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Sample records for urea combustion route

  1. A simple urea-based route to ternary metal oxynitride nanoparticles

    SciTech Connect

    Gomathi, A.; Reshma, S.; Rao, C.N.R.

    2009-01-15

    Ternary metal oxynitrides are generally prepared by heating the corresponding metal oxides with ammonia for long durations at high temperatures. In order to find a simple route that avoids use of gaseous ammonia, we have employed urea as the nitriding agent. In this method, ternary metal oxynitrides are obtained by heating the corresponding metal carbonates and transition metal oxides with excess urea. By this route, ternary metal oxynitrides of the formulae MTaO{sub 2}N (M=Ca, Sr or Ba), MNbO{sub 2}N (M=Sr or Ba), LaTiO{sub 2}N and SrMoO{sub 3-x}N{sub x} have been prepared successfully. The oxynitrides so obtained were generally in the form of nanoparticles, and were characterized by various physical techniques. - Graphical abstract: Nanoparticles of ternary metal oxynitrides can be synthesized by means of urea route. Given is the TEM image of the nanoparticles of CaTaO{sub 2}N so obtained and the insets show the SAED pattern and HREM image of the nanoparticles.

  2. Urea

    Integrated Risk Information System (IRIS)

    EPA / 635 / R - 10 / 005F www.epa.gov / iris TOXICOLOGICAL REVIEW OF UREA ( CAS No . 57 - 13 - 6 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) July 2011 U.S . Environmental Protection Agency Washington , DC ii DISCLAIMER This document has been reviewed in acc

  3. Photocatalytic degradation of methylene blue on Sn-doped titania nanoparticles synthesized by solution combustion route

    SciTech Connect

    Bhange, P.D.; Awate, S.V.; Gholap, R.S.; Gokavi, G.S.; Bhange, D.S.

    2016-04-15

    Highlights: • Series of Sn-doped titania nanoparticles were prepared by solution combustion synthesis method. • Sn-doped titania nanoparticles were tested for degradation of MB under UV light irradiation. • The maximum Sn doping in the TiO{sub 2} lattice is found to be less than 10%. • The crystallite size decreases with increase in the Sn content. • The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the photocatalytic activity. - Abstract: Series of tin-doped titania nanoparticles with varying tin content in the range 0–20 mol% have been prepared by solution combustion synthesis route using urea as a fuel. The structure, surface morphology and optical activity of Sn-doped TiO{sub 2} nanoparticles were investigated by various analytical techniques such as powder XRD, SEM, TEM, UV–vis and N{sub 2} adsorption study. The crystalline structures of the various phases were studied by rietveld refinement of the XRD data. The photocatalytic performance of Sn-doped titania nanoparticles were tested for degradation of MB under UV and visible light irradiation. The results reveal that the photocatalytic activity increases with increase in tin content which may be due to decrease in crystallite size with increase in surface area. The doping of Sn into TiO{sub 2} lattice hinders the recombination of electrons and holes thus enhance the quantum efficiency of photocatalytic reaction.

  4. Synthesis of nanocrystalline yttria doped ceria powder by urea-formaldehyde polymer gel auto-combustion process

    SciTech Connect

    Biswas, M.; Prabhakaran, K. . E-mail: kp2952002@yahoo.co.uk; Gokhale, N.M.; Sharma, S.C.

    2007-04-12

    Nanocrystalline yttria doped ceria powder has been prepared by auto-combustion of a transparent gel formed by heating an aqueous acidic solution containing methylol urea, urea, cerium(III) nitrate and yttrium(III) nitrate. The TGA and DSC studies showed the combustion reaction of the gel initiated at 225 deg. C and completed within a short period of time. XRD spectrum of the combustion product reveals the formation of phase pure cubic yttria doped ceria during the combustion process. Loose agglomerate of yttria doped ceria particle obtained by the combustion reaction could be easily deagglomerated by planetary ball milling and the powder obtained contains particles in the size range of 0.05-3.3 {mu}m with D {sub 50} value of 0.13 {mu}m. The powder particles are aggregate of nanocrystallites with a wide size range of 14-105 nm. Pellets prepared by pressing the yttria doped ceria powder sintered to 95.2% TD at 1400 deg. C.

  5. Design and synthesis of urea-linked aromatic oligomers--a route towards convoluted foldamers.

    PubMed

    Mousseau, James J; Xing, Liyan; Tang, Nathalie; Cuccia, Louis A

    2009-10-05

    Herein we report the design and synthesis of crescent-shaped and helical urea-based foldamers, the curvature of which is controlled by varying the constituent building blocks and their connectivity. These oligomers are comprised of two, three or five alternating aromatic heterocycles (pyridazine, pyrimidine or pyrazine) and methyl-substituted aromatic carbocycles (tolyl, o-xylyl or m-xylyl) connected together through urea linkages. A crescent-shaped conformational preference is encoded within these pi-conjugated urea-linked oligomers based on intramolecular hydrogen bonding and steric interactions; the degree of curvature is tuned by the urea connectivity to the heterocycles and the aryl groups. NMR characterization of these foldamers confirms the intramolecular hydrogen-bonded conformation expected (Z,E configuration of the urea bond) in both the pyridazyl and pyrimidyl foldamers in solution. An X-ray crystal structure of the N(3),N(6)-diisobutylpyridazine-4,6-diamine-o-tolyl urea-linked foldamer (4) confirms the presence of N-H...N hydrogen bonds between the heterocyclic nitrogen atom and the free hydrogen of the urea linkage. Additionally, the tolyl methyl group interacts unfavourably with the urea carbonyl oxygen, thus destabilising the alternate planar conformation.

  6. Synthesis of mesoporous silica-alumina materials via urea-templated sol-gel route and their catalytic performance for THF polymerization

    NASA Astrophysics Data System (ADS)

    Ge, Yuanyuan; Jia, Zhiqi; Gao, Chunguang; Gao, Pengfei; Zhao, Lili; Zhao, Yongxiang

    2014-10-01

    A series of mesoporous silica-alumina materials was successfully synthesized by using urea as a low-cost template via sol-gel routes. The characterization results showed that the employ of urea enhanced the porosity of the silica-alumina materials and made the pore size distributions become narrower. The specific surface area, pore volume and pore diameter of SAU-X firstly increased and then decreased as the urea concentration increased from 0 to 60 wt %, and the maximums were obtained at 40 wt % urea concentration. All samples were tested for the THF polymerization. Among them, SAU-40 exhibited the highest activity and the longest catalyst life due to its superior porosity.

  7. Superconductivity, structure visualization, mechanical strength promotion and Raman spectra of hafnium-doped-123-YBCO synthesized via urea precursor route

    NASA Astrophysics Data System (ADS)

    Elsabawy, Khaled M.

    2011-08-01

    The pure YBCO (YBa2Cu3O7) and its variant hafnium containing superconductors with general formula: Y1-xHfxBa2Cu3Oz, where x = 0.1, 0.2, and 0.4 mole, respectively, were synthesized by solution route using urea as precursor forming agent. X-ray measurements indicated that Hf4+ ions have a negligible effect on the main crystalline structure and substitute Y-sites successfully in lattice structure of 123-YBCO at low levels of hafnium doping (x = 0.1 → 0.2 mole). From SE-microscopy mapping and EDX elemental analysis Hf4+ was detected qualitatively with good approximation to the actual molar ratio but not observed at 123-YBCO grain boundaries which confirm that hafnium (IV) has diffused regularly into material bulk of superconducting 123-YBCO-phase at low levels of concentrations. Structure visualization of Hf-doped-123-YBCO was made to confirm success of hafnium substitutions inside crystal lattice on Y-sites of 123-YBCO superconductors. Hafnium dopings affected sharply on the main vibrating modes of YBCO regime particularly on the apical oxygen (O4) vibrational mode A1g. Magnetic susceptibility measurements proved that hafnium dopings have strong effect on the transport properties of YBCO-composites regime. Hafnium promotes mechanical tensile coefficient recording maxima 35.7 MPa for x = 0.4 mole.

  8. Route to chaos for combustion instability in ducted laminar premixed flames

    NASA Astrophysics Data System (ADS)

    Kabiraj, Lipika; Saurabh, Aditya; Wahi, Pankaj; Sujith, R. I.

    2012-06-01

    Complex thermoacoustic oscillations are observed experimentally in a simple laboratory combustor that burns lean premixed fuel-air mixture, as a result of nonlinear interaction between the acoustic field and the combustion processes. The application of nonlinear time series analysis, particularly techniques based on phase space reconstruction from acquired pressure data, reveals rich dynamical behavior and the existence of several complex states. A route to chaos for thermoacoustic instability is established experimentally for the first time. We show that, as the location of the heat source is gradually varied, self-excited periodic thermoacoustic oscillations undergo transition to chaos via the Ruelle-Takens scenario.

  9. Urea metabolism in plants.

    PubMed

    Witte, Claus-Peter

    2011-03-01

    Urea is a plant metabolite derived either from root uptake or from catabolism of arginine by arginase. In agriculture, urea is intensively used as a nitrogen fertilizer. Urea nitrogen enters the plant either directly, or in the form of ammonium or nitrate after urea degradation by soil microbes. In recent years various molecular players of plant urea metabolism have been investigated: active and passive urea transporters, the nickel metalloenzyme urease catalyzing the hydrolysis of urea, and three urease accessory proteins involved in the complex activation of urease. The degradation of ureides derived from purine breakdown has long been discussed as a possible additional metabolic source for urea, but an enzymatic route for the complete hydrolysis of ureides without a urea intermediate has recently been described for Arabidopsis thaliana. This review focuses on the proteins involved in plant urea metabolism and the metabolic sources of urea but also addresses open questions regarding plant urea metabolism in a physiological and agricultural context. The contribution of plant urea uptake and metabolism to fertilizer urea usage in crop production is still not investigated although globally more than half of all nitrogen fertilizer is applied to crops in the form of urea. Nitrogen use efficiency in crop production is generally well below 50% resulting in economical losses and creating ecological problems like groundwater pollution and emission of nitric oxides that can damage the ozone layer and function as greenhouse gasses. Biotechnological approaches to improve fertilizer urea usage bear the potential to increase crop nitrogen use efficiency.

  10. Landslide remediation on Ohio State Route 83 using clean coal combustion by-products

    SciTech Connect

    Payette, R.; Chen, X.Y.; Wolfe, W.; Beeghly, J.

    1995-12-31

    In the present work, a flue gas desulfurization (FGD) by-product was used to reconstruct the failed portion of a highway embankment. The construction process and the stability of the repaired embankment are examined. State Route 83 in Cumberland, Ohio has been damaged by a slow moving slide which has forced the Ohio Department of Transportation to repair the roadway several times. In the most recent repair FGD by-products obtained from American Electric Power`s Tidd PFBC plant were used to construct a wall through the failure plane to prevent further slippage. In order to evaluate the utility of using coal combustion by-products in this type of highway project the site was divided into three test sections. In the first repair section, natural soil removed form the slide area was recompacted and replaced according to standard ODOT construction practices. In the second section the natural soil was field mixed with the Tidd PFBC ash in approximately equal proportions. The third section was all Tidd ash. The three test sections were capped by a layer of compacted Tidd ash or crushed stone to provide a wearing surface to allow ODOT to open the roadway before applying a permanent asphalt surface. Measurement of slope movement as well as water levels and quality have begun at the site in order to evaluate long term project performance. The completion of this project should lead to increased acceptance of FGD materials in construction projects. Monetary savings will be realized in avoiding some of the disposal costs for the waste, as well as in the reduced reliance on alternative engineering materials.

  11. Banyan latex: a facile fuel for the multifunctional properties of MgO nanoparticles prepared via auto ignited combustion route

    NASA Astrophysics Data System (ADS)

    Kumar, M. R. Anil; Nagaswarupa, H. P.; Anantharaju, K. S.; Gurushantha, K.; Pratapkumar, C.; Prashantha, S. C.; Shashishekar, T. R.; Nagabhushana, H.; Sharma, S. C.; Vidya, Y. S.; Daruka Prasad, B.; Vivek Babu, C. S.; Vishnu Mahesh, K. R.

    2015-09-01

    MgO nanoparticles (MNPs) were prepared by a solution combustion route using banyan tree (BT) latex and glycine as fuels. The powder x-ray diffraction results indicate the formation of a single cubic phase and the crystallite size obtained from transmission electron microscopy was found to be ˜10-15 nm. Scanning electron microscopy result reveals spherical-shaped particles obtained with BT latex. However, in a chemical route, porous and agglomerated particles were obtained. The energy band gap of MNPs obtained using BT latex and a chemical route were found to be in the range 4.85-5.0 eV. Photoluminescence peaks observed at 473, 514, and 588 nm when excited at 433 nm, which were attributed to surface defects. The enhanced photocatalytic activities of spherical MgO were due to smaller crystallite size, higher surface defects, dye sensitization, and capability to reduce the electron-hole pair recombination. Further, green-synthesized MNPs exhibit superior antifungal activity against various plant pathogens. The present studies demonstrated a green engineering route for the synthesis of multifunctional MNPs using BT latex.

  12. Nanocrystalline particle coatings on alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route.

    PubMed

    Kim, Sang Woo; Jung, Young Mi

    2007-11-01

    We have suggested ultrafine particle coating processes for preparing nanocrystalline particle coated alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route, which is environmentally friendly. The nanometric ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of alumina was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The synthetic crystalline size and morphology were greatly dependent on pH and temperature. By adding ammonium aluminum sulfate solution dispersed the alpha-alumina core particle in the ammonium hydrogen carbonate aqueous solution, nanometric AACH with a size of 5 nm was tightly bonded and uniformly coated on the core powder due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of aluminum oxide. The synthetic precursor rapidly converted to amorphous- and y-alumina phase without significant change in the morphological features through decomposition of surface complexes and thermal-assisted phase transformation. As a result, the nanocrystalline polymorphic particle coated alpha-alumina core powders with highly uniform distribution were prepared from the route of carbonate precipitation and thermal-assisted combustion.

  13. Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

    NASA Astrophysics Data System (ADS)

    Murugesan, C.; Perumal, M.; Chandrasekaran, G.

    2014-09-01

    Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 409 cm-1 assigned to octahedral site which are shifted to 590 cm-1 and 412 cm-1 for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties.

  14. Hydrogen-Assisted IC Engine Combustion as a Route to Hydrogen Implementation

    SciTech Connect

    Andre Boehman; Daniel Haworth

    2008-09-30

    The 'Freedom Car' Initiative announced by the Bush Administration has placed a significant emphasis on development of a hydrogen economy in the United States. While the hydrogen-fueled fuel-cell vehicle that is the focus of the 'Freedom Car' program would rely on electrochemical energy conversion, and despite the large amount of resources being devoted to its objectives, near-term implementation of hydrogen in the transportation sector is not likely to arise from fuel cell cars. Instead, fuel blending and ''hydrogen-assisted'' combustion are more realizable pathways for wide-scale hydrogen utilization within the next ten years. Thus, a large potential avenue for utilization of hydrogen in transportation applications is through blending with natural gas, since there is an existing market for natural-gas vehicles of various classes, and since hydrogen can provide a means of achieving even stricter emissions standards. Another potential avenue is through use of hydrogen to 'assist' diesel combustion to permit alternate combustion strategies that can achieve lower emissions and higher efficiency. This project focused on developing the underlying fundamental information to support technologies that will facilitate the introduction of coal-derived hydrogen into the market. Two paths were envisioned for hydrogen utilization in transportation applications. One is for hydrogen to be mixed with other fuels, specifically natural gas, to enhance performance in existing natural gas-fueled vehicles (e.g., transit buses) and provide a practical and marketable avenue to begin using hydrogen in the field. A second is to use hydrogen to enable alternative combustion modes in existing diesel engines, such as homogeneous charge compression ignition, to permit enhanced efficiency and reduced emissions. Thus, this project on hydrogen-assisted combustion encompassed two major objectives: (1) Optimization of hydrogen-natural gas mixture composition and utilization through laboratory

  15. Structural and optical properties of ZnO: K synthesized by sol-gel auto-combustion route

    SciTech Connect

    Krithiga, R. Sankar, S.; Subhashree, G.; Bharathi, R. Niruban

    2015-06-24

    The structural and optical behavior of ZnO and ZnO doped with K synthesized by solution combustion route is reported in this article. The XRD patterns confirm the substitution of K atoms into ZnO lattice. There are no secondary peaks observed in the XRD patterns. The band gap of the K doped samples show a red shift on comparison with the bandgap of ZnO. The photoluminescence spectral study discloses the quenching behavior of UV emission and the aggrandizing blue emission when K content increases. The rich presence of defects is confirmed from the optical analysis and a practical mechanism, involving Zn{sub i} for the origin of the blue emission in ZnO is discussed here.

  16. Spray-combustion synthesis: efficient solution route to high-performance oxide transistors.

    PubMed

    Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P H; Bedzyk, Michael J; Ferragut, Rafael; Marks, Tobin J; Facchetti, Antonio

    2015-03-17

    Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations.

  17. Spray-combustion synthesis: Efficient solution route to high-performance oxide transistors

    PubMed Central

    Yu, Xinge; Smith, Jeremy; Zhou, Nanjia; Zeng, Li; Guo, Peijun; Xia, Yu; Alvarez, Ana; Aghion, Stefano; Lin, Hui; Yu, Junsheng; Chang, Robert P. H.; Bedzyk, Michael J.; Ferragut, Rafael; Marks, Tobin J.; Facchetti, Antonio

    2015-01-01

    Metal-oxide (MO) semiconductors have emerged as enabling materials for next generation thin-film electronics owing to their high carrier mobilities, even in the amorphous state, large-area uniformity, low cost, and optical transparency, which are applicable to flat-panel displays, flexible circuitry, and photovoltaic cells. Impressive progress in solution-processed MO electronics has been achieved using methodologies such as sol gel, deep-UV irradiation, preformed nanostructures, and combustion synthesis. Nevertheless, because of incomplete lattice condensation and film densification, high-quality solution-processed MO films having technologically relevant thicknesses achievable in a single step have yet to be shown. Here, we report a low-temperature, thickness-controlled coating process to create high-performance, solution-processed MO electronics: spray-combustion synthesis (SCS). We also report for the first time, to our knowledge, indium-gallium-zinc-oxide (IGZO) transistors having densification, nanoporosity, electron mobility, trap densities, bias stability, and film transport approaching those of sputtered films and compatible with conventional fabrication (FAB) operations. PMID:25733848

  18. Structural and magnetic properties of hexagonal barium ferrite synthesized through the sol-gel combustion route

    NASA Astrophysics Data System (ADS)

    Zahari, Muhammad Hanif bin; Guan, Beh Hoe; Chuan, Lee Kean

    2016-11-01

    Single-phased barium ferrite with the chemical formula of BaFe12O19 was synthesized through the sol-gel combustion method by using stoichiometric amounts of the precursor materials Structural characterizations were done through X-ray diffraction (XRD) analysis. The magnetic properties were determined through vibrating sample magnetometer (VSM) measurement. Pure single-phased BaFe12O19 was successfully obtained at 850°C without any accompanying secondary phases. This was reflected in the magnetic measurements where a prominent hysteresis was displayed by the synthesized powder. Values as high as 50.37 emu/g, 2984.9 G and 26.15 emu/g was observed for the magnetic saturation, coercivity and remanence respectively.

  19. Combustion

    NASA Technical Reports Server (NTRS)

    Bulzan, Dan

    2007-01-01

    An overview of the emissions related research being conducted as part of the Fundamental Aeronautics Subsonics Fixed Wing Project is presented. The overview includes project metrics, milestones, and descriptions of major research areas. The overview also includes information on some of the emissions research being conducted under NASA Research Announcements. Objective: Development of comprehensive detailed and reduced kinetic mechanisms of jet fuels for chemically-reacting flow modeling. Scientific Challenges: 1) Developing experimental facilities capable of handling higher hydrocarbons and providing benchmark combustion data. 2) Determining and understanding ignition and combustion characteristics, such as laminar flame speeds, extinction stretch rates, and autoignition delays, of jet fuels and hydrocarbons relevant to jet surrogates. 3) Developing comprehensive kinetic models for jet fuels.

  20. Comparison of structural and luminescence properties of Dy{sub 2}O{sub 3} nanopowders synthesized by co-precipitation and green combustion routes

    SciTech Connect

    Chandrasekhar, M.; Nagabhushana, H.; Sudheerkumar, K.H.; Dhananjaya, N.; Sharma, S.C.; Kavyashree, D.; Shivakumara, C.; Nagabhushana, B.M.

    2014-07-01

    Highlights: • Dy{sub 2}O{sub 3} nanopowders were prepared by co-precipitation and eco-friendly green combustion route using plant latex. • Both the products show excellent chromaticity coordinates in the white region, which were quite useful for white LED’s. • Thermoluminescence response of the Dy{sub 2}O{sub 3} product prepared by green synthesis was higher when compared to co-precipitation route. • Structural parameters of Dy{sub 2}O{sub 3} were estimated using Rietveld refinement. • The development of nanosize materials using eco-friendly resources was an attractive non-hazardous chemical route. - Abstract: Dysprosium oxide (Dy{sub 2}O{sub 3}) nanopowders were prepared by co-precipitation (CP) and eco-friendly green combustion (GC) routes. SEM micrographs prepared by CP route show smooth rods with various lengths and diameters while, GC route show porous, agglomerated particles. The results were further confirmed by TEM. Thermoluminescence (TL) responses of the nanopowder prepared by both the routes were studied using γ-rays. A well resolved glow peak at 353 °C along with less intense peak at 183 °C was observed in GC route while, in CP a single glow peak at 364 °C was observed. The kinetic parameters were estimated using Chen’s glow peak route. Photoluminescence (PL) of Dy{sub 2}O{sub 3} shows peaks at 481, 577, 666 and 756 nm which were attributed to Dy{sup 3+} transitions of {sup 4}F{sub 9/2}⟶{sup 6}H{sub 15/2}, {sup 6}H{sub 13/2}, {sup 6}H{sub 11/2} and {sup 6}H{sub 9/2}, respectively. Color co-ordinate values were located in the white region as a result the product may be useful for the fabrication of WLED’S.

  1. New pseudopeptidic cross-linker containing urea bonds: study of its degradation routes in aqueous media using capillary electrophoresis-mass spectrometry.

    PubMed

    Pérez, Paloma; Simó, Carolina; Neusüss, Christian; Pelzing, Matthias; San Roman, Julio; Cifuentes, Alejandro; Gallardo, Alberto

    2006-03-01

    An accelerated degradation study has been performed on TLT, a pseudopeptide that includes esterified tyrosine and lysine linked by urea bonds, as well as on their derivatives, i.e., a dimethacrylic cross-linker (DMTLT) and a poly(dimethylacrylamide) cross-linked with DMTLT. The monitoring and analytical characterization has been carried out by capillary electrophoresis-mass spectrometry (CE-MS), using ion trap and time-of-flight MS analyzers. Several degradative species have been identified, and a kinetic analysis of the variation of their concentration with time has been obtained. During the initial stages of degradation, there is a competition between hydrolysis of the ester groups and cyclization by nucleophilic attack of the NHs of the urea groups to the carbonyl ester group. At higher degradation time (weeks or months), evidences of backbone breakdown, including urea hydrolysis, have been found.

  2. A facile green synthesis of Sm2O3 nanoparticles via microwave-assisted urea precipitation route and their optical properties

    NASA Astrophysics Data System (ADS)

    Xue, Hansong; Zhang, Weina; Li, Xinyu; You, Xiaochang; Rao, Jinsong; Pan, FuSheng

    2017-03-01

    Samarium oxide (Sm2O3) nanoparticles with a narrow size distribution were successfully synthesized by microwave-assisted using urea as precipitant without surfactant or template. The Sm2O3 particles were characterized using X-ray diffraction analysis, field-emission scanning electron microscopy, field-emission transmission electron microscopy and ultraviolet-visible-near-infrared spectrophotometer. The results showed that the samples prepared with different concentration of urea had different particle sizes. When the concentration of urea was 1.2 mol/L, the sample had the smallest particle size. A possible mechanism for the formation of the nanoparticles was proposed. Optical properties of Sm2O3 nanoparticles showed that the nanoparticles had a strong absorption property in the deep ultraviolet region between 200 nm and 270 nm. [Figure not available: see fulltext.

  3. Investigation of structural and luminescence properties of Ho(3+) doped YAlO3 nanophosphors synthesized through solution combustion route.

    PubMed

    Premkumar, H B; Ravikumar, B S; Sunitha, D V; Nagabhushana, H; Sharma, S C; Savitha, M B; Mohandas Bhat, S; Nagabhushana, B M; Chakradhar, R P S

    2013-11-01

    YAlO3:Ho(3+) (1-5mol%) nanophosphors have been prepared by solution combustion route using oxalyl dihydrazide (ODH) as a fuel. The final product was well characterized by powder X-ray diffraction (PXRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), UV-Vis, etc. PXRD patterns confirm the formation of highly crystalline orthorhombic phase structure. SEM and TEM studies show the particles are dumbbell shape, highly agglomerated and nano-size (∼30nm). The direct energy band gap (Eg) values estimated from Tauc's relation were found to be in the range 5.76-5.99eV. Photoluminescence (PL) studies show green (540 and 548nm) and red (645 and 742nm) emissions upon excited at 452nm wavelength. The emission peaks at ∼742 and 645nm was associated with the transitions of (5)F4→(5)I7 and (5)F5→(5)I8 respectively. The higher energy bands located at 540 and 548nm were associated with (5)F4, (5)S2→(5)I8 transitions. Thermoluminescence (TL) studies of γ-irradiated YAlO3:Ho(3+) (1-5mol%) show two glow peaks at 223 and 325°C recorded at a heating rate of 2.5°Cs(-1). The 223°C glow peak follow linear behavior up to 1kGy and after that, it showed sub-linearity. Up to 1kGy, the phosphor is quite useful in radiation dosimetry. The kinetic parameters (E, b and s) were estimated from glow peak shape method. The CIE coordinate values lies within the green region. Therefore, the present phosphors may have potential application in WLEDs as green phosphor.

  4. Influence of fuel on phase formation of ZnFe{sub 2}O{sub 4} prepared by self-propagated combustion route

    SciTech Connect

    Venkatesan, K.; Babu, D. Rajan

    2015-06-24

    Zinc iron oxide (ZnFe{sub 2}O{sub 4}) nanoparticles were prepared by self-propagated combustion route.The fuel plays a major role on the formation of structure and particle size. Here three different fuels like alanine, glycine and proline were used to synthesis the zinc iron oxide nanoparticle. Influence of combustion nature through the fuel, the phase formation, particle size, band gap and surface morphology has been modified. The prepared powder was characterized by powder X-ray diffraction method (PXRD), field-emission scanning electron microscopy (FE-SEM) and the composition of the material was analysed by X-ray energy dispersive spectroscopy (EDAX).The elemental mapping was confirmed the uniform distribution of Zn, Fe and O elements in the prepared material of ZnFe{sub 2}O{sub 4}.

  5. A facile gel-combustion route for fine particle synthesis of spinel ferrichromite: X-ray and Mössbauer study on effect of Mg and Ni content

    SciTech Connect

    Vader, V.T.; Achary, S.N.; Meena, S.S.

    2014-02-01

    Highlights: • A novel and facile synthesis route. • Transformation of system from random to inverse spinel. • Appearance of superparamagnetism phase. - Abstract: A novel nitrate–citrate gel combustion route was used to prepare fine particle of a series Mg{sub 1−x}Ni{sub x}FeCrO{sub 4} (0.0 ≤ x ≤ 1.0) and its structural properties were investigated. The in situ oxidizing environment provided by the nitrate ions in the gel increases the rate of oxidation and lowers the decomposition temperature of component. All the samples after sintering were characterized at room temperature by X-ray diffraction (XRD) method and Mössbauer spectroscopy techniques. The X-ray and Mössbauer studies confirmed the single phase cubic spinel structure with all Fe ions in 3+ charge state. XRD and Mössbauer studies revealed that the samples of x = 0.0, and 0.2 are random spinel and show rather broad lines, while x = 0.4–1.0 are inverse spinel.

  6. UREA INFRASTRUCTURE FOR UREA SCR NOX REDUCTION

    SciTech Connect

    Bunting, Bruce G.

    2000-08-20

    Urea SCR is currently the only proven NOX aftertreatment for diesel engines - high NOX reduction possible - some SCR catalyst systems are robust against fuel sulfur - durability has been demonstrated - many systems in the field - long history in other markets - Major limitations to acceptance - distribution of urea solution to end user - ensuring that urea solution is added to vehicle.

  7. Structural and optical characterization of Er-alkali-metals codoped MgO nanoparticles synthesized by solution combustion route

    NASA Astrophysics Data System (ADS)

    Sivasankari, J.; Selvakumar Sellaiyan, S.; Sankar, S.; Devi, L. Vimala; Sivaji, K.

    2017-01-01

    Pure MgO, rare-earth (Er) doped MgO (MgO:Er), and alkali metal ions (Li, Na and K) co-doped MgO:Er [i.e. MgO: Er+X (X=Li, Na, and K)] nanopowders were synthesized by solution combustion method and characterized. The XRD analysis reveals the cubic structure and the substitution of dopants and co-dopants in MgO. Annealing at 800 °C, increases the sizes of nano-crystallites of all samples appreciably, indicating the grain growth and the improvement in crystallinity of all the samples. Increase in lattice parameter, d spacing and band gap were observed after annealing. Structural and morphological analysis using scanning electron microscope (SEM) and transmission electron microscope (TEM) studies has shown that the samples contain structures like agglomerated clusters. FT-IR spectra confirm the stretching mode of hydroxyl groups, carbonate and presence of MgO bonding. The characteristic wavelength ranging from 2600 cm-1 to 3000 cm-1 were assigned to transition of 4S3/2→4I13/2 and 4I11/2→4I15/2 of Er3+.

  8. PSynthesis, characterization and electromagnetic properties of Zn-substituted CoFe2O4 via sucrose assisted combustion route

    NASA Astrophysics Data System (ADS)

    Gabal, M. A.; Al-Juaid, A. A.; Al-Rashed, S. M.; Hussein, M. A.; Al-Marzouki, F.

    2017-03-01

    Nanocrystalline Co1-xZnxFe2O4 ferrites (0.0≤x≤0.1) were synthesized via simple, economic and environmentally friend sucrose auto-combustion method. An appropriate mechanism for complexation process as well as ferrites formation was suggested and discussed. The detailed structural studies were estimated through X-ray diffractometer (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM) measurements. The results confirmed the formation of mixed spinel phase with cubic structure and exhibited a gradual decrease in the crystal size from 58 nm to 20 nm by the addition of zinc. Based on the obtained structural parameters, an appropriate cation distribution was suggested and reinforced via electrical and magnetic properties measurements. Hysteresis loops measurements, indicated ferromagnetic characteristics, with hard magnetic properties, for the samples with 0.0≤x≤0.6. The samples with higher Zn-content exhibited paramagnetic properties. The changes in the magnetization and coercivity by the addition of zinc can be discussed in the view of the influence of cationic stoichiometry and magneto-crystalline anisotropy, respectively. The huge decrease in the magnetization value at x≥0.8 suggested a shift from ferromagnetic to paramagnetic characteristics. Ac-conductivity as well as dielectric constant behaviors reinforced this magnetic transition. The obtained Curie transition temperatures (TC) were gradually shifted to lower temperatures by the addition of zinc. The addition of zinc results in the substitution of Co2+ ions in the octahedral sites thus, decreases B-B hopping probability, decreases conductivity and consequently increases activation energy. The most predominant conduction mechanisms in the ferromagnetic and paramagnetic regions are expected to be due to electron hoppings between different valence state ions and small positive polaron migration, respectively.

  9. Optical and EPR Spectroscopic Studies of Deep Red Light Emitting Fe-Doped LiAl5O8 Phosphor Prepared Via Propellant Combustion Route

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Sivaramaiah, G.; Rao, J. L.; Singh, N.; Mohapatra, M.; Singh, P. K.; Pathak, M. S.; Dhoble, S. J.

    2016-12-01

    LiAl5O8 doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe3+-O2-. On excitation with 293 nm, emission band for the Fe3+ ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe3+ ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe3+ present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe3+ ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K.

  10. Optical and EPR Spectroscopic Studies of Deep Red Light Emitting Fe-Doped LiAl5O8 Phosphor Prepared Via Propellant Combustion Route

    NASA Astrophysics Data System (ADS)

    Singh, Vijay; Sivaramaiah, G.; Rao, J. L.; Singh, N.; Mohapatra, M.; Singh, P. K.; Pathak, M. S.; Dhoble, S. J.

    2017-03-01

    LiAl5O8 doped with Fe was synthesized by a propellant combustion route at furnace temperature of 773 K. The phosphor was characterized using powder x-ray diffraction, optical absorption, electron paramagnetic resonance (EPR) and photoluminescence spectroscopic techniques. The optical absorption spectrum exhibits a broad band at 242 nm characteristic of charge transfer between Fe3+-O2-. On excitation with 293 nm, emission band for the Fe3+ ion was observed at 687 nm. The CIE (International Commission on Illumination or Commission Internationale de l'Elcairage) coordinates for the system were evaluated adopting standard procedure which suggested that the system can be effective as a deep red emitting phosphor. The EPR spectrum of this phosphor exhibits a number of resonance signals characteristic of Fe3+ ions. The resonance signals at g = 3.16, 2.27 are attributed to Fe3+ present at tetrahedral site with an axial symmetry. The resonance signals at g = 1.98 and 1.43 are attributed to Fe3+ ions in octahedral site with an axial symmetry. Various EPR parameters such as the number of spins, Gibbs free energy, magnetic susceptibility, Curie constant and effective magnetic moment values are calculated and compared at room temperature and 110 K.

  11. Flash synthesis of Li2TiO3 powder by microwave-induced solution combustion

    NASA Astrophysics Data System (ADS)

    Zhou, Qilai; Tao, Liyao; Gao, Yue; Xue, Lihong; Yan, Youwei

    2014-12-01

    Nano-crystalline Li2TiO3 powder was prepared by a microwave-induced solution combustion synthesis (MSCS) route using urea as fuel. It is observed that combustion reaction, which did not occur by conventional heating, happened when microwave heating was induced. The as-synthesized Li2TiO3 powder exhibits a narrow size distribution. In MSCS, the total metal ion concentration (Cm) in the starting solution plays an important role. By changing Cm values in starting solution, SCS process including ignition time, combustion period and reaction rate can be controlled. The as-prepared powder could be sintered up to 92.6% of the theoretical density at 1223 K.

  12. In vivo urea cycle flux distinguishes and correlates with phenotypic severity in disorders of the urea cycle

    PubMed Central

    Lee, Brendan; Yu, Hong; Jahoor, Farook; O'Brien, William; Beaudet, Arthur L.; Reeds, Peter

    2000-01-01

    Urea cycle disorders are a group of inborn errors of hepatic metabolism that result in often life-threatening hyperammonemia and hyperglutaminemia. Clinical and laboratory diagnosis of partial deficiencies during asymptomatic periods is difficult, and correlation of phenotypic severity with either genotype and/or in vitro enzyme activity is often imprecise. We hypothesized that stable isotopically determined in vivo rates of total body urea synthesis and urea cycle-specific nitrogen flux would correlate with both phenotypic severity and carrier status in patients with a variety of different enzymatic deficiencies of the urea cycle. We studied control subjects, patients, and their relatives with different enzymatic deficiencies affecting the urea cycle while consuming a low protein diet. On a separate occasion the subjects either received a higher protein intake or were treated with an alternative route medication sodium phenylacetate/benzoate (Ucephan), or oral arginine supplementation. Total urea synthesis from all nitrogen sources was determined from [18O]urea labeling, and the utilization of peripheral nitrogen was estimated from the relative isotopic enrichments of [15N]urea and [15N]glutamine during i.v. co-infusions of [5-(amide)15N]glutamine and [18O]urea. The ratio of the isotopic enrichments of 15N-urea/15N-glutamine distinguished normal control subjects (ratio = 0.42 ± 0.06) from urea cycle patients with late (0.17 ± 0.03) and neonatal (0.003 ± 0.007) presentations irrespective of enzymatic deficiency. This index of urea cycle activity also distinguished asymptomatic heterozygous carriers of argininosuccinate synthetase deficiency (0.22 ± 0.03), argininosuccinate lyase deficiency (0.35 ± 0.11), and partial ornithine transcarbamylase deficiency (0.26 ± 0.06) from normal controls. Administration of Ucephan lowered, and arginine increased, urea synthesis to the degree predicted from their respective rates of metabolism. The 15N-urea/15N-glutamine ratio

  13. Physiological and molecular ontogeny of branchial and extra-branchial urea excretion in posthatch rainbow trout (Oncorhynchus mykiss).

    PubMed

    Zimmer, Alex M; Wood, Chris M

    2016-02-01

    All teleost fish produce ammonia as a metabolic waste product. In embryos, ammonia excretion is limited by the chorion, and fish must detoxify ammonia by synthesizing urea via the ornithine urea cycle (OUC). Although urea is produced by embryos and larvae, urea excretion (J(urea)) is typically low until yolk sac absorption, increasing thereafter. The aim of this study was to determine the physiological and molecular characteristics of J(urea) by posthatch rainbow trout (Oncorhynchus mykiss). Following hatch, whole body urea concentration decreased over time, while J(urea) increased following yolk sac absorption. From 12 to 40 days posthatch (dph), extra-branchial routes of excretion accounted for the majority of J(urea), while the gills became the dominant site for J(urea) only after 55 dph. This represents the most delayed branchial ontogeny of any process studied to date. Urea transporter (UT) gene expression in the gills and skin increased over development, consistent with increases in branchial and extra-branchial J(urea). Following exposure to 25 mmol/l urea, the accumulation and subsequent elimination of exogenous urea was much greater at 55 dph than 12 dph, consistent with increased UT expression. Notably, UT gene expression in the gills of 55 dph larvae increased in response to high urea. In summary, there is a clear increase in urea transport capacity over posthatch development, despite a decrease in OUC activity.

  14. Chemiresistor urea sensor

    DOEpatents

    Glass, Robert S.

    1997-01-01

    A sensor to detect and quantify urea in fluids resulting from hemodialysis procedures, and in blood and other body fluids. The sensor is based upon a chemiresistor, which consists of an interdigitated array of metal fingers between which a resistance measured. The interdigitated array is fabricated on a suitable substrate. The surface of the array of fingers is covered with a coating containing the enzyme urease which catalyzes the hydrolysis of urea to form the ammonium ion, the bicarbonate ion, and hydroxide-chemical products which provide the basis for the measured signal. In a typical application, the sensor could be used at bedside, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. Also, the chemiresistor used to detect urea, can be utilized with a reference chemiresistor which does not contain urease, and connected in a differential measurement arrangement, such that the reference chemiresistor would cancel out any fluctuations due to background effects.

  15. Utilizing maleic acid as a novel fuel for synthesis of PbFe{sub 12}O{sub 19} nanoceramics via sol–gel auto-combustion route

    SciTech Connect

    Ansari, Fatemeh; Soofivand, Faezeh; Salavati-Niasari, Masoud

    2015-05-15

    PbFe{sub 12}O{sub 19} nanostructures were prepared in an aqueous solution by the sol–gel auto-combustion method using Pb(NO{sub 3}){sub 2} and Fe(NO{sub 3}){sub 3} as starting materials and various carboxylic acids, including oxalic acid, malonic acid, succinic acid and maleic acid as fuel and reducing and capping agents. The as-synthesized products were characterized by X- ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectroscopy. The effect of carboxylic acid type, Pb{sup +} {sup 2} to carboxylic acid molar ratio, and calcination temperature was investigated on the morphology of the products and several experiments were carried out to obtain the optimal reaction conditions. It was found that the phase and the morphology of the products are influenced by the investigated parameters. Furthermore, vibrating sample magnetometer (VSM) was used to study the magnetic properties of PbFe{sub 12}O{sub 19} samples. - Graphical abstract: Display Omitted - Highlights: • PbFe{sub 12}O{sub 19} nanoceramics were synthesized from Fe(NO{sub 3}){sub 3} and Pb(NO{sub 3}){sub 2} via the sol–gel auto combustion method. • The maleic acid can be instead of common capping agent and fuel in auto-combustion sol–gel. • The synthesized PbFe{sub 12}O{sub 19} is a hard magnetic material. • The specific saturation magnetization and coercivity are 27 emu/g and 1900 Oe, respectively.

  16. Molecular evolution of urea amidolyase and urea carboxylase in fungi

    PubMed Central

    2011-01-01

    Background Urea amidolyase breaks down urea into ammonia and carbon dioxide in a two-step process, while another enzyme, urease, does this in a one step-process. Urea amidolyase has been found only in some fungal species among eukaryotes. It contains two major domains: the amidase and urea carboxylase domains. A shorter form of urea amidolyase is known as urea carboxylase and has no amidase domain. Eukaryotic urea carboxylase has been found only in several fungal species and green algae. In order to elucidate the evolutionary origin of urea amidolyase and urea carboxylase, we studied the distribution of urea amidolyase, urea carboxylase, as well as other proteins including urease, across kingdoms. Results Among the 64 fungal species we examined, only those in two Ascomycota classes (Sordariomycetes and Saccharomycetes) had the urea amidolyase sequences. Urea carboxylase was found in many but not all of the species in the phylum Basidiomycota and in the subphylum Pezizomycotina (phylum Ascomycota). It was completely absent from the class Saccharomycetes (phylum Ascomycota; subphylum Saccharomycotina). Four Sordariomycetes species we examined had both the urea carboxylase and the urea amidolyase sequences. Phylogenetic analysis showed that these two enzymes appeared to have gone through independent evolution since their bacterial origin. The amidase domain and the urea carboxylase domain sequences from fungal urea amidolyases clustered strongly together with the amidase and urea carboxylase sequences, respectively, from a small number of beta- and gammaproteobacteria. On the other hand, fungal urea carboxylase proteins clustered together with another copy of urea carboxylases distributed broadly among bacteria. The urease proteins were found in all the fungal species examined except for those of the subphylum Saccharomycotina. Conclusions We conclude that the urea amidolyase genes currently found only in fungi are the results of a horizontal gene transfer event from

  17. Study of influence of fuel on dielectric and ferroelectric properties of bismuth titanate ceramics synthesized using solution based combustion technique

    NASA Astrophysics Data System (ADS)

    Subohi, Oroosa; Kumar, G. S.; Malik, M. M.; Kurchania, Rajnish

    2015-03-01

    The effect of fuel characteristics on the processing and properties of bismuth titanate (BIT) ceramics obtained by solution combustion route using different fuels are reported in this paper. Dextrose, urea and glycine were used as fuel in this study. The obtained bismuth titanate ceramics were characterized by using XRD, SEM at different stages of sample preparation. It was observed that BIT obtained by using dextrose as fuel shows higher dielectric constant and higher remnant polarization due to smaller grain size and lesser c-axis growth as compared to the samples with urea and glycine as fuel. The electrical behavior of the samples with respect to temperature and frequency was also investigated to understand relaxation phenomenon.

  18. Synthesis of Y1-xAlxBa2Cu3O7-δ via combustion route: Effects of Al2O3 nanoparticles on superconducting properties

    NASA Astrophysics Data System (ADS)

    Mohd Suan, Mohd Shahadan; Johan, Mohd Rafie

    2017-02-01

    Combustion reaction was used to synthesis Al2O3 nanoparticles embedded Y1-xAlxBa2Cu3O7-δ simultaneously. The effects of Al2O3 nanoparticles with nominal molar mass (xmol) of 0.02, 0.04, 0.06, 0.08 and 0.10 towards the critical current density JC of Y1-xAlxBa2Cu3O7-δ were verified by magnetic measurement. Resulted XRD patterns revealed that the calcined samples consist of pure Al2O3 and Y1-xAlxBa2Cu3O7-δ phases which had been confirmed by EDX results. The SEM images showed that Al2O3 nanoparticles ( 10 nm) were distributed in polycrystalline YBa2Cu3O7-δ grains and grain boundaries. The presence of higher concentration of Al2O3 nanoparticles has developed Al3+ rich spots which diffused within the YBa2Cu3O7-δ superconducting matrix to form Y1-xAlxBa2Cu3O7-δ and was confirmed by EDX analysis. The samples were electrically superconducting at temperature above 85 K as measured by using standard four-probe technique. The magnetic field (H) dependent magnetization (M), M-H hysteresis loops measured at 77 K for xmol≤0.06 samples are significantly improved attributed to the increase of trapped fluxes in the samples. Remarkable increase of magnetic JC (H) in Al2O3 nanoparticles added samples compared to the as prepared polycrystalline YBa2Cu3O7-δ sample indicating strong pinning effect. It is suggested that well-distributed Al2O3 nanoparticles in the polycrystalline YBa2Cu3O7-δ matrix achieved via auto-combustion reaction has efficiently pin the magnetic vortex. The magnetic JC was optimized to 6 kAcm-2 in xmol=0.06 sample. On the other hand, insignificant magnetic JC improvement in xmol≥0.08 samples is probably resulted from the agglomerated Al2O3 nanoparticles in Y1-xAlxBa2Cu3O7-δ phase.

  19. Chemiresistor urea sensor

    DOEpatents

    Glass, R.S.

    1997-12-16

    A sensor is disclosed to detect and quantify urea in fluids resulting from hemodialysis procedures, and in blood and other body fluids. The sensor is based upon a chemiresistor, which consists of an interdigitated array of metal fingers between which a resistance measured. The interdigitated array is fabricated on a suitable substrate. The surface of the array of fingers is covered with a coating containing the enzyme urease which catalyzes the hydrolysis of urea to form the ammonium ion, the bicarbonate ion, and hydroxide-chemical products which provide the basis for the measured signal. In a typical application, the sensor could be used at bedside, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. Also, the chemiresistor used to detect urea, can be utilized with a reference chemiresistor which does not contain urease, and connected in a differential measurement arrangement, such that the reference chemiresistor would cancel out any fluctuations due to background effects. 16 figs.

  20. Use of polyurea from urea for coating of urea granules.

    PubMed

    Lu, Panfang; Zhang, Yanfei; Jia, Cong; Li, Yufeng; Mao, Zhiquan

    2016-01-01

    A new type of controlled release fertilizers coated with polyurea was prepared. The granulated urea was firstly changed into a liquid urea by heating as the coating liquid. By spraying uniformly the urea was coated with the polyurea synthesized by the reaction of isocyanates with a liquid urea. The effects of different modifiers on N release characteristics of polyurea-coated urea (PCU) were studied. The morphology and chemical structure of PCU coating materials was investigated by SEM and FTIR. We studied the nitrogen release characteristics of the PCU applied in both water and soil, and the biodegradability of PCU coating after buried in soil. The results showed that PCU reduced nitrogen release rate and exhibited excellent controlled release property. The PCU coating materials could biodegrade in soil. This indicated that the low cost PCU products from urea are expected to use in agricultural and horticultural applications.

  1. Mössbauer and magnetic studies of nanocrystalline zinc ferrites synthesized by microwave combustion method

    NASA Astrophysics Data System (ADS)

    Mahmoud, Mohamed; Hassan, Azza Mohamed; Ahmed, Mamdouh Abdel aal; Zhu, Kaixin; Ganeshraja, Ayyakannu Sundaram; Wang, Junhu

    2016-12-01

    Zinc ferrite nano-crystals were synthesized by a microwave assisted combustion route with varying the urea to metal nitrates (U/N) molar ratio The process takes only a few minutes to obtain Zinc ferrite powders. The Effect of U/N ratio on the obtained phases, particle size, magnetization and structural properties has been investigated. The specimens were characterized by XRD, Mössbauer and VSM techniques. The sample prepared with urea/metal nitrate ratio of 1/1 was a poorly crystalline phase with very small crystallite size. A second phase is also detected in the sample. The crystallite size increases while the second phase decrease with increasing the urea ratio. The saturation magnetization and coercivity of the as prepared nano-particles changed with the change of the U/N ratio. The powder with the highest U/N ratio showed the presence of an unusually high saturation magnetization of 16 emu/g at room temperature. The crystallinity of the as prepared powder was developed by annealing the samples at 700 ∘C and 900 ∘C. Both the saturation magnetization ( Ms) and the remnant magnetization ( Mr) were found to be highly dependent upon the annealing temperature. Mössbauer studies show magnetic ordering in the powder even at room temperature. The Mössbauer and the magnetic parameters of this fraction are different from the standard values for bulk zinc ferrite.

  2. Toxicology of urea formaldehyde and polyurethane foam insulation.

    PubMed

    Harris, J C; Rumack, B H; Aldrich, F D

    1981-01-16

    Two types of foam insulation are in wide use. Urea formaldehyde foam is a relatively inexpensive, easily installed, and efficient insulation. Toxicity from this insulation is related to release of free formaldehyde into the home. Mild to incapacitating symptoms have been reported in occupants of urea formaldehyde-insulated homes. Airborne formaldehyde levels frequently have exceeded standards set for occupational exposure. The long-term consequences of such exposure are unknown. Because of publicity over the toxicity of urea formaldehyde foam, many physicians and patients have confused urea formaldehyde and polyurethane foam. Unlike urea formaldehyde, polyurethane foam is fully cured before construction. Toxicity occurs only during manufacture and curing. To date, there have been no reports to our knowledge of toxicity in occupants of polyurethane-insulated homes. However, toxicity caused by pyrolysis products may occur during combustion in homes insulated with either type of insulation. This report details 48 patients in whom complete medical data were obtained out of the first 100 patients contacting the Rocky Mountain Poison Center.

  3. Quantum chemistry-assisted synthesis route development

    NASA Astrophysics Data System (ADS)

    Hori, Kenji; Sumimoto, Michinori; Murafuji, Toshihiro

    2015-12-01

    We have been investigating "quantum chemistry-assisted synthesis route development" using in silico screenings and applied the method to several targets. Another example was conducted to develop synthesis routes for a urea derivative, namely 1-(4-(trifluoromethyl)-2-oxo-2H-chromen-7-yl)urea. While five synthesis routes were examined, only three routes passed the second in silico screening. Among them, the reaction of 7-amino-4-(trifluoromethyl)-2H-chromen-2-one and O-methyl carbamate with BF3 as an additive was ranked as the first choice for synthetic work. We were able to experimentally obtain the target compound even though its yield was as low as 21 %. The theoretical result was thus consistent with that observed. The summary of transition state data base (TSDB) is also provided. TSDB is the key to reducing time of in silico screenings.

  4. Quantum chemistry-assisted synthesis route development

    SciTech Connect

    Hori, Kenji; Sumimoto, Michinori; Murafuji, Toshihiro

    2015-12-31

    We have been investigating “quantum chemistry-assisted synthesis route development” using in silico screenings and applied the method to several targets. Another example was conducted to develop synthesis routes for a urea derivative, namely 1-(4-(trifluoromethyl)-2-oxo-2H-chromen-7-yl)urea. While five synthesis routes were examined, only three routes passed the second in silico screening. Among them, the reaction of 7-amino-4-(trifluoromethyl)-2H-chromen-2-one and O-methyl carbamate with BF{sub 3} as an additive was ranked as the first choice for synthetic work. We were able to experimentally obtain the target compound even though its yield was as low as 21 %. The theoretical result was thus consistent with that observed. The summary of transition state data base (TSDB) is also provided. TSDB is the key to reducing time of in silico screenings.

  5. Combustion noise

    NASA Technical Reports Server (NTRS)

    Strahle, W. C.

    1977-01-01

    A review of the subject of combustion generated noise is presented. Combustion noise is an important noise source in industrial furnaces and process heaters, turbopropulsion and gas turbine systems, flaring operations, Diesel engines, and rocket engines. The state-of-the-art in combustion noise importance, understanding, prediction and scaling is presented for these systems. The fundamentals and available theories of combustion noise are given. Controversies in the field are discussed and recommendations for future research are made.

  6. Combustion synthesis and thermoluminescence in YAlO3:Dy3+

    NASA Astrophysics Data System (ADS)

    Dhadade, I. H.; Moharil, S. V.; Dhoble, S. J.; Rahangdale, S. R.

    2016-05-01

    In the Y2O3-Al2O3 system, compounds Y3Al5O12 (yttrium aluminum garnet, YAG),YAlO3 (yttrium aluminum perovskite, YAP), and Y4Al2O9(yttrium aluminate monoclinic, YAM) are well known. Though several soft chemical routes have been explored for synthesis of YAG, YAP and YAM, most of these methods are complex. Moreover, phase pure materials are not obtained in one step and prolonged annealing at temperatures around 1000°C is necessary. In this paper, one step combustion synthesis of the compound YAlO3:Dy3+ is reported using a modified procedure and employing mixed (glycine + urea) fuel. Powder X-ray diffraction patterns confirm the pervoskite phase of YAlO3. Thermoluminescence study shows linear response in wide dose range (0.2 - 1 KGy) suggest the possibility of the present phosphor in dosimeter application.

  7. Computational Combustion

    SciTech Connect

    Westbrook, C K; Mizobuchi, Y; Poinsot, T J; Smith, P J; Warnatz, J

    2004-08-26

    Progress in the field of computational combustion over the past 50 years is reviewed. Particular attention is given to those classes of models that are common to most system modeling efforts, including fluid dynamics, chemical kinetics, liquid sprays, and turbulent flame models. The developments in combustion modeling are placed into the time-dependent context of the accompanying exponential growth in computer capabilities and Moore's Law. Superimposed on this steady growth, the occasional sudden advances in modeling capabilities are identified and their impacts are discussed. Integration of submodels into system models for spark ignition, diesel and homogeneous charge, compression ignition engines, surface and catalytic combustion, pulse combustion, and detonations are described. Finally, the current state of combustion modeling is illustrated by descriptions of a very large jet lifted 3D turbulent hydrogen flame with direct numerical simulation and 3D large eddy simulations of practical gas burner combustion devices.

  8. Simulating Combustion

    NASA Astrophysics Data System (ADS)

    Merker, G.; Schwarz, C.; Stiesch, G.; Otto, F.

    The content spans from simple thermodynamics of the combustion engine to complex models for the description of the air/fuel mixture, ignition, combustion and pollutant formation considering the engine periphery of petrol and diesel engines. Thus the emphasis of the book is on the simulation models and how they are applicable for the development of modern combustion engines. Computers can be used as the engineers testbench following the rules and recommendations described here.

  9. Physiological and molecular ontogeny of branchial and extra-branchial urea excretion in posthatch rainbow trout (Oncorhynchus mykiss)

    PubMed Central

    Wood, Chris M.

    2015-01-01

    All teleost fish produce ammonia as a metabolic waste product. In embryos, ammonia excretion is limited by the chorion, and fish must detoxify ammonia by synthesizing urea via the ornithine urea cycle (OUC). Although urea is produced by embryos and larvae, urea excretion (Jurea) is typically low until yolk sac absorption, increasing thereafter. The aim of this study was to determine the physiological and molecular characteristics of Jurea by posthatch rainbow trout (Oncorhynchus mykiss). Following hatch, whole body urea concentration decreased over time, while Jurea increased following yolk sac absorption. From 12 to 40 days posthatch (dph), extra-branchial routes of excretion accounted for the majority of Jurea, while the gills became the dominant site for Jurea only after 55 dph. This represents the most delayed branchial ontogeny of any process studied to date. Urea transporter (UT) gene expression in the gills and skin increased over development, consistent with increases in branchial and extra-branchial Jurea. Following exposure to 25 mmol/l urea, the accumulation and subsequent elimination of exogenous urea was much greater at 55 dph than 12 dph, consistent with increased UT expression. Notably, UT gene expression in the gills of 55 dph larvae increased in response to high urea. In summary, there is a clear increase in urea transport capacity over posthatch development, despite a decrease in OUC activity. PMID:26608657

  10. Mixing cations with different alkyl chain lengths markedly depresses the melting point in deep eutectic solvents formed from alkylammonium bromide salts and urea.

    PubMed

    Chen, Zhengfei; Greaves, Tamar L; Warr, Gregory G; Atkin, Rob

    2017-02-16

    The melting point of a deep eutectic solvent formed from a ternary mixture of ethylammonium bromide (EABr), butylammonium bromide (BABr) and urea is 10 °C, which is almost 40 °C lower than the melting points of binary DESs formed from either EABr:urea or BABr:urea mixtures. This reveals a new route to prepare room temperature DESs via mixing different cations.

  11. "Recalculating Route".

    PubMed

    Baum, Neil

    2015-01-01

    Can you imagine going to a doctor who uses a paper chart, sends you a bill on a ledger card, and handwrites a prescription? You wouldn't have a great deal of confidence that the clinical skills of the doctor were up to date. This would be an example of a doctor who did not "recalculate his or her route." This article provides 10 examples of adjustments that have been made in medicine where the route has been recalculated.

  12. Urea Biosynthesis Using Liver Slices

    ERIC Educational Resources Information Center

    Teal, A. R.

    1976-01-01

    Presented is a practical scheme to enable introductory biology students to investigate the mechanism by which urea is synthesized in the liver. The tissue-slice technique is discussed, and methods for the quantitative analysis of metabolites are presented. (Author/SL)

  13. What Is a Urea Cycle Disorder?

    MedlinePlus

    ... urine and removed from the body. In urea cycle disorders, the nitrogen accumulates in the form of ammonia, a highly toxic substance, resulting in hyperammonemia (elevated blood ... and severity of urea cycle disorders is highly variable. This depends on the ...

  14. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkylated urea. 721.9892 Section 721... Alkylated urea. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an alkylated urea (PMN P-93-1649) is subject to reporting under...

  15. Predictive model for segmented poly(urea)

    NASA Astrophysics Data System (ADS)

    Gould, P. J.; Cornish, R.; Frankl, P.; Lewtas, I.

    2012-08-01

    Segmented poly(urea) has been shown to be of significant benefit in protecting vehicles from blast and impact and there have been several experimental studies to determine the mechanisms by which this protective function might occur. One suggested route is by mechanical activation of the glass transition. In order to enable design of protective structures using this material a constitutive model and equation of state are needed for numerical simulation hydrocodes. Determination of such a predictive model may also help elucidate the beneficial mechanisms that occur in polyurea during high rate loading. The tool deployed to do this has been Group Interaction Modelling (GIM) - a mean field technique that has been shown to predict the mechanical and physical properties of polymers from their structure alone. The structure of polyurea has been used to characterise the parameters in the GIM scheme without recourse to experimental data and the equation of state and constitutive model predicts response over a wide range of temperatures and strain rates. The shock Hugoniot has been predicted and validated against existing data. Mechanical response in tensile tests has also been predicted and validated.

  16. Urea biosensor for hemodialysis monitoring

    DOEpatents

    Glass, R.S.

    1999-01-12

    This research discloses an electrochemical sensor capable of detecting and quantifying urea in fluids resulting from hemodialysis procedures. The sensor is based upon measurement of the pH change produced in an aqueous environment by the products of the enzyme-catalyzed hydrolysis of urea. The sensor may be fabricated using methods amenable to mass fabrication, resulting in low-cost sensors and thus providing the potential for disposable use. In a typical application, the sensor could be used in treatment centers, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. The sensor can also be utilized to allow at-home testing to determine if dialysis was necessary. Such a home monitor is similar, in principle, to devices used for blood glucose testing by diabetics, and would require a blood droplet sample by using a finger prick. 9 figs.

  17. Urea biosensor for hemodialysis monitoring

    DOEpatents

    Glass, Robert S.

