according to ASTM E-595 that it is suitable for space flight use. Tests of physical properties of the cured devolatilized resin were compared with those of the as received silicone. The devolatilized silicones are slightly harder, have a higher tear resistance and higher tensile strengths.

  10. [Study of purity tests for silicone resins].

    PubMed

    Sato, Kyoko; Otsuki, Noriko; Ohori, Akio; Chinda, Mitsuru; Furusho, Noriko; Osako, Tsutomu; Akiyama, Hiroshi; Kawamura, Yoko

    2012-01-01

    In the 8th edition of Japan's Specifications and Standards for Food Additives, the purity test for silicone resins requires the determination of the refractive index and kinetic viscosity of the extracted silicone oil, and allows for only a limited amount of silicon dioxide. In the purity test, carbon tetrachloride is used to separate the silicone oil and silicon dioxide. To exclude carbon tetrachloride, methods were developed for separating the silicone oil and silicon dioxide from silicone resin, which use hexane and 10% n-dodecylbenzenesulfonic acid in hexane. For silicone oil, the measured refractive index and kinetic viscosity of the silicone oil obtained from the hexane extract were shown to be equivalent to those of the intact silicone oil. In regard to silicon dioxide, it was confirmed that, following the separation with 10% n-dodecylbenzenesulfonic acid in hexane, the level of silicon dioxide in silicone resin can be accurately determined. Therefore, in this study, we developed a method for testing the purity of silicone resins without the use of carbon tetrachloride, which is a harmful reagent. PMID:23243991

  11. 21 CFR 573.940 - Silicon dioxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed in accordance with the following conditions: (a) The food additive is manufactured by vapor phase hydrolysis...

  12. 21 CFR 573.940 - Silicon dioxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ..., FEEDS, AND RELATED PRODUCTS FOOD ADDITIVES PERMITTED IN FEED AND DRINKING WATER OF ANIMALS Food Additive Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed in accordance with the following conditions: (a) The food additive is manufactured by vapor phase hydrolysis...

  13. Cured Meat Consumption, Lung Function, and Chronic Obstructive Pulmonary Disease among United States Adults

    PubMed Central

    Jiang, Rui; Paik, David C.; Hankinson, John L.; Barr, R. Graham

    2007-01-01

    Rationale: Cured meats are high in nitrites. Nitrites generate reactive nitrogen species that may cause nitrative and nitrosative damage to the lung resulting in emphysema. Objective: To test the hypothesis that frequent consumption of cured meats is associated with lower lung function and increased odds of chronic obstructive pulmonary disease (COPD). Methods: Cross-sectional study of 7,352 participants in the Third National Health and Nutrition Examination Survey, 45 years of age or more, who had adequate measures of cured meat, fish, fruit, and vegetable intake, and spirometry. Results: After adjustment for age, smoking, and multiple other potential confounders, frequency of cured meat consumption was inversely associated with FEV1 and FEV1/FVC but not FVC. The adjusted differences in FEV1 between individuals who did not consume cured meats and those who consumed cured meats 1 to 2, 3 to 4, 5 to 13, and 14 or more times per month were −37.6, −11.5, −42.0, and −110 ml, respectively (p for trend < 0.001). Corresponding differences for FEV1/FVC were −0.91, −0.54, −1.13, and −2.13% (p for trend = 0.001). These associations were not modified by smoking status. The multivariate odds ratio for COPD (FEV1/FVC ⩽ 0.7 and FEV1 < 80% predicted) was 1.78 (95% confidence interval, 1.29–2.47) comparing the highest with the lowest category of cured meat consumption. The corresponding odds ratios for mild, moderate, and severe COPD were 1.11, 1.46, and 2.41, respectively. Conclusions: Frequent cured meat consumption was associated independently with an obstructive pattern of lung function and increased odds of COPD. Additional studies are required to determine if cured meat consumption is a causal risk factor for COPD. PMID:17255565

  14. 7 CFR 29.3502 - Air-cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Air-cured. 29.3502 Section 29.3502 Agriculture... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3502 Air-cured. Tobacco cured under natural atmospheric conditions without the use...

  15. 7 CFR 29.3502 - Air-cured.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Air-cured. 29.3502 Section 29.3502 Agriculture... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3502 Air-cured. Tobacco cured under natural atmospheric conditions without the use...

  16. 7 CFR 29.6002 - Air-cured.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Air-cured. 29.6002 Section 29.6002 Agriculture... INSPECTION Standards Definitions § 29.6002 Air-cured. Tobacco cured under natural atmospheric conditions..., pole-burn, and shed-burn in damp weather. Air-cured tobacco should not carry the odor of smoke or...

  17. 7 CFR 29.3502 - Air-cured.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Air-cured. 29.3502 Section 29.3502 Agriculture... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3502 Air-cured. Tobacco cured under natural atmospheric conditions without the use...

  18. 7 CFR 29.3002 - Air-cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Air-cured. 29.3002 Section 29.3002 Agriculture... Air-cured. Tobacco cured under natural atmospheric conditions. Artificial heat is sometimes used to control excess humidity during the curing period to prevent house-burn and barn-burn in damp weather....

  19. 7 CFR 29.3002 - Air-cured.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Air-cured. 29.3002 Section 29.3002 Agriculture... Air-cured. Tobacco cured under natural atmospheric conditions. Artificial heat is sometimes used to control excess humidity during the curing period to prevent house-burn and barn-burn in damp weather....

  20. 7 CFR 29.3502 - Air-cured.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Air-cured. 29.3502 Section 29.3502 Agriculture... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3502 Air-cured. Tobacco cured under natural atmospheric conditions without the use...

  1. 7 CFR 29.6002 - Air-cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false Air-cured. 29.6002 Section 29.6002 Agriculture... INSPECTION Standards Definitions § 29.6002 Air-cured. Tobacco cured under natural atmospheric conditions..., pole-burn, and shed-burn in damp weather. Air-cured tobacco should not carry the odor of smoke or...

  2. 7 CFR 29.6002 - Air-cured.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false Air-cured. 29.6002 Section 29.6002 Agriculture... INSPECTION Standards Definitions § 29.6002 Air-cured. Tobacco cured under natural atmospheric conditions..., pole-burn, and shed-burn in damp weather. Air-cured tobacco should not carry the odor of smoke or...

  3. 7 CFR 29.3002 - Air-cured.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false Air-cured. 29.3002 Section 29.3002 Agriculture... Air-cured. Tobacco cured under natural atmospheric conditions. Artificial heat is sometimes used to control excess humidity during the curing period to prevent house-burn and barn-burn in damp weather....

  4. 7 CFR 29.3002 - Air-cured.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false Air-cured. 29.3002 Section 29.3002 Agriculture... Air-cured. Tobacco cured under natural atmospheric conditions. Artificial heat is sometimes used to control excess humidity during the curing period to prevent house-burn and barn-burn in damp weather....

  5. 7 CFR 29.6002 - Air-cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Air-cured. 29.6002 Section 29.6002 Agriculture... INSPECTION Standards Definitions § 29.6002 Air-cured. Tobacco cured under natural atmospheric conditions..., pole-burn, and shed-burn in damp weather. Air-cured tobacco should not carry the odor of smoke or...

  6. 7 CFR 29.3002 - Air-cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Air-cured. 29.3002 Section 29.3002 Agriculture... Air-cured. Tobacco cured under natural atmospheric conditions. Artificial heat is sometimes used to control excess humidity during the curing period to prevent house-burn and barn-burn in damp weather....

  7. 7 CFR 29.3502 - Air-cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Air-cured. 29.3502 Section 29.3502 Agriculture... INSPECTION Standards Official Standard Grades for Dark Air-Cured Tobacco (u.s. Types 35, 36, 37 and Foreign Type 95) § 29.3502 Air-cured. Tobacco cured under natural atmospheric conditions without the use...

  8. 7 CFR 58.412 - Coolers or curing rooms.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 3 2010-01-01 2010-01-01 false Coolers or curing rooms. 58.412 Section 58.412 Agriculture Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Standards....412 Coolers or curing rooms. Coolers or curing rooms where cheese is held for curing or storage...

  9. Structural Evolution of Silica Gel and Silsesquioxane Using Thermal Curing.

    PubMed

    Hu, Nan; Rao, YuanQiao; Sun, Shengtong; Hou, Lei; Wu, Peiyi; Fan, Shaojuan; Ye, Bangjiao

    2016-08-01

    The curing of coatings of two types of siloxane containing materials, silica gel and silsesquioxane, at a modest temperature (<280℃) was studied with in situ heating Fourier transform infrared spectroscopy (FT-IR) in combination with perturbation correlation moving window (PCMW) and two-dimensional correlation spectroscopy (2D-COS) analyses. The result revealed detailed structural evolution of these two different gels. When the silica gel was heated, (Si-O)6 rings appeared from the random Si-O-Si network formed after sol gel reaction, followed by condensation of silanol groups. Upon further heating, the existing (Si-O)4 rings were broken down and converted into (Si-O)6 structures, and finally isolated silanols appeared. The transition from (Si-O)4 rings to (Si-O)6 rings was observed by IR and further confirmed with positron annihilation lifetime spectroscopy (PALS). In comparison, during the curing of hybrid silsesquioxane, the condensation of silanols happens immediately upon heating without the rearrangement of Si-O-Si network. Afterwards, the fraction of (Si-O)6 ring structure increased. (Si-O)4 structures exhibited higher stability in hybrid silsesquioxanes. In addition, the amount of silanols in silsesquioxane continued to reduce without the generation of isolated silanol in the end. The different curing behavior of silsesquioxanes from silica gel originates from the organic groups in silsesquioxanes, which lowers the cross-linking density and reduces the rigidity of siloxane network. PMID:27340213

  10. Siloxane containing addition polyimides

    NASA Technical Reports Server (NTRS)

    Maudgal, S.; St. Clair, T. L.

    1984-01-01

    Addition polyimide oligomers have been synthesized from bis(gamma-aminopropyl) tetramethyldisiloxane and 3, 3', 4, 4'-benzophenonetetracarboxylic dianhydride using a variety of latent crosslinking groups as endcappers. The prepolymers were isolated and characterized for solubility (in amide, chlorinated and ether solvents), melt flow and cure properties. The most promising systems, maleimide and acetylene terminated prepolymers, were selected for detailed study. Graphite cloth reinforced composites were prepared and properties compared with those of graphite/Kerimid 601, a commercially available bismaleimide. Mixtures of the maleimide terminated system with Kerimid 601, in varying proportions, were also studied.

  11. 21 CFR 172.480 - Silicon dioxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food...

  12. 21 CFR 573.940 - Silicon dioxide.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 6 2013-04-01 2013-04-01 false Silicon dioxide. 573.940 Section 573.940 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...

  13. 21 CFR 573.940 - Silicon dioxide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 6 2014-04-01 2014-04-01 false Silicon dioxide. 573.940 Section 573.940 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...

  14. 21 CFR 172.480 - Silicon dioxide.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Silicon dioxide. 172.480 Section 172.480 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food...

  15. 21 CFR 573.940 - Silicon dioxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 6 2012-04-01 2012-04-01 false Silicon dioxide. 573.940 Section 573.940 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS... Listing § 573.940 Silicon dioxide. The food additive silicon dioxide may be safely used in animal feed...

  16. 21 CFR 172.480 - Silicon dioxide.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food...

  17. 21 CFR 172.480 - Silicon dioxide.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Silicon dioxide. 172.480 Section 172.480 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.480 Silicon dioxide. The food additive silicon dioxide may be safely used in food...

  18. Improved Thermal Property of a Multilayered Graphite Nanoplatelets Filled Silicone Resin Composite

    NASA Astrophysics Data System (ADS)

    Lin, Jin; Zhang, Haiyan; Tang, Muyao; Tu, Wenying; Zhang, Xiubin

    2015-02-01

    We produced graphite nanoplatelets (GNP)/silicone resin composites at various loadings. The utilized GNPs were characterized by two-dimensional structure with high aspect ratio (~1810), and the GNP with approximately 10-30 nm thickness and 10-50 µm in length evenly dispersed throughout the resin matrix, which enables that GNPs effectively act as thermally conductive medium, thus contributed considerably to the formation of an efficient three-dimensional network for heat flow. The thermal conductivities of 5, 10, 15, and 20 wt.% GNP composite were 0.35, 1.02, 1.32, and 2.01 W/(m K), and were ca. 0.9, 4.7, 6.3, and 10.2 times higher than that of silicone resin at room temperature, respectively. The thermal conductivity decreased with elevated temperature in 25-200 °C, which was reminiscent at higher loading. Differential scanning calorimeter analysis showed that GNP addition increased the curing temperature of silicone resin from 90 to 119 °C, probably by hindering the free movement (mobility) of the silicone chains. The result showed that the GNP not only reduced the CTE but also improved the thermal stability of composite simultaneously.

  19. Method of reusably sealing a silicone rubber vacuum bag to a mold for composite manufacture

    NASA Technical Reports Server (NTRS)

    Steinbach, John (Inventor)

    1989-01-01

    A silicone rubber vacuum bag for use in composite article manufacture is reusably sealed to a mold, without mechanical clamping means. The mold-mating portion of the bag is primed with a silicone rubber adhesive, which is cured thereto, and a layer of semiadhesive sealer is applied between the primed mold-mating portion of the bag and the mold.

  20. Ceramic Stereolithography: Additive Manufacturing for Ceramics by Photopolymerization

    NASA Astrophysics Data System (ADS)

    Halloran, John W.

    2016-07-01

    Ceramic stereolithography and related additive manufacturing methods involving photopolymerization of ceramic powder suspensions are reviewed in terms of the capabilities of current devices. The practical fundamentals of the cure depth, cure width, and cure profile are related to the optical properties of the monomer, ceramic, and photo-active components. Postpolymerization steps, including harvesting and cleaning the objects, binder burnout, and sintering, are discussed and compared with conventional methods. The prospects for practical manufacturing are discussed.

  1. Adhesive curing through low-voltage activation

    PubMed Central

    Ping, Jianfeng; Gao, Feng; Chen, Jian Lin; Webster, Richard D.; Steele, Terry W. J.

    2015-01-01

    Instant curing adhesives typically fall within three categories, being activated by either light (photocuring), heat (thermocuring) or chemical means. These curing strategies limit applications to specific substrates and can only be activated under certain conditions. Here we present the development of an instant curing adhesive through low-voltage activation. The electrocuring adhesive is synthesized by grafting carbene precursors on polyamidoamine dendrimers and dissolving in aqueous solvents to form viscous gels. The electrocuring adhesives are activated at −2 V versus Ag/AgCl, allowing tunable crosslinking within the dendrimer matrix and on both electrode surfaces. As the applied voltage discontinued, crosslinking immediately terminated. Thus, crosslinking initiation and propagation are observed to be voltage and time dependent, enabling tuning of both material properties and adhesive strength. The electrocuring adhesive has immediate implications in manufacturing and development of implantable bioadhesives. PMID:26282730

  2. UV curing of nanoparticle reinforced acrylates

    NASA Astrophysics Data System (ADS)

    Bauer, F.; Flyunt, R.; Czihal, K.; Ernst, H.; Naumov, S.; Buchmeiser, M. R.

    2007-12-01

    To improve the surface hardness of radiation cured acrylate coatings, both silica nanoparticles and alumina particles with a few microns in size have been embedded into acrylate formulations. Regular mixing of nanoparticles into acrylate formulations, however, leads to highly viscous solutions inappropriate for coating procedures. The incompatibility of inorganic fillers and organic polymers can be avoided by surface modification of nanoparticles using trialkoxysilanes, which provide an interface between the two dissimilar materials. Nanoparticles modified by methacryloxypropyltrimethoxysilane (MEMO) and vinyltrimethoxysilane (VTMO), both having polymerisation-active groups, may be crosslinked with the acrylate resin. UV curing of the nanocomposites revealed an unexpected lower reactivity of the vinyl groups of VTMO modified silica compared to MEMO grafted on silica. For VTMO modification, DFT calculations showed a decrease of Mulliken atomic charge for the olefinic carbons pointing to a lower reactivity. For UV cured nano/microhybrid composites, a significant improvement of abrasion resistance was obtained.

  3. Lower-curing-temperature PMR polyimides

    NASA Technical Reports Server (NTRS)

    Serafini, T. T.; Delvigs, P.; Vannucci, R. D.

    1981-01-01

    Studies were performed to achieve a lower-curing-temperature PMR polyimide. The use of m-aminostyrene as the end-cap instead of the monoalkyl ester of 5-normbornene-2,3 dicarboxylic acid was investigated in typical PMR formulations. Model compound studies were also performed. Differential scanning calorimetry studies were performed on model compounds and neat resins to establish their melting and curing characteristics. The elevated temperature weight loss characteristics of neat resins and graphite fiber composites were determined. The room temperature and short-time 260 C (500 F) mechanical properties of the composites were also determined. The use of m-aminostyrene end-caps reduced the final cure temperature of PMR resins by about 55 C (100 F), but the composites prepared with these resins are limited to use temperatures of about 260 C (500 F).

  4. The research of UV curing injection molding

    NASA Astrophysics Data System (ADS)

    Xie, Pengcheng; Chang, Le; Song, Le; Cai, Tianze; Ding, Yumei; Yang, Weimin

    2015-05-01

    The micro-injection molding technology and the UV (ultraviolet) curing technique are combined to bring about a new plastic forming method, UV curing injection molding. The mean weight of micro-product is an important process characteristic for UV curing injection molding as well as the surface quality of micro-features is another important process characteristic for this new plastic forming method. This research investigates three effects of processing factors on the mass-change rate of micro-product and the surface quality of micro-features. In every particular, the following two factors are considered: UV material system temperature and the packing pressure. The study revealed that as usual, the micro-products gain weight with the imported increasing UV material system temperature and the improved packing pressure. Meanwhile, the increasing packing pressure also improves the surface quality, yet, warming the UV system temperature up has no effect on the quality of the product.

  5. Outdoor durability of radiation-cured coatings

    SciTech Connect

    Holman, R.; Kennedy, R.

    1997-12-31

    Radiation cured coatings are used almost exclusively on products which have little or no exposure to moisture or the weather; inks, furniture varnishes, floor varnishes and coatings for electronic components. However there is considerable interest in being able to use this technology in exterior environments as a substitute for solvent-borne coatings. A 3-year study examining the possible reasons for the poor durability of radiation curable coatings showed that the resistance of the monomers and oligomers to hydrogen abstraction was crucially important, and the water permeability of the cured coating influenced the long-term adhesion performance. The project concluded that with the appropriate combination of curing technology and monomer/oligomer selection, the prospects of UV curable coatings for outdoor exposure are very encouraging.

  6. Cure-in-place process for seals

    DOEpatents

    Hirasuna, Alan R.

    1981-01-01

    A cure-in-place process which allows a rubber seal element to be deformed to its service configuration before it is cross-linked and, hence, is a plastic and does not build up internal stress as a result of the deformation. This provides maximum residual strength to resist the differential pressure. Furthermore, the process allows use of high modulus formulations of the rubber seal element which would otherwise crack if cured and then deformed to its service configuration, resulting in a seal which has better gap bridging capability. Basically, the process involves positioning an uncured seal element in place, deforming it to its service configuration, heating the seal element, curing it in place, and then fully seating the seal.

  7. Atomic-scale disproportionation in amorphous silicon monoxide.

    PubMed

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  8. Atomic-scale disproportionation in amorphous silicon monoxide

    PubMed Central

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-01-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material. PMID:27172815

  9. Atomic-scale disproportionation in amorphous silicon monoxide

    NASA Astrophysics Data System (ADS)

    Hirata, Akihiko; Kohara, Shinji; Asada, Toshihiro; Arao, Masazumi; Yogi, Chihiro; Imai, Hideto; Tan, Yongwen; Fujita, Takeshi; Chen, Mingwei

    2016-05-01

    Solid silicon monoxide is an amorphous material which has been commercialized for many functional applications. However, the amorphous structure of silicon monoxide is a long-standing question because of the uncommon valence state of silicon in the oxide. It has been deduced that amorphous silicon monoxide undergoes an unusual disproportionation by forming silicon- and silicon-dioxide-like regions. Nevertheless, the direct experimental observation is still missing. Here we report the amorphous structure characterized by angstrom-beam electron diffraction, supplemented by synchrotron X-ray scattering and computer simulations. In addition to the theoretically predicted amorphous silicon and silicon-dioxide clusters, suboxide-type tetrahedral coordinates are detected by angstrom-beam electron diffraction at silicon/silicon-dioxide interfaces, which provides compelling experimental evidence on the atomic-scale disproportionation of amorphous silicon monoxide. Eventually we develop a heterostructure model of the disproportionated silicon monoxide which well explains the distinctive structure and properties of the amorphous material.

  10. Prevent and cure disuse bone loss

    NASA Technical Reports Server (NTRS)

    Jee, Webster S. S.

    1994-01-01

    Anabolic agents like parathyroid hormone and postagladin E-like substances were studied in dogs and rats to determine their effectiveness in the prevention and cure of bone loss due to immobilization. It was determined that postagladin E2 administration prevented immobilization while at the same time it added extra bone in a dose responsive manner. Although bone mass returns, poor trabecular architecture remains after normal ambulation recovery from immobilization. Disuse related bone loss and poor trabecular architecture were cured by post-immobilization postagladin E2 treatment.

  11. [Light-cured glass ionomer cements].

    PubMed

    Nordbø, H

    1989-12-01

    An attempt at improving the properties of glass-ionomer cements is represented by the incorporation of light-cure resin systems. This produces materials which have mechanical properties and moisture sensitivity superior to those of present glass-ionomer cements. Such hybrid materials cure by two different mechanisms: polymerization and salt formation. In particular, the early mechanical properties and water sensitivity of the materials are improved due to the formation of a polymer matrix. The tendency to undergo surface crazing during desiccation is also reduced. Three commercially available products are shortly described. PMID:2640704

  12. Silicone containing solid propellant

    NASA Technical Reports Server (NTRS)

    Ramohalli, K. N. R. (Inventor)

    1980-01-01

    The addition of a small amount, for example 1% by weight, of a liquid silicone oil to a metal containing solid rocket propellant provides a significant reduction in heat transfer to the inert nozzle walls. Metal oxide slag collection and blockage of the nozzle are eliminated and the burning rate is increased by about 5% to 10% thus improving ballistic performance.

  13. Thermal emission and curing efficiency of LED and halogen curing lights.

    PubMed

    Vandewalle, Kraig S; Roberts, Howard W; Tiba, Amer; Charlton, David G

    2005-01-01

    The purpose of this study was to compare the thermal emission and curing efficiency of LED (LEDemetron 1, SDS/Kerr) and QTH (VIP, BISCO) curing lights at maximum output and similar power, power density and energy density using the same light guide. Also, another LED curing light (Allegro, Den-Mat) and the QTH light at reduced power density were tested for comparison. Increase in temperature from the tips of the light guides was measured at 0 and 5 mm in air (23 degrees C) using a temperature probe (Fluke Corp). Pulpal temperature increase was measured using a digital thermometer (Omega Co) and a K-type thermocouple placed on the central pulpal roof of human molars with a Class I occlusal preparation. Measurements were made over 90 seconds with an initial light activation of 40 seconds. To test curing efficiency, resin composites (Z100, A110, 3M/ESPE) were placed in a 2-mm deep and 8-mm wide plastic mold and cured with the LED and QTH curing lights at 1- and 5-mm curing distances. Knoop Hardness Numbers (KHN) were determiped on the top and bottom surfaces (Leco). Bottom hardness values were expressed as a percentage of maximum top hardness. No significant differences were found in maximum thermal emission or KHN ratios between the LED (LEDemetron 1) and the QTH (VIP) at maximum output and similar energy densities (ANOVA/Tukey's; alpha=0.05). PMID:15853113

  14. Light-Cured Self-Etch Adhesives Undergo Hydroxyapatite-Triggered Self-Cure.

    PubMed

    Liu, Y; Bai, X; Liu, Y W; Wang, Y

    2016-03-01

    Light cure is a popular mode of curing for dental adhesives. However, it suffers from inadequate light delivery when the restoration site is less accessible, in which case a self-cure mechanism is desirable to salvage any compromised polymerization. We previously reported a novel self-cure system mediated by ethyl 4-(dimethylamino)-benzoate (4E) and hydroxyapatite (HAp). The present work aims to investigate if such self-cure phenomenon takes place in adhesives that underwent prior inadequate light cure and to elucidate if HAp released from the dental etching process is sufficient to trigger it. Model self-etch adhesives were formulated with various components, including bis[2-methacryloyloxy)ethyl]-phosphate (2MP) as acidic monomer and trimethylbenzoyl-diphenylphosphine oxide (TPO) as photoinitiator. In vitro evolution of degree of conversion (DC) of HAp-incorporated adhesives was monitored by infrared spectroscopy during light irradiation and dark storage. Selected adhesives were allowed to etch and extract HAp from enamel, light-cured in situ, and stored in the dark, after which Raman line mapping was used to obtain spatially resolved DC across the enamel-resin interface. Results showed that TPO+4E adhesives reached DC similar to TPO-only counterparts upon completion of light irradiation but underwent another round of initiation that boosted DC to ~100% regardless of HAp level or prior light exposure. When applied to enamel, TPO-only adhesives had ~80% DC in resin, which gradually descended to ~50% in enamel, whereas TPO+4E adhesives consistently scored ~80% DC across the enamel-resin interface. These observations suggest that polymerization of adhesives that underwent insufficient light cure is salvaged by the novel self-cure mechanism, and such salvaging effect can be triggered by HAp released from dental substrate during the etching process. PMID:26635279

  15. Effects of Various Salts on Physicochemical Properties and Sensory Characteristics of Cured Meat

    PubMed Central

    Choi, Yun-Sang; Kim, Young-Boong; Jeon, Ki-Hong; Kim, Hyun-Wook

    2016-01-01

    This study was carried out to investigate the effects of refined, solar, and bamboo salt on the physico-chemical properties and sensory characteristics of cured pork loin. Moisture, protein, fat, and ash content, lightness, yellowness, cooking yield, and color, juiciness, and tenderness of sensory properties on curing pork loin exhibited no significant differences regardless of the nature of salts. The pH of raw and cooked cured pork loin with added bamboo salt was higher that of other salt treatments. However, the cooking loss, and Warner-Bratzler shear force of cured pork loin with added refined salt was lower than those of solar and bamboo salt pork loins cured. The flavor and overall acceptability scores of treatments with refined salt was higher than those of solar and bamboo salt treatments. The unique flavor of bamboo salt can render it as a functional material for marinating meat products. In addition, the results of this study reveal potential use of bamboo salt in meat curing. PMID:27194922

  16. Recent advances in electron-beam curing of carbon fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Coqueret, Xavier; Krzeminski, Mickael; Ponsaud, Philippe; Defoort, Brigitte

    2009-07-01

    Cross-linking polymerization initiated by high-energy radiation is a very attractive technique for the fabrication of high-performance composite materials. The method offers many advantages compared to conventional energy- and time-consuming thermal curing processes. Free radical and cationic poly-addition chemistries have been investigated in some details by various research groups along the previous years. A high degree of control over curing kinetics and material properties can be exerted by adjusting the composition of matrix precursors as well as by acting on process parameters. However, the comparison with state-of-the-art thermally cured composites revealed the lower transverse mechanical properties of radiation-cured composites and the higher brittleness of the radiation-cured matrix. Improving fiber-matrix adhesion and upgrading polymer network toughness are thus two major challenges in this area. We have investigated several points related to these issues, and particularly the reduction of the matrix shrinkage on curing, the wettability of carbon fibers, the design of fiber-matrix interface and the use of thermoplastic toughening agents. Significant improvements were achieved on transverse strain at break by applying original surface treatments on the fibers so as to induce covalent coupling with the matrix. A drastic enhancement of the K IC value exceeding 2 MPa m 1/2 was also obtained for acrylate-based matrices toughened with high T g thermoplastics.

  17. X-ray-cured carbon-fiber composites for vehicle use

    NASA Astrophysics Data System (ADS)

    Herer, Arnold; Galloway, Richard A.; Cleland, Marshall R.; Berejka, Anthony J.; Montoney, Daniel; Dispenza, Dan; Driscoll, Mark

    2009-07-01

    Carbon-fiber-reinforced composites were cured in molds using X-rays derived from a high-energy, high-current electron beam. X-rays could penetrate the mold walls as well as the fiber reinforcements and polymerize a matrix system. Matrix materials made from modified epoxy-acrylates were tailored to suitably low viscosity so that fiber wetting and adhesion could be attained. Techniques similar to vacuum-assisted resin transfer molding (VARTM) and conventional vacuum bagging of wet lay-ups were used. Inexpensive reinforced polyester molds were used to fabricate vehicle fenders. Moderately low-dose X-ray exposure was sufficient to attain functional properties, such as resistance to heat distortion at temperatures as high as 180 °C. The matrix system contained an impact additive which imparted toughness to the cured articles. "Class A" high gloss surfaces were achieved. Thermo-analytical techniques were used on small-sized samples of X-ray-cured matrix materials to facilitate selection of a system for use in making prototypes of vehicle components. X-rays-penetrated metal pieces that were placed within layers of carbon-fiber twill, which were cured and bonded into a structure that could be mechanically attached without concern over fracturing the composite. X-ray curing is a low temperature process that eliminates residual internal stresses which are imparted by conventional thermo-chemical curing processes.

