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Sample records for urea combustion route

  1. Synthesis of La{sup 3+} doped nanocrystalline ceria powder by urea-formaldehyde gel combustion route

    SciTech Connect

    Biswas, M.; Bandyopadhyay, S.

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer Nano LC synthesized by gel combustion, using urea-formaldehyde fuel for first time. Black-Right-Pointing-Pointer Largely single crystals were produced in average range of 20-30 nm. Black-Right-Pointing-Pointer La{sup 3+} doping increases cell dimension linearly. Black-Right-Pointing-Pointer La{sup 3+} doping introduces ionic point defects but does not change electronic band gap. Black-Right-Pointing-Pointer Presence of Ce{sup 3+} indicates that this synthesis route produces reactive powders. -- Abstract: Nanocrystalline ceria powders doped with various concentrations of lanthanum oxide have been prepared following gel combustion route using for the first time urea-formaldehyde as fuel. The synthesized products were characterized by XRD, FESEM, TEM, PL and UV-vis spectroscopy. Peak positions of XRD were refined and the lattice parameters were obtained by applying Cohen's method. Unit cell parameter increases with concentration of La{sup 3+} ion and the variation is consistently linear. XRD calculations showed the dependence of crystallite size on dopant concentrations at lower level. TEM observation revealed unagglomerated particles to be single crystals in the average range of 20-30 nm. Band gap of the La{sup 3+} doped ceria materials does not change with doping. Spectroscopic experiments proved the existence of Ce{sup 3+} in the formed powder.

  2. 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.

  3. Urea

    Integrated Risk Information System (IRIS)

    Urea ; CASRN : 57 - 13 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effects ) a

  4. TG-FTIR study on urea-formaldehyde resin residue during pyrolysis and combustion.

    PubMed

    Jiang, Xuguang; Li, Chunyu; Chi, Yong; Yan, Jianhua

    2010-01-15

    The pyrolysis and combustion characteristics of urea-formaldehyde resin (UFR) residue were investigated by using thermogravimetric analysis, coupled with Fourier transform infrared spectroscopy (TG-FTIR). It is indicated that the pyrolysis process can be subdivided into three stages: drying the sample, fast thermal decomposition and further cracking process. The total weight loss of 90 wt.% at 950 degrees C is found in pyrolysis, while 74 wt.% of the original mass lost in the second stage is between 195 degrees C and 430 degrees C. The emissions of carbon dioxide, isocyanic acid, ammonia, hydrocyanic acid and carbon monoxide are identified in UFR residue pyrolysis, moreover, isocyanic acid emitted at low temperature is found as the most important nitrogen-containing gaseous product in UFR residue pyrolysis, and there is a large amount of hydrocyanic acid emitted at high temperature. The similar TG and emission characteristics as the first two stages during pyrolysis are found in UFR residue combustion at low temperature. The combustion process almost finishes at 600 degrees C; moreover, carbon dioxide and water are identified as the main gaseous products at high temperature. It is indicated that the UFR residue should be pyrolyzed at low temperature to remove the initial nitrogen, and the gaseous products during pyrolysis should be burnt in high temperature furnace under oxygen-rich conditions for pollutant controlling. PMID:19735979

  5. 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. PMID:21421389

  6. Dielectric properties of Bismuth Titanate (Bi4Ti3O12) synthesized using solution combustion route

    NASA Astrophysics Data System (ADS)

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

    2012-09-01

    Ferroelectric Bismuth Titanate (Bi4Ti3O12) was prepared by solution combustion route with glycine as fuel. The single phase Bismuth Titanate was obtained after calcination at 800 °C, which was confirmed with the help of X-ray diffraction studies and EDS analysis. SEM micrographs of the calcined powders show agglomerated particles, which is typical of combustion synthesis. Behavior of dielectric constant and dielectric loss as a function of temperature of as prepared sample are reported here. Ferroelectric to paraelectric phase transition occurs at the temperature Tc∼650 °C. Impedance studies were made in the frequency range from 1 KHz to 1 MHz. The semicircles observed in the complex impedance diagrams indicate deviation from the Debye behavior. Activation energy of the sample around Tc is found to be ∼0.35 eV and below Tc is ∼0.13 eV, which was calculated using the Arrhenius plots.

  7. 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.

  8. Nanostructures of the binary nitrides, BN, TiN, and NbN, prepared by the urea-route

    SciTech Connect

    Gomathi, A.; Rao, C.N.R. . E-mail: cnrrao@jncasr.ac.in

    2006-05-25

    By heating mixtures of H{sub 3}BO{sub 3}, TiCl{sub 4}, and NbCl{sub 5} with urea in 1:6 molar ratios in the 900-1000 deg. C range, nanoparticles of BN, TiN, and NbN have been obtained, respectively. The nanoparticles are crystalline and have been characterized by electron microscopy and other techniques. By carrying out the urea reaction over Au islands deposited on Si substrates, nanowires of TiN could be obtained.

  9. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties

    NASA Astrophysics Data System (ADS)

    Nassar, Mostafa Y.; Ahmed, Ibrahim S.; Samir, Ihab

    2014-10-01

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350 °C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65 nm was obtained at 800 °C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5 h with pseudo first order rate constants of 5.85 × 10-3 and 8.38 × 10-3 min-1, respectively.

  10. A novel synthetic route for magnesium aluminate (MgAl2O4) nanoparticles using sol-gel auto combustion method and their photocatalytic properties.

    PubMed

    Nassar, Mostafa Y; Ahmed, Ibrahim S; Samir, Ihab

    2014-10-15

    In this paper a novel and inexpensive route for the preparation of spinel magnesium aluminate nanoparticles (MgAl2O4) is proposed. Magnesium aluminate photocatalyst was synthesized via sol-gel auto combustion method using oxalic acid, urea, and citric acid fuels at 350°C. Subsequently, the burnt samples were calcined at different temperatures. The pure spinel MgAl2O4 with average crystallite size 27.7, 14.6 and 15.65nm was obtained at 800°C calcinations using the aforementioned fuels, respectively. The obtained samples were characterized by powder X-ray diffraction, Fourier transform infrared, UV-Vis spectroscopy, transmission electron microscope, scanning electron microscope. The photo catalytic activity of MgAl2O4 product was studied by performing the decomposition of Reactive Red Me 4BL dye under UV illumination or sunlight irradiation. The dye considerably photocatalytically degraded by 90.0% and 95.45% under UV and sunlight irradiation, respectively, within ca. 5h with pseudo first order rate constants of 5.85×10(-3) and 8.38×10(-3)min(-1), respectively. PMID:24835935

  11. 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.

  12. Synthesis of monodisperse spherical nanometer ZrO{sub 2} (Y{sub 2}O{sub 3}) powders via the coupling route of w/o emulsion with urea homogenous precipitation

    SciTech Connect

    Chang, Ying; Dong, Shijie; Wang, Huihu; Du, Kuanhe; Zhu, Qingbiao; Luo, Ping

    2012-03-15

    Graphical abstract: In this paper, the weight loss and reaction evolution of ZrO{sub 2} precursor powders are determined by TG-DTA, and 600 Degree-Sign C is the most reasonable calcination temperature of precursor according to the TG-DTA. At the same time, we study the effect of reaction conditions upon the particle sizes, such as concentration of zirconium nitrate solution, reaction temperature and urea content. TEM micrographs of zirconia powders indicated that ZrO{sub 2} nano-powders prepared via the coupling route of w/o emulsion with homogenous precipitation possess spherical shape and excellent dispersing. Highlights: Black-Right-Pointing-Pointer The monodisperse spherical nanometer ZrO{sub 2} (Y{sub 2}O{sub 3}) powders have been prepared via the coupling route of w/o emulsion with urea homogenous precipitation. Black-Right-Pointing-Pointer The principle of the coupling route of emulsion with homogenous precipitation has been studied. Black-Right-Pointing-Pointer The concentration of zirconium nitrate, reaction temperature of water bath and the quantity of urea effect regularly on the average particle size of products. -- Abstract: Using xylol as the oil phase, span-80 as the surfactant, and an aqueous solution containing zirconium (3 mol% Y{sub 2}O{sub 3}) and urea as the water phase, tetragonal phase ZrO{sub 2} nano-powders have been prepared via the coupling route of w/o emulsion with urea homogenous precipitation. The effects of the zirconium concentration, the reaction temperature and the urea content on the average size of the products have been examined. The as-prepared ZrO{sub 2} powders and the precursor powders were characterized by TGA-DTA, XRD, TEM and BET. Experimental results indicate that ZrO{sub 2} powders prepared via the coupling route of w/o emulsion with urea homogenous precipitation possess some excellent characteristics, such as well-rounded spherical shape and excellent dispersing.

  13. Dermal Uptake from Airborne Organics as an Important Route of Human Exposure to E-Waste Combustion Fumes.

    PubMed

    Wu, Chen-Chou; Bao, Lian-Jun; Tao, Shu; Zeng, Eddy Y

    2016-07-01

    Skin absorption of gaseous organic contaminants is an important and relevant mechanism in human exposure to such contaminants, but has not been adequately examined. This article demonstrates that dermal uptake from airborne contaminants could be recognized as a significant exposure route for local residents subjecting to combustion fume from e-waste recycling activities. It is particularly true for organic pollutants which have high dermal penetration rates and large skin-air partition coefficients, such as low molecular weight plasticizers and flame retardants. PMID:26937778

  14. 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.

  15. 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. PMID:18047085

  16. Energy storage performance of urea combustion derived nanocrystalline-Li2MnSiO4 as a novel electrode material for symmetric supercapacitor

    NASA Astrophysics Data System (ADS)

    Chaturvedi, Prerna; Sil, Anjan; Sharma, Yogesh

    2016-05-01

    A novel symmetric supercapacitor (SSC) consisting of urea combustion derived mesoporous Li2MnSiO4 (LMS) in aqueous electrolyte is investigated for the first time. The morphological and surface area analysis were conducted using FESEM and N2 adsorption/desorption measurements confirming the presence of mesopores with good surface area of nanocrystalline LMS. The electrochemical investigation of the SSC is examined using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) cycling, and the results are complimented with electrochemical impedance spectroscopy (EIS) in 2 M KOH aqueous solution. SSC exhibits the specific capacitance (Cs) of 40(±2) F g-1 at 3 mV s-1 and 42(±2) F g-1 at 0.1 A g-1 in voltage window ranging from -0.65 V to +0.65 V. GCD analysis illustrates good capacity retention and cyclability up to 1000 cycles. This improved performance of LMS in terms of rate capability, cyclability is mainly attributed to its unique morphology where high surface area and mesoporosity enables facile and smooth transportation of foreign electrolytic ions, and thereby increase the participation of active material in device.

  17. 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

  18. 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.

  19. 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. PMID:25733848

  20. 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

  1. 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.

  2. A comparative study on structural, morphological and luminescence characteristics of Zn3(VO4)2 phosphor prepared via hydrothermal and citrate-gel combustion routes

    NASA Astrophysics Data System (ADS)

    Pitale, Shreyas S.; Gohain, Mukut; Nagpure, I. M.; Ntwaeaborwa, O. M.; Bezuidenhoudt, Barend C. B.; Swart, H. C.

    2012-05-01

    Comparison of structural, morphological and spectroscopic properties of zinc vanadate Zn3(VO4)2 phosphor synthesized via two different methods, viz. citrate-gel combustion and hydrothermal reaction, is presented. Highly crystalline and pure phase micro-rods are achieved by citrate-gel combustion route. The hydrothermal reaction products exhibit ribbon like structures. X-ray photoelectron spectroscopic investigation reveals the presence of multiple oxidation states of vanadium in the hydrothermally synthesized phosphor. Luminescence properties have also been compared and the effect of divalent cationic substitution (Ca, Mg) is presented.

  3. 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.

  4. Influence of the Processing Route in the Microstructure and Mechanical Properties of NiAl/TiB2 Composites Produced by Combustion Synthesis

    NASA Astrophysics Data System (ADS)

    Torres, Ricardo D.; Lepienski, Carlos M.; Moore, John J.; Reimanis, Ivar E.

    2009-04-01

    In this work, dense NiAl/TiB2 composites with varying amounts of TiB2 were produced by combustion synthesis routes. The morphology of the TiB2 phase in the composite has been modified by changing the reactants in the initial powder mixture. In the first processing route, NiAl and TiB2 phases were obtained from Ni, Al, Ti, and B elemental powders. In the second processing route, TiB2 was added, instead of Ti and B, along with Ni and Al to produce NiAl and TiB2 phases. The XRD performed on the products of both processing routes confirmed that the synthesized phases were indeed TiB2 and NiAl. The NiAl grain size is smaller for the composites obtained in the first processing route. In addition, the first processing route leads to clusters of TiB2 submicron particles in which the matrix is either TiB2 or NiAl depending on the starting composition. The second processing route results in less dense composites in which the matrix is the NiAl and the TiB2 exists as dispersed platelets. The hardness ( H) and Young’s modulus ( E) were observed to be higher for composites produced by the first processing route. This difference in the mechanical properties is caused by the difference in microstructure, as well as the difference in porosity between the two processing routes.

  5. 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. PMID:23835056

  6. A single phase, red emissive Mg2SiO4:Sm3+ nanophosphor prepared via rapid propellant combustion route.

    PubMed

    Naik, Ramachandra; Prashantha, S C; Nagabhushana, H; Sharma, S C; Nagaswarupa, H P; Anantharaju, K S; Nagabhushana, B M; Premkumar, H B; Girish, K M

    2015-04-01

    Mg2SiO4:Sm3+ (1-11 mol%) nanoparticles were prepared by a rapid low temperature solution combustion route. The powder X-ray diffraction (PXRD) patterns exhibit orthorhombic structure with α-phase. The average crystallite size estimated using Scherer's method, W-H plot and strain-size plots were found to be in the range 25-50 nm and the same was confirmed by Transmission Electron Microscopy (TEM). Scanning electron microscopy (SEM) pictures show porous structure and crystallites were agglomerated. The effect of Sm3+ cations on luminescence of Mg2SiO4 was well studied. Interestingly the samples could be effectively excited with 315 nm and emitted light in the red region, which was suitable for the demands of high efficiency WLEDs. The emission spectra consists of four main peaks which can be assigned to the intra 4-f orbital transitions of Sm3+ ions 4G5/2→6H5/2 (576 nm), 4G5/2→6H7/2 (611 nm), 4G5/2→6H9/2 (656 nm) and 4G5/2→6H11/2 (713 nm). The optimal luminescence intensity was obtained for 5 mol% Sm3+ ions. The CIE (Commission International de I'Eclairage) chromaticity co-ordinates were calculated from emission spectra, the values (0.588, 0.386) were close to the NTSC (National Television Standard Committee) standard value of red emission. Coordinated color temperature (CCT) was found to be 1756 K. Therefore optimized Mg2SiO4:Sm3+ (5 mol%) phosphor was quite useful for solid state lighting. PMID:25638435

  7. A single phase, red emissive Mg2SiO4:Sm3+ nanophosphor prepared via rapid propellant combustion route

    NASA Astrophysics Data System (ADS)

    Naik, Ramachandra; Prashantha, S. C.; Nagabhushana, H.; Sharma, S. C.; Nagaswarupa, H. P.; Anantharaju, K. S.; Nagabhushana, B. M.; Premkumar, H. B.; Girish, K. M.

    2015-04-01

    Mg2SiO4:Sm3+ (1-11 mol%) nanoparticles were prepared by a rapid low temperature solution combustion route. The powder X-ray diffraction (PXRD) patterns exhibit orthorhombic structure with α-phase. The average crystallite size estimated using Scherer's method, W-H plot and strain-size plots were found to be in the range 25-50 nm and the same was confirmed by Transmission Electron Microscopy (TEM). Scanning electron microscopy (SEM) pictures show porous structure and crystallites were agglomerated. The effect of Sm3+ cations on luminescence of Mg2SiO4 was well studied. Interestingly the samples could be effectively excited with 315 nm and emitted light in the red region, which was suitable for the demands of high efficiency WLEDs. The emission spectra consists of four main peaks which can be assigned to the intra 4-f orbital transitions of Sm3+ ions 4G5/2 → 6H5/2 (576 nm), 4G5/2 → 6H7/2 (611 nm), 4G5/2 → 6H9/2 (656 nm) and 4G5/2 → 6H11/2 (713 nm). The optimal luminescence intensity was obtained for 5 mol% Sm3+ ions. The CIE (Commission International de I'Eclairage) chromaticity co-ordinates were calculated from emission spectra, the values (0.588, 0.386) were close to the NTSC (National Television Standard Committee) standard value of red emission. Coordinated color temperature (CCT) was found to be 1756 K. Therefore optimized Mg2SiO4:Sm3+ (5 mol%) phosphor was quite useful for solid state lighting.

  8. 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}.

  9. Disposition of exogenous urea and effects of diet in rats.

    PubMed

    Nomura, Naruaki; Matsumoto, Satoshi; Nishimura, Yuka; Terauchi, Yoshiaki; Fujii, Toshihiko

    2006-01-01

    Although breath test using 13C-labeled urea (CAS 57-13-6, UBT) is becoming popular for the diagnosis of Helicobacter pylori (H. pylori) infection, disposition of exogenously given urea is not fully understood. The purpose of the present study is to elucidate the disposition of exogenous urea and to consider its relation with the UBT safety and biobehavior of endogenous urea. With 14C-labeled urea ([14C]urea), the absorption, distribution, metabolism and excretion including that into breathed air after its administration in trace to large doses in rats were investigated. [14C]Urea was given to fasted and non-fasted rats through intravenous and oral routes. It was found that the disposition of exogenous [14C]urea behaves in a similar way as endogenous urea, and a sufficiently large capacity for disposing urea in rats was suggested from the linear pharmacokinetics within the wide dose range of [14C]urea (2-1000 mg/kg). The safety of urea in UBT was also revealed by consideration of its dose and human urea body pool. It was also suggested that diet stimulates both systemic (as observed after the intravenous dose) and pre-systemic (as with the oral route) decompositions of urea into carbon dioxide and ammonia, but does not affect the renal elimination and distribution pattern in rat tissues. The findings in this study provide us with the quantitative information concerning not only the safety and disposition of urea as a diagnostic agent, but also the biobehavior of endogenous urea in ureotelism. PMID:16618019

  10. 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.

  11. Optical properties and chemical composition analyses of mixed rare earth oxyorthosilicate (R2SiO5, R=La, Gd and Y) doped Dy3+ phosphors prepared by urea-assisted solution combustion method

    NASA Astrophysics Data System (ADS)

    Ogugua, S. N.; Shaat, S. K. K.; Swart, H. C.; Ntwaeaborwa, O. M.

    2015-08-01

    Dysprosium (Dy3+) doped lanthanum gadolinium oxyorthosilicate (LaGdSiO5), lanthanum yttrium oxyorthosilicate (LaYSiO5) and gadolinium yttrium oxyorthosilicate (GdYSiO5) phosphors (in powder form) were synthesized by urea-assisted combustion method. The X-ray diffractometer analysis confirmed that the LaGdSiO5, LaYSiO5 and GdYSiO5 crystalized in monoclinic phases. The chemical composition of the phosphors was analyzed by measuring the atomic and molecular ionic species using the time of flight secondary ion mass spectroscopy (ToF SIMS). In addition, ToF SIMS imaging technique was used to determine the distribution of the Dy3+ dopant ions on the surface on the phosphors. The average crystallite sizes and lattice strains of the phosphor were increased by Dy3+ doping. The field emission scanning electron microscope images showed that the powders were made up of an agglomeration of particles with no regular shape. The photoluminescence data showed narrow line emission peaks at the wavelengths of 485 nm (minor emission) and 573 nm (major emission) associated with the f→f transitions of Dy3+. The photoluminescence (PL) measurements showed that the emission peak of LaGdSiO5:Dy3+ was ~3× more intense than those of LaYSiO5:Dy3+ and GdYSiO5:Dy3+ when excited using monochromatic xenon lamp with a wavelength of 241 nm. However, when the powders were excited using a 325 nm He-Cd laser, the highest PL emission intensity was observed from GdYSiO5:Dy3+.

  12. EPR investigation on synthesis of Lithium zinc vanadate using sol-gel-combustion route and its optical properties

    NASA Astrophysics Data System (ADS)

    Pathak, Nimai; Gupta, Santosh K.; Prince, Angelina; Kadam, R. M.; Natarajan, V.

    2014-01-01

    The present work describes the synthesis of Lithium zinc vanadate (LiZnVO4) nanophosphor prepared by sol-gel-combustion method and its optical properties. The prepared sample was characterized by X-ray diffraction, SEM, electron paramagnetic resonance and photoluminescence spectroscopy. X-ray diffraction study showed the formation of pure LiZnVO4 at 600 °C with distorted phenacite structure. SEM investigation revealed that the phosphor powder has spherical morphology with particle size of about 100-200 nm. EPR study showed the change of coordination sphere around vanadium from axially distorted octahedral symmetry to tetrahedral geometry along with the change in oxidation state of vanadium ion from +4 to +5. The emission spectrum showed a broad emission at 543 nm with λex = 375 nm. The decay time obtained on mono-exponential fitting was 8.3 μs. The colour coordinates of the system were evaluated using CIE index diagram to be 0.31 and 0.41, which suggest that the prepared material is a potential green emitting phosphor. A bright green colour emission was also observed directly from this phosphor upon excitation with an UV source.

  13. Synthesis and spectroscopic characterization of nanoparticles of TiO2 doped with Pt produced via the self-combustion route

    NASA Astrophysics Data System (ADS)

    Lopera, A. A.; Chavarriaga, E. A.; Estupiñan, H. A.; Valencia, I. C.; Paucar, C.; Garcia, C. P.

    2016-05-01

    Titanium oxide (TiO2) is the most important semiconductor used in photocatalysis. For that reason, most recent scientific studies have focused on improving the absorbance of this material in the visible region. In this paper, we report on the production of nanopowders of TiO2 doped with platinum via the solution combustion synthesis method, using glycine as a fuel at concentrations of 0.3, 0.6, 0.9, and 1.2% w/w of Pt with respect to TiO2 (Pt / TiO2), in order to study the influence of the dopant content on the absorbance spectrum in the visible region. The structure of the samples was characterized using x-ray diffraction and Raman spectroscopy, which confirmed the production of a pure anatase phase. VIS diffuse reflectance spectroscopy confirmed that in the visible region the samples doped with Pt absorb within the range of 400 nm to 800 nm. Field emission scanning electron microscopy and transmission electron microscopy showed the formation of TiO2 nanoparticles with an average size of 13 nm and with spherical morphology. Colorimetry (Commission Internationale de l’Eclairage L *, a *, b *) confirmed photocatalytic activity for the degradation of rhodamine B using visible light. It was concluded that the route of synthesis and the Pt content play important roles in the absorbance spectrum and the activation energy of TiO2.

  14. Phase evolution and morphology of nanocrystalline BaCe0.9Er0.1O3-δ proton conducting oxide synthesised by a novel modified solution combustion route

    NASA Astrophysics Data System (ADS)

    Babu, A. S.; Bauri, Ranjit

    2015-12-01

    Pure BaCeO3 and 10 mol% Er2O3 doped BaCeO3 (BCE) was synthesised by a novel modified solution combustion synthesis (MCS) route wherein the pH of the precursor solution was varied and the phase formation and morphology were compared with those obtained in conventional solution combustion synthesis (SCS). X-ray diffraction (XRD) studies confirmed the presence of the undesirable BaCO3 phase in the calcined powders prepared using SCS route whereas the powders synthesised with the modified (MCS) route exhibited a single perovskite phase after calcination. Variation in the pH of the precursor solution resulted in a morphology change from a mix of irregular and globular at pH 4 to more spherical at pH 6 and 8. Fourier transform infrared spectroscopy (FT-IR) studies revealed that calcination time has more pronounced effect on phase formation than calcination temperature. A calcination time of 10 h at 1000 °C resulted in negligible amount of BaCO3. Such prolonged calcination treatment resulted in substantial grain growth in the SCS sample while the MCS samples were still in the nanocrystalline form. Absence of the ceria peak (464 cm-1) in the Raman spectra confirmed the presence of a single perovskite BaCeO3 phase in the sintered pellets as well.

  15. Urea Utilization by Leptospira

    PubMed Central

    Kadis, Solomon; Pugh, William L.

    1974-01-01

    One representative of each of five different pathogenic serotypes of Leptospira as well as one saprophytic strain were capable of growing on medium containing urea in place of an ammonium salt as a nitrogen source. Growth of all of the organisms tested on 1% urea was substantial, but only those that exhibited strong urease activity could grow to any appreciable extent on urea at a concentration as high as 2%. Intact urea-grown cells of the pathogenic serotypes tested (grippotyphosa and icterohaemorrhagiae) exhibited urease activity, with the level of activity of the former being considerably greater. No urease could be detected in cells of the saprophytic strain. When the pathogenic leptospires were sonicated or treated with toluene, the urease activity was greatly enhanced. When cultivated on NH4Cl, neither intact nor disrupted cells of any of the strains tested exhibited any urease activity. Cells of the grippotyphosa and icterohaemorrhagiae strains exhibited diauxic growth when cultivated in the presence of both NH4Cl and urea, whereas only monophasic growth could be detected for the saprophytic test strain. The experimental data on urea utilization and urease activity, when considered in the light of previously reported findings on leptospiral pathology, renal physiology, and the role of urease in other bacterial infections, suggests a significant role for leptospiral urease (in addition to other factors) in determining localization of the organism in the kidney and contributing to the resultant kidney pathology. PMID:4426709

  16. 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. PMID:26608657

  17. Detection of Interstellar Urea

    NASA Astrophysics Data System (ADS)

    Kuo, Hsin-Lun; Remijan, Anthony J.; Snyder, Lewis E.; Looney, Leslie W.; Friedel, Douglas N.; Lovas, Francis J.; McCall, Benjamin J.; Hollis, Jan M.

    2010-11-01

    Urea, a molecule discovered in human urine by H. M. Rouelle in 1773, has a significant role in prebiotic chemistry. Previous BIMA observations have suggested that interstellar urea [(NH2)2CO] is a compact hot core molecule such as other large molecules (e.g. methyl formate and acetic acid). We have conducted an extensive search for urea toward the high mass hot molecular core Sgr B2(N-LMH) using BIMA, CARMA and the IRAM 30 m. Because the spectral lines of heavy molecules like urea tend to be weak and hot cores display lines from a wide range of molecules, it is necessary to detect a number of urea lines and apply sophisticated statistical tests before having confidence in an identification. The 1 mm resolution of CARMA enables favorable coupling of the source size and synthesized beam size, which was found to be essential for the detection of weak signals. We have detected a total of 65 spectral lines (32 molecular transitions and 33 unidentified transitions), most of which are narrower than the SEST survey (Nummelin et al. 1998) due to the small synthesized beam (2.5" x 2") of CARMA. It significantly resolves out the contamination by extended emission and reveals the eight weak urea lines that were previously blended with nearby transitions. Our analysis indicates that these lines are likely to be urea since the resulting observed line frequencies are coincident with a set of overlapping connecting urea lines, and the observed line intensities are consistent with the expected line strengths of urea. In addition, we have developed a new statistical approach to examine the spatial correlation between the observed lines by applying the Student's t test to the high resolution channel maps obtained from CARMA. The t test shows consistent spatial distributions from all eight candidate lines, suggesting a common molecular origin, urea. Our t test method could have a broad impact on the next generation of arrays, such as ALMA, because the new arrays will require a method

  18. 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.

  19. Urea Cycle Disorders.

    PubMed

    Kleppe, Soledad; Mian, Asad; Lee, Brendan

    2003-07-01

    Urea cycle disorders comprise a group of inborn errors of metabolism that represent unique gene-nutrient interactions whose significant morbidity arises from acute and chronic neurotoxicity associated with often massive hyperammonemia. Current paradigms of treatment are focused on controlling the flux of nitrogen transfer through the hepatic urea cycle by a combination of dietary and pharmacologic approaches. Evolving paradigms include the development of cell and gene therapies. Current research is focused on understanding the pathophysiology of ammonia-mediated toxicity and prevention of neural injury. PMID:12791198

  20. Influence of fuel/oxidizer ratio on lattice parameters and morphology of combustion synthesized ZnO powders

    NASA Astrophysics Data System (ADS)

    Sharma, Suchinder K.; Pitale, Shreyas S.; Manzar Malik, M.; Dubey, R. N.; Qureshi, M. S.; Ojha, Siddharth

    2010-02-01

    We report synthesis of ZnO powders via dry combustion route. Among various parameters affecting the product formation during combustion synthesis, one is Fuel-to-oxidizer (F/O) ratio. In the present work, we have used urea as fuel and as a habit modifier. The crystallinity of ZnO is insensitive to F/O variations and fuel lean combustion procedures also leads to appropriate ZnO phase formation. Profile fitting analysis is carried out to correlate the observed and standard diffraction patterns for various samples coded SSD1 to SSD13. Williamson-Hall plot elucidates important contribution of size and strain in the diffraction pattern. Good correlation of lattice parameters is found to exist between calculated and standard values. Wealth of morphological forms (hexagonal pyramidal, spheriulitic, platelet ) and a systematic growth trend is observed. Tailored morphological and consequentially engineered physical properties can be harnessed from ZnO when urea is used. The hexagonal pyramids are anticipated to be suitable for electronic and optoelectronic devices such as field emitters, optoelectronic devices for medical diagnostics, etc. The same morphology can be easily achieved via variation in urea content through cost effective technique.

  1. The urea cycle disorders.

    PubMed

    Helman, Guy; Pacheco-Colón, Ileana; Gropman, Andrea L

    2014-07-01

    The urea cycle is the primary nitrogen-disposal pathway in humans. It requires the coordinated function of six enzymes and two mitochondrial transporters to catalyze the conversion of a molecule of ammonia, the α-nitrogen of aspartate, and bicarbonate into urea. Whereas ammonia is toxic, urea is relatively inert, soluble in water, and readily excreted by the kidney in the urine. Accumulation of ammonia and other toxic intermediates of the cycle lead to predominantly neurologic sequelae. The disorders may present at any age from the neonatal period to adulthood, with the more severely affected patients presenting earlier in life. Patients are at risk for metabolic decompensation throughout life, often triggered by illness, fasting, surgery and postoperative states, peripartum, stress, and increased exogenous protein load. Here the authors address neurologic presentations of ornithine transcarbamylase deficiency in detail, the most common of the urea cycle disorders, neuropathology, neurophysiology, and our studies in neuroimaging. Special attention to late-onset presentations is given. PMID:25192511

  2. Urea distribution in renal failure

    PubMed Central

    Blackmore, D. J.; Elder, W. J.; Bowden, C. H.