    1999-01-01

    An electrochemical sensor capable of detecting and quantifying urea in fluids resulting from hemodialysis procedures. The sensor is based upon measurement of the pH change produced in an aqueous environment by the products of the enzyme-catalyzed hydrolysis of urea. The sensor may be fabricated using methods amenable to mass fabrication, resulting in low-cost sensors and thus providing the potential for disposable use. In a typical application, the sensor could be used in treatment centers, in conjunction with an appropriate electronics/computer system, in order to determine the hemodialysis endpoint. The sensor can also be utilized to allow at-home testing to determine if dialysis was necessary. Such a home monitor is similar, in principle, to devices used for blood glucose testing by diabetics, and would require a blood droplet sample by using a finger prick.

  18. Biofuels Combustion

    NASA Astrophysics Data System (ADS)

    Westbrook, Charles K.

    2013-04-01

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly.

  19. Biofuels combustion.

    PubMed

    Westbrook, Charles K

    2013-01-01

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. Research efforts on so-called second- and third-generation biofuels are discussed briefly.

  20. Biofuels combustion*

    SciTech Connect

    Westbrook, Charles K.

    2013-01-04

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acids and used primarily to replace or supplement conventional diesel fuels. As a result, research efforts on so-called second- and third-generation biofuels are discussed briefly.

  1. Bubble Combustion

    NASA Technical Reports Server (NTRS)

    Corrigan, Jackie

    2004-01-01

    A method of energy production that is capable of low pollutant emissions is fundamental to one of the four pillars of NASA s Aeronautics Blueprint: Revolutionary Vehicles. Bubble combustion, a new engine technology currently being developed at Glenn Research Center promises to provide low emissions combustion in support of NASA s vision under the Emissions Element because it generates power, while minimizing the production of carbon dioxide (CO2) and nitrous oxides (NOx), both known to be Greenhouse gases. and allows the use of alternative fuels such as corn oil, low-grade fuels, and even used motor oil. Bubble combustion is analogous to the inverse of spray combustion: the difference between bubble and spray combustion is that spray combustion is spraying a liquid in to a gas to form droplets, whereas bubble combustion involves injecting a gas into a liquid to form gaseous bubbles. In bubble combustion, the process for the ignition of the bubbles takes place on a time scale of less than a nanosecond and begins with acoustic waves perturbing each bubble. This perturbation causes the local pressure to drop below the vapor pressure of the liquid thus producing cavitation in which the bubble diameter grows, and upon reversal of the oscillating pressure field, the bubble then collapses rapidly with the aid of the high surface tension forces acting on the wall of the bubble. The rapid and violent collapse causes the temperatures inside the bubbles to soar as a result of adiabatic heating. As the temperatures rise, the gaseous contents of the bubble ignite with the bubble itself serving as its own combustion chamber. After ignition, this is the time in the bubble s life cycle where power is generated, and CO2, and NOx among other species, are produced. However, the pollutants CO2 and NOx are absorbed into the surrounding liquid. The importance of bubble combustion is that it generates power using a simple and compact device. We conducted a parametric study using CAVCHEM

  2. Biofuels combustion*

    DOE PAGES

    Westbrook, Charles K.

    2013-01-04

    This review describes major features of current research in renewable fuels derived from plants and from fatty acids. Recent and ongoing fundamental studies of biofuel molecular structure, oxidation reactions, and biofuel chemical properties are reviewed, in addition to combustion applications of biofuels in the major types of engines in which biofuels are used. Biofuels and their combustion are compared with combustion features of conventional petroleum-based fuels. Two main classes of biofuels are described, those consisting of small, primarily alcohol, fuels (particularly ethanol, n-butanol, and iso-pentanol) that are used primarily to replace or supplement gasoline and those derived from fatty acidsmore » and used primarily to replace or supplement conventional diesel fuels. As a result, research efforts on so-called second- and third-generation biofuels are discussed briefly.« less

  3. Method for reducing nitrogen oxides in combustion effluents

    DOEpatents

    Zauderer, Bert

    2000-01-01

    Method for reducing nitrogen oxides (NO.sub.x) in the gas stream from the combustion of fossil fuels is disclosed. In a narrow gas temperature zone, NO.sub.x is converted to nitrogen by reaction with urea or ammonia with negligible remaining ammonia and other reaction pollutants. Specially designed injectors are used to introduce air atomized water droplets containing dissolved urea or ammonia into the gaseous combustion products in a manner that widely disperses the droplets exclusively in the optimum reaction temperature zone. The injector operates in a manner that forms droplet of a size that results in their vaporization exclusively in this optimum NO.sub.x -urea/ammonia reaction temperature zone. Also disclosed is a design of a system to effectively accomplish this injection.

  4. Effect of alternative pathway therapy on branched chain amino acid metabolism in urea cycle disorder patients.

    PubMed

    Scaglia, Fernando; Carter, Susan; O'Brien, William E; Lee, Brendan

    2004-04-01

    Urea cycle disorders (UCDs) are a group of inborn errors of hepatic metabolism caused by the loss of enzymatic activities that mediate the transfer of nitrogen from ammonia to urea. These disorders often result in life-threatening hyperammonemia and hyperglutaminemia. A combination of sodium phenylbutyrate and sodium phenylacetate/benzoate is used in the clinical management of children with urea cycle defects as a glutamine trap, diverting nitrogen from urea synthesis to alternatives routes of excretion. We have observed that patients treated with these compounds have selective branched chain amino acid (BCAA) deficiency despite adequate dietary protein intake. However, the direct effect of alternative therapy on the steady state levels of plasma branched chain amino acids has not been well characterized. We have measured steady state plasma branched chain and other essential non-branched chain amino acids in control subjects, untreated ornithine transcarbamylase deficiency females and treated null activity urea cycle disorder patients in the fed steady state during the course of stable isotope studies. Steady-state leucine levels were noted to be significantly lower in treated urea cycle disorder patients when compared to either untreated ornithine transcarbamylase deficiency females or control subjects (P<0.0001). This effect was reproduced in control subjects who had depressed leucine levels when treated with sodium phenylacetate/benzoate (P<0.0001). Our studies suggest that this therapeutic modality has a substantial impact on the metabolism of branched chain amino acids in urea cycle disorder patients. These findings suggest that better titration of protein restriction could be achieved with branched chain amino acid supplementation in patients with UCDs who are on alternative route therapy.

  5. Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea-formaldehyde resin synthesis.

    PubMed

    Steinhof, Oliver; Kibrik, Éléonore J; Scherr, Günter; Hasse, Hans

    2014-04-01

    Urea-formaldehyde resins are bulk products of the chemical industry. Their synthesis involves a complex reaction network. The present work contributes to its elucidation by presenting results from detailed NMR spectroscopic studies with different methods. Besides (1)H NMR and (13)C NMR, (15)N NMR spectroscopy is also applied. (15)N-enriched urea was used for the investigations. A detailed NMR signal assignment and a model of the reaction network of the hydroxymethylation step of the synthesis are presented. Because of its higher spectral dispersion and the fact that all key reactions directly involve the nitrogen centers, (15)N NMR provides a much larger amount of detail than do (1)H and (13)C NMR spectroscopy. Symmetric and asymmetric dimethylol urea can be clearly distinguished and separated from monomethylol urea, trimethylol urea, and methylene-bridged urea. The existence of hemiformals of methylol urea is confirmed. 1,3,5-Oxadiazinan-4-on (uron) and its derivatives were not found in the reaction mixtures investigated here but were prepared via alternative routes. The molar ratios of formaldehyde to urea were 1, 2, and 4, the pH values 7.5 and 8.5, and the reaction temperature 60 °C.

  6. Turbulent combustion

    SciTech Connect

    Talbot, L.; Cheng, R.K.

    1993-12-01

    Turbulent combustion is the dominant process in heat and power generating systems. Its most significant aspect is to enhance the burning rate and volumetric power density. Turbulent mixing, however, also influences the chemical rates and has a direct effect on the formation of pollutants, flame ignition and extinction. Therefore, research and development of modern combustion systems for power generation, waste incineration and material synthesis must rely on a fundamental understanding of the physical effect of turbulence on combustion to develop theoretical models that can be used as design tools. The overall objective of this program is to investigate, primarily experimentally, the interaction and coupling between turbulence and combustion. These processes are complex and are characterized by scalar and velocity fluctuations with time and length scales spanning several orders of magnitude. They are also influenced by the so-called {open_quotes}field{close_quotes} effects associated with the characteristics of the flow and burner geometries. The authors` approach is to gain a fundamental understanding by investigating idealized laboratory flames. Laboratory flames are amenable to detailed interrogation by laser diagnostics and their flow geometries are chosen to simplify numerical modeling and simulations and to facilitate comparison between experiments and theory.

  7. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Urea. 184.1923 Section 184.1923 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Substances Affirmed as GRAS § 184.1923 Urea. (a) Urea (CO(NH2)2, CAS Reg. No. 57-13-6) is the diamide...

  8. Urea and its formation in coelacanth liver.

    PubMed

    Brown, G W; Brown, S G

    1967-02-03

    Urea occurs in liver of the coelacanth Latimeria chalumnae to the extent of about 1.7 percent by weight. It was determined quantitatively by reaction with 1-phenyl-1,2-propanedione-2-oxime (Archibald reagent) and by measurement of ammonia released upon treatment with urease. Arginase and ornithine carbamoyltransferase, enzymes instrumental in the formation of urea in typical ureotelic vertebrates, occur in homogenates of coelacanth liver. Formed in part by the ornithine-urea cycle, urea may have an osmoregulatory function in the coelacanth as it has in elasmobranchs.

  9. Regenerative combustion device

    DOEpatents

    West, Phillip B.

    2004-03-16

    A regenerative combustion device having a combustion zone, and chemicals contained within the combustion zone, such as water, having a first equilibrium state, and a second combustible state. Means for transforming the chemicals from the first equilibrium state to the second combustible state, such as electrodes, are disposed within the chemicals. An igniter, such as a spark plug or similar device, is disposed within the combustion zone for igniting combustion of the chemicals in the second combustible state. The combustion products are contained within the combustion zone, and the chemicals are selected such that the combustion products naturally chemically revert into the chemicals in the first equilibrium state following combustion. The combustion device may thus be repeatedly reused, requiring only a brief wait after each ignition to allow the regeneration of combustible gasses within the head space.

  10. The Chinese soft-shelled turtle, Pelodiscus sinensis, excretes urea mainly through the mouth instead of the kidney.

    PubMed

    Ip, Yuen K; Loong, Ai M; Lee, Serene M L; Ong, Jasmine L Y; Wong, Wai P; Chew, Shit F

    2012-11-01

    The Chinese soft-shelled turtle, Pelodiscus sinensis, is well adapted to aquatic environments, including brackish swamps and marshes. It is ureotelic, and occasionally submerges its head into puddles of water during emersion, presumably for buccopharyngeal respiration. This study was undertaken to test the hypothesis that the buccophyaryngeal cavity constitutes an important excretory route for urea in P. sinensis. Results indicate that a major portion of urea was excreted through the mouth instead of the kidney during immersion. When restrained on land, P. sinensis occasionally submerged their head into water (20-100 min), during which urea excretion and oxygen extraction occurred simultaneously. These results indicate for the first time that buccopharyngeal villiform processes (BVP) and rhythmic pharyngeal movements were involved in urea excretion in P. sinensis. Urea excretion through the mouth was sensitive to phloretin inhibition, indicating the involvement of urea transporters (UTs). In addition, saliva samples collected from the buccopharyngeal surfaces of P. sinensis injected intraperitoneally with saline contained ~36 mmol N l(-1) urea, significantly higher than that (~2.4 mmol N l(-1)) in the plasma. After intraperitoneal injection with 20 μmol urea g(-1) turtle, the concentration of urea in the saliva collected from the BVP increased to an extraordinarily high level of ~614 μmol N ml(-1), but the urea concentration (~45 μmol N ml(-1)) in the plasma was much lower, indicating that the buccopharyngeal epithelium of P. sinensis was capable of active urea transport. Subsequently, we obtained from the buccopharyngeal epithelium of P. sinensis the full cDNA sequence of a putative UT, whose deduced amino acid sequence had ~70% similarity with human and mouse UT-A2. This UT was not expressed in the kidney, corroborating the proposition that the kidney had only a minor role in urea excretion in P. sinensis. As UT-A2 is known to be a facilitative urea

  11. Impacts of active urea secretion into pars recta on urine concentration and urea excretion rate

    PubMed Central

    Layton, Anita T; Bankir, Lise

    2013-01-01

    It has been observed experimentally that early distal tubular urea flow exceeds urea delivery by the proximal convoluted tubule to the pars recta and loop of Henle. Moreover, the fractional excretion of urea in the urine may exceed values compatible with the reabsorption known to occur in the proximal convoluted tubule in the cortex. A likely explanation for these observations is that urea may be actively secreted into the pars recta, as proposed in a few studies. However, this hypothesis has yet to be demonstrated experimentally. In this study, we used a mathematical model of the renal medulla of the rat kidney to investigate the impacts of active urea secretion in the intrarenal handling of urea and in the urine concentrating ability. The model represents only the outer and inner medullary zones, with the actions taking place in the cortex incorporated via boundary conditions. Blood flow in the model vasculature is divided into plasma and red blood cell compartments. We compared urea flow rates and other related model variables without and with the hypothetical active urea secretion in the pars recta. The simulation suggests that active urea secretion induces a “urea-selective” improvement in urine concentrating ability by enhancing the efficiency of urea excretion without requiring a higher urine flow rate, and with only modest changes in the excretion of other solutes. These results should encourage experimental studies in order to assess the existence of an active urea secretion in the rodent kidney. PMID:24058732

  12. Advanced Combustion

    SciTech Connect

    Holcomb, Gordon R.

    2013-03-11

    The activity reported in this presentation is to provide the mechanical and physical property information needed to allow rational design, development and/or choice of alloys, manufacturing approaches, and environmental exposure and component life models to enable oxy-fuel combustion boilers to operate at Ultra-Supercritical (up to 650{degrees}C & between 22-30 MPa) and/or Advanced Ultra-Supercritical conditions (760{degrees}C & 35 MPa).

  13. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... Substances Affirmed as GRAS § 184.1923 Urea. (a) Urea (CO(NH2)2, CAS Reg. No. 57-13-6) is the diamide of carbonic acid and is also known as carbamide. It is a white, odorless solid and is commonly produced...

  14. Extraction of urea and ammonium ion

    NASA Technical Reports Server (NTRS)

    Anselmi, R. T.; Husted, R. R.; Schulz, J. R.

    1977-01-01

    Water purification system keeps urea and ammonium ion concentration below toxic limits in recirculated water of closed loop aquatic habitat. Urea is first converted to ammonium ions and carbon dioxide by enzygmatic action. Ammonium ions are removed by ion exchange. Bioburden is controlled by filtration through 0.45 micron millipore filters.

  15. [Urea formation in the after operational liver].

    PubMed

    Savilov, P N

    2016-01-01

    The effect of resection of the left lobe of the liver (LR, 15-20% og the organ weight) on hepatic urea formation was investigated in 84 albino rats. The objects of study were the surgery left (LLP), inoperable middle (MLP) lobe of the liver, blood (aorta, v. hepatica, v. porta) and choledochal bile. They studied the urea content. Arginase activity was examined in liver homogenate. On the day 3 and day 7 after resection reduced arginase activity was detected. LR caused a decrease of urea in v. hepatica, but increased urea content in the arterial blood and v. porta. Increase in bile urea on day 7 it was replaced by a decrease observed on day 14 of the postsurgery period. The concentration of urea in the liver on the 3rd day after LR was below the norm, and on the 7th and 14th day was within it. The results indicate a violation of urea operated by hepatocytes of the liver and extrahepatic activation mechanisms of the formation of urea.

  16. Isotopic Analysis of the Explosive Urea Nitrate and Its Component Ions for Forensic Applications

    NASA Astrophysics Data System (ADS)

    Aranda, R.; Stern, L. A.; McCormick, M. C.; Mothershead, R. F.; Barrow, J. A.

    2008-12-01

    Urea nitrate (UN) is an explosive used in improvised explosive devices. UN (CH5N2O+NO3-) can be synthesized from readily available chemicals and was the main explosive used in the 1993 bombing of the World Trade Center. Isotopic analysis of this explosive has the potential to elucidate the isotopic ratios of the starting materials and geographic information on the location of synthesis. However, depending on the synthesis of the explosive, variable amounts of residual nitric acid may remain, yielding differing contributions of the components to the bulk UN δ15N values. Since δ15N nitrate values cannot be extrapolated from a single component and the bulk value, it is critical to separate the explosive into urea° and potassium nitrate. Therefore, we developed a method to isolate the components of UN for isotopic analysis through the neutralization of urea and separation via methanol washes. The urea in the explosive is neutralized with a 1.1:1 mole ratio of potassium hydroxide:urea in water resulting in urea° and potassium nitrate. The solution is then dried and the urea and potassium nitrate are separated using methanol. Urea and nitrate were isolated from samples of pre-blast UN and the completeness of the extraction was confirmed with a urease assay and a nitrate detection assay on the appropriate components. Isotopic analysis of the isolated urea and potassium nitrate were performed using an EA-IRMS, with the addition of sucrose to the potassium nitrate to aid combustion. For samples of relatively pure UN, the bulk UN δ15N value is stoichiometrically equivalent to the measured δ15N values of the isolated urea and nitrate in a 2:1 ratio. However, some explosive samples contained an excess of nitric acid due to poor preparation. As a result, the bulk UN δ15N values were biased towards the δ15N value of the nitrate. We are conducting experiments to compare the isotopic values of the initial starting reactants in the UN synthesis and the isotopic composition

  17. Urea transport through composite polyallylamine membranes

    NASA Technical Reports Server (NTRS)

    Ballou, E. V.; Kubo, L. Y.; Spitze, L. A.; Wydeven, T.; Clark, J. A.

    1977-01-01

    Polyallylamine composite reverse osmosis membranes were prepared by plasma polymerization and deposition onto small-pored cellulose acetate/cellulose nitrate films. The polyallylamine coated the porous substrate with a thin uniform polymer film which exhibited water permeability and urea rejection, of interest because of the potential application of reverse osmosis to urine purification in closed environmental systems. The flux of C-14 labeled urea was studied under the influence of osmotic gradients provided by sodium chloride solutions. The urea flux was found to be enhanced by an osmotic pressure gradient in the same direction and diminished, but not prevented, by an opposing osmotic pressure gradient. Consideration is given to the mechanism of the urea transport, as well as to the influence of concentration polarization on the experimental results. The minimization of coupled flow in pores of a critical size range is apparently necessary to improve urea rejection.

  18. Transport characteristics of urea transporter-B.

    PubMed

    Yang, Baoxue

    2014-01-01

    UT-B represents the major urea transporter in erythrocytes, in addition to being expressed in kidney descending vasa recta, brain, spleen, ureter, bladder, and testis. Expression of urea transporter UT-B confers high urea permeability to mammalian erythrocytes. Erythrocyte membranes are also permeable to various urea analogues, suggesting common transport pathways for urea and structurally similar solutes. UT-B is highly permeable to urea and the chemical analogues formamide, acetamide, methylurea, methylformamide, ammonium carbamate, and acrylamide, each with a Ps > 5.0 × 10(-6) cm/s at 10 °C. The amides formamide, acetamide, acrylamide, and butyramide efficiently diffuse across lipid bilayers. The urea analogues dimethylurea, acryalmide, methylurea, thiourea, and methylformamide inhibit UT-B-mediated urea transport by >60 % by a pore-blocking mechanism. UT-B is also a water channel in erythrocytes and has a single-channel water permeability that is similar to aquaporin-1. Whether UT-B is an NH3 channel still needs further study. Urea permeability (Purea) in erythrocytes differs between different mammals. Carnivores (dog, fox, cat) exhibit high Purea. In contrast, herbivores (cow, donkey, sheep) show much lower Purea. Erythrocyte Purea in human and pig (omnivores) was intermediate. Rodents and lagomorphs (mouse, rat, rabbit) have Purea intermediate between carnivores and omnivores. Birds that do not excrete urea and do not express UT-B in their erythrocytes have very low values. In contrast to Purea, water permeability is relatively similar in all mammals studied. This chapter will provide information about the transporter characteristics of UT-B.

  19. Impact of urea on detergent micelle properties.

    PubMed

    Broecker, Jana; Keller, Sandro

    2013-07-09

    Co-solvents, such as urea, can entail drastic changes in the micellization behavior of detergents. We present a systematic quantification of the impact of urea on the critical micellar concentration, the micellization thermodynamics, and the micelle size in three homologous series of commonly used non-ionic alkyl detergents. To this end, we performed demicellization experiments by isothermal titration calorimetry and hydrodynamic size measurements by dynamic light scattering on alkyl maltopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides at urea concentrations of 0-8 M. For all detergents studied, we found that the critical micellar concentration increases exponentially because the absolute Gibbs free energy of micellization decreases linearly over the entire urea concentration range, as does the micelle size. In contrast, the enthalpic and entropic contributions to micellization reveal more complex, nonlinear dependences on urea concentration. Both free energy and size changes are more pronounced for long-chain detergents, which bury more apolar surface area upon micelle formation. The Gibbs free energy increments per methylene group within each detergent series depend on urea concentration in a linear fashion, although they result from the entropic term for alkyl maltosides but are of enthalpic origin for cyclohexyl alkyl maltosides. We compare our results to transfer free energies of amino acid side chains, relate them to protein-folding data, and discuss how urea-induced changes in detergent micelle properties affect in vitro investigations on membrane proteins.

  20. Ammonia sanitisation of sewage sludge using urea.

    PubMed

    Fidjeland, Jørgen; Lalander, Cecilia; Jönsson, Håkan; Vinnerås, Björn

    2013-01-01

    The aim of the study was to develop a simple, low-cost treatment for sewage sludge using urea as a sanitising agent. Sewage sludge was spiked with Enterococcus faecalis and Salmonella typhimurium, treated with 0.5, 1, 1.5 and 2% w/w urea at laboratory scale, and the viability was monitored during 4 months of storage at 4, 10 and 22 °C (only 0.5%). A linear relationship was identified between Salmonella spp. inactivation rate and ammonia (NH3) concentration. Temperature had a positive impact on Salmonella spp. inactivation at higher temperatures, but in the range 4-10 °C temperature influenced this inactivation merely by its impact on the ammonia equilibrium. Enterococcus spp. was more persistent and a lag phase of up to 11 weeks was observed. Higher temperature and ammonia concentration reduced the lag phase duration significantly, and also had a clear effect on the inactivation rate for the treatments with 0.5% urea at 22 °C and 2% urea at 4 and 10 °C. Urea sanitisation of sewage sludge can give a 2 log10 reduction of Enterococcus spp. and more than a 5 log10 reduction of Salmonella spp. within 6 weeks with either 0.5% w/w urea at 22 °C or 2% urea at 10 °C.

  1. Concentration levels of urea in swimming pool water and reactivity of chlorine with urea.

    PubMed

    De Laat, Joseph; Feng, Wentao; Freyfer, Diab Adams; Dossier-Berne, Florence

    2011-01-01

    This study investigated the reactivity of chlorine with urea which is the main nitrogen contaminant introduced into swimming pool water by bathers. In the first part of this study, analyses showed that the mean concentrations of urea and TOC determined from 50 samples of municipal swimming pool were equal to 18.0 μM (s.d. 11.7) and 3.5 mg C L(-1) (s.d. 1.6), respectively. The mean value for the urea contribution to the TOC content was 6.3% (s.d. 3.3). The rate of decomposition of urea in swimming pool water measured during the closure time of the facility was very slow (decay at the rate of ≈ 1% per hour in the presence of 1.6-1.8 mg L(-1) of free chlorine). In the second part of this work, experiments carried out with phosphate buffered solutions of urea ([Urea](0) = 1 mM; [Cl(2)](0)/[Urea](0): 0.5-15 mol/mol; pH 7.4 ± 0.2; reaction time: 0-200 h) showed that long term chlorine demand of urea was about 5 mol Cl(2)/mol of urea. Chlorination led to a complete mineralization of organic carbon into CO(2) for a chlorine dose of 3.5 mol/mol and to the formation of 0.7-0.8 mol NO(3)(-)/mol of urea for chlorine dose of 8-10 mol/mol. Experiments conducted with dilute solutions of urea ([Urea](0) = 50 μM; pH ≈ 7.3) confirmed that the degradation rate of urea by chlorine is very slow under conditions simulating real swimming pool water.

  2. The Chinese soft-shelled turtle, Pelodiscus sinensis, decreases nitrogenous excretion, reduces urea synthesis and suppresses ammonia production during emersion.

    PubMed

    Ip, Yuen K; Lee, Serene M L; Wong, Wai P; Chew, Shit F

    2013-05-01

    The objective of this study was to examine the effects of 6 days of emersion on nitrogen metabolism and excretion in the Chinese soft-shelled turtle, Pelodiscus sinensis. Despite having a soft shell with a cutaneous surface that is known to be water permeable, P. sinensis lost only ~2% of body mass and was able to maintain its hematocrit and plasma osmolality, [Na(+)] and [Cl(-)] during 6 days of emersion. During emersion, it ameliorated water loss by reducing urine output, which led to a reduction (by 29-76%) in ammonia excretion. In comparison, there was a more prominent reduction (by 82-99%) in urea excretion during emersion due to a lack of water to flush the buccopharyngeal epithelium, which is known to be the major route of urea excretion. Consequently, emersion resulted in an apparent shift from ureotely to ammonotely in P. sinensis. Although urea concentration increased in several tissues, the excess urea accumulated could only account for 13-22% of the deficit in urea excretion. Hence, it can be concluded that a decrease (~80%) in urea synthesis occurred in P. sinensis during the 6 days of emersion. Indeed, emersion led to significant decreases in the activity of some ornithine-urea cycle enzymes (argininosuccinate synthetase/argininosuccinate lyase and arginase) from the liver of P. sinensis. As a decrease in urea synthesis occurred without the accumulation of ammonia and total free amino acids, it can be deduced that ammonia production through amino acid catabolism was suppressed with a proportional reduction in proteolysis in P. sinensis during emersion. Indeed, calculated results revealed that there could be a prominent decrease (~88%) in ammonia production in turtles after 6 days of emersion. In summary, despite being ureogenic and ureotelic in water, P. sinensis adopted a reduction in ammonia production, instead of increased urea synthesis, as the major strategy to ameliorate ammonia toxicity and problems associated with dehydration during

  3. Combustion chemistry

    SciTech Connect

    Brown, N.J.

    1993-12-01

    This research is concerned with the development and use of sensitivity analysis tools to probe the response of dependent variables to model input variables. Sensitivity analysis is important at all levels of combustion modeling. This group`s research continues to be focused on elucidating the interrelationship between features in the underlying potential energy surface (obtained from ab initio quantum chemistry calculations) and their responses in the quantum dynamics, e.g., reactive transition probabilities, cross sections, and thermal rate coefficients. The goals of this research are: (i) to provide feedback information to quantum chemists in their potential surface refinement efforts, and (ii) to gain a better understanding of how various regions in the potential influence the dynamics. These investigations are carried out with the methodology of quantum functional sensitivity analysis (QFSA).

  4. Urea and deuterium mixtures at high pressures

    SciTech Connect

    Donnelly, M. Husband, R. J.; Frantzana, A. D.; Loveday, J. S.; Bull, C. L.; Klotz, S.

    2015-03-28

    Urea, like many network forming compounds, has long been known to form inclusion (guest-host) compounds. Unlike other network formers like water, urea is not known to form such inclusion compounds with simple molecules like hydrogen. Such compounds if they existed would be of interest both for the fundamental insight they provide into molecular bonding and as potential gas storage systems. Urea has been proposed as a potential hydrogen storage material [T. A. Strobel et al., Chem. Phys. Lett. 478, 97 (2009)]. Here, we report the results of high-pressure neutron diffraction studies of urea and D{sub 2} mixtures that indicate no inclusion compound forms up to 3.7 GPa.

  5. Coulometric titration of urea with electrogenerated hypobromite.

    PubMed

    Kato, Jun; Koseki, Takuma; Aoki, Yukie; Yamada, Ayako; Tanaka, Tatsuhiko

    2013-01-01

    A definitive method is described for the indirect assay of several tens of milligrams of urea by coulometric titration. Urea was decomposed in concentrated sulfuric acid using a Kjeldahl flask. Subsequently, the formed ammonium ion was titrated with electrogenerated hypobromite ion in a sodium bromide-sodium tetraborate medium of pH 8.6, with amperometric end-point detection. Parameters affecting the pretreatment procedure were evaluated. The optimized conditions included the heating of 2 g of urea at around 300°C for 2 h with 10 cm(3) of sulfuric acid. Under the proposed conditions, the assay value with expanded uncertainty (k = 2), 99.870 ± 0.026%, agreed well with the certified value of NIST SRM 912a urea, 99.9 ± 0.1%.

  6. High nonlinear optical anisotropy of urea nanofibers

    NASA Astrophysics Data System (ADS)

    Isakov, D.; de Matos Gomes, E.; Belsley, M.; Almeida, B.; Martins, A.; Neves, N.; Reis, R.

    2010-07-01

    Nanofibers consisting of the optically nonlinear organic molecule urea embedded in both poly(ethylene oxide) (PEO) and poly(vinyl alcohol) (PVA) polymers were produced by the electrospinning technique. The second-harmonic generation produced by aligned fiber mats of these materials displays a strong dependence on the polarization of the incident light. In PVA-urea nanofibers the effectiveness in generating of the second-harmonic light is as high as that of a pure urea powder with an average grain size of 110 μm. The results suggest that single crystalline urea nanofibers were achieved with a long-range crystalline order extending into the range of 2-4 μm with PVA as the host polymer.

  7. Solution combustion synthesis of strontium aluminate, SrAl2O4, powders: single-fuel versus fuel-mixture approach.

    PubMed

    Ianoş, Robert; Istratie, Roxana; Păcurariu, Cornelia; Lazău, Radu

    2016-01-14

    The solution combustion synthesis of strontium aluminate, SrAl2O4, via the classic single-fuel approach and the modern fuel-mixture approach was investigated in relation to the synthesis conditions, powder properties and thermodynamic aspects. The single-fuel approach (urea or glycine) did not yield SrAl2O4 directly from the combustion reaction. The absence of SrAl2O4 was explained by the low amount of energy released during the combustion process, in spite of the highly negative values of the standard enthalpy of reaction and standard Gibbs free energy. In the case of single-fuel recipes, the maximum combustion temperatures measured by thermal imaging (482 °C - urea, 941 °C - glycine) were much lower than the calculated adiabatic temperatures (1864 °C - urea, 2147 °C - glycine). The fuel-mixture approach (urea and glycine) clearly represented a better option, since (α,β)-SrAl2O4 resulted directly from the combustion reaction. The maximum combustion temperature measured in the case of a urea and glycine fuel mixture was the highest one (1559 °C), which was relatively close to the calculated adiabatic temperature (1930 °C). The addition of a small amount of flux, such as H3BO3, enabled the formation of pure α-SrAl2O4 directly from the combustion reaction.

  8. 21 CFR 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Urea nitrogen test system. 862.1770 Section 862....1770 Urea nitrogen test system. (a) Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  9. 21 CFR 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Urea nitrogen test system. 862.1770 Section 862....1770 Urea nitrogen test system. (a) Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  10. 21 CFR 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Urea nitrogen test system. 862.1770 Section 862....1770 Urea nitrogen test system. (a) Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  11. 21 CFR 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Urea nitrogen test system. 862.1770 Section 862....1770 Urea nitrogen test system. (a) Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  12. 21 CFR 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Urea nitrogen test system. 862.1770 Section 862....1770 Urea nitrogen test system. (a) Identification. A urea nitrogen test system is a device intended to measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  13. Synthesis of functional materials in combustion reactions

    SciTech Connect

    Zhuravlev, V. D. Bamburov, V. G.; Ermakova, L. V.; Lobachevskaya, N. I.

    2015-12-15

    The conditions for obtaining oxide compounds in combustion reactions of nitrates of metals with organic chelating–reducing agents such as amino acids, urea, and polyvinyl alcohol are reviewed. Changing the nature of internal fuels and the reducing agent-to-oxidizing agent ratio makes possible to modify the thermal regime of the process, fractal dimensionality, morphology, and dispersion of synthesized functional materials. This method can be used to synthesize simple and complex oxides, composites, and metal powders, as well as ceramics and coatings. The possibilities of synthesis in combustion reactions are illustrated by examples of αand γ-Al{sub 2}O{sub 3}, YSZ composites, uranium oxides, nickel powder, NiO and NiO: YSZ composite, TiO{sub 2}, and manganites, cobaltites, and aluminates of rare earth elements.

  14. Combustion Fundamentals Research

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Increased emphasis is placed on fundamental and generic research at Lewis Research Center with less systems development efforts. This is especially true in combustion research, where the study of combustion fundamentals has grown significantly in order to better address the perceived long term technical needs of the aerospace industry. The main thrusts for this combustion fundamentals program area are as follows: analytical models of combustion processes, model verification experiments, fundamental combustion experiments, and advanced numeric techniques.

  15. Coal combustion science

    SciTech Connect

    Hardesty, D.R.; Baxter, L.L.; Fletcher, T.H.; Mitchell, R.E.

    1990-11-01

    The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center (PETC) Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency (IEA) Coal Combustion Science Project. Specific tasks include: coal devolatilization, coal char combustion, and fate of mineral matter during coal combustion. 91 refs., 40 figs., 9 tabs.

  16. Liquid chromatographic determination of urea in water-soluble urea-formaldehyde fertilizer products and in aqueous urea solutions: collaborative study.

    PubMed

    Hojjatie, Michael M; Abrams, Dean E; Parham, Thomas M; Balthrop, J; Beine, R; Dickinson, V; Hartshorn, J; Herald, S; Latimer, G; Padmore, J; Pleasants, S; Riter, K; Roser, R; Schmunck, G; Sensmeier, R; Smith, V; Taylor, L; Volgas, G

    2004-01-01

    Water soluble urea-formaldehyde (UF) fertilizers, manufactured by complex reaction of urea and formaldehyde, typically contain varying amounts of unreacted urea. A liquid chromatography method for the analysis of urea in these products, and in aqueous urea solutions, was collaboratively studied. An amine chromatography column was used to separate the unreacted urea from numerous UF reaction products present in these liquid fertilizers. Unreacted urea was determined by using external urea standards with UV detection at 195 nm. The standards and test samples were prepared in the mobile phase of 85% (v/v) acetonitrile in water. Ten laboratories analyzed 5 different UF-based commercial products containing unreacted urea in the range of 6 to 17% by weight, and 5 different concentrations of urea in water equivalent to commercial products of that nature. The aqueous urea solutions contained 2-20% urea (w/w). The range of s(R) values for the 5 UF-based commercial fertilizers was 0.49-1.02 and the %RSD(R) was 1.94-6.14. The s(R) range for the 5 urea solutions was 0.10 to 0.79 and the %RSD(R) range was 2.54 to 4.88. The average recovery of urea from the aqueous urea solutions was 96-103%. Therefore, this method is capable of monitoring urea nitrogen manufacturers' label claims and total nitrogen claims in those cases where urea is the sole source of plant food nitrogen. Based on the collaborative study data, the authors recommend this method be approved for AOAC Official First Action status.

  17. Transport of sodium and urea in outer medullary descending vasa recta.

    PubMed Central

    Pallone, T L; Work, J; Myers, R L; Jamison, R L

    1994-01-01

    We dissected and perfused outer medullary vasa recta (OMVR) from vascular bundles in the rat. Permeabilities of sodium (PNa) and urea (Pu) were simultaneously determined from the lumen-to-bath efflux of 22Na and [14C]urea. PNa and Pu were also measured by in vivo microperfusion of descending (DVR) and ascending vasa recta (AVR) at the papillary tip of Munich-Wistar rats. In some OMVR PNa was indistinguishable from zero. The mean +/- SE of PNa (x 10(-5), cm/s) in OMVR was 76 +/- 9. Pu in OMVR was always very high (x 10(-5), cm/s), 360 +/- 14. There was no correlation between OMVR PNa and Pu. Inner medullary AVR and DVR had PNa of 115 +/- 10 and 75 +/- 10, respectively, and Pu of 121 +/- 10 and 76 +/- 11, respectively. PNa and Pu in papillary vasa recta were always nearly identical and highly correlated. Transport of [14C] urea in OMVR was reversibly inhibited by addition of unlabeled urea or phloretin to the bath and lumen, providing evidence for carrier-mediated transport. These data suggest that sodium and urea might traverse the wall of inner medullary vasa recta by a paracellular pathway while urea also crosses by a transcellular route in OMVR. Electron microscopic examination of seven in vitro perfused OMVR revealed no fenestrations and exposure of these vessels to 10 microM calcium ionophore A23187 or 1 nM angiotensin II resulted in reversible contraction, suggesting that in vitro perfused OMVR are DVR only. Images PMID:8282790

  18. Combustible particluate fuel heater

    SciTech Connect

    Collins, B.H.; Jurgens, H.J.W.

    1986-01-21

    This patent describes a combustible particulate fired heater. It consists of: a combustion chamber defined by upright side walls extending between open top and bottom ends; an enclosure surrounding the combustion chamber; a retort within the combustion chamber adjacent the bottom end and having a lower particulate receiving end and an upper open end; feed conveyor means leading through the enclosure to the retort for delivering metered quantities of combustible particulates to the lower particulate receiving end of the retort; primary combustion air supply means having a primary combustion air supply manifold extending at least partially about the upper open end of the retort; primary air control means on the primary air supply means for selectively allowing entry of combustion air from outside the enclosure in to the retort; secondary combustion air supply means including a secondary air supply manifold within the combustion chamber above the primary combustion air supply manifold; secondary air control means independent of the primary air control means for selectively allowing entry of secondary air from outside the enclosure to an area within the combustion chamber above the retort; an exhaust duct opening into the enclosure; and vacuum means connected to the exhaust duct for producing a pressure differential between the area confined by the enclosure and the ambient atmosphere such that ambient air is drawn through at least one of the combustion air supply means to induce a high level of gasification and to support combustion at the retort and for drawing combustion exhaust gases out through the exhaust duct.

  19. Combustion technologies

    SciTech Connect

    Barsin, J.A.

    1994-12-31

    The presentation will cover the highlights of sludge, providing information as to where it comes from, projection of how much more is expected, what is sludge, what can be done with them, and finally focus in one combustion technology that can be utilized and applied to recycle sludge. The author is with Gotaverken Energy Systems Inc. where for the past 100 years they have been involved in the recovery of chemicals in chemical pulp mills. One week ago, our name was changed to Kvaerner Pulping Inc. to better reflect our present make-up which is a combination of Kamyr AB (suppliers of proprietary highly engineered totally chlorine free chemical pulp manufacturing systems, including digesters, O{sub 2} delignification systems, and bleach plant systems) and Goetaverken. Sludges that we are concerned with derive from several sources within chemical pulp mills such as: such as primary clarifier sludges, secondary clarifier sludges, and most recently those sludges derived from post consumer paper and board recycle efforts including de-inking and those from the thermal mechanical pulping processes. These sludges have been classified as non-hazardous therefore, residue can be landfilled, but the volumes involved are growing at an alarming rate.

  20. SNCR De-NOx within a moderate temperature range using urea-spiked hydrazine hydrate as reductant.

    PubMed

    Chen, H; Chen, D Z; Fan, S; Hong, L; Wang, D

    2016-10-01

    In this research, urea-spiked hydrazine hydrate solutions are used as reductants for the Selective Non-Catalytic Reduction (SNCR) De-NOx process below 650 °C. The urea concentration in the urea/hydrazine hydrate solutions is chosen through experimental and theoretical studies. To determine the mechanism of the De-NOx process, thermogravimetric analysis (TGA) of the urea/hydrazine hydrate solutions and their thermal decomposition in air and nitrogen atmospheres were studied to understand their decomposition behaviours and redox characteristics. Then a plug flow reactor (PFR) model was adopted to simulate the De-NOx processes in a pilot scale tubular reactor, and the calculated De-NOx efficiency vs. temperature profiles were compared with experimental results to support the mechanism and choose the proper reductant and its reaction temperature. Both the experimental and calculated results show that when the urea is spiked into hydrazine hydrate solution to make the urea-N content approximately 16.7%-25% of the total N content in the solution, better De-NOx efficiencies can be obtained in the temperature range of 550-650 °C, under which NH3 is inactive in reducing NOx. And it is also proved that for these urea-spiked hydrazine hydrate solutions, the hydrazine decomposition through the pathway N2H4 + M = N2H3 + H + M is enhanced to provide radical H, which is active to reduce NO. Finally, the reaction routes for SNCR De-NOx process based on urea-spiked hydrazine hydrate at the proper temperature are proposed.

  1. Evolutionary aspects of urea utilization by fungi

    PubMed Central

    Navarathna, Dhammika H.M.L.P.; Harris, Steven D.; Roberts, David D.; Nickerson, Kenneth W.

    2009-01-01

    The higher fungi exhibit a dichotomy with regard to urea utilization. The hemiascomycetes use urea amidolyase (DUR1,2) whereas all other higher fungi use the nickel-containing urease. Urea amidolyase is an energy dependent biotin-containing enzyme. It likely arose prior to the Euascomycete/Hemiascomycete divergence ca. 350 million years ago by insertion of an unknown gene into one copy of a duplicated methylcrotonyl CoA carboxylase (MccA). The dichotomy between urease and urea amidolyase coincides precisely with that for the Ni/Co transporter (Nic1p) which is present in the higher fungi that use urease and absent in those that do not. We suggest that the selective advantage for urea amidolyase is that it allowed the hemiascomycetes to jettison all Ni2+ and Co2+ dependent metabolism and thus to have two fewer transition metals whose concentrations need to be regulated. Also, the absence of MccA in the hemiascomycetes coincides with and may explain their production of fusel alcohols. PMID:20100286

  2. Combustion 2000

    SciTech Connect

    2000-06-30

    This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 2.2.5.2 Laboratory and Bench Scale Activities

  3. Combustion 2000

    SciTech Connect

    A. Levasseur; S. Goodstine; J. Ruby; M. Nawaz; C. Senior; F. Robson; S. Lehman; W. Blecher; W. Fugard; A. Rao; A. Sarofim; P. Smith; D. Pershing; E. Eddings; M. Cremer; J. Hurley; G. Weber; M. Jones; M. Collings; D. Hajicek; A. Henderson; P. Klevan; D. Seery; B. Knight; R. Lessard; J. Sangiovanni; A. Dennis; C. Bird; W. Sutton; N. Bornstein; F. Cogswell; C. Randino; S. Gale; Mike Heap

    2001-06-30

    . To achieve these objectives requires a change from complete reliance of coal-fired systems on steam turbines (Rankine cycles) and moving forward to a combined cycle utilizing gas turbines (Brayton cycles) which offer the possibility of significantly greater efficiency. This is because gas turbine cycles operate at temperatures well beyond current steam cycles, allowing the working fluid (air) temperature to more closely approach that of the major energy source, the combustion of coal. In fact, a good figure of merit for a HIPPS design is just how much of the enthalpy from coal combustion is used by the gas turbine. The efficiency of a power cycle varies directly with the temperature of the working fluid and for contemporary gas turbines the optimal turbine inlet temperature is in the range of 2300-2500 F (1260-1371 C). These temperatures are beyond the working range of currently available alloys and are also in the range of the ash fusion temperature of most coals. These two sets of physical properties combine to produce the major engineering challenges for a HIPPS design. The UTRC team developed a design hierarchy to impose more rigor in our approach. Once the size of the plant had been determined by the choice of gas turbine and the matching steam turbine, the design process of the High Temperature Advanced Furnace (HITAF) moved ineluctably to a down-fired, slagging configuration. This design was based on two air heaters: one a high temperature slagging Radiative Air Heater (RAH) and a lower temperature, dry ash Convective Air Heater (CAH). The specific details of the air heaters are arrived at by an iterative sequence in the following order:-Starting from the overall Cycle requirements which set the limits for the combustion and heat transfer analysis-The available enthalpy determined the range of materials, ceramics or alloys, which could tolerate the temperatures-Structural Analysis of the designs proved to be the major limitation-Finally the commercialization

  4. Go the Yeshiva Route?

    ERIC Educational Resources Information Center

    Miles, Leland

    1981-01-01

    The Supreme Court's decision in the National Labor Relations Board v. Yeshiva University court case is discussed. National reactions to the case, arguments in favor of the Yeshiva route, arguments against the Yeshiva route, and financial considerations are discussed. (MLW)

  5. Combustion 2000

    SciTech Connect

    1999-12-31

    This report presents work carried out under contract DE-AC22-95PC95144 ''Combustion 2000 - Phase II.'' The goals of the program are to develop a coal-fired high performance power generation system (HIPPS) that is capable of: {lg_bullet} thermal efficiency (HHV) {ge} 47% {lg_bullet} NOx, SOx, and particulates {le} 10% NSPS (New Source Performance Standard) {lg_bullet} coal providing {ge} 65% of heat input {lg_bullet} all solid wastes benign {lg_bullet} cost of electricity {le} 90% of present plants Phase I, which began in 1992, focused on the analysis of various configurations of indirectly fired cycles and on technical assessments of alternative plant subsystems and components, including performance requirements, developmental status, design options, complexity and reliability, and capital and operating costs. Phase I also included preliminary R&D and the preparation of designs for HIPPS commercial plants approximately 300 MWe in size. Phase II, had as its initial objective the development of a complete design base for the construction and operation of a HIPPS prototype plant to be constructed in Phase III. As part of a descoping initiative, the Phase III program has been eliminated and work related to the commercial plant design has been ended. The rescoped program retained a program of engineering research and development focusing on high temperature heat exchangers, e.g. HITAF development (Task 2); a rescoped Task 6 that is pertinent to Vision 21 objectives and focuses on advanced cycle analysis and optimization, integration of gas turbines into complex cycles, and repowering designs; and preparation of the Phase II Technical Report (Task 8). This rescoped program deleted all subsystem testing (Tasks 3, 4, and 5) and the development of a site-specific engineering design and test plan for the HIPPS prototype plant (Task 7). Work reported herein is from: {lg_bullet} Task 2.2.4 Pilot Scale Testing {lg_bullet} Task 2.2.5.2 Laboratory and Bench Scale Activities

  6. Fundamentals of Gas Turbine combustion

    NASA Technical Reports Server (NTRS)

    Gerstein, M.

    1979-01-01

    Combustion problems and research recommendations are discussed in the areas of atomization and vaporization, combustion chemistry, combustion dynamics, and combustion modelling. The recommendations considered of highest priority in these areas are presented.

  7. Wood plastic composite at different urea concentrations

    NASA Astrophysics Data System (ADS)

    Husain, M. M.; Khan, Mubarak A.; Ali, K. M. Idriss; Hasan, A. J. M. Moynul

    1995-04-01

    Wood plastic composite (WPC) has been prepared with a low grade wood simul ( Salmalia malabarica) of Bangladesh under Co-60 gamma irradiation using MMA as the bulk monomer combined with methanol as the swelling solvent at different urea concentrations. Effect of a second solute such as NVP, TPGDA and TMPTA in the impregnating solution is evaluated. NVP appears to be the best co-additive/second solute among all the additives used to yield the composite with the highest polymer loading (PL) and tensile strength (TS) at 0.5% urea concentration.

  8. The incidence of urea cycle disorders

    PubMed Central

    Summar, Marshall L.; Koelker, Stefan; Freedenberg, Debra; Le Mons, Cynthia; Haberle, Johannes; Lee, Hye-Seung; Kirmse, Brian

    2014-01-01

    A key question for urea cycle disorders is their incidence. In the United States two UCDs, argininosuccinic synthetase and lyase deficiency, are currently detected by newborn screening. We used newborn screening data on over 6 million births and data from the large US and European longitudinal registries to determine how common these conditions are. The incidence for the United States is predicted to be 1 urea cycle disorder patient for every 35,000 births presenting about 113 new patients per year across all age groups. PMID:23972786

  9. [Effects of urea and coated urea on harmful gases concentrations in plastic greenhouse].

    PubMed

    Zhou, Xihong; Zeng, Qingru; Mao, Xiaoyun; Zhang, Litian; Liao, Bohan; Tie, Baiqing; Liao, Zongwen

    2006-09-01

    With simulation test and plastic greenhouse experiment, this paper studied the effects of urea and minerals- coated urea on the soil pH and harmful gases concentrations in plastic greenhouse. The results showed that under simulated condition, the application of these'two N fertilizers led to an initial increase of soil pH, which reached the maximum (an increment of > 50%) within the first week and dropped to the initial level by the end of the fifth week. In plastic greenhouse, applying urea and coated urea resulted in the increase of NH3, NO2 and O3 concentrations. The daily volatilization amount of NH3 and NO2 was higher in urea treatment than in coated urea treatment, and the highest value in urea treatment was 42.36 microg x m(-3) x d(-1) for NH3, 41.95 microg x m(-3) x d(-1) for NO2, and 86.00 microg x m(-3) x d(-1) for O3. The volatilization intensity of NH3 and NO2 was influenced by temperature and sunlight, while the O3 concentration was influenced by sunlight.

  10. Urea recycling from the renal pelvis in sheep: A study with ( sup 14 C)urea

    SciTech Connect

    Cirio, A.; Boivin, R. )

    1990-05-01

    To test the hypothesis that urea can be recycled from the renal pelvis, (14C)urea diluted in native urine (1 microCi/ml) was perfused (0.5 ml/min) into one of the pelvises of sheep fed either normal (NP) or low (LP)-protein diets. Blood samples were obtained from the ipsilateral renal vein and from the carotid artery throughout the perfusions. 14C activity determinations in urine and plasma demonstrated a flux of (14C)urea from the pelvis to renal vein blood (40,000 in NP and 130,000 disintegrations/min in LP sheep, P less than 0.01). The corresponding flux of native urea was only 1.5 times higher in NP than in LP sheep (6.8 +/- 1.1 vs. 4.7 +/- 2.9 mumol/min, not significant) despite their 8 times higher urinary concentration of urea. The fraction of filtered urea that was reabsorbed in the pelvis was larger in LP sheep (7.5 +/- 3.7 vs. 1.9 +/- 0.7% in NP sheep, P less than 0.05). A fraction of urea is thus actually recycled from the renal pelvis in sheep, and this pelvic retention is enhanced in LP animals. The importance of this phenomenon in the nitrogen economy is discussed.

  11. Stability of urea in solution and pharmaceutical preparations.

    PubMed

    Panyachariwat, Nattakan; Steckel, Hartwig

    2014-01-01

    The stability of urea in solution and pharmaceutical preparations was analyzed as a function of temperature (25°-60°C), pH (3.11-9.67), and initial urea concentration (2.5%-20%). This study was undertaken to (i) obtain more extensive, quantitative information relative to the degradation of urea in both aqueous and non-aqueous solutions and in pharmaceutical preparations, and (ii) test the effects of initial urea concentration, pH, buffer, and temperature values on urea degradation. The stability analysis shows that urea is more stable at the pH range of 4-8 and the stability of urea decreases by increase in temperature for all pH values. Within the experimental range of temperature and initial urea concentration values, the lowest urea degradation was found with lactate buffer pH 6.0. The urea decomposition rate in solution and pharmaceutical preparations shows the dependence of the initial urea concentrations. At higher initial urea concentrations, the rate of degradation is a decreasing function with time. This suggests that the reverse reaction is a factor in the degradation of concentrated urea solution. For non-aqueous solvents, isopropanol showed the best effort in retarding the decomposition of urea. Since the losses in urea is directly influenced by its stability at a given temperature and pH, the stability analysis of urea by the proposed model can be used to prevent the loss and optimize the operating condition for urea-containing pharmaceutical preparations.

  12. Flameless Combustion Workshop

    DTIC Science & Technology

    2005-09-20

    future roadmap. "Flameless Combustion " is characterized by high stability levels with virtually no thermoacoustic instabilities, very low lean... future roadmap. "Flameless Combustion " is characterized by high stability levels with virtually no thermoacoustic instabilities, very low lean stability...C. Bruno, Italy 1430-1500 Technology to Ramjet Combustion Application of FLameless H. Mongia , GE Transportation, 1500-1530 Combustion (FLC) for

  13. Generation of semicarbazide from natural azine development in foods, followed by reaction with urea compounds.

    PubMed

    Abernethy, Grant A

    2015-01-01

    This paper proposes a mechanism to explain the trace levels of natural semicarbazide occasionally observed in foods. The analytical derivative of semicarbazide, 2-nitrobenzaldehyde semicarbazone, is often measured as a metabolite marker to detect the widely banned antibiotic nitrofurazone. However, this marker is not specific as semicarbazide may be present in foods for several reasons other than exposure to nitrofurazone. In some cases, an entirely natural origin of semicarbazide is suspected, although up until now there was no explanation about how semicarbazide could occur naturally. In this work, semicarbazide is proposed as being generated from natural food compounds via an azine intermediate. Hydrazine, in the form of azines or hydrazones, may be generated in dilute aqueous solution from the natural food compounds ammonia, hydrogen peroxide and acetone, following known oxidation chemistry. When this mixture was prepared in the presence of ureas such as allantoin, urea, biuret or hydroxyurea, and then analysed by the standard method for the determination of semicarbazide, 2-nitrobenzaldehyde semicarbazone was detected. 2-Nitrobenzaldehyde aldazine was also found, and it may be a general marker for azines in foods. This proposal, that azine formation is central to semicarbazide development, provides a convergence of the published mechanisms for semicarbazide. The reaction starts with hydrogen peroxide, peracetic acid, atmospheric oxygen or hypochlorite; generates hydrazine either by an oxaziridine intermediate or via the chlorination of ammonia; and then either route may converge on azine formation, followed by reaction with a urea compound. Additionally, carbamate ion may speculatively generate semicarbazide by reaction with hydrazine, which might be a significant route in the case of the hypochlorite treatment of foods or food contact surfaces. Significantly, detection of 2-nitrobenzaldehyde semicarbazone may be somewhat artefactual because semicarbazide can

  14. Mechanisms of droplet combustion

    NASA Technical Reports Server (NTRS)

    Law, C. K.

    1982-01-01

    The fundamental physico-chemical mechanisms governing droplet vaporization and combustion are discussed. Specific topics include governing equations and simplifications, the classical d(2)-Law solution and its subsequent modification, finite-rate kinetics and the flame structure, droplet dynamics, near- and super-critical combustion, combustion of multicomponent fuel blends/emulsions/suspensions, and droplet interaction. Potential research topics are suggested.

  15. Synthesis and characterization of chitosan alkyl urea.

    PubMed

    Wang, Jing; Jiang, Ji-Zhou; Chen, Wei; Bai, Zheng-Wu

    2016-07-10

    Chitosan is a versatile material employed for various purposes in many fields including the development of chiral stationary phases for enantioseparation. Chitosan alkyl urea is a kind of intermediate used to prepare enantioseparation materials. In order to synthesize the intermediates, in the present work, a new way to prepare chitosan alkyl urea has been established: chitosan was first reacted with methyl chloroformate yielding N-methoxyformylated chitosan, which was then converted to chitosan alkyl urea through amine-ester exchange reaction. With a large excess of methyl chloroformate and primary amine of low stereohindrance, the amino group in chitosan could be almost completely converted to ureido group. The as-prepared chitosan alkyl urea derivatives were characterized by IR, (1)H NMR, (13)C NMR,(1)H-(1)H COSY and (1)H-(13)C HSQC NMR spectra. The chemical shifts of hydrogen and carbon atoms of glucose unit were assigned. It was found that the degree of substitution was obviously lower if cyclopropyl amine, aniline, tert-butyl amine and diethyl amine were used as reactants for the amine-ester exchange reaction. The reason was explained with the aid of theoretical calculations.

  16. Aldehyde-containing urea-absorbing polysaccharides

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr. (Inventor)

    1977-01-01

    A novel aldehyde containing polymer (ACP) is prepared by reaction of a polysaccharide with periodate to introduce aldehyde groups onto the C2 - C3 carbon atoms. By introduction of ether and ester groups onto the pendant primary hydroxyl solubility characteristics are modified. The ACP is utilized to absorb nitrogen bases such as urea in vitro or in vivo.

  17. State alternative route designations

    SciTech Connect

    Not Available

    1989-07-01

    Pursuant to the Hazardous Materials Transportation Act (HMTA), the Department of Transportation (DOT) has promulgated a comprehensive set of regulations regarding the highway transportation of high-level radioactive materials. These regulations, under HM-164 and HM-164A, establish interstate highways as the preferred routes for the transportation of radioactive materials within and through the states. The regulations also provide a methodology by which a state may select alternative routes. First,the state must establish a ``state routing agency,`` defined as an entity authorized to use the state legal process to impose routing requirements on carriers of radioactive material (49 CFR 171.8). Once identified, the state routing agency must select routes in accordance with Large Quantity Shipments of Radioactive Materials or an equivalent routing analysis. Adjoining states and localities should be consulted on the impact of proposed alternative routes as a prerequisite of final route selection. Lastly, the states must provide written notice of DOT of any alternative route designation before the routes are deemed effective.

  18. State alternative route designations

    SciTech Connect

    Not Available

    1989-07-01

    Pursuant to the Hazardous Materials Transportation Act (HMTA), the Department of Transportation (DOT) has promulgated a comprehensive set of regulations regarding the highway transportation of high-level radioactive materials. These regulations, under HM-164 and HM-164A, establish interstate highways as the preferred routes for the transportation of radioactive materials within and through the states. The regulations also provide a methodology by which a state may select alternative routes. First,the state must establish a state routing agency,'' defined as an entity authorized to use the state legal process to impose routing requirements on carriers of radioactive material (49 CFR 171.8). Once identified, the state routing agency must select routes in accordance with Large Quantity Shipments of Radioactive Materials or an equivalent routing analysis. Adjoining states and localities should be consulted on the impact of proposed alternative routes as a prerequisite of final route selection. Lastly, the states must provide written notice of DOT of any alternative route designation before the routes are deemed effective.

  19. Defining Dynamic Route Structure

    NASA Technical Reports Server (NTRS)

    Zelinski, Shannon; Jastrzebski, Michael

    2011-01-01

    This poster describes a method for defining route structure from flight tracks. Dynamically generated route structures could be useful in guiding dynamic airspace configuration and helping controllers retain situational awareness under dynamically changing traffic conditions. Individual merge and diverge intersections between pairs of flights are identified, clustered, and grouped into nodes of a route structure network. Links are placed between nodes to represent major traffic flows. A parametric analysis determined the algorithm input parameters producing route structures of current day flight plans that are closest to todays airway structure. These parameters are then used to define and analyze the dynamic route structure over the course of a day for current day flight paths. Route structures are also compared between current day flight paths and more user preferred paths such as great circle and weather avoidance routing.

  20. Urea retranslocation from senescing Arabidopsis leaves is promoted by DUR3-mediated urea retrieval from leaf apoplast.