  18. The Effect of Curing Temperature on the Fracture Toughness of Fiberglass Epoxy Composites

    NASA Astrophysics Data System (ADS)

    Ryan, Thomas J.

    The curing reaction in a thermoset polymer matrix composite is often accelerated by the addition of heat in an oven or autoclave. The heat added increases the rate of the polymerization reaction and cross-linking in the material. The cure cycle used (temperature, pressure and time) can therefore alter the final material properties. This research focuses on how the curing temperature (250, 275, 300 °F) affects the yield strength and the mode I interlaminar fracture toughness, GI, of a unidirectional S-2 glass epoxy composite. The test method that was used for the tension test was ASTM D3039 and the test method for the mode I interlaminar fracture toughness, the double cantilever beam (DCB) test, was ASTM D5528. The DCB specimens were fabricated with a non-adhesive insert at the midplane of the composite that serves as the initiatior of the delamination. Opening forces were then applied to the specimen, causing the crack propagation. The results show that increasing the cure temperature by 50 °F increased the tensile strength by 10% (86.54 - 94.73 ksi) and decreased the fracture toughness 20% (506.23 - 381.31 J/m 2). Thus, the curing temperature can cause a trade-off between these two properties, which means that the curing cycle will need to be altered based on the intended use and the required material properties.

  19. Injectable silicone barrier isolates underground leaks

    SciTech Connect

    Parkinson, G.

    1995-05-01

    The ability to install impermeable subsurface barriers quickly and cheaply to keep spills and other below-ground contamination from spreading is an appealing idea. However, traditional systems, such as plastic or concrete barriers, are labor intensive and costly to install. Such ``brute force`` methods typically involve excavation, hauling, permitting and increased risk of exposure to workers. A new approach, based on the injection of silicone, is under development at Lawrence Berkeley Laboratory. In a small-scale field test conducted in January in Los Banos, CA researchers injected a specially developed polymer into the ground, forming a ``grouted`` barrier that extended 6 to 20 ft below the surface. Despite the heterogeneous nature of the subsurface -- which included sand, clay, gravel and stones -- the injection plume that formed was nearly symmetrical. Once cured, the polymer grouting was uniform, even within low-permeability clays. In addition to protecting aquifers from mobile contaminants, the barrier system allows a spill to be contained indefinitely until remediation scheme is worked out.

  20. Heat transfer properties and thermal cure of glass-ionomer dental cements.

    PubMed

    Gavic, Lidia; Gorseta, Kristina; Glavina, Domagoj; Czarnecka, Beata; Nicholson, John W

    2015-10-01

    Under clinical conditions, conventional glass-ionomer dental cements can be cured by application of heat from dental cure lamps, which causes acceleration in the setting. In order for this to be successful, such heat must be able to spread sufficiently through the cement to enhance cure, but not transmit heat so effectively that the underlying dental pulp of the tooth is damaged. The current study was aimed at measuring heat transfer properties of modern restorative glass-ionomers to determine the extent to which they meet these twin requirements. Three commercial glass ionomer cements (Ionofil Molar, Ketac Molar and Equia™ Fill) were used in association with three different light emitting diode cure lamps designed for clinical use. In addition, for each cement, one set of specimens was allowed to cure without application of a lamp. Temperature changes were measured at three different depths (2, 3 and 4 mm) after cure times of 20, 40 and 60 s. The difference among the tested groups was evaluated by ANOVA (P < 0.05) and post hoc Newman-Keuls test. All brands of glass-ionomer showed a small inherent setting exotherm in the absence of heat irradiation, but much greater temperature increases when exposed to the cure lamp. However, temperature rises did not exceed 12.9 °C. Application of the cure lamp led to the establishment of a temperature gradient throughout each specimen. Differences were typically significant (P < 0.05) and did not reflect the nominal power of the lamps, because those lamps have variable cooling systems, and are designed to optimize light output, not heating effect. Because the thermal conductivity of glass-ionomers is low, temperature rises at 4 mm depths were much lower than at 2 mm. At no time did the temperature rise sufficiently to cause concern about potential damage to the pulp. PMID:26411445

  1. Curing light intensity effects on wear resistance of two resin composites.

    PubMed

    St-Georges, Annie J; Swift, Edward J; Thompson, Jeffrey Y; Heymann, Harald O

    2002-01-01

    This in vitro study evaluated the wear resistance of resin composite polymerized using four different light-curing systems. For this, a well-defined cylindrical cavity preparation (4.0 mm in diameter x 3.0 mm in depth) was made in a ceramic block (n=4 per material/light condition). Uncured material, either a universal hybrid composite (Herculite XRV) or a flowable hybrid composite (Revolution Formula 2), was packed and light-cured from the top surface only with one of the four light-curing units: 1) a conventional quartz-tungsten-halogen light, 2) a soft-start light, 3) an argon-ion laser or 4) a plasma-arc curing light. After storing the specimens in deionized water at 37 degrees C for 24 hours, the excess cured material was ground through successive grits up to a final 1200-grit SiC abrasive. The specimens were placed in deionized water at 37 degrees C for an additional 24 hours. Wear simulation was performed using a four-station Leinfelder-type three-body wear device. A slurry of water and unplasticized polymethylmethacrylate beads, simulating an artificial food bolus, was placed on the surface of each resin-composite-restored ceramic block. The entire cycling procedure was carried out 400,000 times. Impressions of each resin composite surface were taken with polyvinylsiloxane and epoxy replicas were made. Wear analyses were conducted by generating tracings across the worn surface of epoxy replicas using profilometer scans. For the universal hybrid composite and the flowable hybrid composite, the lowest wear occurred in specimens that were cured using the conventional quartz-tungsten-halogen light, and the highest wear was detected on those specimens made using the argon-ion laser. For both resin composites, the mean wear for specimens cured using the argon-ion laser was significantly higher than that of the specimens cured with the three other lights, which were statistically similar. PMID:12120780

  2. Repair bond strength of dual-cured resin composite core buildup materials

    PubMed Central

    El-Deeb, Heba A.; Ghalab, Radwa M.; Elsayed Akah, Mai M.; Mobarak, Enas H.

    2015-01-01

    The reparability of dual-cured resin composite core buildup materials using a light-cured one following one week or three months storage, prior to repair was evaluated. Two different dual-cured resin composites; Cosmecore™ DC automix and Clearfil™ DC automix core buildup materials and a light-cured nanofilled resin composite; Filtek™ Z350 XT were used. Substrate specimens were prepared (n = 12/each substrate material) and stored in artificial saliva at 37 °C either for one week or three months. Afterward, all specimens were ground flat, etched using Scotchbond™ phosphoric acid etchant and received Single Bond Universal adhesive system according to the manufacturers’ instructions. The light-cured nanofilled resin composite (Filtek™ Z350 XT) was used as a repair material buildup. To determine the cohesive strength of each solid substrate material, additional specimens from each core material (n = 12) were prepared and stored for the same periods. Five sticks (0.8 ± 0.01 mm2) were obtained from each specimen (30 sticks/group) for microtensile bond strength (μTBS) testing. Modes of failure were also determined. Two-way ANOVA revealed a significant effect for the core materials but not for the storage periods or their interaction. After one week, dual-cured resin composite core buildup materials (Cosmecore™ DC and Clearfil™ DC) achieved significantly higher repair μTBS than the light-cured nanofilled resin composite (Filtek™ Z350 XT). However, Clearfil™ DC revealed the highest value, then Cosmecore™ DC and Filtek™ Z350 XT, following storage for 3-month. Repair strength values recovered 64–86% of the cohesive strengths of solid substrate materials. The predominant mode of failure was the mixed type. Dual-cured resin composite core buildup materials revealed acceptable repair bond strength values even after 3-month storage. PMID:26966567

  3. Campus Violence: Kinds, Causes, and Cures.

    ERIC Educational Resources Information Center

    Whitaker, Leighton C., Ed.; Pollard, Jeffrey W., Ed.

    This volume offers 14 papers on the types, sources, and possible cures of violence on college campuses from prominent workers in higher education. Following a preface the titles are: (1) "Conceptualizing Campus Violence: Definitions, Underlying Factors, and Effects" by Mary L. Roark; (2) "Administrative Perspectives on Disruptive Student Conduct"…

  4. Resin Characterization in Cured Composite Materials

    NASA Technical Reports Server (NTRS)

    Young, P. R.; Chang, A.

    1985-01-01

    Molecular-level characterization of polymeric matrix resin in cured graphite-reinforced composite materials now determined through analysis of diffuse reflectance (DR) with Fourier Transform Infrared (FTIR) spectroscopy. Improved analytical method based on diffuse reflectance. DR/ FTIR technique successfully applied to analysis of several different composites and adhesives impossible to analyze by conventional methods.

  5. Adhesive curing options for photonic packaging

    NASA Astrophysics Data System (ADS)

    Martin, Steven C.; Hubert, Manfred; Tam, Robin

    2002-06-01

    Varying the intensity of illumination used to cure photoactivated adhesives has been applied in medical and dental applications to improve the performance of polymer materials. For example, it has been observed that dental polymer composite materials express reduced shrinkage, important for durability of non-amalgam restorations, by introducing a phased time-intensity cure schedule. This work identified that curing conditions could influence the final properties of materials, and suggested the possibility of extending the characteristics that could be influenced beyond shrinkage to humidity resistance, Tg, outgassing and other important material properties. Obviously, these results have important ramifications for the photonic industry, with current efforts focused on improved manufacturing techniques. Improvement in low cost packaging solutions, including adhesives, will have to be made to bring the component cost down to address the needs of Metro and similar markets. However, there are perceived problems with the widespread use of adhesives, the most prevalent of these involving long term durability of the bond. Devices are typically aligned to sub-micron precision using active feedback and then must be locked in position to maintain performance. In contrast to traditional fastening methods, adhesive bonding is a highly attractive option due to the ease of deployment, lower equipment costs, and improved flexibility. Moreover, using methods analogous to those employed in dental applications, materials properties of photonic adhesives may be tailored using a programmed cure approach.

  6. Finally: A Cure for the Skills Gap.

    ERIC Educational Resources Information Center

    Rauschenberger, John

    2001-01-01

    The Manufacturing Skill Standards Council was established to create a system of skill standards, assessments, and certification designed to ensure a qualified, mobile work force to meet the needs of the economy in the 21st century. The system would provide a long-term cure for the skills gap confronting manufacturers. (JOW)

  7. Fiber-optic epoxy composite cure sensor. I. Dependence of refractive index of an autocatalytic reaction epoxy system at 850 nm on temperature and extent of cure

    NASA Astrophysics Data System (ADS)

    Lam, Kai-Yuen; Afromowitz, Martin A.

    1995-09-01

    We discuss the behavior of the refractive index of a typical epoxy-aromatic diamine system. Near 850 nm the index of refraction is found to be largely controlled by the density of the epoxy. Models are derived to describe its dependence on temperature and extent of cure. Within the range of temperatures studied, the refractive index decreases linearly with increasing temperature. In addition, as the epoxy is cured, the refractive index increases linearly with conversion to the gel point. >From then on, shrinkage in the volume of the epoxy is restricted by local viscosity. Therefore the linear relationship between the refractive index and the extent of cure does not hold beyond the gel point.

  8. The electrophotonic silicon biosensor.

    PubMed

    Juan-Colás, José; Parkin, Alison; Dunn, Katherine E; Scullion, Mark G; Krauss, Thomas F; Johnson, Steven D

    2016-01-01

    The emergence of personalized and stratified medicine requires label-free, low-cost diagnostic technology capable of monitoring multiple disease biomarkers in parallel. Silicon photonic biosensors combine high-sensitivity analysis with scalable, low-cost manufacturing, but they tend to measure only a single biomarker and provide no information about their (bio)chemical activity. Here we introduce an electrochemical silicon photonic sensor capable of highly sensitive and multiparameter profiling of biomarkers. Our electrophotonic technology consists of microring resonators optimally n-doped to support high Q resonances alongside electrochemical processes in situ. The inclusion of electrochemical control enables site-selective immobilization of different biomolecules on individual microrings within a sensor array. The combination of photonic and electrochemical characterization also provides additional quantitative information and unique insight into chemical reactivity that is unavailable with photonic detection alone. By exploiting both the photonic and the electrical properties of silicon, the sensor opens new modalities for sensing on the microscale. PMID:27624590

  9. Palladium contamination in silicon

    NASA Astrophysics Data System (ADS)

    Polignano, M. L.; Mica, I.; Ceresoli, M.; Codegoni, D.; Somaini, F.; Bianchi, I.; Volonghi, D.

    2015-04-01

    In this work palladium is characterized as a silicon contaminant by recombination lifetime, DLTS, C-V and C-t measurements of palladium-implanted wafers. Palladium introduced by ion implantation is found to remain in the solid solution in silicon after rapid thermal treatments, and to be a very effective recombination center. For this reason recombination lifetime measurements are the most sensitive method to detect palladium in silicon. Two palladium-related levels were found by DLTS in p-type material. One of these levels corresponds to a level reported in the literature as the single donor level of substitutional palladium. For what concerns MOS capacitors, palladium is responsible for negative oxide charge and for degradation of the generation lifetime. In addition, palladium is confirmed to be a very fast diffuser, which segregates at the wafer surface even with low temperature treatments (250 °C). Microscopy inspections showed that palladium precipitates and surface defects were formed upon segregation.

  10. Effect of UV curing time on physical and electrical properties and reliability of low dielectric constant materials

    SciTech Connect

    Kao, Kai-Chieh; Cheng, Yi-Lung; Chang, Wei-Yuan; Chang, Yu-Min; Leu, Jihperng

    2014-11-01

    This study comprehensively investigates the effect of ultraviolet (UV) curing time on the physical, electrical, and reliability characteristics of porous low-k materials. Following UV irradiation for various periods, the depth profiles of the chemical composition in the low-k dielectrics were homogeneous. Initially, the UV curing process preferentially removed porogen-related CH{sub x} groups and then modified Si-CH{sub 3} and cage Si-O bonds to form network Si-O bonds. The lowest dielectric constant (k value) was thus obtained at a UV curing time of 300 s. Additionally, UV irradiation made porogen-based low-k materials hydrophobic and to an extent that increased with UV curing time. With a short curing time (<300 s), porogen was not completely removed and the residues degraded reliability performance. A long curing time (>300 s) was associated with improved mechanical strength, electrical performance, and reliability of the low-k materials, but none of these increased linearly with UV curing time. Therefore, UV curing is necessary, but the process time must be optimized for porous low-k materials on back-end of line integration in 45 nm or below technology nodes.

  11. Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1993-01-01

    Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

  12. Silicon nitride/silicon carbide composite powders

    DOEpatents

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

    1996-06-11

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

  13. Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

    NASA Technical Reports Server (NTRS)

    Kranbuehl, D. E.

    1985-01-01

    Dynamic dielectric analysis (DDA) is used to study curing polymer systems and thermoplastics. Measurements are made over a frequency range of six decades. This wide range of frequencies increases the amount of information which can be obtained. The data is analyzed in terms of the frequency dependence of the complex permittivity epsilon sup *, specific conductivity sigma (ohm/cm) and the relaxation time tau, parameters which are characteristic of the cure state of the material and independent of the size of the sample.

  14. Conductance tomography of conductive filaments in intrinsic silicon-rich silica RRAM† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr04982b Click here for additional data file.

    PubMed Central

    Montesi, Luca; Hudziak, Stephen; Mehonic, Adnan

    2015-01-01

    We present results from an imaging study of filamentary conduction in silicon suboxide resistive RAM devices. We used a conductive atomic force microscope to etch through devices while measuring current, allowing us to produce tomograms of conductive filaments. To our knowledge this is the first report of such measurements in an intrinsic resistance switching material. PMID:26482563

  15. Radiation curing of polyester resin modified with acrylic acid and its salts

    NASA Astrophysics Data System (ADS)

    Szalińska, H.; Pietrzak, M.; Janowska, G.

    Polyester resin containing acrylic acid or its salts was cured with γ 60Co radiation. The course of curing was examined, the gel content and polymerization shrinkage were measured and also thermographic and IR absorption analyses were carried out. It was found that manganese, iron and copper acrylates inhibited the curing of resin while the remaining additives showed a slightly stimulating action. All the additives decreased the polymerization shrinkage by a factor of 2-3 and iron acrylate by as much as 8 times (up to 1%). They also increased the activation energy of the thermal decomposition of resin, and calcium, barium and copper acrylates increased the thermal stability of resin by 20 K. IR absorption spectra showed that acrylic acid and its salts reacted mainly with the monomeric component of the resin (styrene) whereas iron and copper acrylates first attacked the unsaturated bonds of the oligoester.

  16. Cationic cure kinetics of a polyoxometalate loaded epoxy nanocomposite

    SciTech Connect

    Anderson, Benjamin J.

    2012-08-06

    The reaction cure kinetics of a novel polyoxometalate (POM) loaded epoxy nanocomposite is described. The POM is dispersed in the epoxy resin up to volume fractions of 0.1. Differential scanning calorimetry measurements show the cure of the epoxy resin to be sensitive to the POM loading. A kinetics study of the cure exotherm confirms that POM acts as a catalyst promoting cationic homopolymerization of the epoxy resin. The cure reaction is shown to propagate through two cure regimes. A fast cure at short time is shown to be propagation by the activated chain end (ACE) mechanism. A slow cure at long time is shown to be propagation by the activated monomer (AM) mechanism. The activation energies for the fast and slow cure regimes agree well with other epoxy based systems that have been confirmed to propagate by the ACE and AM mechanisms.

  17. A Study of Upgraded Phenolic Curing for RSRM Nozzle Rings

    NASA Technical Reports Server (NTRS)

    Smartt, Ziba

    2000-01-01

    A thermochemical cure model for predicting temperature and degree of cure profiles in curing phenolic parts was developed, validated and refined over several years. The model supports optimization of cure cycles and allows input of properties based upon the types of material and the process by which these materials are used to make nozzle components. The model has been refined to use sophisticated computer graphics to demonstrate the changes in temperature and degree of cure during the curing process. The effort discussed in the paper will be the conversion from an outdated solid modeling input program and SINDA analysis code to an integrated solid modeling and analysis package (I-DEAS solid model and TMG). Also discussed will be the incorporation of updated material properties obtained during full scale curing tests into the cure models and the results for all the Reusable Solid Rocket Motor (RSRM) nozzle rings.

  18. Electron Beam Curing of Polymer Matrix Composites - CRADA Final Report

    SciTech Connect

    Janke, C. J.; Howell, Dave; Norris, Robert E.

    1997-05-01

    The major cost driver in manufacturing polymer matrix composite (PMC) parts and structures, and one of the elements having the greatest effect on their quality and performance, is the standard thermal cure process. Thermal curing of PMCs requires long cure times and high energy consumption, creates residual thermal stresses in the part, produces volatile toxic by-products, and requires expensive tooling that is tolerant of the high cure temperatures.

  19. New type of measuring and intelligent instrument for curing tobacco

    NASA Astrophysics Data System (ADS)

    Yi, Chui-Jie; Huang, Xieqing; Chen, Tianning; Xia, Hong

    1993-09-01

    A new type of measuring intelligent instrument for cured tobacco is presented in this paper. Based on fuzzy linguistic control principles the instrument is used to controlling the temperature and humidity during cured tobacco taking 803 1 singlechip computer as a center controller. By using methods of fuzzy weighted factors the cross coupling in curing procedures is decoupled. Results that the instrument has producted indicate the fuzzy controller in the instrument has perfect performance for process of cured tobacco as shown in figure

  20. Hydrodynamic slip in silicon nanochannels

    NASA Astrophysics Data System (ADS)

    Ramos-Alvarado, Bladimir; Kumar, Satish; Peterson, G. P.

    2016-03-01

    Equilibrium and nonequilibrium molecular dynamics simulations were performed to better understand the hydrodynamic behavior of water flowing through silicon nanochannels. The water-silicon interaction potential was calibrated by means of size-independent molecular dynamics simulations of silicon wettability. The wettability of silicon was found to be dependent on the strength of the water-silicon interaction and the structure of the underlying surface. As a result, the anisotropy was found to be an important factor in the wettability of these types of crystalline solids. Using this premise as a fundamental starting point, the hydrodynamic slip in nanoconfined water was characterized using both equilibrium and nonequilibrium calculations of the slip length under low shear rate operating conditions. As was the case for the wettability analysis, the hydrodynamic slip was found to be dependent on the wetted solid surface atomic structure. Additionally, the interfacial water liquid structure was the most significant parameter to describe the hydrodynamic boundary condition. The calibration of the water-silicon interaction potential performed by matching the experimental contact angle of silicon led to the verification of the no-slip condition, experimentally reported for silicon nanochannels at low shear rates.

  1. UV curing with water based materials

    SciTech Connect

    Beck, E.; Haeussling, L.; Jaeger, U.

    1995-12-01

    Conventional coatings technology requires a large effort to reduce emissions of organic solvents and other volatile organic components. Alleviations, yet not a solution to this problem are high solids coatings formulations or even powder coatings technology. An entirely different concept is used in radiation curing of coatings, where all the elements of the originally low molar mass components of the coating formulation are polymerized into one large network. Thus there should be no emissions of low molar mass compounds from UV- or Electron beam cured films. Water as a diluent in UV-curable formulations can either be used directly as a solvent or in emulsions (with the help of emulsifying agents) without a loss in performance of coatings properties, such as hardness, elasticity and reactivity. To the contrary, the prearrangement of functionalities in the final coating due to the prior phase separation in the emulsion seems to slightly increase hardness and adhesion as well as elasticity.

  2. Aloe vera as cure for lichen planus.

    PubMed

    Patil, Bharati A; Bhaskar, Hebbar Pragati; Pol, Jyoti S; Sodhi, Amandeep; Madhu, Asha V

    2013-01-01

    Oral lichen planus is a difficult condition to treat because of its chronic nature. Various treatment modalities have resulted in partial regression of symptoms but not a complete cure. Aloe vera, a product with minimal adverse effects, can be tried to treat this disorder. A 38-year-old male patient diagnosed with lichen planus of the skin and the oral mucosa was suffering from severe pain and a burning sensation intraorally and pruritus of the skin lesions. Considering the extensive involvement, an herbal alternative was considered. The patient was prescribed aloe vera juice and gel application for two months. At the nine-month follow-up, the patient was symptom-free and totally cured of the intraoral and skin lesions. PMID:24245466

  3. Light-Curing Adhesive Repair Tapes

    NASA Technical Reports Server (NTRS)

    Allred, Ronald; Haight, Andrea Hoyt

    2009-01-01

    Adhesive tapes, the adhesive resins of which can be cured (and thereby rigidized) by exposure to ultraviolet and/or visible light, are being developed as repair patch materials. The tapes, including their resin components, consist entirely of solid, low-outgassing, nonhazardous or minimally hazardous materials. They can be used in air or in vacuum and can be cured rapidly, even at temperatures as low as -20 C. Although these tapes were originally intended for use in repairing structures in outer space, they can also be used on Earth for quickly repairing a wide variety of structures. They can be expected to be especially useful in situations in which it is necessary to rigidize tapes after wrapping them around or pressing them onto the parts to be repaired.

  4. Contactless optoelectronic technique for monitoring epoxy cure.

    PubMed

    Cusano, A; Buonocore, V; Breglio, G; Calabrò, A; Giordano, M; Cutolo, A; Nicolais, L

    2000-03-01

    We describe a novel noninvasive optical technique to monitor the refractive-index variation in an epoxy-based resin that is due to the polymerization process. This kind of resin is widely used in polymer matrix composites. It is well known that the process of fabricating a thermoset-based composite involves mass and heat transfer coupled with irreversible chemical reactions that induce physical changes. To improve the quality and the reliability of these materials, monitoring the cure and optimization of the manufacturing process are of key importance. We discuss the basic operating principles of an optical system based on angle deflection measurements and present typical cure-monitoring results obtained from optical characterization. The method provides a flexible, high-sensitivity, material-independent, low-cost, noninvasive tool for monitoring real-time refractive-index variation. PMID:18337994

  5. Is There a Cure for Cushing's Syndrome?

    MedlinePlus

    ... Small Business Programs Activities and opportunities geared toward small businesses Peer Review Review of the scientific & technical merit of grant applications Contacts for NICHD Funding Information ... It also is possible that a person cured of Cushing’s disease might not recover their previous mental strength, including memory, but any functional difference is usually small. 4 , 5 People whose Cushing’s syndrome was caused ...

  6. Photothermal Monitoring Of Curing Of Polymers

    NASA Technical Reports Server (NTRS)

    Rooney, Michael

    1993-01-01

    Time-resolved infrared radiometry (TRIR) adapted to monitoring curing of some polymers in production. Proposal part of continuing effort to perfect production of hydroxy-terminated polybutadiene for use in liners of solid-fuel rocket motors. Applicable to monitoring changing states of many other materials in process. TRIR, non-contact technique implemented with remotely situated equipment and better suited to use in production.

  7. Using Sex to Cure the Genome

    PubMed Central

    Rocha, Eduardo P. C.

    2016-01-01

    The diversification of prokaryotes is accelerated by their ability to acquire DNA from other genomes. However, the underlying processes also facilitate genome infection by costly mobile genetic elements. The discovery that cells can uptake DNA by natural transformation was instrumental to the birth of molecular biology nearly a century ago. Surprisingly, a new study shows that this mechanism could efficiently cure the genome of mobile elements acquired through previous sexual exchanges. PMID:26987049

  8. Coating and curing apparatus and methods

    DOEpatents

    Brophy, Brenor L.; Gonsalves, Peter R.; Maghsoodi, Sina; Colson, Thomas E.; Yang, Yu S.; Abrams, Ze'ev R.

    2016-04-19

    Disclosed is a coating apparatus including flow coating and roll-coating that may be used for uniform sol-gel coating of substrates such as glass, solar panels, windows or part of an electronic display. Also disclosed are methods for substrate preparation, flow coating and roll coating. Lastly, systems and methods for curing sol-gel coatings deposited onto the surface of glass substrates using high temperature air-knives, infrared emitters and direct heat applicators are disclosed.

  9. Coating and curing apparatus and methods

    DOEpatents

    Brophy, Brenor L; Maghsoodi, Sina; Neyman, Patrick J; Gonsalves, Peter R; Hirsch, Jeffrey G; Yang, Yu S

    2015-02-24

    Disclosed are coating apparatus including flow coating and roll-coating that may be used for uniform sol-gel coating of substrates such as glass, solar panels, windows or part of an electronic display. Also disclosed are methods for substrate preparation, flow coating and roll coating. Lastly systems and methods for skin curing sol-gel coatings deposited onto the surface of glass substrates using a high temperature air-knife are disclosed.

  10. Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope. Thesis

    NASA Technical Reports Server (NTRS)

    Justi, S.

    1985-01-01

    It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

  11. Thick film silicon growth techniques

    NASA Technical Reports Server (NTRS)

    Bates, H. E.; Jewett, D. N.; Mlavsky, A. I.; White, V. E.

    1974-01-01

    One inch wide silicon ribbons up to 14 inches long have been produced from graphite dies. Several different techniques have been employed to improve the semiconductor purity of silicon. This has resulted in a general increase in quality although the techniques involved have not been optimized. The power factor of uncoated ribbon solar cells produced for material evaluation has increased to approximately 75% of those evaluation cells made from commercial silicon. The present limitation is believed due to low lifetime. Additional work has continued with new die materials; however, only composite dies of SiO2 and C show significant potential at this time.