    1963-01-01

    An assessment of intracellular urea removed during haemodialysis has been made from urea extraction and plasma urea estimations. An apparent wide variation in the movement of intracellular urea in patients with acute renal failure from obstetric and traumatic causes and with chronic renal failure is reported. A method for the estimation of red cell water urea is presented. In two patients with chronic renal failure the red cell urea level was much higher than would have been expected from the plasma urea level before dialysis. In two obstetric patients there was no such discrepancy. The conclusion is drawn that research should be directed to variations of intracellular metabolism in renal failure before a more rational approach can be made to its management. PMID:16811009

  3. Towards optoelectronic urea biosensors.

    PubMed

    Pokrzywnicka, Marta; Koncki, Robert; Tymecki, Łukasz

    2015-03-01

    Integration of immobilized enzymes with light-emitting diodes (LEDs) leads to the development of optoelectronic enzyme-based biosensors. In this work, urease, used as a model enzyme, immobilized in the form of an open-tubular microbioreactor or biosensing membrane that has been integrated with two red LEDs. It forms complete, fiberless, miniaturized, and extremely economic biooptoelectronic devices useful for nonstationary measurements under flow analysis conditions. Both enzyme-based biodevices, operating according to the paired emitter detector diode (PEDD) principle, allow relatively fast, highly sensitive, and well-reproducible urea detection in the millimolar range of concentrations. Potential analytical applications of the developed urea bioPEDDs have been announced. Both presented constructions will be easily adapted for the development of other optoelectronic biosensors exploring various enzyme-based schemes of biodetection. PMID:25619983

  4. 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.

  5. 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. PMID:27119061

  6. 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.

  7. Solution combustion synthesis of CeO{sub 2}-CeAlO{sub 3} nano-composites by mixture-of-fuels approach

    SciTech Connect

    Aruna, S.T.; Kini, N.S. Rajam, K.S.

    2009-04-02

    Nano-composites of CeO{sub 2}-CeAlO{sub 3} are synthesised by solution combustion method employing (a) urea and (b) a mixture of urea and glycine as fuels with corresponding metal nitrates. The as-prepared powders are all nano-sized (5-30 nm) and the same is confirmed by broadening of the X-ray diffraction peaks and transmission electron microscopy. A starting composition of Ce:Al in the atomic ratio 4:6 gives rise to different phases depending on the fuel being used for combustion. When urea alone is used as fuel, nano-crystalline CeO{sub 2} phase is formed with Al{sub 2}O{sub 3} being in the amorphous state. When the mixture of fuels is used, a mixture of nano-sized CeO{sub 2} and CeAlO{sub 3} phases is obtained. However, upon sintering at 1400 deg. C in air, the stable phases CeO{sub 2} and {alpha}-Al{sub 2}O{sub 3} are formed in both the cases. Combustion synthesis using mixture-of-fuels is proposed to be a route to stabilise low oxidation compounds such as CeAlO{sub 3}.

  8. Urea and urea nitrate decomposition pathways: a quantum chemistry study.

    PubMed

    Tokmakov, Igor V; Alavi, Saman; Thompson, Donald L

    2006-03-01

    Electronic structure calculations have been performed to investigate the initial steps in the gas-phase decomposition of urea and urea nitrate. The most favorable decomposition pathway for an isolated urea molecule leads to HNCO and NH3. Gaseous urea nitrate formed by the association of urea and HNO3 has two isomeric forms, both of which are acid-base complexes stabilized by the hydrogen-bonding interactions involving the acidic proton of HNO3 and either the O or N atoms of urea, with binding energies (D0(o), calculated at the G2M level with BSSE correction) of 13.7 and 8.3 kcal/mol, respectively, and with estimated standard enthalpies of formation (delta(f)H298(o) of -102.3 and -97.1 kcal/mol, respectively. Both isomers can undergo relatively facile double proton transfer within cyclic hydrogen-bonded structures. In both cases, HNO3 plays a catalytic role for the (1,3) H-shifts in urea by acting as a donor of the first and an acceptor of the second protons transferred in a relay fashion. The double proton transfer in the carbonyl/hydrogen bond complex mediates the keto-enol tautomerization of urea, and in the other complex the result is the breakdown of the urea part to the HNCO and NH3 fragments. The enolic form of urea is not expected to accumulate in significant quantities due to its very fast conversion back to H2NC(O)NH2 which is barrierless in the presence of HNO3. The HNO3-catalyzed breakdown of urea to HNCO and NH3 is predicted to be the most favorable decomposition pathway for gaseous urea nitrate. Thus, HNCO + NH3 + HNO3 and their association products (e.g., ammonium nitrate and isocyanate) are expected to be the major initial products of the urea nitrate decomposition. This prediction is consistent with the experimental T-jump/FTIR data [Hiyoshi et al. 12th Int. Detonation Symp., Aug 11-16, San Diego, CA, 2002]. PMID:16494387

  9. A simple solution combustion route for the preparation of metal-doped TiO2 nanoparticles and their photocatalytic degradation properties.

    PubMed

    Ni, Yonghong; Zhu, Yan; Ma, Xiang

    2011-04-14

    In this paper, we report the successful synthesis of metal ion-doped TiO(2) nanoparticles via a simple solution combustion method employing a mixture of ethanol and ethyleneglycol (v/v = 30/20) as the solvent, tetra-n-butyl titanate [Ti(OC(4)H(9))(4), TBOT] as the titanium source and oxygen gas in the atmosphere as the oxygen source, in the presence of small amounts of metal ions such as Cu(2+), Mn(2+), Ce(3+) and Sn(4+). The as-obtained products were characterized by means of powder X-ray diffraction (XRD), energy dispersive X-ray spectrometry (EDS) and scanning electron microscopy (SEM). The UV-vis diffuse reflectance spectra (DRS) and photoluminescence (PL) spectra of various metal ion-doped products were investigated. Experiments showed that the metal ion-doped TiO(2) nanoparticles presented a stronger photocatalytic ability for the degradation of organic dyes, including Pyronine B, Safranine T and Methylene blue (MB), under visible light/254 nm UV light irradiation than commercial P25 within the same time. PMID:21369610

  10. 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.

  11. 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.

  12. National Urea Cycle Disorders Foundation

    MedlinePlus

    ... urea cycle in regulating nitric oxide in the human body, the study is being conducted by Dr. ... a major discovery in ASA deficiency that transforms human science. The research has been published in Nature ...

  13. Urea phosphate as granular or fluid fertilizers

    SciTech Connect

    Blouin, G.M.

    1984-01-01

    Studies are being conducted of the production and agronomic characteristics of the phosphoric acid-urea adduct, urea phosphate, and of the various granular and fluid fertilizers that can be produced from it. Flowsheets are given for the production of urea phosphate. Characteristics of unpurified and purified urea phosphate are also given. (DLC)

  14. 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.

  15. "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. PMID:26399043

  16. New enzymatic assay for serum urea nitrogen using urea amidolyase.

    PubMed

    Kimura, Shigeki; Iyama, Shigeru; Yamaguchi, Yoshihisa; Kanakura, Yuzuru

    2003-01-01

    We established an enzymatic assay for measurement of serum urea nitrogen using urea amidolyase (EC 3.5.1.45) from yeast species. The method is based on hydrolysis of urea by the enzyme. In this assay, we eliminated endogenous ammonium ion by use of glutamate dehydrogenase (EC 1.4.1.4). Then in the presence of urea amido-lyase, ATP, bicarbonate, magnesium, and potassium ions, ammonium ion was produced proportionally to urea concentration in serum. The concentra-tion of ammonium ion formed was determined by adding GLDH to produce NADP(+) in the presence of 2-oxoglutarate and NADPH. We then monitored the change of absorbance at 340 nm. The inhibitory effect of calcium ion on this assay was eliminated by adding glyco-letherdiamine-N, N, N', N'-tetraacetic acid to the reaction system. The with-in-assay coefficient of variations (CVs) of the present method were 1.80-3.76% (n = 10) at 2.8-19.0 mmol/L, respectively. The day-to-day CVs were 2.23-4.59%. Analytical recovery was 92-115%. The presence of ascorbic acid, bilirubin, hemoglobin, lipemic material, ammo-nium ion, or calcium ion did not affect this assay system. The correlation be-tween values obtained with the present method (y) and those by another enzy-matic method (x) was 0.997 (y = 1.02x - 0.10 mmol/L, Sy/x = 0.841, n = 100), with a mean difference of -0.18 +/- 0.86 mmol/L [(values by reference method - that of present method) +/- SD] using the Bland-Altman technique. J. Clin. Lab. Anal. 17:52-56, 2003. PMID:12640627

  17. 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 ...

  18. 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)

  19. 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...

  20. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 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...

  1. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Urea. 184.1923 Section 184.1923 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) DIRECT FOOD....1923 Urea. (a) Urea (CO(NH2)2, CAS Reg. No. 57-13-6) is the diamide of carbonic acid and is also...

  2. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 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...

  3. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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...

  4. 40 CFR 721.9892 - Alkylated urea.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 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...

  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. 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.

  7. 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.

  8. 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.

  9. Metabolism of urea by Chlorella vulgaris.

    PubMed

    Hodson, R C; Thompson, J F

    1969-05-01

    Urea metabolism was studied with nitrogen-starved cells of Chlorella vulgaris Beijerinck var. viridis (Chodat), a green alga which apparently lacks urease. Incorporation of radioactivity from urea-(14)C into the alcohol-soluble fraction was virtually eliminated in cell suspensions flushed with 10% CO(2) in air. This same result was obtained when expected acceptors of urea carbon were replenished by adding ornithine and glucose with the urea. Several carbamyl compounds, which might be early products of urea metabolism and a source of the (14)CO(2), were not appreciably labeled. If cells were treated with cyanide at a concentration which inhibited ammonia uptake completely and urea uptake only slightly, more than half of the urea nitrogen taken up was found in the medium as ammonia. Cells under nitrogen gas in the dark were unable to take up urea or ammonia, but the normal rate of uptake was resumed in light. Since 3-(3,4-dichlorophenyl)-1,1-dimethylurea did not selectively inhibit this uptake, an active respiration supported by light-dependent oxygen evolution in these cells was ruled out. A tentative scheme for urea metabolism is proposed to consist of an initial energy-dependent splitting of urea into carbon dioxide and ammonia. This reaction in Chlorella is thought to differ from a typical urease-catalyzed reaction by the apparent requirement of a high energy compound, possibly adenosine triphosphate. PMID:5783973

  10. 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.

  11. 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.

  12. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false 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...

  13. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false 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...

  14. 21 CFR 184.1923 - Urea.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false 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...

  15. 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 CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of Specific Substances Affirmed as GRAS § 184.1923 Urea....

  16. 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.

  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. PMID:25298342

  19. Combustion detector

    NASA Technical Reports Server (NTRS)

    Trimpi, R. L.; Nealy, J. E.; Grose, W. L. (Inventor)

    1973-01-01

    A device has been developed for generating a rapid response signal upon the radiation-emitting combustion reaction of certain gases in order to provide a means for the detection and identification of such reaction and concurrently discriminate against spurious signals. This combustion might be the first stage of a coal mine explosion process, and thereby this device could provide a warning of the impending explosion in time to initiate quenching action. This device has the capability of distinguishing between the light emitted from a combustion reaction and the light emitted by miners' lamps, electric lamps, welding sparks or other spurious events so that the quenching mechanism is triggered only when an explosion-initiating combustion occurs.

  20. 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.

  1. Combustion physics

    NASA Astrophysics Data System (ADS)

    Jones, A. R.

    1985-11-01

    Over 90% of our energy comes from combustion. By the year 2000 the figure will still be 80%, even allowing for nuclear and alternative energy sources. There are many familiar examples of combustion use, both domestic and industrial. These range from the Bunsen burner to large flares, from small combustion chambers, such as those in car engines, to industrial furnaces for steel manufacture or the generation of megawatts of electricity. There are also fires and explosions. The bountiful energy release from combustion, however, brings its problems, prominent among which are diminishing fuel resources and pollution. Combustion science is directed towards finding ways of improving efficiency and reducing pollution. One may ask, since combustion is a chemical reaction, why physics is involved: the answer is in three parts. First, chemicals cannot react unless they come together. In most flames the fuel and air are initially separate. The chemical reaction in the gas phase is very fast compared with the rate of mixing. Thus, once the fuel and air are mixed the reaction can be considered to occur instantaneously and fluid mechanics limits the rate of burning. Secondly, thermodynamics and heat transfer determine the thermal properties of the combustion products. Heat transfer also plays a role by preheating the reactants and is essential to extracting useful work. Fluid mechanics is relevant if work is to be performed directly, as in a turbine. Finally, physical methods, including electric probes, acoustics, optics, spectroscopy and pyrometry, are used to examine flames. The article is concerned mainly with how physics is used to improve the efficiency of combustion.

  2. Urea Output by L3 Teladorsagia circumcincta and some Properties of Two Urea Producing Enzymes

    PubMed Central

    Muhamad, N; Walker, LR; Simcock, DC; Pedley, KC; Simpson, HV; Brown, S

    2013-01-01

    Background Like several other parasites, Teladorsagia circumcincta secretes or excretes urea, but neither the rate of efflux nor the possible metabolic sources of the urea has been considered. Methods Parasites were maintained by passage through sheep. Urea efflux was measured using phenol/hypochlorite after treatment with urea aminohydrolase. The kinetics of creatine amidinohydrolase and arginine amidinohydrolase were characterised by coupling the reactions with urea aminohydrolase and glutamate dehydrogenase. Results Infective L3 T. circumcincta secreted or excreted urea at 25% of the rate of NH3/NH4 +. The rate of urea efflux was about 84 pmol h−1 (103 larvae)−1 over 4 hours, corresponding to about 11 nmol h−1 mg−1 protein. We could not detect urea aminohydrolase activity, but urea production by both creatine amidinohydrolase and arginine amidinohydrolase could be detected. The apparent K m and V max of creatine amidinohydrolase were 1.1 mM and 48 nmol h−1 mg−1 protein, respectively, and the activity was greatest at pH 8. The apparent K m and V max of arginine amidinohydrolase were 0.7 mM and 62 nmol h−1 mg−1 protein, respectively, and the activity was greatest at pH 7.9. Conclusion The activity of creatine amidinohydrolase and arginine amidinohydrolase was sufficient to account for the rate of urea secretion or excretion. PMID:23682271

  3. 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. PMID:21115186

  4. Enzymatic Characterization of a Prokaryotic Urea Carboxylase

    PubMed Central

    Kanamori, Takeshi; Kanou, Norihisa; Atomi, Haruyuki; Imanaka, Tadayuki

    2004-01-01

    We identified the first prokaryotic urea carboxylase (UCA) from a member of the alpha subclass of the class Proteobacteria, Oleomonas sagaranensis. This enzyme (O. sagaranensis Uca) was composed of 1,171 amino acids, and its N-terminal region resembled the biotin carboxylase domains of various biotin-dependent carboxylases. The C-terminal region of the enzyme harbored the Met-Lys-Met motif found in biotin carboxyl carrier proteins. The primary structure of the enzyme was 45% identical to that of the urea carboxylase domain of urea amidolyase from Saccharomyces cerevisiae. O. sagaranensis Uca did not harbor the allophanate hydrolase domain found in the yeast enzyme, but a separate gene with structural similarity was found to be adjacent to the uca gene. Purified recombinant O. sagaranensis Uca displayed ATP-dependent carboxylase activity towards urea (Vmax = 21.2 μmol mg−1 min−1) but not towards acetyl coenzyme A (acetyl-CoA) and propionyl-CoA, indicating that the gene encoded a bona fide UCA and not an acetyl-CoA or propionyl-CoA carboxylase. The enzyme also exhibited high levels of activity towards acetamide and formamide. Kinetic parameters of the enzyme reaction were determined with ATP, urea, acetamide, and formamide. O. sagaranensis could grow on urea, acetamide, and formamide as sole nitrogen sources; moreover, ATP-dependent urea-degrading activity was found in cells grown with urea but not in cells grown with ammonia. The results suggest that the UCA of this organism may be involved in the assimilation of these compounds as nitrogen sources. Furthermore, orthologues of the O. sagaranensis uca gene were found to be widely distributed among Bacteria. This implies that there are two systems of urea degradation in Bacteria, a pathway catalyzed by the previously described ureases and the UCA-allophanate hydrolase pathway identified in this study. PMID:15090492

  5. Effect of urea on biomimetic aggregates.

    PubMed

    Florenzano, F H; Politi, M J

    1997-02-01

    The effect of urea on biomimetic aggregates (aqueous and reversed micelles, vesicles and monolayers) was investigated to obtain insights into the effect of the denaturant on structured macromolecules. Direct evidence obtained from light scattering (static and dynamic), monolayer maximum isothermal compression and ionic conductivity measurements, together with indirect evidence from fluorescence photodissociation, fluorescence suppression, and thermal reactions, strongly indicates the direct interaction mechanism of urea with the aggregates. Preferential solvation of the surfactant headgroups by urea results in an increase in the monomer dissociation degree (when applied), which leads to an increase in the area per headgroup and also in the loss of counterion affinities. PMID:9239302

  6. Hydrothermal synthesis of Mg-Al hydrotalcites by urea hydrolysis

    SciTech Connect

    Rao, M. Mohan . E-mail: mandapati@iict.res.in; Reddy, B. Ramachandra; Jayalakshmi, M.; Jaya, V. Swarna; Sridhar, B.

    2005-02-15

    We report a simple method to prepare hydrotalcites involving both urea hydrolysis and hydrothermal synthetic conditions. Out of a series of Mg/Al ratios tried, pure hydrotalcite like phase was obtained for Mg/Al ratios of 1:1 and 2:1. Unlike in conventional co-precipitation method we succeeded in preparing Mg/Al ratio of 1:1 by this route. The high temperature (180 deg. C) applied and pressure developed in the autoclave during the synthesis might have altered the topochemical transformation. The materials were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared, thermo gravimetric and differential thermal analysis and transmission electron microscopy.

  7. 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

  8. 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.

  9. 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...

  10. 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...

  11. 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...

  12. 21 CFR § 862.1770 - Urea nitrogen test system.

    Code of Federal Regulations, 2014 CFR

    2015-04-01

    ... 21 Food and Drugs 8 2015-04-01 2015-04-01 false Urea nitrogen test system. § 862.1770 Section Â... Systems § 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,...

  13. Biofuels combustion*

    DOE PAGESBeta

    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

  14. 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.

  15. 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.

  16. 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

  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. 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.

  19. Nitrous Oxide Gas Fluxes in a Potato Field Following Application of Urea and Coated Urea Fertilizers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Application of urea and other forms of nitrogen (N) fertilizer can generate atmospheric emissions of nitrous oxide (N2O), which is a potent greenhouse gas. Field experiments were conducted on a loamy sand soil in Becker, Minnesota to evaluate the effects of soluble and coated forms of urea on N2O fl...

  20. Winter Wheat and Maize Response to Urea Ammonium Nitrate and a New Urea Formaldehyde Polymer Fertilizer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Slow release nitrogen (N) fertilizers have potential to improve yield and nitrogen use efficiency (NUE) in winter wheat (Triticum aestivum L.) and maize (Zea mays L.). A slow release urea formaldehyde polymer (UFP) was compared with conventional aqueous urea-ammonium nitrate (UAN) [(NH2)2CO, NH4NO3]...

  1. Synthesis and Characterization of Branched Poly(ester urea)s with Different Branch Density

    NASA Astrophysics Data System (ADS)

    Yu, Jiayi; Becker, Matthew

    2015-03-01

    A new class of L-phenylalanine-based poly(ester urea)s (PEU) was developed that possess tunable mechanical properties, water uptake ability and degradation rates. Our preliminary data has shown that 1,6-hexanediol L - phenylalanine-based poly(ester urea)s possesses an elastic modulus nearly double that of poly(lactic acid). My work details the synthesis of a series of L - phenylalanine-based poly(ester urea)s possessing a variation in diol chain length and in branch density and shows how these subtle structural differences influence the mechanical properties and in vitro biodegradation rates. The elastic moduli span a range of values that overlap with several currently clinically available degradable polymers. Increasingly the diol chain lengths increases the amount of flexible segment in the chemical structure, which results in reduced elastic modulus values and increased values of elongation at break. Increasing the amount of branch monomer incorporated into the system reduces the molecular entanglement, which also results in decreased elastic modulus values and increased values of elongation at break. The L - phenylalanine-based poly(ester urea)s also exhibited a diol length dependent degradation process that varied between 1-5 % over 16 weeks. Compared with PLLA, PEUs degrade more quickly and the rate can be tuned by changing the diol chain length. PEUs absorb more water and the water uptake ability can be tuned by changing the branch density. This work was supported by Akron Functional Materials Center.

  2. 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. PMID:27427778

  3. Reaction mechanism for chlorination of urea.

    PubMed

    Blatchley, Ernest R; Cheng, Mingming

    2010-11-15

    Experiments were conducted to elucidate the mechanism of the reaction between free chlorine and urea. In combination with findings of previous investigations, the results of these experiments indicate a process by which urea undergoes multiple N-chlorination steps. The first of these steps results in the formation of N-chlorourea; this step appears to require Cl₂ to proceed and is the overall rate-limiting step in the reaction for conditions that correspond to most swimming pools. N-Chlorourea then appears to undergo further chlorine substitution; the fully N-chlorinated urea molecule is hypothesized to undergo hydrolysis and additional chlorination to yield NCl₃ as an intermediate. NCl₃ is hydrolyzed to yield NH₂Cl and NHCl₂, with subsequent decay to stable end products, including N₂ and NO₃⁻. Conversion of urea-N to nitrate is pH-dependent. The pattern of nitrate yield is believed to be attributable to the fact that when urea serves as the source of reduced-N, entry into the reactions that describe chlorination of ammoniacal nitrogen is through NCl₃, whereas when NH₃ is the source of reduced-N, entry to these reactions is through NH₂Cl. PMID:20964367

  4. Synthesis, thermal and spectral characterization of nanosized Ni xMg 1- xAl 2O 4 powders as new ceramic pigments via combustion route using 3-methylpyrozole-5-one as fuel

    NASA Astrophysics Data System (ADS)

    Ahmed, Ibrahim S.; Shama, Sayed A.; Dessouki, Hassan A.; Ali, Ayman A.

    2011-10-01

    New Ni xMg 1- xAl 2O 4 nanosized in different composition (0.1 ≤ x ≤ 0.8) powders have been synthesized successively for first time by using low temperature combustion reaction (LTCR) of corresponding metal chlorides, carbonates and nitrates as salts with 3-methylpyrozole-5-one (3MP5O) as fuel at 300 °C in open air furnace. Magnesium aluminate spinel (MgAl 2O 4) was used as crystalline host network for the synthesis of nickel-based nano ceramic pigments. The structure of prepared samples was characterized by using different techniques such as thermal analysis (TG-DTG/DTA), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). UV/Visible and Diffuse reflectance spectroscopy (DRS) using CIE- L* a* b* parameters methods have been used for color measurements. The obtained results reveal that Ni xMg 1- xAl 2O 4 powder of samples is formed in the single crystalline and pure phase with average particle size of 6.35-33.11 nm in the temperature range 500-1200 °C. The density, particle size, shape and color are determined for all prepared samples with different calcination time and temperature.

  5. Synthesis, thermal and spectral characterization of nanosized Ni(x)Mg(1-x)Al2O4 powders as new ceramic pigments via combustion route using 3-methylpyrozole-5-one as fuel.

    PubMed

    Ahmed, Ibrahim S; Shama, Sayed A; Dessouki, Hassan A; Ali, Ayman A

    2011-10-15

    New Ni(x)Mg(1-x)Al(2)O(4) nanosized in different composition (0.1≤x≤0.8) powders have been synthesized successively for first time by using low temperature combustion reaction (LTCR) of corresponding metal chlorides, carbonates and nitrates as salts with 3-methylpyrozole-5-one (3MP5O) as fuel at 300°C in open air furnace. Magnesium aluminate spinel (MgAl(2)O(4)) was used as crystalline host network for the synthesis of nickel-based nano ceramic pigments. The structure of prepared samples was characterized by using different techniques such as thermal analysis (TG-DTG/DTA), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and transmission electron microscopy (TEM). UV/Visible and Diffuse reflectance spectroscopy (DRS) using CIE-L*a*b* parameters methods have been used for color measurements. The obtained results reveal that Ni(x)Mg(1-x)Al(2)O(4) powder of samples is formed in the single crystalline and pure phase with average particle size of 6.35-33.11 nm in the temperature range 500-1200°C. The density, particle size, shape and color are determined for all prepared samples with different calcination time and temperature. PMID:21783407

  6. 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.

  7. Urea kinetic modeling: comparing the options.

    PubMed

    Hoenich, N A; Keir, M J; Hildreth, K; Woffindin, C; Goodall, R; Vanholder, R; Ward, M K

    1993-09-01

    In this study 6 commercially produced kinetic modeling packages utilizing a variable volume, single pool urea model, as well as formulae to determine the delivery of therapy, have been compared by applying to each the same set of rigorously collected data for a group of 12 patients. Comparison of the kinetically derived parameters (urea generation rate [G], urea distribution volume [V], delivery of therapy [Kt/V], and normalized protein catabolic rate [nPCR]) showed that the values obtained for both G and V differed between packages owing to the numerical methods and the clearance used in the solution of the differential equations. Although a broad agreement between the values established for Kt/V and nPCR was noted, the 95% limits of agreement indicated that it would be prudent to exercise caution when comparing results established by different modeling packages. PMID:8240076

  8. 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).

  9. A perfusion study of the handling of urea and urea analogues by the gills of the dogfish shark (Squalus acanthias).

    PubMed

    Wood, Chris M; Liew, Hon Jung; De Boeck, Gudrun; Walsh, Patrick J

    2013-01-01

    The branchial mechanism of urea retention in elasmobranchs was investigated using an in vitro isolated-perfused head preparation, as well as in vivo samples, in the spiny dogfish shark. Both in vivo and in control saline perfusions containing 350 mmol L(-1) urea, calculated intracellular urea concentrations in gill epithelial cells were close to extracellular concentrations. Urea efflux to the external water fell only non-significantly, and calculated gill intracellular urea concentration did not change when perfusate urea concentration was reduced from 350 to 175 mmol L(-1) with osmotic compensation by 175 mmol L(-1) mannitol. However, when the urea analogues thiourea or acetamide were present in the perfusate at concentrations equimolar (175 mmol L(-1)) to those of urea (175 mmol L(-1)), urea efflux rates were increased 4-fold and 6.5-fold respectively, and calculated gill intracellular urea concentrations were depressed by about 55%. Analogue efflux rates were similar to urea efflux rates. Previous studies have argued that either the basolateral or apical membranes provided the limiting permeability barrier, and/or that a back-transporter on the basolateral membranes of gill cells is responsible for urea retention. The present results provide new evidence that the apical membrane is the limiting factor in maintaining gill urea impermeability, and raise the prospect that a urea back-transporter, which can be competitively inhibited by thiourea and acetamide, operates at the apical membrane. PMID:23638369

  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. [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. PMID:17147165

  12. 1H NMR relaxation in urea

    NASA Astrophysics Data System (ADS)

    Taylor, R. E.; Bacher, Alfred D.; Dybowski, C.

    2007-11-01

    Proton NMR spin-lattice relaxation times T1 were measured for urea as a function of temperature. An activation energy of 46.3 ± 4.7 kJ/mol was extracted and compared with the range of 38-65 kJ/mol previously reported in the literature as measured by different magnetic resonance techniques. In addition, proton NMR spin-lattice relaxation times in the rotating frame T1 ρ were measured as a function of temperature. These measurements provide acquisition conditions for the 13C and 15N CP/MAS spectra of pure urea in the crystalline phase.

  13. Why Urea Eliminates Ammonia Rather Than Hydrolyzes in Aqueous Solution

    PubMed Central

    Alexandrova, Anastassia N.; Jorgensen, William L.

    2010-01-01

    A joint QM/MM and ab initio study on the decomposition of urea in the gas phase and in aqueous solution is reported. Numerous possible mechanisms of intramolecular decomposition and hydrolysis have been explored; intramolecular NH3-elimination assisted by a water molecule is found to have the lowest activation energy. The solvent effects were elucidated using the TIP4P explicit water model with free energy perturbation (FEP) calculations in conjunction with QM/MM Monte Carlo simulations. The explicit representation of the solvent was found to be essential for detailed resolution of the mechanism, identification of the rate-determining step, and evaluation of the barrier. The assisting water molecule acts as a hydrogen shuttle for the first step of the elimination reaction. The forming zwitterionic intermediate, H3NCONH, participates in 8–9 hydrogen bonds with water molecules. Its decomposition is found to be the rate-limiting step, and the overall free energy of activation for the decomposition of urea in water is computed to be ca. 37 kcal/mol; the barrier for hydrolysis by an addition/elimination mechanism is found to be ca. 40 kcal/mol. The differences in the electronic structure of the transition states of the NH3-elimination and hydrolysis were examined via natural bond order analysis. Destruction of urea’s resonance stabilization during hydrolysis via an addition/elimination mechanism, and its preservation in the rearrangement to the H3NCONH intermediate were identified as important factors in determining the preferred reaction route. PMID:17249815

  14. 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

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

    PubMed Central

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

    2015-01-01

    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. PMID:25440717

  16. APPLICATION OF MILK UREA NITROGEN VALUES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Statistical analyses using both linear and multi-component regression and mixed effects models have been applied to a number of databases relating milk urea nitrogen (MUN) to factors important for N utilization in lactating dairy cows. Concentrations of MUN are highly correlated to BUN, which is a s...

  17. Continuous Crystallization of Urea-Water Mixture

    NASA Astrophysics Data System (ADS)

    Hokamura, Taku; Ohkubo, Hidetoshi; Watanabe, Satoshi; Seki, Mitsuo; Murakoshi, Hiromichi

    Ice slurries have been used as environmentally-friendly secondary refrigerants. In addition to such ice slurries, aqueous solutions in slurry-state have also been put to practical use at temperatures below 0 oC. Urea-water mixture is a multi-component substance that has a eutectic point. If we can form a two-phase fluid substance by the liquid-solid phases at the eutectic point, it can be used as a fluid latent heat storage material, which will maintain the secondary refrigerant in a heat exchanger at constant temperature. In the present study, we propose a urea-water mixture as a novel functional thermal fluid that can be used as a fluid latent heat material. To demonstrate its feasibility, we first measured the latent heat and density of a urea-water mixture, and then used a counter-flow double tube heat exchanger to produce a liquid-solid two-phase flow of the urea-water mixture. This work demonstrates that it is possible to make a fluid latent heat storage material continuously from an aqueous solution at the eutectic point by flowing it through a double tube heat exchanger equipped with a stirrer.