    PubMed

    Bohner, Anne; Kojima, Soichi; Hajirezaei, Mohammad; Melzer, Michael; von Wirén, Nicolaus

    2015-02-01

    In plants, urea derives either from root uptake or protein degradation. Although large quantities of urea are released during senescence, urea is mainly seen as a short-lived nitrogen (N) catabolite serving urease-mediated hydrolysis to ammonium. Here, we investigated the roles of DUR3 and of urea in N remobilization. During natural leaf senescence urea concentrations and DUR3 transcript levels showed a parallel increase with senescence markers like ORE1 in a plant age- and leaf age-dependent manner. Deletion of DUR3 decreased urea accumulation in leaves, whereas the fraction of urea lost to the leaf apoplast was enhanced. Under natural and N deficiency-induced senescence DUR3 promoter activity was highest in the vasculature, but was also found in surrounding bundle sheath and mesophyll cells. An analysis of petiole exudates from wild-type leaves revealed that N from urea accounted for >13% of amino acid N. Urea export from senescent leaves further increased in ureG-2 deletion mutants lacking urease activity. In the dur3 ureG double insertion line the absence of DUR3 reduced urea export from leaf petioles. These results indicate that urea can serve as an early metabolic marker for leaf senescence, and that DUR3-mediated urea retrieval contributes to the retranslocation of N from urea during leaf senescence.

  1. A test of improved force field parameters for urea: molecular-dynamics simulations of urea crystals.

    PubMed

    Özpınar, Gül Altınbaş; Beierlein, Frank R; Peukert, Wolfgang; Zahn, Dirk; Clark, Timothy

    2012-08-01

    Molecular-dynamics (MD) simulations of urea crystals of different shapes (cubic, rectangular prismatic, and sheet) have been performed using our previously published force field for urea. This force field has been validated by calculating values for the cohesive energy, sublimation temperature, and melting point from the MD data. The cohesive energies computed from simulations of cubic and rectangular prismatic urea crystals in vacuo at 300 K agreed very well with the experimental sublimation enthalpies reported at 298 K. We also found very good agreement between the melting points as observed experimentally and from simulations. Annealing the crystals just below the melting point leads to reconstruction to form crystal faces that are consistent with experimental observations. The simulations reveal a melting mechanism that involves surface (corner/edge) melting well below the melting point, and rotational disordering of the urea molecules in the corner/edge regions of the crystal, which then facilitates the translational motion of these molecules.

  2. Quantitative determination of urea concentrations in cell culture medium

    PubMed Central

    Zawada, Robert J.X.; Kwan, Peggy; Olszewski, Kellen L.; Llinas, Manuel; Huang, Shu-Gui

    2009-01-01

    Urea is the major nitrogenous end product of protein metabolism in mammals. Here, we describe a quantitative, sensitive method for urea determination using a modified Jung reagent. This assay is specific for urea and is unaffected by ammonia, a common interferent in tissue and cell cultures. We demonstrate that this convenient colorimetric microplate-based, room temperature assay can be applied to determine urea synthesis in cell culture. PMID:19448747

  3. Quantitative determination of urea concentrations in cell culture medium.

    PubMed

    Zawada, Robert J X; Kwan, Peggy; Olszewski, Kellen L; Llinas, Manuel; Huang, Shu-Gui

    2009-06-01

    Urea is the major nitrogenous end product of protein metabolism in mammals. Here, we describe a quantitative, sensitive method for urea determination using a modified Jung reagent. This assay is specific for urea and is unaffected by ammonia, a common interferent in tissue and cell cultures. We demonstrate that this convenient colorimetric microplate-based, room temperature assay can be applied to determine urea synthesis in cell culture.

  4. Urea transporters and sweat response to uremia.

    PubMed

    Keller, Raymond W; Bailey, James L; Wang, Yanhua; Klein, Janet D; Sands, Jeff M

    2016-06-01

    In humans, urea is excreted in sweat, largely through the eccrine sweat gland. The urea concentration in human sweat is elevated when compared to blood urea nitrogen. The sweat urea nitrogen (UN) of patients with end-stage kidney disease (ESRD) is increased when compared with healthy humans. The ability to produce sweat is maintained in the overwhelming majority of ESRD patients. A comprehensive literature review found no reports of sweat UN neither in healthy rodents nor in rodent models of chronic kidney disease (CKD). Therefore, this study measured sweat UN concentrations in healthy and uremic rats. Uninephrectomy followed by renal artery ligation was used to remove 5/6 of renal function. Rats were then fed a high-protein diet to induce uremia. Pilocarpine was used to induce sweating. Sweat droplets were collected under oil. Sweat UN was measured with a urease assay. Serum UN was measured using a fluorescent ortho-pthalaldehyde reaction. Immunohistochemistry (IHC) was accomplished with a horseradish peroxidase and diaminobenzidine technique. Sweat UN in uremic rats was elevated greater than two times compared to healthy pair-fed controls (220 ± 17 and 91 ± 15 mmol/L, respectively). Post hoc analysis showed a significant difference between male and female uremic sweat UN (279 ± 38 and 177 ± 11 mmol/L, respectively.) IHC shows, for the first time, the presence of the urea transporters UT-B and UT-A2 in both healthy and uremic rat cutaneous structures. Future studies will use this model to elucidate how rat sweat UN and other solute excretion is altered by commonly prescribed diuretics.

  5. Malleable and Recyclable Poly(urea-urethane) Thermosets bearing Hindered Urea Bonds.

    PubMed

    Zhang, Yanfeng; Ying, Hanze; Hart, Kevin R; Wu, Yuxiao; Hsu, Aaron J; Coppola, Anthony M; Kim, Tae Ann; Yang, Ke; Sottos, Nancy R; White, Scott R; Cheng, Jianjun

    2016-09-01

    Poly(urea-urethane) thermosets containing the 1-tert-butylethylurea (TBEU) structure feature a reversible dissociation/association process of their covalent linkages under mild conditions. Unlike conventional thermosets, TBEU-based poly(urea-urethane) thermosets maintain their malleability after curing. Under high temperature (100 °C) and applied pressure (300 kPa), ground TBEU thermoset powder can be remolded to bulk after 20 min.

  6. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Sodium nitrate-urea complex. 176.320 Section 176... Substances for Use Only as Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium... the provisions of this section. (a) Sodium nitrate-urea complex is a clathrate of approximately...

  7. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Sodium nitrate-urea complex. 176.320 Section 176... Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a..., packaging, transporting, or holding food, subject to the provisions of this section. (a) Sodium...

  8. MICROWAVE-ASSISTED PREPARATION OF CYCLIC UREAS FROM DIAMINES

    EPA Science Inventory

    Rajender S. Varma* and Yong-Jin Kim
    Cyclic ureas are useful intermediates for a variety of pharmaceuticals and pesticides. One of the attractive approaches for the synthesis of cyclic ureas uses condensation of diamines with urea as a carbonyl source under dynamic evacuation. ...

  9. 76 FR 77015 - Solid Urea From Russia and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-12-09

    ... COMMISSION Solid Urea From Russia and Ukraine Determination On the basis of the record \\1\\ developed in the... antidumping duty orders on solid urea from Russia and Ukraine would be likely to lead to continuation or... 2011), entitled Solid Urea from Russia and Ukraine: Investigation Nos. 731-TA- 340-E and 340-H...

  10. 76 FR 15339 - Solid Urea From Russia and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-21

    ... COMMISSION Solid Urea From Russia and Ukraine AGENCY: United States International Trade Commission. ACTION... orders on solid urea from Russia and Ukraine. SUMMARY: The Commission hereby gives notice that it will...)) to determine whether revocation of the antidumping duty orders on solid urea from Russia and...

  11. Synthesis, Characterization, and Sensitivity Analysis of Urea Nitrate (UN)

    DTIC Science & Technology

    2015-04-01

    ARL-TR-7250 ● APR 2015 US Army Research Laboratory Synthesis, Characterization, and Sensitivity Analysis of Urea Nitrate (UN...Characterization, and Sensitivity Analysis of Urea Nitrate (UN) by William M Sherrill Weapons and Materials Research Directorate...Characterization, and Sensitivity Analysis of Urea Nitrate (UN) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S

  12. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Sodium nitrate-urea complex. 176.320 Section 176... Substances for Use Only as Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component of articles intended for use in...

  13. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Sodium nitrate-urea complex. 176.320 Section 176... Substances for Use Only as Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component of articles intended for use in...

  14. 21 CFR 176.320 - Sodium nitrate-urea complex.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Sodium nitrate-urea complex. 176.320 Section 176... Substances for Use Only as Components of Paper and Paperboard § 176.320 Sodium nitrate-urea complex. Sodium nitrate-urea complex may be safely used as a component of articles intended for use in...

  15. Opportunities in pulse combustion

    SciTech Connect

    Brenchley, D.L.; Bomelburg, H.J.

    1985-10-01

    In most pulse combustors, the combustion occurs near the closed end of a tube where inlet valves operate in phase with the pressure amplitude variations. Thus, within the combustion zone, both the temperature and the pressure oscillate around a mean value. However, the development of practical applications of pulse combustion has been hampered because effective design requires the right combination of the combustor's dimensions, valve characteristics, fuel/oxidizer combination, and flow pattern. Pulse combustion has several additional advantages for energy conversion efficiency, including high combustion and thermal efficiency, high combustion intensity, and high convective heat transfer rates. Also, pulse combustion can be self-aspirating, generating a pressure boost without using a blower. This allows the use of a compact heat exchanger that may include a condensing section and may obviate the need for a chimney. In the last decade, these features have revived interest in pulse combustion research and development, which has resulted in the development of a pulse combustion air heater by Lennox, and a pulse combustion hydronic unit by Hydrotherm, Inc. To appraise this potential for energy savings, a systematic study was conducted of the many past and present attempts to use pulse combustion for practical purposes. The authors recommended areas where pulse combustion technology could possibly be applied in the future and identified areas in which additional R and D would be necessary. Many of the results of the study project derived from a special workshop on pulse combustion. This document highlights the main points of the study report, with particular emphasis on pulse combustion application in chemical engineering.

  16. Protein stabilization by urea and guanidine hydrochloride.

    PubMed

    Bhuyan, Abani K

    2002-11-12

    The urea, guanidine hydrochloride, salt, and temperature dependence of the rate of dissociation of CO from a nonequilibrium state of CO-bound native ferrocytochrome c has been studied at pH 7. The heme iron of ferrocytochrome c in the presence of denaturing concentrations of guanidine hydrochloride (GdnHCl) and urea prepared in 0.1 M phosphate, pH 7, binds CO. When the unfolded protein solution is diluted 101-fold into CO-free folding buffer, the protein chain refolds completely, leaving the CO molecule bonded to the heme iron. Subsequently, slow thermal dissociation of the CO molecule yields to the heme coordination of the native M80 ligand. Thus, the reaction monitors the rate of thermal conversion of the CO-liganded native ferrocytochrome c to the M80-liganded native protein. The rate of this reaction, k(diss), shows a characteristic dependence on the presence of nondenaturing concentrations of the denaturants in the reaction medium. The rate decreases by approximately 1.9-3-fold as the concentration of GdnHCl in the refolding medium increases from nearly 0 to approximately 2.1 M. Similarly, the rate decreases by 1.8-fold as the urea concentration is raised from 0.l to approximately 5 M. At still higher concentrations of the denaturants the denaturing effect sets in, the protein is destabilized, and hence the CO dissociation rate increases sharply. The activation energy of the reaction, E(a), increases when the denaturant concentration in the reaction medium is raised: from 24.1 to 28.3 kcal mol(-1) for a 0.05-2.1 M rise in GdnHCl and from 25.2 to 26.9 kcal mol(-1) for a 0.1-26.9 M increase in urea. Corresponding to these increases in denaturant concentrations are also increases in the activation entropy, S(diss)/R, where R is the gas constant of the reaction. The denaturant dependence of these kinetic and thermodynamic parameters of the CO dissociation reaction suggests that binding interactions with GdnHCl and urea can increase the structural and energetic

  17. Short communication: Urea hydrolysis in dairy cattle manure under different temperature, urea, and pH conditions.

    PubMed

    Moraes, L E; Burgos, S A; DePeters, E J; Zhang, R; Fadel, J G

    2017-03-01

    The objective of the study was to quantify the rate of urea hydrolysis in dairy cattle manure under different initial urea concentration, temperature, and pH conditions. In particular, by varying all 3 factors simultaneously, the interactions between them could also be determined. Fresh feces and artificial urine solutions were combined into a slurry to characterize the rate of urea hydrolysis under 2 temperatures (15°C and 35°C), 3 urea concentrations in urine solutions (500, 1,000, and 1,500 mg of urea-N/dL), and 3 pH levels (6, 7, and 8). Urea N concentration in slurry was analyzed at 0.0167, 1, 2, 4, 6, 8, 12, 16, 20, and 24 h after initial mixing. A nonlinear mixed effects model was used to determine the effects of urea concentration, pH, and temperature treatments on the exponential rate of urea hydrolysis and to predict the hydrolysis rate for each treatment combination. We detected a significant interaction between pH and initial urea level. Increasing urea concentration from 1,000 to 1,500 mg of urea-N/dL decreased the rate of urea hydrolysis across all pH levels. Across all pH and initial urea levels, the rate of urea hydrolysis increased with temperature, but the effect of pH was only observed for pH 6 versus pH 8 at the intermediate initial urea concentration. The fast rates of urea hydrolysis indicate that urea was almost completely hydrolyzed within a few hours of urine mixing with feces. The estimated urea hydrolysis rates from this study are likely maximum rates because of the thorough mixing before each sampling. Although considerable mixing of feces and urine occurs on the barn floor of commercial dairy operations from cattle walking through the manure, such mixing may be not as quick and thorough as in this study. Consequently, the urea hydrolysis rates from this study indicate the maximum loss of urea and should be accounted for in management aimed at mitigating ammonia emissions from dairy cattle manure under similar urea concentration, p

  18. Combustion modeling in internal combustion engines

    NASA Technical Reports Server (NTRS)

    Zeleznik, F. J.

    1976-01-01

    The fundamental assumptions of the Blizard and Keck combustion model for internal combustion engines are examined and a generalization of that model is derived. The most significant feature of the model is that it permits the occurrence of unburned hydrocarbons in the thermodynamic-kinetic modeling of exhaust gases. The general formulas are evaluated in two specific cases that are likely to be significant in the applications of the model.

  19. View southwest along Route Canterbury Road (Route 169) showing commercial ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    View southwest along Route Canterbury Road (Route 169) showing commercial and residential buildings on the east and west sides of the road - Brooklyn Green, North Green, South Green, & West Green, parts of Brown Road, Canterbury Road (Route 169), Hartford Road (Route 6), Hyde Road, Pomfret Road (Route 169), Prince Hill Road, Providence Road (Route 6), Wauregan Road (Routes 169 & 205), & Wolf Den Road, Brooklyn, Windham County, CT

  20. Proxies for Anonymous Routing

    DTIC Science & Technology

    1996-01-01

    Michael G. Reed, Paul F. Syverson, and David M. Goldschlag. Proxies for Anonymous Routing, 12th Annual Computer Security Applications Conference...San Diego, CA, December 9-13, 1996. Proxies for Anonymous Routing Michael G. Reed, Paul F. Syverson, and David M. Goldschlag Naval Research Laboratory...implemented. Onion routing provides application independent, real-time, and bi-directional anonymous connections that are resistant to both

  1. Boiler using combustible fluid

    DOEpatents

    Baumgartner, H.; Meier, J.G.

    1974-07-03

    A fluid fuel boiler is described comprising a combustion chamber, a cover on the combustion chamber having an opening for introducing a combustion-supporting gaseous fluid through said openings, means to impart rotation to the gaseous fluid about an axis of the combustion chamber, a burner for introducing a fluid fuel into the chamber mixed with the gaseous fluid for combustion thereof, the cover having a generally frustro-conical configuration diverging from the opening toward the interior of the chamber at an angle of between 15/sup 0/ and 55/sup 0/; means defining said combustion chamber having means defining a plurality of axial hot gas flow paths from a downstream portion of the combustion chamber to flow hot gases into an upstream portion of the combustion chamber, and means for diverting some of the hot gas flow along paths in a direction circumferentially of the combustion chamber, with the latter paths being immersed in the water flow path thereby to improve heat transfer and terminating in a gas outlet, the combustion chamber comprising at least one modular element, joined axially to the frustro-conical cover and coaxial therewith. The modular element comprises an inner ring and means of defining the circumferential, radial, and spiral flow paths of the hot gases.

  2. Contact Graph Routing

    NASA Technical Reports Server (NTRS)

    Burleigh, Scott C.

    2011-01-01

    Contact Graph Routing (CGR) is a dynamic routing system that computes routes through a time-varying topology of scheduled communication contacts in a network based on the DTN (Delay-Tolerant Networking) architecture. It is designed to enable dynamic selection of data transmission routes in a space network based on DTN. This dynamic responsiveness in route computation should be significantly more effective and less expensive than static routing, increasing total data return while at the same time reducing mission operations cost and risk. The basic strategy of CGR is to take advantage of the fact that, since flight mission communication operations are planned in detail, the communication routes between any pair of bundle agents in a population of nodes that have all been informed of one another's plans can be inferred from those plans rather than discovered via dialogue (which is impractical over long one-way-light-time space links). Messages that convey this planning information are used to construct contact graphs (time-varying models of network connectivity) from which CGR automatically computes efficient routes for bundles. Automatic route selection increases the flexibility and resilience of the space network, simplifying cross-support and reducing mission management costs. Note that there are no routing tables in Contact Graph Routing. The best route for a bundle destined for a given node may routinely be different from the best route for a different bundle destined for the same node, depending on bundle priority, bundle expiration time, and changes in the current lengths of transmission queues for neighboring nodes; routes must be computed individually for each bundle, from the Bundle Protocol agent's current network connectivity model for the bundle s destination node (the contact graph). Clearly this places a premium on optimizing the implementation of the route computation algorithm. The scalability of CGR to very large networks remains a research topic

  3. Atomic scale insights into urea-peptide interactions in solution.

    PubMed

    Steinke, Nicola; Gillams, Richard J; Pardo, Luis Carlos; Lorenz, Christian D; McLain, Sylvia E

    2016-02-07

    The mechanism by which proteins are denatured by urea is still not well understood, especially on the atomic scale where these interactions occur in vivo. In this study, the structure of the peptide GPG has been investigated in aqueous urea solutions in order to understand the combination of roles that both urea and water play in protein unfolding. Using a combination of neutron diffraction enhanced by isotopic substitution and computer simulations, it was found, in opposition with previous simulations studies, that urea is preferred over water around polar and charged portions of the peptides. Further, it appears that while urea directly replaces water around the nitrogen groups on GPG that urea and water occupy different positions around the peptide bond carbonyl groups. This suggests that urea may in fact weaken the peptide bond, disrupting the peptide backbone, thus ultimately causing denaturation.

  4. 1-Furfuryl-3-furoylthio-urea.

    PubMed

    Estévez-Hernández, O; Duque, J; Ellena, J; Corrêa, Rodrigo S

    2008-05-24

    The title compound, C(11)H(10)N(2)O(3)S, was synthesized from furoyl isothio-cyanate and furfurylamine in dry acetone. The thio-urea group is in the thio-amide form. The trans-cis geometry of the thio-urea group is stabilized by intra-molecular hydrogen bonding between the carbonyl and cis-thio-amide and results in a pseudo-S(6) planar ring which makes dihedral angles of 2.5 (3) and 88.1 (2)° with the furoyl and furfuryl groups, respectively. There is also an intra-molecular hydrogen bond between the furan O atom and the other thio-amide H atom. In the crystal structure, mol-ecules are linked by two inter-molecular N-H⋯O hydrogen bonds, forming dimers. These dimers are stacked within the crystal structure along the [010] direction.

  5. Slow ammonia release from urea: rumen and metabolism studies.

    PubMed

    Owens, F N; Lusby, K S; Mizwicki, K; Forero, O

    1980-03-01

    A new slow-release urea (SRU) made by coating prilled urea with a tung oil-linseed oil-talc-catalyst mixture was evaluated for ammonia-nitrogen release rate, animal acceptability, toxicity and effects on dry matter digestibility, diet intake and nitrogen retention. When added at a level equal to 1% urea in an 80% concentrate steer diet and fed twice daily, SRU gave a ruminal ammonia-nitrogen peak 1 hr postfeeding of 32 mg/dl compared to a peak from prilled urea of 53 mg/dl at 30 minutes. Bi-hourly feeding of prilled urea and SRU produced similar rumen ammonia-nitrogen levels and demonstrated that SRU was almost completely hydrolyzed in the rumen. Steers fasted for 26 hr and refed with supplements containing 10% urea from prilled urea had rumen ammonia levels of 120 ml/dl and showed muscle tremors 35 min after feeding. Rumen ammonia levels of steers fed equivalent urea from SRU remained below 35 ml/dl and exhibited no toxicity symptoms. Sheep fed ad libitum cottonseed hulls were offered a supplement containing 5% or 10% urea from urea or SRU once daily. Intake of SRU supplement was 7 and 17% greater, while cottonseed hull intakes were similar for sheep fed urea or SRU at the 5 and 10% levels. In a nitrogen balance trial, steers were fed ad libitum cottonseed hulls unsupplemented or supplemented with isonitrogenous amounts of SRU, prilled urea or soybean meal. Added nitrogen from all sources increased cottonseed hull intake. Steers fed SRU consumed more (P less than .05) cottonseed hulls than steers fed urea. Dry matter digestibility and nitrogen retention values tended to be highest for steers fed soybean meal supplement with little difference noted between prilled urea and SRU supplements.

  6. Urea-induced denaturation of preQ1-riboswitch.

    PubMed

    Yoon, Jeseong; Thirumalai, D; Hyeon, Changbong

    2013-08-14

    Urea, a polar molecule with a large dipole moment, not only destabilizes folded RNA structures but can also enhance the folding rates of large ribozymes. Unlike the mechanism of urea-induced unfolding of proteins, which is well understood, the action of urea on RNA has barely been explored. We performed extensive all-atom molecular dynamics simulations to determine the molecular underpinnings of urea-induced RNA denaturation. Urea displays its denaturing power in both secondary and tertiary motifs of the riboswitch structure. Our simulations reveal that the denaturation of RNA structures is mainly driven by the hydrogen-bonding and stacking interactions of urea with the bases. Through detailed studies of the simulation trajectories, we found that geminate pairs between urea and bases due to hydrogen bonds and stacks persist only ~0.1-1 ns, which suggests that the urea-base interaction is highly dynamic. Most importantly, the early stage of base-pair disruption is triggered by penetration of water molecules into the hydrophobic domain between the RNA bases. The infiltration of water into the narrow space between base pairs is critical in increasing the accessibility of urea to transiently disrupted bases, thus allowing urea to displace inter-base hydrogen bonds. This mechanism--water-induced disruption of base pairs resulting in the formation of a "wet" destabilized RNA followed by solvation by urea--is the exact opposite of the two-stage denaturation of proteins by urea. In the latter case, initial urea penetration creates a dry globule, which is subsequently solvated by water, leading to global protein unfolding. Our work shows that the ability to interact with both water and polar or nonpolar components of nucleotides makes urea a powerful chemical denaturant for nucleic acids.

  7. Lump wood combustion process

    NASA Astrophysics Data System (ADS)

    Kubesa, Petr; Horák, Jiří; Branc, Michal; Krpec, Kamil; Hopan, František; Koloničný, Jan; Ochodek, Tadeáš; Drastichová, Vendula; Martiník, Lubomír; Malcho, Milan

    2014-08-01

    The article deals with the combustion process for lump wood in low-power fireplaces (units to dozens of kW). Such a combustion process is cyclical in its nature, and what combustion facility users are most interested in is the frequency, at which fuel needs to be stoked to the fireplace. The paper defines the basic terms such as burnout curve and burning rate curve, which are closely related to the stocking frequency. The fuel burning rate is directly dependent on the immediate thermal power of the fireplace. This is also related to the temperature achieved in the fireplace, magnitude of flue gas losses and the ability to generate conditions favouring the full burnout of the fuel's combustible component, which, at once ensures the minimum production of combustible pollutants. Another part of the paper describes experiments conducted in traditional fireplaces with a grate, at which well-dried lump wood was combusted.

  8. A longitudinal study of urea cycle disorders.

    PubMed

    Batshaw, Mark L; Tuchman, Mendel; Summar, Marshall; Seminara, Jennifer

    2014-01-01

    The Urea Cycle Disorders Consortium (UCDC) is a member of the NIH funded Rare Diseases Clinical Research Network and is performing a longitudinal study of 8 urea cycle disorders (UCDs) with initial enrollment beginning in 2006. The consortium consists of 14 sites in the U.S., Canada and Europe. This report summarizes data mining studies of 614 patients with UCDs enrolled in the UCDC's longitudinal study protocol. The most common disorder is ornithine transcarbamylase deficiency, accounting for more than half of the participants. We calculated the overall prevalence of urea cycle disorders to be 1/35,000, with 2/3rds presenting initial symptoms after the newborn period. We found the mortality rate to be 24% in neonatal onset cases and 11% in late onset cases. The most common precipitant of clinical hyperammonemic episodes in the post-neonatal period was intercurrent infections. Elevations in both blood ammonia and glutamine appeared to be biomarkers for neurocognitive outcome. In terms of chronic treatment, low protein diet appeared to result in normal weight but decreased linear growth while N-scavenger therapy with phenylbutyrate resulted in low levels of branched chain amino acids. Finally, we found an unexpectedly high risk for hepatic dysfunction in patients with ornithine transcarbamylase deficiency. This natural history study illustrates how a collaborative study of a rare genetic disorder can result in an improved understanding of morbidity and disease outcome.

  9. A longitudinal study of urea cycle disorders

    PubMed Central

    Batshaw, Mark L.; Tuchman, Mendel; Summar, Marshall; Seminara, Jennifer

    2014-01-01

    The urea cycle disorders consortium (UCDC) is a member of the NIH funded Rare Diseases Clinical Research Network and is performing a longitudinal study of 8 urea cycle disorders (UCD) with initial enrollment beginning in 2006. The consortium consists of 14 sites in the U.S., Canada and Europe. This report summarizes data mining studies of 614 patients with UCD enrolled in the UCDC’s longitudinal study protocol. The most common disorder is ornithine transcarbamylase deficiency, accounting for more than half of the participants. We calculated the overall prevalence of urea cycle disorders to be 1/35,000, with 2/3rds presenting initial symptoms after the newborn period. We found the mortality rate to be 24% in neonatal onset cases and 11% in late onset cases. The most common precipitant of clinical hyperammonemic episodes in the post-neonatal period was intercurrent infections. Elevations in both blood ammonia and glutamine appeared to be biomarkers for neurocognitive outcome. In terms of chronic treatment, low protein diet appeared to result in normal weight but decreased linear growth while N-scavenger therapy with phenybutyrate resulted in low levels of branched chain amino acids. Finally, we found an unexpectedly high risk for hepatic dysfunction in patients with ornithine transcarbamylase deficiency. This natural history study illustrates how a collaborative study of a rare genetic disorder can result in an improved understanding of morbidity and disease outcome. PMID:25135652

  10. Fuels Combustion Research.

    DTIC Science & Technology

    1984-07-18

    uncertainties in the future sources and characteristics of fuels has emphasized the need to better understand fuel effects on combustion , e.g. energy release...experimentally to be made. Unsuccessful comparisons can lead to impro- vements in modelling concepts . Two simplified models for the combustion of slurry...AD-A149 186 FUELS COMBUSTION RESEACCH(U) PRINCETON UNIV NJ DEPT OF i/i MECHANICAL AND AEROSPACE ENGINEERING F L DRYER ET AL. 18 JUL 84 NAE-i668 AFOSR

  11. Coal combustion products

    USGS Publications Warehouse

    Kalyoncu, R.S.; Olson, D.W.

    2001-01-01

    Coal-burning powerplants, which supply more than half of U.S. electricity, also generate coal combustion products, which can be both a resource and a disposal problem. The U.S. Geological Survey collaborates with the American Coal Ash Association in preparing its annual report on coal combustion products. This Fact Sheet answers questions about present and potential uses of coal combustion products.

  12. Supersonic combustion engine and method of combustion initiation and distribution

    SciTech Connect

    Stickler, D.B.; Ballantyne, A.; Kyuman Jeong.

    1993-06-29

    A supersonic combustion ramjet engine having a combustor with a combustion zone intended to channel gas flow at relatively high speed therethrough, the engine comprising: means for substantially continuously supplying fuel into the combustion zone; and means for substantially instantaneously igniting a volume of fuel in the combustion zone for providing a spatially controlled combustion distribution, the igniting means having means for providing a diffuse discharge of energy into the volume, the volume extending across a substantially complete cross-sectional area of the combustion zone, the means for discharging energy being capable of generating free radicals within the volume of reactive fuel in the combustion zone such that fuel in the volume can initiate a controlled relatively rapid combustion of fuel in the combustion zone whereby combustion distribution in relatively high speed gas flows through the combustion zone can be initiated and controlled without dependence upon a flame holder or relatively high local static temperature in the combustion zone.

  13. Tripropellant combustion process

    NASA Technical Reports Server (NTRS)

    Kmiec, T. D.; Carroll, R. G.

    1988-01-01

    The addition of small amounts of hydrogen to the combustion of LOX/hydrocarbon propellants in large rocket booster engines has the potential to enhance the system stability. Programs being conducted to evaluate the effects of hydrogen on the combustion of LOX/hydrocarbon propellants at supercritical pressures are described. Combustion instability has been a problem during the development of large hydrocarbon fueled rocket engines. At the higher combustion chamber pressures expected for the next generation of booster engines, the effect of unstable combustion could be even more destructive. The tripropellant engine cycle takes advantage of the superior cooling characteristics of hydrogen to cool the combustion chamber and a small amount of the hydrogen coolant can be used in the combustion process to enhance the system stability. Three aspects of work that will be accomplished to evaluate tripropellant combustion are described. The first is laboratory demonstration of the benefits through the evaluation of drop size, ignition delay and burning rate. The second is analytical modeling of the combustion process using the empirical relationship determined in the laboratory. The third is a subscale demonstration in which the system stability will be evaluated. The approach for each aspect is described and the analytical models that will be used are presented.

  14. Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha

    1998-01-01

    Liquid fuel combustion provides a major portion of the world's energy supply. In most practical combustion devices, liquid burns after being separated into a droplet spray. Essential to the design of efficient combustion systems is a knowledge of droplet combustion behavior. The microgravity environment aboard spacecraft provides an opportunity to investigate the complex interactions between the physical and chemical combustion processes involved in droplet combustion without the complications of natural buoyancy. Launched on STS-83 and STS-94 (April 4 and July 1, 1997), the Droplet Combustion Experiment (DCE) investigated the fundamentals of droplet combustion under a range of pressures (0.25 to 1 atm), oxygen mole fractions (<0.5), and droplet sizes (1.5 to 5 mm). Principal DCE flight hardware features were a chamber to supply selected test environments, the use of crew-inserted bottles, and a vent system to remove unwanted gaseous combustion products. The internal apparatus contained the droplet deployment and ignition mechanisms to burn single, freely deployed droplets in microgravity. Diagnostics systems included a 35-mm high-speed motion picture camera (see the following sequence of photos) with a backlight to photograph burning droplets and a camcorder to monitor experiment operations. Additional diagnostics included an ultraviolet-light-sensitive CCD (charge couple discharge) camera to obtain flame radiation from hydroxyl radicals (see the final figure) and a 35-mm SLR (single-lens-reflex) camera to obtain color still photographs of the flames.

  15. Combustion Byproducts Recycling Consortium

    SciTech Connect

    Paul Ziemkiewicz; Tamara Vandivort; Debra Pflughoeft-Hassett; Y. Paul Chugh; James Hower

    2008-08-31

    Ashlines: To promote and support the commercially viable and environmentally sound recycling of coal combustion byproducts for productive uses through scientific research, development, and field testing.

  16. Automatic routing module

    NASA Technical Reports Server (NTRS)

    Malin, Janice A.

    1987-01-01

    Automatic Routing Module (ARM) is a tool to partially automate Air Launched Cruise Missile (ALCM) routing. For any accessible launch point or target pair, ARM creates flyable routes that, within the fidelity of the models, are optimal in terms of threat avoidance, clobber avoidance, and adherence to vehicle and planning constraints. Although highly algorithmic, ARM is an expert system. Because of the heuristics applied, ARM generated routes closely resemble manually generated routes in routine cases. In more complex cases, ARM's ability to accumulate and assess threat danger in three dimensions and trade that danger off with the probability of ground clobber results in the safest path around or through difficult areas. The tools available prior to ARM did not provide the planner with enough information or present it in such a way that ensured he would select the safest path.

  17. Influence of milk urea concentration on fractional urea disappearance rate from milk to blood plasma in dairy cows.

    PubMed

    Spek, J W; Dijkstra, J; Bannink, A

    2016-05-01

    The relationship between milk urea nitrogen (MUN; mg of N/dL) and urinary N excretion is affected, among others, by diurnal dynamics in MUN, which in turn is largely influenced by feed intake pattern and characteristics of urea transfer from blood plasma to milk and vice versa. This study aimed to obtain insight in urea transfer characteristics within the mammary gland and from the mammary gland to blood plasma in dairy cows at various concentrations of plasma urea nitrogen (PUN; mg of N/dL) and MUN. Urea transfer from milk to blood plasma and urea transfer within the mammary gland itself was evaluated in a 4×4 Latin square design using 4 lactating multiparous Holstein-Friesian cows (milk production of 39.8±4.70kg/d and 90±3.9 d in milk). Treatments consisted of 4 primed continuous intravenous urea infusions of 0, 5, 10, and 15g of urea/h. Boluses of [(15)N(15)N]urea were injected in cistern milk at 20, 60, and 100 min before the 1700h milking. Milk was collected in portions of approximately 2 L at the 1700h milking. Milk samples were analyzed for urea and enrichment of (15)N-urea. Results from one cow were discarded because of leakage of milk from the teats after injection of boluses of [(15)N(15)N]urea. Increasing urea infusion rate linearly increased PUN from 11.4 (0g of urea/h) to 25.9mg/dL (15g of urea/h) and MUN from 10.3 (0g of urea/h) to 23.5 (15g of urea/h) mg of N/dL. The percentage of injected [(15)N(15)N]urea recovered from milk at the time of injection was not affected by urea infusion rate and varied between 65.1 and 73.0%, indicating that a substantial portion of injected [(15)N(15)N]urea was not accounted for by collected milk. The estimated fractional disappearance rate of (15)N-urea from milk to blood (Kurea; per hour) linearly increased from 0.429 (0g of urea/h) to 0.641 per hour (15g of urea/h). Cistern injected [(15)N(15)N]urea diffused within 20 min after injection toward alveoli milk. Calculations with the average Kurea estimated in this

  18. Fifteenth combustion research conference

    SciTech Connect

    1993-06-01

    The BES research efforts cover chemical reaction theory, experimental dynamics and spectroscopy, thermodynamics of combustion intermediates, chemical kinetics, reaction mechanisms, combustion diagnostics, and fluid dynamics and chemically reacting flows. 98 papers and abstracts are included. Separate abstracts were prepared for the papers.

  19. Coal Combustion Science

    SciTech Connect

    Hardesty, D.R.; Fletcher, T.H.; Hurt, R.H.; Baxter, L.L. )

    1991-08-01

    The objective of this activity is to support the Office of Fossil Energy in executing research on coal combustion science. This activity consists of basic research on coal combustion that supports both the Pittsburgh Energy Technology Center Direct Utilization Advanced Research and Technology Development Program, and the International Energy Agency Coal Combustion Science Project. Specific tasks for this activity include: (1) coal devolatilization - the objective of this risk is to characterize the physical and chemical processes that constitute the early devolatilization phase of coal combustion as a function of coal type, heating rate, particle size and temperature, and gas phase temperature and oxidizer concentration; (2) coal char combustion -the objective of this task is to characterize the physical and chemical processes involved during coal char combustion as a function of coal type, particle size and temperature, and gas phase temperature and oxygen concentration; (3) fate of mineral matter during coal combustion - the objective of this task is to establish a quantitative understanding of the mechanisms and rates of transformation, fragmentation, and deposition of mineral matter in coal combustion environments as a function of coal type, particle size and temperature, the initial forms and distribution of mineral species in the unreacted coal, and the local gas temperature and composition.

  20. Plasma Assisted Combustion

    DTIC Science & Technology

    2007-02-28

    2005) AIAA–2005–0405. [99] E.M. Van Veldhuizen (ed) Electrical Discharges for Environmental Purposes: Fun- damentals and Applications (New York: Nova...in russian), 18, 4, 1982, 48-51. [238] Combustion Chemestry , ed. W. Gardiner-Jr, Moscow, Mir, 1988. [239] G.P.Tewari, J.R.Wilson, Combust. Flame, 24

  1. Japan's microgravity combustion science program

    NASA Technical Reports Server (NTRS)

    Sato, Junichi

    1993-01-01

    Most of energy used by us is generated by combustion of fuels. On the other hand, combustion is responsible for contamination of our living earth. Combustion, also, gives us damage to our life as fire or explosive accidents. Therefore, clean and safe combustion is now eagerly required. Knowledge of the combustion process in combustors is needed to achieve proper designs that have stable operation, high efficiency, and low emission levels. However, current understanding on combustion is far from complete. Especially, there is few useful information on practical liquid and solid particle cloud combustion. Studies on combustion process under microgravity condition will provide many informations for basic questions related to combustors.

  2. Understanding individual routing behaviour.

    PubMed

    Lima, Antonio; Stanojevic, Rade; Papagiannaki, Dina; Rodriguez, Pablo; González, Marta C

    2016-03-01

    Knowing how individuals move between places is fundamental to advance our understanding of human mobility (González et al. 2008 Nature 453, 779-782. (doi:10.1038/nature06958)), improve our urban infrastructure (Prato 2009 J. Choice Model. 2, 65-100. (doi:10.1016/S1755-5345(13)70005-8)) and drive the development of transportation systems. Current route-choice models that are used in transportation planning are based on the widely accepted assumption that people follow the minimum cost path (Wardrop 1952 Proc. Inst. Civ. Eng. 1, 325-362. (doi:10.1680/ipeds.1952.11362)), despite little empirical support. Fine-grained location traces collected by smart devices give us today an unprecedented opportunity to learn how citizens organize their travel plans into a set of routes, and how similar behaviour patterns emerge among distinct individual choices. Here we study 92 419 anonymized GPS trajectories describing the movement of personal cars over an 18-month period. We group user trips by origin-destination and we find that most drivers use a small number of routes for their routine journeys, and tend to have a preferred route for frequent trips. In contrast to the cost minimization assumption, we also find that a significant fraction of drivers' routes are not optimal. We present a spatial probability distribution that bounds the route selection space within an ellipse, having the origin and the destination as focal points, characterized by high eccentricity independent of the scale. While individual routing choices are not captured by path optimization, their spatial bounds are similar, even for trips performed by distinct individuals and at various scales. These basic discoveries can inform realistic route-choice models that are not based on optimization, having an impact on several applications, such as infrastructure planning, routing recommendation systems and new mobility solutions.

  3. Understanding individual routing behaviour

    PubMed Central

    Stanojevic, Rade; Papagiannaki, Dina; Rodriguez, Pablo; González, Marta C.

    2016-01-01

    Knowing how individuals move between places is fundamental to advance our understanding of human mobility (González et al. 2008 Nature 453, 779–782. (doi:10.1038/nature06958)), improve our urban infrastructure (Prato 2009 J. Choice Model. 2, 65–100. (doi:10.1016/S1755-5345(13)70005-8)) and drive the development of transportation systems. Current route-choice models that are used in transportation planning are based on the widely accepted assumption that people follow the minimum cost path (Wardrop 1952 Proc. Inst. Civ. Eng. 1, 325–362. (doi:10.1680/ipeds.1952.11362)), despite little empirical support. Fine-grained location traces collected by smart devices give us today an unprecedented opportunity to learn how citizens organize their travel plans into a set of routes, and how similar behaviour patterns emerge among distinct individual choices. Here we study 92 419 anonymized GPS trajectories describing the movement of personal cars over an 18-month period. We group user trips by origin–destination and we find that most drivers use a small number of routes for their routine journeys, and tend to have a preferred route for frequent trips. In contrast to the cost minimization assumption, we also find that a significant fraction of drivers' routes are not optimal. We present a spatial probability distribution that bounds the route selection space within an ellipse, having the origin and the destination as focal points, characterized by high eccentricity independent of the scale. While individual routing choices are not captured by path optimization, their spatial bounds are similar, even for trips performed by distinct individuals and at various scales. These basic discoveries can inform realistic route-choice models that are not based on optimization, having an impact on several applications, such as infrastructure planning, routing recommendation systems and new mobility solutions. PMID:26962031

  4. Routing Vehicles with Ants

    NASA Astrophysics Data System (ADS)

    Tan, Wen Fang; Lee, Lai Soon; Majid, Zanariah Abdul; Seow, Hsin Vonn

    Routing vehicles involve the design of an optimal set of routes for a fleet of vehicles to serve a number of customers with known demands. This research develops an Ant Colony Optimization for the vehicle routing with one central depot and identical vehicles. The procedure simulates the behavior of real ants that always find the shortest path between their nest and a food source through a form of communication, pheromone trail. Finally, preliminary results on the learning of the algorithm testing on benchmark data set will be presented in this paper.

  5. [Plasma urea along with every plasma creatinine test?].

    PubMed

    van Zwam, Marloes; Wetzels, Jack F M; Willems, Hans L

    2013-01-01

    The concentration of plasma creatinine and the estimated glomerular filtration rate, calculated from plasma creatinine, age, weight, and gender, are used to assess kidney function. In routine clinical practice the concentration of plasma urea is often determined at the same time as the creatinine concentration. Urea is a waste product of the breakdown of amino acids and is excreted by the kidneys. Thus reduced kidney function results in a rise of blood urea. In addition, the urea concentration is determined by protein supply and catabolism. The sensitivity and specificity of urea in the diagnosis of kidney dysfunction are therefore low. In only a limited number of cases might measuring urea be helpful in determining the cause of reduced kidney function.

  6. Urea formaldehyde foam: a dangerous insulation

    SciTech Connect

    Keough, C.

    1980-12-01

    Insulating a home with urea formaldehyde foam can lead to severe health problems due to poisoning from formaldehyde gas. Respiratory problems, allergies, memory loss, and mental problems can result from exposure to foam insulation fumes. Research is now under way at the Chemical Industry Inst., Univ. of Washington, and other institutions to learn more about the health effects of formaldehyde foam and to develop possible remedies to these problems. Several states are either banning or controlling the use of this type of home insulation.

  7. Urea hydrolysis and calcium carbonate reaction fronts

    NASA Astrophysics Data System (ADS)

    Fox, D. T.; Redden, G. D.; Henriksen, J.; Fujita, Y.; Guo, L.; Huang, H.

    2010-12-01

    The mobility of toxic or radioactive metal contaminants in subsurface environments can be reduced by the formation of mineral precipitates that form co-precipitates with the contaminants or that isolate them from the mobile fluid phase. An engineering challenge is to control the spatial distribution of precipitation reactions with respect to: 1) the location of a contaminant, and 2) where reactants are introduced into the subsurface. One strategy being explored for immobilizing contaminants, such as Sr-90, involves stimulating mineral precipitation by forming carbonate ions and hydroxide via the in situ, microbially mediated hydrolysis of urea. A series of column experiments have been conducted to explore how the construction or design of such an in situ reactant production strategy can affect the temporal and spatial distribution of calcium carbonate precipitation, and how the distribution is coupled to changes in permeability. The columns were constructed with silica gel as the porous media. An interval midway through the column contained an adsorbed urease enzyme in order to simulate a biologically active zone. A series of influent solutions were injected to characterize hydraulic properties of the column (e.g., bromide tracer), profiles of chemical conditions and reaction products as the enzyme catalyzes urea hydrolysis (e.g., pH, ammonia, urea), and changes that occur due to CaCO3 precipitation with the introduction of a calcium+urea solutions. In one experiment, hydraulic conductivity was reduced as precipitate accumulated in a layer within the column that had a higher fraction of fine grained silica gel. Subsequent reduction of permeability and flow (for a constant head condition) resulted in displacement of the hydrolysis and precipitation reaction profiles upstream. In another experiment, which lacked the physical heterogeneity (fine grained layer), the precipitation reaction did not result in loss of permeability or flow velocity and the reaction profile

  8. Urea-adipic acid (2/1).

    PubMed

    Chang, Hai-Sheng; Lin, Jian-Li

    2011-06-01

    The asymmetric unit of the title co-crystal, 2CH(4)N(2)O·C(6)H(10)O(4), contains two urea mol-ecules and two half-mol-ecules of adipic acid; the latter are completed by crystallographic inversion symmetry. The crystal packing is stabilized by O-H⋯O and N-H⋯O hydrogen bonds, generating a chain along [110]. Additional weak inter-chain O-H⋯O and N-H⋯O inter-molecular inter-actions lead to the formation of a three-dimensional network.

  9. Functional Nanomaterials from Bis-urea Macrocycles

    NASA Astrophysics Data System (ADS)

    Dawn, Sandipan

    Self-assembly of bis-urea macrocycles usually give tubular crystals with nano-sized channels that we use as molecular container. These molecular containers alter the reactivity, stability, and chemical behavior of the reactants entrapped within them. This dissertation is focused on bulk synthesis, material characterization and applications of a self-assembled tubular molecular container. This crystalline straw-like container is developed from cyclic bis-urea macrocycles containing two C-shaped phenylethynylene units and two urea groups. These macrocycles afford a large open channel with a diameter of ˜9 A and it can accommodate larger solid guests such as coumarin and its methylated derivatives, stilbenes, acenaphthylene and styrenes. We developed the method to introduce these solid guests into the channel from its solution. We characterized the tubular host as well as different host*guest complexes by solid-state techniques including PXRD, CP MAS 13C NMR, fluorescence and UV-vis spectroscopy. These guests usually undergo non selective photoreaction in solid-state with very low percent conversion and produce different photodimers and/or isomers. Within our molecular container, a number of guests showed photo-dimerization with amazing selectivity and enhanced conversion in the solid-state. We also performed molecular modeling studies to find out the reason behind this unprecedented selectivity. We found the orientation of the guest molecules inside the channel as well as the stability of the photoproducts within the confinement determines the outcome of the reactions. We also developed a 5,5'-bipyridine containing bis-urea macrocycle and formed its complexes with metals. These complexes have potential to further assemble through dative bonds, hydrogen bonding and aryl stacking interactions to afford metal organic framework (MOF). We found the Ag complex forms oligomers and polymers. In the polymer structure it forms infinite chains comprised of "box" like unit cell

  10. IRIS Toxicological Review of Urea (External Review Draft) ...

    EPA Pesticide Factsheets

    EPA conducted a peer review and public comment of the scientific basis of a draft report supporting the human health hazard and dose-response assessment of Urea that when finalized will appear on the Integrated Risk Information System (IRIS) database. The draft Toxicological Review of Urea provides scientific support and rationale for the hazard and dose-response assessment pertaining to chronic exposure to Urea.

  11. The Synthesis of Guanidine from Urea. Part 3

    DTIC Science & Technology

    1949-11-01

    The formation of 0-othyl-isourca, by condensation of urea and diothyl sulphate under anhydrous conditions and in absence of solvent, has boon studied...products. 2. i. Introduction Previous work (1) showed that guanidino could be synthesiscd from urea by mothylation, using dimethyl sulphate under anhydrous ...that the best agonts, of those examined, for the etherification, i.e. O-al ylation, ef urea aro the dialkyl sulphates working unler anhydrous

  12. Class network routing

    DOEpatents

    Bhanot, Gyan; Blumrich, Matthias A.; Chen, Dong; Coteus, Paul W.; Gara, Alan G.; Giampapa, Mark E.; Heidelberger, Philip; Steinmacher-Burow, Burkhard D.; Takken, Todd E.; Vranas, Pavlos M.

    2009-09-08

    Class network routing is implemented in a network such as a computer network comprising a plurality of parallel compute processors at nodes thereof. Class network routing allows a compute processor to broadcast a message to a range (one or more) of other compute processors in the computer network, such as processors in a column or a row. Normally this type of operation requires a separate message to be sent to each processor. With class network routing pursuant to the invention, a single message is sufficient, which generally reduces the total number of messages in the network as well as the latency to do a broadcast. Class network routing is also applied to dense matrix inversion algorithms on distributed memory parallel supercomputers with hardware class function (multicast) capability. This is achieved by exploiting the fact that the communication patterns of dense matrix inversion can be served by hardware class functions, which results in faster execution times.

  13. New potent calcimimetics: II. Discovery of benzothiazole trisubstituted ureas.

    PubMed

    Deprez, Pierre; Temal, Taoues; Jary, Hélène; Auberval, Marielle; Lively, Sarah; Guédin, Denis; Vevert, Jean-Paul

    2013-04-15

    Following the identification of trisubstituted ureas as a promising new chemical series of allosteric modulators of the calcium sensing receptor (CaSR), we further explored the SAR around the urea substitution, leading to the discovery of benzothiazole urea compound 13. This compound is a potent calcimimetic with an EC50=20 nM (luciferase assay). Evaluated in an in vivo model of chronic renal failure (short term and long term in 5/6 nephrectomized rats), benzothiazole urea 13 significantly decreased PTH levels after oral administration while keeping calcemia within the normal range.

  14. Urea impedes the hydrophobic collapse of partially unfolded proteins.

    PubMed

    Stumpe, Martin C; Grubmüller, Helmut

    2009-05-06

    Proteins are denatured in aqueous urea solution. The nature of the molecular driving forces has received substantial attention in the past, whereas the question how urea acts at different phases of unfolding is not yet well understood at the atomic level. In particular, it is unclear whether urea actively attacks folded proteins or instead stabilizes unfolded conformations. Here we investigated the effect of urea at different phases of unfolding by molecular dynamics simulations, and the behavior of partially unfolded states in both aqueous urea solution and in pure water was compared. Whereas the partially unfolded protein in water exhibited hydrophobic collapses as primary refolding events, it remained stable or even underwent further unfolding steps in aqueous urea solution. Further, initial unfolding steps of the folded protein were found not to be triggered by urea, but instead, stabilized. The underlying mechanism of this stabilization is a favorable interaction of urea with transiently exposed, less-polar residues and the protein backbone, thereby impeding back-reactions. Taken together, these results suggest that, quite generally, urea-induced protein unfolding proceeds primarily not by active attack. Rather, thermal fluctuations toward the unfolded state are stabilized and the hydrophobic collapse of partially unfolded proteins toward the native state is impeded. As a result, the equilibrium is shifted toward the unfolded state.

  15. Reliable Internet Routing

    DTIC Science & Technology

    2011-09-01

    constraints [38]), and the destination of the packet (as needed for blackholing , motivated by security or politics). In particular, we admit as “typical...reducing convergence time, or adding mech- anisms to detect transient loops and blackholes , we avoid dynamic routing protocols entirely [18]. Our...solution can significantly reduce the occurrence of route blackholing and data interception caused either by malicious attacks or accidental

  16. Combustion Synthesis of Magnesium Aluminate

    SciTech Connect

    Kale, M. A.; Joshi, C. P.; Moharil, S. V.

    2011-10-20

    In the system MgO-Al{sub 2}O{sub 3}, three compounds MgAl{sub 2}O{sub 4}, MgAl{sub 6}O{sub 10}(also expressed as-Mg{sub 0.4}Al{sub 2.4}O{sub 4}) and MgAl{sub 26}O{sub 40} are well known. Importance of the first two is well established. Magnesium aluminate (MgAl{sub 2}O{sub 4}) spinel is a technologically important material due to its interesting thermal properties. The MgAl{sub 2}O{sub 4} ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl{sub 2}O{sub 4} is due to various applications such as humidity-sensing and PEM fuel cells, TL/OSL dosimetry of the ionizing radiations, white light source. Interest in the MgAl{sub 6}O{sub 10} has aroused due to possible use as a substrate for GaN growth. Attempt was made to synthesize these compounds by the combustion synthesis using metal nitrates as oxidizer and urea as a fuel. Compounds MgAl{sub 2}O{sub 4} and MgAl{sub 6}O{sub 10} were formed in a single step, while MgAl{sub 26}O{sub 40} was not formed by this procedure. Activation of MgAl{sub 6}O{sub 10} by rare earth ions like Ce{sup 3+}, Eu{sup 3+} and Tb{sup 3+} and ns{sup 2} ion Pb{sup 2+} could be achieved. Excitation bands for MgAl{sub 6}O{sub 10} are at slightly shorter wavelengths compared to those reported for MgAl{sub 2}O{sub 4}.

  17. 21 CFR 177.1900 - Urea-formaldehyde resins in molded articles.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Urea-formaldehyde resins in molded articles. 177... Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea... section, urea-formaldehyde resins are those produced when 1 mole of urea is made to react with not...

  18. Effect of urea and urea-gamma treatments on cellulose degradation of Thai rice straw and corn stalk

    NASA Astrophysics Data System (ADS)

    Banchorndhevakul, Siriwattana

    2002-08-01

    Cellulose degradation of 20% urea treated and 20% urea-10 kGy gamma treated Thai rice straw and corn stalk showed that combination effect of urea and gamma radiation gave a higher % decrease in neutral detergent fiber (NDF), acid detergent fiber (ADF), acid detergent lignin (ADL), cellulose, hemicellulose, and lignin and cutin in comparison with urea effect only for both room temperature storage and room temperature +258 K storage. The results also indicated that cellulose degradation proceeded with time, even at 258 K. A drastic drop to less than half of the original contents in NDF, ADF, and ADL could not be obtained in this study.

  19. Alternate Fuels Combustion Research

    DTIC Science & Technology

    1984-07-01

    AFWAL-TR-84-2042 ESL-TR-84-29 ALTERNATE FUELS COMBUSTION RESEARCH 0) PRATT & WHITNEY CANADA MISSISSAUGA, ONTARIO CANADA In JULY 1984 Final Report for...in small engincs. -291 REFERENCES 1. Gratton, M., Sampath, P., " Alternate Fuels Combustion Research Phase If", Pratt & Whitney Canada , AFWAL-TR-83-2057...for Period May 80 Sep e ALTERNATE FUELS COMBUSTION RESEARCHMa80-Sp3 4. PERFORMING ORIJ. REPORT NUMBER 7. AUTNOR(s) 4. 60ONTRA-CT-WI GANUMNER(s) *M

  20. Dry low combustion system with means for eliminating combustion noise

    DOEpatents

    Verdouw, Albert J.; Smith, Duane; McCormick, Keith; Razdan, Mohan K.

    2004-02-17

    A combustion system including a plurality of axially staged tubular premixers to control emissions and minimize combustion noise. The combustion system includes a radial inflow premixer that delivers the combustion mixture across a contoured dome into the combustion chamber. The axially staged premixers having a twist mixing apparatus to rotate the fluid flow and cause improved mixing without causing flow recirculation that could lead to pre-ignition or flashback.

  1. Sandia Combustion Research: Technical review

    SciTech Connect

    1995-07-01

    This report contains reports from research programs conducted at the Sandia Combustion Research Facility. Research is presented under the following topics: laser based diagnostics; combustion chemistry; reacting flow; combustion in engines and commercial burners; coal combustion; and industrial processing. Individual projects were processed separately for entry onto the DOE databases.

  2. Combustion Technology Outreach

    NASA Technical Reports Server (NTRS)

    1995-01-01

    Lewis' High Speed Research (HSR) Propulsion Project Office initiated a targeted outreach effort to market combustion-related technologies developed at Lewis for the next generation of supersonic civil transport vehicles. These combustion-related innovations range from emissions measurement and reduction technologies, to diagnostics, spray technologies, NOx and SOx reduction of burners, noise reduction, sensors, and fuel-injection technologies. The Ohio Aerospace Institute and the Great Lakes Industrial Technology Center joined forces to assist Lewis' HSR Office in this outreach activity. From a database of thousands of nonaerospace firms considered likely to be interested in Lewis' combustion and emission-related technologies, the outreach team selected 41 companies to contact. The selected companies represent oil-gas refineries, vehicle/parts suppliers, and manufacturers of residential furnaces, power turbines, nonautomobile engines, and diesel internal combustion engines.

  3. Fluidized coal combustion

    NASA Technical Reports Server (NTRS)

    Moynihan, P. I.; Young, D. L.

    1979-01-01

    Fluidized-bed coal combustion process, in which pulverized coal and limestone are burned in presence of forced air, may lead to efficient, reliable boilers with low sulfur dioxide and nitrogen dioxide emissions.

  4. Studies in premixed combustion

    SciTech Connect

    Sivashinsky, G.I.

    1992-01-01

    This report discusses the following topics on premixed combustion: theory of turbulent flame propagation; pattern formation in premixed flames and related problems; and pattern formation in extended systems. (LSP)

  5. TENORM: Coal Combustion Residuals

    EPA Pesticide Factsheets

    Burning coal in boilers to create steam for power generation and industrial applications produces a number of combustion residuals. Naturally radioactive materials that were in the coal mostly end up in fly ash, bottom ash and boiler slag.

  6. Dynamic effects of combustion

    NASA Technical Reports Server (NTRS)

    Oppenheim, A. K.

    1982-01-01

    The dynamic effects of combustion are due to the evolution of exothermic energy and its deposition in the compressible medium where the process takes place. The paper examines the dynamics of combustion phenomena, including ignition, turbulent flame propagation (inflammation), explosion, and detonation, with emphasis on their exothermic characteristics. Ignition and explosion are treated as problems of nonlinear mechanics, and their dynamic behavior is described in terms of phase space models and cinematographic laser shear interferograms. The results of a numerical random vortex model of turbulent flame propagation are confirmed in a combustion tunnel experiment, where it was observed that a fresh mixture of burnt and unburnt gases can sustain combustion with a relatively small expenditure of overall mass flow, due to the increasing specific volume of burnt gases inside the flame front. An isentropic pressure wave is found to precede the accelerating flame in the process of detonation, and components of this presssure wave are shown to propagate at local sonic velocities.

  7. Molecular Basis of the Apparent Near Ideality of Urea Solutions

    PubMed Central

    Kokubo, Hironori; Rösgen, Jörg; Bolen, D. Wayne; Pettitt, B. Montgomery

    2007-01-01

    Activity coefficients of urea solutions are calculated to explore the mechanism of its solution properties, which form the basis for its well-known use as a strong protein denaturant. We perform free energy simulations of urea solutions in different urea concentrations using two urea models (OPLS and KBFF models) to calculate and decompose the activity coefficients. For the case of urea, we clarify the concept of the ideal solution in different concentration scales and standard states and its effect on our subsequent analysis. The analytical form of activity coefficients depends on the concentration units and standard states. For both models studied, urea displays a weak concentration dependence for excess chemical potential. However, for the OPLS force-field model, this results from contributions that are independent of concentration to the van der Waals and electrostatic components whereas for the KBFF model those components are nontrivial but oppose each other. The strong ideality of urea solutions in some concentration scales (incidentally implying a lack of water perturbation) is discussed in terms of recent data and ideas on the mechanism of urea denaturation of proteins. PMID:17693466

  8. Molecular Basis of the Apparent Near Ideality of Urea Solutions.

    SciTech Connect

    Kokubo, Hironori; Rosgen, Jorg; Bolen, D Wayne; Pettitt, Bernard M.