  12. The dental curing light: A potential health risk.

    PubMed

    Price, Richard B T; Labrie, Daniel; Bruzell, Ellen M; Sliney, David H; Strassler, Howard E

    2016-08-01

    Powerful blue-light emitting dental curing lights are used in dental offices to photocure resins in the mouth. In addition, many dental personnel use magnification loupes. This study measured the effect of magnification loupes on the "blue light hazard" when the light from a dental curing light was reflected off a human tooth. Loupes with 3.5x magnification (Design for Vision, Carl Zeiss, and Quality Aspirator) and 2.5x magnification (Design for Vision and Quality Aspirator) were placed at the entrance of an integrating sphere connected to a spectrometer (USB 4000, Ocean Optics). A model with human teeth was placed 40 cm away and in line with this sphere. The light guide tip of a broad-spectrum Sapphire Plus (Den-Mat) curing light was positioned at a 45° angle from the facial surface of the central incisor. The spectral radiant power reflected from the teeth was recorded five times with the loupes over the entrance into the sphere. The maximum permissible cumulative exposure times in an 8-hr day were calculated using guidelines set by the ACGIH. It was concluded that at a 40 cm distance, the maximum permissible cumulative daily exposure time to light reflected from the tooth was approximately 11 min without loupes. The weighted blue irradiance values were significantly different for each brand of loupe (Fisher's PLSD p < 0.05) and were up to eight times greater at the pupil than when loupes were not used. However, since the linear dimensions of the resulting images would be 2.5 to 3.5x larger on the retina, the image area was increased by the square of the magnification and the effective blue light hazard was reduced compared to without the loupes. Thus, although using magnification loupes increased the irradiance received at the pupil, the maximum cumulative daily exposure time to reflected light was increased up to 28 min. Further studies are required to determine the ocular hazards of a focused stare when using magnification loupes and the effects of other

  13. Demonstration of Mer-Cure Technology for Enhanced Mercury Control

    SciTech Connect

    John Marion; Dave O'Neill; Kevin Taugher; Shin Kang; Mark Johnson; Gerald Pargac; Jane Luedecke; Randy Gardiner; Mike Silvertooth; Jim Hicks; Carl Edberg; Ray Cournoyer; Stanley Bohdanowicz; Ken Peterson; Kurt Johnson; Steve Benson; Richard Schulz; Don McCollor; Mike Wuitshick

    2008-06-01

    Alstom Power Inc. has completed a DOE/NETL-sponsored program (under DOE Cooperative Agreement No. De-FC26-07NT42776) to demonstrate Mer-Cure{trademark}, one of Alstom's mercury control technologies for coal-fired boilers. The Mer-Cure{trademark}system utilizes a small amount of Mer-Clean{trademark} sorbent that is injected into the flue gas stream for oxidation and adsorption of gaseous mercury. Mer-Clean{trademark} sorbents are carbon-based and prepared with chemical additives that promote oxidation and capture of mercury. The Mer-Cure{trademark} system is unique in that the sorbent is injected into an environment where the mercury capture kinetics is accelerated. The full-scale demonstration program originally included test campaigns at two host sites: LCRA's 480-MW{sub e} Fayette Unit No.3 and Reliant Energy's 190-MW{sub e} Shawville Unit No.3. The only demonstration tests actually done were the short-term tests at LCRA due to budget constraints. This report gives a summary of the demonstration testing at Fayette Unit No.3. The goals for this Mercury Round 3 program, established by DOE/NETL under the original solicitation, were to reduce the uncontrolled mercury emissions by 90% at a cost significantly less than 50% of the previous target of $60,000/lb mercury removed. The results indicated that Mer-Cure{trademark} technology could achieve mercury removal of 90% based on uncontrolled stack emissions. The estimated costs for 90% mercury control, at a sorbent cost of $0.75 to $2.00/lb respectively, were $13,400 to $18,700/lb Hg removed. In summary, the results from demonstration testing show that the goals established by DOE/NETL were met during this test program. The goal of 90% mercury reduction was achieved. Estimated mercury removal costs were 69-78% lower than the benchmark of $60,000/lb mercury removed, significantly less than 50% of the baseline removal cost.

  14. The effect of Low Earth Orbit exposure on some experimental fluorine and silicon-containing polymers

    NASA Technical Reports Server (NTRS)

    Connell, John W.; Young, Philip R.; Kalil, Carol G.; Chang, Alice C.; Siochi, Emilie J.

    1994-01-01

    Several experimental fluorine and silicon-containing polymers in film form were exposed to low Earth orbit (LEO) on a Space Shuttle flight experiment (STS-46, Evaluation of Oxygen Interaction with Materials, EOIM-3). The environmental parameters of primary concern were atomic oxygen (AO) and ultraviolet (UV) radiation. The materials were exposed to 2.3 plus or minus 0.1 x 10(exp 20) oxygen atoms/sq cm and 30.6 UV sun hours during the flight. In some cases, the samples were exposed at ambient, 120 C and 200 C. The effects of exposure on these materials were assessed utilizing a variety of characterization techniques including optical, scanning electron (SEM) and scanning tunneling (STM) microscopy, UV-visible (UV-VIS) transmission, diffuse reflectance infrared (DR-FTIR), x-ray photoelectron (XPS) spectroscopy, and in a few cases, gel permeation chromatography (GPC). In addition, weight losses of the films, presumably due to AO erosion, were measured. The fluorine-containing polymers exhibited significant AO erosion and exposed films were diffuse or 'frosted' in appearance and consequently displayed dramatic reductions in optical transmission. The silicon-containing films exhibited minimum AO erosion and the optical transmission of exposed films was essentially unchanged. The silicon near the exposed surface in the films was converted to silicate/silicon oxide upon AO exposure which subsequently provided protection for the underlying material. The silicon-containing epoxies are potentially useful as AO resistant coatings and matrix resins as they are readily processed into carbon fiber reinforced composites and cured via electron radiation.

  15. Petrous Apex Cholesterol Granuloma: Importance of Pedicled Nasoseptal Flap in Addition to Silicone T-tube for Prevention of Occlusion of Drainage Route in Transsphenoidal Approach—A Technical Note

    PubMed Central

    SHIBAO, Shunsuke; TODA, Masahiro; TOMITA, Toshiki; SAITO, Katsuya; OGAWA, Kaoru; KAWASE, Takeshi; YOSHIDA, Kazunari

    2015-01-01

    Recently, petrous apex cholesterol granulomas (CGs) have been treated via the endoscopic endonasal transsphenoidal approach (EEA) using a silicone tube, to prevent drainage route occlusion. Occlusion of the drainage route has led to problems with recurrence. The aim of this report is to describe the use of a surgical technique to prevent drainage route occlusion. In surgical technique, the posterolateral wall of the sphenoid sinus was opened by EEA. After cyst debridement, a vascularized nasoseptal flap with a width of approximately 4 cm was inserted into the lumen with a silicone T-tube with a diameter of 7 mm. This technique was used in two patients: the first patient during the second operation after recurrence following occlusion of the drainage route, and the second patient during the first operation. Opening of the cyst wall was confirmed endoscopically in both patients 12–24 months after surgery, even after removal of the T-tube. In conclusion, the use of a pedicled nasoseptal flap with a silicone tube is useful to prevent CG recurrence, by paranasal cavitization of the cystic cavity. PMID:25797784

  16. Effect of electron water curing and electron charging curing on concrete strength

    SciTech Connect

    Yu, Q.; Sugita, S.; Sawayama, K.; Isojima, Y.

    1998-09-01

    By charging normal water under an appropriate electric voltage, electron water can be produced. With its small molecule cluster and high activity, the water has been found to have applications in many fields. This study showed that: (1) by curing concrete specimens in electron water, concrete strength was increased by at least 5% and by more than 15% at early ages in comparison to that of the concrete cured in normal water at the same temperature; and (2) by electron charging curing the strength of concrete could also be improved, especially its 1-day strength, which was increased by as high as 50% relative to that of control specimens. The possible reason for the strength increase of concrete by both curing methods is that the curing water and the water in concrete both have small molecule clusters and high activity caused by the charging treatment, resulting in the improvement on cement hydration and the decrease in average pore size and the volumes of large pores of concrete.

  17. Microhardness and Young's modulus of a bonding resin cured with different curing units.

    PubMed

    Yamauti, Monica; Nikaido, Toru; Ikeda, Masaomi; Otsuki, Masayuki; Tagami, Junji

    2004-12-01

    This study evaluated the microhardness and Young's modulus of a photocurable bonding resin, Clearfil SE Bond (SE), cured with four curing units at different distances. The curing units used were: Candelux (Quartz-tungsten halogen), Lux-O-Max (Blue light emitting diode), Arc-light (Plasma-arc), and Rayblaze (Metal halide). Discs of bonding resin were prepared using vinyl molds and were photocured at the top surface with light tip at three different distances (contact, 2 and 4 mm). After 24 hours of storage in water at 37 degrees C, the specimens were sectioned into halves, embedded in epoxy resin, and polished. The microhardness and Young's modulus of this bonding resin were measured using a nanoindentation tester. Six specimens were prepared for each group. The data was statistically analyzed using two-way ANOVA test and Tukey multiple comparison test (p < 0.01). The microhardness of SE was affected by light source and distance, as was Young's modulus. Candelux and Rayblaze presented the highest hardness and Young's modulus results. Both properties presented high values when the curing unit tip was maintained in contact with the irradiated surface. Increasing the distance between the curing unit tip and the irradiated surface decreased the hardness and Young's modulus of SE. PMID:15688707

  18. Characterization of the relationship of the cure cycle chemistry to cure cycle processing properties

    NASA Technical Reports Server (NTRS)

    Kranbuehl, D. E.

    1986-01-01

    Dynamic Dielectric measurements made over a wide range of frequency provide a sensitive and convenient means for monitoring the cure process in thermosets and thermoplastics. The measurement of dielectric relaxation is one of only a few instrumental techniques available for studying molecular properties in both the liquid and solid states. Furthermore, it is probably the only convenient experimental technique for studying the polymerization process of going from a monomeric liquid of varying viscosity to a crosslinked, insoluble, high temperature solid. The objective of the research is to develop on-line dielectric instrumentation for quantitative nondestructive material evaluation and closed loop smart cure cycle control. The key is to relate the chemistry of the cure cycle process to the dielectric properties of the polymer system by correlating the time, temperature, and frequency dependent dielectric measurements with chemical characterization measurements. Measurement of the wide variation in magnitude of the complex permittivity with both frequency and state of cure, coupled with chemical characterization work, have been shown in the laboratory to have the potential to determine: resin quality, composition and age; cure cycle window boundaries; onset of flow and point of maximum flow; extent of and completion of reaction; evolution of volatiles; T sub g; and, crosslinking and molecular weight buildup.

  19. [Care, the caring, the cure and the caregiver].

    PubMed

    Morvillers, Jean-manuel

    2015-09-01

    Due to the multiple meanings of the concept of care and its diverse cultural meanings, the purpose of this article is to address this concept, starting with clarification of its etymological origins. In addition to this clarification, the objectives of this paper are to highlight the rapport between care and cure, the implications of care in health care team management. The etymological analysis is made starting from encyclopaedic writings, to discuss the original meaning of the concept. The results of this analysis show that the original meaning of care is anchored on affects and feeling, lead to caring. Therefore, a personal dimension is inherent to it. This reflection tries to show that care does not oppose to cure, but that it is imperative to incresae nurses to the personal dimension in care to become caring with the management support. The conclusion reveals that a personal dimension of caring, supported by human values associated, participate to the professional dimension of the nursing role. Thus, these two dimensions that must grow together, are unavoidable for nursing pratice. PMID:26685556

  20. Paediatric HIV: Progress on Prevention, Treatment and Cure

    PubMed Central

    Kim, Maria H; Ahmed, Saeed; Abrams, Elaine J.

    2015-01-01

    Purpose of review This review provides an update on current developments with prevention, treatment and cure strategies in the field of pediatric HIV. Recent findings/Summary There has been tremendous progress in the prevention and treatment of pediatric HIV infection. With new strategies for prevention of mother-to-child transmission, we are growing ever closer towards elimination of pediatric HIV, though challenges with retention of pregnant woman and their HIV-exposed infants remain. Ongoing vigilance regarding the potential hazards of in utero ART exposure to infants continues with no significant alarms yet identified. Though cure has not been achieved, evidence of the impact of early treatment on reducing HIV-1 reservoir size with subsequent prolonged remission has enlivened efforts to rapidly identify and treat HIV-infected newborns. There is an increasing array of treatment options for pediatric patients and reassuring evidence regarding long-term complications of ART. Unfortunately, despite evidence suggesting the benefit of early treatment, timely identification and treatment of children remains a challenge. Better strategies for effective case-finding and engagement in care are urgently needed in addition to an improved understanding of how to retain HIV-positive children and adolescents on treatment. However, further emboldened by recent international commitments and robust global support, the future is hopeful. PMID:26709366

  1. SureCure ®-A new material to reduces curing time and improve curing reproducibility of lead-acid batteries

    NASA Astrophysics Data System (ADS)

    Boden, David P.; Loosemore, Daniel V.; Botts, G. Dean

    This paper introduces a technology that considerably reduces the time to cure the positive plates of lead-acid batteries. In each of several full-scale trials at automotive and industrial battery manufacturers, the simple replacement of 1 wt.% of leady oxide with finely-divided tetrabasic lead sulfate (SureCure™ by Hammond Group Inc.) is shown to accelerate significantly the conversion of tribasic lead sulfate (3BS) to tetrabasic lead sulfate (4BS) in the curing process while improving crystal structure and reproducibility. Shorter curing times result in reduced labour and energy costs, as well as reduced fixed (curing chambers and plant footprint) and working (plate inventory) capital investment.

  2. Argon Ion Laser Polymerized Acrylic Resin: A Comparative Analysis of Mechanical Properties of Laser Cured, Light Cured and Heat Cured Denture Base Resins

    PubMed Central

    Murthy, S Srinivasa; Murthy, Gargi S

    2015-01-01

    Background: Dentistry in general and prosthodontics in particular is evolving at greater pace, but the denture base resins poly methyl methacrylate. There has been vast development in modifying chemically and the polymerization techniques for better manipulation and enhancement of mechanical properties. One such invention was introduction of visible light cure (VLC) denture base resin. Argon ion lasers have been used extensively in dentistry, studies has shown that it can polymerize restorative composite resins. Since composite resin and VLC resin share the same photo initiator, Argon laser is tested as activator for polymerizing VLC resin. In the Phase 1 study, the VLC resin was evaluated for exposure time for optimum polymerization using argon ion laser and in Phase 2; flexural strength, impact strength, surface hardness and surface characteristics of laser cured resin was compared with light cure and conventional heat cure resin. Materials and Methods: Phase 1; In compliance with American Dental Association (ADA) specification no. 12, 80 samples were prepared with 10 each for different curing time using argon laser and evaluated for flexural strength on three point bend test. Results were compared to established performance requirement specified. Phase 2, 10 specimen for each of the mechanical properties (30 specimen) were polymerized using laser, visible light and heat and compared. Surface and fractured surface of laser, light and heat cured resins were examined under scanning electron microscope (SEM). Results: In Phase 1, the specimen cured for 7, 8, 9 and 10 min fulfilled ADA requirement. 8 min was taken as suitable curing time for laser curing. Phase 2 the values of mechanical properties were computed and subjected to statistical analysis using one-way ANOVA and Tukey post-hoc test. The means of three independent groups showed significant differences between any two groups (P < 0.001). Conclusion: Triad VLC resin can be polymerized by argon ion laser with

  3. In-Situ Cure Monitoring of the Immidization Reaction of PMR-15

    NASA Technical Reports Server (NTRS)

    Cossins, Sheryl; Kellar, Jon J.; Winter, Robb M.

    1997-01-01

    Glass fiber reinforced polymer composites are becoming widely used in industry. With this increase in production, an in-situ method of quality control for the curing of the polymer is desirable. This would allow for the production of high-quality parts having more uniform properties.' Recently, in-situ fiber optic monitoring of polymer curing has primarily focused on epoxy resins and has been performed by Raman or fluorescence methods. In addition, some infrared (IR) investigations have been performed using transmission or ATR cells. An alternate IR approach involves using optical fibers as a sensor by utilizing evanescent wave spectroscopy.

  4. Chemical analysis of electron beam curing of positive photoresist

    NASA Astrophysics Data System (ADS)

    Ross, Matthew F.; Christensen, Lorna D.; Magvas, John

    1994-05-01

    In this paper the chemical and thermal properties of electron beam cured photoresist were investigated and compared with conventional thermal curing methods. The photoresist used in this investigation was AZ P.4620, a positive novolak based photoresist formulated for thick film applications. The films were exposed with varying dosages using an electron beam photoresist curing system. The photoresist films were then analyzed for residual solvent content, photoactive compound decomposition, percentage of crosslinking, and film shrinkage as a function of exposure dose. These properties were then compared with the properties of resist films cured using conventional thermal curing methods. A model of photoresist curing chemistry as a function of dose is proposed as well as a method for optimizing the cure of the photoresist for different applications.

  5. High Tg and fast curing epoxy-based anisotropic conductive paste for electronic packaging

    NASA Astrophysics Data System (ADS)

    Keeratitham, Waralee; Somwangthanaroj, Anongnat

    2016-03-01

    Herein, our main objective is to prepare the fast curing epoxy system with high glass transition temperature (Tg) by incorporating the multifunctional epoxy resin into the mixture of diglycidyl ether of bisphenol A (DGEBA) as a major epoxy component and aromatic diamine as a hardener. Furthermore, the curing behavior as well as thermal and thermomechanical properties were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). It was found that Tg obtained from tan δ of DGEBA/aromatic diamine system increased from 100 °C to 205 °C with the presence of 30 percentage by weight of multifunctional epoxy resin. Additionally, the isothermal DSC results showed that the multifunctional epoxy resin can accelerate the curing reaction of DGEBA/aromatic diamine system. Namely, a high degree of curing (˜90%) was achieved after a few minutes of curing at low temperature of 130 °C, owing to a large number of epoxy ring of multifunctional epoxy resin towards the active hydrogen atoms of aromatic diamine.

  6. Unique Curing Properties through Living Polymerization in Crosslinking Materials: Polyurethane Photopolymers from Vinyl Ether Building Blocks.

    PubMed

    Kirschbaum, Stefan; Landfester, Katharina; Taden, Andreas

    2015-05-01

    Photopolymers with unique curing capabilities were produced by combining living cationic polymerization with network formation and restricted polymer motion. A vinyl ether diol was synthesized as a functional building block and reacted with isophorone diisocyanate to form a highly functionalized vinyl ether polyurethane as a model system with high crosslinking ability. When using a cationic photoinitiator, fast polymerization is observed upon short UV irradiation. Curing proceeds in the absence of light and under ambient conditions without oxygen inhibition. Cationic active sites become trapped dormant species upon network-induced vitrification and surprisingly remain living for several days. The polymerization can be reactivated by additional UV irradiation and/or raised temperature. The curing behavior was studied in detail by using UV and FT-NIR coupled rheology and photo-DSC to simultaneously study spectroscopic and mechanical information, as well as thermal effects. PMID:25776255

  7. Towards Multidisciplinary HIV-Cure Research: Integrating Social Science with Biomedical Research.

    PubMed

    Grossman, Cynthia I; Ross, Anna Laura; Auerbach, Judith D; Ananworanich, Jintanat; Dubé, Karine; Tucker, Joseph D; Noseda, Veronica; Possas, Cristina; Rausch, Dianne M

    2016-01-01

    The quest for a cure for HIV remains a timely and key challenge for the HIV research community. Despite significant scientific advances, current HIV therapy regimens do not completely eliminate the negative impact of HIV on the immune system; and the economic impact of treating all people infected with HIV globally, for the duration of their lifetimes, presents significant challenges. This article discusses, from a multidisciplinary approach, critical social, behavioral, ethical, and economic issues permeating the HIV-cure research agenda. As part of a search for an HIV cure, both the perspective of patients/participants and clinical researchers should be taken into account. In addition, continued efforts should be made to involve and educate the broader community. PMID:26642901

  8. Modeling the curing process of thick-section autoclave cured composites

    NASA Technical Reports Server (NTRS)

    Loos, A. C.; Dara, P. H.

    1985-01-01

    Temperature gradients are significant during cure of large area, thick-section composites. Such temperature gradients result in nonuniformly cured parts with high void contents, poor ply compaction, and variations in the fiber/resin distribution. A model was developed to determine the temperature distribution in thick-section autoclave cured composites. Using the model, long with temperature measurements obtained from the thick-section composites, the effects of various processing parameters on the thermal response of the composites were examined. A one-dimensional heat transfer model was constructed for the composite-tool assembly. The governing differential equations and associated boundary conditions describing one-dimensional unsteady heat-conduction in the composite, tool plate, and pressure plate are given. Solution of the thermal model was obtained using an implicit finite difference technique.

  9. Silicon microdosimetry.

    PubMed

    Agosteo, Stefano; Pola, Andrea

    2011-02-01

    Silicon detectors are being studied as microdosemeters since they can provide sensitive volumes of micrometric dimensions. They can be applied for assessing single-event effects in electronic instrumentation exposed to complex fields around high-energy accelerators or in space missions. When coupled to tissue-equivalent converters, they can be used for measuring the quality of radiation therapy beams or for dosimetry. The use of micrometric volumes avoids the contribution of wall effects to the measured spectra. Further advantages of such detectors are their compactness, cheapness, transportability and a low sensitivity to vibrations. The following problems need to be solved when silicon devices are used for microdosimetry: (i) the sensitive volume has to be confined in a region of well-known dimensions; (ii) the electric noise limits the minimum detectable energy; (iii) corrections for tissue-equivalency should be made; (iv) corrections for shape equivalency should be made when referring to a spherical simulated site of tissue; (v) the angular response should be evaluated carefully; (vi) the efficiency of a single detector of micrometric dimensions is very poor and detector arrays should be considered. Several devices have been proposed as silicon microdosemeters, based on different technologies (telescope detectors, silicon on insulator detectors and arrays of cylindrical p-n junctions with internal amplification), in order to satisfy the issues mentioned above. PMID:21112892

  10. Food additives

    MedlinePlus

    Food additives are substances that become part of a food product when they are added during the processing or making of that food. "Direct" food additives are often added during processing to: Add nutrients ...

  11. Effect of Particular Breed on the Chemical Composition, Texture, Color, and Sensorial Characteristics of Dry-cured Ham

    PubMed Central

    Seong, Pil Nam; Park, Kuyng Mi; Kang, Sun Moon; Kang, Geun Ho; Cho, Soo Hyun; Park, Beom Young; Van Ba, Hoa

    2014-01-01

    The present study demonstrates the impact of specific breed on the characteristics of dry-cured ham. Eighty thighs from Korean native pig (KNP), crossbreed (Landrace×Yorkshire)♀×Duroc♂ (LYD), Berkshire (Ber), and Duroc (Du) pig breeds (n = 10 for each breed) were used for processing of dry-cured ham. The thighs were salted with 6% NaCl (w/w) and 100 ppm NaNO2, and total processing time was 413 days. The effects of breed on the physicochemical composition, texture, color and sensory characteristics were assessed on the biceps femoris muscle of the hams. The results revealed that the highest weight loss was found in the dry-cured ham of LYD breed and the lowest weight loss was found in Ber dry-cured ham. The KNP dry-cured ham contain higher intramuscular fat level than other breed hams (p<0.05). It was observed that the dry-cured ham made from KNP breed had the lowest water activity value and highest salt content, while the LYD dry-cure ham had higher total volatile basic nitrogen content than the Ber and Du hams (p<0.05). Zinc, iron and total monounsaturated fatty acids levels were higher in KNP ham while polyunsaturated fatty acids levels were higher in Du ham when compared to other breed hams (p<0.05). Additionally, the KNP dry-cured ham possessed higher Commission International de l’Eclairage (CIE) a* value, while the Du dry-cured ham had higher L*, CIE b* and hue angle values (p<0.05). Furthermore, breed significantly affected the sensory attributes of dry-cured hams with higher scores for color, aroma and taste found in KNP dry-cured ham as compared to other breed hams (p<0.05). The overall outcome of the study is that the breed has a potential effect on the specific chemical composition, texture, color and sensorial properties of dry-cured hams. These data could be useful for meat processors to select the suitable breeds for economical manufacturing of high quality dry-cured hams. PMID:25083111

  12. All-silicone prestrain-locked interpenetrating polymer network elastomers: free-standing silicone artificial muscles with improved performance and robustness

    NASA Astrophysics Data System (ADS)

    Brochu, P.; Stoyanov, H.; Niu, X.; Pei, Q.

    2013-05-01

    We present a novel all-silicone prestrain-locked interpenetrating polymer network (all-S-IPN) elastomer for use as a muscle-like actuator. The elastomer is fabricated using a combination of two silicones: a soft room temperature vulcanizing (RTV) silicone that serves as the host elastomer matrix, and a more rigid high temperature vulcanizing (HTV) silicone that acts to preserve the prestrain in the host network. In our novel S-IPN fabrication procedure we co-dissolve the RTV and HTV silicones in a common solvent, cast thin films, and allow the RTV silicone to cure before applying prestrain and finally curing the HTV silicone to lock in the prestrain. The free-standing prestrain-locked silicones show a performance improvement over standard free-standing silicone films, with a linear strain of 25% and an area strain of 45% when tested in a diaphragm configuration. We show that the process can also be used to improve electrode adhesion and stability as well as improve the interlayer adhesion in multilayer actuators. We demonstrate that, when coupled with carbon nanotube electrodes, fault-tolerance through self-clearing can be observed. We use the fault-tolerance and improved interlayer adhesion to demonstrate stable long-life (>30 000 cycles at >20% strain) actuation and repeated high-performance actuation (>500 cycles at ∼40% strain) of prestrained free-standing multilayer actuators driving a load.

  13. Tribological properties of sintered polycrystalline and single crystal silicon carbide

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.; Srinivasan, M.

    1982-01-01

    Tribological studies and X-ray photoelectron spectroscopy analyses were conducted with sintered polycrystalline and single crystal silicon carbide surfaces in sliding contact with iron at various temperatures to 1500 C in a vacuum of 30 nPa. The results indicate that there is a significant temperature influence on both the friction properties and the surface chemistry of silicon carbide. The main contaminants on the as received sintered polycrystalline silicon carbide surfaces are adsorbed carbon, oxygen, graphite, and silicon dioxide. The surface revealed a low coefficient of friction. This is due to the presence of the graphite on the surface. At temperatures of 400 to 600 C graphite and copious amount of silicon dioxide were observed on the polycrystalline silicon carbide surface in addition to silicon carbide. At 800 C, the amount of the silicon dioxide decreased rapidly and the silicon carbide type silicon and carbon peaks were at a maximum intensity in the XPS spectra. The coefficients of friction were high in the temperature range 400 to 800 C. Small amounts of carbon and oxygen contaminants were observed on the as received single crystal silicon carbide surface below 250 C. Silicon carbide type silicon and carbon peaks were seen on the silicon carbide in addition to very small amount of graphite and silicon dioxide at temperatures of 450 to 800 C.

  14. Purification and deposition of silicon by an iodide disproportionation reaction

    DOEpatents

    Wang, Tihu; Ciszek, Theodore F.

    2002-01-01

    Method and apparatus for producing purified bulk silicon from highly impure metallurgical-grade silicon source material at atmospheric pressure. Method involves: (1) initially reacting iodine and metallurgical-grade silicon to create silicon tetraiodide and impurity iodide byproducts in a cold-wall reactor chamber; (2) isolating silicon tetraiodide from the impurity iodide byproducts and purifying it by distillation in a distillation chamber; and (3) transferring the purified silicon tetraiodide back to the cold-wall reactor chamber, reacting it with additional iodine and metallurgical-grade silicon to produce silicon diiodide and depositing the silicon diiodide onto a substrate within the cold-wall reactor chamber. The two chambers are at atmospheric pressure and the system is open to allow the introduction of additional source material and to remove and replace finished substrates.

  15. Silicon surface passivation by silicon nitride deposition

    NASA Technical Reports Server (NTRS)

    Olsen, L. C.

    1984-01-01

    Silicon nitride deposition was studied as a method of passivation for silicon solar cell surfaces. The following three objectives were the thrust of the research: (1) the use of pecvd silicon nitride for passivation of silicon surfaces; (2) measurement techniques for surface recombination velocity; and (3) the importance of surface passivation to high efficiency solar cells.

  16. Curing of yeast [PSI+] prion by guanidine inactivation of Hsp104 does not require cell division.

    PubMed

    Wu, Yue-Xuan; Greene, Lois E; Masison, Daniel C; Eisenberg, Evan

    2005-09-01

    Propagation of the yeast prion [PSI+], a self-replicating aggregated form of Sup35p, requires Hsp104. One model to explain this phenomenon proposes that, in the absence of Hsp104, Sup35p aggregates enlarge but fail to replicate thus becoming diluted out as the yeast divide. To test this model, we used live imaging of Sup35p-GFP to follow the changes that occur in [PSI+] cells after the addition of guanidine to inactivate Hsp104. After guanidine addition there was initially an increase in aggregation of Sup35p-GFP; but then, before the yeast divided, the aggregates began to dissolve, and after approximately 6 h the Sup35-GFP looked identical to the Sup35-GFP in [psi+] cells. Although plating studies showed that the yeast were still [PSI+], this reduction in aggregation suggested that curing of [PSI+] by inactivation of Hsp104 might be independent of cell division. This was tested by measuring the rate of curing of [PSI+] cells in both dividing and nondividing cells. Cell division was inhibited by adding either alpha factor or farnesol. Remarkably, with both of these methods, we found that the rate of curing was not significantly affected by cell division. Thus, cell division is not a determining factor for curing [PSI+] by inactivating Hsp104 with guanidine. Rather, curing apparently occurs because Sup35-GFP polymers slowly depolymerize in the absence of Hsp104 activity. Hsp104 then counteracts this curing possibly by catalyzing formation of new polymers. PMID:16123122

  17. High specific activity silicon-32

    DOEpatents

    Phillips, D.R.; Brzezinski, M.A.

    1996-06-11

    A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidation state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.

  18. High specific activity silicon-32

    DOEpatents

    Phillips, Dennis R.; Brzezinski, Mark A.

    1996-01-01

    A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution to from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidization state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.

  19. Food additives

    PubMed Central

    Spencer, Michael

    1974-01-01

    Food additives are discussed from the food technology point of view. The reasons for their use are summarized: (1) to protect food from chemical and microbiological attack; (2) to even out seasonal supplies; (3) to improve their eating quality; (4) to improve their nutritional value. The various types of food additives are considered, e.g. colours, flavours, emulsifiers, bread and flour additives, preservatives, and nutritional additives. The paper concludes with consideration of those circumstances in which the use of additives is (a) justified and (b) unjustified. PMID:4467857

  20. Electron beam curing of polymer matrix composites

    SciTech Connect

    Janke, C.J.; Wheeler, D.; Saunders, C.