  18. 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.

  19. 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. PMID:27106154

  20. 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. PMID:22281810

  1. 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. PMID:27273880

  2. 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.

  3. 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.

  4. 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.

  5. 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...

  6. Synergetic Effects of Nanoporous Support and Urea on Enzyme Activity

    SciTech Connect

    Lei, Chenghong; Shin, Yongsoon; Liu, Jun; Ackerman, Eric J.

    2007-02-01

    Here we report that synergetic effects of functionalized nanoporous support and urea on enzyme activity enhancement. Even in 8.0 M urea, the specific activity of GI entrapped in FMS was still higher than the highest specific activity of GI free in solution, indicating the strong tolerance of GI in FMS to the high concentration of urea.

  7. 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. ...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. Synthesis of functional materials in combustion reactions

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    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-Al2O3, YSZ composites, uranium oxides, nickel powder, NiO and NiO: YSZ composite, TiO2, and manganites, cobaltites, and aluminates of rare earth elements.

  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. Reconsidering the Lack of Urea Toxicity in Dialysis Patients.

    PubMed

    Massy, Ziad A; Pietrement, Christine; Touré, Fatouma

    2016-09-01

    Urea is an old uremic toxin which has been used for many years as a global biomarker of CKD severity and dialysis adequacy. Old studies were not in favor of its role as a causal factor in the pathogenesis of complications associated with the uremic state. However, recent experimental and clinical evidence is compatible with both direct and indirect toxicity of urea, particularly via the deleterious actions of urea-derived carbamylated molecules. Further studies are clearly needed to explore the potential relevance of urea-related CKD complications for patient management, in particular the place of new therapeutic strategies to prevent urea toxicity. PMID:27174444

  15. 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).

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

    PubMed

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

    2016-02-01

    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. PMID:26764567

  17. Small-Molecule Inhibitors of Urea Transporters

    PubMed Central

    Verkman, Alan S.; Esteva-Font, Cristina; Cil, Onur; Anderson, Marc O.; Li, Fei; Li, Min; Lei, Tianluo; Ren, Huiwen; Yang, Baoxue

    2015-01-01

    Urea transporter (UT) proteins, which include isoforms of UT-A in kidney tubule epithelia and UT-B in vasa recta endothelia and erythrocytes, facilitate urinary concentrating function. Inhibitors of urea transporter function have potential clinical applications as sodium-sparing diuretics, or ‘urearetics,’ in edema from different etiologies, such as congestive heart failure and cirrhosis, as well as in syndrome of inappropriate antidiuretic hormone (SIADH). High-throughput screening of drug-like small molecules has identified UT-A and UT-B inhibitors with nanomolar potency. Inhibitors have been identified with different UT-A versus UT-B selectivity profiles and putative binding sites on UT proteins. Studies in rodent models support the utility of UT inhibitors in reducing urinary concentration, though testing in clinically relevant animal models of edema has not yet been done. PMID:25298345

  18. Gaseous emissions from waste combustion.

    PubMed

    Werther, Joachim

    2007-06-18

    An overview is given on methods and technologies for limiting the gaseous emissions from waste combustion. With the guideline 2000/76/EC recent European legislation has set stringent limits not only for the mono-combustion of waste in specialized incineration plants but also for co-combustion in coal-fired power plants. With increased awareness of environmental issues and stepwise decrease of emission limits and inclusion of more and more substances into the network of regulations a multitude of emission abatement methods and technologies have been developed over the last decades. The result is the state-of-the-art waste incinerator with a number of specialized process steps for the individual components in the flue gas. The present work highlights some new developments which can be summarized under the common goal of reducing the costs of flue gas treatment by applying systems which combine the treatment of several noxious substances in one reactor or by taking new, simpler routes instead of the previously used complicated ones or - in the case of flue gas desulphurisation - by reducing the amount of limestone consumption. Cost reduction is also the driving force for new processes of conditioning of nonhomogenous waste before combustion. Pyrolysis or gasification is used for chemical conditioning whereas physical conditioning means comminution, classification and sorting processes. Conditioning yields a fuel which can be used in power plants either as a co-fuel or a mono-fuel and which will burn there under much better controlled conditions and therefore with less emissions than the nonhomogeneous waste in a conventional waste incinerator. Also for cost reasons, co-combustion of wastes in coal-fired power stations is strongly pressing into the market. Recent investigations reveal that the co-firing of waste can also have beneficial effects on the operating behavior of the boiler and on the gaseous emissions. PMID:17339077

  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. Brain imaging in Urea cycle disorders

    PubMed Central

    Gropman, Andrea

    2012-01-01

    Urea Cycle Disorders (UCD) represent a group of rare inborn errors of metabolism that carry a high risk of mortality and neurological morbidity resulting from the effects of accumulation of ammonia and other biochemical intermediates. These disorders result from single gene defects involved in the detoxification pathway of ammonia to urea. UCD include deficiencies in any of the six enzymes and two membrane transporters involved in urea biosynthesis. It has previously been reported that approximately half of infants who present with hyperammonemic coma in the newborn period die of cerebral edema; and those who survive 3 days or more of coma invariably have intellectual disability [1]. In children with partial defects there is an association between the number and severity of recurrent hyperammonemic (HA) episodes (i.e. with or without coma) and subsequent cognitive and neurologic deficits [2]. However, the effects of milder or subclinical HA episodes on the brain are largely unknown. This review discusses the results of neuroimaging studies performed as part of the NIH funded Rare Diseases Clinical Research Center in Urea Cycle Disorders and focuses on biomarkers of brain injury in ornithine transcarbamylase deficiency (OTCD). We used anatomic imaging, functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), and 1H /13C magnetic resonance spectroscopy (MRS) to study clinically stable adults with partial OTCD. This allowed us to determine alterations in brain biochemistry associated with changes in cell volume and osmolarity and permitted us to identify brain biomarkers of HA. We found that white matter tracts underlying specific pathways involved in working memory and executive function are altered in subjects with OTCD (as measured by DTI), including those heterozygous women who were previously considered asymptomatic. An understanding of the pathogenesis of brain injury in UCD is likely to advance our knowledge of more common disorders of

  1. 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

  2. Neurological implications of urea cycle disorders

    PubMed Central

    Summar, M.; Leonard, J. V.

    2013-01-01

    Summary The urea cycle disorders constitute a group of rare congenital disorders caused by a deficiency of the enzymes or transport proteins required to remove ammonia from the body. Via a series of biochemical steps, nitrogen, the waste product of protein metabolism, is removed from the blood and converted into urea. A consequence of these disorders is hyperammonaemia, resulting in central nervous system dysfunction with mental status changes, brain oedema, seizures, coma, and potentially death. Both acute and chronic hyperammonaemia result in alterations of neurotransmitter systems. In acute hyperammonaemia, activation of the NMDA receptor leads to excitotoxic cell death, changes in energy metabolism and alterations in protein expression of the astrocyte that affect volume regulation and contribute to oedema. Neuropathological evaluation demonstrates alterations in the astrocyte morphology. Imaging studies, in particular 1H MRS, can reveal markers of impaired metabolism such as elevations of glutamine and reduction of myoinositol. In contrast, chronic hyperammonaemia leads to adaptive responses in the NMDA receptor and impairments in the glutamate–nitric oxide–cGMP pathway, leading to alterations in cognition and learning. Therapy of acute hyperammonaemia has relied on ammonia-lowering agents but in recent years there has been considerable interest in neuroprotective strategies. Recent studies have suggested restoration of learning abilities by pharmacological manipulation of brain cGMP with phosphodiesterase inhibitors. Thus, both strategies are intriguing areas for potential investigation in human urea cycle disorders. PMID:18038189

  3. The effect of urea:nitrate ratio on the structure and luminescence properties of YVO4:Dy3+ phosphors

    NASA Astrophysics Data System (ADS)

    Foka, K. E.; Dejene, B. F.; Swart, H. C.

    2016-01-01

    YVO4:Dy3+ phosphor has been successfully synthesised using combustion method. The dependence of the properties of YVO4:Dy3+ phosphor upon urea:nitrate concentration was investigated. The single tetragonal phase was observed by x-ray diffraction spectra. A highly crystalline YVO4:Dy3+ sample was obtained when increasing the ratio of the urea to 2. The estimated crystalline sizes from the Scherrer's formula were found to be 20, 38, 33, 30, and 27 nm for the sample prepared with the ratio of 1, 2, 2.5, 3 and 4, respectively. The formation of agglomerated particles was observed by Scanning electron microscope images and it was observed that when increasing the concentration of urea further, flake-like particles formed. The diffuse reflectance spectra of YVO4:Dy3+ with various ratios of urea indicated that the determined optical band gap was ranging from 3.3 to 2.3 eV. Luminescence properties of YVO4:Dy3+ showed that the phosphor emit yellow colour at 573 nm and blue colour at 482 nm corresponding to 4F9/2→6H13/2 and 4F9/2→6H15/2 transitions, respectively. A very weak band at 663 nm which correspond to the 4F9/2→6H11/2 transition was also observed. It was found that the Photoluminescent emission intensity increased with an increase in the ratio of urea and reached a maximum at 2 then decreased when increasing the ratio of urea further.

  4. One step combustion synthesis and thermoluminescence in Y3Al5O12:Ce3+

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    In the present paper one step combustion synthesis of compound Y3Al5O12:Ce3+ is reported using a modified procedure and employing mixed (Urea + Glycine) as fuel. Powder X-ray diffraction confirms the formation of said compound. Thermoluminescence study over the wide gamma exposure (1KGy - 13 KGy) Suggests the possible use of the phosphor in dosimetric application.

  5. 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

  6. 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.

  7. 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.

  8. 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.

  9. ROUTE-SPECIFIC DOSIMETRY

    EPA Science Inventory

    The capacity to perform route-to-route extrapolation of toxicity data is becoming increasingly crucial to the Agency, with a number of strategies suggested and demonstrated. One strategy involves using a combination of existing data and modeling approaches. This strategy propos...

  10. 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.

  11. Exceptionally Active and Stable Spinel Nickel Manganese Oxide Electrocatalysts for Urea Oxidation Reaction.

    PubMed

    Periyasamy, Sivakumar; Subramanian, Palaniappan; Levi, Elena; Aurbach, Doron; Gedanken, Aharon; Schechter, Alex

    2016-05-18

    Spinel nickel manganese oxides, widely used materials in the lithium ion battery high voltage cathode, were studied in urea oxidation catalysis. NiMn2O4, Ni1.5Mn1.5O4, and MnNi2O4 were synthesized by a simple template-free hydrothermal route followed by a thermal treatment in air at 800 °C. Rietveld analysis performed on nonstoichiometric nickel manganese oxide-Ni1.5Mn1.5O4 revealed the presence of three mixed phases: two spinel phases with different lattice parameters and NiO unlike the other two spinels NiMn2O4 and MnNi2O4. The electroactivity of nickel manganese oxide materials toward the oxidation of urea in alkaline solution is evaluated using cyclic voltammetric measurements. Ni1.5Mn1.5O4 exhibits excellent redox characteristics and lower charge transfer resistances in comparison with other compositions of nickel manganese oxides and nickel oxide prepared under similar conditions.The Ni1.5Mn1.5O4modified electrode oxidizes urea at 0.29 V versus Ag/AgCl with a corresponding current density of 6.9 mA cm(-2). At a low catalyst loading of 50 μg cm(-2), the urea oxidation current density of Ni1.5Mn1.5O4 in alkaline solution is 7 times higher than that of nickel oxide and 4 times higher than that of NiMn2O4 and MnNi2O4, respectively. PMID:27123873

  12. 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

  13. 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

  14. Final report of the safety assessment of Urea.

    PubMed

    2005-01-01

    Although Urea is officially described as a buffering agent, humectant, and skin-conditioning agent-humectant for use in cosmetic products, there is a report stating that Urea also is used in cosmetics for its desquamating and antimicrobial action. In 2001, the Food and Drug Administration (FDA) reported that Urea was used in 239 formulations. Concentrations of use for Urea ranged from 0.01% to 10%. Urea is generally recognized as safe by FDA for the following uses: side-seam cements for food contact; an inhibitor or stabilizer in pesticide formulations and formulations applied to animals; internal sizing for paper and paperboard and surface sizing and coating of paper and paper board that contact water-in-oil dairy emulsions, low-moisture fats and oils, moist bakery products, dry solids with surface containing no free fats or oil, and dry solids with the surface of fat or oil; and to facilitate fermentation of wine. Urea is the end product of mammalian protein metabolism and the chief nitrogenous compound of urine. Urea concentrations in muscle, liver, and fetuses of rats increased after a subcutaneous injection of Urea. Urea diffused readily through the placenta and into other maternal and fetal organs. The half-life of Urea injected into rabbits was on the order of several hours, and the reutilization rate was 32.2% to 88.8%. Urea given to rats by a bolus injection or continuous infusion resulted in distribution to the following brain regions: frontal lobe, caudate nucleus, hippocampus, thalamus plus hypothalamus, pons and white matter (corpus callosum). The permeability constant after treatment with Urea of whole skin and the dermis of rabbits was 2.37 +/- 0.13 (x 10(6)) and 1.20 +/- 0.09 (x10(3)) cm/min, respectively. The absorption of Urea across normal and abraded human skin was 9.5% +/- 2.3% and 67.9% +/- 5.6%, respectively. Urea increased the skin penetration of other compounds, including hydrocortisone. No toxicity was observed for Urea at levels as high

  15. Urea synthesis in rats fed diet containing kidney beans.

    PubMed

    Scislowski, P W; Grant, G; Harris, I; Pickard, K; Pusztai, A

    1992-10-01

    When rats were fed a diet containing kidney bean (Phaesolus vulgaris) urea excretion was increased 3-5 fold. Isolated liver mitochondria from rats fed the kidney bean diet produced 40% more citrulline in the presence of arginine than mitochondria isolated from control rats. Mitochondrial activities of urea cycle enzymes and N-acetylglutamate synthetase were similar in animals fed diets containing kidney bean or lactalbumin. The possible mechanisms causing acute urea production in rats fed with kidney bean are discussed. PMID:1445392

  16. The electrophoresis of transferrins in urea/polyacrylamide gels.

    PubMed Central

    Evans, R W; Williams, J

    1980-01-01

    The denaturation of transferrin by urea has been studied by (a) electrophoresis in polyacrylamide gels incorporating a urea gradient, (b) measurements of the loss of iron-binding capacity and (c) u.v. difference spectrometry. In human serum transferrin and hen ovotransferrin the N-terminal and C-terminal domains of the iron-free protein were found to denature at different urea concentrations. Images Fig. 1. Fig. 2. Fig. 3. Fig. 4. Fig. 7. PMID:7213345

  17. 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. PMID:26962031

  18. 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

  19. Tris-ureas as transmembrane anion transporters.

    PubMed

    Olivari, Martina; Montis, Riccardo; Berry, Stuart N; Karagiannidis, Louise E; Coles, Simon J; Horton, Peter N; Mapp, Lucy K; Gale, Philip A; Caltagirone, Claudia

    2016-08-01

    Nine tris-urea receptors (L(1)-L(9)) have been synthesised and shown to coordinate to a range of anionic guests both by (1)H NMR titration techniques and single crystal X-ray structural analysis. The compounds have been shown to be capable of mediating the exchange of chloride and nitrate and also chloride and bicarbonate across POPC or POPC : cholesterol 7 : 3 vesicle bilayer membranes at low transporter loadings. An interesting dependency of anion transport on the nature of the cation is evidence to suggest that a M(+)/Cl(-) cotransport process may also contribute to the release of chloride from the vesicles. PMID:27383134

  20. 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.

  1. 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.

  2. 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

  3. Quantitative assessment of urea, glucose and ammonia changes in human dental plaque and saliva following rinsing with urea and glucose.

    PubMed

    Singer, D L; Kleinberg, I

    1983-01-01

    The rates of three processes associated with the rise and fall in plaque pH, that normally occur following a urea rinse, were determined: (i) disappearance of urea from plaque, (ii) disappearance of urea from saliva and (iii) formation and disappearance from plaque of the ammonia produced by the plaque bacteria from the urea. Also examined were two processes associated with the fall and rise in pH following a glucose rinse: the disappearance of glucose from plaque and from saliva. Entry into plaque of either urea or glucose during rinsing was immediate; the subsequent disappearance of both from the plaque was slow and followed first-order kinetics. The ammonia formation and urea-disappearance results suggested that clearance of urea from the plaque occurred mainly by bacterial degradation and not by diffusion out of the plaque. The rate constants for ammonia formation and for its subsequent disappearance from the plaque made it clear why a rapid rise and a slow subsequent fall in the pH occurs after urea rinsing. The rate constants enabled calculation of the ammonia produced as a percentage of the urea utilized. Only 16-26 per cent of the urea was recovered as ammonia and the remainder of the urea-N was stored probably as NH2 moieties of certain amino acids. Such storage may enable the plaque bacteria to maintain the pH at an elevated level for an extended period of time by bacterial production of ammonia from these stored compounds after the urea ceases to be available as a source of substrate. PMID:6580848

  4. 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.

  5. 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...

  6. Railroad Routing Model

    Energy Science and Technology Software Center (ESTSC)

    1995-01-05

    INTERLINE/PC is an interactive program designed to simulate the routing practices of the United States rail system. The rail industry is divided into a large number of independent competing companies. The INTERLINE data base represents these rail companies as 94 separate subnetworks. An additional two subnetworks represent navigable inland/intracoastal and deep draft marine routes. Interchange points between individual rail systems and waterway systems are also identified.

  7. 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.

  8. Properties of Combustion Gases

    NASA Technical Reports Server (NTRS)

    Wear, J. D.; Jones, R. E.; Trout, A. M.; Mcbride, B. J.

    1986-01-01

    New series of reports: First report lists data from combustion of ASTM Jet A fuel and dry air; second report presents tables and figures for combustion-gas properties of natural-gas fuel and dry air, and equivalent ratios.

  9. Internal combustion engine with multiple combustion chambers

    SciTech Connect

    Gruenwald, D.J.

    1992-05-26

    This patent describes a two-cycle compression ignition engine. It comprises one cylinder, a reciprocable piston moveable in the cylinder, a piston connecting rod, a crankshaft for operation of the piston connecting rod, a cylinder head enclosing the cylinder, the upper surface of the piston and the enclosing surface of the cylinder head defining a cylinder clearance volume, a first combustion chamber and a second combustion chamber located in the cylinder head. This patent describes improvement in means for isolating the combustion process for one full 360{degrees} rotation of the crankshaft; wherein the combustion chambers alternatively provide for expansion of combustion products in the respective chambers into the cylinder volume near top dead center upon each revolution of the crankshaft.

  10. Maximal combustion temperature estimation

    NASA Astrophysics Data System (ADS)

    Golodova, E.; Shchepakina, E.

    2006-12-01

    This work is concerned with the phenomenon of delayed loss of stability and the estimation of the maximal temperature of safe combustion. Using the qualitative theory of singular perturbations and canard techniques we determine the maximal temperature on the trajectories located in the transition region between the slow combustion regime and the explosive one. This approach is used to estimate the maximal temperature of safe combustion in multi-phase combustion models.

  11. 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.

  12. 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 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  13. 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 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... measure urea nitrogen (an end-product of nitrogen metabolism) in whole blood, serum, plasma, and...

  14. 40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 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...

  15. 40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 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...

  16. 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.

  17. 40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 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...

  18. 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...

  19. 40 CFR 721.9925 - Aminoethylethylene urea methacrylamide.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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...

  20. 76 FR 15339 - Solid Urea From Russia and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-21

    ... its notice of institution (75 FR 74746, December 1, 2010) were adequate and that the respondent... 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...

  1. Measuring urea persistence, distribution and transport on coastal plain soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The persistence and mobility of urea, an organic form of nitrogen present in animal manures and commercial fertilizers, has rarely been studied and measured, because it is assumed to undergo rapid hydrolysis to ammonia. However, preliminary studies have shown urea to exist in leachate and runoff sev...

  2. Symposium (International) on Combustion, 18th, 1980

    SciTech Connect

    Anon

    1980-08-01

    This conference proceedings contains 196 papers. 181 papers are indexed separately. Topics covered include: combustion generated pollution; propellant combustion; fluidized bed combustion; combustion of droplets and spray; premixed flame studies; fire studies; flame stabilization; coal flammability; chemical kinetics; turbulent combustion; soot; coal combustion; modeling of combustion processes; combustion diagnostics; detonations and explosions; ignition; internal combustion engines; combustion studies; and furnaces.

  3. 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.

  4. Combustion and core noise

    NASA Astrophysics Data System (ADS)

    Mahan, J. Robert; Karchmer, Allen

    1991-08-01

    Two types of aircraft power plant are considered: the gas turbine and the reciprocating engine. The engine types considered are: the reciprocating engine, the turbojet engine, the turboprop engine, and the turbofan engine. Combustion noise in gas turbine engines is discussed, and reciprocating-engine combustion noise is also briefly described. The following subject areas are covered: configuration variables, operational variables, characteristics of combustion and core noise, sources of combustion noise, combustion noise theory and comparison with experiment, available prediction methods, diagnostic techniques, measurement techniques, data interpretation, and example applications.

  5. Dispersion Interactions between Urea and Nucleobases Contribute to the Destabilization of RNA by Urea in Aqueous Solution

    PubMed Central

    Kasavajhala, Koushik; Bikkina, Swetha; Patil, Indrajit; MacKerell, Alexander D.; Priyakumar, U. Deva

    2015-01-01

    Urea has long been used to investigate protein folding and, more recently, RNA folding. Studies have proposed that urea denatures RNA by participating in stacking interactions and hydrogen bonds with nucleic acid bases. In this study, the ability of urea to form unconventional stacking interactions with RNA bases is investigated using ab initio calculations (RI-MP2 and CCSD(T) methods with the aug-cc-pVDZ basis set). A total of 29 stable nucleobase-urea stacked complexes are identified in which the intermolecular interaction energies (up to −14 kcal/mol) are dominated by dispersion effects. Natural bond orbital (NBO) and atoms in molecules (AIM) calculations further confirm strong interactions between urea and nucleobases. Calculations on model systems with multiple urea and water molecules interacting with a guanine base lead to a hypothesis that urea molecules along with water are able to form cage-like structures capable of trapping nucleic acid bases in extrahelical states by forming both hydrogen bonded and dispersion interactions, thereby contributing to the unfolding of RNA in the presence of urea in aqueous solution. PMID:25668757

  6. A nonenzymatic biosensor based on gold electrodes modified with peptide self-assemblies for detecting ammonia and urea oxidation.

    PubMed

    Bianchi, Roberta C; da Silva, Emerson Rodrigo; Dall'Antonia, Luiz H; Ferreira, Fabio Furlan; Alves, Wendel Andrade

    2014-09-30

    We have developed a nonenzymatic biosensor for the detection of ammonia and urea oxidation based on the deposition of peptide microstructures onto thiolated gold electrodes. FF-MNSs/MCP/Au assemblies were obtained by modifying gold substrates with 4-mercaptopyridine (MCP), followed by coating with l,l-diphenylalanine micro/nanostructures (FF-MNSs) grown in the solid-vapor phase. Benzene rings and amide groups with peptide micro/nanostructures interact with synthetic NH4(+) receptors through cation-π and hydrogen bonding. AuOH clusters on the Au surface provided the catalytic sites. The application of a predetermined concentration of analytes at the peptide interfaces activated the catalytic sites. We observed a relationship between the stability of films and the crystal structure of peptides, and we organized the FF-MNSs into an orthorhombic symmetry that was the most suitable assembly for creation of our biosensors. At 0.1 mol L(-1) NaOH, these FF-MNSs/MCP/Au electrodes have electrocatalytic properties regarding ammonia and urea oxidation that are comparable to those of enzyme-based architectures. Under optimal conditions, the electrocatalytic response is proportional to the ammonia and urea concentration in the range 0.1-1.0 mmol L(-1). The sensitivity was calculated as 2.83 and 81.3 μA mmol L(-1) cm(-2) for ammonia and urea, respectively, at +0.40 V (vs SCE). Our detection method is easy to follow, does not require a mediator or enzyme, and has strong potential for detecting urea via nonenzymatic routes. PMID:25188339

  7. 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. PMID:27215558

  8. 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.

  9. Opportunities in pulse combustion

    NASA Astrophysics Data System (ADS)

    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.

  10. Route based forecasting

    NASA Astrophysics Data System (ADS)

    Zuurendonk, I. W.; Wokke, M. J. J.

    2009-09-01

    Road surface temperatures can differ several degrees on a very short distance due to local effects. In order to get more insight in the local temperature differences and to develop safer gritting routes, Meteogroup has developed a system for route based temperature forecasting. The standard version of the road model is addressed to forecast road surface temperature and condition for a specific location. This model consists of two parts. First a physical part, based on the energy balance equations. The second part of the model performs a statistical correction on the calculated physical road surface temperature. The road model is able to create a forecast for one specific location. From infrared measurements, we know that large local differences in road surface temperature exist on a route. Differences can be up to 5 degrees Celsius over a distance of several hundreds of meters. Based on those measurements, the idea came up to develop a system that forecasts road surface temperature and condition for an entire route: route based forecasting. The route is split up in sections with equal properties. For each section a temperature and condition will be calculated. The main factors that influence the road surface temperature are modelled in this forecasting system: •The local weather conditions: temperature, dew point temperature, wind, precipitation, weather type, cloudiness. •The sky view: A very sheltered place will receive less radiation during daytime and emit less radiation during nighttime. For a very open spot, the effects are reversed. •The solar view: A road section with trees on the southern side, will receive less solar radiation during daytime than a section with tress on the southern side. The route based forecast shows by means of a clear Google Maps presentation which sections will be slippery at what time of the coming night. The final goal of this type of forecast, is to make dynamical gritting possible: a variable salt amount and a different

  11. 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.

  12. 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.

  13. Prescribing hemodialysis using a weekly urea mass balance model.

    PubMed

    Leypoldt, J K; Kablitz, C; Gregory, M C; Senekjian, H O; Cheung, A K

    1991-01-01

    Prescribing hemodialysis by monitoring only predialysis BUN concentrations is not sufficient to guarantee adequate therapy. Results from the National Cooperative Dialysis Study have suggested that hemodialysis therapy is adequate if the protein catabolic rate is maintained greater than 1 g/day/kg body weight and simultaneously if sufficient hemodialysis is prescribed to maintain either a time-averaged BUN concentration (TACurea) less than 50 mg/dl or a value of Kt/V greater than unity. In the present study mathematical relationships were derived from a weekly urea mass balance model that permit an evaluation of TACurea and of protein catabolism via the urea generation rate (G) without the need for conventional urea kinetic modeling. The parameters TACurea and G were simply calculated from a midweek predialysis BUN concentration (BUNMW) by: TACurea = 0.7 BUNMW G = 0.7 BUNMW(Kr + Kd tau/T) where Kr, Kd, tau and T denote residual renal urea clearance, dialyzer urea clearance, number of minutes of hemodialysis per week, and number of minutes total in a week, respectively. Clinical results from 139 modeling sessions on 91 patients demonstrated that TACurea and G derived from urea kinetic modeling correlated highly with those calculated from the above equations (r = 0.96 and 0.94, respectively). It is concluded that individualized hemodialysis prescription and adequacy of therapy can be assessed by monitoring TACurea and G by calculation from a weekly urea mass balance model. PMID:1819316

  14. Bioelectrochemical conversion of urea to nitrogen using aminated carbon electrode.

    PubMed

    Watanabe, Hiroaki; Nishi, Hideki; Hamana, Hiroshi; Sekioka, Naoyuki; Wang, Xiuyun; Uchiyama, Shunichi

    2009-01-01

    Urea decomposes to ammonia and carbon dioxide via carbamic acid, and amine groups can be introduced to the glassy carbon electrode surface during the electrode oxidation of carbamic acid. This modified carbon electrode has excellent catalytic activity of the oxidation of carbamic acid, and can be used to electrooxidize urea by combining urease reaction and electrode oxidation. We found that nitrogen gas is finally produced by the carbamic acid produced from urea. The production of nitrogen was confirmed by gas chromatography-mass spectrometry, and fragment pattern of hydrazine was also detected in the electrolyzed solution of urea. We intend to describe new electrochemical conversion system of urea to harmless nitrogen gas. The electrode oxidation current of urea was decreased by addition of radical trapping agent such as DMPO (5,5-dimethyl-1-pyrroline N-oxide), and this fact suggests that carbamic acid radical couples to form nitrogen-nitrogen bond, and this dimer is oxidized to nitrogen. The electrode oxidation current of urea became larger when oxygen was removed. This fact indicates that the intermediate species (probably hydrazine) produced by the electrolysis is oxidized by not only electrode reaction but also oxygen. PMID:25084444

  15. 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. PMID:27063259

  16. 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.

  17. 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)

  18. 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.

  19. 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.

  20. Chroman and tetrahydroquinoline ureas as potent TRPV1 antagonists.

    PubMed

    Schmidt, Robert G; Bayburt, Erol K; Latshaw, Steven P; Koenig, John R; Daanen, Jerome F; McDonald, Heath A; Bianchi, Bruce R; Zhong, Chengmin; Joshi, Shailen; Honore, Prisca; Marsh, Kennan C; Lee, Chih-Hung; Faltynek, Connie R; Gomtsyan, Arthur

    2011-03-01

    Novel chroman and tetrahydroquinoline ureas were synthesized and evaluated for their activity as TRPV1 antagonists. It was found that aryl substituents on the 7- or 8-position of both bicyclic scaffolds imparted the best in vitro potency at TRPV1. The most potent chroman ureas were assessed in chronic and acute pain models, and compounds with the ability to cross the blood-brain barrier were shown to be highly efficacious. The tetrahydroquinoline ureas were found to be potent CYP3A4 inhibitors, but replacement of bulky substituents at the nitrogen atom of the tetrahydroisoquinoline moiety with small groups such as methyl can minimize the inhibition. PMID:21315587

  1. Combustion of Micropowdered Biomass

    NASA Astrophysics Data System (ADS)

    Geil, Ethan; Thorne, Robert

    2009-03-01

    Combustion of finely powdered biomass has the potential to replace heating oil, which accounts for a significant fraction of US oil consumption, in heating, cooling and local power generation applications. When ground to 30-150 micron powders and dispersed in air, wood and other biomass can undergo deflagrating combustion, as occurs with gaseous and dispersed liquid fuels. Combustion is very nearly complete, and in contrast to sugar/starch or cellulose-derived ethanol, nearly all of the available plant mass is converted to usable energy so the economics are much more promising. We are exploring the fundamental combustion science of biomass powders in this size range. In particular, we are examining how powder size, powder composition (including the fraction of volatile organics) and other parameters affect the combustion regime and the combustion products.