    2007-11-01

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. Activity coefficients of urea solutions are calculated to explore the mechanism of its solution properties, which form the basis for its well-known use as a strong protein denaturant. We perform free energy simulations of urea solutions in different urea concentrations using two urea models (OPLS and KBFF models) to calculate and decompose the activity coefficients. For the case of urea, we clarify the concept of the ideal solution in different concentration scales and standard states and its effect on our subsequent analysis. The analytical form of activity coefficients depends on the concentration units and standard states. For both models studied, urea displays a weak concentration dependence for excess chemical potential. However, for the OPLS force-field model, this results from contributions that are independent of concentration to the van der Waals and electrostatic components whereas for the KBFF model those components are nontrivial but oppose each other. The strong ideality of urea solutions in some concentration scales (incidentally implying a lack of water perturbation) is discussed in terms of recent data and ideas on the mechanism of urea denaturation of proteins.

  9. Effects of low urea concentrations on protein-water interactions.

    PubMed

    Ferreira, Luisa A; Povarova, Olga I; Stepanenko, Olga V; Sulatskaya, Anna I; Madeira, Pedro P; Kuznetsova, Irina M; Turoverov, Konstantin K; Uversky, Vladimir N; Zaslavsky, Boris Y

    2017-01-01

    Solvent properties of aqueous media (dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) were measured in the coexisting phases of Dextran-PEG aqueous two-phase systems (ATPSs) containing .5 and 2.0 M urea. The differences between the electrostatic and hydrophobic properties of the phases in the ATPSs were quantified by analysis of partitioning of the homologous series of sodium salts of dinitrophenylated amino acids with aliphatic alkyl side chains. Furthermore, partitioning of eleven different proteins in the ATPSs was studied. The analysis of protein partition behavior in a set of ATPSs with protective osmolytes (sorbitol, sucrose, trehalose, and TMAO) at the concentration of .5 M, in osmolyte-free ATPS, and in ATPSs with .5 or 2.0 M urea in terms of the solvent properties of the phases was performed. The results show unambiguously that even at the urea concentration of .5 M, this denaturant affects partitioning of all proteins (except concanavalin A) through direct urea-protein interactions and via its effect on the solvent properties of the media. The direct urea-protein interactions seem to prevail over the urea effects on the solvent properties of water at the concentration of .5 M urea and appear to be completely dominant at 2.0 M urea concentration.

  10. 40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Aminoethylethylene urea methacrylamide... Substances § 721.9925 Aminoethylethylene urea methacrylamide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified generically as an aminoethylethylene...

  11. Generalities on combustion instabilities

    NASA Astrophysics Data System (ADS)

    Kuentzmann, Paul

    The main manifestations of combustion instabilities are reviewed, and the specific characteristics of instabilities in solid-propellant rocket engines are analyzed, with the Minuteman III third-stage engine and the SRB engine of Titan 34 D considered as examples. The main approaches for predicting combustion instabilities are discussed, including the linear approach based on the acoustic balance, the nonlinear mode-coupling approach, and the nonlinear approach using numerical calculation. Projected directions for future research are also examined.

  12. Scramjet Combustion Processes

    DTIC Science & Technology

    2010-09-01

    plan for these flights is as follows: Scramjet Combustion Processes RTO-EN-AVT-185 11 - 21 HyShot 5 – A Free-Flying Hypersonic Glider HyShot...5 will be a hypersonic glider designed to fly at Mach 8. It will separate from its rocket booster in space and perform controlled manoeuvres as it...RTO-EN-AVT-185 11 - 1 Scramjet Combustion Processes Michael Smart and Ray Stalker Centre for Hypersonics The University of Queensland

  13. Sandia Combustion Research Program

    SciTech Connect

    Johnston, S.C.; Palmer, R.E.; Montana, C.A.

    1988-01-01

    During the late 1970s, in response to a national energy crisis, Sandia proposed to the US Department of Energy (DOE) a new, ambitious program in combustion research. Shortly thereafter, the Combustion Research Facility (CRF) was established at Sandia's Livermore location. Designated a ''user facility,'' the charter of the CRF was to develop and maintain special-purpose resources to support a nationwide initiative-involving US inventories, industry, and national laboratories--to improve our understanding and control of combustion. This report includes descriptions several research projects which have been simulated by working groups and involve the on-site participation of industry scientists. DOE's Industry Technology Fellowship program, supported through the Office of Energy Research, has been instrumental in the success of some of these joint efforts. The remainder of this report presents results of calendar year 1988, separated thematically into eleven categories. Referred journal articles appearing in print during 1988 and selected other publications are included at the end of Section 11. Our traditional'' research activities--combustion chemistry, reacting flows, diagnostics, engine and coal combustion--have been supplemented by a new effort aimed at understanding combustion-related issues in the management of toxic and hazardous materials.

  14. Coal combustion system

    DOEpatents

    Wilkes, Colin; Mongia, Hukam C.; Tramm, Peter C.

    1988-01-01

    In a coal combustion system suitable for a gas turbine engine, pulverized coal is transported to a rich zone combustor and burned at an equivalence ratio exceeding 1 at a temperature above the slagging temperature of the coal so that combustible hot gas and molten slag issue from the rich zone combustor. A coolant screen of water stretches across a throat of a quench stage and cools the combustible gas and molten slag to below the slagging temperature of the coal so that the slag freezes and shatters into small pellets. The pelletized slag is separated from the combustible gas in a first inertia separator. Residual ash is separated from the combustible gas in a second inertia separator. The combustible gas is mixed with secondary air in a lean zone combustor and burned at an equivalence ratio of less than 1 to produce hot gas motive at temperature above the coal slagging temperature. The motive fluid is cooled in a dilution stage to an acceptable turbine inlet temperature before being transported to the turbine.

  15. Urea enhances the photodynamic efficiency of methylene blue.

    PubMed

    Nuñez, Silvia C; Yoshimura, Tania M; Ribeiro, Martha S; Junqueira, Helena C; Maciel, Cleiton; Coutinho-Neto, Maurício D; Baptista, Maurício S

    2015-09-01

    Methylene blue (MB) is a well-known photosensitizer used mostly for antimicrobial photodynamic therapy (APDT). MB tends to aggregate, interfering negatively with its singlet oxygen generation, because MB aggregates lean towards electron transfer reactions, instead of energy transfer with oxygen. In order to avoid MB aggregation we tested the effect of urea, which destabilizes solute-solute interactions. The antimicrobial efficiency of MB (30 μM) either in water or in 2M aqueous urea solution was tested against a fungus (Candida albicans). Samples were kept in the dark and irradiation was performed with a light emitting diode (λ = 645 nm). Without urea, 9 min of irradiation was needed to achieve complete microbial eradication. In urea solution, complete eradication was obtained with 6 min illumination (light energy of 14.4 J). The higher efficiency of MB/urea solution was correlated with a smaller concentration of dimers, even in the presence of the microorganisms. Monomer to dimer concentration ratios were extracted from the absorption spectra of MB solutions measured as a function of MB concentration at different temperatures and at different concentrations of sodium chloride and urea. Dimerization equilibrium decreased by 3 and 6 times in 1 and 2M urea, respectively, and increased by a factor of 6 in 1M sodium chloride. The destabilization of aggregates by urea seems to be applied to other photosensitizers, since urea also destabilized aggregation of Meso-tetra(4-n-methyl-pyridyl)porphyrin, which is a positively charged porphyrin. We showed that urea destabilizes MB aggregates mainly by causing a decrease in the enthalpic gain of dimerization, which was exactly the opposite of the effect of sodium chloride. In order to understand this phenomenon at the molecular level, we computed the free energy for the dimer association process (ΔG(dimer)) in aqueous solution as well as its enthalpic component in aqueous and in aqueous/urea solutions by molecular dynamics

  16. Structure and permeation mechanism of a mammalian urea transporter

    SciTech Connect

    Levin, Elena J.; Cao, Yu; Enkavi, Giray; Quick, Matthias; Pan, Yaping; Tajkhorshid, Emad; Zhou, Ming

    2012-09-17

    As an adaptation to infrequent access to water, terrestrial mammals produce urine that is hyperosmotic to plasma. To prevent osmotic diuresis by the large quantity of urea generated by protein catabolism, the kidney epithelia contain facilitative urea transporters (UTs) that allow rapid equilibration between the urinary space and the hyperosmotic interstitium. Here we report the first X-ray crystal structure of a mammalian UT, UT-B, at a resolution of 2.36 {angstrom}. UT-B is a homotrimer and each protomer contains a urea conduction pore with a narrow selectivity filter. Structural analyses and molecular dynamics simulations showed that the selectivity filter has two urea binding sites separated by an approximately 5.0 kcal/mol energy barrier. Functional studies showed that the rate of urea conduction in UT-B is increased by hypoosmotic stress, and that the site of osmoregulation coincides with the location of the energy barrier.

  17. Postmortem Blood Sugar and Blood Urea Nitrogen Determinations

    PubMed Central

    Fekete, John F.; Kerenyi, Norbert A.

    1965-01-01

    Glucose and urea nitrogen determinations were made on blood and cerebrospinal fluid samples collected during 160 postmortem examinations in order to determine the usefulness of such tests in diagnosing diabetes and uremia at the time of autopsy. The results indicated that: (1) Blood is unsuitable for postmortem glucose determination, and no postmortem normal can be established. (2) Cerebrospinal fluid gave more uniform but very low glucose values. (3) Diabetics as a group had very high postmortem glucose levels but showed a marked overlap with non-diabetics. (4) Infants less than 3 months of age showed high postmortem glucose values. (5) Postmortem blood urea nitrogen and cerebrospinal fluid urea nitrogen levels were within normal limits in previously healthy persons who died suddenly from accidental causes. (6) Hospital autopsy cases had high urea nitrogen levels. (7) Postmortem urea nitrogen levels higher than 100 mg.% were indicative of uremia. PMID:14285288

  18. Hydrolyzable polyureas bearing hindered urea bonds.

    PubMed

    Ying, Hanze; Cheng, Jianjun

    2014-12-10

    Hydrolyzable polymers are widely used materials that have found numerous applications in biomedical, agricultural, plastic, and packaging industrials. They usually contain ester and other hydrolyzable bonds, such as anhydride, acetal, ketal, or imine, in their backbone structures. Here, we report the first design of hydrolyzable polyureas bearing dynamic hindered urea bonds (HUBs) that can reversibly dissociate to bulky amines and isocyanates, the latter of which can be further hydrolyzed by water, driving the equilibrium to facilitate the degradation of polyureas. Polyureas bearing 1-tert-butyl-1-ethylurea bonds that show high dynamicity (high bond dissociation rate), in the form of either linear polymers or cross-linked gels, can be completely degraded by water under mild conditions. Given the simplicity and low cost for the production of polyureas by simply mixing multifunctional bulky amines and isocyanates, the versatility of the structures, and the tunability of the degradation profiles of HUB-bearing polyureas, these materials are potentially of very broad applications.

  19. Collective network routing

    DOEpatents

    Hoenicke, Dirk

    2014-12-02

    Disclosed are a unified method and apparatus to classify, route, and process injected data packets into a network so as to belong to a plurality of logical networks, each implementing a specific flow of data on top of a common physical network. The method allows to locally identify collectives of packets for local processing, such as the computation of the sum, difference, maximum, minimum, or other logical operations among the identified packet collective. Packets are injected together with a class-attribute and an opcode attribute. Network routers, employing the described method, use the packet attributes to look-up the class-specific route information from a local route table, which contains the local incoming and outgoing directions as part of the specifically implemented global data flow of the particular virtual network.

  20. Understanding Route Aggregation

    DTIC Science & Technology

    2010-03-09

    routing anomalies, and is fingered to be the cause of many reported loops and blackholes . In this paper, we posit that the problem arises from a lack of...Route aggre- gation can also result in blackholes [18], which are surprisingly prevalent in the Internet [11]. We illustrate these known anomalies with...advertisement Forwarding paths A B C 10.1.30.0/24 10.1.16.0/22 10.1.16.0/2010.1.16.0/20 Figure 4: Illustration of a blackhole . forwards the packet to Y

  1. Improving long term outcomes in urea cycle disorders-report from the Urea Cycle Disorders Consortium.

    PubMed

    Waisbren, Susan E; Gropman, Andrea L; Batshaw, Mark L

    2016-07-01

    The Urea Cycle Disorders Consortium (UCDC) has conducted, beginning in 2006, a longitudinal study (LS) of eight enzyme deficiencies/transporter defects associated with the urea cycle. These include N-acetylglutamate synthase deficiency (NAGSD); Carbamyl phosphate synthetase 1 deficiency (CPS1D); Ornithine transcarbamylase deficiency (OTCD); Argininosuccinate synthetase deficiency (ASSD) (Citrullinemia); Argininosuccinate lyase deficiency (ASLD) (Argininosuccinic aciduria); Arginase deficiency (ARGD, Argininemia); Hyperornithinemia, hyperammonemia, homocitrullinuria (HHH) syndrome (or mitochondrial ornithine transporter 1 deficiency [ORNT1D]); and Citrullinemia type II (mitochondrial aspartate/glutamate carrier deficiency [CITRIN]). There were 678 UCD patients enrolled in 14 sites in the U.S., Canada, and Europe at the writing of this paper. This review summarizes findings of the consortium related to outcome, focusing primarily on neuroimaging findings and neurocognitive function. Neuroimaging studies in late onset OTCD offered evidence that brain injury caused by biochemical dysregulation may impact functional neuroanatomy serving working memory processes, an important component of executive function and regulation. Additionally, there were alteration in white mater microstructure and functional connectivity at rest. Intellectual deficits in OTCD and other urea cycle disorders (UCD) vary. However, when neuropsychological deficits occur, they tend to be more prominent in motor/performance areas on both intelligence tests and other measures. In some disorders, adults performed significantly less well than younger patients. Further longitudinal follow-up will reveal whether this is due to declines throughout life or to improvements in diagnostics (especially newborn screening) and treatments in the younger generation of patients.

  2. Acute toxicity assessment of choline by inhalation, intraperitoneal and oral routes in Balb/c mice.

    PubMed

    Mehta, Amit Kumar; Arora, Naveen; Gaur, Shailendra Nath; Singh, Bhanu Pratap

    2009-08-01

    Studies suggest that choline has potential to be used as a dietary supplement and a drug for immune inflammatory diseases like asthma and rhinitis. But there are apprehensions regarding adverse effects of choline when given orally in high doses. To address this knowledge gap, toxicity assessment of choline chloride was carried out by intranasal (i.n.), oral and intraperitoneal (i.p.) routes in Balb/c mice for 28days. Body weight, food and water consumption of mice were recorded daily. Hematology and clinical chemistry were assessed to check hepatocellular functions and morphological alterations of the cells. Splenocyte counts were analysed for evaluating cellular immunity. Liver function test was performed by assaying different enzyme systems in serum such as, urea, blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT), and aspartate aminotransferase (AST). Body weight, food and water consumption did not differ between mice treated with choline and the saline control group. Hematologic and biochemical variables were not affected with any increase in serum toxicity marker enzymes indicating normal liver functioning. Choline administration did not affect total cholesterol and high density lipoprotein levels as compared to their respective controls. Urea and blood urea nitrogen levels in choline treated mice were not different than controls. Creatinine level was, however, higher than control in i.p. treatment group, but other parameters were normal. In conclusion, the repeated consumption of choline chloride via i.n. and oral or i.p. routes did not cause toxicity in mice in the toxicological endpoints examined.

  3. Hydrologic Flood Routing.

    ERIC Educational Resources Information Center

    Heggen, Richard J.

    1982-01-01

    Discusses a short classroom-based BASIC program which routes stream flow through a system of channels and reservoirs. The program is suitable for analyses of open channel conveyance systems, flood detention reservoirs, and combinations of the two. (Author/JN)

  4. Submarine cable route survey

    SciTech Connect

    Herrouin, G.; Scuiller, T.

    1995-12-31

    The growth of telecommunication market is very significant. From the beginning of the nineties, more and more the use of optical fiber submarine cables is privileged to that of satellites. These submarine telecommunication highways require accurate surveys in order to select the optimum route and determine the cable characteristics. Advanced technology tools used for these surveys are presented along with their implementation.

  5. A solid phase honey-like channel method for synthesizing urea-ammonium chloride cocrystals on industrial scale

    NASA Astrophysics Data System (ADS)

    Xue, Bingchun; Mao, Meiling; Liu, Yanhong; Guo, Jinyu; Li, Jing; Liu, Erbao

    2016-05-01

    Unanticipated a new and simple urea-ammonium chloride cocrystal synthesis method on industrial scale was found during attempts to produce a kind of granulated compound fertilizer. The aggregation of fertilizer powder can make the interaction among particles from loose to close, which generate mechanical pressure and in turn act as the driving force to benefit cocrystal growth. Additionally, the honeycomb-like channels constructed by other coexisting compound make the water evaporates more moderate, which can help the formation of supersaturated solution at suitable rate, further promote the growth of cocrystal. This approach possibly opens a new route toward the developing methodologies for cocrystal synthesis.

  6. Salvage of blood urea nitrogen in sheep is highly dependent on plasma urea concentration and the efficiency of capture within the digestive tract.

    PubMed

    Sunny, N E; Owens, S L; Baldwin, R L; El-Kadi, S W; Kohn, R A; Bequette, B J

    2007-04-01

    The aims of this study were 1) to determine whether transfer of blood urea to the gastrointestinal tract (GIT) or the efficiency of capture of urea N within the GIT is more limiting for urea N salvage, and 2) to establish the relationship between plasma urea concentration and recycling of urea N to the GIT. We used an i.v. urea infusion model in sheep to elevate the urea entry rate and plasma concentrations, thus avoiding direct manipulation of the rumen environment that otherwise occurs when feeding additional N. Four growing sheep (28.1 +/- 0.6 kg of BW) were fed a low-protein (6.8% CP, DM basis) diet and assigned to 4 rates of i.v. urea infusion (0, 3.8, 7.5, or 11.3 g of urea N/d; 10-d periods) in a balanced 4 x 4 Latin square design. Nitrogen retention (d 6 to 9), urea kinetics([(15)N2]urea infusion over 80 h), and plasma AA were determined. Urea infusion increased apparent total tract digestibility of N (29.9 to 41.3%) and DM (47.5 to 58.9%), and N retention (1.45 to 5.46 g/d). The plasma urea N entry rate increased (5.1 to 21.8 g/d) with urea infusion, as did the amount of urea N entering the GIT (4.1 to 13.2 g/d). Urea N transfer to the GIT increased with plasma urea concentration, but the increases were smaller at greater concentrations of plasma urea. Anabolic use of urea N within the GIT also increased with urea infusion (1.43 to 2.98 g/d; P = 0.003), but anabolic use as a proportion of GIT entry was low and decreased (35 to 22%; P = 0.003) with urea infusions. Consequently, much (44 to 67%) of the urea N transferred to the GIT returned to the liver for resynthesis of urea (1.8 to 9.2 g/d; P < 0.05). The present results suggest that transfer of blood urea to the GIT is 1) highly related to blood urea concentration, and 2) less limiting for N retention than is the efficiency of capture of recycled urea N by microbes within the GIT.

  7. Diaryl Urea: A Privileged Structure in Anticancer Agents.

    PubMed

    Garuti, Laura; Roberti, Marinella; Bottegoni, Giovanni; Ferraro, Mariarosaria

    2016-01-01

    The diaryl urea is an important fragment/pharmacophore in constructing anticancer molecules due to its near-perfect binding with certain acceptors. The urea NH moiety is a favorable hydrogen bond donor, while the urea oxygen atom is regarded as an excellent acceptor. Many novel compounds have been synthesized and evaluated for their antitumor activity with the successful development of sorafenib. Moreover, this structure is used to link alkylating pharmacophores with high affinity DNA binders. In addition, the diaryl urea is present in several kinase inhibitors, such as RAF, KDR and Aurora kinases. Above all, this moiety is used in the type II inhibitors: it usually forms one or two hydrogen bonds with a conserved glutamic acid and one with the backbone amide of the aspartic acid in the DFG motif. In addition, some diaryl urea derivatives act as Hedgehog (Hh) ligands, binding and inhibiting proteins involved in the homonymous Hh signaling pathway. In this review we provide some of the methodologies adopted for the synthesis of diaryl ureas and a description of the most representative antitumor agents bearing the diaryl urea moiety, focusing on their mechanisms bound to the receptors and structure-activity relationships (SAR). An increased knowledge of these derivatives could prompt the search to find new and more potent compounds.

  8. Kinetic study on urea uptake with chitosan based sorbent materials.

    PubMed

    Xue, Chen; Wilson, Lee D

    2016-01-01

    A one-pot kinetic uptake study of urea in aqueous solution with various chitosan sorbent materials such as pristine chitosan, cross-linked chitosan with glutaraldehyde from low (C-1) to higher (C-2) glutaraldehyde content, and a Cu(II) complex of a glutaraldehyde cross-linked chitosan material (C-3) is reported herein. The kinetic uptake profiles were analyzed by the pseudo-first order (PFO) and pseudo-second-order (PSO) models, respectively. The uptake rate constant of urea and the sorption capacity (qe) of high molecular weight (HMW) chitosan, C-1, C-2, and C-3 were best described by the PFO model. The uptake rate constant of urea with the various sorbents is listed in ascending order: HMW chitosanurea/g sorbent) for the sorbent/urea systems are listed in ascending order: HMW chitosan (48.1)≈C-1 (44.7)urea uptake and greater adsorption capacity when compared with pristine chitosan. The observed trends are in agreement with the greater surface accessibility and pore structure properties of cross-linked chitosan based on scanning electron microscopy studies. These results further illustrate the rational design of chitosan-based materials for the controlled uptake of urea in aquatic environments.

  9. Advanced Subsonic Combustion Rig

    NASA Technical Reports Server (NTRS)

    Lee, Chi-Ming

    1998-01-01

    Researchers from the NASA Lewis Research Center have obtained the first combustion/emissions data under extreme future engine operating conditions. In Lewis' new world-class 60-atm combustor research facility--the Advanced Subsonic Combustion Rig (ASCR)--a flametube was used to conduct combustion experiments in environments as extreme as 900 psia and 3400 F. The greatest challenge for combustion researchers is the uncertainty of the effects of pressure on the formation of nitrogen oxides (NOx). Consequently, U.S. engine manufacturers are using these data to guide their future combustor designs. The flametube's metal housing has an inside diameter of 12 in. and a length of 10.5 in. The flametube can be used with a variety of different flow paths. Each flow path is lined with a high-temperature, castable refractory material (alumina) to minimize heat loss. Upstream of the flametube is the injector section, which has an inside diameter of 13 in. and a length of 0.5-in. It was designed to provide for quick changeovers. This flametube is being used to provide all U.S. engine manufacturers early assessments of advanced combustion concepts at full power conditions prior to engine production. To date, seven concepts from engine manufacturers have been evaluated and improved. This collaborated development can potentially give U.S. engine manufacturers the competitive advantage of being first in the market with advanced low-emission technologies.

  10. Environmentally conscious coal combustion

    SciTech Connect

    Hickmott, D.D.; Brown, L.F.; Currier, R.P.

    1997-08-01

    This is the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project was to evaluate the environmental impacts of home-scale coal combustion on the Navajo Reservation and develop strategies to reduce adverse health effects associated with home-scale coal combustion. Principal accomplishments of this project were: (1) determination of the metal and gaseous emissions of a representative stove on the Navajo Reservation; (2) recognition of cyclic gaseous emissions in combustion in home-scale combustors; (3) `back of the envelope` calculation that home-scale coal combustion may impact Navajo health; and (4) identification that improved coal stoves require the ability to burn diverse feedstocks (coal, wood, biomass). Ultimately the results of Navajo home-scale coal combustion studies will be extended to the Developing World, particularly China, where a significant number (> 150 million) of households continue to heat their homes with low-grade coal.

  11. Microgravity Combustion Diagnostics Workshop

    NASA Technical Reports Server (NTRS)

    Santoro, Gilbert J. (Editor); Greenberg, Paul S. (Editor); Piltch, Nancy D. (Editor)

    1988-01-01

    Through the Microgravity Science and Applications Division (MSAD) of the Office of Space Science and Applications (OSSA) at NASA Headquarters, a program entitled, Advanced Technology Development (ATD) was promulgated with the objective of providing advanced technologies that will enable the development of future microgravity science and applications experimental flight hardware. Among the ATD projects one, Microgravity Combustion Diagnostics (MCD), has the objective of developing advanced diagnostic techniques and technologies to provide nonperturbing measurements of combustion characteristics and parameters that will enhance the scientific integrity and quality of microgravity combustion experiments. As part of the approach to this project, a workshop was held on July 28 and 29, 1987, at the NASA Lewis Research Center. A small group of laser combustion diagnosticians met with a group of microgravity combustion experimenters to discuss the science requirements, the state-of-the-art of laser diagnostic technology, and plan the direction for near-, intermediate-, and long-term programs. This publication describes the proceedings of that workshop.

  12. Combustion chamber noise suppressor

    SciTech Connect

    Livingston, A.M.

    1986-08-19

    A combustion chamber is described for a hot fog generating machine comprising a hollow cylindrical combustion chamber shell having a closure plate at one end and outlet means at the opposite end for directing hot combustion gasses to a fogging nozzle, air inlet means disposed adjacent the outlet means, fuel inlet means and ignition means mounted in the closure plate and liner means disposed concentrically within the cylindrical combustion chamber for controlling the flow of air and combustion gasses within the shell. The liner means includes a liner base having a frustroconical configuration with the smaller diameter end thereof disposed in communication with the outlet means and with the larger diameter end thereof disposed in spaced relation to the shell, circumferentially spaced, longitudinally extending fins extending outwardly from the liner base intermediate the liner base and the shell, a cylindrical liner midsection having circumferentially spaced fins extending outwardly therefrom between the midsection and the shell with the fins supporting the midsection on the larger diameter end of the liner base.

  13. Combustion in fluidized beds

    SciTech Connect

    Dry, F.J.; La Nauze, R.D. )

    1990-07-01

    Circulating fluidized-bed (CFB) combustion systems have become popular since the late 1970s, and, given the current level of activity in the area,it is clear that this technology has a stable future in the boiler market. For standard coal combustion applications, competition is fierce with mature pulverized-fuel-based (PF) technology set to maintain a strong profile. CFB systems, however, can be more cost effective than PF systems when emission control is considered, and, as CFB technology matures, it is expected that an ever-increasing proportion of boiler installations will utilize the CFB concept. CFB systems have advantages in the combustion of low-grade fuels such as coal waste and biomass. In competition with conventional bubbling beds, the CFB boiler often demonstrates superior carbon burn-out efficiency. The key to this combustion technique is the hydrodynamic behavior of the fluidized bed. This article begins with a description of the fundamental fluid dynamic behavior of the CFB system. This is followed by an examination of the combustion process in such an environment and a discussion of the current status of the major CFB technologies.

  14. Methodology for concurrent determination of urea kinetics and the capture of recycled urea nitrogen by ruminal microbes in cattle.

    PubMed

    Wickersham, T A; Titgemeyer, E C; Cochran, R C

    2009-03-01

    We measured the incorporation of recycled urea-nitrogen (N) by ruminal microbes, using five ruminally and duodenally fistulated steers (237 kg) fed low-quality grass hay (47 g crude protein/kg dry matter (DM)). Three received 1 kg/day of soybean meal (SBM) and two received no supplemental protein (control). The experiment was 15 days long. Background enrichments of 15N were measured on day 9 and continuous jugular infusion of 0.12 g/day [15N15N]urea began on day 10. Daily samples of urine, feces, ruminal bacteria and duodenal digesta from days 10 through 14 were used to determine plateaus in 15N enrichment. Duodenal and bacterial samples collected on day 15 were used to measure duodenal N flows. Bacterial N flow was calculated as duodenal N flow multiplied by duodenal 15N enrichment divided by bacterial 15N enrichment. Bacterial N from recycled urea-N was calculated as bacterial N flow multiplied by bacterial 15N enrichment divided by urinary urea 15N enrichment. Urinary enrichment of [15N15N]urea plateaued within 24 h, whereas 14N15N urea plateaued within 48 h of [15N15N]urea infusion. Bacteria reached a plateau in 15N enrichment within 24 h and duodenal samples within 48 h. Urea production was 17.6 g of urea-N/day for control and 78.0 g/day for SBM. Gut entry was 0.99 g of urea-N/g of urea-N produced for control and 0.87 g/g for SBM. Incorporation of recycled N into microbial N was 9.0 g of N/day for control and 23.0 g/day for SBM. Recycled urea-N accounted for 0.33 g of N/g of microbial N at the duodenum for control and 0.27 g/g for SBM. Our methods allowed measurement of incorporation of recycled urea-N into ruminal microbial N.

  15. Combustible structural composites and methods of forming combustible structural composites

    DOEpatents

    Daniels, Michael A.; Heaps, Ronald J.; Steffler, Eric D.; Swank, W. David

    2013-04-02

    Combustible structural composites and methods of forming same are disclosed. In an embodiment, a combustible structural composite includes combustible material comprising a fuel metal and a metal oxide. The fuel metal is present in the combustible material at a weight ratio from 1:9 to 1:1 of the fuel metal to the metal oxide. The fuel metal and the metal oxide are capable of exothermically reacting upon application of energy at or above a threshold value to support self-sustaining combustion of the combustible material within the combustible structural composite. Structural-reinforcing fibers are present in the composite at a weight ratio from 1:20 to 10:1 of the structural-reinforcing fibers to the combustible material. Other embodiments and aspects are disclosed.

  16. LES of Mild Combustion using Pareto-efficient Combustion Adaptation

    NASA Astrophysics Data System (ADS)

    Wu, Hao; Evans, Michael; Ihme, Matthias

    2015-11-01

    Moderate or Intense Low-Oxygen Dilution (MILD) combustion is a combustion regime that provides opportunities for improved thermal efficiency and reduced pollutant emissions. In this study, large-eddy simulation is used to investigate the ignition, mixing, and stabilization of a jet flame in this kinetics-controlled combustion regime. The combustion process is modeled by a Pareto-efficient combustion (PEC) formulation that optimally combines reaction-transport and chemistry combustion models. In this approach, a three-stream flamelet/progress variable model is used as a computationally efficient description of equilibrated flame regions, and a finite-rate chemistry representation is employed to accurately represent the ignition behavior and flame stabilization. Through comparisons with experiments and simulations with single-regime combustion models, it will be shown that this Pareto-efficient combustion submodel assignment accurately captures important dynamics in complex turbulent flame configurations.

  17. Combustible structural composites and methods of forming combustible structural composites

    DOEpatents

    Daniels, Michael A.; Heaps, Ronald J.; Steffler, Eric D; Swank, William D.

    2011-08-30

    Combustible structural composites and methods of forming same are disclosed. In an embodiment, a combustible structural composite includes combustible material comprising a fuel metal and a metal oxide. The fuel metal is present in the combustible material at a weight ratio from 1:9 to 1:1 of the fuel metal to the metal oxide. The fuel metal and the metal oxide are capable of exothermically reacting upon application of energy at or above a threshold value to support self-sustaining combustion of the combustible material within the combustible structural composite. Structural-reinforcing fibers are present in the composite at a weight ratio from 1:20 to 10:1 of the structural-reinforcing fibers to the combustible material. Other embodiments and aspects are disclosed.

  18. Urea encapsulation in modified starch matrix for nutrients retention

    NASA Astrophysics Data System (ADS)

    Naz, Muhammad Yasin; Sulaiman, Shaharin Anwar; Ariff, Mohd. Hazwan Bin Mohd.; Ariwahjoedi, Bambang

    2014-10-01

    It has been estimated that 20-70% of the used urea goes to the environment via leaching, nitrification and volatilization which not only harms the environment but also reduces the urea efficiency. By coating the urea granules, the farmers can achieve high urea performance through controlling the excess release of nitrogen. Up until now, different materials have been tested for nutrients retention. However, most of them are either expensive or unfriendly to the environment. Being cheap and biodegradable materials, the starches may also be used to coat the urea fertilizer for controlling the nutrients release. However, the pure starches do not meet the standards set by many industrial processes due to their slow tacking and too low viscosities and should be modified for getting smooth, compact and mechanically stronger coatings. In these studies, the tapioca starch was modified by reacting it with urea and different masses of borax. The prepared solutions were used to coat the urea granules of 3.45 mm average diameter. Different volumes (1, 1.5 and 2 mL) of each solution were used to coat 30 g of urea fluidized above the minimum level of fluidization. It was noticed that the coating thickness, percent coating, dissolution rate and percent release follow an increasing trend with an increase of solution volume; however, some random results were obtained while investigating the solution volume effects on the percent release. It was seen that the nutrients percent release over time increases with an increase in solution volume from 1 to 1.5 mL and thereafter reaches to a steady state. It confirms that the 1.5 mL of solution for 30 g urea samples will give the optimized coating results.

  19. Selective permeability barrier to urea in shark rectal gland.

    PubMed

    Zeidel, Joshua D; Mathai, John C; Campbell, John D; Ruiz, Wily G; Apodaca, Gerard L; Riordan, John; Zeidel, Mark L

    2005-07-01

    Elasmobranchs such as the dogfish shark Squalus acanthius achieve osmotic homeostasis by maintaining urea concentrations in the 300- to 400-mM range, thus offsetting to some degree ambient marine osmolalities of 900-1,000 mosmol/kgH(2)O. These creatures also maintain salt balance without losing urea by secreting a NaCl-rich (500 mM) and urea-poor (18 mM) fluid from the rectal gland that is isotonic with the plasma. The composition of the rectal gland fluid suggests that its epithelial cells are permeable to water and not to urea. Because previous work showed that lipid bilayers that permit water flux do not block flux of urea, we reasoned that the plasma membranes of rectal gland epithelial cells must either have aquaporin water channels or must have some selective barrier to urea flux. We therefore isolated apical and basolateral membranes from shark rectal glands and determined their permeabilities to water and urea. Apical membrane fractions were markedly enriched for Na-K-2Cl cotransporter, whereas basolateral membrane fractions were enriched for Na-K-ATPase. Basolateral membrane osmotic water permeability (P(f)) averaged 4.3 +/- 1.3 x 10(-3) cm/s, whereas urea permeability averaged 4.2 +/- 0.8 x 10(-7) cm/s. The activation energy for water flow averaged 16.4 kcal/mol. Apical membrane P(f) averaged 7.5 +/- 1.6 x 10(-4) cm/s, and urea permeability averaged 2.2 +/- 0.4 x 10(-7) cm/s, with an average activation energy for water flow of 18.6 kcal/mol. The relatively low water permeabilities and high activation energies argue strongly against water flux via aquaporins. Comparison of membrane water and urea permeabilities with those of artificial liposomes and other isolated biological membranes indicates that the basolateral membrane urea permeability is fivefold lower than would be anticipated for its water permeability. These results indicate that the rectal gland maintains a selective barrier to urea in its basolateral membranes.

  20. Ames Hybrid Combustion Facility

    NASA Technical Reports Server (NTRS)

    Zilliac, Greg; Karabeyoglu, Mustafa A.; Cantwell, Brian; Hunt, Rusty; DeZilwa, Shane; Shoffstall, Mike; Soderman, Paul T.; Bencze, Daniel P. (Technical Monitor)

    2003-01-01

    The report summarizes the design, fabrication, safety features, environmental impact, and operation of the Ames Hybrid-Fuel Combustion Facility (HCF). The facility is used in conducting research into the scalability and combustion processes of advanced paraffin-based hybrid fuels for the purpose of assessing their applicability to practical rocket systems. The facility was designed to deliver gaseous oxygen at rates between 0.5 and 16.0 kg/sec to a combustion chamber operating at pressures ranging from 300 to 900. The required run times were of the order of 10 to 20 sec. The facility proved to be robust and reliable and has been used to generate a database of regression-rate measurements of paraffin at oxygen mass flux levels comparable to those of moderate-sized hybrid rocket motors.

  1. Thermodynamics and combustion modeling

    NASA Technical Reports Server (NTRS)

    Zeleznik, Frank J.

    1986-01-01

    Modeling fluid phase phenomena blends the conservation equations of continuum mechanics with the property equations of thermodynamics. The thermodynamic contribution becomes especially important when the phenomena involve chemical reactions as they do in combustion systems. The successful study of combustion processes requires (1) the availability of accurate thermodynamic properties for both the reactants and the products of reaction and (2) the computational capabilities to use the properties. A discussion is given of some aspects of the problem of estimating accurate thermodynamic properties both for reactants and products of reaction. Also, some examples of the use of thermodynamic properties for modeling chemically reacting systems are presented. These examples include one-dimensional flow systems and the internal combustion engine.

  2. Droplet Combustion Experiment movie

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Droplet Combustion Experiment (DCE) was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1 mission (STS-83, April 4-8 1997; the shortened mission was reflown as MSL-1R on STS-94). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.1 MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300164.html.

  3. Internal combustion engine

    DOEpatents

    Baker, Quentin A.; Mecredy, Henry E.; O'Neal, Glenn B.

    1991-01-01

    An improved engine is provided that more efficiently consumes difficult fuels such as coal slurries or powdered coal. The engine includes a precombustion chamber having a portion thereof formed by an ignition plug. The precombustion chamber is arranged so that when the piston is proximate the head, the precombustion chamber is sealed from the main cylinder or the main combustion chamber and when the piston is remote from the head, the precombustion chamber and main combustion chamber are in communication. The time for burning of fuel in the precombustion chamber can be regulated by the distance required to move the piston from the top dead center position to the position wherein the precombustion chamber and main combustion chamber are in communication.

  4. Fluidized-bed combustion

    SciTech Connect

    Botros, P E

    1990-04-01

    This report describes the activities of the Morgantown Energy Technology Center's research and development program in fluidized-bed combustion from October 1, 1987, to September 30, 1989. The Department of Energy program involves atmospheric and pressurized systems. Demonstrations of industrial-scale atmospheric systems are being completed, and smaller boilers are being explored. These systems include vortex, multi-solid, spouted, dual-sided, air-cooled, pulsed, and waste-fired fluidized-beds. Combustion of low-rank coal, components, and erosion are being studied. In pressurized combustion, first-generation, combined-cycle power plants are being tested, and second-generation, advanced-cycle systems are being designed and cost evaluated. Research in coal devolatilization, metal wastage, tube corrosion, and fluidization also supports this area. 52 refs., 24 figs., 3 tabs.

  5. Antipollution combustion chamber

    SciTech Connect

    Caruel, J.E.; Gastebois, P.M.

    1981-01-27

    The invention concerns a combustion chamber for turbojet engines. The combustion chamber is of the annular type and consists of two coaxial flame tubes opening into a common dilution and mixing zone. The inner tube is designed for low operating ratings of the engine, the outer tube for high ratings. Air is injected as far upstream as possible into the dilution zone, to enhance the homogenization of the gaseous flow issuing from the two tubes prior to their passage into the turbine and to assure the optimum radial distribution of temperatures. The combustion chamber according to the invention finds application in a particularly advantageous manner in turbojet engines used in aircraft propulsion because of the reduced emission of pollutants it affords.

  6. Forced cocurrent smoldering combustion

    SciTech Connect

    Dosanjh, S.S.; Pagni, P.J.; Fernandez-Pello, A.C.

    1987-05-01

    An analytic model of the propagation of smoldering combustion through a very porous solid fuel is presented. Here smoldering is initiated at the top of a long, radially insulated, uniform fuel cylinder, so that the smolder wave propagates downward, opposing an upward forced flow of oxidizer. Because the solid fuel and the gaseous oxidizer enter the reaction zone from the same direction, this configuration is referred to as cocurrent (or premixed-flame-like). It is assumed that the propagation of the smolder wave is one-dimensional and steady in a frame of reference moving with the wave. Buoyancy is included and shown to be negligible in the proposed application of a smoldering combustion experiment for use on the Space Shuttle. Radiation heat transfer is incorporated using the diffusion approximation and smoldering combustion is modeled by a finite rate, one-step reaction mechanism.

  7. Route repetition and route retracing: effects of cognitive aging.

    PubMed

    Wiener, Jan M; Kmecova, Hana; de Condappa, Olivier

    2012-01-01

    Retracing a recently traveled route is a frequent navigation task when learning novel routes or exploring unfamiliar environments. In the present study we utilized virtual environments technology to investigate age-related differences in repeating and retracing a learned route. In the training phase of the experiment participants were guided along a route consisting of multiple intersections each featuring one unique landmark. In the subsequent test phase, they were guided along short sections of the route and asked to indicate overall travel direction (repetition or retracing), the direction required to continue along the route, and the next landmark they would encounter. Results demonstrate age-related deficits in all three tasks. More specifically, in contrast to younger participants, the older participants had greater problems during route retracing than during route repetition. While route repetition can be solved with egocentric response or route strategies, successfully retracing a route requires allocentric processing. The age-related deficits in route retracing are discussed in the context of impaired allocentric processing and shift from allocentric to egocentric navigation strategies as a consequence of age-related hippocampal degeneration.

  8. Studies in combustion dynamics

    SciTech Connect

    Koszykowski, M.L.

    1993-12-01

    The goal of this program is to develop a fundamental understanding and a quantitative predictive capability in combustion modeling. A large part of the understanding of the chemistry of combustion processes comes from {open_quotes}chemical kinetic modeling.{close_quotes} However, successful modeling is not an isolated activity. It necessarily involves the integration of methods and results from several diverse disciplines and activities including theoretical chemistry, elementary reaction kinetics, fluid mechanics and computational science. Recently the authors have developed and utilized new tools for parallel processing to implement the first numerical model of a turbulent diffusion flame including a {open_quotes}full{close_quotes} chemical mechanism.

  9. Alternate Fuels Combustion Research

    DTIC Science & Technology

    1983-10-01

    AFWAL-TR-83-2057 AD A13 8 5 7 5 ALTERNATE FUELS COMBUSTION RESEARCH PHASE RI ’~*~~4 & IWITEY CMAAA * ’s~t:Uwz, ONTARIO October 1983 I•oerls Report...83-2057 P_______________ C TITLE (mod ,,--tt-) 5. TYPE OF REPORT A PERIOD COVERED Alternate Fuels ioahusticn Research Interim Report for Period Phase...I$. KEY WORDS (Continue on reverse sirte it necessear and identify by block number) FUELS ALTERNATE FUELS GAS TURBINE COMBUSTION EXHAUST EMISSIONS 0

  10. Thermal ignition combustion system

    DOEpatents

    Kamo, Roy; Kakwani, Ramesh M.; Valdmanis, Edgars; Woods, Melvins E.

    1988-01-01

    The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m.degree. C. and a specific heat greater than 480 J/kg.degree. C. with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber.

  11. Thermal ignition combustion system

    DOEpatents

    Kamo, R.; Kakwani, R.M.; Valdmanis, E.; Woods, M.E.

    1988-04-19

    The thermal ignition combustion system comprises means for providing walls defining an ignition chamber, the walls being made of a material having a thermal conductivity greater than 20 W/m C and a specific heat greater than 480 J/kg C with the ignition chamber being in constant communication with the main combustion chamber, means for maintaining the temperature of the walls above a threshold temperature capable of causing ignition of a fuel, and means for conducting fuel to the ignition chamber. 8 figs.

  12. Transition nozzle combustion system

    DOEpatents

    Kim, Won-Wook; McMahan, Kevin Weston; Maldonado, Jaime Javier

    2016-11-29

    The present application provides a combustion system for use with a cooling flow. The combustion system may include a head end, an aft end, a transition nozzle extending from the head end to the aft end, and an impingement sleeve surrounding the transition nozzle. The impingement sleeve may define a first cavity in communication with the head end for a first portion of the cooling flow and a second cavity in communication with the aft end for a second portion of the cooling flow. The transition nozzle may include a number of cooling holes thereon in communication with the second portion of the cooling flow.

  13. Toxicology of Biodiesel Combustion products

    EPA Science Inventory

    1. Introduction The toxicology of combusted biodiesel is an emerging field. Much of the current knowledge about biological responses and health effects stems from studies of exposures to other fuel sources (typically petroleum diesel, gasoline, and wood) incompletely combusted. ...

  14. Combuster. [low nitrogen oxide formation

    NASA Technical Reports Server (NTRS)

    Mckay, R. A. (Inventor)

    1978-01-01

    A combuster is provided for utilizing a combustible mixture containing fuel and air, to heat a load fluid such as water or air, in a manner that minimizes the formation of nitrogen oxide. The combustible mixture passes through a small diameter tube where the mixture is heated to its combustion temperature, while the load fluid flows past the outside of the tube to receive heat. The tube is of a diameter small enough that the combustible mixture cannot form a flame, and yet is not subject to wall quench, so that combustion occurs, but at a temperature less than under free flame conditions. Most of the heat required for heating the combustible mixture to its combustion temperature, is obtained from heat flow through the walls of the pipe to the mixture.

  15. Hydrolyzable Polyureas Bearing Hindered Urea Bonds

    PubMed Central

    2015-01-01

    Hydrolyzable polymers are widely used materials that have found numerous applications in biomedical, agricultural, plastic, and packaging industrials. They usually contain ester and other hydrolyzable bonds, such as anhydride, acetal, ketal, or imine, in their backbone structures. Here, we report the first design of hydrolyzable polyureas bearing dynamic hindered urea bonds (HUBs) that can reversibly dissociate to bulky amines and isocyanates, the latter of which can be further hydrolyzed by water, driving the equilibrium to facilitate the degradation of polyureas. Polyureas bearing 1-tert-butyl-1-ethylurea bonds that show high dynamicity (high bond dissociation rate), in the form of either linear polymers or cross-linked gels, can be completely degraded by water under mild conditions. Given the simplicity and low cost for the production of polyureas by simply mixing multifunctional bulky amines and isocyanates, the versatility of the structures, and the tunability of the degradation profiles of HUB-bearing polyureas, these materials are potentially of very broad applications. PMID:25406025

  16. Quantum crystallographic charge density of urea.

    PubMed

    Wall, Michael E

    2016-07-01

    Standard X-ray crystallography methods use free-atom models to calculate mean unit-cell charge densities. Real molecules, however, have shared charge that is not captured accurately using free-atom models. To address this limitation, a charge density model of crystalline urea was calculated using high-level quantum theory and was refined against publicly available ultra-high-resolution experimental Bragg data, including the effects of atomic displacement parameters. The resulting quantum crystallographic model was compared with models obtained using spherical atom or multipole methods. Despite using only the same number of free parameters as the spherical atom model, the agreement of the quantum model with the data is comparable to the multipole model. The static, theoretical crystalline charge density of the quantum model is distinct from the multipole model, indicating the quantum model provides substantially new information. Hydrogen thermal ellipsoids in the quantum model were very similar to those obtained using neutron crystallography, indicating that quantum crystallography can increase the accuracy of the X-ray crystallographic atomic displacement parameters. The results demonstrate the feasibility and benefits of integrating fully periodic quantum charge density calculations into ultra-high-resolution X-ray crystallographic model building and refinement.

  17. Quantum crystallographic charge density of urea

    DOE PAGES

    Wall, Michael E.

    2016-06-08

    Standard X-ray crystallography methods use free-atom models to calculate mean unit-cell charge densities. Real molecules, however, have shared charge that is not captured accurately using free-atom models. To address this limitation, a charge density model of crystalline urea was calculated using high-level quantum theory and was refined against publicly available ultra-high-resolution experimental Bragg data, including the effects of atomic displacement parameters. The resulting quantum crystallographic model was compared with models obtained using spherical atom or multipole methods. Despite using only the same number of free parameters as the spherical atom model, the agreement of the quantum model with the datamore » is comparable to the multipole model. The static, theoretical crystalline charge density of the quantum model is distinct from the multipole model, indicating the quantum model provides substantially new information. Hydrogen thermal ellipsoids in the quantum model were very similar to those obtained using neutron crystallography, indicating that quantum crystallography can increase the accuracy of the X-ray crystallographic atomic displacement parameters. Lastly, the results demonstrate the feasibility and benefits of integrating fully periodic quantum charge density calculations into ultra-high-resolution X-ray crystallographic model building and refinement.« less

  18. Quantum crystallographic charge density of urea

    SciTech Connect

    Wall, Michael E.

    2016-06-08

    Standard X-ray crystallography methods use free-atom models to calculate mean unit-cell charge densities. Real molecules, however, have shared charge that is not captured accurately using free-atom models. To address this limitation, a charge density model of crystalline urea was calculated using high-level quantum theory and was refined against publicly available ultra-high-resolution experimental Bragg data, including the effects of atomic displacement parameters. The resulting quantum crystallographic model was compared with models obtained using spherical atom or multipole methods. Despite using only the same number of free parameters as the spherical atom model, the agreement of the quantum model with the data is comparable to the multipole model. The static, theoretical crystalline charge density of the quantum model is distinct from the multipole model, indicating the quantum model provides substantially new information. Hydrogen thermal ellipsoids in the quantum model were very similar to those obtained using neutron crystallography, indicating that quantum crystallography can increase the accuracy of the X-ray crystallographic atomic displacement parameters. Lastly, the results demonstrate the feasibility and benefits of integrating fully periodic quantum charge density calculations into ultra-high-resolution X-ray crystallographic model building and refinement.

  19. Novel urea and bis-urea primaquine derivatives with hydroxyphenyl or halogenphenyl substituents: Synthesis and biological evaluation.

    PubMed

    Perković, I; Antunović, M; Marijanović, I; Pavić, K; Ester, K; Kralj, M; Vlainić, J; Kosalec, I; Schols, D; Hadjipavlou-Litina, D; Pontiki, E; Zorc, B

    2016-11-29

    A series of novel compounds 3a-j and 6a-j with primaquine and hydroxyl or halogen substituted benzene moieties bridged by urea or bis-urea functionalities were designed, synthesized and evaluated for biological activity. The title compounds were prepared using benzotriazole as the synthon, through several synthetic steps. 3-[3,5-Bis(trifluoromethyl)phenyl]-1-{4-[(6-methoxyquinolin-8-yl)amino]pentyl}urea (3j) was the most active urea and 1-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]-3-[3-(trifluoromethyl)phenyl]urea (6h) the most active bis-urea derivative in antiproliferative screening in vitro against eight tested cancer cell lines. Urea derivatives 3a-g with hydroxy group or one halogen atom showed moderate antiproliferative effects against all the tested cell lines, but stronger activity against breast carcinoma MCF-7 cell line, while trifluoromethyl derivatives 3h-j showed antiproliferative effects against all the tested cell lines in low micromolar range. Finally, bis-ureas with hydroxy and fluoro substituents 6a-d showed extreme selectivity and chloro or bromo derivatives 6e-g high selectivity against MCF-7 cells (IC50 0.1-2.6 μM). p-Fluoro derivative 6d, namely 3-(4-fluorophenyl)-1-[({4-[(6-methoxyquinolin-8-yl)amino]pentyl}carbamoyl)amino]urea, is the most promising compound. Further biological experiments showed that 6d affected cell cycle and induced cell death of MCF-7 cell line. Due to its high activity against MCF-7 cell line (IC50 0.31 μM), extreme selectivity and full agreement with the Lipinski's and Gelovani's rules for prospective small molecular drugs, 6d may be considered as a lead compound in development of breast carcinoma drugs. Urea 3b and almost all bis-ureas showed high antioxidant activity in DPPH assay, but urea derivatives were more active in lipid peroxidation test. Only few compounds exhibited weak inhibition of soybean lipoxygenase. Compound 3j exhibited the strongest antimicrobial activity in susceptibility

  20. Increasingly minimal bias routing

    DOEpatents

    Bataineh, Abdulla; Court, Thomas; Roweth, Duncan

    2017-02-21

    A system and algorithm configured to generate diversity at the traffic source so that packets are uniformly distributed over all of the available paths, but to increase the likelihood of taking a minimal path with each hop the packet takes. This is achieved by configuring routing biases so as to prefer non-minimal paths at the injection point, but increasingly prefer minimal paths as the packet proceeds, referred to herein as Increasing Minimal Bias (IMB).

  1. ARPANET Routing Algorithm Improvements

    DTIC Science & Technology

    1978-10-01

    IMPROVEMENTS . .PFOnINI ORG. REPORT MUNDER -- ) _ .. .... 3940 7, AUT񓂏(c) .. .. .. CONTRACT Of GRANT NUMSlet e) SJ. M. /Mc~uillan E. C./Rosen I...8217), this problem may persist for a very long time, causing extremely bad performance throughout the whole network (for instance, if w’ reports that one of...algorithm may naturally tend to oscillate between bad routing paths and become itself a major contributor to network congestion. These examples show

  2. Onion Routing Access Configurations

    DTIC Science & Technology

    2000-01-01

    eavesdropping and trac analysis. Thus it hides not only the data being sent, but who is talking to whom. Onion Routing’s anonymous connections are bidirec...Keywords: Security, privacy, anonymity , trac analysis. 1 Introduction Preserving privacy means not only hiding the con- tent of messages, but also...communication over a public network. It pro- vides anonymous connections that are strongly resis- tant to both eavesdropping and trac analysis. The

  3. Reversed flow fluidized-bed combustion apparatus

    DOEpatents

    Shang, Jer-Yu; Mei, Joseph S.; Wilson, John S.

    1984-01-01

    The present invention is directed to a fluidized-bed combustion apparatus provided with a U-shaped combustion zone. A cyclone is disposed in the combustion zone for recycling solid particulate material. The combustion zone configuration and the recycling feature provide relatively long residence times and low freeboard heights to maximize combustion of combustible material, reduce nitrogen oxides, and enhance sulfur oxide reduction.

  4. Microdetermination of urea in urine using p-dimethylaminobenzaldehyde /PDAB/

    NASA Technical Reports Server (NTRS)

    Geiger, P. J.

    1969-01-01

    Adaptation of the p-dimethylaminobenzaldehyde method for determining urea concentration in urine is an improved micromechanical method. Accuracy and precision are satisfactory. This method avoids extra steps of deproteinizing or removing normal urinary chromogens.

  5. Urea biosensors based on PVC membrane containing palmitic acid.

    PubMed

    Karakuş, Emine; Pekyardimci, Sule; Esma, Kiliç

    2005-01-01

    A new urea biosensor was prepared by immobilizing urease with four different procedures on poly(vinylchloride) (PVC) ammonium membrane electrode containing palmitic acid by using nonactine as an ammonium-ionophore. The analytical characteristics were investigated and were compared those of the biosensor prepared by using carboxylated PVC. The effect of pH, buffer concentration, temperature, urease concentration, stirring rate and enzyme immobilization procedures on the response to urea of the enzyme electrode were investigated. The linear working range and sensitivity of the biosensor were also determined. The urea biosensor prepared by using the PVC membranes containing palmitic acid showed more effective performance than those of the carboxylated PVC based biosensors. Additionally, urea assay in serum was successfully carried out by using the standard addition method.

  6. Influence of Ficoll on urea induced denaturation of fibrinogen

    NASA Astrophysics Data System (ADS)

    Sankaranarayanan, Kamatchi; Meenakshisundaram, N.

    2016-03-01

    Ficoll is a neutral, highly branched polymer used as a molecular crowder in the study of proteins. Ficoll is also part of Ficoll-Paque used in biology laboratories to separate blood to its components (erythrocytes, leukocytes etc.,). Role of Ficoll in the urea induced denaturation of protein Fibrinogen (Fg) has been analyzed using fluorescence, circular dichroism, molecular docking and interfacial studies. Fluorescence studies show that Ficoll prevents quenching of Fg in the presence of urea. From the circular dichroism spectra, Fg shows conformational transition to random coil with urea of 6 M concentration. Ficoll helps to shift this denaturation concentration to 8 M and thus constraints by shielding Fg during the process. Molecular docking studies indicate that Ficoll interacts favorably with the protein than urea. The surface tension and shear viscosity analysis shows clearly that the protein is shielded by Ficoll.

  7. Online measurement of urea concentration in spent dialysate during hemodialysis

    NASA Astrophysics Data System (ADS)

    Olesberg, Jonathon T.; Armitage, Ben; Arnold, Mark A.; Flanigan, Michael

    2002-05-01

    We describe on-line optical measurements of urea concentration during the regular hemodialysis treatment of several patients. The spectral measurements were performed in the effluent dialysate stream after the dialysis membrane using an FTIR spectrometer equipped with a flow-through cell. Spectra were recorded across the 5000-4000 cm-1 (2.0-2.5 micrometers at 1-minute intervals. Optically determined concentrations matched concentrations obtained from standard chemical assays with a root-mean-square error of 0.29 mM for urea (0.8 mg/dl urea nitrogen), 0.03 mM for creatinine, 0.11 mM for lactate, and 0.22 mM for glucose. The observed concentration ranges were 0-11 mM for urea, 0-0.35 mM for creatinine, 0-0.75 mM for lactate, and 9-12.5 mM for glucose.

  8. Binding studies of creatinine and urea on iron-nanoparticle.

    PubMed

    Banerji, Biswadip; Pramanik, Sumit Kumar

    2015-01-01

    Kidney diseases are complicated and can be fatal. Dialysis and transplantation are the only survival solutions to the patients suffering from kidney failures. Both hemodialysis and peritoneal dialysis are risky, due to the possibility of infection and these are expensive and time consuming. The development of simple and reliable technique for the clearance of creatinine and urea from the body is an important part of biotechnology. We have synthesized an iron nanoparticle (INP) and studied its binding with creatinine and urea. The DLS, TEM, AFM, FT-IR and Powder-XRD studies demonstrate strong binding of creatinine and urea to the nanoparticles. This finding may be helpful if it is used in the dialysis technologies. The proposed method may substantially decrease dialysis time and improve its quality in terms of urea and creatinine clearances.

  9. Formation of urea and guanidine by irradiation of ammonium cyanide.

    NASA Technical Reports Server (NTRS)

    Lohrmann, R.

    1972-01-01

    Aqueous solutions of ammonium cyanide yield urea, cyanamide and guanidine when exposed to sunlight or an unfiltered 254 nm ultraviolet source. The prebiotic significance of these results is discussed.

  10. Exploring the cocrystallization potential of urea and benzamide.

    PubMed

    Cysewski, Piotr; Przybyłek, Maciej; Ziółkowska, Dorota; Mroczyńska, Karina

    2016-05-01

    The cocrystallization landscape of benzamide and urea interacting with aliphatic and aromatic carboxylic acids was studied both experimentally and theoretically. Ten new cocrystals of benzamide were synthesized using an oriented samples approach via a fast dropped evaporation technique. Information about types of known bi-component cocrystals augmented with knowledge of simple binary eutectic mixtures was used for the analysis of virtual screening efficiency among 514 potential pairs involving aromatic carboxylic acids interacting with urea or benzamide. Quantification of intermolecular interaction was achieved by estimating the excess thermodynamic functions of binary liquid mixtures under supercooled conditions within a COSMO-RS framework. The smoothed histograms suggest that slightly more potential pairs of benzamide are characterized in the attractive region compared to urea. Finally, it is emphasized that prediction of cocrystals of urea is fairly direct, while it remains ambiguous for benzamide paired with carboxylic acids. The two known simple eutectics of urea are found within the first two quartiles defined by excess thermodynamic functions, and all known cocrystals are outside of this range belonging to the third or fourth quartile. On the contrary, such a simple separation of positive and negative cases of benzamide miscibility in the solid state is not observed. The difference in properties between urea and benzamide R2,2(8) heterosynthons is also documented by alterations of substituent effects. Intermolecular interactions of urea with para substituted benzoic acid analogues are stronger compared to those of benzamide. Also, the amount of charge transfer from amide to aromatic carboxylic acid and vice versa is more pronounced for urea. However, in both cases, the greater the electron withdrawing character of the substituent, the higher the binding energy, and the stronger the supermolecule polarization via the charge transfer mechanism.