    1998-01-08

    The purpose of the CRADA was to conduct research and development activities to better understand and utilize the electron beam PMC curing technology. This technology will be used to replace or supplement existing PMC thermal curing processes in Department of Energy (DOE) Defense Programs (DP) projects and American aircraft and aerospace industries. This effort involved Lockheed Martin Energy Systems, Inc./Lockheed Martin Energy Research Corp. (Contractor), Sandia National Laboratories, and ten industrial Participants including four major aircraft and aerospace companies, three advanced materials companies, and three electron beam processing organizations. The technical objective of the CRADA was to synthesize and/or modify high performance, electron beam curable materials that meet specific end-use application requirements. There were six tasks in this CRADA including: Electron beam materials development; Electron beam database development; Economic analysis; Low-cost Electron Beam tooling development; Electron beam curing systems integration; and Demonstration articles/prototype structures development. The contractor managed, participated and integrated all the tasks, and optimized the project efforts through the coordination, exchange, and dissemination of information to the project participants. Members of the Contractor team were also the principal inventors on several electron beam related patents and a 1997 R and D 100 Award winner on Electron-Beam-Curable Cationic Epoxy Resins. The CRADA achieved a major breakthrough for the composites industry by having successfully developed high-performance electron beam curable cationic epoxy resins for use in composites, adhesives, tooling compounds, potting compounds, syntactic foams, etc. UCB Chemicals, the world`s largest supplier of radiation-curable polymers, has acquired a license to produce and sell these resins worldwide.

  1. Method for one-to-one polishing of silicon nitride and silicon oxide

    NASA Technical Reports Server (NTRS)

    Babu, Suryadevara V. (Inventor); Natarajan, Anita (Inventor)

    2009-01-01

    The present invention provides a method of removing silicon nitride at about the same removal rate as silicon dioxide by CMP. The method utilizes a polishing slurry that includes colloidal silica abrasive particles dispersed in water and additives that modulate the silicon dioxide and silicon nitride removal rates such that they are about the same. In one embodiment of the invention, the additive is lysine or lysine mono hydrochloride in combination with picolinic acid, which is effective at a pH of about 8. In another embodiment of the invention, the additive is arginine in combination with picolinic acid, which is effective at a pH of about 10.

  2. The development of low temperature curing adhesives

    NASA Technical Reports Server (NTRS)

    Green, H. E.; Sutherland, J. D.; Hom, J. M.; Sheppard, C. H.

    1975-01-01

    An approach for the development of a practical low temperature (293 K-311 K/68 F-100 F) curing adhesive system based on a family of amide/ester resins was studied and demonstrated. The work was conducted on resin optimization and adhesive compounding studies. An improved preparative method was demonstrated which involved the reaction of an amine-alcohol precursor, in a DMF solution with acid chloride. Experimental studies indicated that an adhesive formulation containing aluminum powder provided the best performance when used in conjunction with a commercial primer.

  3. Lower-curing-temperature PMR polyimides

    NASA Technical Reports Server (NTRS)

    Delvigs, P.

    1982-01-01

    Partial substitution of a p-aminostyrene end-cap for the monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid lowered the final cure temperature of typical PMR resins from 600 F to 500 F. The weight loss characteristics of neat resins and graphite fiber composites prepared by using the mixed end-cap approach were determined at 600 F. The room temperature and short-time elevated temperature mechanical properties of the composites at 550 F and 600 F were determined. The mechanical property retention characteristics of the composites at 550 F and 600 F are discussed.

  4. Role of Silicone Surfactant in Flexible Polyurethane Foam.

    PubMed

    Zhang; Macosko; Davis; Nikolov; Wasan

    1999-07-15

    Grafted copolymers which consist of a polydimethylsiloxane backbone and polyethylene oxide-co-propylene oxide pendant groups are used as surfactants to stabilize the foam cells in the flexible polyurethane foaming process. The mechanical properties of the cured polyurethane foam such as air permeability and foam cell size are affected significantly by the structure of the silicone surfactant used in the formulation. It is shown that silicone surfactant has an important impact on both the bubble generation and the cell window stabilization stage. A series of silicone surfactants with different structures was tested. Surfactants with higher silicone content will provide lower surface tension and thus help increase the number of air bubbles introduced during mixing. These air bubbles serve as the starting point for foam cell growth. As a result, the cured polyurethane foam made with higher silicone content surfactant has a smaller bubble size. It is also shown that silicone surfactant can reduce the cell window drainage rate due to the surface tension gradient along the cell window. The Gibbs film elasticity, the dynamic film elasticity, and the film drainage rate were measured for the first time versus surfactant composition. Surfactants with longer siloxane backbones are shown to give higher film elasticity. Using the vertical film drainage and foam column tests, it is shown that surfactants with higher film elasticity will yield slower drainage rate and better foam cell stability. Copyright 1999 Academic Press. PMID:10419661

  5. 22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

    SciTech Connect

    Geissbühler, Jonas Werner, Jérémie; Martin de Nicolas, Silvia; Hessler-Wyser, Aïcha; Tomasi, Andrea; Niesen, Bjoern; De Wolf, Stefaan; Barraud, Loris; Despeisse, Matthieu; Nicolay, Sylvain; Ballif, Christophe

    2015-08-24

    Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. We circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

  6. 22.5% efficient silicon heterojunction solar cell with molybdenum oxide hole collector

    NASA Astrophysics Data System (ADS)

    Geissbühler, Jonas; Werner, Jérémie; Martin de Nicolas, Silvia; Barraud, Loris; Hessler-Wyser, Aïcha; Despeisse, Matthieu; Nicolay, Sylvain; Tomasi, Andrea; Niesen, Bjoern; De Wolf, Stefaan; Ballif, Christophe

    2015-08-01

    Substituting the doped amorphous silicon films at the front of silicon heterojunction solar cells with wide-bandgap transition metal oxides can mitigate parasitic light absorption losses. This was recently proven by replacing p-type amorphous silicon with molybdenum oxide films. In this article, we evidence that annealing above 130 °C—often needed for the curing of printed metal contacts—detrimentally impacts hole collection of such devices. We circumvent this issue by using electrodeposited copper front metallization and demonstrate a silicon heterojunction solar cell with molybdenum oxide hole collector, featuring a fill factor value higher than 80% and certified energy conversion efficiency of 22.5%.

  7. Toughening reinforced epoxy composites with brominated polymeric additives

    NASA Technical Reports Server (NTRS)

    Nir, Z.; Gilwee, W. J., Jr. (Inventor)

    1985-01-01

    Cured polyfunctional epoxy resins including tris (hydroxyphenyl) methane triglycidyl ether are toughened by addition of polybrominated polymeric additives having an EE below 1500 to the pre-cure composition. Carboxy terminated butadiene acrylonitrile rubber is optionally present in the precure mixture as such or as a pre-formed copolymer with other reactants. Reinforced composites, particularly carbon reinforced composites, of these resins are disclosed and shown to have improved toughness.

  8. Critical parameters for electron beam curing of cationic epoxies and property comparison of electron beam cured cationic epoxies versus thermal cured resins and composites

    SciTech Connect

    Janke, C.J.; Norris, R.E.; Yarborough, K.; Havens, S.J.; Lopata, V.J.

    1997-01-16

    Electron beam curing of composites is a nonthermal, nonautoclave curing process offering the following advantages compared to conventional thermal curing: substantially reduced manufacturing costs and curing times; improvements in part quality and performance; reduced environmental and health concerns; and improvements in material handling. In 1994 a Cooperative Research and Development Agreement (CRADA), sponsored by the Department of Energy Defense Programs and 10 industrial partners, was established to advance electron beam curing of composites. The CRADA has successfully developed hundreds of new toughened and untoughened resins, offering unlimited formulation and processing flexibility. Several patent applications have been filed for this work. Composites made from these easily processable, low shrinkage material match the performance of thermal cured composites and exhibit: low void contents comparable to autoclave cured composites (less than 1%); superb low water absorption values in the same range as cyanate esters (less than 1%); glass transition temperatures rivaling those of polyimides (greater than 390 C); mechanical properties comparable to high performance, autoclave cured composites; and excellent property retention after cryogenic and thermal cycling. These materials have been used to manufacture many composite parts using various fabrication processes including hand lay-up, tow placement, filament winding, resin transfer molding and vacuum assisted resin transfer molding.

  9. Degree of conversion of two dual-cured resin cements light-irradiated through zirconia ceramic disks

    PubMed Central

    Kim, Min-Jeong; Kim, Kyo-Han; Kim, Young-Kyung

    2013-01-01

    PURPOSE The aim of this Fourier transform infrared (FTIR) spectroscopic study was to measure the degree of conversion (DC) of dual-cured resin cements light-irradiated through zirconia ceramic disks with different thicknesses using various light-curing methods. MATERIALS AND METHODS Zirconia ceramic disks (KT12) with three different thicknesses (1.0, 2.0, and 4.0 mm) were prepared. The light transmittance of the disks was measured using ultraviolet visible near-infrared spectroscopy. Four different light-curing protocols were used by combining two curing light modes (Elipar TriLight (standard mode) and bluephase G2 (high power mode)) with light-exposure times of 40 and 120 seconds. The DCs of the two dual-cured resin cements (Duo-Link and Panavia F2.0) light-irradiated through the disks was analyzed at three time intervals (3, 7, and 10 minutes) by FTIR spectroscopy. The data was analyzed using repeated measures ANOVA (α=.05).Two-way ANOVA and Tukey post hoc test were used to analyze the 10 minute DC results. RESULTS The 1.0 mm thick disk exhibited low light transmittance (<25%), and the transmittance decreased considerably with increasing disk thickness. All groups exhibited significantly higher 10 minute DC values than the 3 or 7 minute values (P<.05), but some exceptions were observed in Duo-Link. Two-way ANOVA revealed that the influence of the zirconia disk thickness on the 10 minute DC was dependent on the light-curing methods (P<.001). This finding was still valid even at 4.0 mm thickness, where substantial light attenuation took place. CONCLUSION The curing of the dual-cured resin cements was affected significantly by the light-curing technique, even though the additional chemical polymerization mechanism worked effectively. PMID:24353887

  10. Sensory properties, consumer liking and choice determinants of Lucanian dry cured sausages.

    PubMed

    Braghieri, Ada; Piazzolla, Nicoletta; Carlucci, Angela; Bragaglio, Andrea; Napolitano, Fabio

    2016-01-01

    Based on a food choice questionnaire we identified as the most influential aspects affecting consumer choice of Lucanian dry cured sausages: taste, animal health and addition of preservatives. Therefore, as a second step we conducted a study to assess the effect of preservative addition on sausage sensory properties and consumer liking, with a particular emphasis on taste. The addition of preservatives did not change the perception of taste attributes by an experienced panel, whereas differences were detected in terms of odor, texture and color attributes. However, consumers did not express a preference for a particular product in terms of overall liking, taste/flavor liking and texture liking, whereas appearance liking was higher for sausages containing preservatives. Since sausage taste was unaffected by the addition of preservative, in order to prevent the potentially detrimental effect of a label indicating their presence, producers should make an effort to obtain high quality Lucanian dry cured sausages without using them. PMID:26398006

  11. Morphological Characterization of Silicone Hydrogels

    NASA Astrophysics Data System (ADS)

    Gido, Samuel

    2007-03-01

    Silicone hydrogel materials are used in the latest generation of extended wear soft contact lenses. To ensure comfort and eye health, these materials must simultaneously exhibit high oxygen permeability and high water permeability / hydrophilicity. The materials achieve these opposing requirements based on bicontinuous composite of nanoscale domains of oxygen permeable (silicones) and hydrophilic (water soluble polymer) materials. The microphase separated morphology of silicone hydrogel contact lens materials was imaged using field emission gun scanning transmission electron microscopy (FEGSTEM), and atomic force microscopy (AFM). Additional morphological information was provided by small angle X-ray scattering (SAXS). These results all indicate a nanophase separated structure of silicone rich (oxygen permeable) and carbon rich (water soluble polymer) domains separated on a length scale of about 10 nm.

  12. Out-of-Autoclave Cure Composites

    NASA Technical Reports Server (NTRS)

    Hayes, Brian S.

    2015-01-01

    As the size of aerospace composite parts exceeds that of even the largest autoclaves, the development of new out-of-autoclave processes and materials is necessary to ensure quality and performance. Many out-of-autoclave prepreg systems can produce high-quality composites initially; however, due to long layup times, the resin advancement commonly causes high void content and variations in fiber volume. Applied Poleramic, Inc. (API), developed an aerospace-grade benzoxazine matrix composite prepreg material that offers more than a year out-time at ambient conditions and provides exceptionally low void content when out-of-autoclave cured. When compared with aerospace epoxy prepreg systems, API's innovation offers significant improvements in terms of out-time at ambient temperature and the corresponding tack retention. The carbon fiber composites developed with the optimized matrix technology have significantly better mechanical performance in terms of hot-wet retention and compression when compared with aerospace epoxy matrices. These composites also offer an excellent overall balance of properties. This matrix system imparts very low cure shrinkage, low coefficient of thermal expansion, and low density when compared with most aerospace epoxy prepreg materials.

  13. CURE: Clean use of reactor energy

    SciTech Connect

    1990-05-01

    This paper presents the results of a joint Westinghouse Hanford Company (Westinghouse Hanford)-Pacific Northwest Laboratory (PNL) study that considered the feasibility of treating radioactive waste before disposal to reduce the inventory of long-lived radionuclides, making the waste more suitable for geologic disposal. The treatment considered here is one in which waste would be chemically separated so that long-lived radionuclides can be treated using specific processes appropriate for the nuclide. The technical feasibility of enhancing repository performance by this type of treatment is considered in this report. A joint Westinghouse Hanford-PNL study group developed a concept called the Clean Use of Reactor Energy (CURE), and evaluated the potential of current technology to reduce the long-lived radionuclide content in waste from the nuclear power industry. The CURE process consists of three components: chemical separation of elements that have significant quantities of long-lived radioisotopes in the waste, exposure in a neutron flux to transmute the radioisotopes to stable nuclides, and packaging of radionuclides that cannot be transmuted easily for storage or geologic disposal. 76 refs., 32 figs., 24 tabs.

  14. Adhesive Properties of Cured Phenylethynyl Containing Imides

    NASA Technical Reports Server (NTRS)

    Jensen, Brian J.; Chang, Alice C.

    1997-01-01

    Considerable attention has been directed towards acetylene terminated oligomers over the last 20 years' and recent work has focused on phenylethynyl terminated imide (PETI) oligomers. These reactive oligomers possess several features which make them attractive candidates for use as composite matrices and adhesives. The phenylethynyl group can be readily incorporated into many different functionalized oligomers. The reactive oligomers possess relatively low melt viscosities and thermally cure without the evolution of volatile by-products. Once cured, they typically display high glass transition temperatures (Tgs), excellent solvent resistance and high mechanical properties. new modified phenylethynyl-terminated imide (LaRC MPEI) oligomers were synthesized at various molecular weights utilizing a small amount of trifunctional amine. As long as the amount of triamine is relatively small, this approach produces a mixture of linear, star-shaped and branched polymer chains that has lower melt and solution viscosity than an equivalent molecular weight linear phenylethynyl terminated imide oligomers. The work reported herein involves the synthesis and characterization of a copolymer using this approach and the preparation of blends utilizing a phenylethynyl containing reactive plasticizer of lower molecular weight called LaRC LV-121. The chemistry and properties of this new MPEI as well as some blends of MPEI with LV-121, are presented and compared to the linear version, LARC-PETI-5.

  15. Dr. Hall and the work cure.

    PubMed

    Reed, Kathlyn L

    2005-01-01

    Herbert James Hall, MD (1870-1923), was a pioneer in the systematic and organized study of occupation as therapy for persons with nervous and mental disorders that he called the "work cure." He began his work in 1904 during the early years of the Arts and Crafts Movement in the United States. His primary interest was the disorder neurasthenia, a condition with many symptoms including chronic fatigue, stress, and inability to work or perform everyday tasks. The prevailing treatment of the day was absolute bed rest known as the "rest cure." Hall believed that neurasthenia was not caused by overwork but by faulty living habits that could be corrected through an ordered life schedule and selected occupations. He identified several principles of therapy that are still used today including graded activity and energy conservation. Dr. Adolph Meyer credits Hall for organizing the ideas on the therapeutic use of occupation (Meyer, 1922). Hall also provided the name American Occupational Therapy Association for the professional organization and served as the fourth president. For his many contributions to the profession Hall deserves to be recognized as a major contributor to the development and organization of occupational therapy. PMID:23927746

  16. Radiation curing of carbon fibre composites

    NASA Astrophysics Data System (ADS)

    Spadaro, G.; Alessi, S.; Dispenza, C.; Sabatino, M. A.; Pitarresi, G.; Tumino, D.; Przbytniak, G.

    2014-01-01

    Epoxy/carbon fibre reinforced composites were produced by means of e-beam irradiation through a pulsed 10 MeV electron beam accelerator. The matrix consisted of a difunctional epoxy monomer (DGEBA) and an initiator of cationic polymerisation, while the reinforcement was a unidirectional high modulus carbon fibre fabric. Dynamic mechanical thermal analysis was carried out in order to determine the cross-linking degree. The analysis pointed out a nonuniformity in the cross-linking degree of the e-beam cured panels, with the formation of clusters at low Tg (glass transition temperature) and clusters at high Tg. An out-of-mould post irradiation thermal treatment on e-beam cured samples provides a higher uniformity in the network although some slight degradation effects. Mode I delamination fracture toughness and Interlaminar Shear Strength (ISS) were also investigated by means of Double Cantilever Beam (DCB) and Short Beam Shear tests, respectively. Results from this mechanical characterisation allowed to correlate fracture toughness of the bulk matrix resin, cross-linking density and fibre/matrix interaction to the delamination fracture behaviour of the fibre reinforced material.

  17. A comparison of ultraviolet-curing and self-curing polymers in preventive, restorative and orthodontic dentistry.

    PubMed

    Lee, H L; Orlowski, J A; Rogers, B J

    1976-06-01

    Both self-cured and UV-cured resin-base dental materials are used in preventive, restorative, and orthodontic dentistry. Polymerization is initiated in both systems by free radicals. Self-curing materials generate free radicals by means of chemical compounds included in their formulation. UV-curing systems rely upon externally-supplied, long wavelength, ultraviolet radiation to produce free radicals within the material. Therefore, although the major chemical components of both systems are similar in many respects, each system has particular advantages and disadvantages over the other, which must be recognized by the practitioner. Substantial differences exist, for example, in the color stability of these two types of materials, because of the fact that the UV-cured system cannot include UV absorbers, which protect the self-cured systems from discoloration after exposure to sunlight. UV-cured systems require a limitation on the maximum depth of filled restorative that can be cured at one time, since the filler particles attenuate UV radiation. The limit-layer is generally established as 1-1-5 mm maximum thickness. Therefore, UV-cured filled systems are more time-consuming in restorations of deeper cavities. This liability is also in evidence as it affects the degree of polymerization of UV-cured filled systems. The uncertainty of complete polymerization is apparently responsible for highly erratic compressive strength data found with UV-cured restoratives. Normally, the amount of unpolymerized monomer is much less predictable in UV-cured systems, over that which is obtained in self-cured materials. The presence of a larger fraction of unpolymerized monomer creates a greater potential for pulpal injury from UV-cured restorative materials. The catalyst used in several UV-cured systems is benzoin methyl ether, a compound of rather high toxicity (LD50:300 mg/kg). The safety of using UV radiation in the vicinity of oral mucosa has not been firmly established. The design

  18. Using a centrifuge for quality control of pre-wetted lightweight aggregate in internally cured concrete

    NASA Astrophysics Data System (ADS)

    Miller, Albert E.

    Early age shrinkage of cementitious systems can result in an increased potential for cracking which can lead to a reduction in service life. Early age shrinkage cracking can be particularly problematic for high strength concretes, which are often specified due to their high strength and low permeability. However, these high strength concretes frequently exhibit a reduction in the internal relative humidity (RH) due to the hydration reaction (chemical shrinkage) and self-desiccation which results in a bulk shrinkage, termed autogenous shrinkage, which is substantial at early ages. Due to the low permeability of these concretes, standard external curing is not always efficient in addressing this reduction in internal RH since the penetration of water can be limited. Internal curing has been developed to reduce autogenous shrinkage. Internally cured mixtures use internal reservoirs filled with fluid (generally water) that release this fluid at appropriate times to counteract the effects of self-desiccation thereby maintaining a high internal RH. Internally cured concrete is frequently produced in North America using pre-wetted lightweight aggregate. One important aspect associated with preparing quality internally cured concrete is being able to determine the absorbed moisture and surface moisture associated with the lightweight aggregate which enables aggregate moisture corrections to be made for the concrete mixture. This thesis represents work performed to develop a test method using a centrifuge to determine the moisture state of pre-wetted fine lightweight aggregate. The results of the test method are then used in a series of worksheets that were developed to assist field technicians when performing the tests and applying the results to a mixture design. Additionally, research was performed on superabsorbent polymers to assess their ability to be used as an internal curing reservoir.

  19. Adhesive strength and curing rate of marine mussel protein extracts on porcine small intestinal submucosa*

    PubMed Central

    Ninan, Lal; Stroshine, R L; Wilker, J.J.; Shi, Riyi

    2008-01-01

    An adhesive protein extracted from marine mussel (Mytilus edulis) was used to bond strips of connective tissue for the purpose of evaluating the use of curing agents to improve adhesive curing. Specifically, mussel adhesive protein solution (MAPS, 0.5 mM dihydroxyphenylalanine) was applied, with or without the curing agents, to the ends of two overlapping strips of porcine small intestinal submucosa. The bond strength of this lap joint was determined after curing for 1 h at room temperature (25°C). The strength of joints formed using only MAPS or with only the ethyl, butyl or octyl cyanoacrylate adhesives were determined. Although joints bonded using ethyl cyanoacrylate were strongest, those using MAPS were stronger than those using butyl and octyl cyanoacrylates. The addition of 25 mM solutions of the transition metal ions V5+, Fe3+ and Cr6+, which are all oxidants, increased the bond strength of the MAPS joints. The V5+ gave the strongest bonds and the Fe3+ the second strongest. In subsequent tests with V5+ and Fe3+ solutions, the bond strength increased with V5+ concentration, but it did not increase with Fe3+ concentration. Addition of 250 mM V5+ gave a very strong bond. PMID:17434815

  20. Process Formulations And Curing Conditions That Affect Saltstone Properties

    SciTech Connect

    Reigel, M. M.; Pickenheim, B. R.; Daniel, W. E.

    2012-09-28

    The first objective of this study was to analyze saltstone fresh properties to determine the feasibility of reducing the formulation water to premix (w/p) ratio while varying the amount of extra water and admixtures used during processing at the Saltstone Production Facility (SPF). The second part of this study was to provide information for understanding the impact of curing conditions (cure temperature, relative humidity (RH)) and processing formulation on the performance properties of cured saltstone.

  1. Sample size calculation for the proportional hazards cure model.

    PubMed

    Wang, Songfeng; Zhang, Jiajia; Lu, Wenbin

    2012-12-20

    In clinical trials with time-to-event endpoints, it is not uncommon to see a significant proportion of patients being cured (or long-term survivors), such as trials for the non-Hodgkins lymphoma disease. The popularly used sample size formula derived under the proportional hazards (PH) model may not be proper to design a survival trial with a cure fraction, because the PH model assumption may be violated. To account for a cure fraction, the PH cure model is widely used in practice, where a PH model is used for survival times of uncured patients and a logistic distribution is used for the probability of patients being cured. In this paper, we develop a sample size formula on the basis of the PH cure model by investigating the asymptotic distributions of the standard weighted log-rank statistics under the null and local alternative hypotheses. The derived sample size formula under the PH cure model is more flexible because it can be used to test the differences in the short-term survival and/or cure fraction. Furthermore, we also investigate as numerical examples the impacts of accrual methods and durations of accrual and follow-up periods on sample size calculation. The results show that ignoring the cure rate in sample size calculation can lead to either underpowered or overpowered studies. We evaluate the performance of the proposed formula by simulation studies and provide an example to illustrate its application with the use of data from a melanoma trial. PMID:22786805

  2. Filament Guides for Silicon-Ribbon Growth

    NASA Technical Reports Server (NTRS)

    Morrison, A. D.

    1985-01-01

    Contamination reduced in modified growth system. In Silicon-ribbongrowth apparatus, capillary filament guides are integral parts of crucible, extending from bottom to top of melt. Addition of guides expected to result in better thermal control of growth process and higher silicon purity.

  3. Bending strength and depth of cure of light-cured composite resins irradiated using filters that simulate enamel.

    PubMed

    Arikawa, H; Kanie, T; Fujii, K; Shinohara, N

    2004-01-01

    This study evaluates the light-attenuating effects of enamel on the properties of light-cured restorative resins using simple experimental filters. Three filters were designed to replicate the light transmittance characteristics of 0.5, 1.0 and 1.5 mm thick human enamel. The bending strength, depth of cure, and levels of residual monomer for 12 shades of three commercial light-cured composite resins were examined. These resins were cured either using direct irradiation from a light source or irradiation through one of the filters. For all materials, the bending strength and depth of cure of specimens irradiated through a filter were lower and the levels of residual monomer were higher than those found in specimens irradiated directly. The results indicate that the light-attenuating effect of enamel reduces the polymerization efficiency, resulting in poorer mechanical properties of light-cured composite resins. PMID:15125601

  4. Effect of curing mode on the hardness of dual-cured composite resin core build-up materials.

    PubMed

    Arrais, César Augusto Galvão; Kasaz, Aline de Cerqueira; Albino, Luís Gustavo Barrote; Rodrigues, José Augusto; Reis, Andre Figueiredo

    2010-01-01

    This study evaluated the Knoop Hardness (KHN) values of two dual-cured composite resin core build-up materials and one resin cement exposed to different curing conditions. Two dual-cured core build-up composite resins (LuxaCore-Dual, DMG; and FluoroCore2, Dentsply Caulk), and one dual-cured resin cement (Rely X ARC, 3M ESPE) were used in the present study. The composite materials were placed into a cylindrical matrix (2 mm in height and 3 mm in diameter), and the specimens thus produced were either light-activated for 40 s (Optilux 501, Demetron Kerr) or were allowed to self-cure for 10 min in the dark (n = 5). All specimens were then stored in humidity at 37 degrees C for 24 h in the dark and were subjected to KHN analysis. The results were submitted to 2-way ANOVA and Tukey's post-hoc test at a pre-set alpha of 5%. All the light-activated groups exhibited higher KHN values than the self-cured ones (p = 0.00001), regardless of product. Among the self-cured groups, both composite resin core build-up materials showed higher KHN values than the dual-cured resin cement (p = 0.00001). LuxaCore-Dual exhibited higher KHN values than FluoroCore2 (p = 0.00001) when they were allowed to self-cure, while no significant differences in KHN values were observed among the light-activated products. The results suggest that dual-cured composite resin core build-up materials may be more reliable than dual-cured resin cements when curing light is not available. PMID:20658046

  5. Food additives.

    PubMed

    Berglund, F

    1978-01-01

    The use of additives to food fulfils many purposes, as shown by the index issued by the Codex Committee on Food Additives: Acids, bases and salts; Preservatives, Antioxidants and antioxidant synergists; Anticaking agents; Colours; Emulfifiers; Thickening agents; Flour-treatment agents; Extraction solvents; Carrier solvents; Flavours (synthetic); Flavour enhancers; Non-nutritive sweeteners; Processing aids; Enzyme preparations. Many additives occur naturally in foods, but this does not exclude toxicity at higher levels. Some food additives are nutrients, or even essential nutritents, e.g. NaCl. Examples are known of food additives causing toxicity in man even when used according to regulations, e.g. cobalt in beer. In other instances, poisoning has been due to carry-over, e.g. by nitrate in cheese whey - when used for artificial feed for infants. Poisonings also occur as the result of the permitted substance being added at too high levels, by accident or carelessness, e.g. nitrite in fish. Finally, there are examples of hypersensitivity to food additives, e.g. to tartrazine and other food colours. The toxicological evaluation, based on animal feeding studies, may be complicated by impurities, e.g. orthotoluene-sulfonamide in saccharin; by transformation or disappearance of the additive in food processing in storage, e.g. bisulfite in raisins; by reaction products with food constituents, e.g. formation of ethylurethane from diethyl pyrocarbonate; by metabolic transformation products, e.g. formation in the gut of cyclohexylamine from cyclamate. Metabolic end products may differ in experimental animals and in man: guanylic acid and inosinic acid are metabolized to allantoin in the rat but to uric acid in man. The magnitude of the safety margin in man of the Acceptable Daily Intake (ADI) is not identical to the "safety factor" used when calculating the ADI. The symptoms of Chinese Restaurant Syndrome, although not hazardous, furthermore illustrate that the whole ADI

  6. Patienthood in medieval Tuscany: beliefs and cures.

    PubMed

    Lawless, Catherine

    2016-06-01

    This paper focuses on intersections of holy and sick bodies in the Tuscan Middle Ages to examine how the faithful accessed miraculous cures from contact with, or belief in, the relics of the saints. Rather than examine the relationship between the long dead martyrs (whose relics were abundant), however, it will look at the relationship between relatively recent saints and their devotees. The miracles discussed are traditional-that is, they are found in the lives of many saints and are not exceptional. It is hoped, however, that by concentrating on Tuscany, some insights can be secured on the relationship between Tuscan individuals of the late middle ages and those of their community who were recognised, either officially or through vox populi, as saints. PMID:27174846

  7. What Will It Take to Cure HIV?

    PubMed

    Ananworanich, Jintanat

    2015-01-01

    Investigational strategies to attempt HIV cure or remission include very early initiation of antiretroviral therapy to limit the latent HIV reservoir and preinfection vaccination. In the setting of viral suppression, strategies include reactivation of latently infected cells (eg, through "shock" therapy with histone deacetylase inhibitors or other agents); use of broadly neutralizing antibodies, therapeutic vaccines, immunotoxins, or other immune-based therapies to kill latently infected cells; and gene editing to induce target cell resistance (eg, by eliminating the CC chemokine receptor 5 [CCR5] coreceptor). Improved ability to detect and quantify very low levels of virus is needed. This article summarizes a presentation by Jintanat Ananworanich, MD, PhD, at the IAS-USA continuing education program held in New York, New York, in October 2014. PMID:26200707

  8. Method for Molding Structural Parts Utilizing Modified Silicone Rubber

    NASA Technical Reports Server (NTRS)

    Weiser, Erik S. (Inventor); Baucom, Robert M. (Inventor); Snoha, John J. (Inventor)

    1998-01-01

    This invention improves upon a method for molding structural parts from preform material. Preform material to be used for the part is provided. A silicone rubber composition containing entrained air voids is prepared. The silicone rubber and preform material assembly is situated within a rigid mold cavity used to shape the preform material to die desired shape. The entire assembly is heated in a standard heating device so that the thermal expansion of the silicone rubber exerts the pressure necessary to force the preform material into contact with the mold container. The introduction of discrete air voids into the silicone rubber allows for accurately controlled pressure application on the preform material at the cure temperature.