  2. 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.

  3. 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.

  4. Numerical simulations in combustion

    NASA Technical Reports Server (NTRS)

    Chung, T. J.

    1989-01-01

    This paper reviews numerical simulations in reacting flows in general and combustion phenomena in particular. It is shown that use of implicit schemes and/or adaptive mesh strategies can improve convergence, stability, and accuracy of the solution. Difficulties increase as turbulence and multidimensions are considered, particularly when finite-rate chemistry governs the given combustion problem. Particular attention is given to the areas of solid-propellant combustion dynamics, turbulent diffusion flames, and spray droplet vaporization.

  5. 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.

  6. Diesel engine combustion processes

    SciTech Connect

    1995-12-31

    Diesel Engine Combustion Processes guides the engineer and research technician toward engine designs which will give the ``best payoff`` in terms of emissions and fuel economy. Contents include: Three-dimensional modeling of soot and NO in a direct-injection diesel engine; Prechamber for lean burn for low NOx; Modeling and identification of a diesel combustion process with the downhill gradient search method; The droplet group micro-explosions in W/O diesel fuel emulsion sprays; Combustion process of diesel spray in high temperature air; Combustion process of diesel engines at regions with different altitude; and more.

  7. 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.

  8. Weather routing in long-distance Mediterranean routes

    NASA Astrophysics Data System (ADS)

    Delitala, A. M. S.; Gallino, S.; Villa, L.; Lagouvardos, K.; Drago, A.

    2010-10-01

    The selection of ship routes based on modern weather forecasting is a mean of computing optimum shipping routes thereby increasing safety and comfort at sea, cutting down on transit time, and reducing fuel consumption. Further empirical research in the effectiveness of modern weather routing applications is required especially in applications concerning shorter routes in enclosed seas of limited geographical extent such as the Mediterranean Sea. The present study used two climatological simulations to test this state-of-the-art approach to ship routing. Simulations represented two theoretical routes: (1) a route between Italy and Greece and (2) a route between Cyprus and Italy. Both routes were analyzed across varying simulated climatic conditions and the results were compared with those of control routes. Furthermore, results were analyzed in terms of passenger and crew comfort, bunker consumption by ships, and time of crossing. The first simulation showed that weather routing would improve ship performance on 37% of days while the second simulation revealed that weather routing would support ship captains virtually all the time.

  9. 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. PMID:27437111

  10. Quantum crystallographic charge density of urea

    DOE PAGESBeta

    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 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

  11. 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

  12. Quantum crystallographic charge density of urea

    PubMed Central

    Wall, Michael E.

    2016-01-01

    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. PMID:27437111

  13. 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. PMID:25406025

  14. Masked Proportional Routing

    NASA Technical Reports Server (NTRS)

    Wolpert, David

    2004-01-01

    Masked proportional routing is an improved procedure for choosing links between adjacent nodes of a network for the purpose of transporting an entity from a source node ("A") to a destination node ("B"). The entity could be, for example, a physical object to be shipped, in which case the nodes would represent waypoints and the links would represent roads or other paths between waypoints. For another example, the entity could be a message or packet of data to be transmitted from A to B, in which case the nodes could be computer-controlled switching stations and the links could be communication channels between the stations. In yet another example, an entity could represent a workpiece while links and nodes could represent, respectively, manufacturing processes and stages in the progress of the workpiece towards a finished product. More generally, the nodes could represent states of an entity and the links could represent allowed transitions of the entity. The purpose of masked proportional routing and of related prior routing procedures is to schedule transitions of entities from their initial states ("A") to their final states ("B") in such a manner as to minimize a cost or to attain some other measure of optimality or efficiency. Masked proportional routing follows a distributed (in the sense of decentralized) approach to probabilistically or deterministically choosing the links. It was developed to satisfy a need for a routing procedure that 1. Does not always choose the same link(s), even for two instances characterized by identical estimated values of associated cost functions; 2. Enables a graceful transition from one set of links to another set of links as the circumstances of operation of the network change over time; 3. Is preferably amenable to separate optimization of different portions of the network; 4. Is preferably usable in a network in which some of the routing decisions are made by one or more other procedure(s); 5. Preferably does not cause an

  15. IRIS TOXICOLOGICAL REVIEW OF UREA (EXTERNAL REVIEW DRAFT)

    EPA Science Inventory

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

  16. Microbial urea-formaldehyde degradation involves a new enzyme, methylenediurease.

    PubMed

    Jahns, T; Schepp, R; Siersdorfer, C; Kaltwasser, H

    1998-01-01

    The enzymic mechanism of metabolization of urea-formaldehyde condensation products (methyleneureas; MU) and the fate of the degradation products ammonium, urea and formaldehyde were studied in bacteria isolated from garden soil, which were able to use methyleneureas as the sole source of nitrogen for growth. An organism identified as Ochrobactrum anthropi completely degraded methylenediurea (MDU) and dimethylenetriurea (DMTU) to urea, ammonia, formaldehyde and carbon dioxide. An enzyme designated as methylenediurease (methylenediurea deiminase; MDUase) was responsible for the degradation of both MDU and DMTU as well as higher polymerized MU. Growth on MU as the nitrogen source specifically induced the synthesis of this enzyme, which seems to be located in the periplasm of the bacterium. Under these growth conditions, urease as well as NAD-specific formaldehyde and formiate dehydrogenase were expressed to high levels, efficiently using the products of MU degradation, and high-affinity transport systems for urea and ammonia were synthesized scavenging the environment for these products. PMID:10526991

  17. 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.

  18. 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.

  19. 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.

  20. Hydrogen production via urea electrolysis using a gel electrolyte

    NASA Astrophysics Data System (ADS)

    King, Rebecca L.; Botte, Gerardine G.

    2011-03-01

    A technology was demonstrated for the production of hydrogen and other valuable products (nitrogen and clean water) through the electrochemical oxidation of urea in alkaline media. In addition, this process remediates toxic nitrates and prevents gaseous ammonia emissions. Improvements to urea electrolysis were made through replacement of aqueous KOH electrolyte with a poly(acrylic acid) gel electrolyte. A small volume of poly(acrylic acid) gel electrolyte was used to accomplish the electrochemical oxidation of urea improving on the previous requirement for large amounts of aqueous potassium hydroxide. The effect of gel composition was investigated by varying polymer content and KOH concentrations within the polymer matrix in order to determine which is the most advantageous for the electrochemical oxidation of urea and production of hydrogen.

  1. 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. PMID:27052722

  2. Urea Metabolism in Beef Steers Fed Tall Fescue, Orchardgrass, or Gamagrass Hays

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two experiments were conducted to assess effects of endophyte treatments (Exp. 1), forage species, and supplementation (Exp. 2) on urea production, excretion, and recycling in beef steers. Infusion of 15,15N-urea and enrichment of urea in urine samples were used to calculate urea N entry and recyc...

  3. 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

  4. 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. PMID:27092411

  5. Molecular Complexation and Phase Diagrams of Urea/PEG Mixtures

    NASA Astrophysics Data System (ADS)

    Fu, Guoepeng; Kyu, Thein

    2014-03-01

    Polyethylene glycol (PEG) and urea complexation has been known to form a stable crystal due to molecular complexation. The effect of molecular weight of PEG on the phase diagrams of its blends with urea has been explored. In the case of high molecular weight PEG8k/urea, the observed phase diagram is azeotrope, accompanied by eutectoid reactions in the submerged phases such as induced stable ``alpha'' phase crystals and metastable ``beta'' phase crystals. The metastable crystal can transform to stable crystal under a certain thermal annealing condition. However, the phase diagram of PEG1k/urea is of coexistence loop, whereas PEG400/urea exhibits eutectic character. Subsequently, the change of azeotrope to eutectic behavior with PEG molecular weight is analyzed in the context of the combined Flory-Huggins theory of liquid-liquid demixing and phase field theory of crystal solidification. Of particular interest is that only a very small urea amount (2 wt%) is needed to form a stable inclusion crystal via complexation with PEG. Potential application in lithium battery is discussed based on AC impedance spectroscopy and cyclic voltammetry. Supported by NSF-DMR 1161070.

  6. Transport of urea at low concentrations in Chlamydomonas reinhardi.

    PubMed

    Williams, S K; Hodson, R C

    1977-04-01

    Urea transport into the unicellular green alga Chlamydomonas reinhardi was investigated to further our understanding of controls operating on urea catabolism in this organism. Transport into cells grown with acetate and deprived of ammonia is a saturable process, mediated by at least two systems operating maximally at different external urea concentrations. The lower concentration system, with an apparent Km for urea of 5.1 micron, was the object of detailed study. Transport of urea from a saturating concentration (57 micron) into ammonia- and acetate-grown cells freshly suspended in ammonia-limited medium was not detected. Upon further culturing in the absence of ammonia, derepression occurred with transport ability, first appearing at about 1 h , reaching a maximum at about 2 h, and maintaining this maximum at least 5 h. In contrast to this, CO2-grown cells became derepressed more slowly, and maximum transport ability was not maintained. Addition of ammonia or methylamine (5 mM) during nitrogen deprivation prevented further increases in transport ability and caused loss of previously acquired transport ability. Cycloheximide (10 microng/ml) had a similar effect. Energy uncouplers or dark, anaerobic conditions depressed transport. By these criteria, transport from low urea concentrations is mediated by a process that requires protein synthesis and activation by cellular energy, and the process has a rapid rate of turnover and of deactivation by ammonia. PMID:856784

  7. 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.

  8. ASRM combustion instability studies

    NASA Technical Reports Server (NTRS)

    Strand, L. D.

    1992-01-01

    The objectives of this task were to measure and compare the combustion response characteristics of the selected propellant formulation for the Space Shuttle Advanced Solid Rocket Motor (ASRM) with those of the current Redesigned Solid Rocket Motor (RSRM) formulation. Tests were also carried out to characterize the combustion response of the selected propellant formulation for the ASRM igniter motor.

  9. 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.

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

    PubMed

    Li, Fa-tang; Wang, Qing; Ran, Jingrun; Hao, Ying-juan; Wang, Xiao-jing; Zhao, Dishun; Qiao, Shi Zhang

    2015-01-21

    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. PMID:25482071

  11. Combustion Synthesis of Magnesium Aluminate

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    In the system MgO-Al2O3, three compounds MgAl2O4, MgAl6O10 (also expressed as- Mg0.4Al2.4O4) and MgAl26O40 are well known. Importance of the first two is well established. Magnesium aluminate (MgAl2O4) spinel is a technologically important material due to its interesting thermal properties. The MgAl2O4 ceramics also find application as humidity sensors. Apart from the luminescence studies, the interest in MgAl2O4 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 MgAl6O10 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 MgAl2O4 and MgAl6O10 were formed in a single step, while MgAl26O40 was not formed by this procedure. Activation of MgAl6O10 by rare earth ions like Ce3+, Eu3+ and Tb3+ and ns2 ion Pb2+ could be achieved. Excitation bands for MgAl6O10 are at slightly shorter wavelengths compared to those reported for MgAl2O4.

  12. 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}.

  13. Recycling of polyurethane-urea RIM

    SciTech Connect

    Xiao, H.X.; Kresta, J.E.; Suthar, B.; Li, X.H.

    1997-12-31

    Polyurethane-urea (PUU) RIM are crosslinked materials, which cannot be reprocessed or recycled by using the conventional process. The chemical decrosslinking reaction or transesterification of themosetting polyurethanes by using various inorganic and organic catalysts were investigated. The recycling of waste PUU RIM materials (unpainted, painted and filler reinforced) through decrosslinking (transesterification) using low molecular weight glycols in presence of catalyst was evaluated. It was established that the transestification of PUU RIM can be carried out at the low glycol (EG)/RIM ratio (15/84.5) and that the usual recovery step for the excess glycol (EG) can be avoided resulting in an economical process. The process was scaled up in a 50 gallon reactor at the LymTal International Inc. successfully. It was established that the products from the decrosslinking of PUU RIM are a mixture of the liquid oligomers (LOs) containing urethane, OH and NH{sub 2} groups. These functional groups in LOs exhibit many potential applications as raw materials in the preparation of RIM coatings, adhesives, foams, sealants and composites. PUU RIM made from LOs exhibited promising and interesting results. Both solvent-based and waterborne urethane coatings could be made from LOs. Urethane adhesives made from LOs showed improvement of properties with increasing amounts of LOs. Structural adhesives based on epoxy and LOs were prepared and the effects of equivalent ratios and curing conditions on the adhesive strength of the epoxy/LO adhesives were investigated. Solvent-free coating based on epoxy and LOs was prepared and their properties were determined. Both wood fiber and glass fabric reinforced composites were prepared by using epoxy and LOs and they exhibited interesting properties for different potential applications.

  14. Creatine metabolism in urea cycle defects.

    PubMed

    Boenzi, Sara; Pastore, Anna; Martinelli, Diego; Goffredo, Bianca Maria; Boiani, Arianna; Rizzo, Cristiano; Dionisi-Vici, Carlo

    2012-07-01

    Creatine (Cr) and phosphocreatine play an essential role in energy storage and transmission. Maintenance of creatine pool is provided by the diet and by de novo synthesis, which utilizes arginine, glycine and s-adenosylmethionine as substrates. Three primary Cr deficiencies exists: arginine:glycine amidinotransferase deficiency, guanidinoacetate methyltransferase deficiency and the defect of Cr transporter SLC6A8. Secondary Cr deficiency is characteristic of ornithine-aminotransferase deficiency, whereas non-uniform Cr abnormalities have anecdotally been reported in patients with urea cycle defects (UCDs), a disease category related to arginine metabolism in which Cr must be acquired by de novo synthesis because of low dietary intake. To evaluate the relationships between ureagenesis and Cr synthesis, we systematically measured plasma Cr in a large series of UCD patients (i.e., OTC, ASS, ASL deficiencies, HHH syndrome and lysinuric protein intolerance). Plasma Cr concentrations in UCDs followed two different trends: patients with OTC and ASS deficiencies and HHH syndrome presented a significant Cr decrease, whereas in ASL deficiency and lysinuric protein intolerance Cr levels were significantly increased (23.5 vs. 82.6 μmol/L; p < 0.0001). This trend distribution appears to be regulated upon cellular arginine availability, highlighting its crucial role for both ureagenesis and Cr synthesis. Although decreased Cr contributes to the neurological symptoms in primary Cr deficiencies, still remains to be explored if an altered Cr metabolism may participate to CNS dysfunction also in patients with UCDs. Since arginine in most UCDs becomes a semi-essential aminoacid, measuring plasma Cr concentrations might be of help to optimize the dose of arginine substitution. PMID:22644604

  15. 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.

  16. 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.

  17. Catalytic hydrolysis of urea with fly ash for generation of ammonia in a batch reactor for flue gas conditioning and NOx reduction

    SciTech Connect

    Sahu, J.N.; Gangadharan, P.; Patwardhan, A.V.; Meikap, B.C.

    2009-01-15

    Ammonia is a highly volatile noxious material with adverse physiological effects, which become intolerable even at very low concentrations and present substantial environmental and operating hazards and risk. Yet ammonia has long been known to be used for feedstock of flue gas conditioning and NOx reduction. Urea as the source of ammonia for the production of ammonia has the obvious advantages that no ammonia shipping, handling, and storage is required. The process of this invention minimizes the risks and hazards associated with the transport, storage, and use of anhydrous and aqueous ammonia. Yet no such rapid urea conversion process is available as per requirement of high conversion in shorter time, so here we study the catalytic hydrolysis of urea for fast conversion in a batch reactor. The catalyst used in this study is fly ash, a waste material originating in great amounts in combustion processes. A number of experiments were carried out in a batch reactor at different catalytic doses, temperatures, times, and at a constant concentration of urea solution 10% by weight, and equilibrium and kinetic studies have been made.

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective was to establish the relationships between transfer of blood urea-N to the digestive tract (GIT) and utilisation of recycled urea-N within the GIT, and to determine which of these two mechanisms of the urea recycling process places greater limits on N salvage by growing sheep. Four gro...

  19. VHDL Control Routing Simulator

    SciTech Connect

    Venard, J.

    1995-07-10

    The control router simulates a backplane consisting of up to 16 slot. Slot 0, reserved for a control module (cr-ctrl), generates the system clocks and provides the serial interface to the Gating Logic. The remaining 15 slots (1-15) contain routing modules (cr mod), each having up to 64 serial inputs and outputs with FIFOs. Messages to be transmitted to the Control Router are taken from text files. There are currently 17 such source files. In the model, the serial output of each source is connected to multiple receivers, so that there are 8 identical messages transmitted to the router for each message file entry.

  20. Fuel mixture approach for solution combustion synthesis of Ca{sub 3}Al{sub 2}O{sub 6} powders

    SciTech Connect

    Ianos, Robert Lazau, Ioan; Pacurariu, Cornelia; Barvinschi, Paul

    2009-07-15

    Single-phase 3CaO.Al{sub 2}O{sub 3} powders were prepared via solution combustion synthesis using a fuel mixture of urea and {beta}-alanine. The concept of using this fuel mixture comes from the individual reactivity of calcium nitrate and aluminum nitrate with respect to urea and {beta}-alanine. It was proved that urea is the optimum fuel for Al(NO{sub 3}){sub 3} whereas {beta}-alanine is the most suitable fuel for Ca(NO{sub 3}){sub 2}. X-ray diffraction and thermal analysis investigations revealed that heating at 300 deg. C the precursor mixture containing the desired metal nitrates, urea and {beta}-alanine triggers a vigorous combustion reaction, which yields single-phase nanocrystalline 3CaO.Al{sub 2}O{sub 3} powder (33.3 nm). In this case additional annealing was no longer required. The use of a single fuel failed to ensure the formation of 3CaO.Al{sub 2}O{sub 3} directly from the combustion reaction. After annealing at 900 deg. C for 1 h, the powders obtained by using a single fuel (urea or {beta}-alanine) developed a phase composition comprising of 3CaO.Al{sub 2}O{sub 3}, 12CaO.7Al{sub 2}O{sub 3} and CaO.

  1. 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.

  2. Gas turbine combustion instability

    SciTech Connect

    Richards, G.A.; Lee, G.T.

    1996-09-01

    Combustion oscillations are a common problem in development of LPM (lean premix) combustors. Unlike earlier, diffusion style combustors, LPM combustors are especially susceptible to oscillations because acoustic losses are smaller and operation near lean blowoff produces a greater combustion response to disturbances in reactant supply, mixing, etc. In ongoing tests at METC, five instability mechanisms have been identified in subscale and commercial scale nozzle tests. Changes to fuel nozzle geometry showed that it is possible to stabilize combustion by altering the timing of the feedback between acoustic waves and the variation in heat release.

  3. Combustion in supersonic flow

    NASA Technical Reports Server (NTRS)

    Northam, G. B.

    1985-01-01

    A workshop on combustion in supersonic flow was held in conjunction with the 21st JANNAF Combustion Meeting at Laurel, Maryland on October 3 to 4 1984. The objective of the workshop was to establish the level of current understanding of supersonic combustion. The workshop was attended by approximately fifty representatives from government laboratories, engine companies, and universities. Twenty different speakers made presentations in their area of expertise during the first day of the workshop. On the second day, the presentations were discussed, deficiencies in the current understanding defined, and a list of recommended programs generated to address these deficiencies. The agenda for the workshop is given.

  4. Intelligent route surveillance

    NASA Astrophysics Data System (ADS)

    Schoemaker, Robin; Sandbrink, Rody; van Voorthuijsen, Graeme

    2009-05-01

    Intelligence on abnormal and suspicious behaviour along roads in operational domains is extremely valuable for countering the IED (Improvised Explosive Device) threat. Local sensor networks at strategic spots can gather data for continuous monitoring of daily vehicle activity. Unattended intelligent ground sensor networks use simple sensing nodes, e.g. seismic, magnetic, radar, or acoustic, or combinations of these in one housing. The nodes deliver rudimentary data at any time to be processed with software that filters out the required information. At TNO (Netherlands Organisation for Applied Scientific Research) research has started on how to equip a sensor network with data analysis software to determine whether behaviour is suspicious or not. Furthermore, the nodes should be expendable, if necessary, and be small in size such that they are hard to detect by adversaries. The network should be self-configuring and self-sustaining and should be reliable, efficient, and effective during operational tasks - especially route surveillance - as well as robust in time and space. If data from these networks are combined with data from other remote sensing devices (e.g. UAVs (Unmanned Aerial Vehicles)/aerostats), an even more accurate assessment of the tactical situation is possible. This paper shall focus on the concepts of operation towards a working intelligent route surveillance (IRS) research demonstrator network for monitoring suspicious behaviour in IED sensitive domains.

  5. 14C-urea breath test in C pylori gastritis.

    PubMed Central

    Rauws, E A; Royen, E A; Langenberg, W; Woensel, J V; Vrij, A A; Tytgat, G N

    1989-01-01

    14C-urea breath test was used to detect Campylobacter pylori colonisation in 129 consecutive non-ulcer dyspepsia patients. Fasting patients were given 3 microCi (110 kBq) of 14C-labelled urea after a test meal. Breath samples were collected at 10 minute intervals for 90 minutes and the C-14 activity was counted on a liquid scintillation analyser. Urea derived 14CO2 appears in the exhaled breath of Campylobacter pylori culture positive individuals within 20-30 minutes. Likelihood analysis revealed a most favourable cut off level of [0.07% dose 14C-urea/mmol CO2] multiplied by body weight at t = 40 minutes, to separate culture positive from culture negative subjects. Using this upper limit of normal, a positive likelihood ratio of 50 and a negative likelihood ratio of 0.05 was calculated. Sensitivity of the test was 95% and specificity 98%. The 14C-urea breath test is a simple, sensitive and non-invasive test, that detects viable C pylori microorganism and semiquantitatively assesses the bacterial load of C pylori colonisation. Administration of a single dose of colloidal bismuth subcitrate resulted in a rapid decrease in 14CO2 excretion, so this test can be used to confirm eradication of the bacterium in therapeutic trials without endoscopy, or need for culture. PMID:2753404

  6. Urease immobilized fluorescent gold nanoparticles for urea sensing.

    PubMed

    Parashar, Upendra Kumar; Nirala, Narsingh R; Upadhyay, Chandan; Saxena, P S; Srivastava, Anchal

    2015-05-01

    We report a surfactant-free synthesis of monodispersed gold nanoparticles (AuNPs) with average size of 15 nm. An approach for visual and fluorescent sensing of urea in aqueous solution based on shift in surface plasmon band (SPB) maxima as well as quench in fluorescence intensity. To enable the urea detection, we functionalized the thiol-capped gold nanoparticles with urease, the enzyme specific to urea using carbodiimide chemistry. The visible color changed of the gold colloidal solution from red to blue (or purple); this was evident from quenching in absorbance and fluorescence intensity, is the principle applied here for the sensing of urea. The solution turns blue when the urea concentration exceeds 8 mg/dL which reveals visual lower detection limit. The lower detection limits governed by the fluorescence quenching were found 5 mg/dL (R(2) = 0.99) which is highly sensitive and selective compared to shift in SPB maxima. The approach depicted here seems to be important in clinical diagnosis. PMID:25809996

  7. 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.

  8. THE REGULATION OF UREA-BIOSYNTHESIS ENZYMES IN VERTEBRATES.

    PubMed

    MORA, J; MARTUSCELLI, J; ORTIZ PINEDA, J; SOBERON, G

    1965-07-01

    1. Carbamoyl phosphate synthetase, ornithine transcarbamoylase, the arginine-synthetase system and arginase were measured in the livers of ammoniotelic, ureotelic and uricotelic animals. The chelonian reptiles, whose nitrogen excretory patterns vary according to the habitat, and the Mexican axolotl, a neotenic species, were also studied. 2. The levels of the activities of the first three enzymes mentioned correlate with the amount of nitrogen excreted as urea. 3. The terrestrial turtle, which excretes mainly uric acid, maintains a high arginase activity but has very low levels of the activities of the other three enzymes. 4. The first three enzymes of the urea cycle vary in the phylogenic scale in a co-ordinated manner, which suggests that they are under the same regulatory mechanism. 5. Urea formation from endogenous arginine in vitro has a low efficiency in the Mexican axolotl. 6. The induction of metamorphosis in the Mexican axolotl by the administration of l-tri-iodothyronine, which causes a shift from ammonio-ureotelism to complete ureotelism, is accompanied by an increase mainly in carbamoyl phosphate synthetase and also by an improvement in the efficiency of hydrolysis of endogenous arginine in vitro to give urea. 7. The results obtained by differential centrifugation of the urea-cycle enzymes in rat and Mexican-axolotl livers are presented. The location requirements for the integration of a metabolic cycle are discussed. PMID:14343146

  9. The regulation of urea-biosynthesis enzymes in vertebrates

    PubMed Central

    Mora, J.; Martuscelli, J.; Ortiz-Pineda, Juana; Soberón, G.

    1965-01-01

    1. Carbamoyl phosphate synthetase, ornithine transcarbamoylase, the arginine-synthetase system and arginase were measured in the livers of ammoniotelic, ureotelic and uricotelic animals. The chelonian reptiles, whose nitrogen excretory patterns vary according to the habitat, and the Mexican axolotl, a neotenic species, were also studied. 2. The levels of the activities of the first three enzymes mentioned correlate with the amount of nitrogen excreted as urea. 3. The terrestrial turtle, which excretes mainly uric acid, maintains a high arginase activity but has very low levels of the activities of the other three enzymes. 4. The first three enzymes of the urea cycle vary in the phylogenic scale in a co-ordinated manner, which suggests that they are under the same regulatory mechanism. 5. Urea formation from endogenous arginine in vitro has a low efficiency in the Mexican axolotl. 6. The induction of metamorphosis in the Mexican axolotl by the administration of l-tri-iodothyronine, which causes a shift from ammonio-ureotelism to complete ureotelism, is accompanied by an increase mainly in carbamoyl phosphate synthetase and also by an improvement in the efficiency of hydrolysis of endogenous arginine in vitro to give urea. 7. The results obtained by differential centrifugation of the urea-cycle enzymes in rat and Mexican-axolotl livers are presented. The location requirements for the integration of a metabolic cycle are discussed. PMID:14343146

  10. 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. PMID:18439628

  11. Photoluminescence of Eu{sup 3+}-doped LaPO{sub 4} nanocrystals synthesized by combustion method

    SciTech Connect

    Xiu Zhiliang; Liu Suwen; Lue Mengkai . E-mail: mklu@icm.sdu.edu.cn; Zhang Haiping; Zhou Guangjun

    2006-03-09

    Eu{sup 3+}-doped LaPO{sub 4} nanocrystals were synthesized for the first time by a combustion method with urea as a fuel calcined at 700 deg. C. The diffraction profile of the obtained sample was indexed as a monoclinic monazite-structure by X-ray diffraction (XRD) data. The obtained nanocrystals appeared to be short rod-like with diameters of 5-10 nm and lengths of 20-70 nm. The luminescence intensities of Eu{sup 3+}-doped LaPO{sub 4} nanocrystals were found to be strongly dependent on the quantities of urea added and the concentration of Eu{sup 3+}.

  12. 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.

  13. 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.

  14. 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.

  15. 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

  16. 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. PMID:25793220

  17. COMBUSTION - RISK MANAGEMENT

    EPA Science Inventory

    This research involves the characterization of waste combustion systems and their emissions along with the development and evaluation of techniques to prevent emissions formation and/or control their release. This area addresses incinerators and industrial systems burning wastes...

  18. 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.

  19. 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.

  20. 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)

  1. 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

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

    PubMed

    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

  3. Is the urea cycle involved in Alzheimer’s disease?

    PubMed Central

    Hansmannel, Franck; Sillaire, Adeline; Kamboh, M. Ilyas; Lendon, Corinne; Pasquier, Florence; Hannequin, Didier; Laumet, Geoffroy; Mounier, Anais; Ayral, Anne-Marie; DeKosky, Steven T.; Hauw, Jean-Jacques; Berr, Claudine; Mann, David; Amouyel, Philippe; Campion, Dominique; Lambert, Jean-Charles

    2010-01-01

    Since previous observations indicated that the urea cycle may have a role in the Alzheimer’s disease (AD) process, we set out to quantify the expression of each gene involved in the urea cycle in control and AD brains and establish whether these genes could be genetic determinants of AD. We first confirmed that all the urea cycle enzyme genes are expressed in the AD brain. The expression of arginase 2 was greater in the AD brain than in the control brain. The presence of the rare arginase 2 allele rs742869 was associated with an increase in the risk of AD in men and with an earlier age at onset for both genders. None of the other genes in the pathway appeared to be differentially expressed in the AD brain or act as genetic determinants of the disease. PMID:20693631

  4. 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.

  5. Combustion furnace and burner

    SciTech Connect

    McElroy, J. G.

    1985-12-03

    The combustion system includes a hearth lined with refractory, a combustion chamber formed in the refractory, an air manifold mounted on the hearth, a plurality of gas manifold extending through the air manifold and into the combustion chamber, and a diffuser mounted on the manifolds to cause turbulence in the air/gas mixture. The gas manifolds include aspirating means for combining the air and gas. The combustion chamber is elongated and has an elongated neck with a flue gas exit slot over which the work piece passes. The flue gas from the combustion of the air/gas mixture in the combustion chamber increases in velocity as the flue gas passes through the elongated neck and exits the flue gas exit slot. The slot has a length sufficient to permit the work piece to rotate 360/sup 0/ as the work piece rotates and travels through the hearth. This causes the work piece to be uniformly heated over every square inch of its surface.

  6. 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.