  11. Combustible dust tests

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The sugar dust explosion in Georgia on February 7, 2008 killed 14 workers and injured many others (OSHA, 2009). As a consequence of this explosion, OSHA revised its Combustible Dust National Emphasis (NEP) program. The NEP targets 64 industries with more than 1,000 inspections and has found more tha...

  12. Combustion Fundamentals Research

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The various physical processes that occur in the gas turbine combustor and the development of analytical models that accurately describe these processes are discussed. Aspects covered include fuel sprays; fluid mixing; combustion dynamics; radiation and chemistry and numeric techniques which can be applied to highly turbulent, recirculating, reacting flow fields.

  13. WASTE COMBUSTION SYSTEM ANALYSIS

    EPA Science Inventory

    The report gives results of a study of biomass combustion alternatives. The objective was to evaluate the thermal performance and costs of available and developing biomass systems. The characteristics of available biomass fuels were reviewed, and the performance parameters of alt...

  14. Spray combustion stability project

    NASA Technical Reports Server (NTRS)

    Jeng, San-Mou; Litchford, Ron J.

    1992-01-01

    This report summarizes research activity on the Spray Combustion Stability Project, characterizes accomplishments and current status, and discusses projected future work. The purpose is to provide a concise conceptual overview of the research effort to date so the reader can quickly assimilate the gist of the research results and place them within the context of their potential impact on liquid rocket engine design technology.

  15. Monopropellant combustion system

    NASA Technical Reports Server (NTRS)

    Berg, Gerald R. (Inventor); Mueller, Donn C. (Inventor); Parish, Mark W. (Inventor)

    2005-01-01

    An apparatus and method are provided for decomposition of a propellant. The propellant includes an ionic salt and an additional fuel. Means are provided for decomposing a major portion of the ionic salt. Means are provided for combusting the additional fuel and decomposition products of the ionic salt.

  16. Coal combustion research

    SciTech Connect

    Daw, C.S.

    1996-06-01

    This section describes research and development related to coal combustion being performed for the Fossil Energy Program under the direction of the Morgantown Energy Technology Center. The key activity involves the application of chaos theory for the diagnosis and control of fossil energy processes.

  17. Preparation and affinity identification of glutamic acid-urea small molecule analogs in prostate cancer

    PubMed Central

    Zhang, Zhiwei; Zhu, Zheng; Yang, Deyong; Fan, Weiwei; Wang, Jianbo; Li, Xiancheng; Chen, Xiaochi; Wang, Qifeng; Song, Xishuang

    2016-01-01

    In recent years, study concerning activity inhibitors of prostate-specific membrane antigen (PSMA) has been concentrated on the glutamic urea (Glu-urea-R) small molecule and its analogs. The present study aimed to synthesize 4 analogs of Glu-urea-R and identify the affinities of these compounds to PSMA. The compounds were synthesized from raw materials, and the experimental procedures of the present study were in accordance with standard techniques under anhydrous and anaerobic conditions. Glu-urea-Lysine (Glu-urea-Lys), Glu-urea-Ornithine (Glu-urea-Orn), Glu-urea-Glutamine (Glu-urea-Gln) and Glu-urea-Asparagine (Glu-urea-Asn) were successfully synthesized, and their structures were confirmed to be as desired using nuclear magnetic resonance spectroscopy and mass spectrometry. An affinity assay was performed to detect the affinity between the various compounds and PSMA expressed from the prostate cancer LNCap cell line. Glu-urea-Gln had the highest affinity to PSMA, followed by Glu-urea-Asn, Glu-urea-Orn and Glu-urea-Lys. In conclusion, the present study demonstrated that Glu-urea-R specifically binds PSMA expressed in the LNCap cell line and inhibits its activity. PMID:27446384

  18. 77 FR 64464 - Solid Urea From the Russian Federation: Antidumping Duty Administrative Review; 2010-2011

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-10-22

    ... International Trade Administration Solid Urea From the Russian Federation: Antidumping Duty Administrative... administrative review of the antidumping duty order on solid urea from the Russian Federation (Russia). The... order on solid urea from Russia. See Solid Urea From the Russian Federation: Preliminary Results...

  19. NiO nanoparticle-based urea biosensor.

    PubMed

    Tyagi, Manisha; Tomar, Monika; Gupta, Vinay

    2013-03-15

    NiO nanoparticles (NiO-NPs) have been exploited successfully for the fabrication of a urea biosensor. A thin film of NiO nanoparticles deposited on an indium tin oxide (ITO) coated glass substrate serves as an efficient matrix for the immobilisation of urease (Ur), the specific enzyme for urea detection. The prepared bioelectrode (Ur/NiO-NP/ITO/glass) is utilised for urea sensing using cyclic voltammetry and UV-visible spectroscopy. NiO nanoparticles act as electro-catalytic species that are based on the shuttling of electrons between Ni(2+) and Ni(3+) in the octahedral site and result in an enhanced electrochemical current response. The prepared bioelectrode (Ur/NiO-NPs/ITO/glass) exhibits a high sensitivity of 21.3 μA/(mM (*) cm(2)) and a good linearity in a wide range (0.83-16.65 Mm) of urea concentrations with fast response time of 5s. The low value of the Michaelis-Menten constant (K(m)=0.34 mM) indicates the high affinity of Ur towards the analyte (urea). The high catalytic activity, along with the redox behaviour of NiO-NPs, makes it an efficient matrix for the realisation of a urea biosensor.

  20. Analysis of the Sub-Millimeter Rotational Spectrum of Urea

    NASA Astrophysics Data System (ADS)

    Thomas, Jessica R.; Fosnight, Alyssa M.; Medvedev, Ivan R.

    2013-06-01

    Urea, ((NH_{2})_{2}CO), has broad presence in biological species. As a byproduct of human metabolism, this molecule is commonly tested for in blood to diagnose different pathologies. Furthermore, urea is seen in interstellar medium and its detection could yield valuable insight into the mechanisms governing star formation. Despite the prevalence of urea, an absence exists in recorded frequencies of this molecule. The new generation of the sub-millimeter telescopes, such as ALMA, HERSCHEL, and SOFIA, allows detection of interstellar molecular spectra at unprecedented spatial and spectral resolutions. The knowledge of the precise frequencies of spectra transitions present in interstellar molecular clouds would alleviate the problem of spectral congestion and aid in molecular identification. This paper reports the most recent investigation of the submillimeter/terahertz gas phase spectrum of urea. Up until now, only the microwave laboratory spectrum of urea's vibrational ground state has been available. This paper reports the high-resolution spectra of urea in the sub-millimeter range, and extends the spectroscopic assignment of the rotational transitions in the vibrational ground state. Additionally, the assignment of the first vibrational state and tentative assignments of two additional vibrational states have been made.

  1. Active urea transport in lower vertebrates and mammals.

    PubMed

    Bankir, Lise

    2014-01-01

    Some unicellular organisms can take up urea from the surrounding fluids by an uphill pumping mechanism. Several active (energy-dependent) urea transporters (AUTs) have been cloned in these organisms. Functional studies show that active urea transport also occurs in elasmobranchs, amphibians, and mammals. In the two former groups, active urea transport may serve to conserve urea in body fluids in order to balance external high ambient osmolarity or prevent desiccation. In mammals, active urea transport may be associated with the need to either store and/or reuse nitrogen in the case of low nitrogen supply, or to excrete nitrogen efficiently in the case of excess nitrogen intake. There are probably two different families of AUTs, one with a high capacity able to establish only a relatively modest transepithelial concentration difference (renal tubule of some frogs, pars recta of the mammalian kidney, early inner medullary collecting duct in some mammals eating protein-poor diets) and others with a low capacity but able to maintain a high transepithelial concentration difference that has been created by another mechanism or in another organ (elasmobranch gills, ventral skin of some toads, and maybe mammalian urinary bladder). Functional characterization of these transporters shows that some are coupled to sodium (symports or antiports) while others are sodium-independent. In humans, only one genetic anomaly, with a mild phenotype (familial azotemia), is suspected to concern one of these transporters. In spite of abundant functional evidence for such transporters in higher organisms, none have been molecularly identified yet.

  2. Urea-induced oxidative damage in Elodea densa leaves.

    PubMed

    Maleva, Maria; Borisova, Galina; Chukina, Nadezda; Prasad, M N V

    2015-09-01

    Urea being a fertilizer is expected to be less toxic to plants. However, it was found that urea at 100 mg L(-1) caused the oxidative stress in Elodea leaves due to the formation of reactive oxygen species (ROS) and lipid peroxidation that are known to stimulate antioxidant pathway. Urea at a concentration of 500 and 1000 mg L(-1) decreased low-molecular-weight antioxidants. In this case, the antioxidant status of plants was supported by the activity of antioxidant enzymes such as superoxide dismutase and guaiacol peroxidase. A significant increase in the soluble proteins and -SH groups was observed with high concentrations of urea (30-60 % of control). Thus, the increased activity of antioxidant enzymes, low-molecular-weight antioxidants, and induced soluble protein thiols are implicated in plant resistance to oxidative stress imposed by urea. We found that guaiacol peroxidase plays an important role in the removal of the peroxide in Elodea leaves exposed to 1000 mg L(-1)of urea.

  3. Discovery of enantioselectivity of urea inhibitors of soluble epoxide hydrolase.

    PubMed

    Manickam, Manoj; Pillaiyar, Thanigaimalai; Boggu, PullaReddy; Venkateswararao, Eeda; Jalani, Hitesh B; Kim, Nam-Doo; Lee, Seul Ki; Jeon, Jang Su; Kim, Sang Kyum; Jung, Sang-Hun

    2016-07-19

    Soluble epoxide hydrolase (sEH) hydrolyzes epoxyeicosatrienoic acids (EETs) in the metabolic pathway of arachidonic acid and has been considered as an important therapeutic target for chronic diseases such as hypertension, diabetes and inflammation. Although many urea derivatives are known as sEH inhibitors, the enantioselectivity of the inhibitors is not highlighted in spite of the stereoselective hydrolysis of EETs by sEH. In an effort to explore the importance of enantioselectivity in the urea scaffold, a series of enantiomers with the stereocenter adjacent to the urea nitrogen atom were prepared. The selectivity of enantiomers of 1-(α-alkyl-α-phenylmethyl)-3-(3-phenylpropyl)ureas showed wide range differences up to 125 fold with the low IC50 value up to 13 nM. The S-configuration with planar phenyl and small alkyl groups at α-position is crucial for the activity and selectivity. However, restriction of the free rotation of two α-groups with indan-1-yl or 1,2,3,4-tetrahydronaphthalen-1-yl moiety abolishes the selectivity between the enantiomers, despite the increase in activity up to 13 nM. The hydrophilic group like sulfonamido group at para position of 3-phenylpropyl motif of 1-(α-alkyl-α-phenylmethyl-3-(3-phenylpropyl)urea improves the activity as well as enantiomeric selectivity. All these ureas are proved to be specific inhibitor of sEH without inhibition against mEH.

  4. Urea and ureolytic activity in lakes of different trophic status.

    PubMed

    Siuda, Waldemar; Chróst, Ryszard J

    2006-01-01

    Urea and uraease (U-ase) activity were determined in water samples taken from the surface layers of 17 lakes of different trophic status. Urea concentrations were inversely correlated with the trophic status of the studied lakes and varied from below the detection limit to 25 micromol l(-1). Maximal potential ureolytic activity (V(max)) ranged from 0.2 to 7.0 micromol l(-1) h(-1). The highest urea concentrations and the lowest U-ase activities were recorded in the spring, whereas the lowest urea concentrations and the highest rates of urea hydrolysis were observed late in summer, during heavy phytoplankton blooms. Since in the majority of the Great Mazurian Lakes microplankton growth was limited by nitrogen supply, urea was an important N source for both auto- and heterotrophic planktonic microorganisms throughout the growth period. U-ase activity was mainly related to the seston. Only up to 25% of total activity could be attributed to free enzymes dissolved in lake water. In epilimnetic water samples the bulk of the ureolytic activity originated from seston-attached bacteria. However, a positive, statistically significant correlation between ureolytic activity and chlorophyll a (Chl(a)) concentrations suggests that phytoplankton may also be responsible for at least a some of the observed ureolytic activity in the highly eutrophic Great Mazurian Lakes.

  5. Robustness of airline route networks

    NASA Astrophysics Data System (ADS)

    Lordan, Oriol; Sallan, Jose M.; Escorihuela, Nuria; Gonzalez-Prieto, David

    2016-03-01

    Airlines shape their route network by defining their routes through supply and demand considerations, paying little attention to network performance indicators, such as network robustness. However, the collapse of an airline network can produce high financial costs for the airline and all its geographical area of influence. The aim of this study is to analyze the topology and robustness of the network route of airlines following Low Cost Carriers (LCCs) and Full Service Carriers (FSCs) business models. Results show that FSC hubs are more central than LCC bases in their route network. As a result, LCC route networks are more robust than FSC networks.

  6. How does the urea dynamics differ from water dynamics inside the reverse micelle?

    PubMed

    Sengupta, Abhigyan; Khade, Rahul V; Hazra, Partha

    2011-09-29

    In this study, the urea dynamics inside AOT reverse micelle (RM) has been monitored without intervention of water using time-resolved fluorescence techniques from the picosecond to nanosecond time regime. It has been observed that urea dynamics inside the reverse micelle is severely retarded compared to water RM due to the formation of highly networked urea cluster inside the RM. Time-resolved fluorescence anisotropy study also confirms the existence of a confined environment around the dye at higher concentrations of urea inside the reverse micelle. The dynamics of urea-water mixtures inside AOT reverse micelle has also been monitored with increasing urea concentration to get insight about the effect of urea on the overall solvation dynamics feature. It has been observed that with the increase in urea concentration, the overall dynamics becomes slower, and it infers the presence of few water or urea molecules, those strongly associated with surrounding urea and (or) water by hydrogen bonds.

  7. Low emission internal combustion engine

    DOEpatents

    Karaba, Albert M.

    1979-01-01

    A low emission, internal combustion compression ignition engine having a cylinder, a piston movable in the cylinder and a pre-combustion chamber communicating with the cylinder near the top thereof and in which low emissions of NO.sub.x are achieved by constructing the pre-combustion chamber to have a volume of between 70% and 85% of the combined pre-chamber and main combustion chamber volume when the piston is at top dead center and by variably controlling the initiation of fuel injection into the pre-combustion chamber.

  8. Modelling of CWS combustion process

    NASA Astrophysics Data System (ADS)

    Rybenko, I. A.; Ermakova, L. A.

    2016-10-01

    The paper considers the combustion process of coal water slurry (CWS) drops. The physico-chemical process scheme consisting of several independent parallel-sequential stages is offered. This scheme of drops combustion process is proved by the particle size distribution test and research stereomicroscopic analysis of combustion products. The results of mathematical modelling and optimization of stationary regimes of CWS combustion are provided. During modeling the problem of defining possible equilibrium composition of products, which can be obtained as a result of CWS combustion processes at different temperatures, is solved.

  9. Biohydrogen Production: Strategies to Improve Process Efficiency through Microbial Routes

    PubMed Central

    Chandrasekhar, Kuppam; Lee, Yong-Jik; Lee, Dong-Woo

    2015-01-01

    The current fossil fuel-based generation of energy has led to large-scale industrial development. However, the reliance on fossil fuels leads to the significant depletion of natural resources of buried combustible geologic deposits and to negative effects on the global climate with emissions of greenhouse gases. Accordingly, enormous efforts are directed to transition from fossil fuels to nonpolluting and renewable energy sources. One potential alternative is biohydrogen (H2), a clean energy carrier with high-energy yields; upon the combustion of H2, H2O is the only major by-product. In recent decades, the attractive and renewable characteristics of H2 led us to develop a variety of biological routes for the production of H2. Based on the mode of H2 generation, the biological routes for H2 production are categorized into four groups: photobiological fermentation, anaerobic fermentation, enzymatic and microbial electrolysis, and a combination of these processes. Thus, this review primarily focuses on the evaluation of the biological routes for the production of H2. In particular, we assess the efficiency and feasibility of these bioprocesses with respect to the factors that affect operations, and we delineate the limitations. Additionally, alternative options such as bioaugmentation, multiple process integration, and microbial electrolysis to improve process efficiency are discussed to address industrial-level applications. PMID:25874756

  10. Biohydrogen production: strategies to improve process efficiency through microbial routes.

    PubMed

    Chandrasekhar, Kuppam; Lee, Yong-Jik; Lee, Dong-Woo

    2015-04-14

    The current fossil fuel-based generation of energy has led to large-scale industrial development. However, the reliance on fossil fuels leads to the significant depletion of natural resources of buried combustible geologic deposits and to negative effects on the global climate with emissions of greenhouse gases. Accordingly, enormous efforts are directed to transition from fossil fuels to nonpolluting and renewable energy sources. One potential alternative is biohydrogen (H2), a clean energy carrier with high-energy yields; upon the combustion of H2, H2O is the only major by-product. In recent decades, the attractive and renewable characteristics of H2 led us to develop a variety of biological routes for the production of H2. Based on the mode of H2 generation, the biological routes for H2 production are categorized into four groups: photobiological fermentation, anaerobic fermentation, enzymatic and microbial electrolysis, and a combination of these processes. Thus, this review primarily focuses on the evaluation of the biological routes for the production of H2. In particular, we assess the efficiency and feasibility of these bioprocesses with respect to the factors that affect operations, and we delineate the limitations. Additionally, alternative options such as bioaugmentation, multiple process integration, and microbial electrolysis to improve process efficiency are discussed to address industrial-level applications.

  11. Instability Free Routing: Beyond One Protocol Instance

    DTIC Science & Technology

    2008-12-01

    assigned a Rout- ing Information Base (RIB) [13]. This database is used to store the routing information related to the routing process (e.g., routes...presents routing anomalies that can derive from route selection by itself, i.e., without any route redis - tribution configured between the routing... redis - tributed into the RIP protocol, all RIP messages received from the neighbors are in fact discarded independently of the AD values. This

  12. Storage and flood routing

    USGS Publications Warehouse

    Carter, R.W.; Godfrey, R.G.

    1960-01-01

    The basic equations used in flood routing are developed from the law of continuity. In each method the assumptions are discussed to enable the user to select an appropriate technique. In the stage-storage method the storage is related to the mean gage height in the reach under consideration. In the discharge-storage method the storage is determined, from weighted values of inflow and outflow discharge. In the reservoir-storage method the storage is considered as a function of outflow discharge alone. A detailed example is given for each method to illustrate that particular technique.

  13. Time Resolved FTIR Analysis of Combustion of Ethanol and Gasoline Combustion in AN Internal Combustion Engine

    NASA Astrophysics Data System (ADS)

    White, Allen R.; Sakai, Stephen; Devasher, Rebecca B.

    2011-06-01

    In order to pursue In Situ measurements in an internal combustion engine, a MegaTech Mark III transparent spark ignition engine was modified with a sapphire combustion chamber. This modification will allow the transmission of infrared radiation for time-resolved spectroscopic measurements by an infrared spectrometer. By using a Step-scan equipped Fourier transform spectrometer, temporally resolved infrared spectral data were acquired and compared for combustion in the modified Mark III engine. Measurements performed with the FTIR system provide insight into the energy transfer vectors that precede combustion and also provides an in situ measurement of the progress of combustion. Measurements were performed using ethanol and gasoline.

  14. The Modification of Polyurethane Foams Using New Boroorganic Polyols (II) Polyurethane Foams from Boron-Modified Hydroxypropyl Urea Derivatives

    PubMed Central

    2014-01-01

    The work focuses on research related to determination of application possibility of new, ecofriendly boroorganic polyols in rigid polyurethane foams production. Polyols were obtained from hydroxypropyl urea derivatives esterified with boric acid and propylene carbonate. The influence of esterification type on properties of polyols and next on polyurethane foams properties was determined. Nitrogen and boron impacts on the foams' properties were discussed, for instance, on their physical, mechanical, and electric properties. Boron presence causes improvement of dimensional stability and thermal stability of polyurethane foams. They can be applied even at temperature 150°C. Unfortunately, introducing boron in polyurethanes foams affects deterioration of their water absorption, which increases as compared to the foams that do not contain boron. However, presence of both boron and nitrogen determines the decrease of the foams combustibility. Main impact on the decrease combustibility of the obtained foams has nitrogen presence, but in case of proper boron and nitrogen ratio their synergic activity on the combustibility decrease can be easily seen. PMID:24587721

  15. The modification of polyurethane foams using new boroorganic polyols (II) polyurethane foams from boron-modified hydroxypropyl urea derivatives.

    PubMed

    Zarzyka, Iwona

    2014-01-01

    The work focuses on research related to determination of application possibility of new, ecofriendly boroorganic polyols in rigid polyurethane foams production. Polyols were obtained from hydroxypropyl urea derivatives esterified with boric acid and propylene carbonate. The influence of esterification type on properties of polyols and next on polyurethane foams properties was determined. Nitrogen and boron impacts on the foams' properties were discussed, for instance, on their physical, mechanical, and electric properties. Boron presence causes improvement of dimensional stability and thermal stability of polyurethane foams. They can be applied even at temperature 150 °C. Unfortunately, introducing boron in polyurethanes foams affects deterioration of their water absorption, which increases as compared to the foams that do not contain boron. However, presence of both boron and nitrogen determines the decrease of the foams combustibility. Main impact on the decrease combustibility of the obtained foams has nitrogen presence, but in case of proper boron and nitrogen ratio their synergic activity on the combustibility decrease can be easily seen.

  16. New Routing Metrics for ADHOC Network Routing Protocols

    NASA Astrophysics Data System (ADS)

    Reddy, P. C.

    2014-12-01

    The performance and reliability of Internet is measured using different quantities. When the quantities measured are essential and have wide range of acceptance then they are called metrics. Performance metrics enable comparison and selection among the alternatives. In computer networks, metrics are used to evaluate an application, protocol etc. Routing in adhoc networks is nontrivial. Routing protocols for adhoc networks are still evolving and there is need for continuous evaluation of them. In the literature existing, several routing protocols are evaluated using standard metrics under different conditions. This paper proposes new metrics for evaluation of routing protocols and uses them to evaluate the adhoc network routing protocols AODV, DSR, DSDV and TORA. Simulation environment is created using NS-2 simulator. Typical range of speeds, pause times and data rates are used. The results provide new insights in to the working of the routing protocols.

  17. Thermoluminescent dosimetric comparison for two different MgB4O7:Dy production routes

    NASA Astrophysics Data System (ADS)

    Souza, L. F.; Vidal, R. M.; Souza, S. O.; Souza, D. N.

    2014-11-01

    There are several routes employed for the production of synthetic magnesium tetraborate, for example, sol-gel method, combustion, wet reaction synthesis, solid-state route and precipitation (crystal growth). The most commonly used synthesis methods are the wet reaction (precipitation) and solid-state synthesis; both production routes are efficient, but is very difficult to find a direct comparison for them. The present work proposes a direct comparison of both production routes used for magnesium tetraborate synthesis for thermoluminescent (TL) dosimetry. In this work, MgB4O7:Dy was prepared by both methods, wet reaction or precipitation-route 1, and solid-state synthesis -route 2, with the same amount of dopant (0.1%). In the first part of work, the crystalline phases were confirmed by X-ray diffraction (XRD) and it was observed that MgB4O7:Dy can be obtained satisfactorily through both routes, although a very intense crystalline phase of H3BO3 for the powder produced through route 1 was observed. The dose response curve of MgB4O7 pellets (produced for both routes) presents linear behavior when the materials are irradiated with 60Co in the dose range of 10-100 Gy. The results showed that both methods produce MgB4O7:Dy efficiently; however, solid-state synthesis produces MgB4O7:Dy more sensitive to gamma radiation.

  18. Combustion engine system

    NASA Technical Reports Server (NTRS)

    Houseman, John (Inventor); Voecks, Gerald E. (Inventor)

    1986-01-01

    A flow through catalytic reactor which selectively catalytically decomposes methanol into a soot free hydrogen rich product gas utilizing engine exhaust at temperatures of 200 to 650 C to provide the heat for vaporizing and decomposing the methanol is described. The reactor is combined with either a spark ignited or compression ignited internal combustion engine or a gas turbine to provide a combustion engine system. The system may be fueled entirely by the hydrogen rich gas produced in the methanol decomposition reactor or the system may be operated on mixed fuels for transient power gain and for cold start of the engine system. The reactor includes a decomposition zone formed by a plurality of elongated cylinders which contain a body of vapor permeable, methanol decomposition catalyst preferably a shift catalyst such as copper-zinc.

  19. Stratified combustion engine

    SciTech Connect

    Solheim, R.G.

    1987-03-17

    The method is described of operating an internal combustion engine having a cylinder with an inner wall. The method comprises admitting, adjacent to the inner wall of the cylinder, a quantity of substantially pure air in a spirally rapidly rotating layer and directing all of the quantity uniformly coaxially relative to the cylinder and toward and against only the adjacent inner wall of the cylinder, and held thereat by Coanda effect and centrifugal force. This is done while also admitting a quantity of fuel mixture in a non-rotating and non-turbulent manner between the layer of rotating pure air and the longitudinal axis of the cylinder, compressing the rotating pure air and the non-rotating fuel mixture simultaneously and firing the non-rotating fuel mixture and exhausting the products of combustion and pure air uniformly coaxially relative to the cylinder and only from a region adjacent to the inner wall and uniformly and completely from the inner wall.

  20. Dynamic features of combustion

    NASA Technical Reports Server (NTRS)

    Oppenheim, A. K.

    1985-01-01

    The dynamic features of combustion are discussed for four important cases: ignition, inflammation, explosion, and detonation. Ignition, the initiation of a self-sustained exothermic process, is considered in the simplest case of a closed thermodynamic system and its stochastic distribution. Inflammation, the initiation and propagation of self-sustained flames, is presented for turbulent flow. Explosion, the dynamic effects caused by the deposition of exothermic energy in a compressible medium, is illustrated by self-similar blast waves with energy deposition at the front and the adiabatic non-self-similar wave. Detonation, the most comprehensive illustration of all the dynamic effects of combustion, is discussed with a phenomenological account of the development and structure of the wave.

  1. Supersonic Combustion Ramjet Research

    DTIC Science & Technology

    2012-08-01

    4.2 Ignition, Flameholding, and Flame Propagation in Supersonic Flows ......................... 18 4.2.1 Plasma -Assisted Ignition and Flameholding...high- speed flows), plasma -assisted combustion, flameholding (particularly in a high-speed flow), and development and application of diagnostic...Flameholding, and Flame Propagation in Supersonic Flows 4.2.1 Plasma -Assisted Ignition and Flameholding Key questions that have guided this

  2. Combustion powered linear actuator

    DOEpatents

    Fischer, Gary J.

    2007-09-04

    The present invention provides robotic vehicles having wheeled and hopping mobilities that are capable of traversing (e.g. by hopping over) obstacles that are large in size relative to the robot and, are capable of operation in unpredictable terrain over long range. The present invention further provides combustion powered linear actuators, which can include latching mechanisms to facilitate pressurized fueling of the actuators, as can be used to provide wheeled vehicles with a hopping mobility.

  3. Spray combustion stability project

    NASA Technical Reports Server (NTRS)

    Jeng, San-Mou; Litchford, Ron J.

    1990-01-01

    This report summarizes research activity on the Spray Combustion Stability Project, characterizes accomplishments and current status, and discusses projected future work. The purpose is to provide a concise conceptual overview of the research effort so the reader can quickly assimilate the gist of the research results and place them within the context of their potential impact on liquid rocket engine design technology. Therefore, this report does not elaborate on many of the detailed technical aspects of the research program.

  4. Industrial Combustion Coordinated Rulemaking.

    PubMed

    Melton, Lula H

    1996-08-01

    The following article is excerpted from the document Industrial Combustion Coordinated Rulemaking - Proposed Organizational Structure and Process, which is available from the Technology Transfer Network (TTN), a computer bulletin board. To access the TTN, call (919) 541-5742; to obtain help with the TTN, call (919) 541-5384. The Industrial Combustion Coordinated Rulemaking (ICCR) document is evolving, reflecting an ongoing dialogue with various stakeholders; therefore, there may be changes between this article and the ICCR as it is implemented. EPA would like to thank all stakeholders (e.g., representatives from various companies and trade associations, state and local air pollution control agencies, and environmental organizations) who have offered suggestions and comments on development of the ICCR. As mentioned in the implications statement, the overall goal of the ICCR is to develop a unified set of federal air emissions regulations. The proposed ICCR will achieve this goal by: • Obtaining active participation from stakeholders, including environmental groups, regulated industries, and state and local regulatory agencies in all phases of regulatory development. • Coordinating the schedule and approach for development of regulations under Sections 111, 112, and 129 of the Clean Air Act that affect ICI combustion. • Determining the most effective ways to address the environmental issues associated with toxic and criteria pollutants from the range of combustion sources. • More effectively considering interactions among the regulations by analyzing the combined benefits and economic impacts of the group of Section 111, 112, and 129 regulations. • Considering strategies to simplify the regulations and allow flexibility in the methods of compliance while maintaining full environmental benefits.

  5. Combustion Characteristics of Sprays

    DTIC Science & Technology

    1989-08-01

    regarded by implication or otherwise, or in any way licensing the holder or any other person or corporation, or conveying any rights or permission to...00 _’N 1. TI TLE inctuat Security CZaaafication5 Combustion Characteristics of Sprays 12. PERSONAL AUTHOR(S) Sohrab, Siavash H. 13& TYPE OF REPORT...to ?!HF of rich butane/air 3unsen flames. .lso, the rotacion speed and :he oerodic temDeracure fluc:uations of rotacfng ?HF are examined. :’!naily

  6. Combustible Cartridge Case Characterization

    DTIC Science & Technology

    1984-02-01

    University (NYU) has resulted in the selection of two cross-linked melamine / formaldehyde acrylic styrene resin systems that can be used in the beater additive... melamine resin Akaradit II stabilizer 20. ABSTRACT (con) Test coupons of combustible cartridge case material were fabricated using these recommended...and agitated for 30 min before the pH was slowly lowered to 3 with p-toluene sulfonic acid. In order to maintain this pH in the felting tank, it was

  7. Spontaneous combustion of hydrogen

    NASA Technical Reports Server (NTRS)

    Nusselt, Wilhelm; Pothmann, PH

    1923-01-01

    It is shown by the author's experiments that hydrogen which escapes to the atmosphere through openings in the system may burn spontaneously if it contains dust. Purely thermal reasoning can not account for the combustion. It seems to be rather an electrical ignition. In order to determine whether the cause of the spontaneous ignition was thermo-chemical, thermo-mechanical, or thermo-electrical, the experiments in this paper were performed.

  8. The Diesel Combustion Collaboratory: Combustion Researchers Collaborating over the Internet

    SciTech Connect

    C. M. Pancerella; L. A. Rahn; C. Yang

    2000-02-01

    The Diesel Combustion Collaborator (DCC) is a pilot project to develop and deploy collaborative technologies to combustion researchers distributed throughout the DOE national laboratories, academia, and industry. The result is a problem-solving environment for combustion research. Researchers collaborate over the Internet using DCC tools, which include: a distributed execution management system for running combustion models on widely distributed computers, including supercomputers; web-accessible data archiving capabilities for sharing graphical experimental or modeling data; electronic notebooks and shared workspaces for facilitating collaboration; visualization of combustion data; and video-conferencing and data-conferencing among researchers at remote sites. Security is a key aspect of the collaborative tools. In many cases, the authors have integrated these tools to allow data, including large combustion data sets, to flow seamlessly, for example, from modeling tools to data archives. In this paper the authors describe the work of a larger collaborative effort to design, implement and deploy the DCC.

  9. Internal combustion engine using premixed combustion of stratified charges

    DOEpatents

    Marriott, Craig D.; Reitz, Rolf D. (Madison, WI

    2003-12-30

    During a combustion cycle, a first stoichiometrically lean fuel charge is injected well prior to top dead center, preferably during the intake stroke. This first fuel charge is substantially mixed with the combustion chamber air during subsequent motion of the piston towards top dead center. A subsequent fuel charge is then injected prior to top dead center to create a stratified, locally richer mixture (but still leaner than stoichiometric) within the combustion chamber. The locally rich region within the combustion chamber has sufficient fuel density to autoignite, and its self-ignition serves to activate ignition for the lean mixture existing within the remainder of the combustion chamber. Because the mixture within the combustion chamber is overall premixed and relatively lean, NO.sub.x and soot production are significantly diminished.

  10. Device for improved combustion

    SciTech Connect

    Polomchak, R.W.; Yacko, M.

    1988-03-08

    A device for improved combustion is described comprising: a tubular housing member having a first end and a second end, the first and second ends each having a circular opening therethrough; a combustion chamber disposed about the second end of the-tubular-housing member; a first conduit member extending from the first end of the tubular housing member and in fluid communication with the circular opening in the first end of the tubular housing member so as to allow the passage of air therethrough; a second conduit member axially disposed within the first conduit member and extending through the first conduit member and through the tubular housing member to the circular opening the second end of the tubular housing member so as to allow the passage of fuel therethrough; means for effecting turbulence in the air passing through the tubular housing member; means for effecting turbulence in the fuel passing through the second conduit member; means for intermixing and emitting the turbulent air and the fuel in a mushroom shaped configuration with the turbulent air surrounding the mushroom shaped configuration so as to substantially eliminate noxious waste gases as by-product of combustion of the air and fuel mixture.

  11. Strobes: an oscillatory combustion.

    PubMed

    Corbel, Justine M L; Lingen, Joost N J; Zevenbergen, John F; Gijzeman, Onno L J; Meijerink, Andries

    2012-04-26

    Strobe compositions belong to the class of solid combustions. They are mixtures of powdered ingredients. When ignited, the combustion front evolves in an oscillatory fashion, and flashes of light are produced by intermittence. They have fascinated many scientists since their discovery at the beginning of the 20th century. However, the chemical and physical processes involved in this curious oscillatory combustion remain unknown. Several theories have been proposed: One claims that two different reactions occur: one during the slow dark phase and another during the fast flash phase. The alternation between the phases is ascribed to heat variations. Other theories suggest that the formation of intermediate species during the dark phase and the change of phase are caused by variations in their concentration. A ternary strobe composition with ammonium perchlorate, magnalium, and barium sulfate is analyzed. The role of barium sulfate is studied by replacing it by other metal sulfates that have different physical properties (melting points), and the burning of the compositions is recorded with a high-speed camera and a spectrometer coupled with a charge-coupled device (CCD) camera. Experimental results show noticeable differences in the physical and chemical processes involved in the strobe reactions.

  12. Droplet Combustion Experiment (DCE)

    NASA Technical Reports Server (NTRS)

    Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Williams, Forman A.

    1998-01-01

    The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

  13. Porous Cross-Linked Polyimide-Urea Networks

    NASA Technical Reports Server (NTRS)

    Meador, Mary Ann B. (Inventor); Nguyen, Baochau N. (Inventor)

    2015-01-01

    Porous cross-linked polyimide-urea networks are provided. The networks comprise a subunit comprising two anhydride end-capped polyamic acid oligomers in direct connection via a urea linkage. The oligomers (a) each comprise a repeating unit of a dianhydride and a diamine and a terminal anhydride group and (b) are formulated with 2 to 15 of the repeating units. The subunit was formed by reaction of the diamine and a diisocyanate to form a diamine-urea linkage-diamine group, followed by reaction of the diamine-urea linkage-diamine group with the dianhydride and the diamine to form the subunit. The subunit has been cross-linked via a cross-linking agent, comprising three or more amine groups, at a balanced stoichiometry of the amine groups to the terminal anhydride groups. The subunit has been chemically imidized to yield the porous cross-linked polyimide-urea network. Also provided are wet gels, aerogels, and thin films comprising the networks, and methods of making the networks.

  14. Ocean urea fertilization for carbon credits poses high ecological risks.

    PubMed

    Glibert, Patricia M; Azanza, Rhodora; Burford, Michele; Furuya, Ken; Abal, Eva; Al-Azri, Adnan; Al-Yamani, Faiza; Andersen, Per; Anderson, Donald M; Beardall, John; Berg, G Mine; Brand, Larry; Bronk, Deborah; Brookes, Justin; Burkholder, Joann M; Cembella, Allan; Cochlan, William P; Collier, Jackie L; Collos, Yves; Diaz, Robert; Doblin, Martina; Drennen, Thomas; Dyhrman, Sonya; Fukuyo, Yasuwo; Furnas, Miles; Galloway, James; Granéli, Edna; Ha, Dao Viet; Hallegraeff, Gustaaf; Harrison, John; Harrison, Paul J; Heil, Cynthia A; Heimann, Kirsten; Howarth, Robert; Jauzein, Cécile; Kana, Austin A; Kana, Todd M; Kim, Hakgyoon; Kudela, Raphael; Legrand, Catherine; Mallin, Michael; Mulholland, Margaret; Murray, Shauna; O'Neil, Judith; Pitcher, Grant; Qi, Yuzao; Rabalais, Nancy; Raine, Robin; Seitzinger, Sybil; Salomon, Paulo S; Solomon, Caroline; Stoecker, Diane K; Usup, Gires; Wilson, Joanne; Yin, Kedong; Zhou, Mingjiang; Zhu, Mingyuan

    2008-06-01

    The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed.

  15. Ocean Urea Fertilization for Carbon Credits Poses High Ecological Risks

    PubMed Central

    Glibert, Patricia M.; Azanza, Rhodora; Burford, Michele; Furuya, Ken; Abal, Eva; Al-Azri, Adnan; Al-Yamani, Faiza; Andersen, Per; Beardall, John; Berg, G. Mine; Brand, Larry; Bronk, Deborah; Brookes, Justin; Burkholder, JoAnn M.; Cembella, Allan; Cochlan, William P.; Collier, Jackie; Collos, Yves; Diaz, Robert; Doblin, Martina; Drennen, Thomas; Dyhrman, Sonya; Fukuyo, Yasuwo; Furnas, Miles; Galloway, James; Granéli, Edna; Ha, Dao Viet; Hallegraeff, Gustaaf; Harrison, John; Harrison, Paul J.; Heil, Cynthia A.; Heimann, Kirsten; Howarth, Robert; Jauzein, Cécile; Kana, Austin A.; Kana, Todd M.; Kim, Hakgyoon; Kudela, Raphael; Legrand, Catherine; Mallin, Michael; Mulholland, Margaret; Murray, Shauna; O’Neil, Judith; Pitcher, Grant; Qi, Yuzao; Rabalais, Nancy; Raine, Robin; Seitzinger, Sybil; Solomon, Caroline; Stoecker, Diane K.; Usup, Gires; Wilson, Joanne; Yin, Kedong; Zhou, Mingjiang; Zhu, Mingyuan

    2017-01-01

    The proposed plan for enrichment of the Sulu Sea, Philippines, a region of rich marine biodiversity, with thousands of tonnes of urea in order to stimulate algal blooms and sequester carbon is flawed for multiple reasons. Urea is preferentially used as a nitrogen source by some cyanobacteria and dinoflagellates, many of which are neutrally or positively buoyant. Biological pumps to the deep sea are classically leaky, and the inefficient burial of new biomass makes the estimation of a net loss of carbon from the atmosphere questionable at best. The potential for growth of toxic dinoflagellates is also high, as many grow well on urea and some even increase their toxicity when grown on urea. Many toxic dinoflagellates form cysts which can settle to the sediment and germinate in subsequent years, forming new blooms even without further fertilization. If large-scale blooms do occur, it is likely that they will contribute to hypoxia in the bottom waters upon decomposition. Lastly, urea production requires fossil fuel usage, further limiting the potential for net carbon sequestration. The environmental and economic impacts are potentially great and need to be rigorously assessed. PMID:18439628

  16. Gaseous emissions during concurrent combustion of biomass and non-recyclable municipal solid waste

    PubMed Central

    2011-01-01

    Background Biomass and municipal solid waste offer sustainable sources of energy; for example to meet heat and electricity demand in the form of combined cooling, heat and power. Combustion of biomass has a lesser impact than solid fossil fuels (e.g. coal) upon gas pollutant emissions, whilst energy recovery from municipal solid waste is a beneficial component of an integrated, sustainable waste management programme. Concurrent combustion of these fuels using a fluidised bed combustor may be a successful method of overcoming some of the disadvantages of biomass (high fuel supply and distribution costs, combustion characteristics) and characteristics of municipal solid waste (heterogeneous content, conflict with materials recycling). It should be considered that combustion of municipal solid waste may be a financially attractive disposal route if a 'gate fee' value exists for accepting waste for combustion, which will reduce the net cost of utilising relatively more expensive biomass fuels. Results Emissions of nitrogen monoxide and sulphur dioxide for combustion of biomass are suppressed after substitution of biomass for municipal solid waste materials as the input fuel mixture. Interactions between these and other pollutants such as hydrogen chloride, nitrous oxide and carbon monoxide indicate complex, competing reactions occur between intermediates of these compounds to determine final resultant emissions. Conclusions Fluidised bed concurrent combustion is an appropriate technique to exploit biomass and municipal solid waste resources, without the use of fossil fuels. The addition of municipal solid waste to biomass combustion has the effect of reducing emissions of some gaseous pollutants. PMID:21284885

  17. Feedback control of combustion oscillations in combustion chambers

    NASA Astrophysics Data System (ADS)

    Wei, Wei; Wang, Jing; Li, Dong-hai; Zhu, Min; Xue, Ya-li

    2010-11-01

    Model-based algorithms are generally employed in active control of combustion oscillations. Since practical combustion processes consist of complex thermal and acoustic couplings, their accurate models and parameters may not be obtained in advance economically, a model free controller is necessary for the control of thermoacoustic instabilities. Active compensation based control algorithm is applied in the suppression of combustion instabilities. Tuning the controller parameters on line, the amplitudes of the acoustic waves can be modulated to desired values. Simulations performed on a control oriented, typical longitudinal oscillations combustor model illustrate the controllers' capability to attenuate combustion oscillations.

  18. Anonymous Connections and Onion Routing

    DTIC Science & Technology

    1998-01-01

    Anonymous Connections and Onion Routing Michael G. Reed, Paul F. Syverson, and David M. Goldschlag Naval Research Laboratory Abstract Onion Routing...eavesdropping and trac analysis. Onion routing’s anonymous connections are bidirectional and near real- time, and can be used anywhere a socket connection...can be used. Any identifying information must be in the data stream carried over an anonymous connec- tion. An onion is a data structure that is

  19. Crystal structure of a bacterial homologue of the kidney urea transporter

    SciTech Connect

    Levin, Elena J.; Quick, Matthias; Zhou, Ming

    2010-03-19

    Urea is highly concentrated in the mammalian kidney to produce the osmotic gradient necessary for water re-absorption. Free diffusion of urea across cell membranes is slow owing to its high polarity, and specialized urea transporters have evolved to achieve rapid and selective urea permeation. Here we present the 2.3 {angstrom} structure of a functional urea transporter from the bacterium Desulfovibrio vulgaris. The transporter is a homotrimer, and each subunit contains a continuous membrane-spanning pore formed by the two homologous halves of the protein. The pore contains a constricted selectivity filter that can accommodate several dehydrated urea molecules in single file. Backbone and side-chain oxygen atoms provide continuous coordination of urea as it progresses through the filter, and well-placed {alpha}-helix dipoles provide further compensation for dehydration energy. These results establish that the urea transporter operates by a channel-like mechanism and reveal the physical and chemical basis of urea selectivity.

  20. Crystal structure of a bacterial homolog of the kidney urea transporter

    PubMed Central

    Levin, Elena J.; Quick, Matthias; Zhou, Ming

    2010-01-01

    Urea is highly concentrated in mammalian kidney to produce the osmotic gradient necessary for water re-absorption. Free diffusion of urea across cell membranes is slow due to its high polarity, and specialized urea transporters have evolved to achieve rapid and selective urea permeation. Here we present the 2.3 Å structure of a functional urea transporter from the bacterium Desulfovibrio vulgaris. The transporter is a homotrimer, and each subunit contains a continuous membrane-spanning pore formed by the two homologous halves of the protein. The pore contains a constricted selectivity filter that can accommodate multiple dehydrated urea molecules in single file. Backbone and side chain oxygen atoms provide continuous coordination of urea as it progresses through the filter, and well-placed α-helix dipoles provide additional compensation for dehydration energy. These results establish that the urea transporter operates by a channel-like mechanism and reveal the physical and chemical basis of urea selectivity. PMID:19865084

  1. Improving Ammonium and Nitrate Release from Urea Using Clinoptilolite Zeolite and Compost Produced from Agricultural Wastes

    PubMed Central

    Omar, Latifah; Ahmed, Osumanu Haruna; Majid, Nik Muhamad Ab.

    2015-01-01

    Improper use of urea may cause environmental pollution through NH3 volatilization and NO3− leaching from urea. Clinoptilolite zeolite and compost could be used to control N loss from urea by controlling NH4+ and NO3− release from urea. Soil incubation and leaching experiments were conducted to determine the effects of clinoptilolite zeolite and compost on controlling NH4+ and NO3− losses from urea. Bekenu Series soil (Typic Paleudults) was incubated for 30, 60, and 90 days. A soil leaching experiment was conducted for 30 days. Urea amended with clinoptilolite zeolite and compost significantly reduced NH4+ and NO3− release from urea (soil incubation study) compared with urea alone, thus reducing leaching of these ions. Ammonium and NO3− leaching losses during the 30 days of the leaching experiment were highest in urea alone compared with urea with clinoptilolite zeolite and compost treatments. At 30 days of the leaching experiment, NH4+ retention in soil with urea amended with clinoptilolite zeolite and compost was better than that with urea alone. These observations were because of the high pH, CEC, and other chemical properties of clinoptilolite zeolite and compost. Urea can be amended with clinoptilolite zeolite and compost to improve NH4+ and NO3− release from urea. PMID:25793220

  2. Improving ammonium and nitrate release from urea using clinoptilolite zeolite and compost produced from agricultural wastes.

    PubMed

    Omar, Latifah; Ahmed, Osumanu Haruna; Ab Majid, Nik Muhamad

    2015-01-01

    Improper use of urea may cause environmental pollution through NH3 volatilization and NO3 (-) leaching from urea. Clinoptilolite zeolite and compost could be used to control N loss from urea by controlling NH4 (+) and NO3 (-) release from urea. Soil incubation and leaching experiments were conducted to determine the effects of clinoptilolite zeolite and compost on controlling NH4 (+) and NO3 (-) losses from urea. Bekenu Series soil (Typic Paleudults) was incubated for 30, 60, and 90 days. A soil leaching experiment was conducted for 30 days. Urea amended with clinoptilolite zeolite and compost significantly reduced NH4 (+) and NO3 (-) release from urea (soil incubation study) compared with urea alone, thus reducing leaching of these ions. Ammonium and NO3 (-) leaching losses during the 30 days of the leaching experiment were highest in urea alone compared with urea with clinoptilolite zeolite and compost treatments. At 30 days of the leaching experiment, NH4 (+) retention in soil with urea amended with clinoptilolite zeolite and compost was better than that with urea alone. These observations were because of the high pH, CEC, and other chemical properties of clinoptilolite zeolite and compost. Urea can be amended with clinoptilolite zeolite and compost to improve NH4 (+) and NO3 (-) release from urea.

  3. Design and testing of an independently controlled urea SCR retrofit system for the reduction of NOx emissions from marine diesels.

    PubMed

    Johnson, Derek R; Bedick, Clinton R; Clark, Nigel N; McKain, David L

    2009-05-15

    Diesel engine emissions for on-road, stationary and marine applications are regulated in the United States via standards set by the Environmental Protection Agency (EPA). A major component of diesel exhaust that is difficult to reduce is nitrogen oxides (NOx). Selective catalytic reduction (SCR) has been in use for many years for stationary applications, including external combustion boilers, and is promising for NOx abatement as a retrofit for mobile applications where diesel compression ignition engines are used. The research presented in this paper is the first phase of a program focused on the reduction of NOx by use of a stand-alone urea injection system, applicable to marine diesel engines typical of work boats (e.g., tugs). Most current urea SCR systems communicate with engine controls to predict NOx emissions based on signals such as torque and engine speed, however many marine engines in use still employ mechanical injection technology and lack electronic communication abilities. The system developed and discussed in this paper controls NOx emissions independentof engine operating parameters and measures NOx and exhaust flow using the following exhaust sensor inputs: absolute pressure, differential pressure, temperature, and NOx concentration. These sensor inputs were integrated into an independent controller and open loop architecture to estimate the necessary amount of urea needed, and the controller uses pulse width modulation (PWM) to power an automotive fuel injector for airless urea delivery. The system was tested in a transient test cell on a 350 hp engine certified at 4 g/bhp-hr of NOx, with a goal of reducing the engine out NOx levels by 50%. NOx reduction capabilities of 41-67% were shown on the non road transient cycle (NRTC) and ICOMIA E5 steady state cycles with system optimization during testing to minimize the dilute ammonia slip to cycle averages of 5-7 ppm. The goal of 50% reduction of NOx can be achieved dependent upon cycle. Further

  4. Energy Conversion and Combustion Sciences

    DTIC Science & Technology

    2012-03-08

    Rotational /Continuous Detonation • Only Single Initiation needed (Circumvent Initiation/DDT difficulty/loss in PDE ) • 10-100x cycle rate increase • Near...new fuels: 1. Rotational or Continuous Detonation (intense/concentrated combustion); 2. Flameless combustion (distributed combustion process...Steady Exit Flow *CFD Courtesy of NRL Rotational Detonation : (PI: Schauer, AFRL/RZ, working with NRL) Rotational Approach Allows Continuous

  5. Waste-to-Chemicals for a Circular Economy: The Case of Urea Production (Waste-to-Urea).

    PubMed

    Antonetti, Elena; Iaquaniello, Gaetano; Salladini, Annarita; Spadaccini, Luca; Perathoner, Siglinda; Centi, Gabriele

    2017-03-09

    The economics and environmental impact of a new technology for the production of urea from municipal solid waste, particularly the residue-derived fuel (RdF) fraction, is analyzed. Estimates indicate a cost of production of approximately €135 per ton of urea (internal rate of return more than 10 %) and savings of approximately 0.113 tons of CH4 and approximately 0.78 tons of CO2 per ton of urea produced. Thus, the results show that this waste-to-urea (WtU) technology is both economically valuable and environmentally advantageous (in terms of saving resources and limiting carbon footprint) for the production of chemicals from municipal solid waste in comparison with both the production of urea with conventional technology (starting from natural gas) and the use of RdF to produce electrical energy (waste-to-energy). A further benefit is the lower environmental impact of the solid residue produced from RdF conversion. The further benefit of this technology is the possibility to realize distributed fertilizer production.

  6. Combustion characteristics of husk charcoal

    SciTech Connect

    Shimizu, H.; Kimura, T.; Nishiyama, Y.; Terui, T.

    1984-07-01

    This paper analyzes the factors involved in the extraordinary temperature generation in husk combustion furnaces, and investigates methods of protecting furnaces from heat damage. The combustion characteristics of fixed carbon in rice husks are examined in relation to the air flow rate using different husk charcoals. The theoretical flame temperature in a practical bed was determined from the combustion propagation velocity. It is determined that deviation from the regression line relating the combustion propagation velocity with the specific air flow rate showed a slight correlation with the bulk density of the charcoal samples used.

  7. Microgravity Smoldering Combustion Takes Flight

    NASA Technical Reports Server (NTRS)

    1996-01-01

    The Microgravity Smoldering Combustion (MSC) experiment lifted off aboard the Space Shuttle Endeavour in September 1995 on the STS-69 mission. This experiment is part of series of studies focused on the smolder characteristics of porous, combustible materials in a microgravity environment. Smoldering is a nonflaming form of combustion that takes place in the interior of combustible materials. Common examples of smoldering are nonflaming embers, charcoal briquettes, and cigarettes. The objective of the study is to provide a better understanding of the controlling mechanisms of smoldering, both in microgravity and Earth gravity. As with other forms of combustion, gravity affects the availability of air and the transport of heat, and therefore, the rate of combustion. Results of the microgravity experiments will be compared with identical experiments carried out in Earth's gravity. They also will be used to verify present theories of smoldering combustion and will provide new insights into the process of smoldering combustion, enhancing our fundamental understanding of this frequently encountered combustion process and guiding improvement in fire safety practices.

  8. Light Duty Efficient, Clean Combustion

    SciTech Connect

    Stanton, Donald W.

    2011-06-03

    Cummins has successfully completed the Light Duty Efficient Clean Combustion (LDECC) cooperative program with DoE. This program was established in 2007 in support of the Department of Energy’s Vehicles Technologies Advanced Combustion and Emissions Control initiative to remove critical barriers to the commercialization of advanced, high efficiency, emissions compliant internal combustion (IC) engines for light duty vehicles. Work in this area expanded the fundamental knowledge of engine combustion to new regimes and advanced the knowledge of fuel requirements for these diesel engines to realize their full potential. All of our objectives were met with fuel efficiency improvement targets exceeded.

  9. Flammability of Heterogeneously Combusting Metals

    NASA Technical Reports Server (NTRS)

    Jones, Peter D.

    1998-01-01

    Most engineering materials, including some metals, most notably aluminum, burn in homogeneous combustion. 'Homogeneous' refers to both the fuel and the oxidizer being in the same phase, which is usually gaseous. The fuel and oxidizer are well mixed in the combustion reaction zone, and heat is released according to some relation like q(sub c) = delta H(sub c)c[((rho/rho(sub 0))]exp a)(exp -E(sub c)/RT), Eq. (1) where the pressure exponent a is usually close to unity. As long as there is enough heat released, combustion is sustained. It is useful to conceive of a threshold pressure beyond which there is sufficient heat to keep the temperature high enough to sustain combustion, and beneath which the heat is so low that temperature drains away and the combustion is extinguished. Some materials burn in heterogeneous combustion, in which the fuel and oxidizer are in different phases. These include iron and nickel based alloys, which burn in the liquid phase with gaseous oxygen. Heterogeneous combustion takes place on the surface of the material (fuel). Products of combustion may appear as a solid slag (oxide) which progressively covers the fuel. Propagation of the combustion melts and exposes fresh fuel. Heterogeneous combustion heat release also follows the general form of Eq.(1), except that the pressure exponent a tends to be much less than 1. Therefore, the increase in heat release with increasing pressure is not as dramatic as it is in homogeneous combustion. Although the concept of a threshold pressure still holds in heterogeneous combustion, the threshold is more difficult to identify experimentally, and pressure itself becomes less important relative to the heat transfer paths extant in any specific application. However, the constants C, a, and E(sub c) may still be identified by suitable data reduction from heterogeneous combustion experiments, and may be applied in a heat transfer model to judge the flammability of a material in any particular actual

  10. Gas separation process using membranes with permeate sweep to remove CO.sub.2 from gaseous fuel combustion exhaust

    DOEpatents

    Wijmans, Johannes G [Menlo Park, CA; Merkel, Timothy C [Menlo Park, CA; Baker, Richard W [Palo Alto, CA

    2012-05-15

    A gas separation process for treating exhaust gases from the combustion of gaseous fuels, and gaseous fuel combustion processes including such gas separation. The invention involves routing a first portion of the exhaust stream to a carbon dioxide capture step, while simultaneously flowing a second portion of the exhaust gas stream across the feed side of a membrane, flowing a sweep gas stream, usually air, across the permeate side, then passing the permeate/sweep gas back to the combustor.

  11. Nonaaqua-praseodymium triiodide-thio-urea (1/2).

    PubMed

    Antonenko, Taisia A; Alikberova, Lyudmila Yu; Albov, Dmitry V

    2012-02-01

    The title compound, [Pr(H(2)O)(9)]I(3)·2CS(NH(2))(2), an adduct of nona-aqua-praseodymium triiodide with two thio-urea mol-ecules, is composed from [Pr(H(2)O)(9)](3+) cations (polyhedron: monocapped tetra-gonal anti-prism), noncoordinated thio-urea mol-ecules and iodide anions. The components are evidently connected by hydrogen bonds but in the presence of heavy atoms water H atoms have not been located. The complex cation and one of the two independent iodide anions are located on a twofold axis.

  12. Fuels Combustion Research.

    DTIC Science & Technology

    1983-11-22

    sufficient ions pre- sent to nucleate all particles. In the search for an appropriate mechanism a suggestion of Thomas [14J that Diels - Alder ... condensation ) type reactions were fast and this possible nucleation route for soot formation was considered. The thinking followed the lines that any soot...sense, Diels - Alder reactions are very much like electrostatic reactions and if one examines the resonance structures of most compounds which undergo Diels

  13. Combustion Byproducts Recycling Consortium

    SciTech Connect

    Ziemkiewicz, Paul; Vandivort, Tamara; Pflughoeft-Hassett, Debra; Chugh, Y Paul; Hower, James

    2008-08-31

    Each year, over 100 million tons of solid byproducts are produced by coal-burning electric utilities in the United States. Annual production of flue gas desulfurization (FGD) byproducts continues to increase as the result of more stringent sulfur emission restrictions. In addition, stricter limits on NOx emissions mandated by the 1990 Clean Air Act have resulted in utility burner/boiler modifications that frequently yield higher carbon concentrations in fly ash, which restricts the use of the ash as a cement replacement. Controlling ammonia in ash is also of concern. If newer, “clean coal” combustion and gasification technologies are adopted, their byproducts may also present a management challenge. The objective of the Combustion Byproducts Recycling Consortium (CBRC) is to develop and demonstrate technologies to address issues related to the recycling of byproducts associated with coal combustion processes. A goal of CBRC is that these technologies, by the year 2010, will lead to an overall ash utilization rate from the current 34% to 50% by such measures as increasing the current rate of FGD byproduct use and increasing in the number of uses considered “allowable” under state regulations. Another issue of interest to the CBRC would be to examine the environmental impact of both byproduct utilization and disposal. No byproduct utilization technology is likely to be adopted by industry unless it is more cost-effective than landfilling. Therefore, it is extremely important that the utility industry provide guidance to the R&D program. Government agencies and privatesector organizations that may be able to utilize these materials in the conduct of their missions should also provide input. The CBRC will serve as an effective vehicle for acquiring and maintaining guidance from these diverse organizations so that the proper balance in the R&D program is achieved.

  14. Combustion Branch Website Development

    NASA Technical Reports Server (NTRS)

    Bishop, Eric

    2004-01-01

    The NASA combustion branch is a leader in developing and applying combustion science to focused aerospace propulsion systems concepts. It is widely recognized for unique facilities, analytical tools, and personnel. In order to better communicate the outstanding research being done in this Branch to the public and other research organization, a more substantial website was desired. The objective of this project was to build an up-to-date site that reflects current research in a usable and attractive manner. In order to accomplish this, information was requested from all researchers in the Combustion branch, on their professional skills and on the current projects. This information was used to fill in the Personnel and Research sections of the website. A digital camera was used to photograph all personnel and these photographs were included in the personnel section as well. The design of the site was implemented using the latest web standards: xhtml and external css stylesheets. This implementation conforms to the guidelines recommended by the w3c. It also helps to ensure that the web site is accessible by disabled users, and complies with Section 508 Federal legislation (which mandates that all Federal websites be accessible). Graphics for the new site were generated using the gimp (www.gimp.org) an open-source graphics program similar to Adobe Photoshop. Also, all graphics on the site were of a reasonable size (less than 20k, most less than 2k) so that the page would load quickly. Technologies such as Macromedia Flash and Javascript were avoided, as these only function on some clients which have the proper software installed or enabled. The website was tested on different platforms with many different browsers to ensure there were no compatibility issues. The website was tested on windows with MS IE 6, MSIE 5 , Netscape 7, Mozilla and Opera. On a Mac, the site was tested with MS IE 5 , Netscape 7 and Safari.