  9. Stratospheric experiments on curing of composite materials

    NASA Astrophysics Data System (ADS)

    Chudinov, Viacheslav; Kondyurin, Alexey; Svistkov, Alexander L.; Efremov, Denis; Demin, Anton; Terpugov, Viktor; Rusakov, Sergey

    2016-07-01

    Future space exploration requires a large light-weight structure for habitats, greenhouses, space bases, space factories and other constructions. A new approach enabling large-size constructions in space relies on the use of the technology of polymerization of fiber-filled composites with a curable polymer matrix applied in the free space environment on Erath orbit. In orbit, the material is exposed to high vacuum, dramatic temperature changes, plasma of free space due to cosmic rays, sun irradiation and atomic oxygen (in low Earth orbit), micrometeorite fluence, electric charging and microgravitation. The development of appropriate polymer matrix composites requires an understanding of the chemical processes of polymer matrix curing under the specific free space conditions to be encountered. The goal of the stratospheric flight experiment is an investigation of the effect of the stratospheric conditions on the uncured polymer matrix of the composite material. The unique combination of low residual pressure, high intensity UV radiation including short-wave UV component, cosmic rays and other aspects associated with solar irradiation strongly influences the chemical processes in polymeric materials. We have done the stratospheric flight experiments with uncured composites (prepreg). A balloon with payload equipped with heater, temperature/pressure/irradiation sensors, microprocessor, carrying the samples of uncured prepreg has been launched to stratosphere of 25-30 km altitude. After the flight, the samples have been tested with FTIR, gel-fraction, tensile test and DMA. The effect of cosmic radiation has been observed. The composite was successfully cured during the stratospheric flight. The study was supported by RFBR grants 12-08-00970 and 14-08-96011.

  10. Crystalline Silicon Solar Cells

    NASA Astrophysics Data System (ADS)

    Green, Martin A.

    2015-10-01

    The following sections are included: * Overview * Silicon cell development * Substrate production * Cell processing * Cell costs * Opportunities for improvement * Silicon-supported thin films * Summary * Acknowledgement * References

  11. Photophysical ablation of porous silicon

    NASA Astrophysics Data System (ADS)

    Aksenov, Valerii P.; Mikhailova, G. N.

    2004-07-01

    Laser ablation of porous silicon as a function of laser wavelength and width of silicon nanowires was studied in our experiments. The time-resolved evolution of the cloud of the porous silicon particles produced by laser ablation is studied in situ by the analysis of the kinetics of photoluminescence signal. The laser ablation of porous silicon produced by pulses of 532 nm or 337 nm radiation with addition of synchronized power pulses of 1064 nm radiation. The cloud of the nanometer-sized silicon crystallites had the high enhancement of luminescence quantum efficiency in the red region of spectra. The slow PL kinetics component, which is due to the localized carriers, decays on a millisecond time scale. The squeezed electron-hole plasma heating by IR-laser radiation may produce a damage of silicon nanowires. The fragments of nanowires in cloud must be smaller, than the critical length. The energy of excitation of e-h pair in fragment with contribution of longitude quantum modes must be lower than energy of the excited photons. Particles with lesser length don't absorb excited laser radiation and don't damage. For this case we may speak about the quantum mechanism of laser ablation of nanowires.

  12. Study of silicone-based materials for the packaging of optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Lin, Yeong-Her

    The first part of this work is to evaluate the main materials used for the packaging of high power light-emitting diodes (LEDs), i.e., the die attach materials, the encapsulant materials, and high color rendering index(CRI) sol-gel composite materials. All of these materials had been discussed the performance, reliability, and issues in high power LED packages. High power white LEDs are created either from blue or near-ultraviolet chips encapsulated with a yellow phosphor, or from red-green-blue LED light mixing systems. The phosphor excited by blue LED chip was mostly used in experiment of this dissertation. The die attach materials contains filler particles possessing a maximum particle size less than 1.5 mum in diameter blended with epoxy polymer matrix. Such compositions enable thin bond line thickness, which decreases thermal resistance that exists between thermal interface materials and the corresponding mating surfaces. The thermal conductivity of nano silver die attach materials is relatively low, the thermal resistance from the junction to board is just 1.6 KW-1 in the bond line thickness of 5.3 mum, which is much lower than the thermal resistance using conventional die attach materials. The silicone die attach adhesive made in the lab cures through the free radical reaction of epoxy-functional organopolysiloxane and through the hydrosilylation reaction between alkenyl-functional organopolysiloxane and silicone-boned hydrogen-functional organopolysiloxane. By the combination of the free radical reaction and the hydrosilylation reaction, the low-molecular-weight silicone oil will not be out-migrated and not contaminate wire bondability to the LED chip and lead frame. Hence, the silicone die attach adhesive made in the lab can pass all reliability tests, such as operating life test JEDEC 85°C/85RH and room temperature operating life test. For LED encapsulating materials, most of commercial silicone encapsulants still suffer thermal/radiation induced

  13. Colour Stability of Heat and Cold Cure Acrylic Resins

    PubMed Central

    Ganesh, P R; Reddy, Madan Mohan; Ebenezar, A.V. Rajesh; Sivakumar, G

    2015-01-01

    Introduction: To evaluate the colour stability of heat and cold cure acrylic resins under simulated oral conditions with different colorants. Materials and Methods: Three different brands of heat cure acrylic resin and two rapid cure auto polymerizing acrylic resin of commercial products such as Trevelon Heat Cure (THC), DPI Heat cure (DHC), Pyrax Heat Cure (PHC), DPI Cold cure (DCC) and Acralyn-R-Cold cure (ACC) have been evaluated for discoloration and colour variation on subjecting it to three different, commonly employed food colorants such as Erythrosine, Tartarizine and Sunset yellow. In order to simulate the oral condition the food colorants were diluted with artificial saliva to the samples taken up for the study. These were further kept in an incubator at 37°C ± 1°C. The UV-visible spectrophotometer has been utilized to evaluate the study on the basis of CIE L* a* b* system. The prepared samples for standard evaluation have been grouped as control group, which has been tested with a white as standard, which is applicable for testing the colour variants. Results: The least colour changes was found to be with Sunset Yellow showing AE* value of 3.55 with heat cure acrylic resin branded as PHC material and the highest colour absorption with Tartarizine showing AE* value of 12.43 in rapid cure autopolymerzing acrylic resin material branded as ACC material. Conclusion: ACC which is a self cure acrylic resin shows a higher colour variation to the tartarizine food coloration. There were not much of discoloration values shown on the denture base resins as the food colorants are of organic azodyes. PMID:25738078

  14. Determination of the viability of Toxoplasma gondii in cured ham using bioassay: influence of technological processing and food safety implications.

    PubMed

    Bayarri, Susana; Gracia, María J; Lázaro, Regina; Pe Rez-Arquillué, Consuelo; Barberán, Montserrat; Herrera, Antonio

    2010-12-01

    Toxoplasmosis is a zoonotic disease caused by the protozoan Toxoplasma gondii and distributed worldwide. Ingestion of viable cysts from infected raw or undercooked meat is an important route of horizontal transmission of the parasite to humans. Little information is available concerning the effect of commercial curing on cysts of T. gondii. This study is the first in which the influence of processing of cured ham on the viability of T. gondii has been evaluated, using bioassay to assess the risk of infection from eating this meat product. Naturally infected pigs were selected for the study, and a mouse concentration bioassay technique was used to demonstrate viable bradyzoites of T. gondii in porcine tissues and hams. No viable parasites were found in the final product (14 months of curing) based on results of the indirect immunofluorescence assay and histological and PCR analyses. Our results indicate that the consumption of hams cured as described here poses an insignificant risk of acquiring toxoplasmosis. However, additional studies are required to evaluate the safety of ham products cured under different conditions of curing time, salt, and nitrite concentration. PMID:21219742

  15. Bio-based epoxy/chitin nanofiber composites cured with amine-type hardeners containing chitosan.

    PubMed

    Shibata, Mitsuhiro; Enjoji, Motohiro; Sakazume, Katsumi; Ifuku, Shinsuke

    2016-06-25

    Sorbitol polyglycidyl ether (SPE) which is a bio-based water-soluble epoxy resin was cured with chitosan (CS) and/or a commercial water-soluble polyamidoamine- or polyetheramine-type epoxy hardener (PAA or PEA). Furthermore, biocomposites of the CS-cured SPE (CS-SPE) and CS/PAA- or CS/PEA-cured SPE (SPE-CA or SPE-CE) biocomposites with chitin nanofiber (CNF) were prepared by casting and compression molding methods, respectively. The curing reaction of epoxy and amino groups of the reactants was confirmed by the FT-IR spectral analysis. SPE-CS and SPE-CA were almost transparent films, while SPE-CE was opaque. Transparency of SPE-CS/CNF and SPE-CA/CNF became a little worse with increasing CNF content. The tanδ peak temperature of SPE-CS was higher than those of SPE-PAA and SPE-PEA. SPE-CA or SPE-CE exhibited two tanδ peak temperatures related to glass transitions of the CS-rich and PAA-rich or PEA-rich moieties. The tanδ peak temperatures related to the CS-rich and PAA-rich moieties increased with increasing CNF content. A higher order of tensile strengths and moduli of the cured resins was SPE-CS≫SPE-CA>SPE-CE. The tensile strength and modulus of each sample were much improved by the addition of 3wt% CNF, while further addition of CNF caused a lowering of the strength and modulus. PMID:27083797

  16. Modified silicon carbide whiskers

    DOEpatents

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

    1991-05-21

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

  17. Modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1991-01-01

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

  18. Additive effects on the toughening of unsaturated polyester resins

    SciTech Connect

    Suspene, L.; Yang, Y.S.; Pascault, J.P.

    1993-12-31

    An elastomer additive, carboxy-terminated acrylonitrile-butadiene copolymer, was used for toughening in the free radical cross-linking copolymerization of unsaturated polyester (UP) resins. For molded parts, Charpy impact behavior was generally enhanced and the number of catastrophic failures was reduced. The miscibility and interfacial properties of additive and resin blends play important roles in the toughening process. Phase-diagram studies showed that the elastomer additive is immiscible with the UP resin and is phase-separated from the resin matrix during curing. This phase-separation phenomenon is similar to that in the low-profile mechanism of UP resins. Additive-resin system miscibility greatly influences curing morphology. Microvoids occurred in the additive phase of cured resin because of shrinkage stress. The intrinsic inhomogeneity of the polyester network and the existence of microvoids in the final product limit the toughening effect of additives on unsaturated polyester resins. 49 refs., 13 figs., 3 tabs.

  19. Mental Retardation: The Search for Cures. Research Monograph Number 7.

    ERIC Educational Resources Information Center

    Menolascino, Frank J.; Neman, Ronald

    The booklet describes the Association for Retarded Citizens' (ARC's) goal of coordinating efforts to seek a cure for mental retardation. Cures are defined as any intervention that would significantly increase intellectual functioning and adaptive behavior beyond the upper level of retardation. It is explained that because of the variety of causes…

  20. 7 CFR 29.2269 - Fire-cured.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2269 Fire... 7 Agriculture 2 2014-01-01 2014-01-01 false Fire-cured. 29.2269 Section 29.2269 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  1. 7 CFR 29.2269 - Fire-cured.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2269 Fire... 7 Agriculture 2 2012-01-01 2012-01-01 false Fire-cured. 29.2269 Section 29.2269 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  2. 7 CFR 29.2269 - Fire-cured.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2269 Fire... 7 Agriculture 2 2011-01-01 2011-01-01 false Fire-cured. 29.2269 Section 29.2269 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  3. 7 CFR 29.2269 - Fire-cured.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2269 Fire... 7 Agriculture 2 2010-01-01 2010-01-01 false Fire-cured. 29.2269 Section 29.2269 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  4. 7 CFR 29.2269 - Fire-cured.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... INSPECTION Standards Official Standard Grades for Virginia Fire-Cured Tobacco (u.s. Type 21) § 29.2269 Fire... 7 Agriculture 2 2013-01-01 2013-01-01 false Fire-cured. 29.2269 Section 29.2269 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections,...

  5. Improved method facilitates debulking and curing of phenolic impregnated asbestos

    NASA Technical Reports Server (NTRS)

    Gaines, P.

    1966-01-01

    Workpieces covered with phenolic impregnated asbestos tape and then wrapped with a specified thickness of nylon yarn under pressure, are debulked and cured in a standard oven. This method of debulking and curing is used in the fabrication of ablative chambers for the Gemini and Apollo attitude control engines.

  6. Geopolymeric materials prepared using Class F fly ash and elevated temperature curing

    SciTech Connect

    Bakharev, T. . E-mail: tanya.bakharev@eng.monash.edu.au

    2005-06-01

    This paper reports the results of the study of the influence of elevated temperature curing on phase composition, microstructure and strength development in geopolymer materials prepared using Class F fly ash and sodium silicate and sodium hydroxide solutions. In particular, the effect of storage at room temperature before the application of heat on strength development and phase composition was studied. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and SEM were utilised in this study. Long precuring at room temperature before application of heat was beneficial for strength development in all studied materials, as strength comparable to 1 month of curing at elevated temperature can develop in this case only after 24 h of heat curing. The main product of reaction in the geopolymeric materials was amorphous alkali aluminosilicate gel. However, in the case of sodium hydroxide activator in addition to it, traces of chabazite, Linde Type A, Na-P1 (gismondine) zeolites and hydroxysodalite were also present. The type of zeolite present and composition of aluminosilicate gel were dependent on the curing history.

  7. Cure reaction of epoxy resins catalyzed by graphite-based nanofiller

    NASA Astrophysics Data System (ADS)

    Corcione, C. Esposito; Acocella, Maria Rosaria; Giuri, Antonella; Maffezzoli, Alfonso; Guerra, Gaetano

    2015-12-01

    A significant effort was directed to the synthesis of graphene stacks/epoxy nanocomposites and to the analysis of the effect of a graphene precursor on cure reaction of a model epoxy matrix. A comparative thermal analysis of epoxy resins filled with an exfoliated graphite oxide eGO were conducted. The main aim was to understand the molecular origin of the influence of eGO on the Tg of epoxy resins. The higher Tg values previously observed for low curing temperatures, for epoxy resins with graphite-based nanofillers, were easily rationalized by a catalytic activity of graphitic layers on the reaction between the epoxy and amine groups of the resin, which leads to higher crosslinking density in milder conditions. A kinetic analysis of the cure mechanism of the epoxy resin associated to the catalytical activity of the graphite based filler was performed by isothermal DSC measurements. The DSC results showed that the addition of graphite based filler greatly increased the enthalpy of epoxy reaction and the reaction rate, confirming the presence of a catalytic activity of graphitic layers on the crosslinking reaction between the epoxy resin components (epoxide oligomer and di-amine). A kinetic modelling analysis, arising from an auto-catalyzed reaction mechanism, was finally applied to isothermal DSC data, in order to predict the cure mechanism of the epoxy resin in presence of the graphite based nanofiller.

  8. Use of free silicon in liquid phase sintering of silicon nitrides and sialons

    DOEpatents

    Raj, Rishi; Baik, Sunggi

    1985-11-12

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic.

  9. Use of free silicon in liquid phase sintering of silicon nitrides and sialons

    DOEpatents

    Raj, R.; Baik, S.

    1985-11-12

    This invention relates to the production of improved high density nitrogen based ceramics by liquid-phase densification of silicon nitride or a compound of silicon-nitrogen-oxygen-metal, e.g. a sialon. In the process and compositions of the invention minor amounts of finely divided silicon are employed together with the conventional liquid phase producing additives to enhance the densification of the resultant ceramic. 4 figs.

  10. Role of surface-reaction layer in HBr/fluorocarbon-based plasma with nitrogen addition formed by high-aspect-ratio etching of polycrystalline silicon and SiO2 stacks

    NASA Astrophysics Data System (ADS)

    Iwase, Taku; Matsui, Miyako; Yokogawa, Kenetsu; Arase, Takao; Mori, Masahito

    2016-06-01

    The etching of polycrystalline silicon (poly-Si)/SiO2 stacks by using VHF plasma was studied for three-dimensional NAND fabrication. One critical goal is achieving both a vertical profile and high throughput for multiple-stack etching. While the conventional process consists of multiple steps for each stacked layer, in this study, HBr/fluorocarbon-based gas chemistry was investigated to achieve a single-step etching process to reduce process time. By analyzing the dependence on wafer temperature, we improved both the etching profile and rate at a low temperature. The etching mechanism is examined considering the composition of the surface reaction layer. X-ray photoelectron spectroscopy (XPS) analysis revealed that the adsorption of N–H and Br was enhanced at a low temperature, resulting in a reduced carbon-based-polymer thickness and enhanced Si etching. Finally, a vertical profile was obtained as a result of the formation of a thin and reactive surface-reaction layer at a low wafer temperature.

  11. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study

    PubMed Central

    D, Krishnakanth Reddy; V, Kishore M S; Safeena, Safeena

    2013-01-01

    Background: The purpose of this study was to determine shear bond strength and the effect on the bracket/ adhesive failure mode when an acidic primer and other etchants were used to condition the enamel surface before bonding. Materials & Methods: Group I: Brackets bonded with Ultimate cure-on-light Light-cure composite adhesive system. Group II: Brackets bonded with Ortho-one no-mix. Self-cure composite adhesive system. Group III: Brackets bonded with Light-cure glass ionomer adhesive system. Group IV: Brackets bonded with Transbond plus self etching primer. Results: The results of this study indicated that the shear bond strength when using Transbond plus self etching primer showed the highest bond strength Group- IV(8.69 2.54 MPa) followed by Ultimate cure-on-light Group-I (8.62 1.84 MPa), Ortho-one no-mix (Bisco Inc. USA)Group-II (8.07 1.72 MPa), and least bond strength was seen in G.C. Fuji Ortho L.C. Group-III (6.01 1.6) MPa Conclusion: Use of self etching primer saves chairside time and satisfactory high bond strength was obtained. Care should be taken during debonding of ceramic brackets How to cite this article: Reddy K D, Kishore M S V, Safeena S. Shear Bond Strength of Acidic Primer, Light-Cure Glass Ionomer, Light-Cure and Self Cure Composite Adhesive Systems - An In Vitro Study. J Int Oral Health 2013; 5(3):73-78. PMID:24155606

  12. Potlining Additives

    SciTech Connect

    Rudolf Keller

    2004-08-10

    In this project, a concept to improve the performance of aluminum production cells by introducing potlining additives was examined and tested. Boron oxide was added to cathode blocks, and titanium was dissolved in the metal pool; this resulted in the formation of titanium diboride and caused the molten aluminum to wet the carbonaceous cathode surface. Such wetting reportedly leads to operational improvements and extended cell life. In addition, boron oxide suppresses cyanide formation. This final report presents and discusses the results of this project. Substantial economic benefits for the practical implementation of the technology are projected, especially for modern cells with graphitized blocks. For example, with an energy savings of about 5% and an increase in pot life from 1500 to 2500 days, a cost savings of $ 0.023 per pound of aluminum produced is projected for a 200 kA pot.

  13. Phosphazene additives

    SciTech Connect

    Harrup, Mason K; Rollins, Harry W

    2013-11-26

    An additive comprising a phosphazene compound that has at least two reactive functional groups and at least one capping functional group bonded to phosphorus atoms of the phosphazene compound. One of the at least two reactive functional groups is configured to react with cellulose and the other of the at least two reactive functional groups is configured to react with a resin, such as an amine resin of a polycarboxylic acid resin. The at least one capping functional group is selected from the group consisting of a short chain ether group, an alkoxy group, or an aryloxy group. Also disclosed are an additive-resin admixture, a method of treating a wood product, and a wood product.

  14. Progress toward curing HIV infections with hematopoietic stem cell transplantation.

    PubMed

    Smiley, Stephen T; Singh, Anjali; Read, Sarah W; Sharma, Opendra K; Finzi, Diana; Lane, Clifford; Rice, Jeffrey S

    2015-01-15

    Combination antiretroviral therapy can suppress human immunodeficiency virus (HIV) infection but cannot completely eradicate the virus. A major obstacle in the quest for a cure is the difficulty in targeting and measuring latently infected cells. To date, a single person seems to have been cured of HIV. Hematopoietic stem cell transplantation (HSCT) preceded this cancer patient's long-term sustained HIV remission, but researchers have been unable to replicate this cure, and the mechanisms that led to HIV remission remain to be established. In February 2014, the National Institute of Allergy and Infectious Diseases sponsored a workshop that provided a venue for in-depth discussion of whether HSCT could be exploited to cure HIV in cancer patients requiring such procedures. Participants also discussed how HSCT might be applied to a broader community of HIV-infected persons in whom the risks of HSCT currently outweigh the likelihood and benefits of HIV cure. PMID:25273081

  15. Use of light-curing units in orthodontics.

    PubMed

    Goyal, Amit; Hurkadle, Jyothikiran; Magegowda, Shivalinga; Bhatia, Pankaj

    2013-08-01

    Because of their wide field of applications, light-curing units are now indispensable for orthodontists and general dentists; thus, it is important to be familiar with the various types of light-curing units, their history, specifications, advantages, and disadvantages. For this review, a search of the PubMed database (from 1966 to March 2010) was conducted using the search term "curing lights orthodontics". Eligibility of the selected studies was determined by reading the abstracts of articles identified by the search. All the articles that met the inclusion criteria were selected, and the articles collected. The reference lists of the retrieved articles were also hand searched for any applicable studies that might have been missed in the database searches. When selecting curing lights for an office, many variables need to be considered. Armed with knowledge about each curing-light category, orthodontists can evaluate their unique practice style and select the appropriate light/lights. PMID:23371892

  16. Curing system for high voltage cross linked cables

    DOEpatents

    Bahder, George; Katz, Carlos; Bopp, Louis A.

    1978-01-01

    This invention makes extruded, vulcanized, high voltage cables insulated with thermosetting compounds at much higher rates of production and with superior insulation of reduced thickness and with reduced cavities or voids in the insulation. As the cable comes from an extruder, it passes into a curing chamber with a heat booster that quickly raises the insulation to a temperature at which it is cured much more quickly than with steam heating of the prior art. A high temperature liquid in contact with the insulation maintains the high temperature; and because of the greater curing heat, the cable can travel through the curing chamber at a faster rate and into a cooling tube where it contacts with a cooling liquid under high pressure. The insulation compound is treated to reduce the size of cavities; and the high pressure maintained by the curing and cooling mediums prevent expansion of cavities before the insulation is set.

  17. Tough, High-Performance, Thermoplastic Addition Polymers

    NASA Technical Reports Server (NTRS)

    Pater, Ruth H.; Proctor, K. Mason; Gleason, John; Morgan, Cassandra; Partos, Richard

    1991-01-01

    Series of addition-type thermoplastics (ATT's) exhibit useful properties. Because of their addition curing and linear structure, ATT polymers have toughness, like thermoplastics, and easily processed, like thermosets. Work undertaken to develop chemical reaction forming stable aromatic rings in backbone of ATT polymer, combining high-temperature performance and thermo-oxidative stability with toughness and easy processibility, and minimizing or eliminating necessity for tradeoffs among properties often observed in conventional polymer syntheses.

  18. 7 CFR 30.38 - Class 3; air-cured types and groups.

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... produced principally in the Green River section of Kentucky. (g) Type 37. That type of air-cured or sun-cured tobacco commonly known as Virginia Sun-cured, Virginia Sun and Air-cured, or Dark Air-cured...

  19. 7 CFR 30.38 - Class 3; air-cured types and groups.

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... produced principally in the Green River section of Kentucky. (g) Type 37. That type of air-cured or sun-cured tobacco commonly known as Virginia Sun-cured, Virginia Sun and Air-cured, or Dark Air-cured...

  20. 7 CFR 30.38 - Class 3; air-cured types and groups.

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... produced principally in the Green River section of Kentucky. (g) Type 37. That type of air-cured or sun-cured tobacco commonly known as Virginia Sun-cured, Virginia Sun and Air-cured, or Dark Air-cured...

  1. 7 CFR 30.38 - Class 3; air-cured types and groups.

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... produced principally in the Green River section of Kentucky. (g) Type 37. That type of air-cured or sun-cured tobacco commonly known as Virginia Sun-cured, Virginia Sun and Air-cured, or Dark Air-cured...

  2. Stress evolution in a conductive adhesive during curing and cooling

    NASA Astrophysics Data System (ADS)

    Mei, Yuhai

    2000-10-01

    There is increasing interest in using conductive adhesives, which are composites of polymers and conductive fillers, as replacements for solder in different types of microelectronic assemblies. However, conductive adhesives still suffer from several deficiencies, such as unstable electrical conductivity and inadequate adhesion. The reliability of the conductive adhesive joints is always one of the major considerations during their design and operation, and the curing and thermal stresses generated in polymers and composites during curing, cooling and thermal cycling play a very important role in determining reliability. Because of the mismatch in the mechanical properties between the conductive adhesive and the substrate, appreciable curing and thermal stress is generated during manufacturing, which may be detrimental to the reliability of conductive adhesive joints. In this dissertation, an interactive linear viscoelastic model which considers interaction between the initial gel network and the other networks that form during curing is proposed to simulate stress and volume shrinkage during the thermoset curing process, and an effective method for measuring volume shrinkage during the thermoset cure is developed. A systematic experimental study of the material properties of the conductive adhesive and its epoxy matrix during the curing and cooling processes has been conducted. Based on these experimental data, stresses generated during several spatially homogeneous curing and cooling processes of the conductive adhesive and its epoxy matrix are also calculated. It is found that the conductive adhesive possesses mechanical properties which are substantially different from those of the constituents, and that the conductive adhesive has a relaxation process which is similar to its matrix and generates appreciable curing and thermal stresses during curing and cooling. Finally, a processing procedure designed to provide desired residual stresses is discussed.

  3. Prepreg cure monitoring using diffuse reflectance-FTIR. [Fourier Transform Infrared Technique

    NASA Technical Reports Server (NTRS)

    Young, P. R.; Chang, A. C.

    1984-01-01

    An in situ diffuse reflectance-Fourier transform infrared technique was developed to determine infrared spectra of graphite fiber prepregs as they were being cured. A bismaleimide, an epoxy, and addition polyimide matrix resin prepregs were studied. An experimental polyimide adhesive was also examined. Samples were positioned on a small heater at the focal point of diffuse reflectance optics and programmed at 15 F/min while FTIR spectra were being scanned, averaged, and stored. An analysis of the resulting spectra provided basic insights into changes in matrix resin molecular structure which accompanied reactions such as imidization and crosslinking. An endo-exothermal isomerization involving reactive end-caps was confirmed for the addition polyimide prepregs. The results of this study contribute to a fundamental understanding of the processing of composites and adhesives. Such understanding will promote the development of more efficient cure cycles.