  7. Development of C3-Symmetric Tris-Urea Low-Molecular-Weight Gelators.

    PubMed

    Yamanaka, Masamichi

    2016-04-01

    This article describes recent developments in C3 -symmetric tris-urea low-molecular-weight gelators and their applications. The C3 -symmetric tris-ureas are excellent frameworks to form supramolecular polymers through noncovalent interactions. In organic solvents, hydrophobic tris-ureas form supramolecular gels. Amphiphilic tris-ureas form supramolecular gels in aqueous media. Functional supramolecular gels were prepared by introducing appropriate functional groups into the outer sphere of tris-ureas. Supramolecular hydrogels obtained from amphiphilic tris-ureas were used in the electrophoresis of proteins. These electrophoreses results showed several unique characteristics compared to typical electrophoreses results obtained using polyacrylamide matrices. PMID:26915980

  8. VHDL Control Routing Simulator

    Energy Science and Technology Software Center (ESTSC)

    1995-07-10

    The control router simulates a backplane consisting of up to 16 slot. Slot 0, reserved for a control module (cr-ctrl), generates the system clocks and provides the serial interface to the Gating Logic. The remaining 15 slots (1-15) contain routing modules (cr mod), each having up to 64 serial inputs and outputs with FIFOs. Messages to be transmitted to the Control Router are taken from text files. There are currently 17 such source files. Inmore » the model, the serial output of each source is connected to multiple receivers, so that there are 8 identical messages transmitted to the router for each message file entry.« less

  9. Cleaner co-combustion of lignite-biomass-waste blends by utilising inhibiting compounds of toxic emissions.

    PubMed

    Skodras, G; Palladas, A; Kaldis, S P; Sakellaropoulos, G P

    2007-04-01

    In this paper, the co-combustion behaviour of coal with wastes and biomass and the related toxic gaseous emissions were investigated. The objective of this work is to add on towards a cleaner co-combustion of lignite-waste-biomass blends by utilizing compounds that could inhibit the formation of toxic pollutants. A series of co-combustion tests was performed in a pilot scale incinerator, and the emissions of polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) were measured. The co-combustion behaviour of lignite with olive kernels, MDF and sawdust was studied and the ability of additives such as urea, almond shells and municipal sewage sludge to reduce the PCDD/F emissions was examined. All blends were proven good fuels and reproducible combustion conditions were achieved. The addition of inhibitors prior to combustion showed in some cases, relatively high PCDD/F emissions reduction. Among the inhibitors tested, urea seems to achieve a reduction of PCDD/F emissions for all fuel blends, while an unstable behaviour was observed for the others. PMID:17204304

  10. Anion recognition by oligo-(thio)urea-based receptors.

    PubMed

    Jia, Chuandong; Zuo, Wei; Zhang, Dan; Yang, Xiao-Juan; Wu, Biao

    2016-07-26

    Oligo-(thio)ureas have proven to be a promising class of receptors that are widely applied in anion recognition. This article aims to present some recent progress in the construction of oligoureas and their anion coordination (recognition) chemistry. Typical examples of metal-coordination assisted and covalently connected oligo-(thio)urea receptors are summarized, with focus on geometry characteristics required for achieving complementary binding of a target anion. Special emphasis is given to ortho-phenylene-connected oligoureas in the application of anion binding and the self-assembly of important supramolecular architectures, including helicates, tetrahedral cages, and so on. PMID:27352298

  11. Reinvestigation of growth of urea thiosemicarbazone monohydrate crystal

    NASA Astrophysics Data System (ADS)

    Srinivasan, Bikshandarkoil R.; Raghavaiah, Pallepogu; Nadkarni, V. S.

    2013-08-01

    The reaction of urea with thiosemicarbazide in 1:1 mole ratio in aqueous solution does not result in the formation of urea thiosemicarbazone monohydrate crystal, as reported by Hanumantharao, Kalainathan and Bhagavannarayana [Spectrochim. Acta A91 (2012) 345-351]. A reinvestigation of the reported reaction reveals that the crystal obtained is the starting material namely thiosemicarbazide, which has been unambiguously confirmed with the aid of infrared and 1H NMR spectra and single crystal X-ray structure determination. Analysis of 1H NMR spectrum reveals that thiosemicarbazide exhibits thione-thiol tautomerism in solution. In contrast, thiosemicarbazide exists as the thione tautomer in the solid state.

  12. 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. PMID:22346801

  13. Deactivation of free and stabilized acid phosphatase by urea.

    PubMed

    Gianfreda, L; Marrucci, G; Greco, G

    1986-11-01

    Tests on acid phosphatase (E.G. 3.1.3.2) deactivation by urea have been performed at two pH values. Two conditions have been used: native enzyme operating batch-wise in dilute solution and stabilized enzyme in continuous flow ultrafiltration membrane reactor. Stabilization is achieved by confining the enzyme within a concentrated solution of a linear chain polymer that forms a polarization layer over the membrane. The results provide significant information on the kinetics and thermodynamics of the complex phenomena taking place during deactivation. Deactivation by urea is also compared with thermal deactivation. PMID:18555278

  14. Urea- and Thiourea-Catalyzed Aminolysis of Carbonates.

    PubMed

    Blain, Marine; Yau, Honman; Jean-Gérard, Ludivine; Auvergne, Rémi; Benazet, Dominique; Schreiner, Peter R; Caillol, Sylvain; Andrioletti, Bruno

    2016-08-23

    The aminolysis of (poly)carbonates by (poly)amines provides access to non-isocyanate polyurethanes (NIPUs) that are toxic-reagent-free analogues of polyurethanes (PUs). Owing to their low reactivity, the ring opening of cyclic carbonates requires the use of a catalyst. Herein, we report that the more available and cheaper ureas could advantageously be used for catalyzing the formation of NIPUs at the expense of the thiourea analogues. In addition, we demonstrate a medium-range pKa of the (thio)urea and an unqeual substitution pattern is critical for controlling the efficiency of the carbonate opening. PMID:27467779

  15. [Improvement of skin moisture and skin texture with urea therapy].

    PubMed

    Puschmann, M; Gogoll, K

    1989-01-01

    A significant increase in skin moisture and an improvement in skin smoothness after application of a urea-containing cream was noticed in a large number of volunteers with healthy skin and in neurodermitis patients compared with untreated skin and with vehicle. The effect was shown after one application (short-term test) as well as after repeated application (long-term test). Regular application of preparation containing urea increases the moisture of a the skin and improves the skin's smoothness compared with its previous condition, with untreated skin, and with placebo preparations. PMID:2807927

  16. 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

  17. 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. PMID:24587721

  18. 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

  19. 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. PMID:23435478

  20. Urea is a dynamic pool of bioavailable nitrogen in coral reefs

    NASA Astrophysics Data System (ADS)

    Crandall, J. B.; Teece, M. A.

    2012-03-01

    Urea may be an important source of nitrogen in low nutrient coral reef environments because corals and other organisms can assimilate it easily and it is found throughout ocean waters. We measured the distribution and concentrations of urea in seagrass beds, areas of schooling fish, coral formations and bottom sediments in the Upper Florida Keys Reef Tract. The flux of urea from bottom sediments was also measured. Ambient concentrations of urea in the offshore reefs were similar to the concentrations of nitrate and ammonium. Seagrass beds, areas of schooling fish and coral formations had elevated concentrations of urea that were up to eight times higher than nitrate in the system. Numerous ephemeral hotspots of urea that were 8-20 times the ambient urea concentration existed in seagrass beds, areas of schooling fish, and above sediments. Coastal areas and inland canals had high urea concentrations where urban runoff and septic effluents were prevalent, but there was no anthropogenic influence in the offshore habitats. Urea concentrations above bottom sediments were not different from ambient concentrations and benthic flux chamber incubations showed biological activity in carbonaceous sediments but no net urea production. The decrease in urea concentrations from coasts and inland waterways to a consistent ambient concentration in the offshore reef system and ephemeral hotspots of high urea concentration suggest that urea is a dynamic pool of bioavailable nitrogen in the reefs of the Upper Florida Keys.

  1. Synthesis of glycerol carbonate from glycerol and urea with gold-based catalysts.

    PubMed

    Hammond, Ceri; Lopez-Sanchez, Jose A; Ab Rahim, Mohd Hasbi; Dimitratos, Nikolaos; Jenkins, Robert L; Carley, Albert F; He, Qian; Kiely, Christopher J; Knight, David W; Hutchings, Graham J

    2011-04-21

    The reaction of glycerol with urea to form glycerol carbonate is mostly reported in the patent literature and to date there have been very few fundamental studies of the reaction mechanism. Furthermore, most previous studies have involved homogeneous catalysts whereas the identification of heterogeneous catalysts for this reaction would be highly beneficial. This is a very attractive reaction that utilises two inexpensive and readily available raw materials in a chemical cycle that overall, results in the chemical fixation of CO(2). This reaction also provides a route to up-grade waste glycerol produced in large quantities during the production of biodiesel. Previous reports are largely based on the utilisation of high concentrations of metal sulfates or oxides, which suffer from low intrinsic activity and selectivity. We have identified heterogeneous catalysts based on gallium, zinc, and gold supported on a range of oxides and the zeolite ZSM-5, which facilitate this reaction. The addition of each component to ZSM-5 leads to an increase in the reaction yield towards glycerol carbonate, but supported gold catalysts display the highest activity. For gold-based catalysts, MgO is the support of choice. Catalysts have been characterised by XRD, TEM, STEM and XPS, and the reaction has been studied with time-on-line analysis of products via a combination of FT-IR spectroscopy, HPLC, (13)C NMR and GC-MS analysis to evaluate the reaction pathway. Our proposed mechanism suggests that glycerol carbonate forms via the cyclization of a 2,3-dihydroxypropyl carbamate and that a subsequent reaction of glycerol carbonate with urea yields the carbamate of glycerol carbonate. Stability and reactivity studies indicate that consecutive reactions of glycerol carbonate can limit the selectivity achieved and reaction conditions can be selected to avoid this. The effect of the catalyst in the proposed mechanism is discussed. PMID:21258674

  2. Transgenic Restoration of Urea Transporter A1 Confers Maximal Urinary Concentration in the Absence of Urea Transporter A3.

    PubMed

    Klein, Janet D; Wang, Yanhua; Mistry, Abinash; LaRocque, Lauren M; Molina, Patrick A; Rogers, Richard T; Blount, Mitsi A; Sands, Jeff M

    2016-05-01

    Urea has a critical role in urinary concentration. Mice lacking the inner medullary collecting duct (IMCD) urea transporter A1 (UT-A1) and urea transporter A3 (UT-A3) have very low levels of urea permeability and are unable to concentrate urine. To investigate the role of UT-A1 in the concentration of urine, we transgenically expressed UT-A1 in knockout mice lacking UT-A1 and UT-A3 using a construct with a UT-A1 gene that cannot be spliced to produce UT-A3. This construct was inserted behind the original UT-A promoter to yield a mouse expressing only UT-A1 (UT-A1(+/+)/UT-A3(-/-)). Western blot analysis demonstrated UT-A1 in the inner medulla of UT-A1(+/+)/UT-A3(-/-) and wild-type mice, but not in UT-A1/UT-A3 knockout mice, and an absence of UT-A3 in UT-A1(+/+)/UT-A3(-/-) and UT-A1/UT-A3 knockout mice. Immunohistochemistry in UT-A1(+/+)/UT-A3(-/-) mice also showed negative UT-A3 staining in kidney and other tissues and positive UT-A1 staining only in the IMCD. Urea permeability in isolated perfused IMCDs showed basal permeability in the UT-A1(+/+)/UT-A3(-/-) mice was similar to levels in wild-type mice, but vasopressin stimulation of urea permeability in wild-type mice was significantly greater (100% increase) than in UT-A1(+/+)/UT-A3(-/-) mice (8% increase). Notably, basal urine osmolalities in both wild-type and UT-A1(+/+)/UT-A3(-/-) mice increased upon overnight water restriction. We conclude that transgenic expression of UT-A1 restores basal urea permeability to the level in wild-type mice but does not restore vasopressin-stimulated levels of urea permeability. This information suggests that transgenic expression of UT-A1 alone in mice lacking UT-A1 and UT-A3 is sufficient to restore urine-concentrating ability. PMID:26407594

  3. Producing gestures facilitates route learning.

    PubMed

    So, Wing Chee; Ching, Terence Han-Wei; Lim, Phoebe Elizabeth; Cheng, Xiaoqin; Ip, Kit Yee

    2014-01-01

    The present study investigates whether producing gestures would facilitate route learning in a navigation task and whether its facilitation effect is comparable to that of hand movements that leave physical visible traces. In two experiments, we focused on gestures produced without accompanying speech, i.e., co-thought gestures (e.g., an index finger traces the spatial sequence of a route in the air). Adult participants were asked to study routes shown in four diagrams, one at a time. Participants reproduced the routes (verbally in Experiment 1 and non-verbally in Experiment 2) without rehearsal or after rehearsal by mentally simulating the route, by drawing it, or by gesturing (either in the air or on paper). Participants who moved their hands (either in the form of gestures or drawing) recalled better than those who mentally simulated the routes and those who did not rehearse, suggesting that hand movements produced during rehearsal facilitate route learning. Interestingly, participants who gestured the routes in the air or on paper recalled better than those who drew them on paper in both experiments, suggesting that the facilitation effect of co-thought gesture holds for both verbal and nonverbal recall modalities. It is possibly because, co-thought gesture, as a kind of representational action, consolidates spatial sequence better than drawing and thus exerting more powerful influence on spatial representation. PMID:25426624

  4. Modelling Routes towards Learning Goals

    ERIC Educational Resources Information Center

    Tattersall, Colin; Janssen, Jose; van den Berg, Bert; Koper, Rob

    2006-01-01

    Purpose: This paper aims to define the need for a route modelling language in e-learning, identifying requirements and candidate languages, before providing a recommended approach. Design/methodology/approach: Several sources of requirements are drawn from the literature then used to review available approaches to route modelling. The best…

  5. Dynamic Message Routing Using Processes

    NASA Astrophysics Data System (ADS)

    Scheibler, Thorsten; Karastoyanova, Dimka; Leymann, Frank

    The Enterprise Service Bus (ESB) is composable middleware that provides applications with services such as message routing and transformation, service composition, dynamic discovery, transactional support, coordination, security features, and others. In an ESB supporting SOAP message exchange, routing algorithms typically follow the sequential SOAP message processing model, where SOAP headers are the main artefacts used to specify the message route and the processing of the payload by intermediaries along that route. This model supports neither alternative nor parallel message routes. In the case of a failing intermediary node this leads to a failure in the message delivery. Moreover, the execution order of services on SOAP message payloads at the intermediaries cannot be prescribed. In this paper, we demonstrate how these deficiencies of the SOAP message processing model can be addressed. We introduce an approach that allows for specifying SOAP message routing logic in terms of BPEL processes. We show that parallel and alternative routes for SOAP messages can be modelled and executed, and the order of services that process a message at intermediaries can be predefined to accommodate the correct processing sequence as required by the concrete application domain. Features like dynamic discovery of services and flexible service composition are leveraged to enable flexible SOAP message routing.

  6. [Alternative routes for insulin administration].

    PubMed

    Lassmann-Vague, V

    1994-01-01

    Ideally, insulin administration should be done through portal route, with a precise kinetic. It should also lead to a reproducible biologic effect, with minimal side-effects and be acceptable for the majority of diabetic patients. Many alternative routes of insulin administration try to fulfill one or more of these criteria. Intraperitoneal route is already used with implantable pumps. It has proven safety and metabolic efficacy, particularly upon the reduction of severe hypoglycaemia. Nasal route could provide a rapid kinetic, but its long-term utilisation depends on improvement of bioavailability and studies of local toxicity. Results concerning intrabronchic insulin seem promising, but are still preliminary. In the future, the choice among these alternative routes of insulin administration will be guided by the development of a closed-loop system. PMID:8001707

  7. Dynamics of nanoparticle combustion

    NASA Astrophysics Data System (ADS)

    Allen, David James

    A heterogeneous shock tube was used to ignite and measure the combustion behavior of the nano-aluminum suspension behind reflected shock waves. The burning time and particle temperatures were measured using optical diagnostics. In order to use pyrometry measurements for nano-aluminum particles, the emissivity of nano-alumina particles was also measured using the shock tube to heat the particles to known temperatures. The burning time and peak particle temperature results suggested that heat transfer models currently used for burning nanoparticles may significantly overestimate heat losses during combustion. By applying conventional non-continuum heat transfer correlations to burning nano-aluminum particles, the observed peak temperatures, which greatly exceed the ambient temperature, should only be observable if the burning time were very short, of the order of 1 mus, whereas the observed burning time is two orders of magnitude larger. These observations can be reconciled if the energy accommodation coefficient for these conditions is of the order of 0.005, which is the value suggested by Altman, instead of approximately unity, which is the common assumption. A simple model was developed for nano-aluminum particle combustion focusing on a surface controlled reaction as evidenced by experimental data and heat transfer to the surroundings. The simple model supports a low energy accommodation coefficient as suggested by Altman. This result has significant implications on the heat transfer and performance of the nanoparticles in combustion environments. Direct measurement is needed in order to decouple the accommodation coefficient from the assumed combustion mechanism in the simple model. Time-resolved laser induced incandescence measurements were performed to measure the accommodation coefficient of nano-alumina particles in various gaseous environments. The accommodation coefficient was found to be 0.03, 0.07, and 0.15 in helium, nitrogen, and argon respectively at

  8. 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.

  9. 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.

  10. 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.

  11. High efficiency RCCI combustion

    NASA Astrophysics Data System (ADS)

    Splitter, Derek A.

    An experimental investigation of the pragmatic limits of Reactivity Controlled Compression Ignition (RCCI) engine efficiency was performed. The study utilized engine experiments combined with zero-dimensional modeling. Initially, simulations were used to suggest conditions of high engine efficiency with RCCI. Preliminary simulations suggested that high efficiency could be obtained by using a very dilute charge with a high compression ratio. Moreover, the preliminary simulations further suggested that with simultaneous 50% reductions in heat transfer and incomplete combustion, 60% gross thermal efficiency may be achievable with RCCI. Following the initial simulations, experiments to investigate the combustion process, fuel effects, and methods to reduce heat transfer and incomplete combustion reduction were conducted. The results demonstrated that the engine cycle and combustion process are linked, and if high efficiency is to be had, then the combustion event must be tailored to the initial cycle conditions. It was found that reductions to engine heat transfer are a key enabler to increasing engine efficiency. In addition, it was found that the piston oil jet gallery cooling in RCCI may be unnecessary, as it had a negative impact on efficiency. Without piston oil gallery cooling, it was found that RCCI was nearly adiabatic, achieving 95% of the theoretical maximum cycle efficiency (air standard Otto cycle efficiency).

  12. 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.

  13. 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.

  14. Urea: A Clinically Oriented Overview from Bench to Bedside.

    PubMed

    Friedman, Adam J; von Grote, Erika C; Meckfessel, Matthew H

    2016-05-01

    Urea is an important hygroscopic component of the epidermis, where it participates in the maintenance of skin hydration as part of the skin's source of natural moisturizing factor (NMF) in the outer most layers. Xerotic skin, which is frequently characterized as NMF-deficient, is a unifying trait of dermatoses such as atopic dermatitis (AD), psoriasis, and ichthyosis vulgaris. The reduced hygroscopic potential of pathologically dry skin leads to unregulated transepidermal water loss (TEWL), epidermal hyperproliferation, and inhibited desquamation; all which clinically translate to hyperkeratotic and possibly pruritic skin. Common underlying etiologies link these dermatoses to aberrant expression of genes encoding epidermal structural and catalytic proteins. Intervention of dry skin pathologies with topical moisturizer formulations is a foundational management strategy. For over a century urea-containing formulations have been used in a concentration-dependent manner to restore skin hydration, thin hyperkeratosis, debride dystrophic nails, and enhance topical drug penetration. Recently, urea's role in skin hydration and repair has expanded to include regulation of epidermal genes necessary for proper barrier function. Taken together, urea's versatility in topical formulations and broad range of therapeutic mechanism highlights its utility to clinicians and benefit to patients.

    J Drugs Dermatol. 2016;15(5):633-639. PMID:27168272

  15. 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.

  16. IRIS Toxicological Review of Urea (Interagency Science Discussion Draft)

    EPA Science Inventory

    EPA is releasing the draft report, Toxicological Review of Urea,, that was distributed to Federal agencies and White House Offices for comment during the Science Discussion step of the IRIS Assessment Development Process. C...

  17. IRIS Toxicological Review of Urea (Interagency Science Consultation Draft)

    EPA Science Inventory

    On September 28, 2010, the Toxicological Review of Urea and the charge to external peer reviewers were released for external peer review and public comment. The Toxicological Review and charge were reviewed internally by EPA and by other federal agencies and White House Of...

  18. Peptidyl-urea based inhibitors of soluble epoxide hydrolases

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We prepared a series of amino acid derived cyclohexyl and adamantyl ureas and tested them as inhibitors of the human soluble epoxide hydrolase, and obtained very potent compounds (K(I)=15nM) that are >10-fold more soluble than previously described sEH inhibitors. While our lead compound 2 showed low...

  19. Reduction in slow intercompartmental clearance of urea during dialysis

    SciTech Connect

    Bowsher, D.J.; Krejcie, T.C.; Avram, M.J.; Chow, M.J.; Del Greco, F.; Atkinson, A.J. Jr.

    1985-04-01

    The kinetics of urea and inulin were analyzed in five anesthetized dogs during sequential 2-hour periods before, during, and after hemodialysis. The distribution of both compounds after simultaneous intravenous injection was characterized by three-compartment models, and the total volumes of urea (0.66 +/- 0.05 L/kg) and inulin (0.19 +/- 0.01 L/kg) distribution were similar to expected values for total body water and extravascular space, respectively. Intercompartmental clearances calculated before dialysis were used to estimate blood flows to the fast and slow equilibrating compartments. In agreement with previous results, the sum of these flows was similar to cardiac output, averaging 101% of cardiac output measured before dialysis (range 72% to 135%). Dialysis was accompanied by reductions in the slow intercompartmental clearances of urea (81%) and inulin (47%), which reflected a 90% attenuation in blood flow supplying the slow equilibrating compartments. This was estimated to result in a 10% average reduction in the efficiency with which urea was removed by dialysis (range 2.0% to 16.4%). Mean arterial pressure fell by less than 5% during dialysis, but total peripheral resistance increased by 47% and cardiac output fell by 35%. In the postdialysis period, total peripheral resistance and cardiac output returned toward predialysis values, but blood flow to the slow equilibrating peripheral compartment was still reduced by 80%. These changes parallel activation of the renin-angiotensin system, but further studies are required to establish causality.

  20. Crystal Engineering with Urea and Thiourea Hydrogen-Bonding Groups

    SciTech Connect

    Custelcean, Radu

    2008-01-01

    The utilization of N,N{prime}-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.

  1. 75 FR 74746 - Solid Urea From Russia and Ukraine

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-12-01

    ... part 207), as most recently amended at 74 FR 2847 (January 16, 2009). \\1\\ No response to this request... solid urea from the Union of Soviet Socialist Republics (``USSR'') (52 FR 26367). On June 29, 1992... state (57 FR 28828). Following first five-year reviews by Commerce and the Commission,...

  2. Past tense route priming.

    PubMed

    Cohen-Shikora, Emily R; Balota, David A

    2013-03-01

    The present research examined whether lexical (whole word) or more rule-based (morphological constituent) processes can be locally biased by experimental list context in past tense verb inflection. In Experiment 1, younger and older adults completed a past tense inflection task in which list context was manipulated across blocks containing regular past tense verbs (e.g. REACH-REACHED) or irregular past tense verbs (TEACH-TAUGHT). Critical targets, consisting of half regular and half irregular verbs, were embedded within blocks and participants' inflection response latency and accuracy were assessed. The results yielded a cross-over interaction in response latencies for both young and older adults. In the regular context there was a robust regularity effect: regular target verbs were conjugated faster than irregular target verbs. In contrast, in the irregular context, irregular target verbs were conjugated faster than regular target verbs. Experiment 2 used the same targets but in the context of either standard nonwords or nonwords ending in "-ED" to test the possibility of a phonological basis for the effect. The effect of context was eliminated. The results support the notion that distinct processes in past tense verb production can be locally biased by list context and, as shown in Experiment 2, this route priming effect was not due to phonological priming. PMID:23291293

  3. 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.

  4. 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.

  5. 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.

  6. Hybrid rocket combustion study

    NASA Astrophysics Data System (ADS)

    Strand, L. D.; Ray, R. L.; Cohen, N. S.

    1993-06-01

    The objectives of this study of 'pure' or 'classic' hybrids are to (1) extend our understanding of the boundary layer combustion process and the critical engineering parameters that define this process, (2) develop an up-to-date hybrid fuel combustion model, and (3) apply the model to correlate the regression rate and scaling properties of potential fuel candidates. Tests were carried out with a hybrid slab window motor, using several diagnostic techniques, over a range of motor pressure and oxidizer mass flux conditions. The results basically confirmed turbulent boundary layer heat and mass transfer as the rate limiting process for hybrid fuel decomposition and combustion. The measured fuel regression rates showed good agreement with the analytical model predictions. The results of model scaling calculations to Shuttle SRM size conditions are presented.

  7. 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.

  8. Hybrid rocket combustion study

    NASA Technical Reports Server (NTRS)

    Strand, L. D.; Ray, R. L.; Cohen, N. S.

    1993-01-01

    The objectives of this study of 'pure' or 'classic' hybrids are to (1) extend our understanding of the boundary layer combustion process and the critical engineering parameters that define this process, (2) develop an up-to-date hybrid fuel combustion model, and (3) apply the model to correlate the regression rate and scaling properties of potential fuel candidates. Tests were carried out with a hybrid slab window motor, using several diagnostic techniques, over a range of motor pressure and oxidizer mass flux conditions. The results basically confirmed turbulent boundary layer heat and mass transfer as the rate limiting process for hybrid fuel decomposition and combustion. The measured fuel regression rates showed good agreement with the analytical model predictions. The results of model scaling calculations to Shuttle SRM size conditions are presented.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. Combustion synthesis of fullerenes

    SciTech Connect

    Mckinnon, J.T.; Bell, W.L. ); Barkley, R.M. )

    1992-01-01

    This paper reports the isolation of C{sub 60} and C{sub 70} from combustion soot that is produced in high-temperature, low-pressure premixed flat flames. A critical parameter for high fullerene yields in combustion appears to be a very high flame temperature. Equilibrium calculations indicate that low pressures are important, but the experimental evidence is not clear at this time. Combustion synthesis yields fullerenes with a C{sub 70}/C{sub 60} ratio of about 40%, as compared with the 12% reported for electric-arc-generated fullerenes. The overall yields from carbon are very low (ca. 0.03%) but the soot studied had been produced in flames that were in no way optimized for fullerene production.

  14. Characterization of degeneration process in thermo-acoustic combustion instability using dynamical systems theory

    NASA Astrophysics Data System (ADS)

    Hayashi, Kenta; Gotoda, Hiroshi; Okuno, Yuta; Tachibana, Shigeru; Tokyo University of Science Collaboration; Japan Aerospace Exploration Agency Collaboration

    2015-11-01

    We have experimentally investigated the degeneration process of combustion instability in a lean premixed gas-turbine model combustor on the basis of dynamical systems theory. Our previous study reported that with increasing the equivalence ratio, the dynamical behavior of combustion state close to lean blowout transits from stochastic fluctuations to periodic thermoacoustic combustion oscillations via low-dimensional chaotic oscillations. The further increase in the equivalence ratio gives rise to the quasi-periodic oscillations and the subsequent chaotic oscillations with small amplitudes. The route to chaotic oscillations is quantitatively shown by the use of nonlinear time series analysis involving the color recurrence plots, permutation entropy and local predictor.

  15. Apical membrane limits urea permeation across the rat inner medullary collecting duct.

    PubMed Central

    Star, R A

    1990-01-01

    Urea diffuses across the terminal inner medullary collecting duct (IMCD) via a facilitated transport pathway. To examine the mechanism of transcellular urea transport, membrane-apparent urea (Purea) and osmotic water (Pf) permeabilities of IMCD cells were measured by quantitative light microscopy in isolated IMCD-2 tubules perfused in the absence of vasopressin. Basolateral membrane Pf, determined by addition of raffinose to the bath, was 69 microns/s. Basolateral membrane Purea, determined by substituting urea for raffinose without change in osmolality, was 14 X 10(-5) cm/s. Bath phloretin inhibited basolateral Purea by 85% without a significant effect on Pf. The basolateral reflection coefficient for urea, determined by addition of urea in the presence of phloretin, was 1.0. These results indicate that urea crosses the basolateral membrane by diffusion, and not by solvent drag. In perfused tubules, the rate of cell swelling following substitution of urea for mannitol was significantly greater with bath than lumen changes. After correcting for membrane surface area, the basolateral membrane was twofold more permeable than the apical membrane. Conclusions: (a) in the absence of vasopressin, urea permeation across the IMCD cell is limited by the apical membrane; (b) the basolateral membrane contains a phloretin-sensitive urea transporter; (c) transepithelial urea transport occurs by movement of urea through the IMCD cell. PMID:2212006

  16. PHYSIOLOGY AND YIELD RESPONSES OF COTTON TO FOLIAR UREA WITH NBPT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Urea is the most recommended foliar N source, due to its relatively low toxicity, quick absorption, and low cost. However, in the literature reports of yield increments with foliar urea application are not consistent. The objectives of this research were to study foliar urea assimilation in cotton...

  17. 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...

  18. 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...

  19. EFFECT OF FOLIAR APPLICATION OF UREA WITH NBPT ON THE PHYSIOLOGY AND YIELD OF COTTON

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Urea is the most recommended foliar N source, due to its relatively low toxicity, quick absorption, and low cost. However, reports of yield improvements with foliar urea application are not consistent. The objectives of this research were to study foliar urea assimilation in cotton and to test the ...

  20. Aspects of urea metabolism in ruminants with reference to the goat.

    PubMed

    Harmeyer, J; Martens, H

    1980-10-01

    In goats and other ruminants, urea functions as a source of nitrogen for protein biosynthesis in the digestive tract. Ammonia can be absorbed in the digestive system when formed in excessive quantitites and enhance formation of urea, or it can be derived from urea of blood plasma when its formation from feed sources is small. Entry rates of urea into plasma may vary from 4 to 80 mumol/min per kg.75 body weight depending on dietary conditions. Urea formation is related to nitrogen intake of which approximately 70% passes into the urea pool of plasma. Irreversible losses of urea of plasma into the digestive tract vary between 10 and 90% depending on the protein to energy ratios of the diet. Entry of urea from plasma into the rumen appears to be a passive process which is sensitive to short-term changes of urea concentrations in plasma. Permeability of ruminal epithelium to urea may be altered by fermentation products of rumen (ammonia, carbon dioxide, volatile fatty acids). The influx of nitrogen into the rumen is related to needs for nitrogen of microbial populations and is associated with changes of renal excretion and tubular reabsorption of urea. Combined gastrointestinal and renal responses exert a synergistic effect on improved utilization of urea of plasma when uptake of dietary nitrogen is limited in goats and other ruminants. PMID:7451710

  1. 40 CFR 721.10533 - Amine-modified urea-formaldehyde polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Amine-modified urea-formaldehyde... Specific Chemical Substances § 721.10533 Amine-modified urea-formaldehyde polymer (generic). (a) Chemical... as amine-modified urea-formaldehyde polymer (PMN P-12-182) is subject to reporting under this...