  15. Combustion Byproducts Recycling Consortium

    SciTech Connect

    Paul Ziemkiewicz; Tamara Vandivort; Debra Pflughoeft-Hassett; Y. Paul Chugh; James Hower

    2008-08-31

    Each year, over 100 million tons of solid byproducts are produced by coal-burning electric utilities in the United States. Annual production of flue gas desulfurization (FGD) byproducts continues to increase as the result of more stringent sulfur emission restrictions. In addition, stricter limits on NOx emissions mandated by the 1990 Clean Air Act have resulted in utility burner/boiler modifications that frequently yield higher carbon concentrations in fly ash, which restricts the use of the ash as a cement replacement. Controlling ammonia in ash is also of concern. If newer, 'clean coal' combustion and gasification technologies are adopted, their byproducts may also present a management challenge. The objective of the Combustion Byproducts Recycling Consortium (CBRC) is to develop and demonstrate technologies to address issues related to the recycling of byproducts associated with coal combustion processes. A goal of CBRC is that these technologies, by the year 2010, will lead to an overall ash utilization rate from the current 34% to 50% by such measures as increasing the current rate of FGD byproduct use and increasing in the number of uses considered 'allowable' under state regulations. Another issue of interest to the CBRC would be to examine the environmental impact of both byproduct utilization and disposal. No byproduct utilization technology is likely to be adopted by industry unless it is more cost-effective than landfilling. Therefore, it is extremely important that the utility industry provide guidance to the R&D program. Government agencies and private-sector organizations that may be able to utilize these materials in the conduct of their missions should also provide input. The CBRC will serve as an effective vehicle for acquiring and maintaining guidance from these diverse organizations so that the proper balance in the R&D program is achieved.

  16. Hydrothermally treated oil palm empty fruit bunch cellulose with urea and its dissolution in NaOH-Urea solvent system

    NASA Astrophysics Data System (ADS)

    Baharin, Khairunnisa Waznah; Zakaria, Sarani; Gan, Sinyee; Jaafar, Sharifah Nabihah Syed; Chia, Chin Hua

    2016-11-01

    Cellulose from Oil Palm Empty fruit bunch (OPEFB) fiber was hydrothermally treated by using autoclave which is immersed in an oil bath at 160 °C for 6 h. OPEFB cellulose was mixed with aqueous urea and stirred for 30 min to obtain a homogenous mixture before transferred into the autoclave. The effect of different cellulose to urea mass ratio (1:4, 1:6 and 1:8) on the molecular weight, degree of polymerization and solubility of the treated cellulose dissolved in NaOH and urea solvent system was studied. The result shows that the solubility of cellulose from OPEFB fiber increased while the molecular weight of cellulose decreased due to the pretreatment done on the OPEFB fiber.

  17. Combustion of White Phosphorus

    NASA Astrophysics Data System (ADS)

    Keiter, Richard L.; Gamage, Chaminda P.

    2001-07-01

    The reaction of white phosphorus with pure oxygen is conveniently and safely demonstrated by carrying out the reaction in a retort that has its open end submerged in water. After filling the retort with oxygen gas, a small amount of white phosphorus is introduced and heated with a hot-plate until it ignites. The spectacular reaction leads to consumption and expulsion of oxygen gas, creation of a partial vacuum in the retort, and back suction of water that extinguishes the combustion. Featured on the Cover

  18. Lithium Combustion: A Review

    DTIC Science & Technology

    1990-12-01

    lithium vapors generated with air formed an intense white flame that produced branched- chain condensation aerosol particles, of concentrations 򓆄 mg/im3...generated chain -aggregate lithium combustion aerosols in dry, COg-free air prior to reaction with 0, 0.10, 0.50, 1.0, 1.75, or 5.0% CO in air at a...In order to burn in gaseous chlorine or in bromine or iodine vapor, lithium needs to be heated. With iodine vapor, the reaction is accompanied by

  19. Hybrid fluidized bed combuster

    DOEpatents

    Kantesaria, Prabhudas P.; Matthews, Francis T.

    1982-01-01

    A first atmospheric bubbling fluidized bed furnace is combined with a second turbulent, circulating fluidized bed furnace to produce heat efficiently from crushed solid fuel. The bed of the second furnace receives the smaller sizes of crushed solid fuel, unreacted limestone from the first bed, and elutriated solids extracted from the flu gases of the first bed. The two-stage combustion of crushed solid fuel provides a system with an efficiency greater than available with use of a single furnace of a fluidized bed.

  20. Interaction between dietary content of protein and sodium chloride on milk urea concentration, urinary urea excretion, renal recycling of urea, and urea transfer to the gastrointestinal tract in dairy cows.

    PubMed

    Spek, J W; Bannink, A; Gort, G; Hendriks, W H; Dijkstra, J

    2013-09-01

    Dietary protein and salt affect the concentration of milk urea nitrogen (MUN; mg of N/dL) and the relationship between MUN and excretion of urea nitrogen in urine (UUN; g of N/d) of dairy cattle. The aim of the present study was to examine the effects of dietary protein and sodium chloride (NaCl) intake separately, and their interaction, on MUN and UUN, on the relationship between UUN and MUN, on renal recycling of urea, and on urea transfer to the gastrointestinal tract. Twelve second-parity cows (body weight of 645±37 kg, 146±29 d in milk, and a milk production of 34.0±3.28 kg/d), of which 8 were previously fitted with a rumen cannula, were fitted with catheters in the urine bladder and jugular vein. The experiment had a split-plot arrangement with dietary crude protein (CP) content as the main plot factor [116 and 154 g of CP/kg of dry matter (DM)] and dietary NaCl content as the subplot factor (3.1 and 13.5 g of Na/kg of DM). Cows were fed at 95% of the average ad libitum feed intake of cows receiving the low protein diets. Average MUN and UUN were, respectively, 3.90 mg of N/dL and 45 g of N/d higher for the high protein diets compared with the low protein diets. Compared with the low NaCl diets, MUN was, on average, 1.74 mg of N/dL lower for the high NaCl diets, whereas UUN was unaffected. We found no interaction between dietary content of protein and NaCl on performance characteristics or on MUN, UUN, urine production, and renal clearance characteristics. The creatinine clearance rate was not affected by dietary content of protein and NaCl. Urea transfer to the gastrointestinal tract, expressed as a fraction of plasma urea entry rate, was negatively related to dietary protein, whereas it was not affected by dietary NaCl content. We found no interaction between dietary protein and NaCl content on plasma urea entry rate and gastrointestinal urea entry rate or their ratio. The relationship between MUN and UUN was significantly affected by the class variable

  1. AIR EMISSIONS FROM SCRAP TIRE COMBUSTION

    EPA Science Inventory

    The report discusses air emissions from two types of scrap tire combustion: uncontrolled and controlled. Uncontrolled sources are open tire fires, which produce many unhealthful products of incomplete combustion and release them directly into the atmosphere. Controlled combustion...

  2. Path planning during combustion mode switch

    SciTech Connect

    Jiang, Li; Ravi, Nikhil

    2015-12-29

    Systems and methods are provided for transitioning between a first combustion mode and a second combustion mode in an internal combustion engine. A current operating point of the engine is identified and a target operating point for the internal combustion engine in the second combustion mode is also determined. A predefined optimized transition operating point is selected from memory. While operating in the first combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion engine to approach the selected optimized transition operating point. When the engine is operating at the selected optimized transition operating point, the combustion mode is switched from the first combustion mode to the second combustion mode. While operating in the second combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion to approach the target operating point.

  3. Plasma igniter for internal-combustion engines

    NASA Technical Reports Server (NTRS)

    Breshears, R. R.; Fitzgerald, D. J.

    1978-01-01

    Hot ionized gas (plasma) ignites air/fuel mixture in internal combustion engines more effectively than spark. Electromagnetic forces propel plasma into combustion zone. Combustion rate is not limited by flame-front speed.

  4. Theoretical study on the structures and properties of mixtures of urea and choline chloride.

    PubMed

    Sun, Hui; Li, Yan; Wu, Xue; Li, Guohui

    2013-06-01

    In this work, we investigated in detail the structural characteristics of mixtures of choline chloride and urea with different urea contents by performing molecular dynamic (MD) simulations, and offer possible explanations for the low melting point of the eutectic mixture of choline chloride and urea with a ratio of 1:2. The insertion of urea molecules was found to change the density distribution of cations and anions around the given cations significantly, disrupting the long-range ordered structure of choline chloride. Moreover, with increasing urea concentration, the hydrogen bond interactions between choline cations and Cl(-) anions decreased, while those among urea molecules obviously increased. From the hydrogen bond lifetimes, it was found that a ratio of 1:2 between choline chloride and urea is necessary for a reasonable strength of hydrogen bond interaction to maintain the low melting point of the mixture of choline chloride with urea. In addition, it was also deduced from the interaction energies that a urea content of 67.7 % may make the interactions of cation-anion, cation-urea and anion-urea modest, and thus results in the lower melting point of the eutectic mixture of choline chloride and urea. The present results may offer assistance to some extent for understanding the physicochemical properties of the eutectic mixture of choline chloride and urea, and give valuable information for the further development and application of deep eutectic solvents.

  5. Some Factors Affecting Combustion in an Internal-Combustion Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Cohn, Mildred

    1936-01-01

    An investigation of the combustion of gasoline, safety, and diesel fuels was made in the NACA combustion apparatus under conditions of temperature that permitted ignition by spark with direct fuel injection, in spite of the compression ratio of 12.7 employed. The influence of such variables as injection advance angle, jacket temperature, engine speed, and spark position was studied. The most pronounced effect was that an increase in the injection advance angle (beyond a certain minimum value) caused a decrease in the extent and rate of combustion. In almost all cases combustion improved with increased temperature. The results show that at low air temperatures the rates of combustion vary with the volatility of the fuel, but that at high temperatures this relationship does not exist and the rates depend to a greater extent on the chemical nature of the fuel.

  6. Preliminary assessment of combustion modes for internal combustion wave rotors

    NASA Technical Reports Server (NTRS)

    Nalim, M. Razi

    1995-01-01

    Combustion within the channels of a wave rotor is examined as a means of obtaining pressure gain during heat addition in a gas turbine engine. Several modes of combustion are considered and the factors that determine the applicability of three modes are evaluated in detail; premixed autoignition/detonation, premixed deflagration, and non-premixed compression ignition. The last two will require strong turbulence for completion of combustion in a reasonable time in the wave rotor. The compression/autoignition modes will require inlet temperatures in excess of 1500 R for reliable ignition with most hydrocarbon fuels; otherwise, a supplementary ignition method must be provided. Examples of combustion mode selection are presented for two core engine applications that had been previously designed with equivalent 4-port wave rotor topping cycles using external combustion.

  7. An emergency response mobile robot for operations in combustible atmospheres

    NASA Technical Reports Server (NTRS)

    Stone, Henry W. (Inventor); Ohm, Timothy R. (Inventor)

    1993-01-01

    A mobile, self-powered, self-contained, and remote-controlled robot is presented. The robot is capable of safely operating in a combustible atmosphere and providing information about the atmosphere to the operator. The robot includes non-sparking and non-arcing electro-mechanical and electronic components designed to prevent the robot from igniting the combustible atmosphere. The robot also includes positively pressurized enclosures that house the electromechanical and electronic components of the robot and prevent intrusion of the combustible atmosphere into the enclosures. The enclosures are interconnected such that a pressurized gas injected into any one of the enclosures is routed to all the other enclosures through the interconnections. It is preferred that one or more sealed internal channels through structures intervening between the enclosures be employed. Pressure transducers for detecting if the pressure within the enclosures falls below a predetermined level are included. The robot also has a sensing device for determining the types of combustible substances in the surrounding atmosphere, as well as the concentrations of each type of substance relative to a pre-determined lower explosive limit (LEL). In addition, the sensing device can determine the percent level of oxygen present in the surrounding atmosphere.

  8. Emergency response mobile robot for operations in combustible atmospheres

    NASA Technical Reports Server (NTRS)

    Stone, Henry W. (Inventor); Ohm, Timothy R. (Inventor)

    1995-01-01

    A mobile, self-powered, self-contained, and remote-controlled robot is presented. The robot is capable of safely operating in a combustible atmosphere and providing information about the atmosphere to the operator. The robot includes non-sparking and non-arcing electro-mechanical and electronic components designed to prevent the robot from igniting the combustible atmosphere. The robot also includes positively pressurized enclosures that house the electromechanical and electronic components of the robot and prevent intrusion of the combustible atmosphere into the enclosures. The enclosures are interconnected such that a pressurized gas injected into any one of the enclosures is routed to all the other enclosures through the interconnections. It is preferred that one or more sealed internal channels through structures intervening between the enclosures be employed. Pressure transducers for detecting if the pressure within the enclosures falls below a predetermined level are included. The robot also has a sensing device for determining the types of combustible substances in the surrounding atmosphere, as well as the concentrations of each type of substance relative to a pre-determined lower explosive limit (LEL). In addition, the sensing device can determine the percent level of oxygen present in the surrounding atmosphere.

  9. Combustion synthesis and characterization of nanocrystalline WO3.

    PubMed

    Morales, Walter; Cason, Michael; Aina, Olawunmi; de Tacconi, Norma R; Rajeshwar, Krishnan

    2008-05-21

    The energy payback time associated with the semiconductor active material is an important parameter in a photovoltaic solar cell device. Thus lowering the energy requirements for the semiconductor synthesis step or making it more energy-efficient is critical toward making the overall device economics more competitive relative to other nonpolluting energy options. In this communication, combustion synthesis is demonstrated to be a versatile and energy-efficient method for preparing inorganic oxide semiconductors such as tungsten trioxide (WO3) for photovoltaic or photocatalytic solar energy conversion. The energy efficiency of combustion synthesis accrues from the fact that high process temperatures are self-sustained by the exothermicity of the combustion process, and the only external thermal energy input needed is for dehydration of the fuel/oxidizer precursor mixture and bringing it to ignition. Importantly, we show that, in this approach, it is also possible to tune the optical characteristics of the oxide semiconductor (i.e., shift its response toward the visible range of the electromagnetic spectrum) in situ by doping the host semiconductor during the formative stage itself. As a bonus, the resultant material shows enhanced surface properties such as markedly improved organic dye uptake relative to benchmark samples obtained from commercial sources. Finally, this synthesis approach requires only very simple equipment, a feature that it shares with other "mild" inorganic semiconductor synthesis routes such as sol-gel chemistry, chemical bath deposition, and electrodeposition. The present study constitutes the first use of combustion synthesis for preparing WO3 powder comprising nanosized particles.

  10. Fuel Effects on Gas Turbine Combustion

    DTIC Science & Technology

    1983-01-01

    W. S., Combustion Considerations for Future Jet Fuels, Sixteenth Symposium (International) on Combustion , The Combustion Institute, pp. 1631-1638...AFWAL-TR-83-2004 -. i FUEL EFFECTS ON SGAS TURBINE COMBUSTION A. H. Lefebvre <.A t • Combustion Laboratory Thermal Science and Propulsion Center...PERIOD COVEREDFinal Report for Period FUEL EFFECTS ON GAS TURBINE COMBUSTION 21 Sep 81 - 23 Dec 82 6. PERFORMING OIG. REPORT NUMBER ś. AUT"HOR(.) S

  11. Combustion of Methane Hydrate

    NASA Astrophysics Data System (ADS)

    Roshandell, Melika

    A significant methane storehouse is in the form of methane hydrates on the sea floor and in the arctic permafrost. Methane hydrates are ice-like structures composed of water cages housing a guest methane molecule. This caged methane represents a resource of energy and a potential source of strong greenhouse gas. Most research related to methane hydrates has been focused on their formation and dissociation because they can form solid plugs that complicate transport of oil and gas in pipelines. This dissertation explores the direct burning of these methane hydrates where heat from the combustion process dissociates the hydrate into water and methane, and the released methane fuels the methane/air diffusion flame heat source. In contrast to the pipeline applications, very little research has been done on the combustion and burning characteristics of methane hydrates. This is the first dissertation on this subject. In this study, energy release and combustion characteristics of methane hydrates were investigated both theoretically and experimentally. The experimental study involved collaboration with another research group, particularly in the creation of methane hydrate samples. The experiments were difficult because hydrates form at high pressure within a narrow temperature range. The process can be slow and the resulting hydrate can have somewhat variable properties (e.g., extent of clathration, shape, compactness). The experimental study examined broad characteristics of hydrate combustion, including flame appearance, burning time, conditions leading to flame extinguishment, the amount of hydrate water melted versus evaporated, and flame temperature. These properties were observed for samples of different physical size. Hydrate formation is a very slow process with pure water and methane. The addition of small amounts of surfactant increased substantially the hydrate formation rate. The effects of surfactant on burning characteristics were also studied. One finding

  12. Liquid propellant rocket combustion instability

    NASA Technical Reports Server (NTRS)

    Harrje, D. T.

    1972-01-01

    The solution of problems of combustion instability for more effective communication between the various workers in this field is considered. The extent of combustion instability problems in liquid propellant rocket engines and recommendations for their solution are discussed. The most significant developments, both theoretical and experimental, are presented, with emphasis on fundamental principles and relationships between alternative approaches.

  13. Manifold methods for methane combustion

    SciTech Connect

    Yang, B.; Pope, S.B.

    1995-10-01

    Great progresses have been made in combustion research, especially, the computation of laminar flames and the probability density function (PDF) method in turbulent combustion. For one-dimensional laminar flames, by considering the transport mechanism, the detailed chemical kinetic mechanism and the interactions between these two basic processes, today it is a routine matter to calculate flame velocities, extinction, ignition, temperature, and species distributions from the governing equations. Results are in good agreement with those obtained for experiments. However, for turbulent combustion, because of the complexities of turbulent flow, chemical reactions, and the interaction between them, in the foreseeable future, it is impossible to calculate the combustion flow field by directly integrating the basic governing equations. So averaging and modeling are necessary in turbulent combustion studies. Averaging, on one hand, simplifies turbulent combustion calculations, on the other hand, it introduces the infamous closure problems, especially the closure problem with chemical reaction terms. Since in PDF calculations of turbulent combustion, the averages of the chemical reaction terms can be calculated, PDF methods overcome the closure problem with the reaction terms. It has been shown that the PDF method is a most promising method to calculate turbulent combustion. PDF methods have been successfully employed to calculate laboratory turbulent flames: they can predict phenomena such as super equilibrium radical levels, and local extinction. Because of these advantages, PDF methods are becoming used increasingly in industry combustor codes.

  14. PDF Modeling of Turbulent Combustion

    DTIC Science & Technology

    2008-11-30

    extend methodologies for the modeling and simulation of turbulent combustion. Probability density function (PDF) calculations were performed of piloted...were developed to implement the combined methodology of large-eddy simulation (LES) and filtered density function (FDF). Second-order schemes were...was to advance and extend methodologies for the modeling and simulation of turbulent combustion. Probability density function (PDF) calculations were

  15. Method for in situ combustion

    DOEpatents

    Pasini, III, Joseph; Shuck, Lowell Z.; Overbey, Jr., William K.

    1977-01-01

    This invention relates to an improved in situ combustion method for the recovery of hydrocarbons from subterranean earth formations containing carbonaceous material. The method is practiced by penetrating the subterranean earth formation with a borehole projecting into the coal bed along a horizontal plane and extending along a plane disposed perpendicular to the plane of maximum permeability. The subterranean earth formation is also penetrated with a plurality of spaced-apart vertical boreholes disposed along a plane spaced from and generally parallel to that of the horizontal borehole. Fractures are then induced at each of the vertical boreholes which project from the vertical boreholes along the plane of maximum permeability and intersect the horizontal borehole. The combustion is initiated at the horizontal borehole and the products of combustion and fluids displaced from the earth formation by the combustion are removed from the subterranean earth formation via the vertical boreholes. Each of the vertical boreholes are, in turn, provided with suitable flow controls for regulating the flow of fluid from the combustion zone and the earth formation so as to control the configuration and rate of propagation of the combustion zone. The fractures provide a positive communication with the combustion zone so as to facilitate the removal of the products resulting from the combustion of the carbonaceous material.

  16. New urea-absorbing polymers for artificial kidney machines

    NASA Technical Reports Server (NTRS)

    Mueller, W. A.; Hsu, G. C.; Marsh, H. E., Jr.

    1975-01-01

    Etherified polymer is made from modified cellulose derivative which is reacted with periodate. It will absorb 2 grams of urea per 100 grams of polymer. Indications are that polymers could be used to help remove uremic wastes in artificial kidneys, or they could be administered orally as therapy for uremia.

  17. Prebiotic formation of polyamino acids in molten urea

    NASA Astrophysics Data System (ADS)

    Mita, H.; Nomoto, S.; Terasaki, M.; Shimoyama, A.; Yamamoto, Y.

    2005-04-01

    It is important for research into the origins of life to elucidate polyamino acid formation under prebiotic conditions. Only a limited set of amino acids has been reported to polymerize thermally. In this paper we demonstrate a novel thermal polymerization mechanism in a molten urea of alkylamino acids (i.e. glycine, alanine, β-alanine, α-aminobutyric acid, valine, norvaline, leucine and norleucine), which had been thought to be incapable of undergoing thermal polymerization. Also, aspartic acid was found to polymerize in molten urea at a lower temperature than that at which aspartic acid alone had previously been thermally polymerized. Individual oligomers produced in heating experiments on urea-amino acid mixtures were analysed using a liquid chromatograph mass spectrometer. Major products in the reaction mixture were three different types of polyamino acid derivatives: N-carbamoylpolyamino acids, polyamino acids containing a hydantoin ring at the N-terminal position and unidentified derivatives with molecular weights that were greater by 78 than those of the corresponding peptide forms. The polymerization reaction occurred by taking advantage of the high polarity of molten urea as well as its dehydrating ability. Under the presumed prebiotic conditions employed here, many types of amino acids were thus revealed to undergo thermal polymerization.

  18. 75 FR 74746 - Solid Urea From Russia and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-01

    ... From the Federal Register Online via the Government Publishing Office INTERNATIONAL TRADE COMMISSION Solid Urea From Russia and Ukraine AGENCY: United States International Trade Commission. ACTION... conduct of these reviews and rules of general application, consult the Commission's Rules of Practice...

  19. Crystal engineering with urea and thiourea hydrogen-bonding groups.

    PubMed

    Custelcean, Radu

    2008-01-21

    The utilization of N,N'-disubstituted ureas and thioureas as design elements in the synthesis of crystalline organic solids is reviewed. These hydrogen-bonding units are versatile yet predictable building blocks that can be rationally employed in both crystal assembly and functionalization.

  20. IRIS Toxicological Review of Urea (External Review Draft)

    EPA Science Inventory

    EPA conducted a peer review and public comment of the scientific basis of a draft report supporting the human health hazard and dose-response assessment of Urea that when finalized will appear on the Integrated Risk Information System (IRIS) database.

  1. Urea modified cottonseed protein adhesive for wood composite products

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cottonseed protein has the potential to be used as renewable and environmentally friendly adhesives in wood products industry. However, the industry application was limited by its low mechanical properties, low water resistance and viscosity. In this work, urea modified cottonseed protein adhesive w...

  2. Tailoring of analytical performances of urea biosensors using nanomaterials

    NASA Astrophysics Data System (ADS)

    Nouira, W.; Barhoumi, H.; Maaref, A.; Jaffrézic Renault, N.; Siadat, M.

    2013-03-01

    This paper is a contribution to the study of enzymatic sensors based on nanoparticles of iron oxide (FeNPs). Urease enzyme was immobilized on FeNPs using layer-by-layer (LbL) deposition method. FeNPs were first coated with polyelectrolytes (PE): Poly (allylamine hydrochloride), PAH and Poly (sodium 4-styrenesulfonate), PSS for enzyme immobilization and then with enzyme. It has been confirmed through zeta potential measurements of FeNPs that the enzyme is immobilized on the surface. We evaluated the sensitivity of biosensors for urea by potentiometric and capacitive measurements on silicon / silica / FeNP-LBL-urease structures. The recorded capacity-potential curves (C-V) show a significant shift of flat band potential towards negative potentials in the presence of urea, the observed values of sensitivity vary between 30 and 40 mV/p[urea]. It has been shown that the proposed method for the immobilization of urease can increase the dynamic range of urea detection (10-4M to 10-1M) compared to the immobilization of urease without FeNP (10-3.5 M to 10-2.5 M). When the number of PAH-PSS layers was increased the sensitivity of detection was modified. This effect is due to partial inhibition of the enzyme in presence of FeNPs, which was shown by measurements in homogeneous phase.

  3. Urea destabilizes RNA by forming stacking interactions and multiple hydrogen bonds with nucleic acid bases.

    PubMed

    Priyakumar, U Deva; Hyeon, Changbong; Thirumalai, D; Mackerell, Alexander D

    2009-12-16

    Urea titration of RNA by urea is an effective approach to investigate the forces stabilizing this biologically important molecule. We used all atom molecular dynamics simulations using two urea force fields and two RNA constructs to elucidate in atomic detail the destabilization mechanism of folded RNA in aqueous urea solutions. Urea denatures RNA by forming multiple hydrogen bonds with the RNA bases and has little influence on the phosphodiester backbone. Most significantly we discovered that urea engages in stacking interactions with the bases. We also estimate, for the first time, the m-value for RNA, which is a measure of the strength of urea-RNA interactions. Our work provides a conceptual understanding of the mechanism by which urea enhances RNA folding rates.

  4. NASA Microgravity Combustion Science Program

    NASA Technical Reports Server (NTRS)

    King, Merrill K.

    1997-01-01

    Combustion is a key element of many critical technologies used by contemporary society. For example, electric power production, home heating, surface and air transportation, space propulsion, and materials synthesis all utilize combustion as a source of energy. Yet, although combustion technology is vital to our standard of living, it poses great challenges to maintaining a habitable environment. For example, pollutants, atmospheric change and global warming, unwanted fires and explosions, and the incineration of hazardous wastes are major problem areas which would benefit from improved understanding of combustion. Effects of gravitational forces impede combustion studies more than most other areas of science since combustion involves production of high-temperature gases whose low density results in buoyant motion, vastly complicating the execution and interpretation of experiments. Effects of buoyancy are so ubiquitous that their enormous negative impact on the rational development of combustion science is generally not recognized. Buoyant motion also triggers the onset of turbulence, yielding complicating unsteady effects. Finally, gravity forces cause particles and drops to settle, inhibiting deconvoluted studies of heterogeneous flames important to furnace, incineration and power generation technologies. Thus, effects of buoyancy have seriously limited our capabilities to carry out 'clean' experiments needed for fundamental understanding of flame phenomena. Combustion scientists can use microgravity to simplify the study of many combustion processes, allowing fresh insights into important problems via a deeper understanding of elemental phenomena also found in Earth-based combustion processes and to additionally provide valuable information concerning how fires behave in microgravity and how fire safety on spacecraft can be enhanced.

  5. Route visualization using detail lenses.

    PubMed

    Karnick, Pushpak; Cline, David; Jeschke, Stefan; Razdan, Anshuman; Wonka, Peter

    2010-01-01

    We present a method designed to address some limitations of typical route map displays of driving directions. The main goal of our system is to generate a printable version of a route map that shows the overview and detail views of the route within a single, consistent visual frame. Our proposed visualization provides a more intuitive spatial context than a simple list of turns. We present a novel multifocus technique to achieve this goal, where the foci are defined by points of interest (POI) along the route. A detail lens that encapsulates the POI at a finer geospatial scale is created for each focus. The lenses are laid out on the map to avoid occlusion with the route and each other, and to optimally utilize the free space around the route. We define a set of layout metrics to evaluate the quality of a lens layout for a given route map visualization. We compare standard lens layout methods to our proposed method and demonstrate the effectiveness of our method in generating aesthetically pleasing layouts. Finally, we perform a user study to evaluate the effectiveness of our layout choices.

  6. SERUM AND PAROTID FLUIS UREA-LEVELS IN UNREALOADED HEALTHY YOUNG ADULTS

    DTIC Science & Technology

    Forty-four healthy young adult male subjects were given oral doses of urea, and parotid fluid and serum urea levels were studied for 1 to 3 hours. A...highly significant correlation between urea in serum and in parotid fluid (r equals 0.982) was found. The indication was that, with flow rate...carefully controlled, parotid fluid could be used interchangeably with serum in urea determination, regardless of the magnitude of the blood concentration. (Author)

  7. Performance of cellulose acetate butyrate membranes in hyperfiltration of sodium chloride and urea feed solution

    NASA Technical Reports Server (NTRS)

    Wydeven, T.; Leban, M.

    1973-01-01

    Cellulose acetate butyrate (CAB) membranes are shown to give high salt and urea rejection with water flux of about 3 gallons/sq ft per day at 600 psig. Membranes prepared from a formulation containing glyoxal show a significant increase in flux and decrease in salt and urea rejection with drying time. Zero drying time gives maximum urea and salt rejection and is therefore most suitable for hyperfiltration of sodium chloride and urea feed solution.

  8. Ionic liquid self-combustion synthesis of BiOBr/Bi24O31Br10 heterojunctions with exceptional visible-light photocatalytic performances

    NASA Astrophysics Data System (ADS)

    Li, Fa-Tang; Wang, Qing; Ran, Jingrun; Hao, Ying-Juan; Wang, Xiao-Jing; Zhao, Dishun; Qiao, Shi Zhang

    2014-12-01

    Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg L-1 of MO under visible-light (λ > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L-1 of RhB and 30 mg

  9. Combustion instability control in the model of combustion chamber

    NASA Astrophysics Data System (ADS)

    Akhmadullin, A. N.; Ahmethanov, E. N.; Iovleva, O. V.; Mitrofanov, G. A.

    2013-12-01

    An experimental study of the influence of external periodic perturbations on the instability of the combustion chamber in a pulsating combustion. As an external periodic disturbances were used sound waves emitted by the electrodynamics. The purpose of the study was to determine the possibility of using the method of external periodic perturbation to control the combustion instability. The study was conducted on a specially created model of the combustion chamber with a swirl burner in the frequency range from 100 to 1400 Hz. The study found that the method of external periodic perturbations may be used to control combustion instability. Depending on the frequency of the external periodic perturbation is observed as an increase and decrease in the amplitude of the oscillations in the combustion chamber. These effects are due to the mechanisms of synchronous and asynchronous action. External periodic disturbance generated in the path feeding the gaseous fuel, showing the high efficiency of the method of management in terms of energy costs. Power required to initiate periodic disturbances (50 W) is significantly smaller than the thermal capacity of the combustion chamber (100 kW).

  10. Multiuser Droplet Combustion Apparatus Developed to Conduct Combustion Experiments

    NASA Technical Reports Server (NTRS)

    Myhre, Craig A.

    2001-01-01

    A major portion of the energy produced in the world today comes from the combustion or burning of liquid hydrocarbon fuels in the form of droplets. However, despite vigorous scientific examinations for over a century, researchers still lack a full understanding of many fundamental combustion processes of liquid fuels. Understanding how these fuel droplets ignite, spread, and extinguish themselves will help us develop more efficient ways of energy production and propulsion, as well as help us deal better with the problems of combustion-generated pollution and fire hazards associated with liquid combustibles. The ability to conduct more controlled experiments in space, without the complication of gravity, provides scientists with an opportunity to examine these complicated processes closely. The Multiuser Droplet Combustion Apparatus (MDCA) supports this continued research under microgravity conditions. The objectives are to improve understanding of fundamental droplet phenomena affected by gravity, to use research results to advance droplet combustion science and technology on Earth, and to address issues of fire hazards associated with liquid combustibles on Earth and in space. MDCA is a multiuser facility designed to accommodate different combustion science experiments. The modular approach permits the on-orbit replacement of droplet combustion principal investigator experiments such as different fuels, droplet-dispensing needles, and droplet-tethering mechanisms. Large components such as the avionics, diagnostics, and base-plate remain on the International Space Station to reduce the launch mass of new experiments. MDCA is also designed to operate in concert with ground systems on Earth to minimize the involvement of the crew during orbit.

  11. Use of natural and biobased materials for controlled-release of urea in water: Environmental applications

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Urea pearls were encapsulated in cloisite-based matrices using different natural materials (lignin, beeswax and latex) to control the release of urea over time. It was found that all cloisite-based fertilizer tablets showed better release profiles than neat urea tablets. The best release profile was...

  12. 21 CFR 177.1900 - Urea-formaldehyde resins in molded articles.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Urea-formaldehyde resins in molded articles. 177... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the food-contact...

  13. 21 CFR 177.1900 - Urea-formaldehyde resins in molded articles.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Urea-formaldehyde resins in molded articles. 177... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the food-contact...

  14. 21 CFR 177.1900 - Urea-formaldehyde resins in molded articles.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Urea-formaldehyde resins in molded articles. 177... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the food-contact...

  15. 76 FR 35405 - Solid Urea From the Russian Federation: Preliminary Results of Antidumping Duty Administrative...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-17

    ... International Trade Administration Solid Urea From the Russian Federation: Preliminary Results of Antidumping... review of the antidumping duty order on solid urea from the Russian Federation (Russia). The review... solid urea from the Union of Soviet Socialist Republics (Soviet Union). See Antidumping Duty Order;...

  16. 40 CFR 721.9920 - Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Urea, (hexahydro-6-methyl-2... Specific Chemical Substances § 721.9920 Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance urea,...

  17. 76 FR 66690 - Solid Urea From the Russian Federation: Final Results of Antidumping Duty Administrative Review

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-10-27

    ... International Trade Administration Solid Urea From the Russian Federation: Final Results of Antidumping Duty... of the administrative review of the antidumping duty order on solid urea from the Russian Federation. The solid urea subject to this review was produced and exported by MCC EuroChem (EuroChem). The...

  18. 21 CFR 177.1900 - Urea-formaldehyde resins in molded articles.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Urea-formaldehyde resins in molded articles. 177... for Use as Basic Components of Single and Repeated Use Food Contact Surfaces § 177.1900 Urea-formaldehyde resins in molded articles. Urea-formaldehyde resins may be safely used as the food-contact...

  19. 78 FR 67335 - Solid Urea From the Russian Federation: Final Results of Antidumping Duty Administrative Review...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-11-12

    ... International Trade Administration Solid Urea From the Russian Federation: Final Results of Antidumping Duty... duty order on solid urea from the Russian Federation (Russia). For the final results, we continue to... solid urea from Russia.\\1\\ We invited interested parties to comment on the Preliminary Results....

  20. Enantioselective Michael addition/iminium ion cyclization cascades of tryptamine-derived ureas.

    PubMed

    Aillaud, Isabelle; Barber, David M; Thompson, Amber L; Dixon, Darren J

    2013-06-21

    A Michael addition/iminium ion cyclization cascade of enones with tryptamine-derived ureas under BINOL phosphoric acid (BPA) catalysis is reported. The cascade reaction tolerates a wide variety of easily synthesized tryptamine-derived ureas, including those bearing substituents on the distal nitrogen atom of the urea moiety, affording polyheterocyclic products in good yields and good to excellent enantioselectivities.

  1. Fate and surface transport of urea in a coastal plain soil: a rainfall simulation study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The surface transport of urea has rarely been studied since it is assumed to undergo rapid hydrolysis to ammonia. However, studies have shown urea to exist in estuarine and coastal waters. Urea in small amounts can trigger the diatom Pseudo-nitzschia spp. to produce the toxin domoic acid, which is o...

  2. 75 FR 78243 - Propionic Acid and Salts, Urea Sulfate, Methidathion, and Methyl Parathion; Registration Review...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-15

    ... AGENCY Propionic Acid and Salts, Urea Sulfate, Methidathion, and Methyl Parathion; Registration Review... pesticides propionic acid and salts, case no. 4078, urea sulfate, case no. 7213, methidathion, case no. 0034... pesticides in the table below--propionic acid and salts, case 4078, urea sulfate, case no. 7213,...

  3. Space Station Freedom combustion research

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1992-01-01

    Extended operations in microgravity, on board spacecraft like Space Station Freedom, provide both unusual opportunities and unusual challenges for combustion science. On the one hand, eliminating the intrusion of buoyancy provides a valuable new perspective for fundamental studies of combustion phenomena. On the other hand, however, the absence of buoyancy creates new hazards of fires and explosions that must be understood to assure safe manned space activities. These considerations - and the relevance of combustion science to problems of pollutants, energy utilization, waste incineration, power and propulsion systems, and fire and explosion hazards, among others - provide strong motivation for microgravity combustion research. The intrusion of buoyancy is a greater impediment to fundamental combustion studies than to most other areas of science. Combustion intrinsically heats gases with the resulting buoyant motion at normal gravity either preventing or vastly complicating measurements. Perversely, this limitation is most evident for fundamental laboratory experiments; few practical combustion phenomena are significantly affected by buoyancy. Thus, we have never observed the most fundamental combustion phenomena - laminar premixed and diffusion flames, heterogeneous flames of particles and surfaces, low-speed turbulent flames, etc. - without substantial buoyant disturbances. This precludes rational merging of theory, where buoyancy is of little interest, and experiments, that always are contaminated by buoyancy, which is the traditional path for developing most areas of science. The current microgravity combustion program seeks to rectify this deficiency using both ground-based and space-based facilities, with experiments involving space-based facilities including: laminar premixed flames, soot processes in laminar jet diffusion flames, structure of laminar and turbulent jet diffusion flames, solid surface combustion, one-dimensional smoldering, ignition and flame

  4. Fluids and Combustion Facility-Combustion Integrated Rack

    NASA Technical Reports Server (NTRS)

    Francisco, David R.

    1998-01-01

    This paper describes in detail the concept of performing Combustion microgravity experiments in the Combustion Integrated Rack (CIR) of the Fluids and Combustion Facility (FCF) on the International Space Station (ISS). The extended duration microgravity environment of the ISS will enable microgravity research to enter into a new era of increased scientific and technological data return. The FCF is designed to increase the amount and quality of scientific and technological data and decrease the development cost of an individual experiment relative to the era of Space Shuttle experiments. This paper also describes how the FCF will cost effectively accommodate these experiments.

  5. Experimental and modeling study of the effect of CO and H2 on the urea DeNO(x) process in a 150kW laboratory reactor.

    PubMed

    Javed, M Tayyeb; Nimmo, W; Gibbs, B M

    2008-01-01

    An experimental and modeling investigation has been performed to study the effect of process additives, H2 and CO on NO(x) removal from flue gases by a selective non-catalytic reduction process using urea as a reducing agent. Experiments were performed with a flow reactor in which flue gas was generated by the combustion of propane in air at 3% excess oxygen and the desired levels of initial NO(x) (500ppm) were achieved by doping the flame with ammonia. Experiments were performed throughout the temperature range of interest, i.e. from 850 to 1200 degrees C for investigation of the effects of the process additives on the performance of aqueous urea DeNO(x). Subsequently, computational kinetic modeling with SENKIN code was performed to analyze the performance of urea providing a direct comparison of modeling prediction with experimental measurements. With CO addition, a downwards shift of 215 degrees C in the peak reduction temperature from 1125 to 910 degrees C was observed during the experimentation while the kinetic modeling suggests it to be 150 degrees C, i.e. from 1020 to 870 degrees C. The addition of H2 impairs the peak NO(x) reduction but suggests a low temperature application of the process. A downward shift of 250 degrees C in the peak reduction temperature, from 1020 to 770 degrees C, was observed during kinetic modeling studies. The kinetic modeling shows a good qualitative agreement with the experimental observations and reveals additional information about the process.

  6. Dual-Mode Combustion

    NASA Technical Reports Server (NTRS)

    Goyne, Christopher P.; McDaniel, James C.

    2002-01-01

    The Department of Mechanical and Aerospace Engineering at the University of Virginia has conducted an investigation of the mixing and combustion processes in a hydrogen fueled dual-mode scramjet combustor. The experiment essentially consisted of the "direct connect" continuous operation of a Mach 2 rectangular combustor with a single unswept ramp fuel injector. The stagnation enthalpy of the test flow simulated a flight Mach number of 5. Measurements were obtained using conventional wall instrumentation and laser based diagnostics. These diagnostics included, pressure and wall temperature measurements, Fuel Plume Imaging (FPI) and Particle Image Velocimetry (PIV). A schematic of the combustor configuration and a summary of the measurements obtained are presented. The experimental work at UVa was parallel by Computational Fluid Dynamics (CFD) work at NASA Langley. The numerical and experiment results are compared in this document.

  7. Microwave-assisted synthesis of N-pyrazole ureas and the p38alpha inhibitor BIRB 796 for study into accelerated cell ageing.

    PubMed

    Bagley, Mark C; Davis, Terence; Dix, Matthew C; Widdowson, Caroline S; Kipling, David

    2006-11-21

    Microwave irradiation of substituted hydrazines and beta-ketoesters gives 5-aminopyrazoles in excellent yield, which can be transformed to the corresponding N-carbonyl derivatives by treatment with an isocyanate or chloroformate. Derivatization of 4-nitronaphth-1-ol using predominantly microwave heating methods and reaction with an N-pyrazole carbamate provides a rapid route to the N-pyrazole urea BIRB 796 in high purity, as a potent and selective inhibitor of p38alpha mitogen-activated protein kinase for the study of accelerated ageing in Werner syndrome cells.

  8. High Efficiency, Clean Combustion

    SciTech Connect

    Donald Stanton

    2010-03-31

    Energy use in trucks has been increasing at a faster rate than that of automobiles within the U.S. transportation sector. According to the Energy Information Administration (EIA) Annual Energy Outlook (AEO), a 23% increase in fuel consumption for the U.S. heavy duty truck segment is expected between 2009 to 2020. The heavy duty vehicle oil consumption is projected to grow between 2009 and 2050 while light duty vehicle (LDV) fuel consumption will eventually experience a decrease. By 2050, the oil consumption rate by LDVs is anticipated to decrease below 2009 levels due to CAFE standards and biofuel use. In contrast, the heavy duty oil consumption rate is anticipated to double. The increasing trend in oil consumption for heavy trucks is linked to the vitality, security, and growth of the U.S. economy. An essential part of a stable and vibrant U.S. economy is a productive U.S. trucking industry. Studies have shown that the U.S. gross domestic product (GDP) is strongly correlated to freight transport. Over 90% of all U.S. freight tonnage is transported by diesel power and over 75% is transported by trucks. Given the vital role that the trucking industry plays in the economy, improving the efficiency of the transportation of goods was a central focus of the Cummins High Efficient Clean Combustion (HECC) program. In a commercial vehicle, the diesel engine remains the largest source of fuel efficiency loss, but remains the greatest opportunity for fuel efficiency improvements. In addition to reducing oil consumption and the dependency on foreign oil, this project will mitigate the impact on the environment by meeting US EPA 2010 emissions regulations. Innovation is a key element in sustaining a U.S. trucking industry that is competitive in global markets. Unlike passenger vehicles, the trucking industry cannot simply downsize the vehicle and still transport the freight with improved efficiency. The truck manufacturing and supporting industries are faced with numerous

  9. Microgravity combustion of dust suspensions

    NASA Technical Reports Server (NTRS)

    Lee, John H. S.; Peraldi, Olivier; Knystautas, Rom

    1993-01-01

    Unlike the combustion of homogeneous gas mixtures, there are practically no reliable fundamental data (i.e., laminar burning velocity, flammability limits, quenching distance, minimum ignition energy) for the combustion of heterogeneous dust suspensions. Even the equilibrium thermodynamic data such as the constant pressure volume combustion pressure and the constant pressure adiabatic flame temperature are not accurately known for dust mixtures. This is mainly due to the problem of gravity sedimentation. In normal gravity, turbulence, convective flow, electric and acoustic fields are required to maintain a dust in suspension. These external influences have a dominating effect on the combustion processes. Microgravity offers a unique environment where a quiescent dust cloud can in principle be maintained for a sufficiently long duration for almost all combustion experiments (dust suspensions are inherently unstable due to Brownian motion and particle aggregation). Thus, the microgravity duration provided by drop towers, parabolic flights, and the space shuttle, can all be exploited for different kinds of dust combustion experiments. The present paper describes some recent studies on microgravity combustion of dust suspension carried out on the KC-135 and the Caravelle aircraft. The results reported are obtained from three parabolic flight campaigns.

  10. Filtration combustion: Smoldering and SHS

    NASA Technical Reports Server (NTRS)

    Matkowsky, Bernard J.

    1995-01-01

    Smolder waves and SHS (self-propagating high-temperature synthesis) waves are both examples of combustion waves propagating in porous media. When delivery of reactants through the pores to the reaction site is an important aspect of the process, it is referred to as filtration combustion. The two types of filtration combustion have a similar mathematical formulation, describing the ignition, propagation and extinction of combustion waves in porous media. The goal in each case, however, is different. In smoldering the desired goal is to prevent propagation, whereas in SHS the goal is to insure propagation of the combustion wave, leading to the synthesis of desired products. In addition, the scales in the two areas of application may well differ. For example, smoldering generally occurs at a relatively low temperature and with a smaller propagation velocity than SHS filtration combustion waves. Nevertheless, the two areas of application have much in common, so that mechanisms learned about in one application can be used to advantage in the other. In this paper we discuss recent results in the areas of filtration combustion.

  11. Structure Study of Cellulose Fibers Wet-Spun from Environmentally Friendly NaOH/Urea Aqueous Solutions

    SciTech Connect

    Chen,X.; Burger, C.; Wan, F.; Zhang, J.; Rong, L.; Hsiao, B.; Chu, B.; Cai, J.; Zhang, L.

    2007-01-01

    In this study, structure changes of regenerated cellulose fibers wet-spun from a cotton linter pulp (degree of polymerization {approx}620) solution in an NaOH/urea solvent under different conditions were investigated by simultaneous synchrotron wide-angle X-ray diffraction (WAXD) and small-angle X-ray scattering (SAXS). WAXD results indicated that the increase in flow rate during spinning produced a better crystal orientation and a higher degree of crystallinity, whereas a 2-fold increase in draw ratio only affected the crystal orientation. When coagulated in a H{sub 2}SO{sub 4}/Na{sub 2}SO{sub 4} aqueous solution at 15 {sup o}C, the regenerated fibers exhibited the highest crystallinity and a crystal orientation comparable to that of commercial rayon fibers by the viscose method. SAXS patterns exhibited a pair of meridional maxima in all regenerated cellulose fibers, indicating the existence of a lamellar structure. A fibrillar superstructure was observed only at higher flow rates (>20 m/min). The conformation of cellulose molecules in NaOH/urea aqueous solution was also investigated by static and dynamic light scattering. It was found that cellulose chains formed aggregates with a radius of gyration, R{sub g}, of about 232 nm and an apparent hydrodynamic radius, R{sub h}, of about 172 nm. The NaOH/urea solvent system is low-cost and environmentally friendly, which may offer an alternative route to replace more hazardous existing methods for the production of regenerated cellulose fibers.

  12. Evaluation of the Determination of Free Urea in Water-Soluble Liquid Fertilizers Containing Urea and Ureaforms by Urease and HPLC Methods.

    PubMed

    Hojjatie, Michael M; Abrams, Dean

    2015-01-01

    Currently there are three AOAC Official Methods for the determination of urea in fertilizers. AOAC Official Method 959.03, Urea in Fertilizers, Urease Method, First Action 1959, Final Action 1960, is based on the use of fresh commercial 1% urease solution, or preparation of such solution from urease powder in water, or from jack bean meal in water. AOAC Official Method 983.01, Urea and Methyleneureas (Water-Soluble) in Fertilizers, First Action 1983, Final Action 1984, is based on LC with a refractive index detector using water as the mobile phase and a C18 column. AOAC Official Method 2003.14, Determination of Urea in Water- Soluble Urea-Formaldehyde Fertilizer Products and in Aqueous Urea Solutions, First Action 2003, Final Action 2008, is based on LC with a UV detector using acetonitrile-water (85+15, v/v) mobile phase and a propylamine column. The urea method, AOAC Official Method 959.03, is very much dependent on the nature of the urease enzyme. The method was developed in 1960 and used for simple urea fertilizer solutions. With the advent of complex fertilizer compositions, especially with the class of liquid triazone fertilizers and water-soluble urea forms, the analyses of free urea in these fertilizers by the urease method is often inaccurate and inconsistent. AOAC Official Method 983.01 is not always reliable due to the interference of some of the components of these fertilizers, and due to the fact that the use of water as the mobile phase does not always separate the free urea from other components. AOAC Official Method 2003.14 was subjected to ring test studies that showed it could be used for the determination of "free urea" in these classes of fertilizers with good accuracy and precision.

  13. Cortisol-sensitive urea transport across the gill basolateral membrane of the gulf toadfish (Opsanus beta).

    PubMed

    Rodela, Tamara M; Gilmour, Kathleen M; Walsh, Patrick J; McDonald, M Danielle

    2009-08-01

    Gulf toadfish (Opsanus beta) use a unique pulsatile urea excretion mechanism that allows urea to be voided in large pulses via the periodic insertion or activation of a branchial urea transporter. The precise cellular and subcellular location of the facilitated diffusion mechanism(s) remains unclear. An in vitro basolateral membrane vesicle (BLMV) preparation was used to test the hypothesis that urea movement across the gill basolateral membrane occurs through a cortisol-sensitive carrier-mediated mechanism. Toadfish BLMVs demonstrated two components of urea uptake: a linear element at high external urea concentrations, and a phloretin-sensitive saturable constituent (K(m) = 0.24 mmol/l; V(max) = 6.95 micromol x mg protein(-1) x h(-1)) at low urea concentrations (<1 mmol/l). BLMV urea transport in toadfish was unaffected by in vitro treatment with ouabain, N-ethylmaleimide, or the absence of sodium, conditions that are known to inhibit sodium-coupled and proton-coupled urea transport in vertebrates. Transport kinetics were temperature sensitive with a Q(10) > 2, further suggestive of carrier-mediated processes. Our data provide evidence that a basolateral urea facilitated transporter accelerates the movement of urea between the plasma and gills to enable the pulsatile excretion of urea. Furthermore, in vivo infusion of cortisol caused a significant 4.3-fold reduction in BLMV urea transport capacity in lab-crowded fish, suggesting that cortisol inhibits the recruitment of urea transporters to the basolateral membrane, which may ultimately affect the size of the urea pulse event in gulf toadfish.

  14. SOHC type internal combustion engine

    SciTech Connect

    Fujii, N.; Iwata, T.; Oikawa, T.

    1989-01-10

    An SOHC type internal combustion engine is described comprising a cylinder head which has a combustion chamber defined therein, a camshaft carried thereon, an ignition plug mounting hole opening to a center portion of a top surface of the combustion chamber and a protecting cylinder formed therein with an ignition plug insertion hole. The journal for the camshaft has a diameter larger than a path of rotation of a lobe of a cam on the camshaft and is supported by a bearing hole formed in a camshaft receiving wall which is provided on the cylinder head. The protecting cylinder and the camshaft receiving wall are formed in a single piece.

  15. Green urea synthesis catalyzed by hematite nanowires in magnetic field

    NASA Astrophysics Data System (ADS)

    Yahya, Noorhana; Qureshi, Saima; Rehman, Zia ur; Alqasem, Bilal; Fai Kait, Chong

    2017-04-01

    The catalytic activity of hematite (α-Fe2O3) nanowires under the influence of magnetic field on urea synthesis is considered green. The adsorption and subsequent dissociative reaction of hydrogen, nitrogen and carbon dioxide gases on the α-Fe2O3 (111) nanowires were investigated using the density functional theory (DFT) method. The average adsorption energy is -4.12 kcal/mole at different sites. The adsorption of gases resulted in a difference in density and net spin of electrons from 68 to 120 and 0-21 respectively. In addition, it induces magnetic moment value of 36.33 μB, which confirms the enhanced magnetic behaviour of hematite. α-Fe2O3 nanowires (NWs) synthesized by heating iron wire in a box furnace at (750-800) °C and as synthesized α-Fe2O3 nanoparticles (NPs) were received to use as a catalyst in the magnetic reaction of urea synthesis. X-ray Diffractometer (XRD) confirms the peaks of rhombohedral structure of α-Fe2O3 and Raman spectrum analyses confirms the α-Fe2O3 peaks at 410 cm-1, 500 cm-1 and 616 cm-1. The needle-like shape of hematite nanowires with length ranging from 16-25) μm and diameter from 74 to 145 nm confirmed by Field emission scanning electron microscopy (FESEM). The magnetic properties of the nanowires exhibited different levels of saturation magnetization, for α-Fe2O3 perpendicularly aligned direction (13.18 emu/g) and random direction (10.73 emu/g). Urea synthesis was done under magnetic field ranges from 0.0 to 2.5 T. The activation energy of α-Fe2O3 NWs for urea production is lower than NPs in the range of 0-1 T, whereas it is reversed for higher magnetic induction values. Fourier transform infrared spectroscopy (FTIR) confirmed the formation of urea at the peaks of 1690-1600 cm-1. This green urea employing magnetically induced method could be a contender to the Haber-Bosch process currently used by the current industry which utilizes high temperature and high pressure.

  16. Carboxyl functionalization of carbon fibers via aryl diazonium reaction in molten urea to enhance interfacial shear strength

    NASA Astrophysics Data System (ADS)

    Wang, Yuwei; Meng, Linghui; Fan, Liquan; Wu, Guangshun; Ma, Lichun; Zhao, Min; Huang, Yudong

    2016-01-01

    Using molten urea as the solvent, carbon fibers were functionalized with carboxylic acid groups via aryl diazonium reaction in 15 min to improve their interfacial bonding with epoxy resin. The surface functionalization was quantified by X-ray photoelectron spectroscopy, which showed that the relative surface coverage of carboxylic acid groups increased from an initial percentage of 3.17-10.41%. Mechanical property test results indicated that the aryl diazonium reaction in this paper could improve the interfacial shear strength by 66%. Meanwhile, the technique did not adopt any pre-oxidation step to produce functional groups prior to grafting and was shown to maintain the tensile strength of the fibers. This methodology provided a rapid, facile and economically viable route to produce covalently functionalized carbon fibers in large quantities with an eco-friendly method.

  17. Modelling and mutational analysis of Aspergillus nidulans UreA, a member of the subfamily of urea/H+ transporters in fungi and plants

    PubMed Central

    Sanguinetti, Manuel; Amillis, Sotiris; Pantano, Sergio; Scazzocchio, Claudio; Ramón, Ana

    2014-01-01

    We present the first account of the structure–function relationships of a protein of the subfamily of urea/H+ membrane transporters of fungi and plants, using Aspergillus nidulans UreA as a study model. Based on the crystal structures of the Vibrio parahaemolyticus sodium/galactose symporter (vSGLT) and of the Nucleobase-Cation-Symport-1 benzylhydantoin transporter from Microbacterium liquefaciens (Mhp1), we constructed a three-dimensional model of UreA which, combined with site-directed and classical random mutagenesis, led to the identification of amino acids important for UreA function. Our approach allowed us to suggest roles for these residues in the binding, recognition and translocation of urea, and in the sorting of UreA to the membrane. Residues W82, Y106, A110, T133, N275, D286, Y388, Y437 and S446, located in transmembrane helixes 2, 3, 7 and 11, were found to be involved in the binding, recognition and/or translocation of urea and the sorting of UreA to the membrane. Y106, A110, T133 and Y437 seem to play a role in substrate selectivity, while S446 is necessary for proper sorting of UreA to the membrane. Other amino acids identified by random classical mutagenesis (G99, R141, A163, G168 and P639) may be important for the basic transporter's structure, its proper folding or its correct traffic to the membrane. PMID:24966243

  18. 49 CFR 172.544 - COMBUSTIBLE placard.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false COMBUSTIBLE placard. 172.544 Section 172.544... SECURITY PLANS Placarding § 172.544 COMBUSTIBLE placard. (a) Except for size and color, the COMBUSTIBLE... on the COMBUSTIBLE placard must be red. The symbol, text, class number and inner border must be...

  19. Protocol independent adaptive route update for VANET.

    PubMed

    Rasheed, Asim; Ajmal, Sana; Qayyum, Amir

    2014-01-01

    High relative node velocity and high active node density have presented challenges to existing routing approaches within highly scaled ad hoc wireless networks, such as Vehicular Ad hoc Networks (VANET). Efficient routing requires finding optimum route with minimum delay, updating it on availability of a better one, and repairing it on link breakages. Current routing protocols are generally focused on finding and maintaining an efficient route, with very less emphasis on route update. Adaptive route update usually becomes impractical for dense networks due to large routing overheads. This paper presents an adaptive route update approach which can provide solution for any baseline routing protocol. The proposed adaptation eliminates the classification of reactive and proactive by categorizing them as logical conditions to find and update the route.

  20. Protocol Independent Adaptive Route Update for VANET

    PubMed Central

    Rasheed, Asim; Qayyum, Amir

    2014-01-01

    High relative node velocity and high active node density have presented challenges to existing routing approaches within highly scaled ad hoc wireless networks, such as Vehicular Ad hoc Networks (VANET). Efficient routing requires finding optimum route with minimum delay, updating it on availability of a better one, and repairing it on link breakages. Current routing protocols are generally focused on finding and maintaining an efficient route, with very less emphasis on route update. Adaptive route update usually becomes impractical for dense networks due to large routing overheads. This paper presents an adaptive route update approach which can provide solution for any baseline routing protocol. The proposed adaptation eliminates the classification of reactive and proactive by categorizing them as logical conditions to find and update the route. PMID:24723807

  1. Effect of urea on protein separation by ion-exchange chromatography.

    PubMed

    Khademi, Fatemeh; Mostafaie, Ali

    2010-05-01

    Ion-exchange chromatography (IEC) is the most frequently used chromatographic technique for the separation of proteins and peptides. In this article, the effects of urea on IEC separation of kiwifruit actinidin, egg white and urinary proteins were examined. The purity and relative amount of each protein in different conditions (in the presence or absence of urea) were compared with each other. The three parameters, including resolution, selectivity and efficiency of column in the presence of urea, were calculated and compared with the absence of urea. The results revealed that urea improved the purity of proteins and the resolution, selectivity and efficiency of IEC in separation of studied proteins.

  2. Chelate effects in sulfate binding by amide/urea-based ligands.

    PubMed

    Jia, Chuandong; Wang, Qi-Qiang; Begum, Rowshan Ara; Day, Victor W; Bowman-James, Kristin

    2015-07-07

    The influence of chelate and mini-chelate effects on sulfate binding was explored for six amide-, amide/amine-, urea-, and urea/amine-based ligands. Two of the urea-based hosts were selective for SO4(2-) in water-mixed DMSO-d6 systems. Results indicated that the mini-chelate effect provided by a single urea group with two NH binding sites appears to provide enhanced binding over two amide groups. Furthermore, additional urea binding sites incorporated into the host framework appeared to overcome to some extent competing hydration effects with increasing water content.