  4. Effect of three types of light-curing units on 5-year colour changes of light-cured composite.

    PubMed

    Tak, Onjen; Altintas, Subutay Han; Ozturk, Nilgun; Usumez, Aslihan

    2009-03-01

    The purpose of this study was to determine colour changes in a composite cured with tungsten-halogen, light-emitting diode (LED) or a plasma arc after 5 years. Five specimens 10 mm in diameter and 2 mm in height were prepared using Hybrid (Clearfil AP-X) composite for each test group. The corresponding specimens were cured with a tungsten-halogen curing light, a LED unit or with a plasma arc. Specimens were stored in light-proof boxes for 5 years after the curing procedure to avoid further exposure to light and stored in 37 degrees C in 100% humidity. Colorimetric values of the specimens immediately after curing and after 5 years were measured using colorimeter. The DeltaE*( ab ) values varied significantly depending on the curing unit used (p < 0.001). Curing time did not affect the colour changes of the specimens (p = 0.4). The results of this study suggest that composite materials undergo measurable changes due to the curing unit exposure. PMID:18769947

  5. Temperature and curing time affect composite sorption and solubility

    PubMed Central

    de CASTRO, Fabrício Luscino Alves; CAMPOS, Bruno Barbosa; BRUNO, Kely Firmino; REGES, Rogério Vieira

    2013-01-01

    Objective: This study evaluated the effect of temperature and curing time on composite sorption and solubility. Material and Methods: Seventy five specimens (8x2 mm) were prepared using a commercial composite resin (ICE, SDI). Three temperatures (10º C, 25º C and 60º C) and five curing times (5 s, 10 s, 20 s, 40 s and 60 s) were evaluated. The specimens were weighed on an analytical balance three times: A: before storage (M1); B: 7 days after storage (M2); C: 7 days after storage plus 1 day of drying (M3). The storage solution consisted of 75% alcohol/25% water. Sorption and solubility were calculated using these three weights and specimen dimensions. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U Tests (α=5%). Results: The results showed that time, temperature and their interaction influenced the sorption and solubility of the composite (p<0.05). At 60º C, the composite sorption showed an inverse relationship with the curing time (p<0.05). The composite cured for 5 s showed higher sorption for the 40 s or 60 s curing times when compared with all temperatures (p<0.05). Curing times of 20 s and 40 s showed similar sorption data for all temperatures (p>0.05). The 60º C composite temperature led to lower values of sorption for all curing times when compared with the 10º C temperature (p<0.05). The same results were found when comparing 10º C and 25º C (p<0.05), except that the 20 s and 40 s curing times behaved similarly (p>0.05). Solubility was similar at 40 s and 60 s for all temperatures (p>0.05), but was higher at 10º C than at 60º C for all curing times (p<0.05). When the composite was cured at 25º C, similar solubility values were found when comparing the 5 s and 10 s or 20 s and 40 s curing times (p>0.05). Conclusion: In conclusion, higher temperatures or longer curing times led to lower sorption and solubility values for the composite tested; however, this trend was only significant in specific combinations of temperature and

  6. Integrated analysis of low profile unsaturated polyester and vinylester resins cured at low temperatures

    NASA Astrophysics Data System (ADS)

    Cao, Xia

    Unsaturated polyester and vinylester resins are used in a wide variety of applications. These materials provide high structural stability, increased resistance to solvent and temperature, and improved mechanical stability. Low profile additives have been found highly effective in eliminating the polymerization shrinkage of unsaturated polyester resins in high temperature molding processes such as compression molding of SMC and injection molding of BMC. In recent years, the improvement focuses on the development of low temperature and low-pressure fabrication techniques, such as low temperature/low pressure SMC, RTM, SCRIMP, to significantly reduce the tooling cost. However, poor performance of low profile additives and high residual reactivity in low temperature molding processes unavoidably undermine further applications of unsaturated polyester and vinylester resins. Therefore, there is considerable potential for improving the process through greater technical understanding of reaction and volume shrinkage control mechanism in low temperature cure of unsaturated polyester and vinylester resins. An integrated analysis is carried out in this study to investigate the reaction kinetics and shrinkage control of unsaturated polyester or vinylester resins with low profile additives cured at low temperatures. A differential scanning calorimeter (DSC), a Fourier transform infrared spectrometer (FTIR), and a rheometrics dynamic analyzer (RDA) are used to study the reaction kinetics and rheological behaviors. A dilatometer is applied to study the volume change. A scanning electron microscopy (SEM) and an optical microscopy are employed to investigate the structure and morphology evolution during curing. The effects of curing agents including initiator, promoter, and comonomer on the low temperature polymerization are investigated. These experiments are designed to provide information regarding the polymerization mechanism and microstructure evolution throughout the free

  7. Silicon: the health benefits of a metalloid.

    PubMed

    Martin, Keith R

    2013-01-01

    Silicon is the second most abundant element in nature behind oxygen. As a metalloid, silicon has been used in many industrial applications including use as an additive in the food and beverage industry. As a result, humans come into contact with silicon through both environmental exposures but also as a dietary component. Moreover, many forms of silicon, that is, Si bound to oxygen, are water-soluble, absorbable, and potentially bioavailable to humans presumably with biological activity. However, the specific biochemical or physiological functions of silicon, if any, are largely unknown although generally thought to exist. As a result, there is growing interest in the potential therapeutic effects of water-soluble silica on human health. For example, silicon has been suggested to exhibit roles in the structural integrity of nails, hair, and skin, overall collagen synthesis, bone mineralization, and bone health and reduced metal accumulation in Alzheimer's disease, immune system health, and reduction of the risk for atherosclerosis. Although emerging research is promising, much additional, corroborative research is needed particularly regarding speciation of health-promoting forms of silicon and its relative bioavailability. Orthosilicic acid is the major form of bioavailable silicon whereas thin fibrous crystalline asbestos is a health hazard promoting asbestosis and significant impairment of lung function and increased cancer risk. It has been proposed that relatively insoluble forms of silica can also release small but meaningful quantities of silicon into biological compartments. For example, colloidal silicic acid, silica gel, and zeolites, although relatively insoluble in water, can increase concentrations of water-soluble silica and are thought to rely on specific structural physicochemical characteristics. Collectively, the food supply contributes enough silicon in the forms aforementioned that could be absorbed and significantly improve overall human health

  8. Upgrading Metallurgical-Grade Silicon

    NASA Technical Reports Server (NTRS)

    Woerner, L. M.; Moore, E. B.

    1985-01-01

    Closed-loop process produces semiconductor-grade silicon. Metallurgical-grade silicon converted to ultrapure silicon by reacting with hydrogen and silicon tetrahalide to form trihalosilane, purifying this intermediate and again decomposing to high purity silicon in third stage. Heterogeneously and homogeneously nucleated polycrystalline silicon used in semiconductor device applications and in silicon photovoltaic solar cell fabrication.

  9. Silicon Micromachining

    NASA Astrophysics Data System (ADS)

    Elwenspoek, Miko; Jansen, Henri V.

    2004-08-01

    This comprehensive book provides an overview of the key techniques used in the fabrication of micron-scale structures in silicon. Recent advances in these techniques have made it possible to create a new generation of microsystem devices, such as microsensors, accelerometers, micropumps, and miniature robots. The authors underpin the discussion of each technique with a brief review of the fundamental physical and chemical principles involved. They pay particular attention to methods such as isotropic and anisotropic wet chemical etching, wafer bonding, reactive ion etching, and surface micromachining. There is a special section on bulk micromachining, and the authors also discuss release mechanisms for movable microstructures. The book is a blend of detailed experimental and theoretical material, and will be of great interest to graduate students and researchers in electrical engineering and materials science whose work involves the study of micro-electromechanical systems (MEMS).

  10. Improved dispersion of silicon nitride whiskers

    SciTech Connect

    Shih, W.H.; Buchta, M.

    1995-10-01

    To improve the dispersion of silicon nitride whiskers in aqueous suspensions, a standard dispersant used in glass fiber industry, 3-aminopropyltriethoxysilane (APS) is added. It was found that the viscosity of the whisker suspensions is lowered and the centrifuged density of the suspensions is increased with the addition of the APS. The pH values of suspensions before and after the addition of APS indicate that ASP extracts H{sup +} ions from the solutions and the adsorption of APS on silicon nitride is saturated in the experiment. The results indicate a colloidal route to the processing of ceramic composites with silicon nitride whiskers as reinforcements.

  11. Dry-cured ham restructured with fibrin.

    PubMed

    Romero de Ávila, M D; Hoz, L; Ordóñez, J A; Cambero, M I

    2014-09-15

    The viability of a fibrinogen-thrombin system (FT) to bind fresh deboned hams for incorporation in the salting and ripening processes, to produce cured ham, was studied. The effects of the different processing variables (pH, NaCl concentration, temperature and gelation time) on FT, a meat emulsion mixed with FT, fresh pork portions and deboned hams restructured with FT were analyzed. The most stable and firmest fibrin gels were obtained after 6h of adding the FT, with less than 2% NaCl and pH 7-8.4. Scanning electron microscopy of the fibrin gel showed fibrillar structures with a high degree of cross-linking and a high density. Two structures were found in the binding area of restructured meat; one in the central part with similar characteristics to fibrin gels and, another in the area of contact between the meat surfaces, where a filamentous structure connected the fibrin gels with the muscle bundles. PMID:24767091

  12. High-speed curing by laser irradiation

    NASA Astrophysics Data System (ADS)

    Decker, Christian

    1999-05-01

    Laser-assisted processing of multifunctional systems is a very efficient method for achieving high-speed curing of photosensitive resins. With acrylate functionalized monomers and polymers, crosslinking was achieved upon a few millisecond exposure to a UV laser beam, in the presence of a radical-type photoinitiator. The polymerization reaction was followed in real-time by infrared spectroscopy and shown to proceed with long kinetic chains (up to 20,000 functional groups polymerized per initiating radical). An acrylate functionalized polyester proved to be the most reactive system, with formation of a tightly cross-linked and strickly insoluble polymer. Its high sensitivity makes this photoresist particularly well suited for laser direct imaging applications. Similar results have been obtained with epoxy and vinyl ether functionalized polymers, which undergo a fast cationic polymerization in the presence of a photogenerated protonic acid. Interpenetrating polymer networks have been synthetized by laser irradiation of blends of acrylate and epoxy-functionalized oligomers to obtain polymers that combine the elastomeric character of cross-linked polyurethanes and the toughness of epoxy polymers. These laser-sensitive polymers are to be used as photoresists to produce microcircuits, as protective coatings of optical fibers, as recording media in holography and as photocurable resins in stereolithography.

  13. Colloidal characterization of silicon nitride and silicon carbide

    NASA Technical Reports Server (NTRS)

    Feke, Donald L.

    1986-01-01

    The colloidal behavior of aqueous ceramic slips strongly affects the forming and sintering behavior and the ultimate mechanical strength of the final ceramic product. The colloidal behavior of these materials, which is dominated by electrical interactions between the particles, is complex due to the strong interaction of the solids with the processing fluids. A surface titration methodology, modified to account for this interaction, was developed and used to provide fundamental insights into the interfacial chemistry of these systems. Various powder pretreatment strategies were explored to differentiate between true surface chemistry and artifacts due to exposure history. The colloidal behavior of both silicon nitride and carbide is dominated by silanol groups on the powder surfaces. However, the colloid chemistry of silicon nitride is apparently influenced by an additional amine group. With the proper powder treatments, silicon nitride and carbide powder can be made to appear colloidally equivalent. The impact of these results on processing control will be discussed.

  14. Thin silicon solar cells

    SciTech Connect

    Hall, R.B.; Bacon, C.; DiReda, V.; Ford, D.H.; Ingram, A.E.; Cotter, J.; Hughes-Lampros, T.; Rand, J.A.; Ruffins, T.R.; Barnett, A.M.

    1992-12-01

    The silicon-film design achieves high performance by using a dun silicon layer and incorporating light trapping. Optimally designed thin crystalline solar cells (<50 microns thick) have performance advantages over conventional thick devices. The high-performance silicon-film design employs a metallurgical barrier between the low-cost substrate and the thin silicon layer. Light trapping properties of silicon-film on ceramic solar cells are presented and analyzed. Recent advances in process development are described here.

  15. Screening and identification of five serum proteins as novel potential biomarkers for cured pulmonary tuberculosis

    PubMed Central

    Wang, Chong; Wei, Li-Liang; Shi, Li-Ying; Pan, Zhi-Fen; Yu, Xiao-Mei; Li, Tian-Yu; Liu, Chang-Ming; Ping, Ze-Peng; Jiang, Ting-Ting; Chen, Zhong-Liang; Mao, Lian-Gen; Li, Zhong-Jie; Li, Ji-Cheng

    2015-01-01

    Rapid and efficient methods for the determination of cured tuberculosis (TB) are lacking. A total of 85 differentially expressed serum proteins were identified by iTRAQ labeling coupled with two-dimensional liquid chromatography-tandem mass spectrometry (2D LC-MS/MS) analysis (fold change >1.50 or <0.60, P < 0.05). We validated albumin (ALB), Rho GDP-dissociation inhibitor 2 (ARHGDIB), complement 3 (C3), ficolin-2 (FCN2), and apolipoprotein (a) (LPA) using the enzyme-linked immunosorbent assay (ELISA) method. Significantly increased ALB and LPA levels (P = 0.036 and P = 0.012, respectively) and significantly reduced ARHGDIB, C3, and FCN2 levels (P < 0.001, P = 0.035, and P = 0.018, respectively) were observed in cured TB patients compared with untreated TB patients. In addition, changes in ALB and FCN2 levels occurred after 2 months of treatment (P < 0.001 and P = 0.030, respectively). We established a cured TB model with 87.10% sensitivity, 79.49% specificity, and an area under the curve (AUC) of 0.876. The results indicated that ALB, ARHGDIB, C3, FCN2, and LPA levels might serve as potential biomarkers for cured TB. Our study provides experimental data for establishing objective indicators of cured TB and also proposes potential markers for evaluating the efficacy of anti-TB drugs. PMID:26499913

  16. Amorphous silicon carbide films prepared using vaporized silicon ink

    NASA Astrophysics Data System (ADS)

    Masuda, Takashi; Shen, Zhongrong; Takagishi, Hideyuki; Ohdaira, Keisuke; Shimoda, Tatsuya

    2014-03-01

    The deposition of wide-band-gap silicon films using nonvacuum processes rather than conventional vacuum processes is of substantial interest because it may reduce cost. Herein, we present the optical and electrical properties of p-type hydrogenated amorphous silicon carbide (a-SiC:H) films prepared using a nonvacuum process in a simple chamber with a vaporized silicon ink consisting of cyclopentasilane, cyclohexene, and decaborane. The incorporation of carbon into the silicon network induced by the addition of cyclohexene to the silicon ink resulted in an increase in the optical band gap (Eg) of films from 1.56 to 2.11 eV. The conductivity of films with Eg < 1.9 eV is comparable to that of conventional a-SiC:H films prepared using a vacuum process, while the films with Eg > 1.9 eV show lower conductivity than expected because of the incorporation of excess carbon without the formation of Si-C bonds.

  17. Curing of polymer thermosets via click reactions and on demand processes

    NASA Astrophysics Data System (ADS)

    Brei, Mark Richard

    In the first project, an azide functional resin and tetra propargyl aromatic diamines were fabricated for use as a composite matrix. These systems take already established epoxy/amine matrices and functionalize them with click moieties. This allows lower temperatures to be used in the production of a thermoset part. These new systems yield many better mechanical properties than their epoxy/amine derivatives, but their Tgs are low in comparison. The second project investigates the characterization of a linear system based off of the above azide functional resin and a difunctional alkyne. Through selectively choosing catalyst, the linear system can show regioselectivity to either a 1,4-disubstituted triazole, or a 1,5-disubstituted triazole. Without the addition of catalyst, the system produces both triazoles in almost an equal ratio. The differently catalyzed systems were cured and then analyzed by 1H and 13C NMR to better understand the structure of the material. The third project builds off of the utility of the aforementioned azide/alkyne system and introduces an on-demand aspect to the curing of the thermoset. With the inclusion of copper(II) within the azide/alkyne system, UV light is able to catalyze said reaction and cure the material. It has been shown that the copper(II) loading levels can be extremely small, which helps in reducing the copper's effect on mechanical properties The fourth project takes a look at polysulfide-based sealants. These sealants are normally cured via an oxidative reaction. This project took thiol-terminated polysulfides and fabricated alkene-terminated polysulfides for use as a thiol-ene cured material. By changing the mechanism for cure, the polysulfide can be cured via UV light with the use of a photoinitiator within the thiol/alkene polysulfide matrix. The final chapter will focus on a characterization technique, MALDI-TOF, which was used to help characterize the above materials as well as many others. By using MALDI-TOF, the

  18. [Adhesion of dental silicone rubber material to thermoplastic material for mouthguards].

    PubMed

    Yokota, Kayoko

    2010-03-01

    A preliminary study revealed that an autopolymerization addition silicone resilient denture relining material (SI) had excellent shock absorption properties similar to those of thermoplastic materials commonly used for mouthguards (ethylene-vinyl acetate: EVA). The aim of the present study was to examine the bonding strength of SI and EVA using a newly-developed adhesive prototype. Delamination tests and tensile strength tests were performed to compare the bonding strengths of SI on EVA prepared under the following four conditions: 1) Control condition (no preparation; C), 2) Sandblasting (S), 3) Bonding with the adhesive prototype (M), and 4) Combination of sandblasting preparation and bonding with the adhesive prototype (SM). The mean bonding strength (S. D.) of the delamination tests under the C, S, M and SM conditions were 0.167 (0.003) N/mm, 0.273 (0.034) N/mm, 0.242 (0.027) N/mm and 0.506 (0.113) N/mm, respectively. The mean bonding strength (S. D.) of the tensile strength tests under the C, S, M and SM conditions were 0.006 (0.011) MPa, 0.081 (0.105) MPa, 0.231 (0.069) MPa and 0.590 (0.041) MPa, respectively. Two-way analysis of variances and Tukey's HSD test detected that the combination of sandblasting preparation and bonding with the adhesive prototype significantly improved the bonding strength between SI and EVA. The results indicate that the self-curing addition silicone resilient denture relining material may adhere to the thermoplastic material prepared by combined application of sandblasting and the adhesive prototype, suggesting the potential of the dental silicone rubber material as a material for repairing mouthguards in clinical practice. PMID:20415249

  19. Palladium interaction with silicon carbide

    NASA Astrophysics Data System (ADS)

    Gentile, M.; Xiao, P.; Abram, T.

    2015-07-01

    In this work the palladium interaction with silicon carbide is investigated by means of complementary analytical techniques such as thermogravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Thermoscans were carried out on pellets of palladium, α-SiC and β-SiC high purity powders in the temperature range comprised between 293 K and 1773 K, in order to study the effect of temperature on the palladium-silicon carbide reaction. Thermoscans of α-SiC pellets containing 5 at.%Pd show that during differential calorimetry scans three exothermic peaks occurred at 773 K, 1144 K and 1615 K, while thermoscans of β-SiC pellets containing 3 at.%Pd and 5 at.%Pd do not show peaks. For the pellet α-SiC-5 at.%Pd XRD spectra reveal that the first peak is associated with the formation of Pd3Si and SiO2 phases, while the second peak and the third peak are correlated with the formation of Pd2Si phase and the active oxidation of silicon carbide respectively. Thermogravimetry scans show weight gain and weight loss peaks due to the SiO2 phase formation and the active oxidation. Additionally XPS fittings reveal the development of SiCxOy phase during the first exothermic peak up to the temperature of 873 K. The experimental data reveals that alpha silicon carbide is attacked by palladium at lower temperatures than beta silicon carbide and the reaction mechanism between silicon carbide and palladium is strongly affected by silicon carbide oxidation.

  20. Variation of Resin Properties Through the Thickness of Cured Samples

    NASA Technical Reports Server (NTRS)

    1984-01-01

    It is the purpose of this work to gain knowledge of the glassy materials used as matrices in composites and to study the homogeneity resulting from the curing process. An attempt is made to link the glass transition quantitatively with the presence of a given material. Expoxy resins containing various amounts of hardener (TGDDM/DDS system) were cured in a muffle furnace at 473 K for seven hours. The glass transition temperature, T sub g versus weight minus percent of hardener in the epoxy resin were measured. A limit was rapidly reached in T sub g at only two percent hardener. Thus, the glass transition of the fully cured epoxy-amine matrix seems not much different from the epoxide-epoxide cure. The T sub g versus cure-time for the epoxide-epoxide reaction was also studied. My 720 was cured by itself in an oil bath at 473 K for different lengths of time. The T sub g was found to increase exponentially with the cure time, and a maximum T sub g of about 450 K was reached after eleven hours. The reaction was found to be inhibited by running the sample under argon.

  1. Effect of rapid curing procedures on polymer implant materials.

    PubMed

    Gettleman, L; Nathanson, D; Myerson, R L

    1977-01-01

    This investigation of standard curing methods for PMMA implants has demonstrated that alternate means of using the air oven may produce good strength properties along with a considerable degree of porosity, when desired, in a relatively short period of time. Curing of polymers in a pressure pot offers few advantages owing to the length of time required to produce, at best, equivalent strength for the porous materials. The method also poses dangers inherent in the use of superheated salt solution or hot glycerin. The autoclave is widely used in dental offices for sterilizing and will fully and consistently cure polymers within 30 minutes. The best properties for the PMMA resin were achieved with this method (61 MPa or 9,130 p.s.i., tensile strength). The microwave oven has become relatively inexpensive in recent years, and it offers time savings of up to 90 per cent which would be beneficial in implant dentistry or in dental laboratory procedures in general. The exact condition for curing particular polymers must be carefully determined to adjust the time of irradiation in order not to under- or overcure the polymer object. Curing polymers which contain intrinsic foaming agents under pressure conditions slightly reduced the total pore volume. But, pore volume and pore diameter in the large-bead polymers are determined predominantly by packing conditions, not curing conditions. Biologic tolerance to materials cured by these methods in primates is presently being evaluated. PMID:264323

  2. Electron Beam Cured Epoxy Resin Composites for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Janke, Christopher J.; Dorsey, George F.; Havens, Stephen J.; Lopata, Vincent J.; Meador, Michael A.

    1997-01-01

    Electron beam curing of Polymer Matrix Composites (PMC's) is a nonthermal, nonautoclave curing process that has been demonstrated to be a cost effective and advantageous alternative to conventional thermal curing. Advantages of electron beam curing include: reduced manufacturing costs; significantly reduced curing times; improvements in part quality and performance; reduced environmental and health concerns; and improvement in material handling. In 1994 a Cooperative Research and Development Agreement (CRADA), sponsored by the Department of Energy Defense Programs and 10 industrial partners, was established to advance the electron beam curing of PMC technology. Over the last several years a significant amount of effort within the CRADA has been devoted to the development and optimization of resin systems and PMCs that match the performance of thermal cured composites. This highly successful materials development effort has resulted in a board family of high performance, electron beam curable cationic epoxy resin systems possessing a wide range of excellent processing and property profiles. Hundreds of resin systems, both toughened and untoughened, offering unlimited formulation and processing flexibility have been developed and evaluated in the CRADA program.

  3. Photopatternable silicone compositions for electronic packaging applications

    NASA Astrophysics Data System (ADS)

    Harkness, Brian R.; Gardner, Geoff B.; Alger, James S.; Cummings, Michelle R.; Princing, Jennifer; Lee, Yeong; Meynen, Herman; Gonzales, Mario; Vandevelde, Bart; Vanden Bulcke, Mathieu; Winters, Christophe; Beyne, Eric

    2004-05-01

    A growing need for low stress high temperature thick film materials has prompted the development of new spin-coatable photopatternable silicones (Dow Corning WL-5000 series) to assist manufactures in building the next generation of electronic devices. These new negative-tone materials can be easily coated onto electronic substrates and patterned using standard i-line and broadband lithographic processes. Films ranging from 6 to 50 μm have been demonstrated with patterned features resolved to an aspect ratio of less than 1.3. The etched regions provide a sloped sidewall and curved surfaces to facilitate metallization processes. The films are cured at low temperatures (150 to 250°C) to provide low modulus values in the range of 150 to 500 MPa, are inherently hydrophobic, and are based on cure chemistry that is acid free and delivers thermally stable cross-links. As a result, the films show very little shrinkage during thermal cure (~2%), do not require extended high temperature processing, and provide a very low residual stress (<8 MPa). They also show excellent thermal stability and mechanical integrity when exposed to high temperatures. A simple wet process has been developed to facilitate film rework and allow for sacrificial layer applications.

  4. Calcium and α-tocopherol suppress cured-meat promotion of chemically induced colon carcinogenesis in rats and reduce associated biomarkers in human volunteers123

    PubMed Central

    Martin, Océane CB; Santarelli, Raphaelle L; Taché, Sylviane; Naud, Nathalie; Guéraud, Françoise; Audebert, Marc; Dupuy, Jacques; Meunier, Nathalie; Attaix, Didier; Vendeuvre, Jean-Luc; Mirvish, Sidney S; Kuhnle, Gunter CG; Cano, Noel; Corpet, Denis E

    2013-01-01

    Background: Processed meat intake has been associated with increased colorectal cancer risk. We have shown that cured meat promotes carcinogen-induced preneoplastic lesions and increases specific biomarkers in the colon of rats. Objectives: We investigated whether cured meat modulates biomarkers of cancer risk in human volunteers and whether specific agents can suppress cured meat–induced preneoplastic lesions in rats and associated biomarkers in rats and humans. Design: Six additives (calcium carbonate, inulin, rutin, carnosol, α-tocopherol, and trisodium pyrophosphate) were added to cured meat given to groups of rats for 14 d, and fecal biomarkers were measured. On the basis of these results, calcium and tocopherol were kept for the following additional experiments: cured meat, with or without calcium or tocopherol, was given to dimethylhydrazine-initiated rats (47% meat diet for 100 d) and to human volunteers in a crossover study (180 g/d for 4 d). Rat colons were scored for mucin-depleted foci, putative precancer lesions. Biomarkers of nitrosation, lipoperoxidation, and cytotoxicity were measured in the urine and feces of rats and volunteers. Results: Cured meat increased nitroso compounds and lipoperoxidation in human stools (both P < 0.05). Calcium normalized both biomarkers in rats and human feces, whereas tocopherol only decreased nitro compounds in rats and lipoperoxidation in feces of volunteers (all P < 0.05). Last, calcium and tocopherol reduced the number of mucin-depleted foci per colon in rats compared with nonsupplemented cured meat (P = 0.01). Conclusion: Data suggest that the addition of calcium carbonate to the diet or α-tocopherol to cured meat may reduce colorectal cancer risk associated with cured-meat intake. This trial was registered at clinicaltrials.gov as NCT00994526. PMID:24025632

  5. Changes on degree of conversion of dual-cure luting light-cured with blue LED

    NASA Astrophysics Data System (ADS)

    Bandéca, M. C.; El-Mowafy, O.; Saade, E. G.; Rastelli, A. N. S.; Bagnato, V. S.; Porto-Neto, S. T.

    2009-05-01

    The indirect adhesive procedures constitute recently a substantial portion of contemporary esthetic restorative treatments. The resin cements have been used to bond tooth substrate and restorative materials. Due to recently introduction of the self-bonding resin luting cement based on a new monomer, filler and initiation technology has become important to study the degree of conversion of these new materials. In the present work the polymerization reaction and the filler content of dual-cured dental resin cements were studied by means of infra-red spectroscopy (FT-IR) and thermogravimetry (TG). Twenty specimens were made in a metallic mold (8 mm diameter × 1 mm thick) from each of 2 cements, Panavia® F2.0 (Kuraray) and RelyX™ Unicem Applicap (3M/ESPE). Each specimen was cured with blue LED with power density of 500 mW/cm2 for 30 s. Immediately after curing, 24 and 48 h, and 7 days DC was determined. For each time interval 5 specimens were pulverized, pressed with KBr and analyzed with FT-IR. The TG measurements were performed in Netzsch TG 209 under oxygen atmosphere and heating rate of 10°C/min from 25 to 700°C. A two-way ANOVA showed DC (%) mean values statistically significance differences between two cements ( p < 0.05). The Tukey’s test showed no significant difference only for the 24 and 48 h after light irradiation for both resin cements ( p > 0.05). The Relx-Y™ Unicem mean values were significantly higher than Panavia® F 2.0. The degree of conversion means values increasing with the storage time and the filler content showed similar for both resin cements.

  6. Buried oxide layer in silicon

    DOEpatents

    Sadana, Devendra Kumar; Holland, Orin Wayne

    2001-01-01

    A process for forming Silicon-On-Insulator is described incorporating the steps of ion implantation of oxygen into a silicon substrate at elevated temperature, ion implanting oxygen at a temperature below 200.degree. C. at a lower dose to form an amorphous silicon layer, and annealing steps to form a mixture of defective single crystal silicon and polycrystalline silicon or polycrystalline silicon alone and then silicon oxide from the amorphous silicon layer to form a continuous silicon oxide layer below the surface of the silicon substrate to provide an isolated superficial layer of silicon. The invention overcomes the problem of buried isolated islands of silicon oxide forming a discontinuous buried oxide layer.

  7. Electron beam curing of epoxy resins by cationic polymerization

    SciTech Connect

    Janke, C.J.; Dorsey, G.F.; Havens, S.J.