  2. 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...

  3. 40 CFR 721.9920 - Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 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,...

  4. 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...

  5. 40 CFR 721.10533 - Amine-modified urea-formaldehyde polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Amine-modified urea-formaldehyde... Specific Chemical Substances § 721.10533 Amine-modified urea-formaldehyde polymer (generic). (a) Chemical... as amine-modified urea-formaldehyde polymer (PMN P-12-182) is subject to reporting under this...

  6. 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...

  7. 40 CFR 721.9920 - Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 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,...

  8. 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,...

  9. 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...

  10. 40 CFR 721.9920 - Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 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,...

  11. 40 CFR 721.9920 - Urea, (hexahydro-6-methyl-2-oxopyrimidinyl)-.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 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,...

  12. Combustibility of tetraphenylborate solids

    SciTech Connect

    Walker, D.D.

    1989-05-03

    Liquid slurries expected under normal in-tank processing (ITP) operations are not ignitible because of their high water content. However, deposits of dry solids from the slurries are combustible and produce dense, black smoke when burned. The dry solids burn similarly to Styrofoam and more easily than sawdust. It is the opinion of fire hazard experts that a benzene vapor deflagration could ignite the dry solids. A tetraphenylborate solids fire will rapidly plug the waste tank HEPA ventilation filters due to the nature of the smoke produced. To prevent ignition and combustion of these solids, the waste tanks have been equipped with a nitrogen inerting system.

  13. Combustion pressure sensor arrangement

    SciTech Connect

    Sawamoto, K.; Nagaishi, H.; Takeuchi, K.

    1986-07-29

    A combustion pressure sensor arrangement in an internal combustion engine having a cylinder head, comprising: a plug seating formed in the cylinder head; an annular pressure sensor; an ignition plug screwed into the cylinder head in such a manner that the pressure sensor is clamped between the ignition plug and the plug seating; an ignition plug accommodation hole formed in the cylinder head for accommodating therein the ignition plug; and a guide sleeve joined at one end thereof to the outer periphery of the pressure sensor and fitted in the ignition plug accommodation hole, wherein the one end of the guide sleeve is fitted on the outer periphery of the pressure sensor.

  14. 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.

  15. 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.

  16. 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.

  17. A Combustion Laboratory for Undergraduates.

    ERIC Educational Resources Information Center

    Peters, James E.

    1985-01-01

    Describes a combustion laboratory facility and experiments for a senior-level (undergraduate) course in mechanical engineering. The experiment reinforces basic thermodynamic concepts and provides many students with their first opportunity to work with a combustion system. (DH)

  18. 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. ...

  19. 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.

  20. MUNICIPAL WASTEWATER SLUDGE COMBUSTION TECHNOLOGY

    EPA Science Inventory

    The publication describes and evaluates the various municipal sludge combustion systems. It also emphasizes the necessity for considering and evaluating the costs involved in the total sludge management train, including dewatering, combustion, air pollution control, and ash dispo...

  1. 14 CFR 121.95 - Route width.

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ..., FLAG, AND SUPPLEMENTAL OPERATIONS Approval of Routes: Domestic and Flag Operations § 121.95 Route width... routes in the case of certificate holders conducting flag operations) have a width equal to...

  2. Reverse flood routing with the inverted Muskingum storage routing scheme

    NASA Astrophysics Data System (ADS)

    Koussis, A. D.; Mazi, K.; Lykoudis, S.; Argiriou, A. A.

    2012-01-01

    This work treats reverse flood routing aiming at signal identification: inflows are inferred from observed outflows by orienting the Muskingum scheme against the wave propagation direction. Routing against the wave propagation is an ill-posed, inverse problem (small errors amplify, leading to large spurious responses); therefore, the reverse solution must be smoothness-constrained towards stability and uniqueness (regularised). Theoretical constrains on the coefficients of the reverse routing scheme assist in error control, but optimal grids are derived by numerical experimentation. Exact solutions of the convection-diffusion equation, for a single and a composite wave, are reverse-routed and in both instances the wave is backtracked well for a range of grid parameters. In the arduous test of a square pulse, the result is comparable to those of more complex methods. Seeding outflow data with random errors enhances instability; to cope with the spurious oscillations, the reversed solution is conditioned by smoothing via low-pass filtering or optimisation. Good-quality inflow hydrographs are recovered with either smoothing treatment, yet the computationally demanding optimisation is superior. Finally, the reverse Muskingum routing method is compared to a reverse-solution method of the St. Venant equations of flood wave motion and is found to perform equally well, at a fraction of the computing effort. This study leads us to conclude that the efficiently attained good inflow identification rests on the simplicity of the Muskingum reverse routing scheme that endows it with numerical robustness.

  3. 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.

  4. Fuels research: Combustion effects overview

    NASA Technical Reports Server (NTRS)

    Haggard, J. B., Jr.

    1980-01-01

    The effects of broadened property fuels on gas turbine combustors were assessed. Those physical and chemical properties of fuels that affect aviation gas turbine combustion were isolated and identified. Combustion sensitivity to variations in particular fuel properties were determined. Advanced combustion concepts and subcomponents that could lessen the effect of using broadened property fuels were also identified.

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

    PubMed

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

    2014-06-01

    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

  6. Effect of time duration of ruminal urea infusions on ruminal ammonia concentrations and portal-drained visceral extraction of arterial urea-N in lactating Holstein cows.

    PubMed

    Røjen, B A; Kristensen, N B

    2012-03-01

    The effects of a 6 versus 24h ruminal urea infusion in lactating dairy cows fed a basal diet deficient in N on ruminal ammonia concentration, arterial urea-N concentration, net portal-drained viscera (PDV) urea-N flux, arterial urea-N extraction across the PDV, and renal urea-N kinetics were investigated. Three Danish Holstein cows fitted with ruminal cannulas and permanent indwelling catheters in major splanchnic blood vessels were randomly allocated to a 3 × 3 Latin square design with 21-d periods. Treatments were ventral ruminal infusion of water for 24h (water INF), 24-h infusion of 15 g of urea/kg of dry matter intake (DMI; 24-h INF), and 6-h infusion of 15 g of urea/kg of DMI (6-h INF). The 6-h INF was initiated 0.5h after the afternoon feeding, and ran until 2230 h. Eight sample sets of arterial, portal, and hepatic blood, ruminal fluid, and urine were obtained at 0.5h before the morning feeding and 0.5, 1.5, 2.5, 3.5, 4.5, 5.5, and 6.5h after feeding (i.e., 9 to 15.5h after the 6h infusion was terminated). A substantial decrease in DMI for 6-h INF compared with 24-h INF and water INF was observed, and it has to be recognized that DMI may have confounding effects. However, the experimental setting plan was met (i.e., to cause changes in the daily pattern of ruminal ammonia and blood urea-N concentrations). The arterial urea-N concentration for 24-h INF and 6-h INF were greater than the arterial urea-N concentration with water INF throughout the sampling window. However, the arterial urea-N concentration for 6-h INF decreased steadily with sampling time reflecting a carryover effect from the ruminal urea infusion. The ruminal ammonia concentration and net portal flux of ammonia for 6-h INF were not different from water INF; hence, no carryover effect on ruminal ammonia concentration was observed. The portal flux of urea-N was not affected by treatment (i.e., even the combination of low ruminal ammonia and high arterial urea-N concentration with 6-h INF was

  7. 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.

  8. Nonlinear Combustion Instability Prediction

    NASA Technical Reports Server (NTRS)

    Flandro, Gary

    2010-01-01

    The liquid rocket engine stability prediction software (LCI) predicts combustion stability of systems using LOX-LH2 propellants. Both longitudinal and transverse mode stability characteristics are calculated. This software has the unique feature of being able to predict system limit amplitude.

  9. 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...

  10. Droplet Combustion Experiment Operates

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 12, 1997, MET:11/07:00 (approximate). DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The 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 experiment elapsed time is shown at the bottom of the composite image. 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-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (119KB JPEG, 658 x 982 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300171.html.

  11. 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.

  12. Internal combustion engine

    SciTech Connect

    Beaudsin, N.

    1984-05-22

    An internal combustion engine wherein the rod connecting the piston to the crankshaft has an enlarged portion defining a track which a crankshaft element cooperatingly engages; the track is topologically shaped so that the effect exerted by the crankshaft element on the connecting rod is reduced and/or cancelled for a given travel distance of the crankshaft element in the track.

  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. 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.

  15. Supersonic-combustion rocket

    NASA Technical Reports Server (NTRS)

    Weber, R. J.; Franciscus, L. C. (Inventor)

    1973-01-01

    A supersonic combustion rocket is provided in which a small rocket motor is substituted for heavy turbo pumps in a conventional rocket engine. The substitution results in a substantial reduction in rocket engine weight. The flame emanating from the small rocket motor can act to ignite non-hypergolic fuels.

  16. 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.

  17. Alcoholic Hepatitis Markedly Decreases the Capacity for Urea Synthesis

    PubMed Central

    Glavind, Emilie; Aagaard, Niels Kristian; Grønbæk, Henning; Møller, Holger Jon; Orntoft, Nikolaj Worm; Vilstrup, Hendrik; Thomsen, Karen Louise

    2016-01-01

    Background and Aim Data on quantitative metabolic liver functions in the life-threatening disease alcoholic hepatitis are scarce. Urea synthesis is an essential metabolic liver function that plays a key regulatory role in nitrogen homeostasis. The urea synthesis capacity decreases in patients with compromised liver function, whereas it increases in patients with inflammation. Alcoholic hepatitis involves both mechanisms, but how these opposite effects are balanced remains unclear. Our aim was to investigate how alcoholic hepatitis affects the capacity for urea synthesis. We related these findings to another measure of metabolic liver function, the galactose elimination capacity (GEC), as well as to clinical disease severity. Methods We included 20 patients with alcoholic hepatitis and 7 healthy controls. The urea synthesis capacity was quantified by the functional hepatic nitrogen clearance (FHNC), i.e., the slope of the linear relationship between the blood α-amino nitrogen concentration and urea nitrogen synthesis rate during alanine infusion. The GEC was determined using blood concentration decay curves after intravenous bolus injection of galactose. Clinical disease severity was assessed by the Glasgow Alcoholic Hepatitis Score and Model for End-Stage Liver Disease (MELD) score. Results The FHNC was markedly decreased in the alcoholic hepatitis patients compared with the healthy controls (7.2±4.9 L/h vs. 37.4±6.8 L/h, P<0.01), and the largest decrease was observed in those with severe alcoholic hepatitis (4.9±3.6 L/h vs. 9.9±4.9 L/h, P<0.05). The GEC was less markedly reduced than the FHNC. A negative correlation was detected between the FHNC and MELD score (rho = -0.49, P<0.05). Conclusions Alcoholic hepatitis markedly decreases the urea synthesis capacity. This decrease is associated with an increase in clinical disease severity. Thus, the metabolic failure in alcoholic hepatitis prevails such that the liver cannot adequately perform the metabolic up

  18. 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.

  19. Synthesis and stacked conformations of symmetrical and unsymmetrical oligo-ureas of metaphenylenediamine.

    PubMed

    Clayden, Jonathan; Lemiègre, Loïc; Helliwell, Madeleine

    2007-03-30

    The addition of substituted anilines to nitro-substituted isocyanates followed by reduction generates new aniline-substituted ureas, which can be further extended in a one- or two-directional iterative manner to form oligomeric ureas based on a m-phenylenediamine monomer. Oligo-ureas with up to eight urea linkages are reported. Fully N-substituted oligo-ureas are crystalline, and the X-ray crystal structures display ring-stacked conformations. 1H NMR studies indicate that the stacked conformation persists in solution. PMID:17343415

  20. 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.

  1. Reverse flood routing with the inverted Muskingum storage routing scheme

    NASA Astrophysics Data System (ADS)

    Koussis, A. D.; Mazi, K.; Lykoudis, S.; Argyriou, A.

    2010-09-01

    Motivation On occasion, flood related questions are posed in the reverse from the conventional sense, e.g.: Which inflow created the flow observed at cross-section X, or the flood profile observed along reach Y? This is a signal identification type problem (hydrologic forensics). A related question concerns the operation of a reservoir, via optimal outflow control, so as to minimise downstream flood damage. Solution of the aforementioned problems requires routing of floods in the upstream direction. This is an inverse problem, and as such it is not well posed. In routing against the wave propagation, small errors in the flow measurements, or rounding errors, are amplified leading to instability, i.e., to spurious, large changes in the response (inflow hydrograph). Therefore, for the reverse solution to be stable it must be constrained by a smoothness condition; this however does not ensure its uniqueness. Storage routing models as approximate diffusion wave models By appropriate choice of their parameter values, storage routing models approximate closely diffusion-wave (DW) behaviour, if dominant flood propagation mode is that of kinematic waves (KW), which is very often true. We solve the flood signal identification problem by reversing the Muskingum routing scheme. The Muskingum routing scheme derives from a first-order accurate FD discretisation of the KW equation yet yields second-order accurate DW solutions by matching the numerical diffusion coefficient of that KW equation solution scheme to the DW equation’s hydraulic diffusion coefficient. Formulation and testing of a reverse routing scheme based on Muskingum routing Theoretical analysis of the reversed Muskingum routing scheme yields nominal grid design rules; however, we study optimal grid design mainly by numerical experimentation. First, we reverse an exact outflow hydrograph (a single-wave solution of the convection-diffusion equation), and then demonstrate the scheme’s ability to reverse

  2. Urea uptake enhances barrier function and antimicrobial defense in humans by regulating epidermal gene expression

    PubMed Central

    Grether-Beck, Susanne; Felsner, Ingo; Brenden, Heidi; Kohne, Zippora; Majora, Marc; Marini, Alessandra; Jaenicke, Thomas; Rodriguez-Martin, Marina; Trullas, Carles; Hupe, Melanie; Elias, Peter M.; Krutmann, Jean

    2012-01-01

    Urea is an endogenous metabolite, known to enhance stratum corneum hydration. Yet, topical urea anecdotally also improves permeability barrier function, and it appears to exhibit antimicrobial activity. Hence, we hypothesized that urea is not merely a passive metabolite, but a small-molecule regulator of epidermal structure and function. In 21 human volunteers, topical urea improved barrier function in parallel with enhanced antimicrobial peptide (LL-37 and β-defensin-2) expression. Urea both stimulates expression of, and is transported into keratinocytes by two urea transporters, UT-A1 and UT-A2, and by aquaporin 3, 7 and 9. Inhibitors of these urea transporters block the downstream biological effects of urea, which include increased mRNA and protein levels for: (i) transglutaminase-1, involucrin, loricrin and filaggrin; (ii) epidermal lipid synthetic enzymes, and (iii) cathelicidin/LL-37 and β-defensin-2. Finally, we explored the potential clinical utility of urea, showing that topical urea applications normalized both barrier function and antimicrobial peptide expression in a murine model of atopic dermatitis (AD). Together, these results show that urea is a small-molecule regulator of epidermal permeability barrier function and antimicrobial peptide expression after transporter uptake, followed by gene regulatory activity in normal epidermis, with potential therapeutic applications in diseased skin. PMID:22418868

  3. 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

    2015-03-01

    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. PMID:25498618

  4. Heat regenerative external combustion engine

    NASA Astrophysics Data System (ADS)

    Duva, Anthony W.

    1993-10-01

    A heat regenerative external combustion engine is disclosed. The engine includes fuel inlet means which extends along the exhaust passage and/or combustion chamber in order to preheat the fuel, To provide for preheating by gases in both the combustion chamber and the exhaust passage, the combustion chamber is arranged annularly around the drive shaft and between the cylinders. This configuration also is advantageous in that it reduces the noise of combustion. The engine of the invention is particularly well-suited for use in a torpedo.

  5. 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.

  6. Urea cycle regulation by mitochondrial sirtuin, SIRT5.

    PubMed

    Nakagawa, Takashi; Guarente, Leonard

    2009-06-01

    Mammalian sirtuins have diverse roles in aging, metabolism and disease. Recently we reported a new function for SIRT5 in urea cycle regulation. Our study uncovered that SIRT5 localized to mitochondria matrix and deacetylates carbamoyl phosphate synthetase 1 (CPS1), an enzyme which is the first and rate-limiting step of urea cycle. Deacetylation of CPS1 by SIRT5 resulted in activation of CPS1 enzymatic activity. Indeed, SIRT5-deficient mice failed to up-regulate CPS1 activity and showed hyper ammonemia during fasting. Similar effects are also observed on high protein diet or calorie restriction. These data indicate SIRT5 also has an emerging role in the metabolic adaptation to fasting, high protein diet and calorie restriction. PMID:20157539

  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. The use of urea by Evernia prunastri thalli.

    PubMed

    Blanco, M J; Suárez, C; Vicente, C

    1984-10-01

    Thalli of Evernia prunastri floated on 40 mM urea synthesize urease (EC3.5.1.5) which is, in part, retained in the cells as well as secreted into the external medium. By using [(14)C]urea, it has been shown that the (14)CO2 evolved by the action of urease is mainly incorporated into phenolic compounds. Evernic acid has the highest radioactivity when incubations are carried out in the light. The orsellinate moiety of this molecule contains ten times more radioactivity than the everninic acid moiety. This could be explained by the assumption that orsellinic acid is the first product of cyclisation of the polyketide chain in the biosynthetic pathway. PMID:24253163

  9. 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. PMID:24723807

  10. 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

  11. 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.

  12. Multiresidue HPLC methods for phenyl urea herbicides in water.

    PubMed

    Ruberu, S R; Draper, W M; Perera, S K

    2000-09-01

    High-performance liquid chromatography (HPLC) methods for the determination of phenyl urea herbicides in water are described. The target compounds include chlortoluron, diuron, fluometuron, isoproturon, linuron, metobromuron, metoxuron, monuron, neburon, and siduron. Water was subjected to solid phase extraction (SPE) using either automated SPE with 47 mm C(18) Empore disks or on-line precolumn concentration. Herbicides were separated on a C(18) reversed phase column with an acetonitile-water gradient and were detected with either a diode array detector (DAD) or a postcolumn photolysis and derivatization (PPD) detector system. Photolysis converted the phenyl ureas to monoalkylamines that were derivatized to fluorescent isoindoles by reaction with o-phthalaldehyde and 2-mercaptoethanol. The DAD monitoring at 245 nm was linear over three decades with instrument detection limits of approximately 0.01 mg/L. SPE efficiency was between 48 and 70% in laboratory reagent water, but use of the internal standard quantitation method improved accuracy. High total dissolved solids and total organic carbon values in surface water improved recoveries relative to laboratory reagent water for all of the phenyl ureas. In Colorado River water spiked at 1 or 50 microg/L, mean recoveries ranged from 74 to 104%. Method detection limits (MDLs) ranged from 4 to 40 ng/L (parts per trillion) with the DAD instrument. PPD detection was highly specific but resulted in a slight loss in chromatographic efficiency and average MDLs approximately 5 times higher using a single set of detection conditions. The study indicates that methods based on SPE followed by HPLC with diode array or PPD detection have practical utility for trace analysis of phenyl ureas in drinking water or surface waters. PMID:10995323

  13. Design, synthesis, and bioactivity study of novel benzoylpyridazyl ureas.

    PubMed

    Sun, Ranfeng; Zhang, Yonglin; Bi, Fuchun; Wang, Qingmin

    2009-07-22

    A series of novel benzoylpyridazyl ureas were designed and synthesized from maleic anhydride and hydrazine monohydrate. These benzoylureas were identified by (1)H NMR spectroscopy and element analysis. The bioactivities of the new compounds were evaluated. These compounds exhibited larvicidal activities against oriental armyworm, and in particular, compound 13 displayed comparable activity to the commercial insecticide Hexaflumuron. Most of these compounds also had some larvicidal activities against mosquito. Interestingly, some compounds showed good plant growth regulatory activities. PMID:19601668

  14. 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.

  15. High and Low Affinity Urea Root Uptake: Involvement of NIP5;1.

    PubMed

    Yang, Huayiu; Menz, Jochen; Häussermann, Iris; Benz, Martin; Fujiwara, Toru; Ludewig, Uwe

    2015-08-01

    Urea is the most widespread nitrogen (N) fertilizer worldwide and is rapidly degraded in soil to ammonium by urease. Ammonium is either taken up by plant roots or is further processed to nitrate by soil microorganisms. However, urea can be taken up by roots and is further degraded to ammonium by plant urease for assimilation. When urea is supplied under sterile conditions, it acts as a poor N source for seedlings or adult Arabidopsis thaliana plants. Here, the gene expression of young seedlings exposed to urea and ammonium nitrate nutrition was compared. Several primary metabolism and transport genes, including those for nitrate and urea, were differentially expressed in seedlings. However, urease and most major intrinsic proteins were not differentially expressed, with the exception of NIP6;1, a urea-permeable channel, which was repressed. Furthermore, little overlap with the gene expression with ammonium as the sole N source was observed, confirming that pure urea nutrition is not associated with the ammonium toxicity syndrome in seedlings. The direct root uptake of urea was increased under boron deficiency, in both the high and low affinity range. This activity was entirely mediated by the NIP5;1 channel, which was confirmed to transport urea when expressed in oocytes. The uptake of urea in the high and low affinity range was also determined for maize and wheat roots. The urea uptake by maize roots was only about half that of wheat, but was not stimulated by boron deficiency or N deficiency in either species. This analysis identifies novel components of the urea uptake systems in plants, which may become agronomically relevant to urea uptake and utilization, as stabilized urea fertilizers become increasingly popular. PMID:25957355

  16. An improved generalized AMBER force field (GAFF) for urea.

    PubMed

    Ozpinar, Gül Altinbaş; Peukert, Wolfgang; Clark, Timothy

    2010-09-01

    We describe an improved force field parameter set for the generalized AMBER force field (GAFF) for urea. Quantum chemical computations were used to obtain geometrical and energetic parameters of urea dimers and larger oligomers using AM1 semiempirical MO theory, density functional theory at the B3LYP/6-31G(d,p) level, MP2 and CCSD ab initio calculations with the 6-311++G(d,p), aug-cc-pVDZ, aug-cc-pVTZ, and aug-cc-pVQZ basis sets, and with the CBS-QB3 and CBS-APNO complete basis set methods. Seven different urea dimer structures were optimized at the MP2/aug-cc-pVDZ level to obtain accurate interaction energies. Atomic partial charges were calculated at the MP2/aug-cc-pVDZ level with the restrained electrostatic potential (RESP) fitting approach. The interaction energies computed with these new RESP charges in the force field are consistent with those obtained from CCSD and MP2 calculations. The linear dimer structure calculated using the force field with modified geometrical parameters and the new RESP charge set agrees well with available experimental data. PMID:20162312

  17. 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

  18. Hydrophobic Association in Mixed Urea-TMAO Solutions.

    PubMed

    Ganguly, Pritam; van der Vegt, Nico F A; Shea, Joan-Emma

    2016-08-01

    The formation of a hydrophobic core is key to the folding and resulting function of most proteins in the cell. In several organisms, as well as in many in vitro experiments, protein folding is modulated by the presence of osmolytes, but the mechanism by which hydrophobic association occurs is not well understood. We present a study of the solvation thermodynamics of hydrophobic self-association in mixed-osmolyte urea-TMAO solutions, with neopentane as a model hydrophobic molecule. Using molecular dynamics simulations and the Kirkwood-Buff theory of solutions, we show that a sensitive balance between the TMAO-water and the TMAO-urea interactions governs the osmolyte-induced changes in hydrophobic association in mixed urea-TMAO solutions. This balance must be correctly incorporated in force-field parametrization because hydrophobic association can be either enhanced or prevented all together by slightly increasing or decreasing the osmolyte-water affinity and osmolyte-osmolyte self-affinity of TMAO molecules. PMID:27440555

  19. 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.

  20. 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.

  1. Combustion of Gaseous Mixtures

    NASA Technical Reports Server (NTRS)

    Duchene, R

    1932-01-01

    This report not only presents matters of practical importance in the classification of engine fuels, for which other means have proved inadequate, but also makes a few suggestions. It confirms the results of Withrow and Boyd which localize the explosive wave in the last portions of the mixture burned. This being the case, it may be assumed that the greater the normal combustion, the less the energy developed in the explosive form. In order to combat the detonation, it is therefore necessary to try to render the normal combustion swift and complete, as produced in carbureted mixtures containing benzene (benzol), in which the flame propagation, beginning at the spark, yields a progressive and pronounced darkening on the photographic film.

  2. 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.

  3. 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.

  4. Fluidized bed combustion

    SciTech Connect

    Sowards, N.K.; Murphy, M.L.

    1992-04-07

    This patent describes a method of incinerating a fuel containing difficult to remove tramp comprising wire. It comprises placing of a fluid bed within a downwardly and inwardly tapered centrally hollow air distributor disposed within a lower portion of a vessel; introducing fuel comprising combustible material and tramp comprising wire into the fluid bed; incinerating the combustible material in the fluid bed accommodating downward migration within the fluid bed of the wire without a central obstruction to such migration; in the course of performing the incinerating step, fluidizing the bed solely by introducing inwardly at several tiered locations directed air into the bed only around the tapered periphery along the lower portion of the vessel from a plurality of inwardly and downwardly parallel sites as causing the bed material and tramp to migrate downwardly and inwardly without central bed obstruction toward a discharge site.

  5. 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.

  6. 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.

  7. Catalytic combustion nears application

    SciTech Connect

    1994-11-01

    This article is a brief review of efforts to develope a catalytic combustion system with emissions levels less than 10 ppm. Two efforts are discussed: (1) tests by General Electric using a GE Frame 7E/9E and 7F/9F gas turbine, and (2) tests by AES using a Kawasaki M1A-13A industrial gas turbine. The latter also employs a heat recovery steam generator and produces 3 MWe and 28,000 lbm/hr of steam.

  8. 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.

  9. 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.

  10. 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.

  11. Spray combustion stability

    NASA Technical Reports Server (NTRS)

    Liang, Pak-Yan; Jeng, S. M.; Litchford, Ronald

    1995-01-01

    The central purpose of this project is the improvement of liquid-fueled rocket motor design technology in order to assist the establishment of economical commercial access to space through the development of engines with enhanced performance and reliability. Specific research effort in the project is focused on spray physics and associated combustion instability phenomena. Results garnered from this work will contribute to the development of new computational tools for design of stable liquid propellant rocket engines. The specific objectives of the research effort include identifying and evaluating physical submodels which pertain to spray combustion stability with the idea of enhancing or refining existing submodels with a more comprehensive approach. In particular, any refinements to the spray combustion physical submodels which are achieved during the project will be channeled back to Rocketdyne for incorporation in their ARICC liquid rocket combustor code as second generation improvements. Also, as the ARICC code forms the basis or future CFD development, some effort is devoted to an evaluation of the code's capability for modeling oscillating pressure waves within the combustor.

  12. 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.

  13. Spray combustion modeling

    NASA Technical Reports Server (NTRS)

    Bellan, J.

    1997-01-01

    Concern over the future availability of high quality liquid fuels or use in furnaces and boilers prompted the U. S. Department of Energy (DOE) to consider alternate fuels as replacements for the high grade liquid fuels used in the 1970's and 1980's. Alternate fuels were defined to be combinations of a large percentage of viscous, low volatility fuels resulting from the low end of distillation mixed with a small percentage of relatively low viscosity, high volatility fuels yielded by the high end of distillation. The addition of high volatility fuels was meant to promote desirable characteristics to a fuel that would otherwise be difficult to atomize and burn and whose combustion would yield a high amount of pollutants. Several questions thus needed to be answered before alternate fuels became commercially viable. These questions were related to fuel atomization, evaporation, ignition, combustion and pollutant formation. This final report describes the results of the most significant studies on ignition and combustion of alternative fuels.

  14. 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.

  15. Advances in Urea cycle Neuroimaging: Proceedings from the 4th International symposium on Urea cycle disorders, Barcelona, Spain, September 2013

    PubMed Central

    Pacheco-Colon, Ileana; Fricke, Stanley; VanMeter, John; Gropman, M.D.

    2014-01-01

    Our previous imaging research performed as part of a Urea Cycle Rare Disorders Consortium (UCRDC) grant, has identified specific biomarkers of neurologic injury in ornithine transcarbamylase deficiency, OTCD. While characterization of mutations can be achieved in most cases, this information does not necessarily predict the severity of the underlying neurological syndrome. The biochemical consequences of any mutation may be modified additionally by a large number of factors, including contributions of other enzymes and transport systems that mediate flux through the urea cycle, diet and other environmental factors. These factors likely vary from one patient to another, and they give rise to heterogeneity of clinical severity. Affected cognitive domains include non-verbal learning, fine motor processing, reaction time, visual memory, attention, and executive function. Deficits in these capacities may be seen in symptomatic patients, as well as asymptomatic carriers with normal IQ and correlate with variances in brain structure and function in these patients. Using neuroimaging we can identify biomarkers that reflect the downstream impact of UCDs on cognition. This manuscript is a summary of the presentation from the 4th International Consortium on Urea cycle disorders held in, Barcelona, Spain, September 2, 2014. PMID:25066103

  16. 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.

  17. 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.

  18. 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. PMID:14621175

  19. Urea nitrate, an exceptionally easy-to-make improvised explosive: studies towards trace characterization.

    PubMed

    Tamiri, Tsippy; Rozin, Rinat; Lemberger, Nitay; Almog, Joseph

    2009-09-01

    Urea nitrate is a powerful improvised explosive, frequently used by terrorists in the Israeli arena. It was also used in the first World Trade Center bombing in New York in February 1993. It is difficult to identify urea nitrate in post-explosion debris, since only a very small fraction survives the blast. Also, in the presence of water, it readily decomposes to its original components, urea and nitric acid. It is suspected that post-blast debris of urea nitrate can be confused with ammonium nitrate, the main solid product of urea nitrate thermal decomposition. In a comprehensive study towards identification of urea nitrate in post-blast traces, a spectrophotometric technique for quantitative determination of urea nitrate was developed, and conditions were found for extraction and separation of un-exploded traces of urea nitrate with minimal decomposition. Nevertheless, out of 28 samples collected from a series of three controlled firings of urea nitrate charges, only one gave the typical adduct ion by liquid chromatography/mass spectrometry analysis. We found that urea nitrate can be extracted from solid mixtures to organic solvents by using Crown ethers as "host compounds." The adducts thus formed are solid, crystalline compounds that can be characterized by microanalysis and spectroscopic techniques. PMID:19575193

  20. 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.