  3. Salting-Out of Methane in the Aqueous Solutions of Urea and Glycine-Betaine.

    PubMed

    Dixit, Mayank Kumar; Siddique, Asrar A; Tembe, B L

    2015-08-27

    We have studied the hydrophobic association and solvation of methane molecules in aqueous solutions of urea and glycine betaine (GB). We have calculated the potentials of mean force (PMFs) between methane molecules in water, aqueous GB, aqueous urea and aqueous urea-GB mixtures. The PMFs and equilibrium constants indicate that both urea and GB increase the hydrophobic association of methane. Calculation of thermodynamic parameters shows that the association of methane is stabilized by entropy whereas solvation is favored by enthalpy. In the case of the water-urea-GB mixture, both hydrophobic association and solvation are stabilized by entropy. From the investigation of radial distribution functions, running coordination numbers and excess coordination numbers, we infer that both urea and GB are preferentially excluded from methane surface in the mixtures of osmolytes and methane is preferentially solvated by water molecules in all the mixtures. The favorable exclusion of both urea and GB from the methane surface suggests that both urea and GB increase the interaction between methane molecules, i.e., salting-out of methane. We observe that addition of both urea and GB to water enhances local water structure. The calculated values of diffusion constants of water also suggest enhanced water-water interactions in the presence of urea and GB. The calculated free energies of methane in these mixtures show that methane is less soluble in the mixtures of urea and GB than in water. The data on solvation free energies support the observations obtained from the PMFs of methane molecules.

  4. Polar or apolar--the role of polarity for urea-induced protein denaturation.

    PubMed

    Stumpe, Martin C; Grubmüller, Helmut

    2008-11-01

    Urea-induced protein denaturation is widely used to study protein folding and stability; however, the molecular mechanism and driving forces of this process are not yet fully understood. In particular, it is unclear whether either hydrophobic or polar interactions between urea molecules and residues at the protein surface drive denaturation. To address this question, here, many molecular dynamics simulations totalling ca. 7 micros of the CI2 protein in aqueous solution served to perform a computational thought experiment, in which we varied the polarity of urea. For apolar driving forces, hypopolar urea should show increased denaturation power; for polar driving forces, hyperpolar urea should be the stronger denaturant. Indeed, protein unfolding was observed in all simulations with decreased urea polarity. Hyperpolar urea, in contrast, turned out to stabilize the native state. Moreover, the differential interaction preferences between urea and the 20 amino acids turned out to be enhanced for hypopolar urea and suppressed (or even inverted) for hyperpolar urea. These results strongly suggest that apolar urea-protein interactions, and not polar interactions, are the dominant driving force for denaturation. Further, the observed interactions provide a detailed picture of the underlying molecular driving forces. Our simulations finally allowed characterization of CI2 unfolding pathways. Unfolding proceeds sequentially with alternating loss of secondary or tertiary structure. After the transition state, unfolding pathways show large structural heterogeneity.

  5. Choline chloride/urea as an effective plasticizer for production of cellulose films.

    PubMed

    Wang, Sha; Peng, Xinwen; Zhong, Linxin; Jing, Shuangshuang; Cao, Xuefei; Lu, Fachuang; Sun, Runcang

    2015-03-06

    Recently, choline chloride/urea (ChCl/urea), a typical deep eutectic solvent (DES), has been found to possess various applications in organic synthesis, electrochemistry, and nanomaterial preparation. Herein we reported the first attempt to plasticize regenerated cellulose film (RCF) using ChCl/urea as an effective plasticizer. Meanwhile, RCFs plasticized with glycerol and sorbitol were also prepared for comparison. The plasticized RCFs were investigated by Fourier transform infrared (FT-IR) spectroscopy, wide-angle X-ray diffraction (XRD), atomic force microscopy (AFM), and mechanical testing. Transparent and soft RCFs could be successfully prepared in the presence of ChCl/urea, and high elongation at break (34.88%) suggested a significant plasticizing efficiency. No new crystal and phase separation occurred to ChCl/urea plasticized RCFs. The thermal stability of ChCl/urea plasticized RCF was lowered. These results indicated that ChCl/urea was an effective plasticizer for producing cellulose films.

  6. Piezoelectric urea biosensor based on immobilization of urease onto nanoporous alumina membranes.

    PubMed

    Yang, Zhengpeng; Si, Shihui; Dai, Hongjuan; Zhang, Chunjing

    2007-06-15

    The urease was immobilized onto nanoporous alumina membranes prepared by the two-step anodization method, and a novel piezoelectric urea sensing system with separated porous alumina/urease electrode has been developed through measuring the conductivity change of immobilized urease/urea reaction. The process of urease immobilization was optimized and the performance of the developed urea biosensor was evaluated. The obtained urea biosensor presented high-selectivity monitoring of urea, better reproducibility (S.D.=0.02, n=6), shorter response time (30s), wider linear range (0.5 microM to 3mM), lower detection limit (0.2 microM) and good long-term storage stability (with about 76% of the enzymatic activity retained after 30 days). The clinical analysis of the urea biosensor confirmed the feasibility of urea detection in urine samples.

  7. A self assembled monolayer based microfluidic sensor for urea detection

    NASA Astrophysics Data System (ADS)

    Srivastava, Saurabh; Solanki, Pratima R.; Kaushik, Ajeet; Ali, Md. Azahar; Srivastava, Anchal; Malhotra, B. D.

    2011-07-01

    Urease (Urs) and glutamate dehydrogenase (GLDH) have been covalently co-immobilized onto a self-assembled monolayer (SAM) comprising of 10-carboxy-1-decanthiol (CDT) via EDC-NHS chemistry deposited onto one of the two patterned gold (Au) electrodes for estimation of urea using poly(dimethylsiloxane) based microfluidic channels (2 cm × 200 μm × 200 μm). The CDT/Au and Urs-GLDH/CDT/Au electrodes have been characterized using Fourier transform infrared (FTIR) spectroscopy, contact angle (CA), atomic force microscopy (AFM) and electrochemical cyclic voltammetry (CV) techniques. The electrochemical response measurement of a Urs-GLDH/CDT/Au bioelectrode obtained as a function of urea concentration using CV yield linearity as 10 to 100 mg dl-1, detection limit as 9 mg dl-1 and high sensitivity as 7.5 μA mM-1 cm-2.

  8. Flameless Combustion for Gas Turbines

    NASA Astrophysics Data System (ADS)

    Gutmark, Ephraim; Li, Guoqiang; Overman, Nick; Cornwell, Michael; Stankovic, Dragan; Fuchs, Laszlo; Milosavljevic, Vladimir

    2006-11-01

    An experimental study of a novel flameless combustor for gas turbine engines is presented. Flameless combustion is characterized by distributed flame and even temperature distribution for high preheat air temperature and large amount of recirculating low oxygen exhaust gases. Extremely low emissions of NOx, CO, and UHC are reported. Measurements of the flame chemiluminescence, CO and NOx emissions, acoustic pressure, temperature and velocity fields as a function of the preheat temperature, inlet air mass flow rate, exhaust nozzle contraction ratio, and combustor chamber diameter are described. The data indicate that larger pressure drop promotes flameless combustion and low NOx emissions at the same flame temperature. High preheated temperature and flow rates also help in forming stable combustion and therefore are favorable for flameless combustion.

  9. Putting combustion optimization to work

    SciTech Connect

    Spring, N.

    2009-05-15

    New plants and plants that are retrofitting can benefit from combustion optimization. Boiler tuning and optimization can complement each other. The continuous emissions monitoring system CEMS, and tunable diode laser absorption spectroscopy TDLAS can be used for optimisation. NeuCO's CombustionOpt neural network software can determine optimal fuel and air set points. Babcock and Wilcox Power Generation Group Inc's Flame Doctor can be used in conjunction with other systems to diagnose and correct coal-fired burner performance. The four units of the Colstrip power plant in Colstrips, Montana were recently fitted with combustion optimization systems based on advanced model predictive multi variable controls (MPCs), ABB's Predict & Control tool. Unit 4 of Tampa Electric's Big Bend plant in Florida is fitted with Emerson's SmartProcess fuzzy neural model based combustion optimisation system. 1 photo.

  10. Thermophysics Characterization of Kerosene Combustion

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See

    2001-01-01

    A one-formula surrogate fuel formulation and its quasi-global combustion kinetics model are developed to support the design of injectors and thrust chambers of kerosene-fueled rocket engines. This surrogate fuel model depicts a fuel blend that properly represents the general physical and chemical properties of kerosene. The accompanying gaseous-phase thermodynamics of the surrogate fuel is anchored with the heat of formation of kerosene and verified by comparing a series of one-dimensional rocket thrust chamber calculations. The quasi-global combustion kinetics model consists of several global steps for parent fuel decomposition, soot formation, and soot oxidation and a detailed wet-CO mechanism to complete the combustion process. The final thermophysics formulations are incorporated with a computational fluid dynamics model for prediction of the combustion efficiency of an unielement, tripropellant combustor and the radiation of a kerosene-fueled thruster plume. The model predictions agreed reasonably well with those of the tests.

  11. Loop-bed combustion apparatus

    DOEpatents

    Shang, Jer-Yu; Mei, Joseph S.; Slagle, Frank D.; Notestein, John E.

    1984-01-01

    The present invention is directed to a combustion apparatus in the configuration of a oblong annulus defining a closed loop. Particulate coal together with a sulfur sorbent such as sulfur or dolomite is introduced into the closed loop, ignited, and propelled at a high rate of speed around the loop. Flue gas is withdrawn from a location in the closed loop in close proximity to an area in the loop where centrifugal force imposed upon the larger particulate material maintains these particulates at a location spaced from the flue gas outlet. Only flue gas and smaller particulates resulting from the combustion and innerparticle grinding are discharged from the combustor. This structural arrangement provides increased combustion efficiency due to the essentially complete combustion of the coal particulates as well as increased sulfur absorption due to the innerparticle grinding of the sorbent which provides greater particle surface area.

  12. Fifth International Microgravity Combustion Workshop

    NASA Technical Reports Server (NTRS)

    Sacksteder, Kurt (Compiler)

    1999-01-01

    This conference proceedings document is a compilation of 120 papers presented orally or as poster displays to the Fifth International Microgravity Combustion Workshop held in Cleveland, Ohio on May 18-20, 1999. The purpose of the workshop is to present and exchange research results from theoretical and experimental work in combustion science using the reduced-gravity environment as a research tool. The results are contributed by researchers funded by NASA throughout the United States at universities, industry and government research agencies, and by researchers from at least eight international partner countries that are also participating in the microgravity combustion science research discipline. These research results are intended for use by public and private sector organizations for academic purposes, for the development of technologies needed for the Human Exploration and Development of Space, and to improve Earth-bound combustion and fire-safety related technologies.

  13. Combustion Science for Cleaner Fuels

    SciTech Connect

    Ahmed, Musahid

    2014-10-17

    Musahid Ahmed discusses how he and his team use the Advanced Light Source (ALS) to study combustion chemistry at our '8 Big Ideas' Science at the Theater event on October 8th, 2014, in Oakland, California.

  14. Combustion Science for Cleaner Fuels

    ScienceCinema

    Ahmed, Musahid

    2016-07-12

    Musahid Ahmed discusses how he and his team use the Advanced Light Source (ALS) to study combustion chemistry at our '8 Big Ideas' Science at the Theater event on October 8th, 2014, in Oakland, California.

  15. Sixth International Microgravity Combustion Workshop

    NASA Technical Reports Server (NTRS)

    Sacksteder, Kurt (Compiler)

    2001-01-01

    This conference proceedings document is a compilation of papers presented orally or as poster displays to the Sixth International Microgravity Combustion Workshop held in Cleveland, Ohio on May 22-24, 2001. The purpose of the workshop is to present and exchange research results from theoretical and experimental work in combustion science using the reduced-gravity environment as a research tool. The results are contributed by researchers funded by NASA throughout the United States at universities, industry and government research agencies, and by researchers from international partner countries that are also participating in the microgravity combustion science research discipline. These research results are intended for use by public and private sector organizations for academic purposes, for the development of technologies needed for Human Exploration and Development of Space, and to improve Earth-bound combustion and fire-safety related technologies.

  16. Antimicrobial activities of N-chloramines and diazolidinyl urea.

    PubMed Central

    Llabres, C M; Ahearn, D G

    1985-01-01

    A combination of MICs of an N-chloramine, a simple chlorinated amino acid, and diazolidinyl urea gave synergistic activity against bacteria, but not fungi. The two compounds at a higher concentration, 0.1 and 0.3%, respectively, gave synergistic inhibition of fungi; kill times were 1 h for Trichophyton tonsurans, 3 h for Aspergillus niger and Fusarium moniliforme, and 6 h for Aspergillus fumigatus. PMID:3920962

  17. Growth of urea crystals by physical vapor transport

    NASA Technical Reports Server (NTRS)

    Feigelson, R. S.; Route, R. K.; Kao, T.-M.

    1985-01-01

    This work demonstrates that high optical quality crystals of urea can be grown by the physical vapor transport method. The unique features of this method are compared with growth from methanol/water solutions. High growth rates, exceeding 2.5 mm/day, were achieved, and cm-size optical quality single crystals were obtained. Details of the growth technique and the physical properties of the crystals are presented.

  18. Reverse osmosis membrane of high urea rejection properties. [water purification

    NASA Technical Reports Server (NTRS)

    Johnson, C. C.; Wydeven, T. J. (Inventor)

    1980-01-01

    Polymeric membranes suitable for use in reverse osmosis water purification because of their high urea and salt rejection properties are prepared by generating a plasma of an unsaturated hydrocarbon monomer and nitrogen gas from an electrical source. A polymeric membrane is formed by depositing a polymer of the unsaturated monomer from the plasma onto a substrate, so that nitrogen from the nitrogen gas is incorporated within the polymer in a chemically combined form.

  19. Initial supersonic combustion facility measurements

    NASA Technical Reports Server (NTRS)

    Krauss, Roland H.; Whitehurst, R. Bradford, III; Abitt, John D., III; Segal, Corin; Mcdaniel, James C.

    1989-01-01

    A combustion test tunnel designed for continuous operation to 2000 K was assembled. Flow quality of a Mach 2 nozzle for use with this tunnel was examined using an array of impact probes. The performance of gas shields used to protect optical windows was examined using both shadowgraphs and planar laser induced iodine fluorescence. High speed videography was used to aid in design of pressure relief panels related to hydrogen combustion testing safety.

  20. Smoldering Combustion Experiments in Microgravity

    NASA Technical Reports Server (NTRS)

    Walther, David C.; Fernandez-Pello, A. Carlos; Urban, David L.

    1997-01-01

    The Microgravity Smoldering Combustion (MSC) experiment is part of a study of the smolder characteristics of porous combustible materials in a microgravity environment. Smoldering is a non-flaming form of combustion that takes place in the interior of porous materials and takes place in a number of processes ranging from smoldering of porous insulation materials to high temperature synthesis of metals. The objective of the study is to provide a better understanding of the controlling mechanisms of smolder, both in microgravity and normal-gravity. As with many forms of combustion, gravity affects the availability of oxidizer and transport of heat, and therefore the rate of combustion. Microgravity smolder experiments, in both a quiescent oxidizing environment, and in a forced oxidizing flow have been conducted aboard the NASA Space Shuttle (STS-69 and STS-77 missions) to determine the effect of the ambient oxygen concentration and oxidizer forced flow velocity on smolder combustion in microgravity. The experimental apparatus is contained within the NASA Get Away Special Canister (GAS-CAN) Payload. These two sets of experiments investigate the propagation of smolder along the polyurethane foam sample under both diffusion driven and forced flow driven smoldering. The results of the microgravity experiments are compared with identical ones carried out in normal gravity, and are used to verify present theories of smolder combustion. The results of this study will provide new insights into the smoldering combustion process. Thermocouple histories show that the microgravity smolder reaction temperatures (Ts) and propagation velocities (Us) lie between those of identical normal-gravity upward and downward tests. These observations indicate the effect of buoyancy on the transport of oxidizer to the reaction front.

  1. Lean premixed/prevaporized combustion

    NASA Technical Reports Server (NTRS)

    Lefebvre, A. H. (Editor)

    1977-01-01

    Recommendations were formulated on the status and application of lean premixed/prevaporized combustion to the aircraft gas turbine for the reduction of pollutant emissions. The approach taken by the NASA Stratospheric Cruise Emission Reduction Program (SCERP) in pursuing the lean premixed/prevaporized combustion technique was also discussed. The proceedings contains an overview of the SCERP program, the discussions and recommendations of the participants, and an overall summary.

  2. National Combustion Code: Parallel Performance

    NASA Technical Reports Server (NTRS)

    Babrauckas, Theresa

    2001-01-01

    This report discusses the National Combustion Code (NCC). The NCC is an integrated system of codes for the design and analysis of combustion systems. The advanced features of the NCC meet designers' requirements for model accuracy and turn-around time. The fundamental features at the inception of the NCC were parallel processing and unstructured mesh. The design and performance of the NCC are discussed.

  3. Modeling of microgravity combustion experiments

    NASA Technical Reports Server (NTRS)

    Buckmaster, John

    1995-01-01

    This program started in February 1991, and is designed to improve our understanding of basic combustion phenomena by the modeling of various configurations undergoing experimental study by others. Results through 1992 were reported in the second workshop. Work since that time has examined the following topics: Flame-balls; Intrinsic and acoustic instabilities in multiphase mixtures; Radiation effects in premixed combustion; Smouldering, both forward and reverse, as well as two dimensional smoulder.

  4. The Fluids and Combustion Facility

    NASA Technical Reports Server (NTRS)

    Kundu, Sampa

    2004-01-01

    Microgravity is an environment with very weak gravitational effects. The Fluids and Combustion Facility (FCF) on the International Space Station (ISS) will support the study of fluid physics and combustion science in a long-duration microgravity environment. The Fluid Combustion Facility's design will permit both independent and remote control operations from the Telescience Support Center. The crew of the International Space Station will continue to insert and remove the experiment module, store and reload removable data storage and media data tapes, and reconfigure diagnostics on either side of the optics benches. Upon completion of the Fluids Combustion Facility, about ten experiments will be conducted within a ten-year period. Several different areas of fluid physics will be studied in the Fluids Combustion Facility. These areas include complex fluids, interfacial phenomena, dynamics and instabilities, and multiphase flows and phase change. Recently, emphasis has been placed in areas that relate directly to NASA missions including life support, power, propulsion, and thermal control systems. By 2006 or 2007, a Fluids Integrated Rack (FIR) and a Combustion Integrated Rack (CIR) will be installed inside the International Space Station. The Fluids Integrated Rack will contain all the hardware and software necessary to perform experiments in fluid physics. A wide range of experiments that meet the requirements of the international space station, including research from other specialties, will be considered. Experiments will be contained in subsystems such as the international standard payload rack, the active rack isolation system, the optics bench, environmental subsystem, electrical power control unit, the gas interface subsystem, and the command and data management subsystem. In conclusion, the Fluids and Combustion Facility will allow researchers to study fluid physics and combustion science in a long-duration microgravity environment. Additional information is

  5. Effect of urea concentration on growth of Ureaplasma urealyticum (T-strain mycoplasma).

    PubMed

    Kenny, G E; Cartwright, F D

    1977-10-01

    The effect of urea on growth of Ureaplasma urealyticum type VIII was studied by cultivating the organisms in a dialysate broth, prepared from soy peptone and autoclaved yeast, supplemented with 5% dialyzed horse serum, 100 mM 2-(N-morpholino)ethane sulfonic acid buffer (pH 5.75), and defined amounts of urea. Without urea, growth did not occur. Total growth was directly related to urea concentration. The least amount of urea that supported growth was 0.032 mM, which resulted in 3 x 10(4) colony-forming units per ml. The maximum yield of organisms, 8.0 x 10(7) colony-forming units per ml, was observed at 32 mM urea. Growth was limited not only by urea concentration, but also by the buffer capacity of the medium. The maximum amount of 2-(N-morpholino)ethane sulfonic acid buffer that could be employed was 100 mM; at higher concentrations, growth was inhibited. The yield of U. urealyticum was small even in medium with 32 mM urea and 100 mM 2-(N-morpholino)ethane sulfonic acid buffer: 0.63 mg of protein per liter of culture containing 5 x 10(10) total colony-forming units. The molar growth yield was 20 mg of protein per mol of urea. The growth rate was also a function of urea concentration. Generation times ranged from 8 h at 0.032 mM urea to 1.6 h at 3.2 mM urea, where the substrate level was saturating. The K(s) value for growth was 2.0 x 10(-4) M urea. Thus, urea is a growth-limiting factor for U. urealyticum, but remarkably large amounts of this substrate are required.

  6. UREA TRANSPORT BY HEPATOCYTES AND RED BLOOD CELLS OF SELECTED ELASMOBRANCH AND TELEOST FISHES

    PubMed

    Walsh; Wood; Perry; Thomas

    1994-08-01

    Although urea transport is receiving increased attention in mammalian systems, very little is known about urea transport in fish tissues. This study examined mechanisms of urea transport in red blood cells and hepatocytes from the lesser spotted dogfish (Scyliorhinus canicula), Atlantic stingray (Dasyatis sabina), turbot (Scopthalmus maximus), redfish (Scianops ocellatus), gulf toadfish (Opsanus beta) and oyster toadfish (Opsanus tau). Urea appeared to be passively distributed in both tissues (i.e. there was no difference between plasma and tissue urea concentrations). Additionally, a number of in vitro experiments examining [14C]urea flux were performed. In red blood cells from all species except redfish, urea transport occurred via simple passive diffusion, but redfish red blood cells showed a small (25 %) phloretin-sensitive uptake component. In hepatocytes of the two elasmobranch species (dogfish and stingray), urea efflux was also by simple passive diffusion. However, urea efflux in toadfish (both O. beta and O. tau) hepatocytes exhibited a marked phloretin-sensitivity, and O. beta hepatocytes were used in further experiments with other inhibitors and treatments. Urea transport in O. beta had a relatively high specificity for urea compared with the urea analogues acetamide, thiourea and N-methylurea, was unaffected by phloridzin and extracellular Na+ removal, and was not inhibited by physiological levels of glucose (0.5­10 mmol l-1). A phloretin-sensitive glucose transport, that was not inhibited by physiological levels of urea, was discovered in O. beta hepatocytes. The results are discussed in terms of patterns of species distribution and similarities between urea and glucose transport.

  7. Developing Hypothetical Inhibition Mechanism of Novel Urea Transporter B Inhibitor

    NASA Astrophysics Data System (ADS)

    Li, Min; Tou, Weng Ieong; Zhou, Hong; Li, Fei; Ren, Huiwen; Chen, Calvin Yu-Chian; Yang, Baoxue

    2014-07-01

    Urea transporter B (UT-B) is a membrane channel protein that specifically transports urea. UT-B null mouse exhibited urea selective urine concentrating ability deficiency, which suggests the potential clinical applications of the UT-B inhibitors as novel diuretics. Primary high-throughput virtual screening (HTVS) of 50000 small-molecular drug-like compounds identified 2319 hit compounds. These 2319 compounds were screened by high-throughput screening using an erythrocyte osmotic lysis assay. Based on the pharmacological data, putative UT-B binding sites were identified by structure-based drug design and validated by ligand-based and QSAR model. Additionally, UT-B structural and functional characteristics under inhibitors treated and untreated conditions were simulated by molecular dynamics (MD). As the result, we identified four classes of compounds with UT-B inhibitory activity and predicted a human UT-B model, based on which computative binding sites were identified and validated. A novel potential mechanism of UT-B inhibitory activity was discovered by comparing UT-B from different species. Results suggest residue PHE198 in rat and mouse UT-B might block the inhibitor migration pathway. Inhibitory mechanisms of UT-B inhibitors and the functions of key residues in UT-B were proposed. The binding site analysis provides a structural basis for lead identification and optimization of UT-B inhibitors.

  8. Antibacterial kaolinite/urea/chlorhexidine nanocomposites: Experiment and molecular modelling

    NASA Astrophysics Data System (ADS)

    Holešová, Sylva; Valášková, Marta; Hlaváč, Dominik; Madejová, Jana; Samlíková, Magda; Tokarský, Jonáš; Pazdziora, Erich

    2014-06-01

    Clay minerals are commonly used materials in pharmaceutical production both as inorganic carriers or active agents. The purpose of this study is the preparation and characterization of clay/antibacterial drug hybrids which can be further included in drug delivery systems for treatment oral infections. Novel nanocomposites with antibacterial properties were successfully prepared by ion exchange reaction from two types of kaolinite/urea intercalates and chlorhexidine diacetate. Intercalation compounds of kaolinite were prepared by reaction with solid urea in the absence of solvents (dry method) as well as with urea aqueous solution (wet method). The antibacterial activity of two prepared samples against Enterococcus faecalis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa was evaluated by finding the minimum inhibitory concentration (MIC). Antibacterial studies of both samples showed the lowest MIC values (0.01%, w/v) after 1 day against E. faecalis, E. coli and S. aureus. A slightly worse antibacterial activity was observed against P. aeruginosa (MIC 0.12%, w/v) after 1 day. Since samples showed very good antibacterial activity, especially after 1 day of action, this means that these samples can be used as long-acting antibacterial materials. Prepared samples were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The experimental data are supported by results of molecular modelling.

  9. Influence of papain urea copper chlorophyllin on wound matrix remodeling.

    PubMed

    Telgenhoff, Dale; Lam, Kan; Ramsay, Sarah; Vasquez, Valerie; Villareal, Kristine; Slusarewicz, Paul; Attar, Paul; Shroot, Braham

    2007-01-01

    The purpose of this study was to examine the dermal and epidermal alterations associated with wound healing in wounds treated with papain urea copper chlorophyllin (PUC), papain-urea, copper chlorophyllin, or urea base ointment and compare these with moist wound care using a porcine full-thickness infected wound model. All the wounds were evaluated postsurgery for erythema, transepidermal water loss, microscopic morphology, and changes in protein expression. Examination of stained paraffin sections revealed an increase in the number of keratinocytes present in the epidermis of the PUC and papain-treated pigs, relative to moist control. This increase in keratinocyte number corresponded to an increase in the movement of the keratinocytes into the underlying dermis in the form of rete pegs. In the dermis, there appeared to be an increase in blood vessel formation, collagen I deposition, and mature collagen in the papain and PUC treated tissues. The quality of healing appears to be enhanced based on the number of keratinocytes present in the epidermis, the extensive rete peg formation, the increase in vasculature, and the increase in collagen birefringence.

  10. Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite

    PubMed Central

    Das, Gautam; Yoon, Hyon Hee

    2015-01-01

    An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm−2·mM−1. The biosensor achieved a broad linear range of detection (0.12–12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection. PMID:26346240

  11. Developing Hypothetical Inhibition Mechanism of Novel Urea Transporter B Inhibitor

    PubMed Central

    Li, Min; Tou, Weng Ieong; Zhou, Hong; Li, Fei; Ren, Huiwen; Chen, Calvin Yu-Chian; Yang, Baoxue

    2014-01-01

    Urea transporter B (UT-B) is a membrane channel protein that specifically transports urea. UT-B null mouse exhibited urea selective urine concentrating ability deficiency, which suggests the potential clinical applications of the UT-B inhibitors as novel diuretics. Primary high-throughput virtual screening (HTVS) of 50000 small-molecular drug-like compounds identified 2319 hit compounds. These 2319 compounds were screened by high-throughput screening using an erythrocyte osmotic lysis assay. Based on the pharmacological data, putative UT-B binding sites were identified by structure-based drug design and validated by ligand-based and QSAR model. Additionally, UT-B structural and functional characteristics under inhibitors treated and untreated conditions were simulated by molecular dynamics (MD). As the result, we identified four classes of compounds with UT-B inhibitory activity and predicted a human UT-B model, based on which computative binding sites were identified and validated. A novel potential mechanism of UT-B inhibitory activity was discovered by comparing UT-B from different species. Results suggest residue PHE198 in rat and mouse UT-B might block the inhibitor migration pathway. Inhibitory mechanisms of UT-B inhibitors and the functions of key residues in UT-B were proposed. The binding site analysis provides a structural basis for lead identification and optimization of UT-B inhibitors. PMID:25047372

  12. Amperometric urea biosensors based on sulfonated graphene/polyaniline nanocomposite.

    PubMed

    Das, Gautam; Yoon, Hyon Hee

    2015-01-01

    An electrochemical biosensor based on sulfonated graphene/polyaniline nanocomposite was developed for urea analysis. Oxidative polymerization of aniline in the presence of sulfonated graphene oxide was carried out by electrochemical methods in an aqueous environment. The structural properties of the nanocomposite were characterized by Fourier-transform infrared, Raman spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscopy techniques. The urease enzyme-immobilized sulfonated graphene/polyaniline nanocomposite film showed impressive performance in the electroanalytical detection of urea with a detection limit of 0.050 mM and a sensitivity of 0.85 (μA · cm(-2)·mM(-1). The biosensor achieved a broad linear range of detection (0.12-12.3 mM) with a notable response time of approximately 5 seconds. Moreover, the fabricated biosensor retained 81% of its initial activity (based on sensitivity) after 15 days of storage at 4°C. The ease of fabrication coupled with the low cost and good electrochemical performance of this system holds potential for the development of solid-state biosensors for urea detection.

  13. Catalytic combustion with steam injection

    NASA Technical Reports Server (NTRS)

    Anderson, D. N.; Tacina, R. R.

    1982-01-01

    The effects of steam injection on (1) catalytic combustion performance, and (2) the tendency of residual fuel to burn in the premixing duct upstream of the catalytic reactor were determined. A petroleum residual, no. 2 diesel, and a blend of middle and heavy distillate coal derived fuels were tested. Fuel and steam were injected together into the preheated airflow entering a 12 cm diameter catalytic combustion test section. The inlet air velocity and pressure were constant at 10 m/s and 600 kPa, respectively. Steam flow rates were varied from 24 percent to 52 percent of the air flow rate. The resulting steam air mixture temperatures varied from 630 to 740 K. Combustion temperatures were in the range of 1200 to 1400 K. The steam had little effect on combustion efficiency or emissions. It was concluded that the steam acts as a diluent which has no adverse effect on catalytic combustion performance for no. 2 diesel and coal derived liquid fuels. Tests with the residual fuel showed that upstream burning could be eliminated with steam injection rates greater than 30 percent of the air flow rate, but inlet mixture temperatures were too low to permit stable catalytic combustion of this fuel.

  14. Aerovalve pulse combustion: Technical note

    SciTech Connect

    Richards, G.A.; Gemmen, R.S.; Narayanaswami, L.

    1994-07-01

    The authors present a mathematical model and an experimental investigation of aerodynamically valved pulse combustion. The model uses a control-volume approach to solve conservation laws in several regions of a pulse combustor. Mixing between the fresh charge and combustion products is modeled as a two-step process, with the mixing occurring slowly for a specified eddy time during each cycle, and then changing to a higher rate. Results of model simulations demonstrate that eddy time plays a significant role in determining the frequency and amplitude of combustion oscillation. The authors show that short eddy times produce steady, rather than pulsating, combustion. And they show that changes to the mixing process alter the temperature-species history of combustion gases in a manner that could prevent or promote the formation of nitrogen oxides, depending on specific mixing rates. The relatively simple control-volume approach used in this model allows rapid investigation of a wide range of geometric and operating parameters, and also defines characteristic length and time scales relevant to aerovalve pulse combustion. Experimental measurements compare favorably to model predictions. The authors place particular emphasis on time-averaged pressure differences through the combustor, which act as an indicator of pressure gain performance. They investigate both operating conditions and combustor geometry, and they show that a complex interaction between the inlet and exit flows of a combustor makes it difficult to produce general correlations among the various parameters. They use a scaling rule to produce a combustor geometry capable of producing pressure gain.

  15. Industrial Facility Combustion Energy Use

    DOE Data Explorer

    McMillan, Colin

    2016-08-01

    Facility-level industrial combustion energy use is calculated from greenhouse gas emissions data reported by large emitters (>25,000 metric tons CO2e per year) under the U.S. EPA's Greenhouse Gas Reporting Program (GHGRP, https://www.epa.gov/ghgreporting). The calculation applies EPA default emissions factors to reported fuel use by fuel type. Additional facility information is included with calculated combustion energy values, such as industry type (six-digit NAICS code), location (lat, long, zip code, county, and state), combustion unit type, and combustion unit name. Further identification of combustion energy use is provided by calculating energy end use (e.g., conventional boiler use, co-generation/CHP use, process heating, other facility support) by manufacturing NAICS code. Manufacturing facilities are matched by their NAICS code and reported fuel type with the proportion of combustion fuel energy for each end use category identified in the 2010 Energy Information Administration Manufacturing Energy Consumption Survey (MECS, http://www.eia.gov/consumption/manufacturing/data/2010/). MECS data are adjusted to account for data that were withheld or whose end use was unspecified following the procedure described in Fox, Don B., Daniel Sutter, and Jefferson W. Tester. 2011. The Thermal Spectrum of Low-Temperature Energy Use in the United States, NY: Cornell Energy Institute.

  16. Direct simulation of turbulent combustion

    NASA Technical Reports Server (NTRS)

    Poinsot, T. J.

    1990-01-01

    Understanding and modeling of turbulent combustion are key-problems in the computation of numerous practical systems. Because of the lack of analytical theories in this field and of the difficulty of performing precise experiments, direct simulation appears to be one of the most attractive tools to use in addressing this problem. The present work can be split into two parts: (1) Development and validation of a direct simulation method for turbulent combustion; (2) Applications of the method to premixed turbulent combustion problems. The goal of part 1 is to define and to test a numerical method for direct simulation of reacting flows. A high level of confidence should be attached to direct simulation results, and this can only be achieved through extensive validation tests. In part 2, direct simulation is used to address some of the many critical problems related to turbulent combustion. At the present time, I have limited this work to premixed combustion and considered only four basic issues: (1) The effect of pressure waves on flame propagation; (2) The interaction between flame fronts and vortices; (3) The influence of curvature on premixed flame fronts; and (4) The validation of flamelet models for premixed turbulent combustion.

  17. Combustion instability analysis

    NASA Technical Reports Server (NTRS)

    Chung, T. J.

    1990-01-01

    A theory and computer program for combustion instability analysis are presented. The basic theoretical foundation resides in the concept of entropy-controlled energy growth or decay. Third order perturbation expansion is performed on the entropy-controlled acoustic energy equation to obtain the first order integrodifferential equation for the energy growth factor in terms of the linear, second, and third order energy growth parameters. These parameters are calculated from Navier-Stokes solutions with time averages performed on as many Navier-Stokes time steps as required to cover at least one peak wave period. Applications are made for a 1-D Navier-Stokes solution for the Space Shuttle Main Engine (SSME) thrust chamber with cross section area variations taken into account. It is shown that instability occurs when the mean pressure is set at 2000 psi with 30 percent disturbances. Instability also arises when the mean pressure is set at 2935 psi with 20 percent disturbances. The system with mean pressures and disturbances more adverse that these cases were shown to be unstable.

  18. Internal combustion engine

    SciTech Connect

    Matsuura, M.; Nakamori, M.; Honda, S.; Ishida, Y.; Nakanishi, T.

    1988-05-03

    An internal combustion engine is described comprising: (a) an engine body having a chamber; (b) a crankshaft rotatably mounted on the engine body; (c) a camshaft rotatably mounted on the engine body; (d) an oil lubricated endless transmission member extended around and operatively engaged with the crankshaft and the camshaft, the endless transmission member being movable along a closed path of travel in the chamber; (e) a tensioner hanger comprising an upper hanger member detachably secured to the engine body and a lower hanger member secured at an upper portion thereof to the upper hanger member, the upper hanger member having oil passage means adapted to receive lubrication oil from the endless transmission member at an inlet and guide the oil downwardly therethrough to an outlet; (f) a hollow mounting member affixed at an upper portion thereof to a lower portion of the lower hanger member of the tensioner hanger; (g) a hydraulic lock mechanism comprising a hollow cylinder and a plunger slidably received in the cylinder to define a hydraulic chamber in the cylinder; (h) a replenishable oil reservoir defined by a funnel-shaped space between the mounting member and the cylinder for receiving oil from the oil passage means and for holding the oil received therein; and (i) a tensioner member movably attached to the engine body and operatively engaged with the plunger.

  19. Asymmetrical internal combustion engine

    SciTech Connect

    Barret, P.

    1983-03-08

    An internal combustion engine adapted to be powered by a burnable gaseous fuel includes one cylinder, first and second pistons reciprocally movable in the cylinder substantially in opposite directions, inlet and outlet valves for controlling the flow of the gaseous fuel into the cylinder, and the exhaust of the burnt fuel therefrom, respectively, and a linkage device connected to the pistons for converting the reciprocating movement thereof into a rotary movement. The linkage device includes change-of-rate-of-displacement devices for increasing the rate of velocity in the maximum acceleration range, and for reducing the rate of displacement in the maximum velocity range of one piston with respect to the other piston, first and second piston rods pivotably connected to the first and second pistons, respectively, first and second crankshafts pivotably connected to the first and second piston rods, rotatable about first and second axes disposed substantially parallel to, and displaced by a predetermined angle from one another, respectively, and a gear train coupling the first and second crankshafts to one another. The gear train includes first and second fixedly mounted gearwheels, first and second concentrically mounted gear wheels, and a position-shiftable coupling mechanism for coupling the first gear wheels and the second gear wheels to one another, respectively, and an engaging device for meshing the eccentrically mounted gear wheels with one another.

  20. Chemical Looping Combustion Kinetics

    SciTech Connect

    Edward Eyring; Gabor Konya

    2009-03-31

    One of the most promising methods of capturing CO{sub 2} emitted by coal-fired power plants for subsequent sequestration is chemical looping combustion (CLC). A powdered metal oxide such as NiO transfers oxygen directly to a fuel in a fuel reactor at high temperatures with no air present. Heat, water, and CO{sub 2} are released, and after H{sub 2}O condensation the CO{sub 2} (undiluted by N{sub 2}) is ready for sequestration, whereas the nickel metal is ready for reoxidation in the air reactor. In principle, these processes can be repeated endlessly with the original nickel metal/nickel oxide participating in a loop that admits fuel and rejects ash, heat, and water. Our project accumulated kinetic rate data at high temperatures and elevated pressures for the metal oxide reduction step and for the metal reoxidation step. These data will be used in computational modeling of CLC on the laboratory scale and presumably later on the plant scale. The oxygen carrier on which the research at Utah is focused is CuO/Cu{sub 2}O rather than nickel oxide because the copper system lends itself to use with solid fuels in an alternative to CLC called 'chemical looping with oxygen uncoupling' (CLOU).

  1. MUNICIPAL WASTE COMBUSTION ASSESSMENT ...

    EPA Pesticide Factsheets

    The report defines and characterizes types of medical waste, discusses the impacts of burning medical waste on combustor emissions, and outlines important handling and operating considerations. Facility-specific design, handling, and operating practiced are also discussed for municipal waste combustors (MWCs) that reportedly accept medical waste in the U.S., Europe, and Canada. nly very limited data are available on the emission impacts associated with the combustion of medical waste in MWGs. Especially lacking is information needed to fully evaluate the impacts on acid gas, dioxin, and metals emissions, as well as the design and operating requirements for complete destruction of solvents, cytotoxic chemicals, and pathogens. The EPA's Office of Air Quatity Planning and Standards is developing emission standards and guidelines for new and existing MWCs under Sections 111(b) and 111(d) of the Clean Air Act. In support of these regulatory development efforts, the Air and Energy Engineering Research Laboratory in EPA's Office of Research and Development has conducted an assessment to examine the incineration of medical waste in MWGs from an emission standpoint. Potential worker safety and health problems associated with handling of medical wastes and residues were also identified. information

  2. NASA Microgravity Combustion Science Program

    NASA Technical Reports Server (NTRS)

    King, Merrill K.

    1999-01-01

    Combustion has been a subject of increasingly vigorous scientific research for over a century, not surprising considering that combustion accounts for approximately 85% of the world's energy production and is a key element of many critical technologies used by contemporary society. Although combustion technology is vital to our standard of living, it also poses great challenges to maintaining a habitable environment. A major goal of combustion research is production of fundamental (foundational) knowledge that can be used in developing accurate simulations of complex combustion processes, replacing current "cut-and-try" approaches and allowing developers to improve the efficiency of combustion devices, to reduce the production of harmful emissions, and to reduce the incidence of accidental uncontrolled combustion. With full understanding of the physics and chemistry involved in a given combustion process, including details of the unit processes and their interactions, physically accurate models which can then be used for parametric exploration of new combustion domains via computer simulation can be developed, with possible resultant definition of radically different approaches to accomplishment of various combustion goals. Effects of gravitational forces on earth impede combustion studies more than they impede most other areas of science. The effects of buoyancy are so ubiquitous that we often do not appreciate the enormous negative impact that they have had on the rational development of combustion science. Microgravity offers potential for major gains in combustion science understanding in that it offers unique capability to establish the flow environment rather than having it dominated by uncontrollable (under normal gravity) buoyancy effects and, through this control, to extend the range of test conditions that can be studied. It cannot be emphasized too strongly that our program is dedicated to taking advantage of microgravity to untangle complications caused

  3. Industrial Combustion Technology Roadmap: A Technology Roadmap by and for the Industrial Combustion Community (1999)

    SciTech Connect

    none,

    1999-04-01

    Combustion system users and manufacturers joined forces in 1999 to develop the Industrial Combustion Technology Roadmap. The roadmap outlines R&D priorities for developing advanced, highly efficient combustion systems that U.S. industry will require in the future.

  4. Channel routing for VLSI layout

    NASA Astrophysics Data System (ADS)

    Schory, Michael

    1988-12-01

    Channel routing for VLSI layout is reviewed and a set of features required of an industrial channel router is defined. A channel router, CAR, was implemented, based on the Greedy and Detour routers. Integrated circuit design is discussed, with attention to the various channel routing problems and models. The major requirements for an industrial channel router to be integrated within general cells and standard cells routing environments are discussed and their fulfillment in CAR is considered. CAR comprises: the Greedy router functionality; the Detour router's obstacle, obstruction and switch box extensions; rectilinear channels; ports located not on standard and immediately surrounding layers; middle ports within the channel; jog on conflict-only to reduce jog use; single layer jogs; and partial pre-routing and dynamic layer optimization. Special features of CAR include: extension of the net definition with a short range tendency; definition of net preferred track; net visibility range in rectilinear channels; an extended area mechanism to deal with obstacles, rectilinear edges, pre-routing and ports on unusual layers; unified jog cost evaluation functions; unified, efficient jog selection; a general evaluation function for track worth; and a net connectivity part to control and handle split nets. Examples are presented of CAR operations.

  5. The Consistent Vehicle Routing Problem

    SciTech Connect

    Groer, Christopher S; Golden, Bruce; Edward, Wasil

    2009-01-01

    In the small package shipping industry (as in other industries), companies try to differentiate themselves by providing high levels of customer service. This can be accomplished in several ways, including online tracking of packages, ensuring on-time delivery, and offering residential pickups. Some companies want their drivers to develop relationships with customers on a route and have the same drivers visit the same customers at roughly the same time on each day that the customers need service. These service requirements, together with traditional constraints on vehicle capacity and route length, define a variant of the classical capacitated vehicle routing problem, which we call the consistent VRP (ConVRP). In this paper, we formulate the problem as a mixed-integer program and develop an algorithm to solve the ConVRP that is based on the record-to-record travel algorithm. We compare the performance of our algorithm to the optimal mixed-integer program solutions for a set of small problems and then apply our algorithm to five simulated data sets with 1,000 customers and a real-world data set with more than 3,700 customers. We provide a technique for generating ConVRP benchmark problems from vehicle routing problem instances given in the literature and provide our solutions to these instances. The solutions produced by our algorithm on all problems do a very good job of meeting customer service objectives with routes that have a low total travel time.

  6. Central East Pacific Flight Routing

    NASA Technical Reports Server (NTRS)

    Grabbe, Shon; Sridhar, Banavar; Kopardekar, Parimal; Cheng, Nadia

    2006-01-01

    With the introduction of the Federal Aviation Administration s Advanced Technology and Oceanic Procedures system at the Oakland Oceanic Center, a level of automation now exists in the oceanic environment to potentially begin accommodating increased user preferred routing requests. This paper presents the results of an initial feasibility assessment which examines the potential benefits of transitioning from the fixed Central East Pacific routes to user preferred routes. As a surrogate for the actual user-provided routing requests, a minimum-travel-time, wind-optimal dynamic programming algorithm was developed and utilized in this paper. After first describing the characteristics (e.g., origin airport, destination airport, vertical distribution and temporal distribution) of the westbound flights utilizing the Central East Pacific routes on Dec. 14-16 and 19-20, the results of both a flight-plan-based simulation and a wind-optimal-based simulation are presented. Whereas the lateral and longitudinal distribution of the aircraft trajectories in these two simulations varied dramatically, the number of simulated first-loss-of-separation events remained relatively constant. One area of concern that was uncovered in this initial analysis was a potential workload issue associated with the redistribution of traffic in the oceanic sectors due to thc prevailing wind patterns.

  7. Spherical combustion clouds in explosions

    NASA Astrophysics Data System (ADS)

    Kuhl, A. L.; Bell, J. B.; Beckner, V. E.; Balakrishnan, K.; Aspden, A. J.

    2013-05-01

    This study explores the properties of spherical combustion clouds in explosions. Two cases are investigated: (1) detonation of a TNT charge and combustion of its detonation products with air, and (2) shock dispersion of aluminum powder and its combustion with air. The evolution of the blast wave and ensuing combustion cloud dynamics are studied via numerical simulations with our adaptive mesh refinement combustion code. The code solves the multi-phase conservation laws for a dilute heterogeneous continuum as formulated by Nigmatulin. Single-phase combustion (e.g., TNT with air) is modeled in the fast-chemistry limit. Two-phase combustion (e.g., Al powder with air) uses an induction time model based on Arrhenius fits to Boiko's shock tube data, along with an ignition temperature criterion based on fits to Gurevich's data, and an ignition probability model that accounts for multi-particle effects on cloud ignition. Equations of state are based on polynomial fits to thermodynamic calculations with the Cheetah code, assuming frozen reactants and equilibrium products. Adaptive mesh refinement is used to resolve thin reaction zones and capture the energy-bearing scales of turbulence on the computational mesh (ILES approach). Taking advantage of the symmetry of the problem, azimuthal averaging was used to extract the mean and rms fluctuations from the numerical solution, including: thermodynamic profiles, kinematic profiles, and reaction-zone profiles across the combustion cloud. Fuel consumption was limited to ˜ 60-70 %, due to the limited amount of air a spherical combustion cloud can entrain before the turbulent velocity field decays away. Turbulent kinetic energy spectra of the solution were found to have both rotational and dilatational components, due to compressibility effects. The dilatational component was typically about 1 % of the rotational component; both seemed to preserve their spectra as they decayed. Kinetic energy of the blast wave decayed due to the

  8. Salting effects on protein components in aqueous NaCl and urea solutions: toward understanding of urea-induced protein denaturation.

    PubMed

    Li, Weifeng; Zhou, Ruhong; Mu, Yuguang

    2012-02-02

    The mechanism of urea-induced protein denaturation is explored through studying the salting effect of urea on 14 amino acid side chain analogues, and N-methylacetamide (NMA) which mimics the protein backbone. The solvation free energies of the 15 molecules were calculated in pure water, aqueous urea, and NaCl solutions. Our results show that NaCl displays strong capability to salt out all 15 molecules, while urea facilitates the solvation (salting-in) of all the 15 molecules on the other hand. The salting effect is found to be largely enthalpy-driven for both NaCl and urea. Our observations can explain the higher stability of protein's secondary and tertiary structures in typical salt solutions than that in pure water. Meanwhile, urea's capability to better solvate protein backbone and side-chain components can be extrapolated to explain protein's denaturation in aqueous urea solution. Urea salts in molecules through direct binding to solute surface, and the strength is linearly dependent on the number of heavy atoms of solute molecules. The van der Waals interactions are found to be the dominant force, which challenges a hydrogen-bonding-driven mechanism proposed previously.

  9. Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion

    NASA Astrophysics Data System (ADS)

    Zarur, Andrey J.; Ying, Jackie Y.

    2000-01-01

    Catalysts play an important role in many industrial processes, but their use in high-temperature applications-such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals-is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300°C. Here we use sol-gel processing in reverse microemulsions to produce discrete barium hexaaluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications.

  10. Reverse microemulsion synthesis of nanostructured complex oxides for catalytic combustion

    PubMed

    Zarur; Ying

    2000-01-06

    Catalysts play an important role in many industrial processes, but their use in high-temperature applications-such as energy generation through natural gas combustion, steam reforming and the partial oxidation of hydrocarbons to produce feedstock chemicals--is problematic. The need for catalytic materials that remain stable and active over long periods at high operation temperatures, often in the presence of deactivating or even poisoning compounds, presents a challenge. For example, catalytic methane combustion, which generates power with reduced greenhouse-gas and nitrogen-oxide emissions, is limited by the availability of catalysts that are sufficiently active at low temperatures for start-up and are then able to sustain activity and mechanical integrity at flame temperatures as high as 1,300 degrees C. Here we use sol-gel processing in reverse microemulsions to produce discrete barium hexa-aluminate nanoparticles that display excellent methane combustion activity, owing to their high surface area, high thermal stability and the ultrahigh dispersion of cerium oxide on the their surfaces. Our synthesis method provides a general route to the production of a wide range of thermally stable nanostructured composite materials with large surface-to-volume ratios and an ultrahigh component dispersion that gives rise to synergistic chemical and electronic effects, thus paving the way to the development of catalysts suitable for high-temperature industrial applications.

  11. Jet plume injection and combustion system for internal combustion engines

    DOEpatents

    Oppenheim, A.K.; Maxson, J.A.; Hensinger, D.M.

    1993-12-21

    An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure. 24 figures.

  12. Jet plume injection and combustion system for internal combustion engines

    DOEpatents

    Oppenheim, Antoni K.; Maxson, James A.; Hensinger, David M.

    1993-01-01

    An improved combustion system for an internal combustion engine is disclosed wherein a rich air/fuel mixture is furnished at high pressure to one or more jet plume generator cavities adjacent to a cylinder and then injected through one or more orifices from the cavities into the head space of the cylinder to form one or more turbulent jet plumes in the head space of the cylinder prior to ignition of the rich air/fuel mixture in the cavity of the jet plume generator. The portion of the rich air/fuel mixture remaining in the cavity of the generator is then ignited to provide a secondary jet, comprising incomplete combustion products which are injected into the cylinder to initiate combustion in the already formed turbulent jet plume. Formation of the turbulent jet plume in the head space of the cylinder prior to ignition has been found to yield a higher maximum combustion pressure in the cylinder, as well as shortening the time period to attain such a maximum pressure.

  13. Effect of undegradable intake protein supplementation on urea kinetics and microbial use of recycled urea in steers consuming low-quality forage.

    PubMed

    Wickersham, Tryon A; Titgemeyer, Evan C; Cochran, Robert C; Wickersham, Erin E

    2009-01-01

    We evaluated the effect of undegradable intake protein (UIP) on urea kinetics and microbial incorporation of urea-N in ruminally and duodenally fistulated steers (n 4; 319 kg) provided ad libitum access to grass hay in a 4 x 4 Latin square. Casein was continuously infused abomasally in amounts of 0, 62, 124 and 186 mg N/kg body weight per d to simulate provision of UIP. Periods were 13 d long with 7 d for adaptation and 6 d for collection. Jugular infusion of [15N15N]urea followed by determination of urinary enrichment of [15N15N]urea and [14N15N]urea was used to measure urea kinetics. Forage and N intake increased (quadratic, P<0.02) with increasing UIP. Urea synthesis was 27.1, 49.9, 82.2 and 85.8 g urea-N/d for 0, 62, 124 and 186 diets, respectively (linear, P<0.01). The proportion of urea synthesis that entered the gastrointestinal tract was 0.96 for steers receiving no UIP and decreased linearly (P=0.05) to a low of 0.89 for steers receiving 186. The amount of urea entering the gastrointestinal tract was least for 0 (26.3) and increased (linear, P<0.01) to 48.7, 77.2 and 76.6 g urea-N/d for 62, 124 and 186 diets, respectively. Microbial incorporation of recycled urea-N increased quadratically (P=0.04) from 13.9 for 0 to 47.7 g N/d for 124. The proportion of microbial N derived from recycled urea increased (quadratic, P=0.05) from 0.31 to 0.58 between 0 and 124 and dropped to 0.44 for 186 mg N/kg body weight per d. UIP increased intake of hay and provided a N source for ruminal microbes via urea recycling.

  14. Engine combustion control responsive to location and magnitude of peak combustion pressure

    SciTech Connect

    Tombley, D.E.

    1987-11-17

    A combustion control is described for an internal combustion engine of the type having combustion chambers, means for supplying a combustible charge to and igniting the combustible charge within each combustion chamber, power output apparatus including a rotating crankshaft, and means for sensing the crankshaft angle (LPP) and magnitude (MPP) of peak combustion pressure for each combustion chamber. The combustion control consists of: means for deriving the average magnitude of peak combustion pressure (AMPP); means for determining base values; memory means for storing tables of LPP ignition trim values, MPP ignition trim values and A/F trim values for each combustion chamber; means for comparing the sensed LPP value for each combustion chamber with a desired LPP value (DLPP) for that combustion chamber and adjusting the LPP ignition trim value for the predetermined engine operating parameters; means for comparing the MPP value for each combustion chamber with the average magnitude of peak combustion pressure; means to adjust the A/F trim value in the rich direction and reset the MPP ignition trim value; means to adjust the MPP ignition trim value in the advance direction; means to adjust the A/F trim value in the lean direction and reset the MPP ignition trim value; means for determining the combustible charge mixture for each combustion chamber from the base value thereof and the A/F trim value for the sensed predetermined engine operating parameters; means for determining the ignition timing for each combustion.

  15. Trends in the spin combustion of thermites

    SciTech Connect

    Dvoryankin, A.V.; Merzhanov, A.G.; Strunina, A.G.

    1982-09-01

    This article presents results on the main laws of spin combustion for thermite compositions. Examines the combustion in various thermite systems with various degrees of component dilution with reaction products in order to choose the objects. Discusses effects of external factors, effects of system parameters, and temperature distribution in spin combustion. Finds that oscillatory combustion (synchronous pulsation in the combustion rate at all points on the front) and spin modes (spiral displacement of a luminous focus) are separated by a combustion mode in the form of a set of luminous points moving in a random fashion over the combustion front; the low-calorie spin mode is sensitive to shift in the general heat balance in either sense during the combustion; and in the spin mode, the combustion is substantially influenced by the topology of the surface.

  16. Transport and transformation of de-icing urea from airport runways in a constructed wetland system.

    PubMed

    Thorén, A K; Legrand, C; Herrmann, J

    2003-01-01

    Urea, NH2-CO-NH2, is used as a de-icing agent at Kalmar Airport, southeast Sweden. During 1998-2001, urea contributed on average 30% of the yearly nitrogen (N) transport of 41,000 kg via Törnebybäcken stream to the coastal zone of the Baltic Sea. In order to reduce stream transport of N from airport, agricultural and other diffuse sources, a wetland was constructed in 1996. Annual wetland retention of total-N varied in the range of 2,500-8,100 kg (6-36% of influent) during 1998-2001, according to mass balances calculated from monthly sampling. During airport de-icing, January-March 2001,660 kg urea-N out of 2,600 kg applied urea-N reached the wetland according to daily sampling. This indicated that 75% of the urea was transformed before entering the wetland. Urea was found to be only a minor part (8%) of total-N in the wetland influent. Calculations of cumulative urea-N loads at the wetland inlet and outlet respectively, showed a significant urea transformation during February 2001 with approximately 40% of the incoming urea-N being transformed in the wetland system. These results show that significant amounts of urea can be transformed in a wetland system at air temperatures around 0 degree C.

  17. Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies.

    SciTech Connect

    Kokubo, Hironori; Pettitt, Bernard M.

    2007-02-15

    The research described in this product was performed in part in the Environmental Molecular Sciences Laboratory, a national scientific user facility sponsored by the Department of Energy's Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. We performed molecular dynamics simulations of urea solutions at different concentrations with two urea models (OPLS and KBFF) to examine the structures responsible for the thermodynamic solution properties. Our simulation results showed that hydrogen-bonding properties such as the average number of hydrogen bonds and their lifetime distributions were nearly constant at all concentrations between infinite dilution and the solubility limit. This implies that the characterization of urea-water solutions in the molarity concentration scale as nearly ideal is a result of facile local hydrogen bonding rather than a global property. Thus, urea concentration does not influence the local propensity for hydrogen bonds, only how they are satisfied. By comparison, the KBFF model of urea donated fewer hydrogen bonds than OPLS. We found that the KBFF urea model in TIP3P water better reproduced the experimental density and diffusion constant data. Preferential solvation analysis showed that there were weak urea-urea and water-water associations in OPLS solution at short distances, but there were no strong associations. We divided urea molecules into large, medium, and small clusters to examine fluctuation properties and found that any particular urea molecule did not stay in the same cluster for a long time. We found neither persistent nor large clusters.

  18. Preferential Solvation in Urea Solutions at Different Concentrations: Properties from Simulation Studies

    SciTech Connect

    Kokubo, Hironori; Pettitt, Bernard M.

    2007-04-21

    We performed molecular dynamics simulations of urea solutions at different concentrations with two urea models (OPLS and KBFF) to examine the structures responsible for the thermodynamic solution properties. Our simulation results showed that hydrogen-bonding properties such as the average number of hydrogen bonds and their lifetime distributions were nearly constant at all concentrations between infinite dilution and the solubility limit. This implies that the characterization of urea-water solutions in the molarity concentration scale as nearly ideal is a result of facile local hydrogen bonding rather than a global property. Thus, urea concentration does not influence the local propensity for hydrogen bonds, only how they are satisfied. By comparison, the KBFF model of urea donated fewer hydrogen bonds than OPLS. We found that the KBFF urea model in TIP3P water better reproduced the experimental density and diffusion constant data. Preferential solvation analysis showed that there were weak urea-urea and water-water associations in OPLS solution at short distances, but there were no strong associations. We divided urea molecules into large, medium, and small clusters to examine fluctuation properties and found that any particular urea molecule did not stay in the same cluster for a long time. We found neither persistent nor large clusters.

  19. A study on the indirect urea dosing method in the Selective Catalytic Reduction system

    NASA Astrophysics Data System (ADS)

    Brzeżański, M.; Sala, R.

    2016-09-01

    This article presents the results of studies on concept solution of dosing urea in a gas phase in a selective catalytic reduction system. The idea of the concept was to heat-up and evaporate the water urea solution before introducing it into the exhaust gas stream. The aim was to enhance the processes of urea converting into ammonia, what is the target reductant for nitrogen oxides treatment. The study was conducted on a medium-duty Euro 5 diesel engine with exhaust line consisting of DOC catalyst, DPF filter and an SCR system with a changeable setup allowing to dose the urea in liquid phase (regular solution) and to dose it in a gas phase (concept solution). The main criteria was to assess the effect of physical state of urea dosed on the NOx conversion ratio in the SCR catalyst. In order to compare both urea dosing methods a special test procedure was developed which consisted of six test steps covering a wide temperature range of exhaust gas generated at steady state engine operation condition. Tests were conducted for different urea dosing quantities defined by the a equivalence ratio. Based on the obtained results, a remarkable improvement in NOx reduction was found for gas urea application in comparison to the standard liquid urea dosing. Measured results indicate a high potential to increase an efficiency of the SCR catalyst by using a gas phase urea and provide the basis for further scientific research on this type of concept.