    1996-12-31

    A Cooperative Research and Development Agreement (CRADA) sponsored by the Department of Energy Defense Programs and 10 industrial partners has been established to develop high performance Electron Beam (EB) curable polymer matrix composites. EB curing of composites has a number of advantages over conventional thermal curing. Composites cured by EB have much shorter cure times, lower overall energy requirements, and reduced thermal stresses in the cured part. Furthermore, less expensive tooling can be used since the process occurs at lower temperatures. Preliminary investigations have determined that conventional epoxy resins can be cured at selectable temperatures with high glass transition temperatures (essentially the same as with thermal curing), while still exhibiting equivalent or comparable mechanical properties. A cationic photoinitiator at a concentration of 1-3 parts per hundred of the epoxy resin is required for this process. Gamma cell screening of cationic photoinitiators with bisphenol A, bisphenol F, and cycloaliphatic epoxies demonstrated that diaryliodonium salts of weakly nucleophilic anions such as hexafluoroantimonate are most effective. Diaryliodonium salts were also found to be the most effective initiators for the cationic polymerization of epoxy resins when a high energy/power electron beam accelerator was used as the source of ionizing radiation. For example Dow Tactix 123 (bisphenol A epoxy) containing 3 phr (4-octyloxyphenyl) phenyliodonium hexafluoroantimonate was irradiated at a total dosage of 100 kGy. Glass transition temperature (tan delta) of the cured material as determined by dynamic mechanical analysis was 182{degrees}C as compared to 165{degrees}C for the thermally cured material.

  8. Processing of reaction-bonded silicon carbide without residual silicon phase

    SciTech Connect

    Messner, R.P.; Chiang, Y.M.

    1988-08-01

    Reaction-bonded silicon carbide free of the residual silicon phase that has previously limited upper use temperatures and mechanical properties has been synthesized by the infiltration of carbonaceous preforms using alloyed silicon melts. In this approach, rejection of the alloying components from the primary reacted silicon carbide phase into the remaining liquid forms a secondary refractory silicide, in a potentially broad and controllable range of volume fractions. Dense SiC-MoSi/sub 2/ materials free of residual silicon and residual carbon have been synthesized. In addition to a fully-infiltrated monolith, surface coatings on a carbon body have been synthesized by control of processing parameters. In each, the absence of free silicon and incorporation of the secondary phase is expected to improve mechanical properties. 14 references.

  9. Mathematical Model Of Curing Behavior Of A Polymer

    NASA Technical Reports Server (NTRS)

    Loomis, Willard C.; Beyer, Rodney B.; Liu, Edmund K. S.

    1995-01-01

    Mathematical model predicts selected aspects of chemical, thermal and mechanical responses of polymeric liner and propellant materials during curing process. Predictions made both prior to processing and during process in quasi-real time. Developed specifically for use in designing and analyzing process in which bondline materials (including polymeric liners) and propellant cast and cured in rocket motor. With modifications, model applicable to curing of other polymeric materials. Further development may provide direct "in-line" program for calculations, including comparisons, in real time. This will constitute basis for more sophisticated control of process.

  10. A cure for AIDS: a matter of timing?

    PubMed

    Shytaj, Iart Luca; Savarino, Andrea

    2013-01-01

    Despite the huge clinical success of antiretroviral therapy, several factors such as side effects, requirement of life-long adherence, high cost, incomplete access to therapies and development of drug resistance make the quest for an ultimate cure of HIV/AIDS a worldwide priority of biomedical research. In this respect, several sterilizing or functional cures have been reported in the last years in both non-human primates and humans. This review provides a summary of the main results achieved so far, outlining their strengths as well as their limitations. A synthetic interpretation of these results could be pivotal in order to develop an effective and widely available cure. PMID:24267982

  11. Remnant percolative disorder in highly-cured networks

    SciTech Connect

    Adolf, D.; Hance, B.; Martin, J.E. )

    1993-05-24

    The authors have previously reported viscoelastic measurements demonstrating that fully-cured networks and critical gels exhibit similar relaxation spectra, implying that fully-cured networks are somewhat ill- connected. Here, they present restricted valence percolation simulations of networks well beyond the percolation transition that explicitly display remnant disorder over length scales less than the correlation length of the network. They conclude that the topology of highly-cured networks is not well described by a regular three- dimensional tennis net but is ill-connected over length scales that correspond to relaxation modes of practical interest.

  12. Measuring Vapors To Monitor the State of Cure of a Resin

    NASA Technical Reports Server (NTRS)

    Cramer, Elliott; Perey, Daniel F.; Yost, William T.

    2006-01-01

    A proposed noninvasive method of monitoring the cure path and the state of cure of an epoxy or other resin involves measurement of the concentration( s) of one or more compound(s) in the vaporous effluent emitted during the curing process. The method is based on the following general ideas: (1) The concentrations of the effluent compounds in the vicinity of the curing resin are approximately proportional to the instantaneous rate of curing. (2) As curing proceeds at a given temperature, subsequent decreases in the concentrations are indicative of approaching completion of cure; that is, the lower are the concentrations, the more nearly complete is the cure.

  13. High Efficiency, Low Cost Solar Cells Manufactured Using 'Silicon Ink' on Thin Crystalline Silicon Wafers

    SciTech Connect

    Antoniadis, H.

    2011-03-01

    Reported are the development and demonstration of a 17% efficient 25mm x 25mm crystalline Silicon solar cell and a 16% efficient 125mm x 125mm crystalline Silicon solar cell, both produced by Ink-jet printing Silicon Ink on a thin crystalline Silicon wafer. To achieve these objectives, processing approaches were developed to print the Silicon Ink in a predetermined pattern to form a high efficiency selective emitter, remove the solvents in the Silicon Ink and fuse the deposited particle Silicon films. Additionally, standard solar cell manufacturing equipment with slightly modified processes were used to complete the fabrication of the Silicon Ink high efficiency solar cells. Also reported are the development and demonstration of a 18.5% efficient 125mm x 125mm monocrystalline Silicon cell, and a 17% efficient 125mm x 125mm multicrystalline Silicon cell, by utilizing high throughput Ink-jet and screen printing technologies. To achieve these objectives, Innovalight developed new high throughput processing tools to print and fuse both p and n type particle Silicon Inks in a predetermined pat-tern applied either on the front or the back of the cell. Additionally, a customized Ink-jet and screen printing systems, coupled with customized substrate handling solution, customized printing algorithms, and a customized ink drying process, in combination with a purchased turn-key line, were used to complete the high efficiency solar cells. This development work delivered a process capable of high volume producing 18.5% efficient crystalline Silicon solar cells and enabled the Innovalight to commercialize its technology by the summer of 2010.

  14. Silicon quantum dots for biological applications.

    PubMed

    Chinnathambi, Shanmugavel; Chen, Song; Ganesan, Singaravelu; Hanagata, Nobutaka

    2014-01-01

    Semiconductor nanoparticles (or quantum dots, QDs) exhibit unique optical and electronic properties such as size-controlled fluorescence, high quantum yields, and stability against photobleaching. These properties allow QDs to be used as optical labels for multiplexed imaging and in drug delivery detection systems. Luminescent silicon QDs and surface-modified silicon QDs have also been developed as potential minimally toxic fluorescent probes for bioapplications. Silicon, a well-known power electronic semiconductor material, is considered an extremely biocompatible material, in particular with respect to blood. This review article summarizes existing knowledge related to and recent research progress made in the methods for synthesizing silicon QDs, as well as their optical properties and surface-modification processes. In addition, drug delivery systems and in vitro and in vivo imaging applications that use silicon QDs are also discussed. PMID:23949967

  15. Whisker-reinforced heat-cured dental resin composites: effects of filler level and heat-cure temperature and time.

    PubMed

    Xu, H H

    2000-06-01

    Currently available dental resin composites are inadequate for use in large stress-bearing crown and multiple-unit restorations. The aim of this study was to reinforce heat-cured composites with ceramic whiskers. It was hypothesized that whiskers substantially strengthen heat-cured composites. It was further hypothesized that whisker filler level and heat-cure temperature and time significantly influence composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers for improved retention in the matrix. The whisker filler mass fraction was varied from 0% to 79%, the heat-cure temperature from 80 degrees C to 180 degrees C, and cure time from 10 min to 24 hrs. Flexural strength, work-of-fracture, and fracture toughness of the composites were measured, and specimen fracture surfaces were examined with scanning electron microscopy. Filler level had a significant effect on composite properties. The whisker composite with 70% filler level had a flexural strength in MPa (mean +/- SD; n = 6) of 248 +/- 23, significantly higher than 120 +/- 16 of an inlay/onlay composite control and 123 +/- 21 of a prosthetic composite control (Tukey's multiple comparison test; family confidence coefficient = 0.95). Heat-cure time also played a significant role. At 120 degrees C, the strength of composite cured for 10 min was 178 +/- 17, lower than 236 +/- 14 of composite cured for 3 hrs. The strength of whisker composite did not degrade after water-aging for 100 d. In conclusion, heat-cured composites were substantially reinforced with whiskers. The reinforcement mechanisms appeared to be whiskers bridging and resisting cracks. The strength and fracture toughness of whisker composite were nearly twice those of currently available inlay/onlay and prosthetic composites. PMID:10890718

  16. Polycrystalline silicon study: Low-cost silicon refining technology prospects and semiconductor-grade polycrystalline silicon availability through 1988

    NASA Technical Reports Server (NTRS)

    Costogue, E. N.; Ferber, R.; Lutwack, R.; Lorenz, J. H.; Pellin, R.

    1984-01-01

    Photovoltaic arrays that convert solar energy into electrical energy can become a cost effective bulk energy generation alternative, provided that an adequate supply of low cost materials is available. One of the key requirements for economic photovoltaic cells is reasonably priced silicon. At present, the photovoltaic industry is dependent upon polycrystalline silicon refined by the Siemens process primarily for integrated circuits, power devices, and discrete semiconductor devices. This dependency is expected to continue until the DOE sponsored low cost silicon refining technology developments have matured to the point where they are in commercial use. The photovoltaic industry can then develop its own source of supply. Silicon material availability and market pricing projections through 1988 are updated based on data collected early in 1984. The silicon refining industry plans to meet the increasing demands of the semiconductor device and photovoltaic product industries are overviewed. In addition, the DOE sponsored technology research for producing low cost polycrystalline silicon, probabilistic cost analysis for the two most promising production processes for achieving the DOE cost goals, and the impacts of the DOE photovoltaics program silicon refining research upon the commercial polycrystalline silicon refining industry are addressed.

  17. Maleate/vinyl ether UV-cured coatings: Effects of composition on curing and properties

    SciTech Connect

    Noren, G.K.

    1996-10-01

    The effect of the composition of the maleate polyester and the vinyl ether terminated compound on their UV-curing and properties has been investigated. Linear unsaturated polyester resins based on maleic anhydride and 1,5-pentane diol were synthesized. The molecular weight of the unsaturated polyesters was varied by changing the ratio of maleic anhydride to 1,5-pentane diol and the double bond equivalent weight was varied by replacing maleic anhydride with succinic anhydride. Coating formulations containing these unsaturated polyesters, triethylene glycol divinyl ether and a free radical photoinitiator were crosslinked in the presence of UV light. The coatings were very brittle, exhibiting tensile strengths in the range of 1.5-4.0 MPa and elongations of only 3-7%. Diethyl maleate and isobutyl vinyl ether were effective diluents for reducing viscosity but reduced the cure speed. A vinyl ether urethane oligomer was synthesized and enhanced the flexibility and toughness of the coatings when substituted for triethylene glycol divinyl ether.

  18. New Perspectives in Silicon Micro and Nanophotonics

    NASA Astrophysics Data System (ADS)

    Casalino, M.; Coppola, G.; De Stefano, L.; Calio, A.; Rea, I.; Mocella, V.; Dardano, P.; Romano, S.; Rao, S.; Rendina, I.

    2015-05-01

    In the last two decades, there has been growing interest in silicon-based photonic devices for many optical applications: telecommunications, interconnects and biosensors. In this work, an advance overview of our results in this field is presented. Proposed devices allow overcoming silicon intrinsic drawbacks limiting its application as a photonic substrate. Taking advantages of both non-linear and linear effects, size reduction at nanometric scale and new two-dimensional emerging materials, we have obtained a progressive increase in device performance along the last years. In this work we show that a suitable design of a thin photonic crystal slab realized in silicon nitride can exhibit a very strong field enhancement. This result is very promising for all photonic silicon devices based on nonlinear phenomena. Moreover we report on the fabrication and characterization of silicon photodetectors working at near-infrared wavelengths based on the internal photoemission absorption in a Schottky junction. We show as an increase in device performance can be obtained by coupling light into both micro-resonant cavity and waveguiding structures. In addition, replacing metal with graphene in a Schottky junction, a further improve in PD performance can be achieved. Finally, silicon-based microarray for biomedical applications, are reported. Microarray of porous silicon Bragg reflectors on a crystalline silicon substrate have been realized using a technological process based on standard photolithography and electrochemical anodization of the silicon. Our insights show that silicon is a promising platform for the integration of various optical functionalities on the same chip opening new frontiers in the field of low-cost silicon micro and nanophotonics.

  19. Simulation of SMC compression molding: Filling, curing, and volume changes

    SciTech Connect

    Hill, R.R. Jr.

    1992-01-01

    Sheet molding compound (SMC) is a composite material made from polyester resin, styrene, fiberglass reinforcement, and other additives. It is widely recognized that SMC is a good candidate for replacing sheet metals of automotive body exteriors because SMC is relatively inexpensive, has a high strength-to-density ratio, and has good corrosion resistance. The focus of this research was to develop computer models to simulate the important features of SMC compression molding (i.e., material flow, heat transfer, curing, material expansion, and shrinkage), and to characterize these features experimentally. A control volume/finite element approach was used to obtain the pressure and velocity fields and to compute the flow progression during compression mold filling. The energy equation and a kinetic model were solved simultaneously for the temperature and conversion profiles. A series of molding experiments was conducted to record the flow-front location and material temperature. Predictions obtained from the model were compared to experimental results which incorporated a non-isothermal temperature profile, and reasonable agreement was obtained.

  20. UV-cured adhesives for carbon fiber composite applications

    NASA Astrophysics Data System (ADS)

    Lu, Hsiao-Chun

    monomer. Acetone, tetrahydrofuran (THF) and chloroform were used as well as their anhydrous solvents. The UV exposure times and curing times of new UV-based resins were tested. FT-IR, DSC and DMA were used to investigate structure, glass transition temperatures(Tg) and properties of polymer. In summary, the UV-based adhesive was applied to adhesively bonded hard patch and soft patch repair. In addition, new UV-based resins were formulated for the VaRTM process. The in-field repair can be effective and efficient by using UV adhesives.

  1. Factors affecting dry-cured ham consumer acceptability.

    PubMed

    Morales, R; Guerrero, L; Aguiar, A P S; Guàrdia, M D; Gou, P

    2013-11-01

    The objectives of the present study were (1) to compare the relative importance of price, processing time, texture and intramuscular fat in purchase intention of dry-cured ham through conjoint analysis, (2) to evaluate the effect of dry-cured ham appearance on consumer expectations, and (3) to describe the consumer sensory preferences of dry-cured ham using external preference mapping. Texture and processing time influenced the consumer preferences in conjoint analysis. Red colour intensity, colour uniformity, external fat and white film presence/absence influenced consumer expectations. The consumer disliked hams with bitter and metallic flavour and with excessive saltiness and piquantness. Differences between expected and experienced acceptability were found, which indicates that the visual preference of consumers does not allow them to select a dry-cured ham that satisfies their sensory preferences of flavour and texture. PMID:23816516

  2. 52. photographer unknown 9 October 1935 CURING CONCRETE BLOCKS FOR ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    52. photographer unknown 9 October 1935 CURING CONCRETE BLOCKS FOR BASE OF SOUTH HALF OF SPILLWAY DAM. INSPECTION TUNNEL FORM IN BACKGROUND. - Bonneville Project, Bonneville Dam, Columbia River, Bonneville, Multnomah County, OR

  3. Room-Temperature-Cured Copolymers for Lithium Battery Gel Electrolytes

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B.; Tigelaar, Dean M.

    2009-01-01

    Polyimide-PEO copolymers (PEO signifies polyethylene oxide) that have branched rod-coil molecular structures and that can be cured into film form at room temperature have been invented for use as gel electrolytes for lithium-ion electric-power cells. These copolymers offer an alternative to previously patented branched rod-coil polyimides that have been considered for use as polymer electrolytes and that must be cured at a temperature of 200 C. In order to obtain sufficient conductivity for lithium ions in practical applications at and below room temperature, it is necessary to imbibe such a polymer with a suitable carbonate solvent or ionic liquid, but the high-temperature cure makes it impossible to incorporate and retain such a liquid within the polymer molecular framework. By eliminating the high-temperature cure, the present invention makes it possible to incorporate the required liquid.

  4. Investigation on the electron-beam curing of vinylester resin

    NASA Astrophysics Data System (ADS)

    Xiancong, Huang; Meiwu, Shi; Guotai, Zhou; Hong, Zhou; Xiaopeng, Hao; Chunlan, Zhou

    2008-05-01

    A typical vinylester resin, Derakane 411-350, was electron-beam (EB) cured without initiators. The curing process was investigated by gel-fraction testing, FTIR and Raman spectroscopies. Both dynamic numerical analysis and positron annihilation life spectroscopy were utilized to analyze the microstructure of resin samples irradiated with different doses and dose rates. Resin irradiated with the same dose at a low dose rate achieved a higher degree of cure than those samples irradiated with a high dose rate. Resin irradiated with low dose rates had a lower free-volume fraction with smaller interstices and a more uniform microstructure. The glass-transition temperature of the resin increased with increasing irradiation dose. The mechanical properties of the EB-cured resin confirmed the analysis of changes in microstructure arising from irradiation.

  5. GENERAL ENVIRONMENTAL CORPORATION; CURE ELECTROCOAGULATION TECHNOLOGY: INNOVATIVE TECHNOLOGY EVALUATION REPORT

    EPA Science Inventory

    The CURE electrocoagulation technology was demonstrated under the Superfund Innovative Technology Evaluation (SITE) program at the U.S. Department of Energy (DOE) Rocky Flats Environmental Technology Site (RFETS), where water from the solar evaporation ponds (SEPs) was contaminat...

  6. Desorption and use of saturated lightweight aggregate in internal curing

    NASA Astrophysics Data System (ADS)

    Briatka, P.; Makýš, P.

    2011-09-01

    Roughly 20 years ago there was a brand new concrete-curing concept presented in the U.S. based on providing "extra curing" water from inside the concrete. The extra water shoul be added to concrete during mixing, but is bound to some kind of carrier, so it does not alter the water-cement ratio. This technique, known as Internal Curing (IC) keeps the cement paste moist from the first moment when it normally would start to desiccate and is not mature enough to apply conventional means of curing. The durability and effectiveness of IC depend on the boundary conditions at the site as well as the properties of the carrier - in this case, Lightweight Aggregate (LWA), which, after the water soaking, replaces some part of the Normalweight Aggregate (NWA). This work deals with LWA (available on the European market) in the context of its properties affecting the efficiency of IC.

  7. Global strategies are required to cure and eliminate HBV infection.

    PubMed

    Revill, Peter; Testoni, Barbara; Locarnini, Stephen; Zoulim, Fabien

    2016-04-01

    Chronic HBV infection results in >1 million deaths per year from cirrhosis and liver cancer. No known cure for chronic HBV exists, due in part to the continued presence of transcriptionally active DNA in the nucleus that is not directly targeted by current antiviral therapies. A coordinated approach is urgently needed to advance an HBV cure worldwide, such as those established in the HIV field. We propose the establishment of an International Coalition to Eliminate Hepatitis B Virus (ICE-HBV) to facilitate the formation of international working groups on HBV virology, immunology, innovative tools and clinical trials: to promote awareness and education as well as to drive changes in government policy and ensure funds are channelled to HBV cure research and drug development. With the ICE-HBV in place, it should be possible to enable a HBV cure within the next decade. PMID:26907881

  8. Method for curing polymers using variable-frequency microwave heating

    DOEpatents

    Lauf, R.J.; Bible, D.W.; Paulauskas, F.L.

    1998-02-24

    A method for curing polymers incorporating a variable frequency microwave furnace system designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity is disclosed. By varying the frequency of the microwave signal, non-uniformities within the cavity are minimized, thereby achieving a more uniform cure throughout the workpiece. A directional coupler is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter is provided for measuring the power delivered to the microwave furnace. A second power meter detects the magnitude of reflected power. The furnace cavity may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing. 15 figs.

  9. Method for curing polymers using variable-frequency microwave heating

    DOEpatents

    Lauf, Robert J.; Bible, Don W.; Paulauskas, Felix L.

    1998-01-01

    A method for curing polymers (11) incorporating a variable frequency microwave furnace system (10) designed to allow modulation of the frequency of the microwaves introduced into a furnace cavity (34). By varying the frequency of the microwave signal, non-uniformities within the cavity (34) are minimized, thereby achieving a more uniform cure throughout the workpiece (36). A directional coupler (24) is provided for detecting the direction of a signal and further directing the signal depending on the detected direction. A first power meter (30) is provided for measuring the power delivered to the microwave furnace (32). A second power meter (26) detects the magnitude of reflected power. The furnace cavity (34) may be adapted to be used to cure materials defining a continuous sheet or which require compressive forces during curing.

  10. Light-curing polymers for laser plasma generation

    NASA Astrophysics Data System (ADS)

    Loktionov, E. Y.; Protasov, Y. S.; Protasov, Y. Y.; Telekh, V. D.

    2015-07-01

    Solid rather than liquid media are used in pulsed laser plasma generators despite sophisticated transportation and dosing system need for a long-term operation. Liquid media could be more preferable due to transfer and dosing (down to 10-14 L) being well developed, but plasma generation of those results in intense droplet formation and kinetic energy losses. Combination of liquids transportation advantages and solids plasma generation efficiency might resolve this trade-off. Liquid-to-solid transition can be induced by cooling down to sublimation temperature, thermo-, photo- or electron induced polymerization (curing). Light cured polymers seem to be very useful as active media for plasma generators, since they can be solidified very fast (ca. 30 ms) just before impact. We considered experimentally several UV- curing polymer and mixtures ablation regimes and supply schemes for laser plasma generation. The best results were obtained for liquid polymer at high-power pulsed irradiation matching curing optimum wavelength.

  11. Epoxy foams using multiple resins and curing agents

    DOEpatents

    Russick, Edward M.; Rand, Peter B.

    2000-01-01

    An epoxy foam comprising a plurality of resins, a plurality of curing agents, at least one blowing agent, at least one surfactant and optionally at least one filler and the process for making. Preferred is an epoxy foam comprising two resins of different reactivities, two curing agents, a blowing agent, a surfactant, and a filler. According to the present invention, an epoxy foam is prepared with tailorable reactivity, exotherm, and pore size by a process of admixing a plurality of resins with a plurality of curing agents, a surfactant and blowing agent, whereby a foamable mixture is formed and heating said foamable mixture at a temperature greater than the boiling temperature of the blowing agent whereby said mixture is foamed and cured.

  12. Investigation of Adhesive Bond Cure Conditions using Nonlinear Ultrasonic Methods

    NASA Technical Reports Server (NTRS)

    Berndt, Tobias P.; Green, Robert E., Jr.

    1999-01-01

    The objective of this presentation is to investigate various cure conditions of adhesive bonds using nonlinear ultrasonic methods with water coupling. Several samples were used to obtain normal incidence, oblique incidence, and wave mixing.

  13. Synthesis and properties of transparent cycloaliphatic epoxy-silicone resins for opto-electronic devices packaging

    NASA Astrophysics Data System (ADS)

    Gao, Nan; Liu, WeiQu; Yan, ZhenLong; Wang, ZhengFang

    2013-01-01

    Cycloaliphatic epoxy-silicone resins were successfully synthesized through a two-step reaction route: (і) hydrosilylation of 1,3,5,7-tetramethylcyclotetrasiloxane (TMCTS) and 1,2-epoxy-4-vinyl-cyclohexane (VCMX), (іі) blocking of unreacted Sisbnd H in (і) with n-butanol. The molecular structures of the cycloaliphatic epoxy-silicone resins were characterized by Fourier transform infrared (FT-IR) and nuclear magnetic resonance (1H NMR and 29Si NMR). High grafting efficiencies of epoxy groups were confirmed by 1H NMR combined with weighting results, indicating over 90 mol% of cycloaliphatic epoxy were grafted on the silicone resins. Subsequently, Sisbnd H groups from TMCTS were almost totally consumed after the blocking reactions. In comparison with commercial available cycloaliphatic epoxy resin 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (ERL-4221) cured by MHHPA, the cured cycloaliphatic epoxy-silicone resins exhibited better thermal stability, lower water absorption and higher UV/thermal resistance. Moreover, the characteristics of transmittance (>90%, 800 nm), 5 wt.% mass loss temperature (>330 °C) and no yellowing during thermal aging at 120 °C or UV aging for 288 h of the cured cycloaliphatic epoxy-silicone resins, made them possible for power light-emitting diode (LED) encapsulants, or other packaging materials, like optical lenses, and electronic sealings.

  14. Feasibility study for the development of low temperature curing adhesives

    NASA Technical Reports Server (NTRS)

    Green, H. E.; Sutherland, J. D.; Sheppard, C. H.

    1974-01-01

    The feasibility of a new approach for the development of stable, easily handled, room temperature (293 K - 311 K) curing adhesives was studied and demonstrated. The work concentrated on a family of unsaturated amide/ester resins. Twelve candidate resins were synthesized and tested for completeness of cure at room temperature, adhesion to aluminum and titanium, shear strength, moisture resistance and heat stability. The three most promising candidate resins were selected and recommended for further development.

  15. Electron Beam-Cure Polymer Matrix Composites: Processing and Properties

    NASA Technical Reports Server (NTRS)

    Wrenn, G.; Frame, B.; Jensen, B.; Nettles, A.

    2001-01-01

    Researchers from NASA and Oak Ridge National Laboratory are evaluating a series of electron beam curable composites for application in reusable launch vehicle airframe and propulsion systems. Objectives are to develop electron beam curable composites that are useful at cryogenic to elevated temperatures (-217 C to 200 C), validate key mechanical properties of these composites, and demonstrate cost-saving fabrication methods at the subcomponent level. Electron beam curing of polymer matrix composites is an enabling capability for production of aerospace structures in a non-autoclave process. Payoffs of this technology will be fabrication of composite structures at room temperature, reduced tooling cost and cure time, and improvements in component durability. This presentation covers the results of material property evaluations for electron beam-cured composites made with either unidirectional tape or woven fabric architectures. Resin systems have been evaluated for performance in ambient, cryogenic, and elevated temperature conditions. Results for electron beam composites and similar composites cured in conventional processes are reviewed for comparison. Fabrication demonstrations were also performed for electron beam-cured composite airframe and propulsion piping subcomponents. These parts have been built to validate manufacturing methods with electron beam composite materials, to evaluate electron beam curing processing parameters, and to demonstrate lightweight, low-cost tooling options.

  16. Characterization of dental composite curing kinetics using dynamic light scattering

    NASA Astrophysics Data System (ADS)

    Wells-Gray, Elaine M.; Kirkpatrick, Sean J.; Sakaguchi, Ron L.

    2009-02-01

    Polymer resin composites are a class of widely used restorative dental materials that undergo a complex polymerization curing process that has been the subject of substantial research. This study uses speckle correlation methods based on dynamic light scattering as a tool to monitor the rate and extent of dental composite polymerization during and after photo-curing. Thin disc-shaped samples (<2mm) were constructed using composite consisting of 50:50 BisGMA/TEGDMA resin, quartz silica filler particles, and camphorquinone as photo-initiator. A 633 nm HeNe laser beam was used to probe the top surface of the sample via a backscattered speckle pattern, while the bottom surface was illuminated with a halogen curing lamp (peak wavelength=470nm) to initiate the polymerization reaction. The speckle patterns were recorded with a CCD camera, and stored as a 'speckle cube' for post processing. Correlation values of the intensity fluctuation were calculated on a pixel-by-pixel basis for pairs of subsequent speckle images and then ensemble averaged. Results show a sharp decrease in correlation at the onset of curing, indicating a large amount of double bond conversion and movement within the composite. Correlation values then quickly increase, eventually reaching a plateau near unity, indicating cessation of molecular rearrangement. The kinetic behavior demonstrated by our correlation curves are in good agreement with curing data found in the literature, and demonstrate the usefulness of this technique for monitoring dental composite curing.

  17. Vacuum Ultraviolet Curing of Low-k Organosilicate Dielectrics

    NASA Astrophysics Data System (ADS)

    Zheng, Huifeng

    The goal of this project is to optimize the vacuum-ultraviolet spectrum to identify those wavelengths that will have the most beneficial effect on improving dielectric properties and minimizing damage. To do this, the effects of vacuum-ultraviolet radiation (VUV) on organosilicate glass (SiCOH) will be examined. Changes to the electrical, chemical and mechanical properties of low-k organosilicate dielectrics induced by vacuum-ultraviolet radiation are investigated. VUV-generated changes to the permittivity and dielectric thickness are measured with both capacitance-voltage characteristics and a reflectometer. FTIR measurements are utilized to find the effect of VUV irradiation on chemical properties of SiCOH and XPS with nanoindentation measurements are used to investigate changes in mechanical properties. Measurements of the band gap and defect-state concentrations of SiCOH are made with VUV spectroscopy. These investigations are used to optimize VUV or UV/VUVexposure conditions to determine the wavelengths and intensities that can mitigate processing-induced damage. Thus, a "UV/VUV curing" process can be established and comparisons between UV/VUV curing and conventional industrial UV curing will be made. Investigations have shown that a combined UV/VUV curing could overcome some drawbacks of industrially UV curing and improve properties of dielectrics more efficiently than UV curing.