  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. PMID:26002019

  2. Active urea transport and an unusual basolateral membrane composition in the gills of a marine elasmobranch.

    PubMed

    Fines, G A; Ballantyne, J S; Wright, P A

    2001-01-01

    In elasmobranch fishes, urea occurs at high concentrations (350-600 mM) in the body fluids and tissues, where it plays an important role in osmoregulation. Retention of urea by the gill against this huge blood-to-water diffusion gradient requires specialized adaptations to the epithelial cell membranes. Experiments were performed to determine the mechanisms and structural features that facilitate urea retention by the gill of the spiny dogfish Squalus acanthias. Analysis of urea uptake by gill basolateral membrane vesicles revealed the presence of a phloretin-sensitive (half inhibition 0.09 mM), sodium-coupled, secondary active urea transporter (Michaelis constant = 10.1 mM, maximal velocity = 0.34 micromol. h(-1). mg protein(-1)). We propose that this system actively transports urea out of the gill epithelial cells back into the blood against the urea concentration gradient. Lipid analyses of the basolateral membrane revealed high levels of cholesterol contributing to the highest reported cholesterol-to-phospholipid molar ratio (3.68). This unique combination of active urea transport and modification of the phospholipid bilayer membrane is responsible for decreasing the gill permeability to urea and facilitating urea retention by the gill of Squalus acanthias. PMID:11124129

  3. 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.

  4. 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.

  5. 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.

  6. Cow level sampling factors affecting analysis and interpretation of milk urea concentrations in 2 dairy herds.

    PubMed Central

    Eicher, R; Bouchard, E; Tremblay, A

    1999-01-01

    The goals of this study were to determine the influence of the variations among udder quarters, the somatic cell count, the time of sampling during the day, sample conservation, and centrifugation on milk urea (UREA) concentrations, and to propose a sample collection procedure for herds that are not on a Dairy Herd Improvement (DHI) program. Forty cows from 2 herds with different feeding practices were randomly selected. The quarter sampled and the somatic cell count did not significantly influence UREA concentrations. Milk urea concentrations were highest in the morning. The diurnal pattern was not influenced by intrinsic factors like parity, days postpartum, or daily milk yield. The UREA concentrations were significantly higher after refrigeration for one week (mean UREA change = +0.41 +/- 0.24 mmol/L, P = 0.0001) and freezing for one month (mean UREA change = +1.52 +/- 1.25 mmol/L, P = 0.0001). Urea concentrations were slightly higher in lactoserum than in whole milk (mean UREA difference = +0.17 +/- 0.24 mmol/L, P = 0.0001). Although this study included only 2 herds and does not allow extrapolation, differences were found in the diurnal pattern of UREA in these 2 herds, which possibly reflect differences in feeding strategy. With consideration of these results, a 6-point sampling procedure for herds that are not on a DHI program is proposed. PMID:10416068

  7. 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

  8. Salivary concentrations of urea released from a chewing gum containing urea and how these affect the urea content of gel-stabilized plaques and their pH after exposure to sucrose.

    PubMed

    Dawes, C; Dibdin, G H

    2001-01-01

    The objectives were to: (1) determine the salivary concentrations of urea during 20 min chewing of a sugar-free gum containing 30 mg of urea; (2) measure the degree to which this urea would diffuse into a gel-stabilized plaque; (3) study the effect of the urea on the fall and subsequent rise in pH (Stephan curve) on exposure to 10% sucrose for 1 min; (4) model the measurements 2 and 3 mathematically. In point 1, the salivary urea concentration of the 12 subjects peaked at 47 mmol/l in the first 2 min of gum chewing, falling within 15 min to the unstimulated salivary concentration of 3.4 mmol/l. Recovery of urea from the saliva averaged 81.5%. 'Plaques' of 1% agarose or 67% dead bacteria in agarose accumulated urea from the saliva roughly as expected, whereas those plaques containing 8% live and 59% dead Streptococcus vestibularis showed negligible accumulation. Computer modelling showed this difference to be due to urease of live bacteria breaking down the urea as rapidly as it entered the plaque. Simulation of the effect of gum chewing subsequent to initiation of a Stephan curve in the latter type of plaque showed a rapid rise in pH but then a fall again on return to unstimulated conditions. This fall had not been seen in previous studies, with Streptococcus oralis, nor was it predicted by the computer modelling. Neither experimental simulation nor computer modelling suggested that chewing urea-containing gum before exposure to sucrose would have any effect on a subsequent Stephan curve. Thus chewing gum is only likely to inhibit caries when it is chewed after consumption of fermentable carbohydrate, rather than before. PMID:11641570

  9. 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

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

    DOEpatents

    Wijmans Johannes G.; Merkel, Timothy C.; Baker, Richard W.

    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. Impact of wire topology on channel routing

    SciTech Connect

    Blair, J.R.S.

    1986-01-01

    Channel routing is a method that has been widely used to overcome the inherent difficulties in the routing stage of automated VLSI chip and printed circuit board design. Almost all previous work on channel routing has restricted the wires to paths that are strictly monotonic (i.e., paths that do not backtrack in either the horizontal or vertical direction). The impact on single layer channel routing of wire topologies that provide considerably more wire routing flexibility than has previously been allowed is addressed here. A hierarchy of routing classes stemming from these generalized wire topologies is defined. It is shown that each of the routing classes is applicable to both the two row routing scenario (river routing) and the single row routing scenario. The routing classes are examined to see if the flexibility provided by the new wire types is useful for single row routing. Global routing under the channel routing scenario is briefly examined. In particular, a simplistic two layer global channel routing problem is shown to be NP-complete using two separate optimization criteria.

  12. 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).

  13. Measurement of spray combustion processes

    NASA Technical Reports Server (NTRS)

    Peters, C. E.; Arman, E. F.; Hornkohl, J. O.; Farmer, W. M.

    1984-01-01

    A free jet configuration was chosen for measuring noncombusting spray fields and hydrocarbon-air spray flames in an effort to develop computational models of the dynamic interaction between droplets and the gas phase and to verify and refine numerical models of the entire spray combustion process. The development of a spray combustion facility is described including techniques for laser measurements in spray combustion environments and methods for data acquisition, processing, displaying, and interpretation.

  14. Fourth International Microgravity Combustion Workshop

    NASA Technical Reports Server (NTRS)

    Sacksteder, Kurt R. (Compiler)

    1997-01-01

    This Conference Publication contains 84 papers presented at the Fourth International Microgravity Combustion Workshop held in Cleveland, Ohio, from May 19 to 21, 1997. The purpose of the workshop was twofold: to exchange information about the progress and promise of combustion science in microgravity and to provide a forum to discuss which areas in microgravity combustion science need to be expanded profitably and which should be included in upcoming NASA Research Announcements (NRA).

  15. 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. PMID:26094194

  16. 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

  17. GC-MS determination of ratios of stable-isotope labelled to natural urea using [13C15N2]urea for studying urea kinetics in serum and as a means to validate routine methods for the quantitative assay of urea in dialysate.

    PubMed

    Wolthers, B G; Tepper, T; Withag, A; Nagel, G T; de Haan, T H; van Leeuwen, J J; Stegeman, C A; Huisman, R M

    1994-02-01

    A GC-MS determination of urea in serum or spent dialysate is described, using 13C15N2-labelled urea and assaying the area ratio of labelled to natural urea by mass fragmentographic monitoring of fragments m/e 153 and 156, after its eventual conversion into the trimethylsilylether-derivative of 2-hydroxypyrimidine. The procedure can be successfully applied in the follow-up of the disappearance of labelled urea in serum after intravenous injection in man, enabling kinetic parameters of urea to be established, e.g. for purposes of studying the effectiveness of dialysis procedures. Furthermore the method can be used for validation of routine methods for measuring urea in other fluids, in particular dialysate. Examples are given of both applications of the GC-MS method described. PMID:8033352

  18. Kinetic barriers in the isomerization of substituted ureas: implications for computer-aided drug design.

    PubMed

    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. PMID:27272323

  19. [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%. PMID:16961255

  20. 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

  1. 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.

  2. 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.

  3. Composite propellant combustion modeling studies

    NASA Technical Reports Server (NTRS)

    Ramohalli, K.

    1977-01-01

    A review is presented of theoretical and experimental studies of composite propellant combustion. The theoretical investigations include a model of the combustion of a nonmetallized ammonium perchlorate (AP) propellant (noting time scales for vapor-phase combustion and the condensed phase) and response functions in pressure-coupled oscillations. The experimental studies are discussed with reference to scale-modeling apparatus, flame standoff distance versus velocity as a function of pressure, and results from T-burner firings of a nonmetallized AP/polysulfide propellant. Research applications including problems with nitramine propellants, the feasibility of stop-restart rockets with salt quench, and combustion problems in large boosters are outlined.

  4. Synthesis of Li 2MO 3 ( M = Ti or Zr) by the combustion method

    NASA Astrophysics Data System (ADS)

    Cruz, Daniel; Pfeiffer, Heriberto; Bulbulian, Silvia

    2006-05-01

    The advantages and disadvantages of the combustion method to prepare Li 2TiO 3 and Li 2ZrO 3 ceramics were studied. Firstly, the ceramic powders were prepared by the combustion process using LiOH, MO 2 (where M = Ti or Zr) and urea in different molar ratios (from 2:1:3 to 3:1:3) at different temperatures for 5 minutes. Li 2TiO 3 and Li 2ZrO 3 were also obtained by the solid-state method, and the results were compared with those obtained by the combustion process. The powders were characterized by X-ray diffraction and scanning electron microscopy. It was found that the combustion process reduces the synthesis time of Li 2TiO 3 (1 minute at 750 °C), but it does not have any advantage on producing Li 2ZrO 3, due to thermodynamic factors. On the other hand, the combustion process produces carbon contaminants in the solids. It was necessary to add excess of lithium hydroxide, in order to compensate the quantity of Li sublimated during the production of the ceramics. Finally, it seems that both reactions follow the same mechanism, which is determined by the lithium diffusion into the metal oxides.

  5. The charge density of urea from synchrotron diffraction data.

    PubMed

    Birkedal, Henrik; Madsen, Dennis; Mathiesen, Ragnvald H; Knudsen, Kenneth; Weber, Hans-Peter; Pattison, Philip; Schwarzenbach, Dieter

    2004-09-01

    The charge density of urea is studied using very high precision single-crystal synchrotron-radiation diffraction data collected at the Swiss-Norwegian Beam Lines at ESRF. An unprecedented resolution of 1.44 A(-1) in sin theta;/lambda is obtained at 123 K. The optimization of the experiment for charge-density studies is discussed. The high precision of the data allowed the refinement of a multipole model extending to hexadecapoles and quadrupoles on the heavy and H atoms, respectively, as well as a liberal treatment of radial functions. The topological properties of the resulting electron density are analysed and compared with earlier experimental results as well as with periodic Hartree-Fock calculations. The properties of the strongly polarized C-O bond agree with trends derived from previous experimental results while the ab initio calculations differ significantly. The results indicate that the description of the C-O bond requires more flexible basis sets in the theoretical calculations. The calculated integrated atomic charges are much larger than the observed ones. It is suggested that the present experimental results provide new target values for validation of future ab initio calculations. The molecular dipole moment derived from the integrated atomic properties is the same as the one obtained from the multipole model even though the individual atomic contributions differ. Comparison with literature data for urea in solution and the gas phase yields a dipole enhancement in the solid of about 1.5 D. The thermal expansion of urea is determined using synchrotron powder diffraction data. With decreasing temperature, an increasing anisotropic strain is observed. PMID:15477674

  6. Remote calorimetric detection of urea via flow injection analysis.

    PubMed

    Gaddes, David E; Demirel, Melik C; Reeves, W Brian; Tadigadapa, Srinivas

    2015-12-01

    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. PMID:26479269

  7. Urea, but not guanidinium, destabilizes proteins by forming hydrogen bonds to the peptide group.

    PubMed

    Lim, Woon Ki; Rösgen, Jörg; Englander, S Walter

    2009-02-24

    The mechanism by which urea and guanidinium destabilize protein structure is controversial. We tested the possibility that these denaturants form hydrogen bonds with peptide groups by measuring their ability to block acid- and base-catalyzed peptide hydrogen exchange. The peptide hydrogen bonding found appears sufficient to explain the thermodynamic denaturing effect of urea. Results for guanidinium, however, are contrary to the expectation that it might H-bond. Evidently, urea and guanidinium, although structurally similar, denature proteins by different mechanisms. PMID:19196963

  8. Juvenile amphibians do not avoid potentially lethal levels of urea on soil substrate.

    PubMed

    Hatch, A C; Belden, L K; Scheessele, E; Blaustein, A R

    2001-10-01

    We examined the effects of a forest fertilizer (urea) on newly metamorphosed terrestrial amphibians (Western toads, Bufo boreas; Cascades frogs, Rana cascadae; long-toed salamanders, Ambystoma macrodactylum; and roughskin newts, Taricha granulosa). We examined avoidance behavior of Western toads and Cascades frogs on both paper towel and soil substrates dosed with urea (control and 100 kg N/ha and an additional treatment of 50 kg N/ha for Western toads on soil substrate) and avoidance behavior of long-toed salamanders on soil substrate dosed with urea. We further examined the survival and feeding behavior of all four species exposed to urea on soil substrate (100 kg N/ha) for 5 d. Juvenile Western toads and Cascades frogs avoided paper towels dosed with urea but did not avoid urea-dosed soil substrate. However, Western toads and Cascades frogs both suffered significant mortality when exposed to urea on a soil substrate for 5 d. Furthermore, after adjusting for weight, we found that urea-exposed juvenile Western toads and Cascades frogs consumed significantly fewer prey items (crickets) compared with nonexposed control animals. Long-toed salamanders did not discriminate against soil substrate dosed with urea, and neither long-toed salamanders nor roughskin newts died or reduced prey consumption as a result of urea exposure. Juvenile amphibians may not be able to detect and avoid harmful levels of urea fertilizer on a natural substrate. Furthermore, anthropogenic stressors such as urea fertilizer can significantly reduce the survival and prey consumption of juvenile amphibians. These effects are important to consider in light of possible threats to the conservation status of many amphibian species. PMID:11596767

  9. Infrared studies on o-, m- and p-cresol-urea (1:1) complexes

    NASA Astrophysics Data System (ADS)

    Dobrowolski, J. Cz.

    1990-03-01

    Complex formation between urea and o-, m- and p-cresol in 1,2-dichloroethane solutions was investigated by i.r. spectroscopy. Analogical 1:1 urea-phenol complex was reevaluated. Those complexes are formed by CO⋯H hydrogen bonding. In solution the NH urea groups do not play any significant role. The i.r. temperature studies allowed us to determine the enthalpy and entropy of formation of 1:1 complex.

  10. Urea effect on aggregation and adsorption of sodium dioctylsulfosuccinate in water.

    PubMed

    Thapa, U; Ismail, K

    2013-09-15

    Understanding the mechanism that controls the folding/unfolding of proteins in the presence of urea continues to be a subject of research, and since micelles mimic biological aggregates, equal importance has been given to the study of surfactants in the presence of urea. Despite several studies on the effect of urea on the behavior of reverse micelles and microemulsions based on sodium dioctylsulfosuccinate (AOT), the urea effect on AOT regular micelles has not been investigated and hence it is studied herein by using surface tension, steady-state fluorescence, and dynamic light scattering methods. The effect of urea on the behavior of AOT is found to be different below and above 1.0 mol kg(-1) urea (c(u)). The critical micelle concentration (cmc) is almost independent of urea concentration below c(u), whereas it increases with increasing urea amount above c(u). In AOT+urea aqueous solution below c(u), added NaCl at a particular critical concentration (c*) induces sudden increase in the values of (i) counterion binding constant, (ii) aggregation number, (iii) fluorescence intensity ratio of pyrene excimer to monomer, and (iv) hydrodynamic diameter of AOT aggregate, whereas such changes are suppressed by urea above c(u). NaCl-induced shape change in AOT micelle takes place if urea concentration is below c(u), but hindered above c(u). The adsorption behavior of AOT at the air-solution interface as a function of NaCl is also found to be different below and above c(u). The urea effect is explained in terms of increase in the polarity of the medium, better solvation of head groups and counterions, and weakening of head group-head group and head group-counterion interactions. PMID:23827480

  11. 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.

  12. 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,…

  13. 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…

  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. Smoldering combustion analyses

    SciTech Connect

    Dosanjh, S.S.

    1986-01-01

    Smoldering combustion propagation through very porous solid materials is examined. Due to the microgravity environment, smolder propagation is assumed to be one-dimensional. Two configurations are considered: (1) cocurrent, premixed-flame-like or reverse; (2) countercurrent, diffusion-flame-like or forward. In cocurrent smoldering combustion, both forced and free flow are analytically represented. It is assumed that the propagation of the smolder wave is steady in a frame of reference moving with the wave. Smoldering is described by a finite-rate, one-step, oxidation reaction, and radiation heat transfer is incorporated using a diffusion approximation. A straightforward extension of the activation energy asymptotics analysis presented by Williams yields an expression for a dimensionless eigenvalue, ..lambda.., thus determining the final temperature, T/sub f/ A global energy balance then determines the smolder velocity, v. Explicit expressions are derived for the smolder velocity, v, and the final temperature, T/sub f/. An approximate extinction criterion is identified. A model of unsteady, forced, countercurrent smoldering combustion is also presented. Smoldering is represented utilizing a two step mechanism consisting of a pyrolysis reaction followed by a char oxidation reaction. A flame sheet approximation is used to model the oxidation reaction. It is assumed that pyrolysis occurs at a known temperature, T/sub p/. Two cases are considered: (1) no residual as, nu/sub a/M/sub a/ = 0, and (2) an ash layer forming beneath the oxidation zone, nu/sub a/M/sub a/ not equal to 0. The residual ash serves as insulation, and its presence leads to higher peak temperatures. Explicit expressions are derived for the oxidation velocity, v, the maximum temperature, T/sub m/, and the pyrolysis front velocity, v/sub p/.

  16. 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.

  17. 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.

  18. 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.

  19. Continuous monitoring of urea in blood during dialysis.

    PubMed

    Thavarungkul, P; Håkanson, H; Holst, O; Mattiasson, B

    1991-01-01

    Urease was immobilized to porous glass and used in combination with a conductivity meter for determining urea in standard solutions as well as in blood from a patient undergoing dialysis. The sampling unit involves a possibility for heparinization at the sampling point and a dialysis step prior to exposure to the enzyme column. The unit operates in a linear mode in the concentration range 5-50 mM. Monitoring of dialysis process gave good correlation with off-line analyses. PMID:2059398

  20. 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

  1. Significantly enhanced dehydrogenation properties of calcium borohydride combined with urea.

    PubMed

    Chu, Hailiang; Qiu, Shujun; Liu, Lin; Zou, Yongjin; Xiang, Cuili; Zhang, Huanzhi; Xu, Fen; Sun, Lixian; Zhou, Huaiying; Wu, Guotao

    2014-11-01

    The interaction of [BH(x)]- and [NH(x)]-containing species gives rise to molecular hydrogen and the establishment of the B-N bond. Up to now, metal amides and ammonia are the commonly used [NH(x)] sources. Herein, urea, an organic carbonyl diamide, was used to react with Ca(BH4)2. A new type of complex hydride Ca(BH4)2·4CO(NH2)2 was synthesized with release of ca. 5.2 wt% hydrogen below 250 °C. PMID:25186984

  2. Nitrogen doped TiO2 nano-particles: Phase control by solution combustion method

    NASA Astrophysics Data System (ADS)

    Bapna, Komal; Choudhary, R. J.; Phase, D. M.; Shastri, Sheetal; Prasad, R.; Ahuja, B. L.

    2016-05-01

    N-doped TiO2 nano powders were prepared by sol-gel solution combustion method. The influence of different fuels (urea and citric acid) used in obtaining N-TiO2 nano particles in similar conditions (heat treatment, amount of precursors) has been investigated. The growth of different phases of TiO2 (anatase and rutile) is strongly affected by the ligands and the dehydration reaction. Reduction in the band gap of TiO2 and features observed in the XPS spectra confirm the incorporation of N into TiO2 matrix.

  3. 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.

  4. Spray combustion stability

    NASA Technical Reports Server (NTRS)

    Liang, Pak-Yan; Jeng, San-Mou; Litchford, Ronald

    1989-01-01

    The central purpose of this project is the improvement of liquid-fueled rocket motor design technology in order to assist the establishment of economical commercial access to space through the development of engines with enhanced performance and reliability. Specific research effort is focused on spray physics and associated combustion instability phenomena. Results concerning high pressure droplet gasification model, droplet turbulent dispersion model, and spray atomization model will contribute to the development of new computational tools for design of stable liquid propellant rocket engines.

  5. Lagrangian Simulation of Combustion

    SciTech Connect

    Ahmed F. Ghoniem

    2008-05-01

    A Lagrangian approach for the simulation of reactive flows has been developed during the course of this project, and has been applied to a number of significant and challenging problems including the transverse jet simulations. An efficient strategy for parallel domain decomposition has also been developed to enable the implementation of the approach on massively parallel architecture. Since 2005, we focused our efforts on the development of a semi-Lagrangian treatment of diffusion, and fast and accurate Lagrangian simulation tools for multiphysics problems including combustion.

  6. Occurrence of benzo(a)pyrene in combustion effluents of kerosene and diesel burners

    SciTech Connect

    Gharaibeh, S.H.; Abuirjeie, M.A.; Hunaiti, A.A.

    1988-09-01

    Due to limited Jordanian resources, kerosene and diesel burners have been widely used for heating homes and water, warming bread, grilling meat and cooking food. Jordan annually imports and average of 204 tons of burners which corresponds to approximately 20,400 burners. Considerable amounts of combustion products are produced such as gases, aerosols and polycyclic aromatic hydrocarbons (PAH), especially benzo(a)pyrene (Bp), the well known carcinogen for man and animal. Since most Jordanians use burners more than five months a year, a considerable amount of combustion effluents accumulate indoors. Some of these materials can enter the human body via various routes, and are potential health hazards. Little information is available about the chemical nature and amount of the combustion effluents produced by these burners; therefore the present study was designed to screen for benzo(a)pyrene in the indoor-accumulated combustion effluent.

  7. 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

  8. 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.

  9. 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.

  10. Stand-alone sensors monitor for combustible gas leaks

    SciTech Connect

    Not Available

    1991-01-01

    Elizabeth Gas Co., a gas distribution company in New Jersey, has added a network of combustible gas sensors to a computer system already in place for continuous monitoring of gas leaks. The computer center at the company's Erie St. facility controls all dispatching, which includes routing gas through the system and controlling gas pressure. The system uses redundant Hewlett-Packard A900 central processing units (CPU), 6 monitors, including a Mitsubishi 35-in. color monitor, and Fisher control software. The company's primary tank farm, which contains over a million gallons of propane and LNG, is located near several chemical plants, an oil refinery and a residential neighborhood. To monitor for combustible leaks at the site, the company installed 49 stand-alone combustible gas sensors manufactured by Mine Safety Appliances Co. (MSA) of Pittsburgh, Pa. The sensors are designed to measure the concentrations of propane and LNG and trigger alarms at 20% of the lower explosive limit (LEL). The sensors are diffusion types that sample ambient air rather than drawing in samples through a pump. Using the principle of catalytic oxidation, the sensors produce a signal proportional to the concentration of combustible gas in the atmosphere. If gas is detected above 20% of the LEL, a relay driver signal is sent into a remote annunciator panel which contains LED alarm displays for each sensor. The remote annunciator panel also houses a 24 VDC power supply.

  11. Access routes for nutritional therapy.

    PubMed

    Waitzberg, D L; Plopper, C; Terra, R M

    2000-12-01

    Enteral nutrition (EN) and total parenteral nutrition (TPN) may provide life-sustaining therapy for surgical patients. The duration of nutritional therapy (enteral or parenteral) implies distinct access routes. We review the main aspects related to access routes for nutrient delivery. The enteral route, whenever feasible, is preferred. For EN lasting less than 6 weeks, nasoenteric tubes are the route of choice. Conversely, enterostomy tubes should be used for longer-term enteral feeding and can be placed surgically or with fluoroscopic and endoscopic assistance. The first choice for patients who will not be submitted to laparotomy is percutaneous endoscopic gastrostomy. Postpyloric access, although not consensual, must be considered when there is a high risk of aspiration. For intravenous delivery of nutrients lasting less than 10 days, the peripheral route can be used. However, because of frequent infusion phlebitis, its role is still in discussion. Central venous catheters (CVCs) for TPN delivery may be (1) nonimplantable, percutaneous, nontunneled-used for a few days to 3 to 4 weeks; (2) partially implantable, percutaneous, tunneled-used for longer periods and permanent access; or (3) totally implantable subcutaneous ports-also used for long-term or permanent access. The subclavian vein is usually the insertion site of choice for central venous catheters. Implantable ports are associated with lower rates of septic complications than percutaneous CVCs. The catheter with the least number of necessary lumens should be applied. Central venous nutrient delivery can also be accomplished through peripherally inserted central catheters, which avoid insertion-related risks. PMID:11193710

  12. Studies with 15N-labeled ammonia and urea in the malnourished child

    PubMed Central

    Read, W. W. C.; McLaren, D. S.; Tchalian, Marie; Nassar, Siham

    1969-01-01

    Investigations using ammonium citrate-15N and urea-15N showed that children in the acute stage of kwashiorkor and marasmus receiving a diet of adequate protein content retained a considerable percentage of the label from both compounds. Excretion of both total 15N and urea-15N was subnormal and elimination was virtually completed 36 hr after administration of the isotope. During recovery from kwashiorkor total 15N excretion had approached normal a month after commencement of rehabilitation. Urea-15N excretion was still slightly subnormal after 3 months. In marasmus urea-15N formed a normal proportion of total 15N excretion after 1 month, although total 15N excretion then was still low. Ammonia nitrogen was retained to a greater extent than urea nitrogen in all cases. As it is known that a considerable amount of urea is degraded to ammonia in the gastrointestinal tract, it seems probable that urea nitrogen became available for use after this degradation. Examination of blood from one marasmic child after feeding ammonia-15N and from another after intravenous injection of urea-15N showed incorporation of the label into blood cells and plasma proteins. This did not occur in well nourished controls. It is concluded that ammonia and urea as sources of nonessential nitrogen may play an important part in protein metabolism in the malnourished child. PMID:5771193

  13. 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

  14. Concomitant polymorphs of 1,3-bis(3-fluorophenyl)urea.

    PubMed

    Capacci-Daniel, Christina A; Bertke, Jeffery A; Dehghan, Shoaleh; Hiremath-Darji, Rupa; Swift, Jennifer A

    2016-09-01

    Hydrogen bonding between urea functionalities is a common structural motif employed in crystal-engineering studies. Crystallization of 1,3-bis(3-fluorophenyl)urea, C13H10F2N2O, from many solvents yielded concomitant mixtures of at least two polymorphs. In the monoclinic form, one-dimensional chains of hydrogen-bonded urea molecules align in an antiparallel orientation, as is typical of many diphenylureas. In the orthorhombic form, one-dimensional chains of hydrogen-bonded urea molecules have a parallel orientation rarely observed in symmetrically substituted diphenylureas. PMID:27585933

  15. Metabolic control of urea catabolism in Chlamydomonas reinhardi and Chlorella pyrenoidosa.

    PubMed

    Hodson, R C; Williams, S K; Davidson, W R

    1975-03-01

    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. The urea breath test: a non-invasive clinical tool for detecting Helicobacter pylori infection.

    PubMed

    Perri, F; Ghoos, Y; Hiele, M; Andriulli, A; Rutgeerts, P

    1995-03-01

    The urea breath test exploits the urease enzyme of Helicobacter pylori. The hydrolysis of labelled urea releases labelled carbon dioxide that is excreted in the breath. Distribution of urea throughout the stomach prevents sampling errors and allows for semiquantitative assessment of the extent of Helicobacter pylori infection. The urea breath test is very specific and sensitive and can be proposed as the method of choice for detecting Helicobacter pylori infection in ulcer patients before and after eradicating treatment as well as in epidemiological studies. PMID:7579592

  17. 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.

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. 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

  3. Ni-WC/C nanocluster catalysts for urea electrooxidation

    NASA Astrophysics Data System (ADS)

    Wang, Lu; Li, Mingtao; Huang, Zhiyu; Li, Yingming; Qi, Suitao; Yi, Chunhai; Yang, Bolun

    2014-10-01

    A nanocluster Ni-WC/C electrocatalyst is prepared through a sequential impregnation method and is used for the urea electrooxidation in alkaline conditions. The micro-morphology, lattice parameter, composition and surface states of Ni-WC/C particles are determined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX) and X-ray photoelectron spectrometry (XPS) analysis. The electrooxidation activity and stability of the Ni-WC/C catalyst are also investigated by cyclic voltammograms and chronoamperograms. Characterization results indicate that the Ni nanoclusters are uniformly distributed on the WC/C framework, and the Ni-WC/C catalyst shows high electrocatalytic activity and stability for urea electrooxidation. The maximum current density at the Ni-WC/C electrode is almost 700 mA cm-2 mg-1 which is one order of magnitude higher than that at the Ni/C electrode, and the steady current density at the Ni-WC/C electrode is also markedly improved. Furthermore, the ESA values and XPS spectra indicate that the enhanced performance of the Ni-WC/C catalyst could be attributed to the structure effect and electron effect between nickel and tungsten carbide.

  4. PLATELET ADHESION TO POLYURETHANE UREA UNDER PULSATILE FLOW CONDITIONS

    PubMed Central

    Navitsky, Michael A.; Taylor, Joshua O.; Smith, Alexander B.; Slattery, Margaret J.; Deutsch, Steven; Siedlecki, Christopher A.; Manning, Keefe B.