  20. ENSURING THE AVAILABILITY AND RELIABILITY OF UREA DOSING FOR ON-ROAD AND NON-ROAD

    SciTech Connect

    Barton, G; Lonsdale, B

    2003-08-24

    The purpose of this presentation is to address two important issues. The first issue is nationwide availability of urea. The second is assurance by the engine maker that the engine cannot operate without urea. In regard to the first issue, North American urea production can support SCR needs for the Heavy Duty truck industry. The existing distribution methods, pathways and technology could be utilized for urea supply with no new invention required. Urea usage and storage capacity on vehicles would support long distances between tank refills, as SCR could be initially rolled out with a limited infrastructure. The price of urea should be less than diesel fuel and urea SCR should have a fuel economy advantage over competing technologies. It can be in place by 2007. In regard to the second issue, sensor technology exists to monitor urea tank level and verify that the fluid in the tank is urea. NOx sensors are available to monitor tailpipe NOx, ensuring the entire SCR system is functioning properly, and inferring that urea is in the system. The monitoring system could be used to monitor compliance, record faults, and initiate enforcement actions as necessary. The monitoring system could initiate actions to encourage compliance.

  1. Non-enzymatic detection of urea using unmodified gold nanoparticles based aptasensor.

    PubMed

    Kumar, Piyush; Lambadi, Paramesh Ramulu; Navani, Naveen Kumar

    2015-10-15

    Biosensing nitrogenous compounds like urea is required to control the incidents of Economically Motivated Adulteration (EMA). In this study, we report the FluMag Systematic Evolution of Ligands by Exponential Enrichment (FluMag-SELEX) method to isolate a urea specific DNA aptamer with a dissociation constant (Kd) of 232 nM. The interaction of DNA aptamer with urea has been confirmed by affinity assay, CD analysis, melting curve analysis and truncation studies. Unlike other urea sensing methods reported so far, using this urea aptamer, we demonstrate a simple, 'non-enzymatic' easy-to-use, dual readout aptasensor that exploits unmodified gold nanoparticles (AuNPs) to transduce the signals of aptamer binding to urea in terms of intrinsic fluorescence differences and color changes simultaneously. This method is free from complicated sample processing and labeling steps. The urea aptasensor displays high selectivity for urea and is free from interference from common milk adulterants. The developed aptasensor reliably detects urea adulteration in milk. The response signals linearly correlate with the increasing concentrations of urea in milk ranging from 20mM to 150 mM with detection limit of 20mM. We also show that this aptasensor can also be used as a simple fluorescence based "turn-on" sensor. The results obtained in this study are comparable to the commercial urease based detection methods.

  2. Synergistic behavior of glycine betaine-urea mixture: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Kumar, Narendra; Kishore, Nand

    2013-09-01

    Glycine betaine (GB) is one of the most important osmolyte which is known to stabilize proteins as well as counteract the denaturing effect of urea. There have been many studies indicating protein stabilization and counteraction of the effect of urea by GB. However, the exact mechanism of counteraction is still debated and is of important research interest. In this study, distribution functions, hydrogen bonds, and energetics were analysed to understand different interactions between GB and urea, and their solvation properties in presence of each other. The results show that in the GB-urea mixture, GB acted as a stronger osmolyte and urea became a weaker denaturing agent than its individual counterparts. The increase in the solvation of urea and GB in GB-urea mixture and their mutual interactions through hydrogen bonding and coulombic energy resulted in more involvement of GB and urea with solvent as well as with themselves. This might result in the increase of the exclusion of GB from protein surface and decrease in the protein-urea interactions in the mixture. This synergistic behavior might be the prime reason for the counteraction of denaturing effect of urea by GB.

  3. Supracervical hysterectomy - the vaginal route.

    PubMed

    Wilczyński, Miłosz; Cieślak, Jarosław; Malinowski, Andrzej

    2014-06-01

    Removal of the cervix during hysterectomy is not mandatory. There has been no irrefutable evidence so far that total hysterectomy is more beneficial to patients in terms of pelvic organ function. The procedure that leaves the cervix intact is called a subtotal hysterectomy. Traditional approaches to this surgery include laparoscopic and abdominal routes. Vaginal total hysterectomy has been proven to present many advantages over the other approaches. Therefore, it seems that this route should also be applied in the case of subtotal hysterectomy. We present 9 cases of patients who underwent subtotal hysterectomy performed through the vagina for benign gynecological diseases.

  4. Routing Algorithm Exploits Spatial Relations

    NASA Technical Reports Server (NTRS)

    Okino, Clayton; Jennings, Esther

    2004-01-01

    A recently developed routing algorithm for broadcasting in an ad hoc wireless communication network takes account of, and exploits, the spatial relationships among the locations of nodes, in addition to transmission power levels and distances between the nodes. In contrast, most prior algorithms for discovering routes through ad hoc networks rely heavily on transmission power levels and utilize limited graph-topology techniques that do not involve consideration of the aforesaid spatial relationships. The present algorithm extracts the relevant spatial-relationship information by use of a construct denoted the relative-neighborhood graph (RNG).

  5. Combustion Byproducts Recycling Consortium

    SciTech Connect

    Paul Ziemkiewicz; Tamara Vandivort; Debra Pflughoeft-Hassett; Y. Paul Chugh; James Hower

    2008-08-31

    The Combustion Byproducts Recycling Consortium (CBRC) program was developed as a focused program to remove and/or minimize the barriers for effective management of over 123 million tons of coal combustion byproducts (CCBs) annually generated in the USA. At the time of launching the CBRC in 1998, about 25% of CCBs were beneficially utilized while the remaining was disposed in on-site or off-site landfills. During the ten (10) year tenure of CBRC (1998-2008), after a critical review, 52 projects were funded nationwide. By region, the East, Midwest, and West had 21, 18, and 13 projects funded, respectively. Almost all projects were cooperative projects involving industry, government, and academia. The CBRC projects, to a large extent, successfully addressed the problems of large-scale utilization of CCBs. A few projects, such as the two Eastern Region projects that addressed the use of fly ash in foundry applications, might be thought of as a somewhat smaller application in comparison to construction and agricultural uses, but as a novel niche use, they set the stage to draw interest that fly ash substitution for Portland cement might not attract. With consideration of the large increase in flue gas desulfurization (FGD) gypsum in response to EPA regulations, agricultural uses of FGD gypsum hold promise for large-scale uses of a product currently directed to the (currently stagnant) home construction market. Outstanding achievements of the program are: (1) The CBRC successfully enhanced professional expertise in the area of CCBs throughout the nation. The enhanced capacity continues to provide technology and information transfer expertise to industry and regulatory agencies. (2) Several technologies were developed that can be used immediately. These include: (a) Use of CCBs for road base and sub-base applications; (b) full-depth, in situ stabilization of gravel roads or highway/pavement construction recycled materials; and (c) fired bricks containing up to 30%-40% F

  6. Computing and combustion

    NASA Technical Reports Server (NTRS)

    Thompson, Daniel

    2004-01-01

    Coming into the Combustion Branch of the Turbomachinery and Propulsion Systems Division, there was not any set project planned out for me to work on. This was understandable, considering I am only at my sophmore year in college. Also, my mentor was a division chief and it was expected that I would be passed down the line. It took about a week for me to be placed with somebody who could use me. My first project was to write a macro for TecPlot. Commonly, a person would have a 3D contour volume modeling something such as a combustion engine. This 3D volume needed to have slices extracted from it and made into 2D scientific plots with all of the appropriate axis and titles. This was very tedious to do by hand. My macro needed to automate the process. There was some education I needed before I could start, however. First, TecPlot ran on Unix and Linux, like a growing majority of scientific applications. I knew a little about Linux, but I would need to know more to use the software at hand. I took two classes at the Learning Center on Unix and am now comfortable with Linux and Unix. I already had taken Computer Science I and II, and had undergone the transformation from Computer Programmer to Procedural Epistemologist. I knew how to design efficient algorithms, I just needed to learn the macro language. After a little less than a week, I had learned the basics of the language. Like most languages, the best way to learn more of it was by using it. It was decided that it was best that I do the macro in layers, starting simple and adding features as I went. The macro started out slicing with respect to only one axis, and did not make 2D plots out of the slices. Instead, it lined them up inside the solid. Next, I allowed for more than one axis and placed each slice in a separate frame. After this, I added code that transformed each individual slice-frame into a scientific plot. I also made frames for composite volumes, which showed all of the slices in the same XYZ space. I

  7. Combustion Instabilities Modeled

    NASA Technical Reports Server (NTRS)

    Paxson, Daniel E.

    1999-01-01

    NASA Lewis Research Center's Advanced Controls and Dynamics Technology Branch is investigating active control strategies to mitigate or eliminate the combustion instabilities prevalent in lean-burning, low-emission combustors. These instabilities result from coupling between the heat-release mechanisms of the burning process and the acoustic flow field of the combustor. Control design and implementation require a simulation capability that is both fast and accurate. It must capture the essential physics of the system, yet be as simple as possible. A quasi-one-dimensional, computational fluid dynamics (CFD) based simulation has been developed which may meet these requirements. The Euler equations of mass, momentum, and energy have been used, along with a single reactive species transport equation to simulate coupled thermoacoustic oscillations. A very simple numerical integration scheme was chosen to reduce computing time. Robust boundary condition procedures were incorporated to simulate various flow conditions (e.g., valves, open ends, and choked inflow) as well as to accommodate flow reversals that may arise during large flow-field oscillations. The accompanying figure shows a sample simulation result. A combustor with an open inlet, a choked outlet, and a large constriction approximately two thirds of the way down the length is shown. The middle plot shows normalized, time-averaged distributions of the relevant flow quantities, and the bottom plot illustrates the acoustic mode shape of the resulting thermoacoustic oscillation. For this simulation, the limit cycle peak-to-peak pressure fluctuations were 13 percent of the mean. The simulation used 100 numerical cells. The total normalized simulation time was 50 units (approximately 15 oscillations), which took 26 sec on a Sun Ultra2.

  8. Advanced Subsonic Combustion Rig Developed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    The Advanced Subsonic Combustion Rig (ASCR), a unique, state-of-the-art facility for conducting combustion research, is located at the NASA Lewis Research Center in Cleveland, Ohio. The ASCR, which was nearing completion at the close of 1995, will be capable of simulating the very high pressure and high temperature conditions that are expected to exist in future, advanced subsonic gas turbine (jet) engines. Future environmental regulations will require much cleaner burning (more environmentally friendly) aircraft engines. The ASCR is critical to the development of these cleaner engines. It will allow NASA and U.S. aircraft engine industry researchers to identify and test promising clean-burning gas turbine engine combustion concepts under the pressure and temperature conditions that are expected for those future engines. Combustion processes will be investigated for a variety of next-generation aircraft engine sizes, including engines for large, long-range aircraft (with typical trip lengths of about 3000 mi) and for regional aircraft (with typical trip lengths of about 400 mi). The ASCR design was conceived and initiated in 1993, and fabrication and construction of the rig, including the buildup of an advanced control room, took place throughout 1994 and 1995. In early 1996, the ASCR will be operational for obtaining research data. The ASCR is an intricate part of the NASA Advanced Subsonic Technology Propulsion Program, which is aimed at developing technologies critical to the next generation of gas turbine engines. This effort is in collaboration with the U.S. aircraft gas turbine engine industry. A goal of the Advanced Subsonic Technology Propulsion Program is to develop combustion concepts and technologies that will result in gas turbine engines that produce 50 percent less nitrous oxide (NO_x) pollutants than current engines do. This facility is unique in its capability to simulate advanced subsonic engine pressure, temperature, and air flow rate conditions

  9. Fluids and Combustion Facility: Combustion Integrated Rack Modal Model Correlation

    NASA Technical Reports Server (NTRS)

    McNelis, Mark E.; Suarez, Vicente J.; Sullivan, Timothy L.; Otten, Kim D.; Akers, James C.

    2005-01-01

    The Fluids and Combustion Facility (FCF) is a modular, multi-user, two-rack facility dedicated to combustion and fluids science in the US Laboratory Destiny on the International Space Station. FCF is a permanent facility that is capable of accommodating up to ten combustion and fluid science investigations per year. FCF research in combustion and fluid science supports NASA's Exploration of Space Initiative for on-orbit fire suppression, fire safety, and space system fluids management. The Combustion Integrated Rack (CIR) is one of two racks in the FCF. The CIR major structural elements include the International Standard Payload Rack (ISPR), Experiment Assembly (optics bench and combustion chamber), Air Thermal Control Unit (ATCU), Rack Door, and Lower Structure Assembly (Input/Output Processor and Electrical Power Control Unit). The load path through the rack structure is outlined. The CIR modal survey was conducted to validate the load path predicted by the CIR finite element model (FEM). The modal survey is done by experimentally measuring the CIR frequencies and mode shapes. The CIR model was test correlated by updating the model to represent the test mode shapes. The correlated CIR model delivery is required by NASA JSC at Launch-10.5 months. The test correlated CIR flight FEM is analytically integrated into the Shuttle for a coupled loads analysis of the launch configuration. The analysis frequency range of interest is 0-50 Hz. A coupled loads analysis is the analytical integration of the Shuttle with its cargo element, the Mini Payload Logistics Module (MPLM), in the Shuttle cargo bay. For each Shuttle launch configuration, a verification coupled loads analysis is performed to determine the loads in the cargo bay as part of the structural certification process.

  10. Subgrid Combustion Modeling for the Next Generation National Combustion Code

    NASA Technical Reports Server (NTRS)

    Menon, Suresh; Sankaran, Vaidyanathan; Stone, Christopher

    2003-01-01

    In the first year of this research, a subgrid turbulent mixing and combustion methodology developed earlier at Georgia Tech has been provided to researchers at NASA/GRC for incorporation into the next generation National Combustion Code (called NCCLES hereafter). A key feature of this approach is that scalar mixing and combustion processes are simulated within the LES grid using a stochastic 1D model. The subgrid simulation approach recovers locally molecular diffusion and reaction kinetics exactly without requiring closure and thus, provides an attractive feature to simulate complex, highly turbulent reacting flows of interest. Data acquisition algorithms and statistical analysis strategies and routines to analyze NCCLES results have also been provided to NASA/GRC. The overall goal of this research is to systematically develop and implement LES capability into the current NCC. For this purpose, issues regarding initialization and running LES are also addressed in the collaborative effort. In parallel to this technology transfer effort (that is continuously on going), research has also been underway at Georgia Tech to enhance the LES capability to tackle more complex flows. In particular, subgrid scalar mixing and combustion method has been evaluated in three distinctly different flow field in order to demonstrate its generality: (a) Flame-Turbulence Interactions using premixed combustion, (b) Spatially evolving supersonic mixing layers, and (c) Temporal single and two-phase mixing layers. The configurations chosen are such that they can be implemented in NCCLES and used to evaluate the ability of the new code. Future development and validation will be in spray combustion in gas turbine engine and supersonic scalar mixing.

  11. Turbulent Combustion in SDF Explosions

    SciTech Connect

    Kuhl, A L; Bell, J B; Beckner, V E

    2009-11-12

    A heterogeneous continuum model is proposed to describe the dispersion and combustion of an aluminum particle cloud in an explosion. It combines the gas-dynamic conservation laws for the gas phase with a continuum model for the dispersed phase, as formulated by Nigmatulin. Inter-phase mass, momentum and energy exchange are prescribed by phenomenological models. It incorporates a combustion model based on the mass conservation laws for fuel, air and products; source/sink terms are treated in the fast-chemistry limit appropriate for such gasdynamic fields, along with a model for mass transfer from the particle phase to the gas. The model takes into account both the afterburning of the detonation products of the C-4 booster with air, and the combustion of the Al particles with air. The model equations were integrated by high-order Godunov schemes for both the gas and particle phases. Numerical simulations of the explosion fields from 1.5-g Shock-Dispersed-Fuel (SDF) charge in a 6.6 liter calorimeter were used to validate the combustion model. Then the model was applied to 10-kg Al-SDF explosions in a an unconfined height-of-burst explosion. Computed pressure histories are compared with measured waveforms. Differences are caused by physical-chemical kinetic effects of particle combustion which induce ignition delays in the initial reactive blast wave and quenching of reactions at late times. Current simulations give initial insights into such modeling issues.

  12. Aviation combustion toxicology: an overview.

    PubMed

    Chaturvedi, Arvind K

    2010-01-01

    Aviation combustion toxicology is a subspecialty of the field of aerospace toxicology, which is composed of aerospace and toxicology. The term aerospace, that is, the environment extending above and beyond the surface of the Earth, is also used to represent the combined fields of aeronautics and astronautics. Aviation is another term interchangeably used with aerospace and aeronautics and is explained as the science and art of operating powered aircraft. Toxicology deals with the adverse effects of substances on living organisms. Although toxicology borrows knowledge from biology, chemistry, immunology, pathology, physiology, and public health, the most closely related field to toxicology is pharmacology. Economic toxicology, environmental toxicology, and forensic toxicology, including combustion toxicology, are the three main branches of toxicology. In this overview, a literature search for the period of 1960-2007 was performed and information related to aviation combustion toxicology collected. The overview included introduction; combustion, fire, and smoke; smoke gas toxicity; aircraft material testing; fire gases and their interactive effects; result interpretation; carboxyhemoglobin and blood cyanide ion levels; pyrolytic products of aircraft engine oils, fluids, and lubricants; and references. This review is anticipated to be an informative resource for aviation combustion toxicology and fire-related casualties.

  13. A tool for debugging internet multicast routing

    SciTech Connect

    Agarwal, D.; Floyd, S.

    1994-03-01

    In this paper the authors describe a debugging tool that is an effective means of analyzing problems with multicast packet routing in a network. Multicast packet routing is a source-driven distributed calculation performed by the routers in a multicast network. The routes taken by multicast packets are difficult to predict manually due to the large number of variables that must be considered. The multicast route debugging tool allows off-line investigation of the route taken by a multicast packet and the effects of network modifications on that route. The tool has already proved useful in debugging the problems that have occurred in the experimental Internet Multicast Backbone. The multicast route debugging tool currently predicts multicast routes of packets using the distance-vector truncated-broadcast algorithm implemented for Internet multicast traffic. They will be upgrading the tool to allow the user to choose other multicast routing algorithms.

  14. Judaism and the Silk Route.

    ERIC Educational Resources Information Center

    Foltz, Richard

    1998-01-01

    Demonstrates that the Judeans traveled along the Ancient Silk Route. Discusses the Iranian influence on the formation of Jewish religious ideas. Considers the development of Jewish trade networks, focusing on the Radanites (Jewish traders), the Jewish presence in the Far East, and the survival of Judaism in central Asia. (CMK)

  15. Dynamic Weather Routes Architecture Overview

    NASA Technical Reports Server (NTRS)

    Eslami, Hassan; Eshow, Michelle

    2014-01-01

    Dynamic Weather Routes Architecture Overview, presents the high level software architecture of DWR, based on the CTAS software framework and the Direct-To automation tool. The document also covers external and internal data flows, required dataset, changes to the Direct-To software for DWR, collection of software statistics, and the code structure.

  16. Roots/Routes: Part II

    ERIC Educational Resources Information Center

    Swanson, Dalene M.

    2009-01-01

    This narrative acts as an articulation of a journey of many routes. Following Part I of the same research journey of rootedness/routedness, it debates the nature of transformation and transcendence beyond personal and political paradoxes informed by neoliberalism and related repressive globalizing discourses. Through a more personal, descriptive,…

  17. Genetic algorithms for route discovery.

    PubMed

    Gelenbe, Erol; Liu, Peixiang; Lainé, Jeremy

    2006-12-01

    Packet routing in networks requires knowledge about available paths, which can be either acquired dynamically while the traffic is being forwarded, or statically (in advance) based on prior information of a network's topology. This paper describes an experimental investigation of path discovery using genetic algorithms (GAs). We start with the quality-of-service (QoS)-driven routing protocol called "cognitive packet network" (CPN), which uses smart packets (SPs) to dynamically select routes in a distributed autonomic manner based on a user's QoS requirements. We extend it by introducing a GA at the source routers, which modifies and filters the paths discovered by the CPN. The GA can combine the paths that were previously discovered to create new untested but valid source-to-destination paths, which are then selected on the basis of their "fitness." We present an implementation of this approach, where the GA runs in background mode so as not to overload the ingress routers. Measurements conducted on a network test bed indicate that when the background-traffic load of the network is light to medium, the GA can result in improved QoS. When the background-traffic load is high, it appears that the use of the GA may be detrimental to the QoS experienced by users as compared to CPN routing because the GA uses less timely state information in its decision making.

  18. Planning Safe Routes to School.

    ERIC Educational Resources Information Center

    Appleyard, Bruce S.

    2003-01-01

    Describes "Safe Routes to School" efforts in the United States and other countries to make walking and biking to school the transportation of choice. Offers a plan of action for formulating and carrying out such a program and information on funding sources. (EV)

  19. Roots/Routes: Part I

    ERIC Educational Resources Information Center

    Swanson, Dalene M.

    2009-01-01

    This narrative and poetic rendering acts as an articulation of a journey of many routes. It is a storying of critical research issues and events as performances of lived experience. It is a metissage of hybrid, but interrelated, themes that find cohesion through fragmentation and coalescence, severance, and regrowth. These themes are invoked by…

  20. Alternative Routes for Teacher Certification.

    ERIC Educational Resources Information Center

    Education Commission of the States, Denver, CO.

    This publication presents a series of charts, designed for quick reference, which describe the status of alternative teacher certification routes in each of the 50 states. The charts were prepared in response to an increasing number of inquiries from educators, policy makers, and the public. Information was gathered by telephone surveys of state…

  1. The effect of CP concentration in the diet on urea kinetics and microbial usage of recycled urea in cattle: a meta-analysis.

    PubMed

    Batista, E D; Detmann, E; Valadares Filho, S C; Titgemeyer, E C; Valadares, R F D

    2017-01-10

    In ruminants, urea recycling is considered an evolutionary advantage. The amount of urea recycled mainly depends of the nitrogen (N) intake and the amount of organic matter (OM) digested in the rumen. Because recycled N contributes to meeting microbial N requirements, accurate estimates of urea recycling can improve the understanding of efficiency of N utilization and N losses to the environment. The objective of this study was to evaluate urea kinetics and microbial usage of recycled urea N in ruminants using a meta-analytical approach. Treatment mean values were compiled from 25 studies with ruminants (beef cattle, dairy cows and sheep) which were published from 2001 to 2016, totalling 107 treatment means. The data set was analyzed according to meta-analysis techniques using linear or non-linear mixed models, taking into account the random variations among experiments. Urea N synthesized in the liver (UER) and urea N recycled to the gut (GER) linearly increased (P<0.001) as N intake (g/BW0.75) increased, with increases corresponding to 71.5% and 35.2% of N intake, respectively. The UER was positively associated (P<0.05) with dietary CP concentration and the ratio of CP to digestible OM (CP:DOM). Maximum curvature analyses identified 17% dietary CP as the point where there was a prominent increase in hepatic synthesis of urea N, likely due to an excess of dietary N leading to greater ammonia absorption. The GER:UER decreased with increasing dietary CP concentration (P<0.05). At dietary CP⩾19%, GER:UER reached near minimal values. The fraction of UER eliminated as urinary urea N and the contribution of urea N to total urinary N were positively associated with dietary CP (P<0.05), both reaching values near the plateau when dietary CP was 17%. The fractions of GER excreted in the feces and utilized for anabolism decreased, whereas the fraction of GER returned to the ornithine cycle increased with dietary CP concentration (P<0.05). Recycled urea N assimilated by

  2. Thermal Model of the Promoted Combustion Test

    NASA Technical Reports Server (NTRS)

    Jones, Peter D.

    1996-01-01

    Flammability of metals in high pressure, pure oxygen environments, such as rocket engine turbopumps, is commonly evaluated using the Promoted Combustion Test (PCT). The PCT emphasizes the ability of an ignited material to sustain combustion, as opposed to evaluating the sample's propensity to ignite in the first place. A common arrangement is a rod of the sample material hanging in a chamber in which a high pressure, pure oxygen environment is maintained. An igniter of some energetically combusting material is fixed to the bottom of the rod and fired. This initiates combustion, and the sample burns and melts at its bottom tip. A ball of molten material forms, and this ball detaches when it grows too large to be supported by surface tension with the rod. In materials which do not sustain combustion, the combustion then extinguishes. In materials which do sustain combustion, combustion re-initiates from molten residue left on the bottom of the rod, and the melt ball burns and grows until it detaches again. The purpose of this work is development of a PCT thermal simulation model, detailing phase change, melt detachment, and the several heat transfer modes. Combustion is modeled by a summary rate equation, whose parameters are identified by comparison to PCT results. The sensitivity of PCT results to various physical and geometrical parameters is evaluated. The identified combustion parameters may be used in design of new PCT arrangements, as might be used for flammability assessment in flow-dominated environments. The Haynes 214 nickel-based superalloy, whose PCT results are applied here, burns heterogeneously (fuel and oxidizer are of different phases; combustion takes place on the fuel surface). Heterogeneous combustion is not well understood. (In homogeneous combustion, the metal vaporizes, and combustion takes place in an analytically treatable cloud above the surface). Thermal modeling in heterogeneous combustion settings provides a means for linking test

  3. Dynamic urea bond for the design of reversible and self-healing polymers.

    PubMed

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-01-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

  4. Dynamic urea bond for the design of reversible and self-healing polymers

    NASA Astrophysics Data System (ADS)

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-02-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-urea)s capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials.

  5. Kinetic barriers in the isomerization of substituted ureas: implications for computer-aided drug design

    NASA Astrophysics Data System (ADS)

    Loeffler, Johannes R.; Ehmki, Emanuel S. R.; Fuchs, Julian E.; Liedl, Klaus R.

    2016-05-01

    Urea derivatives are ubiquitously found in many chemical disciplines. N, N'-substituted ureas may show different conformational preferences depending on their substitution pattern. The high energetic barrier for isomerization of the cis and trans state poses additional challenges on computational simulation techniques aiming at a reproduction of the biological properties of urea derivatives. Herein, we investigate energetics of urea conformations and their interconversion using a broad spectrum of methodologies ranging from data mining, via quantum chemistry to molecular dynamics simulation and free energy calculations. We find that the inversion of urea conformations is inherently slow and beyond the time scale of typical simulation protocols. Therefore, extra care needs to be taken by computational chemists to work with appropriate model systems. We find that both knowledge-driven approaches as well as physics-based methods may guide molecular modelers towards accurate starting structures for expensive calculations to ensure that conformations of urea derivatives are modeled as adequately as possible.

  6. Dynamic urea bond for the design of reversible and self-healing polymers

    PubMed Central

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-01-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-ureas) capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials. PMID:24492620

  7. Effect of urea addition on giant reed ensilage and subsequent methane production by anaerobic digestion.

    PubMed

    Liu, Shan; Ge, Xumeng; Liew, Lo Niee; Liu, Zhe; Li, Yebo

    2015-09-01

    The effect of urea addition on giant reed ensilage and sequential anaerobic digestion (AD) of the ensiled giant reed was evaluated. The dry matter loss during ensilage (up to 90 days) with or without urea addition was about 1%. Addition of 2% urea enhanced production of lactic acid by about 4 times, and reduced production of propionic acid by 2-8 times. Besides, urea addition reduced degradation of cellulose and hemicellulose, and increased degradation of lignin in giant reed during ensilage. Ensilage with or without urea addition had no significant effects on the enzymatic digestibility of giant reed, but ensilage with urea addition achieved a cumulative methane yield of 173 L/kg VS, which was 18% higher than that of fresh giant reed. The improved methane yield of giant reed could be attributed to the production of organic acids and ethanol during ensilage.

  8. [Rate of controlled-release urea pervasion through membrane determined by ultraviolet spectrophotometry].

    PubMed

    Zuo, Xiu-jin; Wang, Zhen-xin; Dai, Xiao-min; Zhou, Yi; Ma, Xiao-jun

    2006-06-01

    Application of controlled-release nitrogenous fertilizers can improve the efficiency of fertilizers and reduce the environmental pollution. Controlled-release urea (coated urea) is one of the controlled-release nitrogenous fertilizers developed quickly in the recent years. The rate of controlled-release urea pervasion through membrane is the most important index of the capacity of controlled release. There is a maximum absorption at lambda=426 nm with complex in acidic solution, using p-dimethylaminozenzaldehyde as color reagent, and the absorbance exhibits a linear reponses to the urea concentration over the range of 7.5-210 microg x mL(-1). The method for determining the rate of controlled-release urea pervasion through membrane was realized through determining the content of urea in the liquor, the recovery efficiency of the method is 96.1%-103.9%.

  9. A modified manual method for the determination of urea in seawater using diacetylmonoxime reagent

    NASA Astrophysics Data System (ADS)

    Mulvenna, Pamela F.; Savidge, Graham

    1992-05-01

    A manual method for the quantitative determination of urea in seawater was developed based on the reaction of urea with diacetylmonoxime. Critical factors include the treatment of collection bottles, sample storage, pre-filtration techniques, water purification, reaction temperature and reproducible cooling of samples during analysis. The limit of detection was 0·14 μg-at urea-N 1 -1 with Beer's Law being obeyed in the range tested of 0-15 μg-at urea-N 1 -1. The precision (±1 SD) of replicate samples of 1,2 and 15 μg-at urea-N 1 -1 was 0·024, 0·019 and 0·03 μg-at urea-N 1 -1 ( n = 10) respectively.

  10. Mössbauer and magnetization studies of nickel ferrite nanoparticles synthesized by the microwave-combustion method

    NASA Astrophysics Data System (ADS)

    Mahmoud, M. H.; Elshahawy, A. M.; Makhlouf, Salah A.; Hamdeh, H. H.

    2013-10-01

    Nanocrystalline nickel ferrite was synthesized from its stoichiometric metal nitrates and urea mixtures, using a microwave assisted combustion method. The process was a convenient, inexpensive and an efficient method for formation of NiFe2O4 nanomaterials. Effect of urea/metal nitrates ratio on the obtained phases, particle size and magnetic properties has been investigated by various techniques. Saturation magnetization of 50 emu/g was observed at room temperature for larger particles, and it decreases with decreasing particle size. The coercivity attains a maximum value of 170 Oe when the particle size was ~20 nm, and decreases with increasing particle size. Mössbauer spectra measured at RT for some representative samples show a combination of ordered and superparamagnetic behavior, whereas those collected at 20 K elucidate the nature of the obtained phases and cation distribution.

  11. Remote calorimetric detection of urea via flow injection analysis.

    PubMed

    Gaddes, David E; Demirel, Melik C; Reeves, W Brian; Tadigadapa, Srinivas

    2015-12-07

    The design and development of a calorimetric biosensing system enabling relatively high throughput sample analysis are reported. The calorimetric biosensor system consists of a thin (∼20 μm) micromachined Y-cut quartz crystal resonator (QCR) as a temperature sensor placed in close proximity to a fluidic chamber packed with an immobilized enzyme. Layer by layer enzyme immobilization of urease is demonstrated and its activity as a function of the number of layers, pH, and time has been evaluated. This configuration enables a sensing system where a transducer element is physically separated from the analyte solution of interest and is thereby free from fouling effects typically associated with biochemical reactions occuring on the sensor surface. The performance of this biosensing system is demonstrated by detection of 1-200 mM urea in phosphate buffer via a flow injection analysis (FIA) technique. Miniaturized fluidic systems were used to provide continuous flow through a reaction column. Under this configuration the biosensor has an ultimate resolution of less than 1 mM urea and showed a linear response between 0-50 mM. This work demonstrates a sensing modality in which the sensor itself is not fouled or contaminated by the solution of interest and the enzyme immobilized Kapton® fluidic reaction column can be used as a disposable cartridge. Such a system enables reuse and reliability for long term sampling measurements. Based on this concept a biosensing system is envisioned which can perform rapid measurements to detect biomarkers such as glucose, creatinine, cholesterol, urea and lactate in urine and blood continuously over extended periods of time.

  12. Problems in the management of urea cycle disorders.

    PubMed

    Wilcken, Bridget

    2004-04-01

    Several recent reviews describe the management of urea cycle disorders. There is much agreement on diet, alternative pathway therapy, maintenance of arginine and ornithine levels in acute and chronic management, sick-day regimens, and some aspects of monitoring. However, differences remain in several areas, and physicians at most treatment centers have relatively little experience, because these disorders are rare. Early suspicion of the diagnosis of a urea cycle disorder, and prompt referral to a tertiary center is vital. Drug treatment using chronic administration of sodium benzoate has been abandoned by some centers, but the acceptability of phenylbutyrate is an issue for many patients. Using citrulline chronically is not always successful in recommended doses, and may result in an arginine level too low for maximum control. Appetite and nutrition problems are common. One major concern is the early identification and management of chronic catabolism, theoretically easy, but hard in practice. Biochemical measurement problems complicate monitoring, and there are disagreements about the optimum way of identifying OTC carriers. It is not always clear whom to treat. Within a kindred with an early-onset phenotype, an asymptomatic newborn girl may need treatment for some undetermined time, but target values for monitoring are not clear. In late-onset phenotypes, management of asymptomatic males identified by family screening is also difficult. Most centers do not have sufficient cases to solve these conundrums, some of which require further multicenter study. This paper examines the recommendations of a consensus conference on management, outlines some remaining problems, and incorporates in the text the points raised in open discussion during a session of a symposium held in Sydney in 2003 entitled "New Developments in Urea Cycle Disorders."

  13. Lyapunov spectrum in turbulent combustion

    NASA Astrophysics Data System (ADS)

    Hassanaly, Malik; Raman, Venkat

    2016-11-01

    Transient flame evolution is an important flow problem for many practical applications (for example high-altitude relight, ignition in internal combustion engines, unstart in scramjets). Current approaches to combustion modeling utilize assumptions that are valid mainly for statistically stationary processes. In order to understand the transient problem, a dynamic systems approach is followed here. The propagation of a flame in a turbulent channel flow is used as a canonical turbulent combustion system and is analyzed with the Lyapunov theory. In particular, the Lyapunov spectrum for this flow is computed using multiple coordinated simulations. For a range of flow conditions, dimensionality of the state-space is determined. It is shown that the internal structure of the flame plays a critical role in determining the response of the system to perturbations in the flow.

  14. Novel Active Combustion Control Valve

    NASA Technical Reports Server (NTRS)

    Caspermeyer, Matt

    2014-01-01

    This project presents an innovative solution for active combustion control. Relative to the state of the art, this concept provides frequency modulation (greater than 1,000 Hz) in combination with high-amplitude modulation (in excess of 30 percent flow) and can be adapted to a large range of fuel injector sizes. Existing valves often have low flow modulation strength. To achieve higher flow modulation requires excessively large valves or too much electrical power to be practical. This active combustion control valve (ACCV) has high-frequency and -amplitude modulation, consumes low electrical power, is closely coupled with the fuel injector for modulation strength, and is practical in size and weight. By mitigating combustion instabilities at higher frequencies than have been previously achieved (approximately 1,000 Hz), this new technology enables gas turbines to run at operating points that produce lower emissions and higher performance.

  15. Major research topics in combustion

    SciTech Connect

    Hussaini, M.Y.; Kumar, A.; Voigt, R.G.

    1992-01-01

    The Institute for Computer Applications in Science and Engineering (ICASE) and NASA Langley Research Center (LaRC) hosted a workshop on October 2--4, 1989 to discuss some combustion problems of technological interest to LaRC and to foster interaction with the academic community in these research areas. The topics chosen for this purpose were flame structure, flame holding/extinction, chemical kinetics, turbulence-kinetics interaction, transition to detonation, and reacting free shear layers. This document contains the papers and edited versions of general discussions on these topics. The lead paper set the stage for the meeting by discussing the status and issues of supersonic combustion relevant to the scramjet engine. Experts were then called upon to review the current knowledge in the aforementioned areas, to focus on how this knowledge can be extended and applied to high-speed combustion, and to suggest future directions of research in these areas.

  16. Influence of urea additives on micellar morphology/protein conformation.

    PubMed

    Gull, Nuzhat; Kumar, Sanjeev; Ahmad, Basir; Khan, Rizwan Hassan; Kabir-ud-Din

    2006-08-01

    The present study highlights the fact that the effect of additives (urea, monomethylurea, thiourea) on the supramolecular assemblies and proteins is strikingly similar. To investigate the effect, a viscometeric study on sphere-to-rod transition (s-->r) was undertaken in a system (3.5% tetradecyltrimethylammonium bromide+0.05 M NaBr + 1-pentanol [P.M. Lindemuth, G.L. Bertand, J. Phys. Chem. 97 (1993) 7769]) in the presence and absence of the said additives. [1-pentanol] needed for s-->r (i.e. [1-pentanol]s-->r) was determined from the relative viscosity versus [1-pentanol] profiles. It was observed that the additives preponed as well as postponed s-->r depending upon their nature and concentrations. These effects are explained in terms of increased polarity of the medium and the adsorption ability of urea/monomethylurea on the charged surfactant monomers of the micelle. In case of thiourea, postponement of s-->r was observed throughout which is attributed to its structure. To derive an analogy between micelles and proteins the additive-induced conformational changes of the protein, bovine serum albumin (BSA) was taken to monitor secondary structural changes and tryptophanyl fluorescence. A marked increase in secondary structure (far-UVCD) and increased tryptophanyl fluorescence with a marked blue shift in lambdamax was observed in presence of low concentrations of urea or alkylurea. This indicates that a more compact environment is created in presence of these additives, if added judiciously. Addition of thiourea to BSA caused a marked quenching without any significant change in lambdamax. The large decrease in tryptophanyl emission in presence of low thiourea concentrations seems to be specific and related to thiourea structure as no corresponding changes were observed in urea/alkylurea. All these effects pertaining to protein behavior fall in line with that of morphological observations on the present as well as surfactant systems studied earlier [S. Kumar, N

  17. Health effects of urea formaldehyde foam insulation: evidence of causation.

    PubMed Central

    Norman, G R; Newhouse, M T

    1986-01-01

    Studies of health effects of urea formaldehyde foam insulation (UFFI) were critically reviewed by means of accepted rules for evidence of causation. Three categories of health effects were examined: reported symptoms, primarily of the upper respiratory tract, lower respiratory tract disease and cancer. Most of the studies purporting to demonstrate health effects of UFFI failed to meet minimal methodologic criteria for evidence of causation. Evidence from the adequate studies provides little support for the hypothesis of a causative role of UFFI in health problems. PMID:3512066

  18. Functional materials from self-assembled bis-urea macrocycles.

    PubMed

    Shimizu, Linda S; Salpage, Sahan R; Korous, Arthur A

    2014-07-15

    CONSPECTUS: This Account highlights the work from our laboratories on bis-urea macrocycles constructed from two C-shaped spacers and two urea groups. These simple molecular units assembled with high fidelity into columnar structures guided by the three-centered urea hydrogen bonding motif and aryl stacking interactions. Individual columns are aligned and closely packed together to afford functional and homogeneous microporous crystals. This approach allows for precise and rational control over the dimensions of the columnar structure simply by changing the small molecular unit. When the macrocyclic unit lacks a cavity, columnar assembly gives strong pillars. Strong pillars with external functional groups such as basic lone pairs can expand like clays to accept guests between the pillars. Macrocycles that contain sizable interior cavities assemble into porous molecular crystals with aligned, well-defined columnar pores that are accessible to gases and guests. Herein, we examine the optimal design of the macrocyclic unit that leads to columnar assembly in high fidelity and probe the feasibility of incorporating a second functional group within the macrocycles. The porous molecular crystals prepared through the self-assembly of bis-urea macrocycles display surface areas similar to zeolites but lower than MOFs. Their simple one-dimensional channels are well-suited for studying binding, investigating transport, diffusion and exchange, and monitoring the effects of encapsulation on reaction mechanism and product distribution. Guests that complement the size, shape, and polarity of the channels can be absorbed into these porous crystals with repeatable stoichiometry to form solid host-guest complexes. Heating or extraction with an organic solvent enables desorption or removal of the guest and subsequent recovery of the solid host. Further, these porous crystals can be used as containers for the selective [2 + 2] cycloadditions of small enones such as 2-cyclohexenone or 3

  19. [Diagnosis and treatment of urea cycle disorders in adult patients].

    PubMed

    Maillot, F; Blasco, H; Lioger, B; Bigot, A; Douillard, C

    2016-10-01

    Urea cycle disorders (UCDs) are inborn errors of metabolism in which the clinical picture is mostly due to ammonia intoxication. UCD onset may be observed at any age. Acute decompensations of UCDs include neuro-psychiatric symptoms such as headache, confusion, convulsions, ataxia, agitation or delirium, as well as digestive symptoms, namely nausea and vomiting along with abdominal pain. Acute decompensations may lead to an irreversible coma in the absence of specific therapy. The first step is to measure promptly ammonemia in such patients, and start appropriate therapy on an emergency basis.

  20. Combustion instability modeling and analysis

    SciTech Connect

    Santoro, R.J.; Yang, V.; Santavicca, D.A.; Sheppard, E.J.

    1995-12-31

    It is well known that the two key elements for achieving low emissions and high performance in a gas turbine combustor are to simultaneously establish (1) a lean combustion zone for maintaining low NO{sub x} emissions and (2) rapid mixing for good ignition and flame stability. However, these requirements, when coupled with the short combustor lengths used to limit the residence time for NO formation typical of advanced gas turbine combustors, can lead to problems regarding unburned hydrocarbons (UHC) and carbon monoxide (CO) emissions, as well as the occurrence of combustion instabilities. The concurrent development of suitable analytical and numerical models that are validated with experimental studies is important for achieving this objective. A major benefit of the present research will be to provide for the first time an experimentally verified model of emissions and performance of gas turbine combustors. The present study represents a coordinated effort between industry, government and academia to investigate gas turbine combustion dynamics. Specific study areas include development of advanced diagnostics, definition of controlling phenomena, advancement of analytical and numerical modeling capabilities, and assessment of the current status of our ability to apply these tools to practical gas turbine combustors. The present work involves four tasks which address, respectively, (1) the development of a fiber-optic probe for fuel-air ratio measurements, (2) the study of combustion instability using laser-based diagnostics in a high pressure, high temperature flow reactor, (3) the development of analytical and numerical modeling capabilities for describing combustion instability which will be validated against experimental data, and (4) the preparation of a literature survey and establishment of a data base on practical experience with combustion instability.

  1. A current perspective on the compensatory effects of urea and methylamine on protein stability and function.

    PubMed

    Rahman, Safikur; Warepam, Marina; Singh, Laishram R; Dar, Tanveer Ali

    2015-11-01

    Urea is a strong denaturant and inhibits many enzymes but is accumulated intracellularly at very high concentrations (up to 3-4 M) in mammalian kidney and in many marine fishes. It is known that the harmful effects of urea on the macromolecular structure and function is offset by the accumulation of an osmolytic agent called methylamine. Intracellular concentration of urea to methylamines falls in the ratio of 2:1 to 3:2 (molar ratio). At this ratio, the thermodynamic effects of urea and methylamines on protein stability and function are believed to be algebraically additive. The mechanism of urea-methylamine counteraction has been widely investigated on various approaches including, thermodynamic, structural and functional aspects. Recent advances have also revealed atomic level insights of counteraction and various molecular dynamic simulation studies have yielded significant molecular level informations on the interaction between urea and methylamines with proteins. It is worthwhile that urea-methylamine system not only plays pivotal role for the survival and functioning of the renal medullary cells but also is a key osmoregulatory component of the marine elasmobranchs, holocephalans and coelacanths. Therefore, it is important to combine all discoveries and discuss the developments in context to physiology of the mammalian kidney and adaptation of the marine organisms. In this article we have for the first time reviewed all major developments on urea-counteraction systems to date. We have also discussed about other additional urea-counteraction systems discovered so far including urea-NaCl, urea-myoinsoitol and urea-molecular chaperone systems. Insights for the possible future research have also been highlighted.

  2. Thiomonas sp. CB2 is able to degrade urea and promote toxic metal precipitation in acid mine drainage waters supplemented with urea

    PubMed Central

    Farasin, Julien; Andres, Jérémy; Casiot, Corinne; Barbe, Valérie; Faerber, Jacques; Halter, David; Heintz, Dimitri; Koechler, Sandrine; Lièvremont, Didier; Lugan, Raphael; Marchal, Marie; Plewniak, Frédéric; Seby, Fabienne; Bertin, Philippe N.; Arsène-Ploetze, Florence

    2015-01-01

    The acid mine drainage (AMD) in Carnoulès (France) is characterized by the presence of toxic metals such as arsenic. Several bacterial strains belonging to the Thiomonas genus, which were isolated from this AMD, are able to withstand these conditions. Their genomes carry several genomic islands (GEIs), which are known to be potentially advantageous in some particular ecological niches. This study focused on the role of the “urea island” present in the Thiomonas CB2 strain, which carry the genes involved in urea degradation processes. First, genomic comparisons showed that the genome of Thiomonas sp. CB2, which is able to degrade urea, contains a urea genomic island which is incomplete in the genome of other strains showing no urease activity. The urease activity of Thiomonas sp. CB2 enabled this bacterium to maintain a neutral pH in cell cultures in vitro and prevented the occurrence of cell death during the growth of the bacterium in a chemically defined medium. In AMD water supplemented with urea, the degradation of urea promotes iron, aluminum and arsenic precipitation. Our data show that ureC was expressed in situ, which suggests that the ability to degrade urea may be expressed in some Thiomonas strains in AMD, and that this urease activity may contribute to their survival in contaminated environments. PMID:26441922

  3. Chemical kinetics and combustion modeling

    SciTech Connect

    Miller, J.A.

    1993-12-01

    The goal of this program is to gain qualitative insight into how pollutants are formed in combustion systems and to develop quantitative mathematical models to predict their formation rates. The approach is an integrated one, combining low-pressure flame experiments, chemical kinetics modeling, theory, and kinetics experiments to gain as clear a picture as possible of the process in question. These efforts are focused on problems involved with the nitrogen chemistry of combustion systems and on the formation of soot and PAH in flames.

  4. Combustion-augmented laser ramjets

    NASA Astrophysics Data System (ADS)

    Horisawa, Hideyuki; Tamada, Kazunobu; Kimura, Itsuro

    2006-05-01

    A preliminary study of combustion-augmented laser-ramjets was conducted, in which chemical propellant such as a gaseous hydrogen/air mixture was utilized and detonated with a focused laser beam in order to obtain a higher impulse compared to the case only using lasers. CFD analysis of internal conical-nozzle flows and experimental measurements including impulse measurement were conducted to evaluate effects of chemical reaction on thrust performance improvement. From the results, a significant improvement in the thrust performances was confirmed with addition of a small amount of hydrogen to propellant air, or in combustion-augmented operation.

  5. Engine Combustion Network Experimental Data

    DOE Data Explorer

    Maintained by the Engine Combustion Department of Sandia National Laboratories, data currently available on the website includes reacting and non-reacting sprays in a constant-volume chamber at conditions typical of diesel combustion. The data are useful for model development and validation because of the well-defined boundary conditions and the wide range of conditions employed. A search utility displays data based on experimental conditions such as ambient temperature, ambient density, injection pressure, nozzle size, fuel, etc. Experiment-related visualizations are also available. (Specialized Interface)

  6. Combustion energy of fullerene soot

    SciTech Connect

    Man, Naoki; Nagano, Yatsuhisa; Kiyobayashi, Tetsu; Sakiyama, Minoru )

    1995-02-23

    The standard energy of combustion of fullerene soot generated in arc discharge was determined to be [minus]36.0 [+-] 0.5 kJ g[sup [minus]1] by oxygen-bomb combustion calorimetry. The value was much closer to those of C[sub 60] and C[sub 70] than that of graphite. This result provides an energetic reason for the remarkable yield of fullerenes in arc discharge and supports the mechanism of fullerene formation, where fullerenes are the lowest energy products. Fullerene onion formation is interpreted in terms of energy relaxation of the fullerene soot. 20 refs., 1 tab.

  7. Numerical approaches to combustion modeling

    SciTech Connect

    Oran, E.S.; Boris, J.P. )

    1991-01-01

    This book presents a series of topics ranging from microscopic combustion physics to several aspects of macroscopic reactive-flow modeling. As the reader progresses into the book, the successive chapters generally include a wider range of physical and chemical processes in the mathematical model. Including more processes, however, usually means that they will be represented phenomenologically at a cruder level. In practice the detailed microscopic models and simulations are often used to develop and calibrate the phenomenologies used in the macroscopic models. The book first describes computations of the most microscopic chemical processes, then considers laminar flames and detonation modeling, and ends with computations of complex, multiphase combustion systems.

  8. Combustion heater for oil shale

    DOEpatents

    Mallon, Richard G.; Walton, Otis R.; Lewis, Arthur E.; Braun, Robert L.

    1985-01-01

    A combustion heater for oil shale heats particles of spent oil shale containing unburned char by burning the char. A delayed fall is produced by flowing the shale particles down through a stack of downwardly sloped overlapping baffles alternately extending from opposite sides of a vertical column. The delayed fall and flow reversal occurring in passing from each baffle to the next increase the residence time and increase the contact of the oil shale particles with combustion supporting gas flowed across the column to heat the shale to about 650.degree.-700.degree. C. for use as a process heat source.

  9. Combustion heater for oil shale

    DOEpatents

    Mallon, R.; Walton, O.; Lewis, A.E.; Braun, R.

    1983-09-21

    A combustion heater for oil shale heats particles of spent oil shale containing unburned char by burning the char. A delayed fall is produced by flowing the shale particles down through a stack of downwardly sloped overlapping baffles alternately extending from opposite sides of a vertical column. The delayed fall and flow reversal occurring in passing from each baffle to the next increase the residence time and increase the contact of the oil shale particles with combustion supporting gas flowed across the column to heat the shale to about 650 to 700/sup 0/C for use as a process heat source.

  10. Survey of Hydrogen Combustion Properties

    NASA Technical Reports Server (NTRS)

    Drell, Isadore L; Belles, Frank E

    1958-01-01

    This literature digest of hydrogen-air combustion fundamentals presents data on flame temperature, burning velocity, quenching distance, flammability limits, ignition energy, flame stability, detonation, spontaneous ignition, and explosion limits. The data are assessed, recommended values are given, and relations among various combustion properties are discussed. New material presented includes: theoretical treatment of variation in spontaneous ignition lag with temperature, pressure, and composition, based on reaction kinetics of hydrogen-air composition range for 0.01 to 100 atmospheres and initial temperatures of 0 degrees to 1400 degrees k.

  11. Promoted Combustion Test Propagation Rate Data

    NASA Technical Reports Server (NTRS)

    Borstorff, J.; Jones, P.; Lowery, F.

    2002-01-01

    Combustion propagation rate data were examined for potential use in benchmarking a thermal model of the Promoted Combustion Test (PCT), and also for potential use in measuring the repeatability of PCT results.

  12. Method for storing radioactive combustible waste

    DOEpatents

    Godbee, H.W.; Lovelace, R.C.

    1973-10-01

    A method is described for preventing pressure buildup in sealed containers which contain radioactively contaminated combustible waste material by adding an oxide getter material to the container so as to chemically bind sorbed water and combustion product gases. (Official Gazette)

  13. Development of a Premixed Combustion Capability for Scramjet Combustion Experiments

    NASA Technical Reports Server (NTRS)

    Rockwell, Robert D.; Goyne, Christopher P.; Rice, Brian E.; Chelliah, Harsha; McDaniel, James C.; Edwards, Jack R.; Cantu, Luca M. L.; Gallo, Emanuela C. A.; Cutler, Andrew D.; Danehy, Paul M.

    2015-01-01

    Hypersonic air-breathing engines rely on scramjet combustion processes, which involve high speed, compressible, and highly turbulent flows. The combustion environment and the turbulent flames at the heart of these engines are difficult to simulate and study in the laboratory under well controlled conditions. Typically, wind-tunnel testing is performed that more closely approximates engine testing rather than a careful investigation of the underlying physics that drives the combustion process. The experiments described in this paper, along with companion data sets being developed separately, aim to isolate the chemical kinetic effects from the fuel-air mixing process in a dual-mode scramjet combustion environment. A unique fuel injection approach is taken that produces a nearly uniform fuel-air mixture at the entrance to the combustor. This approach relies on the precombustion shock train upstream of the dual-mode scramjet combustor. A stable ethylene flame anchored on a cavity flameholder with a uniformly mixed combustor inflow has been achieved in these experiments allowing numerous companion studies involving coherent anti-Stokes Raman scattering (CARS), particle image velocimetry (PIV), and planar laser induced fluorescence (PLIF) to be performed.

  14. Imaging Renal Urea Handling in Rats at Millimeter Resolution using Hyperpolarized Magnetic Resonance Relaxometry

    PubMed Central

    Reed, Galen D.; von Morze, Cornelius; Verkman, Alan S.; Koelsch, Bertram L.; Chaumeil, Myriam M.; Lustig, Michael; Ronen, Sabrina M.; Bok, Robert A.; Sands, Jeff M.; Larson, Peder E. Z.; Wang, Zhen J.; Larsen, Jan Henrik Ardenkjær; Kurhanewicz, John; Vigneron, Daniel B.

    2016-01-01

    In vivo spin spin relaxation time (T2) heterogeneity of hyperpolarized [13C,15N2]urea in the rat kidney was investigated. Selective quenching of the vascular hyperpolarized 13C signal with a macromolecular relaxation agent revealed that a long-T2 component of the [13C,15N2]urea signal originated from the renal extravascular space, thus allowing the vascular and renal filtrate contrast agent pools of the [13C,15N2]urea to be distinguished via multi-exponential analysis. The T2 response to induced diuresis and antidiuresis was performed with two imaging agents: hyperpolarized [13C,15N2]urea and a control agent hyperpolarized bis-1,1-(hydroxymethyl)-1-13C-cyclopropane-2H8. Large T2 increases in the inner-medullar and papilla were observed with the former agent and not the latter during antidiuresis. Therefore, [13C,15N2]urea relaxometry is sensitive to two steps of the renal urea handling process: glomerular filtration and the inner-medullary urea transporter (UT)-A1 and UT-A3 mediated urea concentrating process. Simple motion correction and subspace denoising algorithms are presented to aid in the multi exponential data analysis. Furthermore, a T2-edited, ultra long echo time sequence was developed for sub-2 mm3 resolution 3D encoding of urea by exploiting relaxation differences in the vascular and filtrate pools. PMID:27570835

  15. Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa.

    PubMed Central

    Hodson, R C; Williams, S K; Davidson, W R

    1975-01-01

    In the unicellular green alga Chlamydomonas reinhardi (strain y-1), synthesis of the enzymes required for urea hydrolysis is under substrate induction control by urea and under end product repression control by ammonia. Hydrolysis of urea if effected by the sequential action of the discrete enzymes urea carboxylase and allophanate lyase, collectively called urea amidolyase. The carboxylase converts urea to allophanate in a reaction requiring biotin, adenosine 5'-triphosphate, and Mg2+. The lyase hydrolzyes allophanate to ammonium ions and bicarbonate. Neither activity is present in more than trace amounts when cultures are grown with ammonia or urea plus ammonia, or when they are starved for nitrogen for 8 h. Urea in the absence of ammonia induces both activities 10 to 100 times the basal levels. Addition of ammonia to an induced culture causes complete cessation of carboxylase accumulation and an 80% depression of lyase accumulation. Ammonia does not reduce urea uptake by repressed cells, so it does not prevent induction by the mechanism of inducer exclusion. The unicellular green alga Chlorella pyrenoidosa (strain 3 Emerson) also has discrete carboxylase and lyase enzymes, but only the carboxylase exhibits metabolic control. PMID:1116994

  16. Implementation of direct routing mobile IP for solving triangular routing

    NASA Astrophysics Data System (ADS)

    Jang, Jongwook; Jang, SeongHo; Park, Miri; Lee, Dae-bong

    2001-10-01

    Mobility support on the network layer is of special importance, as the network layer holds together the huge Internet with common protocol IP. Although based on possibility different wireless or wired technologies, all nodes of the network should be able to communicate. Therefore, mobile IP(an extension of the classical IP) has been designed which enablemobility in the Internet without changing existing wired systems. However, mobile IP leaves some points unsolved. Especially, if it comes to security, efficiency of the packet flow that is called triangular routing. Especially triangular routing can cause unnecessary overhead for the network. Furthermore latency can increase dramatically. This is particularly unfortunate if two communicating hosts are separated by transatlantic links. In order to this problem, many methods like IPv6 and ROMIP are proposed. But these methods have limitation. In other words, they have not compatibility because of needing modification of original IP scheme. Especially ROMIP is very complex and the overhead of control message and processing are serious. The problem of inconsistency of Binding caches may occur too. We therefore propose and analyze the performance of the DRMIP (Direct Routing Mobile IP) which do not modify IP source needed in the sender, is compatible with IP and Mobile IP.

  17. Combustion Behavior of Free Boron Slurry Droplets,

    DTIC Science & Technology

    2014-09-26

    Shockwaves 11, 189. Faeth, G.M. (1984). Status of boron combustion research. AFOSR Specialists Meeting on Boron Combustion, June, 1984. Friedman, R...containing water. Combust. Explosion and Shockwaves 17,9. Glassman, I., Williams, F.A., and Antaki, P. (1982). A physica] and chemical interpretation...temperature environment. Combust. Explosion and Shockwaves 15, 691. Johns, J.W.C. (1961) The absorption spectrum of BOz. Can. J. Phy§. 39, 1738. Kaskan, W.E

  18. Experimental and Computational Characterization of Combustion Phenomena

    DTIC Science & Technology

    2006-05-01

    Fundamental Combustion Advanced Combustor Concepts Combustor Demonstration and Transition Figure 1. A design philosophy for transitioning basic...PFP UNCLASSIFIED [4] W.-W. Kim, S. Menon, and H. Mongia , “Large-Eddy Simulation of a Gas Turbine Combustor Flow,” Combust . Sci. Technol. 143, 25-62...AFRL-PR-WP-TM-2006-2131 EXPERIMENTAL AND COMPUTATIONAL CHARACTERIZATION OF COMBUSTION PHENOMENA Dr. James R. Gord Combustion Branch (AFRL

  19. Simulation study on combustion of biomass

    NASA Astrophysics Data System (ADS)

    Zhao, M. L.; Liu, X.; Cheng, J. W.; Liu, Y.; Jin, Y. A.

    2017-01-01

    Biomass combustion is the most common energy conversion technology, offering the advantages of low cost, low risk and high efficiency. In this paper, the transformation and transfer of biomass in the process of combustion are discussed in detail. The process of furnace combustion and gas phase formation was analyzed by numerical simulation. The experimental results not only help to optimize boiler operation and realize the efficient combustion of biomass, but also provide theoretical basis for the improvement of burner technology.

  20. Combustion products generating and metering device

    NASA Technical Reports Server (NTRS)

    Wiberg, R. E.; Klisch, J. A. (Inventor)

    1971-01-01

    An apparatus for generating combustion products at a predetermined fixed rate, mixing the combustion products with air to achieve a given concentration, and distributing the resultant mixture to an area or device to be tested is described. The apparatus is comprised of blowers, a holder for the combustion product generating materials (which burn at a predictable and controlled rate), a mixing plenum chamber, and a means for distributing the air combustion product mixture.