  18. [Research on structure and UV curing behaviors of novel cardanol-based unsaturated resins using FTIR spectrum analysis method].

    PubMed

    Li, Shou-Hai; Yang, Xue-Juan; Li, Mei; Huang, Kun; Xia, Jian-Ling

    2013-10-01

    Two dissimilar cardanol-based unsaturated resin monomers were prepared via simple ring-opening and etherification reaction by utilizing the reactivity between phenolic hydroxyl and epoxy group with the aid of cardanol as raw material. The transformations of different groups were characterized using Fourier transform infrared (FTIR) during the synthesis process, the resin monomers' structure was further analyzed using the 1H-nuclear magnetic resonance (1H-NMR) and gel permeation chromatography (GPC), and the UV curing behaviors of resin monomers were studied by means of FTIR method. In addition, the thermal stability of UV cured resin monomers were also tested by thermogravimetric analysis (TGA). The molecular structure analysis demonstrated that these two target products were successfully synthesized. UV curing behaviors analysis showed that the prepared cardanol-based unsaturated resin monomers could reach ultimate curing level within 30 s. TGA results showed that the molecular structure and the content of double bond had critical influence on their thermal stability. The main initial thermal decomposition temperature of these two cured resin monomers was all above 350 degrees C. PMID:24409711

  19. Effect of Curing Temperature and Composition on the Performance Properties of Saltstone - 12473

    SciTech Connect

    Reigel, Marissa M.; Harbour, John R.; Edwards, Tommy B.

    2012-07-01

    When freshly mixed Saltstone is placed into a vault at the Savannah River Site, the heat of hydration produced during curing causes the temperature of the grout to increase. It is not uncommon for the temperature of the grout to increase by 30 to 50 deg. C above the starting temperature depending on the vault size and location, environmental conditions and pour schedule. For example, temperatures measured by thermocouples in one cell have exceeded 70 deg. C. The elevated temperatures, once reached, can extend for weeks or even months. Recent studies at Savannah River National Laboratory (SRNL) have shown that curing simulated Saltstone mixes at elevated temperatures can lead to reduced compressive strength and dynamic Young's modulus as well as increased total porosity when compared to the same grout mixes cured at 20 deg. C. Samples cured at 60 deg. C can have hydraulic conductivities approximately 600 times greater than samples cured at 20 deg. C. Previous studies have shown that the 60 deg. C cured mix had a dynamic Young's modulus that was half that of the mix cured at 20 deg. C. However, high temperature curing may not always have negative effects on the performance properties of the grout. These results indicate that higher curing temperatures can significantly alter the performance properties that are inputs for the Saltstone Performance Assessment. The Saltstone formulation (mix design) must produce a grout waste form that meets both placement and performance properties. A statistically designed set of mixes was developed to determine key process and compositional factors that affect the performance properties of Saltstone grout. A total of 27 mixes were batched and tested. There are eight baseline mixes that contain high and low values of aluminate concentration, varying w/p ratio, and varying fly ash content in the premix. Each of the eight mixes was cured at 22, 40 and 60 deg. C. The three additional reference mixes batched at the beginning, middle and

  20. Curing of epoxy resins with 1-DI(2-chloroethoxyphosphinyl) methyl-2,4 and -2,6-diaminobenzene

    NASA Technical Reports Server (NTRS)

    Mikroyannidis, J. A.; Kourtides, D. A.

    1983-01-01

    Fire resistant compositions were prepared using 1-di(2-chloroethoxy-phosphinyl)methyl-2,4- and -2,6-diaminobenzene (DCEPD) as a curing agent for typical epoxy resins such as EPON 828 (Shell), XD 7342 (Dow), and My 720 (Ciba Geigy). In addition, compositions of these three epoxy resins with common curing agents such as m-phenylenediamine (MPD) or 4,4'-diaminodiphenylsulphone (DDS) were studied to compare their reactions with those of DCEPD. The reactivity of the three curing agents toward the epoxy resins, measured by differential calorimetry (DSC), was of the order MPD DCEPD DDS. The relatively lower reactivity of DCEPD toward epoxy resins was attributed to electronic effects.

  1. Thick-film materials for silicon photovoltaic cell manufacture

    NASA Technical Reports Server (NTRS)

    Field, M. B.

    1977-01-01

    Thick film technology is applicable to three areas of silicon solar cell fabrication; metallization, junction formation, and coating for protection of screened ohmic contacts, particularly wrap around contacts, interconnection and environmental protection. Both material and process parameters were investigated. Printed ohmic contacts on n- and p-type silicon are very sensitive to the processing parameters of firing time, temperature, and atmosphere. Wrap around contacts are easily achieved by first printing and firing a dielectric over the edge and subsequently applying a low firing temperature conductor. Interconnection of cells into arrays can be achieved by printing and cofiring thick film metal pastes, soldering, or with heat curing conductive epoxies on low cost substrates. Printed (thick) film vitreous protection coatings do not yet offer sufficient optical uniformity and transparency for use on silicon. A sprayed, heat curable SiO2 based resin shows promise of providing both optical matching and environmental protection.

  2. Interdigitated design of a thermoelectric microgenerator based on silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Donmez, I.; Salleras, M.; Calaza, C.; Santos, J. D.; Gadea, G.; Morata, A.; Dávila, D.; Tarancón, A.; Fonseca, L.

    2015-05-01

    Silicon nanowires thermoelectric properties are much better than those of silicon bulk. Taking advantage of silicon microfabrication techniques and compatibilizing the device fabrication with the CVD-VLS silicon nanowire growth, we present a thermoelectric microgenerator based on silicon nanowire arrays with interdigitated structures which enhance the power density compared to previous designs presented by the authors. The proposed design features a thermally isolated silicon platform on the silicon device layer of an SOI silicon wafer. This silicon platform has vertical walls exposing <111< planes where gold nanoparticles are deposited by galvanic displacement. These gold nanoparticles act as seeds for the silicon nanowires. The growth takes place in a CVD with silane precursor, and uses the Vapor-Solid-Liquid synthesis. Once the silicon nanowires are grown, they connect the silicon platform with the silicon bulk. The proposed thermoelectric generator is unileg, which means that only one type of semiconductor is used, and the second connection is made through a metal. In addition, to improve the thermal isolation of the silicon platform, multiple trenches of silicon nanowire arrays are used, up to a maximum of nine. After packaging the device with nanowires, we are able to measure the Seebeck voltage and the power obtained with different operation modes: harvesting mode, where the bottom device is heated up, and the silicon platform is cooled down by natural or forced convection, and test mode, where a heater integrated on the silicon platform is used to produce a thermal gradient.

  3. EB curing and cure grafting of novel CT monomer complexes: comparison with UV process and extension of the technique to thiol-ene systems

    NASA Astrophysics Data System (ADS)

    Dennis, Gary R.; Garnett, John L.; Zilic, Elvis

    2004-09-01

    EB curing and cure grafting of charge transfer (CT) monomer complexes is discussed. The complexes studied involve representative donors (D) such as vinyl ethers and typical acceptors (A) including maleates, maleimides and acrylates also oligomers. The EB results are compared with UV curing and cure grafting of the same complexes. The work has been extended to include EB/UV curing and cure grafting of thiol-ene systems. The significance of these results in the potential commercial application of these complexes is discussed.

  4. In vitro wear of composite with varied cure, filler level, and filler treatment.

    PubMed

    Condon, J R; Ferracane, J L

    1997-07-01

    For the clinical wear of composite filing materials to be reduced, compositional factors such as degree of cure, filler level, and silanation level should be optimized. An oral-wear-stimulating machine was used to explore the effects of these factors on abrasion and attrition wear as well as on opposing enamel wear. The composites were made from Sr glass (1-2 micron avg) and a 50/50 Bis-GMA/TEGDMA resin. Series I (A-D, E) were light-cured (Triad II) for 9, 12, 25, and 40 sec/side to produce degree of cure (DC) as measured by FTIR of 56, 60, 61, and 63%, respectively. E received an additional heat cure (120 degrees C for 10 min) to reach a DC of 66%. Series II (D, F-I) were filled to 62, 53, 48, 37, and 28 vol%, respectively. In series III (D, J-M), the portion of fillers treated with a silane coupler (MPS) was 100, 80, 60, 40, and 20%, respectively. Samples were cycled 50,000 times against an enamel antagonist in a poppy seed/PMMA slurry in the oral wear simulator to produce abrasion (load = 20 N) and attrition (load = 70 N) simultaneously. Wear depth (micron: n = 5) was measured by profilometry. Results for each series were analysed by ANOVA/Turkey's (p < or = 0.05). The wear depths did reflect cure values, though only the abrasion difference for E < A was significant. Greater wear was correlated with lower filler levels (r2 = 0.88; p < 0.05), significantly increasing below 48 vol% (G). Wear increased linearly as the percent of silane-treated fillers was reduced (r2 = 0.99; p < 0.05). Abrasion and attrition did not differ significantly for any composite. Wear of the opposing enamel was largely unchanged by these factors. Compositional factors including degree of cure, filler level, and silanation directly affected the wear resistance of dental composites evaluated in an oral wear simulator. PMID:9207774

  5. Relationship between ecophysiological factors, growth and ochratoxin A contamination of dry-cured sausage based matrices.

    PubMed

    Rodríguez, Alicia; Capela, Daniela; Medina, Ángel; Córdoba, Juan J; Magan, Naresh

    2015-02-01

    could help to make appropriate technological modifications during the sausage ripening process. Thus, our findings may help in informed decision-making in relation to temperature and salt additions at the beginning of processing/curing. Such changes may favour colonisation of starter cultures over OTA producing Penicillia and minimise OTA contamination risks in dry-cured sausages. This may be then effectively incorporated into the hygienic production system in the framework of HACCP. PMID:25437060

  6. Microhardness of composite resin cured through different primary tooth thicknesses with different light intensities and curing times: In vitro study

    PubMed Central

    Mazhari, Fatemeh; Ajami, Behjatolmolok; Moazzami, Saied Mostafa; Baghaee, Bahareh; Hafez, Bahareh

    2016-01-01

    Objective: The aim of this study was to evaluate the effect of increased exposure time and light intensity on microhardness of cured composite through different thicknesses of tooth structure in primary teeth. Materials and Methods: One hundred and seventy cylindrical resin composite specimens were prepared. All specimens were divided into 17 experimental and control groups. “Light-emitting diode” light curing unit (LCU) applied directly or through 1, 2, and 3 mm thicknesses tooth slices for experimental groups. The irradiation protocols were 25 and 50 s at 650 mW/cm2 and 15 and 30 s at 1100 mW/cm2. The “quartz-tungsten-halogen” LCU (400 mW/cm2) for 40 s was used in control group. Microhardness was measured by the Vickers hardness test. Results: Indirectly cured specimens and those cured through a 1 mm thick tooth structure, an increase in intensity caused hardness drop. In the specimens cured through 2 and 3 mm thick tooth structures, increased intensity and/or exposure time did not show any appropriate changes on microhardness. Conclusion: Irradiation through a 1.0 mm thick tooth slice resulted in reduced microhardness although it was still within the clinically acceptable level. The hardness values of the specimens cured through 2 or 3 mm thick tooth slices fell below the clinically acceptable level even after doubling the exposure time and/or light intensity. PMID:27095897

  7. Optical characterization of polysilazane based silica thin films on silicon substrates

    NASA Astrophysics Data System (ADS)

    Ricci, Pier Carlo; Gulleri, Gianluca; Fumagalli, Francesco; Carbonaro, Carlo Maria; Corpino, Riccardo

    2013-01-01

    In this work polysilazane based silica thin films grown on multilayer structures of different ultra-thin barriers (UTBs) on silicon substrates were studied. The silica thin films were obtained by polysilazane spin coating deposition (also called SOD, spin-on dielectrics) upon different UTB liners (silicon nitride or silicon dioxide). By curing the SOD with thermal treatments the polysilazane is converted into silica thin films. The degree of conversion to SiO2 was analyzed and the oxide local structure was studied in terms of Sisbnd Osbnd Si bridges by FTIR spectroscopy. Steady state and time resolved luminescence were applied to further characterize the oxide structure, the substrate-silica interfaces and the presence of defects. The analysis revealed the presence of dioxasilirane, dbnd Si(O2), and silylene, dbnd Si:, defect centers in the samples grown on silicon nitride UTB, while these defects are not observed in samples grown on silicon oxide UTB.

  8. Consequences of Atomic Oxygen Interaction With Silicone and Silicone Contamination on Surfaces in Low Earth Orbit

    NASA Technical Reports Server (NTRS)

    Banks, Bruce A.; deGroh, Kim K.; Rutledge, Sharon K.; Haytas, Christy A.

    1999-01-01

    The exposure of silicones to atomic oxygen in low Earth orbit causes oxidation of the surface, resulting in conversion of silicone to silica. This chemical conversion increases the elastic modulus of the surface and initiates the development of a tensile strain. Ultimately, with sufficient exposure, tensile strain leads to cracking of the surface enabling the underlying unexposed silicone to be converted to silica resulting in additional depth and extent of cracking. The use of silicone coatings for the protection of materials from atomic oxygen attack is limited because of the eventual exposure of underlying unprotected polymeric material due to deep tensile stress cracking of the oxidized silicone. The use of moderate to high volatility silicones in low Earth orbit has resulted in a silicone contamination arrival at surfaces which are simultaneously being bombarded with atomic oxygen, thus leading to conversion of the silicone contaminant to silica. As a result of these processes, a gradual accumulation of contamination occurs leading to deposits which at times have been up to several microns thick (as in the case of a Mir solar array after 10 years in space). The contamination species typically consist of silicon, oxygen and carbon. which in the synergistic environment of atomic oxygen and UV radiation leads to increased solar absorptance and reduced solar transmittance. A comparison of the results of atomic oxygen interaction with silicones and silicone contamination will be presented based on the LDEF, EOIM-111, Offeq-3 spacecraft and Mir solar array in-space results. The design of a contamination pin-hole camera space experiment which uses atomic oxygen to produce an image of the sources of silicone contamination will also be presented.

  9. Process for producing silicon

    DOEpatents

    Olson, Jerry M.; Carleton, Karen L.

    1984-01-01

    A process for producing silicon includes forming an alloy of copper and silicon and positioning the alloy in a dried, molten salt electrolyte to form a solid anode structure therein. An electrically conductive cathode is placed in the electrolyte for plating silicon thereon. The electrolyte is then purified to remove dissolved oxides. Finally, an electrical potential is applied between the anode and cathode in an amount sufficient to form substantially pure silicon on the cathode in the form of substantially dense, coherent deposits.

  10. Thermal processing of EVA encapsulants and effects of formulation additives

    SciTech Connect

    Pern, F.J.; Glick, S.H.

    1996-05-01

    The authors investigated the in-situ processing temperatures and effects of various formulation additives on the formation of ultraviolet (UV) excitable chromophores, in the thermal lamination and curing of ethylene-vinyl acetate (EVA) encapsulants. A programmable, microprocessor-controlled, double-bag vacuum laminator was used to study two commercial as formulated EVA films, A9918P and 15295P, and solution-cast films of Elvaxrm (EVX) impregnated with various curing agents and antioxidants. The results show that the actual measured temperatures of EVA lagged significantly behind the programmed profiles for the heating elements and were affected by the total thermal mass loaded inside the laminator chamber. The antioxidant Naugard P{trademark}, used in the two commercial EVA formulations, greatly enhances the formation of UV-excitable, short chromophores upon curing, whereas other tested antioxidants show little effect. A new curing agent chosen specifically for the EVA formulation modification produces little or no effect on chromophore formation, no bubbling problems in the glass/EVX/glass laminates, and a gel content of {approximately}80% when cured at programmed 155{degrees}C for 4 min. Also demonstrated is the greater discoloring effect with higher concentrations of curing-generated chromophores.

  11. Electrodeposition of molten silicon

    DOEpatents

    De Mattei, Robert C.; Elwell, Dennis; Feigelson, Robert S.

    1981-01-01

    Silicon dioxide is dissolved in a molten electrolytic bath, preferably comprising barium oxide and barium fluoride. A direct current is passed between an anode and a cathode in the bath to reduce the dissolved silicon dioxide to non-alloyed silicon in molten form, which is removed from the bath.

  12. Ionic Liquid-Modified Thermosets and Their Nanocomposites: Dispersion, Exfoliation, Degradation, and Cure

    NASA Astrophysics Data System (ADS)

    Throckmorton, James A.

    This dissertation explores the application of a room temperature ionic liquid (RTIL) to problems in the chemistry, processing, and modification of thermosetting polymers. In particular, the solution properties and reaction chemistry of 1-ethyl-3-methyl imidazolium dicyanamide (EMIM-DCN) are applied to problems of nanoparticle dispersion and processing, graphite exfoliation, cyanate ester (CE) cure, and the environmental degradation of CEs. Nanoparticle Dispersion: Nanocomposite processing can be simplified by using the same compound as both a nanoparticle solvent and an initiator for polymerization. This dual-function molecule can be designed both for solvent potential and reaction chemistry. EMIM-DCN, previously shown by our lab to act as an epoxy initiator, is used in the synthesis of silica and acid expanded graphite composites. These composites are then characterized for particle dispersion and physical properties. Individual particle dispersion of silica nanocomposites is shown, and silica nanocomposites at low loading show individual particle dispersion and improved modulus and fracture toughness. GNP nanocomposites show a 70% increase in modulus along with a 10-order of magnitude increase in electrical conductivity at 6.5 vol%, and an electrical percolation threshold of 1.7 vol%. Direct Graphite Exfoliation By Laminar Shear: This work presents a laminar-shear alternative to chemical processing and chaotic flow-fields for the direct exfoliation of graphite and the single-pot preparation of nanocomposites. Additionally, we develop the theory of laminar flow through a 3-roll mill, and apply that theory to the latest developments in the theory of graphite interlayer shear. The resulting nanocomposite shows low electrical percolation (0.5 vol%) and low thickness (1-3 layer) graphite/graphene flakes. Additionally, the effect of processing conditions by rheometry and comparison with solvent-free conditions reveal the interactions between processing and matrix

  13. Cure characterization and process modeling of soy-based composites

    NASA Astrophysics Data System (ADS)

    Liang, Guanghui

    This work deals with cure characteristics of soy-based resin system, fabrication of pultruded soy-based composites, and analysis of flexible polymeric foams. In the first part of this work, the cure kinetics and rheology of the soy-based resin system were studied. The cure kinetics models of the different resin formulations were developed. A neural network based model was developed to provide an efficient approach for rheology characterization. The analytical expressions of cure kinetics and rheology developed for soy-based epoxy resin system can be readily applied into numerical modeling of composite manufacturing processes. In the second part of this work, the analytical cure kinetics model developed for the soy-based epoxy resin system was applied in pultrusion process modeling. A finite element model was established and implemented in the commercial ABAQUS code to predict the temperature and the degree of cure of the pultruded soy-based composites. An on-line cure monitoring system was developed to measure the temperature profile in the pultrusion die. The numerical results show good agreement with the experimental findings. The soy-based resin system is a viable alternative to petroleum based epoxy resins for the pultrusion process. In the third part of this work, a novel constitutive model for elastomeric foam material based on neural network is presented. The neural network approach provides an efficient constitutive model and can be readily implemented into commercial finite element packages. It has the potential to be used in various applications related to analysis of polymeric foam materials.

  14. Black Silicon Enhanced Thin Film Silicon Photovoltaic Devices

    SciTech Connect

    Martin U. Pralle; James E. Carey

    2010-07-31

    SiOnyx has developed an enhanced thin film silicon photovoltaic device with improved efficiency. Thin film silicon solar cells suffer from low material absorption characteristics resulting in poor cell efficiencies. SiOnyx’s approach leverages Black Silicon, an advanced material fabricated using ultrafast lasers. The laser treated films show dramatic enhancement in optical absorption with measured values in excess of 90% in the visible spectrum and well over 50% in the near infrared spectrum. Thin film Black Silicon solar cells demonstrate 25% higher current generation with almost no impact on open circuit voltage as compared with representative control samples. The initial prototypes demonstrated an improvement of nearly 2 percentage points in the suns Voc efficiency measurement. In addition we validated the capability to scale this processing technology to the throughputs (< 5 min/m2) required for volume production using state of the art commercially available high power industrial lasers. With these results we clearly demonstrate feasibility for the enhancement of thin film solar cells with this laser processing technique.

  15. Silicones containing pendant biocides for antifouling coatings.

    PubMed

    Thomas, Johnson; Choi, Seok-Bong; Fjeldheim, Renae; Boudjouk, Philip

    2004-01-01

    The preparation of biocide-incorporated silicone coatings for antifouling/fouling release applications is described. The biocide Triclosan (5-chloro-2-(2, 4-dichlorophenoxy) phenol) was modified with alkenyl moieties and incorporated into a silicone backbone through covalent bonds. The presence of the biocide on the coating surface was expected to deter fouling organisms from attaching to the surface of the coating. Allyl glycidyl ether was used to provide crosslink functionalities. Resins were cured using vinyl-terminated polydimethylsiloxane for hydrosilyl functionality and 1, 3-cyclohexane-bis (methylamine) for epoxy crosslinking functionality. Coatings were characterized by static water contact angle measurements and dynamic mechanical thermal analysis. Synthetic control over the incorporation of crosslink functionalities within the polymer resin allowed tuning of the surface of the coating and of mechanical properties. Resistance to macrofouling was tested by static immersion tests in the Indian River Lagoon at the Florida Institute of Technology from 15 October 2003 to 13 November 2003. Preliminary results showed that the coatings prepared from biocide-incorporated silicones with the appropriate bulk modulus significantly reduced macrofouling. PMID:15621644

  16. Physicochemical Characteristics of Beef Jerky Cured with Salted-fermented Anchovy and Shrimp

    PubMed Central

    Kim, Gap-Don; Go, Gwang-woong; Lim, Hyun-Jung; Jung, Eun-Young; Seo, Hyun-Woo; Jeong, Jin-Yeon; Joo, Seon-Tea; Yang, Han-Sul

    2014-01-01

    The aim of this study is to evaluate the availability of salted and fermented fish (SFF) including salted and fermented anchovy (SFA) and shrimp (SFS) as a marinade of beef jerky. In curing solutions, half (SFA 1 and SFS 1) or whole (SFA 2 and SFS 2) salt-water was replaced with SFF juices. Higher water activity (aw) was found in the beef jerky cured with SFFs than the control (C) (p< 0.05). The SFFs had the effect of causing a decrease in hardness and an increase in cohesiveness (p<0.05). Among the treatment samples, springiness was the highest in SFA2 and SFS2 (p<0.05) and the lowest values of Warner-Bratzler shear force were found in SFA1 and SFA2 (p<0.05). The SFFs also had the effect of increasing the flavor of the sensory properties; however, color measurements from both the instrumental surface color (L*, a*, b*, chroma, and hue angle) and color of sensory evaluation were decreased by addition of SFFs (p<0.05). Therefore, we conclude the SFFs can improve the texture and sensory properties of the beef jerky. In particular, the SFS is a good ingredient for the curing solution. However, studies are still needed on improving the aw, pH, and surface color of the beef jerky to apply the SFFs for making beef jerky. PMID:26760751

  17. Properties and osteoblast cytocompatibility of self-curing acrylic cements modified by glass fillers.

    PubMed

    Lopes, P; Garcia, M P; Fernandes, M H; Fernandes, M H V

    2013-11-01

    Materials filled with a silicate glass (MSi) and a borate glass (MB) were developed and compared in terms of their in vitro behavior. The effect of filler composition and concentration (0, 30, 40 and 50 wt%) on the curing parameters, residual monomer, water uptake, weight loss, bioactivity, mechanical properties (bending and compression) and osteoblast cytocompatibility was evaluated. The addition of bioactive glass filler significantly improved the cements curing parameters and the mechanical properties. The most relevant results were obtained for the lower filler concentration (30 t%) a maximum flexural strength of 40.4 Pa for MB3 and a maximum compressive strength of 95.7 MPa for MSi3. In vitro bioactivity in acellular media was enhanced by the higher glass contents in the cements. Regarding the biological assessment, the incorporation of the silicate glass significantly improved osteoblast cytocompatibility, whereas the presence of the borate glass resulted in a poor cell response. Nevertheless it was shown that the surviving cells on the MB surface were in a more differentiated stage compared to those growing over non-filled poly(methyl methacrylate). Results suggest that the developed formulations offer a high range of properties that might be interesting for their use as self-curing cements. PMID:22918184

  18. Optimal cure cycle design of a resin-fiber composite laminate

    NASA Technical Reports Server (NTRS)

    Hou, Jean W.; Hou, Tan H.; Sheen, Jeen S.

    1987-01-01

    Fibers reinforced composites are used in many applications. The composite parts and structures are often manufactured by curing the prepreg or unmolded material. The magnitudes and durations of the cure temperature and the cure pressure applied during the cure process have significant consequences on the performance of the finished product. The goal of this study is to exploit the potential of applying the optimization technique to the cure cycle design. The press molding process of a polyester is used as an example. Various optimization formulations for the cure cycle design are investigated. Recommendations are given for further research in computerizing the cure cycle design.

  19. Posttherapeutic Cure Criteria in Chagas' Disease: Conventional Serology followed by Supplementary Serological, Parasitological, and Molecular Tests

    PubMed Central

    Silva, A. R.; Do Bem, V. A. L.; Bahia, M. T.; Martins-Filho, O. A.; Dias, J. C. P.; Albajar-Viñas, P.; Torres, R. M.; Lana, M.

    2012-01-01

    We performed a critical study of conventional serology, followed by supplementary serological, parasitological, and molecular tests, to assess the response to etiologic treatment of Chagas' disease. A group of 94 Chagas' disease patients treated with benznidazole at least 10 years earlier were evaluated from the laboratory and clinical points of view. When conventional serology (enzyme-linked immunosorbent assay [ELISA], indirect immunofluorescence [IIF], and indirect hemagglutination [IHA]) and classic criteria (consistent results with any two of the three tests) or more rigorous criteria (consistent results from the three tests) were used, 10.6% and 8.5% of patients were considered treated and cured (TC) by classic and rigorous criteria, respectively. Patients were then evaluated using supplementary (recombinant ELISA and Trypanosoma cruzi excreted-secreted antigen blotting [TESA-blot]), parasitological (hemoculture), and molecular (PCR) tests. The results of recombinant ELISA were similar to those with the rigorous criterion (three consistent test results). The TESA-blot group showed a higher percentage (21.3%) of negative results than the groups defined by either cure criterion. Hemoculture and PCR gave negative results for all treated and cured (TC) patients, regardless of the criterion used. Recombinant ELISA and TESA-blot tests showed negative results for 70% and 87.5% of the patients categorized as TC by the classic and three-test criteria, respectively. For patients with discordant conventional serology, the supplementary serological and molecular tests were the decisive factor in determining therapeutic failure. Clinical evaluation showed that 62.5% of TC patients presented with the indeterminate form of the disease. Additionally, treated patients with negative TESA-blot results should be reevaluated later with all methodologies used here to verify whether TESA-blot is a reliable way to determine early parasitological cure of Chagas' disease. PMID

  20. The effect of saliva decontamination procedures on dentin bond strength after universal adhesive curing

    PubMed Central

    Kim, Jayang; Hong, Sungok; Choi, Yoorina

    2015-01-01

    Objectives The purpose of this study was to investigate the effectiveness of multiple decontamination procedures for salivary contamination after curing of a universal adhesive on dentin bond strength according to its etch modes. Materials and Methods Forty-two extracted bovine incisors were trimmed by exposing the labial dentin surfaces and embedded in cylindrical molds. A universal adhesive (All-Bond Universal, Bisco) was used. The teeth were randomly divided into groups according to etch mode and decontamination procedure. The adhesive was applied according to the manufacturer's instructions for a given etch mode. With the exception of the control groups, the cured adhesive was contaminated with saliva for 20 sec. In the self-etch group, the teeth were divided into three groups: control, decontamination with rinsing and drying, and decontamination with rinsing, drying, and adhesive. In the etch-and-rinse group, the teeth were divided into four groups: control, decontamination with rinsing and drying, decontamination with rinsing, drying, and adhesive, and decontamination with rinsing, drying, re-etching, and reapplication of adhesive. A composite resin (Filtek Z350XT, 3M ESPE) was used for filling and was cured on the treated surfaces. Shear bond strength was measured, and failure modes were evaluated. The data were subjected to one-way analysis of variation and Tukey's HSD test. Results The etch-and-rinse subgroup that was decontaminated by rinse, drying, re-etching, and reapplication of adhesive showed a significantly higher bond strength. Conclusions When salivary contamination occurs after curing of the universal adhesive, additional etching improves the bond strength to dentin. PMID:26587416