    2014-01-01

    Platelet adhesion to a polyurethane urea surface is a precursor to thrombus formation within blood-contacting cardiovascular devices, and platelets have been found to adhere strongly to polyurethane surfaces below a shear rate of approximately 500 s−1. The aim of the current work is to determine platelet adhesion properties to the polyurethane urea surface as a function of time varying shear exposure. A rotating disk system is used to study the influence of steady and pulsatile flow conditions (e.g. cardiac inflow and sawtooth waveforms) for platelet adhesion to the biomaterial surface. All experiments retain the same root mean square angular rotation velocity (29.63 rad/s) and waveform period. The disk is rotated in platelet rich bovine plasma for two hours with adhesion quantified by confocal microscopy measurements of immunofluorescently labeled bovine platelets. Platelet adhesion under pulsating flow is found to exponentially decay with increasing shear rate. Adhesion levels are found to depend upon peak platelet flux and shear rate regardless of rotational waveform. In combination with flow measurements, these results may be useful for predicting regions susceptible to thrombus formation within ventricular assist devices. PMID:24721222

  5. Voltamperometric Discrimination of Urea and Melamine Adulterated Skimmed Milk Powder

    PubMed Central

    Hilding-Ohlsson, Astrid; Fauerbach, Jonathan A.; Sacco, Natalia J.; Bonetto, M. Celina; Cortón, Eduardo

    2012-01-01

    Nitrogen compounds like urea and melamine are known to be commonly used for milk adulteration resulting in undesired intoxication; a well-known example is the Chinese episode occurred in 2008. The development of a rapid, reliable and economic test is of relevance in order to improve adulterated milk identification. Cyclic voltammetry studies using an Au working electrode were performed on adulterated and non-adulterated milk samples from different independent manufacturers. Voltammetric data and their first derivative were subjected to functional principal component analysis (f-PCA) and correctly classified by the KNN classifier. The adulterated and non-adulterated milk samples showed significant differences. Best results of prediction were obtained with first derivative data. Detection limits in milk samples adulterated with 1% of its total nitrogen derived from melamine or urea were as low as 85.0 mg·L−1 and 121.4 mg·L−1, respectively. We present this method as a fast and robust screening method for milk adulteration analysis and prevention of food intoxication. PMID:23112709

  6. Nitrogen leaching from Douglas-fir forests after urea fertilization.

    PubMed

    Flint, Cynthia M; Harrison, Rob B; Strahm, Brian D; Adams, A B

    2008-01-01

    Leaching of nitrogen (N) after forest fertilization has the potential to pollute ground and surface water. The purpose of this study was to quantify N leaching through the primary rooting zone of N-limited Douglas-fir [Pseudotsuga menziesii (Mirb.) Franco] forests the year after fertilization (224 kg N ha(-1) as urea) and to calculate changes in the N pools of the overstory trees, understory vegetation, and soil. At six sites on production forests in the Hood Canal watershed, Washington, tension lysimeters and estimates of the soil water flux were used to quantify the mobilization and leaching of NO(3)-N, NH(4)-N, and dissolved organic nitrogen below the observed rooting depth. Soil and vegetation samples were collected before fertilization and 1 and 6 mo after fertilization. In the year after fertilization, the total leaching beyond the primary rooting zone in excess of control plots was 4.2 kg N ha(-1) (p = 0.03), which was equal to 2% of the total N applied. The peak NO(3)-N concentration that leached beyond the rooting zone of fertilized plots was 0.2 mg NO(3)-N L(-1). Six months after fertilization, 26% of the applied N was accounted for in the overstory, and 27% was accounted for in the O+A horizon of the soil. The results of this study indicate that forest fertilization can lead to small N leaching fluxes out of the primary rooting zone during the first year after urea application. PMID:18689739

  7. 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.

  8. 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.

  9. 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.

  10. Fluidized bed combustion of coal

    NASA Astrophysics Data System (ADS)

    Tatebayashi, J.; Okada, Y.; Yano, K.; Takada, T.; Handa, K.

    The effect of various parameters on combustion efficiency, desulfurization efficiency and NO emission in fluidized bed combustion of coal were investigated by using two test combustors whose sectional areas were 200 mm and 500 mm square. It has been revealed that by employing two-stage combustion and setting the primary air ratio, secondary air injection height and other parameters to optimum levels, NO emission can be greatly reduced while barely impairing combustion efficiency or desulfurization efficiency. Also, NO emission of less than 50 ppm and desulfurization efficiency of as high as 93% were achieved. These results have ensured good prospects for the development of a coal combustion boiler system which can satisfy the strictest environmental protection regulations, without installing special desulfurization and de-NO(X) facilities.

  11. Mission Success for Combustion Science

    NASA Technical Reports Server (NTRS)

    Weiland, Karen J.

    2004-01-01

    This presentation describes how mission success for combustion experiments has been obtained in previous spaceflight experiments and how it will be obtained for future International Space Station (ISS) experiments. The fluids and combustion facility is a payload planned for the ISS. It is composed of two racks: the fluids Integrated rack and the Combustion INtegrated Rack (CIR). Requirements for the CIR were obtained from a set of combustion basis experiments that served as surrogates for later experiments. The process for experiments that fly on the ISS includes proposal selection, requirements and success criteria definition, science and engineering reviews, mission operations, and postflight operations. By following this process, the microgravity combustion science program has attained success in 41 out of 42 experiments.

  12. Solvation of sodium octanoate micelles in concentrated urea solution studied by means of molecular dynamics simulations.

    PubMed

    de Moura, André Farias; Bernardino, Kalil; de Oliveira, Osmair Vital; Freitas, Luiz Carlos Gomide

    2011-12-15

    The effects of urea on self-assembling remains a challenging topic on surface chemistry, and computational modeling may have a role on the unraveling of the molecular mechanisms underlying these effects. Bearing that in mind, we performed a set of molecular dynamics simulations to assess the effects of urea on the self-assembling properties of sodium octanoate, an anionic surfactant, as compared to the aggregation of the same surfactant in pure water as the solvent. The concentration of free monomers increased 3-fold in the presence of urea, in agreement with the accepted view that urea should increase monomer solubility. Regarding the size distribution of micellar aggregates, the urea solution favored smaller micelles and a narrower distribution. Preferential solvation by either water or urea changed along the surfactant molecules, from urea-rich shells around apolar atoms at the end of the hydrophobic tails to nearly no urea at the polar headgroups. This solvation profile is consistent with two different hypotheses from the literature: on one hand, urea molecules interact directly with apolar atoms from the hydrophobic tails, acting as a surfactant, and on the other hand the presence of urea molecules increases the hydration of polar sites. Another important observation regards the solvent structure, which exhibits a complex composition profile around both water and urea molecules. Although the solvent structure was appreciably different in each case, the free energy calculations for the dissociation of a pair of octanoate molecules pointed to a purely enthalpic free energy loss in urea solution, a finding that does not lend support to the third hypothesis that is often claimed as accounting for the urea effects, namely, that urea disrupts water structure and that this structural change decreases the hydrophobic effect due to an entropy change. The presence of urea had no significant effect on the molecular structure of the surfactant molecules, although it

  13. Urea's action on the hydrophobic interaction in physical and biophysical systems

    NASA Astrophysics Data System (ADS)

    Berne, B. J.

    2009-03-01

    For more than a century, urea has been commonly used as an agent for denaturing proteins. However, the mechanism behind its denaturing power is still not well understood. The mechanism of denaturation of proteins by urea is explored using all-atom microseconds molecular dynamics simulations of hen lysozyme generated on BlueGene/L. Accumulation of urea around lysozyme shows that water molecules are expelled from the first hydration shell of the protein. We observe a two stage penetration of the protein, with urea penetrating the hydrophobic core before water, forming a ``dry globule." The direct dispersion interaction between urea and the protein backbone and sidechains is stronger than for water, which gives rise to the intrusion of urea into the protein interior and also to urea's preferential binding to all regions of the protein. This is augmented by preferential hydrogen bond formation between the urea carbonyl and the backbone amides which contributes to the breaking of intra-backbone hydrogen bonds. Our study supports the ``direct interaction mechanism" whereby urea has a stronger dispersion interaction with protein than water. We also show by molecular dynamics simulations that a 7 M aqueous urea solution unfolds a chain of purely hydrophobic groups which otherwise adopts a compact structure in pure water. The unfolding process arises due to a weakening of hydrophobic interactions between the polymer groups. Again the action of urea is found to be direct, through its preferential binding to the polymer or plates. It is, therefore, acting like a surfactant capable of forming hydrogen bonds with the solvent. The preferential binding and the consequent weakened hydrophobic interactions are driven by enthalpy and are related to the difference in the strength of the attractive dispersion interactions of urea and water with the polymer chain or plate. We also show that the indirect mechanism, in which urea acts as a chaotrope, is not a likely cause of urea

  14. Quantifying Functional Group Interactions that Determine Urea Effects on Nucleic Acid Helix Formation

    PubMed Central

    Guinn, Emily J.; Schwinefus, Jeffrey J.; Cha, Hyo Keun; McDevitt, Joseph L.; Merker, Wolf E.; Ritzer, Ryan; Muth, Gregory W.; Engelsgjerd, Samuel W.; Mangold, Kathryn E.; Thompson, Perry J.; Kerins, Michael J.; Record, Thomas

    2013-01-01

    Urea destabilizes helical and folded conformations of nucleic acids and proteins, as well as protein-nucleic acid complexes. To understand these effects, extend previous characterizations of interactions of urea with protein functional groups, and thereby develop urea as a probe of conformational changes in protein and nucleic acid processes, we obtain chemical potential derivatives (μ23 = dμ2/dm3) quantifying interactions of urea (component 3) with nucleic acid bases, base analogs, nucleosides and nucleotide monophosphates (component 2) using osmometry and hexanol-water distribution assays. Dissection of these μ23 yields interaction potentials quantifying interactions of urea with unit surface areas of nucleic acid functional groups (heterocyclic aromatic ring, ring methyl, carbonyl and phosphate O, amino N, sugar (C,O)); urea interacts favorably with all these groups, relative to interactions with water. Interactions of urea with heterocyclic aromatic rings and attached methyl groups (as on thymine) are particularly favorable, as previously observed for urea-homocyclic aromatic ring interactions. Urea m-values determined for double helix formation by DNA dodecamers near 25°C are in the range 0.72 to 0.85 kcal mol−1 m−1 and exhibit little systematic dependence on nucleobase composition (17–42% GC). Interpretation of these results using the urea interaction potentials indicates that extensive (60–90%) stacking of nucleobases in the separated strands in the transition region is required to explain the m-value. Results for RNA and DNA dodecamers obtained at higher temperatures, and literature data, are consistent with this conclusion. This demonstrates the utility of urea as a quantitative probe of changes in surface area (ΔASA) in nucleic acid processes. PMID:23510511

  15. [Source analysis of urea-N in Lake Taihu during summer].

    PubMed

    Han, Xiao-Xi; Zhu, Guang-Wei; Xu, Hai; Wilhelm, Steven W; Qin, Bo-Qiang; Li, Zhao-Fu

    2014-07-01

    To study the effect of urea nitrogen on the ecosystem of Lake Taihu, we conducted urea and various nitrogen analysis for the water samples collected from the lake and surrounding rivers during summer. The ecological index analysis of 82 sites in rivers and lake yielded the following results: (1) The urea nitrogen contents in Taihu ranged from 0.011 to 0.161 mg x L(-1), which was high in the northwest and low in the southeast, related to the main pollution sources distribution of its drainage basin. (2) The dissolved nitrogen was dominated by inorganic nitrogen and the ratio between ammonia nitrogen and nitrate nitrogen was 5: 1. The average percentage of urea nitrogen in total nitrogen, dissolved nitrogen, dissolved organic nitrogen and bioavailable nitrogen was respectively 2.28%, 5.91%, 15.86%, and 6.22%, which showed a significant ecological function in Taihu. (3) Urea nitrogen concentration in river was more than twice that in lake, and the lake river concentration was slightly higher than the river into the lake. (3) In Taihu, there was a transformation relationship between urea nitrogen and the nitrogen in other forms. It showed that urea nitrogen had a significant positive correlation with permanganate index and the other forms of nitrogen, and a significant negative correlation with dissolved oxygen. In addition, urea nitrogen was weakly and positively correlated with chlorophyll a, while closely related to the spatial distribution of benthos and zooplankton species. All the results above showed that urea nitrogen was the bridge of organic and inorganic nitrogen transformation, and was the sign of nitrogen cycle of Lake Taihu, which was controlled by the circulating rate. High nitrogen content (especially the organic nitrogen) and low dissolved oxygen content were the key contributors to the increased urea nitrogen content. In Taihu, the urea nitrogen content was affected by both exogenous input and endogenous release. PMID:25244836

  16. Examining urea flux across the intestine of the spiny dogfish, Squalus acanthias.

    PubMed

    Gary Anderson, W; McCabe, Chris; Brandt, Catherine; Wood, Chris M

    2015-03-01

    Recent examination of urea flux in the intestine of the spiny dogfish shark, Squalus acanthias, has shown that feeding significantly enhances urea uptake across the intestine, and this was significantly inhibited following mucosal addition of phloretin. The present study examined potential mechanisms of urea uptake across the dogfish intestine in starved and fed dogfish. Unidirectional flux chambers were used to examine the kinetics of urea uptake, and to determine the influence of sodium, ouabain, competitive urea analogues, and phloretin on urea uptake across the gut of fed dogfish. Intestinal epithelial preparations from starved and fed dogfish were mounted in Ussing chambers to examine the effect of phloretin on bidirectional solute transport across the intestine. In the unidirectional studies, the maximum uptake rate of urea was found to be 35.3±6.9 μmol.cm(-2).h(-1) and Km was found to be 291.8±9.6 mM in fed fish, and there was a mild inhibition of urea uptake following mucosal addition of competitive agonists. Addition of phloretin, Na-free Ringers and ouabain to the mucosal side of intestinal epithelia also led to a significant reduction in urea uptake in fed fish. In the Ussing chamber studies there was a net influx of urea in fed fish and a small insignificant efflux in starved fish. Addition of phloretin blocked urea uptake in fed fish when added to the mucosal side. Furthermore, phloretin had no effect on ion transport across the intestinal epithelia with the exception of the divalent cations, magnesium and calcium. PMID:25479361

  17. FITC-tagged macromolecule-based alginate microspheres for urea sensoring

    NASA Astrophysics Data System (ADS)

    Joshi, Abhijeet; Chaudhari, Rashmi; Srivastava, Rohit

    2014-04-01

    Urea is an important biomarker for identification of kidney diseases. Early urea detection using a specific and sensitive technique can significantly reduce the mortality of patients. The research aims at developing fluorescence-based FITCmediated pH and urea measurement. A system containing FITC-dextran in alginate microspheres was developed using air-driven atomization. pH/Urea biosensor was characterized using optical microscopy, SEM, and CLSM. Urea biosensing studies were performed by exposing different standard solutions of pH and urea standard solutions using fluorescence spectroscopy (λex=488 nm and λem=520 nm). FITC-dextran was entrapped using an encapsulation unit and alginate microspheres were formed. The microspheres were found to be uniform and spherical in nature with sizes (50±10μ). FITC-dextran was found to be uniformly distributed in the alginate microspheres as per the CLSM scans. Urea biosensing studies indicate that a linear correlation was observed with increasing urea concentrations. The said microspheres can be used to detect changes in pH from 4-8 units owing to its linear response in this range. FITC dextran loaded alginate microspheres showed an improved range of detection upto 7 mM in comparison to 1.5 mM when in solution phase in a study with urea concentrations from 0-50 mM. The pH and urea detection was accurate to an extent of interday variation of 5%. FITC-dextran loaded alginate microspheres show a great potential for usage as a pH and urea biosensor for early detection of kidney diseases.

  18. Computerized Bus Routing in San Francisco.

    ERIC Educational Resources Information Center

    Caswell, Peter J.; Jungherr, J. Anton

    1979-01-01

    A computerized routing and scheduling system for the San Francisco Public Schools includes the batch processing of bus route assignments and schedules for all schools and the online terminal processing of daily changes. (Author/MLF)

  19. 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.

  20. Daisy Found on 'Route 66'

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This composite image from the panoramic camera on NASA's Mars Exploration Rover Spirit gives an approximately true-color rendering of a daisy-like pattern of brushed circles that Spirit produced on a rock called 'Route 66.' Spirit used the rock abrasion tool to complete this 6-position 'RAT daisy' on sol 99. It took this image on sol 100, April 14, 2004.

    The purpose for these large brushings is to create a large enough patch of treated surface area for the miniature thermal emission spectrometer to analyze. Scientists had previously conducted a brushing like this one on the rock 'Mazatzal.' The brushed area of Route 66 looks very different from the brushed area of Mazatzal, leading scientists to think that the rocks although both light in tone actually have different coating types.

  1. Multicast Routing of Hierarchical Data

    NASA Technical Reports Server (NTRS)

    Shacham, Nachum

    1992-01-01

    The issue of multicast of broadband, real-time data in a heterogeneous environment, in which the data recipients differ in their reception abilities, is considered. Traditional multicast schemes, which are designed to deliver all the source data to all recipients, offer limited performance in such an environment, since they must either force the source to overcompress its signal or restrict the destination population to those who can receive the full signal. We present an approach for resolving this issue by combining hierarchical source coding techniques, which allow recipients to trade off reception bandwidth for signal quality, and sophisticated routing algorithms that deliver to each destination the maximum possible signal quality. The field of hierarchical coding is briefly surveyed and new multicast routing algorithms are presented. The algorithms are compared in terms of network utilization efficiency, lengths of paths, and the required mechanisms for forwarding packets on the resulting paths.

  2. Blind Alley Aware ACO Routing Algorithm

    NASA Astrophysics Data System (ADS)

    Yoshikawa, Masaya; Otani, Kazuo

    2010-10-01

    The routing problem is applied to various engineering fields. Many researchers study this problem. In this paper, we propose a new routing algorithm which is based on Ant Colony Optimization. The proposed algorithm introduces the tabu search mechanism to escape the blind alley. Thus, the proposed algorithm enables to find the shortest route, even if the map data contains the blind alley. Experiments using map data prove the effectiveness in comparison with Dijkstra algorithm which is the most popular conventional routing algorithm.

  3. Use of urea-molasses-multinutrient block and urea-treated rice straw for improving dairy cattle productivity in Vietnam.

    PubMed

    Vu, D D; Cuong, L X; Dung, C A; Hai, P H

    1999-01-27

    After conducting a preliminary survey, a feeding trial was carried out to determine the effect of urea-molasses-multinutrient block (UMMB) and urea-treated rice straw (UTRS) as a feed supplement on the productivity of dairy cows. Sixty Holstein-Friesian crossbred cows on 11 smallholder farms were divided equally into control, UMMB and UTRS supplementation groups. Milk yield and feed intake were recorded daily. Milk fat content, body weight and body condition score (BSC) of each cow were determined at two week intervals. Milk samples for progesterone analysis were collected once a week commencing one month after parturition. Data were recorded for date of onset of ovarian activity, estrus, insemination, and conception rate. Milk production increased by 10.3-11.9% and milk fat content increased by 3-5%, therefore, profit for farmers increased by US $0.55-0.73 per cow per day (exchange rate US $1 = VN $11,000). The intervals from calving to onset of ovarian activity (91-94 days), to estrus (110-114 days), to conception (121-122 days) and the calving interval (13.4-13.6 months) in the trial groups were significantly shorter than those in the control group (112, 135, 152 days and 14.4 months, respectively. PMID:10081798

  4. [Effects of coated controlled release urea combined with conventional urea on winter wheat growth and soil NO3- -N].

    PubMed

    Yi, Wen-ping; Sun, Zhe; Wu, Liang; Shi, Gui-fang; Zhu, Guo-liang; Li, Ya-xing; Gu, Jia-lin; Xu, Qiu-ming

    2011-03-01

    Field experiments were conducted to study the effects of different dosages coated controlled release urea (PCU60, 60 d release duration) combined with conventional urea (U) used as basal on the winter wheat grain yield, nitrogen (N) recovery rate, and soil NO3- -N content, etc. Five treatments were installed, i.e., U (CK), 10% PCU60+90% U (PU1), 20% PCU60+80% U (PU2), 30% PCU60+70% U (PU3), and 40% PCU60+60% U (PU4). In the meantime, a comparative analysis was also carried out on the PCU60 N release characteristics under field condition and in 25 "C static water. At the same N dosage, all the test indices in treatment PU4 were significantly higher, with the grain yield, N recovery rate, total N accumulation amount, total tiller number and aboveground biomass at ripening stage, and economic benefit increased by 5.6%, 14.6%, 7.2%, 2.6%, 7.5%, and 984.3 yuan x hm(-2), respectively, compared with those in treatment U. The accumulation amount of NO3- -N in 0-100 cm soil layer in all treatments ranged in 39.70-49.93 kg x hm-2, and was the lowest (39.70 kg x hm(-2)) in treatment PU4. The N release pattern of PCU60 under field condition better fitted the N absorption characteristics of winter wheat. PMID:21657025

  5. 46 CFR 45.175 - Applicable routes.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 2 2012-10-01 2012-10-01 false Applicable routes. 45.175 Section 45.175 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart applies to the following...

  6. 46 CFR 45.175 - Applicable routes.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 2 2011-10-01 2011-10-01 false Applicable routes. 45.175 Section 45.175 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart applies to the following...

  7. 46 CFR 45.175 - Applicable routes.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 2 2013-10-01 2013-10-01 false Applicable routes. 45.175 Section 45.175 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart applies to the following...

  8. 46 CFR 45.175 - Applicable routes.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Applicable routes. 45.175 Section 45.175 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart applies to the following...

  9. 46 CFR 45.175 - Applicable routes.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 2 2014-10-01 2014-10-01 false Applicable routes. 45.175 Section 45.175 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED) LOAD LINES GREAT LAKES LOAD LINES Unmanned River Barges on Lake Michigan Routes § 45.175 Applicable routes. This subpart applies to the following...

  10. Combustion in porous media

    SciTech Connect

    Dillon, J.

    1999-09-01

    A 2.8-liter tube-shaped combustion vessel was constructed to study flame propagation and quenching in porous media. For this experiment, hydrogen-air flames propagating horizontally into abed of 6 mm diameter glass beads were studied. Measurements of pressure and temperature along the length of the tube were used to observe flame propagation of quenching. The critical hydrogen concentration for Hz-air mixtures was found to be 11.5%, corresponding to a critical Peclet number of Pe* = 37. This value is substantially less than the value of Pe* = 65 quoted in the literature, for example Babkin et al. (1991). It is hypothesized that buoyancy and a dependence of Pe on the Lewis number account for the discrepancy between these two results.

  11. Combustion of viscous hydrocarbons

    SciTech Connect

    Hayes, M.E.; Hrebenar, K.R.; Murphy, P.L.; Futch, L.E. Jr.; Deal, J.F. III; Bolden, P.L. Jr.

    1987-08-04

    A method is described for utilizing viscous hydrocarbons as combustible pre-atomized fuels, comprising: (A) forming a hydrocarbon-in-water emulsion using an effective amount of a surfactant package comprising at least one water-soluble surfactant, the hydrocarbon-in-water emulsion (1) comprising a hydrocarbon characterized by API gravity of about 20/sup 0/ API or less, viscosity of about 1000 centipoise or greater at 212/sup 0/F., a paraffin content of about 50% by weight or less and, an aromatic content of about 15% by weight or greater, and (2) having a hydrocarbon water ratio from about 60:40 to about 90:10 by volume; and (B) burning the resultant hydrocarbon-in-water emulsion.

  12. 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.

  13. 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

  14. Evaluation of carbon dioxide emission factor from urea during rice cropping season: A case study in Korean paddy soil

    NASA Astrophysics Data System (ADS)

    Kim, Gil Won; Jeong, Seung Tak; Kim, Gun Yeob; Kim, Pil Joo; Kim, Sang Yoon

    2016-08-01

    Fertilization with urea can lead to a loss of carbon dioxide (CO2) that was fixed during the industrial production process. The extent of atmospheric CO2 removal from urea manufacturing was estimated by the Industrial Processes and Product Use sector (IPPU sector). On its basis, the Intergovernmental Panel on Climate Change (IPCC) has proposed a value of 0.2 Mg C per Mg urea (available in 2006 revised IPCC guidelines for greenhouse gas inventories), which is the mass fractions of C in urea, as the CO2 emission coefficient from urea for the agricultural sector. Notably, due to the possibility of bicarbonate leaching to waters, all C in urea might not get released as CO2 to the atmosphere. Hence, in order to provide an accurate value of the CO2 emission coefficient from applied urea in the rice ecosystem, the CO2 emission factors were characterized under different levels of 13C-urea applied paddy field in the current study. The total CO2 fluxes and rice grain yields increased significantly with increasing urea application (110-130 kg N ha-1) and thereafter, decreased. However, with increasing 13C-urea application, a significant and proportional increase of the 13CO2sbnd C emissions from 13C-urea was also observed. From the relationships between urea application levels and 13CO2sbnd C fluxes from 13C-urea, the CO2sbnd C emission factor from urea was estimated to range between 0.0143 and 0.0156 Mg C per Mg urea. Thus, the CO2sbnd C emission factor of this study is less than that of the value proposed by IPCC. Therefore, for the first time, we propose to revise the current IPCC guideline value of CO2sbnd C emission factor from urea as 0.0143-0.0156 Mg C per Mg urea for Korean paddy soils.

  15. Enhancing the urea-N use efficiency in maize (Zea mays) cultivation on acid soils amended with zeolite and TSP.

    PubMed

    Ahmed, Osumanu H; Hussin, Aminuddin; Ahmad, Husni M H; Rahim, Anuar A; Majid, Nik Muhamad Abd

    2008-01-01

    Ammonia loss significantly reduces the urea-N use efficiency in crop production. Efforts to reduce this problem are mostly laboratory oriented. This paper reports the effects of urea amended with triple superphosphate (TSP) and zeolite (Clinoptilolite) on soil pH, nitrate, exchangeable ammonium, dry matter production, N uptake, fresh cob production, and urea-N uptake efficiency in maize (Zea mays) cultivation on an acid soil in actual field conditions. Urea-amended TSP and zeolite treatments and urea only (urea without additives) did not have long-term effect on soil pH and accumulation of soil exchangeable ammonium and nitrate. Treatments with higher amounts of TSP and zeolite significantly increased the dry matter (stem and leaf) production of Swan (test crop). All the treatments had no significant effect on urea-N concentration in the leaf and stem of the test crop. In terms of urea-N uptake in the leaf and stem tissues of Swan, only the treatment with the highest amount of TSP and zeolite significantly increased urea-N uptake in the leaf of the test crop. Irrespective of treatment, fresh cob production was statistically not different. However, all the treatments with additives improved urea-N uptake efficiency compared to urea without additives or amendment. This suggests that urea amended with TSP and zeolite has a potential of reducing ammonia loss from surface-applied urea. PMID:18454247

  16. Room temperature removal of NO by activated carbon fibres loaded with urea and La2O3.

    PubMed

    Lu, Pei; Zeng, Zheng; Li, Caiting; Zeng, Guangming; Guo, Jing; Jiang, Xiao; Zhai, Yunbo; Fan, Xiaopeng

    2012-01-01

    In this paper, catalytic samples of 10, 20, 30, 40 and 50% (w/w) urea/activated carbon fibre (AFC), 10% urea--5% La2O3/ACF, 10% urea--10% La2O3/ACF, 10% urea--15% La2O3/ACF, 20% urea--5% La2O3/ACF, 20% urea--10% La2O3/ACF, and 20% urea-15% La2O3/ACF were prepared and used for removal of NO under the condition of: NO, 500 ppm; O2, 21%; N2, balance, gas space velocity = 10000 m3 x h(-1) m(-3), total gas flow = 266.7 mL min(-1), temperature = 30 degreesC, relative humidity = 0%. The physical and chemical properties of the prepared catalysts were characterized by surface area measurements (BET) and scanning electron microscopy studies. Furthermore, the catalytic stability of 10% urea--5% La2O3/ACF under different concentrations of NO and O2 were also studied. The results showed that, among the prepared urea/ACF samples, 20% urea/ACF yielded the highest NO conversion at room temperature. Meanwhile, among the prepared urea--La2O3/ACF catalysts, 10% urea--5% La2O3/ACF yielded the highest NO conversion. Both 20% urea/ACF and 10% urea--5% La2O3/ACF could yield over 95% NO conversion at ambient temperature. However, 10% urea--5% La2O3/ACF had a more stable activity than that of 20% urea/ACF. The catalytic and characterization experimental results, including BET, thermogravimetric analysis and Fourier transform infrared analysis, showed that the NO selective catalytic reduction mechanism of urea-La2O3/ACF was different from that of ACF and urea/ACF. The NO was purified by ACF mainly by adsorption, whereas there was mainly a reduction reaction when NO was purified by urea/ACF or urea-La2O3/ACF. ACF-C was not only the catalyst but also the reducing agent for urea/ACF, whereas, for urea-La2O3/ACF, the catalytic centre was La2O3, and ACF was mainly the carrier. These differences resulted in the higher and more stable NO removal by 10% urea--5% La2O3/ACF. PMID:22720430

  17. 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

  18. Combustion A Study in theory, fact and application

    SciTech Connect

    Chomiak, J. )

    1990-01-01

    This book provides a view of combustion science. It presents an account of combustion theory, with an emphasis on turbulent flame phenomena and coal combustion and fire problems. It discusses combustion design, research fundamentals and combustion technology.

  19. Dialysis system. [using ion exchange resin membranes permeable to urea molecules

    NASA Technical Reports Server (NTRS)

    Mueller, W. A. (Inventor)

    1978-01-01

    The improved hemodialysis system utilizes a second polymeric membrane having dialyzate in contact with one surface and a urea decomposition solution in contact with the other surface. The membrane selectively passes urea from the dialyzate into the decomposition solution, while preventing passage of positively charged metal ions from the dialyzate into the solution and ammonium ions from the solution into the dialyzate.

  20. Water-mediated interactions between trimethylamine-N-oxide and urea.

    PubMed

    Hunger, Johannes; Ottosson, Niklas; Mazur, Kamila; Bonn, Mischa; Bakker, Huib J

    2015-01-01

    The amphiphilic osmolyte trimethylamine-N-oxide (TMAO) is commonly found in natural organisms, where it counteracts biochemical stress associated with urea in aqueous environments. Despite the important role of TMAO as osmoprotectant, the mechanism behind TMAO's action has remained elusive. Here, we study the interaction between urea, TMAO, and water in solution using broadband (100 MHz-1.6 THz) dielectric spectroscopy. We find that the previously reported tight hydrogen bonds between 3 water molecules and the hydrophilic amine oxide group of TMAO, remain intact at all investigated concentrations of urea, showing that no significant hydrogen bonding occurs between the two co-solutes. Despite the absence of direct TMAO-urea interactions, the solute reorientation times of urea and TMAO show an anomalous nonlinear increase with concentration, for ternary mixtures containing equal amounts of TMAO and urea. The nonlinear increase of the reorientation correlates with changes in the viscosity, showing that the combination of TMAO and urea cooperatively enhances the hydrogen-bond structure of the ternary solutions. This nonlinear increase is indicative of water mediated interaction between the two solutes and is not observed if urea is combined with other amphiphilic solutes. PMID:25138965